JPH09216078A - Method and equipment for laser beam welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent weld joint without generating defective welds even when a member to be welded is thin, or when a clearance is present between members to be welded by reducing the melted area of a base metal at a joined part to realize the high-speed welding. SOLUTION: In performing the laser beam welding by butting two plates 3, 4 of different thickness, the laser beam is radiated diagonally from the thick plate side so as to offset the position of radiation on the side of the thick plate 3 from a joined part 1. The area of the melted part is reduced to realize the high-speed welding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser welding method and a laser welding apparatus for butt welding two welding members having different thicknesses with a laser beam.

[0002]

2. Description of the Related Art In the manufacturing process of automobile body panels and the like, a method of butt-welding two steel plates having different thicknesses and then finishing the welded product into a desired shape by pressing or drawing is already in practical use. Has been converted. This method has a better material yield than the conventional method, that is, the case of pressing a single plate to integrally mold a large part, and the pressed individual parts are joined by means such as welding to obtain the final shape. Compared with the case where it is obtained, it has advantages such as reduction of the number of molds and the joining process, and further, using plated steel plate only in the portion where corrosion resistance is required, or requiring strength. Since it is possible to use a thick steel plate only for the part, this is an effective method for reducing the material / manufacturing cost and reducing the weight of the body.

In this case, welding is generally carried out by laser welding, which has the advantages that thermal strain is small and the strength of the joint is less likely to decrease. FIG. 3 is a schematic view of such a butt laser welding. As shown in the figure, in the conventional case, a laser beam is provided along a vertical axis (5) from directly above a joint (1) of two fixed steel plates. Of the two welded members (3) and (4) butted to each other while irradiating the laser beam and sending the beam exit port (2) in the vertical direction of the paper surface (the welding member may be sent with the beam exit port fixed). doing. In the drawing, the beam is radiated aiming at the joint part (1), but in actuality, the irradiation position of the laser beam is set to the thick plate material (3) in consideration of misalignment and non-uniformity of linearity of the work. Often slightly offset to the side. However, even in this case, the beam irradiation direction is the vertical direction.

[0004]

However, in recent years,
As laser welding becomes more efficient, higher speed is required, and this request is also made in the butt laser welding described above. Generally, in order to increase the speed of laser welding, it is effective to reduce the melting area in the base metal, but in the conventional method shown in FIG. 3, the melting portion (7) is relatively small as shown in FIG. Since the welding speed is limited to a wide range, the actual speed cannot be increased sufficiently.

On the other hand, as one method of butt laser welding, as shown in FIG. 5, the laser emitting port (2) is tilted toward the thin plate material (4) side with respect to the vertical axis (5), and the laser beam is joined. There is a publicly known method of irradiating the corner portion (6) of the above (see JP-A-63-168286). According to the experiment, according to this method, as shown in FIG. 6, the area of the fusion zone (7) in the base material is the fusion zone (7) obtained by the above method (FIG. 3).
Since it is much smaller than the area of, the speedup is considered to be achievable.

However, in the method of FIG. 5, it is difficult to accurately aim at the corner portion (6), so that the base material melting may be biased to one member, leading to welding failure. In this case, if the thickness is biased toward the thick side under the same welding conditions, the amount of melting the base metal will increase with respect to the amount of heat input, resulting in a lack of penetration depth. As a result, the amount of burnout is reduced. Further, even if these defects do not occur, the mechanical strength may be insufficient due to the misalignment between the fusion zone and the joint due to misalignment. Since these phenomena generally appear more prominently as the plate thickness becomes thinner, they become a major obstacle in reducing the weight of the body panel.

Further, since there is little melting of the base material on the thick plate (3) side, there is a tendency for excess molten metal to run short.
When there is a gap (g) between both members (3) and (4), the undercut (8) cannot be filled up as shown in FIG.
May occur. This undercut (8)
This does not occur as long as the welding surfaces of both members (3) and (4) have a high linear accuracy and can be reliably brought into surface contact with each other. It is difficult to make surface contact with each other over the entire area, and it is unavoidable that a gap (g) is formed between both members although the size is small.

Therefore, the present invention aims to eliminate the drawbacks of the above two methods at the same time. That is, it is possible to obtain a good welded joint without causing welding failure even if there is a gap between the welding members, while making the base material molten area in the joint part small so that the welding speed can be increased. The purpose is to do.

[0009]

In order to achieve the above object,
In the present invention, when two plate materials having different thicknesses are butted and laser welded, a laser beam is obliquely irradiated from the thick plate material side, and the irradiation position is offset to the thick plate material side from the joint portion. did.

