JP4099642B2 - Laser welding method for surface-treated steel sheet - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser welding method for lap welding of surface-treated steel plates, and more particularly to a laser welding method suitable for lap welding of plated steel plates.
[0002]
[Prior art]
For example, when laser welding is performed by superimposing galvanized steel sheets or aluminum plated steel sheets, the plating component evaporates due to the heat of the laser beam if the adhesion of the overlapping surfaces is good and there is no gap at all. Since there is no escape space, welding defects such as blowholes will occur.
Therefore, conventionally, when laser-welding the above-described plated steel sheet, generally a protrusion or a recess is formed on at least one of the two plated steel sheets to be welded, and a minute gap ( The gas generated by the evaporation of the plating component is allowed to escape through the minute gaps (for example, JP-A-10-216974, JP-A-2000-162388, JP-B-6). -73755 publication etc.). However, according to the countermeasures described above, projections or recesses are usually formed by pressing, so that dimensional variations in their height or depth are likely to occur, and if the minute gap is too small, gas When the drawing is insufficient and, on the other hand, it is too large, the molten metal is melted down, and there is a problem that it is difficult to stably secure the desired welding quality.
[0003]
[Problems to be solved by the invention]
On the other hand, for example, in Japanese Patent Application Laid-Open No. Hei 8-1411761, a gap material solvent in which a bead-shaped gap material is mixed in a solvent is applied to one surface of two plated steel sheets to be welded, and through this gap material solvent, A laser welding method is described in which, after two plated steel sheets are overlaid, the solvent is evaporated by natural drying or forced drying, and a minute gap is formed between the steel sheets by the remaining bead-like gap material. According to this method, by selecting an appropriate size of the bead-like gap material, a desired gap can be secured between the steel plates, which contributes to a stable improvement in welding quality.
[0004]
However, according to the laser welding method described in this publication, since a gap material solvent in which a bead-like gap material is mixed with a solvent is used, a drying process for evaporating the solvent is indispensable. There is a problem that it takes time and sacrifices productivity, and also increases the cost burden.
The present invention has been made in view of the above-mentioned problems, and the problem is that the fine solid particles in a dry state can be directly used as a gap material, and thus a special post-treatment such as a drying process is performed. An object of the present invention is to provide a laser welding method for a surface-treated steel sheet that is unnecessary and contributes to improvement of productivity and reduction of manufacturing cost.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a method in which fine solid particles are adhered to one of two surface-treated steel sheets to be welded, and then the other surface treatment is performed on the one surface-treated steel sheet via the fine solid particles. In the laser welding method of a surface-treated steel sheet in which the steel sheets are overlapped and then laser welded to the overlapped portion, the fine solid particles are supplied onto the one surface-treated steel sheet and irradiated with a laser beam, the fine solid the particles characterized by welded to the surface-treated steel sheet.
In the laser welding method of the surface-treated steel sheet thus performed, fine solid particles are attached to one surface-treated steel sheet in advance, so it is necessary to perform a special post-treatment such as drying after the two steel sheets are superposed. Disappear. Moreover, since the fine solid particles are welded using a laser beam, the fine solid particles can be easily and reliably adhered to the surface-treated steel sheet.
In the present invention, when the fine solid particles are attached to the surface-treated steel sheet, the fine solid particles are passed through the powder passage in the laser torch by using a laser torch having a powder passage around the optical path of the laser beam. It can be supplied smoothly.
In the present invention, two surface-treated steel sheets may be superposed via fine solid particles, and then an appropriate clamping force may be applied to the two surface-treated steel sheets. In this case, the fine solid particles The overlap between the two collapses to improve the degree of dispersion, and partly larger particles bite into the steel sheet, so that a desired gap can be accurately secured between the two steel sheets.
In the present invention, the type of fine solid particles is arbitrary, but it is desirable to use metal particles for shot peening because they are available at a relatively low cost. In this case, as the metal particles, it is desirable to select a material that is easily fused with the base material of the surface-treated steel sheet to be welded and that does not adversely affect the quality.
The present invention is not limited to the type of the surface-treated steel sheet, but when selecting a plated steel sheet having a plating layer containing a metal that evaporates at a relatively low temperature, the occurrence of blowholes can be suppressed. Especially useful.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
1-3 show the laser welding method according to the present invention step by step. This embodiment is intended to laser weld a plated steel sheet having a plating layer containing a metal that evaporates at a relatively low temperature, for example, a galvanized steel sheet, an aluminum plated steel sheet, a nickel-galvanized steel sheet, etc. 1 and 2 have shown the plated steel plate (surface-treated steel plate) which has the plating layers 1a and 2a on both surfaces.
