冷挤压活塞销上凸模的受力分析及表面强化

Stress Analysis and Surface Strengthening of Cold Extruding Upper Male Die for Piston Pins

采用动态电阻应变仪对汽车活塞销冷挤压上凸模进行了应力测试,结果表明:上凸模在工作时主要承受大压小拉的交变应力和附加弯曲应力,易造成疲劳断裂。分析了工况条件和受力情况,提出了正常热处理+磨削+软氮化处理+滚压工艺的复合强化工艺。生产实践表明,该工艺大大改善了上凸模表层的微观凹凸程度,延缓了疲劳裂纹的萌生与扩展,使模具寿命得到了大幅度提高。

The stress of cold extruding upper male die for piston pins used in a car was measured by adopting dynamic resistance strain instrument.The working condition and stress situation were analyzed.The results obtained indicate that the cold extruding upper male die bears the alternate stress of big compression force and small pulling force as well as bending stress.The fatigue break often occurs against the upper male dies.The compound strengthening processing of normal heat treatment+grinding+tuff-nitriding+rolling is proposed.The study indicates that the process can greatly decrease the ruggedness of the upper male dies,and delay the initiating and expanding of the fatigue crack.Productive practice shows that the process mentioned above greatly increases the use life f the dies.