Further, the device of the present invention is a device for abutting and laser-welding two plate materials having different thicknesses, wherein the laser beam is obliquely irradiated from the thick plate material side to the beam emission port, and The irradiation position is arranged to be offset to the thick plate material side with respect to the joint portion.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, according to the present invention, the beam emission port (2) is made thicker than the vertical axis (5) so that the horizontal component of the laser beam faces the thin plate (4) side. )
The beam irradiation position is offset to the thick plate material (3) side with respect to the joint portion (1).
Thereby, the laser beam is obliquely irradiated from the thick plate material (3) side toward the thin plate material (4) side, and the irradiation position is close to the joint part (1) on the surface of the thick plate material (3). It becomes the position to do.

When a tomographic photograph of a welded product welded by this method is taken, as shown in FIG. 2, the area of the fusion zone (7) becomes smaller than that of the welded product of the conventional method (see FIG. 4). It could be confirmed. Therefore, compared with such a conventional method, high-speed welding is possible and productivity can be improved.

Further, in the present invention, unlike the method shown in FIG. 5, since the laser beam is irradiated aiming at the surface of the thick plate material (3), the irradiation position of the beam may be slightly different from the specified position for some reason. Even if they are deviated, there is not much difference in the amount of base material melted. Therefore, even in such a case, stable welding can be performed, and the quality of welding does not depend on the thickness of the welding member as in the conventional method. Moreover,
The upper corners (9) of the thick plate material (3) due to beam irradiation
Melts and disappears, the surplus melting amount of the base material increases as compared with the method of FIG. 5 in which the corner (9) remains unmelted. Therefore, even if there is a gap between both members (3) and (4), the shortage can be compensated by the molten metal to obtain a smooth weld without undercut, and two plate materials with low end face precision can be welded well. It will be possible. Further, since the upper corner portion (9) of the thick plate material (3) disappears, wear of the mold is reduced even in the case of press molding after welding, and the corner portion (9) remains as compared with the method of FIG. It is also possible to improve the die life.

The present inventors conducted a comparative experiment with the conventional method shown in FIG. 3 under the following conditions in order to confirm the effect of the present invention. However, in any case, shear-cut low carbon steel was used as the welding members (3) and (4), and the welding length was 500 mm.
And The inclination angle α (see FIG. 1) of the laser beam in the method of the present invention is 7 °, and the offset amount s is 0.1.
5 mm.

・ Thick plate material thickness t = 3.0 mm ・ Thin plate material 〃 t = 1.8 mm ・ Laser output P = 5.0 kw ・ Shield gas G = 30 liters / min ・ Argon ・ Defocus amount Df = ± As a result of the 0 mm experiment, in the conventional method, the welding speed at which no welding failure occurred was about 3 m / min, but in the method of the present invention, stable welding can be performed even at a speed of 5 m / min. The effect of the invention was proved.

The optimum tilt angle α of the laser beam is
Is difficult to specify because it depends on the welding conditions such as the thickness and material of the welded member and the laser output.
If within the range of approximately 2 ° ≦ α ≦ 15 °, a certain effect is achieved. The optimum offset amount s is also difficult to specify for the same reason, but is generally 0.05 mm ≦ s ≦ 0.3.
It may be in the range of mm.

[0018]

As described above, according to the present invention, as compared with the conventional method of vertically irradiating a laser beam, the area of the melted portion is small and high-speed welding is possible, so that the productivity can be improved. it can.

Further, without being influenced by the thickness of the plate material,
Stable and good welding can be performed. Further, even if there is a gap between both plate materials, a smooth welded part without undercut can be obtained, and good butt welding is possible even between plate materials having low end face accuracy.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a laser welding method and a laser welding apparatus according to the present invention.

FIG. 2 is a vertical cross-sectional view of a joint after welding by the method of the present invention.

FIG. 3 is a vertical sectional view showing a conventional general butt laser welding method.

4 is a vertical cross-sectional view of a joint after welding by the welding method shown in FIG.

FIG. 5 is a vertical sectional view showing another example of a conventional butt laser welding method.

6 is a vertical cross-sectional view of a joint after welding by the welding method shown in FIG.

7 is a vertical cross-sectional view of a joint after welding by the welding method shown in FIG.

[Explanation of symbols]

 1 joining part 2 beam exit port 3 thick plate material 4 thin plate material S offset amount

Claims (2)

[Claims] 1. When two plates having different thicknesses are butted against each other and laser-welded, a laser beam is obliquely irradiated from the thick plate side and the irradiation position is offset from the joint to the thick plate side. Laser welding method characterized by. 2. An apparatus for laser welding two plate materials having different thicknesses by abutting each other, wherein a laser beam is obliquely irradiated from a thick plate material side to a beam emission port, and the irradiation position is joined. A laser welding device, wherein the laser welding device is arranged so as to be offset toward the thick plate material side from the portion.