Notes For ME 403 Part-I

Students are suggested to refer to the class notes in addition to the following.

Q. Classification of welding processes

Welding processes

1. Fusion Welding

Arc welding

o Shielded Metal Arc Welding (SMAW);

o Flux Cored Arc Welding (FCAW);

o Submerged Arc Welding (SAW);

o Metal Inert Gas Welding (MIG, GMAW);

o Tungsten Inert Gas Arc Welding (TIG, GTAW);

o Electroslag Welding (ESW);

o Plasma Arc Welding (PAW);

Resistance Welding (RW);

o Spot Welding (RSW);

o Flash Welding (FW);

o Resistance Butt Welding (UW) ;

o Seam Welding (RSEW);

Gas Welding (GW);

o Oxyacetylene Welding (OAW);

o Oxyhydrogen Welding (OHW);

o Pressure Gas Welding (PGW);

2. Solid State Welding (SSW);

Forge Welding (FOW);

Cold Welding (CW);

Roll Welding (RW);

Friction Welding (FRW);

Explosive Welding (EXW);

Diffusion Welding (DFW);

Ultrasonic Welding (USW);

3. Special Welding Processes

Thermit Welding (TW);

Electron Beam Welding (EBW);

Laser Welding (LW).

Oxy-fuel Gas Welding

Oxyfuel gas welding refers to a group of welding processes that use the flame produced by the

combustion of a fuel gas and oxygen as the source of heat.

There are three major processes within the OFW group:

1. oxyacetylene welding

2. oxyhydrogen welding,

3. pressure gas welding.

There is one process of minor OFW, Oxy Fuel welding industrial significance, known as air acetylene

welding, in which heat is obtained from the combustion of acetylene with air. Welding with

methylacetone-propadiene gas (MAPP gas) is also an oxy fuel procedure

(Oxyfuel gas welding )Acetylene is more widely than other gases. It produces a temperature of about

3250oC in a two stage reaction.

In the first stage the supplied oxygen and acetylene react to produce carbon monoxide and hydrogen.

This reaction occurs near the tip of the torch and generates intense heat.

C2H2+O2 --------> 2CO +H2+ heat

In the second stage reaction involves the combustion of the CO and H2 and occurs just beyond the first

combustion zone.

2CH+O2 --------> 2CO2 + heat

H2+1/2O2 --------> H2O+ heat

The two stage combustion process produces a flame having two distinct regions. The maximum

temperature occurs near the end of the inner cone, where the first stage of combustion is complete. Most

welding should be performed with the torch positioned so that this point of maximum temperature is just

above the metal being welded. The outer envelope of the flame serves to preheat the metal and, at the

same time, provides shielding from oxidation, since oxygen from the surrounding air is consumed in the

secondary combustion.

Advantages of Oxy-Acetylene Welding :

It's easy to learn.

The equipment is cheaper than most other types of welding rigs (MIG/TIG welding)

The equipment is more portable than most other types of welding rigs (MIG/TIG welding)

Oxy/Acetylene equipment can also be used to "flame-cut" large pieces of material.

Disadvantages of Oxy-Acetylene Welding :

Limited power density

Very low welding speed

Severe distortion

Oxy/Acetylene weld lines are much rougher in appearance than other kinds of welds, and require

more finishing if neatness is required.

Oxy/Acetylene welds have large heat affected zones (areas around the weld line that have had

their mechanical properties adversely affected by the welding process).

