引进及国产大截面塑料注射模脱模顶杆的失效行为

On the Failure of Pushing Rods in Large Cross-Section Dies for Plastic Injection

研究了引进日本及国产大截面塑料注射模脱模顶杆在相近锁模力下的失效行为.分析结果表明,日本顶杆在注塑50万次后以磨损的形式失效,国产顶杆在注塑10万次后以弯曲断裂的形式失效.前者比后者具有高的使用寿命,这是因为日本顶杆选用的是含铬的结构钢,并采取了调质处理后再表面淬火的热处理工艺,使之获得了表层高硬度及心部综合机械性能好的特性,从而阻止了早期失效行为的出现.

Two pushing rods in large cross-section dies for plastic injection, one made in Japan and the other in China, were found ineffective. The chemical composition, metallurgical quality, micro-constituents, microhardness and heat treatment process of the two rods have been investigated. It is confirmed that the Japanese made rod is made of SCM455H steel and treated by heat refining and case hardening. Its surface hardness is about HRC63 and central hardness is in the range 30-32. the Chinese-made rod is made of 50Mn steel and treated by one-piece hardening. Its surface hardness is lower than central hardness, the former is HRC38 and the latter is HRC58 because of decarburation. The failure of the Japanese-made rod is apparently due to wear while that of the Chinese-made one is due to bending and fracture. This is the reason why the working life of the home-made rod is shorter than that of the rod made in Japan.