Combining stabilization local PWHT with the secondary heating method to prevent failure of AISI TP347 thick-walled pipe girth welds

The cracking problem of the AISI TP347 thick-walled pipes frequently occurs during welding, stabilization local PWHT, and service in industry. Aiming to effectively reduce the risk of cracking, the welding residual stress distribution and temperature evolution of the AISI TP347 pipe girth welds during stabilization local PWHT were investigated by experiments and finite element analysis. The key process parameters were studied, including temperature uniformity along the thickness direction, heated band width, and cooling modes of the stabilization local PWHT. In addition, the secondary heating method was used to reduce the harmful residual stress on the inner surface of the AISI TP347 pipes. The results show that due to the strong temperature penetration and high energy utilization efficiency of induction heating, the maximum average temperature difference between the inner and outer surfaces without insulation on the inner surface during the holding stage is 40 ℃. Moreover, the holding stage is a dangerous time, and it is easy to crack on the outer surface during the stabilization local PWHT. The maximum axial stress on the outer surface is reduced below the yield strength, which can prevent cracking during heat treatment. Considering the temperature uniformity and heated band width on thermal stress during the holding stage, the heated band width is recommended to be at least 3 R t . Furthermore, slow cooling for residual stress relief is better than air cooling and does not affect the microstructure. Additionally, secondary heating is used after stabilization local PWHT, which can effectively reduce the residual stress on the inner surface. Combining optimized stabilization local PWHT with secondary heating can reduce the risk of cracking and improve the safety and reliability of the AISI TP347 pipe.