| 摘要 |
PURPOSE:To provide a hardened hoop member having excellent flexural fatigue strength by controlling the size of the non-metallic inclusions in a carbon steel hardened hoop and martensitic stainless steel hardened hoop member after application of residual compressive stress to the surface to a specific value or below. CONSTITUTION:The size of the non-metallic inclusions in the above-described hardened hoop member after application of residual compressive stress to the surface by barrel working, shot blasting, etc. is controlled to <=2.5mu max. The control of the quantity and size of the non-metallic inclusions is usually accomplished by decreasing the amt. of the oxygen in the steel, special refining, changing of a deoxidizing element, etc. A safety factor of 2X10<6> number of repetition can be taken for the fatigue limit as shown in the figure for the flexural fatigue S-N curve after, for example, barrel working, of the hardened hoop obtd. in the above-mentioned way. The material having excellent flexural fatigue strength is thus made manufacturable even if the material having excessive high quality is not manufactured from the standpoint of producing hardened hoop. |
