JP2007160326A - Method of laser welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of laser welding, which method does not generate gas and splash from the coating film of welding material, and does not require complicated clearance control using a fixture, and can secure a stable welding quality having high repeatability. <P>SOLUTION: In a first process for removing a coating film, respective pealing zones H<SB>10</SB>determined at the portions corresponding to welding points W of a steel plate 12 are irradiated by converging a pulse laser beam LBa for removing the coating film, and galvanized coating films 10 within the pealing zones H<SB>10</SB>are sublimated and removed by the energy of the pulse laser beam LBa. In a second process for laser spot welding, the welding points W of the welding materials (12, 14) are irradiated by converging a pulse laser beam LBb for laser beam welding from the reverse side (above) of the stainless steel plate 14, and the stainless steel plate 14 and the steel plate 12 are welded by the energy of the pulse laser beam LBb. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laser welding method, and more particularly to a method for laser welding a metal member on which a film such as plating or coating is formed.

FIG. 11 and FIG. 12 show actions and problems in conventional laser welding in which a metal member surface-treated with galvanization is a material to be welded.
In FIG. 11, the lower metal plate 100 of two metal plates stacked one above the other is made of steel, for example, and a galvanized film 102 is formed on the surface thereof. The upper metal plate 104 is made of an uncoated metal such as stainless steel.

  As shown in FIG. 11, the laser beam Lb is usually focused and irradiated from the back (upper side) of the metal plate 104 without a coating toward a desired welding point W. Then, as shown in FIG. 12, the upper metal plate 104 is melted first in the vicinity of the welding point W by the energy of the laser beam Lb, and then the lower metal plate 100 is also melted. At this time, the plating film 102 is sublimated or vaporized at the boundary between the two metal plates 100 and 104, and a so-called explosion phenomenon occurs in which the laser melting portion 106 is blown away from the inside. Such explosions not only deteriorate the welding quality (joining strength, flatness, appearance, etc.), but also the plating film 102 is missing or damaged extensively around the welding point W and the corrosion protection function of the plating is lost. There is also a problem of being

  In order to prevent such explosion due to vaporization of the plating film 102, conventionally, as shown in FIG. 13, a gap G is formed by sandwiching a shim member 108 between the two metal plates 100 and 104, and the plating film 102. The method of extracting the sublimate (zinc gas) S generated from the side of the gap G is performed.

  However, in the conventional laser welding method using the shim member 108 as described above, the work of sandwiching the shim member 108 between the two metal plates 100 and 104 before welding and extracting it after welding is very troublesome. For certain reasons, the certainty and reproducibility of creating a constant gap G are low. In addition, the thickness of the shim member 108 is limited to about 100 μm even if the thickness of the shim member 108 is extremely thin as compared with the thickness of the plating film 102 which is usually several microns or less, and management of a minute gap is extremely difficult. In addition, the upper layer metal plate 104 must be melted to fill the gap G and then the lower layer metal plate 100 must be melted, and that much laser energy is required. In addition, the vicinity of the weld may be deformed by excessive energy laser irradiation. Furthermore, even with this method, the problem remains that the plating film 102 is peeled or damaged more than necessary by the laser energy around the welding point W and the corrosion resistance is lost. In addition, although said example was a case where a to-be-welded member has a film | membrane of galvanization, the same problem has generate | occur | produced also when it has other film | membranes, such as metal plating and coating.

  The present invention has been made in view of the circumstances as described above, and does not generate gas or explode from the coating of the material to be welded, and does not require troublesome gap management using a jig, and is highly reproducible and stable. An object of the present invention is to provide a laser welding method capable of guaranteeing welding quality.

  In order to achieve the above object, a first laser welding method of the present invention is a laser welding method in which a second metal member is laser welded to a first metal member having a coating on the surface at a desired welding point. Then, the laser beam of 1 is irradiated to the peeling region including the welding point of the first metal member and the vicinity thereof, and the coating in the peeling region is removed by the energy of the first laser beam. A first step of superimposing the first metal member and the second metal member on the first metal member or the second metal member from behind the second metal member toward the welding point. A second step of irradiating a laser beam and welding the first metal member and the second metal member at the welding point by the energy of the second laser beam.

