welding manual 1995

Highway Maintenance WELDING

Techniques and Applications

Cornell Local Roads Program416 Riley–Robb Hall

Ithaca, New York 14853–5701phone: (607) 255–8033

fax: (607) 255–4080e–mail: [email protected]

web: www.clrp.cornell.edu

CORNELL LOCAL ROADS PROGRAM

Highway Maintenance Welding

2 Cornell Local Roads Program

Highway Maintenance WELDING

Techniques and Applications

by Tom Cook

Instructor Department of Biological and Environmental Engineering

Cornell University

CORNELL LOCAL ROADS PROGRAM 416 Riley–Robb Hall

Ithaca, New York 14853–5701 phone: (607) 255–8033

fax: (607) 255–4080 e–mail: [email protected]

web: www.clrp.cornell.edu

April 1991 (edited and reprinted 1995)

CLRP Report #95–5

PREFACE This manual was written for distribution to participants in two training courses: Highway Maintenance Welding Techniques and Applications, and Advanced Maintenance Welding Techniques and Applications. The basic welding techniques course has been offered by the Cornell Local Roads Program since 1985. The advanced course was offered for the first time in 1990. The author of this workbook is Tom Cook, who is an Instructor in the Department of Biological and Environmental Engineering (Power and Machinery Group) at Cornell University. Mr. Cook has taught the basic and advanced welding courses for the Local Roads Program. The content of this manual is directed to new and experienced welders who perform routine, maintenance welding in local highway departments. A variety of welding techniques and safety issues are presented here. The original illustrations in this workbook were drawn by Tom Cook and Susan Mackay. Other illustrations were reprinted with permission of Cornell University. Funding for the Local Roads Program is provided jointly by the New York State Department of Transportation, the Federal Highway Administration, and Cornell University. For further information about this manual and related training programs, contact the Local Roads Program.

Toni Rosenbaum Associate Director

Cornell Local Roads Program (reprinted) March 1995

Table of contents 1 Introduction.......................................................................................................................1 2 Safety ................................................................................................................................3 2.1 Potential hazards ......................................................................................................3 2.2 Protection .................................................................................................................3 2.3 Precautions for gas welding .....................................................................................5 3 Torch uses .......................................................................................................................11 3.1 Welding..................................................................................................................11 3.2 Cutting with a torch ...............................................................................................15 4 Metal identification.........................................................................................................21 4.1 Spark test................................................................................................................21 4.2 File and chisel tests ................................................................................................23 4.3 Magnetic test..........................................................................................................23 4.4 Identifying steel manufacturing processes.............................................................23 4.5 Fracture test for cast iron .......................................................................................23 4.6 Flame test ...............................................................................................................24 5 Heat treatment.................................................................................................................25 6 Arc welding.....................................................................................................................29 6.1 Welding machines..................................................................................................29 6.2 Duty cycle ..............................................................................................................30 6.3 Alternating and direct current ................................................................................30 6.4 Electrodes...............................................................................................................31 6.5 Establishing the arc ................................................................................................32 6.6 Arc cutting .............................................................................................................34 6.7 Arc welding safety .................................................................................................36 7 Out–of–position welding ................................................................................................37 7.1 Low hydrogen and maintenance electrodes...........................................................37 7.2 Vertical welding.....................................................................................................39 7.3 Overhead welding ..................................................................................................40 8 Hard facing and surfacing metals ...................................................................................41 9 Welding defects ..............................................................................................................45 10 Cast iron and its repair ....................................................................................................51 11 Soldering.........................................................................................................................55

12 Welding specialty metals ................................................................................................59 12.1 Aluminum ..............................................................................................................59 12.2 Magnesium.............................................................................................................60 12.3 Stainless steel .........................................................................................................60 12.4 Phosphor–copper....................................................................................................61 12.5 White or pot metals and zinc die cast ....................................................................61 13 Advanced welding processes ..........................................................................................63 13.1 Tungsten inert gas welding (TIG)..........................................................................63 13.2 Metallic inert gas welding (MIG) ..........................................................................65 13.3 Flux–core arc welding (FCAW) ............................................................................68 13.4 Plasma arc cutting (PAC).......................................................................................68 14 Tank repair and equipment maintenance ........................................................................71 14.1 Tank repair .............................................................................................................71 14.2 Maintenance of welding equipment.......................................................................73 APPENDICES A References and acknowledgements ................................................................................75 B Information sources ........................................................................................................75 C Video tapes......................................................................................................................75 D ASW/ASTM number system ..........................................................................................76 E Welding dos and donts....................................................................................................77

List of figures 1 Fire extinguisher ...............................................................................................................5 2 Oxyacetylene equipment...................................................................................................7 3 Oxyacetylene regulator .....................................................................................................8 4 Location of “O” ring seals on an oxyacetylene welding tip ...........................................11 5 Torch flames ...................................................................................................................13 6 Rod and torch orientation................................................................................................13 7 End view of oxyacetylene braze weld ............................................................................14 8 Oxyacetylene cutting torch and tip .................................................................................16 9 Cutting with an acetylene torch ......................................................................................16 10 Cutting bar and direction ................................................................................................18 11 Piercing a hole with oxyacetylene cutting torch .............................................................19 12 Cutting pipe.....................................................................................................................19 13 Spark patterns..................................................................................................................21 14 Spark patterns .................................................................................................................22 15 Hardening and tempering a cold chisel...........................................................................26 16 Continuous amperage adjustment ...................................................................................29 17 Arc and rod base .............................................................................................................33 18 Piercing a hole with electric arc......................................................................................35 19 Electrode position for vertical ‘tee” weld .......................................................................39 20 Overhead welding ...........................................................................................................40 21 Hard facing grid pattern ..................................................................................................42 22 Welding defects ..............................................................................................................44 23 Cracking..........................................................................................................................46 24 Effects of heating and cooling ........................................................................................47 25 Back–step welding ..........................................................................................................48 26 Jack straightening............................................................................................................49 27 Cast iron welding ............................................................................................................53 28 TIG system......................................................................................................................63 29 TIG torch tip ...................................................................................................................64 30 MIG welding system.......................................................................................................66 31 FCAW tip........................................................................................................................68 32 PAC tip............................................................................................................................69 33 Fuel tank repair ...............................................................................................................73

List of tables 1 Tempering colors for various tools .................................................................................27 2 Selecting solder...............................................................................................................56

2 Safety

Cornell Local Roads Program 1

1 INTRODUCTION A maintenance welder must wear more than one hat. Welders must be able to repair, maintain, and fabricate with technical skill. Welders also must be able to anticipate problems, and to determine the reasons for failure. Welders will not be able to predict every case of high speed and overload. Human nature implies that there will be imperfect welding jobs. Welders must keep everything in balance within the limits of weight, space, time, and cost. When modifying existing designs or planning new construction, welders must consider what is “fair wear and tear,” then build a project a bit better. With an eye towards making things better, welders should be aware of new and improved techniques and methods that will result in stronger, lighter, faster, and less costly repairs. There have been tremendous technological improvements in welding within the last few years, but most are not aimed at maintenance welders. The majority of the procedures that welders use have existed for more than 40 years. You must determine what will work for each individual situation. This workbook is designed to give new and experienced welders basic, practical methods and techniques for maintenance welding. Safety is considered so important, that it is presented early in the manual in Chapter 2 and then again in Chapter 6. The basic principles of torch use, arc welding, and metal identification are discussed in Chapters 3, 4, and 5. Later there are chapters about welding objects that are in hard–to–reach positions, cast iron repair, heat treatment, and soldering. Chapters 12 and 13 present advanced techniques for more experienced welders.

2 Safety


2 SAFETY The welder's job is to create sparks. Recognizing the hazards and dangers of welding is essential. Every shop, building, or site has potential danger. Welders must be aware of each one, be prepared to deal with them, and learn how to react to unexpected danger. 2.1 Potential hazards Flammable materials likely found in welding facilities include:

• Gas ● Small gas engine tanks • Kerosene ● Hydraulic oil and cylinders • Diesel tanks ● Flammable rags and clothing • Oil drums ● Lumber • Paint cans and drums ● Hoses • Alcohol containers ● Belts • Penetrating oils ● Seat cushions • Cleaning agents ● Soundproofing • Drains ● Electrical wire insulation

Consider every flammable item as a potential fire hazard. Observe wisely and remove or cover hazards. Sparks from a cutting torch will travel 35–40 feet, so be extremely observant and careful. Even the best welders can't detect fires they can't hear, smell, or feel. Appointing someone to act as a conscientious fire watch is important when working on large exposures. The fire watch is there to keep you informed, to be your eyes and ears. Be sure that person takes the job seriously and has extinguishing tools available. The intense welding arc creates harmful ultraviolet (UV) rays, which destroy living tissue. The rays create nasty burns and the potential for skin cancers. Cover exposed skin. 2.2 Protection Welding gas fumes are toxic in mild quantities, creating flu–like symptoms, resulting in aching muscles and nausea. Create a safe environment for yourself and others before you begin a welding project. Some suggested protection measures are:

• Eliminate fumes or work with natural ventilation when possible • Use a small fan to clear the air, and be mindful of coworkers in the vicinity



• Cut or weld galvanized items outside • Drink plenty of milk to counter the action of the heavy metal zinc from galvanizing • Keep fresh air flowing (Simple dust masks will filter only large particles from the air.

Fresh, clean air is the best and cheapest solution. Many welders develop chronic lung disease from long–time exposure to fumes.)

• Cover exposed skin to protect from UV rays 2.2.1 Proper eye shielding For electric arc, use a shade 10–11 lens to protect your eyes; the darker, the better. For oxyacetylene cutting and welding, use a shade 4–5 lens. Wear shields to avoid ruining your eyes. Arc burn is not just a short–term pain. The long–term effect is the loss of night vision, when the eye's rod receptors are damaged. They are neither repairable nor replaceable. Screening should be used to protect others in the shop, and welders should be provided with proper protective eye wear. 2.2.2 Protective clothing Cotton is best. Avoid polyesters, nylons, or blends because these will burn or melt and fuse to the skin. Frayed cotton edges, which may smolder, can be patted out with the bare hand and will not stick to you. Beginning or advanced welders will see an improvement in their abilities through the use of leathers. You can ruin an otherwise competent welding bead by flinching and shaking when hit by flying hot sparks. Sleeves, capes, or full leather jackets provide coverage. If commercial leathers are unavailable, use cast-off leather or suede jackets. Never throw away leather gloves without removing all the usable live leather for cover–ups or guards. These can be safety–pinned around anything that needs protection. 2.2.3 Fire extinguishers Think about exposure to hazards before an accident occurs. Are there adequate fire extinguishers and power available? Don't start a welding project without sufficient extinguishing power. Always have a number of back–up systems. Be sure that every system is charged and available, and that you or your designated fire watch know how to use the extinguisher properly. Every shop should contain the following items:

• Metal bucket of water • Cotton • Canvas or wool rags • Bucket or box of sand • Asbestos or fiberglass shielding

2 Safety


• A dry chemical fire extinguisher (powdered chemical similar to simple baking soda

driven by an inert dry nitrogen gas) • A second type of fire extinguisher (carbon dioxide, halon, or other ABC type)

Chemical fire extinguishers should be fully charged and well shaken before use to ensure that the dry powder will be fully ejected. Aim at the base of a fire to smother it. Chemical extinguishers are best for situations where grease and oil are present. However, they leave a residue which can be difficult to clean and may even ruin implements, such as electronic equipment or carburetors. Carbon dioxide leaves no residue. A dry chemical extinguisher rarely seals after a first use. The powder will usually prevent the valve assembly from completely closing, thus allowing the propellent gas to leak, rendering a dry chemical extinguisher useless for a later application. Make sure that the extinguisher is recharged after use. Consider another type of fire extinguisher that uses carbon dioxide as a covering gas to drive out hydrocarbon–fuel air mix in any container where there is a chance of ignition. A small charge of carbon dioxide is insurance against an explosion and possible death or injury. One unit can be used expressly for this purpose. Keep others fully charged. 2.3 Precautions for gas welding The explosive power of welding gases is well–known. It is very important to understand the precautions and how to safely establish the desired welding gas pressures. 2.3.1 Suggested precautions The following is a list of suggested precautions when using explosive welding gases (see Appendix D):

• Don't transport cylinders with the regulators on. In the event of an accident the regulators can act as a lever, snapping the tank valve off (federal regulation)

• Don't transport cylinders in a closed vehicle • Chain cylinders tightly to prevent accidental tipping • A cylinder storage area should be well–ventilated, close to an access door, out of high

traffic areas, and adequately chained for lockup • Post signs noting the hazardous nature of welding gases • Use full and empty designators • Provide an adequate cart for each set of cylinders (This will allow for easy transport

within the shop, putting the regulators within reach of the welder)

Figure 1 Fire extinguisher



2.3.2 Oxyacetylene gas set–up Acetylene is the most versatile welding gas. It has the highest flame temperature (6,300 degrees F) and the most efficient ratio of oxygen consumption. Because it has a noxious odor, a leak can be readily detected in small quantities. A drawback is the unstable nature of acetylene gases between 15–30 psi (pounds–per–square–inch), and its tendency to become explosive as a free gas beyond 30 psi. To overcome this, line pressures should never exceed 15 psi. Acetylene is stored at 250+ psi by forcing the gas into solution with the liquid solvent, acetone, within the cylinder. Because the gas must be forced into solution it is a very slow process. Filling usually takes seven hours. The following conditions result in limits on the use of acetylene in the shop:

The cylinder should always be used in the upright position (if the cylinder has been laid down, wait at least five minutes before using to allow any liquid to drain out of the valve area).

The rate of withdrawal cannot exceed the rate at which the acetylene comes out of solution (approximately 1/7 of the total tank capacity per hour). Exceeding the withdrawal rate results in the release of solvent and tank debris which can ruin the system, creating costly repairs. This limits the tip sizes or the time that a specific tip can be used.

After placing the cylinders in a cart or carrier and chaining them firmly, take the following steps to ensure safe operation:

1. Remove the tank cap. Release a small amount of gas to purge the tank outlet valve and orifice of debris. Clean the mating face of the tank valve with a clean, dry cloth.

2. Shake the regulator and gently tap the stem assembly in the palm. You will note small

brass chips that were in the system. These small chips can work their way into the regulator valve assembly, preventing them from fully seating, or scoring the regulator stem face. Clean the stem face with a clean dry cloth. No grease or oil should ever be used on any gas fitting.

