集材-50、东方红-54(75)拖拉机使用的从动鼓材质为HT20～40,内表面需插齿,不允许有孔洞,砂眼等铸造缺陷。过去采用的铸造工艺是阶梯式切线浇口,多年求废品率一直高达68％。主要废品为夹砂、夹渣、气孔、铁豆。原因是浇注系统设计不合理,金属液浇入后,在离心力作用下。会将比重轻的杂质推向型腔中心而粘附存砂芯表面。改进后的工艺为底注浇口。成品率可达90％以上。加工余量也比过去小,铸件重从 Skidding -50, Dongfanghong -54 (75) Tractor drum material used for the HT20 ~ 40, the inner surface to be tooth, not allowed to holes, trachoma and other casting defects. Casting process used in the past is a ladder-tangential gate, rejection rate for many years has been as high as 68%. The main waste sand folder, slag, porosity, iron beans. The reason is pouring system design is unreasonable, pouring liquid metal, under the action of centrifugal force. The proportion of light impurities will push the center of the cavity and adhere to the surface of the sand core. Improved process for the bottom note gate. Yield rate up to 90%. Machining margins smaller than in the past, casting heavy from