扩散时间对真空低压渗碳20CrMnTi钢组织与硬度的影响

doi:10.13251/j.issn.0254-6051.2025.02.040

摘要/Abstract

摘要： 采用真空低压脉冲渗碳工艺对20CrMnTi渗碳钢进行表面真空渗碳处理,渗碳后进行840 ℃油淬及180 ℃回火处理,分析扩散时间对渗碳层碳浓度、硬度、显微组织的影响。结果表明,20CrMnTi钢真空低压脉冲渗碳后,当扩散处理时间较短为1125 min时,由于表面碳浓度梯度大,在表层与亚表层之间产生较大内应力,容易产生内裂纹。扩散时间延长至2125 min时,表层碳含量显著降低,由1.30%降低至0.80%,碳含量由表层至心部变化缓慢,表层硬度变化平缓。扩散时间较短时,淬火后表层形成大尺寸碳化物以及大量残留奥氏体,当扩散时间延长后,表层组织中碳化物尺寸及残留奥氏体含量均显著降低。20CrMnTi钢经960 ℃脉冲真空低压渗碳处理52 min+扩散2125 min,降温至840 ℃进行油淬,并在180 ℃低温回火2 h,渗层碳化物等级为1级,心部组织等级为2级,有效渗碳层深度约为3.12 mm,硬度由表层至心部变化平缓,满足渗碳要求。

关键词: 20CrMnTi钢, 真空渗碳, 扩散时间, 微观组织, 硬度梯度

Abstract: 20CrMnTi carburizing steel was subjected to vacuum carburizing treatment by using vacuum low-pressure pulse carburizing technology and quenching and tempering treatment, and the effect of diffusion time on the carbon concentration of the carburized layer, hardness, and microstructure was analyzed. The results show that after vacuum low-pressure pulse carburizing, when the diffusion time is short, e. g., 1125 min, due to the large surface carbon concentration gradient, significant internal stress is generated between the surface and subsurface layers, which can easily lead to internal cracks. When the diffusion time extends to 2125 min, the surface carbon content significantly decreases from 1.30% to 0.80%, the carbon content changes slowly from the surface to the core, and the surface hardness changes smoothly. When the diffusion time is short, after quenching, large-sized carbides and a large amount of retained austenite are observed in the surface layer. When the diffusion time prolongs, the carbide size and retained austenite content in the surface structure are significantly reduced. After 960 ℃ pulse vacuum low-pressure carburizing treatment for 52 min+diffusion for 2125 min, cooling to 840 ℃ for oil quenching, and then tempering at 180 ℃ for 2 h, the carbide in the carburized layer is grade 1, the core microstructure is grade 2, and the effective depth of carburized layer is about 3.12 mm, and the hardness changes smoothly from the surface to core, meeting the requirements of carburizing.

Key words: 20CrMnTi steel, vacuum carburizing, diffusion time, microstructure, hardness gradient

中图分类号:

TG156.8⁺1

于朋翰, 严昊明, 杨帅, 于兴福, 刘永吉, 代友贵. 扩散时间对真空低压渗碳20CrMnTi钢组织与硬度的影响[J]. 金属热处理, 2025, 50(2): 251-255.

Yu Penghan, Yan Haoming, Yang Shuai, Yu Xingfu, Liu Yongji, Dai Yougui. Effect of diffusion time on microstructure and hardness of 20CrMnTi steel after vacuum low-pressure carburizing[J]. Heat Treatment of Metals, 2025, 50(2): 251-255.

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