What are the requirements for the materials used for forged parts?

The materials for forgings are mainly carbon steel and alloy steel of various compositions, followed by aluminum, magnesium, copper, titanium, etc. and their alloys. The original state of materials includes bar stock, ingot, metal powder and liquid metal. The ratio of cross sectional area of metal before deformation to that after deformation is called forging ratio. The correct selection of forging ratio, reasonable heating temperature and holding time, reasonable initial and final forging temperature, reasonable deformation amount and deformation speed have a great relationship to improve product quality and reduce cost.

Generally, round or square bars are used as blanks for medium and small forgings. The grain structure and mechanical properties of the bar are uniform and good, the shape and size are accurate, and the surface quality is good, which is convenient for mass production. As long as the heating temperature and deformation conditions are reasonably controlled, the forging with good performance can be forged without large forging deformation.

Ingots are only used for heavy forgings. The ingot is an as cast structure with large columnar crystals and loose centers. Therefore, the columnar crystal must be broken into fine grains through large plastic deformation, and then be compacted loosely to obtain excellent metal structure and mechanical properties.

The powder metallurgy preforms after pressing and sintering can be made into powder forgings by flash free die forging under hot state. The forging powder is close to the density of general die forgings, has good mechanical properties, and has high precision, which can reduce subsequent cutting. Powder forgings have uniform internal structure and no segregation, which can be used to manufacture small gears and other workpieces. However, the price of powder is much higher than that of ordinary bars, which limits its application in production.

Apply static pressure to the liquid metal poured in the mold chamber to make it solidify, crystallize, flow, plastic deformation and shape under the pressure, and then obtain the required shape and performance of the die forgings. Liquid metal die forging is a forming method between die casting and die forging, which is especially suitable for complex thin-walled parts that are difficult to form in general die forging.

In addition to ordinary materials, such as carbon steel and alloy steel with various compositions, followed by aluminum, magnesium, copper, titanium, etc. and their alloys, wrought alloys of iron base superalloys, nickel base superalloys, and cobalt base superalloys are also forged or rolled. However, these alloys are relatively difficult to forge because of their relatively narrow plastic zones, and the heating temperatures of different materials, There are strict requirements for opening and final forging temperatures.