Laser processing method

Abstract

The laser processing method includes the following steps: moving the workpiece relative to a plurality of laser spots including the first spot, the second spot, and the third spot in such a manner that the linearly arranged first spot, second spot, and third spot sequentially pass through the processing object portion of the workpiece, thereby processing the workpiece. With respect to the total amount of the energy of the laser at the first spot, the second spot, and the third spot, the ratio of the energy at the first spot is 20% or more and 30% or less, the ratio of the energy at the second spot is 20% or more and 30% or less, and the ratio of the energy at the third spot is 45% or more and 55% or less.

Description

Technical Field

[0001] The present disclosure relates to a laser processing method. Background Art

[0002] It is known to process a workpiece such as metal using a laser spot formed by condensing a laser.

[0003] Patent Document 1 discloses that: three condensing spots are formed from the laser from one optical fiber, and these three condensing spots are used for welding a metal material (workpiece). In addition, Patent Document 1 describes the following: in the welding of a metal material, in order to suppress the rapid heating caused by the laser spot and the generation of defects caused by cooling, preheating is performed by the foremost condensing spot among the three condensing spots, main processing is performed by the next condensing spot, and slow cooling is performed by the last condensing spot.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Laid-Open No. 2000-271773 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] However, in a laser processing apparatus such as a laser welding apparatus used in an ironmaking production line or the like, it is desired to increase the processing speed while maintaining the processing quality. However, in processing using a laser spot, it is difficult to increase the processing speed while maintaining the processing quality. For example, if the energy density at the laser spot is increased in order to increase the processing speed, a small and deep key hole is formed in the workpiece. In this case, in the workpiece, the distance between the key hole and the solid-liquid interface becomes narrow, and it is easy for metal vapor to be ejected suddenly from the narrow molten pool, so it is considered that spattering (i.e., reduction in processing quality) of the molten metal is likely to occur.

[0009] In view of the above circumstances, an object of at least one embodiment of the present invention is to provide a laser processing method capable of increasing the processing speed while suppressing a reduction in processing quality.

[0010] Means for Solving the Problems

[0011] The laser processing method according to at least one embodiment of the present invention includes the following steps:

[0012] The workpiece is moved relative to a plurality of laser spots including the first spot, the second spot, and the third spot so that the first spot, the second spot, and the third spot arranged in a straight line sequentially pass through the processing target portion of the workpiece, thereby processing the workpiece.

[0013] With respect to the total amount of the energy of the laser at the first light spot, the second light spot, and the third light spot,

[0014] The ratio of the energy at the first light spot is 20% or more and 30% or less,

[0015] The ratio of the energy at the second light spot is 20% or more and 30% or less,

[0016] The ratio of the energy at the third light spot is 45% or more and 55% or less.

[0017] Advantageous Effects of Invention

[0018] According to at least one embodiment of the present invention, there is provided a laser processing method capable of improving the processing speed while suppressing a decrease in processing quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 FIG. is a schematic diagram showing an example of a laser processing apparatus for implementing a laser processing method according to several embodiments.

[0020] Figure 2 FIG. is a schematic view of a processing target portion of a workpiece as viewed from the irradiation direction of the laser.

[0021] Figure 3A FIG. is a schematic view of a processing target portion of a workpiece during the implementation of a laser processing method according to an embodiment.

[0022] Figure 3B FIG. is a schematic view of a processing target portion of a workpiece during the implementation of a laser processing method according to an embodiment.

[0023] Figure 4 FIG. is a schematic diagram showing an example of a laser processing apparatus for implementing a laser processing method according to several embodiments.

[0024] Figure 5 FIG. is a schematic diagram showing an example of a laser processing apparatus for implementing a laser processing method according to several embodiments.

[0025] Figure 6 FIG. is a schematic diagram showing an example of a laser processing apparatus for implementing a laser processing method according to several embodiments. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] Hereinafter, several embodiments of the present invention will be described with reference to the drawings. Note that the dimensions, materials, shapes, relative arrangements, etc. of the constituent elements described as embodiments or shown in the drawings are not intended to limit the scope of the present invention thereto, but are merely illustrative examples.

[0027] (Structure of Laser Processing Device)

[0028] First, a laser processing device for implementing several laser processing methods will be described. Figure 1 And Figures 4 - 6 Figs. are schematic diagrams showing an example of a laser processing device for implementing the laser processing methods of several embodiments. As shown in this figure, a laser processing device 1 of one embodiment includes a laser oscillator 2, an optical fiber 4, a laser irradiation unit 6, a collimating optical system 8, and a condensing optical system 10. The laser irradiation unit 6, the collimating optical system 8, and the condensing optical system 10 constitute a processing head, which is housed in a housing (not shown) and supported by the housing.

