JP2008049392A - Laser welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple and easy method which enables high-quality welding when performing the lap welding of workpieces comprising metals in which at least one of overlapped faces of the metals is surface-treated. <P>SOLUTION: The welding method includes: superposing the upper and lower plates 10 and 12 so as to form a gap G1 between the lower surface 10b of the upper plate 10 and the upper 12a of the lower 12; forming a projection 18 projected from the lower surface 10b of the upper plate 10 by irradiating a first laser L1 penetrating the upper plate 10 along the welding portion 14 of the upper surface 10a of the upper plate 10; and then welding the upper and lower plates 10 and 12 by irradiating a second laser L2 from the upper surface 10a of the plate 10 in such a state that the plates 10 and 12 are clamped and fixed by abutting the projection 18 on the upper surface 12a of the plate 12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser welding method for performing lap welding of a workpiece made of a metal having at least one of its overlapping surfaces surface-treated.

  For example, surface-treated metal plates such as galvanized steel plates are widely used as structural members such as automobile bodies. When such metal plates (workpieces) are overlapped and laser-welded, plating between the overlapping surfaces of the workpieces, for example, zinc is evaporated in the galvanized steel sheet, and the vapor is blown into the melted part to blow holes or the like. May cause poor welding (rough bead). This is a problem caused because the boiling point of zinc coated on the surface (906 ° C.) is lower than the melting point of iron (about 1500 ° C.).

  Conventionally, various methods for solving the above problems have been proposed. For example, in Patent Literature 1, when laser lap welding is performed on a metal in which at least one of the overlapping surfaces is coated with a material having a boiling point lower than the melting point of the base metal, the laser irradiation side metal (upper workpiece) is used. After irradiating the first laser whose penetration depth d is 0.6 to 0.95 times the wall thickness t and forming a convex portion on the lower surface of the metal, a gap is created between the overlapping surfaces. A method of melting and joining workpieces by irradiating a second laser is described.

  In Patent Document 2, in a method of welding an overlapped portion of galvanized steel sheets using at least two lasers, after heating and evaporating galvanization of a joining region by a first laser, the joining region is obtained by a second laser. Describes a method of adjusting the diameter and average energy density of each laser and the center-to-center distance between the lasers to predetermined values when welding.

JP 2002-178178 A Japanese Patent Laid-Open No. 2002-160083

  However, in the method described in Patent Document 1, it is necessary to set the penetration depth d by the first laser to 0.6 to 0.95 times the plate thickness t. It is very difficult to perform fine control. Furthermore, since the first laser is irradiated with the workpiece clamped in advance, there is no gap between the overlapping surfaces of the workpieces, and thus the projections as described above are hardly formed.

  Further, in the method described in Patent Document 2, since no gap is provided between the overlapping surfaces of the workpieces, the plating vapor tends to remain after all.

  The present invention has been made in consideration of the above problems, and a laser capable of high-quality welding by a simple method when welding is performed on a workpiece made of a metal having at least one of the overlapping surfaces surface-treated. An object is to provide a welding method.

  The laser welding method of the present invention is a laser welding method for performing welding on a workpiece made of a metal whose surface is treated on at least one of the overlapping surfaces, and between the overlapping surfaces between the lower surface of the upper workpiece and the upper surface of the lower workpiece. After the upper work and the lower work are overlapped with a gap, a laser projecting through the upper work along the welded portion on the upper face of the upper work is irradiated to form a convex portion protruding from the lower face of the upper work. After the first step, after the first step, a second step of narrowing and fixing the upper work and the lower work so that the convex portion comes into contact with the upper surface of the lower work, and the second step And a third step of welding the upper work and the lower work by irradiating a laser from the upper surface of the upper work.

