| 摘要 |
<P>PROBLEM TO BE SOLVED: To reduce manufacturing cost by improving yield by preventing the occurrence of a micro crack starting from a groove bottom of a fracture surface when an annular third intermediate material 21 is diametrically enlarged by form rolling to form a fourth intermediate material 22. <P>SOLUTION: After a circular recess 45 is formed by rocking die forging on one side of a disk-shaped first intermediate material 19, a center portion thereof is punched from the side opposite from the circular recess 45 to form the third intermediate material 21. A fracture surface formed on an inner circumferential surface due to the punching is located at an axial-direction intermediate portion. The fracture surface is squeezed in the initial stage of the rolling work and formed in a smooth surface. Thus, in the stage at which the diameter of the third intermediate material 21 is enlarged, any groove forming a starting point of the occurrence of crack is not present on an inner circumferential surface of the third intermediate material 21. <P>COPYRIGHT: (C)2013,JPO&INPIT |
