Effect of plate thickness and weld position on distortion and residual stress of welded structural steel

Residual stresses are generated as a result of non-uniform temperature distribution during welding and particularly cooling process during fabrication of the welded parts. Residual stresses have a major effect on the overall performance of a component in service. In this instant, the residual stress in the form of angular distortion is primarily caused by shrinkage on longitudinal and transversal direction. Several single v-butt joints on structural steel plates of SS400 are investigated by using different plate thickness and welding positions (1G and 3G). GMAW method was used in the welding process. Measurement of residual stress was carried out on a plate with the thickness of 16 mm on longitudinal, transversal and normal direction by using neutron diffraction method. Results showed that the angular distortion of the welded plates increase with the increase of plate thickness. Welding by vertical position (3G position) resulted in a bigger angular distortion compared to flat position (1G position). The distribution of residual stress varied between tension and compression residual stress along welded area with the range of -10 mm to 10 mm. Measurement of residual stress on the longitudinal direction has the greatest value among two other directions.