| 摘要 |
PURPOSE:To minimize a heat treatment distortion and to prevent the occurrence of quenching crack by a method wherein a key groove is radiated with beams of a high energy density heat source to harden the surface thereof. CONSTITUTION:Laser light 6a generated by a laser oscillator 5 is converged to have such an energy density as can do a surface hardening heat treatment by a lens 7. The key groove of a shaft 1 which is moved by a moving device is treated by heat at the corners 4a and 4b continuously to harden the surface thereof. As a result of this, surface hardened layers 41 and 42 are formed. The shaft thus treated is imparted with a characteristic as indicated by line 11 in a graph, that is with a higher hardness in comparison with a conventional carburized and annealed shaft the characteristic of which is shown by line 10 in the graph. |
