控制压力冒口补缩失效的原因分析及对策

Analysis and Countermeasures on Control Pressure Riser Feeding Failure

介绍了球墨铸铁的补缩过程,根据铁液凝固过程中压力变化规律,分析了控制压力冒口补缩失效的原因,给出相应的对策:(1)如果铸件近冒口颈部位有缩松,可通过增大冒口颈的尺寸来去除,且在可控的范围内,冒口颈的尺寸越大越好;(2)如果冒口不补缩、铸件冒口颈处存在缩孔,可通过缩小内浇道模数,使内浇道及时凝固,利用石墨化膨胀压力达到二次补缩所需最小值,来避免此类缺陷;(3)对于较大球墨铸铁件,需对冒口的形状进行设计,若冒口存在补缩但没有多次补缩的痕迹,可通过锥形冒口的设计来避免铸件的缩孔、缩瘪问题的产生。

The feeding process of nodular iron was introduced. According to molten iron during solidification pressure variation. The failure reasons of control pressure riser feeding was analyzed. The corresponding countermeasures were given :( 1) If there was shrink on casting riser neck,it could be removed by increasing the riser neck size. And within a controllable range,the bigger riser neck size the better on reduce shrink.( 2) If the riser was not feeding and the shrinkage found on casting riser neck,the ingate modulus could be reduced,so that the inner runner solidification in time. Expandable graphite pressure made the minimum required for secondary feeding to avoid such defects.( 3) For larger nodular iron castings,the shape of the riser need to design. If feeding exist but none traces found,a tapered riser design could solve casting shrinkage and flat shrink problem.