jj205 workshop technology tic&mic welding
DESCRIPTION
JJ205 Workshop TechnologyTRANSCRIPT
PRESENTATIONWORKSHOP TECHNOLOGY 2
JJ204GROUP MEMBERS
KATHIRAVAN S/O PARAMASIWANNAAVINDRA PRASAD S/O GANESAN
SIM KAH TIANG
INTRODUCTION GAS SHIELDED ARC WELDING
The primary goal of any welding operation is to make a weld that has the same properties as the base metal.
The only way to produce such-a weld is to protect the molten puddle from the atmosphere
The two general types of gas shielded-arc welding processes are gas tungsten-arc welding (GTA) and gas metal-arc welding (GMA).
GTA is often tilled TIG (tungsten inert gas) and GMA is referred to
as MIG(metal inert gas).
The term inert refers to a gas that will not combine chemically with other elements
GAS SHIELDED ARC WELDING PRINCIPLE
TUNGSTEN INERT GAS
Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding
Is an arc welding process that uses a non-consumable tungsten electrode to produce the weld
Enables the metals and wide range of ferrous alloys to be welded without the use of flux
The weld area is protected from atmospheric contamination by an inert shielding gas (argon or helium)
GTAW is most commonly used to weld thin sections of stainless steel and non-ferrous metals such as aluminum, magnesium, and copper alloys
METAL INERT GAS
• Gas metal arc welding (GMAW), sometimes referred to by its subtypes metal inert gas (MIG) welding or metal active gas (MAG) welding
• Is a welding process in which an electric arc forms between a consumable wire electrode and the workpiece metal(s), which heats the workpiece metal(s), causing them to melt, and join
• Is a process which suitable for welding aluminium,magnesium alloys,plain and low alloy steels,stainless and heat-resistant steel,copper and bronze
• The process can be semi-automatic or automatic
DIFFERENCE BETWEEN GAS SHIELDED ARC WELDING
AND
NORMAL ARC WELDING
ARC WELDING
• Arc welding is a type of welding that uses a welding power supply to create an electric arc between an electrode and the base material to melt the metals at the welding point
• They can use either direct (DC) or alternating (AC) current,
GAS SHIELDED ARC WELDING
• Shielding gases are inert or semi-inert gases that are commonly used in several welding processes
• Inert gases:helium,argon Semi-inert:oxygen,carbon dioxide,hydrogen,nitrogen
• Their purpose is to protect the weld area from oxygen, and water vapour.
• Depending on the materials being welded, these atmospheric gases can reduce the quality of the weld or make the welding more difficult
• Other arc welding processes use other methods of protecting the weld from the atmosphere as well
Shielded metal arc welding (SMAW) - also known as "stick welding", uses an electrode that has flux, the protectant for the puddle, around it. The electrode holder holds the electrode as it slowly melts away. Slag protects the weld puddle from the outside world.
Gas tungsten arc welding (GTAW) - also known as TIG (tungsten, inert gas), uses a non-consumable tungsten electrode to produce the weld. The weld area is protected from atmospheric contamination by an inert shielding gas such as Argon or Helium.
Gas metal arc welding (GMAW) - commonly termed MIG (metal, inert gas), uses a wire feeding gun that feeds wire at an adjustable speed and sprays an argon-based shielding gas or a mix of argon and carbon dioxide (CO2) over the weld puddle to protect it from the outside world.
METHOD OF WELDING FORTIG WELDING
1.Put on safety
gear
2.Connect the TIG
torch
3.Plug your foot
pedal into the machine
4.Select the polarity.
5.Grind the tungsten
6.Set up the gas flow.
7.Set the amperage
8.Clean your
welding material
9.Insert the tungsten
electrode into its collet
10.Clamp the
parts together
11.Tack weld the parts together
12.Hold the TIG torch in your
hand
15.Use your torch to heat up the
base metal
13.Practice using the foot pedals to control the
heat
14.Pick up the filler rod in your other
hand
METHOD OF WELDING FOR MIG WELDING
1.Assemble
your safety gear
2.Select a
comfortable MIG gun
3.Prepare the area to be welded in
4.Obtain the proper wire
5.Prepare the reel
6.Feed the wire to the torch
7.Adjust the
tension
8.Set the welding
machine polarity to
DCEP.
9.Keep a
consistent electrode
length
10.Use the proper
shielding gas
11.Weld a joint using a drag or push
welding technique.
EXAMPLE OF TIG WELDING MACHINE
EXAMPLE OF MIG WELDING MACHINE
Shielding gases for MIG welding
• The basic gas for MIG welding is inert – argon (Ar) or helium (He), or a mixture of both.
• However, small additions of oxygen (O2) or carbon dioxide (CO2) can further stabilize the arc, improve the fluidity and also improve the quality of the weld deposit.
• For stainless steels there are also gases available containing small amounts of hydrogen (H2).
Shielding gases for TIG
• The normal gas for TIG welding is argon or helium, or a mixture.
• In some cases nitrogen (N2) and/or hydrogen (H2) is added in order to achieve special properties.
• For instance, an addition of hydrogen can be used for many conventional stainless steels to increase productivity.
• Alternatively, if nitrogen is added, the weld deposit properties can be improved.
• Oxidizing additions are not used because they destroy the tungsten electrode.
TYPES OF CURRENT
• Both direct current (DC) and alternating current (AC) are used for welding.
• The form of the weld pool and of the weld seam can be influenced by current type and electrode polarity.
