Laser welding method

Abstract

To provide a laser welding method that enlarges a weld diameter without occurrence of blow holes and so on, and can increase weld strength.SOLUTION: A laser welding method overlaps a plurality of metal plates 4, 5, irradiates the metal plates 4, 5 with laser beam LB, and forms a spot weld zone 6. A locus 13 of the leser beam LB is formed by combination of scan movement moving in a scanning direction along a larger diameter circle 11 and oscillation that so oscillates as to draw a small diameter circle 12 having a diameter smaller than the large diameter circle 11.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a laser welding method.

Background Art

[0002] There is known a laser welding method in which two metal plates are overlapped, a laser beam is irradiated onto the surface of the metal plates, and the portion of the metal plates irradiated with the laser beam is melted and joined (spot welding) (see Patent Document 1). The laser irradiation portion (focus) is narrowed in order to concentrate energy. Therefore, in order to widen the melted portion of the metal plates, it is already known as remote laser welding to move the laser irradiation portion so as to draw a predetermined shape (for example, circular) in a short time.

[0003] Patent Document 1 describes a laser welding method in which a laser beam is scanned so as to circulate around the center portion of the melted portion, and then the laser beam is scanned while sequentially setting the welding radius smaller in a concentric circle shape with the scanning locus.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Using the technique described in Patent Document 1, by scanning the laser beam so as to multiply circulate around the center portion of the melted portion and increasing the outer diameter of the spot weld portion, the welding strength increases. However, since the laser beam is irradiated onto the surface of the metal plates many times, particularly the temperature of the center portion of the melted portion rises. Further, if the material to be welded is a plated material, blow holes are generated due to vaporization of the plated metal, and the generation of the blow holes may cause a decrease in the welding strength. Therefore, in the above-described technique, there is a limit to the expansion of the welding diameter.

[0006] Therefore, the present invention aims to provide a laser welding method that can increase welding strength by expanding the welding diameter without generating blowholes or the like. [Means for solving the problem]

[0007] A laser welding method according to one aspect of the present invention is a laser welding method in which multiple metal plates are stacked and laser light is irradiated onto the metal plates to form a spot weld, wherein the trajectory of the laser light is formed by a combination of scanning movement, which moves in a scanning direction along a large diameter circle, and oscillating movement, which swings to trace a small diameter circle with a smaller diameter than the large diameter circle. [Effects of the Invention]

[0008] According to one aspect of the present invention, a laser welding method can be used to increase the welding diameter and thus the welding strength without generating blowholes or the like. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of a laser welding apparatus according to one embodiment. [Figure 2] This figure shows the wobble shape produced by a galvanometer scanner head in a laser welding method according to one embodiment. [Figure 3] This figure shows the trajectory of the laser beam irradiated in a laser welding method according to one embodiment. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below with reference to the drawings.

[0011] [Welding equipment] Figure 1 is a schematic diagram showing an example of a laser welding apparatus 1 according to this embodiment.

[0012] The laser welding apparatus 1 according to this embodiment is a general-purpose welding apparatus that uses semiconductor laser oscillation, commonly referred to as a disk laser welding machine. This laser welding apparatus 1 includes a galvanometer scanner head 2 that causes the laser beam LB for welding to move in a circular motion, and a controller 3 which serves as a control unit for controlling the galvanometer scanner head 2. In the laser welding apparatus 1, it is possible to irradiate the surface of metal plates 4 and 5 with the laser beam LB while it is spirally rotated according to a program set in advance in the controller 3.

[0013] The metal plates 4 and 5 used as weld materials are, for example, galvanized steel plates made by applying zinc plating to high-tensile steel plates. Multiple metal plates 4 and 5 are overlapped. The thickness of metal plate 4 on the upper side of the weld is, for example, 1.2 mm, and the thickness of metal plate 5 on the lower side of the weld is, for example, 2.0 mm. The welding quality is affected by the thickness of both metal plates 4 and 5, but the influence of the material of metal plates 4 and 5 is small. However, the zinc plating vaporizes during welding, so it greatly affects the welding quality.

[0014] Furthermore, the metal plates 4 and 5 used as weldable materials are not particularly limited to galvanized steel plates. The metal plates 4 and 5 used as weldable materials may, for example, be aluminum-plated steel plates for hot pressing, which are steel plates plated with an aluminum and silicon alloy. Moreover, the metal plates 4 and 5 used as weldable materials may be ordinary steel plates that have not been plated.

[0015] [Welding Method] Figure 2 shows an example of the wobble shape produced by the galvanometer scanner head 2 in the laser welding method according to this embodiment. Figure 3 shows an example of the trajectory of the laser beam LB in the laser welding method according to this embodiment.

[0016] In this embodiment, the laser welding method involves stacking multiple metal plates 4 and 5 and irradiating the surface (top surface) of the metal plates 4 and 5 with laser light LB to form a spot weld 6 (see Figure 1).

