| 摘要 |
PROBLEM TO BE SOLVED: To prevent quenching crack at the time of high frequency quenching of a clearance portion by forming a large flange surface and an outer receway surface on the raw material for an inner ring after forging, then forming a surface hardened layer by high-frequency quenching the formed portion and tempering the same, and then forming a clearance groove on a boundary portion between the large flange surface and the outer raceway surface. SOLUTION: A large flange surface 10, an outer raceway surface 9 and a cylindrical part are formed on raw material for an inner ring subjected to a forging process by lathe turning. Subsequently, the turned designated portion is quenched by high-frequency heat treatment, and then tempered. Thus, a surface hardened layer is formed. Subsequently, a clearance groove 11 is formed extending over the whole periphery of a boundary portion between the large flange surface 10 and an outer raceway surface 9 of the formed surface hardened layer by lathe turning. Then, finish grinding is performed. Thus, it is possible to prevent quenching crack, liable to be cuased by heat reservoir in quenching a recess in the high frequency heat treatment process. |
