| 摘要 |
PURPOSE:To simplify work and to improve quality by providing a heat energy absorbing layer on the outside circumferential surface of a base body of a trapezoidal screw, rotating the base body relatively, and irradiating beams having high energy density thereto thereby forming hardened layers in required places. CONSTITUTION:A laser light absorbent is coated on the outside circumference of a base body 11 of a trapezoidal screw formed to a prescribed shape, whereby a heat energy absorbing layer 20 is formed. While the body 11 is rotated, laser light 13b focused to the energy density at which a surface hardening heat treatment is possible is irradiated along the root corner parts 11b of the body 11. The areas that receive the irradiation is quickly heated and when the laser light 13b is moved by the rotation of the body 11, said areas are quickly cooled and hardened, whereby hardened layers 18 are formed. Thereafter, the body 11 is turned over and again the light 13b is irradiated to form hardened layers 19. |