  According to such a method, by irradiating the laser with a gap provided between the overlapping surfaces in the first step, it is possible to reliably form a convex portion on the lower surface of the upper work, and the laser. It is possible to reliably prevent the surface treatment layer (surface treatment portion) that has been heated and evaporated by irradiation, for example, the vapor of the plating portion from remaining. At this time, since the laser is irradiated so as to penetrate the upper workpiece, the convex portion can be formed more reliably, and the plated portion on the overlapping surface is also evaporated in the first step. be able to. For this reason, it is possible to reduce the amount of vapor from the plated portion that is generated during laser irradiation in the third step, and it is possible to more reliably prevent bead roughness after welding. Further, by irradiating the laser in the first step so as to penetrate the upper work as described above, it is possible to improve the working efficiency and reduce the cost by controlling the laser and simplifying the device structure.

  In the laser welding method of the present invention, in the first step, when the height of the gap is set to be equal to or higher than the height of the convex portion formed by the laser, the convex portion is formed by the upper surface of the lower workpiece. Therefore, a convex portion having a desired height can be more reliably formed.

  Further, if the surface treatment layer on the overlapped surface is removed by laser irradiation in the first step, the amount of vapor generated from the surface treatment layer generated during laser irradiation in the third step thereafter can be reduced. This makes it possible to more reliably prevent the bead roughness after welding. In this case, in the laser irradiation in the first step, the effect of reducing the vapor amount can be obtained by removing at least a part of the surface treatment layer on the overlapping surface.

  Furthermore, if the focal spot diameter of the laser irradiated in the third step is set larger than the laser irradiated in the first step, the bead width when welding the upper workpiece and the lower workpiece can be sufficiently secured, so that the welding strength Can be improved.

  According to the present invention, it is possible to reliably form a convex portion between the overlapping surfaces by irradiating a laser with a gap provided between the overlapping surfaces of the workpieces, and the convex portions are clamped when the workpiece is clamped. A gap can be secured between the overlapping surfaces by the portion. Therefore, it is possible to prevent the surface treatment layer on the overlapping surface that is heated and evaporated by laser irradiation, for example, the vapor of the plated portion from remaining in the molten portion.

  In addition, according to the present invention, since the laser is irradiated so as to penetrate the upper workpiece, the convex portion can be more reliably formed and the plated portion on the overlapping surface can be evaporated. it can. Therefore, at the time of welding by subsequent laser irradiation, the amount of vapor from the plated portion can be reduced and reliably released to the outside. For this reason, bead roughening after welding can be more reliably prevented by a simple method, and high-quality welding can be performed.

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

  FIG. 1 is a schematic perspective view showing a state in which workpieces to be welded by a laser welding method according to an embodiment of the present invention are stacked. The laser welding method according to the present embodiment performs laser welding in a state in which an upper plate (upper workpiece) 10 and a lower plate (lower workpiece) 12 which are workpieces made of a surface-treated (coated) metal plate are stacked. It is the welding method which joins.

  Hereinafter, the case where galvanized steel plates are used as the upper plate 10 and the lower plate 12 will be described as an example. That is, as shown in FIG. 1, the upper surface 10a and the lower surface 10b of the upper plate 10 and the upper surface 12a and the lower surface 12b of the lower plate 12 are coated with galvanized Zn constituting the surface treatment layer. In addition, as a workpiece | work which can apply this invention, an aluminum plating steel plate, a chromium plating steel plate, etc. are mentioned other than a galvanization steel plate, for example.

  Next, a laser welding method in which welding is performed after the upper plate 10 and the lower plate 12 are stacked will be described with reference to FIGS. In this laser welding method, laser irradiation comprising a total of two passes by a laser with a small focal diameter (first pass) and a laser with a larger focal diameter (second pass) is performed, and the upper plate 10 and the lower plate 12 are attached. Lap welding.

  2 is a schematic perspective view for explaining a state in which the first laser L1 is irradiated from the upper surface 10a side of the upper plate 10 shown in FIG. 1, and FIG. 3 is a diagram of the first laser L1 shown in FIG. FIG. 4 is a schematic perspective view for explaining a state in which the upper plate 10 and the lower plate 12 are clamped after irradiation, and FIG. 4 irradiates the second laser L2 with the upper plate 10 and the lower plate 12 clamped. It is a schematic perspective view for demonstrating the state which is carrying out. 5A to 5E are schematic cross-sectional views for explaining a cross-sectional state of the work in each step of the laser welding method according to the present embodiment.

