JP5292921B2 - Laser welding method and laser welding apparatus - Google Patents

Description

  The present invention relates to a laser welding method and a laser welding apparatus.

  Conventionally, thin-walled galvanized steel sheets have been used as rust-proof steel sheets for automobiles. When a plurality of such thin steel plates are overlapped and laser-welded, a large number of small holes called porosity are generated in the weld metal due to the generated zinc vapor. It is known that the strength of the welded portion decreases due to the porosity. For this reason, the countermeasure of the porosity as shown, for example in the following patent document 1 is taken.

That is, the elimination of zinc vapor that causes porosity. For example, in order not to leave zinc vapor generated from the galvanized layer between stacked steel plates, a gap is created by interposing fine solid particles between the steel materials to prevent zinc vapor from escaping between steel plates and prevent porosity from being generated. doing.
JP 2003-290955 A

  However, the zinc vapor cannot be released smoothly only by the gap formed by interposing the fine solid particles between the stacked steel plates, and the generation of porosity cannot be reliably prevented.

  Therefore, the present invention has been made to solve such a conventional problem, and in order to reduce the gas generated from the coating layer formed on the surface of the plate material, the coating is performed in advance before laser welding. An object of the present invention is to provide a laser welding method and a laser welding apparatus capable of excluding and extruding a substance forming a coating layer from a portion to be welded by heating and melting the layer and pressing the plate material.

The present invention for achieving the above object is a laser welding method in which at least two plate materials including a plate material having a coating layer formed on the surface thereof are overlapped with each other, irradiated with a laser beam to a welded portion to be welded, and welded. In addition, prior to welding, the plate material is heated to continuously melt the coating layer between the plate materials, and the material that forms the molten coating layer by pressing the plate material while the coating layer is melted A laser welding method comprising: a pressurizing step of extruding a weld from a welded portion; and a welding step of performing continuous welding by continuously irradiating the welded portion with laser light after the pressurization.

In order to achieve the above object, the present invention is a laser welding apparatus in which at least two plate materials including a plate material having a coating layer formed on the surface thereof are overlapped with each other, and a welding portion to be welded is irradiated with a laser beam to perform welding. Prior to welding, the heating means for heating the plate material and continuously melting the coating layer between the plate materials, and the material forming the molten coating layer by pressing the plate material while the coating layer is molten and pressure means to push the weld is a laser welding apparatus characterized by comprising: a welding means for continuously welding by continuously irradiating a laser beam to the weld.

  According to the present invention, the material that forms the coating layer in advance is welded from the welded portion before welding by superimposing the plate materials with the coating layer formed on the surface, melting the coating layers between the plate materials, and pressurizing the plate material. Eliminate outside. As a result, the gas generated from the coating layer by welding can be suppressed in the portion where welding is performed. For this reason, the fall of the welding strength by the porosity resulting from gas can be suppressed, the welding length which can ensure intensity | strength can be improved, and reduction of a correction man-hour can also be aimed at.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments to which the invention is applied will be described with reference to the accompanying drawings.

[First Embodiment]
FIG. 1A is a schematic view showing a laser welding state of the galvanized steel sheet according to the first embodiment. 1B is a schematic view seen from the direction of arrow A in FIG. 1A.

  In the welding method of the present embodiment, as shown in FIG. 1A, two superposed galvanized steel plates 1 and 2 are heated by heating means 3, pressurized by pressurizing means 4, and laser is welded by welding means 5. Light 6 is irradiated and welding is performed. The galvanized steel sheets 1 and 2 are subjected to a series of heating, pressing and welding along the welding direction of the welding means 5.

  In addition, as a board | plate material in which the coating layer was formed in the surface, although a coating layer shows the galvanized steel plate which is a galvanized layer, it is not limited to this.

(Galvanized steel sheet)
The galvanized steel plates 1 and 2 constitute, for example, the body of an automobile, and a galvanized layer is surface-treated on the steel plate for rust prevention. The main material of the steel plate portion is, for example, iron. When superposed, they are held by a tool (not shown) such as a clamp member. The thicknesses t1 and t2 of the galvanized steel plates 1 and 2 are preferably about 1 mm. In the illustration, since the same steel plate is used, the galvanized layer is provided on the overlapping surface of both the galvanized steel plates 1 and 2, but one side is not a galvanized steel plate, but a galvanized steel plate. But you can. There is no need to create a gap between the galvanized steel plates 1 and 2 by embossing or the like, and the galvanized steel plates 1 and 2 can be formed with a single punching die. Therefore, the gap between the galvanized steel plates 1 and 2 may be 0 mm.

