Research On Operational Life Span And Applications Of Coated Electrode Resistance Welding For Galvanized Steel

In this paper, Ni / Ceramic Coated were deposited on the Cr-Zr-Cu electrode by spark deposition technology. And the prepared coated electrode was used for the resistance spot welding of galvanized steel. The electrode life was comprehensively evaluated by the standards of nugget diameter and shear strength of resistance spot welding joints. Scanning electron microscopy and energy dispersive spectroscopy were used to analyze the morphology, structure and composition of both inactive uncoated and coated electrodes. And on this basis, the failure mechanism of both kinds'electrodes in the resistance spot welding process was also analyzed in this paper. Through spot welding tests, the impact of process parameters on the nugget diameter was analyzed, and the coated electrode welding process parameters were optimized by orthogonal test at the same time.The operational life span of uncoated electrode is more than 800 times, while the coated electrode is more than 2,000 times. Compared to the uncoated electrode, the operational span life of coated electrode is 2.5 times more than the uncoated. The mechanism of coated electrode increased the operational span life of the resistance spot welding for galvanized steel are mainly because of two points: improving the plastic deformation resistance of the electrode and restraining the metallurgical reaction between electrode and Zn.When the nugget diameter meets the requirements, the current coated electrode required was 90% of the uncoated, which means 10% energy savings. The time that nugget diameter of coated electrode needed to meet the requirements is shorter than the uncoated ones, so using the coated electrode can improve production efficiency and save both time and energy. And apart from that, the electrode pressure which coated electrode need to reach the maximum nugget diameter is slightly larger than the uncoated ones, but the maximum nugget diameter of coated electrode is bigger than the uncoated. The best process parameters for coated electrode resistance spot welding were as follows: Welding current 8KA, welding time 8CYC, and electrode pressure 3.0KN.The practical application of the coated electrode in products shows that: the coated electrode has longer operational span life and no regular grinding and replacement are needed for the coated electrode, which means greatly improve the efficiency of production. The current uncoated electrode required was 10% of the coated, which means 10% energy savings.