Thermo-mechanical study of single and multi-pass welding of CSEF steel for residual stresses and deformations considering solid state phase transformation

Abstract

The present study involves thermo-mechanical modelling of submerged arc welding of CSEF (Creep Strength Enhanced Ferritic) steel plate of thickness 10 mm as single pass and multi-pass welding. A square butt joint with no edge preparation and a V-butt joint with 15° included angle are considered for SAW welding. The martensitic-austenitic transformation phenomenon in P91 steel was also implemented with specific changes in the properties of the weld and base material. It is observed that SAW process with single pass demonstrates stable residual stress distribution, whereas in multi-pass weld, the residual stresses show uneven distribution across the weld. The longitudinal residual stresses are higher in magnitude comparing to transverse residual stresses for both the welding cases. The single pass SAW weld fusion zone has shown compressive stress throughout the thickness of the plate with maximum value at the top side. However, in multi pass weld, the compressive residual stresses have multiple peak values along the weld thickness. The deflection pattern is not effectively altered with multi pass with slight difference from single pass. Therefore, it is suggested that if possible, single pass weld can be preferred over multi pass weld.