750大型球墨铸铁泵体铸造工艺的改进

Casting Method Improvement of 750 Heavy Nodular Iron Pump Body

介绍了750大型球墨铸铁泵体铸件的技术要求和铸造工艺改进,750泵体铸件材料牌号为QT600-3,质量10 190kg,主要壁厚75 mm,最大壁厚150 mm,铸件要求进行超声波探伤,不允许有缩孔、缩松、夹渣及其它夹杂物。原工艺为:采用呋喃树脂砂造型,铸件外围设置环形浇注系统,内浇道厚度较大,铸件顶部设置4个冷冒口,结果铸件多处产生较严重的缩孔、缩松和夹渣缺陷。后来通过反复试验,采用无冒口铸造工艺,将冷冒口去除,改为薄片形排气片,选择恰当的浇注温度,提高铸型刚度和使用大量的冷铁,利用石墨化膨胀和砂芯热膨胀进行补缩,并将内浇道改为扁薄形,提高挡渣能力,最终消除了上述缺陷,铸件质量完全达到客户要求。

The technical requirements and casting method improvement of 750 pump body were introduced. The material of the 750 pump body was required to be QT600-3 grade nodular cast iron,its main wall thickness was of 75 mm,the casting was required to be inspected by using ultrasonic test and no shrinkage cavities and porosities,slag inclusion and other inclusions existing. The original casting method was:using furan resin sand for molding,setting cycle-shaped gating system around the casting with relatively thick ingates,4 cold open risers were set on the top of the casting. As the result,quite a number of severe shrinkage cavities,porosities and slag inclusions occurred in multiple locations of the casting. Then,by repeated tests and using riser-less casting method,substituting risers with thin venting plates,choosing proper pouring temperature,increasing mold rigidity and using a large numbers of chills in order to use graphitization expansion and hot expansion of the sand cores to compensate shrinkage,changing the high ingates into thin ingates to improving slag skimming ability,the above mentioned defects had been finally eliminated,the quality of the castings completely met client's requirements.