  Further, the second laser welding method of the present invention laser welds a first metal member having a first coating on the surface and a second metal member having a second coating on the surface at a desired welding point. A laser welding method for irradiating a first laser beam to a first peeling region including the welding point of the first metal member and the vicinity thereof, and the first in the first peeling region. Irradiating the second peeling region including the first step of removing the coating film by the energy of the first laser beam and the second peeling region including the welding point of the second metal member and the vicinity thereof. A second step of removing the second film in the second peeling region by the energy of the second laser beam, and the first metal member and the second metal member are overlapped, The first metal member or the second metal A third laser beam is irradiated from behind the material toward the welding point, and the first metal member and the second metal member are welded at the welding point by the energy of the third laser beam. And a third step.

  In the laser welding method of the present invention, when a film is formed on one or both of the first and second metal members, a peeling point including a welding point and the vicinity thereof is set on the metal member with the film. Then, a predetermined laser beam is irradiated to the film to remove the film in the peeling region by laser energy. Thereby, when both metal members are overlapped, a cavity space sandwiched between the two metal members is formed at the location of the peeling region. Here, when the laser beam for laser spot welding is irradiated from the back of the first metal member or the second metal member toward the welding point, the upper metal member melts in the hollow space and becomes the lower metal member. The energy of the laser beam penetrates into the lower metal member through the melted portion of the upper metal member, and the lower metal member also melts. Then, after the laser beam irradiation is stopped, the molten portion of both metal members is solidified to form a weld nugget.

  According to a preferred aspect of the present invention, in the first laser welding method, both the first and second laser beams are pulse laser beams, and in the second laser welding method, the first and second laser beams are used. Both the second and third laser beams are pulsed laser beams. In this case, by generating the pulse laser beam for removing the film and the pulse laser for laser spot welding with the same pulse laser oscillation device, it is possible to reduce the cost of the processing equipment and shorten the processing time.

When using pulsed laser light, the peak power of each laser light is fed.
By maintaining the set values by back control, stable film removal processing and laser spot welding processing with high reproducibility can be performed.

  In addition, the size of the peeling region in the present invention is selected to be the smallest size in which the laser beam pulse laser beam can pass through the peeling region reliably (without hitting the edge) in the subsequent laser spot welding process. Preferably, for example, it can be arbitrarily variably adjusted by changing the irradiation range or irradiation region (for example, beam spot diameter) of the pulse laser beam. Alternatively, the size of the separation region can be adjusted by changing the pulse width of the laser light.

  The present invention can be applied to laser welding of a metal member having a film of any material and film thickness, and is particularly suitable for a metal plate having a film formed by surface treatment, typically plating or painting. Applicable.

  According to the laser welding method of the present invention, due to the configuration and operation as described above, there is no generation of gas or explosion from the coating of the material to be welded, no complicated gap management using a jig is necessary, and reproducibility is high. High stable welding quality can be guaranteed.

  Hereinafter, preferred embodiments of the present invention will be described with reference to FIGS.

  1 to 7 show a laser welding method in one embodiment of the present invention. As an example, one of the workpieces (workpieces) is a steel base plate 12 that has been surface-treated with galvanizing 10 and the other is a metal material without a film, for example, a stainless steel plate 14.

  Usually (when the thickness of the stainless steel plate 14 is not significantly larger than the thickness of the steel plate 12), the base stainless steel plate 14 is aligned on the galvanized steel plate 12, as shown in FIG. And repeat. For example, as shown in FIG. 2, a plurality of welding points W are set at a constant pitch at the portion where the metal plates 12, 14 overlap each other, and each welding point W is described from behind (above) the stainless steel plate 14 as described later. Are irradiated with a predetermined pulse laser beam, and both metal plates 12 and 14 are joined by laser spot welding.

In this embodiment, prior to the laser spot welding process, as shown in FIG. 3 and FIG. 4, pulse laser processing to be described later is performed on each separation region H ₁₀ set in a portion corresponding to each welding point W of the steel plate 12. the pulsed laser beam LBa for film removal from the output unit 16 of the device desired laser irradiation conditions (peak power P, the pulse width T, the beam spot diameter) in irradiated condenser, a galvanized coating 10 of the release region H ₁₀ Sublimation is performed by the laser energy of the pulse laser beam LBa to remove it.

Here, the peeled area H ₁₀ are preferably those containing the vicinity and the welding point W at the laser beam spot and the same shape (circular). That is, the size of the peeled area H ₁₀ is (without striking the edges) securely pulsed laser beam LBb for laser welding a peeled area H ₁₀ in the laser spot welding process steps after that will be described later minimum size that can pass of For example, it can be arbitrarily variably adjusted by changing the irradiation range or irradiation region of the pulse laser beam LBa.

