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Types of annealing and quenching

1、 Type of annealing
1. complete annealing and isothermal annealing
Complete annealing is also called weighing crystallization annealing, which is generally referred to as annealing. This kind of annealing is mainly used for casting, forging and hot rolled sections of various carbon steels and alloy steels with hypoeutectoid composition, and sometimes for welded structures. It is usually used as the final heat treatment of some non reworked parts, or as the pre heat treatment of some workpieces.
2. spheroidizing annealing
Spheroidizing annealing is mainly used for hypereutectoid carbon steel and alloy tool steel (such as steel used for manufacturing cutting tools, measuring tools and molds). Its main purpose is to reduce hardness, improve machinability and prepare for future quenching.
3. stress relief annealing
Stress relief annealing is also called low temperature annealing (or high temperature tempering). This kind of annealing is mainly used to eliminate the residual stress of castings, forgings, weldments, hot rolled pieces, cold drawn pieces, etc. If these stresses are not eliminated, deformation or cracks will occur in the steel parts after a certain period of time or in the subsequent machining process.
2、 During quenching, the most commonly used cooling media are brine, water and oil. The workpiece quenched by brine is easy to obtain high hardness and smooth surface, and it is not easy to produce soft spots that cannot be hardened, but it is easy to cause serious deformation and even cracking of the workpiece. Using oil as quenching medium is only suitable for quenching of some alloy steels or small carbon steel workpieces with greater stability of undercooled austenite