COLD WELDING

CONTENTS:

PRINCIPLE

DEFINITION

CHARACTERISTICS

PROCESS

APPLICATION

ADVANTAGES & DISADVANTAGES

CONCLUSION

PrinciplesCold welding is a method for joining non-ferrous metals and their alloys without using heat, fillers or fluxes. Round wire sections, dissimilar materials and materials of different sizes can all be welded with BWE's proven cold welding technology. A cold weld is generally stronger than the parent material and has the same electrical characteristics.

SolidState

Welding

Electrical

Chemical

Mechanical

Pressure

Pressure &Deformation

Cold Weld

Cold welding is a solid-state process in which pressure is used at room temperature to produce coalescence of metals with substantial deformation at the weld. Both butt and lap joints can be cold welded.

Die

Flash

A: Lap both sides indented E: Draw Weld B: Lap One side indented F: Wire Lap (before and after)C: Edge both side indented G: Mash Cap Joint D: Butt in Tube H: Butt (before and after)

AWS Welding Handbook

At least one of the metals must be ductile without excessive work-hardening.

Total absence of applied heating.Dissimilar metals can be joined.Surface preparation is important

The parts to be welded are first cleaned.

A short section of the part is sheared.

The parts are clamped in a die with some initial extension.

A forging force is applied to complete welding.

Dies

Workpiece Workpiece

Before welding

After welding

Cold welded butt joints are used in the manufacturing of aluminum, copper, gold, silver, and platinum wire.

Most commonly, successive reels of wire are joined for continuous drawing to a smaller diameter.

Aluminum alloys used in cold welding include: 1100, 2319, 3003, all 5000 series, 6061 and 6201.

Equipment

A manually operated cold welding machine (courtesy AWS handbook).

States of Upset During ButtCold Welding

Single Upset Cold Weld inType 1100 Aluminum Wire

Courtesy AWS handbook

Stages in Multiple Upset Cold WeldingAWS Welding Handbook

AWS Welding Handbook

Transverse Flow Lines in aCold Welded Butt Joint

Courtesy AWS handbook

Can Effect Joint Efficiency

Multiple Upset Cold WeldAWS Welding Handbook

Key advantages:

1. Advantages:•Fastest repair capabilities•Virtually no deformation•Limited dismantling.

Disadvantages While speed is an advantage to assemblers, it can also be a limitation. The process is so fast that it does not lend itself to deep drawing of material since the material does not have time to stretch.

"The outer member to be welded must be accelerated at a speed greater than 300 meters per second," says Plum. "When a body moving that fast meets another, it will try to displace it. This is what causes the weld. The movable body meets an immovable body.

CONCLUSIONTransfer of metal and the degree of surface damage during, rubbing are governed by the shear strength of the weld centers formed. The heat developed and the pi tion afforded by oil or other films are here important. For this reason a true picture of the transfer of metal during friction can be obtained only from experiments with the lubricant to be actually used in service in the particular antifriction application.

REFRENCESwww.formulasun.org www.yourdictionary.cOM

www.google.co.in

www.wikipedia.com