[0029] The laser oscillator 2 can also be, for example, a fiber laser oscillator that uses the optical fiber 4 as a medium. In the case of a fiber laser oscillator, laser with a wavelength of 1070 nm to 1080 nm can be obtained. The laser generated by the laser oscillator 2 is transmitted to the optical fiber 4. It should be noted that the laser oscillator 2 is not limited to a fiber laser. In several embodiments, the laser oscillator 2 can also be, for example, a CO2 laser oscillator or a YAG laser oscillator, etc.

[0030] The optical fiber 4 is connected to the laser oscillator 2 on one end side and to the laser irradiation unit 6 on the other end side. The optical fiber 4 is configured to transmit laser from the laser oscillator 2 to the laser irradiation unit 6.

[0031] The laser irradiation unit 6 is configured to irradiate the workpiece 100 with the laser from the optical fiber 4. The collimating optical system 8 is configured to collimate the laser irradiated from the laser irradiation unit 6 in a divergent angle manner, that is, to form the parallel laser. The collimating optical system 8 can include a collimating lens. The condensing optical system 10 is configured to condense the laser (parallel laser) that has passed through the collimating optical system 8. The condensing optical system 10 can include a condensing lens.

[0032] The laser processing device 1 is configured to process the workpiece 100 (such as welding, etc.) by irradiating the processing target portion 102 of the workpiece 100 with the laser having a high energy density condensed by the condensing optical system 10. When processing the workpiece 100, the processing position (i.e., the laser irradiation position) of the workpiece 100 formed by the laser irradiation from the laser processing head is moved by relatively moving the workpiece 100 relative to the laser processing head, thereby performing the processing. The workpiece 100 can be a metal material such as an alloy.

[0033] The laser processing device 1 is configured to form a plurality of laser spots (the condensed spots of the laser formed by the condensing optical system 10) including a first spot P1, a second spot P2, and a third spot P3 arranged in a straight line. As Figure 1 AndFigures 4 - 6 As shown, the laser processing apparatus 1 can be configured to form three laser spots P1 to P3 (see Figure 2 ). It should be noted that Figure 2 is a schematic view of the processing target portion 102 of the workpiece 100 as viewed from the direction in which the laser is irradiated by the laser irradiation unit 6.

[0034] In Figure 1 , Figure 4 and Figure 5 shown in the exemplary embodiment, the laser processing apparatus 1 includes a laser branching unit 12 for branching the laser irradiated from one laser irradiation unit 6 into three beams. Figure 1 , Figure 4 and Figure 5 The laser branching unit 12 shown is provided between the collimating optical system 8 and the condensing optical system 10, and is configured to branch the parallel laser from the collimating optical system 8 into three beams and guide it to the condensing optical system 10.

[0035] In Figure 1 shown in the exemplary embodiment, the laser branching unit 12 includes two inclined prisms 14A and 14B that are spaced apart from each other in the cross-section of the laser from the collimating optical system 8. The positions of the two inclined prisms 14A and 14B in the cross-section of the laser can be adjusted. In this case, the ratio of the energies of the lasers at the three laser spots P1 to P3 (energy distribution) is determined by the insertion amounts of the two inclined prisms 14A and 14B into the cross-section of the laser. In addition, the distance between the spot centers of the three laser spots P1 to P3 is determined by the wedge angle θ of the two inclined prisms 14A and 14B (see Figure 1 ). It should be noted that in Figure 1 , the wedge angle θ of the inclined prisms 14A and 14B is an acute angle, but the wedge angle θ of the inclined prisms 14A and 14B can also be an obtuse angle.

[0036] The diameters (spot diameters) φ1 to φ3 of the laser spots P1 to P3 are determined by the core diameter φ of the optical fiber 4 fiber and the magnification M of the optical system. Here, the magnification M of the optical system is the ratio of the focal length (F f ) of the condensing optical system 10 to the focal length (F c ) of the collimating optical system 8, M = F f / F c . That is, the above-mentioned spot diameter can be adjusted by changing the core diameter φ of the optical fiber fiber , the focal length (F f ) of the condensing optical system 10, the focal length (F c ) of the collimating optical system 8, or the magnification M of the optical system.

