Transactions of Materials and Heat Treatment

Title：Pre-heat treatment process of 20CrMnMoH high performance gear based on reducing heat treatment distortion

Authors：

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KeyWords：

ClassificationCode：TG156

year,vol(issue):pagenumber：2021,46(3):184-191

Abstract：

The phenomenon of non-equilibrium microstructure for bainite produced in the pre-heat treatment process of gear steel 20CrMnMoH was analzed and studied by the method combining theoretical analysis and experimental research. The results show that the cooling rate of gear steel 20CrMnMoH in the conventional pre-heat treatment process cannot be controlled, and the undercooled austenite is easily transformed into bainite and other nonequilibrium structures. According to the structure genetic effects of bainite and other non-equilibrium microstructure, combining with the principle and mechanism of isothermal transformation for undercooled austenite, two times of pre-heat treatment process for isothermal normalizing were designed. Furthermore, the first pre-heat treatment of isothermal normalizing completes the transformation from the non-equilibrium microstructure to the equilibrium microstructure, and the second pre-heat treatment of isothermal normalizing realizes grain refinement and homogenization. Through the process optimization and control, the technical indicators of the metallographic structure of 1-2 grades for gear forgings and the hardness difference of different gear forgings in the same batch ≤5 HB are achieved. The accuracy of finished gear is detected up to level 6, which verifies the effectiveness of pre-heat treatment to reduce the heat treatment distortion of gear and improve the accuracy of gear.

Funds：

国家重点研发计划资助项目(2018YFB2001300)；郑州市重大科技专项（152PZDZX007）

张义帅（1984-），男，博士研究生 E-mail：zhangyishuai@bit.edu.cn 通讯作者：刘华（1962-），男，博士，研究员 E-mail：pformdept@163.com

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