Control of material factors that affect Slewing Bearings life
In order to make the above factors affect the Slewing Bearings life of the material factor in the best condition, first need to control the original steel before quenching the steel, you can take technical measures are: high temperature (1050 ℃) austenitizing speed to 630 ℃ isothermal normalized to obtain false Eutectoid fine pearlite structure, or cold to 420 ℃ isothermal treatment to obtain bainite structure. It is also possible to use rapid annealing of forged rolling to obtain fine granular pearlite structure to ensure that the carbide in the steel is small and evenly distributed. In this state of the original organization in the quenching and heating austenitizing, in addition to melting into the austenite in the carbide, the undissolved carbide will be aggregated into fine particles.
When the original organization in the steel is constant, the carbon content of the quenched martensite (ie, the amount of carbon in the austenite after quenching and heating), the amount of retained austenite and the amount of undissolved carbide mainly depends on the quenching temperature and the holding time , Slewing Bearings With the quenching heating temperature increased (time must be), the number of undissolved carbides in steel to reduce (quenched martensite increased carbon content), the number of retained austenite increased hardness increases with the increase in quenching temperature, After reaching the peak, it decreases with increasing temperature. When the quenching temperature is constant, with the austenitizing time, the number of undissolved carbides decreases, the number of retained austenite increases, the hardness increases, the time is longer, this trend slows down. When the carbides in the original tissue are small, the carbide peaks are hardened to dissolve into the austenite, so that the hardness peaks after quenching are shifted to lower temperatures and appear at shorter austenitizing times.
In summary, GCrl5 steel after quenching of undissolved carbides in about 7%, retained austenite in about 9% (cryptocrystalline martensite average carbon content of 0.55%) for the best tissue composition. Moreover, when the carbide in the original tissue is small and uniform in distribution, Slewing Bearings it is advantageous to obtain a high comprehensive mechanical property when it is reliably controlled at the above-mentioned level of microstructure, and thus has a high service life. It should be noted that the original organization with fine dispersion distribution of carbides, quenching heat insulation, the insoluble small carbides will gather to grow, to coarsen. Therefore, for this original tissue Slewing Bearings parts quenching heating time should not be too long, the use of rapid heating austenitizing quenching process, will be able to obtain a higher comprehensive mechanical properties.
In order to make the Slewing Bearings parts quenched back to the fire after the surface of the larger compressive stress, can be heated in the quenching of carburizing or nitriding atmosphere, a short period of surface carburizing or nitriding. Because of the fact that the actual carbon content of the austenite during the quenching of the steel is not high, much lower than the equilibrium concentration shown on the phase diagram, it can absorb carbon (or nitrogen). When the austenite contains higher carbon or nitrogen, the Ms decreases, and the martensite transformation occurs when the surface is harder than the inner layer and the heart, resulting in a large residual compressive stress. GCrl5 steel with carburizing atmosphere and non-carburizing atmosphere heating quenching (both by low temperature tempering) treatment, the contact fatigue test can be seen, the surface carburizing life than the non-carburizing increased by 1.5 times. Slewing Bearings The reason for this is that the surface of the carburized part has a large residual compressive stress.