Research on welding-induced inhomogeneous stress in thick plate EH40 butt joint considering phase transformation

Abstract

In this work, the inhomogeneous residual stress distribution and evolution of thick plate in single-pass full penetration laser welding are systematically investigated using phase transformation model. The material constitutive model considering solid-state phase transformation according to the actual weld microstructure is proposed to predict the inhomogeneous stress distribution of the welded joint. The inhomogeneous stress distributions along the longitudinal, transverse and thickness direction surfaces of the welded joint are systematically analyzed and deeply discussed, respectively. The results show that there is an obvious inhomogeneous distribution of the temperature field between the start-welding, middle section and end-welding position of the weld. It is obviously observed that the top and bottom surfaces of welded joint produce remarkably high stress areas and high stress gradients. The maximum longitudinal and transverse stress gradient values in the top surface are up to 1240.1 MPa and 1175.7 MPa, respectively. It is found that martensitic transformation is the main reason for the inhomogeneous stress distribution including high stress areas and high stress gradients in thick plate welded joint. The current research is beneficial to reduce the detrimental effects of welding-induced inhomogeneous residual stress on thick plate welded joints.