Mechanism of cryogenic treatment improving electrode life for spot welding zinc-coated steel sheet

In this paper,to improve electrode life of resistance spot welding of hot dip galvanized steel sheet,the way of deep cryogenic treatment of electrodes is put forward.Electrodes for spot welding are treated by deep cryogenic treatment with different deep cryogenic treatment parameters.Deep cryogenic treatment electrodes life experiment is carried out and the experiment results are compared with the non-deep cryogenic treatment electrodes life experiment ones.The electrical conductivities of the deep cryogenic treatment electrodes and the non-deep cryogenic treatment electrodes are tested.The SEM area scanning and the SEM back scattering of the electrodes are carried out.The grain degree of deep cryogenic treatment electrodes and the non-deep cryogenic treatment electrodes are observed by X-Ray Diffraction.The mechanism of cryogenic treatment improving electrode life for resistance spot welding of hot dip galvanized steel plate is summarized.The experimental results show that deep cryogenic treatment makes Cr,Zr in deep cryogenic treatment electrodes emanate dispersedly and makes the grain of deep cryogenic treatment electrodes smaller than non cryogenic treatment ones,so that the electrical conductivity and the thermal conductivity of deep cryogenic treatment electrodes are improved very much,which make electrode life for spot welding hot dip galvanized steel sheet improve obviously.