JP2021133417A - Laser welding method and laser welding device - Google Patents

Abstract

To provide a laser welding method and a laser welding device which suppresses occurrence of sputter to a small extent, and in addition to this, can eliminate a gap between metal plates with thickness of about 5 mm when joining the metal plates by irradiation of laser beam.SOLUTION: According to a laser welding method for joining metal plates W, W by laser welding, when radiating laser beam L along a gap Wa generated between the metal plates W, W while oscillating laser beam L over the gap, an output of laser beam L at oscillation folding parts P1, P2 separated from the gap Wa is so set as to be lower than an output of the laser beam L at an oscillation intermediate part where laser beam L passes above the gap G.SELECTED DRAWING: Figure 1

Description

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

When metal plates having a thickness of about 5 mm are butted and joined as described above, a gap is inevitably generated between the metal plates. When metal plates having such a gap are joined by laser light, in order to eliminate this gap, for example, a laser welding method for oscillating the laser light emitted toward the metal plates has been conventionally adopted. ing.
The "gap" referred to here is a gap generated between the metal plates, and is not a "root gap (root interval)" intentionally provided between the metal plates.

That is, in this laser welding method, the laser beam is reciprocated so as to straddle the gap between the metal plates, and the laser beam is moved along the gap to widen the molten region in the vicinity of this gap and eliminate the gap. ing. A method similar to this laser welding method is described in Patent Document 1.

Japanese Unexamined Patent Publication No. 2014-205166

However, in the conventional laser welding method in which the laser beam is oscillated, the spot diameter of the laser beam is small and the energy density is high, so that a temperature difference is locally generated, and the laser beam irradiated portion and the laser beam non-irradiation caused by this are generated. It is said that a large amount of spatter occurs at the folded portion of the oscillating laser beam (the moving end of the laser beam that reciprocates across the gap between the metal plates) due to a large temperature gradient between the portions. It has a problem, and solving this problem has become a conventional issue.

The present disclosure has been made to solve the above-mentioned conventional problems, and when metal plates having a plate thickness of about 5 mm are butted against each other and joined by irradiation with a laser beam, a gap between the metal plates can be eliminated. Of course, it is an object of the present invention to provide a laser welding method and a laser welding apparatus capable of suppressing spatter generated in and around a gap between metal plates to a small extent.

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

The upper side of FIG. 4 shows a partially enlarged cross section in the direction crossing the gap wa between the metal plates w and w. ms follows and moves. The planar shape of the molten pool ms is schematically shown on the lower side of FIG.

The flow velocity v in the direction of travel of the molten metal (right direction in the drawing) and the melting depth d of the molten pool ms in the molten pool ms both increase or decrease according to the magnitude of the output Lp of the laser beam l.
Therefore, as shown in FIG. 5, when the folded portions P1 and P2 are oscillated without changing while keeping the output Lp of the laser beam l large, the molten metal ms has a flow velocity v and a melting depth of the molten metal. With both d remaining large, the laser beam l reaches the folded-back portion P2 (the portion shaded in FIG. 4 (laser beam non-irradiated portion)).

As described above, when the output Lp of the laser beam l at the folded-back portion P2 of the laser beam l is large (the temperature gradient between the laser beam irradiated portion and the laser beam non-irradiated portion is large), a large inertial force acts on the molten metal. At the time when the laser beam l turns back, the metal vapor left in the deep part of the molten metal is ejected at once from the surface of the molten metal that has cooled, and the bubbles of vaporized gas generated inside the molten pool float up on the surface of the molten metal. When it bursts, the nearby molten metal is blown off, and the upward molten metal flow generated in the molten metal pool behind the keyhole in the welding progress direction increases by increasing the laser output and welding speed. It is considered 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 that oscillates a laser beam, the present discloser increases or decreases the flow velocity and the melting depth of the molten metal in a molten pool that moves following the laser beam according to the magnitude of the laser output. This disclosure has been made with a focus on.

That is, the first aspect of the present disclosure is a laser welding method in which metal plates are joined by laser welding, and the laser light is oscillated so as to straddle the gap between the metal plates while the laser light is emitted along the gap. When irradiating, the laser light in the oscillating folded portion is more than the output of the laser light in the oscillating intermediate portion between the oscillating folded portion on one side of the gap and the oscillating folded portion on the other side through which the laser light passes over the gap. The output of is set low.

