Part Cooling and Quenching

Distortion is very important to bearing races. Not only do we want to preserve the case, or surface, properties given during surface treatments like carburizing and nitriding, but grinding or hard turning is a relatively expensive process. Final dimensional results are critical to bearing performance.

Many manufacturers have elaborate schemes to try to control or minimize distortion, which is the holy grail of bearing heat treatment. Factors include quench media, uniform media flow through the load, stacking, fixture quenching, and the number of times the part was cooled and how it was cooled. Other, less thought-of items include the temperature achieved, how long at temperature, furnace fixture maintenance, rate of heating/uneven heating of the parts, and cooling orientation.

Half a race right next to a radiant tube can have a profound effect on distortion. We can write a whole book on this topic! Needless to say, experience and structured trials are often a proprietary part of the bearing manufacturers’ process. Again, grind stock is money.