金属构件中裂纹的电磁热效应局部跨越止裂

CRACK PREVENTION BY BRIDGING OVER IN METAL COMPONENT UNDER ELECTROMAGNETIC HEATING EFFECT

采用理论分析和实验研究的方法讨论了应用电磁热效应对金属构件中裂纹实施局部跨越止裂的技术。在带有裂纹的模具钢构件上取样,对裂纹处通过点电极进行局部跨越脉冲放电。实验研究和理论分析结果均表明:跨越止裂可以使导体中局部裂纹在裂纹尖端处很小的范围内熔化形成微小的焊口,实现了钝化止裂,遏制了裂纹的扩展。通过对止裂后裂尖的金相组织观察和力学性能测试发现:超细化的条状马氏体、极少量残余奥氏体和细颗粒碳化物的出现极大地提高了裂纹尖端的硬度、韧性和耐磨性。

Heating by an electromagnetic field is an effective method for stopping internal crack propagation in metal die. In this paper, a theoretical analysis and experiment surveys are presented for simulating crack prevention by bridging over near crack tip under electromagnetic heating effect. The theoretical analysis and experiment surveys show that the tip of the crack may be melted and the welded joints can be formed when the crack is arrested by bridging over near crack tip under electromagnetic heating. So, the goal of crack preventing can be reached. The microstructure is analyzed around the crack tip after crack arresting. The superfine Martensite, fine-grained carbon compound and residual Austenites are found around the crack tip. The intensity, ductility and wearing capacity around crack tip are improved under the influence of the superfine structure.