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Lihua Technology(HK) Industrial Co., Ltd.

Ten Commonly Used Quenching Methods

1. Single medium (water, oil, air) quenching
Single medium (water, oil, air) quenching: Quenching the workpiece that has been heated to the quenching temperature into a quenching medium to cool it completely. This is a simple quenching method and is often used for carbon and alloy steel workpieces with simple shapes. The quenching medium is selected according to the heat transfer coefficient, hardenability, size and shape of the parts.

2. Double medium quenching
Dual-medium quenching: The workpiece heated to the quenching temperature is first cooled to the Ms point in a quenching medium with strong cooling capacity, and then transferred to a slow-cooling quenching medium to cool to room temperature to achieve different quenching cooling temperature ranges, and there are The ideal quenching cooling rate. It is used for complex shapes or large workpieces made of high carbon steel and alloy steel, and carbon tool steel is also mostly used in this method. Commonly used cooling media are water-oil, water-nitrate, water-air, oil-air. Generally, water is used as a quick-cooling quenching medium, oil or air is used as a slow-cooling quenching medium, and air is less used.

quenching

3. Martensite graded quenching
Martensitic graded quenching: The steel is austenitized, and then immersed in a liquid medium (salt bath or alkali bath) with a temperature slightly higher or lower than the upper Martens point of the steel, kept for an appropriate time, and the inner and outer parts of the steel are treated. After the layer reaches the medium temperature, it is taken out for air cooling, and the supercooled austenite is slowly transformed into a quenching process of martensite. It is generally used for small workpieces with complex shapes and strict deformation requirements, and high-speed steel and high-alloy steel tools and dies are also commonly quenched by this method.

4. Martensite graded quenching method below Ms point
Martensitic graded quenching method below Ms point: When the bath temperature is lower than the Ms of the workpiece steel and higher than Mf, the workpiece cools faster in the bath, and the same result as the graded quenching can be obtained when the size is larger. Commonly used for larger size low hardenability steel workpieces.

quenching

5. Bainite isothermal quenching method
Bainite isothermal quenching method: The workpiece is quenched into a bath with the lower bainite temperature of the steel at an isothermal temperature, so that the lower bainite transformation occurs. Generally, it is kept in the bath for 30~60min. CNC WeChat public number cncdar bainite isothermal quenching process has three main steps: ① austenitizing treatment; ② cooling treatment after austenitization; and ductile iron castings.

6. Compound quenching method
Compound quenching method: firstly quench the workpiece to below Ms to obtain martensite with a volume fraction of 10%~30%, and then isothermally in the lower bainite area to obtain martensite and bainite structure for the workpiece with larger cross-section. Alloy tool steel workpiece.

7. Pre-cooling isothermal quenching method
Pre-cooling isothermal quenching method: also known as heating isothermal quenching, the parts are first cooled in a bath with a lower temperature (greater than Ms), and then transferred to a bath with a higher temperature to make the austenite undergo isothermal transformation. It is suitable for steel parts with poor hardenability or large workpieces that must be austempered.

8. Delayed cooling quenching method
Delayed cooling quenching method: The parts are pre-cooled in air, hot water, and salt bath to a temperature slightly higher than Ar3 or Ar1, and then single-medium quenching is performed. It is often used for parts with complex shapes and parts with large thickness disparity and small deformation requirements.

9. Quenching and self-tempering method
Quenching and self-tempering method: heat all the workpieces to be treated, but during quenching, only the part that needs to be hardened (usually the working part) is immersed in the quenching liquid for cooling, and when the fire color of the unimmersed part disappears, immediately take it out in the air. Quenching process with medium cooling. The quenching self-tempering method uses the heat that is not completely cooled in the core to be transferred to the surface to temper the surface. Commonly used for impact-bearing tools such as chisels, punches, hammers, etc.

10. Spray quenching method
Jet quenching method: The quenching method of jetting water flow to the workpiece, the water flow can be large or small, depending on the required quenching depth. The spray quenching method does not form a vapor film on the surface of the workpiece, which ensures a deeper hardened layer than that of quenching in conventional water. Mainly used for local surface quenching.
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