3. Place the stem against the tank valve receiving face and begin to tighten the stem nut

by hand. It should go on smoothly. 4. Snub down the stem nut with a tank wrench or small adjustable wrench. Only mild

pressure is required to properly seat the brass faces. 5. Crack the tank valve after backing off the adjusting screw on the regulator. This will

fill the tank side and gauge showing true tank pressure.

2 Safety


6. Close the tank valve. If the tank gauge drops there is a leak between the tank and the

regulator. Find the cause and repair it. The best and safest means of finding a gas leak is with soap suds. Place the suds on any suspected location and watch for bubbling.

7. Open the tank valve and adjust the line pressure screw for the desired line pressure. 8. Close the tank valve. If the tank gauge drops, a leak is present on the line side. Find the

leak and repair. Even small leaks can create a fire hazard. Don't work with leaky systems.

9. If there are no leaks, open the tank valves as follows: Oxygen — Open valve fully until it seats at the top. Acetylene or other fuel gases — Open only a half–turn or until sufficient flow is

reached. These valves should seat in any position. The welder should be able to turn any fuel gas tank valve off with just a twist of the wrist.

Make steps 5–9 standard practice every time you use a cylinder. Failure to thoroughly check the system is wasteful and extremely dangerous.

Figure 2 Oxyacetylene equipment



The tank pressure must be reduced to workable line pressures by use of a regulator (see Figure 3). The regulating mechanism consists of a spring, diaphragm, valve, and chamber arrangement. Given the nature of the gases and pressures any adjustment other than to set line pressures should be left to a qualified professional. Eliminate or reduce two of the biggest causes of regulator malfunction by ensuring that no solvent is ever allowed to reach the regulator, and that chips or other debris are removed from the regulator stem at each tank change. 2.3.3 Check valves Check valves are anti–reverse flow devices designed to protect the system. Due to a clogged tip, an equipment malfunction, or a line being run over it is possible for a surge of gas to lead to excessive pressure, igniting gas within the regulator or line. Check valves protect the system at a very low cost per unit. The Occupational Safety and Health Administration (OSHA) dictates that one set of check valves be placed between the regulator and the hose. Practice has shown that a second set of check valves between the hose and the torch body will protect the hoses also. Restriction of flow within the lines is minimal. Periodically, a check valve should be tested by disconnecting the components and trying to blow back through the line or device. Defective units are occasionally found with the insides gummed open by the release of solvent and debris from the tank. Trying to squeeze the last bit of acetylene from a tank will result in solvent being ejected. A check valve will require one to two psi to open. This protects the system from the unintentional flow of solvent. 2.3.4 Other fuel gases Propane provides a cheaper fuel source, but does not utilize oxygen as efficiently, nor reach the same ultimate temperature, as acetylene. However, it is useful and ultimately less costly for cutting operations, since once the kindling temperature is reached, oxygen does the work of cutting. Propane will not reach kindling temperatures as fast as acetylene, and this also makes welding operations more difficult. Cutting tips and components usually are more expensive for propane.

Figure 3 Oxyacetylene regulator

2 Safety


MAPP gas (a Dow Chemical liquified acetylene compound) is safer to handle than acetylene, but fails to reach the same maximum temperature. Availability is limited and some dealers are reluctant to carry a product that many feel is inferior. Natural gas can be used, but has essentially the same downside as propane.

2 Safety


3 TORCH USES 3.1 Welding Modern oxyacetylene torches are designed to burn an equal amount of acetylene and oxygen. Hence, the name, equal pressure torch. To establish a base pressure that will efficiently mix and burn the gases, a clean tip is necessary. 3.1.1 Setup and preparation Tip cleaning prolongs the life of the tip and ensures a hard–working, efficient flame. The tip cleaning tool consists of a flat file and 10–15 tip cleaning round files. The goal is to restore the smooth orifice of the tip, and to prevent disruption of the gas flow. Any speck of dirt or slag spatter will create a wobble or impede the flow of outside air from reaching the inner flame. Use only the correct size tip cleaner, since jamming a cleaner into the orifice usually results in the difficult task of removing the broken file. The first step is to remove any oxides, dirt, or spatter from the tip face by using the flat file edge as a paring knife to snap off the debris without driving it into the orifice. Next, use a light filing action across the tip face. This should restore the original flat surface. If the face is deeply rutted, outside air will not mix equally with the fuel gas, and will create an off–center pattern that makes control difficult. To remedy this, use a mill file and carefully cut back the face until smooth and true. Do not apply the tip face to a grinding wheel because the soft copper will plug the holes, ruining the tip.

Figure 4 Location of “O” ring seals on an oxyacetylene



A faster method of “trueing” the face is to use a tip–nip, a tool similar to a pencil sharpener. Once the tip face is “trued,” use small and fragile round files. Carefully align each file to ensure that the orifice does not become funnel–shaped. Work the file in and out to gently smooth the walls. Carefully inspect the “O” rings on the tip to see that they are in place and without digs or scrapes. These rings prevent the gases from mixing before they enter the mixing chamber of the welding or cutting tip, and from leaking out at the torch body. The nut on the tip keeps the tip on the body. Therefore, it should only be finger–tight. Place the tip or cutting attachment in the body of the torch handle, so that the tip is at a 90–degree angle to the torch valves. Holding the body in the right hand (for right–handers) with the valves up, the tip should be pointed to the left. This will give you a safe view of the tip while still being able to control the valves in your right hand. To establish a working pressure for the acetylene, set 4–5 psi with the adjusting screw, crack the acetylene body valve 1/8 of a turn, and light the flame with a striker. Be sure to check for exposures one more time before ignition. The following criteria should be met with proper pressure for a specific size:

• The flame will be on the tip not jumping off • There will be no soot from the flame • The flame will be long and smooth

Sufficient pressure will cause the acetylene to suck in enough oxygen from the air to completely burn the gas. Lack of pressure is indicated by a sooty flame, even though the body valve is opened a full turn. If the flame jumps away from the tip excessively, and is not easily controlled by the torch valve, lower the pressure setting on the regulator and wait for the line pressure to stabilize. Set the oxy pressure to match the acetylene. With a cutting tip the acetylene pressure and flame adjustment is the same. The oxy pressure will be set according to the thickness of the steel to be cut and the tip size. 3.1.2 Torch flames The carburizing flame has no oxygen or insufficient oxygen flow to completely burn the fuel gas. The soot (carbon) is unburned fuel. This is obviously a cooler flame than can be obtained with a completely burned fuel and oxy mix. This is a desirable flame for several applications, but the excess carbon will generally ruin most welding operations. The flame will change from bright orange to a shorter, paler orange as oxygen is added. This longer, wispy pale flame is called the feather. The longer the feather, the more carbon present, and the cooler the flame. When the feather has just been removed from the inner bright blue cone, the flame becomes neutral. The length of the inner cone is 1. Having a 1X feather will mean a carburizing flame with feather as long as the inner cone.

2 Safety


The neutral flame is achieved with the feather just removed and the inner cone at its absolute brightest and largest. This is not a range, but is strictly and precisely one point of adjustment. The neutral flame is the most versatile of all the torch flames, allowing the welder to quickly and cleanly heat for myriad tasks. If the correct balance is lost during the process of welding, a loss of efficiency or a change in the base metals will occur. Adjusting for and constantly checking to ensure that the neutral flame is truly neutral will result in high quality cuts and welds free of impurities. This is the hottest and best flame, and care must be taken to always achieve a precise neutral flame. Oxidizing flames occur by adding more oxygen to the neutral flame. The flame will become sharper, more shrill in sound, and lose the bright blue color. Oxidizing flames are used to burn up any excessive carbon, as when brazing. Otherwise, the excessive oxygen creates many problems. The surface of a weld performed with even a slight excess of oxygen is readily identified by a scaly, rough appearance. The interior of such a weld will be porous and lacking in strength. Avoiding excess oxygen will result in cuts with clean–cut edge faces (kerf) and virtual elimination of adhering slag on the underside. 3.1.3 Fusion welding steel Fusion means joining the base metals by actually melting them. Generally, anything thicker than 1/8 inch should be arc–welded for best efficiency. Anything less can easily be torch–welded. Steel welding rod is readily obtained and extremely easy to work with. Many welders have either another means of welding light gauge materials or have given up using the torch for fusion welding steel. The most critical part of fusion welding is flame adjustment. The neutral flame is essential. The tip size will be determined by the actual thickness of the metal to be welded. With insufficient heat a puddle of molten metal is never established. Therefore, any added metal will just sit on the surface. Having too much heat results in melting and sagging the base metal, leaving large holes or voids which require much effort to repair. Set up to weld from right to left (for right–handers.) Apply the flame to the base metal at a 45–degree angle. Keep the inner blue tip of the neutral flame 1/16 to 1/8 inch away. Hold the rod at 30–40 degrees, and only add rod to an established

Figure 5 Torch flames

Figure 6 Rod and torch orientation

3 Torch uses



molten puddle. Add rod by dipping the rod into the bead end of the puddle when the torch flame has been backed up slightly. Remove the rod from the puddle quickly while advancing the torch. If the rod sticks or freezes in the puddle the flame should quickly free it. Do not allow droplets of rod to fall into the puddle as this will lead to excessively porous weld beads and annoying pops due to trapped gases within the puddle. A good bead will be twice the rod diameter in width and 1/2 to 3/4 rod in height. Joining two pieces can be done by veeing the joint, or by leaving a gap the thickness of rod or base metals depending on which is thinner. Then, fill in the void. Ensure that the base metal edges actually melt and slump downward giving a keyhole appearance to the forward edge of the puddle. This will give the bead full penetration from one side. Since the metal will get progressively hotter as the job proceeds, leave a slightly wider gap at the ending than at the beginning. The growing weld bead will have a tendency to pull the edges together. Using a larger rod size as a quench to keep thin pieces from becoming blown through may help. 3.1.4 Braze welding The use of braze welding should never be overlooked as a sound repair method. Brazing rods will yield high–strength joints if the process is done properly. These joints can be achieved without altering the shape of the base metal and can easily be repositioned. Brazing rods can be obtained for many metals, applications, strengths, and temperature ranges. Bronze brazing rods are composed of an alloy of copper and zinc with other metals in small amounts to change one character or another for the specific tasks. Repairing gray cast iron is easily accomplished with low–fuming bronze brazing rods. The following basic technique for obtaining sound joints is the same for all materials:

1. Grind out a 90–degree “V.” Leave alignment keys. These can be ground off and brazed after the initial brazing is done.

2. Cut back the sand skin from the “V” at least the thickness of the casting. The sand skin

contains many impurities that may contaminate the weld. 3. Place the pieces in perfect alignment. 4. Begin heating pieces using a slightly oxidizing flame to remove any excess carbon

from the casting surface. 5. Apply a liberal coating of flux to all surfaces to be joined.

Figure 7 End view of oxyacetylene braze weld

2 Safety


6. Continue to heat holding the flame at a distance to ensure that the complete joint has been preheated to a dull red color.

7. When the flux becomes liquid put a ball of brazing rod in the joint. 8. Watch carefully to ensure that the base metal is not overheated. This temperature will

be approximately 1,400–1,600 degrees F. The ball of brazing rod will flow over the surfaces to be joined, like solder “wets” to copper when the proper temperature is reached. This is called “tinning.”

9. Add brazing rod to the joint until all surfaces are coated with braze (tinned).

10. Finish the joint by spreading the braze over the edges to effectively lock the pieces

together. Continue to build up the braze with successive passes until the weld profile is sufficient for strength.

11. Allow to cool very slowly. Peen carefully with a pointed chipping hammer. Peening

while cooling is preferable to finding a crack next to your weld due to excessive shrinkage of the brazed bead.

Most errors in brazing are due to overheating the base metal. Overheating puts excessive internal stress on the metal or changes its composition. Overheating of the brazing rod will create a white powder band beside the brazed joint. This is due to the zinc being vaporized. In a poorly–ventilated welding area, vapors will cause the same sickness as galvanized fumes. 3.2 Cutting with a torch Cutting steel with oxygen is essentially a chemical reaction. The steel must reach a kindling temperature of 1,600 degrees F for the chemical reaction between iron and oxygen to occur. High purity oxygen (at least 87 percent pure) is required . Welding oxygen is close to 99 percent pure. Impurities or alloys in the steel essentially block or impede the cutting process. Thus, cast iron is easily heated to the kindling range (red hot), but next to impossible to cut due to the high percentage of carbon it contains. Since this chemical reaction generates heat in the process of oxidizing the iron, once a cut is established, the preheated flame can be extinguished and the cut will continue. An extremely steady hand is required to achieve a cut without a preheated flame, but it can be done. The stream of oxygen also blows some intact steel out of the cut. This is not due to torch size as much as the time it takes for the reaction to occur, and the fact that perfect mixing cannot be fully achieved. With larger tip sizes and smaller metal thicknesses the blow–by of oxygen becomes evident. For most efficient use, size the tip for the job. Hand cutting of two–to–three–inch steel plate will require a steady hand, and is about as much as can be accurately cut without some form of mechanical aid.

3 Torch uses



The key elements in making a quality cut are:

• Proper tip size • Clean tip orifices • Pressures based on tip size and metal thickness • Neutral flame with the oxygen–cutting lever depressed • A clean, crisp start when the kindling temperature is just reached • Holding the proper lead once the cut is started (the tip should be angled into the cut;

this will result in a cleaner kerf and faster travel speed) see Figure 9 • Keeping the preheat inner cone flame between 1/16 and 1/8 above the surface • Keeping the travel speed at the maximum (this will minimize the effects of heating on

the remaining metal) • A steady hand and welder confidence in the equipment and setup • Practice

Figure 8 Oxyacetylene cutting torch and tip

Figure 9 Cutting with an acetylene torch

2 Safety


The following conditions and remedies frequently occur when cutting with an acetylene torch:

• Excess slag Slag is burned and melted steel that adheres to the bottom edge of a cut. Removal takes extra effort. A clean cut takes virtually no chipping or further preparation. Try different combinations of travel speed, flame height, pressures, torch angle, or flame intensity. Modify one item at a time until you find what works in a given situation.

• Excessive popping or snapping at the tip that frequently extinguishes the flame

This condition is usually caused by an oxidizing flame. Once the gases are burning violently at the tip, a shrill sound is another key. If the tip gets too hot the gases begin to ignite inside the tip. Cooling the tip and restarting with a properly adjusted neutral flame usually cures the problem. Another sure indicator of an oxidizing flame is a frothy top edge on the cut.

• Formation of a black band on the cut edge

Lowering the flames into the cut will prevent outside make–up oxygen from flowing to the tip, thus the black band of carbon. Raise the tip. The band may also be formed by a carburizing preheat flame. Always adjust to neutral.

