Bearings are an important mechanical basic connection and are widely used in the machinery industry. It can be said that where there is rotation, there is a bearing. As the main means of transportation for people in modern society, the automobile industry has also become the main pillar industry in my country, and bearings also play an important role in it. Bearings can be seen in many security parts of the car, such as steering gears, engines and gearboxes. As a branch of bearings, automotive bearings have special properties such as load-bearing, impact resistance and high-speed rotation, and their performance has an important impact on the safety of passengers, drivers and the vehicle itself. Heat treatment is a key process in the manufacturing process of automobile bearings, and its processing quality and raw materials are two important factors that affect the bearing life. Below, the author briefly expounds the heat treatment technology of automobile bearings from the aspects of material, heat treatment design, heat treatment process, heat treatment equipment, heat treatment technical force and heat treatment development direction of automobile bearing according to his own work experience and knowledge. Automobile bearing heat treatment technology The main function of the main alloying element chromium in automobile bearing steel is to improve the hardenability of the steel, so that the parts can obtain a more uniform structure on the entire section after quenching and tempering. Chromium can form alloy cementite (Fe, Cr) 3C, refine the austenite grains, reduce the overheating sensitivity of the steel during heating, improve wear resistance, and enable the steel to obtain fine needle-like or hidden shapes during quenching. Crystalline martensite makes the steel increase toughness on the basis of high strength. Generally, it is not necessary to perform cryogenic treatment on automobile bearings, unless there are special requirements for the dimensional stability of parts and the content of retained austenite. (1) Production process route of automobile bearing parts The general production route of steel ball rolling elements is: bar stock → ball billet hot pier forming → smooth ball (file) → soft grinding → heat treatment → hard grinding → fine grinding → fine grinding (polishing) ). The general production route of inner and outer rings is: tube material (cold rolling) → annealing → turning → soft grinding → heat treatment → grinding → finishing. The general production route of the cage is: solid cage (nylon): blank → turning → drawing, drilling window → surface treatment. Stamping cage (metal): strip or sheet material→forming→bottom cutting→window punching→slope→expansion→surface treatment. The rolling elements, outer rings and inner rings of automobile bearings, and the second and third generation flanges of wheel hub bearings must be properly heat treated to give full play to the potential of the material itself, obtain the expected performance of the parts and improve the service life of the assembly, mainly including: Spheroidizing annealing, overall quenching + low temperature tempering, chemical heat treatment, induction heat treatment, etc. (2) Overview of heat treatment of key automotive bearing parts The following is a brief introduction to heat treatment equipment, process examples, technical requirements, and development forecasts. The spheroidizing annealing equipment usually uses a protective atmosphere furnace, so that the surface of the annealed parts is less and free of oxidation, and the material utilization rate of the bearing parts can be improved. The heating temperature of the bearing material is 835~850 °C, and the spheroidization temperature is 750~760 °C, as shown in Figure 8. After the ball rolling body is forged, it is used in the continuous nitrogen-based protective atmosphere annealing furnace of Aixelin roller hearth, as shown in Fig. 9a. Spheroidizing annealing temperature is 760 ℃, oxygen potential ≥ 900, dew point ≤ 20 ℃, propane flow rate 0.18±0.02m3/h, furnace pressure 150~300 MPa, hardness ≤ 210 HBW, decarburization layer less than or equal to 0.25 mm, Reticulated carbide ≤CN4.2, the hardness of the steel ball after quenching and tempering is required to be above 60HRC. Nitrogen-based protective atmosphere annealing furnace, protective atmosphere continuous furnace, automatic intermediate frequency quenching and tempering line, heat treatment equipment for automobile bearings It is shown that the production efficiency is high and the energy consumption is low. Common domestic manufacturers include Jiangsu Fengdong, North Industries, and Hangzhou Jinzhou. The inner and outer rings are quenched in a continuous furnace in a protective atmosphere. In order to reduce the deformation, KR468G special bearing quenching oil is used and parameters such as heating temperature time and conveyor belt running speed can be adjusted, or a salt bath can also be used for martensite grading quenching. The process curve is shown in Figure 10. It is shown that the hardness after quenching is 63~64.5 HRC, and the hardness is 61~63 HRC after tempering at 180±10 ℃. The taper of the ring is about 0.05mm, and the cylindricity is ≤0.15mm. The second and third generations of automobile hub bearings have flanges, the material is S55C, and the surface hardness of the quenching area is required to be above 60HRC. An automatic induction quenching production line should be used, as shown in Figure 9c. The cooling medium should be a water-based quenching fluid with adjustable concentration. The quenching fluid pressure should be 0.2~0.6 MPa, the hardness after quenching should be 62~65 HRC, the depth of the hardened layer should be 2.2~3.4 mm, and the roundness should be ≤ 0.1 mm, the hardness is 60~63 HRC after overall tempering at (160±10)℃×(120±5)min, and the microstructure is grade 3~6. With the continuous improvement of domestic heat treatment equipment and production technology, the overall quenching and tempering process curve of bearing parts has basically matured in the production and processing of automobile bearing parts.