Study on the Heating Process and Properties of X80 Induction Heated Bending Pipe

Induction heated bending pipe is an important connecting piece widely used in natural gas pipeline. As the persistent development of natural gas pipeline project, the X80 induction heated bending pipe needed to be developed and studied. The local induction quenching process and the wholly induction quenching process were adopted to develop the Φ1219mm×22mm X80 bending pipe in this paper. The effects of different technologies on the bending pipe property were studied. Based on the pipe-bending machine that can not apply the continuous wholly induction quenching process, a multiple-step wholly induction quenching process was proposed and realized. The study results show that for the X80 bending pipe manufactured via the local induction quenching process, the strength of straight part is higher than the bend part. The toughness of welding seam and heat-affected zone at straight part is lower. The match of property between the straight part and the bend part is not perfect. The continuous wholly induction quenching process improve effectively the toughness of bending pipe, reduce the strength and yield ratio to a certain extent, so the match of property between the straight part and the bend part is reasonable. The multiple-step wholly induction quenching process can also improve the property of the straight part in bending pipe. The property of intermediate zone by double quenching has no clear changes. This kind of process is suitable for the pipe-bending machine that can not provide continuous wholly induction quenching process.