脱碳对55SiCr弹簧钢感应热处理后表面组织和硬度的影响柳洋波1a.DOC

脱碳对55SiCr弹簧钢感应热处理后表面组织和硬度的影响 柳洋波a，张玮a，佟倩a，孙齐松a,刘奋勇b （a首钢技术研究院；b北京铁科首钢轨道技术股份有限公司） 摘要55SiCr弹簧钢通过预热处理，获得了不同形态的表面脱碳。利用高频感应淬火线和回火炉研究了表面脱碳对感应热处理后以及回火后的组织和硬度的影响。实验结果表明：1、表面出现全脱碳，其在淬火时不能转变为马氏体，淬火、回火后的硬度均在150-300HV之间因此要避免产生全脱碳。2、表面出现部分脱碳，在淬火过程中转变为板条马氏体，其硬度较低。但在后续的回火过程中，该马氏体不变化，造成其硬度和基体差距减小。 55SiCr, 表面脱碳，感应热处理，组织，硬度 of decarburization on microstructure and hardness on the surface of 55SiCr spring steel after induction treatment Liu Yangboa,Zhang Weia, Tong Qiana, Sun Qisonga, Liu Fenyongb （Shougang Research Institute of Technology; b Beijing Railway Sciences and Shougang Track Technology Co. Ltd.） Different morphologies of decarburization of 55SiCr spring steels were produced by preheating treatment. By using of the high-frequence induction line and temper furnace, the influences of decarburization on microstructures and hardness after quenched and tempered were studied. Results showed: 1) When complete decarburization occured in the surface of specimens, it could not be quenched to martensite, and its hardness ranged from 150-300HV after quenched and tempered, therefore complete decarburization should be prevented. 2) When partial decarburization occurred in the surface of specimens, it was quenched to plate-likemartensite with lower hardness than that of the matrix. However, the martensite was not changed a bit during tempering, and the difference of hardness between surface and matrix was reduced. Key Words:55SiCr, decarburization, induction treatment, microstructure, hardness 前言 55SiCr是应用于汽车悬架弹簧的高档用钢。悬架弹簧在汽车行驶过程中承受往复压缩运动，起着缓冲和减震作用，因此对弹簧钢的疲劳性能要求特别高，而弹簧钢表面脱碳将严重损害弹簧的疲劳性能。Gildersleeve[1]的研究结果表明，疲劳强度随着表面碳含量的降低而降低。 感应淬火作为一种被广泛采用的热处理方法，具有启动快、加热速度快、氧化烧损少、生产效率高，便于控制、易于实现自动化，减少设备占地面积，工作环境安静、安全、洁净，维护简单等诸多优点，符合当前生产企业节能降耗、清洁生产及保护环境的发展方向[2]。对于弹簧钢，感应加热工艺具备基本不发生粗规格[3-5]。 由于感应加热速度快、时间短缺乏相关的研究本文重点研究以及部分脱碳对淬火及回火后表面组织硬度的演化。 及方法 用弹簧钢SiCr的化学分数，wt%）C、1.51Si、Mn、Cr、剩余Fe及残余元素。经车削加工，去除表面氧化和脱碳层，Φ14mm×100mm的圆棒。 处理深度和min，然后分别将其空冷和炉冷。 图1预处理工艺控制图。 Fig. 1Preheating treatment process of 55SiCr. 利用北京铁科首钢轨