Die Casting’s Blog

A sand casting is a cast part, which is produced by pouring liquid metal a mold made of a mixture of silica sand with addition of clay, moisture and some other additives (green sand) packed around an impression cavity shaped by a pattern). After the molding sand mixture has been packed and compacted around it, the pattern is withdrawn and molten metal is poured into the mold cavity which remains. After the metal has solidified and cooled, the casting is separated from the sand mold. The sand castings are easily recognized due its sand-like texture imparted by the sand mold. As the accuracy of the casting is limited by the green sand making process, there is always some sand residues on the surface of the castings to be removed. It is usually done by shot blasting process, where the casting surface is exposed to a stream of steel or iron shots, blasting its surface until the skin of oxides, silicates and other compounds will be removed. The molding sand going back into the sand processing plant will be remoistured and new additives mixed in. This means that the molding sand is reusable after adjusting its composition, replacing the elements lost in the thermal casting process. The pattern itself may be reused to produce new sand molds. This manual sand molding process that has been known for many centuries opened in the fifties of the twentieth century possibilities of automating the casting production process.

Sand castings may also be produced with molds made of sand that is bonded with materials other than moist clay. Many chemicals and mixture have been designed for this use. When these chemicals are used, they are collectively called "air set" sand castings to distinguish these from "green sand" castings.