• Top of the cut edge is rounded

By traveling too slowly the top edge can be melted by the preheat flame. This usually is accompanied by a large bubbling mass of slag hanging on the bottom. Picking up speed and raising the preheat flames will usually cure this. Increasing the oxygen pressure may also help.

• Spatter buildup on the tip

Excessive oxygen in the preheat flames creates a sparkler effect. Adjust to neutral after a thorough cleaning.

3.2.1 Cutting aids Guide bars and circle cutters are tools to aid you when cutting with a torch. When making a cut of more than a few inches, a guide bar is handy. Square–edged angle iron or bar stock has a tendency to bow away from the cut as an edge gets hot. They also stick to the metal making small adjustments difficult. A used automotive torsion bar makes an excellent cutting tool. The torsion bar will have hex ends (one can be removed). The ends prevent the bar from rolling and keep the bar from touching the surface. This will prevent the bar from overheating and warping as well as ensuring that it can be easily moved when needed. Since the bar is smooth, an angle or bevel can be cut by simply drawing the torch tip along the bar. A bevel cut is lead by lifting the handle of the torch as the torch is drawn toward you. Raise the handle slightly to establish lead in the cut (see Figure 10).

3 Torch uses



The basic circle cutter can be used as designed. The small roller wheels can be adapted as guide wheels to keep the proper flame height on straight cuts also. Used in conjunction with the guide bar you have eliminated two of the most demanding tasks while flame cutting, side–to–side wobble and proper flame height. 3.2.2 Piercing holes One of the most difficult tasks can be easily accomplished by raising the tip 3/4 to 1 inch before hitting the stream and piercing the hole (see Figure 11). This ensures that the oxidized slag will not jump up and clog the tip as frequently happens when the tip is held close. Once the initial hole is pierced, lower the inner cones to within 1/16 inch and finish the hole to exact size. Since most holes must be located correctly, place soapstone chalk indicator lines for reference. 3.2.3 Stud and broken bolt removal Stud and broken bolt removal is easier with a small cutting tip and 30 psi oxygen. Heat the center of the bolt to the kindling temperature, then raise the tip 1 to 11/2 inches, depending on the size of the bolt. Holding the tip rock steady, blow the center out of the bolt. Attempting to widen the pierced hole may create problems with slag being blown into the space between the bolt and the internal threads of the object. As the bolt is heated during the piercing procedure, it will try to expand against the threads of the object it is held by. Since it cannot expand it will grow inward toward the just–pierced hole. Upon cooling, the bolt should be easily removed, as it will have moved away from the threads against which it was originally jammed. A few drops of oil should relieve any friction on the threads. This method can be used on bolts down to and including 3/8 inch.

Figure 10 Cutting bar and direction

2 Safety


3.2.4 Cutting round stock

A simple method of cutting solid round stock is to raise the torch through the stock as opposed to the common practice of cutting across the top. After marking the cut line, start the cut by holding the preheat flame directly on the five o'clock position (if 12 o'clock is top). Once the kindling temperature has been reached, hit the cutting lever to begin. Align the cut with the drawn cut lines, and gently raise the tip through the steel. As the cut progresses it should be observed on the opposite side from the tip and adjusted to meet the line. Keep the preheat flame 1/16 inch from the steel following the contour while raising and slightly rotating the torch tip to maintain bead. This method takes advantage of the fact that heat will rise through the section, aiding the cut and allowing the slag to fall away easily. In addition, the cut lines can always be seen. To lay out a round cut line, simply use a piece of stiff paper with a true edge and roll it around the stock until the true edges overlap. Scribing on the trued and aligned edges will result in perfect circular cut lines every time. 3.2.5 Cutting pipe This method involves the same layout as cutting round stock (see Figure 12). To start the cut, hold at the four o'clock position, raising the torch and leading the tip angle at the same time. Cut as far as possible on the line. This will usually be at about the 12 o'clock position. Stop the cut and roll the pipe to put the stop at the four o'clock position. Begin the cut as before. This will allow an unhindered view of the cut line. Stop at 12 o'clock, and rotate a second time to finish the cut. By cutting upward it is possible to observe the cut line and cut continuously, achieving a high degree of accuracy and a minimum of further cleanup and preparation.

3 Torch uses

Figure 11 Piercing a hole with oxyacetylene cutting torch

Figure 12 Cutting pipe



3.2.6 Gouging The cutting tip must frequently be used to remove old welded beads or to wash rivet heads without cutting deeply into the base metal. A simple procedure is to lower the cutting pressure on the oxygen to six to eight pounds for small removal jobs, and 10–12 pounds for larger. The preheat flames are adjusted as for normal cutting. When the kindling temperature of the bead or rivet is reached, the lever is feathered gently to wash away the stock. When possible, use gravity by placing the object on an angle to aid with slag removal. A special gouging or rivet washing tip is no more than a large center orifice tip with a 45–degree bend in it. A used tip that has been reamed out to a funnel shape in the oxygen orifice will perform the same function as the purchased variety.

2 Safety


4 METAL IDENTIFICATION and CHARACTERISTICS

Welders must properly classify each piece of stock they intend to weld. Common sense and some simple tests will identify almost all of the metals available. Welders are not expected to be metallurgists and to identify every constituent alloy within a metal. However, they should know how to place them within known groups for proper welding techniques and procedures to be effective. 4.1 Spark test The spark test can be a reliable method of classifying metals, since any deviation in composition changes the spark characteristics. Perform this test by holding the metal to be tested against a large, high–speed, power–driven grinding wheel under dim light. Some of the particles that

are ground off are so hot that they glow, igniting in the air. The amount of carbon, as well as other metal alloys in the steel, affect the kind of sparks produced from grinding. Only ferrous metals produce sparks. Figure 13 illustrates various types of sparks. Some examples of metals and their reactions to a spark test are:

• Low carbon steel (up to 0.30 percent carbon): A bright, white spark stream is formed, which is approximately 60 to 70 inches long, and has a large volume of shafts with a few forks and single sprigs.

• Medium carbon steel (0.30 to 0.45 percent carbon): This is a large volume, bright,

white stream, somewhat shorter than that from low carbon steel (55 to 60 inches long). It has more single sprigs, and it has some repeating sprigs.

• High carbon steel (more than 0.45 to 1.7 percent carbon): This is a bright white

stream less than 55 inches long, and having a moderately large volume of fine profusely repeating sprigs.

• Low alloy steels: Other metals alloyed into carbon steel suppress the spark stream in

one way or another. The greater the amount of these metals in carbon steel, the smaller the volume of the spark stream. Manganese alloy steel produces a spark stream very similar to that of high carbon steel, except the shafts are yellow and branches shoot out at right angles. Nickel alloy steel yields a very small orange spark stream with appendages and some tongues. Tungsten alloy steel forms a very short orange red spark stream with pointed shafts.

Figure 13 Spark patterns



• Stainless steels: These steels are alloys of at least four percent chromium and some

nickel with carbon steel. When spark–tested a yellow spark stream is seen to follow the wheel and a short (45 to 50 inches long), white, moderately large volume stream of shafts and tongues come from the wheel.

• Cast irons: All cast irons produce a short, red stream with many yellow repeating

sprigs. There may be some differences in the spark streams among the various kinds of cast irons, but the variations in the chemical composition of one kind of cast iron may alter the spark stream more. The spark stream from malleable iron may not be as red as the other cast irons, and the shafts may be longer. However, this is not always the case. Cast irons are more easily differentiated by observing the fracture. These fracture tests will be discussed later.

• Aluminum and other non–ferrous metals: These metals produce no sparks when

tested because of the absence of carbon and iron.



2 Safety


4.2 File and chisel tests The way a sharp file bites into or skates across the stock will indicate hardness. A chisel can be used to identify cast steel from cast irons. The chisel will chip off gray and white cast iron while rolling up malleable, nodular ductile cast iron or cast steels. 4.3 Magnetic test The magnetic test can be used to identify some metals easily and quickly:

• Magnetic metals – Nickel steel, carbon steel, all cast irons, straight chromium stainless steel, low alloy steel

• Slightly magnetic – Monel, work–hardening manganese steel, work–hardening

austenitic stainless steel, and stainless steel with large amounts of ferrite

• Non–magnetic – Manganese steel, bronze, nickel silver, austenitic stainless steel, tin, brass, aluminum, pewter, zinc alloys, aluminum alloys, magnesium alloys, lead, silver

4.4 Identifying steel manufacturing processes By observing the surface appearance of the steel part, the manufacturing process can be identified. If the part appears to be made in two halves, it is either dropped, forged steel, or cast steel. Steel castings have a rough, unfinished surface called a “sandmold edge” or “casting skin.” Numbers and markings are not sharply defined. Cast steel and cast iron may have similar surface appearances. Dropped forged steel parts have a smoother surface than steel castings, but it is still rough due to oxides which stick to the die during the forging operation. Numbers and markings are clearly stamped on these parts. Steel structural shapes, plates, and bars are either formed by the hot–rolled or cold–rolled method. Hot–rolled steel is softer and has fairly smooth but scalier surfaces than cold–rolled steel, and it is slightly oversized. Cold–rolled steel is known for its smoothness, hardness, and close tolerances. 4.5 Fracture test for cast iron The different types of cast irons can be identified to some extent by the appearance of their fractures in the following ways:

• Gray cast iron – Parts made of this cast iron break without any noticeable amount of bending. The grain structure is coarse throughout, gray in color, and black graphite rubs off the fracture. Examples: engine blocks, bearing housings.

4 Metal identification and characteristics



• White cast iron – A part made of this cast iron also breaks without any noticeable

amount of bending. The grain structure is coarse and crystalline throughout, and is silvery white in color. Examples: exhaust manifolds, stove parts.

• Malleable cast iron – A broken part will show evidence of some bending occurring

before breaking. There is usually a finer grain structure on the periphery of the fracture than in the center, and the center is generally a darker gray. Thin cross sections are completely fine–grained.

• Ductile or nodular cast iron – A considerable amount of bending occurs before the

part breaks. The grain structure is fine and gray colored. 4.6 Flame test Both aluminum and magnesium are lightweight, and they have similar surface appearances. Aluminum filings melt when they are heated with the oxyacetylene flame. Magnesium filings burn with a sparkling white flame. Aluminum casting and zinc die casting are both white. When heated with an oxyacetylene flame, a sharp corner of a zinc die casting will melt more quickly than aluminum, since it is a poor conductor of heat.

2 Safety


5 HEAT TREATMENT The characteristics of metals can be varied by heat treatment. Welders who understand the processes and principles involved will produce stronger and more reliable welds. Carbon steel is an alloy of iron and carbon. Three classes exist:

• Low (.05–.3 percent) • Medium (.3–.45 percent) • High (.45–1.7 percent).

An alloy with more than 1.7 percent carbon becomes cast iron. Other metals may be added to carbon steels to change the characteristics. These are generally classified as alloy steels. The carbon in steel is the same as pencil graphite. When mixed with iron it forms iron carbide, an extremely brittle combination. The grain structure of steel in the annealed (soft) state is very ordered. If steels are heated to what is called the upper transformation–critical temperature (above dull red color), several things will happen. Carbon is now free–floating (in solid solution) with the iron. The steel loses its magnetic property (a magnet is a sure way to check for this critical temperature), and the steel undergoes some internal atomic changes. Overheating steels will ruin the fine–grain structure that ultimately gives steel its character. Any heat treatment process should be timed to ensure that elevated temperatures are not held for too long, allowing the grains to grow. Heat beyond the transformation temperature with caution, and only when necessary. Excessive heating can occur when the base metal glows red after arc welding. If the glow persists, then grains are growing, and will usually be observed in the failed weld at a later date. Keep base metal heat to a minimum. If high–carbon steels are rapidly cooled (quenched) from above the critical temperature (above dull red color and non–magnetic), they become extremely hard. Quenching catches the carbon out of position before it can return to its normal ordered grain structure. This disruption creates a significant amount of bulging and distortion of the grain structure and is understood to cause the extreme hardness of martensite (quenched steel). Anything of extreme hardness is also brittle. Thus, for most applications extreme hardness is undesirable. Metals that are soft are said to be tough, because they can be bent or shaped without breaking. Every tool or piece of steel has a specific characteristic which will be a balance of hardness and toughness, depending on the job required of it. Starting with a quenched, hardened piece of steel, it is possible to reduce the hardness and increase the toughness through a process called “tempering.” Tempering involves reheating the quenched steels to between 400–600 degrees F, and then quenching the steel to set it at the desired balance of hardness and toughness. Only steels with significant amounts of carbon initially present can be heat–treated with success. Heat treatment



of steels with less than .3 percent (low carbon) will result in very little change. Carbon or other hardening agents may be added to the outer few thousandths of an inch of any steel in a process called case hardening. A typical application of hardening and tempering is in the cold chisel, so useful to mechanics and welders. The base metal to make a successful chisel must possess at least .45 percent carbon, and, hopefully, .83 percent. This percentage will give ideal working character to the tool. The stock is usually forged to shape it correctly. The forging range should be 1,450 degrees F (just above non–magnetic, red hot) to 2,100 degrees F maximum (bright cherry red). The expression “strike while the iron is hot,” applies to forging, allowing the metal to cool below 1,450 degrees F. Then striking creates massive internal stressing and probable splitting of the stock, rendering it useless. The following heat treatment processes are useful to the maintenance welder, and can easily be accomplished. Follow these directions carefully for good results:

Hardening — Heat stock to non–magnetic dull red color (critical temperature). Hold for five minutes to ensure that all of the carbon is free floating. Larger stock will require more than five minutes. Quench to produce martensite, a fine–grained, extremely hard, but brittle steel. Complete quenching quickly, plunging the portion to be hardened into cold water for greatest effect.

Tempering — Allow the martensite to be reheated to between 400 degrees and 600 degrees F. When the proper temperature is reached, quench the tool in cold water to set the desired balance of hardness and toughness. It is also possible to select the proper balance by watching the oxides form on a freshly–ground tool surface and quenching at the appropriate color.

