Investigation on Residual Stress Evaluation of T-joint Considering Rolling Stress and Heat Treatment Stress Relaxation

Objectives The welding residual stress seriously affects the mechanical properties and fracture strength of welded structures, so it is necessary to accurately evaluate and reduce the stress. At the same time, TMCP (Thermal Mechanical Control Process) is used in high strength thick steel plates, and there will be complex initial stress inside the plate, which will significantly affect the accurate evaluation of welding residual stress. Methods With 30mm thick EH550 steel sheet as the research object, the common CO2 gas shielded welding was used to complete the multi-layer and multi-pass welding of T-joint. After the welding was cooled to room temperature, the residual stress was measured by non-destructive X-ray diffraction method. The test of removing residual stress by annealing and heat treatment of the joint was completed, and the residual stress after heat treatment was measured. The macro metallography of T-joint cross section was obtained. The finite element mesh model is established according to the macro metallography and welding process parameters of weld, and the rolling stress distribution function of high strength steel plate is proposed. Transient thermal-elastic-plastic finite element analysis is performed in the general finite element software ANSYS to simulate residual stress during welding and heat treatment. Results The predicted residual stress after welding and heat treatment is in good agreement with the measured data. After heat treatment, the extreme residual stress decreased from more than 500MPa to 105MPa. Conclusions The relevant research results can be used for the accurate evaluation and analysis of the welding residual stress of high strength steel plate and the formulation of the process of eliminating the residual stress by annealing heat treatment.