Laser welding device

Abstract

During laser filler welding, a laser head 10 performs a scanning operation at a scanning speed based on a prescribed frequency so as to change, at a tip part of a filler wire WA, the emission position of a laser beam LB along an emission trajectory SD in a direction that intersects with the welding direction WD.

Description

Laser Welding Equipment

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

[0002] Patent Document 1 discloses a welding method in which metal plates are butt-joined by laser welding while a filler wire is added to the gap between the metal plates.

[0003] In Patent Document 1, a laser beam oscillates to cross a gap between metal plates and moves along the gap. As the laser beam moves, a wire supply unit operates to start supplying a filler wire to the gap from the front to the rear in the welding direction.

[0004] Japanese Patent Application Laid-Open No. 2022-077544

[0005] In the conventional invention, the laser beam is oscillated to span the gap between the metal plates in order to eliminate the gap between the metal plates. Although the laser oscillation width is disclosed, nothing is disclosed regarding the frequency at which the laser beam is oscillated. As a result, the filler wire may not be sufficiently irradiated with the laser beam, which may result in the filler wire not being melted smoothly.

[0006] The aspects of the present disclosure have been made in view of the above points, and an object of the present disclosure is to enable smooth melting of a filler wire in laser filler welding.

[0007] A first aspect is a laser welding apparatus comprising: a wire feeder that feeds a filler wire toward a workpiece; a laser head that emits laser light toward the tip of the filler wire to laser filler weld the workpiece; and a manipulator that moves the laser head along a predetermined welding direction, wherein the laser head has an emission position changing unit that performs a scanning operation to change the emission position of the laser light along an emission trajectory in a direction intersecting the welding direction; and a control unit that controls the operation of the emission position changing unit so that the scanning operation is performed at the tip of the filler wire at a scan speed based on a predetermined frequency during the laser filler welding.

[0008] In the first aspect, during laser filler welding, a scanning operation is performed at the tip of the filler wire along an emission locus in a direction intersecting the welding direction at a scanning speed based on a predetermined frequency.

[0009] This allows the filler wire to melt smoothly and mix evenly with the molten molten pool on the workpiece, resulting in a good weld bead with reduced welding defects.

[0010] In a second aspect, in the laser welding apparatus of the first aspect, the filler feed speed VW of the filler wire, the filler feed angle α, the beam diameter DOL of the laser light, and the minimum scan frequency FRQmin satisfy the condition FRQmin = VW · cos(α) / DOL, and the predetermined frequency is equal to or greater than the minimum scan frequency FRQmin.

[0011] In the second mode, the predetermined frequency is set to be equal to or higher than the minimum scan frequency FRQmin.

[0012] In a third aspect, in the laser welding device of the first or second aspect, in the scanning operation, the emission position of the laser light is changed along an emission locus that is perpendicular to the welding direction.

[0013] In the third aspect, by performing a scanning operation along an emission trajectory perpendicular to the welding direction, the filler wire after melting can be stirred in the molten pool of the workpiece.

[0014] In a fourth aspect, in the laser welding device of the first or second aspect, in the scanning operation, the emission position of the laser light is changed along a curved emission locus that protrudes in a direction opposite to the welding direction.

[0015] In the fourth aspect, by performing a scanning operation along a curved emission trajectory that protrudes in the direction opposite to the welding direction, a weld bead can be obtained in which the end portion in the direction opposite to the welding direction is curved.

[0016] In a fifth aspect, in the laser welding apparatus of the first or second aspect, the workpiece is made of a 6000 series or 7000 series aluminum alloy, and the filler wire is made of a 4000 series aluminum alloy.

[0017] In the fifth aspect, by appropriately setting the material of the workpiece and the material of the filler wire, it is possible to suppress the occurrence of defects such as weld cracks.

[0018] According to aspects of the present disclosure, the filler wire can be melted smoothly.

[0019] FIG. 1 is a schematic diagram of a laser welding apparatus according to the first embodiment. FIG. 2 is a side view illustrating the arrangement of a laser beam and a filler wire. FIG. 3 is a plan view illustrating the emission trajectory of the laser beam. FIG. 4 is an enlarged plan view of the tip of the filler wire. FIG. 5 is a graph illustrating a state in which the scan speed is changed linearly. FIG. 6 is a graph illustrating a state in which the scan speed is changed sinusoidally. FIG. 7 is a plan view illustrating the flow of molten filler wire. FIG. 8 is a side cross-sectional view illustrating the flow of molten filler wire. FIG. 9 is a plan view illustrating the emission trajectory of the laser beam in a modified example of the first embodiment. FIG. 10 is a plan view illustrating the emission trajectory of the laser beam in the second embodiment.

