What is welding-
The welding is a process of joining two similar or dissimilar metals by application of heat with or without the application of pressure and addition of filler material. Welding is mainly used for joining metals and their alloys, however it can also be used for joining of other materials such as thermoplastics. Now - a - days welding is extensively used in fabrication of automobiles, aircrafts, ships, electronic equipment, machinery, home appliances, etc., as an alternative of casting or forging or as a replacement of riveted or bolted joints. Welding is also used as a repair medium e.g. , to reunite metal at a crack or to build up a small part that has broken off such as a gear tooth or a bearing surface.
Weldability depends on the following-
(a) Thermal welding
(b) Melting welding
(c) Surface condition
(d) Thermal expansion
(e) Change in microstructure.
Welding can be broadly classified into following two categories-
(a) Plastic welding
(b) Fission welding.
(a) Plastic welding-
In plastic or pressure Welding process, pieces of metal to be joined are heated to a plastic state and then forced together by external pressure. In this method no filler material is used. Plastic welding may be further classified as follows-
 |
| Plastic welding |
(b) Fusion welding-
In fusion or non-pressure welding, the edges of the workpiece to be joined are heated to a temperature above the melting point of the metal and then allow to solidify. A filler material is used during fusion welding. Fusion welding may be further classified as follows- |
| Non plastic welding or fission welding |
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