Forging and heat treatment process of KM bearing | bearing steel
Bearing steel full name rolling bearing steel, with high compressive strength and fatigue limit, high hardness, high wear resistance and certain toughness, good hardenability, very strict control of sulfur and phosphorus, is a high quality steel, can do cold do tool steel. Specific gravity: 7.81
Forging temperature of bearing steel
(1) Starting forging temperature: 1150(1120) Finishing satin temperature: 850(800) degrees.
(2) Remove surface defects before forging, and try to preheat them before heating them quickly.
(3) During warm processing, avoid the blue brittle zone of 200~400 degrees. During hot working, avoid entering high temperature brittle zone (greater than 1250). Avoid entering the hot brittle zone (800~ 950 degrees). Today's Highlights:
(2) Heat treatment after forging
(1) After forging -- pre-heat treatment (spheroidizing annealing) -- Final heat treatment (quenching + low temperature tempering)
(2) Spheroidizing annealing purpose: To reduce hardness, facilitate processing and prepare for quenching.
Spheroidizing annealing process: heating to 750~ 770 degrees, holding for a certain time, and air cooling after slow cooling to below 600 degrees.
(3) Various bearing steel quenching + low temperature tempering and hardness table
Steel quenching temperature and quenching medium low temperature tempering hardness HRC
Water or oil 150~17062~64
GCr9800~830 Water or oil 150~17062~64
Water or oil 150~16062~64
GCr15820 ~ 846 oil 150 ~ 16062 ~ 64
GCr15SiMn800 ~ 840 oil 150 ~ 17062 ~ 64
(3) Quenching and quenching medium
(1) Quenching color (experience) White is the hardest and brittle, yellow is hard and tough, blue is soft and tough.
(2) Quenching medium
A water: The general temperature is not more than 40 degrees, no oil, soap and other impurities.
B salt and alkali aqueous solution: 5 to 10 percent salt or alkali added to water.
The cooling rate of salt solution is ten times that of water, and its hardness is high and uniform, but its microstructure is stressed and has certain rusting effect. The temperature is below 60 degrees.
Alkali solution (caustic sodium solution) is corrosive and has small adaptability.
C oil: including oil, spindle oil, transformer oil, diesel oil, etc. It can reduce deformation and cracking. Carbon steel is not applicable. Oil temperature: 60~ 80 degrees, the highest is not more than 100~120 degrees.
(4) Tempering temperature
Bearing steel adopts low temperature tempering. Temperature: 150~250 degrees. It can reduce the internal stress and brittleness under the premise of maintaining high hardness and high wear resistance, so as to avoid cracking or premature damage during use. Hardness HRC: 58~ 64.