The main heat treatment process of carburizing steel is generally quenching and low temperature tempering after carburizing. The core of the treated part is a low-carbon martensite structure with sufficient strength and toughness, and the surface layer is hard and wear-resistant tempered martensite and a certain amount of fine carbide structure.

Some structural parts work under strong impact and wear conditions, such as gearbox gears on automobiles and tractors, cams and piston pins on internal combustion engines, etc.

According to the working conditions, these parts are required to have high surface hardness and wear resistance, while the core part requires high strength and appropriate toughness, that is, the performance of “hard on the outside and tough on the inside” is required.

In order to take into account the above dual performance, low carbon steel can be used to achieve it through carburizing quenching and low temperature tempering. At this time, the core of the part is the quenched structure of low carbon steel, which ensures high toughness and sufficient strength, while the surface layer (at a certain depth) ) has a high carbon content (0.85% to 1.05%), has a high hardness (HRC>60) after quenching, and can obtain good wear resistance.