Many years ago, when some factories in southern China used the wet clay sand molding process to produce thin-walled small sand cast iron castings, they selected the red sand (Liuhe red sand) produced in Liuhe County, Nanjing City, Jiangsu Province as the molding material, without adding coal powder or bentonite, and mixed with water as the surface sand, which is used for manual molding or knockout molding machine (commonly known as bouncing machine).
The silt content of Liuhe red sand is about 10%, which is wrapped with some clay, the particle size is about 100/200~140/270 mesh, and the content of SiO2 is 76%~79%. When the pouring temperature is not high, the small sand cast iron with smooth surface can be poured. There is no pulverized coal flying in the pouring environment, and there is no gas generated by the combustion of pulverized coal.
The anti-adhesion mechanism of Liuhe red sand may be due to the small particle size of the red sand, the molten iron can not be drilled into the sand mold gap, and the sand mold surface close to the sand mold casting is moderately sintered and densified, which further hinders the penetration of molten iron.