花键冷滚打成形表层加工硬化研究

Research on Work-hardening Behavior of Surface Layer of Spline during Cold Roll-beating

依据冷滚打成形原理,分析花键成形表层加工硬化机理,进行冷滚打成形的仿真和花键试件的扫描电镜实验、透射电镜实验和显微硬度实验,得到了花键成形过程中等效应变和温度分布情况;分析花键表层晶粒、位错和花键齿不同部位的硬度沿硬化层深的变化情况,阐明沿层深方向晶粒大小、位错密度和硬度三者之间的关系,揭示了冷滚打工艺参数对加工硬化程度的影响规律。结果表明:冷滚打成形花键表层加工硬化主要受到位错密度影响,分度圆硬化程度最大,齿廓不同部位硬化程度随着工件进给量的增大而上升,随着滚打轮转速的增大而下降。研究结果为揭示20号钢冷滚打花键成形表层加工硬化行为提供了参考依据。

The work-hardening mechanism of surface layer of spline is analyzed based on the principle of cold-roll beating formation. The cold roll-beating formation is simulated, and the scanning electron micro- scopic and transmission electron microscopic examination and micro hardness test of spline test piece are conducted. The equivalent strain and temperature distribution during the forming process of cold roll- beating are obtained. The variations of grain, dislocation and hardness values at different positions of spline tooth along the direction of hardened layer depth are discussed, the relationships among grain size, dislocation density and hardness along the direction of layer depth are clarified, and the effect of cold roll- beating parameters on the degree of work hardening is revealed. The results show that work-hardening on surface layer of workpiece during high speed cold roll-beating is mainly affected by dislocation density. The hardening degree of pitch circle is maximal, the hardening degree of different positions of tooth pro- file increases with the increase in the feed rate of workpiece, but decreases with the increase in the rota-tional speed of roller. The research results provide a basis for revealing the work-hardening behavior of surface layer of spline of 1020 steel during cold roll-beating.