JP2002361454A - Method for lap welding of aluminum alloy with semiconductor laser beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for a semiconductor laser welding of aluminum alloy plates, by which method the aluminum alloy plates are welded at high speed and weld defect is prevented in a manufacturing line of assembled aluminum plates of automobiles, railroad cars, buildings or the like for which aluminum alloys are used. SOLUTION: In a lap welding of aluminum alloy plates AL1 and AL2 with the semiconductor laser DDL, a groove M is mechanically machined at a point which is irradiated with a laser beam on the surface of the aluminum alloy AL1 and the welding is performed by increasing the substantial absorption rate of the laser beam and increasing the melting efficiency by making the laser beam repeatedly reflect in the groove and propagate inside the groove.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can weld aluminum alloy plates at a high speed in a production line of aluminum alloy plates for assembling automobiles, railway vehicles, buildings, etc., using aluminum alloys. The present invention relates to a semiconductor laser welding method for an aluminum alloy plate that can prevent defects.

[0002]

2. Description of the Related Art Aluminum alloy sheets are used for assembling automobiles, railway cars, buildings, etc., like steel sheets.
It has been practiced to weld aluminum alloy plates at high speed.

[0003] However, welding of aluminum alloys by a laser beam is in a state where good welding is difficult due to high reflection and high thermal conductivity of a laser beam of an aluminum alloy material. Therefore, in order to increase the absorptivity of the laser beam on the aluminum alloy surface, a material having high absorption efficiency at the wavelength of the laser is coated, or fine irregularities are given to the aluminum alloy surface by anodizing by anodic oxidation. A welding technique has been proposed in Japanese Patent Application Laid-Open No. Hei.

[0004] However, the technique described in Japanese Patent Application Laid-Open No. 4270088/1992 requires that the alumite processing by anodic oxidation has low processing resistance in order to improve the absorptivity on the aluminum alloy surface, and that an organic coating is further applied to the surface. And the process is complicated and the practicality is extremely low.

The method of the present invention solves the above-mentioned problems and disadvantages of the conventional method and provides means for achieving lap welding of an aluminum alloy plate.

[0006]

(1) The absorptance of a laser beam on an aluminum alloy surface is greatly improved,
(2) A groove is provided at the irradiation point of the laser beam so that the laser beam is multiple-reflected to improve the overall absorptivity, thereby ensuring stable welding without welding defects. The purpose is to:

[0007]

SUMMARY OF THE INVENTION According to the present invention, there is provided (1) a lap welding of an aluminum alloy plate by a semiconductor laser, wherein a groove is formed at a laser irradiation point on the aluminum alloy surface to thereby reduce a substantial absorption rate of a laser beam. In the method of welding an aluminum alloy using a semiconductor laser, which is characterized by performing up-welding, and (2) in lap welding of an aluminum alloy plate using a semiconductor laser, the angle formed by the groove wall on the surface of the aluminum alloy to be welded is Provided is an aluminum alloy lap welding method using a semiconductor laser that mechanically imparts 45 degrees or less, a depth of 200 μm or more, and a width of 50 μm to 200 μm, irradiates a laser along the groove, and lap welds the aluminum alloy. I do.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for grooving and welding a laser irradiation point on the surface of an aluminum alloy alloy in lap welding of an aluminum alloy plate with a semiconductor laser according to the present invention will be described in detail with reference to the drawings. I do.

FIG. 1 is a schematic view of a method for lap welding an aluminum alloy using a semiconductor laser according to the present invention.

[0010] The aluminum alloy plates AL ₁ and AL ₂ are overlapped, a groove M is machined at a welding position which is a laser irradiation position fp, and a laser beam LB from a semiconductor laser DDL is condensed and irradiated by a condensing lens FL. .

The laser beam fb is subjected to multiple reflections in the groove M to further increase the density and increase the melting efficiency.

[0012]

Table 1 Table 1 Absorption rate of the laser beam of the present invention on the aluminum alloy surface

Table 1 compares the absorptivity on the aluminum alloy surface between the CO ₂ laser beam described in JP-A-4-270088, the YAG laser beam generally used widely, and the wavelength of the semiconductor laser according to the present invention. are doing. The absorption rate when irradiating a laser beam
The melting properties are determined. The CO ₂ laser beam described in JP-A-4-270088 has an absorption of 1% to 2% at a wavelength of 10.6 μm.
As disclosed in the publication, it is necessary to apply a coating substance in order to increase the absorption of the CO ₂ laser beam. The semiconductor laser of the present invention has a wavelength of 13% to 14% at a wavelength of 0.805 μm, has an absorption efficiency of about 7 times or more that of a CO ₂ laser beam, and can be welded by direct laser beam irradiation. The present invention not only improves the wavelength absorption characteristics with the characteristics of the laser beam, but also forms a groove at the irradiation point of the laser beam, further enhances the absorption characteristics of the laser beam, improves the efficiency of lap welding of aluminum alloy, and improves the welding efficiency. It is characterized by having stabilized.

