How do precision casting manufacturers cast parts

Update:20 Dec 2019
Summary:

Upset forging is the use of forging machinery to apply […]

Upset forging is the use of forging machinery to apply pressure to metal blanks to cause plastic deformation, thereby obtaining forgings with certain mechanical properties, a certain shape and size. Forging and stamping are plastic workability, collectively called forging. Forging is a commonly used forming method in mechanical manufacturing. Forging can eliminate loose and welded holes in the as-cast state of the metal. The mechanical properties of forging are usually better than the mechanical properties of the same material. In addition to forgings, important parts of the machine with high loads and severe working conditions are used, in addition to the relatively simple shapes of available rolled plates, profiles or weldments.

Upset press blanks can be divided into cold forging and hot forging during processing. Cold forging is usually performed at room temperature, and hot forging is performed at a temperature above the recrystallization temperature of the ingot metal. Sometimes it will be heated, but forging when the temperature does not exceed the recrystallization temperature is called warm forging. However, this division of labor is not completely unified in production.

The recrystallization temperature of steel is about 460 ° C, but 800 ° C is usually used as the dividing line. Hot forging is performed above 800 ° C and warm or semi-hot forging is performed between 300 ° C and 800 ° C.

The method of upsetting forging can be divided into free forging, die forging, cold forging, radial forging, extrusion, forming rolling, roll forging, rolling and so on. The deformation of the billet under pressure is basically free forging, also known as open forging. The blank deformation of other forging methods is limited by the mold, which is called closed-die forging. Forming rolling, roll forging, boring and other forming tools and the relative rotation between the billet, the billet is gradually press-formed point by point, so it is also called rotary forging.

Forging materials are mainly composed of carbon steel and alloy steel with various components, followed by aluminum, magnesium, copper, titanium, and their alloys. The original state of the material is rod, ingot, metal powder and liquid metal.

General small and medium-sized forgings use round or square bar stock as the blank. The grain structure and mechanical properties of the bar are good, the shape and size are accurate, the surface quality is good, and it is easy to organize mass production. As long as the heating temperature and deformation conditions are properly controlled, large forging deformations can be used to forge excellent forgings.

Ingots are only used for large forgings. An ingot is a cast structure with large columnar grains and a wide center. Therefore, it is necessary to decompose the columnar crystals into fine grains by large plastic deformation and compact them loosely to obtain excellent metal structure and mechanical properties.

Pressed and sintered powder metallurgy preforms can be made into powder forgings by pressure-free forging in the hot state. Forging powder is close to the density of general die forgings, has good mechanical properties, high precision, and can reduce subsequent cutting processes. The powder forging has a uniform internal structure without segregation, and can be used to manufacture small gears and other workpieces. However, the price of powder is much higher than that of ordinary bars, and its application in production is limited.

By applying static pressure to the liquid metal injected into the mold to solidify, crystallize, flow, plastically deform, and shape under pressure, it is possible to obtain a forged piece with the desired shape and performance. Liquid metal forging is a forming method between die casting and swaging. It is especially suitable for complex thin-walled parts that are difficult to form in general forging.