  First, as shown in FIGS. 1 and 5A, the upper plate 10 and the lower plate 12 are overlapped, and between the lower surface 10b of the upper plate 10 and the upper surface 12a of the lower plate 12 (between the overlapping surfaces), which are overlapping surfaces, A predetermined gap G1 is secured. The gap G1 only needs to be provided at least in the peripheral portion along the longitudinal direction of the welded portion 14 assumed on the upper surface 10a of the upper plate 10, and the entire gap between the upper plate 10 and the lower plate 12 is overlapped. There is no need to reach.

  In order to secure the gap G1, for example, a spacer (not shown) may be sandwiched between the upper plate 10 and the lower plate 12, or a jig (not shown) may be used. Further, when the gap G1 can be ensured simply by overlapping the workpieces according to the shape of the workpiece, it is not necessary to use the spacer or the like. That is, in a workpiece in which the shape of the workpiece is processed in advance so that the gap G1 is formed in a state where the workpieces are stacked, or a workpiece in which the gap G1 is naturally formed when stacked by having a curvature or the like, There is no need to use a spacer as described above.

  Next, in a state where the gap G1 is secured between the overlapping surfaces of the upper plate 10 and the lower plate 12, as shown in FIG. 2, the first laser L1 is formed along the welding portion 14 from the upper surface 10a side of the upper plate 10. To scan. At this time, the first laser L1 is irradiated so as to penetrate the upper plate 10 (see FIG. 5B). Thereby, in the melted portion of the upper plate 10 irradiated with the first laser L1 and partially protruding downward from the lower surface 10b, it cools and hardens instantaneously (for example, in about 1/100 second), A convex portion 18 made of a convex bead is formed on the lower surface 10b (first step). At the same time, a bead 20 penetrating the upper plate 10 is formed above the convex portion 18 of the upper plate 10 so as to extend along the welded portion 14.

  Therefore, it is desirable that the gap G1 is set to a height (size) that can reliably form the convex portion 18 between the overlapping surfaces by irradiation of the first laser L1. That is, when the gap G1 is not secured as in the prior art described in Patent Document 2, or when the gap G1 is not sufficiently high and sufficient space is not secured between the overlapping surfaces. This is because the formation (growth) of the convex portion 18 is hindered by the upper surface 12a of the lower plate 12, and it is difficult to form the convex portion 18 having a desired height.

  As the first laser L1, a laser beam having a very small focal diameter, for example, a fiber laser is preferably used, and is irradiated so as to penetrate the upper plate 10 as described above (see FIG. 5B). Then, by heat input until the upper plate 10 penetrates (behind) by the first laser L1, not only the zinc plating Zn on the upper surface 10a surface and the lower surface 10b surface of the upper plate 10 but also the surface of the upper surface 12a of the lower plate 12 Zinc plating Zn also evaporates, and these zinc vapors escape from the gap G1 to the outside (see broken line arrows in FIG. 5B). Further, since the first laser L1 is intended to form the convex portion 18 on the lower surface 10b of the upper plate 10, no excessive output is applied, and furthermore, the upper plate 10 and the lower plate 12 are not accidentally joined. Therefore, it is preferable to use a laser with a narrow focal diameter as described above.

  Next, as shown in FIG. 3, the upper plate 10 and the lower plate 12 are sandwiched and fixed from the upper surface 10 a side of the upper plate 10 and the lower surface 12 b side of the lower plate 12 by a clamping device or the like (not shown). That is, the upper plate 10 and the lower plate 12 are clamped.

  Then, as shown in FIG. 5C, since the convex portion 18 is interposed between the upper plate 10 and the lower plate 12, the convex portion 18 becomes a support, and at least in the peripheral portion of the convex portion 18, The plate 10 and the lower plate 12 are not completely adhered. That is, in a state where the upper plate 10 and the lower plate 12 are clamped, a gap G2 that is substantially equal to the height of the convex portion 18 is formed in the peripheral portion of the convex portion 18 between these overlapping surfaces. In this case, since the height of the gap G2 depends on the height of the convex portion 18, it is naturally lower than the gap G1.

