Nouns about heat treatment of steel

1, steel annealing steel is heated to a certain temperature and heat preservation for a period of time, and then make it slowly cooling, called annealing. Steel annealing is a heat the steel to the phase change or part of the phase change temperature, slow cooling after heat preservation heat treatment method. The purpose of annealing is to eliminate tissue defects, improve the organization make composition uniformity and fine grains, increase mechanical properties of the steel, reduce residual stress; Can decrease the hardness at the same time, improve the plasticity and toughness, improve machinability. So before annealing in order to eliminate and improve both the legacy of tissue defects and internal stress, and to prepare for the follow-up process, so the annealing is belong to the intermediate heat treatment, also called heat treatment in advance. 2 fire is fire, the steel is a steel is heated to above the critical temperature, make all into homogeneous austenitic steel, heat treatment and natural cooling in air. It can eliminate hypereutectoid steel mesh cementite, for hyposteel normalizing can refine crystal lattice, improve comprehensive mechanical properties, low requirements for the parts use the normalized instead of the annealing process is more economic. 3, steel quenching is one of quenching heat the steel above the critical temperature, heat preservation for a period of time, then quickly into the quenching medium, the temperature plummeted, rapid cooling, at the rate of greater than the critical cooling rate, which is mainly composed of martensite and unbalanced heat treatment method of the organization. Can increase strength and hardness of the steel quenching, but to reduce its plasticity. That is commonly used in quenching hardening agent are: water, oil, caustic soda, and salt solution, etc. 4, the steel will have quenching tempering steel reheating to a certain temperature, cooling with a certain method called tempering. Its purpose is to eliminate the quenching of internal stress, reduce the hardness and brittleness, in order to obtain the desired mechanical properties. Tempering points and high temperature tempering, the tempering temperature and low temperature tempering. Tempering and hardening, normalizing, cooperate to use. (1) conditioning treatment: high temperature tempering after quenching heat treatment method is called conditioning treatment. High temperature tempering refers to the 500 - Between 650 ℃ tempering. Conditioning can make the performance of the steel material were adjusted greatly, with the strength, plasticity and toughness are better, has the good comprehensive mechanical properties. 2 aging treatment: in order to eliminate the precision measuring tool or mold, parts in the long-term use of change size, shape, often after low temperature tempering, Low temperature tempering temperature is 150 - 250℃） Before finishing, the workpiece heated to 100 - again Keep 5-150 ℃, 20 hours, this to stabilize the quality of precision parts processing, known as aging. At low temperature or under the condition of dynamic load of steel component aging treatment, to eliminate the residual stress, stable steel organization and size, is particularly important. 5, the surface of the steel heat treatment quenching: (1) surface is the surface of the steel by rapid heating to above the critical temperature, but before the heat could spread to the core cooling rapidly, so that you can put the surface layer was quenched martensite structure, and the heart of no phase change, which is to achieve the constant of surface hardening and the core purpose, suitable for medium carbon steel. 2 chemical heat treatment: refers to the chemical elements of the atom, with the help of atom diffusion ability at high temperature, put it into the workpiece surface layer, to change the chemical composition and structure of the workpiece surface, so as to achieve the specific requirements of the steel surface has the organization and performance of a heat treatment process. According to the seeping into the elements of the chemical heat treatment of different kinds can be divided into the carburizing, nitriding, cyanide, and four metal seeping method, etc. Carburizing, carburizing is directed into the steel surface layer of carbon atoms. Is made of low carbon steel workpiece surface layer with high carbon steel, after quenching and low temperature tempering, the workpiece surface layer with high hardness and wear resistance, and the central part of the workpiece is still maintained a low carbon steel toughness and plasticity. Nitriding: also called nitride, is pointing at the steel surface infiltration process of nitrogen atoms. Its purpose is to improve the surface hardness and wear resistance and increase the fatigue strength, corrosion resistance, etc. At present, a lot of the production of the gas nitriding method. Cyanide: also called carbonitriding, refers to the steel at the same time entering into the process of carbon and nitrogen atoms. It makes has the character of carburizing and nitriding steel surface. Metallic cementation: refers to metal atoms into the surface layer of steel process. It is to make the surface alloying of steel, so that the surface has some features of alloy steel, special steel, such as heat resistance, abrasion resistance, oxidation resistance, corrosion resistance, etc. Is commonly used in the production of the aluminized, chromizing, boronizing, siliconizing, etc.