Journal of Northeastern University Natural Science ›› 2020, Vol. 41 ›› Issue (1): 49-54.DOI: 10.12068/j.issn.1005-3026.2020.01.009

• Materials & Metallurgy • Previous Articles     Next Articles

Effect of Multi-stage Heat Treatment on Microstructure and Properties of High Strength Steel for Flexible Riser

ZHANG Da-zheng1, GAO Xiu-hua1, DU Lin-xiu1, WANG Hong-xuan2   

  1. 1. State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, China; 2. Neptune Offshore Engineering Development Co., Ltd., Tianjin 300384, China.
  • Received:2019-04-28 Revised:2019-04-28 Online:2020-01-15 Published:2020-02-01
  • Contact: GAO Xiu-hua
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Abstract: The microstructure, mechanical properties and hydrogen-induced cracking resistance of high strength steel used for flexible riser after different heat treatments were studied by means of optical microscope(OM), scanning electron microscope(SEM), transmission electron microscope(TEM) and electron back-scattered diffraction(EBSD). The results show that compared with the traditional quenching and tempering treatment, multi-stage heat treatment can refine the microstructure, promote the dispersion of fine precipitates and increase the density of grain boundary so that the strength of the tested steel can be improved greatly. Moreover, since multi-stage heat treatment increases the number of hydrogen traps, reduces the size of precipitates and improves the distribution of hydrogen traps and the hydrogen solubility, the hydrogen-induced cracking resistance of the tested steel is also improved.

Key words: multi-stage heat treatment, flexible riser, low alloy high strength steel, tempered martensite, precipitated phase

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