The foundation of casting materials used in large -scale casting plants in China is that the size of the machine tool has a large casting size, a length of several meters, a mass of more than 10t, and a wall thickness between 15 and 30mm. These requirements include: good precision stability and shock absorption, high elastic modulus, appropriate pressure resistance, moderate hardness and excellent abrasion resistance; they have high deformation resistance, easy to cut, and require lower production. Costs, such as the melting of the sky furnace, use a small number of alloy elements. In order to meet the above requirements, the micro -tissue of the alloy should be a pearl structure. The A -type graphite with a length of less than 250 TIM is evenly distributed and contains a certain amount of binary phosphorus common crystals.

Some large casting plants consider sand casting. According to statistics, in China, 60 ~ 70%of castings are produced with sand, and about 70%of them are produced with clay sand. The main reason is that sand casting is lower than other casting methods, simpler production technology, and shorter production cycle. Therefore, the engine cylinder, cylinder head, crankshaft and other castings of the car are produced by clay wet sand -type process. When the wet model cannot meet the requirements, consider using clay sand surface dry molds, dry molds or other sand.

The weight of the use of sand -shaped casting factories can ranging from several to tens of kilograms, and some weighing up to tens of tons or hundreds of tons can be reached. Generally speaking, for medium and large casts, cast iron parts can be used for resin self -hard sand types, and casting  steel parts can be used for water glass sand, which can make the surface smooth casting, but the cost is higher. Of course, sand castings often require high requirements in terms of accuracy, surface smoothness, density, micro -tissue and mechanical performance. Therefore, in cases of high requirements for these performance, molten mold casting, die casting, low -pressure casting and other methods can be used.