In order to adjust the irradiation range of the pulse laser beam LBa, a method of changing the beam spot diameter of the pulse laser beam LBa is effective in the case of normal one-point irradiation. Alternatively, the peeled area while shifting the irradiation position in H _10. It is also possible to irradiate the pulsed laser beam LBa the minute spot on a plurality of points, the overall irradiation range by changing the number of the cases the irradiation point Can be varied. Alternatively, in either case of the single point irradiation method or the multipoint irradiation method, the irradiation range of the pulse laser beam LBa can be arbitrarily adjusted by changing the pulse width T or the laser energy E (FIG. 5) of the pulse laser beam LBa. it can. The peak power P of the pulse laser beam LBa is determined from the viewpoint that the coating (in this example, galvanized coating) 10 is limited to a predetermined region and is sublimated and removed without causing deformation of the base metal 12. The optimum value is set in accordance with the material of the coating 10, the film thickness, the material of the base metal 12, and the like.

As described above, the peeling region H ₁₀ where the galvanized film 10 is locally removed is formed at the site of all the welding points W of the galvanized steel plate 12. Next, as shown in FIG. 6, the stainless steel plate 14 is aligned and overlapped on the steel plate 12. Then, the peeled area H ₁₀ of the steel plate 12 is the upper surface thereof is covered with a stainless steel plate 14, which disc-shaped cavity (closed) space is formed. This hollow space has the same diameter (for example, 200 to 300 μm) as the peeling region H _10, and has a height (for example, 1 to 5 μm) equal to the film thickness of the galvanized film 10.

Next, with respect to the welding points W of the welded materials (12, 14) superimposed as described above, as shown in FIG. 7, the upper layer side of the welded material, that is, behind the stainless steel plate 14 (upward). Next, the laser beam LBb for laser welding is condensed and irradiated under the desired laser irradiation conditions (peak power P, pulse width T, beam spot diameter) from the above-described emission unit 16, and stainless steel is used at each welding point W. The plate 14 and the steel plate 12 are welded by the laser energy of the pulse laser beam LBb. At this time, the irradiation of the pulsed laser beam LBb, first stainless steel plate 14 of the upper layer melts, crumbling in the cavity space of the separation region H _10. The height (gap) of this hollow space is very narrow, about several μm, and the melted portion of the stainless steel plate 14 reaches the steel plate 12 immediately below it. Then, the laser energy of the pulse laser beam LBb permeates the steel plate 12 through the melted portion of the stainless plate 14 and melts the upper surface thereof. In this way, the stainless steel plate 14 and the steel plate 12 are integrally melted at each welding point W, and solidify after the irradiation of the pulsed laser beam LBb is stopped to form a weld nugget N.

In this laser spot welding method, the energy of the pulse laser beam LBb is efficiently input to the lower steel plate 12 through the cavity space of the peeling region H ₁₀ as described above, It is also important that the laser energy hardly reaches. Thus, the zinc plating film 10 does not sublime at the time of laser welding, so that no zinc gas is generated and no explosion phenomenon occurs. Moreover, since the galvanized film 10 is not damaged by the laser energy around the welding point W, the anticorrosion function can be stably maintained.

  By performing the laser spot welding as described above on all the welding points W of the workpieces (12, 14), it is possible to complete a plate spot welding processed product as shown in FIG.

  In this embodiment, the coating removal process (first process) for the galvanized steel plate 12 and the laser spot welding process (second process) for the welding points W of both metal plates 12 and 14 are performed by one pulse laser processing. I do it with a device.

  FIG. 8 shows a configuration of a pulse laser processing apparatus suitable for use in carrying out the laser welding method in the above embodiment. This pulse laser processing apparatus includes a pulse laser oscillator 18, a laser power source 20, a control unit 22, a laser transmission system 24, a power feedback light receiving element 26, and an index processing stage 28 in addition to the emission unit 16.

  The pulse laser oscillator 18 incorporates a laser medium made of, for example, a YAG rod, a laser excitation means (for example, an excitation light source) for exciting the laser medium, a resonator mirror for resonantly amplifying the laser light, and the like. The laser beam LB is oscillated and output. The laser power source 20 electrically drives laser excitation means in the laser oscillator 18 so as to obtain a desired laser pulse waveform and laser output characteristics under the control of the control unit 22. The laser transmission system 24 includes, for example, an optical fiber and a folding mirror 30, and transmits the pulse laser beam LB (LBa, LBb) from the laser oscillator 18 to the emission unit 16. The emission unit 16 has built-in optical system components such as a condenser lens 32, and irradiates and irradiates the pulse laser beam LB from the laser oscillator 18 toward the welding point W of the workpieces 12 and 14.

