Effect of Nb on CCT curves of Q345 low-Mo fire-resistant steel

doi:10.13251/j.issn.0254-6051.2021.02.005

Abstract

Abstract: Effect of Nb on continuous cooling transformation (CCT) curves of Q345 low-Mo (about 0.25wt%) fire-resistant steel was studied by measuring CCT curves of two Q345 steels with different Nb content. The results show that the CCT curve of Q345 low-Mo fire-resistant steel moves to the right and the critical cooling rate of bainite transformation decreases with Nb addition. At the same time, Nb addition can reduce the critical transformation temperature of austenite and inhibit the transformation from austenite to pearlite, which is beneficial to bainite transformation. In addition, in order to obtain the ideal microstructure (F+B+P) of the Q345 low-Mo fire-resistant steel, the optimal cooling rate of tested steel without addition of Nb should be about 0.28 ℃/s, and that of tested steel with addition of Nb should be about 0.14 ℃/s.

Key words: Nb, fire-resistant steel, CCT curve

CLC Number:

TG142.1

Wan Rongchun, Sun Feng, Fu Liming, Shan Aidang. Effect of Nb on CCT curves of Q345 low-Mo fire-resistant steel[J]. Heat Treatment of Metals, 2021, 46(2): 25-29.

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