Microstructure and Mechanical Behavior of X90 Bend Using Local Induction Bending

• Published in: Transactions of the Indian Institute of Metals 2017, Vol.70 (1), p.115-124
• Main Authors: Wang, Bin, Wang, Liang, Jiang, Yong, Xu, Ming, Lei, Bo-bo, Hu, Yiwen, Wu, Deng, Luo, Zhengyang, Liu, Liyan
• Format: Article
• Language: English
• Subjects: Bainite; Bend properties; Bend strength; Chemistry and Materials Science; Corrosion and Coatings; Ductile-brittle transition; Impact strength; Iron constituents; Materials Science; Mechanical properties; Metallic Materials; Microstructure; Phase transitions; Pipelines; Structural steels; Technical Paper; Tensile strength; Transition temperature; Tribology; Yield strength
• ISSN: 0972-2815; 0975-1645
• DOI: 10.1007/s12666-016-0866-z

The microstructure and mechanical properties was studied for API (American Petroleum Institute) X90 pipeline steel bend, which was formed by local induction heat. It was found that X90 pipeline steel parent microstructure consisted of quasi-polygonal ferrite, granular bainite and a small amount of M/A constituents, which provided a good mechanical property. The yield strength, tensile strength, and yield ratio was 786, 876 MPa, 0.90, respectively. After local induction bending, strain-induced phase transition behavior occurred within the deformation zone. The neutral axis position was almost free from force, for quenching-tempering microstructure with small grains. Compared to the parent pipe, the strength decreased after local induction bending. At −10 °C, the Charpy impact absorbed energy was higher, which showed good toughness. In addition, the ductile–brittle transition temperature was studied during −20 ~ −40 °C in outer arc side. At −60 °C, the impact absorbed energy was 27 J, which was not suitable for a pipeline.