JP4728583B2 - Laser welding method - Google Patents

Description

  The present invention relates to a laser welding method for performing laser welding by irradiating a workpiece made of aluminum or an aluminum alloy with laser light.

Conventionally, for example, when laser welding a workpiece made of aluminum or an aluminum alloy, a laser beam having a high average energy density exceeding 300 kW / cm ² (generally, 1000 kW / cm ² or more) is irradiated. (See Patent Documents 1 and 2).

JP 2002-361454 A JP 2002-148491 A

  However, the conventional laser welding method has the following problems. That is, when a laser beam having a high average energy density is irradiated onto a workpiece made of aluminum or an aluminum alloy as described above, a so-called plasma plume in which a molten material is scattered around, or a metal material is evaporated and vaporized. Etc. are likely to occur.

If spatter or plasma plume is generated during laser welding, the optical system such as a condenser lens in a welding apparatus performing laser welding may be damaged or damaged. In addition, in a workpiece subjected to laser welding, the surface of the formed weld bead becomes irregular, and the welding strength may be reduced.
Further, when a plasma plume is generated, the plasma plume has a property of absorbing the energy of the laser beam, which causes a problem that the welding energy supplied to the workpiece is insufficient.

In order to remove this plasma plume, for example, an assist gas may be sprayed onto a laser welding location. However, if the amount and direction of supply of the assist gas are not appropriate, not only the effective effect of the assist gas can be obtained, but also the assist gas itself causes molten metal oxidation and a defective bead shape. There is also a fear.
In addition, as a countermeasure against the above-mentioned sputtering, for example, there is a countermeasure that a protective glass is provided in the optical system of the laser device. There is a problem of lowering.
As described above, in the conventional laser welding method, various problems have occurred due to the spatter and plasma plume generated during laser welding.

  The present invention has been made in view of the above-mentioned conventional problems, and in laser welding of aluminum or aluminum alloy, a laser welding method capable of forming a weld bead having a good shape while suppressing spatter and plasma plume. It is something to be offered.

The present invention relates to a laser welding method for performing laser welding by irradiating a semiconductor laser beam emitted from a semiconductor laser element onto a workpiece surface, which is a workpiece surface made of aluminum or an aluminum alloy, through a condenser lens.
The semiconductor laser light is condensed using the condensing lens having a focal length of 40 mm or more and 250 mm or less to form a substantially rectangular shape, and the average energy density in the region is 30 kW / cm ^{2 to} 300 kW / An irradiation spot having an aspect ratio which is less than cm ² and whose ratio of the length in the longitudinal direction to the width in the direction perpendicular to the longitudinal direction is more than 2: 1 and not more than 20: 1. And forming on the workpiece surface,
In relative movement of the irradiation spot formation position along the longitudinal direction on the workpiece surface,
As a semiconductor laser welding apparatus for emitting the semiconductor laser light, a plurality of LD bars in which a plurality of semiconductor laser elements are arranged in a line are stacked in a direction substantially perpendicular to the arrangement direction of the semiconductor laser elements in the LD bar. A light emitting surface having a substantially rectangular shape made of an LD stack is provided, and the semiconductor laser light emitted from a plurality of light emitting surfaces is directly irradiated onto the workpiece surface without passing through an optical fiber. In the laser welding method, the irradiation spot, which is a region having a substantially rectangular shape, is formed by utilizing the shape of the light emitting surface of the LD stack.

The laser welding method of the present invention is a method of performing laser welding by irradiating the workpiece made of aluminum or an aluminum alloy with the semiconductor laser light. In this laser welding method, the condensing lens having a focal length of 40 mm or more and 250 mm or less is used, the surface of the workpiece exhibits the substantially rectangular shape or the substantially elliptical shape, and the average energy density is 30 kW / cm ^2. The irradiation spot is formed at a rate of 300 kW / cm ² or more. Furthermore, the irradiation spot formation position is relatively moved along the longitudinal direction of the irradiation spot on the workpiece surface.

  Therefore, according to the laser welding method, a weld bead having a good appearance can be obtained by suppressing generation of spatter and plasma plume during laser welding by the irradiation spot exhibiting an appropriate shape and an appropriate average energy density. Can be formed.

