JPH0433555B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for butt welding metal strips using a laser beam.

(Prior art) Generally, when butt welding the end faces of metal strips using a laser beam, there are two cases in which the strips are sheared and then the sheared ends are brought together and butt welded with zero gap.
There are cases where welding is performed while supplying filler wire to this gap. In either case, the laser beam diameter is usually about 0.2 to 0.8 mm and the gap is about 0 to 0.7 mm. In order to obtain good welding strength, it is necessary to maintain the positional deviation between the beam center line and the butt center line or the gap center line within an accuracy of 0.1 to 0.3 mm.

(Problems to be solved by the invention) Laser beam welding involves welding by transmitting laser light and focusing it with a lens, etc.
Metal mirrors, condensing mirrors, or lenses are used for optical transmission and optical path changes, and changes in this optical system over time.
There was a problem in that the focal position changed by 0.1 to 0.2 mm due to extremely small changes due to wear of the movable parts, and as a result, the welding strength decreased.

(Means for Solving the Problems) The present invention aims to solve the above-mentioned problems and increase the strength of butt welding by laser beam welding. Therefore, according to the present invention, when butt welding metal strips with a laser beam, the laser torch is moved along the butt center line to perform butt welding. A reference groove is formed by a laser beam on a reference plate set offline on the center line, and the position of the laser torch in the line direction is controlled so that the positional deviation between the center line of the reference groove and the butt center line of the strip is zero. However, the metal strip ends are butt welded.

(Example) Figures 1 to 3 show an apparatus used to carry out the present invention, and Figure 1 shows an apparatus for shearing the ends of metal strips to be butt-welded and abutting the end faces; In the figure, 1 and 2 are leading and trailing metal strips, 3 and 4 are welding clamps, and 5 and 6 are shear upper and lower blades.
2 are clamped with welding clamps 3 and 4 respectively, the ends of the metal strips 1 and 2 are sheared with upper and lower shear blades 5 and 6, and either the sheared ends or the welding clamps 3 and 4 are moved. end face 1 of the sheared end
a, 2a are positioned at the abutting position shown in FIG. 2 by means of welding clamps 3, 4.

2 and 3 show a laser beam welding machine, 7 is a laser torch, 8 is its laser condensing lens header, 9 is a laser beam reflecting mirror,
These are integrally connected and mounted on a slider 10, and the slider 10 is slidably mounted on a laser torch traveling frame 11 extending in the width direction of the metal strips 1 and 2, as shown in FIG. A laser torch travel drive screw 12 screwed into the slider 10 and extended along the travel frame 11 is connected to the laser torch travel drive motor 1.
3, by rotating the laser torch 7 forward and backward, the laser torch 7 is aligned with the butt center line A of the metal strips 1 and 2.
It is constructed so that it can move along the Also,
Reference numeral 14 indicates a header lifting motor for moving the laser condensing lens header 8 up and down, and 15 indicates a cross-direction header drive motor for moving the header 8 in a direction perpendicular to the abutting center line A.

Further, a bead position detector 16 is mounted on the slider 10 and is configured to run immediately after the laser torch 7 to detect the welding center line B and measure its position.
6 is input to the calculator 17, the butt center line A and the weld center line B from the shear butt position stored in the calculator 17 are calculated by the calculator, and the cross direction header is driven based on the difference. motor 15
The position of the laser torch 7 is adjusted by servo control so that the welding line center B, that is, the center position of the laser beam, always coincides with the butt center line A.

The bead position detector 16 can be configured, for example, to detect the welding center line B by making magnetic detection elements follow both sides of the welding bead position.

18 is a reference plate installed off-line on an extension of the butt center line A, and 19 indicates its holder.