Materials Suitable for Oxy/Acetylene Welding:

Mild Steel

Brazing can be done on many other materials i.e. aluminum, stainless steel, copper, and brass

Q. Explain Various Types of flames in Oxy fuel gas welding.

Types of Flames:

1. When oxygen is turned on, flame immediately changes into a long white inner area (Feather)

surrounded by a transparent blue envelope is called Carburizing flame (30000c)

2. If the ratio is between 1: l and 1.15.1, all reactions are carried to completion and a neutral flame

is produced. This mixture gives a bright whitish cone surrounded by the transparent blue envelope

is called Neutral flame (It has a balance of fuel gas and oxygen) (32000c).It is used for welding

steels, aluminium, copper and cast iron

3. If more oxygen is added .i.e., higher ratio, such as 1,5:l, the cone becomes darker and more

pointed, while the envelope becomes shorter and more fierce is called Oxidizing flame. Has the

highest temperature about 34000c. It is used for welding brass and brazing operation

Q. Shielded Metal Arc Welding (SMAW)

SMAW is a welding process that uses a flux covered metal electrode to carry an electrical current. The

current forms an arc that jumps a gap from the end of the electrode to the work. The electric arc creates

enough heat to melt both the electrode and the base material(s). Molten metal from the electrode travels

across the arc to the molten pool of base metal where they mix together. As the arc moves away, the

mixture of molten metals solidifies and becomes one piece. The molten pool of metal is surrounded and

protected by a fume cloud and a covering of slag produced as the coating of the electrode burns or

vaporizes. Due to the appearance of the electrodes, SMAW is commonly known as ‘stick’ welding.

SMAW is used primarily because of its low cost, flexibility, portability and versatility. Both the

equipment and electrodes are low in cost and very simple. SMAW is very flexible in terms of the

material thicknesses that can be welded (materials from 1/16” thick to several inches thick can be welded

with the same machine and different settings). It is a very portable process because all that’s required is a

portable power supply (i.e. generator). Finally, it’s quite versatile because it can weld many different

types of metals, including cast iron, steel, nickel & aluminum.

Some of the biggest drawbacks to SMAW are (1) that it produces a lot of smoke & sparks, (2) there is a

lot of post-weld cleanup needed if the welded areas are to look presentable, (3) it is a fairly slow welding

process and (4) it requires a lot of operator skill to produce consistent quality welds.

Q. Flux cored arc welding (FCAW)

Flux cored arc welding (FCAW) is an arc welding process in which the heat for welding is produced by

an arc between a continuously fed tubular electrode wire and the work. Shielding is obtained by a flux

contained within the tubular electrode wire or by the flux and an externally supplied shielding gas.

Advantages

Flux cored arc welding has many advantages for a wide variety of applications.

It often competes with shielded metal arc welding, gas metal arc welding, and submerged arc welding

(SAW) for many applications. Some of the advantages of this process are:

1. It has a high deposition rate and faster travel speeds

2. Using small diameter electrode wires, welding can be done in all positions.

3. Some flux -cored wires do not need an external supply of shielding gas, which simplifies the

equipment.

4. The electrode wire is fed continuously so there is very little time spent on changing electrodes

5. Deposits a higher percentage of the filler metal when compared to shielded metal arc welding.

6. Obtains better penetration than shielded metal arc welding

Limitations

1. Melted contact tip – when the contact tip actually contacts the base metal, fusing the two and

melting the hole on the end

2. Irregular wire feed – typically a mechanical problem

3. Porosity – the gases (specifically those from the flux-core) don’t escape the welded area before

the metal hardens, leaving holes in the welded metal

4. More costly filler material/wire as compared to GMAW

5. The equipment is less mobile and more costly as compared to SMAW or GTAW.

6. The amount of smoke generated can far exceed that of SMAW, GMAW, or GTAW.

7. Changing filler metals requires changing an entire spool. This can be slow and difficult as

compared to changing filler metal for SMAW or GTAW.

8. Creates more fumes than SMAW

FCAW is sutable for following aloys:

Mild and low alloy steels

Stainless steels

Some high nickel alloys

Some wear facing/surfacing alloys

Gas Metal Arc Welding (GMAW)

Gas Metal Arc Welding (GMAW), by definition, is an arc welding process which produces the

coalescence of metals by heating them with an arc between a continuously fed filler metal electrode and

the work. The process uses shielding from an externally supplied gas to protect the molten weld pool.

