Heat Treatment of Metals ›› 2024, Vol. 49 ›› Issue (5): 162-167.DOI: 10.13251/j.issn.0254-6051.2024.05.027

• PROCESS RESEARCH • Previous Articles     Next Articles

Effect of cooling rate on phase transformation behavior of ultra-high strength X90M pipeline steel

Liu Gan1,2, Kong Xianglei1,2, Huang Minghao1,2, Wang Yang1,2, Zhang Yinghui1,2   

  1. 1. State Key Laboratory of Metal Material for Marine Equipment and Application, Anshan Liaoning 114009, China;
    2. Iron and Steel Research Institute of Angang Group, Anshan Liaoning 114009, China
  • Received:2023-10-28 Revised:2024-03-14 Online:2024-05-25 Published:2024-06-28

Abstract: Phase transformation behavior of X90M pipeline steel at different cooling rates was studied by Gleeble-3800 thermal simulation tester. The dynamic CCT curves were plotted based on the thermal expansion curve, Vickers hardness, and microstructure analysis results. The results show that with the increase of cooling rate, the microstructure of the X90M pipeline steel undergoes polygonal ferrite (PF)+bainite (B) → acicular ferrite (AF) → bainitic ferrite (BF) transformation in turn, and its microhardness also gradually increases, showing an overall upward trend. And with the increase of cooling rate, the ferrite is in blocky, acicular and flat morphology in order. Meanwhile, the number of martensite/austenite(M/A) islands increases, the size is refined and the distribution gradually disperses. Under laboratory conditions, adopting a cooling rate of about 30 ℃/s can enable the X90M pipeline steel to obtain a microstructure with high-density dislocations and dispersed small M/A islands.

Key words: X90M pipeline steel, CCT curves, phase transformation behavior, cooling rate, microhardness

CLC Number: