Simple quenching method.

One, a single medium (water, oil, air) quenching

Single medium (water, oil, air) quenching: the workpiece that has been heated to the quenching temperature is quenched in the quenching medium to completely cool it. This is the simplest quenching method, which is often used for carbon steel 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.

Second, dual medium quenching.

Double-medium quenching: firstly, the workpiece heated to quenching temperature is cooled to the vicinity of Ms point in a quenching medium with strong cooling capacity, and then cooled to room temperature in a slowly cooling quenching medium, so as to achieve different quenching cooling temperature ranges and have ideal quenching cooling speed. This method is also widely used in carbon tool steel for complex parts or large workpieces made of high carbon steel and alloy steel.

Commonly used cooling media are water-oil, water-nitrate, water-air and oil-air Generally, water is used as fast quenching medium, oil or air is used as slow quenching medium, and air is rarely used.

Thirdly, martensite is quenched in stages.

Martensite graded quenching: Austenitize the steel, and then immerse it in a liquid medium (salt bath or alkali bath) with a temperature slightly higher or lower than the martensite upper point of the steel, and keep it for a proper time. After the inner and outer layers of the steel reach the middle temperature, they are taken out for air cooling, and the undercooled austenite slowly transforms into martensite.

It is generally used for small workpieces with complex shapes and strict deformation requirements, and is also commonly used for quenching high-speed steel and high-alloy steel molds.

Four. Graded quenching method of martensite below Ms point

Martensite step quenching method below Ms point: When the bath temperature is lower than Ms and higher than Mf, the workpiece will be cooled faster in the bath, and the same result can still be obtained when the size is larger. It is often used for large steel workpieces with low hardenability.

Five, bainite isothermal quenching method

Bainite isothermal quenching method: the workpiece is quenched in a bath with the same temperature as the lower bainite of steel to make it undergo lower bainite transformation, and the temperature is generally kept in the bath for 30~60min. Bainite isothermal quenching process mainly includes three steps: ① Austenitizing treatment; (2) cooling after austenitizing; ③ isothermal treatment of bainite; Commonly used in alloy steel, high carbon steel small size parts and ductile iron castings.

Six, compound quenching method

Compound quenching method: firstly, the workpiece is quenched below Ms to obtain martensite with the volume fraction of 10%~30%, and then isothermal in the lower bainite zone to obtain martensite and bainite structure for the workpiece with large cross section, which is often used for alloy tool steel workpieces.

Seven, precooling isothermal quenching method

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

Eight, delayed cooling quenching method

Delayed cooling quenching method: the parts are precooled in air, hot water and salt bath to a temperature slightly higher than Ar3 or Ar 1, and then quenched with a single medium. It is often used for parts with complex shape, different thickness of each part and small deformation.

Nine, quenching self tempering method

Quenching self-tempering method: the whole workpiece is heated, but in the process of quenching, only the part that needs quenching (usually the working part) is immersed in quenching liquid for cooling, and after the fire color of the unexposed part disappears, it is immediately taken out and cooled in the air. Quenching and self-tempering method is to transfer the heat from the center that is not completely cold to the surface to fire back and forth. Tools commonly used for bearing impact, such as chisels, punches, hammers, etc.

Spray quenching method

Spray quenching: a quenching method of spraying water on the workpiece. The water flow can be large or small, depending on the required quenching depth. Spray quenching method will not form vapor film on the surface of workpiece, so it can ensure that the hardened layer is deeper than in the past. Mainly used for local surface quenching.

Extended data

The purpose of quenching is to make undercooled austenite undergo martensite or bainite transformation to obtain martensite or bainite structure, and then temper at different temperatures to greatly improve the rigidity, hardness, wear resistance, fatigue strength and toughness of steel.

So as to meet the different use requirements of various mechanical parts and tools. It can also meet the special physical and chemical properties of some special steels such as ferromagnetism and corrosion resistance through quenching.

A metal heat treatment process in which a metal workpiece is heated to an appropriate temperature for a period of time and then immersed in a quenching medium for rapid cooling. Commonly used quenching media are salt water, water, mineral oil, air, etc.

Quenching can improve the hardness and wear resistance of metal workpieces, so it is widely used in various tools, molds, measuring tools and parts (such as gears, rollers, carburized parts, etc.). ) requires surface wear resistance. Through quenching and tempering at different temperatures, the strength, toughness and fatigue strength of metals can be greatly improved, and the combination of these properties (comprehensive mechanical properties) can be obtained to meet different application requirements.

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