JP2011156572A - Laser welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser welding method capable of suppressing occurrence of welding defects due to metal vapor by a simple method. <P>SOLUTION: In the laser welding method, first, as an arrangement step, a first plate 12 and a second plate 14 that are configured as a metal plate applied with surface treatment are overlapped and clamped by a jig 16 for clamping; next, as a pretreatment step, a first laser light L1 is irradiated to the first plate 12; at this time, the first laser light L1 does not reach the lower surface treatment part 22b of the first plate 12 and is set to an irradiation condition that the temperature difference of the upper and lower surfaces of the first plate 12 become smaller than that of the second plate 14; accordingly, the second plate 14 is deformed into a shape with an almost V-shaped section by the heat of the first laser light L1 and a first gap 32 is formed between the first plate 12 and the second plate 14; and thereafter, as a welding step, a second laser right L2 is irradiated to reach the second plate 14 from the first plate 12 through the first gap 32, so that the first plate 12 and the second plate 14 are welded. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a laser welding method for performing lap welding by irradiating a laser on a metal plate having at least one of its overlapping surfaces.

  2. Description of the Related Art Conventionally, metal materials that have been improved in corrosion resistance by subjecting a base material to surface treatment (for example, plating treatment) have been widely known, and a typical example is a galvanized steel sheet.

  In general, when laser lap welding is performed on a plurality of galvanized steel sheets, the boiling point of zinc is lower than the melting point of iron (steel), so that the zinc located on the lap surface of the galvanized steel sheets evaporates during welding. As a result, zinc vapor (metal vapor) is generated. And since the said zinc vapor cannot escape to the exterior of a galvanized steel plate, it tries to enter a molten pool. As a result, a part of the molten metal may be blown away and spatter may occur, or zinc vapor may remain in a weld formed by cooling and solidifying the molten pool, thereby generating a blow hole.

  As a countermeasure for such welding defects, a gap is formed as a passage for the zinc vapor between the galvanized steel sheets, and the zinc vapor generated at the time of laser welding is discharged into the gap to thereby release the zinc vapor to the molten pool. What suppresses intrusion is well known.

  As a method of forming the gap between two galvanized steel sheets, there is a method in which a convex portion is formed in advance on the overlapping surface of galvanized steel sheets using a mold or the like. However, since the size of the gap varies due to wear of the mold, it is necessary to frequently manage the mold, which is troublesome.

  Further, as a method not using the mold, a laser beam (first laser beam) is irradiated only on the upper plate in a state where the upper plate and the lower plate are overlapped, and a convex portion is formed on the back surface of the upper plate. By forming the gap between the upper plate and the lower plate, the upper plate and the lower plate are irradiated with a laser beam (second laser beam) having a higher output than the first laser beam. One that is lap welded is known (see Patent Document 1). This document describes that the irradiation position of the second laser beam is most preferably matched with the irradiation position of the first laser beam.

Japanese Patent No. 4356236

  In the welding method of Patent Document 1, when the irradiation position of the second laser beam is made coincident with the irradiation position of the first laser beam, the convex portion is melted by the second laser beam, and thus the gap may disappear. . As a result, the metal vapor generated between the upper plate and the lower plate cannot be discharged into the gap, which may cause a welding defect.

  The present invention has been made in consideration of such problems, and an object of the present invention is to provide a laser welding method capable of suppressing the occurrence of welding defects due to metal vapor by a simple method.

  The laser welding method according to the present invention includes a placement step of stacking a first plate and a second plate made of a metal plate on which at least one of the overlap surfaces is surface-treated, and a surface treatment of the overlap surface provided after the placement step. The first plate is irradiated with the first laser beam so that the temperature difference between the upper and lower surfaces of the first plate is smaller than the temperature difference between the upper and lower surfaces of the second plate within a range that does not reach the formed portion. A pretreatment step, a welding step provided after the pretreatment step, and welding the first plate and the second plate by irradiating the first plate and the second plate with a second laser beam; Is provided.

  Normally, when a plate material is irradiated with a laser beam, a portion heated by the laser beam contracts, so that the plate material is distorted (deformed) into a substantially V-shaped cross section.

