Strengthening mechanism of Nb(C, N) precipitation and controlled cooling process optimization of Nb-containing steel bars under direct rolling condition

doi:10.13251/j.issn.0254-6051.2021.08.025

Abstract

Abstract: In order to improve the problem of insignificant strengthening effect of Nb-containing steel bars when produced by billet direct rolling process, the kinetic behavior of Nb(C, N) precipitation in austenite was calculated through classical nucleation theory, then verified through field controlled cooling process experiments. The results show that the main precipitation modes of Nb (C, N) in austenite are grain boundary nucleation for rolling by using heating furnace and dislocation nucleation for billet direct rolling, and for the composition of tested Nb-containing steel bars, the corresponding nose tip temperature of PTT curves for grain boundary nucleation and dislocation nucleation is about 1000 ℃ and 900 ℃, respectively. The optimum strengthening effect of Nb(C, N) precipitation in direct rolling process can be obtained by setting multi-stage pre-penetrating water between finishing stands to ensure low-enough final rolling temperature.

Key words: direct rolling process, Nb(C, N) precipitation strengthening, nucleation mechanism, controlled cooling process

CLC Number:

TG142.1

Zhang Hongliang, Feng Guanghong, Wang Baoshan. Strengthening mechanism of Nb(C, N) precipitation and controlled cooling process optimization of Nb-containing steel bars under direct rolling condition[J]. Heat Treatment of Metals, 2021, 46(8): 133-138.

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