JPH01233084A - Butt laser welding method for thin sheet - Google Patents

Abstract

PURPOSE:To monitor the quality during welding and to improve the quality of a weld zone by repeatedly performing the welding by a laser beam until the blue flame by the laser welding is observed over the whole length of the butt weld line of a thin sheet. CONSTITUTION:In case of the gap 2 between the butt 1a, 1a of thin sheet 1, 1 exceeding the allowable value of one pass welding a laser beam 7 reaches up to the back face side of the thin sheet 1, 1, the lower part is melted and the lower part of the gap 2 is filled. At this time no blue flame is generated. After one pass completion the gas 2 becomes narrow by the heat contraction. With further laser welding the whole body is remelted and a stabilized blue flame is generated because the gap 2a of the butt part is made narrow at this time. Good butt laser welding can be executed by repeatedly projecting the laser beam 7 until the blue flame is observed over the whole length of the butt weld line like this.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of butt welding thin plates together by laser welding.

[Prior Art] Fig. 4 is a side view showing a welding state for explaining a general butt laser welding means for thin plates.
is two thin plates to be butt welded, generally the butt portion 1a of the thin plates 1, 1.

1a has gaps 2 at appropriate intervals without being in close contact over the entire length of the weld line. Further, 3 is a surface plate attached to a jig 6 and on which each thin plate 1 is placed, 4 is a presser metal fitting that clamps the thin plate 1 between it and the surface plate 3 and is tightened and fixed with bolts 5, and 7 is not shown. This is a laser beam irradiated from a laser light source to the welding line of the butt portion 1a of the thin plate 1.

When attempting to butt laser weld the thin plates 1 at the butt portions 1a, generally the surface plate 3. Holder fitting 4 and bolt 5
The thin plates 1, 1 are fixed on the jig 6 and arranged so that the gap 2 is made as small as possible. In addition, gap 2
will not disappear.

Generally, during laser welding, good welding cannot be achieved unless the gap 2 is less than 1/2 of the beam diameter of the welding area or 1/10 of the thickness of the thin plate 1.

Laser welding is performed by abutting and fixing the thin plates 1 and 1 with the precision described above, and then welding the abutted portion 1a.

The laser beam 7 is irradiated along the welding line 1a, and the thin plates 1, 1. Completely weld and join to the back side of the beam irradiation.

[Problems to be Solved by the Invention] According to the conventional butt laser welding means for thin plates, as mentioned above, the gap 2 must be set to 1/2 of the laser beam diameter or 1/1o or less of the thickness of the thin plate 1. , since the laser beam 7 passes through the gap 2 and cannot melt the thin plates 1,1 and complete welding is not possible, the butt portion 1a of the thin plates 1,1.

In order to keep the gap 2 of 1a within the above-mentioned accuracy, it is necessary to machine the end faces of the thin plates 1 and 1 before welding, and if the gap 2 is large, the filler is not fed and the laser There were problems such as the need for welding, which required a great deal of labor.

This invention was made to solve the above problems, and even if the gap accuracy is not within the accuracy of one-pass welding, it is possible to completely butt thin plates using conventional jigs and laser welding equipment. The object is to obtain a welding method that allows easy welding.

[Means for Solving the Problem] The method for butt laser welding of thin plates according to the present invention includes repeating welding with the laser beam described above until a blue flame (plasma) due to laser welding is observed over the entire length of the butt weld line of the thin plates. It is something to do.

[Function] The method of butt laser welding of thin plates in this invention is performed based on the following principle. In other words, when laser welding is performed, a stable blue flame (plasma) is generated if the welding is performed well.

Therefore, during laser welding, it is constantly observed whether or not a blue flame is generated, and welding with a laser beam is repeatedly performed until it is observed that this blue flame is generated.

Here, blue flame does not occur when the gap at the butt part of the thin plates is not within the accuracy of one-pass welding, but even if the gap exceeds the tolerance, the day focus of the laser beam and the laser beam By reflection at the end face of the thin plate, the laser beam reaches the back side of the thin plate, melting the lower part of the abutting portion, and fusion welding the thin plates. At this time, blue flame does not immediately occur, but the groove between the thin plates is narrowed due to thermal contraction caused by laser welding.

When laser welding is roughly performed on this, the previously formed melt in the lower part is remelted, and the thin plate in the upper part of the abutment part is melted while a blue flame is generated. At this time, the gap between the abutting portions has also become narrower, so the laser beam irradiation remelts the entire body and generates a stable blue frame.

If the laser welding is finished when such a blue frame is observed over the entire length of the butt weld line of the thin plate, it means that good butt laser welding has been performed.

