JPH03110089A - Laser beam butt welding method - Google Patents

Abstract

PURPOSE:To obtain a butt weld zone having a good bead shape and sufficient strength by moving the focal point of a laser beam from the center of the butt part to the inner side in opposite of the end part of strip having a large thickness according to the difference in the thickness of the preceding strip and the succeeding strip. CONSTITUTION:The laser focus aligned heretofore to the center of the butt part is moved by as much as a moving quantity L toward the strip A having the large thickness by moving the processing axis itself in the longitudinal direction of the strip. The processing axis and filler wire feeder of a welding machine for supplying a filler wire 7 are integrally moved, by which the wire is brought into contact with the angle part of a step and the deviation thereof from the laser beam to generate the imperfect melting is prevented. The wire is melted around the corner end part of the strip A by moving the focal point 4 of the laser beam to the inner side in opposite of the end part of the strip A. The preceding and succeeding strips A, B of the weld zone are made into the shape to connect the strips with smooth curves, by which the generation of a notched part is prevented and the working rate is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a line butt laser welding method for continuously processing strips having large thickness differences.

<Prior art> In butt welding of strips using laser light,
As shown in FIG. 4, a laser beam 1 generated from a laser oscillator is focused on the workpiece via a mirror 2 and a lens or a condensing mirror 3, and the laser beam focusing position 4 is set at the rear end of the leading strip 5 and the rear end of the leading strip 5. Butt part 8 with the tip of the row strip 6
(hereinafter referred to as the center of the abutment part) (hereinafter referred to as the center of the abutment part)
1-1236), the thickness of the leading and trailing ends of the strip is different, and the larger the difference in thickness, the more a step will be created at the welded part after welding, and the strength of the welded part will be increased due to the formation of a notch. descend.

Furthermore, in the method of supplying filler wire to the welding part, if there is a difference in thickness, the supply of the filler wire becomes unstable and the filler wire may not be melted and remain after welding. For this purpose, a method of grinding the welded part using a grinding device after welding is usually performed, but the series of operations takes a long time and results in a significant decrease in the operating rate of the device.

Furthermore, the strength of the sliding joint obtained by butt welding objects to be welded with a large difference in thickness using this method is lower than the strength of the welded portion of objects to be welded of the same thickness.

<Problems to be Solved by the Invention> As mentioned above, when performing butt laser welding of strips with a large difference in thickness using the conventional technology, there are the following problems: ■ Decreased operating rate of the device, ■ Grinding of the welded part, ■ Occurrence of welding defects, ■ There is a problem such as a decrease in the strength of the welded part.

The present invention has been made in order to provide a method for butt laser welding of strips having a large difference in thickness, which can solve the above-mentioned problems.

Means for Solving the Problems> The present invention provides a butt laser welding method in which each end of a leading strip and a trailing strip are abutted, and the abutted portions are irradiated with a laser beam for welding. This is a butt laser welding method characterized by moving the focal point of the laser beam from the butt center to the inner side of the opposite end of the thick strip according to the difference in thickness of the strips.

<Function> In the present invention, as shown in Fig. 1, the laser focus, which has conventionally been focused on the butt center, is moved in the longitudinal direction of the strip by moving the processing axis itself using a motor, etc., toward the thicker strip. Move by 1iL.

In the type of welding machine that supplies filler wire 7, the processing axis and filler wire supply device are integrated and moved simultaneously, which causes the wire to come into contact with the corner of the step, deflecting the laser beam and leaving no melt. This can be prevented from occurring.

By moving the laser beam focal point from the thicker corner end to the inner side of the recessed part of the strip A, the corner end of the strip A is melted.

This makes it possible to form a shape in which the leading strip and trailing strip of the welded portion after welding are connected by a smooth curve.

In this way, by minimizing the step difference in the weld, the shape of the weld bead is improved, the occurrence of notches can be prevented, the strength of the weld does not decrease, and the need for grinding can be omitted.
The aforementioned problems can be solved.

<Example> FIG. 2 is a characteristic diagram showing the relationship between the thickness difference, the laser focal position, and the weld zone condition in laser welding of workpieces with a thickness difference operated on a continuous rolling line. From this figure, it is clear that when welding strips with different thicknesses, changing the amount of movement of the laser beam focal point position depending on the thickness difference can yield a welded part with a good bead shape and sufficient strength. Note that Erichsen in FIG. 2 is an abbreviation for Erichsen destructive test results.

When the thickness difference is 0.5m, by moving the focus position from the butt center to the thicker plate by 0.05mm, which is 10% of 0.5, a good bead shape and a good Erichsen test result can be obtained. I was able to get a weld.

As shown in Figure 3, it was confirmed by the post-weld strength test (Erichsen fracture test) that the welding strength significantly decreased when the laser beam focus moved 0.2cm from the butt center. Considering the allowable range of light deviation, in the present invention, the amount of movement of the focal position is set to a maximum of 0.1 degrees.

The maximum thickness difference is 2 by shifting the focal point within 0.1 inch.
．． It was possible to roll the weld on a continuous rolling line without reducing the strength of the welded part and maintain the same strength as the welded part of the same thickness of workpiece.

<Effects of the Invention> By applying the method of the present invention to laser welding in a continuous strip rolling mill, a welded part with a good bead shape and sufficient strength can be obtained.
We were able to reduce the number of troubles caused by poor welding, and achieve zero introduction of a multi-product continuous rolling system.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing the positional relationship between the strip and the laser beam focus, Figure 2 is a characteristic diagram showing the relationship between the thickness difference and the amount of movement of the laser beam focus, and Figure 3 is the focal position and welding area. FIG. 4 is a schematic diagram illustrating laser welding. G... Laser light, 2... Plane mirror 3...
・Condensing mirror・ 4...L nose light focal position,
5... Leading strip, 6... Trailing strip, 7... Filler wire, 8... Butt portion, L
...Transfer III amount, Δ...Strip (large board thickness), I3...Strip (Fi, r\small).

Claims (1)

[Claims] In a butt laser welding method in which each end of a leading strip and a trailing strip are brought together and welded by irradiating the butt portion with a laser beam, according to the difference in thickness between the leading strip and the trailing strip, , a butt laser welding method characterized in that the focal position of the laser beam is moved from the center of the butt part to the inside of the opposite end of the thick strip.