The early failure mode of the rolling bearing, mainly break, the plasticity is out of shape, abrade, corrode and tired, mainly contact fatigue under the normal condition. The intersection of bearing and part fail except condition on active service, mainly restrict by the hardness, intensity, toughness, wearability, corrosion resistant and internal stress state of the steel. Influence the main inherent factor of the performance and state to have several items as follows.
1. Body of horse in a hardened steel
When the primitive organization of high-carbon chromium steel is granulous pearlite, under quenching the flash back state of the low temperature, quench horse’s carbon content of body, obviously influence the mechanics performance of the steel. Intensity, toughness contact fatigue life about 0.55%, resist and press routed ability about 0.42% about 0.5%, the carbon content of body is to quench horses in GCr15 steel 0.5% – 0.56% When, can get and resist the strongest comprehensive mechanics performance of invalid ability.
Should point out horse that get body latent brilliant the intersection of horse and body in this case, the carbon content measured is the average carbon content. In fact, horse’s carbon content in the body is uneven in the little district, near the carbon density around the carbide and is higher than and far away from the original ferrite part of carbide, therefore they begin take place horse temperature that body change different, thus inhibit the intersection of horse and the intersection of body and grow up and micro- display of shape of crystalline grain from and become latent brilliant horse’s body. It can prevent the intersection of high-carbon steel and easy micro- crackle that appear quench, from, and inferior structure its intensity and the intersection of toughness and high the intersection of location and wrong the intersection of lath and the intersection of horse and body. So the intersection of carbon and latent brilliant horse the intersection of bearing and part might get, resist invalid the intersection of ability and best matrice at the body get, when the high-carbon steel is quenched only.
1. Residual body in 2 hardened steel
The high-carbon chromium steel can contain 8% – 20% Ar remain body after quenching normally . It has a fraud too that Ar in the part of the bearing is favorable, in order to promote what is beneficial and abolish what is harmful, Ar content should be appropriate. Because Ar quantity mainly and quenches and heats body terms relevantly, its amount can be influenced and quenched the horse carbon content of the body and quantity not dissolving the carbide, it is more difficult to reflect the impact on mechanics performance of the Ar amount correctly. For this reason, fixed condition, utilize body hot stabilizing treatment craft of the body, by winning different Ar quantity, after this research quenches the low-temperature flash back Ar content is and exposed to the influence of fatigue life to GCr15 steel hardness. With increase of the body content, hardness and contacting fatigue life to increase with it, reduce with it after reaching peak value, but Ar content of its peak value is different, the peak value of the hardness appears about 17% Ar, and exposed to the peak value of fatigue life to appear about 9%. When the experimental load decreases, because Ar quantity increases the influence on contacting fatigue life is reduced. This because of big in influence that quantity does not reduce to intensity a long time as Ar, it increases tough function to be obvious. The reason is when a load is smaller, small quantity out of shape has happened in Ar, have already subdued the stress peak, make Ar already deformed process and strengthen the stress emergency and take place to bring out horse’s body to become and strengthen again. But for instance, when the large load, plasticity that have older Ars out of shape to realize with base part produce stress to be centralized breaking, thus make the life-span reduce. Should point out, the favorable function of Ar must be under Ar steady state, if change spontaneously into horse’s body, will make the toughness of the steel reduce and embrittle sharply.
1. Not dissolving the carbide in 3 hardened steel
Have not dissolved the quantity, topography, size of the carbide, has been distributed in the hardened steel, the influence of primitive organization before the chemical composition and quenching the steel, is also influenced by body condition, have not dissolved the impact on bearing life-span of carbide to study relevantly less. It is in carbide it is hard fragile for looks,except that it is useful to wearability, when not bearing the weight of because can especially take the form of carbide more spherical Cause the stress to be centralized and emerge in the crackle with the matrice, thus will reduce toughness and tired and resist strength. Quench and has not dissolved the carbide except that one’s own performance to the steel has exerted an influence, still influence quenching horse carbon content and Ar content of the body and is distributed, thus produce additional influence on the performance of the steel. In order to announce that has not dissolved the impact on performance of carbide, adopt different steel including carbon quantity, quench, make but the carbon content of body the same as Ar content of horse of it not dissolve the state of the carbide with different content, after 150 ℃flash back, because horse’s body is the same in carbon content, and the hardness is relatively high, dissolve carbide increase big to the intersection of hardness and person who increase on a small quantity, reflect intensity and toughness pigeonhole the routed load and reducing to some extent, concentrate sensitive contact fatigue life on obviously reducing to the stress. So it is harmful to quench and has not dissolved the carbide and cross to the comprehensive mechanics performance of the steel more and fail to resist strength. The appropriate carbon content of reducing the bearing steel is improving and making one of the a route of service life.
Quench and has not dissolved the carbide except that the quantity has influenced material performance, size, topography, distributing and exerting an influence on the material performance too. Have not dissolved the danger of the carbide in the bearing steel in order to avoid, has demanded not to dissolve the little small in quantity carbide , it is small ‘ The size is small , even all kinds of each other has very small difference, and is distributed evenly , round Each carbide all takes the form of ball . Should point out, it is essential that the bearing steel has small quantity that has not dissolved the carbide after being quenched, not only can keep enough wearability but also obtained latent brilliant horse’s essential condition of the body of detailed crystalline grain.
Residual stress after 1.4 quenching flash back
The bearing part still has heavier internal stress after quenching the low-temperature flash back. Residual the intersection of internal stress and favorable and the intersection of fraud and two kinds of states in the part. After a heat treatment of steel, remain and press increase of the stress with the surface, the fatigue strength of the steel thereupon increases, the surface remains internal stress in order to draw at the time of the stress, make the fatigue strength of the steel reduce on the contrary. This because part tired to fail to appear bearing while over drawing the stress, have as surface great press remaining stress, will offset drawing the stress of equal number value, and make the reality of the steel bear and draw the stress number value to reduce and make the extreme of fatigue strength increase, have as surface great draw remaining stress, will until bear draw the intersection of stress and load, superpose and make whom reality of the steel bear draw the stress to obviously increase, even if the extreme of fatigue strength is reduced. So, the surface remain more greatly pressing the stress after making the part of the bearing quench the flash back, improve measure of service life one of whom too big residual stress might cause part out of shape to even fracture certainly, should pay enough attention .
1. Impurity content of 5 steel
The impurity in the steel includes nonmetal inclusion and harmful element ‘ The acid is dissolved Content, their danger to steel performance is often encouraged each other, if the higher the oxygen content is, the more oxide inclusion are. In the steel the impurity and makes a influence against invalid ability to relate to type, property, quantity, size and shape of the impurity to mechanics performance, but usually reduce toughness, plasticity and function of fatigue life.
With the increase of the inclusion size, fatigue strength is reduced with it, and the higher the tensile strength of the steel is, reduce the trend to strengthen. The oxygen content increases in the steel ‘ Oxide is mixed with increasing ,Crooked and tired and is exposed to thereupon reducing under high stress function of fatigue life. So, as to the bearing part working under the high stress, it is essential to reduce and make the oxygen content of using steel. Some research shows, MnS inclusion in the steel, because the shape takes the form of ellipsoid, and can wrap up and endanger bigger oxide and is mixed with, it may even be beneficial that it is influenced smaller so reduce fatigue life, so can control leniently.
