Bearing steel forging and heat treatment process
(A) bearing steel forging temperature
(1) The initial forging temperature: 1150 (1120) Final satin Temperature: 850 (800) degrees.
(2) before forging clear surface defects, as far as possible in the rapid heating after preheating.
(3) warm working, should be 200 to 400 degrees to avoid the blue brittle zone. Thermal processing, should avoid entering the high temperature brittle zone (greater than 1250). Should avoid entering the hot brittle zone (800 ~ 950 degrees). Today's Focus:
(B) heat treatment after forging
(1) ---- after forging pre-heat treatment (annealing of the ball) ---- final heat treatment (quenching and tempering)
(2) spheroidizing Objective: reduce the hardness, ease of processing, as hardening preparation.
Ball annealing process: heating to 750 ~ 770 degrees, holding a certain time, slowly cooled to 600 degrees below air cooling.
(3) a variety of bearing steel quenching and tempering and hardness
Steel quenching temperature and tempering quenching medium hardness HRC
GCr6 800 ~ 820 150 ~ aqueous or oily 17062 ~ 64
GCr9 800 ~ 830 150 ~ aqueous or oily 17062 ~ 64
Water or GCr9SiMn 810 ~ 820 150 ~ 16 062 ~ oil 64
GCr15 820 ~ 846 oil 150 to 160 62 to 64
GCr15SiMn 800 ~ 840 oil 150 to 170 62 to 64
(C) quenching and quenching medium
(1) quenching color (experience) the best and tough white hard and brittle, yellow, hard and tough, blue soft.
(2) quenching medium
A water: general temperature does not exceed 40 degrees, without oil, soap and other impurities.
Salt and alkali solution B: water plus salt or base 5% to 10.
Salt solution 10 times faster than the water cooled, high and uniform hardness, but the stress, and have a certain degree of corrosion effect. Temperature of less than 60 degrees.
Alkaline solution (caustic soda solution) corrosive large and small adaptation range.
C Oil: including oil, spindle oil, transformer oil, diesel oil and the like. Deformation and cracking can be reduced. NA carbon steel. Oil temperature: 60 ~ 80 degrees, with a maximum of 100 to 120 degrees.
(Iv) the tempering temperature
Bearing steel using low-temperature tempering. Temperature: 150 to 250 degrees. You can maintain high hardness and high wear resistance under the premise, reduce stress and brittle, so as not to crack or premature failure when used. Hardness HRC: 58 ~~ 64.
