| 摘要 |
According to one aspect of the present invention, provided is a partially carburized heat treated stainless ferrule, wherein a first region has a first hardness, a second region has a second hardness, the first region comprises: a nitrogen layer in which the concentration of nitrogen is greater than that of carbon; and a carbon layer provided inside the nitrogen layer in which the concentration of carbon is greater than that of nitrogen, and the first hardness is greater than the second hardness. Through such partial heat treatment, the front portion of a region excluding a part to be heat treated is cured by heat treatment, thereby preventing a phenomenon in which rotational torque increases. |
