JPH0225598Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Purpose of the Invention> The present invention relates to a back bar for laser welding. Specifically, during laser welding, it is possible to prevent reflection and scattering of the laser beam at areas other than the welding line, and to prevent this reflection and scattering. This invention relates to a back bar for laser welding that has sufficient strength and rigidity despite the provision of an enlarged slit for prevention.

Recently, high-speed welding machines that use a high-energy-density laser beam as a heat source for butt welding steel plates have been rapidly put into practical use in pickling lines of steel plants, and in fact, they are already in use in some pickling lines. It has come to be served to

Laser welding involves focusing a high-energy-density laser beam into a thin beam using a condensing lens to precisely match the welding line to join the joints.Generally, the purpose is to ensure sufficient welding line accuracy at the butt joint. ,
A backing bar commonly referred to as a "backing metal" is used to press the back side of the butt part.

When welding butt parts of steel plates, etc. using laser welding, if both ends of the butt part are not securely welded, the weld will break midway through the line, so irradiate the laser beam from before the butt part. However, it is necessary to perform welding by moving the welding torch in the width direction of the steel plate, etc., and to irradiate the laser beam until it passes the butt part even at the welding end position.

However, in such cases, the laser beam is irradiated over a substantially longer distance than the welding line, so the laser beam is irradiated directly onto the back bar at areas other than the welding line, that is, on both sides of the welding line, causing damage to the back bar. As a result, the laser beam is reflected and scattered, leading to various emergencies, and a simple block-shaped back bar cannot prevent these problems at all.

Therefore, in order to solve these problems, the present inventors first proposed a new "back bar for laser welding" in Utility Application No. 57-40673. In this back bar, a back bar that comes into contact with the back surfaces of a pair of workpieces to be welded together is mounted on a support frame, and this back bar has a slit opening and a bag-shaped groove that communicates with the slit opening over the entire length. In particular, the bag-shaped groove has a triangular cross section, and a light absorbing material is provided on the supporting frame in a corresponding portion of the bag-shaped groove to absorb the laser beam. Therefore, when irradiating before or after welding,
It is excellent in that even if the laser beam is reflected and scattered, it can be effectively prevented. However, the weak point of this back bar is that when the back bar is lengthened when welding a wide steel plate, the back bar becomes double due to the formation of slits and bag-like grooves over the entire length.
Since the back bar is divided, its mechanical strength is poor, and due to this lack of strength, the back bar bends due to the heat generated during welding, and is also bent due to the pressing force on the butt part, making it difficult to achieve high precision. It is not possible to ensure the matching of
There is a problem in that the back bar needs to be replaced frequently.

The purpose of this invention is to solve the above-mentioned drawbacks, and specifically, it is a laser welding device that does not cause diffuse reflections even when welding other than the welding line, that is, before and after welding, and has sufficient strength and rigidity. The purpose is to provide a backup bar.

<Structure of the invention> This structure and its operation will be explained in more detail with reference to the drawings.

Note that FIG. 1 is a cross-sectional view of a back bar according to one embodiment of the present invention, FIG. 1 a is an exploded perspective view of the back bar shown in FIG. FIG. 3 is a vertical cross-sectional view taken along line A-A in FIG. 1, and FIG. 3 is a vertical cross-sectional view taken along line B-B in FIG.
Moreover, FIG. 3 shows a laser welding machine equipped with such a back bar.

First, as shown in FIG. 3, steel plates 1 and 2, which correspond to the members to be welded, are fed along a line and held at predetermined positions by clamp fittings 6 and 7, respectively. The front end surfaces of the row steel plates 2 are abutted against each other, and a laser torch is run along the welding line of this abutted portion to perform laser welding. In order to improve the accuracy of this abutting portion, opposing ends of the steel plates 1 and 2 may be cut using a shear device (not shown), and the cut surfaces may be abutted against each other.

Further, during welding, the back bar 3 is applied from below the weld line to flatten and support the lower surface of the butt portion.

In addition, the laser beam 8 is narrowed down by a condensing lens 9 in the middle, and its focus is placed on the welding line of the steel plates 1 and 2, and the laser welding is performed while joining the welding trajectories at high speed with a high energy density laser heat source. proceed.