(Heating stage)
FIG. 2A is a schematic view showing a heating state of the galvanized steel sheet according to the present embodiment, and FIG. 2B is a schematic cross-sectional view taken along the line BB of FIG. 2A.

  As shown in FIG. 2A, the heating means 3 is moved along the welding line 9 to heat the welded portion 15 of the galvanized steel plates 1 and 2 so that the two galvanized steel plates 1 and 2 overlap each other. The zinc plating layer 1 is melted to form a zinc liquefied part. The heating means 3 is preferably a plasma irradiation apparatus that irradiates plasma, for example. The plasma irradiation apparatus can easily adjust the temperature for heating the plate material depending on the amount and type of plasma to be generated.

  In the formation of the zinc liquefied part, the galvanized steel sheets 1 and 2 are heated by the heating means 3 in a temperature range from the temperature at which the zinc 11 and 12 of the galvanized layer melt to the temperature at which the steel sheets 13 and 14 do not melt. For example, when the steel plates 13 and 14 are iron, since the melting point of iron is 1535 ° C., the heating means 3 needs to apply heat at a temperature lower than 1535 ° C. to the galvanized steel plates 1 and 2. When the galvanized steel plates 1 and 2 are GI materials (hot dip galvanized steel plates), the coating layer melts in the temperature range of 420 ° C. to 900 ° C., and when GA materials (alloyed hot dip galvanized steel plates) are 665 ° C. to 900 ° C. It becomes a state.

  The width of the zinc liquefied portion formed by heating is optimally set to be equal to or larger than the width of the region to be pressurized in order to remove zinc from the welded portion 15 in the pressurizing step performed after the heating step. The specific width of the zinc liquefied portion is optimally widened from 0.6 to 1.4 mm in addition to the width of the welded portion 15 where welding by laser light irradiation is performed. By expanding to that range, it is possible to sufficiently suppress zinc vapor generated not only in the welded portion 15 but also around the welded portion 15 by welding by laser light irradiation, and to prevent generation of porosity.

  FIG. 3A is a schematic view showing a heating state of the surface of the galvanized steel sheet according to the present embodiment, and FIG. 3B is a schematic cross-sectional view taken along line BB of FIG. 3A.

  The galvanized layer between the two galvanized steel sheets 1 and 2 superposed by heating can be melted, but at the same time, impurities 16 on the heated surface are removed along the weld line 9 as shown in FIG. 3A. You can also The impurities 16 are, for example, press oil and iron scraps remaining in other processing steps. By removing the impurities 16 from the surface to be laser welded, more stable laser welding can be performed.

(Pressurization stage)
FIG. 4A is a schematic view showing a pressurized state of the galvanized steel sheet according to the present embodiment, and FIG. 4B is a schematic cross-sectional view taken along the line BB of FIG. 4A.

  As shown in FIG. 4A, the pressurizing means 4 is moved along the weld line 9 while being pressed against the galvanized steel plates 1 and 2, and the galvanized steel plates 1 and 2 are pressed between the galvanized steel plates 1 and 2. The zinc melted in the heating step is removed from the welded portion 15. The pressurizing step is performed in a state where zinc of the galvanized layer melted in the heating step is melted. The pressurizing unit 4 is, for example, a pin-shaped tool (pressing pin) or a roller-shaped tool (pressing roller) that is pressed along a pressurizing line such as a hydraulic unit or a spring unit. The pressure pin and the pressure roller need to have a strength that is harder than that of the plate material, and the contact portion has the same width as the welded portion 15. The pressure pin is preferably made of ceramic. By using the ceramic pressure pin, it is possible to prevent the pressure pin from being melted by the heat of the heated plate material.

When a cylindrical ceramic pressure pin having a diameter of 8 mm is used by superimposing both 0.8 mm thick galvanized steel sheets, the pressure applied to the galvanized steel sheet is about 0.15-3. 2 kg / mm ² .

  In order to suppress the generation of zinc vapor due to heating by laser light irradiation in the welding process performed after the pressurizing process, it is desirable that the zinc removal range has a range equal to or greater than the portion to be welded. The width of the specific zinc removal range is the same as the width of the zinc liquefied portion, the width of the welded portion where welding by laser light irradiation is performed and the width further expanded from 0.6 to 1.4 mm. Is the best.

  FIG. 5A is a schematic view showing a pressurized state of the surface of the galvanized steel sheet according to the present embodiment, and FIG. 5B is a schematic cross-sectional view taken along the line BB of FIG. 5A.

