交通部戚墅堰机车车辆工厂铸造营的革命职工,遵照毛主席“中国应当对于人类有较大的贡献”的教导,决心改革造型材料,从根本上解决铸件成本高、光洁度不好,难以清铲并影响工人健康的老大难问题。他们在厂党委的领导下,从一九七○年九月开始,以工人为主体的“三结合”小组,试验用石灰石砂(代号“七○砂”)代替了石英砂造型。一年来,经过四百多次试验,浇注了14个品种共200余种铸钢件(最大25吨,最小1公斤,壁厚最厚的近 The revolutionary employees of the Qishuyan locomotive and rolling stock factory of the Ministry of Transport followed the guidance of Chairman Mao’s “China should make greater contributions to mankind” and determined to reform the modelling materials to fundamentally solve the problems of high casting cost, poor finish, difficulty in shoveling and The perilous problem that affects the health of workers. Under the leadership of the factory party committee, they began to use the limestone sand (codenamed “70 sand”) to replace the quartz sand model. In the past year, after more than 400 tests, a total of more than 200 steel castings of 14 varieties were cast (up to 25 tons, minimum 1 kg, and the thickest wall thickness