STUDIES ON WELDBONDING OF STEEL SHEET USING PARTICULATE COMPOSITE ADHESIVE

Abstract

Lap joints of 1.0. mm thick mild steel sheet were prepared by conventional adhesive bonding, composite adhesive bonding (adhesive mixed with metallic aluminium or ceramic alumina particles), resistance spot welding and weld bonding (combination of composite adhesive bond and resistance spot weld) processes. The composite adhesives were prepared by using different amount of particles. Before joining the faying surfaces were prepared by polishing with 120, 400 grade emery papers. The layer thickness of the conventional adhesive and the composite adhesive of the adhesive joints was varied by rolling the green joint under different loads under a Teflon - Roller setup, and it was optimized in reference to the shear tensile strength of the adhesive joints of mild steel prepared by using there adhesives. The particle content (wt %) of the composite adhesives was also optimized inreference to shear - tensile strength of the adhesive joints of mild steel prepared by using there adhesives. During resistance spot welding and weld bonding the welding current and welding time were varied. The conventional adhesive bonds, composite adhesive bonds and weld bonds were cured at temperature of 120° for 60 minutes. The joint properties were studied by shear - tensile test. Microstructure of the joint were studied under optical microscope. The nugget size of the resistance spot welded and weld bonded specimens were also studied under optical microscope. Hardness of the nugget and HAZ in the spot welded and weldbonded specimens were studied. The fatigue properties of the weldbonded specimens were studied, the ultimate shear - tensile load carrying capacity of resistance spot weld and weldbonded joints are compared and correlated with the welding parameters. The correlation of the mechanical properties of the joint with their microstructure, nugget size and hardness were discussed. It is observed that strenght of the composite adhesive bond is higher than the conventional adhesive bond. At suitable process parameters the weldbond has been found to achieve significantly higher mechanical properties than those observed in resistance spot weld, especially under the condition of dynamic loading