箱体铸件裂纹缺陷的成因分析及防止措施

Cause Analysis and Preventive Measures of Cracks in Box Castings

介绍了箱体铸件的结构及技术要求,详细阐述了原生产工艺及铸件出现裂纹的位置和特征,针对840箱体铸件存在不同程度的裂纹进行了分析,认为铸件壁厚不同,凝固速度也不同,因收缩受阻而形成的拉应力将处于高位阶段呈塑性状态的低强度部位拉裂所致。采取了以下措施:(1)砂芯混入激冷效果较好的铬铁矿砂;(2)调整炉料配比及化学成分;(3)增加随流孕育量。生产结果显示:生产验证的568件铸件,均没有发现裂纹,铸件的金相组织和力学性能也均符合技术要求,铸件的裂纹缺陷得到了有效控制。

The structure and technical requirements of box castings were introduced.The original production process and the location and characteristics of the cracks in the castings were described in detail.According to the analysis of different degrees of cracks in 840 box castings,it was believed that the castings had different wall thicknesses and solidification speeds.The cracks were caused by tensile stress due to hindered shrinkage on low-strength parts in the plastic state.The following measures had been taken:(1)The sand core was mixed with better chilling effect chromite sand.(2)The charge ratio and chemical composition were adjusted.(3)The flow inoculation amount was increased.The production results showed that no cracks were found in the 568 castings verified by production,the metallographic structure and mechanical properties of the castings also met the technical requirements,and the crack defects of the castings were effectively controlled.