Effect of heat-input and post-weld heat treatment on residual stress and deformation of butt welded joint made by structural carbon steel A516 grade 70

Abstract

Residual stress and welding deformation are unfavorable factors and always exist in the welded joint. They seriously reduce the working capacity of the welded structure, and at the same time disfigure the aesthetics of the welded structure. Therefore, knowing the influence of the welding parameter, specifically the heat-input, on the residual stress and deformation of the welded joint is of great significance, helping to determine the appropriate welding parameter for each specific welding joint. Welding deformation can be easily measured with common measuring instruments, but determining the residual stress in the welded joint by experiment encounters many difficulties, especially in the interior of the material, so this study proposes a solution to determine the residual stress as well as welding deformation by numerical simulation using SYSWELD software with the least cost and fastest time. The research results show that when welding with a higher heat-input, the residual stress in the welded joint will be greater, causing the longitudinal and transverse deformations to be larger. For a butt welding joint made of structural carbon steel A516 grade 70 with 16 mm thickness, it is necessary to weld 4 passes with the heat-input respectively for the minimum residual stress and deformation are q1=2252 J/mm, q2=2828 J/mm, q3=2458 J/mm, and q4=2878 J/mm. The post-weld heat treatment immediately after welding at 595 oC for 40 minutes will reduce residual stress 3.45 times, reduce longitudinal deformation 2.82 times, reduce transverse deformation 1.54 times, and reduce the angular deformation 1.32 times.