How is resistance welding used in making parts for cars?

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application of resistance welding is in making which all parts of automobile and give the details that different parts of any automobile is fabricated by which process.give details using example of car or truck or any other vehicle.

-- ajay kumar singh (ajay_ritin@yahoo.com), March 26, 2003

Answers

Response to application of resistance welding is in making which all parts of automobile and give the details that different parts of any automobile is fabricated by which process

There are many parts in the vehicle, and there are different designs that make this a complex answer.

Most of the sheet metal is resistance spot welded, usually 2 thickness welds, but many three thickness welds also, ("3T"). There will be some 4T welds, and rarely, a 5T weld. These welds are usually in mild steel, and the low carbon content does not pose metallurgical problems.

Most of these welds are made in galvanized metal, and often with sealer or adhesive in the sheets, causing a multitude of problems.

Side beams are put in the doors, usually HSLA, High Strength Low Alloy, a steel processed to have a smaller grain structure, but still low carbon, so still weldable. This material has some problems with quench sensitivity and spring-back, two problems that require opposite actions with the hold time after the weld. This can be very difficult to deal with, as the 1984 Corvette frame was.

I have recently seen high carbon steel as "anti-intrusion" beams in the doors, and even though the carbon content was 5 times the limit of weldability, (which is .5% carbon-equivalency) we were able to make welds that were as strong as the mild steel doors that carried the beams.

The door hinges are often arc welded, with "plunge welding" or "plug welding", and there are problems with fitup and porosity, due to the galvanized coatings. We insist on all four welds on each hinge to be good, even though the specs say 3 out of 4 is fine..

Saturn does the hinges with a giant projection welder, which in my opinion is a much better way to go, but requires more modern thinking.

For frames of the vehicles that use them, robot MIG welding is usually used.

The components use every process you can think of: Shocks are seam welded after final assembly. The ring on the top is resistance welded to the outer sleeve.

Driveshafts are mig welded. Balance weights put on by projection welds.

Some gears are assembled in a vacuum with electron beam welding.

Metal gas tanks get seam welding, and some parts added, like the filler ring, with capacitive discharge welding.

Studs for the power brake booster are projection welded, and sometimes annealed with a post heat afterward.

Many studs are added to the body to attach accessories and insulation, these are "drawn-arc" studs, done with a special gun from TRW or Warren-Emhart.

Seam welding used to be used for the drip rail, which is a rare item now, and used to be used to join inner to outer wheel wells.

Hem welding used to be used for the outer door skins to the inner, but induction heated epoxy is more popular now.

The steel wheels are welded with flash butt welding, but the cast alloy wheels seem to be used everywhere now.

I imagine there is a lot of plastic welding used for trim, but that is beyond my scope of knowledge.

I have seen rods like shift levers welded with friction or inertial welding, not to be confused with friction stir welding, a completely different (and really neat) process.

Brake shoes are projection welded, but I have seen some that were assembled by "toggle-lock" at Bendix.

I am sure I missed a few dozen applications, so I as my fellow welding specialists to add to this.

Dave Bacon

-- David Bacon (dbacon@updatetechnology.com), March 27, 2003.


In today's unitized cars there are almost high strength steel in every panel. We recommend to use "pre-heating mode" all the time to weld on replacement panels.

The older resistance spot welders did not have this mode but the newer ones have. Related features are "pre-heating" and "soft start".

The Inverter technology (1000 to 5000 Hz transformer) has more powerful weld.

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-- Lennart Naslund (datawelder@prodigy.net), July 20, 2003.


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