Heat Treatment of Metals ›› 2022, Vol. 47 ›› Issue (1): 13-18.DOI: 10.13251/j.issn.0254-6051.2022.01.003

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Continuous cooling transformation of austenite in Nb-V microalloyed high-grade pipeline steel

Ma Qilin1,2, Liu Gang3, Zheng Jian4, Yin Shubiao1, Li Ba2, Liu Qingyou2   

  1. 1. Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming Yunnan 650031, China;
    2. Research Institute of Structural Steels, Central Iron and Steel Research Institute, Beijing 100081, China;
    3. China Petroleum Pipeline Engineering Corporation,Langfang Hebei 065000, China;
    4. National Pipe Network Construction Project Management Branch Company, Langfang Hebei 065000, China
  • Received:2021-09-20 Revised:2021-10-26 Online:2022-01-25 Published:2022-02-18

Abstract: Continuous cooling transformation behavior of subcooled austenite of three different Nb, V microalloyed high-grade pipeline steels with different composition was studied by using thermal simulation test machine, dynamic CCT curve was drawn, and three tested steels were analyzed and compared. The microstructure, microhardness value and dynamic CCT curve. The results show that the ratio of 0.05Nb-0.03V can increase the starting transformation temperature of polygonal ferrite, from 650-700 ℃ for Nb steel to 700-800 ℃, narrowing the temperature transition range of polygonal ferrite, and expanding bainite temperature transformation range of Nb steel is 400-650 ℃, and it is expanded to 350-680 ℃. At the same time, the polygonal ferrite phase transformation is suppressed, so that the pipeline steel can easily obtain the required bainite acicular ferrite structure.

Key words: Nb-V microalloyed steel, pipeline steel, dynamic CCT curve, secondary phase precipitation

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