LASER HARDENING METHOD

Abstract

The invention provides a laser hardening method capable of preventing adjacent already-hardened layers from being annealed. In the laser hardening method of the present invention, conduits C1, C2 and C3 are processed in advance midway between pitches P1 along which a hardening nozzle 190 performs overlap hardening. After moving the nozzle 190 along a center line L3 to process a hardening layer H23, the nozzle 190 is moved in parallel for a single pitch P1 to perform hardening of a hardening layer H24. Thermal energy E1 of the laser beam LB is also irradiated toward the direction of the hardening layer H23, but it is blocked by the conduit C3 that prevents the laser beam from annealing the hardening layer H23.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a laser hardening tool used in the laser hardening method according to the present invention;

FIG. 2 is a cross-sectional side view of the laser hardening tool;

FIG. 3 is an upper view of FIG. 2;

FIG. 4 is an explanatory view showing the outline of the laser hardening method according to the present invention;

FIG. 5 is an explanatory view showing the cross-sectional structure of a work having been hardened by the laser hardening method of the present invention;

FIG. 6 is an explanatory view of a laser hardening process using a laser hardening tool;

FIGS. 7A, 7B and 7C are explanatory views of a laser hardening process using a laser hardening tool;

FIG. 8 is an explanatory view showing the state in which a nozzle has been moved along a center line;

FIG. 9 is an explanatory view showing the state in which laser hardening is performed on an area having a large width dimension; and

FIG. 10 is an explanatory view showing how annealing occurs.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 4 is an explanatory view illustrating the outline of the laser hardening method according to the present invention.

According to the laser hardening method of the present invention, conduits C₁, C₂ and C₃ are provided in advance midway between pitches P₁ along which a hardening nozzle 190 performs overlap hardening.

Here, pitch P₁ is set based on the range of thermal energy distribution of laser irradiation on an object determined by the laser output and laser output mode, the shape of the nozzle, the shape of the lens in a laser oscillator unit, and other factors. Further, a width dimension B₁ of conduits C₁, C₂ and C₃ is also set based on the range of thermal energy distribution of laser irradiation to an object determined by the laser output and laser output mode, the shape of the nozzle, the shape of the lens within a laser oscillator unit, and other factors.

FIG. 4 shows the state in which after the nozzle 190 is moved along a center line L₃ to process a hardening layer H₂₃, the nozzle 190 is moved in parallel for a single pitch P₁ to process a hardening layer H₂₄.

The thermal energy E₁ of the laser beam LB is also irradiated toward the direction of the hardening layer H₂₃, but it is blocked by the conduit C₃ and prevented from annealing the hardening layer H₂₃.

FIG. 5 shows a cross-sectional structure of a work W having been hardened by the laser hardening method of the present invention.

Since the hardening layers H₂₁, H₂₂, H₂₃ and H₂₄ are separated by conduits C₁, C₂ and C₃, the surface subjected to hardening is covered by a uniform hardened layer HS.

Therefore, the grinding and cutting in the post processes are performed on a uniform hardness, by which the process accuracies are improved.

Claims

1. A laser hardening method for condensing a laser beam irradiated from a semiconductor laser stack to create a spot and irradiating the same through a hardening nozzle to perform hardening of a surface of a work; the method comprising a step of forming in advance a conduit between multiple paths on the surface of the work through which the hardening nozzle passes.

2. The laser hardening method according to claim 1, wherein the conduit is formed at a center portion between adjacent paths.