For the precision bearing such as the outer spherical bearing, the process of processing not only needs heat treatment, but also has to experience cold treatment, so that the effect of its final presentation will be more ideal, whether it is the use effect of the outer spherical bearing or its service life, so it can be promoted.
Because the dimensional stability of the precision bearing is required to be high, the internal structure of the ring is retained by the retained austenite, because the retained austenite is an unstable structure, so it will change continuously during the storage and use of the outer spherical bearing, thus changing the bearing essence. Degree. Therefore, the cold treatment process can reduce residual austenite in the microstructure and improve the hardness of the parts.
For the bearing steel commonly used for external spherical bearings, the cold treatment process mainly uses refrigerators and dry ice alcohol solutions. When the bearing is quenched, it is necessary to make the inside and outside of the ring evenly cold to the room temperature before it can start cold treatment, otherwise it is easy to crack; and it requires cold to room temperature and immediately cold treatment, do not hesitate, otherwise it will stop the transformation of austenite to martensite.
In the cold treatment of the ball bearing, the key is to set the temperature, which is based on the termination temperature of martensitic transformation of steel, but at the same time, it can not ignore the influence of cold treatment on mechanical properties and technological factors.
For the outer spherical bearings made of GCr15 steel, the cold treatment usually selects -70 C; the cold treatment temperature of the bearing is -40 to -70 C under the condition that the precision is not very high or the equipment is limited, but if it is super precision bearing, the cold treatment can be done between -70 and -80. But it should not exceed this range, because the temperature of undercooling affects the impact fatigue and contact life of bearings.
After the outer spherical bearing has completed the cold treatment process, it also needs a certain heat preservation time and tempering, in which the heat preservation time is generally 1-1.5H; and the tempering is carried out in time after the bearing temperature is slowly rising to the room temperature, and the temperature rise can not be too fast, otherwise it is easy to crack.