JP2792340B2 - Laser welding method - Google Patents

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 which is used for welding a workpiece by laser light, and particularly suitable for performing laser welding in which a weld joint shape is fillet welding. .

[0002]

2. Description of the Related Art Joint shapes using laser welding are generally superimposed, butted, and filleted. And since the joining strength by welding depends on the area of the joining part, a method of obtaining a larger joining area according to the shape of the joint is being studied.

For example, in the case of butt welding of thick workpieces 51 and 52 as shown in FIG.
Is irradiated from a direction parallel to the bonding surface 54, so that obtaining as deep a penetration as possible leads to an increase in the bonding area. On the other hand, as shown in FIG.
In the lap welding of 52, since the irradiation direction of the laser beam 53 is perpendicular to the joining surface 54, the width of the laser beam 53 is widened or the welding speed is reduced to increase the welding width. I have.

[0004] On the other hand, FIG. 7 shows an example in which fillet welding of workpieces 51 and 52 by laser light 53 is performed.
In the fillet welding, the workpieces 51 and 52 and the laser beam 53 interfere with each other, so that the irradiation direction of the laser beam 53 and the joining surface 54 are parallel to each other. Therefore, the laser beam 53 is inclined with respect to the bonding surface 54, so that a fusion part 55 having a certain angle with respect to the bonding surface 54 is formed.

[0005]

As described above, in laser welding in which the shape of the weld joint of the workpieces 51 and 52 is fillet welding, the joining surface 54 and the melted portion 55 are not parallel, and thus contribute to joining. The portion of the melting portion 55a not to be increased increases,
The contribution of the penetration depth to the expansion of the bonding area is small.

Therefore, in order to obtain a larger joint area, a laser beam having a larger beam diameter is used or processing is performed at a lower welding speed to increase the width of a portion contributing to the joining of the fusion zone. There is a need.

However, in the former case, there is a problem that when the beam diameter is increased while the power density is kept constant, a larger output is required. Also,
In the latter case, there is a problem that productivity is reduced. In any of the methods, since the melting of a portion that does not directly contribute to joining is accompanied, the problem is large in terms of reducing residual stress and welding deformation after welding. Had been an issue.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and is intended to provide a method of forming a work piece and a laser beam even when performing laser welding in which the shape of a weld joint is fillet welding. It is an object of the present invention to perform efficient laser welding without causing interference between the laser welding and minimizing a welded portion that does not contribute to joining and increasing an effective joining length.

[0009]

SUMMARY OF THE INVENTION According to the present invention, a laser beam is irradiated onto a surface of a workpiece and the workpiece is melted to perform a laser welding with a weld joint shape of fillet welding. using a laser beam, the welding direction and rate
It is characterized in that the polarization plane is more desirably inclined at 45 degrees to the side where the bonding plane is present with respect to the plane including the light irradiation direction, and the laser light is irradiated and welded.

[0010]

In the laser welding method according to the present invention, since the above configuration is employed, the molten pool formed during laser welding is not formed in the same direction as the direction of laser beam irradiation, but is formed in the direction of the joint surface. As a result, the penetration depth directly contributes to the enlargement of the bonding area.
Therefore, the welded portion which does not contribute to the joining is minimized and the effective welding length is increased, so that the residual stress and welding deformation after welding are reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a laser welding method according to the present invention will be described with reference to the drawings.

FIG. 1 shows a state in which a laser welding method according to the present invention is performed, and FIG. 2 is an enlarged explanatory view of a main part thereof.

In FIGS. 1 and 2, workpieces 1 and 2 are shown.
Shaped in a state in which the workpiece 1 has been pressed against the workpiece 2
The welded joints 4 are joined at the joint surfaces 4 formed, and the shape of the weld joint is fillet welding.

In performing this fillet welding, a linearly polarized laser beam 3 is used, and the welding progress direction and the laser beam irradiation direction are used.
Angle of the polarization plane to the side where the bonding surface 4 exists with respect to the plane including
Weld by irradiating the laser beam 3 at an angle of θ = 45 degrees.

In the laser welding method according to the present invention, linearly polarized laser light 3 is used.
It is known that the absorptance of the linearly polarized laser light 3 greatly changes depending on the direction of the polarized light with respect to the material and the irradiation angle.

FIG. 3 shows the angle dependence of the absorptance when the laser light is irradiated in the directions of the S-polarized light and the P-polarized light. It has a high absorption rate when illuminated in the direction. And it is said that the incident angle of the laser beam with respect to the molten pool formed during laser welding is about 70 to 80 degrees,
The shape of the fusion zone is greatly affected by the direction of polarized light.

Therefore, the welding progress direction and the laser beam irradiation direction
Angle of the polarization plane to the side where the bonding surface 4 exists with respect to the plane including
When the laser beam 3 is irradiated in a state in which the laser beam 3 is inclined at 45 °, the molten pool has the highest absorptivity in the 45 ° oblique direction in the welding progress direction. Therefore, the molten pool is not coaxial with the laser beam irradiation direction but in the direction of the workpiece 1. It is formed inclined. As a result, as shown in FIGS. 1 and 2, the fusion zone 5 is parallel to the bonding surface 4,
The penetration depth directly contributes to the expansion of the bonding area.

Therefore, since it is possible to minimize the useless molten portion, it is possible to reduce welding deformation and residual stress.

FIG. 4 shows an example of the result of examining the relationship between the welding speed and the effective joining length when fillet welding is performed on a workpiece made of steel at a laser output of 4.5 kW.

In the conventional method, the effective joining length is originally small and depends on the width of the fusion zone. Therefore, even if the welding speed is reduced, the effective joining length does not greatly increase. Thus, since the depth of the fusion zone directly becomes the joining length, the original joining length was also large, and the effective joining length could be further increased by reducing the welding speed.

[0021]

As described above, according to the laser welding method of the present invention, when performing laser welding in which the shape of the weld joint is fillet welding, linearly polarized laser light is used.
Since the laser beam is irradiated to the side where the joining surface is present and the laser light irradiation direction is more desirably inclined at a 45 ° angle with respect to the plane including the welding direction and the laser beam irradiation direction, the welding is performed. It is possible to make the melted part parallel to the joint surface without causing interference of the laser beam and the laser beam. This has the remarkable effect of being possible.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a slope showing an embodiment of a laser welding method according to the present invention.

FIG. 2 is an enlarged explanatory view of a main part of FIG. 1;

FIG. 3 is a graph showing the correlation between laser beam irradiation angles in the directions of P and S polarized light and absorptance.

FIG. 4 is a graph showing the results of comparison of the correlation between the welding speed and the effective joining length between welding by the method of the present invention and welding by the conventional method.

FIG. 5 is an explanatory view of a slope showing butt welding of a thick workpiece.

FIG. 6 is an explanatory side view showing a lap welding of a thin workpiece.

FIG. 7 is an explanatory view of a slope showing an example of fillet welding by a conventional method.

FIG. 8 is an enlarged explanatory view of a main part of FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Workpiece 2 Workpiece 3 Laser beam 4 Joining surface 5 Fused part

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-28487 (JP, A) JP-A-4-28488 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B23K 26/00-26/06

Claims (2)

(57) [Claims] 1. A laser beam is irradiated onto a surface of a workpiece to melt the workpiece, so that when welding is performed with a fillet weld in the shape of a weld joint, a linearly polarized laser beam is used to carry out welding. A laser welding method comprising: irradiating a laser beam with a polarization plane inclined to a side including a bonding surface with respect to a plane including a direction and a laser beam irradiation direction to perform welding. 2. A laser beam is irradiated by using a linearly polarized laser beam with the polarization plane inclined at 45 degrees to the side where the joint surface exists with respect to the plane including the welding progress direction and the laser beam irradiation direction. The laser welding method according to claim 1, wherein the welding is performed.