When laser beam welding the front end of the trailing metal strip 2 to the rear end of the leading metal strip 1 using the above-mentioned device, the rear and front ends of the leading and trailing strips 1 and 2 are welded by welding clamps 3 and 4. After clamping them respectively, shear them with the upper and lower shear blades 5 and 6 (see Figure 1), and then move either one of the welding clamps 3 or 4 to butt the end surfaces 1a and 2a of both sheared ends. , the laser torch 7 is run along this butt center line A,
A laser beam is irradiated on the butt part to perform gas seal welding. Welding is performed while maintaining a constant mechanical relationship between the butt center line A and the laser torch 7, that is, the laser torch 7 follows the frame 11.

However, while the laser beam is being transmitted through various mirrors and lenses in the optical system, slight angular changes may occur (due to temperature, etc.) over a long period of time. Therefore, the beam center may shift slightly from its original position.

After welding is complete, the beam is cut off and returns to the standby position. At this time, the laser output is made very small and the off-line reference plate 18 is continuously irradiated with a beam of about 0.2 to 0.7 kW over a length of 5 mm or more. Since the laser torch 7 is on the same traveling frame as when welding, the beam is irradiated to the same position as when welding. This irradiation trace is formed as a deep groove with a width of 0.02 to 0.05 mm, as shown by C in FIG.
This groove C is further scanned by a bead position detector 16 to detect and position the center line of the groove C and therefore the center line B of the weld bead. The position signal of this welding center line B is input to the calculator 17, and compared with the position of the butt center line A obtained by the shear butt device stored in the calculator 17, and the difference is transmitted to the header drive motor 15. The torch position is adjusted by servo control so that the beam position is always on the butt center line A.

As a result, during actual welding, the laser beam position is always located at the butt position of the welded materials or on the gap center line of the welded materials, and thereby sufficient welding strength can always be obtained.

FIG. 7 shows the butt center line A according to the conventional method,
The welding strength is shown in comparison between a case where there is a positional deviation between the welding center line B and a case where the beam center is controlled within a certain range with respect to the butt center line A according to the present invention.

As shown in FIG. 7, according to the conventional method, the deviation ε between the butt center line A and the beam center occurs by 0.2 to 0.3 mm, and at this time, the number of repeated bending of the welded part is extremely small, and the welding strength is low. When the difference ε between the butt center line and the beam center is controlled within 0.15 mm, the number of repeated bending is 19 times or more, and stable welding strength can be maintained.

(Effects of the Invention) According to the present invention, the beam center from the butt center line during butt welding with a laser beam,
That is, it is possible to almost eliminate positional deviation of the welding center line, thereby achieving the effect that stable welding strength can be maintained.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a strip end shearing device provided in conjunction with a laser beam welding device;
Fig. 2 is a schematic side view of the laser beam welding device, Fig. 3 is a schematic front view of the laser beam welding device shown in Fig. 2, and Fig. 4 shows the state of the laser beam bead on the reference plate. FIG. 5 is an explanatory diagram showing the state of bead-on position detection by the bead position detector. FIG. 6 is an explanatory diagram showing the positional deviation of the laser beam welding center line. FIG. 7 is an explanatory diagram showing the position shown in FIG. 6. It is a graph showing the relationship between the amount of deviation and the number of repeated bending. 1... Leading metal strip, 2... Trailing metal strip, 3, 4... Clamp, 5... Upper shear blade, 6... Lower shear blade, 7... Laser torch,
8... Laser condensing lens header, 9... Laser light reflecting mirror, 10... Slider, 11...
...Laser torch travel frame, 12...Laser torch travel drive screw, 13...Laser torch travel drive motor, 14...Header lifting/lowering motor, 15...Cross direction header moving motor, 1
6... Bead position detector, 17... Arithmetic unit, 18
...Reference plate, 19...Reference plate holder.

Claims (1)

[Claims] 1 When butt welding metal strips using a laser beam, the laser torch is moved along the butt center line to form a reference groove using the laser beam on a reference plate set offline on the butt center line, and the center of this reference groove is A laser beam welding method comprising butt-welding the ends of metal strips while controlling the position of a laser torch in the line direction so that the positional deviation between the line and the butt center line of the strip is zero.