| 摘要 |
PURPOSE:To form a uniformly hardened part having no softened areas in the stage of heating and hardening a shaft or the like by laser by increasing the speed of revolving the shaft or the like and heating the entire part of the hardening part then cooling the same. CONSTITUTION:In the stage of hardening a shaft or the like 11 by irradiating a laser beam 15, an oxidative gas such as oxygen, air or carbon dioxide is ejected through a nozzle 14 and the hardening part is heated with the laser deviated from focus, whereby an oxide film 13 is formed over the entire surface of said part. Next, the number of revolutions of the shaft 11 is increased and while the absorption rate of the laser is increased by the film 13, the hardening part 12 of the shaft 11 is heated uniformly over the entire circumference to the transformation point temp. or above. The irradiation of the laser is ceased, and if necessary, gaseous nitrogen or the like is blown through the nozzle to cool the hardneing part quickly, whereby it is hardened. The generation of softened areas by annealing of the initial hardened part by the heat generated during hardening of the final hardening part on account of slow revolution of the shaft is obviated and the shaft is hardened uniformly. |
