JP7397406B2 - Laser welding method and laser welding device - Google Patents

Description

The present disclosure relates to a laser welding method and a laser welding apparatus used when, for example, metal plates having a thickness of about 5 mm are butted against each other and joined by laser beam irradiation.

When metal plates having a thickness of about 5 mm as described above are butted and joined together, a gap inevitably occurs between the metal plates. When joining metal plates with such a gap using a laser beam, in order to eliminate this gap, conventionally, for example, a laser welding method has been adopted in which the laser beam irradiated between the metal plates is oscillated. ing.
Note that the "gap" mentioned here refers to the gap that occurs between the metal plates, and does not refer to the "root gap" that is intentionally provided between the metal plates.

In other words, in this laser welding method, the laser beam is moved back and forth across the gap between the metal plates, and the laser beam is moved along the gap to widen the molten area near the gap and eliminate the gap. ing. Note that a method similar to this laser welding method is described in Patent Document 1.

Japanese Patent Application Publication No. 2014-205166

However, in the conventional laser welding method that oscillates the laser beam, the laser beam has a small spot diameter and high energy density, which causes local temperature differences between the laser beam irradiated area and the non-laser beam irradiated area. A large amount of spatter is generated at the folding part of the oscillating laser beam (the moving end of the laser beam that moves back and forth across the gap between the metal plates) due to the large temperature gradient between the metal plates. There are some problems, and solving this problem has been a challenge in the past.

The present disclosure has been made in order to solve the above-mentioned conventional problems, and it is possible to eliminate the gap between metal plates when metal plates with a thickness of about 5 mm are butted against each other and joined by irradiation with laser light. Needless to say, it is an object of the present invention to provide a laser welding method and a laser welding apparatus that can reduce spatter generated in the gap between metal plates and in the vicinity thereof.

Here, the mechanism by which a large amount of spatter is generated at the folded portion of the oscillating laser beam will be discussed with reference to FIGS. 4 and 5.

The upper part of FIG. 4 shows a partially enlarged cross section in the direction that crosses the gap wa between the metal plates w, w. As can be seen from this partially enlarged cross section, the oscillating laser beam l has a molten pool indicated by a dashed line. ms follows and moves. The planar shape of the molten pool ms is schematically shown at the bottom of FIG.

The flow velocity v of the molten metal in the traveling direction (rightward direction in the figure) in the molten pool ms and the melting depth d of the molten pool ms both increase or decrease in accordance with the magnitude of the output Lp of the laser beam I.
Therefore, as shown in FIG. 5, if the output Lp of the laser beam l is kept large and oscillated between the folded parts P1 and P2 without changing, the molten pool ms will be formed by the flow velocity v of the molten metal and the melting depth. While d remains large, the laser beam 1 reaches the folded portion P2 (the shaded portion in FIG. 4 (non-laser beam irradiation portion)).

In this way, when the output Lp of the laser beam 1 at the folding portion P2 of the laser beam 1 is large (the temperature gradient between the laser beam irradiated part and the laser beam non-irradiated part is large), a large inertial force acts on the molten metal. The metal vapor left in the deep part of the molten metal when the laser beam is turned back blows out all at once from the surface of the molten metal, which is about to cool, and the bubbles of vaporized gas generated inside the molten pool rise to the surface of the molten pool When it bursts, nearby molten metal is thrown away, and the upward flow of molten metal generated in the molten metal pool behind the keyhole in the welding direction increases by increasing the laser output and welding speed. It is thought that a large amount of spatter s is generated due to the fact that the molten metal on the surface of the molten metal pool becomes sparks and scatters.

As described above, in laser welding in which laser light is oscillated, the flow velocity and melting depth of molten metal in the molten pool that moves following the laser light increase or decrease with the magnitude of the laser output. With this in mind, we have come to the present disclosure.

That is, a first aspect of the present disclosure is a laser welding method for joining metal plates to each other by laser welding, in which the laser beam is oscillated so as to straddle the gap between the metal plates, and the laser beam is applied along the gap. When irradiating, the output of the laser beam is set equal on one side and the other side of the gap when the laser beam moves through the middle part of the oscillator including the top of the gap, and the output of the laser beam is set equal on one side and the other side of the gap, and The configuration is such that the output of the laser light is gradually lowered as it approaches the oscillation folding part.

On the other hand, a second aspect of the present disclosure is a laser welding device that joins metal plates together by laser welding, the laser welding device including a laser head that irradiates a laser beam between the metal plates, and a laser welding device that joins metal plates together by laser welding. Laser welding comprising: a head drive mechanism that moves along a gap; an oscillation mechanism that oscillates laser light so as to straddle the gap; and a control unit that controls the angle of the oscillation mechanism and the output of the laser light by the laser head. In the apparatus, the control unit controls the laser output in synchronization with the operation of the oscillating mechanism, and controls the output of the laser light when the oscillating laser light moves through an oscillating intermediate portion including on the gap to one side of the gap. The output of the laser beam is controlled to be equal on both sides of the gap, and the output of the laser beam is gradually lowered as it approaches the oscillation folding part on one side of the gap and the oscillation folding part on the other side of the gap.

