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Reasons and precautions for bearing rings need to be tempered
Release time：
2019-11-15
The main reasons why bearing rings need to be tempered after quenching are:
The main reasons why bearing rings need to be tempered after quenching are:
1. In order to remove internal stress
2. In order to accelerate the aging effect, the size and shape of the ferrule will not be changed in the subsequent production process.
3. In order to obtain the specified hardness.
The lowest limit of the tempering temperature - that is, the temperature at which the Madden body begins to form. For bearing steel, this temperature is close to 140 degrees. When tempering at lower temperatures, good results are only obtained for very long holding times.
The rise limit of the tempering temperature is determined by the minimum hardness required for the bearing.
When heated above Mk, the Maddenite decomposes to form a troostite structure. At this point the hardness is reduced. At a tempering temperature of 200 degrees, the hardness decreases not much, about three Hrc units. So if the ferrule is properly quenched and its hardness after quenching is 64-65Hrc, its minimum hardness can be counted as 61Hrc.
This hardness is equivalent to the required hardness that can generally guarantee the best working life of the bearing ring.
In practice, the time for tempering the bearing rings is two hours. Tempering should be done with a stove or a trough. Chamber furnaces are not used at all because the internal temperature distribution is uneven, especially at low temperatures. A so-called circulating furnace with forced air circulation should be used.
The troughs used have salt baths and oil troughs with fast and uniform heat transfer, but they also have the disadvantage that the ferrules need special cleaning after they are removed from the troughs.
1. In order to remove internal stress
2. In order to accelerate the aging effect, the size and shape of the ferrule will not be changed in the subsequent production process.
3. In order to obtain the specified hardness.
The lowest limit of the tempering temperature - that is, the temperature at which the Madden body begins to form. For bearing steel, this temperature is close to 140 degrees. When tempering at lower temperatures, good results are only obtained for very long holding times.
The rise limit of the tempering temperature is determined by the minimum hardness required for the bearing.
When heated above Mk, the Maddenite decomposes to form a troostite structure. At this point the hardness is reduced. At a tempering temperature of 200 degrees, the hardness decreases not much, about three Hrc units. So if the ferrule is properly quenched and its hardness after quenching is 64-65Hrc, its minimum hardness can be counted as 61Hrc.
This hardness is equivalent to the required hardness that can generally guarantee the best working life of the bearing ring.
In practice, the time for tempering the bearing rings is two hours. Tempering should be done with a stove or a trough. Chamber furnaces are not used at all because the internal temperature distribution is uneven, especially at low temperatures. A so-called circulating furnace with forced air circulation should be used.
The troughs used have salt baths and oil troughs with fast and uniform heat transfer, but they also have the disadvantage that the ferrules need special cleaning after they are removed from the troughs.