In particular, as described above, laser welding is performed by relatively moving the formation position of the irradiation spot of the semiconductor laser light exhibiting a substantially rectangular shape or a substantially elliptical shape as described above. A semiconductor laser beam having a relatively small energy density can be instantaneously irradiated to a point for a relatively long time, and as a result, sufficient welding energy can be provided.
Therefore, for example, rapid heating at the irradiation spot as in the case of irradiating the semiconductor laser light through one optical fiber and rapid cooling after the heating can be suppressed, thereby suppressing welding distortion and the like. A weld bead can be formed. Further, since the laser beam welding is performed by moving the irradiation spot elongated in the longitudinal direction in the longitudinal direction, fine laser processing with a narrow weld bead, which is a feature of laser welding, can be realized.

If the average energy density of the irradiation spot is less than 30 kW / cm ² , the workpiece base material may be insufficiently melted, or the welding speed may be reduced, resulting in inefficiency. On the other hand, if the average energy density is 300 kW / cm ² or more, there is a risk of so-called deep penetration welding where the melting depth from the workpiece surface is deep. In this case, spatter, plasma plume, etc. occur. However, the appearance of the weld bead is likely to be poor.

  Furthermore, when the focal length of the condenser lens to be used is less than 40 mm, the distance between the light emitting surface and the workpiece surface in the semiconductor laser welding apparatus is shortened, and there is a possibility that they interfere with each other. On the other hand, when the focal length exceeds 300 mm, the irradiation spot is enlarged due to diffraction of the semiconductor laser light and the like, the average energy density is lowered, and the energy efficiency may be lowered.

In the present invention, the combination of the materials of the workpiece to be laser welded may be aluminum or aluminum alloy having the same composition, or may be a combination of aluminum or aluminum alloy having different compositions.
As the average energy density of the irradiation spot, and more preferably in a ^{30kW / cm 2 ~200kW / cm 2} .

Further, as a semiconductor laser welding apparatus that emits the semiconductor laser light, a plurality of LD bars in which a plurality of semiconductor laser elements are arranged in a row are stacked in a direction substantially orthogonal to the arrangement direction of the semiconductor laser elements in the LD bar. The semiconductor laser light emitted from a plurality of light emitting surfaces is directly applied to the work surface without passing through an optical fiber. What is comprised so that it may irradiate is used.

  Conventionally, for example, the irradiation shape of the semiconductor laser light through an optical fiber has been a substantially circular shape, but in this case, the shape of the light emitting surface configured in the substantially rectangular shape is actively utilized. The irradiation spot shape exhibiting the substantially rectangular shape or the substantially elliptical shape can be efficiently formed.

Moreover, the aspect ratio which is the ratio of the length in the longitudinal direction of the irradiation spot to the width in the direction perpendicular to the longitudinal direction is in the range of more than 2: 1 and 20: 1 or less . Thereby , the shape of the said irradiation spot can be made still more suitable, and a more favorable weld bead can be formed.

If the aspect ratio is 2: 1 or less, the average energy density has to be lowered, and there is a risk that rapid heating or rapid cooling may occur in the front-rear direction in which the irradiation spot moves relatively. On the other hand, if the aspect ratio exceeds 20: 1, the average energy density is lowered, and welding may not be possible or distortion may occur during welding.
The aspect ratio is more preferably 3: 1 to 15: 1, and further preferably 8: 1 to 12: 1.

The wavelength of the semiconductor laser light is preferably 700 nm or more and 1000 nm or less ( claim 2 ).
In this case, since the absorption rate on the surface of the workpiece made of aluminum or an aluminum alloy is high, laser welding can be performed with high energy efficiency.
More preferably, the wavelength of the semiconductor laser light is 800 nm or more and 950 nm or less.

Moreover, it is preferable that the said aluminum alloy is JIS1000 type | system | group, JIS3000 type | system | group, JIS5000 type | system | group, or JIS6000 type | system | group ( Claim 3 ).
In this case, sputtering or plasma plume is likely to occur during laser welding, so the semiconductor laser welding method of the present invention is particularly effective.
Here, JIS refers to Japanese Industrial Standard, and the JISX000 series aluminum alloy refers to an aluminum alloy material in the X000 range standardized by Japanese Industrial Standard.

The average energy density at the irradiation spot is preferably 50 kW / cm ² or more and 100 kW / cm ² or less ( claim 4 ).
In this case, it is possible to obtain a weld bead exhibiting a better appearance by further suppressing the range of the average energy density at the irradiation spot and further suppressing spatter and plasma plume during laser welding.