The alloy material range for GMAW includes: carbon steel, stainless steel, aluminum, magnesium,

copper, nickel, silicon bronze and tubular metal-cored surfacing alloys.

Advantages of GMAW

The GMAW process enjoys widespread use because of its ability to provide high quality welds, for a

wide range of ferrous and non-ferrous alloys, at a low price. GMAW also has the following advantages:

• The ability to join a wide range of material types and thicknesses.

• Simple equipment components are readily available and affordable.

• GMAW has higher electrode efficiencies, usually between 93% and 98%, when compared to other

welding processes.

• Higher welder efficiencies and operator factor, when compared to other open arc welding processes.

• GMAW is easily adapted for high-speed robotic, hard automation and semiautomatic welding

applications.

• All-position welding capability.

• Excellent weld bead appearance.

• Lower hydrogen weld deposit — generally less than 5 mL/100 g of weld metal.

• Lower heat input when compared to other welding processes.

• A minimum of weld spatter and slag makes weld clean up fast and easy.

• Less welding fumes when compared to SMAW (Shielded Metal Arc Welding) and FCAW (Flux-Cored

Arc welding) processes

• Generally, lower cost per length of weld metal deposited when compared to other open arc welding

processes.

• Lower cost electrode.

• Handles poor fit-up with GMAW-S and STT modes.

• Reduced welding fume generation.

• Minimal post-weld cleanup.

Limitations of GMAW

• The lower heat input characteristic of the short-circuiting mode of metal transfer restricts its use to thin

materials.

• The higher heat input axial spray transfer generally restricts its use to thicker base materials.

• The higher heat input mode of axial spray is restricted to flat or horizontal welding positions.

• The use of argon based shielding gas for axial spray and pulsed spray transfer modes is more expensive

than 100% carbon dioxide (CO2).

GAS TUNGSTEN ARC WELDING GTAW

An arc is established between the end of a tungsten electrode and the parent metal at the joint line.

The electrode is not melted and the welder keeps the arc gap constant. The current is controlled by the

power-supply unit.

A filler metal, usually available in 1 m lengths of wire, can be added to the leading edge of the pool

as required. The molten pool is shielded by an inert gas which replaces the air in the arc area. Argon

and helium are the most commonly used shielding gases.

ADVANTAGES

GTAW produces precise and clean, nearly spatter free welds on almost all metals with superior

quality in comparison to the other arc welding processes. It has found use in the aerospace, food

processing, and nuclear industries. It is particularly useful on smaller sectioned parts and on

reactive metals such as titanium.

It can be used with filler metal or without filler metal (autogenous). This process allows the heat

source and filler metal additions to be controlled independently.

It is easily automated and can produce welds in all positions, even with intricate geometries.

Superior quality welds, generally free from spatter, porosity, or other defects

Precise control of arc and fusion characteristics

Weld almost all metals

Used with or without filler wire

Easily automated

Used in all positions

Intricate geometries weldable

DISADVANTAGES

Deposition rates are lower with GTAW than any other arc welding process. In general, the

process is limited to thicknesses of 3/8-inch or less since productivity makes the process cost

prohibitive. Tungsten inclusions or contamination of the weld pool may occur if the electrode

touches the weld pool or proper gas

Higher operator skill Required

Sensitive to draft

shielding is not maintained

Manual GTAW requires more dexterity and welder coordination than with manual GMAW or

SMAW. As with the other gas shielded processes, drafts can blow away the shielding gas,

which limits the outdoor use of the process.

