JPS6224883A - Laser beam surface treatment of circumferential part - Google Patents

Abstract

PURPOSE:To subject the circumferential part of a material to be treated to a uniform and defectless surface treatment by forming laser light to a luminous flux of an annular section having a prescribed axial line by an optical system and moving the same along the common axial line of the optical system and the circumferential part of the material to be treated. CONSTITUTION:The laser light 2 is made incident on a circular conical mirror 1 from above to below. The laser light 2 is reflected by a reflection surface 1a and is emitted in the annular sectional shape having the axial line 2a. The emitted light is focused onto the circumference centering at the axial center of an inside peripheral surface. The focused light is positioned to the circumferential part 4a at the top end edge of the surface 4 and the laser light 2 is irradiated into the circumference in the circumferential part 4a. The surface of the circumferential part 4a is subjected to the surface treatment such as build-up welding and alloying treatment by such laser light 2. The radius of the circumference of the laser light to be irradiated to the material 5 to be treated increases if the circular conical mirror 1 is moved upward along the axial center of the surface 4, i.e., the axial center of the circumferential part 4a. The plane between the circumferential parts 4a and 4b is thus beautifully surface-treated.

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a laser surface treatment method for performing surface treatments such as overlay welding and surface alloying by irradiating a circumferential portion of a material to be treated with a laser beam. be.

Conventional Technology As is well known, laser light has a high energy density, and this property is used widely as a heat source for processing such as welding, cutting, and drilling. It is also used for surface alloying and surface hardening. Conventionally, such a laser beam is used to irradiate a circumferential area such as the inner circumferential surface of a hole in a material to be treated, and then apply a surface effect such as overlay welding or surface alloying to the circumferential area. To perform the treatment, a spot of laser light is irradiated to one point on the circumference (for example, the inner circumferential surface), the material to be treated or the laser beam is rotated around the axis of the circumference, and the spot is placed on the circumference. The above-mentioned surface treatment is performed by continuously moving the material around the circumference, and the surface treatment of the circumferential part is performed by moving the material to be treated or the spot along the axis of the circumferential part. .

One example of this conventional technique is proposed in US Pat. No. 4,059,876, which will be explained based on FIG. FIG. 4 shows an apparatus used in this method, in which a mirror 8 is placed in a cylinder 12 with an open top, and a mirror 9 is fixed to the outside of the cylinder 12 by an arm 13. A boat 14 is provided on the cylinder wall between the mirrors 8 and 9 to allow laser light to pass therethrough.

The laser beam irradiated downward from the upper part of the cylinder 12 is reflected by the mirror 8 and further by the mirror 9, and is changed to an oblique direction, and is directed to the circumferential part 11, which is a part of the inner circumferential surface of the material to be treated 10. A single point is irradiated diagonally from above. A drive belt 15 is hung around the upper outer circumferential portion 12a of the cylinder 12, and the belt 15 rotates the cylinder 12 around the optical axis of the laser beam to direct the irradiation spot of the laser beam to the circle of the circumferential portion 11. The material to be treated 10 is moved in the vertical direction while being moved on the circumference, thereby performing surface treatment on the inner circumferential surface.

Problems to be Solved by the Invention However, prior art, such as U.S. Pat.
According to No. 876, the irradiation spot of the laser beam is moved continuously on the circumference of the material to be treated, and the material to be treated or the spot is moved in the vertical direction so that the irradiation spot of the laser beam is moved in the circumferential region, for example, inside the material. Since the surface treatment is performed on the circumferential surface, the starting point and end point of the surface treatment always exist on the inner circumferential surface to which the laser beam irradiation spot has moved.

Due to the existence of such a start point and end point, when overlay welding is performed, for example, an excessive buildup is likely to occur at the start point, and defects such as craters are likely to occur at the end point.

These defects, such as craters, have a negative effect on the strength as defects on the surface of the first joint, and may become a starting point for weld cracking due to stress concentration. Further, due to excessive build-up or craters, the thickness of the build-up weld becomes uneven, and the surface of the weld becomes uneven, resulting in poor shape.

