Method of forming bearing ring resistant to season cracking
A method sets a retained austenite amount of an edge of a bearing ring of a bearing to between 3% or more and 20% or less. The method includes exposing the bearing ring to an environment having a temperature in the range of 850° C. to 930° C., an ammonia concentration, and a carbon concentration C·P in a range of 0.9 to 1.1%, for a period of not more than 5 hours. The ammonia concentration of the environment is in a range of 4 to 7 CFH. The temperature of the environment is then reduced to a temperature in a range of 800° C. to 830° C. for a second period of at least 30 minutes. The bearing ring is next quenched in oil and then heat treated in an environment set to a temperature of 160° C. to 200° C. and then air cooled.
1 . A method of producing a bearing ring with a retained austenite concentration of 3% to 20% in an edge surface, comprising:
forming a bearing ring of carbon steel; and
exposing the bearing ring to an environment having a temperature in the range of 850° C. to 930° C. an ammonia concentration, and a carbon concentration C·P in a range of 0.9 to less than 1.1%, for a period of not more than 5 hours.
2 . The method of claim 1 further comprising setting the ammonia concentration of the environment in a range of 4 to 7 CFH.
3 . The method of claim 2 further comprising reducing the temperature of the environment to a temperature in a range of 800° C. to 830° C. for a second period of at least 30 minutes after the period of not more than 5 hours is expired.
4 . The method of claim 3 further comprising removing the bearing ring from the environment at the end of the second period and quenching the bearing ring in oil at a temperature in a range of 60° C. to 100° C.
5 . The method of claim 4 further comprising tempering the bearing ring after the quenching in an environment set to a temperature of 160° C. to 200° C.
6 . The method of claim 5 further comprising air cooling the bearing ring after the quenching.
7 . The method of claim 6 wherein the carbon steel is high carbon chromium steel corresponding to Japanese Industrial Standards SUJ2.
8 . The method of claim 6 wherein the carbon steel is machine structural use steel corresponding to Japanese Industrial Standards S55C.
9 . The method of claim 1 further comprising setting an ammonia concentration of the environment is in the range of 4 to less than 7 CFH.
10 . The method of claim 9 further comprising reducing the temperature of the environment to a temperature in a range of 800° C. to 830° C. for a second period of at least 30 minutes after the period of not more than 5 hours is expired.
11 . The method of claim 10 further comprising removing the bearing ring from the environment at the end of the second period and quenching the bearing ring in oil at a temperature in a range of 60° C. to 100° C.
12 . The method of claim 11 further comprising tempering the bearing ring after the quenching in an environment set to a temperature in a range of 160° C. to 200° C.
13 . The method of claim 12 further comprising air cooling the bearing ring after the quenching.
14 . The method of claim 13 wherein the carbon steel is high carbon chromium steel corresponding to Japanese Industrial Standards SUJ2.
15 . The method of claim 13 wherein the carbon steel is machine structural use steel corresponding to Japanese Industrial Standards S55C.
16 . A method of producing a bearing ring with a retained austenite concentration of 3% to 20% in an edge surface, comprising:
forming a bearing ring of carbon steel; and
exposing the bearing ring to an environment having a temperature in the range of 850° C. to 930° C., an ammonia concentration of the environment in the range of 4 to less than 7 CFH, and a carbon concentration for a period of not more than 5 hours.
17 . The method of claim 16 further comprising setting the carbon concentration C·P in a range of 0.9 to less than 1.1%,
18 . The method of claim 17 further comprising reducing the temperature of the environment to a temperature in a range of 800° C. to 830° C. for a second period of at least 30 minutes after the period of not more than 5 hours is expired.
19 . The method of claim 18 further comprising removing the bearing ring from the environment at the end of the second period and quenching the bearing ring in oil at a temperature in a range of 60° C. to 100° C.
20 . The method of claim 19 further comprising tempering the bearing ring after the quenching in an environment set to a temperature in a range of 160° C. to 200° C.
21 . The method of claim 20 further comprising air cooling the bearing ring after the quenching.
22 . The method of claim 21 wherein the carbon steel is high carbon chromium steel corresponding to Japanese Industrial Standards SUJ2.
23 . The method of claim 21 wherein the carbon steel is machine structural use steel corresponding to Japanese Industrial Standards S55C.