304不锈钢胶囊模具模针开裂的失效原因分析

Fracture Failure on 304 Austenitic Stainless Steel Needle Used in Capsule Mold

通过对化学成分、加工工艺、显微组织和断口形貌进行分析,研究了某胶囊加工工厂加工的胶囊模具模针底部的断裂原因。结果表明,模针断裂主要原因是胶囊模具在使用过程中所受的循环应力、晶间腐蚀和应力腐蚀的联合作用下形成的。该奥氏体不锈钢在加工过程中,底部支座与模针之间存在一个直角突变,在动载荷的作用下,直角突变部位形成一个较大的应力集中。由于模针长期处于潮湿的环境中,直角突变部位极易成为疲劳破坏的起点。

The reasons for the fracture failure of needle used in capsule mold were investigated by analyzing chemical composition, processing technology analysis, microstructure and fracture morphology. The results show that the cyclic stress and intergranular corrosion and stress corrosion is the main reason for the facture failure of the needle used in capsule mold. In the process of machining, the austenitic stainless steel has a rectangular mutation at the bottom of pedestal and moldneedle. Under the action of dynamic load and in the damp environment for a long time, the rectangular mutation forms a larger stress concentration, which is easy to become the starting point of fatigue damage.