Study on mechanical properties of resistance spot welded joints with single pulse unequal thickness of 22MnB5/DP590
In this paper,the single pulse resistance spot welding technology was used to study the sec-tion characteristics and tensile properties of 22MnB5/DP590 spot welding joints with varying thickness section under different welding current and welding time,and the variation of microhardness of spot welding joints was analyzed.The results show that the welding current has little effect on the penetra-tion and core thickness of the base metal.With the increase of welding current,the weld core moves to-wards the thicker DP590 side,and both weld diameter and tensile shear of the joint increase.Compared with the welding current,prolonging welding time has significant effect on the indentation rate and core offset of the joint.With the increase of welding time,the penetration of the base metal and the thickness of the molten core decrease.The diameter of the molten core decreases when the welding time is 1 000 ms,but the tensile shear keeps increasing.The microhardness values of spot welded joints from high to low are as follows:22MnB5 side heat affected zone → molten core zone →DP590 side heat af-fected zone.Under the action of tensile shear,the joint tensile fracture modes include interface fracture,partial interface fracture and core pulling out fracture.It is concluded that given 3.8 kN of welding force the optimum welding conditions for varying section of DP590/22MnB5 are 8.5 kA of welding current and 160 ms of welding time.
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