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In order to make import bearings parts after quenching and tempering surface residual compressive stress can be larger, carburizing or nitriding is fed into the quenching heating the atmosphere for a short time, the surface carburizing or nitriding. Because the steel quenching austenite during the actual carbon content is not high, much lower than the phase diagram showing the equilibrium concentration, therefore can absorb carbon (or nitrogen). When the austenite containing higher carbon or nitrogen, the Ms decreased, when quenching surface than the inner and center after the occurrence of martensitic transformation, the pressure caused the residual stress greatly. GCrl5 steel in carburizing atmosphere and non carburizing atmosphere heating quenching (both by low temperature tempering) after the treatment, the contact fatigue test can be seen that the surface carburizing carburizing life than did not increase by 1.5 times.
The main influence factors of high carbon chromium steel rolling material imported bearing service life of parts and control degree:
(1) carbide steel in the original tissue before quenching the requirement of fine and dispersed. Can be made of high temperature austenitizing temperature of 630 DEG C and or high temperature of 420 DEG C, and can also be realized by forging residual heat fast annealing process.
(2) for GCr15 steel after quenching, requested access to hidden crystal martensite, 9% of the average carbon content of about 0.55% about Ar and about 7% of undissolved carbides in microstructure of uniform, round state. Can use the quenching temperature and time to control the microstructure of the obtained.
(3) parts quenching after low temperature tempering requirements of surface residual compressive stress is larger, which helps to improve fatigue resistance. Can be used for the surface treatment process of carburizing or nitriding in short time when in quenching heating, making the surface residual compressive stress is larger.
(4) made of steel imports the bearing parts, requirements are high purity, is the main content of reduced O2, N2, P, oxides and phosphide. Can be used in electro slag remelting, vacuum smelting technology measures to make the material of oxygen content is less than or equal to 15PPM is appropriate.