风泵活塞是内燃机车上的重要零件之一,其材质为铝合金LOW-EX,主要技术要求为,表面光洁度??7,不得有铸造缺陷,并需经10～15公斤/厘米~2的液压试验(图1). 以前一直采用砂型铸造,从1964年到1965年初,先后铸造数十次,质量均很差,存在砂眼、夹渣及缩松等缺陷.后又改用硬模砂芯铸造,废品率仍高达 Air pump piston is one of the important parts on the diesel locomotive, the material is aluminum alloy LOW-EX, the main technical requirements for the surface finish ?? 7, casting defects, and subject to 10 ~ 15 kg / cm ~ 2 Hydraulic test (Figure 1) .It has been the sand casting, from 1964 to early 1965, has cast dozens of times, the quality is poor, there is trachoma, slag and shrinkage and other defects.Subsequently use the hard core Casting, rejection rate is still high