[0007]
In laser welding, first, a laser torch 10 which will be described in detail later on one side of one plated steel sheet 1 of two plated steel sheets 1 and 2 to be welded along the weld line as shown in FIG. The fine solid particles 3 are welded using (FIG. 4). Here, steel beads for shot peening are used as the fine solid particles 3, and the size thereof is about 130 μm in average particle size.
[0008]
Next, as shown in FIG. 2, the other plated steel sheet 2 is superposed on one plated steel sheet 1 on which the fine solid particles 3 are welded, and both are clamped by the clamp units 4 and 4. At this time, since the fine solid particles 3 are welded on one plated steel plate 1, even if the plated steel plate 1 is handled appropriately or the other plated steel plate 2 is shockedly overlapped, The solid particles 3 do not move, and therefore no special attention is required for the superposition operation of the two plated steel plates 1 and 2. Further, by setting the clamping force by the clamping unit 4 to an appropriate magnitude, the overlap between the fine solid particles 3 is collapsed and the degree of dispersion is improved, and some of the larger grains 3 bite into the plated steel sheet 1 or 2. As a result, a desired gap δ corresponding to the average particle diameter of the fine solid particles 3 is ensured between the two plated steel plates 1 and 2.
[0009]
After completion of the above preparation, as shown in FIG. 3, the laser beam B is irradiated from a laser torch (not shown) to the overlapping portion of the two plated steel plates 1 and 2, and the laser torch is moved at a constant speed along the weld line. Move with. In this case, as a matter of course, the plated steel plates 1 and 2 may be moved while fixing the position of the laser torch. Then, the portion irradiated with the laser beam B is heated and melted, and a weld metal (weld bead) 5 is formed through a minute gap δ between the two plated steel plates 1 and 2. 2 and laser welded to each other. At this time, the components (zinc, aluminum, etc.) of the plated layers 1a, 1b of the plated steel sheets 1, 2 existing on the weld line are evaporated by the heat of the laser beam B. The gas generated by this evaporation is two sheets. Are discharged to the outside through the minute gap δ between the plated steel sheets 1 and 2, so that no blowhole is formed in the weld metal 5. In addition, since the fine solid particles 3 existing on the weld line are dissolved in the weld metal 5, the volume of the weld metal 5 is increased, and the shrinkage is reduced accordingly, and the risk of burn-off is reduced. Furthermore, since the steel beads are used here as the fine solid particles 3, they are easily fused with the base materials of the surface-treated steel plates 1 and 2 to be welded, and the quality is not adversely affected.
[0010]
Here, the laser torch 10 for welding the fine solid particles 3 to one plated steel sheet 1 has two powder passages 12 disposed around the optical path 11 of the laser beam B ′ as well shown in FIG. It has a heavy nozzle structure. This laser torch 10 is frequently used for overlaying (for cladding), for example, for overlaying a valve seat portion of a cylinder head, and here, the fine solid particles 3 are quantitatively supplied to the powder passage 12. Like that. In the present embodiment, the intensity of the laser beam B ′ emitted from the optical path 11 and the moving speed of the laser torch 10 are appropriately set, and the supply amount of the fine solid particles 3 supplied to the powder passage 12 is appropriately set. By setting, the fine solid particles 3 are dispersed and welded on the plated steel sheet 1. In this case, for example, as shown in FIG. 5, the shape (pattern) of the laser beam B ′ is set to an oval shape, and the laser torch 10 is moved so that the major axis D is orthogonal to the weld line. Along the width of the weld bead 5 (FIG. 3), the fine solid particles 3 can be dispersed and welded in a band shape with a width that is sufficiently wider.
[0011]
As a method of welding the fine solid particles 3 to the surface-treated steel sheet 1 by laser beam , fine solid particles are distributed in advance along the weld line on the upper surface of the surface-treated steel sheet 1 and are welded using a general-purpose laser torch. The method can be adopted .
Further, the kind of the fine solid particles 3 is also arbitrary, and other metal beads or non-metal (ceramic) beads can be used instead of the steel beads. However, when selecting the fine solid particles 3, it is necessary to select a material that is easy to fuse with the base material of the surface-treated steel sheet to be welded and that does not adversely affect quality.
Furthermore, this invention does not ask | require the kind of surface treatment steel plate to apply, In addition to the various plated steel plates 1 and 2 mentioned above, it is applicable also to the coating or coated steel plate which gave various coating or coating.