  The molten galvanized layer between the two galvanized steel sheets 1 and 2 stacked by pressing can be pushed out, but at the same time, as shown in FIG. The impurities 16 can be mechanically removed along the weld line 9 and more stable laser welding can be performed.

  FIG. 6A is a schematic diagram illustrating a state of a mating surface of the galvanized steel sheet after the pressing step according to the present embodiment, and FIG. 6B is a schematic cross-sectional view taken along line BB in FIG. 6A.

  The zinc pushed out of the welded portion 15 by the pressure pin changes from the molten state to the solid state again at the brazing portion 18 between the galvanized steel sheets. Solidified zinc surrounds the laser junction and exists between the plates. Similarly to the galvanized layer for surface treatment of the steel sheet, the solidified zinc of the brazing portion 18 has a function of preventing rust.

  Therefore, since zinc plays a role of brazing when liquefied and solidified by preheating, the welding strength is improved. Furthermore, since zinc surrounds the laser joint and the water-tightness of the laser welded portion is improved, the rust prevention effect of the galvanized steel sheet is further improved.

(Welding stage)
FIG. 7A is a schematic view showing a welded state of the galvanized steel sheet according to the present embodiment, and FIG. 7B is a schematic cross-sectional view taken along line BB of FIG. 7A.

As shown in FIG. 7A, the galvanized steel sheets 1 and 2 are welded and welded to the galvanized steel sheets 1 and 2 by heat applied by the irradiation of the laser beam 6. Heating by irradiation with the laser beam 6 is performed following the same locus as the heating means and the pressure pin. A laser beam (not shown) output from a laser beam generator (not shown) is adjusted by the optical system means 5 so as to be focused on the surfaces of the galvanized steel sheets 1 and 2, irradiated with a laser beam 21, and galvanized. The welds of the steel plates 1 and 2 are welded. As the laser beam 6, for example, a CO ₂ laser or a YAG laser can be used. The galvanized steel sheets 1 and 2 can be continuously welded 8 by moving the optical system means 5 along the weld line. Since zinc is removed from the welded portion, porosity is unlikely to occur at the portion where continuous welding 8 is applied.

  Finally, in this embodiment, as shown in FIG. 1A, a plasma irradiation device 3 as a heating means, a pressure pin 4 as a pressure means, and a laser as a welding means are applied to the galvanized steel sheets 1 and 2. The irradiation device (laser head) 5 is attached to and integrated with a robot arm or the like, and continuously performs a series of steps (heating, pressing, welding), but the present invention is not limited thereto. Each process can be performed while relatively moving each means and the galvanized steel sheet. Moreover, although it processes, moving a heating means, a pressurization means, and a welding means with respect to a galvanized steel plate, it can also process by moving a galvanized steel plate itself.

  By a series of these processes (heating, pressurization, welding), the zinc of the welded portion 15 is pushed out and solidifies in situ, so that no zinc remains at the site where the welding is performed. For this reason, it is possible to suppress a decrease in welding strength due to porosity, to improve the weld length capable of ensuring the strength, and to reduce the number of correction steps.

  In addition, in welding of steel sheets having galvanized layers, welding can be performed even when the gap between the steel sheets is 0 mm, so that a positive mark for welding for adjusting the pressure to hold the galvanized steel sheet and providing a gap between the steel sheets All the troublesome fine adjustments such as setting of the embossed portion and the like are unnecessary.

  Since the strength guarantee rate is remarkably improved, the welding length can be shortened here compared to the conventional case where welding is performed with a larger safety factor. Thereby, welding time can also be shortened.

[Second Embodiment]
In the first embodiment, the plasma is output from the plasma irradiation device, and the galvanized layer between the galvanized steel sheets is melted by irradiation and irradiation along the welding line. The galvanized layer may be melted by moving along the weld line. As the heating device, it is preferable to use, for example, an infrared irradiation device or a laser beam irradiation device having a weak output.

  FIG. 8A is a schematic view showing the heating state of the galvanized steel sheet according to the present embodiment, and FIG. 8B is a schematic view seen from the direction of arrow A in FIG. 8A. The laser beam 20 for heating is irradiated along the weld line in an output state lower than the output of the laser beam 21 for welding or in a state where the welding position is not focused. Heating by the laser beam 20 for heating is performed at 419.5 ° C. or higher at which zinc is melted and 1535 ° C. or lower at which the steel plate itself of the galvanized steel plate is not melted. The width for melting the galvanized layer is the same as that of the first embodiment.

