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A material factor affecting bearing life
      Early failure in the form of rolling bearings, mainly broken, plastic deformation, wear, corrosion and fatigue, under normal conditions, mainly contact fatigue. In addition to the failure of the bearing parts of the service conditions, mainly by the steel hardness, strength, toughness, wear resistance, corrosion resistance and stress state constraints. The main internal factors affecting these properties and there are several states.
      Martensite hardened steel 1.1
      Carbon chromium steel raw tissue granular pearlite in quenching and tempering state quenched martensite carbon content, significantly affect the mechanical properties of steel. Strength and toughness at around 0.5%, contact fatigue life of about 0.55%, compressive crushing capacity of about 0.42%, while GCr15 steel quenched martensite carbon content of 0.5% to 0.56%, the strongest available anti-lapse mechanical properties.
      It should be noted, in this case the martensite is implicit martensite obtained, the carbon content was measured by the average carbon content. In fact, the amount of carbon in the martensite region is slightly uneven, the carbon concentration is higher than away from the close surrounding carbide carbide in ferrite portion, so that they start the martensite transformation temperature is different, thus inhibiting the grain growth and microstructure of martensite morphology display becomes hidden martensite. It is easy to form high-carbon steel can be avoided quenching microcracking, and its sub-structure high strength and toughness of the strip plate martensite dislocation. Therefore, access to anti-bearing parts may fail to get the best capability matrix carbon martensite hidden only when high-carbon steel quenching.
      1.2 retained austenite in hardened steel
      Normal high carbon chromium steel after quenching, may contain 8% ~ 20% Ar (residual austenite). Bearing parts of Ar advantages and disadvantages, in order to better bring, Ar content should be appropriate. Due to the amount of principal and Ar quenching austenite conditions, and how much it would affect the number of carbon quenched martensite and undissolved carbides, difficult to accurately reflect the amount of influence on the mechanical properties of Ar. For this purpose, fixed Albright conditions, using body heat of austenite stabilization process in order to obtain different amount of Ar, in this study the effects of Ar content on GCr15 steel hardness and contact fatigue life after quenching and tempering. With the increase in the content of austenite, both hardness and consequent contact fatigue life increases, reaches a peak and then subsequently decreased, but the peak of the Ar content of different hardness peak at about 17% Ar, and the contact fatigue life peak at about 9%. When the test load is reduced, the amount of the increase due to the impact of Ar contact fatigue life decreases. This is because when the time is not more than the amount of Ar to reduce the impact strength, while toughening effect is more obvious. The reason is that when the load is small, Ar small amount of deformation occurs, both reduced the stress peaks, and so Ar process has strengthened and the occurrence of deformation stress and strain induced martensite transformation and strengthening. However, if the load is large, Ar large plastic deformation and stress concentration matrix of the partial rupture, so that life expectancy is reduced. Should be noted that the beneficial effects of Ar must be stable under Ar, if spontaneously into martensite, will drastically reduce the toughness of the steel brittle.
      1.3 hardened steel undissolved carbides
      Hardened steel undissolved carbides number, morphology, size distribution, chemical composition of both the affected and hardened steel before the original organization, but also affected the austenitic condition, the relevant undissolved carbides on bearing life less impact studies. Carbide phase is hard and brittle, in addition to abrasion than beneficial, because the carrier will (especially non-spherical carbide) with the substrate and cracks caused by stress concentration, which decrease the toughness and fatigue resistance. Quenching undissolved carbides in addition to its impact on the performance of steel, but also affect the carbon content and the content and distribution of Ar quenched martensite, resulting in an additional impact on the performance of the steel. In order to reveal the impact on performance of undissolved carbides, using different carbon content of the steel, the carbon content of martensite after quenching it and Ar content of dissolved carbon content the same without different state, after 150 ℃ tempering, Due to the same carbon content of martensite, and high hardness, and therefore a small amount of undissolved carbides little higher hardness values ??increased, reflecting the strength and toughness of crushing load is decreased, stress concentration is sensitive contact fatigue life significantly reduced. So much undissolved carbides hardening mechanical properties of steel and failure resistance is harmful. Appropriate to reduce the carbon content of bearing steel is one of the ways to improve the service life of parts.
