Skill Analysis: Data Elements Affecting Bearing Life

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Skill Analysis: Data Elements Affecting Bearing Life

Source: China Bearing Network Time: 2018-05-26
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Early failure modes of rolling bearings; primary cracking, plastic deformation, wear, corrosion and fatigue; under normal conditions, the first is fatigue. The failure of bearing parts is in addition to the conditions of service; the hardness, strength, durability and resistance of steel are the primary. Grinding, corrosion resistance and internal stress conditions are constrained. The main connotation factors affecting these functions and conditions are as follows.
When the martensite high carbon chromium steel in the quenched steel is originally arranged as granular pearlite; in the quenching low temperature tempering condition; the carbon content of the quenched martensite; significantly affects the mechanical function of the steel. The strength and the resistance are at 0.5%. Left and right; touch fatigue life is about 0.55%; anti-crushing can be around 0.44%; when GCr15 steel quenching martensite carbon content is from 0.5% to 0.56%, can achieve anti-failure Can be the strongest inductive mechanical function.
It should be noted that the martensite obtained in this case is cryptocrystalline martensite; the measured carbon content is the uniform carbon content. In practice, the carbon content in the martensite is uneven in the microdomain. The concentration of carbon around the carbides is higher than that of the original ferrites away from the carbides; therefore, the temperature at which they start martensite transformation is different; then the growth of the martensite grains and the appearance of the microscopic shape are followed. It becomes cryptocrystalline martensite. It can prevent microcracks which are easy to appear when quenching high carbon steel; and its sub-layout is dislocation-type lath martensite with high strength and resistance. Therefore; only when high carbon steel When the medium carbon cryptocrystalline martensite is obtained during quenching, the bearing parts can achieve the best resistance to failure.
Residual austenitic high carbon chromium steel in hardened steel after normal quenching; can be rich in 8% to 20% Ar (residual austenite). Ar in the bearing parts has advantages and disadvantages; in order to benefit the disadvantages; Ar content should be appropriate. Because the amount of Ar is mainly related to the austenitizing condition of quenching heating; how much it affects the carbon content of quenched martensite and the amount of undissolved carbide; it is difficult to correctly reflect the influence of Ar amount on mechanical function. Fixed austenitic conditions; using austenite thermal stabilization treatment process; to obtain different amounts of Ar; here, the effect of Ar content on the hardness and touch fatigue life of GCr15 steel after quenching low temperature tempering is studied. Increase in the content of the body; hardness and touch fatigue life are added accordingly; after reaching the peak, it decreases accordingly; but the peak Ar content is different; the hardness peak is around 17% Ar; and the touch fatigue life The peak value is around 9%. When the experimental load is reduced; the effect of the increase in the amount of Ar on the fatigue life of the touch is reduced. This is because when the amount of Ar is small, the effect on the strength drop is small; and the toughening effect is compared. Significant. The reason is that the load is small At the time of Ar; a few deformations of Ar; both the stress peaks are reduced; the deformed Ar processing strengthening and the stress-strain-induced martensitic transformation are strengthened. However, if the load is large, the larger plastic deformation of Ar and the basic understanding part The stress is gathered and cracked; then the life is reduced. It should be pointed out that the beneficial effect of Ar is necessary to be stable under Ar; if it is spontaneously transformed into martensite; the resistance of steel will be drastically reduced and embrittled.
The amount, trace, size and dispersion of undissolved carbides in hardened steel in hardened steel; affected by the chemical composition of steel and the original arrangement before quenching; and affected by austenitizing conditions; The effect of undissolved carbide on the bearing life is less. The carbide is a hard and brittle phase; in addition to the good wear resistance; the load will cause (especially the carbide is non-spherical) and the matrix will cause stress to collect. Cracking occurs; then resistance and fatigue resistance are reduced. Quenching of undissolved carbides not only affects the function of the steel itself; it also affects the carbon content and Ar content of the quenched martensite and the distribution; then the function of the steel is added In order to remind the effect of undissolved carbides on the function; choose steel with different carbon content; after quenching, the martensite carbon content is the same as the Ar content and the undissolved carbide content is different; after 150 °C After tempering; because martensite has the same carbon content; and the hardness is higher; therefore, a small increase in undissolved carbides has little increase in hardness; a crushing load reflecting strength and resistance is reduced; sensitivity to stress gathering of The fatigue life of touch is significantly reduced. Therefore, excessive quenching of undissolved carbide is harmful to the inductive mechanical function and failure resistance of steel. Properly reducing the carbon content of bearing steel is one of the methods to improve the service life of the workpiece.
Quenching of undissolved carbides has an effect on the data function; scale, tracing, and dispersion also affect the data function. In order to prevent damage to undissolved carbides in the bearing steel; less undissolved carbides are required (less quantity) ǔ叽缧.(16)龋ù笮”舜舜嗖詈嗖詈. 曳 龋 龋 (16) 玻 蓟锝猿 L蓟锝猿 is endangered. It should be noted that there is a small amount of undissolved carbide after bearing steel quenching is necessary; Adhere to the wear resistance of the meet; and is also a necessary condition for obtaining fine-grained cryptocrystalline martensite.
Residual stress bearing parts after quenching and tempering after quenching and low temperature tempering; still have large internal stress. Residual internal stress in parts has advantages and disadvantages. After heat treatment of steel parts; followed by increase of residual residual compressive stress The fatigue strength of the steel increases accordingly; when the residual internal stress is the tensile stress, the fatigue strength of the steel is decreased. This is because the fatigue failure of the part is exhibited when the excessive tensile stress is received; when the external pressure is large When the stress remains; it will offset the tensile stress of the equality value; and let the steel accept the tensile stress value minus 蛊@颓慷燃拗翟龈撸拗翟龈撸北砻嬗薪洗罄αΣ写媸保嵊氤惺艿睦αυ The testicles are ridiculous and the smuggling value of the sputum 惺艿睦αγ飨 龃螅 龃螅 龃螅 颓慷 颓慷 颓慷 颓慷 颓慷 颓慷 颓慷 颓慷 颓慷 因而 因而 因而 因而 因而 因而 因而 因而 因而 因而 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承One of the methods (of course, excessive residual stress can lead to deformation or even cracking of the part; it should be given satisfaction).
Impurity content of steel Impurities in steel contain non-metallic inclusions and harmful elements (acid-soluble) content; their damage to steel function tends to grow with each other; for example, the higher the oxygen content; the more oxide impurities are. The effect of impurities on the mechanical function and the resistance to failure of the part is related to the type, nature, quantity, size and shape of the impurity; however, it generally has the effect of reducing the tolerance, plasticity and fatigue life.
With the increase of the scale of the impurities; the fatigue strength decreases accordingly; and the tensile strength of the steel is higher; the downward trend is increased. The oxygen content in the steel is increased (the oxide noisy is increased); the tortuous fatigue and the fatigue of the touch fatigue are Under the high stress effect, it also decreases. Therefore, regarding the bearing parts operating under high stress; it is necessary to reduce the oxygen content of the steel for production. Some studies indicate that the MnS impurities in the steel; due to the shape of the ellipsoid, And it can wrap large oxides and noisy, so it has little effect on the decline of fatigue life and can also be beneficial, so it can be manipulated from wide.
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