Spot Welding of Iron-based and Cobalt-based Amorphous Alloy Foils (Report 2)

Further examinations and considerations were carried out for Foil S of Fe-Si-B alloy, Foil A of Fe-Co-Si-B alloy, Foil B of Fe-Ni-Mo-B alloy and Foil C of Co-Fe-Ni-Mo-Si-B alloy.Tensile shear strength of Foil B single spot-welded joints somewhat increased with the increase both in electrode force and in charging voltage, but fracture modes of these joints did not change so much. This result suggests that the increased electrode force could not suppress crystallization of Foil B weld nuggets.Tensile shear strength of Foil C single spot-welded joints did not vary so much; these joints were welded at various capacitances up to 700μF and both at a constant peak welding current of 1118 A and. at a higher electrode force of 83.1 N.Crystallization temperature Tx and melting temperature Tm of these foils were estimated through DSC in the course of heating. The order of the ratio Tx/Tm fairly relates to the order of spotweldability of these foils.Weld nuggets of Foil C produced by irradiating a defocused Nd-YAG laser beam pulse maintained the amorphous state, whereas weld nuggets of the other foils crystallized under the same condition.