Welding process of dissimilar metals controlled by PLC and it’s microstructure and properties

The effects of welding current and welding speed on the forming, microstructure and mechanical properties of Q890D steel/AZ31 alloy dissimilar metal welded joints were studied, and the mechanism of welding parameters on the interface zone of Q890D steel/AZ31 alloy dissimilar metal welded joints was analyzed. With the increase of welding current, the alpha-Mg grains in weld zone coarsen obviously, the thickness of interfacial layer increases, the unconnected defects decrease, and the crack sensitivity increases. With the increase of welding speed, the alpha-Mg grains in weld zone refine obviously, the thickness of interfacial layer decreases and the local unconnected defects increase. With the increase of welding current or welding speed, the tensile strength of the welded joint increases first and then decreases, when the welding current is 85 A and the welding speed is 45 cm/min, the welded joint has the highest strength and better appearance. The influence of welding current and welding speed on mechanical properties of Q890D steel/AZ31 alloy MIG welded joint is mainly related to the change of welding line energy and microstructure of interface zone. Keywords: Q890D steel/AZ31 alloy, MIG welding, Welding parameters, Microstructure, Mechanical propertie