(Example 1)
This example relates to a laser welding method for an aluminum alloy. The contents of this embodiment will be described with reference to FIGS.
In the laser welding method of this example, as shown in FIG. 1, the semiconductor laser light emitted from the semiconductor laser element 11 (see FIG. 2) constituting the semiconductor laser welding apparatus 1 is converted into aluminum or Laser welding is performed by irradiating the workpiece surface 201 which is the surface of the workpiece 20 made of an aluminum alloy.

In the laser welding method of this example, a semiconductor laser beam is condensed using a condensing lens having a focal length of 40 mm or more and 250 mm or less to form a substantially rectangular shape or a substantially elliptical shape, and an average in the region An irradiation spot 150 (see FIGS. 4 and 5) having an energy density of 30 kW / cm ² or more and less than 300 kW / cm ² is formed on the work surface 201, and the formation position of the irradiation spot 150 is determined on the work surface 201. The relative movement is made along the longitudinal direction.
This content will be described in detail below.

  The semiconductor laser welding apparatus 1 of this example is an apparatus having a light emitting unit 10 that emits semiconductor laser light having a wavelength of 808 nm, as shown in FIG. As shown in FIGS. 2 and 3, the light emitting unit 10 includes an LD bar 12 in which a plurality of semiconductor laser elements 11 are arranged in a row in a direction substantially orthogonal to the arrangement direction of the semiconductor laser elements 11 in the LD bar 12. It is composed of a plurality of stacked LD stacks 15. The LD stack 15 forms a light emitting surface 100 having a substantially rectangular shape. In the semiconductor laser welding apparatus 1, semiconductor laser light is emitted from one LD stack 15 having the light emitting surface 100 having a substantially rectangular shape, and an irradiation spot 150 having a substantially rectangular or substantially elliptical shape is formed on the work surface. Form.

  As shown in the figure, the semiconductor laser welding apparatus 1 is configured to be laser-welded on a workpiece 20 placed on a welding table 103 and fixed by a pressing member 101. The welding table 103 is configured to move in the longitudinal direction of the irradiation spot 150 formed on the work surface 201 in a state where the work 20 is placed. In the semiconductor laser welding apparatus 1, the formation position of the irradiation spot 150 can be relatively moved along the longitudinal direction on the workpiece surface 201 by the above-described movement operation of the welding table 103.

  Further, as shown in FIG. 1, the semiconductor laser welding apparatus 1 has an assist gas nozzle 102 that supplies a shielding gas toward a welding location. In this example, argon gas was used as the shielding gas, and the argon gas was sprayed at a rate of 20 liters / minute. In this example, nitrogen gas was sprayed from the side of the welded portion in order to obtain an effect of protecting the condenser lens (not shown) from sputtering and plasma plume.

The semiconductor laser welding apparatus 1 is configured to irradiate the work surface 201 directly with a semiconductor laser beam condensed through a condenser lens without using an optical fiber or the like.
In this example, as the condensing lens, lenses having focal lengths f = 100 mm and 200 mm were prepared.

The semiconductor laser light emitted by the semiconductor laser welding apparatus 1 equipped with a condenser lens of f = 100 mm exhibits an energy distribution shown in FIG. 4 when the vertical surface is irradiated with the laser. FIG. 3A is a three-dimensional display of the energy distribution with its magnitude expressed by height. FIG. 5B shows the energy distribution of the semiconductor laser light having a substantially Gaussian distribution, which is 1 / e ² or more of the maximum output (e is the base of natural logarithm), that is, energy of about 86% or more of the maximum energy. This is a display of a region exhibiting
As shown in the figure, in the semiconductor laser welding apparatus 1 of this example, when a condenser lens with f = 100 mm is used, the average energy density is 179 kW / cm ² and L × W is 0.67 mm × 2.5 mm. The irradiation spot 150 is formed.

When a condenser lens with f = 200 mm is attached, the energy distribution shown in FIG. 5 is exhibited when the vertical surface is irradiated with laser. FIG. 3A is a three-dimensional display of the energy distribution with its magnitude expressed by height. FIG. 4B shows a region exhibiting energy of 1 / e ² or more of the maximum output, that is, approximately 86% or more of the maximum energy, with respect to the energy distribution of the semiconductor laser light substantially exhibiting a Gaussian distribution. .
As shown in the figure, in the semiconductor laser welding apparatus 1 of this example, when a condenser lens of f = 200 mm is used, the average energy density is 51 kW / cm ² and L × W is 1.28 mm × 4.6 mm. The irradiation spot 150 is formed.

