后桥箱体夹砂的形成与预防研究

Research on Formation and Prevention of Sand Inclusion Defects in Rear Axle Box Castings

针对后桥箱体铸件,对现有夹砂解决方案应用的可行性进行了讨论,认为后桥箱体上存在大平面是其产生夹砂的主要原因。进一步的研究表明,砂型表面层不仅受水平热压应力的作用,而且受垂直热压应力的作用,垂直热压应力的存在,减小了致使砂型弯曲断裂的临界水平热压应力。生产验证结果表明,在铸件大平面处设置应力释放筋可以大大降低夹砂缺陷的发生率,应力释放筋不仅减小水平热压应力,而且减小垂直热压应力造成的弯曲挠度,使砂型表面层所受弯矩减小。

In view of rear axle box castings, the application feasibility of existing prevention methods were discussed, and the bigger plane is the major cause to produce sand inclusion defects. The results show that not only there is oriental thermal compressive stress but also vertical thermal compressive stress in the sand mould surface layer. The vertical thermal compressive stress reduce the critical oriental compressive stress, which is the smallest value to cause a fracture when the sand mould surface layer bending deforms. The production verification results show that the stress releasing ribs on the large planes of the casting can greatly reduce the incidence rate of sand inclusion defects. The results show that the stress release ribs reduce the level of thermal compressive stress. The bending deflection is caused by the vertical thermal stress, which can reduce the bending moment, and is helpful to avoid sand inclusions.