FIG. 2 shows a method of applying the method to an aluminum alloy surface.
It shows the shape of the groove. FIG. 2A shows a V shape,
2 (b) is a V shape with a bottom, FIG. 2 (c) is a U shape, and FIG. 2 (d) is a U shape with a projection. 200 μm or more, width 50
There is an effect if it is from 200 μm to 200 μm.

FIG. 3 is a view showing the groove three-dimensionally, and a top view.
M1, front view M2, side view M3. In FIG.
The shape of the groove is shown as a depth Dm, a length Lm, and a width Wm of the groove.

FIG. 4 shows the multiple reflection effect of the laser beam on the inner wall of the groove according to the present invention. FIG.
2.5 degrees, FIG. 4 (b) shows that the apex angle θ of the groove is 45 degrees, and FIG.
(C) is a case where the apex angle θ of the groove is 90 degrees, and when the laser beam LB irradiates the groove, the beam is irradiated with the inner walls MW1 and M
The light is reflected at W2 and travels in the vertex Vp direction. As shown in FIG. 4A, when the apex angle is 22.5 degrees, which is 45 degrees or less, the laser beam repeats reflection at the inner wall at reflection points P1, P2, P3, and P4 more than four times, and the vertex Vp of the groove is repeated. Direction, the density of the laser beam increases, and the melting is accelerated. The incident angle β of the laser beam at each reflection point is expressed by the following equation. When the angle exceeds 90 degrees, the laser beam is emitted out of the groove.

Βn = θ (n1 / 2) (1)

Here, n is the number of the reflection point and n = 1 is the reflection point at which the laser beam first enters the groove and is reflected. The details of the reflection position (number of times) and the incident angle of the laser beam when θ = 22.5 degrees in FIG. 4A are as follows.

When n = 1, β1 = 11.25 degrees, n = 2
, Β2 = 33.75 degrees, n = 3, β3 = 56.
At 25 degrees and n = 4, β4 = 78.75 degrees. As described above, the incident angle is 90 degrees or less even after four reflections, and the reflected laser beam converges toward the apex of the groove.

As shown in FIG. 4 (c), when the apex angle is 45 degrees or more,
In the case of 0 degree, the laser beam is reflected on the inner wall by reflection points P1 and P2.
, And is emitted out of the groove, and does not proceed in the vertex Vp direction. In this state, the density of the laser beam increases, and the improvement in melting is small.

FIG. 4B shows a case where the apex angle is 45 degrees, which is halfway between FIGS. 4A and 4C. The laser beam is reflected four times on the inner wall at the reflection points P1, P2, P3, and P4. However, the reflection at a position apart from the vertex Vp causes a low degree of laser beam focusing, and the effect of multiple reflection is low.

FIG. 5 shows the structure of an aluminum alloy plate lap welding apparatus to which the method for lap welding aluminum alloy plates by a semiconductor laser according to the present invention is applied. The beam LB is condensed by the condensing lens FL, and is irradiated on a welding portion provided with a groove in advance. FIG. 6 is an explanatory view of a mechanism for providing a groove on the surface of an aluminum alloy plate. The laser processing head PHD includes a groove processing punch N3, an upper and lower drive unit N2, and a fixing jig N1.

The processing head PHD has gas inlet / outlet ports Gi, G
and dry air is slightly supplied to prevent the semiconductor laser DDL from moisture. The processing head PH
D has a processing gas insertion port Ga, and supplies an inert gas to prevent oxidation when the aluminum alloy surface is melted.

FIG. 7 compares the results of the lap welding of an aluminum alloy with a semiconductor laser according to the present invention and the results of the lap welding of an aluminum alloy according to the conventional method. The plate thickness was 2 mm for both the upper plate and the lower plate.