[0037] In Figure 4In the illustrated embodiment, the laser branch portion 12 includes a polygon prism 15 disposed in the region through which the laser from the collimation optical system 8 passes. The position of the polygon prism 15 within the cross-section of the laser can be adjusted. In this case, the ratio of the energies of the lasers of the three laser spots P1 to P3 (energy distribution) is determined by the position of the polygon prism 15 within the cross-section of the laser. Further, the distance between the spot centers of the three laser spots P1 to P3 is determined by the wedge angle of the polygon prism 15.

[0038] In Figure 5 the illustrated embodiment, the laser branch portion 12 includes mirrors 16A to 16D arranged to reflect at least a part of the laser from the collimation optical system 8. It should be noted that, Figure 5 the mirror 16C among them is a semi-reflecting mirror that reflects a part of the laser and transmits a part of the laser. Further, the condensing optical system 10 includes three condensing lenses for condensing the three laser beams branched by the mirrors 16A to 16D, respectively. In this case, the ratio of the energies of the lasers of the three laser spots P1 to P3 (energy distribution) and the distance between the spot centers of the three laser spots P1 to P3 are determined by the installation positions and installation angles of the mirrors 16A to 16D.

[0039] In Figure 6 the illustrated embodiment, three laser spots P1 to P3 are formed by the lasers irradiated from the three laser irradiation portions 6. That is, Figure 6 the illustrated laser processing apparatus 1 includes three laser oscillators 2, and the lasers oscillated from these laser oscillators 2 are respectively transmitted through the optical fibers 4 and irradiated from the laser irradiation portions 6. The three laser beams respectively irradiated from the three laser irradiation portions 6 respectively become parallel light by passing through the collimation optical system 8 (collimation lens), and are condensed by the condensing optical system 10 (condensing lens) to form three laser spots P1 to P3. It should be noted that the collimation optical system 8 may also include three collimation lenses respectively corresponding to the three laser irradiation portions 6. Further, the condensing optical system 10 may also include three condensing lenses respectively corresponding to the three laser irradiation portions 6. In Figure 6 the case of the illustrated embodiment, the ratio of the energies of the lasers of the three laser spots P1 to P3 (energy distribution) is determined by the outputs of the three laser oscillators 2. Further, the distance between the spot centers of the three laser spots P1 to P3 is determined by the configurations of the laser irradiation portions 6 and the condensing optical system 10.

[0040] (Laser Processing Method)

[0041] Next, a laser processing method according to several embodiments will be described. The laser processing method according to several embodiments can be executed by the above-described laser processing apparatus 1, for example. In addition, the laser processing method according to several embodiments can also be executed using other laser processing apparatuses.

[0042] In several embodiments, the workpiece 100 is moved relative to the plurality of laser spots P1 to P3 such that the first spot P1, the second spot P2, and the third spot P3 arranged in a straight line sequentially pass through the processing target portion 102 of the workpiece 100, thereby processing the workpiece 100 (processing step). Here, with respect to the total amount (100%) of the energy of the laser at the first spot P1, the second spot P2, and the third spot P3, the ratio E1 of the energy at the first spot P1 is 20% or more and 30% or less, the ratio E2 of the energy at the second spot P2 is 20% or more and 30% or less, and the ratio E3 of the energy at the third spot P3 is 45% or more and 55% or less.

[0043] It should be noted that before processing the workpiece 100 as described above, the laser processing apparatus 1 is adjusted in advance so that the ratio of the energy at the first spot P1 to the third spot P3 falls within the above range.

[0044] Here, Figure 3A and Figure 3B are schematic views of the processing target portion 102 of the workpiece 100 during the execution of the laser processing method according to the above-described embodiment. Figure 3A is a schematic view of the processing target portion 102 of the workpiece 100 as viewed from the direction in which the laser is irradiated by the laser irradiation unit 6, Figure 3B is a schematic cross-sectional view of the workpiece 100.

[0045] Generally, in processing using a laser spot, it is difficult to increase the processing speed while maintaining the processing quality. For example, if the energy density at the laser spot is increased in order to increase the processing speed, small and deep keyholes are formed in the workpiece. In this case, in the workpiece, the distance between the keyhole and the solid-liquid interface becomes narrow, and metal vapor is likely to be ejected suddenly from the narrow molten pool, so it is considered that spattering (i.e., a decrease in processing quality) of the molten metal is likely to occur.

