| 摘要 |
PURPOSE:To equalize the hardness of a piercing part by irradiating a metal working beam such as a laser beam, a light beam, an electron beam, etc., from a shaft end side of the root end of a needle material and executing the annealing to the piercing part of the root end of the needle material. CONSTITUTION:Annealing is executed by irradiating a metal working beam 13 from the axial direction of the root end of a needle material 11, therefore, annealing is performed uniformly to a piercing part 12 of the root end of the needle material 11, and the hardness of the piercing part 12 can be equalized. Also, since the metal working beam 13 irradiates from the axial direction of the needle material 11, it is prevented that a hard part remains in the root end edge part of the needle material 11. In such a way, it is prevented that an erosion phenomenon caused by annealing and an oxide film are formed on the outside peripheral surface of the piercing part 12 of the needle material 11 and polishing for eliminating them can be made unnecessary. |