      In addition to the number of undissolved carbides hardening of the material properties outside influence, size, morphology, distribution also have an impact on the material properties. In order to avoid bearing steel undissolved carbides hazards, requiring less undissolved carbides (small number), small (small size), uniform (size each other by small and evenly distributed), round (each carbides were highly spherical). It should be noted, after a small amount of hardened bearing steel undissolved carbides is necessary, not only to maintain sufficient abrasion resistance, but also a prerequisite to obtain fine-grained cryptocrystalline martensite.
      1.4 residual stress after quenching and tempering
      Bearing parts after quenching and tempering, still has a large internal stress. Advantages and disadvantages of the two states part of the residual stress. After the heat treatment of steel, with the increase of the surface residual compressive stress, the fatigue strength of steel along with it, whereas the inner surface of the residual stress is tensile stress, the fatigue strength of the steel is reduced. This is due to fatigue failure in bear parts is too large tensile stress, and when there is a large surface residual compressive stress, it will offset the tensile stress equal value, leaving the actual steel tensile stress value decreases, the fatigue strength limit increased, when the surface of a larger residual tensile stress when exposed to tensile stress with the superimposed load leaving the actual steel to withstand tensile stress significantly increases the fatigue strength even if the lower limit value. Therefore, the bearing parts quenching and tempering larger surface residual stress after, but also one of the measures to improve the life (of course, too much residual stress may cause cracking or deformation of parts should be given enough attention).
      Impurity content of 1.5 Steel
      Impurities in steel and non-metallic inclusions include harmful elements (acid soluble) content, they endanger performance of steel is often fueled each other, such as the oxygen content is higher, the more oxide inclusions. Types of impurities on the mechanical properties of steel and parts failures ability of anti-impurity, nature, number, size and shape of the related, but often have reduced the role of toughness, ductility and fatigue life.
      As the size of the inclusions is increased, reducing the fatigue strength of the attendant, and the higher the tensile strength of steel, reduced tendency to increase. Increased oxygen content in steel (oxide inclusions increase), bending fatigue and contact fatigue life under high stress decreases. Therefore, for the work under high stress bearing parts, lower manufacturing steel oxygen is necessary. Some studies suggest that the MnS inclusions in steel, because of the shape was ellipsoidal, but also against the larger parcel oxide inclusions, therefore reducing its impact on the fatigue life may be even less useful, they can be lenient control.

A material factor affecting bearing life
Early failure in the form of rolling bearings, mainly broken, plastic deformation, wear, corrosion and fatigue, under normal conditions, mainly contact fatigue. In addition to the failure of the bearing parts of the service conditions, mainly by the steel hardness, strength , toughness, wear resistance, corrosion resistance and stress state constraints. The main internal factors affecting these properties and there are several states.
Martensite hardened steel 1.1
Carbon chromium steel raw tissue granular pearlite in quenching and tempering state quenched martensite carbon content, significantly affect the mechanical properties of steel. Strength and toughness at around 0.5%, contact fatigue life of about 0.55%, compressive crushing capacity of about 0.42%, while GCr15 steel quenched martensite carbon content of 0.5% to 0.56%, the strongest available anti-lapse mechanical properties.
It should be noted, in this case the martensite is implicit martensite obtained, the carbon content was measured by the average carbon content. In fact, the amount of carbon in the martensite region is slightly uneven, the carbon concentration is higher than away from the close surrounding carbide carbide in ferrite portion, so that they start the martensite transformation temperature is different, thus inhibiting the grain growth and microstructure of martensite morphology display becomes hidden martensite. It is easy to form high-carbon steel can be avoided quenching microcracking, and its sub-structure high strength and toughness of the strip plate martensite dislocation. Therefore, access to anti-bearing parts may fail to get the best capability matrix carbon martensite hidden only when high-carbon steel quenching.
