JP2017209700A - Joining method of metal plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that a process of laser-welding-joining galvanized steel plate conventionally required laser exposure twice for securing stable weld quality by a method for laser-welding-joining by superposing two sheets of the galvanized steel plate and another steel plate in the present invention.SOLUTION: A stable welding quality can be secured by a single laser irradiation by irradiating a laser beam to a galvanized part of a galvanized steel plate by inclining the laser beam by 30 degrees or more in the inverse direction of the laser advancing direction.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for joining two thin plates by laser welding.

  In recent years, joining methods using laser welding have begun to be used in various industries. However, there are still many restrictions such as materials and bonding conditions to apply, and it is still insufficient to replace the conventional technology.

Japanese Patent Laying-Open No. 2015-66593 JP 2010-23047 A

In Patent Document 1, in order to secure the amount of molten metal, the metal head is raised by irradiating the laser head in an inclined state during the first irradiation, and two thin plates are joined by the second laser irradiation. ing.
In Patent Document 2, when two superposed thin plates such as galvanized steel plates are joined by laser welding, zinc vapor remains inside the welded portion as a gas during laser welding, which causes a reduction in welding quality. Laser irradiation is divided into two times. In the first time, a method is adopted in which the zinc vapor generated is removed by laser irradiation in a defocused state where the laser is out of focus, and the second plate is welded by penetrating to the lower plate. Although this method can reduce welding defects due to the generation of zinc vapor, it is necessary to irradiate the laser twice under different irradiation conditions.
Thus, in the conventional laser welding mentioned above, in order to ensure the stable welding quality, it is necessary to irradiate a laser twice, and work efficiency is bad.
The present invention provides a technique capable of ensuring stable welding quality by one laser irradiation regardless of the presence or absence of a gap between two thin plates.

  The metal plate joining method according to the present invention is a method in which the galvanized steel plates or the galvanized steel plates and steel plates other than the galvanized steel plate are overlapped, and the perpendicular direction of the overlapped portion of the galvanized portion is the laser traveling direction. Is characterized in that the galvanized portion is irradiated with a laser beam tilted by 30 degrees or more in the opposite direction and bonded.

  According to the method for joining metal plates of the present invention, welding quality is not deteriorated, and joining can be performed by one laser irradiation.

It is a detailed block diagram of the laser welding apparatus in Embodiment 1 of this invention. FIG. 3 is an enlarged side view at the time of laser irradiation according to the first embodiment of the present invention. It is a figure which shows the state of a molten pool when the inclination-angle of the laser beam by Embodiment 1 of this invention is 0 degree. It is a figure which shows the state of a molten pool when the angle of the laser beam by Embodiment 1 of this invention is inclined 30 degree | times or more. It is explanatory drawing which shows the operation | movement of the laser beam by Embodiment 2 of this invention.

Embodiment 1
Embodiments of the present invention will be described below. FIG. 1 shows a detailed configuration of a laser welding apparatus for laser welding and joining two thin plates according to Embodiment 1 of the present invention.
FIG. 2 is an enlarged side view showing details of laser light and two metal plates during welding of the laser welding apparatus shown in FIG. In each embodiment, the same reference numerals indicate the same or equivalent configurations.
In FIG. 1, reference numeral 1 denotes two metal plates as objects to be irradiated with laser light. In the present embodiment, for convenience of explanation, the number of metal plates 1 is two, but three or more metal plates may be overlapped. These metal plates are all 2 mm or less in thickness and are stacked without any gaps, and all metal plates use galvanized steel plates or metal plates with similar plating treatment on the surface. And