  According to such a method, the first plate is irradiated with laser light so that the temperature difference between the upper and lower surfaces of the first plate is smaller than the temperature difference between the upper and lower surfaces of the second plate. The second plate can be greatly deformed to have a substantially V-shaped cross section. Accordingly, a gap (first gap) can be easily formed between the first plate and the second plate. Therefore, in the welding process, when the first plate and the second plate are lap welded, the metal vapor generated by evaporation of the surface-treated portion (surface treatment portion) of the overlap surface is released into the gap. Can do. Therefore, since it can suppress that the said metal vapor enters into a molten pool, generation | occurrence | production of the welding defect by this metal vapor can be suppressed. In addition, since the clearance gap between the 1st board and the 2nd board is not formed by the convex part like the said patent document 1, this clearance gap does not lose | disappear with the heat | fever of the said 2nd laser beam.

  In the pretreatment step, the second plate is deformed by heat of the first laser beam transmitted to the second plate through the first plate, and the second plate is deformed between the first plate and the second plate. One gap may be formed, and the welding step may irradiate the second laser beam from the first plate so as to reach the second plate through the first gap.

  Then, by the heat of the second laser light, it is possible to reliably release the metal vapor generated by evaporation from the surface treatment portion of at least one overlapping surface of the first plate and the second plate to the first gap, It is possible to further suppress the metal vapor from entering the molten pool.

  Furthermore, the rigidity of the first plate may be set higher than the rigidity of the second plate. Then, the amount of deformation of the second plate relative to the first plate can be further increased as compared with the case where the rigidity of the first plate is set to be equal to or less than the rigidity of the second plate. Thereby, a 1st clearance gap can be formed reliably.

  The first plate may be formed thicker than the second plate. Then, even when the first plate and the second plate are made of the same material, the rigidity of the first plate can be made higher than the rigidity of the second plate.

  Further, in the arranging step, the second plate and the third plate made of a metal plate on which at least one of the overlapping surfaces is surface-treated are further stacked, and in the pretreatment step, the second plate is deformed by the deformation of the second plate. And a second gap is formed between the third plate, and the welding step allows the second laser beam to pass from the first plate through the first gap, the second plate, and the second gap. Irradiation may be performed to reach two plates.

  Then, the metal vapor generated by evaporation from at least one surface treatment portion of the overlapping surface of the second plate and the third plate can be discharged into the second gap by the heat of the second laser beam. Can be prevented from entering the molten pool. Thereby, also in the lap welding of a 1st board, a 2nd board, and a 3rd board, generation | occurrence | production of the welding defect by a metal vapor | steam can be suppressed.

  According to the present invention, since the first plate is irradiated with laser so that the temperature difference between the upper and lower surfaces of the first plate is smaller than the temperature difference between the upper and lower surfaces of the second plate, the first plate and the A gap can be easily formed between the second plates. Thereby, in a welding process, since the generated metal vapor can be discharged into the gap, generation of welding defects due to the metal vapor can be suppressed.

It is a schematic perspective view which shows the relationship between the jig | tool for a clamp for implementing the laser welding method which concerns on 1st Embodiment, a 1st board, and a 2nd board. It is the flowchart which showed the process of the laser welding method which concerns on 1st Embodiment. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 1, showing a state in which the first plate is irradiated with a first laser beam. It is sectional drawing which showed the molten pool formed by irradiating a 1st laser beam to a 1st plate, and a temperature rising part. It is sectional drawing which shows the state in which the clearance gap was formed between the 1st board and the 2nd board because the 2nd board deform | transformed. It is sectional drawing which shows the molten pool formed by irradiating a 2nd laser beam to a 1st board, a 1st clearance gap, and a 2nd board. It is a schematic perspective view which shows the relationship between the jig | tool for a clamp for implementing the laser welding method which concerns on 2nd Embodiment, a 1st board, and a 2nd board. It is the flowchart which showed the process of the laser welding method which concerns on 2nd Embodiment. FIG. 8 is a cross-sectional view taken along line IX-IX in FIG. 7, showing a state in which the first plate is irradiated with the first laser light. It is sectional drawing which shows the state by which the 2nd clearance gap was formed between the 2nd board and the 3rd board while the 1st clearance gap was formed between the 1st board and the 2nd board by the 2nd board changing. . It is sectional drawing which shows the molten pool formed by irradiating a 2nd laser beam to a 1st board, a 1st clearance gap, a 2nd board, a 2nd clearance gap, and a 3rd board.

  Hereinafter, preferred embodiments of the laser welding method according to the present invention will be exemplified and described in detail with reference to the accompanying drawings.

(First embodiment)
First, as shown in FIG. 1, the laser welding method according to the present embodiment includes a first plate 12, a second plate 14, a clamp treatment for holding the first plate 12 and the second plate 14 in an overlapped state. Using the tool 16, the laser beam is divided into preliminary irradiation and main irradiation, and irradiated to the first plate 12 side.