Less economical than consumable electrode processes for sections thicker than 3/8 inch

Lowest deposition rate of all arc processes

Tungsten inclusions

SUBMERGED ARC WELDING (SAW)

Submerged Arc Welding (SAW) is a common arc welding process. Submerged Arc Welding is so named

because the weld zone and arc are submerged beneath a blanket of flux. When molten, the flux becomes

conductive and provides a current path between the electrode and the work. SAW is normally operated in

the automatic or mechanized mode, however, semi – automatic SAW guns with pressurized or gravity

flux feed delivery are available. Single or multiple electrode wire variations of the process exist. • DC or

AC power can be used, and combination of DC and AC are common on multiple electrode systems. •

Constant voltage welding power supplies are most commonly used. The flux, which is part of the

powder, acts as a thermal insulator, allowing deep penetration of heat into the workpiece. The

consumable electrode is a coil of bare round wire (1.5 − 10 mm diameter) and is fed automatically

through a tube (welding gun). Because the powder is fed by gravity, the SAW process is limited to weld

in a flat or horizontal position. Circular welds can be made on pipes, provided that they are rotated during

welding. The unfused powder can be recovered, treated, and refused.

ADVANTAGES:

High deposition rates.

Great intensities of heat can be generated and kept concentrated to weld thicker sections with

deep penetrations.

The submerged process can be used for welding in exposed areas with relatively high winds.

High heat concentration supports considerably higher welding speeds.

Welding is carried out without sparks, smoke, flash or spatter.

Practically no edge preparation is necessary.

Low distortion

Welds produced are sound, uniform, ductile, corrosion resistant, and have good impact value.

Very neat appearance and smooth weld shapes can be obtained.

50% to 90% of the flux is recoverable.

LIMITATIONS

Limited to ferrous and some nickel based alloys.

Normally limited to long straight seams or rotated pipes or vessels.

Flux and slag residue can present a health and safety concern.

Requires inter-pass and post weld slag removal.

The flux needs replacing of the same on the joint which is not always possible.

Flux is subjected to contamination that may cause weld porosity.

Weld metal chemistry is difficult to control. A change in welding variables especially when

using alloyed fluxes may affect weld metal composition adversely.

Cast iron, Aluminium alloys, Magnesium alloys, Lead and Zinc cannot be welded by this

process.

PLASMA ARC WELDING (PAW)

Plasma arc welding a type of arc welding process that produces coalescence of metals by heating them

with a constricted arc between an electrode and the work piece (transferred arc) or between the electrode

and the water-cooled constricting nozzle (non transferred arc). Plasma is a gaseous mixture of positive

ions, electrons and neutral gas molecules.

Process of heat production:

Gas is heated to an extremely high temperature and ionized so that it becomes electrically conductive.

PAW process uses this plasma to transfer an electric arc to the work piece. The metal to be welded is

melted by the intense heat of the arc and fuses together.

There are two methods in PAW

1. Transferred arc mode:

Arc is struck between the electrode(-) and the work piece(+)

Used for high speed welding and

Used to weld Ceramics, steels, Aluminum alloys, Copper alloys, Titanium alloys, Nickel

alloys.

2. Non-transferred mode:

Arc is struck between the electrode(-) and the nozzle(+), thus eliminating the necessity to have

the work as a part of the electrical system.

Arc process produces plasma of relatively low energy density.

Since the work piece in non-transferred plasma arc welding is not a part of electric circuit, the

plasma arc torch may move from one work piece to other without extinguishing the arc.

ADVANTAGES:

Permits faster metal deposition rate and high arc travel speed as compared to TIG

Uniform penetration with high welding rate is possible

Stability of arc and Excellent weld quality

Can produce radiographic quality weld at high speed

Can weld steel pieces up to about half inch thick, square butt joint

Useful for semi automatic and automatic processes.

Process is very fast and clean

Requires less operator skill due to good tolerance of arc to misalignments;

High penetrating capability (keyhole effect);

LIMITATIONS:

Special protection is required as Infrared and UV Radiations is produced

Consumption of Inert Gas is high

Needs high power electrical equipment.

Gives out ultraviolet and infrared radiation.

Operation produces a high noise of the order of 100dB.

Expensive equipment;

Can weld only upto 25mm thickness.

High distortions and wide welds as a result of high heat input (in transferred arc process).

More chances of Electrical hazards.