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present invention, its applications, or its uses.

[0021] First Embodiment As shown in FIG. 1 , a laser welding device 1 includes a laser oscillator 2 , a transmission fiber 3 , a manipulator 6 , a control unit 7 , a laser head 10 , and a wire feeder 25 .

[0022] The laser oscillator 2 oscillates a laser beam LB based on a command from the control unit 7. An incident end of a transmission fiber 3 is connected to the laser oscillator 2. An exit end of the transmission fiber 3 is connected to a laser head 10. The laser beam LB is transmitted from the laser oscillator 2 to the laser head 10 via the transmission fiber 3.

[0023] The wire feeder 25 has at least a pair of feed rollers 27 and a wire nozzle 28. The feed rollers 27 are rotated by a feed motor (not shown). The feed rollers 27 feed a filler wire WA for welding.

[0024] The wire nozzle 28 is supported by the laser head 10 via a support portion 29. The wire nozzle 28 guides the filler wire WA toward the welding point of the workpiece WK.

[0025] The manipulator 6 has a plurality of arms. The laser head 10 is attached to the tip of the arm of the manipulator 6. The manipulator 6 moves the laser head 10 relative to the workpiece WK based on a command from the control unit 7.

[0026] The control unit 7 controls the operations of the manipulator 6, the laser head 10, and the wire feeder 25. The control unit 7 also has a function of controlling the start and stop of output of the laser beam LB, the output intensity of the laser beam LB, etc., in addition to the movement speed of the laser head 10 caused by the manipulator 6. The control unit 7 controls the operation of an emission position change unit 15 of the laser head 10, which will be described later.

[0027] The laser head 10 emits a laser beam LB oscillated by the laser oscillator 2 toward a workpiece WK. The laser head 10 accommodates a collimator lens 11, a reflecting mirror 12, a condenser lens 13, and an emission position change unit 15 therein.

[0028] The collimator lens 11 collimates the laser light LB that has entered the laser head 10 via the transmission fiber 3 .

[0029] The reflecting mirror 12 reflects the laser beam LB collimated by the collimator lens 11 toward the condenser lens 13. The condenser lens 13 condenses the laser beam LB. The laser beam LB condensed by the condenser lens 13 enters the emission position changing unit 15.

[0030] The emission position changing unit 15 changes the emission position of the laser beam LB relative to the workpiece WK. The emission position changing unit 15 is configured by, for example, a galvanometer mirror. The laser beam LB, whose emission position has been changed by the emission position changing unit 15, is emitted toward the workpiece WK.

[0031] 2, the laser welding apparatus 1 performs laser filler welding while moving the laser beam LB and the filler wire WA in a predetermined welding direction WD. The welding direction WD indicates the direction of movement of the laser head 10 when the workpiece WK is fixed. In the drawing, the laser beam LB is drawn to be irradiated perpendicularly to the workpiece WK, but the laser beam LB may also be irradiated obliquely to the workpiece WK.

[0032] In laser filler welding, a filler wire WA is fed to a workpiece WK. In Fig. 2, the filler feed direction is FD and the filler feed angle is α. A laser beam LB is emitted to a portion where a tip end WT of the filler wire WA contacts the workpiece WK or in the vicinity thereof.

[0033] 3, the emission position changing unit 15 of the laser head 10 performs a scanning operation to change the emission position of the laser beam LB along an emission locus SD in a direction intersecting the welding direction WD. In the example shown in FIG. 3, the scanning operation is performed so as to change the emission position of the laser beam LB along a straight-line locus SD1, which is the emission locus SD perpendicular to the welding direction WD.

[0034] During laser filler welding, a scanning operation is performed on the tip WT of the filler wire WA at a scanning speed based on a predetermined frequency.

[0035] In this way, by performing a scanning operation near the tip WT of the filler wire WA using a preset emission trajectory and scanning speed, the filler wire WA can be smoothly melted. Furthermore, the melted filler wire WA can be uniformly mixed into the molten pool of the workpiece WK, resulting in a good weld bead with reduced welding defects.

