The effect of varied welding currents and cycles on thin sheet mild steel with heat treatment process for resistance spot weld

Abstract

This report is about the experimental study on the effects of welding current and cycles on the weldability of resistance spot welded low carbon steel with heat treatment process. The heat treatment processes that been used in this experimental are annealing, normalizing and quenching. Two pieces of low carbon steel plate were welded together as lap joint by using resistance spot welding. The joints were produced using different welding current which were 2 kAmp, 4 kAmp, and 6 kAmp with difference cycles starting from 2, 4 and 6 cycles. To observe the effect of the varied parameter on the joints, three types of testing were carried out which were tensile-shear test, microhardness test and the measurement the size of nugget with heat affected zone (HAZ). Microscopic analysis was used to get the microstructures to achieve the each heat treatment structure. The properties that obtained are correlate with the effect of varies welding currents and cycles. From the result obtained, it was found that the maximum load of tensile shear test increases as the welding current and cycles increased. For the hardness distribution analysis, the increasing welding current and cycles do not give a major influence difference on the of hardness distribution of the welds where the area of HAZ in each samples show the high values. There was also found that the increasing welding currents and cycles increased the weld diameters.