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Metal Heat Treatment
Heat treatment of materials (annealing) is used in practice to achieve the desired texture and material properties.
It could be classified as final processing of the product but also as an intermediate step in the processing of semi-finished product.
The basic operation of the heat treatment is annealing, which is the basic unit of the technological process and the heat treatment comprises heating to the annealing temperature, hold at temperature, and cooling to room temperature.
Annealing steel can be divided according to the temperature used, respectively. of the phase transition to take place in the steel:
It could be classified as final processing of the product but also as an intermediate step in the processing of semi-finished product.
The basic operation of the heat treatment is annealing, which is the basic unit of the technological process and the heat treatment comprises heating to the annealing temperature, hold at temperature, and cooling to room temperature.
Annealing steel can be divided according to the temperature used, respectively. of the phase transition to take place in the steel:
- annealing without recrystallization
- annealing with recrystallization
Annealing without recrystallization
The blank or finished ohrievanýna the temperature at which there is a phase change ferrite and cementite to austenite.- Stress annealing:
annealing aim is to reduce internal tension steel path relaxation incurred in prior treatment such as. after the rough machining or welding. It is carried out by heating the steel to a temperature in the range 500-650 ° C and hold at the temperature for about 1 -2 hours. - Recrystallization annealing:
It is used to remove the hardening Cold formed. The original deformed structure is completely replaced by a new, undistorted structure that is formed through formation of recrystallization nuclei in the deformed structure and growth, thereby replacing the originally distorted structure undistorted. Recrystallization annealing is performed by heating the steel to a temperature of 550-700 ° C svýdržou the temperature for several minutes to 1 hour. - Soft annealing:
soft annealing in order to reduce the hardness of the blank, the process spheroidization of pearlite lamellar, in order to increase machinability of the material, while reducing the wear of the tools required for processing.
Annealing with recrystallization
The blank or the finished product is heated to a temperature at which the phase change of ferrite and cementite to austenite.- Normal annealing:
It is used for the purpose of grain refinement of austenite recrystallization and produce a fine uniform structure resulting in favorable mechanical properties. It is almost normalized annealed steel only podeutektoidné (nadeutektoidné steel is annealed rarely to improve the method of exclusion of secondary cementite, eg. In forgings, where the slow cooling ruled improper by cementite grain boundaries). It is also necessary in castings and forgings, which are in pristine condition uneven structure, if necessary. very rough grain. - Homogenization (diffusion) annealing:
is used to remove the chemical inhomogeneities castings and forgings diffusion. High annealing temperatures are 1100 to 1200 ° C. Dwell time at the temperature it reaches up to 20 hours to sufficiently diffuse processes took place. High annealing temperature and long residence time at high temperatures create suitable conditions for the growth autenitického grain. Grain refinement after homogenization annealing can be achieved in the next normalizing.