[0012]
【Example】
As the two plated steel plates 1 and 2 to be welded, an aluminum plated steel plate having a thickness of 0.8 mm is selected, and as the fine solid particles 3, steel beads having an average particle diameter of 130 μm (BPC080 manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.) are selected. 4), and laser overlaying with a YAG laser was performed using the laser torch 10 having the double nozzle structure shown in FIG. 4, and the fine solid particles 3 were welded to the surface of one plated steel sheet 1 in a band shape. In this laser overlay, as shown in FIG. 5, the laser beam B ′ is set in an ellipse shape having a major axis D = 6.5 mm and a minor axis d = 2 mm, laser intensity = 1.5 kW, torch feed rate = The conditions were 1 m / min, defocus amount = 10 mm, and supply amount of fine solid particles 3 = 0.5 g / sec. After welding, the surface state of the plated steel sheet 1 was observed microscopically.
And after welding the fine solid particle 3 to one plated steel plate 1 in this way, as shown in FIG. 2, the other plated steel plate 2 is overlapped with this, and both of them are applied with a pressing force of 490 Pa by the clamp units 4, 4. After that, laser welding was performed using a general-purpose laser torch under the conditions of laser intensity = 3 kW and torch feed speed = 5 m / min. After welding, the state of the welded portion was observed microscopically.
[0013]
FIG. 6 shows the surface state of the surface-treated steel sheet 1 after performing the above-described laser cladding. On the surface-treated steel sheet 1, fine solid particles 3 are welded in an appropriately dispersed state.
FIG. 7 shows the state of the welded part after laser welding, and welding defects such as blow holes are recognized inside the weld metal 5 formed between the two plated steel sheets 1 and 2. Moreover, the volume of the weld metal 5 is sufficient. Further, fine solid particles 3 are present in the form of particles as they are in the vicinity of the weld metal 5 between the two plated steel plates 1 and 2, and between the two plated steel plates 1 and 2 throughout the welding. It is clear that the minute gap was maintained.
[0014]
【The invention's effect】
As described above, according to laser welding of a surface-treated steel sheet according to the present invention, after supplying fine solid particles in a dry state to one surface-treated steel sheet and welding with a laser beam, the other surface Since the processed steel plates are overlapped and laser welding is performed, after the fine solid particles are deposited, a special post-treatment such as a drying step becomes unnecessary, and an improvement in productivity and a reduction in manufacturing cost can be achieved. Further, the fine solid particles can be easily and surely adhered to the surface-treated steel sheet using a laser beam.
[Brief description of the drawings]
FIG. 1 shows an initial process of a laser welding method according to the present invention, and is a schematic view showing an adhesion state of fine solid particles to one surface-treated steel sheet.
FIG. 2 is a schematic diagram showing an intermediate process of the laser welding method according to the present invention and showing a state of superposition of two surface-treated steel sheets.
FIG. 3 is a schematic diagram showing a final step of the laser welding method according to the present invention and showing a state of a welded portion after laser welding.
FIG. 4 is a schematic view showing a laser torch used in the initial step of the present invention and a state of laser cladding by the laser torch.
FIG. 5 is a schematic diagram showing an example of the shape of a laser beam set when performing laser cladding.
FIG. 6 is a photomicrograph showing the surface state of a surface-treated steel sheet on which fine solid particles are welded by laser overlaying.
FIG. 7 is a photomicrograph showing the state of the weld after laser welding.
[Explanation of symbols]
1, 2 Plated steel sheet (surface-treated steel sheet)
1a, 2a Plating layer 4 Clamp unit 5 Weld metal (weld bead)
10 Double-nozzle laser torch 11 Laser beam optical path 12 Powder path

Claims (5)

After attaching fine solid particles to one of the two surface-treated steel sheets to be welded, the other surface-treated steel sheet is superposed on the one surface-treated steel sheet via the fine solid particles, and then the superposition is performed. in the laser welding method of the surface treated steel sheet part to laser welding and that the laser beam is irradiated, welding the the fine solid particles to the surface treated steel sheet supplies the fine solid particles on the one surface treated on steel A laser welding method for a surface-treated steel sheet.   The method for laser welding a surface-treated steel sheet according to claim 1, wherein fine solid particles are supplied through a powder passage in the laser torch.   The method of laser welding a surface-treated steel sheet according to claim 1 or 2, wherein a clamping force is applied to the two surface-treated steel sheets after the two surface-treated steel sheets are superposed via fine solid particles.   The method of laser welding a surface-treated steel sheet according to any one of claims 1 to 3, wherein metal particles for shot peening are used as the fine solid particles.   The surface-treated steel sheet according to any one of claims 1 to 4, wherein the surface-treated steel sheet is a plated steel sheet.

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