Figure 15 Hardening and tempering a cold chisel

2 Safety


TABLE 1 TEMPERING COLORS FOR VARIOUS TOOLS

Color

Temperature

Degrees F

Tools

Yellow

430

Scrapers, taps, lathe, tools, stone drills

Straw

470

Punches, drills, reamers

Brown

500

Axes, wood chisels, hammer faces

Purple

540

Knives, rivet sets

Dark blue

570

Cold chisels, center punches

Light blue

610

Springs, screwdrivers, wood saws

Hardness Toughness hardest least tough softest toughest

Stress Relieving – Welding creates internal stresses that in critical situations may result in failure. Medium or high–carbon steels are more susceptible to stressing, but can easily be relieved by heating to just below the critical temperature (1,100–1,250 degrees F), holding for sufficient time based on size, and then slowly cooling. Annealing – This is used to soften steels and reduce stresses at the same time. Heat to 50–80 degrees F above the critical temperature (dull red non–magnetic). Hold for five minutes, longer for larger pieces. Then, slowly cool in an insulating material, such as ashes or lime, or completely surround with fiberglass batting. Slow cooling is absolutely necessary. Normalizing – Similar to annealing, but the steel is held at 100 degrees F above critical for a shorter period of time, and then left to cool in still air away from any drafts. This results in a harder steel than annealing but makes the steel easier to machine if milling or turning is necessary. Preheating – Raise the temperature of the base metal to at least 200 degrees F for low carbon, to 700 degrees F for high carbon steels. This will not cure all stressing problems, but will help. Cool slowly. Post heating – High carbon steels may require additional heating after the welding is finished to ensure stress–free, soft welds. Hold at less than preheat temperatures, and then slow cool to produce the desired effects. Case hardening – Only the outside case (skin) is affected to a depth of a few thousandths of an inch, usually a maximum of 7–9 thousandths. The common methods are carburizing and flame hardening.

5 Heat treatment



Carburizing – Adding additional carbon by heating the steel in graphite or coke, and raising to the critical temperature for 30 minutes or more, then quickly quenching the steel to catch the carbon, and create hardened martensite.

Flame hardening – The steel is heated to the critical temperature quickly with an excessively acetylene–rich carburizing flame. The case absorbs the carbon and is set by a quick quench.

Cracking – Use care with any quenching process to avoid cracking the steel. If the inner portion of the steel being quenched is too hot, cracks will appear on the surface ruining the steel. These surface cracks are created due to the extreme shrinkage of the outer layers of steel, while the inner portion is still hot. This extreme difference produces tremendous stresses. To avoid cracking, ensure that the desired maximum temperatures are just met and not exceeded, and that only the portions requiring hardening are heated and actually fast–quenched.

2 Safety


6 ARC WELDING 6.1 Welding machines Arc welding machines must be designed with two major factors in mind: efficiency in producing the heat to create a weld puddle, and protection and safety for the operator. Modern welding machines meet these requirements easily. Welding machines are either a generator/alternator type, where mechanical energy is converted to electrical, or a transformer type, where line voltage is reduced to a safe working current. A transformer type will consist of two coils. The primary coil is powered by the 220–240–330 or 440 volt AC, 60–100 amp line service. Alternating current from the primary coil will induce a current in a secondary coil. The ratio of windings between the two coils will determine the working (electrode and ground) voltage. This ratio will step down the voltage to less than 80 volts to protect welders from direct shock should they become part of the secondary circuit. Touching the electrode while changing it or other such accidental shorting may create a mild tingling shock with no ill effects. This current flow between the ground and the electrode before the arc is struck is known as open circuit voltage (OCV). Others who may come in contact with the circuit should be advised of its nature. OCV will aid in establishing and maintaining the arc, and is seldom set above 65v. The distance or shunting (resistance) between the two coils will determine the amperage output of the unit. This output is actually a step up from 60–100 amps to 225 amps or greater. There are many ways mechanically and electrically within the unit to vary the amperage output. Some will vary the voltage also. Step type transformers will have plugs, taps, or positive switching that will set a specific amperage. These will usually have slight voltage variations within the high and low setting range. Some electrodes will work better with higher or lower voltage at the same amperage setting. Experiment to find the best operating setting. Generator or alternator type welding machines often allow operators to vary the voltage setting independent of the amp setting. Independent voltage control is part of the added expense of this type of machine. Infinitely variable continuous amperage machines offer the advantage of fine tuning the amperage to the individual job. As a welding job progresses the base metal becomes hotter, and welders must compensate by lowering the amp setting a few amps at a time for best control. Continuous current control machines do have some slight drawbacks. Typically, the welding machine coil distance is changed. The sloppiness within the

Figure 16 Continuous amperage adjustment



device allows the mechanism to shake slightly under load, thereby creating the true “buzz box” name given small machines. It also can be slower to change than step type machines. Since the changes in amperage are usually shown on an indicator gauge or needle, some recalibration or adjustment is needed periodically if the needle or indicator becomes damaged (see Figure 16). Many combinations electrically or mechanically are used to adjust voltage and amperage. Generally, the more expensive the machine, the more complex the system. Fortunately, this gives welders more stable arcs to work with and more range for a specific task or job if they are willing to pay for it. 6.2 Duty cycle Welders should always be aware of the limits within their machines. Identifying the high and low amperage settings will tell them what range is available. Unfortunately, most welders don't find out about the duty cycle on their machines until damage has been done. Duty cycle is, “the time within a ten–minute cycle that a welder may be continuously operated.” The purpose of the duty cycle is to ensure that sufficient time is allowed within a ten–minute period for cooling the coils within the machine. As current flows during the welding process the coils become hot. If allowed to overheat, the insulation on the coil windings may burn and arc over, setting the unit on fire. The machine face plate will show the allowable time as a percentage of ten minutes that a machine could weld continuously at a specific amperage. Duty cycles must be maintained to protect machines from internal damage, possible fire, or dead short situations, such as when thawing pipe. Many generator machines have soldered armatures that will be ruined by overheating. Typically, the welding machine slings solder throughout the interior, grinding itself to a halt. Know the duty cycle rating on your machine. 6.3 Alternating and direct current Alternating current (AC) is used in all low–cost welding machines. It provides a stable arc that reverses direction 120 times per second (60 cycles). When working on rusty or pitted metals this “shaking on–off” reversal actually aids the welder in producing a quality bead. With additional cost a machine may be designed to produce rectified direct current (DC) welding amperage. Many electrode fluxes are designed to work only with DC. DC, in effect, gives a directional flow of electrons, and thereby the control of heat can be directed to the base metal or the electrode. Current flow affects the way molten metal is “sucked into or repelled by” the base metal. Electrons flow from positive (+) to negative (–). Reverse polarity (electrode positive DC+) will result in the base metal warming, pulling in the molten metal from the electrode. Straight polarity (work or ground positive DC–) results in the rod heating, keeping the base metal cooler. Each welding job will have an optimum polarity setting based on either the electrode type or the desire to maintain the lowest possible heat on the base metal.

2 Safety


6.4 Electrodes When the arc is struck in stick welding (Shielded Metallic Arc Welding or SMAW), the electrode is melted to provide the filler metal. The combination of core wire and flux coating the wire will determine its strength and operational characteristics. The American Welding Society (AWS) and the American Society for Testing Materials (ASTM) have jointly devised a classification system for identifying welding rods. A color code was originally established, but has been abandoned in recent years by most rod manufacturers. Appendix C (AWS/ASTM Numbering System) summarizes the system for arc welding electrodes. Many electrode (rod) manufacturers have their own systems of designating welding rods. Because many of these rods are proprietary they will not submit them for AWS–ASTM testing. Therefore, buyers should compare the actual results of using a non–tested rod with commonly available standardized welding rods. Welders should make every attempt to lower overall costs by using the best rod available at the best price. Welders should be aware that there are thousands of welding electrodes available by manufacturers. They should use the most cost–effective rod available and should take the time to try brands that are available locally. Shop around and find someone who will provide you low–cost alternatives. An expert sales pitch must be followed with a convincing demonstration on the job to make a believer of a competent welder. Be sure that any welding rod is job–proven and cost–effective. The welder will ultimately pay for each stick of rod in taxes or performance. Make sure that you get the most for your dollar. Four electrode types cover 99 percent of the maintenance welding done on low, medium, or high carbon steels encountered in the workshop. They are:

1. E6011 — AC or DC(+)

• All–position electrode with 60,000+ psi tensile strength (cellulose–organic type flux)

• Deep penetrating, forceful arc, readily removable, thin type slag • Fast freeze for out–of–position work, i.e., spreader sides, bodies, pressure vessels

(water or gas), welds on galvanize, sheet metal, painted, dirty metals, pipes, etc. • Used on mild steels

2. E6013— AC or DC (+) • All position electrode with 60,000+ psi tensile strength • Rutile flux, medium–penetrating low spatter bead is smooth (better appearance

than 6011) • Heavy slag which peels off easily • Requires practice to run overhead • Surfaces must be clean

6 Arc welding



• Fills in gaps where poor fit up is a problem • Easy rod to use for general purpose • Nice on gates or boxes where appearance is important • Used on mild steels

3. E7018 — AC or DC (+)

• All–position, low hydrogen with 70,000+ psi tensile strength. Fluxes hopefully

will eliminate hydrogen embrittlement caused by hydrogen from the air penetrating the molten puddle

• Keep the 7018 dry to avoid moisture from being absorbed by the flux • For use on all steels • May be specified as the rod for medium, high, and alloy type steels used in modern

equipment • Medium penetration, heavy slag formation (for protection), but easily removed • Good for out–of–position welding if amperages are reduced • A short arc length is important to maintain the shielding quality of the flux, and

also to minimize the heat input to the base metal. • Specified for NYS Structural Testing.

4. E8018 — AC or DC (+)

• Low hydrogen, but has greater (80,000+) psi tensile strength. Flux has 25 percent

iron powder resulting in a thicker, heavier flux that may make out–of–position welding somewhat easier

• Use a short arc to ensure sound, strong beads • A minimum of heat will also be an advantage, as less base metal will dilute the

high–strength character of this electrode. Use reverse DC (+) when possible • Use on all high–strength applications or where composition of the base metal is

unknown (must be kept dry like E7018) • Cast steels, frames, bucket edges, plow parts, are typical applications for 8018 • The most common, and probably most versatile, alloying combinations for 8018,

are the C1 and C2 designations. C1 and C2 alloys give the bead a stretchy character that relieves and somewhat overcomes stressing of the bead and the base metal. They are usually the most available types of E8018, along withy C3.

6.5 Establishing the arc Once the arc is established, by touching the electrode to the base metal by tapping or striking like a match, many factors come into play.

2 Safety


The arc is created by the flowing of electrons between the core wire and the grounded base metal. The tremendous heat and light energy released is concentrated to melt the base metal, forming a puddle of molten base metal, while simultaneously melting the core wire. The violence of the reaction creates an arc stream with a digging action that blows or gouges away the face of the metal. The depth of fusion is the actual lower limit of the puddle or digging. The name “fusion” is used because the arc heat melts and combines the rod wire and base metal into a new weld bead alloy, with both materials contributing to the bead's characteristics. As the electrode melts in the arc, the flux coating acts in several ways to aid the welder. Shielding gas or smoke is given off with intensity that prevents outside gases, such as oxygen, nitrogen, and hydrogen, from reaching the molten metal and contaminating it. The flux contains chemicals that combine with impurities in the molten puddle to raise them up and away from the pool. With some fluxes a good percentage is metallic and will actually become part of the weld bead. As the temperature decreases the molten chemicals and impurities form a crust or slag layer over the bead. The slag will act to protect the newly formed bead from further oxidation, and ensure that the weld bead cools slowly below the crust. Slowing the rate of cooling acts to reduce stressing in the immediate weld area. By concentrating the arc, the flux also aids in establishing and maintaining it. The flux coating, rather than the core wire, will determine the nature and characteristics of the electrode.

6 Arc welding

Figure 17 Arc and rod base



There are six factors that will affect the shape of any weld bead. Some are set by the welder before striking the arc.

1. Temperature of the base metal (cold and thick vs thin and hot)

2. Choice of electrode flux type and diameter (based on the task and the temperature of the metal)

3. Amperage set on the welding machine (based on metal temperature and the choice of

electrode)

Factors 4, 5, and 6 are manipulations by the welder after the arc has been struck. 4. Arc length is the distance between the base metal and the tip of the electrode. It should

be the rod diameter or less. Stretching the arc out creates control problems and increases the chance of impurities being trapped in the bead.

5. Speed of electrode travel. Given no side–to–side movement, this should result in a

bead of appropriate width (2–2 1/2 rod diameter) and height (3/4 rod diameter). These are for general purpose electrodes.

6. Electrode angle. This factor has least effect relative to a range of reasonable angles

from 90 to 60 degrees. (80–85 degrees is the ideal). Angle side–to–side is always assumed to be 90 degrees.

Welders should practice technique when possible. By varying one factor at a time and running a two–inch section of bead, observations can be made on finding the best combination for a given project. Varying more than one of the factors will result in confusion. Trying each new batch of rod will give you confidence in the rod, and you will do a better job. Remember that welding is a matter of identification, technique, and control. 6.6 Arc cutting Many welders inadvertently cut stock using the arc welding machine. Intentional arc cutting can result in more efficient use of time and effort. Virtually any metal can be cut with an arc. The tremendous arc heat, in conjunction with the forceful blow of the molten metal in the stream, acts to quickly erode the base metal. Many times a bead of stainless steel or hardfacing is laid in a location that requires removal. Using a grinder can be frustrating, as these metals quickly eat up the abrasives by dulling and overheating them. A fast removal method is to use 1/8–inch 6013 electrode, and roughly 170 amps on AC. This combination rapidly skives off the offending metals leaving a clean surface beneath.

2 Safety


Straight cuts are obtained by heating an edge then using a chopping motion from top edge to bottom, quickly advancing with each stroke. The cut should have neat, clean, straight edges (the kerf). To produce holes, utilize the molten puddle to warm the base metal, then quickly push the rod completely through the center of both the puddle and the base metal (see Figure 18). Use quick chopping motions until the desired hole size or shape is obtained. Often an edge must be quickly removed before welding. The angle may vary, but the method is the same. Establish an arc just back from the top edge, and snap the cutting rod down through the stock. By properly setting up the cut, the bottom edge will remain intact, leaving a crisp cut. Quickly return to the top, and move about half to three–quarters of a rod width away to set up the next quick snap of the rod. Little or no dribble of slag or molten metal should remain on the bottom edge. By holding the electrode at a low angle of 10–15 degrees, it is possible to gouge or cut a notch in flat stock. Once the cut starts the rod is pushed lightly across the surface. A crisp snapping forward advance will leave a circular cupped groove. The depth is easily controlled by the amount of down pressure applied to the rod tip. A second or third pass may be required for more depth. This technique results in clean grooves that are an aid in achieving right–angle bends in flat stock. To take advantage of the heat, bend soon after the gouge is made. Arc–air gouging is a method of stock removal using carbon electrodes that are slowly eroded and a stream of compressed shop air. This method is economical to operate, but initially expensive for the small shop. Using 6013 is not as smooth, but is usually available.

