Bearing steel heat treatment process

Bearing steel full name is rolling bearing steel, high compressive strength and the fatigue limit, high hardness, high wear resistance and certain tenacity, good hardenability, control of sulfur and phosphorus is extremely strict, is a kind of high quality steel. Using the bearing steel materials, most of them are imported from Japan, there is also a part of the domestic development in line with Japan's steel composition, processing technology similar to that of bearing steel, steel grade for SUJ2. SUJ2 bearing steel production methods: steel mill adopts vacuum degassing of smelting method, continuous casting to produce good ( Or molded) , forging forming than 6 above, spheroidizing annealing steel after hot rolling, and then to cold drawing processing; Then, according to the regulation of various technical conditions of supply ( Such as: non-metallic inclusions, the decarburization layer depth and size tolerance, shape, appearance, hardness, organization and other indicators) 。 Bearing steel bar after rotary cut processing a molding, came into my company from the heat treatment process. Before entering the heat treatment process, let's look at what is annealed? What is hardening? What is the temper? Why do you want to for a variety of different process? : 1, annealing annealing is commonly used in the production of heat treatment process of preparation, is to put the steel of heating to proper temperature, heat preservation time, and then slowly cooling, to get closer to the balance of heat treatment process of the organization. Its purpose is to eliminate or reduce the internal stress of casting, forging and welding parts and chemical composition of the organization is not uniformity; Can improve and adjust the mechanical properties and process performance of steel, for our rotary cut processing process ready for the organization ( Simple said: to reduce the hardness, easy to machining, in preparation for the quenching) 。 And we use steel in steel mills is actually 'spheroidizing annealing processing (' Heated to 750-770 degrees, and heat preservation time, slowly cooled to 600 degrees of air cooling) 。 Annealing process of steel types, have complete annealing, incomplete annealing, isothermal annealing, spheroidizing annealing and diffusion annealing, etc. ; Also have recrystallization annealing, the stress and to hydrogen annealing, etc. Should not be introduced here. 2, quenching and tempering: bearing steel quenching and tempering heat treatment process is very important and wide application of process. Quenching can significantly improve the strength and hardness of the steel. If combined with different tempering temperature, can be removed ( Or ease) Quenching stress, and can get strength, hardness and toughness of cooperation, to meet different requirements. So, is inseparable two quenching and tempering heat treatment process. ( 1) Quenching steel is heated to a critical point above, after heat preservation at greater than the critical cooling rate ( Vc) Cooling, to get the bainite martensite or next heat treatment process of the organization. ( 2) Tempering heating is to harden steel to A1 point below a certain temperature heat preservation after a certain time, cooling to room temperature of heat treatment process in the proper manner. It's immediate quenching heat treatment procedures, and determines the steel used in the state of organization and performance, the relationship between the service life of the workpiece, it is the key working procedure. We know some basic knowledge of the heat treatment process, take a look at our rolling ball bearing heat treatment process: vacuum quenching: its biggest characteristic is no oxidation, no deformation, no cracks, for my company the production of precision bearing, using the vacuum heat treatment process from the start. Both Japan's vacuum furnace and domestic vacuum furnace are two vacuum chamber (cold and hot Hot chamber vacuum control at 2. Below 0 pa, cold room at nine. Below 3 pa) , the curve of the heating process of bearing steel, in accordance with relevant provisions of the process ( Temperature and time) To step by step to heat up, the highest to 840 plus or minus 10 ℃; However, oil cooled or air cooled by the cooling medium, oil temperature control in the 60-80 ℃, the highest do not exceed 100-120 ℃. Oil tempering: according to the characteristics of the bearing ring, we adopted oil at low temperature tempering, the temperature control in the 180 plus or minus 10 ℃. Its main purpose to reduce internal stress after quenching and brittleness, stable size, can be on the premise of keep the high hardness and high wear resistance, in order to avoid when using split or premature failure. Hardness HRC: 60-64. Also, for stainless steel bearing products, also must pass through such heat treatment process, of course, the curve of the quenching ( Temperature and time) Is different, the temperature is higher, 1040±10℃） , and time is relatively long. And within half an hour after step quenching and cryogenic processing ( That's been done in front of the paper) , its main function is to reduce the residual austenite in the organization, and a stable organization, improve the stability of the ring precision. But, in cryogenic treatment is to control the content of austenite can't too little, because a certain amount of residual austenite is conducive to the improvement of bearing life. Therefore, all future production of my company all cryogenic processing precision bearing should be.