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In INA bearing a different position can on quenching stress concentration factors (including metallurgy defects,), to the generation of quenching cracks are promoted, but only in the tensile stress field (especially in the maximum tensile stress) will be shown, if the stress field and no promote crack effect in pressure.
The quenching cooling rate is one of the important factors that can affect the quality of quenching and determine the residual stress, is also a can give an important and even decisive influence factors of quenching crack.
In order to achieve the purpose of cooling quenching, usually must be accelerated in high temperature parts section, the critical cooling rate of quenching ability and make more than steel is martensite. The residual stress is uncovered, such doing can increase due to offset the stress effects of the thermal stress, so can reduce the surface tension stress and suppressing the purpose of the longitudinal crack. The effect will vary with the velocity of high temperature cooling speed increase. Moreover, in the case of quenching, the greater the section size of workpiece, although the actual cooling speed is more slow, the danger of cracking instead of the more big.
This is all because of this kind of INA bearing steel heat stress with the size of the actual increase the cooling rate, thermal stress decreases, the stress increases with the size increase, finally formed in tissue stress tension caused by stress on the surface of the action characteristic. Be quite different the traditional concept and with the slow cooling stress smaller. For this kind of steel parts, quenching under normal conditions of high hardenability steel can only be formed. Reliable principle to avoid cracks is to try to minimize cross section of the transformation and martensite not isochronous. Only the martensite transformation zone slow cooling is not enough to prevent the formation of crack.
Only INA bearings generally produced in non hardenability of arc crack, though the overall rapid cooling necessary formation conditions, but its real reasons, but not fast cooling (including martensite transformation zone) itself, but quenching a local position (determined by the geometric structure, cooling) speed in high critical temperature zone significantly slows, so there is no hardening caused by. Produced in large non hardenability in transverse and longitudinal split, the residual thermal stress is the main component of the tensile stress in the hardening center, and in the end quenching hardened section center, first crack formation and from inside to outside extension and cause. In order to avoid this kind of crack, often use water-oil double liquid quenching process.
Rapid cooling section in the implementation of INA bearing in this process, the purpose is to ensure that only the outer metal get martensite organization, and from the perspective of internal stress, then the fast cooling harmful. Secondly, the late slow cooling cooling purposes, not for expansion speed reduces the martensitic transformation and stress value, and is to reduce shrinkage speed metal parts of section temperature difference and center section, so as to reduce the stress value and the final purpose of suppressing the quenching crack.
| Product Model | Inside Diameter | Outside Diameter | Thickness |
| 33019U NTN | 95 | 145 | 39 |
| 32019XU NTN | 95 | 145 | 32 |