Reference numeral 2 denotes a laser oscillator, and the laser oscillator 2 is mainly composed of an excitation light source, a laser medium, and a resonator mirror. The laser light is repeatedly reflected inside the oscillator to amplify the laser light, and the laser light reaching a certain intensity is generated as an oscillator. Output to the outside.
3 is an optical fiber cable for transmitting laser light, 4 is a laser head, and a plurality of pieces are used to condense laser light having a single wavelength and no phase difference to a very small point to obtain high density energy. Built-in mirror. The laser head 4 irradiates the metal plate with high energy density laser light. The laser head 4 is separated from the metal plate 1 by a predetermined focal length and fixed to a robot arm or a frame. The laser light to be irradiated is not a YAG laser, but CW (Continuous Wave) fiber light that constantly irradiates laser light with a constant intensity is used, and the spot diameter of the laser light is preferably 0.5 mm or less. The optimum spot diameter is derived by adjusting the material used, thickness, and laser output.

  Reference numeral 5 denotes a side nozzle. During laser welding, a melted metal reacts with surrounding oxygen, and the welded portion is constantly blown with a shielding gas such as argon gas to shield it from the surrounding air in order to prevent oxidation. It is desirable to spray this shielding gas at a rate of 5 L / min or more.

Reference numeral 7 denotes a base, and the metal plate 1 is placed on the base 7 with the horizontal surface protruding, and the periphery of the metal plate 1 is firmly fixed by the fixing jig 6. The fixing jig 6 may be fixed by any method as long as it can be fixed, such as a clamp method or a bolt method. In the present embodiment, the fixing jig 6 will be described below as a clamping method.
Although not shown, the base 7 is connected to two orthogonal high-precision ball screws, and each of these high-precision ball screws is connected to a servo motor. As a result, the base 7 can be moved at a predetermined distance and speed designated in the horizontal XY direction by an external signal. At this time, since the metal plate 1 fixed by the fixing jig 6 is horizontally installed so that the position is not shifted, the distance between the laser beam and the metal plate is constant regardless of the position where the base 7 operates. It is necessary to become. However, when the size of the metal plate 1 is large, it is not possible to correct the deflection, deformation, etc. of the central portion of the metal plate 1 that is not clamped by simply clamping the periphery of the metal plate 1. There is a concern that the distance between 1 and the laser head 4 may change. Therefore, in preparation for the case where the shape cannot be corrected only by fixing the surrounding clamp of the metal plate 1, a displacement sensor 10 for measuring the distance from the metal plate 1 is attached to the tip of the laser head. May be measured, and the height position of the base 7 may be corrected according to the measured distance.

Next, the operation will be described. The metal plate 1 fixed on the base 7 is irradiated with laser light, but the laser head 4 is tilted 30 degrees or more from the vertical direction.
As a result, the laser light emitted from the laser head 4 is also applied to the metal plate 1 at an angle of 30 degrees or more. At this time, the operation relationship between the laser beam irradiated at an angle and the metal plate 1 is such that the metal plate 1 is in the direction of the arrow in the direction of travel of the metal plate as shown in FIG. 7 is assumed to move in a straight line at a constant speed except during acceleration / deceleration by the operation of the drive mechanism connected to 7.

The focus of the irradiated laser beam is generally adjusted to the upper surface of the metal plate 1, but since the focus of the laser beam has the highest energy, the present invention aims to vaporize the galvanization into steam in the shortest time. ing. Therefore, as shown in FIG. 2, the laser beam is focused on the mating surface between the two stacked metal plates, that is, the intermediate galvanized layer 9 portion.
In addition, the spot diameter of the laser beam greatly affects the fact that zinc plating becomes zinc vapor. If the spot diameter of the laser beam is large with the same output, the area of the laser beam irradiated onto the metal plate 1 increases, and the amount of zinc vapor to be vaporized also increases. Conversely, the smaller the spot diameter of the laser beam with the same output, the smaller the area of the laser beam irradiated onto the metal plate 1, so that the zinc plating becomes zinc vapor in a shorter time than when the spot diameter is large, And the amount of zinc vapor generated is also reduced. As a result, the amount of zinc vapor that causes welding failure is reduced, so the spot diameter should be smaller.

