Annealing
What is the annealing process?
Annealing processes are generally performed at sub-eutectoid temperatures and it is a heat treatment method that improves the material and its workability.
It adds properties such as softening the cast, forged and rolling materials, reducing the stresses in the material, increasing the workability and reducing the brittleness. Thus, the material has the desired mechanical properties at the production stage or at the end of the production. Annealing processes can be applied to steels as well as non-ferrous alloys.
Annealing processes are divided into 3 groups according to the type of atmosphere that the equipment used can provide.
Annealing processes in open atmosphere furnaces;
The advantage of this process is that it is a less costly process than other processes, but since the process atmosphere is air, the material surface is negatively affected by oxygen and other elements in the air. Oxidation (scale) occurs on the surface of the material, which causes discoloration on the surface of the material.
Annealing processes in atmosphere controlled furnaces; (Bright Annealing Process)
In this process, the furnace atmosphere is created in a controlled manner. In this process where nitrogen, helium or hydrogen is used as the furnace atmosphere, the surface of the material after the treatment appears very brightly since there is no oxygen and other unwanted gases.
Annealing processes in vacuum furnaces;
(Bright Annealing Process)
These processes are carried out in vacuum furnaces. Heating and waiting steps in the process are done under vacuum and in the created atmosphere environment. Atmosphere controlled furnaces - the biggest advantage over bright annealing process is that the heating is highly controlled and the possibility of controlled rapid cooling with high pressure.
Types
Normalization Annealing
In this process, the steel is heated to 830-950°C degrees, depending on the carbon content, and then cooled slowly in calm air. The properties that the material will gain as a result of normalization vary according to the pre-treatment condition. The main purpose of the process is to eliminate the undesired properties of the processes such as forging, casting, rolling before the process. (Fining the coarse grains formed and removing residual stress, etc.)
Softening Annealing
In this process, the steel is heated to sub-eutectoid temperatures and depending on the section thickness, the process is carried out by keeping it at this temperature for a certain period of time. Its biggest advantage is that the hardness of the steel is reduced and its ability to be processed and shaped is increased.
Stress Relieving Annealing
In this process, the steel is heated to sub-eutectoid temperatures and depending on the section thickness, the process is carried out by keeping it at this temperature for a certain period of time. Residual stresses in the material are reduced or eliminated by applying after processes such as welding, machining and plastic shaping where residual stresses may occur.
Demagnetization Annealing
It is the process of decreasing the magnetic properties of steels, whose magnetic properties are not desired or which are desired to be at very low values, by keeping them at a certain temperature for a certain period of time.
Spheroidization Annealing
It is the process obtained by transforming cementite in the perlite phase into spherical morphology as a result of holding at certain temperatures and periods in order to increase the workability and shaping capability of the steel.
Aluminum Annealing
These are the processes applied to eliminate the stresses that occur in aluminum manufacturing methods (casting, forging, extrusion, etc.). In addition, as the hardness values decrease as a result of the annealing processes applied to aluminum, the processing and shaping capability increases.
Other annealing processes;
- Re-Crystallization annealing
Ferritizing annealing
Hydrogen embrittlement annealing
Diffusion (Homogenization) annealing
Annealing Processes at Önerler
In our company, atmosphere controlled chamber type furnaces, open and atmosphere controlled annealing furnaces and vacuum furnaces are used for annealing processes.
All of the annealing processes carried out in open, protective and vacuum atmospheres are carried out in our company.
We offer our customers a flexible charge amount opportunity with various furnaces with charging capacities up to 100 - 2000 kg.
All of our furnaces are of German origin and the IPSEN brand, which is a world leader in its field.
With the process control devices in our furnaces, the process is under constant control and the data of the processes are recorded.
Since the establishment of our company in 1967, we have been offering the best quality to our customers with our experience, expert staff and state-of-the-art equipment in the annealing process we have been doing for a period of 50 years.
Benefits of the processes
The stress within the material decreases,
Microstructure of the material is improved,
Magnetic properties are improved,
Low distortion,
Improvement in welded materials,
It is reduced to the required hardness,
Clean surface (bright annealing),
Increasing workability,
Increasing the forming ability.
Tavlama sonrası oluşabilecek problemler
Scale and oxidation can be seen especially in the annealing processes performed in open atmosphere furnaces, and also color changes can occur on the surface of the material. In steels with high hardenability and relatively high alloy, the hardness of the material may increase after the normalization process (due to the formation of martensite and bainite phases in the regions close to the surface), thus processing capability may be negatively affected. In addition, a de-carburization layer can be seen on the surface during the normalization process carried out in open atmosphere furnaces.
In bright annealing processes performed under shielding gas, embrittlement or brittleness may be observed in the material due to poor control of the atmosphere composition.
In vacuum annealing (bright annealing) of high alloy steels (stainless and tool steels), if the furnace parameters are not entered correctly, the properties of the steel may be adversely affected due to the evaporation of certain elements on the material surface.