[0046] Regarding this point, in the above-described embodiment, the energy density at the first spot P1 to the third spot P3 is small at the first spot P1 and the second spot P2, and large at the third spot P3. Therefore, as Figure 3A and Figure 3BAs shown, first, the laser of the first light spot P1 is irradiated onto the processing target portion 102, whereby a shallow keyhole K1 and a molten pool 101 are formed in the processing target portion 102 of the workpiece 100. It should be noted that when the keyhole is shallow, sputtering is not likely to occur. Next, the laser of the second light spot P2 is irradiated onto the molten pool 101 formed by the first light spot P1. While forming a shallow keyhole K2, the distance between the keyhole K2 and the solid-liquid interface 103 (the interface between the molten pool 101 and the base material) is enlarged. That is, as Figure 3A shown, compared with the distance WI between the side of the keyhole K1 formed by the first light spot P1 (the side in the direction orthogonal to the processing direction) and the solid-liquid interface 103, the distance W2 between the side of the keyhole K2 formed by the second light spot P2 and the solid-liquid interface 103 becomes larger. Next, the laser of the third light spot P3 with a high energy density is irradiated onto the relatively shallow and wide molten pool 101 formed as described above to form a deeper keyhole K3. It should be noted that the distance W3 between the side of the keyhole K3 formed by the third light spot P3 and the solid-liquid interface 103 is considered to be equal to or greater than the above-mentioned distance W2.

[0047] In this way, in the above-described embodiment, in a state where a shallow and wide molten pool 101 is formed on the processing target portion 102 of the workpiece 100 by using the first light spot P1 and the second light spot P2 with a relatively small energy density, a deep keyhole K3 is formed by using the third light spot P3 with a relatively large energy density. Therefore, the distance between the deep keyhole K3 and the solid-liquid interface 103 can be ensured to be relatively large. That is, the occurrence of sputtering when irradiating the laser light spot (the third light spot P3) with a large energy density onto the workpiece 100 can be effectively suppressed. Therefore, according to the above-described embodiment, the processing speed can be increased while suppressing the reduction of the processing quality.

[0048] In several embodiments, the energy ratio E1 at the first light spot P1 is greater than the energy ratio E2 at the second light spot P2.

[0049] In the above-described embodiment, for the energy density at the first light spot P1 and the second light spot P2, it is larger at the first light spot P1 and smaller at the second light spot P2. Therefore, the first light spot P1 with a relatively large energy density first passes through the unheated processing target portion (the workpiece), so that a keyhole and a molten pool can be quickly formed in the processing target portion 102 of the workpiece 100. Therefore, the processing speed can be increased more effectively.

[0050] In several embodiments, the diameter (spot diameter) φ1 of the first light spot P1, the diameter φ2 of the second light spot P2, and the diameter φ3 of the third light spot P3 are each 0.25 mm or more and 0.4 mm or less.

[0051] In the above-described embodiment, the diameters φ1 to φ3 of the first light spot P1 to the third light spot P3 are each 0.25 mm or more. Therefore, the workpiece 100 can be effectively heated by each of the laser light spots P1 to P3, and it is easy to obtain the melting amount of the base material required for processing the workpiece 100. Further, in the above-described embodiment, the diameters φ1 to φ3 of the first light spot P1 to the third light spot P3 are each 0.4 mm or less. Therefore, an increase in sputtering due to a large spot diameter can be effectively suppressed. Accordingly, according to the above-described embodiment, it is easy to simultaneously achieve suppression of a decrease in processing quality and an increase in processing speed.

[0052] In several embodiments, the distance L between the centers of two adjacent laser light spots among the plurality of laser light spots P1 to P3 and the average spot diameter φ of the two adjacent laser light spots described above avg The ratio L / φ avg is 2.5 or more and 3.5 or less. That is, the distance L between the centers of the adjacent first light spot P1 and the second light spot P2 12 (see Figure 2 ) and the average spot diameter φ of the first light spot P1 and the second light spot P2 avg (=(φ1 + φ2) / 2) The ratio (2×L 12 ) / (φ1 + φ2) is 2.5 or more and 3.5 or less. Alternatively, the distance L between the centers of the adjacent second light spot P2 and the third light spot P3 23 (see Figure 2 ) and the average spot diameter φ of the second light spot P2 and the third light spot P3 avg (=(φ2 + φ3) / 2) The ratio (2×L 23 ) / (φ2 + φ3) is 2.5 or more and 3.5 or less.

