Can dissimilar materials be spot welded together?
The short answer is yes, but it may be neither simple nor advisable in certain cases if brittle structures are produced by the dissimilar metals mixing in the molten nugget. In particular austenitic stainless steel and carbon steel are not usually spot welded together because the resulting nugget structure risks to be hard and brittle, although it could be studied and modified using the Schaeffler diagram and specially conceived heat treating cycles. Materials having widely different properties require that a heat balance be achieved by compensation. The more conductive material, electrically and thermally, must be heated more as it provides less resistive heat, and the heat is lost more easily by conduction. A common technique uses an electrode of smaller face diameter and higher resistivity facing the more conductive material, or by inserting a foil of poorly conductive material between them. Concerning the number of sheets weldable with a single nugget, normal practice suggests not
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