In the laser welding method and laser welding apparatus according to the present disclosure, the output of the laser beam at the oscillate folded portion remote from the gap between the metal plates is made lower than the output of the laser beam at the intermediate oscillate portion. For example, if the output of the laser beam at the oscillation intermediate portion is 10 kW, the output of the laser beam at the oscillation folding portion is reduced to about 10%, ie, 1 kW.

Note that in the laser welding method and laser welding apparatus according to the present disclosure, the thickness of the metal plates to be joined by laser welding is not particularly limited. For example, a metal plate of 3 to 6 mm, called a so-called intermediate plate, is particularly targeted.

Further, in the laser welding method and laser welding apparatus according to the present disclosure, a YAG laser, a semiconductor laser, or a fiber laser is generally used as the laser, but the laser is not limited to these.

Furthermore, the laser welding method and laser welding device according to the present disclosure can be used for butt joints between metal plates, and the laser welding method and laser welding device according to the present disclosure can also be applied to lap joints between metal plates. be able to.

According to the laser welding method and laser welding apparatus according to the present disclosure, when joining metal plates with a thickness of approximately 5 mm to each other by irradiating laser light, the generation of spatter can be suppressed to a minimum, and the gap between the metal plates can be reduced. A very good effect is that it can be eliminated.

FIG. 1 is a schematic explanatory diagram showing a laser welding device used in a laser welding method according to an embodiment of the present disclosure. FIG. 2 is an explanatory enlarged cross-sectional view showing the state of oscillation of laser light by the laser welding apparatus of FIG. 1 together with the planar shape of a molten pool. 2 is a graph showing changes in laser light output during oscillation by the laser welding apparatus of FIG. 1. FIG. FIG. 2 is an enlarged cross-sectional explanatory diagram showing the state of laser beam oscillation in a conventional laser welding method and the planar shape of a molten pool. 5 is a graph showing changes in laser light output during oscillation in FIG. 4. FIG.

Embodiments of the present disclosure will be described below based on the drawings.
FIG. 1 shows a laser welding device according to an embodiment of the present disclosure, and in this embodiment, a case where the laser welding device according to the present disclosure is used for butt joining of metal plates will be described as an example. .

As schematically shown in FIG. 1, this laser welding apparatus 1 butts and joins metal plates W, W together by laser welding, and includes a laser oscillator 2 and a laser beam supplied from the laser oscillator 2. A laser head 4 that focuses light using an optical system 3 containing a laser beam L and irradiates it between metal plates W, W, an optical fiber 5 that guides the laser light L from the laser oscillator 2 to the laser head 4, and a laser head 4 that is made of metal. A head drive mechanism 6 that moves along the gap Wa between the plates W and W and a reciprocating movement of the laser beam L so as to straddle the gap Wa, that is, between the folded parts P1 and P2 shown in the enlarged circle in FIG. An oscillation mechanism 8 that oscillates the laser beam L, and a control section 10 that controls the oscillation angle of the oscillation mechanism 8, the welding speed of the laser head 4, the laser output, the spot diameter, etc.

The head drive mechanism 6 includes a rail 6a arranged along the gap Wa between the metal plates W and W, and a slider 6b that reciprocates on the rail 6a. In this case, the laser head 4 is fixed to the slider 6b so that the laser beam irradiation direction is parallel to the metal plates W, W and perpendicular to the rail 6a.

The oscillating mechanism 8 is held in a case 9 attached to the slider 6b of the head drive mechanism 6 via a support 7, and includes a scanner mirror 8a that reflects the laser beam L from the laser head 4, and a scanner mirror 8a that reflects the laser beam L from the laser head 4. The scanner motor 8b rotates the mirror 8a within a predetermined range.
That is, the head drive mechanism 6 and the oscillation mechanism 8 operate both to move the laser head 4 together with the slider 6b along the gap Wa between the metal plates W, while the scanner mirror 8a reflects the laser beam L. By rotating within a predetermined range, the laser beam L is moved back and forth in a zigzag pattern so as to straddle the gap Wa.

At this time, in the control unit 10, during the oscillation across the gap Wa by the oscillation mechanism 8, the output of the laser light L is further away from the gap Wa than the output of the laser light L in the middle part of the oscillation where the laser light L passes over the gap Wa. The output of the laser beam L at P1 and P2 is set to be low. For example, when the output of the laser beam L at the middle oscillation portion is 10 kW, the output of the laser beam L at the oscillation folding portions P1 and P2 is set to be reduced to 1 kW, which is about 10% of the output.

