JPH06304772A - Laser beam welding method - Google Patents

Abstract

PURPOSE:To simplify the structure of equipment when at least either of preheating and postheating is carried out by using a laser beam for welding and to reduce the cost. CONSTITUTION:A rack 8 extended along an optical axis of the laser beam is fixed on the side of a welding torch 4 of a laser beam head 1, a gear 11 driven by a driving motor unit 9 is meshed with the rack 8 and the gear 11 is rotated forward and backward, by which the welding torch 4 is made displaceable in the optical axis direction. The position of a focus of the laser beam 7 is located above and a weld zone can be irradiated with the laser beam in the wide range by keeping the welding torch 4 at a specified distance above the weld zone of strips 2 and 3 at the time of preheating and postheating. Consequently, the need to provide a driving mechanism to scan the laser beam is eliminated and the cost of the laser beam welding equipment capable of carrying out preheating and postheating can be reduced by the simple structure.

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 in which welding is performed by a laser beam emitted from a laser head toward a welding site.

[0002]

2. Description of the Related Art Conventionally, there is laser welding in which welding is performed by a laser beam emitted from a laser head toward a welded portion. For example, as disclosed in JP-A-61-92792, In some cases, a laser beam is used to perform preheating or postheating before and after welding in order to improve the shaping accuracy and the strength of the welded portion.
However, if the laser beam is focused as much as possible to narrow the width of the welding bead as in the case of butt welding of thin plates, and the preheating and postheating are performed using the laser beam in that state, the welding bead width Since the effects of preheating and postheating appear only in a narrower range, there is a problem that the effect of improving the strength of the weld is small.

In order to widen the range of influence of the preheat and the postheat, it is conceivable to oscillate the laser beam in a direction intersecting the welding line as disclosed in, for example, Japanese Patent Laid-Open No. 61-111792. But with this method,
A mechanism for moving the laser beam in the welding line direction while oscillating the laser beam in the lateral direction is required, which causes a problem that the device becomes complicated and expensive, and there is a possibility that the device becomes larger.

[0004]

SUMMARY OF THE INVENTION In view of the above problems of the prior art, the main object of the present invention is to provide an apparatus for performing at least one of preheating and postheating using a welding laser beam. An object of the present invention is to provide a laser welding method which has a simple structure and can be manufactured at low cost.

[0005]

According to the present invention, there is provided a laser welding method in which welding is performed by a laser beam emitted from a laser head toward a welded portion. It is achieved by providing a laser welding method characterized in that, when performing at least one of preheating and post-heating for a portion, irradiation is performed by displacing the focal position in welding the laser beam in the optical axis direction. It

[0006]

With this configuration, by displacing the focal position of the laser beam in the optical axis direction, it is possible to irradiate the welded portion with a wider range than the irradiation range at the time of welding. The range of influence of after heat can be expanded.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic side sectional view showing a main part of a welding laser head to which the present invention is applied. This laser head 1 is used in a welding device arranged to join a preceding strip 2 and a following strip 3 by butt welding in a strip feeding path. In this welding device, both strips 2 and 3 are respectively clamped by a clamp device (not shown), and further, both abutting ends are positioned and fixed by an auxiliary clamp device (not shown).

The laser head 1 has a cylindrical welding torch 4 which is supported by a supporting arm (not shown) of a welding device.
A laser generator (not shown) is mounted on the upper surface of the welding torch 4 in the drawing, while being supported so as to be displaceable in the direction shown by an arrow A in the drawing, which is a direction toward and away from the weld between the strips 2 and 3. The optical fiber 5 is connected. The laser light sent into the welding torch 4 via the optical fiber 5 is converted into a focused light by the internal condenser lens 6 and emitted as a laser beam 7 from the lower opening of the welding torch 4 in the figure. ing.

On the side surface of the welding torch 4, a rack 8 is fixedly provided so as to extend in parallel with the optical axis of the laser light passing through the welding torch 4, and the rack 8 has the above-mentioned structure. A gear 11 driven by a drive motor unit 9 attached to the support arm is meshed. Therefore, the welding torch 4 can be displaced in the direction shown by the arrow A in the figure by appropriately rotating the gear 11 in the forward and reverse directions.

The laser head 1 thus constructed
The procedure for welding by is shown below. The strips 2 and 3 are positioned and fixed as described above, and the welded edges 2a of the strips 2 and 3 are butted.
-Preheat 3a. In the preheating, it is necessary to heat a range wider than the width of the welding bead 12 formed by welding, and in this apparatus, the position of the focal point F of the laser beam 7 is adjusted to the edges 2a and 3a as shown in FIG. The welding torch 4 is raised by the distance L in order to separate the welding torch 4 by a predetermined distance L above.

By doing so, as shown in FIG. 2, the laser beam 7 is focused at the position of the distance L above both edges 2a and 3a, so that both edges 2a and 3a are focused.
By the time point 3a is reached, the beam irradiation range is wide. Therefore, it is possible to sufficiently preheat the welded portion without oscillating the laser beam 7. The welding torch 4 is moved in the front and back directions in the figure by a slide device (not shown) to preheat the entire welding line.

After the preheating is completed, the position of the focus F is adjusted to the both edge portions 2
The welding torch 4 is moved down by the distance L in order to perform laser welding in conformity with a.3a. Then, similarly to the above, the welding torch 4 is moved in the front and back directions in the figure by the slide device, and welding is performed over the entire welding line. In addition, when post-heating is performed after welding, the welding torch 4 is raised in the same manner as pre-heating.

The vertical movement of the welding torch 4 can be controlled arbitrarily, and the separation distances of the welding torch 4 at the time of preheating and afterheating can be set separately, depending on the case of preheating and afterheating. Suitable processing can be performed. In this way, the strength of the welded portion can be suitably improved by the prognostic heat treatment.

The drive device for vertically moving the welding torch 4 is not limited to the combination of the rack and the gear of this embodiment, and various drive mechanisms such as a linear drive motor and a direct-acting type cylinder can be used. However, in any case, it suffices if the welding torch 4 can be displaced in the vertical direction, and the structure can be made extremely simple as compared with the structure for causing the amplitude shown in the conventional example. It is also possible to displace the lens.

[0016]

As described above, according to the present invention, since the focal position of the laser beam can be shifted to perform preheating, postheating and welding, a mechanism for vertically moving the laser head in the optical axis direction is provided. The effect is extremely large, for example, a high-quality weld bead can be formed by preheating and post-heating in a range wider than the weld bead width with a device that has a simple structure and is inexpensive. .

[Brief description of drawings]

FIG. 1 is a schematic side sectional view of a main part of a laser head to which the present invention is applied.

FIG. 2 is an enlarged view of a main part showing a laser welding procedure according to the present invention.

[Explanation of symbols]

 1 Laser Head 2/3 Strip 2a / 3a Edge 4 Welding Torch 5 Optical Fiber 6 Condenser Lens 7 Laser Beam 8 Rack 9 Drive Motor Unit 11 Gear 12 Weld Bead

Claims (1)

[Claims] 1. A laser welding method in which welding is performed by a laser beam emitted from a laser head toward a welded portion, wherein at least one of preheating and post-heating of the welded portion is performed, A laser welding method, which comprises irradiating the laser beam while shifting a focal position of the laser beam in the optical axis direction.