  Thus, the height of the convex portion 18 is a height at which a gap G2 having a desired height can be formed between the overlapping surfaces in a state where the upper plate 10 and the lower plate 12 are clamped, that is, a first level described later. When welding is performed with the two lasers L2, it is sufficient if the height is sufficient to allow zinc vapor to escape to the outside.

  Next, in the state where the upper plate 10 and the lower plate 12 are clamped as described above, as shown in FIG. 4, the second laser L2 is located at the same position as the irradiation site of the first laser L1, that is, along the bead 20. To scan. By irradiating the second laser L2 in this way, the upper plate 10 and the lower plate 12 are welded and firmly joined to form a bead 22 along the irradiated portion of the second laser L2 (FIG. 4 and FIG. 5E).

  In this case, since the convex portion 18 is formed by the first laser L1 before the irradiation with the second laser L2, even when the upper plate 10 and the lower plate 12 are clamped, the gap G2 goes to the outside. The zinc vapor from which the zinc plating Zn has evaporated can be released (see the broken line arrow in FIG. 5D). In other words, even when the upper plate 10 and the lower plate 12 are clamped more firmly, for example, by securely forming the convex portion 18 by the first laser L1 and securing the gap G2, Zinc vapor generated by the second laser L2 can be surely released to the outside through the gap G2. As described above, since it is possible to firmly clamp the upper plate 10 and the lower plate 12 at the time of welding by the second laser L2, a welding process by irradiation of the second laser L2 is executed easily and accurately. It is possible to improve the bonding strength and appearance after welding.

  Further, as described above, when the second laser L2 is irradiated to the same position as the irradiation site of the first laser L1, the gap G2 can be used effectively to release zinc vapor from the second laser L2 to the outside. In addition, since the number of beads formed on the workpiece can be minimized, it is easy to ensure the appearance and rust prevention of the workpiece after welding. Note that the irradiation positions of the first laser L1 and the second laser L2 may be different positions depending on the use conditions of the workpiece after welding.

The second laser L2 uses a laser having a larger focal diameter than the first laser L1 in order to form a bead having a width sufficient to obtain a necessary bonding strength between the upper plate 10 and the lower plate 12. Desirable types include, for example, YAG laser, CO ₂ laser, semiconductor excitation laser, and the like. Further, the same laser as the first laser L1 can be used as the second laser L2.

  As described above, according to the laser welding method according to the present embodiment, the first laser L1 is attached to the upper plate 10 in a state where a sufficient gap G1 is secured between the overlapping surfaces between the upper plate 10 and the lower plate 12. Irradiate to penetrate. Therefore, the convex portion 18 having a desired size can be easily and reliably formed on the lower surface 10b of the upper plate 10, and the zinc vapor can be surely released from the gap G1 to the outside. Furthermore, after that, by securing the gap G2 using the convex portion 18, the zinc vapor generated from the zinc plating Zn can be easily released from the gap G2 to the outside during welding by the second laser L2. Thus, according to the laser welding method according to the present embodiment, it is possible to prevent bead roughening by preventing ejection due to zinc vapor during welding.

  At this time, after forming the convex portion 18 by the first laser L1, the upper plate 10 and the lower plate 12 are clamped, so that the workpiece is previously overlapped and clamped as in the prior art described in Patent Document 1 above. Compared with the case where the convex portion is formed, the convex portion 18 having a desired size can be formed more easily and reliably. That is, by clamping the upper plate 10 and the lower plate 12 after forming the convex portion 18, the welding process by the second laser L2 can be performed in a state where the clamping is performed more firmly, so that the welding operation is performed more accurately. And it can be done quickly.

  Further, since the first laser L1 is irradiated so as to penetrate the upper plate 10, the control of the first laser L1 and the device structure can be simplified, and the work efficiency can be improved and the cost can be reduced. This is particularly effective for production lines.

