Welding & Metal Fabrication: Resistance Welding

The deterioration of surfaces is a very real problem in many industries. Wear is the result of impact, erosion, metal-to-metal contact, abrasion, oxidation, and corrosion, or a combination of these. The effects of wear, which are extremely expensive, can be repaired by means of welding. Surfacing with specialized welding filler metals using the normal welding processes is used to replace worn metal with metal that can provide more satisfactory wear than the original. Hardfacing applies a coating for the purpose of reducing wear or loss of material by abrasion, impact, erosion, oxidation, cavitations, etc.

For the successful hard surfacing or overlaying operation a welding procedure should be established. The procedure should be related to the particular part being surfaced and the composition or analysis of the part. It should specify the welding process to be used, the method of application, the prewelding operations such as cleaning, undercutting, etc. The welding procedure should also give the preheat and interpass temperature and any special techniques that should be employed, such as the pattern of hardsurfacing, the method of welding whether beading or weaving, the interface between adjacent beads, and finally, any postwelding operations such as peening and the method of cooling. When a properly developed procedure is followed the service life of the job will be predictable.

Resistance welding is a group of welding processes in which coalescence is produced by the heat obtained from resistance of the work piece to electric current in a circuit of which the work piece is a part and by the application of pressure. There are at least seven important resistance-welding processes.