When joining the metal plates W, W using the laser welding apparatus 1 configured in this way, first, a tab plate T is temporarily attached between each end portion of the metal plates W, W, respectively.

After that, when the laser welding device 1 is started, the supply of laser light L from the laser oscillator 2 to the laser head 4 is started, and the laser head 4 irradiates the metal plate W with the laser light L focused by the optical system 3. It starts towards W.

At the same time, the head drive mechanism 6 and the oscillation mechanism 8 start their respective operations, whereby the laser light L moves along the gap Wa while being oscillated so as to straddle the gap Wa between the metal plates W, W.

In this laser welding device 1, during oscillation across the gap Wa by the oscillation mechanism 8, the output of the laser beam L at the oscillation folding portions P1 and P2 is adjusted to the oscillation intermediate portion (gap Wa) where the laser beam L passes over the gap Wa. The output of the laser beam L is set to be lower than the output of the laser beam L (a portion between the oscillation folding portion P1 on one side of the gap Wa and the oscillation folding portion P2 on the other side of the gap Wa).

That is, as can be seen from the enlarged cross section in the direction across the gap Wa shown in the upper side of FIG. 2, as the laser beam L approaches the folded parts P1 and P2, the laser output is gradually changed from LPh to LPm to LPl. Therefore, the molten pool MS, which moves following the laser beam L, changes from the state shown by the one-dot chain line to the state shown by the two-dot chain line to the state shown by the solid line. As the flow velocity V in the direction) gradually decreases, the melting depth D also gradually becomes shallower. The lower side of FIG. 2 schematically shows the planar shape of the molten pool MS.

Therefore, as shown in FIG. 3, when the output LP of the laser beam L is oscillated between the folding parts P1 and P2 by changing from LPl→LPm→LPh→LPm→LPl as described above, the folding parts P1, P2 In this case, the molten metal reaches the non-irradiated area (the shaded area in FIG. 2) at a slow flow rate V.

In addition, in the folded portions P1 and P2, the amount of metal vapor spouted upward is reduced to the extent that the melting depth D of the molten metal is shallow, and as a result, the amount of spatter generated when the laser beam L is folded back can be suppressed to a small amount. becomes.

In the embodiment described above, the laser head 4 is fixed to the slider 6b so that the laser beam irradiation direction is parallel to the metal plates W and perpendicular to the rail 6a, and the laser beam from the laser head 4 is By rotating the scanner mirror 8a that reflects the light L within a predetermined range, the laser light L is moved back and forth across the gap Wa, but the relative positional relationship between the laser head 4 and the scanner mirror 8a is It is not limited to this.

Furthermore, in the above-described embodiment, the laser beam L is moved back and forth in a zigzag manner so as to straddle the gap Wa, but the movement locus of the laser beam L is not limited to this, and for example, a sine curve. The laser beam L may be moved back and forth across the gap Wa as shown in FIG.

In the embodiments described above, the laser welding method and laser welding device according to the present disclosure are the laser welding method and laser welding device for butt-joining the metal plates W, W, but the present disclosure is not limited thereto. Instead, it is naturally possible to apply the laser welding method and laser welding apparatus according to the present disclosure to lap joints between metal plates.

The configurations of the laser welding method and laser welding apparatus according to the present disclosure are not limited to the above-described embodiments, and can be modified in various ways without departing from the spirit of the invention.

1 Laser welding device 4 Laser head 6 Head drive mechanism 8 Oscillating mechanism 10 Control section L Laser beams P1, P2 Oscillating folding section W Metal plate Wa Gap

Claims (2)

A laser welding method for joining metal plates together by laser welding,
When irradiating the laser beam along the gap while oscillating the laser beam so as to straddle the gap between the metal plates,
The output of the laser beam when the laser beam moves through the oscillation intermediate portion including above the gap is set equal on one side and the other side of the gap, and the oscillation folding portion on one side of the gap and the oscillation folding portion on the other side of the gap are set. A laser welding method in which the output of the laser beam is set to gradually lower as it approaches . A laser welding device that joins metal plates together by laser welding,
a laser head that irradiates laser light between the metal plates;
a head drive mechanism that moves the laser beam along the gap between the metal plates;
an oscillation mechanism that oscillates laser light so as to straddle the gap;
A laser welding device comprising a control unit that controls the angle of the oscillation mechanism and the output of laser light from the laser head,
The control unit controls the laser output in synchronization with the operation of the oscillating mechanism, and controls the output of the laser light when the oscillating laser light moves through an oscillating intermediate portion including above the gap on one side and the other side of the gap. A laser welding device that controls the output of the laser beam to be equal on both sides and to gradually lower the output of the laser beam as it approaches the oscillated folded portion on one side of the gap and the oscillated folded portion on the other side of the gap.

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