[0053] In the above-described embodiment, the above ratio L / φ avg is 2.5 or more. With respect to the average spot diameter φ of two adjacent laser light spots, avg the distance L between the spot centers is relatively large to some extent. Therefore, it is possible to suppress the coalescence of the keyholes formed by two adjacent laser light spots close to each other into one keyhole that is larger in appearance. Therefore, the occurrence of sputtering can be effectively suppressed. Further, in the above-described embodiment, the above ratio L / φ avg is 3.5 or less. With respect to the average spot diameter φ of two adjacent laser light spots, avg, the distance L between the centers of the light spots will not be too large. Therefore, it is possible to suppress the re-solidification caused by the cooling of the molten metal that may occur during the period from when one of the two adjacent laser light spots (the first light spot P1 or the second light spot P2) passes through the processing target portion 102 of the workpiece 100 until the other laser light spot (the second light spot P2 or the third light spot P3) arrives, and it is possible to effectively increase the molten liquid around the keyhole formed by the laser light spot. As a result, it is possible to effectively suppress the occurrence of sputtering when forming a deep keyhole at the third light spot P3.

[0054] In several embodiments, the workpiece 100 includes a pair of plates, and in the above processing step, butt welding of the pair of plates is performed.

[0055] According to the method of the above embodiment, in the butt welding of a pair of plates using multiple laser light spots P1 to P3, it is possible to improve the processing speed while suppressing the deterioration of the processing quality.

[0056] It should be noted that in the case of butt welding between plates, if the diameter of the laser light spot is less than 0.25 mm, it is difficult to obtain a sufficient amount of base material melting that fully satisfies the gap degree between the plates. Therefore, in the case of butt welding between plates, by making the diameters φ1 to φ3 of the first light spot P1 to the third light spot P3 0.25 mm or more, it is easy to sufficiently obtain the amount of base material melting. As a result, it is possible to effectively suppress the deterioration of the welding quality.

[0057] In several embodiments, the distance L between the centers of the first light spot P1 and the third light spot P3 13 (see Figure 2 ) is less than the thickness of the processing target portion 102 of the workpiece 100 (for example, the thickness of the above-mentioned plate).

[0058] For example, when the diameters φ1 to φ3 of the respective laser light spots P1 to P3 are 0.25 mm and the above ratio L / φ avg is 2.5, the thickness of the processing target portion 102 of the workpiece 100 is 1.2 mm or more. Or, when the diameters φ1 to φ3 of the respective laser light spots P1 to P3 are 0.4 mm and the above ratio L / φ avg is 3.5, the thickness of the processing target portion 102 of the workpiece 100 is 2.8 mm or more.

[0059] According to the above embodiment, in the processing using multiple laser light spots P1 to P3 formed in a relatively small area whose length is shorter than the thickness of the processing target portion 102 of the workpiece 100, as described above, it is possible to improve the processing speed while suppressing the deterioration of the processing quality.

[0060] In several embodiments, in the above processing steps, at the first light spot P1 and the second light spot P2, keyholes K1 and K2 having a depth smaller than the thickness of the workpiece 100 are formed on the workpiece 100, and at the third light spot P3, a keyhole K3 penetrating the workpiece 100 is formed on the workpiece 100. That is, the above processing steps are performed at a laser output and a processing speed capable of forming such keyholes K1 to K3.

[0061] According to the above embodiment, at the first light spot P1 and the second light spot P2, keyholes K1 and K2 having a depth smaller than the thickness of the workpiece 100 are formed on the workpiece 100, and at the third light spot P3, a keyhole K3 penetrating the workpiece 100 is formed. Therefore, in processing including a process of forming a keyhole penetrating the workpiece 100 (for example, through-welding such as butt welding of the above-mentioned plates to each other), as described above, the processing speed can be increased while suppressing a decrease in processing quality.

[0062] Example

[0063] Using Figure 1 the laser processing apparatus 1 shown in the figure, under the test conditions of Test Examples 1 to 9 shown in Table 1, butt welding of plates having a thickness of 6 mm was performed according to the above processing steps. That is, the first light spot P1, the second light spot P2, and the third light spot P3 arranged in a straight line were formed by the laser processing apparatus 1, and the plates were relatively moved with respect to the plurality of laser light spots P1 to P3 so that the laser light spots P1 to P3 passed through the processing target portion of the workpiece (plate) in sequence, thereby performing butt welding of the plates to each other. The definitions of the test conditions shown in Table 1 are as follows.

[0064] Spot diameter φ (mm): The diameters of the first light spot to the third light spot (φ = φ1 = φ2 = φ3)

[0065] Distance between spots L (mm): The distance L between the first light spot and the second light spot 12 and the distance L between the second light spot and the third light spot 23 (L = L 12 = L 23 )

[0066] Beam energy ratio E1 to E3 (%): The ratio of the energy at each of the first light spot to the third light spot to the total energy of the laser at the first light spot to the third light spot (100%)

[0067] Welding speed (m / min): The relative speed of the plate with respect to the laser light spots P1 to P3 in the welding direction

[0068] In addition, after the above-mentioned welding, the welding quality (processing quality) of each test example was evaluated. The evaluation indices for the welding quality are as follows. The evaluation results are shown in Tables 1 to 3. (It should be noted that the test conditions of each test example shown in Tables 2 and 3 are the same as those recorded in Table 1.)

