| 摘要 |
PROBLEM TO BE SOLVED: To impart an excellent toughness and straightness to a steering shaft having a ball screw mechanism provided integrally therewith and to secure the rolling life of the helical rolling face of the ball screw mechanism. SOLUTION: In this device, a helical heating coil 16 with a coil radius approximately equal to the average cross-sectional radius of curvature of a thread groove forming the helical rolling face 8 of a steering shaft 1 is placed in proximity to the helical rolling face 8 along the thread groove, and the steering shaft 1 is fed axially while coinciding with the helix angle of the thread groove and being rotated. In this case, a quench-hardened layer with a predetermined, approximately uniform depth is formed on the surface layer of the rolling face 8 to secure the rolling life of the rolling face 8 and to assure an excellent toughness and straightness of the steering shaft 1. |
