High Temperature Materials and Processes (Jul 2021)

Effects of composition and strain rate on hot ductility of Cr–Mo-alloy steel in the two-phase region

  • Zheng Yaxu,
  • Shen Wei,
  • Zhu Liguang,
  • Guo Zhihong,
  • Wang Qi,
  • Feng Jie,
  • Li Yongliang,
  • Cao Ruifang,
  • Wu Jiayi

DOI
https://doi.org/10.1515/htmp-2021-0025
Journal volume & issue
Vol. 40, no. 1
pp. 228 – 240

Abstract

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The hot tensile tests were conducted in this study to investigate the effects of Nb, B, Mo, and V on hot ductility of 25CrMo alloy steel in a temperature range of 650–850°C with strain rates of 0.005 and 0.5 s−1. Besides, the influences of ferrite transformation and precipitates on hot ductility were also investigated by the use of SEM and TEM. Thermo-Calc and J Mat Pro were used for calculating equilibrium precipitates and CCT curves, respectively. The results indicated that the hot ductility is deteriorated with the addition of 0.04% Nb due to Nb(C,N) particles and ferrite transformation. The addition of B inhibits ferrite transformation and improves hot ductility. The hot ductility is improved with increasing strain rate from 0.005 to 0.5 s−1 due to the nucleation and growth behavior of ferrite. The fast strain rate promotes nucleation of ferrite; however, the ferrite has no sufficient time to grow up. The addition of Mo inhibits ferrite transformation and improves hot ductility. The addition of 0.12% V has no obvious effect on ferrite transformation. The hot ductility has deteriorated a little with the addition of 0.12% V due to the solution V that increases stress during hot deformation.

Keywords