The factors affecting the service life of bearing and its control

Early failure mode of the rolling bearing, mainly include: fracture, plastic deformation, wear, corrosion, fatigue under normal conditions the main contact fatigue is the main internal factors: hardness, strength, toughness, wear resistance, corrosion resistance, internal stress state ( The service condition) 1. The martensite hardened steel high carbon chromium steel original organization: granular pearlite quenching + tempering at low temperature, quenching martensite M in carbon content, significantly influence the mechanical properties of the steel GCr15 steel quenching M carbon content is 0. 5% ~ 0. 56% can be obtained the comprehensive mechanics performance of the strongest ability to resist failure. M: cryptocrystalline martensite, measured carbon content is average carbon content. 2. Hardened steel the retained austenite in high carbon chromium steel after normal quenching can contain 8% ~ 20% Ar ( Retained austenite) 。 Ar has both advantages and disadvantages of bearing parts, Ar content should be appropriate. Ar % write the contact fatigue life of hardness, and subsequently increased to peak and then subsequently and reduce the effect of Ar Ar to be in a stable state, if the spontaneous into martensite, will make the steel toughness reduced sharply and embrittlement. Bearing load is small: Ar a small amount of deformation occurs, both to reduce the stress peak, and has the deformation Ar processing reinforcement and stress and strain induced martensite phase transformation and reinforcement, Ar increased to reduce the influence of the bearing contact fatigue life under load is larger: Ar larger plastic deformation, and matrix, the local stress concentration and fracture to reduce 3 life. Hardened steel is not soluble in the amount of carbide not soluble in hardened steel carbide, morphology, size and distribution of steel chemical composition and the influence of the original before quenching organization affected by austenitizing conditions. Bearing ( And are especially carbide spherical) With matrix cause stress concentration and crack, which would reduce the toughness and fatigue resistance. Quenching not dissolve carbide affect the performance of the steel quenching the carbon content of martensite and Ar content and distribution, thus additional impact on the performance of the steel. Quenching is not dissolved carbide too much on comprehensive mechanical properties of steel and failure resistance is harmful. Behind a few not dissolve carbide bearing steel quenching is necessary to obtain fine grain abrasion resistance cryptocrystalline martensite require not less soluble carbide ( Fewer) And small ( Small size) And well, Small size differences, and distributed evenly) , round ( Each grain of carbide spherical) 。 Properly reduce the carbon content of bearing steel is one of the ways to improve the service life of the parts. 4. The residual stress after quenching tempering after quenching temperature tempering the bearing parts, still has a large internal stress. As the increase of the surface residual compressive stress, fatigue strength is increased, Excessive residual stress may cause deformation of the parts) Residual internal stress is tensile stress on the surface, the lower the fatigue strength. 5. The impurity content of impurities of steel, non-metallic inclusions and harmful elements ( Acid soluble) Such as oxygen content is higher, the more the oxide inclusions in steel material's influence on the mechanical properties and the ability to resist the failure parts and the type of impurities, nature, quantity, size, and shape usually have lower toughness and plasticity and the fatigue life for working under high stress of bearing parts, must be reduced with the oxygen content of the steel making exceptions: MnS inclusions in steel shape is elliptic ball to package the harm larger effect on the fatigue life of oxide inclusions reduced smaller may even be beneficial.