l. High temperature deformation quenching
Deformation quenching belongs to the category of deformation heat treatment. High temperature deformation heat treatment is the thermal external process of plastic deformation above recrystallization temperature, including high temperature deformation quenching and high temperature deformation normalizing.
High temperature deformation quenching is the process of heating steel to Ac3 or above,conducting hot working deformation in the stable temperature range of austenite. and then using hot working residual heat quenching, such as residual heat quenching after forging, hot rolling, etc. After quenching of high temperature deformation, high strength and toughness can be obtained by tempering at appropriate temperature. Generally, when the strength is increased by 10% ~30%. The plasticity can be increased by 40%-50%, and the impact value is doubled. Because the deformation temperature is much higher than the recrystallization temperature, the deformation strengthening effect is easy to be weakened by recrystallization, so it is necessary to strictly control the residence time after deformation and before quenching, and quenching cooling should be performed immediately after deformation.
The reasons for the high strength and toughness are as follows:

• The austenite grains and martensitic lath bundles of structural steel can be refined by high temperature deformation quenching;
• Timely quenching after deformation can preserve defects such as high density dislocation produced by deformation. These high density dislocations can promote carbide dispersion and precipitation along the dislocation, and then remain in martensite, resulting in great dispersion strengthening effect. However, martensite itself has high plasticity and toughness because carbon content decreases and lath M increases after carbide is fully precipitated.

2. Low temperature deformation quenching
Low temperature deformation quenching includes low temperature deformation quenching and low temperature deformation is othermal quenching.
Low temperature deformation quenching is a process in which steel is cooled rapidly to the substable temperature range of supercooled austenite after austenitizing, and then quenched. Low temperature deformation heat treatment is only applicable to steels containing more strong carbide forming elements. This kind of steels are stable in the range of 400-600°C, which is convenientfor plastic deformation without non-martensitic transformation.
Low temperature deformation isothermal quenching is the bainite structure obtained by isothermal quenching after the deformation of metastable austenite. Its strength is slightly lower than that of low temperature deformation quenching, but its plasticity and toughness are higher. It is suitable for hot working die and high strength steel small parts.
The reasons for strengthening and toughening are as follows:

•  Martensite inherits the high density dislocation and refined grain of deformed austenite.
•  During the Austenitic deformation.many ultra-microscopic alloy carbides precipitated around the dislocation, which had the effect of nailing the dislocation and made the dislocation movement difficult.
• Due to the precipitation of carbide, the carbon content and alloying element content in austenite are reduced, the Ms point isincreased, the number of strip martensite is increased during quenching, and the toughness of steel is improved.
• The existence of high density dislocation and fine carbide makes the carbide precipitated by tempering more evenly dispersed.