18CrNiMo7-6钢的可控气氛高温渗碳工艺

High temperature carburizing process of 18CrNiMo7-6 steel in controlled atmosphere

基于机车用重载齿轮的热处理工艺要求,对18CrNiMo7-6钢进行920~1050℃的伪渗碳工艺处理,横向对比研究了试验钢经常规渗碳以及不同温度高温渗碳处理后的组织及力学性能;结合Aichelin计算机辅助模拟设计软件工艺模拟结果,制定高温渗碳工艺流程,对18CrNiMo7-6钢制齿轮进行高温渗碳处理,并与常规渗碳齿轮进行了组织及性能的对比研究。结果表明,与热处理前相比,经不同温度和时间的伪渗碳处理后,18CrNiMo7-6钢的综合力学性能均有所下降,但通过控制渗碳后的冷却过程,可以显著提高其最终热处理后综合力学性能;增加渗碳温度和碳势,可以大幅提高渗碳效率;对18CrNiMo7-6钢制齿轮进行最高温度1050℃高温渗碳,渗碳效率提高约65%,经高温渗碳后,齿轮组织、综合力学性能以及单齿弯曲疲劳强度相比于常规渗碳齿轮均未降低。

Based on the heat treatment process requirements of heavy load gear for locomotive,pseudo-carburizing process was carried out on 18 CrNiMo7-6 steel within temperature range of 920-1050℃.The microstructure and mechanical properties of the tested steel after conventional carburizing and high temperature carburizing at different temperatures were compared.Combined with the process simulation results of Aichelin computer aided simulation design software,high temperature carburizing process was developed,and the high temperature carburizing process of the 18 CrNiMo7-6 steel gear was carried out,and the microstructure and properties of the gear were compared with those of the conventional carburizing gear.The results show that the comprehensive mechanical properties of the 18 CrNiMo7-6 steel are decreased after pseudo-carburizing at different temperatures and time,compared with that before heat treatment,but the comprehensive mechanical properties of the 18 CrNiMo7-6 steel can be significantly improved by controlling the cooling process after carburizing.Increasing carburizing temperature and carbon potential can greatly improve carburizing efficiency.The carburizing efficiency of the 18 CrNiMo7-6 steel gear is increased by about 65%at the temperature of 1050℃.Compared with the conventional carburizing gear,the microstructure,comprehensive mechanical properties and single-tooth bending fatigue strength of the gear are not decreased after high temperature carburizing.