To investigate the distribution of longitudinal residual stress and influencing factors of high-strength submerged arc welded circular steel tubes

the nonlinear physical properties of high-strength steel and the latent heat of phase change during the welding process were considered. The uniform heat source model was used to simulate the gas metal arc welding (GMAW) heat source of the first pass

and the double ellipsoid heat source model was used to simulate the submerged arc welding (SAW) heat sources of the second and third passes. The element life and death function was applied to simulate the weld growth process

and continuously modify the surface area of the heat transfer between steel tube and air between the welding load steps. The thermal-structural coupling transient analysis of the three-pass welding process was carried out

and the influences of welding direction

interpass temperature

and welding speed on the distribution of longitudinal residual stress were discussed according to the extended finite element model. Comparison with the test results shows that the finite element model could predict the welding longitudinal residual stress and provide suggestions for the welding process. The longitudinal residual stress distribution pattern of the high-strength submerged arc welded circular steel tube was: the residual tensile stress near the weld was close to the yield of the steel tube

and as the distance from the weld increased

it changed to the maximum value of the residual compressive stress and then became the residual tensile stress again. The welding process is recommended as follows: the first and third passes have the same welding direction but the second pass is reversed

the welding speeds of GMAW and SAW are 4 and 6 mm/s respectively

and the interpass temperature should be kept to a minimum value within the controllable range of the cooling time cost.