The purpose of this work is to evaluate the electrode wear behaviour and the distribution of hardness in a joint made by the resistance spot welding process. The lifetime of electrodes was evaluated by examination of the electrode caps after more than 2000 tests with acceptable welds. A microstructural evaluation by optical microscopy (OM) and scanning electron microscopy (SEM) was carried out. The microstructure of the welded joint is primarily composed of ferrite grains. The microhardness testing results indicated a significant increase in hardness in the weld nugget, caused by the formation of martensite in the fusion zone. The hardness results showed lower values in all regions at the end of the useful lifetime of the electrode. The methodology used for selection of welding parameters has highlighted an optimal combination of 200 kgf electrode force and 9-cycle (cy) welding time, to increase the lifetime of the electrode and to achieve more weld points. Still, the cover electrode tends to form brass (Zn + Cu) on the indentation obtained by spot welding, subsequently reducing the electrode life. The results indicate the importance of combining and optimizing the welding parameters in order to reduce the wear of the electrode used for resistance spot welding.

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This work has a purpose to evaluate the electrode wear behaviour and the distribution of hardness in a joint welded by resistance spot welding process. The lifetime of electrodes was evaluated by examination of the electrode caps after more than 2000 points with acceptable welds. A microstructural evaluation by optical (OM) and scanning electron microscopy (SEM) was carried out. The microstructure of welded joint is primarily composed of ferrite grains. The microhardness test results indicated a significant increase in hardness in the weld nugget, probably due to the formation of martensite in the fusion zone. The hardness results for the four welding parameters selected at the end of the useful lifetime of the electrode were lower in all regions. The methodology used for parameter selection has highlighted an optimal combination of 200kgf electrodes force and 9 cy welding time (cycles), where more weld points were obtained, thereby increasing the lifetime of the electrode. The cover electrode tends to form brass (Zn + Cu) on the indentation obtained after spot welding, subsequently reducing electrode life. The results indicate the importance of combining welding parameters to reduce the electrode wear.@en