RESISTANCE WELDING

Resistance welding is a thermo-electric process in which heat is generated at the interface of the parts to

be joined by passing an electrical current through the parts for a precisely controlled time and under a

controlled pressure (also called force). The name “resistance” welding derives from the fact that the

resistance of the workpieces and electrodes are used in Combination or contrast to generate the heat at

their interface. This is the same principle used in the operation of heating coils. In addition to the bulk

resistances, the contact resistances also play a major role. The contact resistances are influenced by the

surface condition (surface roughness,

cleanliness, oxidation, and platings). The general heat generation formula for resistance welding is:

Heat = I2 x R x t x K

Where

I = the weld current through the workpieces,

R= the electrical resistance (in ohms) of the workpieces,

T= the weld time (in hertz, milliseconds or microseconds), and

K= a thermal constant.

The weld current (I) and the duration of current (t) are controlled by the resistance welding power supply.

The resistance of the workpieces (R) is a function of the weld force and the materials used.

The thermal constant “K” can be affected by part geometry, fixturing and weld force.

The bulk and contact resistance values of the workpieces, electrodes, and their interfaces both cause and

affect the amount of heat generated

ADVANTAGES:

• Very short process time

• No consumables, such as brazing materials, solder, or welding rods

• Operator safety because of low voltage

• Clean and environmentally friendly

• A reliable electro-mechanical joint is formed

A. Resistance Spot Welding

(Method and principle are same as Resistance welding, refer to previous section)

(The picture is only for the purpose of better understanding, not necessarily important for wbut)

Applications of resistance spot welding

Automobile industry

Dental Prosthesis

Batteries

Nuts and Bolts

[ Explanation:

Spot welding is typically used when welding particular types of sheet metal, welded wire mesh or wire

mesh. Thicker stock is more difficult to spot weld because the heat flows into the surrounding metal more

easily. Spot welding can be easily identified on many sheet metal goods, such as metal buckets.

Aluminum alloys can be spot welded, but their much higher thermal conductivity and electrical

conductivity requires higher welding currents. This requires larger, more powerful, and more expensive

welding transformers.

The most common application of spot welding is in the automobile manufacturing industry, where it is

used almost universally to weld the sheet metal to form a car. Spot welders can also be completely

automated, and many of the industrial robots found on assembly lines are spot welders (the other major

use for robots being painting).

Spot welding is also used in the orthodontist's clinic, where small-scale spot welding equipment is used

when resizing metal "molar bands" used in orthodontics.

Another application is spot welding straps to nickel–cadmium or nickel–metal hydride cells to make

batteries. The cells are joined by spot welding thin nickel straps to the battery terminals. Spot welding

can keep the battery from getting too hot, as might happen if conventional soldering were done.

Good design practice must always allow for adequate accessibility. Connecting surfaces should be free of

contaminants such as scale, oil, and dirt, to ensure quality welds. Metal thickness is generally not a factor

in determining good welds.]

Advantages of resistance spot welding

Quick and Easy

No need of Flux and Filler metals

Multiple sheets joined together at the same time

No dangerous open flames

Saves production cost

Dimensional Accuracy

Limitations of resistance spot welding

Difficulty for maintenance or repair

Generally have higher cost than most arc welding equipment

Low tensile and fatigue strength

The full strength of the sheet cannot prevail across a spot welded joint

Resistance Seam Welding

RSEW is modification of spot welding wherein the electrodes are replaced by rotating wheels or

rollers. The electrically conducting rollers produce a spot weld. RSEW can produce a continuous

seam & joint that is liquid and air tight

Description and Operation: The two workpieces to be joined are cleaned to remove dirt, grease and

other oxides either chemically or mechanically to obtain a sound weld. The workpieces are

overlapped and placed firmly between two wheel shaped copper alloy electrodes, which in turn are

connected to a secondary circuit of a step-down transformer. The electrode wheels are driven

mechanically in opposite directions with the workpieces passing between them, while at the same

time the pressure on the joint is maintained. Welding current is passed in series of pulses at proper

intervals through the bearing of the roller electrode wheels • As the current passes through the

electrodes, to the workpiece, heat is generated in the air gap at the point of contact (spot) of the two

workpieces. This heat melts the workpieces locally at the contact point to form a spot weld. Pressure

is applied by air, spring or hydraulically. Under the pressure of continuously rotating electrodes and

the current flowing through them, a series of overlapping spot welds are made progressively along the

joint as shown in the figure. • The weld area is flooded with water to keep the electrode wheels cool

during welding.