[0036] Here, it is preferable that the frequency FRQ during the scanning operation is set to be equal to or higher than the minimum scanning frequency FRQmin, which will be described later.

[0037] The linear trajectory SD1 is a linear trajectory obtained when the laser beam LB is moved back and forth at a predetermined width and frequency in a direction perpendicular to the welding direction WD. Such a scanning operation is effective when the beam diameter of the laser beam LB is sufficiently smaller than the filler diameter of the filler wire WA.

[0038] In the example shown in Figure 4, during laser filler welding, a scanning operation is performed in a range where at least a portion of the laser light LB overlaps a portion of the filler wire WA, that is, in a range where the laser light LB is not spaced further away from the filler wire WA in a direction perpendicular to the welding direction WD.

[0039] Although not shown, during scanning, the scanning speed of the reciprocating movement is kept constant within the scanning range. However, at both ends of the scanning range, for example, at an upper point Q and a lower point P described below, only the scanning direction is changed. The scanning frequency may be set, for example, in the range of 10 Hz to 10 kHz. The scanning speed may be changed depending on the beam position.

[0040] Specifically, the scan speed may be changed linearly according to the beam position, as shown in Fig. 5. In Fig. 5, OS is the scan center. A corresponds to the upper point Q in Fig. 4, which will be described later. B corresponds to the lower point P in Fig. 4, which will be described later.

[0041] Also, as shown in FIG. 6, the scanning speed may be changed sinusoidally in accordance with the beam position.

[0042] 4, the laser beam LB scans along a linear trajectory SD1 perpendicular to the weld line WL with a predetermined scan width SW and a predetermined scan frequency FRQ. The scan center OS during the scanning operation is always located on the weld line WL.

[0043] 4, MS denotes a melt surface at the tip portion WT of the filler wire WA. Specifically, the melt surface MS is a surface formed by melting the tip portion WT of the filler wire WA by irradiating the filler wire WA with laser light LB.

[0044] The melt length ML is the projected length of the melt surface MS of the filler wire WA melted by the laser beam LB in the direction of the weld line WL. In other words, the melt length ML is the melt length of the filler wire WA during half the scan period T.

[0045] In order to smoothly melt the filler wire WA with the laser light LB, it is necessary to melt the entire length (projected length VL) of the filler wire WA fed during a predetermined scanning period. The predetermined scanning period is, for example, a scanning period (half the scanning period T) during which the beam center O of the laser light LB moves from a lower point P to an upper point Q of the filler wire WA.

[0046] As described above, the melt length ML is always equal to the projected length VL. Note that the maximum value of the projected length VL of the fed filler wire WA corresponds to half the beam diameter DOL of the laser light LB.

[0047] In other words, it is necessary to melt all of the filler wire WA over a projection length VL equivalent to half the beam diameter DOL in half the scan period T. The relationship between the melting length ML, the projection length VL, and the beam diameter DOL is expressed by the following equation (1).

[0048] ML=VL≦DOL / 2 (1) Here, if the filler feed speed VW is known, the projected length VL and the projected speed VWL of the filler wire WA in the direction of the welding line WL can be calculated using the following equations (2) and (3).

[0049] VL=(T / 2)·VWL (2) VWL=VW·cos(α) (3) Here, by substituting equations (2) and (3) into equation (1) and rearranging, the following equation (4) can be obtained.

[0050] T≦DOL / [VW·cos(α)] (4) Equation (4) indicates the maximum value of the scan period T for smoothly melting the filler wire WA. Since the scan frequency FRQ is the reciprocal of the scan period T, the minimum scan frequency FRQmin when scanning with the laser light LB can be calculated by the following equation (5).

[0051] FRQmin=VW·cos(α) / DOL (5) From equation (5), it can be seen that when the filler feed angle α is reduced, the minimum frequency FRQmin needs to be increased.

[0052] <Calculation Example of Minimum Scan Frequency> An example of calculating the minimum scan frequency FRQmin will be described below. In the following calculation, the filler feed speed VW is set to 3 m / min (= 50 mm / s), the beam diameter DOL is set to 0.7 mm, and the filler feed angle α is set to 30° and the filler feed angle α is set to 45°.

[0053] When the filler feeding angle α=30°, the following equation (5) is obtained: FRQmin=VW·cos(α) / DOL=50·cos(30) / 0.7=62 Hz.

[0054] On the other hand, when the filler feeding angle α=45°, the following equation (5) is obtained: FRQmin=VW·cos(α) / DOL=50·cos(45) / 0.7=51 Hz.

[0055] As described above, it can be seen that the smaller the filler feed angle α, the higher the minimum scan frequency FRQmin. Note that the numerical values ​​used in the above calculation example are merely examples and are not intended to be limiting.

[0056] 7 and 8, a keyhole KH is formed in the molten pool WP by irradiating the workpiece WK with a laser beam LB. In actual laser welding, the size of the keyhole KH is approximately the same as the beam diameter DOL of the laser beam LB.

[0057] 7 shows a state in which the laser beam LB is moved from the bottom to the top along a linear trajectory SD1. Here, a molten metal flow FL1 indicates the flow of molten metal in the forward direction of the scan of the laser beam LB, and a molten metal flow FL2 indicates the flow of molten metal in the backward direction of the scan. During laser filler welding, the speeds or directions of the molten metal flows FL1 and FL2 are constantly changing.

[0058] Here, when the laser beam LB is not scanned, the molten metal flows FL1 and FL2 are substantially uniform with respect to the welding line WL.

[0059] On the other hand, when the laser beam LB is scanned, the molten metal flows FL1 and FL2 are not uniform with respect to the welding line WL. In the example shown in Fig. 7, the molten metal flow FL1 in the forward direction of the laser beam LB is more active than the molten metal flow FL2 in the backward direction of the scan.

[0060] As shown in FIG. 8, a keyhole KH is formed in the molten pool WP formed by the laser beam LB, so that molten metal flows FL3 and FL4 are formed in the thickness direction of the workpiece WK.

[0061] Here, even when the laser light LB is not scanned, the hot water flows FL3 and FL4 exist, but by scanning the laser light LB, the hot water flows FL3 and FL4 become more active, which is the same as the explanation of the hot water flows FL1 and FL2 described above.

[0062] In this way, by scanning the laser beam LB, the molten metal flows FL1 to FL4 become more active in the vicinity of the keyhole KH of the molten pool WP.

[0063] When laser filler welding is performed on a filler wire WA and a workpiece WK having the same composition, for example, a steel material, the temperature of the filler wire WA immediately after melting is usually different from that of the weld pool WP, and the average temperature of the weld pool WP is usually low in many cases. Here, when the molten metal flow in the weld pool WP is active, as in this embodiment, the high-temperature part of the filler wire WA immediately after melting is more likely to mix with the surrounding lower-temperature parts, reducing unevenness in the temperature distribution in the weld pool WP. As the molten metal solidifies, a more uniform structure is obtained, resulting in a good weld bead.

[0064] Furthermore, in laser filler welding of filler wire WA and workpiece WK with different compositions, such as aluminum alloys, active molten metal flow in the molten pool WP allows the composition of the filler wire WA melted into the molten pool WP to be more uniformly dispersed throughout the molten pool WP. This not only reduces unevenness in temperature distribution, but also in the composition of the molten pool WP, resulting in a more uniform structure when the molten metal solidifies, resulting in a good weld bead. Furthermore, defects such as weld cracks can be suppressed.

[0065] Here, it is preferable that the workpiece WK is made of a 6000 series or 7000 series aluminum alloy, and the filler wire WA is made of a 4000 series aluminum alloy.

[0066] <<Modification of First Embodiment>> Hereinafter, the same parts as those in the first embodiment will be denoted by the same reference numerals, and only the differences will be described.

[0067] 9, in this modification, the scan width SW of the laser beam LB during the scanning operation is set between a scan width SW1 narrower than the filler diameter DOF and a scan width SW2 wider than the filler diameter DOF. Here, the scan width SW is calculated using the following equation (6) in relation to the beam diameter DOL.

[0068] DOF / 2-DOL / 4≦SW≦DOF / 2+DOL / 4 (6) Here, the upper point Q corresponds to the tip of the filler wire WA above the melting surface MS, but the upper point Q1 is located on the melting surface MS but is shorter than ¼ of the beam diameter DOL in the direction of the welding line WL than the upper point Q. On the other hand, the upper point Q2 is located on the circle of the circular beam and longer than ¼ of the beam diameter DOL in the direction of the welding line WL than the upper point Q.

