Metals (Aug 2019)

Influence of Heat Treatment on the Workability of Modified 9Cr-2W Steel with Higher B Content

  • Hyeong Min Heo,
  • Jun Hwan Kim,
  • Sung Ho Kim,
  • Jong Ryoul Kim,
  • Won Jin Moon

DOI
https://doi.org/10.3390/met9080904
Journal volume & issue
Vol. 9, no. 8
p. 904

Abstract

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In this study, the effect of heat treatment on the fracture behavior of alloy B steel with boron (B) contents as high as 130 ppm was investigated. The Alloy B are derived from Gr.92 steel with outstanding creep characteristics. The amounts of minor alloying elements such as B, N, Nb, Ta, and C were optimized to achieve better mechanical properties at high temperatures. Hence, workability of the alloy B and Gr.92 were compared. An increase in the B content affected the phase transformation temperature and texture of the steel. The development of the {111}<uvw> components in γ-fibers depended on the austenite fraction of the steel after the phase transformation. An increase in the B content of the steel increased its α-to-γ phase transformation temperature, thus preventing the occurrence of sufficient transformation under the normalizing condition. Cracks occurred at the point of the elastic-to-plastic deformation transition in the normal direction during the rolling process, thereby resulting in failure. Therefore, it is necessary to avoid intermediate heat treatment conditions, in which γ-fibers do not fully develop, i.e., to avoid an imperfect normalization.

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