A Computational Model for Improving Weld Residual Stresses in Small Diameter Pipes by Induction Heating

Girth welding can produce tensile residual stresses on the pipe inner surface. Because tensile stresses enhance the possibility of stress corrosion cracking, methods for altering the weld-induced stress state are being investigated. One method, Induction Heating for Stress Improvement (IHSI), involves induction heating the pipe while cooling the inner surface. The method is being evaluated using both experimental and computational studies. This paper presents computational results of a 101.66-mm (4-in.) Schedule 80 stainless steel pipe. Results include comparisons of computed values for residual stresses with laboratory data. Computed values of residual stresses and laboratory data are in agreement and, for this case, clearly show that the IHSI process can change weld-induced tensile residual stresses to compressive values. A comparison of computational results for applying the IHSI process to a stress-free pipe and a welded pipe indicate that for geometry and process parameters considered here, the IHSI-induced compressive residual stresses on the pipe inner surface for these two cases are similar. The experimental results presented here show the feasibility of controlling weld-induced residual stresses. The computational results demonstrate a capability for predicting the observed stress behavior. The computational capability then provides an efficient tool to aid in developing ways for controlling residual stresses for other pipe sizes and weldment geometries.