JP2861123B2 - Laser hardening method of shaft - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a laser hardening method for a shaft, and relates to a shaft for performing laser hardening from a diagonally upward direction without applying a laser beam absorbent to a step portion of the shaft. Laser quenching.

[Prior art] Conventionally, as a method of laser hardening a step portion of a shaft to which a large load such as torsion bending is applied, for example, 1) a single mode beam having a Gaussian distribution focused by a lens as disclosed in JP-A-63-118015. At an angle between the optical axis and the axis of the shaft in the range of 45 ° to 70 °, and simultaneously rotating the shaft to heat the surface of the stepped portion, followed by quenching by natural air cooling. 2) A method of reflecting a laser beam on a mirror attached to the tip of a laser head and irradiating the mirror with a desired step as described in JP-A-63-7327 has been proposed.

[Problems to be Solved by the Invention] However, in the processing of the above 1), unless the incident angle is set to 70 ° or more, such as the bottom of the shaft narrow groove, the laser beam does not reach and quenching becomes insufficient or impossible. It may be.

In the above 2), a jig for mounting the mirror must be completed, which is costly. If the shape or size of the step portion changes, the jig must be remodeled each time.

Further, in the above methods 1) and 2), a blackening process is usually performed to improve the absorption of the laser beam. When removing the blackened film after quenching, there was a case where it was difficult because the film was baked by the heat of the laser beam.

The present invention has been made in order to solve the above-described problems, and an object of the present invention is to eliminate a blackening process for improving laser beam absorbability, so that 50 ° ≦ θ <
The method involves irradiating a laser beam at an incident angle of 90 ° to harden the side surfaces, and quench the corners of the steps using the residual heat contributed to quenching the side surfaces and the reflected light from the side surfaces.

Means for Solving the Problems In order to achieve this object, the shaft hardening method of the present invention irradiates a linearly polarized laser beam to the side surface of the shaft at an incident angle of 50 ≦ θ <90 °.

[Operation] In the present invention having the above-described configuration, quenching is particularly performed using a linearly polarized laser beam. This linearly polarized light is composed of P-polarized light having an electric field vector parallel to the plane of incidence and S-polarized light having an electrolytic vector perpendicular to the plane of incidence. The reflectance greatly decreases in the range of ≤θ <90 °,
In particular, it becomes a minimum of about 20% near 845 °, which is called Brewster's angle.

In the conventional laser quenching process, the metal surface to be irradiated was blackened to improve the beam absorption, but utilizing the above properties, a laser beam was incident on the side of the shaft step at a Brewster angle. It can be quenched, and the corners and bottom surface can be quenched using the preheating and reflected beams at that time.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, a shaft 1 which is a workpiece is rotated, and a step portion 4 is immediately irradiated with a laser beam 2. The step portion 4 is divided into a side surface 5 of the step portion, a bottom surface 6 of the step portion, and a corner portion 7. In FIG. 2, the laser beam 2 is applied to the side surface 5.
When irradiated at an incident angle 8 of 50 ° ≦ θ <90 °, the energy of the laser beam 2 is mostly absorbed by the side surface 5 and quenched. The bottom surface 6 and the corner portion 7 are also burned by the increase in the absorption rate of the CO ₂ laser due to the residual heat (FIG. 7) and the heating by the partially reflected laser beam 2. At this time, if the cross-sectional shape of the incident laser beam 2 is circular,
When the beam 9 is called, as shown in FIG. 3 (a), when it hits the side surface, the beam irradiation trace 10 becomes a vertically long elliptical shape, and shows a hardened tissue portion 11 as shown in FIG.

Here, if the irradiation position of the laser beam 2 with respect to the side surface 5 is shifted downward, a portion to be hardened can be selected as shown in FIG. 3B, and the corner portion 7 can be deepened and the bottom surface 6 can be hardened shallowly. Conversely, if it is shifted upward, only the side surface 5 can be hardened as shown in FIG. 3 (c).

On the other hand, not only the irradiation position is changed as described above, but also the cross-sectional shape of the incident laser beam 2 is changed using an appropriate optical system, and as shown in FIG. Since the hardened tissue portion 11 can be changed by deforming into a more flat C beam as shown in (e), an optimal method should be selected according to the degree of wear resistance and fatigue strength required for the stepped portion 4. Can be.

[Effects of the Invention] As is clear from the above, according to the present invention, the laser beam is irradiated at a sharp incident angle on the side surface of the step portion of the shaft to improve the laser beam absorption. It is possible to simultaneously quench one or more or all of the side surface, corner, and bottom surface of the step at the same time as quenching and blackening without applying blackening treatment, and it is troublesome There is an effect that no optical jig or device is required, and labor for removing the blackening agent after quenching can be saved.

[Brief description of the drawings]

1 to 3 show an embodiment of the present invention. FIG. 1 is a perspective view of a shaft, FIG. 2 is a side view of the shaft, and FIG. FIG. 4 is a longitudinal sectional view of a stepped portion and a quenched portion viewed from the axial direction, FIG. 4 is a perspective view for explaining a conventional laser quenching method of a shaft, and FIG. Figure 6 is a longitudinal sectional view of the same hardened portion, FIG. 7 is an iron CO ₂
FIG. 4 is a diagram illustrating the temperature dependence of laser light absorption. DESCRIPTION OF SYMBOLS 1 ... Shaft, 2 ... Laser beam, 3 ... Rotation direction, 4 ... Step part, 5 ... Side surface, 6 ... Bottom surface, 7 ... Corner part, 8 ... Incident angle, 9 ... A beam , 10 ... Beam irradiation trace, 11 ... Hardened tissue part, 12 ... B beam.

Claims (1)

(57) [Claims] When a stepped portion of a shaft is laser-hardened, a laser beam absorbent is not applied to the irradiated portion at all and a laser beam is incident on the side surface of the stepped shaft within a range of 50 ° ≦ θ <90 °. And quenching the corners using reflected light and preheating.