[0017] The laser welding method according to this embodiment performs laser spot welding along a locus 13 that makes one full circle along a large-diameter circle 11 having a diameter D1 larger than a small-diameter circle 12 while continuously rotating the laser beam LB along the small-diameter circle 12 having a small diameter D2. Also, in the laser welding method according to this embodiment, at the very center of the spot welding portion 6, there is a non-irradiation portion 14 where the laser beam LB is not irradiated.

[0018] In the laser welding method according to this embodiment, the locus 13 for irradiating the laser beam LB is formed as a double spiral locus as shown in FIG. 3. Specifically, the locus 13 for irradiating the laser beam LB is formed by a combination of a scanning movement that moves in the scanning direction along the large-diameter circle 11 and a wobbling that continuously draws a small-diameter circle 12 having a diameter smaller than the large-diameter circle 11.

[0019] Also, in the laser welding method according to this embodiment, the locus 13 of the laser beam LB is formed so as to continuously draw a plurality of small-diameter circles 12 while making one full circle along the large-diameter circle 11. That is, while rotating the laser beam LB at a high speed along the small-diameter circle 12, the laser beam LB is made to make one full circle along the large-diameter circle 11 at a scanning speed slower than the rotation speed of the small-diameter circle 12.

[0020] Furthermore, in the laser welding method according to this embodiment, a non-irradiation portion 14 where the laser beam LB is not irradiated is formed at the center of the spot welding portion 6. Since the diameter D2 of the small-diameter circle 12 is smaller than the diameter D1 of the large-diameter circle 11 (D2 < D1), a non-irradiation portion 14 having an outer diameter equal to the difference in diameter (diameter D1 of the large-diameter circle 11 - diameter D2 of the small-diameter circle 12) is formed at the center of the irradiation range 15 due to the irradiation of the laser beam LB (see FIG. 2). For this reason, there is a non-irradiation portion 14 where the laser beam LB is not irradiated at the center of the spot welding portion 6. However, since the laser beam LB is irradiated in the vicinity of the non-irradiation portion 14, the non-irradiation portion 14 temporarily becomes a molten state.

[0021] Note that in Example 2 and FIG. 5 of "Japanese Patent Application Laid-Open No. 2018-192515", an annular welding line group (35) that may be similar to the trajectory of the aforementioned laser beam is described. However, it is different from the present embodiment in that there is no "non-irradiation portion" in the central portion (33) of the annular welding line group (35).

[0022] If welding is performed along a trajectory where the diameters of the small-diameter circle and the large-diameter circle are the same (see FIG. 5 of "Japanese Patent Application Laid-Open No. 2018-192515"), the laser beam will concentrate on the welding center portion many times, resulting in an excessive amount of heat input and the formation of through-holes in the molten portion in some cases.

[0023] [Specific Example] An example of the irradiation conditions of the laser beam is shown below.

[0024] Irradiation energy of the laser beam: Approximately 4500 W Diameter of the large-diameter circle: 4 mm Speed of movement along the large-diameter circle (scanning speed): 35 mm / min Diameter of the small-diameter circle: 3 mm Speed of drawing the small-diameter circle (swing speed): 21 times / second The irradiation energy of the laser beam, the diameter of the large-diameter circle and the speed of movement along the large-diameter circle, the diameter of the small-diameter circle and the speed of drawing the small-diameter circle, etc. can be appropriately changed according to the thickness of the welded material, etc.

[0025] In this specific example, the trajectory 13 for irradiating the laser beam LB draws a large-diameter circle 11 with a diameter D1 of 4 mm while continuously drawing a small-diameter circle 12 with a diameter D2 of 3 mm. Then, the outer diameter D0 of the trajectory 13 of the laser beam LB is 7 mm, and a non-irradiation portion 14 with a diameter of 1 mm is formed in the central portion of the trajectory 13.

[0026] Also, in this specific example, the speed at which the laser beam LB moves along the large-diameter circle 11 is 35 mm / min, and the speed at which the laser beam LB draws the small-diameter circle 12 is 21 times / second. For this reason, the laser beam LB draws the small-diameter circle 12 with a diameter D2 of 3 mm 7.5 times while going around the large-diameter circle 11 with a diameter D1 of 4 mm once.

[0027] Therefore, the trajectory 13 irradiated with laser light LB is formed by combining at least seven arc-shaped portions AR1, AR2, AR3, AR4, AR5, AR6, and AR7 (see Figure 3). In reality, the melted area due to irradiation with laser light LB becomes larger than 7 mm, and the non-irradiated area 14 located in the center of the trajectory 13 irradiated with laser light LB also melts temporarily.

[0028] Furthermore, in this specific embodiment, the laser beam LB is irradiated from the starting point S to the ending point E shown in Figure 3, and the rotation direction of the laser beam LB is counterclockwise in a plan view.

