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Quenching process classification

 
 
The quenching process is one of the major industries in the machinery industry today. It is closely related to the production of quenching technology and belongs to the machine. The results produced by different machines are different.

(1) Liquid quenching
Single-liquid quenching is a quenching operation process in which austenitic product workpiece is quickly immersed in a quenching medium until it is cooled to room temperature. The single-liquid quenching cooling medium is selected based on the fact that the cooling rate of the product workpiece in the medium must be greater than the critical cooling rate of the workpiece steel of the product, and the product workpiece should not be quenched. The single-liquid quenching medium includes water, brine, alkali water, oil and some water-based quenching agents specially designed for special purposes.
(2) Two-liquid quenching
In order to better overcome the shortcomings of single-liquid quenching and to maximize the quenching and cooling of the product workpiece, two kinds of media with different cooling capacities can be used together, that is, the heated product workpiece is first quenched into the first cooling. In a medium with high capacity, it is cooled to a temperature slightly higher than Ms (about 300 ° C), and then immediately transferred to a second medium with less cooling capacity and cooled to room temperature. This quenching cooling method is called two-liquid quenching. .
For some product parts, in order to further slow down the cooling rate below Ms, water quenching or oil quenching can also be used, and air can also be treated as a cooling medium.
(3) Classification quenching (martensitic quenching)
The cooling method is characterized in that the product workpiece is first immersed in a bath having a temperature slightly higher than Ms, and is kept in the bath until the surface of the product workpiece and the center are cooled to the bath temperature, and then the air cooling is taken out. The bath temperature is usually Ms + (10 ~ 20) °C. The composition of the medium in the bath uses a nitrate salt bath, an alkali bath, and a neutral salt bath.
What are the types of quenching processes?


Quenching process
(4) Pre-cooling and quenching
After quenching and heating, the product workpiece is not immediately immersed in the cooling medium. Instead, it is first cooled in the air for a short time. When the workpiece is lowered to a certain temperature, the cooling medium is immersed. This quenching method is called pre-cooling and quenching. Or delay quenching.
The core of pre-cooling quenching is to control the pre-cooling time, and the pre-cooling time is short; the long time may reduce the quenching hardness of the product workpiece (non-martensitic transformation occurs). Because the raw materials of the product parts are different, the shape and shape of the shape vary widely, and it is also affected by the temperature of the furnace and the ambient temperature. Therefore, it is very difficult to accurately measure the pre-cooling time. The key is to master the technology and work experience of the operator.
(5) Local quenching
Some product parts have a high hardness, and other positions have no hardness requirements or require low hardness. In this state, a partial quenching method, that is, a method of quenching only a part of a product workpiece, can be generally used. There are two key forms of local quenching, local heating local cooling and integral heating local cooling. The former is mainly suitable for product workpieces when the salt bath furnace is heated, and the latter box furnace and salt bath furnace can be used.
(6) Cold treatment
The cold treatment is a quenching operation in which the quenched steel is continuously cooled to a temperature below room temperature, and the retained austenite which has not been transformed at room temperature continues to be transformed into martensite.
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