  By focusing the laser beam on the intermediate galvanized layer 9 between the metal plates thus superposed and reducing the spot diameter, the energy of the laser beam is applied to the galvanized portion where the laser energy is to be applied most effectively. Can be given. However, since the focal point of the laser beam enters a deep position, more laser beam energy enters the lower metal plate 1b of the two stacked metal plates 1 as well. There is no problem if this method is used when two metal plates 1 are to be welded through, but the surface of the metal plate 1 opposite to the laser beam irradiation side, that is, two stacked metals When it is not desired to affect the lower surface of the metal plate 1b on the lower side of the plate 1 by thermal distortion due to the laser, through welding is not performed, and the thickness on the lower side of the two stacked metal plates is ½ or less. It is necessary to suppress the penetration depth by laser light to the extent. This can be dealt with by adjusting the output of the laser beam, the welding speed, and the spot diameter as necessary.

  In general, when two galvanized steel sheets are overlapped without gap and laser welding is performed, the intermediate galvanized layer 9 of the overlapped part is instantly evaporated by receiving the energy of the laser beam, and it is a keyhole or melted. Try to go outside through the pond. However, as shown in FIG. 3, the laser beam is irradiated perpendicularly to the metal plate 1, and the laser beam or the metal plate 1 moves horizontally with the metal plate 1. As a result, a molten pool corresponding to the energy of the laser beam is formed on the rear side of the laser beam irradiated to the intermediate galvanized layer 9, and the molten pool is sequentially solidified in a very short time as the laser beam moves. Form. In this case, the generated molten pool is small, and all zinc vapor is covered with an iron member having a melting temperature higher than that of the surrounding galvanizing. It is known that it causes damage to the lens of the laser light irradiation part, or zinc vapor cannot be released from the molten pool, and remains as a pinhole in the molten part, resulting in poor welding.

In the present embodiment, two galvanized steel sheets are overlapped with no gap, and the laser head 4 is tilted 30 degrees or more in the direction opposite to the traveling direction to perform welding. By doing so, the energy of the laser beam incident on the metal plate 1 is lowered, so there is a demerit that the output of the laser beam needs to be larger than that during vertical irradiation, but the laser beam is tilted more than that. By irradiating, the galvanization of the surface of the metal plate can be converted into zinc vapor faster than the conventional vertical irradiation, and the cross-sectional area where the laser beam is in contact with the metal plate 1 or the intermediate galvanized layer 9 increases. The elliptical molten pool can be created by relatively increasing the distance from the front end to the rear end of the generated molten pool. Even if the zinc of the intermediate galvanized layer 9 becomes zinc vapor due to the energy of the laser beam, the molten pool by the inclined laser beam is larger than that at the time of vertical irradiation. Thus, there is an advantage that zinc vapor can be easily released to the outside, and generation of zinc vapor as spatter can be suppressed. Even if zinc vapor spattering occurs during laser welding, the laser head 4 is mounted at an angle, so that the laser beam irradiation lens is less likely to be sputtered and the lens replacement frequency is reduced. I can do it. In addition, since the weld pool of the metal plate 1a on the upper side of the metal plate 1 is longer in the laser beam direction, the weld bead has a molten metal than in the past even if some zinc vapor is generated as spatter. It is possible to fill. Thereby, two or more steel plates can be joined without providing a gap between the steel plates.
The tilt angle of the laser is 30 degrees or more in the present embodiment. However, as described above, by irradiating the laser beam with tilting, the zinc plating on the surface of the metal plate can be performed faster than the conventional vertical irradiation. If it can be made into steam and the distance from the front end to the rear end of the generated molten pool can be made relatively large to create an elliptical molten pool, it can be repeated 30 degrees or more.

