Casting is a kind of metal thermal processing technology that human beings have mastered relatively early, and it has a history of about 6000 years. China has entered the heyday of bronze castings between 1700 and 1000 BC, and the technology has reached a very high level. Casting is the method of casting liquid metal into the casting cavity suitable for the shape of the part, and then cooling and solidifying to obtain the part or blank. The cast material is usually a metal that is originally solid but heated to liquid (e. g., copper, iron, aluminum, tin, lead, etc.), and the material of the mold can be sand, metal, or even ceramic. The methods used will vary according to different requirements.

Casting-a forming method for smelting metal, manufacturing casting molds, and pouring molten metal into the casting molds, and obtaining metal parts with a certain shape, size and performance after solidification
Casting is a process in which the metal is melted into a liquid that meets certain requirements and poured into the mold. After cooling, solidification and cleaning, the process of obtaining a casting with a predetermined shape, size and performance is obtained. Casting blank because of nearly forming, and to achieve the purpose of mechanical processing or a small amount of processing to reduce the cost and reduce the production time to a certain extent, casting is one of the basic processes of modern device manufacturing industry.

There are two main categories of sand casting and special casting.

1 ordinary sand castingThe use of sand as a mold material, also known as sand casting, foundry sand, including wet sand, dry sand and chemical hardening sand three categories, but not all sand can be used for casting. The advantage is that the cost is low, because the sand used in the mold can be reused; the disadvantage is that the production of the mold is time-consuming, and the mold itself cannot be reused, and the finished product can only be obtained after destruction.

1.1 sand mold (core) casting methods: wet sand mold, resin self-hardening sand mold, water glass sand mold, dry mold and surface dry mold, solid mold casting, negative pressure molding.

1.2 sand core manufacturing method: according to the sand core size, shape, production batch and specific production conditions to choose. In production, it can be divided into manual core and machine core.

2 Special castingAccording to the modeling materials, it can be divided into special casting with natural mineral sand as the main modeling materials (such as investment casting, mud casting, shell casting, negative pressure casting, solid casting, ceramic casting, etc.) and special casting with metal as the main mold materials (such as metal mold casting, pressure casting, continuous casting, low pressure casting, centrifugal casting, etc.).

2.1 metal mold casting method

The casting mold is made of a metal with a higher melting point than the raw material. Which is subdivided into gravity casting method, low pressure casting method and high pressure casting method.

The metals that can be cast are also limited by the melting point of the mold.

2.2 dewaxing casting method

This method may be an outer film casting method and a solid casting method.

First copy the object to be cast with wax, then immerse it in a pool containing ceramic (or silica sol [1]) and wait for it to dry, so that the wax copy is coated with a ceramic outer film, and the steps are repeated until the outer film is sufficient to support the casting process (about 1/4 inch to 1/8 inch), then melt the wax in the mold and extract the mold. After that, the mold needs to be high temperature many times, and the hardness can be used for casting.

This method has good accuracy and can be used as a high melting point metal (such as titanium) casting. However, due to the high price of ceramics, and the need for multiple heating and complex production, so the cost is quite expensive.