  The 1st board 12 and the 2nd board 14 are constituted as a metal plate by which surface treatment for improving corrosion resistance was performed, and plating, painting, spraying, etc. are used as the method of the surface treatment, for example. The As the 1st board 12 and the 2nd board 14, a galvanized steel plate etc. are used, for example. As can be seen from FIG. 1, the first plate 12 is formed thicker than the second plate 14. Specifically, the thickness of the first plate 12 is set to be thicker than 1.2 [mm], for example, and the thickness of the second plate 14 is 0.5 [mm] or more and 1.2 [mm] or less. Is set. Thereby, the rigidity of the first plate 12 is higher than the rigidity of the second plate 14.

  The clamping jig 16 has a pair of pressing members 18 provided so as to sandwich the site to be welded, and each pressing member 18 is a surface treatment portion provided on the upper surface of the base material 20 of the first plate 12. (Upper surface treatment portion) The upper pressing portion 18a that presses the 22a toward the second plate 14 and the surface treatment portion (lower surface treatment portion) 26a provided on the lower surface of the base material 24 of the second plate 14 are the first. It includes a lower pressing portion 18b that presses against the plate 12 side.

  In addition, the surface treatment part (lower surface treatment part) provided in the lower surface of the base material 20 of the 1st board 12 by overlapping and clamping the 1st board 12 and the 2nd board 14 with the jig 16 for clamping. 22b and the surface treatment part (upper surface treatment part) 26b provided in the upper surface of the base material 24 of the 2nd board 14 will contact.

  The first laser beam L1 used for the preliminary irradiation melts only the first plate 12 and irradiates the first plate 12 and the second plate 14 from the side of the first plate 12 while the first plate 12 and the second plate 14 are irradiated. The irradiation condition is set such that the heat of the laser beam L1 is transmitted to the second plate 14 via the first plate 12.

  In other words, the first laser beam L1 does not reach the lower surface treatment portion 22b of the first plate 12, and the temperature difference between the upper and lower surfaces of the first plate 12 is larger than the temperature difference between the upper and lower surfaces of the second plate 14. The irradiation conditions are set smaller. Here, the temperature difference means a temperature difference at or near the set output of the first laser L1.

  However, it is preferable that the first laser beam L1 is set to an irradiation condition in which the thermal history (temperature distribution) in the thickness direction of the first plate 12 is substantially constant. This is because the distortion amount (deformation amount) of the first plate 12 by the first laser beam L1 can be made as small as possible. The spot diameter of the first laser beam L1 with respect to the upper surface of the first plate 12 is set to about 600 [μm].

Examples of the type of the first laser beam L1 include a fiber laser, a YAG laser, a CO ² laser, and a semiconductor excitation laser, but the type is not limited.

  The second laser beam L2 used for the main irradiation passes through the first plate 12 and then passes through a gap 32 described later and reaches the second plate 14, thereby welding the first plate 12 and the second plate 14. The irradiation conditions that can be set are set. In addition, the spot diameter with respect to the upper surface of the 1st board 12 of the 2nd laser beam L2 is set to the range of 300 [micrometers]-600 [micrometers].

  The type of the second laser beam L2 is the same as that of the first laser beam L1, and the type is not limited. The second laser beam L2 may be the same as the first laser beam L1, but may be a different laser emitted from a different laser light source.

  Next, the laser welding process according to the present embodiment will be described with reference to FIGS.

  First, as an arranging step, the first plate 12 and the second plate 14 are overlapped and clamped by the clamping jig 16 (step S1 in FIG. 2).

  Subsequently, as shown in FIG. 3, as a pretreatment step, the first laser beam L1 is irradiated to the first plate 12 (step S2). The irradiation position of the first laser L1 is set at the approximate center of the pair of pressing members 18 and 18, and each pressing member 18 is a position that is separated from the irradiation position of the first laser light L1 by about 5 [mm]. Is arranged.

  As a result, as shown in FIG. 4, the irradiated portion of the first laser beam L <b> 1 is heated and melted to form the molten pool 28 and the temperature raising portion 30 is formed around the molten pool 28.

  Specifically, the molten pool 28 remains in the base material 20 of the first plate 12, and the tip thereof is located below the base material 20 of the first plate 12 (the lower surface treatment portion of the first plate 12). 22b). Further, the temperature raising unit 30 reaches the upper portion of the base material 24 of the second plate 14 via the lower surface treatment unit 22b of the first plate 12 and the upper surface treatment unit 26b of the second plate 14. Note that the temperature of the lower portion of the base material 24 and the lower surface treatment portion 26a of the second plate 14 is not increased by the irradiation with the first laser light L1.

