JP2947002B2 - 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, and more particularly to a laser welding method suitable for welding aluminum-based materials.

[0002]

2. Description of the Related Art In recent years, with the progress of aluminum parts for automobile parts, for example, attempts have been made to manufacture a bonnet from an aluminum alloy. In this case, it is necessary to weld the outer panel and the inner panel at the peripheral hemmed portion.However, if a general-purpose spot welding such as for a steel plate is used, the welding portion is greatly deformed by the pressing force from the welding method, Its use will have to be abandoned. On the other hand, the use of MIG welding or TIG welding can be considered as an alternative to spot welding. It is unavoidable that the affected area is enlarged and the amount of shrinkage is increased, and a large distortion is generated in the welded portion and the non-welded portion, and it is unavoidable to correct it.

In recent years, attention has been paid to the application of laser welding to aluminum-based materials, and some attempts have been made to manufacture the bonnet by laser welding (see, for example, "NIKKEL MECHANICAL" 1993.5.3 Nikkei BP).
This laser welding method uses a YAG laser as a laser, guides the laser to a laser torch at the tip of the robot by an optical fiber, moves the laser torch along a welding planning line L, and continuously welds over a predetermined length (about 20 mm). This operation is performed for a plurality of locations (15 to 18 locations). The reason why the YAG laser is used as the laser is that it has a higher absorptance for an aluminum-based material having a higher reflectivity than the CO ₂ laser, and has a small oscillation wavelength of 1.06 μm, so that quartz (SiO ₂ ) This is because absorption is not possible and flexible transmission by an optical fiber is possible, and a large peak output can be obtained by pulse oscillation output.

[0004]

However, according to the laser welding, since continuous welding is performed, although partially, as shown in FIG.
The amount of solidification shrinkage in the welded part (bead) 2 and the amount of heat shrinkage in the heat-affected zone around the bead become relatively large, and to a lesser extent than in the case of MIG welding or TIG welding. There is a problem that distortion is still likely to occur in the hemmed portion 3 and the general portion 4. In addition,
In FIG. 3, 1a is an outer panel, 1b is an inner panel,
An object to be welded 1 is constituted by both.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to reduce solidification shrinkage and heat shrinkage by limiting the welded portion and the heat-affected zone to a narrow range. It is an object of the present invention to provide a laser welding method which suppresses the distortion and greatly contributes to the prevention of distortion.

[0006]

Means for Solving the Problems According to the present invention, in order to achieve the above object, a laser torch is moved along a welding planning line of an object to be welded, and a pulsed YAG laser is emitted from the laser torch to form a spot. Welding on
In the laser welding method, the welded part is
And the speed of movement of the laser torch as formed by the
And the pulse repetition frequency of the YAG laser is controlled .

[0007]

In the laser welding method configured as described above, by appropriately setting the pulse repetition frequency and the moving speed of the laser torch, welding progresses in a spot at a pitch of about 15 mm , and the welded portion and the heat effect. The portion is limited to a narrow range, so that solidification shrinkage and heat shrinkage are greatly suppressed.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a main part of a hood manufactured by laser welding according to the present invention. Since the hood is the same as that shown in FIG. 3, the same parts as those shown in FIG. 3 are denoted by the same reference numerals. In this embodiment, the workpiece 1
A large number of welding portions 10 are formed in a spot at a predetermined pitch P in the hemmed portion (welding portion) 3 of the welding portion 1.
By 0, the outer panel 1a and the inner panel 1b are integrated. Thus, the pitch P of the welded portion 10
Is set to at least 15 mm or more in consideration of the thermal influence between the welded portions. In order to perform the spot welding at such a pitch P, a welding apparatus as shown in FIG. ing.

In FIG. 2, reference numeral 11 denotes a work receiving table on which the workpiece 1 is positioned and mounted, and 12 denotes a multi-axis robot installed adjacent to the work receiving table 11. A laser torch 13 having a built-in optical system is attached. The laser torch 13 is connected to a separately installed YAG laser transmitter 14 via an optical fiber 15, and a pulsed YAG laser is transmitted from the YAG laser transmitter 14 to the laser torch 13 at a predetermined repetition frequency. ing. Reference numeral 16 denotes a robot control device. The robot 12 operates in accordance with the instruction of the robot control device 16, directs the laser torch 13 supported on the wrist portion 12a to the plate surface of the hemming portion 3 of the workpiece 1, and The hemming portion 3 is moved at a predetermined speed along a welding planning line L. Here, Y
The AG laser transmitter 14 has a function of oscillating a YAG laser having an average output of 500 to 700 W, a pulse width of 10 to 20 msec, and a repetition frequency of 6 to 10 Hz.

