Sand casting refers to the casting method of producing castings in sand mold. Steel, iron and most non-ferrous alloy castings can be obtained by sand casting. Because the molding materials used in sand casting are cheap and easy to obtain, and the mold manufacturing is simple, it can adapt to the single piece production, batch production and mass production of castings. For a long time, it has been the basic process in casting production.
Clay and an appropriate amount of water are used as the main binder of molding sand. After making sand mold, it is directly molded and poured in the wet state. Wet mold casting has a long history and is widely used. The strength of green sand depends on the clay slurry formed by mixing clay and water in a certain proportion. Once the molding sand is mixed, it has a certain strength. After being compacted into a sand mold, it can meet the requirements of molding and pouring. Therefore, the amount of clay and moisture in molding sand are very important process factors.
A casting method that uses molding sand and core sand as molding materials to make a mold, and liquid metal fills the mold under gravity to produce castings. Steel, iron and most non-ferrous alloy castings can be obtained by sand casting. Because the molding materials used in sand casting are cheap and easy to obtain, and the mold manufacturing is simple, it can adapt to the single piece production, batch production and mass production of castings. For a long time, it has been the basic process in casting production.
The mold used in sand casting is generally composed of outer sand mold and core. In order to improve the surface quality of castings, a layer of paint is often brushed on the surface of sand mold and core. The main components of the coating are powdery materials and binders with high fire resistance and good high-temperature chemical stability, as well as carriers (water or other solvents) and various additives that are convenient for coating.
The advantages of clay wet sand casting are: ① clay is rich in resources and cheap. ② Most of the used clay wet sand can be recycled after proper sand treatment. ③ The manufacturing cycle of the mold is short and the work efficiency is high. ④ The mixed molding sand can be used for a long time. ⑤ After tamping, the sand mold can still tolerate a small amount of deformation without damage, which is very beneficial to both draft and core. The disadvantages are: ① when mixing sand, viscous clay slurry should be coated on the surface of sand particles, and high-power sand mixing equipment with kneading effect needs to be used, otherwise it is impossible to obtain molding sand with good quality. ② Because the molding sand has quite high strength after mixing, the molding sand is not easy to flow and difficult to pound. Manual molding is laborious and requires certain skills, and the equipment is complex and huge when molding with machines. ③ The rigidity of the mold is not high, and the dimensional accuracy of the casting is poor. ④ Castings are prone to sand flushing, sand inclusion, porosity and other defects.
Clay dry sand mold the wet moisture content of the molding sand used for making this kind of sand mold is slightly higher than that of the molding sand used for green molding.
Clay sand core a simple core made of clay sand.