  In this example, laser welding was performed on the workpiece 20 made of a 1 mm-thick plate-like aluminum alloy (AA5022 and AA6016) using the semiconductor laser welding apparatus 1 described above. Here, the welding speed, which is the moving speed of the laser irradiation position on the workpiece surface 201, was set as an experimental condition, and so-called melt-run welding was performed in which the base material was welded without a filler material without forming a joint. In this example, in laser welding the workpiece 20, the laser output of the semiconductor laser welding apparatus 1 is set to 3 kW.

  The results of the above experiment are shown in FIGS. In these drawings, the horizontal axis defines the welding speed, and the vertical axis defines the back bead width that is the weld bead width on the weld back surface of the plate-like workpiece 20. FIG. 6 shows the experimental results for a workpiece made of AA5022, and FIG. 7 shows the experimental results for a workpiece made of AA6016. Furthermore, in both figures, the result with a condensing lens having a focal length of 100 mm is shown by a solid line a, and the result with a condensing lens having a focal length of 200 mm is shown by a dashed-dotted line b.

According to FIG.6 and FIG.7, the back surface bead width is wider when the condenser lens with f = 200 mm is used. In the case of a condenser lens with f = 200 mm, the penetration welding speed (that is, the welding speed at which the back bead width becomes 0 mm), which is the maximum welding speed at which the irradiated semiconductor laser light can penetrate the workpiece 20, is It was 9 m / min for AA5022, and 6 m / min for AA6016, which was much faster than arc welding.
That is, in the laser welding using the irradiation spot 150 having a substantially rectangular shape or a substantially elliptical shape as in this example, the width of the irradiation spot 150 (the dimension in the direction perpendicular to the longitudinal direction) is set to the backside bead width. It can be seen that the longitudinal dimension affects the penetration welding speed.

  Based on the above knowledge, if the aspect ratio between the length in the longitudinal direction of the irradiation spot 150 by the semiconductor laser beam and the width in the direction perpendicular to the longitudinal direction is 4: 1, the penetration welding speed is 6 m / min. This can greatly improve the efficiency of the laser welding operation.

(Example 2)
This example is an example in which melt-run welding was performed on a plate-like body made of aluminum alloy A5182 and having a thickness of 1 mm based on the semiconductor laser welding method of Example 1. The contents of this example will be described with reference to Table 1.
As shown in Table 1, in this example, laser welding was performed with several welding conditions set, and the penetration welding speed at that time, the presence or absence of spatter and plasma plume, and the quality of the weld bead were examined. Yes.

Of each item in the table, the output (kW) is the laser output set by the semiconductor laser welding apparatus, the average energy density (kW / cm ² ) is the average energy density at the irradiation spot, L (mm) is the length of the irradiation spot in the longitudinal direction, W (mm) is the width of the irradiation spot, and the focal length (mm) is the focal length of the condenser lens used. The speed (m / min) is the maximum welding speed at which the irradiated semiconductor laser light can penetrate the workpiece.

In Table 1, the test data of this example is shown in test numbers 4-6, 10-13, and 16-20. In these test data, the focal length of the condenser lens is 40 mm or more and 250 mm or less, and the aspect ratio which is the ratio of the longitudinal direction in the irradiation spot to the direction perpendicular to the longitudinal direction exceeds 2: 1. It was obtained under preferable welding conditions in which the average energy density is in the range of 20: 1 or less and the average energy density is 30 kW / cm ² or more and less than 300 kW / cm ² .

As shown in the table, according to the welding conditions based on the above test numbers of the present example, a penetration welding speed of 2 m / min or more at which a welding operation can be efficiently performed is realized, and sputter and plasma plumes are realized. The weld bead which suppresses generation | occurrence | production and exhibits a favorable external appearance is obtained.
Other configurations and operational effects are the same as those in the first embodiment.

(Comparative Example 1)
This example is a comparative example in which semiconductor laser welding was performed based on Example 1 and under welding conditions deviating from the preferred range. The contents of this comparative example will be described using Table 1.
The test data of this example are shown in test numbers 1 to 3, 7 to 9, 14, 15, and 21 in Table 1.

