The inner and outer rings and rolling elements of rolling bearings shall have high hardness, contact fatigue strength, good wear resistance and impact toughness. They are generally made of chromium manganese high carbon steel (anti pitting corrosion). Common materials include GCr15 bearing steel, GCr15SiMn bearing steel, gcr6 bearing steel and gcr9 bearing steel. The hardness after quenching shall not be less than 61hrc-65hrc.
GCr15 Bearing Steel
GCr15 bearing steel is a kind of high carbon chromium bearing steel with low alloy content, good performance and the most widely used. After quenching and tempering, it has high and uniform hardness, good wear resistance and high contact fatigue performance. The steel has medium machinability and poor weldability. GCr15 bearing steel, including C0 95-1.05，Mn0. 25-0.45，Si0. 15-0.35。
Good comprehensive performance After spheroidizing annealing, it has good machinability After quenching and tempering, the hardness is high and uniform, and the wear resistance and contact fatigue strength are high Good hot working performance It contains less alloy elements and is cheaper.
GCr15SiMn bearing steel
GCr15SiMn bearing steel has higher wear resistance and hardenability than GCr15, medium cold working plastic deformation, poor weldability, sensitive to white spot formation, and temper brittleness during heat treatment. For manufacturing wall thickness > 12mm Ferrule with outer diameter ≥ 250mm; Steel ball with diameter of 50.8-203.2 and roller with diameter > 22mm; In addition, it can also be used as other mechanical parts requiring high hardness and wear resistance, such as rolls Screw gauge, etc.
GCr15SiMn steel is a high carbon and high chromium bearing steel, which has higher wear resistance and hardenability than GCr15 steel The critical quenching diameter in oil is 90 ~ 110mm (volume fraction is 50% martensite). After oil quenching at 840 ° C, tempering at 350 ° C, and then light quenching, the surface hardness is up to 1096hv and the depth of hardening layer is up to 1mm. In view of the deficiency of heat treatment process of forming roller, precooling and cooling at the thin edge are adopted to produce non martensitic transformation and troostite or sorbite, so as to enhance toughness, reduce stress and then quench as a whole to meet the process requirements.
Cold treatment can improve the dimensional stability of the bearing, or martensite step quenching can be carried out to stabilize the residual austenite and obtain high dimensional stability and high toughness. Forging is generally not recommended for this steel. It is generally used after quenching and low-temperature tempering.
Gcr6 bearing steel
Gcr6 bearing steel is used for measuring tools and cutting tools. The composition of this steel is equivalent to that of gcr6 bearing steel. Its hardenability, hardness and wear resistance are higher than that of carbon tool steel, and the size changes little during heat treatment. It is widely used as measuring tools, such as sample plate, chuck, sample sleeve, gauge, block gauge, ring gauge, thread plug gauge and sample column. It can also be used to manufacture cold working molds such as wire drawing die and cold upsetting die, as well as low-speed cutting tools to cut less hard materials.
Gcr9 bearing steel
The wear resistance and hardenability are higher than gcr6 steel, the machinability is acceptable, the cold strain plasticity is medium, the weldability is poor, it is also sensitive to the formation of white spots, and the heat treatment has the tendency of tempering brittleness. It is used to manufacture steel balls with a diameter of 13.5-25.4mm, tapered rollers with a diameter of 10.3-18.5mm, cylindrical rollers with a diameter of 9.4-17.2 and spherical rollers with a diameter of 9.2-17.1.
Gcr9 steel is a kind of high carbon chromium bearing steel with less alloy content, good properties and the most widely used. After quenching and tempering, it has high hardness, uniform structure, good wear resistance and high contact fatigue performance. The steel has medium machinability and poor weldability.
It is mainly used to make steel balls, rollers and ferrules of internal combustion engines, electric locomotives, automobiles, tractors, machine tools, rolling mills, drilling machines, mining machinery, general machinery, and high-speed rotating high-load mechanical transmission bearings. In addition to making balls and bearing rings, they are sometimes used to make tools, such as dies and measuring tools.