Variation in the Properties of Spot Weldments of Cold Rolled Mild Steel Welded with Filler Metal by Preheating

Abstract

Filler metal addition has been verified as an effective way to refine mechanical behaviour of cold rolled mild steel in resistance spot welding.Negligible quantity of filler metal if added to the spot weld is found to improve mechanical properties of spot weldments , if no variation in composition of base metal and filler metal is allowed.. Looking at practical applications, sensitivity of the Resistance Spot Welding process with filler metal to variation in preheating treatment were experimentally investigated.Filler metal quantity was from 30 mg to 70 mg and preheat heat treatment was kept between 20% to 60%.The material of the filler metal is same as that of base metal and was added at the centre of overlap in lap joint.The experimentation was carried out by spot welding of specimen varying filler metal from 30 mg to 70 mg maintaining preheating cycle constant at 20%.The experimentation was then repeated for different preheat cycles.For 20% to 60% of preheat cycle, maximum breaking point was found to be varying linearly with increase in preheat level. Overall improvement in load bearing and energy absorption capability was observed as majority of specimen fail under the button pullout mode.