Workpiece Property Effect on Resistance Spot Welding

The weldability of resistance spot welding affected by different thermal, physical, and metallurgical properties is extensively investigated by realistically computing transient mass, momentum, energy, species, and magnetic field intensity transport in the alloy workpieces and electrodes. The properties considered are the thickness, radius, equilibrium partition coefficient of workpieces, electrode-to-workpiece electrical conductivity ratio, thermal conductivity ratio, and a joule heat-to-enthalpy change parameter. Resistance spot welding has been widely used in joining thin workpieces in various electronic packaging and manufacturing industries. Understanding of physical mechanisms for easily manipulating and controlling weld qualities in advance is important. This paper accounts for electromagnetic force, heat generations due to contact resistances at the electrode-workpiece interface and faying surface between workpieces, and temperature-dependent bulk resistance of the workpiece. The contact resistances are functions of hardness, temperature, electrode force, and surface condition. The computed results in general dimensionless expressions show that the welding is feasible or onset time is shortened by decreasing thickness, radius, equilibrium partition coefficient of the workpiece, and electrode-to-workpiece electrical conductivity and thermal conductivity ratios, and increasing the joule heat-to-enthalpy change parameter. The corresponding heat transfer and species patterns are also presented.