\

Resistance Projection Welding RPW

One of the limitations of spot welding is difficulty in maintaining the geometry of the electrode

surface during large scale production. Due to repeated use, the tip of the electrodes erode and need

constant replacing.

Projection welding is a modification of spot welding. In this process, the weld is localized by means

of raised sections, or projections, on one or both of the workpieces to be joined. Heat is concentrated

at the projections, which permits the welding of heavier sections or the closer spacing of welds. The

projections can also serve as a means of positioning the workpieces. Projection welding is often used

to weld studs, nuts, and other screw machine parts to metal plate. It is also frequently used to join

crossed wires and bars. This is another high-production process, and multiple projection welds can be

arranged by suitable designing and jigging.

Advantages of Projection Welding:

More than one spot weld can be made in a single operation, so the operation is very fast.

Welding current and pressure required is less

It helps in obtaining a satisfactory heat balance in welding of difficult to weld combinations of

metals and thickness.

Closer spacing of welds is possible

Electrodes can be shaped to act as assembly fixtures for mass welding of parts

Uniform welds with good finish are produced.

Suitable for automation

Filler metals are not used. Hence clean weld joints are obtained

Disadvantages of projection welding:

Projections cannot be made in thin work pieces.

Thin work pieces cannot withstand the electrode pressure

Additional operation is required after the welding process is over.

Equipment is costlier

(more examples)

SOLID STATE WELDING (SSW)

Forge Welding FOW

Forge welding is a welding process in which components to be joined are heated to hot working

temperature range and then forged together by hammering or similar means. It has a historic

significance in development of manufacturing technology.This process dates from about 1000 B.C.,

when blacksmiths learned to weld two pieces of metal. At present date, it is of minor commercial

importance today except for its variants.

Cold Welding CW

Cold Welding is SSW process done by applying high pressure between clean contacting surfaces at

room temperature.

• Cleaning usually done by degreasing and wire brushing immediately before joining

• No heat is applied, but deformation raises work temperature

• At least one of the metals, preferably both, must be very ductile

• Soft aluminum and copper suited to CW

Applications: making electrical connections

Roll Welding ROW

Roll Welding is SSW process in which pressure sufficient to cause coalescence is applied by means

of rolls, either with or without external heat.

• Variation of either forge welding or cold welding, depending on whether heating of workparts is

done prior to process

• If no external heat, it is called cold roll welding

• If heat is supplied, it is called hot roll welding

Applications of Roll Welding

• Cladding stainless steel to mild or low alloy steel for corrosion resistance

• Bimetallic strips for measuring temperature

• "Sandwich" coins for U.S mint

Diffusion Welding DFW

DFW is a SSW process uses heat and pressure, usually in a controlled atmosphere, with sufficient

time for diffusion and coalescence to occur

• Temperatures 0.5 Tm

• Plastic deformation at surfaces is minimal

• Primary coalescence mechanism is solid state diffusion

Limitation: time required for diffusion can range from seconds to hours

Applications of DFW

• Joining of high-strength and refractory metals in aerospace and nuclear industries

• Can be used to join either similar and dissimilar metals

• For joining dissimilar metals, a filler layer of different metal is often sandwiched between base

metals to promote diffusion

Explosive Welding EXW

ESW is a SSW process in which rapid coalescence of two metallic surfaces is caused by the energy of

a detonated explosive. It is commonly used to bond two dissimilar metals, in particular to clad one

metal on top of a base metal over large areas.

