The small-scale resistance spot welding of refractory alloy 50Mo-50Re thin sheet

This paper is a review of the recent studies of small-scale resistance spot welding (SSRSW) of a refractory alloy 50Mo-50Re thin sheet (0.127 mm thick). The effects of seven important welding parameters—hold time, electrode material, electrode shape, ramp time, weld current, electrode force, and weld time—were studied systematically in an attempt to optimize the welding quality. The diameter of a weld nugget was found to be only 30–40% of the electrode diameter in SSRSW. This was due to the relatively low electrode force used in SSRSW compared with the high electrode force employed in large-scale resistance spot welding (LSRSW) where the diameter of the nugget was almost 100% of the electrode diameter. Large pores often found in the nugget during SSRSW could result from shrinkage during solidification due to fast cooling or fromdue to agglomeration of residual volatile elements absorbed during powder metallurgy processing of the material.