Casting is the process of melting metal into a liquid that meets certain requirements and pouring it into a mold. After cooling, curing and cleaning, a casting (part or blank) with a predetermined shape, size and performance is obtained.

The cost of billets produced by casting is low and its economic efficiency can be shown for parts with complex shapes, especially complex inner cavities; At the same time, it has a wide range of adaptability and good comprehensive mechanical properties. Casting is a metal heat treatment technology mastered earlier by mankind, which has a history of about 6,000 years.

There are many types of castings, divided into: ordinary sand castings, including raw sand, dry sand and chemically hardened sand; Special castings, according to the different molding materials, can be divided into special castings with natural mineral sand and gravel as the main molding materials (such as precision castings, clay castings, foundry shell castings, negative die castings, solid castings, ceramic castings, etc.) and special castings with metal as the main mold material (such as metal mold casting, pressure casting, continuous casting, low pressure casting, centrifugal casting, etc.).

The casting process usually includes: (1) preparation of the mold (a container for making liquid metal into a solid casting). The mold can be divided into sand, metal, ceramic, clay, graphite, etc. according to the material used, and can be divided into one time according to the number of uses. The main factors that affect the quality of castings are the quality, semi-permanent and permanent of castings. (2) Melting and pouring of cast metal. Cast metals (cast alloys) mainly include cast iron, cast steel and non-ferrous alloys. (3) Casting processing inspection, casting processing includes removing foreign matter on the core and casting surface, removing protrusions such as dumping risers, shovel burrs and overhanging joints, as well as heat treatment, shaping, rust prevention and rough processing.

Forging is a processing method that uses forging machinery to apply pressure to a metal blank to produce plastic deformation to obtain forgings with certain mechanical properties, certain shapes and sizes.

By forging, the looseness of the cast state of the metal and welded holes can be eliminated, and the mechanical properties of forged parts are generally better than castings of the same material. For mechanically important parts with high loads and harsh working conditions, forgings are mostly used except for simple shapes, profiles or welded parts that can be rolled.

According to the forming method, forging can be divided into: (1) open forging (free forging). The metal between the upper and lower anvils (anvils) is deformed by impact or pressure to obtain the desired forgings, mainly manual forging and mechanical forging. (2) Closed forging. The metal blank is compressed and deformed in a forging die with a certain shape to obtain forgings, which can be divided into die forging, cold head, rotary forging and extrusion. According to the deformation temperature, forging can be divided into hot forging (processing temperature higher than the recrystallization temperature of the blank), warm forging (lower than the recrystallization temperature) and cold forging (normal temperature).

Forging materials are mainly carbon steel and alloy steels of various compositions, followed by aluminum, magnesium, titanium, copper, etc. and their alloys. The original state of the material includes bars, ingots, metal powders, and liquid metals. The ratio of the cross-sectional area of the metal before deformation to the cross-sectional area of the mold after deformation is called the forging ratio. The correct choice of forging ratio has a lot to do with improving product quality and reducing costs.