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In order to make the material factors that affect bearing life at its best, you first need to control before quenching the steel original organization, technical measures that can be taken include: high temperature (1050 ℃) austenitic quick cooling to 630 ℃ isothermal normalizing obtain pseudo- eutectoid fine pearlite, or cooling to 420 ℃ isothermal treatment, access to bainite. Wrought heat can also be used rapid thermal annealing, to obtain fine granular pearlite, carbide steel to ensure fine and evenly distributed. The original organization in this state quenching austenite, in addition to carbide dissolved in austenite, the undissolved carbides will be gathered into a fine granular.
When the steel of the original tissue is constant, the carbon content of quenched martensite (i.e. austenite after quenching the carbon content), the residual austenite volume and undissolved carbides depends on the quenching temperature and hold time With quenching temperature increased (time certain), undissolved carbides in steel to reduce the number (quenched martensite increased carbon content), increase in the number of retained austenite, the hardness is increased first with the quenching temperature increases, peak and then decreases with increasing temperature. When the quenching temperature is constant, with the austenitizing time, reduce the number of undissolved carbides, increased number of retained austenite, hardness increased, a long time, this trend slowed. When the original of carbide fine, because carbides easily dissolved in austenite, the hardness after quenching and the emergence of the peak towards lower temperature austenite in a short time.
In summary, GCrl5 undissolved carbide steel after quenching at about 7%, about 9% of retained austenite (cryptocrystalline martensite, the average carbon content of 0.55% or so) for the best organizations. Moreover, when the original organization carbide fine, evenly distributed when the level of the reliable control of the microstructure of the composition, it is advantageous to obtain high mechanical properties, which have a high life. It should be noted, with a fine dispersed carbides of the original tissue, hardening heat insulation, undissolved carbides grew up together, making it rough. Therefore, with this original organization bearing parts quenching time not too long, the use of rapid heating quenching austenite will get higher mechanical properties.
In order to make the bearing parts after quenching and tempering larger surface residual compressive stress, can pass into the quenching carburizing or nitriding atmosphere for a short time on the surface carburizing or nitriding. Because of this steel quenching the austenite actual carbon content is not high, far below the phase diagram showing the equilibrium concentration, it can absorb carbon (or nitrogen). When austenitic contains high carbon or nitrogen, its Ms lower than the inner surface hardening and martensite transformation occurs after cardiac unit, resulting in a large residual compressive stress. GCrl5 steel to carburizing atmosphere and non-carburizing atmosphere heating quenching (both by low-temperature tempering) treatment, after contact fatigue tests can be seen, carburizing carburizing life than not increased by 1.5 times. The reason is that a larger surface of the carburized part of the residual stress.
Affect carbon chromium steel SKF bearings parts life of the main factors and the degree of control materials are:
(A) before quenching steel carbide original organization requires small dispersion. Austenitizing temperature can be 630 ℃, or 420 ℃ high temperature, Wrought heat can also be used to achieve rapid thermal annealing process.
(2) For the GCr15 steel after quenching, asking for the average carbon content of 0.55% of the cryptocrystalline martensite, about 9% Ar and 7% were uniform, round state undissolved carbides microstructure. Quenching can be used to control the heating temperature and time to get this microstructure.
(3) parts after quenching and tempering requires a larger surface residual compressive stress, which helps to improve the fatigue resistance. Can be heated in the hardening short surface carburizing or nitriding treatment process, so that a larger surface residual compressive stress.
(4) FAG bearings parts made of steel, requires a high purity, mainly to reduce O2, N2, P, oxides, and phosphides content. Can be remelting, vacuum smelting and other technical measures so that the material oxygen ≤ 15PPM appropriate.
Bearing a rotating inner ring and outer ring raceway, the rolling contact with the rolling body is thus running track for the dark side, running track attached to the roller surface is not exceptional, which will be aware of the load conditions, So remove the bearing case, strict attention and observation raceway running track.
If you look at the trajectory, then this will only burden that radial load to bear large axial load, moment load to bear, or the extreme rigidity of the bearing housing inequality. You can check whether the bearing loads and added an unexpected installation error is too large, etc., and become held clues to the cause bearing damage. NSK Bearings out at different load conditions of production running track.
(A) is the inner rotating radial load only when the amount of the ordinary running track.
(C) ~ (h) shows the running track on TIMKEN bearings have a bad influence, most of the relatively short life.
Roller bearings running track, too
(I) is in the inner ring rotating load INA bearings used when adding the correct radial load of the outer ring running track.
(J) the inner and outer rings relative inclination, the larger the deflection axis running track, running track raceway, in its longitudinal direction to produce the light and shade of the load ring at the exit trajectory is inclined, the double row tapered roller bearing inner ring rotates.
(K) indicates that only the outer radial loads burdens the running track. L represents an axial load only by the trajectory. In the inner and outer rings relative inclination large radial load only the case when its trajectory deviation in the two orbital plane 180. Position (m).
| Product Model | Inside Diameter | Outside Diameter | Thickness |
| 7004A NSK | 20 | 42 | 12 |
| 7904C NSK | 20 | 37 | 9 |