Keywords: method, advantages, disadvantages, quenchi, quenching, quenching methods, double liquid, Single liquid, quenching medium, salt bath,

Compare the advantages and disadvantages of several quenching methods

Quenching can be divided into single liquid quenching, double liquid quenching, graded quenching, and isothermal quenching according to different cooling methods. What are the advantages and disadvantages of these quenching methods? Here, various quenching methods and their advantages and disadvantages are listed in the Chengchi Industrial Furnace for reference by heat treatment workers :

1. Single liquid quenching is a quenching operation method in which austenitic chemical components are immersed in a certain quenching medium and cooled to room temperature. Single liquid quenching media include water, saltwater, alkaline water, oil, and specially formulated quenching agents. Generally, carbon steel is quenched and alloy steel is quenched with oil.

The single liquid quenching operation is simple and conducive to achieving mechanization and automation. Its disadvantage is that the cooling rate is limited by the cooling characteristics of the medium, which affects the quenching quality. Single liquid quenching is only suitable for workpieces with simpler shapes for carbon steel.

2. Double liquid quenching is the process of immersing austenitic chemical components in a medium with strong cooling capacity. Before the steel component reaches the temperature of the quenching medium, it is immediately removed and immersed in another medium with weak cooling capacity, such as water before oil or water before air, for cooling. Double liquid quenching reduces deformation and cracking tendency, but the operation is difficult to master and has certain limitations in application.

3. Martensitic graded quenching is a quenching process in which austenitic components are first immersed in a liquid medium (salt bath or alkali bath) with a temperature slightly higher or lower than the martensitic point of steel, held for an appropriate period of time, and then taken out for air cooling after both the inner and outer layers of the steel reach the medium temperature to obtain martensitic structure, also known as graded quenching.

Graded quenching can effectively reduce phase transformation stress and thermal stress, as well as reduce quenching deformation and cracking tendency, by air cooling after the graded temperature stays at the same temperature inside and outside the workpiece. Graded quenching is suitable for alloy steel and high alloy steel workpieces with high deformation requirements, and can also be used for carbon steel workpieces with small cross-sectional dimensions and complex shapes.

4. Bainite isothermal quenching is a quenching process that austenitizes steel parts, rapidly cools them to the bainite transformation temperature range (260-400 ℃), and maintains them isothermal to transform austenite into bainite. It is sometimes also called isothermal quenching. The general insulation time is 30-60 minutes.

5. Composite quenching rapidly cools the workpiece to below Ms to obtain 10% to 20% martensite, and then isothermal in the lower bainite temperature range. This cooling method can enable workpieces with larger cross-sections to obtain M+B microstructure. The martensite formed during pre quenching can promote bainite transformation, and during isothermal quenching, it can also temper the martensite. Composite quenching is used for alloy tool steel workpieces, which can avoid the first type of tempering brittleness and reduce the residual austenite content, i.e. the tendency to deform and crack.

Compressed air quenching, spray quenching and jet quenching are also used for special workpieces.

More Comparison of the advantages and disadvantages of several quenching methods: www.quenchtank.com/view-246.html