Carburized bearing steel has the characteristics of high strength, high toughness and high fatigue life. It is often used in working conditions with large impact loads. Different heat treatment processes produce different microstructures, which are important for the structure of the carburized layer and the mechanical properties of the material. Impact. The carbon concentration of carburized bearing steel is in a state of continuous change from the surface to the core of the carburized layer. At the same time, there is still a mechanical property matching problem between the core structure and the carburized layer. Through the reasonable combination of heat treatment parameters, the carburized layer structure and It is a long and complicated research process to achieve the optimal combination of matrix tissue matching. Moreover, the possible structural defects of carburizing bearing steel during carburizing and subsequent heat treatment, such as network carbide, surface decarburization, excessive retained austenite, etc., also increase the difficulty of heat treatment of carburizing bearing steel. It is also an important research direction of carburized bearing steel to improve the surface properties by controlling the surface structure and core structure of the carburized bearing steel after quenching. Therefore, the carburizing method of carburizing bearing steel, the structural defects and their elimination of carburizing heat treatment, as well as the transformation of surface quenching structure and the control of retained austenite are reviewed, and the future heat treatment direction of carburizing bearing steel is prospected. 1. Overview Rolling bearings are widely used basic components, and bearing steel is an important material for the inner and outer rings and rolling elements of rolling bearings. The world's first bearing steel is GCr15 steel (ASTM 52100), which belongs to high carbon chromium steel. After quenching and tempering, it has high hardness, high wear resistance and high fatigue performance. more than 80% of the total output. However, in some metallurgical chemical, wind turbine, aerospace and other fields that require the use of large and medium-sized bearings, fully hardened bearing steel can no longer meet the requirements of higher impact toughness, longer contact fatigue life and bending fatigue life. Therefore, , Carburized bearing steel came into being. Timken first developed the first carburized wear-resistant bearing steel in 1899, and then developed countries such as the United States, Japan, and Germany successively developed a variety of high-end military applications during the First and Second World Wars. Equipped with carburized bearing steel. Carburized bearing steel is a high-quality low-carbon alloy structural steel, which has strict requirements on metallurgical purity and organizational uniformity. Due to the limitation of technology and equipment level, the domestic research on carburized bearing steel started relatively late. The series of steel grades in my country's current standard CB/T 3203-2006 'Carburizing Bearing Steel' are shown in Table 1, including: Cr-Mo series represented by 20CrMo; Cr-Ni-Mo series represented by 10CrNi3Mo and 20CrNi2Mo ; Cr-Mn-Mo system represented by 20Cr2Mn2Mo. In addition, there are the second generation aviation bearing steel G13Cr4Mo4Ni4V and the third generation aviation bearing gear steel 16Cr14Co12Mo5Ni2. Table 1 my country carburized bearing steel grades and their chemical composition (mass fraction) High hardness, high strength and high wear resistance, and the low carbon lath martensite in the core can provide good toughness, so bearings made of carburized bearing steel can resist large shock loads during operation. In addition, the quenched surface layer of carburized bearing steel will obtain a deep residual compressive stress layer, which enables the bearing to offset part of the external stress during operation, improve durability and prolong fatigue life. Carburizing bearing steel to achieve toughening, carburizing and subsequent heat treatment are very important. Improper process may cause some structural defects, such as: serious network carbides formed on the surface after carburizing, excessive residual austenite on the surface, infiltration Internal oxidation of carbon layer, surface decarburization, etc., will adversely affect the mechanical properties and fatigue life of carburized bearing steel. In order to eliminate the defects of heat treatment structure of carburized bearing steel and improve the performance, domestic and foreign experts and scholars have carried out a lot of research and practice. In this paper, the carburizing method, structural defects and elimination measures of carburizing heat treatment, quenching structure transformation of carburized layer and control of retained austenite are reviewed, and the current status of heat treatment of carburized bearing steel is reviewed. 2. Carburizing method of carburizing bearing steel Carburizing is to promote carbon atoms to penetrate into the surface of the workpiece by certain means, so that the workpiece can obtain a hardened layer of a certain depth, and cooperate with the good toughness of the core to achieve the purpose of strengthening and toughening. According to the different carbon-containing media, carburizing methods can be divided into solid carburizing, liquid carburizing, gas carburizing and ion carburizing. Solid carburizing is to put the workpiece to be carburized together with solid carburizing agent (charcoal + carbonate) into a closed device, and then heat it in a high temperature furnace for a certain period of time, during which the carbonate is gradually decomposed and finally activated carbon atoms are obtained. , When a large number of activated carbon atoms are adsorbed on the surface of the steel, a certain concentration difference will be formed on the surface and inside of the steel, and the surface carbon atoms will diffuse to the inside along the concentration gradient, and a carburized layer of a certain depth will be formed after a long time of heat preservation.