Journal of Northeastern University Natural Science ›› 2015, Vol. 36 ›› Issue (6): 780-785.DOI: 10.12068/j.issn.1005-3026.2015.06.006

• Materials & Metallurgy • Previous Articles     Next Articles

Phase Transformation Behaviors of Boron-Vanadium Microalloyed Steels During the Continuous Cooling

KIM Kwang-su, GAO Cai-ru, DU Lin-xiu   

  1. State Key Laboratory of Rolling and Automation,Northeastern University,Shenyang 110819,China.
  • Received:2014-04-30 Revised:2014-04-30 Online:2015-06-15 Published:2015-06-11
  • Contact: GAO Cai-ru
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Abstract: In order to develop a low cost and high performance boron-vanadium microalloyed steel and establish its TMCP process, the transformation mechanism of the test steel under continuous cooling was studied and the static and dynamic CCT curves of the test steel were also obtained by means of MMS-200 thermo-mechanical simulator. The results showed that, by addition of the trace boron, the stability of overcooling austenite of the vananium microalloyed steel was increased, and the formation of acicular ferrite was promoted, while the bainite can be obtained under wider cooling rates. Compared to the deformed steel, bainite was the major microstructure which obtained in the undeformed steel under the very slow cooling rate even only 0.5℃/s, but when the cooling rate was higher than 5℃/s, fully bainite was obtained in both the deformed and undeformed steels. The stability of austenite was reduced and the formation of the ferrite was promoted by deformation, thus ferrite transformation proceeded under cooling rate lower than 2℃/s and 15℃/s in the boron steel and non-boron steel, respectively. For vanadium microalloyed steel, boron is beneficial to obtaining high strength bainite, therefore when the cooling rate is higher than 5℃/s, Vickers hardness of boron steel is higher than that of non-boron steel under deformed and undeformed status.

Key words: continuous cooling transformation, vanadium microalloyed steel, boron steel, bainite transformation, microstructure

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