| 摘要 |
PURPOSE:To prevent a cylindrical body made of a thin metallic sheet from deforming thermally in the stage of subjecting said cylindrical body to a heat treatment by disposing a columnar core member in said cylindrical body coaxially and subjecting the same to the heat treatment. CONSTITUTION:In subjecting a cylindrical body 10 made of a thin metallic sheet to a heat treatment such as hardening by carburizing or carbonitriding, a columnar core material 20 made of a heat resistant material such as heat resistant stainless steel, ceramics or the like is disposed coaxially in the body 10, and cooling water is passed from the inside and outside of the body 10, whereby said body is hardened. Here if the outside diameter of the material 20 is defined as D1 and the inside diameter of the body 10 as D2, the diameter of the material 20 is so selected as to attain D1=(0.4-0.8)XD2 between D1 and D2. No stagnating parts are produced in the cooling water passing between the inside surface of the body 10 and the outside surface of the material 20, and the body 10 is cooled from the inner side as well at the same speed as that by the cooling from the outer side of said body, whereby the generation of the deformation like hourglass in the body 10 is prevented. |