As shown in the table, under the welding conditions of this example, the focal length of the condenser lens is 40 mm or more and 250 mm or less, and the average energy density at the irradiation spot is 30 kW / cm ² or more and less than 300 kW / cm ^2. At least one of them is not satisfied.

  In the welding conditions of test numbers 1 to 3, 8, 9, and 15, the average energy density at the irradiation spot formed on the workpiece surface is insufficient, and therefore the workpiece base material cannot be sufficiently melted (in the same table, In some cases) and the penetration melting rate is insufficient (the proper penetration melting rate is 2 m / min or more). Therefore, there is a high possibility that the welding operation cannot be performed under these welding conditions or the welding operation cannot be performed efficiently. In the table, problematic phenomena are marked with x.

Under the welding conditions of Test Nos. 7 and 14, the focal length is below the appropriate range, and the aspect ratio of the irradiation spot is 1. For this reason, in semiconductor laser welding under these welding conditions, spatter and plasma plume are generated, resulting in poor appearance of the weld bead.
In Test No. 21, the aspect ratio of the irradiation spot is 1, and the focal length is below the appropriate range, and the average energy density is excessive. Therefore, in the semiconductor laser welding under this welding condition, spatter and plasma plume are generated, and therefore the appearance of the weld bead is poor.

As described above, in the comparative example where the welding conditions deviate from the appropriate range, there is a high possibility that the welding operation cannot be performed efficiently, or the appearance of the weld bead becomes poor due to the occurrence of spatter, plasma plume, or the like.
Other configurations and operational effects are the same as those in the first embodiment.

FIG. 3 is an explanatory view showing a semiconductor laser welding apparatus in Example 1. FIG. 3 is an explanatory diagram showing an LD bar in the first embodiment. FIG. 3 is an explanatory diagram showing an LD stack in the first embodiment. Explanatory drawing which shows the energy distribution in the irradiation spot in Example 1 (focal length = 100 mm). Explanatory drawing which shows the energy distribution in the irradiation spot in Example 1 (focal length = 200 mm). The graph which shows the relationship between the welding speed about the workpiece | work which consists of AA5022 in Example 1, and a back surface bead width. The graph which shows the relationship between the welding speed about the workpiece | work which consists of AA6016 in Example 1, and a back surface bead width.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor laser welding apparatus 10 Light emission part 100 Light emission surface 101 Holding member 102 Assist gas nozzle 103 Welding base 11 Semiconductor laser element 12 LD bar 15 LD stack 150 Irradiation spot 20 Work 201 Work surface

Claims (4)

In a laser welding method of performing laser welding by irradiating a semiconductor laser beam emitted from a semiconductor laser element onto a workpiece surface, which is a workpiece surface made of aluminum or an aluminum alloy, through a condenser lens,
The semiconductor laser light is condensed using the condensing lens having a focal length of 40 mm or more and 250 mm or less to form a substantially rectangular shape, and the average energy density in the region is 30 kW / cm ^{2 to} 300 kW / An irradiation spot having an aspect ratio which is less than cm ² and whose ratio of the length in the longitudinal direction to the width in the direction perpendicular to the longitudinal direction is more than 2: 1 and not more than 20: 1. And forming on the workpiece surface,
In relative movement of the irradiation spot formation position along the longitudinal direction on the workpiece surface,
As a semiconductor laser welding apparatus for emitting the semiconductor laser light, a plurality of LD bars in which a plurality of semiconductor laser elements are arranged in a line are stacked in a direction substantially perpendicular to the arrangement direction of the semiconductor laser elements in the LD bar. A light emitting surface having a substantially rectangular shape made of an LD stack is provided, and the semiconductor laser light emitted from a plurality of light emitting surfaces is directly irradiated onto the workpiece surface without passing through an optical fiber. A laser welding method characterized in that the irradiation spot, which is a region having a substantially rectangular shape, is formed by utilizing the shape of the light emitting surface of the LD stack.   2. The laser welding method according to claim 1, wherein the wavelength of the semiconductor laser light is 700 nm or more and 1000 nm or less.   3. The laser welding method according to claim 1, wherein the aluminum alloy is any one of JIS1000 series, JIS3000 series, JIS5000 series, or JIS6000 series. 4. The laser welding method according to claim 1, wherein the average energy density in the irradiation spot is 50 kW / cm ² or more and 100 kW / cm ² or less.

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