[0029] Furthermore, the rotation direction of the laser beam LB is not limited to counterclockwise in a plan view; it is also possible for the rotation direction of the laser beam LB to be clockwise in a plan view.

[0030] In this specific embodiment, spot welding was performed by tracing a spiral trajectory 13 with the laser beam LB superimposed on a small-diameter circle 12 and a large-diameter circle 11 (see Figure 3).

[0031] As mentioned above, the irradiation energy of the laser beam LB, the diameter D1 of the large diameter circle 11 and the speed at which it moves along the large diameter circle 11, the diameter D2 of the small diameter circle 12 and the speed at which it draws the small diameter circle 12 can be appropriately changed according to the thickness of the material to be welded, etc. For example, when the thickness of the metal plates 4 and 5 is increased, the irradiation energy of the laser beam LB may be increased, and the speed at which it moves along the large diameter circle 11 and the speed at which it draws the small diameter circle 12 may be decreased.

[0032] [Effects and Effects] The effects and advantages of this embodiment will be explained below.

[0033] (1) In the laser welding method according to this embodiment, multiple metal plates 4 and 5 are stacked on top of each other, and a spot weld 6 is formed by irradiating the metal plates 4 and 5 with laser light LB. The trajectory 13 of the laser light LB is formed by a combination of scanning movement, which moves in a scanning direction along a large diameter circle 11, and wobbling, which swings to trace a small diameter circle 12 with a smaller diameter than the large diameter circle 11.

[0034] As described above, spot welding is performed by tracing a spiral trajectory 13 with the laser beam LB tracing a small diameter circle 12 and a large diameter circle 11. In particular, because the diameter D2 of the small diameter circle 12 is smaller than the diameter D1 of the large diameter circle 11, an unirradiated area 14 is formed in the center of the trajectory 13 of the laser beam LB. Therefore, the amount of heat input in the center of the irradiation area 15 due to the irradiation of the laser beam LB is not excessive compared to other parts, and the formation of through holes in the molten area can be suppressed.

[0035] Furthermore, by irradiating the metal plates 4 and 5 with laser beam LB in a spiral pattern, a wider molten area can be formed due to the irradiation of laser beam LB, thereby improving the welding strength (especially the peel strength).

[0036] Furthermore, in this embodiment, scanning motion, which moves the laser beam LB in a scanning direction along the large-diameter circle 11, and oscillation motion, which moves it to trace a small-diameter circle 12 with a smaller diameter than the large-diameter circle 11, are combined. As a result, the undulating metal in the molten area causes vapor generated in the molten area to escape, which has the effect of reducing the occurrence of blowholes in the weld.

[0037] In summary, this embodiment provides a laser welding method that can increase the welding strength by expanding the welding diameter without generating blowholes or the like.

[0038] (2) A non-irradiated area 14 is formed in the center of the spot weld 6, where the laser beam LB is not irradiated.

[0039] Since a non-irradiated area 14 is formed in the center of the trajectory 13 of the laser beam LB, the amount of heat input to the center of the irradiation area 15 due to irradiation by the laser beam LB is not excessive compared to other parts, and the formation of through holes in the molten area can be suppressed.

[0040] (3) The trajectory 13 of the laser beam LB is formed by drawing multiple small-diameter circles 12 while it makes one revolution along the large-diameter circle 11.

[0041] Since the laser beam LB is irradiated onto the metal plates 4 and 5 in a spiral pattern, a wide area of ​​molten material can be formed by the irradiation of the laser beam LB, making it possible to improve the welding strength (especially the peel strength).

[0042] By the way, although the laser welding method of the present invention has been described using the above-described embodiment as an example, various other embodiments can be adopted without departing from the spirit of the present invention, and the invention is not limited to this embodiment. [Explanation of Symbols]

[0043] 1. Laser welding equipment 2 Galvanometer Scanner Heads 3 Controllers 4 metal plate 5 metal plate 6 Spot welds 11 Large diameter circle 12 Small diameter circles 13 Trajectory 14 Non-irradiated area 15. Irradiation range LB laser light D0 Outer diameter of the laser beam irradiation area D1 Diameter of the large circle D2 Diameter of the small circle

Claims

1. A laser welding method comprising overlapping multiple high-tensile steel plates and irradiating the high-tensile steel plates with laser light to form spot welds, The trajectory of the laser beam is formed by a combination of scanning movement, which moves along the scanning direction of the large diameter circle, and oscillating movement, which traces a small diameter circle with a smaller diameter than the large diameter circle. A non-irradiated area is formed in the center of the spot weld, where the laser light is not irradiated, and the non-irradiated area is temporarily melted. Laser welding method.

2. The high-tensile steel sheet is a plated steel sheet. The laser welding method according to claim 1.

3. The trajectory of the laser beam is formed by tracing multiple small-diameter circles while it makes one revolution along the large-diameter circle. The laser welding method according to claim 1 or 2.

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