Transactions of Materials and Heat Treatment

Title：Application of overcooling austenite isothermal transformation in pre-heat treatment for steering shaft tooth

Authors： Zhang Yishuai Sun Hongxing Liu Dan Wang Tao Wang Jinbao Liu Hua

Unit： Zheng Zhou Research Institute of Mechanical Engineering Co. Ltd. China Academy of Machinery Science and Technology Group Co. Ltd. Xi′an Jiaotong University

KeyWords： overcooling austenite steering shaft tooth isothermal transformation metallographic structure hardness

ClassificationCode：TG162.7

year,vol(issue):pagenumber：2019,44(9):167-171

Abstract：

The phenomena of unstable metallographic structure and uneven hardness distribution of steering shaft tooth during pre-heat treatment were studied by combining theoretical analysis with experimental study. The results show that the cooling speed, transformation temperature and transformation time etc. of overcooling austenite during transformation process are the key factors to determine the microstructures and properties. According to the principle and mechanism of austenite decomposition in the process of isothermal transformation for overcooling austenite, the cooling speed was controlled by controlling air volume and blowing time in air cooling chamber, and after cooling, the isothermal structure transformation process was finished in isothermal furnace. Finally, the uniformly distributed F+P microstructures were obtained, and the technical specifications of metallographic structure grade 1-2 for steering gear forgings and hardness difference less than 10 HB of different steering shaft teeth in the same batch were achieved, which provided technical guarantee for reducing heat treatment deformation of gears in subsequent carburizing and quenching process.

Funds：

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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