支承板铸件的开裂失效分析

Cracking Failure Analysis of Supporting Plate Castings

利用金相显微镜、拉伸试验机和布氏硬度计对支承板的显微组织、力学性能和硬度进行了测试。结果表明:支承板的力学性能、金相组织、硬度均符合技术要求,裂纹从表面向心部扩展,裂纹两侧有较多的A型石墨,且裂纹处有较多的碳、氧、铁元素。裂纹产生的主要原因是消失模所用的ESP(可发性聚苯乙烯树脂)模料在浇注过程中造成了表面皱皮(积碳),割裂了金属的基体组织,在受到外力时产生裂纹,沿着积碳从表面向心部扩展。通过采用EPMMA(可发性聚甲基丙烯酸酯)代替EPS、提高浇注温度、采用顶注式浇注以及采用透气性更好的涂料等措施,降低了发气量,解决了支承板的皱皮缺陷。

The microstructure, mechanical properties and hardness of a supporting plate were tested by metallographic microscope, tensile tester and Brinell hardness tester. The results show that the mechanical properties, metallographic microstructure and hardness of the supporting plate meet the technical requirements. The cracks grow from the surface to the center, and there are more A-type graphite on both sides of the cracks, and there are more carbon, oxygen and iron elements in the cracks. The main reason for the crack is that the ESP(expandable polystyrene) mold material used in the lost mold causes a surface wrinkle(carbon deposition) during the pouring process, and the metal matrix microstructure is cut off. When subjected to external force, a crack propagates along the carbon deposition from the surface to the center. By using EPMMA(expandable polymenthylene polymethacrylate) instead of EPS, increasing pouring temperature, using top pouring and coating with better air permeability, the gas generation is reduced, the wrinkle defect of the supporting plate is solved.