Operation method: After heating the steel to Ac3+30~50 degrees or Ac1+30~50 degrees or Ac1 below the temperature (can consult the relevant materials), it is usually slowly cooled with the furnace temperature.
Purpose:
Reduce hardness, improve plasticity, improve cutting and pressure processing functions;
Refine grain, improve mechanical function, prepare for the next step;
Eliminate internal stress during cold and hot working.
Application key:
(1) Suitable for alloy layout steel, carbon steel, alloy steel, high-speed steel forgings, welding parts and supply conditions unqualified raw materials;
(2) Usually annealed in blank condition.

Operation method: The steel parts are heated to 30~50 degrees above Ac3 or Accm, and the cooling rate is slightly greater than that of annealing after insulation.
Purpose:
Reduce hardness, improve plasticity, improve cutting and pressure processing functions;
Refine grain, improve mechanical function, prepare for the next step;
Eliminate internal stress during cold and hot working.
Application key:
Normalizing is usually used as a pre-heat treatment process for forgings, welds and carburized parts. Low carbon and medium carbon carbon layout steel and low alloy steel parts with low functional requirements can also be used as final heat treatment. For ordinary medium and high alloy steels, air cooling can result in complete or partial quenching and therefore cannot be used as a final heat treatment process.

Operation method: The steel is heated to the phase change temperature Ac3 or Ac1 above, held for a period of time, and then cooled rapidly in water, salt, oil, or air.
Intention: Quenching is usually to obtain a high-hardness martensitic arrangement, and sometimes for some high-alloy steels (such as stainless steel, wear-resistant steel) quenching, it is to obtain a single uniform austenitic arrangement to improve wear resistance and corrosion resistance.
Application key:
(1) usually used for carbon steel and alloy steel with carbon content greater than 0.3%;
(2) Quenching can give full play to the strength and wear resistance potential of steel, but together will constitute a large internal stress, reduce the plasticity and impact toughness of steel, so it is necessary to temper in order to obtain better mechanical functions.

Operation method: The quenched steel is heated from scratch to a certain temperature below Ac1, and then cooled in air or oil, hot water or water after heat preservation.
Purpose:
Reduce or eliminate the internal stress after quenching, reduce the deformation and cracking of the workpiece;
Adjust the hardness, improve the plasticity and resistance, and obtain the mechanical function required by the operation; Stable workpiece size.
Application key:
Adhere to the high hardness and wear resistance of steel after quenching with low temperature tempering;
Moderate temperature tempering is used to improve the elastic and yield strength of steel under the condition of insisting on certain toughness;
To adhere to high impact toughness and plasticity, but also meet the strength of tempering with high temperature;
Usually steel tries to prevent tempering between 230 and 280 degrees and stainless steel between 400 and 450 degrees, because a tempering brittleness will occur at this time.

Operation method: high temperature tempering after quenching, the steel is heated to a temperature of 10 to 20 degrees higher than that of quenching, quenching after holding heat, and then tempering at a temperature of 400 to 720 degrees. Purpose:
Improve the cutting function, improve the surface finish;
Reduce the deformation and cracking during quenching;
Achieve outstanding inductive mechanics functions.
Application key:
(1) Suitable for alloy layout steel with high hardenability, alloy east-west steel and high-speed steel;
(2) It can not only be used as the final heat treatment of various more important layouts, but also as the pre-heat treatment of some tight parts, such as lead screws, to reduce deformation.

Operation method: The steel parts are heated to 80~200 degrees, held for 5~20 hours or longer, and then taken out in the air with the furnace to cool.
Purpose:
The arrangement of stable steel parts after quenching reduces the deformation of storage or use time;
Reduce internal stress after quenching and grinding, stable shape and size.
Application key:
(1) suitable for all kinds of steel after quenching;
(2) It is often used for tight workpieces whose shape is no longer required to change, such as tight screw, measuring things, bed chassis, etc.

Operation method: The quenched steel is cooled to -60 ~ -80 degrees or lower in low temperature media (such as dry ice, liquid nitrogen), and the temperature is uniform after taking out the average temperature to room temperature. Purpose:
Convert all or most of the remaining austenite in the hardened steel to martensite, and then improve the hardness, strength, wear resistance and fatigue limits of the steel;
The arrangement of stable steel to the shape and scale of stable steel parts.
Key application:
(1) the steel should be cold treated after quenching, and then tempered by low temperature to eliminate the internal stress during low temperature cooling;
(2) Cold treatment is mainly applicable to alloy steel tight tools, measuring tools and tight parts.

Operation method: Put the steel parts into the carburizing medium, heat to 900 ~ 950 degrees and heat preservation, so that the surface of the steel parts to obtain a certain concentration and depth of carburizing layer.
Objective: To improve the external hardness, wear resistance and fatigue strength of steel parts, and the heart still insists on the resistance status.
Application key:
(1) for low carbon steel and low alloy steel parts with carbon content of 0.15% ~ 0.25%, usually the depth of carburizing layer is 0.5 ~ 2.5mm;
(2) It is necessary to quench after carburizing to obtain martensite on the surface in order to complete the intention of carburizing.

Operation method: The use of active nitrogen atoms differentiated by ammonia at 500 ~ 600 degrees, so that the surface of the steel is full of nitrogen, forming the nitriding layer.
Objective: To improve the hardness, wear resistance, fatigue strength and corrosion resistance of steel parts.
Key application: It is mostly used for medium carbon alloy layout steel rich in aluminum, chromium, molybdenum and other alloying elements, as well as carbon steel and cast iron, usually the nitriding layer depth is 0.025 ~ 0.8mm.

Operation method: Carburizing and nitriding together with the steel surface.
Objective: To improve the hardness, wear resistance, fatigue strength and corrosion resistance of steel parts.
Application key:
(1) Mostly used in low carbon steel, low alloy layout steel and east-west steel parts, usually the nitriding layer depth of 0.02 ~ 3mm;
(2) Quenching and low temperature tempering after nitriding.