6 Arc welding

Figure 18 Piercing a hole with electric arc



Holding objects to be cut or gouged at a slight angle will allow gravity to assist in the removal of slag and molten metal from the cut area. Another technique is to use the shop–compressed air stream to blow away molten stock produced by the 6013 rod. Use the stream carefully, as the cool air quenches the cutting action of the rod when used in excess. Using a small well–aimed stream seems to produce the best results. Quite often cutting must be done on a flat surface and the air stream effectively blows molten slag out of the way. 6.7 Arc welding safety Arc welding safety involves all of the factors mentioned in Chapter 2. The following should be included for arc welding:

• Be sure to wear adequate shielding for eyes and skin • Check for all exposures before striking the arc • Avoid inhaling welding fumes • Ensure that the breaker is off before changing the welder plug pigtail (220v can and

does kill • Be aware of open circuit voltage • Disconnect batteries on vehicles that are to be worked on (Better yet, remove the

battery from the vehicle) • Don't ground through a bearing or electrical wiring system • Adhere to the duty cycle rating posted on the machine

If a fan is used to cool the machine, be sure that it is functional, and that adequate clean air is available to prevent overheating.

2 Safety


7 OUT–OF–POSITION WELDING Vertical and overhead welding require patience, practice, and proper technique to achieve solid welds. Many welders consider themselves spot welders — some spots they can weld; some spots they can't! Frequently, the maintenance welder will be presented with less than ideal conditions. Welding any job is easier if the weld can be run flat. Unfortunately, all equipment or jobs can't be rolled over or flipped around to present the ideal position. Learning to weld successfully in vertical, overhead, or other less ideal positions will result in large savings in time and effort. 7.1 Low hydrogen and maintenance electrodes The high strength, superior bonding, and low failure rate should make low hydrogen (LH) electrodes a primary choice for maintenance welding. Welders should use (LH) electrodes for high–strength applications. Simply put, “they stick better.” When medium, high, or alloy steels are encountered, use the LH group of electrodes. The flux of LH rod is specifically designed to exclude hydrogen from entering the weld puddle and creating a condition called “hydrogen embrittlement.” At the very depth of the zone of fusion hydrogen gas will create a very hard area causing the bead to peel up when under stress. The condition only appears when inferior welds (those lacking LH factor) are placed on medium to high strength steels. Since hydrogen is present in water it is imperative that any low hydrogen rods be kept as dry as possible. Any welding rod should be kept dry, but particular attention must be paid to LH rods or the high strength effect will be lost. The thick, heavy LH flux will keep the pool molten longer, allowing hydrogen impurities plenty of time to rise up. Keep rods on the job site in a closed container until used so that they will be fully effective. If LH rods are inadvertently left out or show a slight rusting, dry them before use. Welding rod is dried in an oven by spreading the rods out on the racks to allow air to circulate, and maintaining a temperature of 325 degrees F for two hours or more, depending on the number of rods and sizes. Bringing the temperature up too high or too fast will cause the flux to split, rendering the rod useless. LH electrodes come in many different designations. Choosing the best or all–around rod can be difficult. Experience has proven that 8018 C2 is best for general use. It has 31/4 percent nickel for a high–strength, high–stretch, forgiving character. The 8018 C2 runs well in the vertical–up and overhead positions so often encountered in maintenance welding. It is readily available through most welding supply operations, and is low–priced given its versatility. It is supplied by some manufacturers in DC+ only flux, so take care to find brands that are AC if the only welding machine available is AC model. If your small AC welder has a high–low range tap, use the low range. This usually produces the crisp arc needed to run LH electrodes. Proper rod storage is important to maintain quality. A storage box can be made inexpensively from a discarded refrigerator and a 5–10 watt electric light. Leave the light on continuously, and



remove a 1/4–inch wedge of the insulating strip from the top of the door. This will allow the water vapor to escape. The following are recommendations for working with LH rods:

• Keep amperage to a minimum. The weld bead will be a combination of melted base metal and filler rod. By minimizing the amperage a minimum amount of base metal will actually be mixed with the filler rod. The flux coating can be used as a fairly reliable indicator of heat. If the slag is tan colored then the heat (amps) was okay. If black, then it was too hot. Reduce amperage to produce minimal heat treatment of the base metal adjacent to the weld. This is sometimes accomplished with one large pass, rather than many small ones.

• Avoid high amperage to “clean up” a welded area. Cleanup should be accomplished with

a torch, grinder, chisel, cutting rod, chipping hammer, or wire brush. Veeing out the joint ensures that a minimum of amperage is required to achieve good penetration.

• LH electrodes are susceptible to pinhole porosity if slag is not completely removed. Steel

is held in the molten state for a longer period of time than with non–LH electrodes. The heavy flux and slag traps heat, allowing for slower quenching, which is an attribute. But, it also gives impurities like trapped or welded–over slag a longer time to rise. The weld zone should be as clean as possible before starting the weld bead. Attempt to work slowly and deliberately with the arc. If the molten metal is not totally surrounded by the gas shield, hydrogen embrittlement may occur.

• Keep the arc as short as possible. Stretching out the arc thins the gas shield and increases

the chance of over–welding impurities. • The LH electrode aids the welder by burning back the rod inside the flux coating a

considerable distance. This ensures that sufficient gas and chemicals from the flux will be present to keep the deposit pure. Unfortunately, the flux quickly coats the end of the electrode when the arc is broken. A simple method to eliminate the frustrations involved in restarting these coated electrodes is to gently tap them on an insulated brick or other nonconductive piece of material. The tapping will remove the coating without exposing so much bare rod that the rod becomes sticky.

• Long arcs are a disadvantage, so shortening the arc length does not hurt the ultimate

strength, and adds to the welder's control. Use a light touch with these electrodes. The heavy flux is nonconductive, and can be used to feel the edge to maintain a uniform arc distance or travel.

• Maintaining a rod angle which is as close to straight in the work as possible will increase

the gas shielding available.

2 Safety


The following summarizes procedures for the use of LH rods:

• Use minimal amperage settings • Watch for correct color as an indicator of heat • Clean the base metal, thoroughly veeing out the joint • Thoroughly clean the slag before making a second pass • Tap off the flux coating for easier restarts • Work as straight into the work as possible • One large pass may reduce base metal stress • Practice

7.2 Vertical welding Vertical welding on all but very light gauge material should be done from bottom to top. This ensures that the welder can see the crater and control the flow of weld metal and slag. Since arc heat is constantly rising, shielding gases and chemicals will be cleansing the work area. Slag inclusions are minimized since adequate time is allowed for slag to rise out of the molten metal. To accomplish a vertical–up position weld, start with the electrode aimed into the corner at about 85–90 degree angle (see Figure 19). This will give maximum shielding and control. As the arc is established, raise the rod slowly making a delta or tree–like pattern when returning to the start. Experiment to find the best pattern for you. A minimal side–to–side action, while gently moving upward in steps of no more than 1/8 inch increments, will ensure that the bead can be easily cleaned of slag. A lumpy bead will result if insufficient side–to–side movement is not used. Examine the slag for color and ease of removal. Edges of the bead should be smooth with no undercutting shown. The bead should be free of grapes, hangers, or dripping lumps. The ideal amp setting will depend on base metal heat, rod diameter, and flux type, as well as welder ability. Multiple passes can be run with a reduction of amperage as the base metal warms. To achieve welds of structural test quality, use only single, vertical, stringer passes, stacking one beside of or on top of the preceding pass. Only the finish pass should be a weave from side to side.

7 Out–of–position welding

Figure 19 Electrode position for vertical “tee” weld



7.3 Overhead welding Overhead welding with LH electrodes is actually easier than with mild steel electrodes (see Figure 20). The heavy flux can be used to virtually drag the rod along the base metals keeping a short arc. This results in dense beads of high quality with a minimum of labor. Multipass welds are accomplished with a reduction of amperage in each successive pass. Usually four passes will be required to complete an overhead fillet of substantial thickness and superior strength. Dripping of flux and molten metal is reduced to a minimum or is nonexistent when the amperage and travel speed is correct. Hold the rod at a 45–degree angle into the corner with the lead angle about 80–85 degrees. As the weld starts, adjust the rod slightly to ensure that the molten metal flows equally on center. If a significant amount of cratering is observed, reduce the amperage. No undercutting should be observed after the flux has been chipped away. Clean thoroughly before adding passes, including chipping and wire brushing. Unfortunately, some impurities will be carried up into the depth of the weld crater if clean–up is poor. Starting the rod is difficult at low amperage and the tendency is to increase amperage to overcome the stickiness. Welders should make every attempt to accomplish the light touch necessary for clean starts in the overhead position by practicing whenever possible.

Figure 20 Overhead welding

2 Safety


8 HARD FACING AND SURFACING METALS

Metals can be hardened to resist wear from crushing, shearing, scraping, or other forms of abuse. Unfortunately, they cannot be wear–proofed. They eventually wear away. Hardened materials can be placed on the surface of base metals to take the wear. These materials come in a variety of hardness and toughness to meet any application requirement. Each is designed to be applied easily to the base metal protecting it from wear, while absorbing the punishment and sacrificing themselves in the process. Methods of application will vary, but the result should be a pattern with sufficient bulk to protect the underlying base metal, but not so much as to significantly increase the horsepower requirement to push or pull the equipment or tool. Wear plates are made of specially–hardened materials, and consequently are difficult to weld on or are easily knocked off due to their extreme hardness. Few are sold with specific ideal applications identified, but are sold as cure–alls to be used wherever resistance to wear is required. Experience has shown few applications where the plate method is cost–effective. Solidly welded bead–on–bead ensures that an area is 100 percent covered, but fails to consider the fact that a tremendous amount of heat is used to apply solid mass of hardened material to the face. Heat softens the underlying steel, resulting in quicker wear–through if the hardened material is eroded, exposing the base metal. Any hard–surfaced tool should be monitored for wear, and once a program of hard surfacing is begun it should be continued. The best and most effective method of applying hardfacing requires observation of the wear patterns on an existing tool or piece of equipment, and then deciding on a design to counter the wear. A new piece of equipment should be used enough to establish a pattern before attempting to speculate on wear areas. New paint will quickly be removed in those areas of heavy wear first. This allows welders an opportunity to chalk in a pattern completely before striking an arc. In this way, all areas will be sufficiently covered. By laying out the complete job it is possible to skip around, preventing any one area from becoming so hot that the base metal is softened. Individual beads should be kept to minimum length. Any restarts should be far enough away to prevent heat build–up. Having a complete pattern gives plenty of opportunity to skip around. Base metal wear can be prevented by trapping particles of stone, gravel, or dirt between beads of hardface, and allowing them to wear on one another. This method will result in a checkerboard or grid pattern with normal spacing between beads of one inch. This distance may vary, depending on the material size encountered. The grid pattern may require slightly more horsepower. However, this is usually not a major factor, since prolonging the life of the equipment is the main objective (Figure 21).



Earth–on–earth wear is effective in protecting base metals, and is usually accomplished with a minimum of change in base metal character if welders spread out their pattern and application rates. Weld beads should be run with minimal amperage, no cratering, and very little, if any, depth of fusion. Any base metal that is melted will become part of the hardfacing bead, thus diluting the hardness available for work. Diluting can be minimized by holding a fairly long arc, and allowing the hardfacing to simply fall off the electrode in large gobs.

Hard facing materials should be applied during normally slow times in the welding shop. The skills involved in applying stick electrode hard facing are minimal. This results in a fine entry–level project for new welders. Buckets and other large pieces of equipment can be hard faced while other normal service is being done in the shop. Remember that this program will require monitoring and occasional renewing. Each operator should be part of the monitoring program, and, if trained properly, can be the applicator. Timeliness results in overall savings by ensuring that a piece of equipment is ready to go when needed. Worn pans, edges, buckets, and shares will take time and money to replace. There is definitely a benefit from an application of hard surfacing material. Costs of hard surfacing electrode or gas rod will vary greatly. Welders should experiment with various brands to find the least expensive but longest lasting material. The cost–to–benefit ratio of hard surfacing is extremely good with minimal cost of materials and labor. The biggest hurdle to overcome in the maintenance welding shop is acceptance of the process. Welders know how long it takes to replace sections of steel that have been worn through or are unsafe and must be plated over. Welders must initiate a program, or expand an existing one, for they will ultimately benefit. The following steps are recommended for hard facing and surfacing metals:

• Initiate or expand a hard facing and surfacing program • Select the proper material for the application • Observe the wear patterns carefully

Figure 21 Hardfacing grid pattern

2 Safety


• Decide on the proper pattern for the job • Draw out the pattern • Use minimum amperage • Use a long arc length • Make only short beads to avoid cracking and overheating • Skip around the pattern, keeping base metal heat to a minimum • Monitor the wear and renew when necessary; preserve the base metal and increase the

ultimate life of the equipment or tool.

8 Hard facing and surfacing metals

2 Safety


9 WELDING DEFECTS A welded joint should be as strong as, if not stronger than, the base metals it holds together. Proper design and welding technique will ensure that the weld is strong, stress free, and true. The factors that will account for the majority of weld defects are:

• Base metal heat • Rod diameter and flux type • Amperage • Arc length • Rate of rod travel • Rod angle • Polarity

Weld defects may include:

Penetration – The weld bead does not extend to full depth or fails to fill the joint area. Many factors can cause poor joint or root penetration, including inadequate amperage, wrong rod size or type, travel speed, arc length or polarity.

Depth of fusion – This defect can be too extreme or inadequate, depending on the rod and technique used. This is a measurement of the crater depth or how much the arc dug into the base metal. It can be due to any of the factors determining bead shape. Improper cleaning of excessive surface oxides (rust) or dirt may prevent the arc from adequately digging in.

Figure 22 Welding defects



Slag inclusions – This is trapped material within the bead. Usually this is caused by poor rod movement or inadequate removal of the slag from a previous bead. When gas welding, these pockets are usually caused by dropping the weld metal into the molten puddle.

Undercutting – This is the result of inadequately filling the arc crater or weld puddle. The addition of more rod with a faster feed rate will usually fill this gap. Give the rod time to melt by slowing the travel speed.

Excessive convexity – This is the result of too much buildup. A weld bead with excessive height or profile will create more shrinkage stress and lower the overall strength of the weld. Its edges act as pivot points for breakage.

Porosities – These are pockets of gas trapped in the weld bead. They are usually caused by over–welding slag, oils, paints, or other impurities. Precleaning by chipping, brushing, or degreasing is required.