Next, the back bar 3 that flatly supports the lower surface of the butt portion in this way is configured to be longer than the width dimension of the steel plates 1 and 2, and is pressed appropriately in accordance with the back surface of the butt portion of the steel plates 1 and 2. and is fixed on the holder 4. On the surface of this back bar 3, the butt portion of the steel plates 1 and 2, that is,
In areas corresponding to the weld line, along the weld line,
As shown in FIG. 2, a groove 3a having a concave cross section is formed. This groove 3a is connected to the back bar 3 as shown in FIG.
The central part of the groove 3a is narrower than the minimum width of the steel plate, and on both sides of the groove 3a, as shown in FIG. 1 and FIG. An enlarged slit 3b is formed which gradually enlarges. As shown in FIG. 1a and FIG. 3, the enlarged slits 3b at both ends are made so that their cross sections are gradually enlarged toward the bottom, and each enlarged slit 3b is continuous from both sides of the groove 3a in the direction of the welding line. form by extending it. The length of the enlarged slit 3b is formed to be sufficiently long by the abutting portion of the steel plates having the maximum width.

Note that the present invention does not have to be used to butt weld a wide steel plate and a narrow steel plate as described above, but it is also possible to weld wide steel plates together.

Therefore, with the back bar 3 having the above configuration, the laser beam is transmitted through the enlarged slit 3b from the welding start point to the welding line and from the welding line end point to the welding end point other than the welding line.
A recess 5 is provided in the holder 4 directly below these enlarged slits 3b, and this recess 5
A light absorber 10 is provided at the bottom of the laser beam, thereby absorbing the laser beam.

Further, the back bar having the above structure can be configured to be divided into left-right symmetrical parts, as shown in FIG.

Therefore, the operation of the laser welding machine equipped with the laser welding back bar having the above structure will be explained as follows.

Prior to welding, as described above, the preceding steel plate 1
The subsequent steel plates 2 are each clamped by clamp fittings 6 and 7, and after cutting the opposing butt ends, the cut end surfaces of both steel plates are accurately butted. Then, the butt portion is clamped and held by the back bar 3, and preparation for welding is completed.

During welding, the welding torch that is waiting at the start of welding emits a laser beam from just before the welding start point of the butt joint, and the laser beam is correctly operated and travels along the welding line, and welding ends after passing through the end point of the welding line. Quit when the point is reached.

In this series of welding processes, the laser beam 8
The irradiation start time and cut-off time have a certain amount of leeway in order to completely weld both sides of the butt part, and while the laser beam is irradiated at a position other than the weld line, the back bar 3 will not expand. The laser beam passes through the slit 3b, and the light absorbing material 1
0 is irradiated and absorbed. On the other hand, since the period when the laser beam substantially touches the welding line is affected by the steel plate, a groove 3a as shown in FIG. 2 is sufficient.

<Effects of the invention> In summary, in the back bar for laser welding according to the present invention, expanding slits that widen toward the bottom are formed in areas other than the weld line where the back bar is directly irradiated with the laser beam, and the lower surface of the material to be welded is A simple groove is formed in the portion that comes into contact with. Therefore, strength problems can be solved even when welding materials to be welded such as wide steel plates, and the safety and butt accuracy of laser welding can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a back bar according to one embodiment of the present invention, FIG. 1 a is an exploded perspective view of the back bar shown in FIG. 1, and FIG.
FIG. 3 is a vertical cross-sectional view taken along line A and FIG. 3 is a vertical cross-sectional view taken along line B--B in FIG. Code, 1, 2...material to be welded (steel plate), 3...back bar, 3a...groove, 3b...enlarged slit,
4... Holder, 6, 7... Clamp device, 8...
...Laser beam, 9...Condensing lens, 10...Light absorbing material.

Claims (1)

[Scope of utility model registration request] In a back bar for laser welding used as a backing metal for the butt part of materials to be welded, a groove is provided in the center along the length direction at a position corresponding to the weld line of the butt part. , an enlarged slit is formed on both sides of this groove and the cross section gradually enlarges toward the bottom, and a laser beam is placed directly below this enlarged slit.
A back bar for laser welding characterized by being provided with a light absorbing material that absorbs the beam.