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Characteristics of Steel Sheet - Heat Treatment
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As temperature increases, structural change (transformation) takes place in the metal. If the cooling speed is quickened, the progress of the transformation is delayed and, as a result, a metal structure that is unusual at a normal temperature can be obtained. Heat treatment is a technical process to obtain metallic features to meet desired requirements through heating and cooling.
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A kind of heat treatment used for cutting tools and blades that have to be harder than what they are cutting: |
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Hardening is done by quickly heating up the material up to a high temperature 1,472 °F (800 °C) and then submerging it in water or oil. As the result of this process, the steel becomes a few times harder. Hardened steel also becomes brittle. | |
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Tempering heats up the metal to around 1,112 °F (600 °C) then gradually cools it. This process increases the toughness of steel. | |
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This heat treatment process decreases metallic grain size after they are made large and rough during heating or casting. By removing eccentric crystallization and residual stress, the metal’s properties are returned to normal. Usually the metal is heated up to 1,472-1,652 °F (800-900 °C) and then gradually cooled down.
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This heat treatment process alters the physical and sometimes chemical properties of a material to increase its ductility and to make it more workable. This may be required after a material has been work hardened by cold working or a hardened. Depending upon the kinds and use of materials, heating temperature, time duration of holding temperature, cooling temperature, and speed has to be adjusted. | | 