[Embodiment of the Invention] An embodiment of the invention will be described below with reference to the drawings. The jigs and laser welding equipment used to carry out the method of butt laser welding of thin plates according to this embodiment are exactly the same as the conventional ones explained with reference to FIG. 4, so their explanation will be omitted.

Now, here, according to FIGS. 1 to 3, thin metal plates 1,
An example in which the method of the present invention is applied to butt welding of thin plates 1 and 1, particularly when the gap 2 between the butt portions 1a and 1a of the thin plates 1 and 1 is larger than the allowable value for 1-pass welding, will be explained. . As mentioned above, FIG. 1 is a cross-sectional view showing the state of the butt part immediately after welding starts when the gap 2 is large, FIG. 2 is a cross-sectional view showing the state of the butt part after completing one pass of welding, and FIG. 1 is a cross-sectional view showing the state of the butt part after two passes of welding, and in each figure, 1 is the thin plate to be butt welded, 1a is the butt part of the thin plate 1, and 2 is the butt of the two thin plates 1, 1. The gap between parts 1a and la,
2a is the gap narrowed by heat shrinkage during one-pass welding (
(described later), 7 is a laser beam, 8 is molten metal formed by one-pass welding, and 9 is molten metal formed by two-pass welding.

During butt laser welding, butt part 1 of thin plate ]-21
If the gap 2 of a, la is larger than the allowable value of corpus welding, it usually produces a stable blue flame (plasma)
This does not occur and good welding is not performed.

However, even if the gap 2 exceeds the allowable value for one-pass welding, the laser beam 7
The thin plate 1. ] - reaches the back side of the abutting portion 1a.

The lower part of the gap 2 is melted, and the lower part of the gap 2 is filled with this molten metal 8. However, at this time, a blue frame does not occur immediately.

Furthermore, after completion of pass welding, the groove between the thin plates 1, 1 is narrowed due to thermal contraction due to laser welding, and the gap 2a is narrowed (see FIG. 2).

When laser welding is repeated with the groove condition changed in this way, the part where the gap was narrow and well joined will be remelted, and the part where the gap has widened will also be melted. The molten metal 8 on the lower side of the groove is remelted and the groove gap narrows, so the laser beam 7
The thin plate 1 at the top of the groove (butt portions 1a, la) is irradiated with
, 1 are also melted (see molten metal 9 in Figure 3).

At this time, as described above, the gap 2a between the abutting portions 1a, 1a is also narrowed, so the entire body is remelted by the laser beam 7 irradiation and a stable blue frame is generated.

If the laser beam 7 was repeatedly irradiated until such a blue frame was observed over the entire length of the butt weld line between the thin plates 1 and 1, the gap 2 would be too wide and good welding would not be possible with one-pass welding. If the laser welding of the parts is completed when the blue flame is observed, the butt laser welding will be performed satisfactorily.

As described above, according to the method of this embodiment, welding with the laser beam 7 is repeatedly performed until a blue flame (plasma) due to laser welding is observed over the entire length of the butt weld line of the thin plate 1.1. While using the conventional device as is, a good joint can be obtained extremely easily even in a welded part with poor groove precision in the abutting parts 1a, la, without worrying about the precision of the gap 2. Additionally, by constantly observing the blue flame, the quality during laser welding can be monitored in real time, which has the advantage of significantly improving the quality of the weld.

In the above embodiment, the case where the thin plate 1 is made of metal has been described, but it may be made of other meltable materials such as ceramics, and the same effects as in the first embodiment can be obtained.

In addition, although the welding conditions for repeated welding were not mentioned in the above embodiments, the welding conditions for the first pass may be the same, or in order to further widen the bead width, the output may be increased or the welding conditions may be You can slow down the speed.

[Effects of the Invention] As described above, according to the present invention, the welding using the laser beam is repeated until a blue frame due to the laser welding is observed over the entire length of the butt weld line of the thin plate, thereby making it possible to improve the conventional apparatus. In addition to making it extremely easy to obtain a good joint even in a welded part with poor groove precision at the butt part, the quality during laser welding can be monitored in real time by observing the blue flame, and the quality of the welded part can be improved. It has the effect of significantly improving

[Brief explanation of the drawing]

1 to 3 are cross-sectional views showing the state of the butt portions welded by the butt laser welding method for thin plates according to an embodiment of the present invention, and FIG. 4 illustrates a general butt laser welding method for thin plates. FIG. In the figure, 1--thin plate, 1a--butt portion, 2° 2a--gap, 7... laser beam. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] In a thin plate butt laser welding method in which thin plates are butted and welded with a laser beam, welding with the laser beam is repeatedly performed until a blue flame due to laser welding is observed over the entire length of the butt weld line of the thin plate. A method for butt laser welding of thin plates characterized by: