| 摘要 |
PURPOSE:To facilitate the working by bringing a steel-made ball which has been finished precisely through a quenching heat treatment after having brought a billet to heading and has been formed in a ball shape, to nitriding, and thereafter, working a hole, a groove and a projecting part, etc., to raise the surface hardness and to drop the inside hardness. CONSTITUTION:From a billet consisting of high carbon chrome bearing steel, etc., a steel ball is brought to quenching treatment through heading and flashing, and thereafter, after the spherical surface 1 has been finished precisely by grinding and lapping, salt bath nitriding is executed. In this case, the inside hardness of the steel ball drops because it is held at a temperature of >=500 deg.C, and a cutting work of an end face 2, a hole 3, etc., can be executed easily. Also, since a nitriding layer is formed on the surface of the spherical surface 1, at the time of chucking in case of working, the spherical surface 1 is not deformed but can be held coaxially with high accuracy. |
