PURPOSE: To harden a crank shaft with extremely good dimensional accuracy by subjecting the center journal which is not yet hardened after hardening of the journal parts and the fillet parts thereof to roll leveling then hardening the respective remaining parts except the specific parts and roll-working the specific parts.
CONSTITUTION: The other journal parts 101, 103, 107, 109 except the center journal part 105 of the crank shaft 1 and the respective fillet parts thereof are subjected to high-frequency hardening. The shaft 1 is then supported and set to a leveling roll device and the journal part 105 which is not yet hardened is subjected to leveling rolling. The pin parts 102, 104, 016, 108 and the respective fillet parts thereof as well as the journal parts except the fillet parts 112, 113 of the journal part 105 are thereafter subjected to high-frequency hardening. Such shaft 1 is set on a fillet roll device 3 and the fillet parts 112, 13 are subjected to roll working with an upper roll 103 and lower rolls 304, 305, by which the structure thereof is made denser and the strength is made higher.
SEYA SHIGEHISA
ITO HITOSHI
INOUE MASAHIRO