Cracking – Cracks next to or within the weld are directly attributable to stress. Some may be caused by excessive shrinkage due to inadequate filling at the ends of a weld bead where the rod was quickly withdrawn. Others occur at the weld margins or deep within the root. Excessive heat is the usual cause. Preheating and postheating will usually cure most stress cracking along with less amperage or flame heat. (see Figure 23)

Formation of martensite and large grain size by welding – These are caused by fast quenching and overheating, respectively. To minimize quenching it is necessary to preheat the base metals. This will reduce the hardening effect created by a large temperature drop and reduce the formation of martensite. A single large pass on medium or high carbon steels is undesirable, since this may create a large and fairly quick drop in

Figure 23 Cracking

2 Safety


temperature. Many small passes will result in a slow buildup of heat with each pass refining the previous one. To eliminate grain growth or reduce it significantly, apply the multiple pass technique with the metal cooling to black heat between each pass.

Distortion – Shrinkage during cooling is a consequence of welding that can't be avoided, but it can be minimized. Distortion is caused by the effects of shrinkage and must be considered with every weld bead run. Welders must anticipate and plan for distortion to ensure that their projects will be straight, true, and stress–free when completed. If a piece of steel is heated and cooled (see Figure 24), the steel will assume a kink when cooled. This is due to unequal heating. Since the whole object can't reach the heat of the weld puddle, differential heating cannot be avoided. An expansion of the heated metal takes place over the entire area, but is restricted on the solid portion of the rod. When restricted the heated metal will compensate by increasing its thickness in the unrestrained dimension. Upon cooling, the metal begins to shrink uniformly in all dimensions, and the restrained ends are pulled in toward the heated area, thus buckling the rod. A weld bead will buckle a plate in a similar manner.

Use the following methods to aid in minimizing the effects of expansion and contraction. 1. Reduce the effects of shrinkage by:

• Reducing over–welding • Using few large passes • Using correct edge preparation (don't “vee” out too much) • Placing the weld as close to the neutral axis or center as possible • Using intermittent or skip welds • Making back–step welds (work back to an existing weld instead of away from it) (see

Figure 25) 2. Use shrinkage to reduce distortion through

• Offsetting parts to allow for distortion • Bending or springing parts out of shape to allow for shrinkage to return them to

original shape

9 Welding defects

Figure 24 Effects of heating and cooling



3. Use other forces to balance shrinkage forces by

• Clamping the work (use “C” clamps or fixtures) • Using counter–balancing welding sequences • Using tack welds • Using localized heating to realign • Using peening to stretch and compress the bead

Straightening – Welders must be able to return objects to their original shape quickly and easily. Many steel shafts, beams, or pipes are bent without the use of heat due to overloading or misuse. Straightening should first be attempted without heat. This guarantees welders of very little permanent damage, and can usually “true” the bent object using little more than a chain and hydraulic jack. If the bend occurs on a machine equipped with hydraulic cylinders the machine can often be used to provide the power needed. Typical straightening requires setting the jack in position as shown in Figure 26, and forcing the jack to act as a cylinder to extend the distance between the chain and the bend. This is the same principle that is frequently employed with the common shop press, but can usually be set up with the bent object in place. Using the yokes or tie downs on the equipment ensures that the object will not twist or fall over, thus saving additional effort. By repairing the object in place, you save time.

Use a porta power type system to make field repairs, if it is available. A simple hydraulic bottle jack of sufficient capacity, and a high strength chain of the logging type, or better, combined with a yoke device for the top of the jack to prevent the chain from slipping off, are the required components. The yoke can be made from a piece of channel with a short section of pipe welded to the base to act as a sleeve on the jack top. This handy set–up can make short work of straightening almost any bent steel object if used with care. Badly kinked shafting or rods may require several attempts, and possibly may not be salvaged without the use of heat.

Figure 25 Backstep welding

2 Safety


The use of heat has some major drawbacks that must be weighed before deciding to apply it. Often the object will be coated with chrome or some other finish that will be burned away or seriously wrinkled, ruining its appearance or sealing ability (for example, the hydraulic cylinder rod). Adding heat may alter the original heat treatment, changing the nature of the object, causing it to fail at low loading levels. A general “rule of thumb” is to attempt a cold straightening if the object was bent cold. By closely observing the surface and noting the resistance felt, those objects that need heat will many times reveal themselves. Soft, malleable steels show very little adverse effects from straightening, and usually return to service none the worse for the experience. High–strength shafting that has been heat–treated to be extremely rigid is also usually brittle, and will often crack if straightening is attempted in large doses. Experience will indicate where these brittle types of steel are used. Trial and error will show which can be successfully field straightened without heat. The welder must remember that every piece of metal has a stretch and yield point that limits the amount of resilience it will have. Exceeding the limits results in failure, but many times an object that looks like it is headed for the scrap pile can be salvaged by simple mechanical means and a little common sense. When heat is used it should always be applied to the inside of the bend area. This ensures that the object will be thicker than the original through the bend section.

9 Welding defects

Figure 26 Jack straightening

2 Safety


10 CAST IRON AND ITS REPAIR Cast iron has a long history. It has been with us for many years, and can be very difficult to repair. Manufacturers have specifications for their products only. Cast iron contains between 1.7 percent and 3 percent carbon. Other ingredients are added to give specific qualities for specific batches and subsequent uses. Since the first cast iron was mixed, heated, and poured into a mold, each batch was tested as a completed product. None of the current manufacturers makes a cast iron for its ease of repair. Castings are made to withstand normal abuse, and seldom anything more. Castings typically are designed to support loads with great compressive strength. Cast iron has very little tensile strength, and therefore is not used where pulling (tensile) forces are frequently applied. Repairs on cast iron are difficult, but can be accomplished successfully if the welder considers a number of factors. The discussion of repairing cast iron must begin with carbon. Carbon gives cast iron its brittle nature and is frequently encountered as free graphite, that contaminates any welding bead that is nearby. Iron carbide is an extremely brittle component that is adequately controlled during the manufacturing process but can create cracking in the adjacent cast iron when produced by the heat of welding. Free graphite is like pencil lead in that it has virtually no tensile strength. Ordinary welding techniques ignore the excessive carbon, and result in almost certain failure, due to the formation of brittle martensite caused by quenching. Manufacturing techniques often include heat treatments, which alter the character of the casting. To make malleable pipe fittings, white cast iron is heat treated. During welding the treatment is removed, resulting in reversion to white cast, an extremely brittle casting totally unsuited for pipe applications. Subsequent failures, especially when working with pressure fittings, can be disastrous. The size and internal dimensions will often limit the welding technique to be used. Gray cast iron engine blocks are typical of this problem. Gray cast iron is easily brazed, but brazing requires high heat which can change the internal dimensions of bearing faces and cylinder walls, thereby requiring additional machining. Most brazing will require heating the whole object uniformly before performing the braze. Heating the entire engine would result in possibly changing every internal dimension. A large casting will require an elaborate oven facility to properly preheat and restore its original character. Repairs to large objects will be tricky, but can be accomplished if the welder is willing to practice the proper technique. Variations in the alloying agents of the casting may well render one casting impossible to weld. Another casting of the same shape and dimension from another batch of ingredients may be easily repaired. Because variations are so great, welders are advised to experiment with techniques before settling on just one for every type of casting encountered. Brazing cast was discussed in Chapter 3, and should only be applied where castings are relatively small or when



dimensions are insignificant. Brazing items that would naturally receive high heat, such as exhaust manifolds or stove parts, must be avoided. Fusion cast gas welding rod is a means of actually melting cast iron and joining the edges with a rod possessing the same brittle cast iron features. This requires a melting temperature of 2,400 degrees F. A flux–coated rod can be obtained, but for best starts and least imperfections, cast iron welding flux should be liberally sprinkled over the edges to be joined. Preparation of the edges will require veeing or beveling at a 45–degree angle, and cutting back the sand skin. This process results in welds matching or exceeding the strength of the base metal, but can rarely be used on large castings due to the high heat zone and inability to reliably predict shrinkage or heat treatment effects. Build–up of small ears or other protrusions with fusion rod is an ideal application. Since this rod will withstand the same heat as the base metal without failure, it can be used successfully on exhaust components if sufficient preheat is applied. A neutral flame is usually used, depending on the amount of free graphite available. This rod flows very similarly to a thick bronze brazing rod. Most fusion rods are very coarse and of odd shape. They are extremely brittle, and care should be used when breaking the rods. Preheat the entire piece to full red color to help eliminate most cracking. Normal solders and silver bearing solders will be discussed in Chapter 11. Each method requires clean surfaces and a good fit up for best strength. Each will have temperature limits. The use of arc welding rods specifically designed for cast irons is well–known. Two forms are available with many variations of each. Steel–for–cast rod is the cheapest of the two rod types. It has several drawbacks and care must be exercised in its use. Where large buildups on gray cast iron are required, the rod can be used if amperage and bead length are kept to bare minimum. High amperage results in excessive heating, creating large areas of brittle iron carbide. Long beads will result in excessive shrinkage, pulling the bead away from the base metal. The weld is not machineable since iron carbide would ruin any tools used to cut it. Nickel–iron rods with little or no iron result in the best welds and can be used on any cast. The application requires strict attention to detail, but can be used to salvage large gray cast engine blocks that may require expensive rebuilding and machining or end up as scrap. Welding with nickel is called cold welding because every attempt is made to keep the casting cool to barely warm. To begin a nickel weld, “vee out” the crack to no more than 60 degrees overall (see Figure 7, page 20). This will allow the bead to reach the bottom (or root), but keeps shrinkage to a minimum. The ends of the crack should be drilled out with an 1/8–inch drill to prevent further cracking beyond the bead area. The root pass should be done with a small 3/32–inch rod size to ensure reaching the bottom. On engine blocks do not “vee” to the opposite side. Fully penetrating the block allows slag or other material to be blown into the engine. Use the lowest amperage setting that results in crisp arc and solid deposits. Set the welding machine on DC– (straight polarity), if possible. To minimize heating the cast, the rod should carry the heat. As the rod melts it should fall in “plops or gobs” rather than a fine spray. There should be no cratering,

2 Safety


as any base cast iron will be drawn into the bead, detracting from the pure soft nickel. Once the bead has been drawn 3/8 inch, withdraw the rod and begin peening. Pure nickel is a soft malleable metal easily shaped but tough enough to give a high strength weld. Peening the bead will effectively stretch out the bead to conform to the original shape of the cast. Since the cast cannot stretch, this will relieve the stresses within the weld. Long beads using nickel have been run occasionally, but long beads have a tendency to fail. Keep the bead short, and continue to peen until you can touch the bead and surrounding metal with a bare finger or thumb. Start a second bead if the crack extends more than three inches. Space beads two inches or so apart to ensure that the beads will act as tacks to hold everything in position over a long run. This spacing will also help spread out any heat. A gentle buildup of heat is acceptable, but should not exceed the heat of hot motor oil in an engine block repair. With the exception of tacks, start all other beads on the tack or bead, and quickly move to the base metal. This ensures a clean transition, minimizing slag inclusions or voids within the bead.

Attempting short cuts by using long beads or high heats will result in losing a valuable block or other piece of equipment. When doing cast iron repair, remember:

• Properly identify the cast type • Have several methods available • Properly prepare the cast for welding by cleaning and veeing • Properly align the pieces • Do not overheat • Peen the weld bead to lower the stresses and prevent cracking • Respect the fragile and tricky nature of cast iron

10 Cast iron and its repair

Figure 27 Cast iron welding

2 Safety


11 SOLDERING Soldering is defined as joining metals with non–ferrous metal having melting temperatures below the base metal. The upper limit of soldering is 800 degrees F, but frequently the welder hears the terms “soft and hard soldering” or “silver solder.” Soft soldering or just plain soldering refers to heating below 800 degrees F. Hard soldering or silver soldering refers to the technique of silver brazing which is done at temperatures above 800 degrees F. Solders bond by actually locking themselves to the base metal. This bond has more strength than the bonding between the solder molecules themselves. When a soldered joint is separated without heat the solder will always leave a thin layer of bonded solder adhering to the base metal. The process of bonding a layer of solder to the base metal is called “wetting.” Tinning refers to putting a thin coating of solder on the base metal that is also wetted to the surface. The requirements for a successful soldering project are:

• Clean base metal surfaces • The proper flux • A heat source • The solder

Soldering has many advantages over other forms of joining. Several important ones are:

• Lower temperatures are used, creating less damage and internal stressing to the base metals

• Many combinations are available for specific applications • It can bond objects of varying thickness and composition • Tools and materials are low cost • Easier to realign/reposition the parts • High speed • Permanent or temporary

The maintenance welder should be able to choose the correct solder, flux, and technique using the following criteria:

• Melting temperature of the solder and base metal • Cost of the solder • Poisonous effect of leaded solders (food use) • Color match of solder to the base metal • Avoiding use of antimony–bearing solders on galvanized metal • Tensile strength of the solder • Copper can be soldered with any solder



Solder comes in many alloys. The most common combination is tin-lead. Tin will constitute from 40 percent to 95 percent of the alloy. Commonly available solders are:

• 40 percent tin/60 percent lead (40–60) • 50 percent tin/50 percent lead (50–50) • 60 percent tin/40 percent lead (60–40) • 63 percent tin/37 percent lead (Eutectoid mixture) • 95 percent tin/5 percent antimony(95–5)

All of these solders have differing melting temperatures and ideal applications. Table 2 will aid in the selection of a solder for a specific job.

TABLE 2 SELECTING SOLDER

TYPE

MELTING TEMPERATURE

USES

40–60

455˚ F

Low cost. Good wetting and strength. Best for plumbing of waste water or general purpose galvanize sheet metal fabrication.

50–50

421˚ F

Easily worked, wets well, good strength. General purpose repair.

60–40

374˚ F

Low temperature, quick setting. Use where low temperature important. Excellent for electrical work. Can be used to repair existing soldered joints as with radiator repairs. Very handy.

63–37

361˚ F

Eutectoid form not readily available. All melts at once.

95–5

464˚ F

No lead solder. Should be used on all potable water systems. Excellent with hot water systems. Use on stainless steel for color match and resistance to corrosion. Use on food handling equipment.

The purpose of the flux is to promote or accelerate the wetting of the solder. Fluxes accomplish one or more of the following:

• Remove surface oxides from the base metal (the metal must be mechanically cleaned to begin with)

• Prevent reoxidation while heating

2 Safety


• Lower the surface tension, making the solder flow readily • Aid in carrying heat to the joint • Etch the surface of the base metal, allowing the solder more bonding area to adhere to

Fluxes are available in three types, depending on the corrosive action required. Since the flux may continue to corrode after the soldering job is finished, it is imperative that the minimum corrosive type be used, and that cleanup occurs, if necessary. Flux types are:

Highly corrosive – These acids are highly corrosive, like battery acid, and must be handled with extreme care. Cleanup is absolutely necessary. These acids will etch the surface and produce superior bonding on any base metal, but are especially useful on stainless steels. They remain active at high temperature, and can be relied upon to flux where a lesser type would be ineffective. A consequence of this is the production of acid salts, which if not neutralized and removed, will ruin the base metal or surrounding parts.

