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Technology of metallic heat treatment is basic knowledge
From;    Author:Stand originally

Heat treatment craft includes to heat commonly, heat preservation, cooling 3 processes, heat only sometimes and cool two processes. These processes join each other, cannot discontinuous. Heating is one of important working procedure of heat treatment. Of metallic heat treatment heat the method is very much, the earliest it is to use charcoal and coal to serve as heat source, use liquid and aeriform fuel then. Electric application makes heat to be controlled easily, and pollute without the environment. Use these heat source to be able to heat directly, also can carry the salt of melt or metal, particle of down to float undertakes heating secondhand.

When the metal heats, workpiece is exposed in air, often produce oxidation, decarbonization (namely content of carbon of surface of steely spare parts reduces) , this has very adverse effect to the exterior function of the spare parts after heat treatment. Consequently the metal should be in normally can accuse atmosphere or salt of medium, melt counteracts protective atmosphere heat in vacuum, also can use coating or pack a method to undertake protective heating.

Heat one of vital technology parameter that temperature is heat treatment craft, choice and control heat temperature, it is the main problem that assures heat treatment quality. Heat the goal that temperature follows the metallic material that is handled and heat treatment is different and different, but it is to heat to change commonly temperature above, in order to acquire high temperature organization. Additionally change needs proper time, because this becomes what metallic workpiece surface achieves a requirement,heat when temperature, still must hold proper time in this temperature, make temperature of inside and outside consistent, make microstructure change complete, this paragraph of time calls heat preservation time. Use high-energy density heats and when exterior heat treatment, heat speed is splitting, do not have heat preservation time commonly, and the heat preservation time of thermo-chemical treatment often longer.

Refrigeration also is the indispensable measure in heat treatment process, because technology is different and cooling method is different, basically be control cooling rate. The cooling rate of general anneal is the slowest, the cooling rate of normalizing is rapidder, quenched cooling rate is rapidder. But because steel is planted,still have diverse demand, for example empty hard steel can use the cooling rate like normalizing to have temper by dipping in water hard.

Craft cardinal principle can divide metallic heat treatment to be mixed for integral heat treatment, surface heat treatment thermo-chemical treatment 3 kinds big. The basis heats medium, heat of temperature and cooling method different, each kinds big can distinguish again the heat treatment craft that is a certain number of differring. Same kind the metal uses different heat treatment technology, can acquire different organization, have different property thereby. Iron and steel is the metal with the widest application on industry, and steely microstructure is most complex also, because this is steely sort of heat treatment craft is various.
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