In order to make the material factors that affect SKF bearings life at its best, you first need to control quenching of steel before the original organization, technical measures that could be taken: the high temperature (1050 ° c) of austenite speed to 630 ° c cooler isothermal normalizing get thin pseudo-eutectoid pearlitic structure, or to 420 ° c cooler isothermal treatment, access to Bainite organization. Forge-rolling fast annealing heat can also be used, access to fine grain pearlitic structure, to ensure that small and uniform distribution of carbides in steel. Original organization in this state when the heating of austenite in quenching, except for outside the carbides into austenite, undissolved gathered into fine granular carbides.
Dang steel in the of original organization must Shi, quenching horse's body of containing carbon volume (that quenching heating Hou of Olympics's body containing carbon volume), and residues Olympics's body volume and is not dissolved carbide volume main depends on quenching heating temperature and maintained time, as quenching heating temperature increased (time must), steel in the is not dissolved carbide number reduced (quenching horse's body containing carbon volume increased), and residues Olympics's body number increased, hardness is first as quenching temperature of increased and increased, reached peak Hou also as temperature of rise and reduced. When quenching temperature when you must, as the austenite of extension of time, no reduction in the number of dissolved carbon, increase in the volume of residual austenitic, high hardness, a long period of time, this trend slowing down. When the original organization of fine carbide in hours, for carbides easily into austenite, so after quenching hardness peaks to lower temperature and occurs in a relatively short time of austenitic.
To sum up, GCrl5 steel after quenching undissolved carbides in about 7%, around 9% of residual austenite (aphanitic average carbon content of martensite in 0. About 55%) is the best organizations. Moreover, when the original organization of carbides in tiny, when distributed, reliable level of control of the above-mentioned composition microstructure, integrated in favour of high mechanical properties, which has a high service life. It should be noted that has a smaller dispersion of carbide distribution the original organization, when quenching heat insulation, small carbide dissolved flock grows up, making it rough. Therefore, this original SKF bearings for quenching heating time should not be too long, using rapid heating of austenite in quenching process, will benefit from more comprehensive mechanical properties.
For SKF bearing parts surface residues large compressive stresses after quenching and tempering, quenching heat into the atmosphere of carburized or nitrided, surface of carburized or nitrided for a short time. Because of this austenite steel quenching heated actual carbon content is not high, far below the equilibrium concentrations on the phase diagram shown, so you can suck carbon (or nitrogen). When austenite after containing high carbon or nitrogen, its Ms to reduce, within the hardened surface of a layer and Martensitic transformation occurs after cardiac Department, resulting in a greater residual compressive stress. GCrl5 non-carburized steels based on carburizing atmosphere and atmosphere hardening (by low-temperature tempering) after processing, can be seen by contact fatigue test, surface carbonization of carburizing by than to raise life expectancy by a factor of 1.5 times. Their reason is that surface with large residual compressive stress of carburized parts.
Effect of high carbon chromium steel main service life of rolling bearings SKF parts material factor and the degree of control as follows:
(1) steel in front of the quenching carbides required small, dispersed in the original organization. Using high temperature austenitic 630 ° c, or 420 ° c high temperature, forging and rolling heat rapid thermal annealing process can also be used to achieve.
(2) for GCr15 steel after quenching, demanded of the average carbon content of around 0.55% aphanitic martensite, 9% Ar and around about the uniform, circular carbide dissolved in a State of microstructure. Hardening heating temperature and time can be used to control the microstructure.
(3) quenching after tempering at low temperature surface residues are required to have a large compressive stresses, which contribute to the improvement of fatigue resistance. Can be used in surface quenching of heated or carburizing nitriding treatment technology for a short time, makes it larger for superficial residual compressive stress.
(4) manufacture of steel used for SKF bearing part, requires a higher level of purity, mainly the reduction of O2, N2, p, content of oxides and phosphorus. Can be electro-slag remelting, vacuum smelting technical measures, such as the oxygen content of the material at 15PPM.



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