LAUSR

Resistance spot welding (RSW) process is the major joining technique in the automobile industry due to its high speed and relatively low cost. Although RSW is widely used, it is difficult to ensure the consistency of joint quality in real production, a common phenomenon in resistance spot welding is expulsion, characterized by the ejection of molten metal during welding linked to excessive current densities. To determine the spot weldability of steels the available welding current range is evaluated. This range is defined by the maximum current without splash and the minimum current still giving an acceptable size of the weld diameter. Previous studies show that the static and dynamic behaviors of spot welders have complex influences on the resistance welding process and weld quality. A criterion of dynamic stiffness has been established here to explain why the welding current range of a given steel grade can depend on the structural stiffness of spot welding machine.