奥氏体化温度对空冷条件下40CrMnSi2Mo钢组织与力学性能的影响

doi:10.13251/j.issn.0254-6051.2024.12.001

摘要/Abstract

摘要： 通过光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)和激光扫描共聚焦显微镜(LSCM)等研究了不同奥氏体化温度(875~975 ℃)对新型Cr-Mn-Si系高强度中碳低合金40CrMnSi2Mo钢在空冷条件下的微观组织和力学性能的影响规律。结果表明,奥氏体化温度为875 ℃和900 ℃时,空冷条件下基体以马氏体组织为主,基体中存在少量未溶相(NbC),原奥氏体晶粒细小稳定性高,抗拉强度分别为1997 MPa和2003 MPa,断后伸长率分别为11.0%和12.0%,断裂韧度分别为70.3 MPa·m^1/2和73.6 MPa·m^1/2。奥氏体化温度为975 ℃时,NbC溶解度增加,钉扎晶界作用减弱,奥氏体晶粒长大稳定性降低,空冷条件下获得粗大贝氏体/马氏体复相组织,抗拉强度为1980 MPa,断后伸长率为10.5%,断裂韧度仅为77.6 MPa·m^1/2。奥氏体晶粒细化对40CrMnSi2Mo钢的强韧性改善效果不明显。试验钢在950 ℃奥氏体化处理后获得超细贝氏体/马氏体复相组织,力学性能达到最佳匹配,抗拉强度为最大值2040 MPa,断后伸长率为12%,同时具有较高的断裂韧度值(86.6 MPa·m^1/2)。

关键词: 2 GPa级40CrMnSi2Mo钢, 贝氏体/马氏体复相组织, 抗拉强度, 断裂韧度

Abstract: Effect of austenitization temperature (875-975 ℃) on the microstructure and mechanical properties of the novel Cr-Mn-Si series high strength medium carbon low alloy 40CrMnSi2Mo steel under air cooling condition was studied by means of optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and laser scanning confocal microscope (LSCM). The results show that when austenitized at 875 ℃ and 900 ℃, the microstructure is dominated by martensite with a small amount of the undissolved precipitates (NbC). The prior austenite grains are fine and stable. The tensile strength is 1997 MPa and 2003 MPa, the elongation is 11.0% and 12.0%, and the fracture toughness is 70.3 MPa·m^1/2 and 73.6 MPa·m^1/2, respectively. When austenitized at 975 ℃, the solubility of NbC increases and the pinning effect decreases. The growth of austenite grain size decreases the thermal stability so that the coarse bainite/martensite multiphase is obtained under air cooling. The tensile strength is 1980 MPa, the elongation is 10.5%, and the fracture toughness is only 77.6 MPa·m^1/2. The effect of the austenite grain refinement on the strength and toughness of the 40CrMnSi2Mo steel is not obvious. The fine bainite/martensite multiphase can be obtained after austenitizing at 950 ℃. The mechanical properties achieve an excellent combination, with the tensile strength of 2040 MPa, the elongation of 12% and the fracture toughness of 86.6 MPa·m^1/2.

Key words: 2 GPa grade 40CrMnSi2Mo steel, bainite/martensite duplex microstructure, tensile strength, fracture toughness

中图分类号:

TG142.1

于林然, 刘赓, 杨卓越, 苏杰, 宁静, 丁雅莉. 奥氏体化温度对空冷条件下40CrMnSi2Mo钢组织与力学性能的影响[J]. 金属热处理, 2024, 49(12): 1-8.

Yu Linran, Liu Geng, Yang Zhuoyue, Su Jie, Ning Jing, Ding Yali. Effect of austenitization temperature on microstructure and mechanical properties of 40CrMnSi2Mo steel under air cooling[J]. Heat Treatment of Metals, 2024, 49(12): 1-8.

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