(1) After forging-preheating treatment (spheroidizing annealing)-final heat treatment (quenching+low temperature tempering)

(2) Spheroidizing annealing aims at reducing hardness, facilitating processing and preparing for quenching.

Spheroidizing annealing process: heating to 750 ~ 770 degrees, keeping the temperature for a certain time, then slowly cooling to below 600 degrees, and air cooling.

(3) Hardness Table of Quenching+Low Temperature Tempering for Various Bearing Steels

Quenching temperature of steel grade and tempering hardness of quenching medium at low temperature HRC

GCr6 800~820 water or oil 150~ 170 62~64

GCr9 800~830 water or oil 150~ 170 62~64

GCr9SiMn 8 10~820 water or oil 150~ 160 62~64

GCr 15 820~846 oil 150~ 160 62~64

GCr 15SiMn 800~840 engine oil 150~ 170 62~64

2, quenching and quenching medium

(1) quenching color (experience) White is the hardest and brittle, yellow is hard and tough, and blue is soft and tough.

(2) Quenching medium

Answer: Water: The temperature generally does not exceed 40 degrees, and there can be no impurities such as oil and soap.

B: aqueous solution of salt and alkali: add 5- 10% salt or alkali to water.

The cooling rate of salt solution is ten times that of water, and its hardness is high and uniform, but its organizational stress is large and it has a certain corrosive effect. The temperature is below 60 degrees.

Alkaline solution (caustic aqueous solution) is corrosive and has a small scope of application.

C: Oil: including engine oil, spindle oil, transformer oil and diesel oil. Deformation and cracking can be reduced. Not applicable to carbon steel. Oil temperature: 60 ~ 80℃, and the maximum temperature shall not exceed 100~ 120℃.

3. Tempering temperature

Bearing steel is tempered at low temperature. Temperature: 150~250 degrees. On the premise of maintaining high hardness and high wear resistance, reduce internal stress and brittleness, and avoid cracking or premature damage during use. Hardness HRC: 58-64.