Before hardening steel to the impact of material factors bearing life at its best, you first need to control the original organization, technical measures that can be taken are: high temperature (1050 ℃) austenitizing speed cooling to 630 ℃ isothermal normalizing obtained pseudo fine pearlite eutectoid or cold to 420 ° C isothermal treatment, bainite. Rapid thermal annealing, fine granular pearlite unwrought waste heat can be used to ensure that small and evenly distributed carbides. Austenitizing original organization in this state quenching, in addition to the integration into the carbide in austenite and undissolved carbides will gather into a fine granular.
    When the steel in the original tissue is constant, the amount of quenched martensite carbonaceous (i.e. quenching heated austenite carbon content), the amount of retained austenite and the amount of undissolved carbides depends primarily on the quenching temperature and holding time With the quenching temperature increased (a certain time), reduce the number of undissolved carbides in the steel (quenched martensite carbon content increased), increased number of retained austenite, hardness first increases with increasing quenching temperature, reached a peak and then decreases as the temperature rises. When the quenching temperature is constant, with the extension of austenitizing time, the number of undissolved carbides reduce the number of retained austenite increased hardness increased, long time, this trend slowed. When the small original tissue carbide, carbide Ease into austenite, so that the hardness after quenching of the peak towards lower temperature and appears in the austenitizing time shorter.
    Summary, GCrl5 steel quenched the undissolved carbides at about 7% residual austenite at around 9% (cryptocrystalline martensite average carbon content of about 0.55%) is the best organization. Moreover, when the original tissue carbide small, uniform distribution, composition reliably control the level of the microstructure is conducive to obtain high mechanical properties, which have a high life. It should be noted that the fine dispersion of carbides original organization, quenching insulation, fine carbides undissolved gathering grew to coarsening. Therefore, should not be too long to have this original organization bearing parts quenching time, the use of rapid heating austenitizing quenching process, will receive higher mechanical properties.
    In order to make the bearing parts greater compressive stress remaining on the surface after quenching and tempering, is heated in the hardening pass into the carburizing or nitriding atmosphere, for a short period of surface carburization or nitriding. Austenitic not actual carbon content of this steel quenching, well below the equilibrium concentration phase diagram shows, so you can suck carbon (or nitrogen). Austenite with high carbon or nitrogen, reduce the Ms quenching surface compared to the inner and center martensitic transformation occurs, resulting in a larger residual compressive stress. The Hardening GCrl5 steel carburizing atmosphere and carburizing atmosphere (both by the low-temperature tempering) after the treatment, the contact fatigue test can be seen, surface carburization life than not carburization increased 1.5 times. The reason is that the surface of the carburized parts having a large residual compressive stress.


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