在毛主席无产阶级革命路线指引下,七○砂造型的应用范围正在扩大,其生产工艺也正日趋完善。为了提高七○砂的保存性能,在前一阶段,我们用纯碱代替混合凝胶体,取得了较好的效果。但是,也带来了铸件水爆性能下降的副作用,特别是薄壁封闭型铸钢件,内部泥芯更不易爆出。而这类铸件,在机车车辆的铸钢配件中所占比例较大,在车辆用配件中尤为突出,几乎占80％以上(按铸件重量计),如:摇枕、侧架、车钩体、弹簧箱、轴箱等。它们的共同特点是:壁薄、表面积较大、外形呈箱 Under the guidance of Chairman Mao’s proletarian revolutionary line, the scope of application of the 1970 sand molding is expanding, and its production process is also getting better and better. In order to improve the preservation performance of Qisha, in the previous stage, we used soda ash instead of mixed gel, and achieved good results. However, it also brings the side effects of the drop of casting water explosion performance, especially the thin-walled enclosed steel castings, the inner clay core is more difficult to burst out. Such castings, a large proportion of the cast steel parts of rolling stock, are particularly prominent in vehicle accessories, accounting for more than 80% (by weight of the castings), such as bolsters, side frames, coupler bodies, Spring box, axle box and so on. Their common features are: thin wall, large surface area, the shape of the box