  The laser irradiation device 66 has a laser processing head (twin spot) that irradiates the divided laser light to different positions. Using a laser beam generator (not shown) having the same laser light source and light source for welding and newly providing a laser processing head 66 makes it possible to carry out the heating process and the welding process, which is advantageous in terms of cost. When dividing the laser beam, the heating laser beam 20 must satisfy the above temperature range of 419.5 ° C. to 900 ° C., and the melting region must also fill the region within 1.4 mm from the weld. The laser beam 21 for use is focused on the galvanized steel plates 1 and 2 and the temperature for melting the steel plates must be 1535 ° C. or higher.

  The laser irradiation device 66 outputs a laser beam 20 for heating, which is one of the laser beams divided forward in the welding direction, to perform heating, and the galvanized layer between the galvanized steel sheets 1 and 2 is melted. . The laser irradiation device 66 and the pressure pin 4 are preferably moved simultaneously in order to remove zinc from the welded portion while the zinc is melted. The laser welding device 66 and the pressure pin 4 are integrated. It may be converted. Pressurization is performed on the galvanized steel sheets 1 and 2 with the pressurizing pin 4 to push out the molten galvanized layer. A laser beam 21 for welding, which is the other of the laser beams divided from the laser irradiation device 66, is output along the locus of heating and pressurization, and the galvanized steel sheets 1 and 2 are welded while being melted.

  By excluding zinc from the portion to be welded, the amount of zinc vapor generated when laser irradiation is performed and welding is also reduced. By suppressing the generation of zinc vapor, the generation of porosity is also reduced, and the effect of improving welding strength and welding quality can be obtained.

[Third Embodiment]
In the present embodiment, heat is applied to a galvanized steel sheet using a high-frequency induction superheater, and the galvanized layer between the galvanized steel sheets is welded by heating the welded portion once.

  FIG. 9 is a schematic view showing a heating state of the galvanized steel sheet according to the present embodiment.

  In the heating of the galvanized steel sheet of this embodiment, the zinc liquefied part around the weld line 9 of the two galvanized steel sheets 1 and 2 is heated by a high frequency induction heating device 30 as shown in FIG. The high-frequency induction heating device 30 includes, for example, a high-frequency induction heating coil in the clamp member, and four high-frequency induction heating devices 30 are installed so as to surround the entire zinc liquefaction unit 15.

  The state of the zinc liquefaction part by the high frequency induction heating device 30 is 419.5 ° C. or higher at which zinc melts and 1535 ° C. or lower at which the steel plate itself of the galvanized steel plate does not melt. While the galvanized layer is melted in the zinc liquefaction part, the same pressurizing process and welding process as those in the first embodiment are performed.

  By excluding zinc from the portion to be welded, the amount of zinc vapor generated when laser irradiation is performed and welding is also reduced. By suppressing the generation of zinc vapor, the generation of porosity is also reduced, and the effect of improving welding strength and welding quality can be obtained.

[Fourth Embodiment]
In the first embodiment, the pressurizing pin is pressed along the welding line and moved while being pressed, but in this embodiment, the galvanized steel sheet is clamped by the clamp member and melted in the heating process from the welded portion by the pressure. In this configuration, the removed zinc is removed.

  FIG. 10 is a schematic view showing a pressurized state of the galvanized steel sheet according to the present embodiment.

  The pressurization to the galvanized steel sheet of this embodiment is performed by installing the clamp member 40 and clamping the galvanized steel sheets 1 and 2 as shown in FIG. When the galvanized steel sheet is pressurized by the clamp member 40, the molten zinc from the welded portion can be pushed out. It is desirable to install the clamp members 40 on both sides of the galvanized steel sheet with the weld line 9 extended. The clamp member 40 may be installed in advance from the stage of overlapping the galvanized steel plates 1 and 2 before the heating step, and the galvanized steel plates 1 and 2 may be sandwiched and pressurized. When heating is performed along the welding line 9 while the galvanized steel sheets 1 and 2 are being pressed by the clamp member 40, the molten zinc is pushed out from the welded portion with the movement of the heating device.

  By excluding zinc from the portion to be welded, the amount of zinc vapor generated when laser irradiation is performed and welding is also reduced. By suppressing the generation of zinc vapor, the generation of porosity is also reduced, and the effect of improving welding strength and welding quality can be obtained.