The light receiving element 26 receives, for example, the leakage light _MLB obtained by the folding mirror 30 of the laser transmission system 24, and supplies an electric signal (laser power detection signal) _SLB representing the light intensity or laser power of the pulsed laser light _LB as a laser power source. Feedback to 20. The laser power source 20 controls the excitation current or the excitation power supplied to the pulse laser oscillator 18 so that the laser power detection signal S _LB from the light receiving element 26 matches the peak power of the set value.

  The index processing stage 28 positions the workpieces 12 and 14 on the stage with respect to the emission unit 16 on the three axes X, Y, and Z under the control of the control unit 22, and in the XY directions, the welding point W can be moved by index feed.

  The control unit 22 is configured as a man-machine interface including a microprocessor (CPU), an input device or operation panel, an output device, a display device, and the like, and controls each part of the laser processing apparatus. In this control unit 22, the pulse laser beam LBa for film removal and the pulse laser beam LBb for laser spot welding can be switched and selectively output, and the peak power P of each pulse laser beam LBa, LBb can be output. Various conditions such as pulse width T and laser irradiation size can be arbitrarily set.

  In the laser spot welding process (second process) of the above-described embodiment, the base stainless steel plate 14 is superposed on the galvanized steel plate 12, and the pulse laser beam LBb for laser welding is applied from above (behind). Condensed irradiation was performed. However, as shown in FIG. 9, it is also possible to invert and vertically irradiate pulsed laser light LBb for laser welding toward the welding points W from behind (above) the steel plate 12. This method may be used, for example, when the thickness of the stainless steel plate 14 is significantly larger than the thickness of the steel plate 12.

In this method, the lower surface of each peeling region H is covered with the stainless steel plate 14 on the back surface side of the steel plate 12 that is the upper layer, and a disk-like cavity space similar to the above is formed there. Here, when the pulse laser beam LBb is irradiated, the plating film 10 on the upper surface is first sublimated and removed in the vicinity of the welding point W, and then the steel plate 12 is melted and the cavity of the separation region H ₁₀ is melted. It collapses onto the stainless steel plate 14 in the space. Then, the laser energy of the pulse laser beam LBb penetrates the stainless steel plate 14 through the melted portion of the steel plate 12 and melts the upper surface thereof. In this way, the steel plate 12 and the stainless steel plate 14 are integrally melted at each welding point W, and solidify after the irradiation of the pulse laser beam LBb is stopped to form a weld nugget N.

  As another embodiment, as shown in FIG. 10, the present invention can be applied even when a film (for example, nickel plating film) 34 is formed not only on the steel plate 12 but also on the stainless steel plate 14.

In this case, prior to the laser spot welding process (second process), the same film removal processing as shown in FIGS. 3 and 4 is also applied to the stainless steel plate 14. That is, a pulse laser beam LBc (not shown) for removing the surface from the emission unit 16 of the pulse laser processing apparatus (FIG. 8) in each peeling region H ₃₄ set at a site corresponding to each welding point W of the stainless steel plate 14. Is condensed and irradiated under desired laser irradiation conditions (peak power P, pulse width T, beam spot diameter), and the coating 34 in the peeling region H ₃₄ is sublimated by the laser energy of the pulse laser beam LBc and removed. The size of the separation region H ₃₄ is also selected to be the smallest size in which the laser beam pulsed laser beam LBb can reliably pass through the separation region H ₃₄ (without hitting the edge) in the laser spot welding process in the subsequent process. Is preferred. In addition, the peak power P of the pulse laser beam LBc is determined from the viewpoint of the sublimation of the coating 34 by reliably sublimating the coating ₃₄ within the peeling region H ₃₄ without causing deformation of the base metal 14. The optimum value may be set according to the material, the film thickness, the material of the base metal 14, and the like.

When the overlapped by aligning the stainless steel plate 14 and steel plate 12 film removal processing has been performed, respectively, as described above in the vertical direction, as shown in FIG. 10, stainless steel on the release region H ₁₀ steel plate 12 The peeling region H ₃₄ of the plate 14 is exactly overlapped to form one disk-shaped hollow space whose upper surface is closed by the stainless steel plate 14 and whose lower surface is closed by the steel plate 12. When the pulse laser beam LBb for laser welding is irradiated, the coating 34 on the upper surface of the stainless steel plate 14 is first sublimated and removed in the vicinity of the welding point W, and then the stainless steel plate 12 is melted and the separation region H is melted. _10, crumble on steel plate 12 in the cavity space of H _34. Then, the laser energy of the pulse laser beam LBb permeates the steel plate 12 through the melted portion of the stainless plate 14 and melts the upper surface thereof. In this way, the stainless steel plate 14 and the steel plate 12 are integrally melted at each welding point W, and solidify after the irradiation of the pulsed laser beam LBb is stopped to form a weld nugget N.

