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Material factors affecting the service life of bearing control - bearing knowledge

by:Waxing     2020-06-07
In order to make the material factors affecting bearing life at its best, you will first need to control before quenching steel original organization, can take technical measures are: high temperature ( 1050℃) Austenitizing rapid cooling to 630 ℃ isothermal normalizing get false eutectoid pearlitic structure, or cold to 420 ℃ isothermal treatment, obtain bainite structure. Also can use forged heat rapid annealing, obtain fine granular pearlite structure, to ensure that the carbide steel small and uniform distribution. This state of the original organization when austenitizing quench heating, in addition to into the austenite carbides, not soluble will gather into fine granular carbides. When the original organization must be in the steel, the carbon content of quenched martensite ( The austenite after quenching heating carbon content) , residual austenite and the body not dissolve carbide mainly depends on the amount of quenching heating temperature and holding time, as the quenching heating temperature increased, A certain time) The decrease in the number of, not soluble in steel carbide ( Quenching martensite increased carbon content) , increasing number of retained austenite, hardness first increases with the increasing of quenching temperature, peak and decreased and then increased with the temperature. When quenching heating temperature must, as the extension of austenitizing time, did not dissolve carbide to reduce the number of retained austenite, hardness is higher, for a long time, to slow this trend. When the original organization of fine carbide hours, because the carbide is easy to dissolve in austenite, thus make the hardness after quenching peaks move to low temperature and occur in a relatively short austenitizing time. To sum up, GCrl5 steel after quenching not dissolve carbide at about 7%, the residual austenite is around 9%, About 55%) As the best organizations. And, when the original organization of carbide small, uniform distribution, the reliable control of the above levels of the microstructure, to obtain high comprehensive mechanical properties, which has high service life. It should be pointed out, has the fine carbide dispersion distribution of the original tissue, quenching heat insulation, not dissolve tiny carbides would gather to grow up, make its coarsening. Therefore, for with the original organization bearing parts quenching heating time shoulds not be too long, the rapid heating austenitizing quenching process, will can obtain higher comprehensive mechanical properties. In order to make the bearing parts quenching tempering after large surface residual compressive stress, could pass infiltration during quenching heating carbon or nitriding atmosphere, on the surface carburizing or nitriding for a short period of time. Because the steel quenching when heated austenitic actual carbon content is not high, far lower than on the phase diagram shows the equilibrium concentration, so it can absorb carbon ( Or nitrogen) 。 When austenite contains higher carbon or nitrogen, the Ms is reduced, quenching surface when the martensitic transformation in the aftermath of the inner layer and center, produce the large residual compression stress. GCrl5 steel by carburizing atmosphere and the atmosphere carburizing quenching ( Both low temperature tempering) After treatment, the contact fatigue test, you can see that the surface carburizing of life than carburized increased 1. 5 times. The reason for carburizing of the surface of the parts has a larger residual compressive stress. Affecting the service life of high carbon chromium steel rolling bearing parts using the main material of factors and the degree of control is: ( 1) In the original organization in front of the quenching steel requirements small, dispersion carbide. Can use high temperature austenitizing 630 ℃ or 420 ℃ high temperature, also can use forged heat to achieve rapid annealing process. ( 2) For GCr15 steel after quenching, demanding the average carbon content is 0. About 55% of cryptocrystalline martensite, 9% Ar, and about 7% is uniform, round state did not dissolve carbide microstructure. Can use quenching heating temperature and time to control the microstructure. ( 3) Parts after quenching temperature tempering requirements surface has a larger residual compressive stress, which will help to improve the fatigue resistance. Can be used in quenching heating surface carburized or short time nitriding process, make the surface has a larger residual compressive stress. ( 4) Manufacturing steel bearing parts, requirement with high purity, mainly is to reduce the O2, N2, the content of P, oxides and phosphide. Can use esr, vacuum smelting technology measures such as the material 15 PPM or less oxygen is advisable.
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