Metal forming is a very common practice in the metallurgy industry that lots of kinds of products are produced. Metal forming processes are generally classified according to the application temperature. In terms of that, there are metal forming applications called cold working and warm working. The other type of metalworking process is hot working, also referred to as hot forming.
Here the hot metalworking process is explained with the general aspects, advantages, disadvantages, and important process parameters.
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The Temperature Range Of Hot Metal Working
As we stated above, the application temperature is the most important parameter of metalworking processes. And the classification of metalworking processes is generally made according to the melting temperature. If the metalworking processes are applied above one-half of the melting temperature of the metal, the process is called hot metalworking.
In practice, hot metalworking processes are made around 0.5*Tm-0.7*Tm. But there can be serious problems in terms of the high temperatures. In the deformation process, heat is also produced because of the deformation itself. And because of this additional heat, the deformation regions can melt, which is not a desirable thing. When the metalworking temperature must be decided, this fact must be considered.
Recrystallization In Hot Metalworking Processes
The most important process characteristic of the hot metalworking process is recrystallization. With the recrystallization of metal parts at high temperatures, deformability increases due to compensation of the work hardening. In some hot metalworking processes, recrystallization is not intended and the process cycle is too rapid for the diffusion of the metal grains for recrystallization. But, complete or partial recrystallization is obtained in the cooling period, after the process.
What Are The Advantages Of Hot Metalforming Processes?
- One of the most important advantages of the hot metal forming process is the extensive deformability of metals at high temperatures. In general, deformation rates obtained in hot metal forming processes could not be obtained with warm and cold metalworking processes.
- We stated in the article about cold metalworking, work hardening is one of the biggest obstacles to extensive deformations. Because of the high temperatures, nearly no work hardening occurs. So, the power and force required to deform metals are low compared with other methods.
- The fracturing of metals can be a problem in cold metal forming processes. This problem can be eliminated with the hot metalworking processes.
- There is no oriented grain structure in hot metalworking processes, so the general strength characteristics of the produced part are highly isotropic.
Main Disadvantages Of Hot Metalworking Processes
In the selection of the required process for metal forming, these disadvantages of the hot metalworking processes must be considered.
- It can be advantageous of requirement lower forces and pressures, but the energy is generally expensed to warm up the metal. So this is a primary disadvantage of the hot metalworking processes.
- Because of the high temperatures, oxidation of the metal is a serious problem. Because of these oxidations, some of the hot metal forming processes are applied under vacuum.
- Dimensional accuracies are low compared with the warm and cold metalworking processes.
- The tools that are generally used in hot metalworking processes tend to have a shorter life. This fact is also related to high temperatures.
These are the general aspects of hot metalworking processes.
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