Annealing: Usually refers to the treatment required to make the material soft and stress-free. For most materials, such as carbon steel, this would mean raising the temperature very high and then cooling very slowly to room temperature.
Quenching annealing: The purpose here is to obtain a "soft" structure again, but slow cooling will adversely affect the material. Typical is 300 series stainless steel. (Also called austenitic stainless steel.) These stainless steels will not undergo any significant phase change in the main body of the material during the heat treatment process, but if they are kept at a certain intermediate temperature, it may lead to the formation of local harmful phases. Or particles. The range of the long time period. To prevent this from happening, the material is rapidly cooled (quenched) from high temperature. (Usually 1050°C), which reduces the residence time of the material in the temperature range of 500 – 850°C. In this temperature range, they will experience the formation of grain boundary carbides, thereby severely reducing the corrosion resistance of the material .
Solution treatment: The main purpose of heat treatment is to ensure that all different alloying elements are uniformly dispersed throughout the material and "dissolved" in the material as much as possible. This is usually performed on castings, because the solidification process during the casting process tends to cause the material to have relatively large differences in certain alloying elements in different parts of the structure. There are often areas with high concentrations of certain elements and low concentrations of other elements. By raising the temperature to the point where a large amount of diffusion occurs, these uneven alloying element concentrations will become uniform. At these high temperatures, certain phases (such as carbides) will also be "dissolved" (dissolved) by the material. In order to retain as many alloy elements as possible in the solution, some materials are usually quenched after solution treatment. Therefore, this is very similar to the quench annealing discussed above.
Quench hardening: In order to make certain materials (such as carbon steel and low alloy steel) have higher hardness, the material can be heated to a certain temperature above which phase change occurs in the material. (For carbon steel, it is usually 950°C.) The material is then rapidly cooled (quenched) to form some metastable phases (such as martensite), resulting in a higher hardness of the material. When materials are hardened by quenching, they are usually brittle.
Tempering: To soften the material that has been hardened in the previous thermal cycle (for example, quench hardening), you can raise the temperature of the material again to a temperature below which the material begins to undergo a bulk phase change (usually heating To 650-700) °C) and leave it there for a while. During this tempering cycle, the hardened martensite is transformed into tempered martensite, which is not as hard as quenched martensite, but is still very hard.
Quenching and tempering: This is a combination of the above two heat treatment cycles.
Relieve stress: When ductile metals are plastically deformed, they will eventually generate a lot of residual stress in the material. Welding also creates these residual stresses around the weld seam. By increasing the temperature of the metal, the yield strength of the metal decreases. (Yield strength is the stress at which a material begins to plastically deform.) When the yield strength drops below the residual stress level due to high temperatures, the material will "relax". This reduces the stress trapped in the material by deformation or welding activity. Carbon steel can usually relieve stress at a temperature of about 600°C. At this temperature, the residual stress is usually reduced to about 30% of the yield strength of the material at room temperature. The main reason for stress relief is that it improves the fracture toughness of the component. It also reduces the possibility of certain corrosion mechanisms (such as stress corrosion cracking).

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