  Furthermore, by passing the first laser L1 through the upper plate 10, not only the zinc plating Zn on the lower surface 10b of the upper plate 10 but also the zinc plating Zn on the upper surface 12a of the lower plate 12 is caused to some extent by the first laser L1. Can be evaporated. Accordingly, it is possible to reduce the generation of zinc vapor between the overlapping surfaces during welding with the second laser L2 at the subsequent stage, and it is possible to more reliably prevent bead roughness after welding. In addition, since the generation of zinc vapor is reduced as described above, the convex portion 18 can be formed to a minimum height, and the height of the gap G2 by the convex portion 18 can be minimized. As a result, an extra gap or the like is not formed between the upper plate 10 and the lower plate 12 after being welded and joined by the second laser L2, and strong welding with a better appearance is possible.

  It should be noted that the present invention is not limited to the above-described embodiment, and it is naturally possible to adopt various configurations without departing from the gist of the present invention.

  For example, the types of the first laser L1 and the second laser L2, the size of the focal diameter, and the like are not necessarily changed, and similar ones may be used.

  Moreover, in the said embodiment, although the upper plate 10 and the lower plate 12 assumed that zinc plating Zn was given to both surfaces, it is not restricted to this, The overlapping surface between the upper plate 10 and the lower plate 12 If the surface treatment (galvanized Zn) is applied to at least one of the lower surface 10b of the upper plate 10 or the upper surface 12a of the lower plate 12, the laser welding method of the present invention is effectively applied. can do.

It is a schematic perspective view which shows the state which accumulated the upper plate and lower plate which are the workpiece | work welded with the laser welding method which concerns on one Embodiment of this invention. It is a schematic perspective view for demonstrating the state which irradiates the 1st laser from the upper surface side of the upper board shown in FIG. It is a schematic perspective view for demonstrating the state which clamps the upper board and the lower board after irradiation of the 1st laser shown in FIG. It is a schematic perspective view for demonstrating the state which has irradiated the 2nd laser in the state which clamped the upper board and the lower board. FIG. 5A is a schematic cross-sectional view for explaining a state in which the upper plate and the lower plate are overlapped, and FIG. 5B explains a state in which the first laser is irradiated on the upper plate and the lower plate shown in FIG. 5A. FIG. 5C is a schematic cross-sectional view for explaining a state in which the upper plate and the lower plate are clamped after irradiating the first laser, and FIG. 5D is an upper plate shown in FIG. 5C. FIG. 5E is a schematic cross-sectional view for explaining a state in which the second laser is irradiated to the lower plate, and FIG. 5E is an outline for explaining a state in which the upper plate and the lower plate are welded by irradiating the second laser. It is sectional drawing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Upper plate 10a, 12a ... Upper surface 10b, 12b ... Lower surface 12 ... Lower plate 14 ... Welded part 18 ... Convex part 20, 22 ... Bead G1, G2 ... Gap L1, L2 ... Laser

Claims (4)

A laser welding method for performing welding on a workpiece made of a metal on which at least one of the overlapping surfaces is surface-treated,
After the upper work and the lower work are overlapped with a gap between the upper and lower surfaces of the upper work and the upper work, the laser passing through the upper work is irradiated along the welded portion of the upper work. And the 1st process of forming the convex part projected from the undersurface of the upper work,
After the first step, a second step of narrowing and fixing the upper work and the lower work so that the convex part comes into contact with the upper surface of the lower work;
After the second step, a third step of irradiating laser from the upper surface of the upper work to weld the upper work and the lower work;
A laser welding method characterized by comprising: The laser welding method according to claim 1, wherein
In the first step, the height of the gap is set to be equal to or higher than the height of the convex portion formed by the laser. In the laser welding method according to claim 1 or 2,
A laser welding method, wherein the surface treatment layer on the overlapped surface is removed by laser irradiation in the first step. In the laser welding method of any one of Claims 1-3,
A laser welding method, wherein a focal spot diameter of the laser irradiated in the third step is set larger than that of the laser irradiated in the first step.

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