On the other hand, when performing surface alloying, the starting point and ending point,
The degree of progress of the alloying reaction differs between the moving parts, and the surface characteristics to be obtained by the alloying reaction become non-uniform.

The basic purpose of the present invention is to solve the above-mentioned problems, and to provide a method for uniformly and with excellent characteristics surface treatment using a laser beam on the circumferential portion of a material to be treated.

Means for Solving the Problems That is, the present invention provides a method for laser surface treatment of a circumferential portion, in which a circumferential portion such as an inner circumferential surface of a material to be treated is irradiated with a laser beam for surface treatment. An optical system that receives light at a constant angle of incidence and emits laser light in a ring-shaped cross section about a predetermined axis is arranged so that the axis and the axis of the inner circumference of the material to be treated substantially coincide; It is characterized in that the optical system or the processed material is moved along the axis.

The optical system is composed of an internal mirror having a conical reflecting surface, and the reflecting surface is a concave surface that is curved concavely with respect to the generatrix of the conical surface, and from above the apex of the mirror to the central axis of the mirror. It is desirable that the laser beam be arranged so as to receive the laser beam at an incident angle along the same direction.

According to this invention, the laser light incident on the optical system is
Since the emitted laser beam has a ring-shaped cross section centered on a predetermined axis, the emitted laser beam simultaneously irradiates the entire circumference of the treated material, and directs the treated material or optical system in the axial direction of the circumference. By moving along the
The circumferential irradiation position of the laser beam can be changed. Since the circumference is irradiated with laser light at the same time, the start and end points of the surface treatment do not appear, and the surface treatment is performed uniformly, thereby preventing defects caused by the presence of the start and end points. If the irradiation position of the laser beam is on the plane of the material to be treated, the diameter of the circumference of the material to be treated increases or decreases due to the movement of the material to be treated or the optical system, and the diameter of the circumference of the material to be treated increases or decreases. A predetermined portion of the plane can be surface-treated in a ring shape. Furthermore, if the irradiation position of the laser beam is placed on the inner peripheral surface of the material to be treated, the diameter of the circumference will not increase or decrease due to movement of the material to be treated or the optical system, and the inner peripheral surface will be kept at a certain length in the contraction direction. Surface treatment can be applied over the area.

The optical system is a conical mirror with a conical reflecting surface, and the reflecting surface is a concave surface that is curved concavely with respect to the generatrix of the conical surface. If arranged so as to receive light, the above-mentioned effect can be achieved by a simple groove, and the laser beam can be focused on the circumference by the concave surface, so that a higher energy density can be obtained.

EXAMPLE An example of the present invention will be described below with reference to the accompanying drawings.

Reference numeral 5 denotes a material to be treated having an inner circumferential surface, and a conical mirror 1 made of copper that is movable in the vertical direction is arranged on the axis of the inner circumferential surface 4 and above the material to be treated 5, with the apex at the top. ing.

The conical reflective surface 1a of the conical mirror 1 is made into a reflective surface by vapor-depositing gold, and is also a concave surface curved concavely with respect to the generatrix 1b. If desired, this conical mirror is provided with a cooling water pipe (not shown) inside, and is cooled with water, for example.

When a laser beam 2 is incident downward from above on this conical mirror 1, the laser beam 2 is reflected by the reflecting surface 1a and emitted in a ring-shaped cross section having an axis 2a, and the axis of the inner circumferential surface 4 is centered on the conical mirror 1. It is focused on the circumference of the center. 1st.
In FIG. 2, this focused light is positioned at a circumferential portion 4a at the upper ai edge of the inner circumferential surface 4, and the laser beam 2 is irradiated on the circumference at the circumferential portion 4a. The surface of the circumferential portion 4a is subjected to surface treatments such as overlay welding and alloying treatment using the laser beam 2. If this conical mirror 1 is moved upward along the axis of the inner circumferential surface 4, that is, the axis of the circumferential portion 4a,
Since the radius of the circumference of the laser beam irradiated onto the material to be treated increases, surface treatment can be performed on the flat surface of the material to be treated 5 from the circumferential portion 4a to the larger diameter circumferential portion 4b. .

