What is the highest temperature the bearing can withstand?

The standard stipulates that the working temperature of #rollingbearings of the generally small and medium-sized motor shall not be higher than 95℃. How high temperature can the #bearing actually withstand? This is mainly limited by the heat resistance temperature of bearing steel, cage, sealing material, and lubricant.

1. Heat treatment size and stable temperature of bearing steel

There is a heat treatment stable temperature for ordinary bearing steel. Below this temperature, the bearing keeps the size stable, and the hardness of bearing steel also meets the requirements of use. The stable temperature of heat treatment of general bearings is 150℃. The heat treatment stability temperature of bearings of specific manufacturers will be different.

FAG:

The bearing with outer diameter < 240mm is 150℃;

The bearing with outer diameter ≥240mm is 200℃;

Other bearings are marked with suffixes.

SKF:

#Deepgrooveballbearing 120℃;

#Cylindricalrollerbearings are 150℃;

#Sphericalrollerbearings are 200℃.

2. Temperature range of bearing cage

Usually, steel or brass cages can withstand a relatively large temperature range, steel cages heat resistant temperature up to 300℃, brass cages up to 250℃, but for nylon cages, generally can withstand -40 ~ +120℃ temperature range.

3. Temperature range of seals

For closed bearings, metal material dust cover, no special consideration of the temperature range.

For rubber seals, this needs to be considered.

Nitrile butadiene rubber (NBR) working temperature range is -40 ~ +120℃, can be stable work within 100℃, short-time work at 120℃;

For fluoroelastomer (FKM), it can work stably at -30 ~ +200℃ and temporarily at 230℃.

4. The allowable temperature range of bearing grease

Temperature is one of the most important factors affecting lubrication life.

With the increase of temperature, the viscosity of the base oil of grease decreases. Based on the life of grease calculated at 70℃, its operating temperature increases by 15℃, the life will be reduced by half.

The allowable working temperature of the motor bearing should be the intersection (the narrowest range) of the allowable temperature range of each component of the bearing, and only within this range can the safety of the bearing be guaranteed. Therefore, whether bearings can operate in a high-temperature environment mainly depends on the choice of lubricants, followed by bearing sealing materials (only for closed bearings) and cages, and finally bearing steel.

In practice, the temperature generally measured in the application is the temperature near the outer ring of the bearing. Different measurement methods and positions can differ by up to 15℃. Generally, the heat dissipation condition of the bearing seat is better than that of the shaft, so the temperature of the inner ring and the rolling body is 5~10℃ higher than that of the outer ring.

Therefore, when the test position is outside the bearing chamber, if the measured temperature is 95℃, the hottest temperature of the inner ring may reach 120℃. It has reached the stable heat resistant temperature of nylon cage, imported deep groove ball bearing steel, and grease.