Research On Welding Residual Stress In Cold-Stretched Welding Test Plate

In oreder to raise yield stress, decrease cost and achieve the purpose of lightweight, plastic deformation is performed to austenitic stainless steel, which is called cold-stretched technology. This technology has been popularized and used in China in recent years.One key point in the appliance of cold-stretched technology is to pass the weld procedure qualification. Nowadays, the focus of research is on the welding method and welding process, while there is a lack of explore and research on weld residual stress in welding seam. To find out the distribution of weld residual stress and its relationship of cold-stretching is necessary for both better understanding of weld procedure qualification and deeper basis of safety assessment.Based on finite element numerical simulation and experimental analysis, the effect of residual stress on mechanical properties was discussed and the suggestion of specimens’ location on welding test plate was given. The following conclusions were obtained:(1) High weld residual stress existed in austenitic stainless steel weld process test plate. The longitudinal stress was tensile stress with high level in central area and low level in both sides, and the maximum value exceeded the yield stress. The transvers stress showed up with tensile stress in central area and compressive stress in both sides, and it was less than the maximum value of longitudinal stress.(2) Pre-tension had a remarkable effect on improve the heterogeneity of weld residual stress distribution. After a 410MPa-stress-control pre-tension, the weld residual stress in welding seam tended to be at a same level.(3) An inner connected between yield stress matching and weld residual stress was found. The phenomenon that different yield stress matching appeared at different place, turned out to be led by different local plastic hardening caused by weld residual stress at different location. Less deformation would appear in pre-tension because of higher yield stress matching caused by higher weld residual stress.(4) The impact energy from impact specimen and the elongation from tensile specimen with welding joint were effected by weld residual stress. In the case of non-tension test plate, attention to the location of specimens should be paid, and a suggestion was given that impact specimens should not be taken from marginal location of the weld procedure plate in the consideration of safety.