ZWZ bearings to rolling bearings of a, the rolling bearing is the operation of the shaft and the shaft seat between the sliding friction is changed into rolling friction, thereby reducing the friction loss of a precision mechanical components. Rolling bearings generally by the inner ring, outer ring, rolling body and keep frame is composed of four parts, the role of the inner ring is with the shaft which is matched with the shaft to rotate together; the outer ring is and the bearing seat are matched to play a supporting role; rolling body is using to keep frame uniform rolling body distribution, ring and the outer ring between, the shape and size and number of directly affects the rolling bearing performance and life; holder can make the rolling bodies uniformly distributed, prevent the rolling body fall off, guiding the rolling body rotation play the role of lubrication.
Precision bearing on the dimensional stability of the higher requirements. Ring quenching (especially marquenching) after internal organization still retains much of the retained austenite, which is unstable, in storage and use of the process, will continue to change, to change the precision bearings, so the cold treatment process, he can reduce retained austenite in the organization and hardness slightly raise the level of parts. But we should also pay attention to austenite too little, or not conducive to the improvement of bearing life.
Rolling bearing cooling technology
(1) after quenching at room temperature to stay:
After quenching, the ferrule is uniform after cooling to room temperature treatment. Otherwise prone to cracking, and after cooling to room temperature immediately cold treatment (usually not more than 30 minutes) otherwise it will terminate the austenite to martensite transformation.
(2) the cold treatment temperature: temperature of cold treatment is mainly according to the martensitic transformation in steel end temperature, you must also consider the effect of cold treatment on the mechanical properties and technological factors.
(3) cold insulation: Although a lot of martensitic transformation is in cold to a certain temperature in an instant to complete, but to make a group ring surface and the heart are to achieve uniformity of cold treatment temperature, heat preservation time, usually in one to one and a half hours or so.
(4) ZWZ bearing cooling after tempering: ring cold treatment on the air, the temperature slowly rose to room temperature and tempering. The temperature can not be too fast, otherwise easy to crack, timely tempering, otherwise ring inside the large residual stress can lead to cracking of the ring, generally not more than two hours. Quality inspection of the cold treatment usually after cold treatment, the main defects of bearing ring is crack, testing available magnetic testing method.
