Finite Element Modelling of side heating for mitigation of residual stress and distortion in SAW welded P91 steel weld

Abstract

In welding, rapid heating and cooling cycles generate residual stresses and distortion. It may affect the product and might make it useless from a geometric accuracy point of view. These might be reduced by decreasing the temperature gradient of the structure near the weld bead using different mitigation techniques. In this research, one of the thermal tensioning methods was FE modelled as side heating on submerged arc welded P91 steel butt joint. The side heating torch location was optimized to perform a comparative study. The bead geometry was also considered in modelling taking submerged arc welding as a high heat input arc welding process. A volumetric double ellipsoidal heat source and a disc shape, surface heat source models were employed to model welding and side heating processes. Element Birth and death technique was applied to model addition of filler material as molten metal during the welding. It was observed that with side heating, edge deflection, as well as angular deformation, mitigated. The best suitable side heating position for minimum angular distortion and edge deflection collectively was observed at a distance of 26 mm. The residual stress distribution was also improved, particularly in the longitudinal direction. It was concluded that thermal gradient plays an important role in deciding the optimize location of the side heating torch to optimize mitigation effect.