Heat treatment
Heat treatment is a process or a combination of several processes for the treatment of workpieces, which are heated and then cooled again in a specific process in order to change material properties. The procedure therefore belongs to the main group Change substance properties . Surrounding agents can change the composition, e.g. B. bring about the carbon or nitrogen content or the crystal lattice, see also tempering .
A hot forming connected or heating process the surface protection not covered by the concept of heat treatment.
Procedure
Heat treatment refers to processes for the treatment of materials through thermal, chemical-thermal or mechanical-thermal effects, with the aim of achieving optimized properties for a specific purpose.
In heat treatment, a fundamental distinction is made between processes that bring about a thorough structural transformation and processes that only cause a transformation on the surface of a workpiece. The former processes include, for example, annealing and hardening ; H. the thermal processes. The second-mentioned processes belong to the diffusion and coating processes or to the thermochemical processes (e.g. carburizing , case hardening , nitriding , boriding ).
Another possibility of classification can be production-oriented or stress-oriented processes.
Manufacturing-oriented processes
- Stress relief annealing
- Soft annealing
- Normalizing
- Coarse grain annealing
- Diffusion annealing
- Recrystallization annealing
- Remuneration
Stress-oriented procedures
Thermal heat treatment
- Hardening
- Remuneration
- Bainitizing
- Surface hardening , etc. a.
Thermochemical heat treatment
- Carburizing
- Carbonitriding
- Nitriding
- Aluminizing
- Silicification
- Vanadize
- Boron
- Nitrocarburizing , etc. a.
Procedure
Above all, metals and their alloys , as well as plastics , are heat-treated for the targeted adjustment of their properties. Heat treatments on ceramics are usually only carried out as part of the manufacturing process (during sintering ).
The material to be treated passes through different temperatures at different times ( temperature-time curve ) and is then cooled at different speeds in different media (water, oil, salt, protective gas, air) depending on the material and process. The range extends from furnace cooling to abrupt quenching in order to set certain technological properties ( strength , hardness , toughness , structure, etc.).
In addition, chemical influences, mechanical or other stresses can have a targeted effect. The respective process is carried out in suitable heat treatment facilities.
A variety of materials can be heat-treated specifically to increase strength, for example certain alloys of aluminum and titanium ( precipitation hardening ) and copper . In all cases, this involves solution heat treatment with quenching and subsequent precipitation hardening . All metallic materials can be annealed . Sometimes this is even absolutely necessary as an intermediate step in cold forming .
Careful heat treatment is important for the profitability of a tool or component. For example, a high-alloy tool steel , if it has been incorrectly heat-treated, may have poorer technological properties than a low-alloy steel that has been correctly heat-treated. A correctly heat-treated and high-alloy tool steel, on the other hand, will have even better mechanical properties.
In order to produce high quality products, efficient control of the processes is necessary. A process that is as energy-saving as possible is also sought in the context of rising energy prices . This includes the sensible use of control and regulation elements, burner technology and a coordinated combination of different refractory products such as light refractory bricks and high-temperature wool / ceramic fiber products.
See also
literature
- Hans-Werner Zoch , Günter Spur : Handbook Heat Treatment and Coating , Hanser, 2015.
