Ten quenching methods, those that have used three or more are all great!

There are ten commonly used quenching methods in heat treatment processes, namely single medium (water, oil, air) quenching; Double medium quenching; Martensitic graded quenching; Martensitic graded quenching method below Ms point; Bainite isothermal quenching method; Composite quenching method; Pre cooling isothermal quenching method; Delayed cooling quenching method; Quenching and self tempering method; Spray quenching method, etc.

1, Single medium (water, oil, air) quenching

Single medium (water, oil, air) quenching: Quenching workpieces that have been heated to quenching temperature into a quenching medium to completely cool them. This is the simplest quenching method, commonly used for carbon steel and alloy steel workpieces with simple shapes. The quenching medium is selected based on the size of the heat transfer coefficient, hardenability, size, shape, etc. of the parts.

2, Dual medium quenching

Dual medium quenching: The workpiece heated to the quenching temperature is first cooled in a quenching medium with strong cooling capacity to near the Ms point, and then transferred to a slow cooling quenching medium to cool to room temperature, in order to achieve different quenching cooling temperature ranges and have a relatively ideal quenching cooling rate. This method is commonly used for large workpieces made of complex shaped parts or high carbon steel, alloy steel, and carbon tool steel. Commonly used cooling media include water oil, water nitrate, water air, and oil air. Generally, water is used as a fast cooling quenching medium, while oil or air is used as a slow cooling quenching medium, with less use of air.

3, Martensitic graded quenching

Martensite graded quenching: Steel is austenitized and subsequently immersed in a liquid medium (salt or alkali bath) with a temperature slightly higher or lower than the upper martensite point of the steel, maintained for an appropriate period of time. After both the inner and outer layers of the steel reach the medium temperature, it is taken out for air cooling, and the undercooled austenite slowly transforms into martensite in the quenching process. Generally used for small workpieces with complex shapes and strict deformation requirements, this method is also commonly used for quenching high-speed steel and high alloy steel molds.

4, Martensitic graded quenching method below Ms point

Martensite graded quenching method below Ms point: When the bath temperature is lower than the Ms of the steel used for the workpiece and higher than Mf, the workpiece cools quickly in the bath, and when the size is larger, the same results as graded quenching can still be obtained. Commonly used for large-sized low hardenability steel workpieces.

5, Bainite isothermal quenching method

Bainite isothermal quenching method: The workpiece is quenched into a bath at the lower bainite temperature of the steel for isothermal quenching, causing it to undergo lower bainite transformation. Generally, it is kept in the bath for 30-60 minutes. The bainite isothermal quenching process mainly consists of three steps: ① austenitization treatment; ② Cooling treatment after austenitization; ③ Isothermal treatment of bainite; Commonly used in small-sized parts of alloy steel, high carbon steel, and ductile iron castings.

6, Composite quenching method

Composite quenching method: First, rapidly cool the workpiece to below Ms to obtain a volume fraction of 10%~30% martensite, and then isothermal in the lower bainite zone to obtain martensite and bainite structure in larger cross-section workpieces, commonly used in alloy tool steel workpieces.

7, Pre cooling isothermal quenching method

Pre cooling isothermal quenching method: also known as heating isothermal quenching, the parts are first cooled in a lower temperature (greater than Ms) bath, and then transferred to a higher temperature bath to undergo isothermal transformation of austenite. Suitable for steel parts with poor hardenability or workpieces with larger dimensions that require isothermal quenching.

8, Delayed cooling quenching method

Delayed cooling quenching method: The parts are first pre cooled in air, hot water, or salt bath to a temperature slightly higher than Ar3 or Ar1, and then subjected to single medium quenching. Commonly used for parts with complex shapes, varying thickness in various parts, and requiring minimal deformation.

9, Quenching and self tempering method

Quenching self tempering method: Heat all the processed workpieces, but during quenching, only the parts that need to be quenched (usually the working parts) are immersed in quenching solution for cooling. Wait until the non immersed parts disappear, and immediately remove the quenching process that is cooled in air. The quenching and self tempering method utilizes the heat that has not fully cooled through the core to transfer to the surface, causing surface tempering. Commonly used tools to withstand impacts, such as chisels, punches, hammers, etc.

10, Spray quenching method

Spray quenching method: A quenching method that sprays water into the workpiece, with water flow varying in size depending on the required quenching depth. The spray quenching method does not form a vapor film on the surface of the workpiece, which ensures the formation of a deeper hardening layer than quenching in Xitong water. Mainly used for local surface quenching.