Cold treatment of NJ 308 bearing drawing rings
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1 the effect of cold treatment
Precision bearing high requirements for dimensional stability; ring quenching (especially the quenching), residual austenite retained more of the internal organization, the residual austenite is unstable in the organization, storage and use of the bearing in the process, will continue to NJ 308 bearing drawing change, and change the precision of the bearing from. Therefore the use of cold processing technology, it can reduce the residual austenite in the organization, slightly increase the hardness of parts.
2 cold treatment process
After quenching at room temperature to stay: after quenching, must make ferrule uniform cooling to room temperature after cold treatment, otherwise easy to crack, cooling to room temperature immediately after the cold treatment (less than 30min), otherwise it will suspend the transformation from austenite to martensite.
Cold treatment temperature: cold treatment temperature mainly according to the martensite transformation temperature of Mf steel is terminated, you must also consider the effect of NJ 308 bearing drawing cold treatment on the mechanical properties and process factors.
For GCr15 steel, cold treatment using -70 DEG C; accuracy is not very high ring or equipment is limited, the cold treatment temperature optional -40 to -70 DEG C; super precision bearings, can be cold processing between -70 to -80 DEG C. Cold temperature affect the bearing impact fatigue and contact life.
Cold treatment: Although the insulation of NJ 308 bearing drawing the martensite transformation is tilting moment finished to a certain temperature in the cold, but in order to make a group of ring surface and the heart are evenly to cold treatment temperature, need heat preservation time, generally 1 ~ 1.5h.
After cold treatment, tempering: ring after cold treatment in the open air, the temperature slowly to room temperature after timely tempering. Temperature can not be too fast, or easy to crack; tempering in time, otherwise the ring inside the large residual stress will lead to ring cracking, generally not more than 2h.
234407BM 234706BM 234406BM 517/2860V/YA 5610/2500 517/1720X1V 527/1181M 510/1180M 517/930 510/670 590/560 510/500 52780 59080 517/368M 51760U 517/238 6207-2ZN 6206-2ZN 6205-2ZN 6204-2ZN 6203-RZ 6203-2ZN 6202N 6202-2ZN 6201-2ZN 6200ZZ 6200-2ZN 62/32-ZN 62/32-Z 62/32N 62/32-2Z 62/32-2RZ 62/32-2RS 62/28-2RZ 62/22-2RZ 61996 61992 61988 61984
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The quenching and cooling to room temperature, placed immediately stay below room temperature environment for a certain period of NJ 308 bearing drawing time, take out at room temperature, the temperature lower than room temperature treatment called cold treatment. Bearing steel cold treatment by refrigeration and dry ice alcohol solution.1 the effect of cold treatment
Precision bearing high requirements for dimensional stability; ring quenching (especially the quenching), residual austenite retained more of the internal organization, the residual austenite is unstable in the organization, storage and use of the bearing in the process, will continue to NJ 308 bearing drawing change, and change the precision of the bearing from. Therefore the use of cold processing technology, it can reduce the residual austenite in the organization, slightly increase the hardness of parts.
2 cold treatment process
After quenching at room temperature to stay: after quenching, must make ferrule uniform cooling to room temperature after cold treatment, otherwise easy to crack, cooling to room temperature immediately after the cold treatment (less than 30min), otherwise it will suspend the transformation from austenite to martensite.
Cold treatment temperature: cold treatment temperature mainly according to the martensite transformation temperature of Mf steel is terminated, you must also consider the effect of NJ 308 bearing drawing cold treatment on the mechanical properties and process factors.
For GCr15 steel, cold treatment using -70 DEG C; accuracy is not very high ring or equipment is limited, the cold treatment temperature optional -40 to -70 DEG C; super precision bearings, can be cold processing between -70 to -80 DEG C. Cold temperature affect the bearing impact fatigue and contact life.
Cold treatment: Although the insulation of NJ 308 bearing drawing the martensite transformation is tilting moment finished to a certain temperature in the cold, but in order to make a group of ring surface and the heart are evenly to cold treatment temperature, need heat preservation time, generally 1 ~ 1.5h.
After cold treatment, tempering: ring after cold treatment in the open air, the temperature slowly to room temperature after timely tempering. Temperature can not be too fast, or easy to crack; tempering in time, otherwise the ring inside the large residual stress will lead to ring cracking, generally not more than 2h.