1.2 retained austenite in hardened steel
Normal high carbon chromium steel after quenching, may contain 8% ~ 20% Ar (residual austenite). Bearing parts of Ar advantages and disadvantages, in order to better bring, Ar content should be appropriate. Due to the amount of principal and Ar quenching austenite conditions, and how much it would affect the number of carbon quenched martensite and undissolved carbides, difficult to accurately reflect the amount of influence on the mechanical properties of Ar. For this purpose, fixed Albright conditions, using body heat of austenite stabilization process in order to obtain different amount of Ar, in this study the effects of Ar content on GCr15 steel hardness and contact fatigue life after quenching and tempering. With the increase in the content of austenite, both hardness and consequent contact fatigue life increases, reaches a peak and then subsequently decreased, but the peak of the Ar content of different hardness peak at about 17% Ar, and the contact fatigue life peak at about 9%. When the test load is reduced, the amount of the increase due to the impact of Ar contact fatigue life decreases. This is because when the time is not more than the amount of Ar to reduce the impact strength, while toughening effect is more obvious. The reason is that when the load is small, Ar small amount of deformation occurs, both reduced the stress peaks, and so Ar process has strengthened and the occurrence of deformation stress and strain induced martensite transformation and strengthening. However, if the load is large, Ar large plastic deformation and stress concentration matrix of the partial rupture, so that life expectancy is reduced. Should be noted that the beneficial effects of Ar must be stable under Ar, if spontaneously into martensite, will drastically reduce the toughness of the steel brittle.
1.3 hardened steel undissolved carbides
Hardened steel undissolved carbides number, morphology, size distribution, chemical composition of both the affected and hardened steel before the original organization, but also affected the austenitic condition, the relevant undissolved carbides on bearing life less impact studies. Carbide phase is hard and brittle, in addition to abrasion than beneficial, because the carrier will (especially non-spherical carbide) with the substrate and cracks caused by stress concentration, which decrease the toughness and fatigue resistance. Quenching undissolved carbides in addition to its impact on the performance of steel, but also affect the carbon content and the content and distribution of Ar quenched martensite, resulting in an additional impact on the performance of the steel. In order to reveal the impact on performance of undissolved carbides, using different carbon content of the steel, the carbon content of martensite after quenching it and Ar content of dissolved carbon content the same without different state, after 150 ℃ tempering, Due to the same carbon content of martensite, and high hardness, and therefore a small amount of undissolved carbides little higher hardness values increased, reflecting the strength and toughness of crushing load is decreased, stress concentration is sensitive contact fatigue life significantly reduced. So much undissolved carbides hardening mechanical properties of steel and failure resistance is harmful. Appropriate to reduce the carbon content of bearing steel is one of the ways to improve the service life of parts.
In addition to the number of undissolved carbides hardening of the material properties outside influence, size, morphology, distribution also have an impact on the material properties. In order to avoid bearing steel undissolved carbides hazards, requiring less undissolved carbides (small number), small (small size), uniform (size each other by small and evenly distributed), round (each carbides were highly spherical). It should be noted, after a small amount of hardened bearing steel undissolved carbides is necessary, not only to maintain sufficient abrasion resistance, but also a prerequisite to obtain fine-grained cryptocrystalline martensite.
1.4 residual stress after quenching and tempering
Bearing parts after quenching and tempering, still has a large internal stress. Advantages and disadvantages of the two states part of the residual stress. After the heat treatment of steel, with the increase of the surface residual compressive stress, the fatigue strength of steel along with it, whereas the inner surface of the residual stress is tensile stress, the fatigue strength of the steel is reduced. This is due to fatigue failure in bear parts is too large tensile stress, and when there is a large surface residual compressive stress, it will offset the tensile stress equal value, leaving the actual steel tensile stress value decreases, the fatigue strength limit increased, when the surface of a larger residual tensile stress when exposed to tensile stress with the superimposed load leaving the actual steel to withstand tensile stress significantly increases the fatigue strength even if the lower limit value. Therefore, the bearing parts quenching and tempering larger surface residual stress after, but also one of the measures to improve the life (of course, too much residual stress may cause cracking or deformation of parts should be given enough attention).
Impurity content of 1.5 Steel
Impurities in steel and non-metallic inclusions include harmful elements (acid soluble) content, they endanger performance of steel is often fueled each other, such as the oxygen content is higher, the more oxide inclusions. Types of impurities on the mechanical properties of steel and parts failures ability of anti-impurity, nature, number, size and shape of the related, but often have reduced the role of toughness, ductility and fatigue life.
As the size of the inclusions is increased, reducing the fatigue strength of the attendant, and the higher the tensile strength of steel, reduced tendency to increase. Increased oxygen content in steel (oxide inclusions increase), bending fatigue and contact fatigue life under high stress decreases. Therefore, for the work under high stress bearing parts, lower manufacturing steel oxygen is necessary. Some studies suggest that the MnS inclusions in steel, because of the shape was ellipsoidal, but also against the larger parcel oxide inclusions, therefore reducing its impact on the fatigue life may be even less useful, they can be lenient control.