On the other hand, the second aspect of the present disclosure is a laser welding apparatus for joining metal plates to each other by laser welding, in which a laser head that irradiates laser light between the metal plates and the laser light between the metal plates. Laser welding including a head drive mechanism that moves along the gap, an oscillating mechanism that oscillates the laser beam so as to straddle the gap, and a control unit that controls the angle of the oscillating mechanism and the output of the laser beam by the laser head. In the apparatus, the control unit controls the laser output in synchronization with the operation of the oscillating mechanism, and the oscillating folding portion on one side and the oscillating folding portion on the other side of the gap through which the oscillating laser beam passes over the gap. The output of the laser beam in the oscillating folded portion is controlled to be lower than the output of the laser beam in the oscillating intermediate portion between the two.

In the laser welding method and the laser welding apparatus according to the present disclosure, the output of the laser beam of the oscillating folded portion away from the gap between the metal plates is made lower than the output of the laser beam of the oscillating intermediate portion. For example, when the output of the laser beam in the oscillating intermediate portion is set to 10 kW, the output of the laser beam in the oscillated folded portion is reduced to about 10% of the output of 1 kW.

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

Further, in the laser welding method and the 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.

Further, the laser welding method and the laser welding apparatus according to the present disclosure can be used for a butt joint between metal plates, and the laser welding method and the laser welding apparatus according to the present disclosure are also applied to a lap joint between metal plates. be able to.

According to the laser welding method and the laser welding apparatus according to the present disclosure, when metal plates having a thickness of about 5 mm are joined by irradiation with laser light, the occurrence of spatter is suppressed to a small extent and the gap between the metal plates is reduced. It has a very good effect that it can be eliminated.

It is a schematic explanatory drawing which shows the laser welding apparatus used in the laser welding method which concerns on one Embodiment of this disclosure. It is an enlarged cross-sectional explanatory view which shows the plane shape of the molten pool together with the state of oscillating the laser beam by the laser welding apparatus of FIG. It is a graph which shows the change of the laser beam output during oscillation by the laser welding apparatus of FIG. It is an enlarged cross-sectional explanatory view which shows the plane shape of the molten pool together with the oscillating state of the laser beam by the conventional laser welding method. It is a graph which shows the change of the laser beam output during the oscillating of FIG.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.
FIG. 1 shows a laser welding apparatus according to an embodiment of the present disclosure, and in the present embodiment, a case where the laser welding apparatus according to the present disclosure is used for butt-joining metal plates will be described as an example. ..

As schematically shown in FIG. 1, this laser welding apparatus 1 butt-bonds metal plates W and W to each other by laser welding, and is a laser oscillator 2 and a laser beam supplied from the laser oscillator 2. A laser head 4 that collects light by an optical system 3 incorporating L and irradiates between the metal plates W, W, an optical fiber 5 that guides a laser beam L from a laser oscillator 2 to a laser head 4, and a metal laser head 4. Between the head drive mechanism 6 that moves along the gap Wa between the plates W and W and the folded portions P1 and P2 that reciprocate the laser beam L so as to straddle the gap Wa, that is, in the enlarged circle of FIG. It includes an oscillating mechanism 8 that oscillates the laser beam L, and a control unit 10 that controls the oscillating angle by the oscillating mechanism 8 and the welding speed, laser output, spot diameter, and the like by the laser head 4.

The head drive mechanism 6 includes a rail 6a arranged along a 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 as to align the laser beam irradiation direction in a direction parallel to the metal plates W and W and orthogonal to the rail 6a.

Further, the oscillating mechanism 8 is held in a case 9 attached to the slider 6b of the head drive mechanism 6 via a support base 7, and a scanner mirror 8a that reflects the laser beam L from the laser head 4 and the scanner. It is composed of a scanner motor 8b that rotates the mirror 8a within a predetermined range.
That is, in the head drive mechanism 6 and the oscillating mechanism 8, both are operated to move the laser head 4 together with the slider 6b along the gap Wa between the metal plates W and W, and the scanner mirror 8a that reflects the laser beam L is reflected. By rotating the laser beam L in a predetermined range, the laser beam L is reciprocated in a zigzag manner so as to straddle the gap Wa.

