Question

Explain any two types of resistance welding processes in detail.

Answer 1

1.Resistance Spot welding: Spot welding is employed to join overlapping strips, sheets or plates of metal at small areas. The pieces are assembled between two electrodes, which must possess high electrical & thermal conductivity and retain the required strength at high temperatures, so they are made of pure copper for a limited amount of service, and of alloys of copper or tungsten, or copper and chromium for continuous working. When current is turned on, the pieces are heated at their contacts to a welding temperature, and with the aid of mechanical pressure the electrodes are forced against the metal to be welded.

 

2. Seam Welding is a Resistance Welding (RW) process used for producing continuous joint of overlapping sheets by passing them between two rotating electrode wheels. Heat generated by the electric current flowing through the contact area and pressure provided by the wheels are sufficient to produce a leak-tight weld. Seam Welding is high speed and clean process. Coolant is used to conserve the electrodes and cool the work rapidly to speed up the operation 

 

3.Projection Welding Projection welding is a modification of spot welding. The current and pressure are localised at the weld section by the use of embossed, machined or coined projections on one or both pieces of the Work. The flattening out of these projections under pressure results in good welds at all points of contact. 

 

4.Flash Welding It is a Resistance Welding (RW) process, in which ends of rods (tubes, sheets) are heated and fused by an arc struck between them and then forged (brought into a contact under a pressure) producing a weld The welded parts are held in electrode clamps, one of which is stationary and the second is movable. 

 

5.Resistance Butt Welding: It is a Resistance Welding (RW) process, in which ends of wires or rods are held under a pressure and heated by an electric current passing through the contact area and producing a weld. The process is similar to Flash Welding; however in Butt Welding pressure and electric current are applied simultaneously in contrast to Flash Welding where electric current is followed by forging pressure application. Butt welding is used for welding small parts. Butt Welding provides joining with no loss of the welded materials.