  At this time, the thermal history in the thickness direction of the first plate 12 becomes substantially constant, and the temperature difference between the upper and lower surfaces of the first plate 12 becomes smaller than the temperature difference between the upper and lower surfaces of the second plate 14. Therefore, as shown in FIG. 5, when the heated portion of the second plate 14 contracts, the second plate 14 is deformed into a substantially V-shaped cross section. In FIG. 5, the deformation of the first plate 12 by the first laser beam L1 is considered to be very small, so the illustration of the deformation of the first plate 12 is omitted. As a result, a gap (first gap) 32 is formed between the first plate 12 and the second plate 14.

  Next, as shown in FIG. 6, as the welding process, the first plate 12 and the second plate 14 are irradiated with the second laser light L2 (step S3). Note that the irradiation position of the second laser beam L2 substantially coincides with the irradiation position of the first laser beam L1. As a result, the second laser light L2 is irradiated to the gap 32.

  When the first plate 12 and the second plate 14 are irradiated with the second laser light L2, the lower surface treatment portion 22b of the first plate 12 and the upper surface treatment portion 26b of the second plate 14 are heated by the heat of the second laser light L2. While evaporating to generate metal vapor, a molten pool 34 is formed from the upper part of the first plate 12 to the lower part of the second plate 14. At this time, as shown by the arrow in FIG. As a result, the metal vapor can be prevented from entering the molten pool 34. Therefore, generation | occurrence | production of the welding defect by this metal vapor | steam can be suppressed.

  Thereafter, the molten pool 34 is cooled and solidified, whereby the first plate 12 and the second plate 14 are welded.

  According to the laser welding method of the present embodiment, since the gap 32 is not formed by the convex portion as described in Patent Document 1, the gap 32 is not lost by the second laser light L2.

  Further, since the second laser beam L2 is applied to the gap 32 formed between the first plate 12 and the second plate 14, the metal vapor can be reliably released into the gap 32.

  Further, since the rigidity of the first plate 12 is set to be larger than the rigidity of the second plate 14, the first plate 12 is compared with the case where the rigidity of the first plate 12 is set to be equal to or lower than the rigidity of the second plate 14. The amount of deformation of the second plate 14 with respect to 12 can be further increased. Thereby, the said clearance gap 32 can be formed reliably.

  The present embodiment is not limited to the laser welding method described above. The irradiation position of the second laser light may not coincide with the irradiation position of the first laser light. In short, the irradiation position of the second laser light may be arbitrarily set as long as it can be applied to the gap.

(Second Embodiment)
Next, a laser welding method according to the second embodiment will be described with reference to FIGS. In the present embodiment, the same reference numerals are assigned to the same components as those in the first embodiment, and duplicate descriptions are omitted.

  In the laser welding method according to the present embodiment, as shown in FIG. 7, a third plate 36 having the same configuration as the first plate 12 is added, and the first plate 12, the second plate 14, and the third plate 36. Are arranged in layers. That is, the third plate 36 includes a base material 38, an upper surface treatment unit 40 a provided on the upper surface of the base material 38, and a lower surface treatment unit 40 b provided on the lower surface of the base material 38.

  The clamping jig 16 is configured such that a first gap 32 and a second gap 42 described later can be formed when the second plate 14 is deformed. In other words, the clamping jig 16 has such rigidity that the first gap 32 and the second gap 42 can be formed when the second plate 14 is deformed.

  The second laser light L2 passes through the first plate 12 and the second plate 14, passes through the first gap 32 and the second gap 42, and reaches the third plate 36. The irradiation conditions are set such that the second plate 14 and the third plate 36 can be welded. In addition, the spot diameter with respect to the upper surface of the 1st board 12 of the 2nd laser beam L2 is set to the range of 300 [micrometers]-600 [micrometers].

  In addition, two second laser beams L <b> 2 are applied to the first plate 12, the second plate 14, and the third plate 36. The irradiation with the second laser light L2 may be performed one by one or two at the same time.

  Next, the process of the laser welding method of this embodiment is demonstrated, referring FIGS.

  First, as an arrangement step, the first plate 12, the second plate 14, and the third plate 36 are overlapped and clamped by the clamping jig 16 (step S11 in FIG. 8).

