Evaluation of Residual Stresses Relaxation by Post Weld Heat Treatment Using Contour Method and X-ray Diffraction Method

The residual stresses in electron beam welded Titanium alloy before and after post weld heat treatment (PWHT) are measured by both of the contour method and X-ray diffraction method. The application of X-ray diffraction method on the surface of welded structure was used to confirm the results of the contour method induced by interpolation from CMM measuring position which is limited near the structure surface. The welding residual stresses are characterized, as well as the residual stress relaxation by PWHT at soaking temperatures of 500 and 650 °C and holding times ranging from 0 min to 2 h respectively. The measured results show that the maximum welding residual stress without PWHT is 550 MPa located inside the plate. The relaxation of the residual stresses from PWHT mainly depend on soaking temperature, and occurs most both in the heating stage and holding stage. The residual stresses are reduced to a limited value after the PWHT with soaking temperature of 650 °C and 2 h.