FIG. 7 (a) shows a method of lap welding of an aluminum alloy plate using a CO ₂ laser proposed in Japanese Patent Application Laid-Open No. 4-270088, in which an absorbing material is applied to the surface of the aluminum alloy in advance, followed by laser welding. The output is P = 4kW,
The speed was V = 0.6 m / min. In this conventional method,
A process of applying an absorbing substance is required, and the processing speed is low. Then, the absorbing substance remains even after welding, which affects the process thereafter. Since the welding is performed by the CO ₂ laser which needs to increase the density of the focused beam, the width of the bead is narrow, and the effective joining width WEB required for the lap welding is used.
But there is a narrow disadvantage. FIG. 7B shows lap welding of an aluminum alloy using a semiconductor laser. Output is P = 4k
W and speed were V = 1 m / min. In this conventional method,
Since no grooves are provided, the width of the melted shape is increased, but the penetration depth cannot be obtained. FIG. 7 (c)
Is the result of the lap welding of the aluminum alloy plate according to the method of the present invention. Output is P = 4kW, speed is V = 1m / min
And According to this method, the result that both the fusion width and the fusion depth greatly exceeded the conventional method was obtained, and the area of the cross section of the fusion portion was about 6 to 10 times as compared with the method of FIG. In particular, the effective joining width WEB required for the lap welding increased nearly twice as compared with the method of FIG. 7B.

As described above, it has been found that the lap welding method of the aluminum alloy sheet according to the method of the present invention has a great effect practically.

[0027]

As described above in detail, the method for lap welding an aluminum alloy plate with a semiconductor laser according to the present invention greatly increases the substantial absorptivity of the laser beam on the aluminum alloy surface, and as a result, the weldability is improved. Deep melting and stable melting. Furthermore, the increase in the substantial absorption has the advantage that the utilization of the laser power is greatly improved.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a lap welding method of an aluminum alloy using a semiconductor laser of the present application.

FIG. 2 is a schematic view of a groove shape provided on the surface of the aluminum alloy according to the present invention.

FIG. 3 is a definition of a groove provided on the surface of an aluminum alloy according to the present invention.

FIG. 4 is an explanatory diagram of a state of multiple reflection of a laser beam on an inner wall of a groove.

FIG. 5 is an explanatory view of a specific configuration of the lap welding method for an aluminum alloy of the present invention.

FIG. 6 is an explanatory view of a method for providing a groove.

FIG. 7 is an explanatory diagram comparing a lap welding method of the present invention and a fusion section of a conventional method.

[Explanation of symbols]

DDL: Semiconductor laser AL1, AL2: Aluminum alloy plate LB: Laser beam FL: Condensing lens fl: Condensed laser beam fp; Focus position M: Groove Wm: Groove width Lm: Groove length Dm: Groove depth Rm: Projection around groove M1, M2, M3: Top view, front view, side view of groove MW1, MW2: Wall in groove P1, P2, P3, P4: Laser beam is reflected by wall in groove Position Vp: Groove tip θ: Angle formed by groove wall LX: Upward distance from groove tip PC: Power cable CW: Water-cooled cable PS: Power supply for semiconductor laser Gi, Go: Cooling gas Ga: Processing Gas N1, N2, N3: Groove processing mechanism WEF: Effective joint width FL M: Absorbing material layer of laser beam

Continuing from the front page (72) Inventor Katsuhiro Minami 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Techno-Laser Technology Center (72) Inventor Masakazu Tsuji 4-9-1, Fushimi, Chuo-ku, Osaka-shi, Osaka Within Hybrid Technology Systems Co., Ltd. (72) Inventor Jun Munemura 4-9-1, Fushimi, Chuo-ku, Osaka-shi, Osaka Within Hybrid Technology Systems Co., Ltd. (72) Inventor Masashi Oikawa Shintomi, Futtsu-shi, Chiba 20-1 Inside the Nippon Steel Techno Research Laser Technology Center (72) Inventor Hiroyuki Yamamoto 20-1 Shintomi, Futtsu City, Chiba Prefecture F-term (reference) 4E068 AA03 AJ01 DA04 DB04

Claims (2)

[Claims] In a lap welding of an aluminum alloy plate by a semiconductor laser, a groove is formed at a laser irradiation point on the surface of the aluminum alloy to increase a substantial absorption rate of a laser beam and perform welding. Aluminum alloy welding method. 2. In lap welding of an aluminum alloy plate using a semiconductor laser, an angle formed by a groove wall on the surface of an aluminum alloy to be welded is 45 degrees or less and a depth of 200 degrees.
A lap welding method for an aluminum alloy using a semiconductor laser, wherein a laser beam is radiated along the groove, and the aluminum alloy is lap welded.