Finite element analysis of in- process thermal mitigation of welding induced residual stresses in 9Cr-1Mo-V steel butt joint considering phase transformation

Abstract

In the current study, thermal load based in- process mitigation techniques have been analyzed its effect on residual stress distribution in submerged arc square butt welded 10 mm thick 9Cr-1Mo-V steel plate. A FE model of SAW processed P91 steel square butt joint is established considering material properties, process parameters and its specific solid-state phase transformation phenomenon to compare experiment results. Further, the in-process mitigation cases are simulated based on established FE model. Transient side heating is found to be more effective in reducing residual stresses transversely the weld region without considering solid state phase transformation. However, transient side heating is not productive for P91 steel welds considering phase transformation. Heat sinking causes sudden drop in residual stress values in HAZ region, while weld bead region showed intense compressive residual stresses for P91 steel weld considering phase transformation. The combined side heating and heat sinking enhanced the mitigation results and yield lower magnitude of residual stress value in weld bead region compared to individual heat treatment. It developed a crown shape surficial distribution of residual stress across the weld bead. It is discovered that in- process mitigation can be effective for P91 steel weld, if mitigation of residual stress is the sole objective.