Selection of raw materials for forging

The recrystallization temperature of steel is about 460 ℃, but 800 ℃ is generally used as the dividing line, and hot forging is higher than 800 ℃; The temperature between 300 ℃ and 800 ℃ is called warm forging or semi hot forging. Forging can be divided into cold forging and hot forging according to the temperature of the blank during processing.

Cold forging is generally processed at room temperature, while hot forging is processed at a recrystallization temperature higher than the blank metal. Sometimes, the forging when it is heated but the temperature does not exceed the recrystallization temperature is called warm forging. However, this division is not completely unified in production.

Forging can be divided into free forging, die forging, cold heading, radial forging, extrusion, forming rolling, roll forging, rolling and so on. The deformation of the blank under pressure is basically free from external restrictions, which is called free forging, also known as open forging; The blank deformation of other forging methods is limited by the die, which is called closed mode forging. The forming tools of forming rolling, roll forging, rolling, etc. have relative rotary motion with the blank, which pressurizes and forms the blank point by point and asymptotically, so it is also called rotary forging.

Generally, small and medium-sized shaft forgings use round or square bars as blanks. 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, shaft forgings with excellent performance can be forged without large forging deformation. The forging materials are mainly carbon steel and alloy steel with various components, followed by aluminum, magnesium, copper, titanium and their alloys. The original state of materials includes bars, ingots, metal powder and liquid metal.