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Manipulation of data elements affecting bearing life
Source: Bearing network time: 2017-09-11
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When the original arrangement in the steel is punctual; the carbon content of the quenched martensite (ie the austenite carbon content after quenching heating), the amount of retained austenite and the amount of undissolved carbide depend primarily on the quenching heating temperature and persistence. Time; followed by quenching heating temperature increase (time must be); steel in the amount of undissolved carbide reduction (hardened martensite carbon content increased), the amount of retained austenite increased; hardness is first added with the increase of quenching temperature; arrival The peak value then decreases with the increase of temperature. When the quenching heating temperature is punctual; the extension of the austenitizing moment; the reduction of the amount of undissolved carbide; the increase of the amount of retained austenite; the increase of hardness; This tendency is slowed down. When the carbides in the original arrangement are fine; because the carbides are easily dissolved into austenite; the hardness peak after quenching is shifted to a lower temperature and occurs at a shorter austenitizing moment.
In summary, the undissolved carbides of GCrl5 steel after quenching are about 7%; the retained austenite is about 9% (the uniform carbon content of cryptocrystalline martensite is about 0.55%) is the best arrangement. And; when the original arrangement of fine carbides. Zhi Ji Ren Bao Hui Kang Kang fresh éŠ å— South halo (19) 橹槌墒 挥 诨竦 诨竦 诨竦 诨竦 诨竦 Ï Ï Ï åŸ½ 埽 埽 埽 埽 埽 埽 埽 埽倜. It should be pointed out; the original arrangement with finely dispersed carbides; the quenching heating and heat preservation; the undissolved fine carbides will gather and grow; roughen them. Thus; the quenching heating moment of the bearing parts with such original arrangement Should not be too long; use the rapid heating austenitizing quenching process; will achieve higher inductive mechanical properties.
In order to quench the bearing parts after quenching and tempering, the surface has a large compressive stress; the carburizing or nitriding atmosphere can be introduced during the quenching heating; the external carburizing or nitriding is performed in a short time. The practice of carbon is not high; it is much lower than the equilibrium concentration shown on the phase diagram; thus it can absorb carbon (or nitrogen). When austenite is rich in higher carbon or nitrogen; its Ms decreases; when quenching The surface layer has a martensite transformation after the inner layer and the core; a large residual compressive stress is generated. The GCrl5 steel is heated and quenched in a carburizing atmosphere and a non-carburizing atmosphere (all subjected to low temperature tempering), and the touch fatigue test is performed. It can be seen that the life of external carburizing is 1.5 times higher than that of non-carburizing. The reason is that the surface of carburized parts has large residual compressive stress.
3 The main data elements and the degree of control that affect the service life of high carbon chromium steel rolling bearing parts are:
.1) The carbide requirements in the original arrangement of the steel before quenching are fine and diffuse. The high temperature austenitizing 630 ° C, or 420 ° C high temperature can also be used, which can also be completed by the wrought waste heat blast annealing process.
.2) After quenching of GCr15 steel; microscopic arrangement of undissolved carbides with a uniform carbon content of about 0.55% cryptocrystalline martensite, about 9% Ar and about 7% in a uniform and round state This microscopic arrangement can be manipulated by quenching the heating temperature and timing.
.3) After the quenching of the parts, the residual surface has a large compressive stress after the tempering; this will contribute to the progress of the fatigue resistance. The treatment process of carburizing or nitriding in a short time at the time of quenching heating may be selected; There is a large compressive stress.
.4) Producing steel for bearing parts; demand has high purity; the first is to reduce the content of O2, N2, P, oxide and phosphide. Optional electroslag remelting; vacuum training and other technical measures to make the data oxygen The quantity ≤ 15PPM is suitable.
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