The method of quenching in heat treatment

Single media hardening

The workpiece is cooled in a medium, such as water quenching or oil quenching. Advantages are simple operation, easy to achieve mechanization, wide application. The disadvantage is that in the water quenching stress, the workpiece is easy to deformation and cracking; Quenching in oil, the cooling speed is small, quenching diameter is small, large workpiece is not easy to quench.

Dual quenching

The workpiece is first cooled to about 300℃ in a medium with strong cooling capacity, and then cooled in a medium with weak cooling capacity. For example, water quenching followed by oil quenching can effectively reduce the internal stress of martensite transformation and reduce the tendency of deformation and cracking of the workpiece. It can be used for quenching the workpiece with complex shape and uneven section. The disadvantage of dual - liquid quenching is that it is difficult to grasp the time of dual - liquid conversion, early conversion is easy to quench hard, late conversion and easy to quench crack. In order to overcome this shortcoming, the graded quenching method was developed.

The workpiece is quenched in low-temperature salt bath or alkali bath furnace. The temperature of salt bath or alkali bath is near Ms point. The workpiece stays at this temperature for 2min ~ 5min, and then it is taken out for air cooling. The purpose of fractional cooling is to make the temperature inside and outside the workpiece more uniform, and to conduct martensite transformation, which can greatly reduce the quenching stress and prevent deformation and cracking. The grading temperature was always slightly higher than the Ms point before, and the temperature inside and outside the workpiece was uniform before entering the martensite region. Improved to a temperature rating slightly below Ms. Practice shows that it is better to grade below Ms points. For example, the high carbon steel mold in the 160℃ alkali bath graded quenching, both hard, deformation and small, so it is widely used.

Isothermal quenching

The workpiece is quenched in an isothermal salt bath. The temperature of the salt bath is at the lower part of the bainite zone (slightly higher than Ms). The workpiece stays isothermal for a long time until the bainite transformation is completed. Isothermal quenching is used for steel above medium carbon to obtain lower bainite to improve strength, hardness, toughness and wear resistance. Low carbon steels are generally not isothermal quenched.

Surface hardening

Surface quenching is a method to quench the steel surface layer to a certain depth while the core part remains unquenched. The surface of the workpiece is quenched by rapid heating, so that the surface of the workpiece quickly to the quenching temperature, in the heat is not enough to penetrate the core of the workpiece immediately cooling, to achieve local quenching.

Induction hardening

Induction heating is the use of electromagnetic induction to produce eddy current in the workpiece and the workpiece will be heated.

There are four basic processes of heat treatment of iron and steel: annealing, normalizing, quenching and tempering.


The workpiece will be heated to the appropriate temperature, according to the material and the size of the workpiece with different insulation time, and then the slow cooling (cooling rate is the slowest) to make the metal internal organization to reach or near equilibrium, obtain good performance and performance, or for further quenching for the organization.

Is the fire

The workpiece will be heated to the appropriate temperature after cooling in the air, the effect of normalizing is similar to annealing, only to get a finer structure, often used to improve the cutting performance of materials, but also sometimes used for some parts with low requirements as the final heat treatment.


In order to reduce the brittleness of steel, the quenched steel is kept warm for a long time at an appropriate temperature higher than room temperature but lower than 710℃, and then cooled. This process is called tempering.


A heat treatment process for obtaining martensite or bainite structures by heating austenitized workpieces and cooling them in an appropriate manner. The most common are water - cold quenching, oil - cold quenching, air - cold quenching.

Annealing, normalizing, quenching and tempering are the "four fires" in the overall heat treatment.


The cooling part of the workpiece during the quenching period.

Partial quenching

Quenching applied only to parts of the workpiece that require hardening.

Gas cooling quenching

Quenching and cooling in vacuum and in neutral and inert gases under high pressure, normal pressure or high pressure.

Surface quenching only for the surface of the workpiece quenching, including induction quenching, contact resistance heating quenching, flame quenching, laser quenching, electron beam quenching.

Air cooling quenching

Quenching cooling with forced flow of air or compressed air as the cooling medium.

Salt water quenching

Quenching and cooling with saline aqueous solution as cooling medium.

Organic quenching

Quenching and cooling of aqueous solution of organic polymer as cooling medium.

Spray quenching

Quench cooling with jet flow as cooling medium.

Spray cooling

The workpiece is quenched and cooled in a mixture of water and air.

Hot bath cooling

The workpiece is quenched and cooled in the hot bath of molten salt, molten alkali, molten metal or high-temperature oil, such as salt bath quenching, lead bath quenching, alkali bath quenching, etc.

Double liquid quenching

After heating the austenitization, the workpiece is immersed in the medium with strong cooling ability, and then transferred to the medium with weak cooling ability immediately when the martensitic transformation is about to take place.


The purpose of quenching and cooling the workpiece under special clamp after heating austenitization is to reduce quenching and cooling distortion.

Through quenching

The hardening of the workpiece from the surface to the core.

Isothermal quenching

After heating austenitizing, the workpiece is cooled rapidly to isothermal maintenance of bainite transition temperature interval, so that the austenitic becomes bainite quenching.

Interrupted quenching

After the workpiece is heated austenitizing, it is immersed in alkali bath or salt bath with slightly higher temperature or slightly lower than M1 point to keep appropriate time. After the workpiece as a whole reaches the temperature of the medium, it is taken out for air cooling to obtain martensite quenching.

The temperature quenching

After quenching and cooling in the temperature range of Ac1-Ac3, the martensite and ferrite microstructure of the subeutectoid steel workpiece were obtained.

Direct quenching

The process of direct quenching and cooling after the workpiece is penetrated with carbon.

Two quenching

After the workpiece is carburized and cooled, it is austenitized at a temperature higher than Ac3 and quenched to refine the core tissue, and then austenitized at a temperature slightly higher than Ac3 to refine the hardening of the infiltrated layer tissue.

Since the cold hardening

After the austenitization of the part or surface of the workpiece is heated rapidly, the heat in the heating zone is transferred to the unheated zone by itself, so that the austenitization zone is quickly cooled and quenched.

Vacuum Pump vacuum pump and vacuum furnaces Grinding Machine, Cnc Lathe, Sawing Machine vacuum furnace
vacuum furnace vacuum pump,vacuum furnaces vacuum pump,liquid ring vacuum pump