[0069] Sputtering: By visual observation, it is evaluated as "good" when the amount of sputtering is small, and as "bad" when the amount of sputtering is large.

[0070] Weld seam (for Test Examples 4, 5, 8, and 9; refer to Tables 2 to 3): It is evaluated as "good" when no underfill occurs on one side or both sides of the two sides of the plate, and as "bad" when underfill occurs.

[0071] [Table 1]

[0072] [Table 1]

[0073]

[0074] As can be seen from Table 1, in Test Examples 3 to 5, 8, and 9 where the beam energy ratio E1 is 20% or more and 30% or less, the beam energy ratio E2 is 20% or more and 30% or less, and the beam energy ratio E3 is 45% or more and 55% or less, when the welding speed is 3.5 m / min or more, the amount of sputtering generated is small and the welding quality is good. In contrast, in Test Examples 1, 2, 6, and 7 where the beam energy ratios E1 to E3 are outside the above ranges, the amount of sputtering generated is large and the welding quality is bad. From this, it can be confirmed that by making the beam energy ratio E1 20% or more and 30% or less, the beam energy ratio E2 20% or more and 30% or less, and the beam energy ratio E3 45% or more and 55% or less, the occurrence of sputtering can be easily suppressed. Therefore, it is easy to improve the processing speed while suppressing the reduction of processing quality.

[0075] Next, as can be seen from Table 2 below, in Test Example 5 within the range where the spot diameter φ of the laser spot is 0.25 mm or more and 0.4 mm or less among Test Examples 4, 5, 8, and 9 where the evaluation result regarding "sputtering" is judged to be good, when the welding speed is 7 m / min or more, no underfill occurs and the welding quality is particularly good. That is, high-speed processing and good processing quality are achieved simultaneously.

[0076] In contrast, in Test Example 8 where the spot diameter φ is less than 0.25 mm, sputtering occurs less during high-speed processing (welding speed is 7 m / min), but insufficient filling is generated. It is considered that this is because the amount of molten base material required for processing the workpiece 100 is not sufficiently obtained due to the small spot diameter φ. In addition, in Test Example 9 where the spot diameter exceeds 0.4 mm, sputtering occurs less during high-speed processing (welding speed is 7 m / min), but insufficient filling is generated. It is considered that this is because sputtering is likely to occur due to the large spot diameter. It should be noted that in Test Example 4 where the spot diameter exceeds 0.4 mm, insufficient filling is not generated, but the processing speed remains at 5 m / min and good results like those in Test Example 5 are not obtained. From this, it can be confirmed that by making the spot diameter φ within the range of 0.25 mm or more and 0.4 mm or less, it is easy to simultaneously achieve suppression of reduction in processing quality and increase in processing speed.

[0077] [Table 2]

[0078] [Table 2]

[0079]

[0080] Next, as can be seen from Table 3 below, in Test Example 5 where the ratio L / φ of the distance L between spots to the spot diameter φ of the laser spot is within the range of 2.5 or more and 3.5 or less among Test Examples 5, 8, and 9 where the evaluation result regarding "sputtering" is judged to be good, when the welding speed is 7 m / min or more, insufficient filling is not generated and the welding quality is particularly good. That is, high-speed processing and good processing quality are simultaneously achieved.

[0081] In contrast, in Test Examples 8 and 9 where the above ratio L / φ is outside the above range, sputtering occurs less during high-speed processing (welding speed is 7 m / min), but insufficient filling is generated. In Test Example 8, since the distance L between spots is relatively large with respect to the spot diameter φ, cooling between spots is easily performed, so it is not possible to effectively expand the width of the molten pool and the volume of the molten pool is insufficient, so there may be insufficient filling. In Test Example 9, since the distance L between spots is relatively small with respect to the spot diameter φ, the molten pool between the keyholes becomes narrow and the keyholes are locally connected to each other, so the molten pool is extruded and falls off from the bottom side, reducing the amount of molten liquid, so there may be insufficient filling. From this, it can be confirmed that by making the ratio L / φ of the distance L between spots to the spot diameter φ of the laser spot within the range of 2.5 or more and 3.5 or less, it is easy to simultaneously achieve suppression of reduction in processing quality and increase in processing speed.

