Material factors of affecting bearing life
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When the original organization in the steel when quenched martensite carbon content (ie, quenching the austenite carbon content), the amount of retained austenite and undissolved carbides depends on the quenching temperature and hold time , as quenching temperature is increased (time certain), the undissolved carbides in the steel decrease in the number of (increased), the increase in the number of retained austenite in quenched martensite carbon content, hardness first increased with the increase of quenching temperature, peak and then decreases with increasing temperature. When quenching temperature is constant, with the extension of the austenitizing time, the number of undissolved carbides reduced the increase in the number of retained austenite, the hardness increased, a longer time, this trend has slowed. Fine carbides in the original tissue, due to the carbide easy integration into the austenite, so that the hardness after quenching peak toward lower temperatures and appeared in a short austenitizing time.
To sum up, the undissolved carbides GCr15 steel after quenching at about 7% of retained austenite (cryptocrystalline martensite, the average carbon content of about 0.55%) is the best organization in about 9%. Moreover, when the original tissue carbide is small, evenly distributed, reliable control of the level of microstructure, is conducive to high mechanical properties, which has a high service life. It should be noted, has a small dispersion of the original organization of the distribution of carbides, quenching the heat insulation, the small amount of undissolved carbides gathering grew to coarsening. Therefore, for the original organization of imported bearing parts with this quenching time not too long, rapid heating, quenching austenite process will receive the higher comprehensive mechanical properties.
In order to imported bearing parts quenched surface residual large compressive stress after tempering, quenching the pass into the atmosphere of carburizing or nitriding, short-term surface carburizing or nitriding. Due to heating of the steel quenching austenite actual carbon content is not high, well below the equilibrium concentration of the phase diagram shows so you can suck carbon (or nitrogen). Austenite containing carbon or nitrogen, its Ms lower surface than the inner and center quenching martensite transformation occurs, resulting in a larger residual stress. After GCrl5 steel Hardening of the carburizing atmosphere and non-carburizing atmosphere (low temperature tempering) treatment, the contact fatigue test can be seen that the surface carburization of life not carburization increased 1.5 fold. The reason is carburized parts surface has a larger residual stress.
Factors and the degree of control of the main material of the carbon chromium steel rolling life of the imported bearing parts are as follows:
(1) the steel requirements of small, dispersed carbides in the original organization before quenching. Can be high-temperature austenitizing 630 ℃ or 420 ℃ high temperature, unwrought waste heat can also be used to rapid thermal annealing process.
(2) For GCr15 steel after quenching, the average carbon content of about 0.55% of cryptocrystalline martensite was uniform, about 9% Ar and 7% of the circular state of undissolved carbides microstructure. Can make use of the quenching temperature and time control of this microstructure.
(3) parts after quenching and tempering requirements of surface residues have a greater compressive stress, which contribute to the improvement of fatigue resistance. Can be used in quenching the surface a short period of time carburizing or nitriding treatment process, making the surface residues have a greater compressive stress.
(4) manufacturing imports of steel bearing parts, requires a higher purity, mainly to reduce the content of O2, N2, P, oxides and phosphides. Can be remelting, vacuum smelting and other technical measures to make the materials, the oxygen content of ≤ 15PPM appropriate.
234407BM 234706BM 234406BM 517/2860V/YA 5610/2500 517/1720X1V 527/1181M 510/1180M 517/930 510/670 590/560 510/500 52780 59080 517/368M 51760U 517/238 6207-2ZN 6206-2ZN 6205-2ZN 6204-2ZN 6203-RZ 6203-2ZN 6202N 6202-2ZN 6201-2ZN 6200ZZ 6200-2ZN 62/32-ZN 62/32-Z 62/32N 62/32-2Z 62/32-2RZ 62/32-2RS 62/28-2RZ 62/22-2RZ 61996 61992 61988 61984
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In order to make the impact of imported material factors bearing life at its best, you first need to control the quenching of steel before the original organization, the technical measures can be taken are: high temperature (1050 ° C) austenitic-speed cooling to 630 ℃ temperature normalizing for pseudo-eutectoid fine pearlite, or cold to 420 ° C, such as processing temperature, to obtain bainite. Unwrought waste heat can be used to rapid thermal annealing, the fine granular pearlite to ensure that small and evenly distributed carbide steel. The original organization of this state in the quenching of austenitizing, in addition to integration into the carbide in austenite, undissolved carbides, will gather into a fine granular.When the original organization in the steel when quenched martensite carbon content (ie, quenching the austenite carbon content), the amount of retained austenite and undissolved carbides depends on the quenching temperature and hold time , as quenching temperature is increased (time certain), the undissolved carbides in the steel decrease in the number of (increased), the increase in the number of retained austenite in quenched martensite carbon content, hardness first increased with the increase of quenching temperature, peak and then decreases with increasing temperature. When quenching temperature is constant, with the extension of the austenitizing time, the number of undissolved carbides reduced the increase in the number of retained austenite, the hardness increased, a longer time, this trend has slowed. Fine carbides in the original tissue, due to the carbide easy integration into the austenite, so that the hardness after quenching peak toward lower temperatures and appeared in a short austenitizing time.
To sum up, the undissolved carbides GCr15 steel after quenching at about 7% of retained austenite (cryptocrystalline martensite, the average carbon content of about 0.55%) is the best organization in about 9%. Moreover, when the original tissue carbide is small, evenly distributed, reliable control of the level of microstructure, is conducive to high mechanical properties, which has a high service life. It should be noted, has a small dispersion of the original organization of the distribution of carbides, quenching the heat insulation, the small amount of undissolved carbides gathering grew to coarsening. Therefore, for the original organization of imported bearing parts with this quenching time not too long, rapid heating, quenching austenite process will receive the higher comprehensive mechanical properties.
In order to imported bearing parts quenched surface residual large compressive stress after tempering, quenching the pass into the atmosphere of carburizing or nitriding, short-term surface carburizing or nitriding. Due to heating of the steel quenching austenite actual carbon content is not high, well below the equilibrium concentration of the phase diagram shows so you can suck carbon (or nitrogen). Austenite containing carbon or nitrogen, its Ms lower surface than the inner and center quenching martensite transformation occurs, resulting in a larger residual stress. After GCrl5 steel Hardening of the carburizing atmosphere and non-carburizing atmosphere (low temperature tempering) treatment, the contact fatigue test can be seen that the surface carburization of life not carburization increased 1.5 fold. The reason is carburized parts surface has a larger residual stress.
Factors and the degree of control of the main material of the carbon chromium steel rolling life of the imported bearing parts are as follows:
(1) the steel requirements of small, dispersed carbides in the original organization before quenching. Can be high-temperature austenitizing 630 ℃ or 420 ℃ high temperature, unwrought waste heat can also be used to rapid thermal annealing process.
(2) For GCr15 steel after quenching, the average carbon content of about 0.55% of cryptocrystalline martensite was uniform, about 9% Ar and 7% of the circular state of undissolved carbides microstructure. Can make use of the quenching temperature and time control of this microstructure.
(3) parts after quenching and tempering requirements of surface residues have a greater compressive stress, which contribute to the improvement of fatigue resistance. Can be used in quenching the surface a short period of time carburizing or nitriding treatment process, making the surface residues have a greater compressive stress.
(4) manufacturing imports of steel bearing parts, requires a higher purity, mainly to reduce the content of O2, N2, P, oxides and phosphides. Can be remelting, vacuum smelting and other technical measures to make the materials, the oxygen content of ≤ 15PPM appropriate.
