The full name of precision bearing steel is rolling precision bearing steel. It has high compressive strength and fatigue limit, high hardness, high wear resistance, certain toughness, good hardenability, and strict control of sulfur and phosphorus. It is a high-quality steel that can be used as cold-worked contact steel. Proportion: 7.81
1. Forging temperature of precision bearing steel
(1) Initial forging temperature: 1150 (1120) and final forging temperature: 850 (800).
(2) Remove surface defects before forging, preheat as much as possible and then quickly heat.
(3) During warm processing, the blue brittle zone of 200 to 400 degrees should be avoided. During hot working, avoid entering the high temperature brittle zone (greater than 1250). Try to avoid entering the hot brittle zone (800 ~ 950). Today’s focus:
2. Heat treatment after forging
(1) After forging,————Pre-heat treatment (spheroidizing annealing)——3354 Final heat treatment (low temperature quenching and tempering)
(2) Spheroidizing annealing aims to reduce the hardness, facilitate processing, and prepare for quenching.
Spheroidizing annealing process: heating to 750 ~ 770, holding for a certain period of time, slowly cooling to below 600, air cooling.
(3) Low temperature quenching and tempering and hardness table of various precision bearing steels
Steel grade quenching temperature and low temperature tempering hardness of quenching medium
GCr6 800~820 Water or oil 150~170 62~64
GCr9 800~830 Water or oil 150~170 62~64
GCr9SiMn 810~820 Water or oil 150~160 62~64
GCr15 820~846 oil 150~160 62~64
GCr15SiMn 800~840 oil 150~170 62~64
3. Quenching and quenching medium
(1) Quenching (experience) white is the hardest and brittle, yellow is hard and tough, blue is soft and tough.
(2) Quenching medium
a Water: Generally, the temperature should not exceed 40, and there should be no impurities such as oil and soap.
b. Aqueous solution of salt and alkali: add 5-10% salt or alkali in the water.
The cooling rate of the salt solution is ten times that of water, the hardness is high and uniform, but the microstructure stress is high, and it has a certain corrosive effect. The temperature is less than 60 degrees.
The lye (aqueous solution of caustic soda) is highly corrosive and has little adaptability.
c Oil: including engine oil, spindle oil, transformer oil, diesel oil, etc. Can reduce deformation and cracking. Not suitable for carbon steel. Oil temperature: 60~~80, the highest is not more than 100~120.
4. Tempering temperature
Precision bearing steel is tempered at low temperature. Temperature: 150~250. On the premise of maintaining high hardness and high wear resistance, internal stress and brittleness can be reduced, and cracking or premature damage during use can be avoided. Hardness HRC: 58 ~ 64.
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