(1) Surface quenching:

The surface of the steel is rapidly heated to above the critical temperature, but the heat is rapidly cooled before it is transmitted to the core, so that the surface layer can be quenched in the martensite structure without phase change in the core. The purpose of surface hardening and the same core is achieved. Suitable for medium carbon steel.

(2) Chemical heat treatment:

It refers to the ability of atoms of chemical elements to penetrate into the surface layer of the workpiece by means of the ability to diffuse atoms at high temperatures to change the chemical composition and structure of the surface layer of the workpiece, so as to achieve the specific requirements of the surface layer of the steel. A heat treatment process for performance. According to the type of infiltrating elements, chemical heat treatment can be divided into four types: carburizing, nitriding, cyanidation and metallizing.

Carburizing: Carburizing refers to the process of infiltrating carbon atoms into the surface layer of steel. It also makes the low carbon steel workpiece have the surface layer of high carbon steel, and after quenching and low temperature tempering, the surface layer of the workpiece has high hardness and wear resistance, while the middle part of the workpiece still maintains the toughness of low carbon steel. Plasticity.

Nitriding: Also known as nitriding, it is a process of infiltrating nitrogen atoms into the surface layer of steel. The purpose is to improve the hardness and wear resistance of the surface layer as well as to improve fatigue strength, corrosion resistance and the like. Gas nitriding is often used in production.

Cyanidation: Also known as carbonitriding, it refers to the process of simultaneously infiltrating carbon and nitrogen atoms into steel. It gives the steel surface the characteristics of carburizing and nitriding.

Metal infiltration: refers to the process of infiltrating a surface layer of steel with metal atoms. It is to alloy the surface layer of steel to make the surface of the workpiece have certain alloy steel and special steel characteristics, such as heat resistance, wear resistance, oxidation resistance and corrosion resistance. Aluminizing, chromizing, boronizing, siliconizing, etc. are commonly used in production.