Spheroidizing annealing of 42CrMoVNb high strength bolt steel

doi:10.13251/j.issn.0254-6051.2020.04.034

Abstract

Abstract: Based on Ac₁ and Ac₃, i.e. 773 ℃ and 811 ℃ respectively, evaluated by the thermal simulation experiment, the spheroidizing annealing treatment with different heating temperatures and holding time was carried out on 42CrMoVNb high strength bolt steel. The spheroidizing evolution and hardness of the steel were analyzed by means of optical microscope, scanning electron microscope, Vickers hardness and cold heading tests. The results show that after spheroidizing annealing at 780 ℃(above Ac₁) for 0.5 h followed by low cooling to 710 ℃ for 6 h or at 750 ℃ (below Ac₁) for 3 h followed by slow cooling to 710 ℃ for 6 h, the steel has good spheroidized structure with low hardness, meanwhile, the morphology of carbides tends to be spherical and uniformly distributed, and the steel has good plasticity and cold heading properties. When spheroidized annealing at 750 ℃, the longer the holding time, the more obvious of carbide spheroidization.

Key words: 42CrMoVNb high strength bolt steel, carbide, spheroidizing annealing

CLC Number:

TG142.1

Yang Zhou, Zhao Xiuming, Sun Jianyu, Liu Kaixuan, Feng Yuyang, Wang Yangxin, Wang Lei. Spheroidizing annealing of 42CrMoVNb high strength bolt steel[J]. Heat Treatment of Metals, 2020, 45(4): 161-165.

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