Intermediate – These are mild acids and bases that still require removal and cleanup, but will produce satisfactory results on most applications. During heating the flux is supposed to decompose, rendering it neutral. But, this cannot be guaranteed. Use these fluxes with caution due to their corrosive nature.

Rosin – These are designed to be active only under heat and are essentially inert unless heated. They are best used on plumbing and electrical applications where neither cleanup nor ingestion is a problem. Avoid contact with the eyes. Other stronger fluxes may be used if the action of rosin type is insufficient, since it is the weakest fluxing agent. Rosin fluxes will generally smoke if the ideal temperature is exceeded, and should be carefully monitored for best solder results.

Use all fluxes with care around the shop. When spilled they can ruin the finish on painted objects or corrode surfaces just like battery acids. When accidents with medium or highly corrosive types occur, quickly flush with water to dilute. Vent the vapors of heated fluxes properly to prevent inhalation and possible long–term, chronic effects. Heat may be applied to the joint in many ways. The soldering copper or iron (the best are solid copper) quickly heats and allows the welder to transfer heat to the object with pinpoint accuracy. Repairing most soldered objects can be accomplished with direct flame of the torch. Use care to prevent igniting surrounding objects and overheating the base metal, creating loss of coatings or burn–through. A simple propane and air torch is generally superior to the acetylene flame, since the propane torch produces much less heat. Large spread–out type flames may be superior for plumbing work where copper pipes or tubing will soak up considerable heat, but are not handy for repair work where precision is often required. Electric soldering irons come in three sizes, with the small pencil type and larger gun size used strictly for electrical wiring applications. They do not generate sufficient heat for sheet metal patching or general repair. The largest electric soldering coppers will have from one–half to two

11 Soldering



pounds of copper in the tip. These large units are slow to heat, but have enough continuous reheating ability to successfully complete most soldering tasks. They are much safer and handier than the open flame method of heating a soldering copper.

Silver brazing (or silver soldering) is actually low temperature brazing, as described in Chapter 3. Normal low fuming brazing rods require working temperatures of between 1,400 and 1,600 degrees F. Silver bearing brazing can be done between 1,100 and 1,300 degrees F, resulting in less stress within the base metals. Silver bearing, low temperature solders are available to span the gap between tin lead and antimony combinations. These silver bearing “soft” solders give the welder the ability to retain strength in the soldered joint at temperatures up to 500 degrees F.

Silver brazing alloys result in high strength only when proper technique is followed. A clean joint area with minimal gap between the base metals is required. Proper fluxing with a true silver brazing flux compatible with the brand of rod will be necessary. Heating the joint with a slightly carburizing flame will ensure that the temperature is brought up slowly and the surfaces are not oxidized. When the flux becomes a clear, glassy fluid, a drop of alloy is applied. If the alloy flows and wets to the surface, more alloy is added to complete the joint. Minimize the use of heat, but ensure that the brazing is done quickly. Allow the joint to slowly cool, then remove excess flux residue with warm water. Silver brazing results in superior strength and minimal stressing to the base metals, even though they may be of dissimilar composition and of varying thickness or mass.

2 Safety


12 WELDING SPECIALTY METALS 12.1 Aluminum Aluminum can be welded in a variety of ways. It must first be properly identified, since magnesium is almost identical in appearance. Heating some small filings results in the filings balling up and becoming a silvery mass. Magnesium will burn brightly, leaving a white powder when ignited. Two major drawbacks when working with aluminum are its excellent conductivity and the almost total lack of color change before melting in its pure form at 1,220 degrees F. Two types of solders are available — those using a flux and fluxless friction solders. Solders requiring flux are thin–flowing mixtures of zinc, tin, aluminum, and other alloys that wet between 400 degrees and 650 degrees F. They require clean surfaces and the proper flux and alloy combination for efficient flow. Cleaning aluminum should always be done with a stainless steel wire brush to avoid contaminating the surface with steel. A gentle flame is applied carefully to the base metals until the flux clears. At this time the solder is added to fill the joint. Fluxless friction welding requires breaking up the surface oxides with the rod or a quick action with a stainless brush to ensure proper bonding. The melting temperature of the fluxless alloy is 700–720 degrees F. This results in high–strength bonding at elevated temperatures, and gives the welder almost the same characteristics as the parent aluminum. A carburizing flame is used to minimize oxide formation and reduce the chance of overheating. The rod must be absolutely clean and free of oxides before application. Aluminum brazing is done in favor of torch fusion welding to reduce the chance of melting the base metal, ruining the original shape and structure. Brazing temperatures are between 1,050 and 1,175 degrees F. This gives the welder only a slight margin before the base metal could melt. A clean surface and vigorous fluxing action is required. The alloy used is of a thin–flowing type, so heavy that “veeing” is not necessary. Since the aluminum will quickly draw away heat, a large tip size with a soft carburizing 2X feather is best. To prevent melt–through, hold the tip at a distance. The flux forms a glassy liquid and the alloy rod should be quickly added. Continue adding fluxed rod until the joint is filled. All flux must be removed, as it is extremely corrosive and will quickly erode the aluminum. When the project is cooled to 200 degrees F the flux may be washed and brushed away. Fusion welding with a torch results in high–strength welds, but is difficult to control due to the fall–away nature of melted aluminum. Proper fluxing must be used to achieve solid bonding with no inclusions or porosities. This is conducted similarly to brazing, but at a more elevated temperature. A backing plate will prevent the parts from falling away, but also acts to slow the heating process and then slow the cooling of the work. If the heat is held elevated for too long, a large grain structure may develop, resulting in cracking and failure. In the absence of better



forms of joining the fusion method will work, but take extreme care or the parts may be totally ruined. Fusion welding requires a special fusion flux capable of retaining its action at 1,200–1,400 degrees F. Heating is best accomplished with the carburizing flame using a 11/2X feather. Torch use of aluminum stick electrodes complete with their own flux coating has proven successful. Aluminum stick electrode welding is an old procedure, but seldom practiced. It should be conducted with moderate amperage and (DC+) reverse, if possible. Since aluminum is such a good conductor, the base metal needs the heat. The rod frequently overheats and cannot be fed into the puddle quite fast enough, which results in a lengthening arc and loss of control. The welder must learn to feed the rod progressively faster as the weld proceeds. Beads are dense and of high quality when done properly. One poor feature of all aluminum stick rods is the poor bonding quality of the flux to the rod. This results in many useless sticks that have lost the flux coating, resulting in an uncontrollable arc. The flux is very susceptible to water and humidity damage, and must be kept sealed and protected at all times. 12.2 Magnesium By carefully monitoring heat and exposure to oxygen, magnesium can be torch–welded using the proper fluxing agent, a backing plate, and neutral flame. Magnesium melts at 1,205 degrees F. The technique is exactly the same as brazing aluminum, except that the backside of the project should be sealed in some way to prevent oxygen from igniting the magnesium. 12.3 Stainless steel Stainless steel can be joined using solders with at least 50 percent tin and a flux of sufficient strength to etch the surface. Heating must be done slowly to prevent overheating the base metal and to allow time for the fluxes to work. Silver brazing is a common means of joining stainless. The joint must be extremely clean and completely covered with flux before heating is attempted. Any areas not coated with flux will not wet. Heating is done with a carburizing 2X flame. When the flux becomes glassy, rod is melted into the joint. Applying heat gently to the opposite side will aid in drawing the solder completely through the joint. Normal brazing at temperatures from 1,300–1,750 degrees F is commonly used. But, take care to ensure cleanliness and thorough flux coating. Use care in adjusting the flame to just neutral. Excess oxygen or acetylene will ruin the project. Stainless steel electrodes are frequently used with great success. The deposits have higher strength than the base metal. Failure usually occurs due to cracking from overheating or other manipulative problems. Identify the type of stainless for best match up of bead and base metal characteristics.

2 Safety


12.4 Phosphor–copper Phosphor–copper is an easy–to–use fluxless brazing rod that flows easily over copper tubing, castings, or for joining copper to brass or bronze. It requires cleaning of the base metal and a flame large enough to heat the highly conductive copper. If it is to be used on brass or bronze the proper flux is recommended. Gently preheat the area with a carburizing flame with a drop of alloy placed on the surface. When the proper flow temperature is reached (1,400–1,450 degrees F) the alloy will wet and flow over the surface. Keep the torch moving to prevent overheating the phosphor–copper and base metal, creating porosities in the bead. 12.5 White or pot metals and zinc die cast Carburetors, door handles, mirror frames, and many other small parts are made of white or pot metals. The most frequently encountered small casting is zinc die cast. All can be loosely called pot metals from the method of mixing the ingredients for each batch in a “pot.” All mixtures are slightly different, with few having truly identical composition. To repair any of these metals successfully, welders should practice. Repairs can usually be achieved by using friction type aluminum or die cast rod. Slumping of the metal occurs shortly after the melting of the repair rod. Take care to avoid losing whole sections of the base metal in a shapeless blob. The use of a backing plate may prevent serious “slumping.” Friction rods require the welder to break up any surface oxidation by stirring or brushing the hot base metal and rod together. Use a 2X carburizing flame to prevent overheating. But, use extreme care, as slumping occurs quickly and with little, if any, warning. Repairs are usually sound and porosity–free, possessing the same or superior strength as the base metal. They are easily machined, ground, or shaped to return the item to service.

12 Welding specialty metals

2 Safety


13 ADVANCED WELDING PROCESSES 13.1 Tungsten inert gas welding (TIG) The heat for the TIG process is created by an electric arc formed between the base metal and a non–consumable tungsten electrode. The shielding gas usually used is pure argon, although argon and helium mixes are used occasionally. Filler metal must be added just like oxyacetylene welding. Extreme high quality and strength can be achieved with the TIG process. Since there is no flux used, no slag is created to contaminate the weld. Oxides are eliminated by completely shielding the molten pool with an inert gas that excludes oxygen, nitrogen, hydrogen, and other harmful atmospheric gases. For welding aluminum, AC current results in superior quality and control. To aid in establishing and maintaining the arc, use a high frequency (HF), low power AC current. The HF allows the welder to start the arc without actually touching the tungsten electrode to the base metal, possibly contaminating it. A longer, more stable arc may be held, thus aiding in control and ensuring longer life for the tungsten electrodes. When using the TIG process on carbon steels or stainless steels, DC straight polarity (DCSP) is recommended (DC–). DCSP results in less bead width, greater penetration, and the ability to weld heavier materials with less stress.

Figure 28 TIG system



Use DC reverse polarity (DCRP) on extremely thin sections since the electrode heats excessively. If DCRP is required, use a much larger tungsten electrode. Welding power sources having both AC and DC provide maintenance welders with the greatest flexibility. A high frequency (HF) unit may be added to a power source giving the arc greater stability. Better welding character is achieved with AC/DC transformer welders specifically equipped with the HF. Remote foot pedal amperage controls also provide on/off control for HF and shielding gas flow. The gas flow precedes the arc and ensures that gas continues to flow for a few seconds after the pedal is lifted to protect the puddle from contamination. The TIG torch holds the electrode and discharges the shielding gas. The electrode is usually tungsten with two percent thorium added for longer life, and stability. Thorium raises the melting temperature of the electrode. Since the electrode is virtually non–consumable, the only way to ruin it is through breakage or contamination. When the tungsten is dipped into the molten puddle or touched by the filler rod, small particles of adhering metal ruin the electrode. It then must be ground clean or broken off and reshaped. With AC current a slight ball on the tip gives best control. To create the ball, switch the welding current to DCRP to overheat the tip, momentarily forming the ball. The ball should be no more than 1 1/2 times the electrode diameter. This forming should be done on a copper plate kept for the purpose of cleansing the electrode. Quite frequently a contaminated electrode may be cleaned by holding the arc over a pure copper for a few seconds. This avoids disassembling the torch to gain access to the electrode. Gas flow is best monitored through use of a flowmeter and a regulator. This allows for precise control of the shielding gas, assuring lowest cost and best coverage. A gas nozzle, lens, or cup of appropriate size, surrounds the electrode to provide sufficient velocity and shield width. It also aides in cooling the lens or nozzle. Water–cooled torches will allow the welder to work at higher amperages and for longer time periods. Overheating of lens, cups, and nozzles results in cracking and poor control. Failure to have sufficient water flow usually results in ruining the hoses supplying both water and gas within the handle. To eliminate one form of overheating, the electrode should protrude from the gas lens or cup by at least 1/4 inch. This prevents trapping of radiant heat when the tungsten is within the lip of the gas cup. Extra–long electrodes will result in a higher rate of contamination. Keeping the electrode close to the work is necessary to ensure a pure high quality weld. The shielding gas can easily be blown away by drafts or wind. Welding should take place only where adequate protection from drafts is possible.

Figure 29 TIG torch tip

2 Safety


The TIG process requires a high degree of precision and practice on the part of the welder, who must be able to set up the process and have adequate hand skill to ensure purity. The base metal and filler metals must be absolutely clean before welding. When working on aluminum, a stainless steel wire brush prevents contaminating the aluminum with steel particles from a normal wire brush. To prevent sagging and contamination a backing piece is frequently used with aluminum. Quite often a shielding material is applied to the back side of the weld to prevent oxidation and discoloration, especially with stainless steel. The following is a list of components required to establish a TIG welding process in the maintenance shop:

• AC/DC welding machine with high frequency (HF) capability • TIG torch (preferably water–cooled) • Argon cylinder regulator and flowmeter • Assorted sizes of tungstens, collets, collet bodies, gas cups, lenses, and nozzles • Cleaning copper • Stainless steel wire brush • Assorted welding wire (filler rods of TIG quality) • Foot control for amperage HF and gas flow start–up and delay.

13.2 Metallic inert gas welding (MIG) Inert gas is used to shield a consumable electrode. The wire electrode is melted using two methods. In the short arc method the wire actually contacts the puddle, melts off, and then restarts. This method is used with low voltage and amperage and occurs about 100 times per second. At higher voltages and amperage a spray arc method results in fine droplets of melted electrode virtually sprayed on the base metal. Travel speeds can be almost doubled using spray arc. The power supply is usually a simple transformer welding machine producing rectified DC reverse polarity (see Figure 30). The amperage may be controlled by switch, plug, or step method. Continuous wire feed is controlled by a rheostat for precision adjustment for each welding situation. Carbon dioxide or an argon–helium–carbon dioxide mixture can be used for the shielding gas, depending on the bead penetration and smoothness desired for steel. Carbon dioxide yields superior penetration, while the multi–gas mixture gives a smoother appearance to the bead. The welding gun consists of the switching mechanism, the wire contact tip, and the gas nozzle. Nozzles come in a variety of shapes to suit the job requirements. Their function is to direct the flow of shielding gas surrounding the weld puddle, preventing oxidation and contamination.

