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Heat treatment: hardening, tempering, normalization.

curing It represents a complex heating operations,cooling and aging metal carbide to obtain the required properties due to changes in the structure and internal structure. Heat treatment is used as the intermediate operation in order to improve machinability, pressure, or as a final stage of the process, which provides details of the required level of properties. When such an operation is carried out as a heat treatment billet heatingWhich is very responsible. The proper heating depends on the final quality of the product. During the heating it is important to consider that the metal changes its structure, properties and characteristics of the metal surface layer, and as a result of interaction with metal atmospheric air is formed on the surface scale. The thickness of the layer of scale depends on the chemical composition of the metal, the temperature and duration of heating. All steel yield oxidation process in different ways. Alloy steelsFor example, to form a dense thin scale layer which protects the metal from further oxidation. carbon steel lose carbon surface layer with a thickness of 2-4mm, which threatens to decrease metal hardness and strength of steel. High-alloyed and high-carbon steel is heated slowly to avoid cracking. Hromnikelivye also referred to as heat-resistant steel, because theyhardly susceptible to oxidation. When the metal is heated to a temperature necessary to take account of the beginning and end of forging, because the strong overheating of the metal leads to burnout, which is why there is a violation of bonds between the grains and the total destruction of the metal. Among the main types of heat treatment should be noted: 1. Annealing - Processing the metal in which the metal is first heated and then slowly cooled in the furnace. Annealing can be of different types, depending on the heating temperature, cooling rate metalla.2. Hardening. It is a type of heat treatmentdifferent materials (metals, glass, alloys), consisting of heating above the critical temperature with subsequent rapid cooling. Running for nonequilibrium structures with high cooling rate. Hardening can be both a polymorphic transformation, also without polymorphic transformation. 3. holiday - This process, the essence of whichIt is heat-treated to tempered martensite or a metal alloy, in which the main processes are the disintegration of martensite, recrystallization and polygonization. Accommodation is performed after quenching, in order to relieve internal stress, to ensure the required performance, and mechanical properties. 4. Normalization. In this case, the product is heated toaustenitic state and then cooled in still air. As a result, internal stresses are reduced normalization is performed recrystallization steel. Compared with the annealing, normalization - the process shorter and more productive. Also there are some types of heat treatment as a chemical heat treatment, carburizing, nitriding, carbonitriding (cyanidation) borating of steel. Metal heat treatment is carried out in furnaces.

Heat treatment: hardening, tempering, normalization.
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