Forging (Hot / Semi-hot)

[Hot work]

FORGING PROCESS

Forging is the non-cutting shaping of metals between two tools. The choice of tool steel is primarily determined by the respective forging process.

Drop forging

Drop forging is carried out by impacting material with a hammer or by applying a great amount of pressure with a forging press or forging machine. 

When forging with a hammer the forging piece is only in contact with the die for a short period of time. Due to this, the die has to withstand lower temperatures. However, the mechanical stress is high. Thus, it is quite important for the hot work tool steel used to have very good toughness properties.

Compared with that, the contact during forging pressing occurs over a longer period of time, which then causes a ­higher temperature strain on the tool. Thus, in such a case hot work tool steels with a chromium-molybdenum base are used, which are singled out as having good tempering resistance, high temperature strength, hot wear resistance, and hot toughness.

Rapid forging

A fully automatic multi-stage press is forging equipment that produces even the most difficult shapes from materials hard to deform in several stages of deformation. This equipment mostly produces rotation symmetric parts.
Heating the slugs, feeding, shearing and deforming take place completely automatically.

Semi hot forging

The term semi hot forging refers to a deformation process in which the workpiece is preheat­ed to such a point that permanent strain hardening occurs under the given deformation conditions. This definition means that the material is deformed below the recrystallization temperature, yet the term is also used for temperatures occurring above this. In practice this is understood to be the deformation of steel in the temperature range of 650 to approx. 950 °C. These temper­atures lie significantly below the conventional forging temperatures of 1100 – 1250 °C.

Selection of product shape