  Subsequently, as shown in FIG. 9, as a pretreatment step, the first laser beam L1 is irradiated to the first plate 12 (step S12). Thereby, as shown in FIG. 10, the 2nd board 14 deform | transforms into a substantially V-shaped cross section similarly to the case of 1st Embodiment.

  As a result, a first gap 32 is formed between the first plate 12 and the second plate 14, and a second gap 42 is formed between the second plate 14 and the third plate 36.

  Next, as shown in FIG. 11, as the welding process, the first plate 12, the second plate 14, and the third plate 36 are irradiated with two second laser beams L2 (step S13). The irradiation position of the second laser beam L2 is offset by a predetermined amount toward the pressing member 18 with respect to the irradiation position of the first laser beam L1. As a result, the second laser beam L2 is applied to the first gap 32 and the second gap 42. That is, the second laser beam L2 is not irradiated to the contact portion between the third plate 36 and the portion of the second plate 14 that has been deformed into a substantially V-shaped cross section.

  When the two second laser beams L2 are applied to the first plate 12, the second plate 14, and the third plate 36, the lower surface treatment unit 26a of the second plate 14 and the upper surface treatment unit 40a of the third plate 36 are used. Is evaporated by the heat of the second laser beam L2 to generate metal vapor, and molten pools 44 and 44 are formed from the upper part of the first plate 12 to the base material 38 of the third plate 36. That is, the metal vapor is generated between the first plate 12 and the second plate 14 and between the second plate 14 and the third plate 36.

  At this time, as shown in FIG. 12, the metal vapor is discharged into the first gap 32 and the second gap 42. As a result, the metal vapor can be prevented from entering the molten pools 44, 44. Therefore, generation | occurrence | production of the welding defect by this metal vapor | steam can be suppressed.

  Thereafter, the molten pools 44 and 44 are cooled and solidified, whereby the first plate 12, the second plate 14, and the third plate 36 are welded.

  The present embodiment is not limited to the laser welding method described above. The number of the second laser light does not need to be two, and may be one or three or more.

  The laser welding method according to the present invention is not limited to the above-described embodiment, and various configurations and methods can be adopted without departing from the gist of the present invention.

  In the laser welding method according to the present invention, the first laser beam and the second laser beam may be continuously irradiated in a linear shape, or may be irradiated intermittently in a dot shape.

  In the above-described embodiment, the first plate is formed thicker than the second plate, so that the rigidity of the first plate is higher than the rigidity of the second plate. However, the first plate is difficult to deform such as high-tensile steel. By configuring with a material, the rigidity of the first plate may be higher than the rigidity of the second plate.

DESCRIPTION OF SYMBOLS 12 ... 1st board 14 ... 2nd board 16 ... Jig for clamping 20, 24, 38 ... Base material 22a, 26b, 40a ... Upper surface treatment part 22b, 26a, 40b ... Lower surface treatment part 32 ... 1st clearance gap 36 ... Third plate 42 ... Second gap L1 ... First laser beam L2 ... Second laser beam

Claims (5)

An arrangement step of overlapping the first plate and the second plate made of a metal plate on which at least one of the overlapping surfaces is surface-treated;
The temperature difference between the upper and lower surfaces of the first plate is smaller than the temperature difference between the upper and lower surfaces of the second plate within a range that is provided after the arranging step and does not reach the surface-treated portion of the overlapping surface. A pretreatment step of irradiating the first plate with a first laser beam,
A welding step, which is provided after the pretreatment step and welds the first plate and the second plate by irradiating the first plate and the second plate with a second laser beam. Laser welding method. The laser welding method according to claim 1, wherein
In the pretreatment step, a first gap is formed between the first plate and the second plate by deformation of the second plate due to heat of the first laser beam transmitted to the second plate through the first plate. Formed,
The laser welding method, wherein the welding step irradiates the second laser beam from the first plate so as to reach the second plate through a first gap. The laser welding method according to claim 2, wherein
The laser welding method according to claim 1, wherein the rigidity of the first plate is set higher than the rigidity of the second plate. The laser welding method according to claim 3,
The laser welding method, wherein the first plate is formed thicker than the second plate. In the laser welding method of any one of Claims 2-4,
In the arranging step, the second plate and the third plate made of a metal plate on which at least one of the overlapping surfaces is surface-treated are further stacked,
In the pretreatment step, a second gap is formed between the second plate and the third plate by deformation of the second plate,
In the welding step, the second laser beam is irradiated from the first plate so as to reach the second plate through the first gap, the second plate, and the second gap. Welding method.

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