Cause Analysis of Low Yield Strength and Tensile Strength of Induction Bending Pipe

The induction bending pipe is an important connector in the oil and gas pipeline, and its function is to adapt to the design requirements of the pipeline and change the direction of the pipeline. Tensile performance is one of the main performance indicators of induction bending pipe, and it is an important basis for induction bending pipe design and safety evaluation. During the tensile test of the Φ813 mm×22.23 mm specification X70M induction bending pipe produced by a steel pipe factory, it was found that the yield strength and tensile strength of the outer arc side pipe body in the transition zone were lower than the standard requirements. The main pipe of the induction bending pipe is a straight seam submerged arc welded pipe, which is bent by a local induction heating process. The local induction heating method is a process in which an induction heating coil is used to form a narrow annular heating belt around the circumference of the curved parent pipe, and the parent pipe is continuously bent while moving. The straight pipe section of the induction bending pipe is not quenched, the bending part is quenched, and then the overall heat treatment of the induction bending pipe is carried out. Tempering heat treatment was adopted, the tempering temperature was 530 °C, the tempering heating rate was 100 °C/h, the temperature was kept for 1 h, and the air cooling process was performed.

The results show that the lower yield strength and tensile strength of the outer arc side of the pipe in the transition zone of the induction bending pipe is because the initial heating temperature of this part is relatively low (below 950 ℃), and the microstructure after quenching and tempering is mostly ferrite. Decreased tensile strength below standard requirements. It is suggested that the heating temperature should be appropriately increased when the pipe bend starts to be pushed so that the mechanical properties of the transition zone can meet the requirements.

Contact Person: Mars Dong

Mobile: 0086 13931703233

Email:[email protected]

www.limingbending.com