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PROJECTION WELDING - STUD WELDING AND ITS PROCESS

Projection welding is a modification of spot welding. The current and pressure are localized at the weld section by the use of the 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. 

Projection welding applies to nearly all the metal combinations that can be spot welded, but the design  must be strong enough to support the projection. Annular, or ring projections are often used on screw machine parts such as bosses and studs which are to be welded to sheets up to approximately 3 mm thick. For thicker sheets a dome type of projection seems to work out better. 

Only clean, scale free surfaces should be used in projection welding. A dirty substance will cause much variation in the resistance between the parts being joined, with resulting variation in current flow and weld strength.

Line projection welds are recommended over a point welds when sections are subject to heavy static and dynamic loads. 

Projection for welding is made on sheet metal, cast, forged or machined parts. A variation is called stud welding. A stud with its ends rounded is held in one electrode and pressed against its mating while current flows to heat the weld. The effect of projection welding is obtained with crossed wires, such as might be welded together into a grill.


Projection Welding



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