• No filler metal used

• No external heat applied

• No diffusion occurs - time is too short

• Bonding is metallurgical, combined with mechanical interlocking that results from a rippled or

wavy interface between the metals

FRICTION WELDING FRW

FRW is a SSW process in which coalescence is achieved by frictional heat combined with pressure

• When properly carried out, no melting occurs at faying surfaces

• No filler metal, flux, or shielding gases normally used

• Process yields a narrow HAZ

• Can be used to join dissimilar metals

• Widely used commercial process, amenable to automation and mass production

Procedural Steps

(1) Rotating part, no contact;

(2) parts brought into contact to generate friction heat;

(3) rotation stopped and axial pressure applied; and

(4) weld created

Applications:

• Shafts and tubular parts

• Industries: automotive, aircraft, farm equipment, petroleum and natural gas

Limitations:

• At least one of the parts must be rotational

• Flash must usually be removed (extra operation)

• Upsetting reduces the part lengths (which must be taken into consideration in product design)

FRICTION STIR WELDING (FSW)

FSW a cylindrical, shouldered tool with a profiled probe is rotated and slowly plunged into the joint

line between two pieces butted together. Frictional heat is generated between the wear resistant

welding tool and the material of the work pieces. The plasticized material is transferred the front edge

of the tool to back edge of the tool probe and it’s forged by the intimate contact of the tool shoulder

and pin profile. • This heat is without reaching the melting point and allows traversing of the tool

along the weld line.

Advantages

Good mechanical properties as in weld condition

Improved saftey due to absence of toxic fumes

No consumables

Easily automated on simple milling machines

Can operate on all positions (vertical,horizontal) etc

Low environment impact

High superior weld strength

Limitations

Work pieces must be rigidly clamped

Exit hole left when tool is withdrawn.

Large down forces required with heavy-duty clamping necessary to hold the plates together.

Less flexible than manual and arc processes (difficulties with thickness variations and non-linear

welds).

Often slower traverse rate than some fusion welding techniques, although this may be offset if fewer

welding passes are required

Suitable materials:

Copper and its alloys

Lead

Titanium and its alloys

Magnesium alloys

Zinc

Plastics

Mild steel

Stainless steel

Nickel alloys

Applications

Shipbuilding and offshore

Aerospace

Automotive

Railways

Fabrication

Robotics

Personal computers

ULTRASONIC WELDING (USW)

Ultrasonic welding uses high-frequency ultrasonic acoustic vibrations which are applied to materials that

are being held together under pressure to create a solid-state weld. The vibration that results is at a

frequency that is appreciably above the range of human hearing, hence the name ultrasonic.

Working procedure:

The ultrasonic machine places pressure on on the component being welded. The ultrasonic horn is

activated and vibrates the two pieces together at a rate of 20,000 or 40,000 hertz. Weld cycle times are

usually less than 1 second.

Advantages of Ultrasonic Welding

• The ability to weld metals of significantly dissimilar melting points that normally form brittle

alloys when joined.

• Welds can be in close proximity to heat sensitive components, such as electronics or

• plastic components (some electronics may be too sensitive for ultrasonic).

• Ultrasonic welds are made without consumables such as glue, solder or filler.

• Use far less energy usage than traditional joining techniques.

• Does not produce exorbitant amount of fumes

• No caustic chemicals

Limitations:

• Large joints (>250 x 300 mm) cannot be welded in a single operation.

• Specifically designed joints are required.

• Ultrasonic vibrations can damage electric components. • Tooling costs for fixtures are high.

Applications :

Applications for ultrasonic welding that includes metals such as wire, connectors, plastic parts with

relatively similar melting points (when two melting points are too different for ultrasonics, look at the

Trinetics infrared non-contact welder), inserting or staking of metal into plastic, bag making, sealing

containers and packaging, food sealing, medical devices and tools, toys, and many other devices