[0082] [Table 3]

[0083] [Table 3]

[0084]

[0085] The outlines of the laser processing methods of several embodiments are described below.

[0086] (1) The laser processing method of at least one embodiment of the present invention includes the following steps:

[0087] The workpiece is relatively moved with respect to a plurality of laser spots including the first spot, the second spot, and the third spot so that the linearly arranged first spot, second spot, and third spot sequentially pass through the processing target portion of the workpiece, thereby processing the workpiece.

[0088] With respect to the total amount of the energy of the laser at the first spot, the second spot, and the third spot,

[0089] The ratio of the energy at the first spot is 20% or more and 30% or less.

[0090] The ratio of the energy at the second spot is 20% or more and 30% or less.

[0091] The ratio of the energy at the third spot is 45% or more and 55% or less.

[0092] In the method of the above (1), for the energy density at the first spot to the third spot, it is smaller at the first spot and the second spot, and larger at the third spot. Therefore, in a state where a relatively shallow and wide molten pool is formed in the processing target portion of the workpiece by the first spot and the second spot with a smaller energy density, a deep keyhole is formed by the third spot with a larger energy density. Therefore, the distance between the deep keyhole formed by the third spot and the solid-liquid interface can be ensured to be relatively large. That is, the occurrence of sputtering when irradiating the workpiece with a laser spot (the third spot) having a large energy density can be effectively suppressed. Therefore, according to the method of the above (1), the processing speed can be increased while suppressing the reduction of the processing quality.

[0093] (2) In several embodiments, on the basis of the method of the above (1),

[0094] The ratio of the energy at the first spot is greater than the ratio of the energy at the second spot.

[0095] According to the method of the above (2), for the energy density at the first spot and the second spot, it is larger at the first spot and smaller at the second spot. Therefore, the first spot with a larger energy density first passes through the unheated processing target portion (the workpiece), so that a keyhole and a molten pool can be formed quickly. Therefore, the processing speed can be increased more effectively.

[0096] (3) In several embodiments, on the basis of the method of the above (1) or (2),

[0097] The diameters of the first light spot, the second light spot, and the third light spot are each 0.25 mm or more and 0.4 mm or less.

[0098] In the method of (3) above, since the diameters of the first to third light spots are each 0.25 mm or more, the workpiece can be effectively heated by each laser light spot, and it is easy to obtain the melting amount of the base material required for processing the workpiece. Further, in the method of (3) above, since the diameters of the first to third light spots are each 0.4 mm or less, an increase in sputtering due to a large light spot diameter can be effectively suppressed. Therefore, according to the method of (3) above, it is easy to simultaneously achieve suppression of a reduction in processing quality and an increase in processing speed.

[0099] (4) In several embodiments, based on any one of the methods of (1) to (3) above,

[0100] The distance L between the centers of two adjacent laser light spots among the plurality of laser light spots and the average light spot diameter φ of the two adjacent laser light spots avg The ratio L / φ avg is 2.5 or more and 3.5 or less.

[0101] According to the method of (4) above, the above ratio L / φ avg is 2.5 or more, and the distance L between the light spot centers is relatively large to some extent with respect to the average light spot diameter φ of two adjacent laser light spots avg . Therefore, it is possible to suppress the coalescence of keyholes formed by two adjacent laser light spots that are close to each other to form a single keyhole that is larger in appearance. Therefore, the occurrence of sputtering can be effectively suppressed. Further, according to the method of (4) above, the above ratio L / φ avg is 3.5 or less, and the distance L between the light spot centers is not too large with respect to the average light spot diameter φ of two adjacent laser light spots avg . Therefore, it is possible to suppress re-solidification caused by the cooling of molten metal that may occur during the period from when one (the first light spot or the second light spot) of two adjacent laser light spots passes through the processing target portion of the workpiece until the other laser light spot (the second light spot or the third light spot) arrives, and it is possible to effectively increase the molten liquid around the keyhole formed by the laser light spot. Thereby, the occurrence of sputtering when forming a deep keyhole using the third light spot can be effectively suppressed.

[0102] (5) In several embodiments, based on any one of the methods of (1) to (4) above,

[0103] The distance between the centers of the first light spot and the third light spot is less than the thickness of the processing target portion of the workpiece.

[0104] According to the method in (5) above, in the processing using a plurality of laser spots formed in a relatively small area whose length is shorter than the thickness of the processing target portion of the workpiece, as described in (1) above, it is possible to improve the processing speed while suppressing the deterioration of processing quality.

