As the bearings are rust-proofed and packaged, they should not be opened until they are ready for installation. In addition, the anti-rust oil applied to the bearings has good lubricating properties and can be used directly without cleaning for general purpose bearings or bearings filled with grease. However, for bearings for instrumentation or bearings used for high speed rotation, clean cleaning oil should be applied to wash away the anti-rust oil, when the bearings are prone to rust and should not be left for a long time.

Shaft and shell inspection cleaning bearings and shell, to confirm that there are no scars or mechanical processing left burrs. There must be no abrasives (SiC, Al2O3, etc.), sand, chips, etc. in the housing. Next, check that the size, shape and machining quality of the shaft and housing are in accordance with the drawings.

Before mounting the bearings, apply mechanical oil to each mating surface of the inspected shaft and housing.

Mounting methods of bearings

The method of mounting bearings varies depending on the type of bearing and the fit conditions.

Since most of them are generally shaft rotating, the inner ring and outer ring can adopt interference fit and clearance fit respectively, while when the outer ring is rotating, the outer ring adopts interference fit.

(1) Press fit

Pressing into the installation of the general use of presses, but also the use of bolts and nuts, if necessary, the use of hand hammer into the installation.

(2) Hot sleeve installation

Heat the bearing in oil to make it expand and then install it on the shaft. The hot sleeve method can make the bearing avoid unnecessary external force and complete the installation work in a short time.

Material factors affecting bearing life

Early failure of rolling bearings takes the form of rupture, plastic deformation, wear, corrosion and fatigue, mainly contact fatigue under normal conditions. Bearing parts failure in addition to service conditions, mainly by the steel hardness, strength, toughness, wear resistance, corrosion resistance and internal stress state constraints. The main intrinsic factors affecting these properties and states are as follows.

Martensite in quenched steel

residual austenite in quenched steel

insoluble carbides in quenched steel

residual stresses after quenching and tempering

impurity content of the steel

In order to make the above material factors affecting bearing life in a better state, the first need to control the original organization of the steel before quenching, can take technical measures are: high temperature (1050 ℃) austenitization speed cooling to 630 ℃ isothermal normalization to obtain pseudo-eutectoid fine pearlite organization, or cold to 420 ℃ isothermal treatment, to obtain bainite organization. Can also use forging and rolling residual heat fast annealing, to obtain fine grain pearlite organization, to ensure that the carbide in the steel is fine and uniform distribution. This state of the original organization in the quenching and heating austenitization, in addition to the dissolved carbide in the austenite, insoluble carbide will gather into fine grains.

When the original organization of steel, quenching martensite carbon content (i.e. quenching and heating of austenite carbon content), residual austenite and the amount of insoluble carbide depends mainly on the quenching and heating temperature and holding time, with quenching and heating temperature increases (time certain), the number of insoluble carbide in steel decreases (quenching and martensite carbon content increases), the number of residual austenite increases, hardness is first with the quenching temperature increase and increase, reaching a peak and then with the increase in temperature and decrease. When the quenching heating temperature is certain, with the austenitization time extension, the number of insoluble carbides decreased, the number of residual austenite increased, the hardness increased, the time is longer, this trend slowed down. When the original organization of the carbide is small, because the carbide is easy to dissolve into the austenite, so that the hardness peak after quenching moved to a lower temperature and appear in a shorter austenitizing time.

In summary, GCrl5 steel after quenching the insoluble carbide in about 7%, residual austenite in about 9% (the average carbon content of cryptocrystalline martensite in about 0.55%) for the better organization composition. Moreover, when the carbides in the original organisation are small and evenly distributed, the microstructure composition at the above-mentioned level is reliably controlled, which facilitates the acquisition of high overall mechanical properties and thus a high service life. It should be noted that the original tissue with fine, diffusely distributed carbides, when quenched and heated and held, the fine, insoluble carbides will gather and grow, coarsening them. Therefore, for the original organization with this bearing parts quenching heating time should not be too long, the use of rapid heating austenitization quenching process, will be able to obtain a higher overall mechanical properties.

In order to make the bearing parts after quenching and tempering surface residual larger compressive stress, can be quenched and heated through the carburizing or nitriding atmosphere, for a short period of time the surface carburizing or nitriding. As this steel quenching and heating austenite actual carbon content is not high, well below the equilibrium concentration shown on the phase diagram, so you can absorb carbon (or nitrogen). When the austenite contains higher carbon or nitrogen, its Ms lower, quenching the surface layer than the inner layer and the heart after the martensitic transformation, resulting in a larger residual compressive stress. gCrl5 steel to carburizing atmosphere and non-carburizing atmosphere heating quenching (both by low temperature tempering) after treatment, by contact fatigue test can be seen, the life of the surface carburizing than non-carburizing increased by 1.5 times. The reason for this is that the surface of carburised parts has a greater residual compressive stress.