FIG. 3 is a diagram showing a state in which the conical mirror 1 is positioned lower than the state shown in FIG.

If the conical mirror 1 is gradually moved downward or upward while irradiating the laser beam 2 onto the circumference of the inner circumferential surface 4, the radius of the circumference by the laser beam 2 will be constant and the irradiation position of the laser beam 2 will be It is moved downward or upward on the inner circumferential surface 4, and the inner circumferential surface is uniformly surface-treated.

Note that in this example, the circumference on which the laser beam is focused and the circumference of the part to be treated are made to match, but the diameters of these circumferences are not made to match, and the circumference is If they are arranged concentrically, the laser beam irradiated to the circumferential portion will form a band with a width at the circumferential portion, so that a desired energy density of the laser beam can be obtained depending on the type of surface treatment. Furthermore, by changing the concave shape of the reflective surface of the conical mirror, for example, the curvature, it is also possible to change the degree of convergence of the laser beam and change the desired energy density. Note that if this concave surface is made into a spherical surface or a parabolic surface of revolution, the laser beam is completely focused on the circumference, so that a higher energy density can be obtained. This reflective surface was formed by gold vapor deposition,
The present invention is not limited to this, and can be appropriately modified to form a reflective surface by other known means.

In this embodiment, the laser beam emitted from the optical system has a large diameter in the downward direction, but by changing the shape of the reflecting surface of the conical mirror 1, it can be made to have a large diameter in the upward direction. Furthermore, it may be ejected laterally, that is, ejected in a disc shape.

In the above description, the optical system uses the above-mentioned conical mirror, but the present invention is not limited to this, and may be configured by a prism, a lens system, or a combination thereof. The present invention can be applied not only to overlay welding or surface alloying on the circumferential portion, but also to various surface treatments such as hardening.

As described in detail, according to the present invention, the optical system converts the laser beam into a ring-shaped beam having a cross section of tJliil constant h1, and the optical system or the axis of the circumference of the material to be treated is ni; a means to move, so? l
The laser beam is simultaneously irradiated on the circumference of the i-treated material, that is, on the circumferential part, and the irradiation position is moved along the axis of the inner circumference, so it is possible that the start and end points of the surface treatment exist on the circumference. Therefore, it is possible to perform a surface treatment with excellent characteristics, which is uniform and free of defects such as bead defects, on the circumferential portion such as the inner circumferential surface.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of the present invention, FIG. 2 is a sectional view, FIG. 3 is a sectional view in another operating state, and FIG. 4 shows a state of surface treatment of the inner peripheral surface by a conventional method. FIG. 1... Conical mirror, 1a... Reflective surface, 2...-
Laser light, 4...inner peripheral surface, 4a, 4b...
Circumferential part, 5... covered 5I! l Materials. Applicant Toyota Motor Corporation Representative Patent Attorney Yutaka 1) Hisashi Take (one idiot) Figure 2 Figure 3

Claims (2)

[Claims] (1) In a circumferential laser surface treatment method in which surface treatment is performed by irradiating a laser beam onto the circumference of a material to be treated, the laser beam is received at a constant angle of incidence and has a ring-shaped cross section centered on a predetermined axis. An optical system that emits a laser beam is arranged so that the axis substantially coincides with the axis of the circumference of the material to be treated, and the optical system or the material to be treated is moved along the axis. A method for laser surface treatment of a circumferential portion. (2) The optical system consists of a conical mirror having a conical reflecting surface, and the reflecting surface is a concave surface that is curved concavely with respect to the generatrix of the conical surface, and from above the apex of the mirror to the central axis of the mirror. Claim 1, characterized in that the laser beam is arranged to receive the laser beam at an incident angle along
Laser surface treatment method for the circumferential portion described in Section 1.