[0105] (6) In several embodiments, based on any one of the methods in (1) to (5) above,

[0106] the workpiece includes a pair of plate materials,

[0107] in the step of the processing, butt welding of the pair of plate materials is performed.

[0108] According to the method in (6) above, in the butt welding of a pair of plate materials using a plurality of laser spots, as described in (1) above, it is possible to improve the processing speed while suppressing the deterioration of processing quality.

[0109] (7) In several embodiments, based on any one of the methods in (1) to (6) above,

[0110] in the step of the processing,

[0111] at the first spot and the second spot, keyholes having a depth smaller than the thickness of the workpiece are formed in the workpiece,

[0112] at the third spot, a keyhole penetrating the workpiece is formed in the workpiece.

[0113] According to the method in (7) above, at the first spot and the second spot, keyholes having a depth smaller than the thickness of the workpiece are formed in the workpiece, and at the third spot, a keyhole penetrating the workpiece is formed. Therefore, in the processing (such as penetration welding) including the process of forming a keyhole penetrating the workpiece, as described in (1) above, it is possible to improve the processing speed while suppressing the deterioration of processing quality.

[0114] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and also includes modified forms of the above embodiments and forms obtained by appropriately combining these forms.

[0115] In this specification, expressions indicating relative or absolute configurations such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" not only represent such configurations in a strict sense, but also represent a state of relative displacement with a tolerance or an angle and distance that can achieve the same function.

[0116] For example, expressions indicating the state of equality of things, such as "identical", "equal", and "homogeneous", not only represent a state of strict equality, but also represent a state where there is a tolerance or a difference in the degree of obtaining the same function.

[0117] In addition, in this specification, expressions indicating shapes, such as a quadrilateral shape and a cylindrical shape, not only represent the shapes of a quadrilateral shape and a cylindrical shape in a strict geometric sense, but also represent shapes including concavo-convex portions, chamfered portions, etc. within a range where the same effect can be obtained.

[0118] In addition, in this specification, expressions such as "comprising", "including", or "having" a constituent element are not exclusive expressions that exclude the existence of other constituent elements.

[0119] Explanation of reference numerals:

[0120] 1 Laser processing device

[0121] 2 Laser oscillator

[0122] 4 Optical fiber

[0123] 6 Laser irradiation unit

[0124] 8 Collimation optical system

[0125] 10 Condensing optical system

[0126] 12 Laser branch unit

[0127] 14A, 14B Tilt prism

[0128] 15 Polygonal prism

[0129] 16A to 16D Reflecting mirror

[0130] 100 Workpiece

[0131] 101 Molten pool

[0132] 102 Processing target portion

[0133] 103 Solid-liquid interface

[0134] K1 to K3 Keyholes

[0135] P1 First light spot (laser light spot)

[0136] P2 Second light spot (laser light spot)

[0137] P3 Third light spot (laser light spot).

Claims

1. A laser processing method, wherein, the laser processing method includes the following processing steps: the workpiece is relatively moved with respect to a plurality of laser spots including the first spot, the second spot, and the third spot in such a manner that the linearly arranged first spot, second spot, and third spot sequentially pass through the processing object portion of the workpiece, thereby processing the workpiece. With respect to the total amount of the energy of the laser at the first spot, the second spot, and the third spot, the ratio of the energy at the first spot is 20% or more and 30% or less, the ratio of the energy at the second spot is 20% or more and 30% or less, the ratio of the energy at the third spot is 45% or more and 55% or less.

2. The laser processing method according to claim 1, wherein, the ratio of the energy at the first spot is greater than the ratio of the energy at the second spot.

3. The laser processing method according to claim 1 or 2, wherein, the diameter of each of the first spot, the second spot, and the third spot is 0.25 mm or more and 0.4 mm or less.

4. The laser processing method according to claim 1 or 2, wherein, The distance L between the centers of two adjacent laser spots among the multiple laser spots and the average spot diameter φ of the two adjacent laser spots avg The ratio L / φ avg is 2.5 or more and 3.5 or less.

5. The laser processing method according to claim 1 or 2, wherein, the distance between the centers of the first spot and the third spot is less than the thickness of the processing object portion of the workpiece.

6. The laser processing method according to claim 1 or 2, wherein, the workpiece includes a pair of plates, and in the processing step, butt welding of the pair of plates is performed.

7. The laser processing method according to claim 1 or 2, wherein, in the processing step, at the first spot and the second spot, keyholes having a depth smaller than the thickness of the workpiece are formed in the workpiece, and at the third spot, a keyhole penetrating the workpiece is formed in the workpiece.

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