At this time, in the control unit 10, during the oscillating across the gap Wa by the oscillating mechanism 8, the oscillating folding portion farther from the gap Wa than the output of the laser beam L in the oscillating intermediate portion where the laser beam L passes over the gap Wa. The output of the laser beam L in P1 and P2 is set to be low. For example, when the output of the laser beam L in the oscillating intermediate portion is set to 10 kW, the output of the laser beam L in the oscillated folding portions P1 and P2 is set to be reduced to about 10% of the output of 1 kW.

When joining the metal plates W and W using the laser welding apparatus 1 configured in this way, first, a tab plate T is temporarily attached between both ends of the metal plates W and W.

After that, when the laser welding apparatus 1 is started, the laser oscillator 2 starts supplying the laser beam L to the laser head 4, and the laser head 4 irradiates the laser beam L focused by the optical system 3 with the metal plate W. It will start towards the W.

At the same time, the head drive mechanism 6 and the oscillating mechanism 8 each start operating, whereby the laser beam L moves along the gap Wa while oscillating so as to straddle the gap Wa between the metal plates W and W.

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

That is, as can be seen from the enlarged cross section in the direction crossing the gap Wa shown on the upper side of FIG. 2, as the laser beam L approaches the folded-back portions P1 and P2, the laser output is gradually changed so as to be LPh → LPm → LPl. Therefore, the molten metal MS that moves following the laser beam L changes from the state indicated by the alternate long and short dash line to the state indicated by the solid line, and the traveling direction of the molten metal in the molten metal MS (right in the figure). As the flow velocity V in the direction) gradually decreases, the melting depth D also gradually becomes shallower. The planar shape of the molten pool MS is schematically shown on the lower side of FIG.

Therefore, as shown in FIG. 3, when the output LP of the laser beam L is oscillated by changing the output LP of the laser beam L in the order of LPl → LPm → LPh → LPm → LPl between the folded portions P1 and P2, the folded portions P1 and P2 In, the molten metal reaches the non-irradiated portion (the portion shaded in FIG. 2) at a slow flow velocity V.

In addition, in the folded portions P1 and P2, the amount of metal vapor ejected upward is reduced by the shallow melting depth D of the molten metal, and as a result, the amount of spatter generated at the time when the laser beam L is folded is suppressed to a small amount. It becomes.

In the above-described embodiment, the laser head 4 is fixed to the slider 6b so that the laser light irradiation direction is aligned in the direction parallel to the metal plates W and W and orthogonal to the rail 6a, and the laser from the laser head 4 is used. By rotating the scanner mirror 8a that reflects the light L within a predetermined range, the laser beam L is reciprocated so as to straddle 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.

Further, in the above-described embodiment, the laser beam L is reciprocated in a zigzag manner so as to straddle the gap Wa, but the movement trajectory of the laser beam L is not limited to this, and for example, a sine curve is used. The laser beam L may be reciprocated across the gap Wa as if drawn.

In the above-described embodiment, the case where the laser welding method and the laser welding apparatus according to the present disclosure are the laser welding method and the laser welding apparatus in which the metal plates W and W are butted and joined to each other is shown, but the present invention is limited to this. Instead, it is naturally possible to apply the laser welding method and the laser welding apparatus according to the present disclosure to lap joints between metal plates.

The configuration of the laser welding method and the laser welding apparatus according to the present disclosure is not limited to the above-described embodiment, and can be variously modified without departing from the spirit of the invention.

1 Laser welding device 4 Laser head 6 Head drive mechanism 8 Oscillating mechanism 10 Control unit L Laser light P1, P2 Oscillating folding part W Metal plate Wa gap

Claims (2)

This is a laser welding method in which metal plates are joined 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 light in the oscillating folded portion is lower than the output of the laser light in the oscillating intermediate portion between the oscillating folded portion on one side and the oscillating folded portion on the other side of the gap through which the laser light passes over the gap. Laser welding method to set. A laser welding device that joins metal plates by laser welding.
A laser head that irradiates laser light between the metal plates and
A head drive mechanism that moves the laser beam along the gap between the metal plates, and
An oscillating mechanism that oscillates the laser beam so as to straddle the gap,
In a laser welding apparatus provided with a control unit that controls the angle of the oscillating mechanism and the output of laser light by the laser head.
The control unit controls the laser output in synchronization with the operation of the oscillating mechanism, and between the oscillating folding portion on one side and the oscillating folding portion on the other side of the gap through which the oscillating laser beam passes over the gap. A laser welding device that controls the output of the laser beam at the oscillating folded portion to be lower than the output of the laser beam at the oscillating intermediate portion of the above.

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