40Cr钢磨削强化的试验与数值仿真

利用磨削过程中产生大量的磨削热使40Cr钢表层的温度升高,超过奥氏体化的温度,然后快速冷却,使40Cr钢表层发生马氏体相变,达到强化40Cr钢表层的目的。在磨床上对40Cr钢进行磨削试验,观测并分析工件横断面相交层的组织变化、厚度值和硬度变化,以及加工后工件表面的粗糙度。借助有限元分析方法,对工件的温度场进行仿真,得出工件各处的温度变化历程,由马氏体相变条件来获得表层马氏体相变层的厚度值。试验结果表明,40Cr钢的表层发生了马氏体相变,表层的硬度值得到极大提高,表面粗糙度也满足常规磨削的要求。由有限元仿真得出的相变层厚度值和试验结果相吻合。因此利用磨削强化技术替代40Cr钢高频淬火强化工艺是可行的,并且这项技术可以对其他合金钢进行强化。借助有限元方法对工件表层的温度场进行仿真,可以预测相变是否发生和相变层的厚度,优化磨削参数,减少试验研究的次数和成本。

EXPERIMENT AND NUMERICAL SIMULATION OF 40Cr STEEL IN GRIND-HARDENING

The dissipated heat in grinding is utilized to induce martensitic phase transformation and strengthen the surface layer of 40Cr steel by raising surface temperature higher than austenic temperature and cooling quickly. The experiment of grinding 40Cr steel is taken in grinding machine. The metallurgical microstructure, depth and hardness of transect phasetransformation layer are analyzed and surface roughness ismeasured. Temperature field and temperature history are simulated based on finite element method. The simulated hardness penetration depth is deduced from every place temperature history of work piece and martensitic phase transformation conditions. The experiment result shows that martensitic phase transformation takes place on the 40Cr steel surface layer in grinding, the hardness of surface layer is improved highly and surface roughness accords with the roughness of traditional grinding. So, it is possible for grind-hardening to take place of induction hardening. The temperature field and history can be simulated based on finite element method to predict the hardness penetration depth and optimize the grinding parameters. Thus the experiment cost and time can be reduced.