Embodiment 2
In the first embodiment, the metal plate 1 is a galvanized or similar plated metal plate. However, in the present embodiment, the metal plate 1b below the stacked metal plates 1 is used. Uses general steel other than galvanized steel sheet and stainless steel sheet. In this case, since the galvanizing amount between the metal plates is halved, the zinc vapor generated from the intermediate galvanized layer 9 during laser welding is also halved, and the conditions for joining the two metal plates are easier than in the first embodiment. It becomes.
In the first embodiment, the laser head 4 is fixed to the upper part of the metal plate 1 and the base 7 to which the metal plate 1 is attached is driven. However, the base 7 is fixed so as not to operate. The laser head 4 may be attached to a robot arm or an XY direct robot, and the laser head side may be configured to be freely operable by an external signal.

  Further, when the laser head 4 or the base 7 is operated at the time of performing the welding by the CW fiber light, the operation of the metal plate 1 and the laser light as well as the linear operation as described in the first embodiment is not limited to FIG. ) Or a method of moving in a zigzag manner as shown in FIG. 5B, or back and forth as shown in FIG. 5C. You may perform suitably the operation | movement which advances ahead, repeating the operation | movement (operation | movement from 101 to 104). These trajectories are different from the linear trajectories, and a part once melted once is melted again. Therefore, it is also possible to reduce the laser beam irradiation energy, or to improve the welding speed and to reduce the energy of the laser beam to be input to the metal plate 1. And since a molten pool will also be formed partially for a longer time, the improvement of welding quality is anticipated.

Embodiment 3 FIG.
A YAG laser is used as a laser beam oscillator used for joining two metal plates. Two or more galvanized steel plates, stainless steel, or the like may be used as the type of metal plate used in the present embodiment, and these metal plates all have a thickness of 2 mm or less and are stacked with no gap. As in the first embodiment, the focus of the YAG laser applied to these metal plates 1 is adjusted to the intermediate galvanized layer 9 between the two superposed metal plates. Similarly to the above, the laser head is tilted by 30 degrees or more, and YAG laser light is irradiated onto the metal plate at the same angle. In order to prevent oxidation of the welded part, a shielding gas such as argon gas is blown during YAG laser irradiation. Since the YAG laser beam is irradiated with pulses, the shield gas is also pulsed in the same way.

  Upon irradiation of the YAG laser beam is good either for either operate or base 7 to operate the laser head 4 can be determined in convenience for the appropriate user, the number is irradiated with YAG laser light to the metal plate ten Even for a short time of ms, the laser head 4 or the base 7 must be operated in the same manner as in the first embodiment without stopping. By doing in this way, similarly to the time of CW fiber light irradiation, a large elliptical molten pool having a long melting region in the irradiation direction is formed in the intermediate galvanized layer 9. Zinc plating on the surface of the metal plate also immediately becomes zinc vapor due to the energy of the YAG laser light, and zinc vapor can be released from the molten pool to the outside. By increasing the irradiation time, the formation of the molten pool can be maintained for a long time, and a large amount of zinc vapor can be expected to be released to the outside.

  The spot diameter is 1.0 mm or less, and the smaller the spot diameter, the smaller the amount of zinc vapor generated. Further, the YAG laser is irradiated at the position where the laser beam is irradiated for the second time at a position advanced about half of the elliptical weld bead formed by the first laser beam irradiation. Because of the pulse oscillation, the energy input to the total metal plate can be reduced by widening the pitch for irradiating YAG laser light compared to welding with CW fiber light.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

  1 metal plate, 2 laser oscillator, 3 fiber cable, 4 laser head, 5 side nozzle, 6 fixture, 7 base, 8 galvanized layer, 9 intermediate galvanized layer, 10 displacement sensor

Claims (3)

  Laser light tilted by 30 degrees or more in the direction opposite to the laser traveling direction with respect to the perpendicular line of the galvanized part of the galvanized steel sheet, or the galvanized steel sheet and other steel sheets other than the galvanized steel sheet. A method for joining metal plates, wherein the galvanized portion is irradiated and joined.   The metal plate joining method according to claim 1, wherein the laser light is CW fiber light or YAG laser light. The metal plate joining method according to claim 1, wherein there is no gap between the two steel plates that are overlapped.

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