电磁热止裂对冷锻钢力学性能影响分析

Analysis on the influence of electromagnetic heat crack-arresting on cold forging steel mechanical properties

对产生圆形裂纹的45号冷锻钢进行了电磁热止裂数值模拟,分析了止裂后裂纹前缘处的温度场、热应力场及残余应力场的变化。结果表明:在止裂瞬间裂纹前缘处的金属材料达到熔点而迅速熔化,在冷却至室温过程中裂纹前缘处应力场始终处于压应力状态,对防止二次裂纹产生和阻止裂纹继续扩展具有重要作用;通过电磁热止裂实验分析表明,强化后试件断口呈现出小而均匀的韧窝;与未强化试件相比强化后试件的抗拉强度提高了14.8%,在相同电压下止裂效果与裂纹的大小成反比,但与未强化前相比止裂效果有明显提高。通过数值模拟和实验分析,验证了电磁热止裂技术对提高冷锻钢力学性能的有效性,为后续工程应用提供了参考。

For cold forging steel 45 with the buried circular crack, the electromagnetic heat crack-arrest process was numerically simulated, and the temperature fields, thermal stresses fields and the residual stress fields on the front of the crack were analyzed after crack-ar- resting. The results show that the metals are melted quickly on the front of the crack at the moment of crack-arresting, and the compressive stress field exists in the whole cooling process. This beneficial stress field has important practical meanings for preventing secondary crack from generating and propagation. The analysis on electromagnetic heat crack-arrest experiment shows that small and uniform dimples appear on the specimen fracture after quenching. Meanwhile the maximum tensile strength increases by 14. 8% comparing with non-quenching specimen. Furthermore, the crack-arrest effect is inversely proportional to the size of crack under the same voltage, so it is improved obviously. Both the simulation and experiment prove that the electromagnetic heat crack-arrest technique can improve mechanical properties of cold forging steel effectively, and it also provides a reference for application in the future.