Impact of process parameters on temperature and residual stress distribution of X80 pipe girth welds

Abstract

This paper studies the impact of process parameters on the temperature field and residual stress distribution of X80 pipe girth welds. The process parameters investigated were welding power, pre-heating temperature, inter-pass temperature, welding speed, diameter-to-thickness ratio (D/t) and restraint. 2D axisymmetric finite element models with a 8-pass girth weld in the middle were established. The thermal analysis was carried out by using the double ellipsoid heat source model. This was followed by mechanical analysis to study the residual stress distributions. The results revealed that the distribution of axial and hoop residual stresses along the center of the weld was generally symmetrical. The welding power had the greatest impact on the maximum temperature of the molten pool. The other parameters had the following sequence in terms of their influence on the maximum temperature of the molten pool: D/t, welding speed, inter-pass temperature and pre-heat temperature. The sequence from large to small that the process parameters affecting the maximum axial residual stress is: restraint > power > inter-pass temperature > pre-heat temperature > D/t > welding speed. However, the sequence changed for the maximum hoop residual stress as: welding speed > inter-pass temperature > power > pre-heat temperature > D/t > Restraint. In general, all process parameters had a greater influence on the axial residual stress than the hoop residual stress.