In order to perform laser welding by the above-mentioned welding apparatus, first, the work 1 is set on the work receiving table 11 and the teaching operation panel (not shown) is operated on the hemming portion 3 of the work 1. Is stored in the robot controller 16 along the welding planning line L. Next, the robot control device 16 is activated and the laser transmitter 14 is activated. Then, the laser torch 13 moves on the welding planning line L at a predetermined speed according to the teaching contents stored in the robot controller 16 in advance, and at the same time, the laser torch 13 emits a pulsed YAG laser at a predetermined repetition frequency. You. The peak output of the pulse oscillation YAG laser is extremely large (tens of kW to several tens of kW).
A welded portion 10 is formed on the hemmed portion 3 as a spot at a predetermined pitch P.

The pitch P of the welding portion 10 is
It is determined by the moving speed (welding speed) of the laser torch 13 and the repetition frequency of the pulse oscillation from the laser transmitter 14. Here, the welding speed and the repetition frequency are adjusted so that the pitch P is at least 15 mm or more. ing. According to the laser welding performed in this manner, the penetration depth becomes sufficient due to the high output of the laser despite the spot-like shape, and the joining of the panels 1a and 1b constituting the workpiece 1 is ensured. . Further, the welding area of the welded portion 10 is limited to a narrow range, and the amount of fusion per point is reduced, so that the solidification shrinkage is significantly smaller than that of the conventional continuous welding of a predetermined length (about 20 mm). . Moreover, since the welds 10 are at least 15 mm apart from each other, the thermal effect between the welds is reduced as much as possible, and the amount of heat shrinkage is significantly reduced as compared with conventional continuous welding. As a result, not only the hemmed portion 3 as a welding portion, but also
Occurrence of distortion in the general portion 4 is significantly suppressed, and the rework is not required. The strength per welding point is smaller than that of the conventional continuous welding of a predetermined length. However, when the pitch P of the welded portions 10 is set to about 15 mm, the strength (rigidity) of the entire bonnet is reduced. Can be secured,
No worries about strength.

Here, the output, pulse width and the like of the YAG laser are appropriately set according to the material or plate thickness of the work 1 to be welded. As an example, an outer panel 1 with a thickness of 1.0 mm
to be welded 1 consisting of a and an inner panel 1b having a thickness of 1.4 mm
, The conditions of a YAG laser output of 650 W, a pulse width of 18 msec, a repetition frequency of 6 Hz, and a welding speed of 90 mm / sec are selected. By welding under these conditions, the pitch P of the welded portion 10 becomes 15 mm. As a result, almost no distortion occurs.

In the above embodiment, an example in which the present invention is applied to the production of a bonnet made of an aluminum alloy has been described. However, the present invention is applicable to any material, and a material which easily generates distortion, for example, a steel plate having an extremely thin plate thickness , Copper-based materials, magnesium-based materials, etc., as well as various parts other than the bonnet. In addition, the applicable welding portion has been described as a hemmed portion, for example, a flange portion,
The present invention can also be applied to a board matching portion and the like. Further, in the above-described embodiment, the laser torch 13 is provided to the multi-axis robot 12, but a device for providing the laser torch 13 is also optional.
-It can be provided to the traveling head on the Y table.
Further, the present invention may be shared with the conventional continuous welding of a predetermined length.

[0015]

As described in detail above, according to the laser welding method according to the present invention, the welded portion is about 15 mm.
Welding is performed in a spot so that it is formed at a certain pitch, so that the welded part and the heat-affected zone can be limited to a narrow range, and the solidification shrinkage and the heat shrinkage are largely suppressed. This is suitable for welding of materials and components that are likely to cause distortion .

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a welding state by laser welding according to the present invention.

FIG. 2 is a perspective view showing an example of a structure of a welding device for performing the method of the present invention.

FIG. 3 is a perspective view schematically showing a state of welding by conventional laser welding.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Workpiece 3 Welding part 10 Welding part 11 Work cradle 12 Robot 13 Laser torch 14 Laser transmitter 15 Optical fiber L Welding planning line

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B23K 26/00-26/18

Claims (1)

(57) [Claims] 1. A laser torch is moved along a welding plan line of an object to be welded, and a pulsed YAG laser is emitted from the laser torch to perform spot welding.
In the laser welding method, the welded part is
And the speed of movement of the laser torch as formed by the
And a pulse repetition frequency of a YAG laser .