EFFECTS OF POLARIITY
• Direct current, straight polarity (electrode negative, DC-EN) → deep penetration
• Direct current, reverse polarity (electrode positive, DC-EP) → low penetration
• Alternating current (AC) → medium penetration
Thus there are three possibilities for welding:• 1.DC-EP The welding current has to be
reduced 10% of the normal welding current
• 2.DC-EN Pure helium is required as a shielding gas and no reduction of the welding current is necessary
• 3.AC The current is required to be reduced to 50-60% of the normal current
ADVANTAGES OF TUNGSTEN INERT GAS WELDING
• Tungsten Inert Gas Welding produces high quality welds.
• The weld is automatically protected by the inert gas during the welding process.
• No slag is produced.
• TIG Welding can be done in any position.
DISADVANTAGES OF TUNGSTEN INERT GAS WELDING
• Tungsten inert gas welding is a slow process.
• Highly skilled labour is needed.
• Welder is exposed to huge intensities of light
.
• TIG welding is more expensive when compared to MIG welding
ADVANTAGESOFMETAL INERT GASWELDING
• Simple to use MIG welding is a simple process. In just a few hours,
welders will be able to learn how to MIG weld. As a matter of fact, the basic MIG welding training can only last for 20 minutes.
• Increases productivity A lot of welders have improved productivity with the
use of MIG welding. They don’t need to regularly change rods or even repeatedly brush the weld. As a result, they will able to work faster and in a cleaner way.
• Great and Simple Welds MIG welding offers better weld pool visibility. The
welding process is very simple and gives you better control. As a result, you will be able to produce a great looking weld.
• Versatile MIG welding has the ability to weld various types of
alloys and metals. You can operate it in a fully automatic or semi automatic way. As a matter of fact, a lot of industries are benefitting a lot from the use of MIG welding. It is used for various metals like copper, mild steel, aluminum, nickel, magnesium, mild steel, and many more.
• Efficient welding MIG welding does not only improve the welding speed,
but it as well improves the quality and overall weld control.
• Cleanliness and efficiency With the use of MIG welding, the loss of alloying
elements will be reduced and minor weld spatter is produced.
DISADVANTAGES OFMETAL INERT GASWELDING
• Expensive MIG welding is actually more expensive primarily
because of the complexity of usage. The frequent replacement of nozzles can actually add up to the total cost.
• Not recommended for outdoor welding MIG welders are highly discouraged to work outside
because MIG welding uses shielding gas and welding outside can actually affect the purity of the weld. The wind outside can compromise the quality of the weld.
• Fast Cooling Rates MIG welding is not covered with slag and so you can
expect that the welded metal will cool at higher rates
• Not recommended for welding thick metals One of the limitations of MIG welding is its
inability to weld thick metals. Because of the property of thick metals, MIG weld will not be able to penetrate deeply. It is only advisable to use in thin metals.
• The use of shielding gas Replacing the shielding gas may actually take
some time and can cause delay while welding.
• Longer preparation time When welding using MIG, the metal should be
prepared thoroughly. The metal should be free from dirt and rust to ensure high quality welding.
DEFECTS OFTUNGSTEN INERT GAS WELDINGANDMETHOD TOPREVENT IT
POOR GAS COVERAGE LEADS TO CONTAMINATION
Weld contamination can occur when shielding gas is not turned on, there is too little or too much gas shielding or the gas is blown away
Check the gas cylinder label to make sure you’re using the right type of gas for TIG welding (generally 100 percent argon, or an argon/helium mix for aluminum)
Consider using a gas lens instead of the standard collet body to provide better gas shielding.
Check all fittings and hoses for leaks. Use a gas leak detection fluid, available at most welding suppliers, over the hose and all fittings. If bubbles form, you have a leak and need to replace defective components.
• SUGARING ON STAINLESS Sugaring (oxidation) occurs around the weld
when it is exposed to oxygen in the air. The best way to prevent sugaring is to ensure you have adequate gas coverage on the front and back of the weld and to be sure that you do not overheat the weld.
• TOO MUCH AMPERAGE ON ALUMINUM Setting the amperage too high on aluminum
creates a wider profile, an ill-defined bead and can potentially lead to burn-through. To solve this problem, reduce amperage and/or increase travel speed.
• CRATERS Craters occur at the end of the weld and lead to
cracking. Causes include instantly dropping the weld power and removing the filler rod too quickly. Adjust your technique and continue to feed the filler rod while slowly reducing current at the end to fill in the crater. Using a TIG welder with a “crater control” function may also help.
• DIRTY BASE AND/OR FILLER METAL All base and filler metals need to be cleaned, whether
it’s mill scale, oxide on aluminum, or dirt and grease. Grind, brush and wipe away all potential contaminants. For cleaning aluminum, dedicate a stainless steel brush to the task to prevent contamination from other metals. Never use brake cleaner!
DEFECTS OF METAL INERT GAS WELDINGAND METHODS TOPREVENT IT
Porosity Gas flow too low or too high Blocked nozzle Leaking gas lines Draughty conditions Nozzles distance from work is too great Painted, wet or oily plate Wet or rusty electrode/wire
Lack of penetration -Current too low Preparation too narrow Root face too large Root gap too small Worn contact tip causing irregular arc Incorrect alignment of plates
Undercut -Speed too fast
• Current too high
• Poor technique
Lack of fusion -Voltage too low
• Current too low or too high
• Irregular surface
• Wrong torch angle
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