13 Advanced welding processes



A number of units are readily adaptable for aluminum, magnesium, and stainless wire welding with only slight modification of the system. Aluminum and magnesium can both be welded using pure argon as the shielding gas. On magnesium sections above 1/8–inch thick an argon helium mixture gives better penetration. Stainless steel requires a mixture of 90 percent helium, 7 1/2 percent argon, 2 1/2 percent carbon dioxide for clean welds free of discoloration and oxidation. The welder should be aware of several operating characteristics that will affect the use of MIG in the shop:

The spool should be kept clean and protected.

The wire should be cleaned and a lubricating fluid applied before the wire enters the drive wheels.

The feed rollers must have proper tension to provide adequate push, but should be loose enough to prevent bird–nesting (snarling) of the wire should it hang up at the tip or within the cable.

Weld spatter clogs the nozzle and tips, reducing the flow of gas and possibly welding the wire to the tip. A quality tip/nozzle dip or spray aids in preventing build up. Careful monitoring and occasional removal of the built–up debris with a hooked pick will prevent most electrode freezing.

Prevent kinking of the feeder cable. Any restriction in feed rate may cause the wire and tip to arc–over, ruining the tip itself. If this occurs, turn off the welding machine, remove the nozzle, and unscrew the tip. Pull out the tip and wire so that the wire may be cut, leaving enough wire to install a new tip. When the tip cannot be unscrewed due to the

Figure 30 MIG welding system

2 Safety


wires' resistance, open the unit and cut the wire carefully between the spool and the drive wheels. File the cut end to round it before rethreading the wire in order to prevent the wire from hanging up in the feed cable liner. Once the new wire is installed in the drive wheels and feed cable adapter, turn on the unit. By not replacing the tip until the electrode wire extends beyond the gun several inches, the welder eliminates the chance of a hang up at the tip cable interface. Set the gas flow starting with a minimum and working upward until the bead is porosity free showing no signs of contamination or oxidation. Insufficient flow will result in a foamy, spongy bead of reddish cast. Gently work up in pressure to ensure sufficient flow while waste is minimized. Excess flow will quench the weld bead, resulting in cooling, cracking, and loss of control. The distance between the nozzle and work will only determine gas shield coverage and not arc length, since this is automatic in the MIG process. Keep the tip and gas nozzle between 1/2 and 3/4 inches from the base metal for proper shielding.

The most important factor in achieving success with the MIG process is travel speed. The width of the arc is minimal depending on wire size, voltage, and amperage. The welder must advance the arc fast enough to produce a thoroughly bonded bead with adequate penetration and no overlap on the bead margin. To achieve thorough fusion of bead to base metal, keep the gun in constant motion. Travel speeds are typically 25–35 feet per minute. These speeds produce narrow, but high strength beads, fully fused to the base metal.

Mushrooming is typical by inexperienced welders. This is the result of piling up the wire with only the base or stem fused to the base metal. Unfortunately, the MIG wire does not seek new or cold metal to bond to but seeks freshly deposited hot bead and simply piles on. A bead may have a perfect contour and surface appearance, but lack any bonding strength. In the stick welding method, the arc is wide and digging, spreading itself over a greater area. The stick also has a flux to aid in keeping the puddle molten longer resulting in better bonding. Rates of travel with the stick are extremely slow in comparison to the MIG. The average 1/8–inch 6013 stick electrode at 90 amps will result in a bead 5/16 inch wide, 3/32 inch high, and 6–7 inches long, and would take over a minute to make. In one minute the MIG, with .035 wire, should have travelled approximately 50 times as far.

Use the multipass weld bead to achieve high strength. Stringer passes result in less shrinkage and distortion. Wide weaves should be discouraged. Between passes a glass–like silicon oxide flux should be chipped away to prevent porosities in the finished bead. The use of MIG welding is rapidly growing. Automatic arc length, less spatter, distortion, high strength, and the ability to work on thin sections lead many welders to think of the MIG process as a cure–all. It is a tool that has limitations like any other. It is more fragile and susceptible to damage, and does not replace the stick welding (SMAW) process in the maintenance welding shop. It should be used on light gauge metals with few exceptions.




13.3 Flux–core arc welding (FCAW) This process may use both a shielding gas and a flux. Automatic drive wheels push the cored wire down to the welding gun. Shielding gas is directed around the wire to protect it from contamination. Carbon dioxide or a mix of argon and carbon dioxide are usually the shielding gases, if used. The welder is able to adjust the welding current (amperage), the speed of the wire feed, and the flow of the shielding gas. This allows setup for almost any welding situation. Advantages of FCAW are many. Very high strength and high quality beads can be obtained with ease. Control of the bead is simple due to visibility and automatic arc length. Because travel speed and rate of deposition are high, distortion is reduced. A range of thicknesses from 1/8 inch to 2 inches may be welded with the FCAW process. A disadvantage of FCAW is needing to maintain several systems in the shop. A large constant voltage DC welding machine with a minimum of 300 amps, 25–50 volts, and 80–100 percent duty cycle is required to power the system. In addition a 110V AC circuit must be available to operate the wire feeder, although some units use part of the welding current for this purpose. A flow meter is required to properly adjust the gas flow for various welding situations. Some carbon monoxide is produced during the welding process, and should be properly vented. The resulting costs prohibit the FCAW process from being used in small shops. Each project will require fine tuning the apparatus. Welds are always best obtained on absolutely clean materials. All flux core welding does not require a gas shield. Many gun and drive mechanisms are simply added to an existing power source. These systems result in high strength welds and automatic arc length control. They are more susceptible to weld contamination and care must be exercised to ensure that travel speed or position does not outstrip shielding ability. Hard surfacing is frequently applied with the FCAW process, and is usually accomplished easily and economically. 13.4 Plasma arc cutting (PAC) This process allows the welder to cut aluminum, magnesium, monel, stainless steel, or any metal that cannot be cut with the oxyacetylene cutting torch. It utilizes compressed shop air heated to a temperature of 15,000 degrees F or more in the electric arc to create a jet of extremely hot gas that will melt, pierce, and cut through any known metal.

Figure 31 Flux–core arc welding tip

2 Safety


A tungsten electrode arc superheats the compressed air so that it is actually a plasma capable of carrying a current. As the plasma leaves the torch head and touches the base metal it is converted back to a gas releasing sufficient heat to melt the metal. The concentrated superheated gas is discharged with sufficient pressure to blow away the metal leaving a very narrow kerf. The cutting process results in extremely clean–cut surfaces, virtually slag free. Since minimal heat is put into the base, metal distortion is almost eliminated. Cutting speeds are up to 300 inches per minute, much faster than oxyacetylene. Precise clean cuts can be achieved on thicknesses up to five inches, depending on the system size. Each plasma arc cutting machine allows the welder to fine–tune the system for the cutting job at hand. Several small units are available, which offer sufficient depth of cut, reliability, and low cost to make the PAC process feasible for the larger maintenance welding shop. The best use of PAC is on those metals that cannot be cut with oxyacetylene, although superior cuts on steel can be achieved. Every shop must evaluate the initial cost as well as the cost of consumable cups and tips that are used in the torch tip. Most small maintenance shops will find that the costs will outweigh the benefits of a PAC unit since they will just simply lack enough fabrication work justify the purchase.


Figure 32 Plasma arc cutting tip (PAC)

2 Safety


14 TANK REPAIR AND MAINTENANCE 14.1 Tank repair Any tank or cell that has contained or is suspected of containing a flammable gas or liquid must be treated with utmost care. Many welders have lost lives and limbs to “safe” repair projects. The most dangerous and frequently encountered situation is that of repairing a leaky fuel tank. One ounce of gasoline when mixed with sufficient air is equivalent to 2/3 pound of TNT dynamite. The best and safest method of repair is not to fix it. However, many times welders do not have this option. The following repair procedure covers the proven, safe method for repairing a sheet metal gas tank so often seen in the repair shop:

1. Totally drain the contents into a safe container for proper disposal. 2. Thoroughly rinse out the interior with plain water. Dispose of the water and fuel mix

safely. 3. Add warm water and at least one cup of detergent to the tank, and thoroughly slosh the

tank so that the detergent adequately cuts the flammable hydrocarbon residues in the tank. An alternative is to steam–clean the tank thoroughly. Rinse out the tank to remove the hydrocarbons that should be in solution with the water.

4. Fill the tank with water, leaving just enough void to allow the metal to be heated

sufficiently for a soldered patch. 5. Add dry ice, a shot of carbon dioxide from the extinguisher or bubble in carbon

dioxide gas from a tank source (if a MIG or TIG is present, disconnect the hose and bubble in the inert gases, carbon dioxide, argon, or a combination.) With the hole to be patched facing up, the accumulating inert gases will drive the lighter air and fuel mixture out through the hole. This shielding effect should be continued until the patch is near completion.

6. Prepare the sheet metal by scraping all paint, undercoating or rust from the patch area.

Most automotive fuel tanks are made of Terne metal, which is mild steel plate coated with a tin–lead combination. The Terne metal makes manufacturing (shaping and soldering) easier to achieve and provides a degree of protection should the tank become scraped or scratched.

7. Prepare a pure copper patch made of light gauge flashing or roofing material. Shape

the patch to fit the contour of the tank. Flux the downside of the patch and thoroughly tin the patch using a 50–50 tin–lead solder for strength, economy, and ease of wetting.



8. Never use an open flame near any fuel container even though precautions have been

taken to ensure safety. Heat a soldering copper to carry heat to the job without flame. 9. Flux the area to receive the patch, and carefully tin an area slightly larger than the

patch using the soldering copper and the 50–50 solder.

10. Reheat the soldering copper and prepare to join the surfaces by cleaning the tinned faces of both the patch and tank. Reflux all surfaces.

11. Apply the tinned patch and place the hot soldering copper on top with as much surface

in contact as possible using the flats of the copper. The flow of inert gas may be stopped to ensure no pressure is built up within the tank.

12. Add flux to the surface of the patch to aid in heat transfer, if needed. The heat of the

copper should pass quickly through the patch to fuse the patch securely to the tank. Move the copper around to lock down the patch on all sides. Additional solder may be added to any area looking suspiciously lacking or in areas of poor fit-up. The soft copper may be shaped by tapping with a mallet when poor fit–up is excessive.

13. Allow the patched area to cool, and wipe the flux from the surface. Soldered joints

should never be quick–cooled. 14. Test the tank by pressurizing the contents and applying soap suds to the patched edges.

At this point any suspect areas around the tank should also be tested with the suds. If no leaks are found, empty, rinse, reinstall, and fill the tank. To prevent the possibility of water from the tank entering the fuel system, add a can of dry gas to the fuel before starting the vehicle and filling it with fuel. This procedure is the result of successfully repairing many tanks without loss. It is safe, but time–consuming. The tendency may be to short–cut a section just because you are in a hurry. Tank repair is a life–or–death matter that must not be taken lightly. The explosive force of fuel and air is well–known. Fuel comes in many forms, and welders should be aware of every single possible combination. Typically, welders will be asked to cut the top out of barrels to make trash containers, etc. These small jobs are usually the most dangerous ones. When it comes to containers, safe materials are non–existent with the exception of water. Asphalt emulsion is a typical “safe” material, yet many welders have found out the hard way about the water mixture. Heating the tank results in conversion of asphalt to explosive gas despite the fact that the water is present. Be careful with all tanks.

2 Safety


14.2 Maintenance of welding equipment Welders should be prepared to readily repair the tools of their trade. Carrying every single item that could possibly fail is ridiculous, if not expensive. A kit of reasonable items can be carried in a small tool box and should go with the welder. The following is a list of repair items frequently used that may save time and effort when a breakdown occurs in the shop or field:

• Spare arc and oxy lenses • “O” rings for the torches • Check valves • Tip cleaners (normal and long length) • Tank wrench • Chalk or soapstone • Striker and flints • Correct size wrenches for hose repair • Allen wrenches to fit the electrode holder • Electrical tape to quickly tape ripped or torn cable insulation • Several 3–inch pieces of 1/2–inch copper pipe with a 3/8–inch hole drilled in a

flattened end (to be used for emergency splicing of cables) • Hose repair kit (should a leak be found or the hose cut; do not tape the leak) • Spare cutting tip • Adjustable wrench

14 Repair and maintenance

Figure 33 Fuel tank repair



The following have proven valuable for a standard set–up to be taken out with every portable welding truck or job:

• Gas or diesel portable arc welding machine/generator with welding cables ground and electrode holder

• Portable grinder large/small • Portable drill and bits • Extension cords • C–clamps • Vise grips • Large file • Large hammer • Chisel • Pry bar • Screwdrivers • Chipping hammer • Wire brush • 2 arc shields with shade 10–11 lens • Gloves • Leathers • Assortment of arc welding rods • Oxygen and acetylene tanks (sufficient pressure with caps) • Oxy shield with shade 4–5 lens • Regulators • Hoses • Torch body • Cutting attachment and assorted welding tips • Tip cleaners • Striker and chalk • Gas welding rods • Brazing rods • Assorted fluxes • Solders and fluxes

2 Safety


APPENDICES

A. References and Acknowledgements

Advanced Farm Metal Work, Lecture and Laboratory Facts and Procedures, Fred G. Lechner, Department of Agricultural Engineering Course 310, Cornell University (Ithaca, New York, 1980) [out of print] Farm Metal Work, Lecture Facts and Procedures, Fred G. Lechner, Department of Agricultural Engineering Course 110, Cornell University (Ithaca, New York, 1977) [out of print] New Lessons in Arc Welding, Lincoln Electric Company, Armco International (Houston, TX, 1982) The Oxy–Acetylene Handbook, A Manual on Oxy–Acetylene Welding and Cutting Procedures, Linde Air Products Company (New York, 1957) Welding: Principles and Practices, Raymond J. Sacks, Bennett & McKnight Publishing Company (Peoria, IL, revised 1976)

B. Video tapes The following video tapes are available to borrow from the Local Roads Program. Tapes are lent free of charge to local roads officials for two weeks. Call 607–255–5437 for complete details.

GI136 Arc Welding SA098 Cylinder and Gas Apparatus Safety

C. Information Sources

American Welding Society (AWS) 2501 NW 7th Street Miami, FL 33125

2 Safety


welding manual 1995

Documents