Research on Resistance Spot Welding Process Window and Spot Welding Consistency of DH590 Cold Rolled Sheet and Its Galvanized Sheet
The process window and spot welding consistency tests were carried out for DH590 cold rolled sheet and its galvanized sheet by resistance spot welding.The tensile-shear test and cross tensile test were carried out for the solder joints,and the microstructure,hardness distribution and fracture morphology of the spot welded joints were analyzed.The results show that compared with that of the cold rolled sheet,the welding process window of DH590 galvanized sheet moves about 2 kA to the right,and the process window range is narrower,the nugget formation is more sufficient and the nugget diameter is bigger when the splash occurs.The microstructures of nugget zone of the both spot welded joints are lath martensite,while the average hardness of nugget zone of the galvanized sheet is higher.In the spot welding consistency test,the nugget diameter reaches the standard requirement,and there is no obvious fluctuation.The failure mode of the solder joints in the process window is mainly pull-out fracture.Lots of shear dimples are observed on the fracture,which shows the characteristics of plastic fracture.
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