[0069] The minimum scan frequency FRQmin is set based on the above-mentioned equation (5).

[0070] The reason why the scan width SW of the laser beam LB is set between a scan width SW1 narrower than the filler diameter DOF and a scan width SW2 wider than the filler diameter DOF will be explained below. Note that in the following explanation, only the upper point Q will be explained, and the explanation of the lower point P will be omitted.

[0071] When scanning with a scan width SW1, the laser beam LB scans from below upward, and when it reaches the upper point Q1, it is a distance of ¼ of the beam diameter DOL until it reaches the upper point Q of the filler wire WA. However, at this distance, there is also heat conduction from the part of the filler wire WA that has already melted, and the laser beam LB can sufficiently melt the remaining part of the melt surface MS.

[0072] In addition, when scanning with the scan width SW1, if the filler diameter DOF and the beam diameter DOL are close, the same effect can be obtained even if the vertical distance between the upper point Q1 and the welding line WL is, for example, 1 / 4 of the filler diameter DOF.

[0073] On the other hand, when scanning with the scan width SW2, the laser beam LB continues scanning a distance of ¼ of the beam diameter DOL after reaching the upper point Q. During this period, the laser beam LB inputs energy near the upper point Q2, and the filler wire WA melted in this portion can be dispersed more uniformly in the molten pool.

[0074] Here, when the feed speed of the filler wire WA is slow, it is preferable to perform the scanning operation with the scan width SW1, whereas when the feed speed of the filler wire WA is fast, it is preferable to perform the scanning operation with the scan width SW2.

[0075] Second Embodiment As shown in FIG. 10, the emission position changing unit 15 of the laser head 10 performs a scanning operation to change the emission position of the laser beam LB along an emission locus SD in a direction intersecting the welding direction WD.

[0076] In the example shown in FIG. 10, a scanning operation is performed so as to change the emission position of the laser beam LB along an arcuate trajectory SD2, which is a curved emission trajectory SD that protrudes in the direction opposite to the welding direction WD.

[0077] This makes it possible to obtain a weld bead whose end in the opposite direction to the welding direction WD is curved.

[0078] 10, the scan center OS and the center of curvature of the arc trajectory SD2 are positioned on the welding line WL. The radius of curvature of the arc trajectory SD2 may be set depending on the conditions of the laser beam LB (e.g., beam power, beam diameter, etc.) and the conditions of the filler wire WA (e.g., filler diameter, material, etc.).

[0079] As described above, the present invention has the highly practical effect of being able to smoothly melt the filler wire, and is therefore extremely useful and has high industrial applicability.

[0080] REFERENCE SIGNS LIST 1 Laser welding device 6 Manipulator 7 Control unit 10 Laser head 15 Emission position change unit 25 Wire feed unit LB Laser light SD Emission trajectory SD1 Linear trajectory SD2 Circular trajectory WA Filler wire WD Welding direction WK Workpiece WT Tip

Claims

1. A laser welding device comprising: a wire feeder that feeds a filler wire toward a workpiece; a laser head that emits laser light toward the tip of the filler wire to laser filler weld the workpiece; and a manipulator that moves the laser head along a predetermined welding direction, wherein the laser head has an emission position changing unit that performs a scanning operation to change the emission position of the laser light along an emission locus in a direction intersecting the welding direction; and a control unit that controls the operation of the emission position changing unit so that the scanning operation is performed at the tip of the filler wire at a scan speed based on a predetermined frequency during the laser filler welding.

2. A laser welding device according to claim 1, wherein the filler wire filler feed speed VW, filler feed angle α, laser beam diameter DOL, and minimum scan frequency FRQmin satisfy the condition FRQmin = VW · cos(α) / DOL, and the predetermined frequency is equal to or greater than the minimum scan frequency FRQmin.

3. A laser welding device according to claim 1 or 2, wherein, in the scanning operation, the emission position of the laser beam is changed along an emission locus that is perpendicular to the welding direction.

4. A laser welding device according to claim 1 or 2, wherein, in the scanning operation, the emission position of the laser beam is changed along a curved emission locus that projects in a direction opposite to the welding direction.

5. A laser welding device according to claim 1 or 2, wherein the workpiece is made of a 6000 series or 7000 series aluminum alloy, and the filler wire is made of a 4000 series aluminum alloy.

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