A is the schematic which shows the laser welding state of the galvanized steel plate by 1st Embodiment, B is the schematic seen from the arrow A direction of FIG. 1A. A is the schematic which shows the heating state of the galvanized steel plate by 1st Embodiment, B is a schematic sectional drawing which follows the BB line of FIG. 2A. A is the schematic which shows the heating state of the surface of the galvanized steel plate by 1st Embodiment, B is a schematic sectional drawing which follows the BB line of FIG. 3A. A is the schematic which shows the pressurization state of the galvanized steel plate by 1st Embodiment, B is a schematic sectional drawing which follows the BB line of FIG. 4A. A is the schematic which shows the pressurization state of the surface of the galvanized steel plate by 1st Embodiment, B is a schematic sectional drawing which follows the BB line of FIG. 5A. A is the schematic which shows the state of the mating surface of the galvanized steel plate after the pressurization process by 1st Embodiment, B is a schematic sectional drawing which follows the BB line of FIG. 6A. A is the schematic which shows the welding state of the galvanized steel plate by 1st Embodiment, B is a schematic sectional drawing which follows the BB line of FIG. 7A. A is the schematic which shows the heating state of the galvanized steel plate by 2nd Embodiment, B is the schematic seen from the arrow A direction of FIG. 8A. It is the schematic which shows the heating state of the galvanized steel plate by 3rd Embodiment. It is the schematic which shows the pressurization state of the galvanized steel plate by 4th Embodiment.

Explanation of symbols

1, 2, galvanized steel sheet,
3 heating means,
4 Pressurizing means,
5 welding means,
6 Laser light,
8 Continuous welding,
9 Welding line,
10 spraying device,
11, 12 Zinc,
13, 14 Iron 15 weld,
16 impurities,
18 Brazing part,
20 Laser light for heating,
21 Laser beam for welding,
30 Clamp member with high frequency induction superheater,
40 Clamp member.

Claims (18)

A laser welding method in which at least two plate materials including a plate material having a coating layer formed on a surface thereof are overlapped with each other, laser light is irradiated to a welded portion to be welded, and welding is performed.
Prior to the welding, heating the plate material, heating the coating layer between the plate material continuously ,
In the state where the coating layer is melted, pressurize the plate material, and pressurize the material forming the molten coating layer from the weld,
This After pressurization, the welding step of continuously welding by continuously irradiating a laser beam to the weld zone,
A laser welding method comprising:   The laser welding method according to claim 1, wherein the heating step heats the weld.   The laser welding method according to claim 2, wherein the pressurizing step pressurizes the weld.   The laser welding method according to any one of claims 1 to 3, wherein the plate material is a galvanized steel sheet including a galvanized layer as the coating layer.   5. The laser welding method according to claim 1, wherein in the heating step, the plate material is irradiated with plasma to heat.   5. The laser welding method according to claim 1, wherein in the heating step, the plate material is irradiated with a laser beam for heating.   2. The pressurizing step includes pressing a pressing pin having a strength harder than that of the plate material and a contact portion having a width comparable to that of the welded portion against the plate material. 7. The laser welding method according to any one of items 6.   The laser welding method according to any one of claims 1 to 6, wherein, in the pressing step, the plate members are sandwiched and pressed by a clamp member.   9. The laser welding method according to claim 8, wherein the overlapped plate members are held by the clamp member prior to heating. A laser welding apparatus that superimposes at least two plate materials including a plate material having a coating layer formed on a surface thereof, irradiates a welding portion to be welded with a laser beam, and performs welding.
Prior to the welding, heating means for heating the plate material and continuously melting the coating layer between the plate materials;
In the state where the coating layer is melted, pressurizing the plate material, and pressurizing means for extruding the material forming the molten coating layer from the weld,
And welding means for continuously welding by continuously irradiating a laser beam to the weld zone,
A laser welding apparatus comprising:   The laser welding apparatus according to claim 10, wherein the heating unit heats the welded portion.   The laser welding apparatus according to claim 11, wherein the pressurizing unit pressurizes the weld.   The laser welding apparatus according to any one of claims 10 to 12, wherein the plate material is a galvanized steel sheet including a galvanized layer as the coating layer.   The laser welding apparatus according to any one of claims 10 to 13, wherein the heating means is a plasma irradiation apparatus that irradiates the plate material with plasma.   14. The laser welding apparatus according to claim 10, wherein the heating unit is a welding unit that irradiates the plate material with a laser beam.   The laser welding apparatus according to any one of claims 10 to 15, wherein the pressurizing unit is a pressurizing pin that presses against the plate material.   The laser welding apparatus according to any one of claims 10 to 15, wherein the pressurizing unit is a clamp member that sandwiches and pressurizes the plate members.   The laser welding apparatus according to claim 17, wherein the superposed plate members are held by the clamp member prior to heating.

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