  The combination of the material to be welded (steel plate 12, stainless plate 14) and the coating (zinc plating coating 10, nickel plating coating 34) in the above-described embodiment is merely an example. The present invention is applicable to a metal member of any material and a film of any material or any surface treatment film. Therefore, regarding the film of the material to be welded (metal member), in addition to the plating process, a film formed by, for example, a coating process, an enamel process, a chemical conversion process, or the like is also possible.

  Moreover, in the above-described embodiment, since the two steps of film removal and laser spot welding are performed by one pulse laser processing apparatus, there is an advantage that the cost of processing equipment can be reduced. However, the film removal process and the laser spot welding process can also be performed by separate laser processing apparatuses. In that case, for example, it is also possible to use a Q-switch type laser processing apparatus for the film removal step.

It is a disassembled sectional view which shows the to-be-welded material which can apply the laser welding method by one Embodiment of this invention. It is a perspective view which shows the joining state of the to-be-welded material in embodiment. It is a perspective view which shows the effect | action of the film removal process in embodiment. It is a longitudinal cross-sectional view which shows the effect | action of the film removal process in embodiment. It is a figure which shows the laser output waveform of the pulse laser beam used with the laser welding method of embodiment. It is a longitudinal cross-sectional view which shows the state of the to-be-welded material before the laser spot welding process in embodiment. It is a longitudinal cross-sectional view which shows the effect | action of the laser spot welding process in embodiment. It is a block diagram which shows the structure of the pulse laser processing apparatus for enforcing the laser welding method in embodiment. It is a longitudinal cross-sectional view which shows the effect | action of the laser spot welding process in one modification. It is a longitudinal cross-sectional view which shows the effect | action of the laser spot welding process by another modification. It is a longitudinal cross-sectional view which shows the conventional general laser welding method. It is a longitudinal cross-sectional view which shows the effect | action of the conventional general laser welding method. It is a longitudinal cross-sectional view which shows the effect | action of the conventional laser welding method using a jig | tool (shim member).

Explanation of symbols

10 Film (galvanized film)
12 Steel plate 14 Stainless steel plate 16 Output unit 18 Pulse laser oscillator 20 Laser power supply 22 Control unit 28 Index processing stage 34 Coating (nickel plating coating)
W welding points H _10, H ₃₄ peeled area

Claims (17)

A laser welding method for laser welding a second metal member to a first metal member having a film on a surface at a desired welding point,
A first laser beam is irradiated to a peeling region including the welding point of the first metal member and the vicinity thereof, and the coating in the peeling region is removed by energy of the first laser beam. Process,
The first metal member and the second metal member are overlapped, and a second laser beam is irradiated from behind the first metal member or the second metal member toward the welding point, A laser welding method comprising: a second step of welding the first metal member and the second metal member with the energy of the second laser beam at the welding point.   The laser welding method according to claim 1, wherein both the first and second laser beams are pulsed laser beams.   The laser welding method according to claim 2, wherein the first and second laser beams are generated by the same pulse laser oscillation device.   The laser welding method according to claim 2 or 3, wherein the peak power of the first laser beam is held at a set value by feedback control.   The laser welding method according to any one of claims 2 to 4, wherein a size of the peeling region is adjusted according to an irradiation range of the first laser light.   The laser welding method according to claim 5, wherein a size of the separation region is adjusted by a beam spot diameter of the first laser light.   The laser welding method according to any one of claims 2 to 4, wherein a size of the peeling region is adjusted by a pulse width of the first laser beam. A laser welding method for laser welding a first metal member having a first film on a surface and a second metal member having a second film on a surface at a desired welding point,
A first laser beam is irradiated to a first peeling region including the welding point of the first metal member and the vicinity thereof, and the first film in the first peeling region is applied to the first laser. A first step of removing by light energy;
A second laser beam is irradiated to a second peeling region including the welding point of the second metal member and the vicinity thereof, and the second film in the second peeling region is applied to the second laser. A second step of removing by light energy;
The first metal member and the second metal member are overlapped, and a third laser beam is irradiated from behind the first metal member or the second metal member toward the welding point, And a third step of welding the first metal member and the second metal member by the energy of the third laser beam at the welding point.   The laser welding method according to claim 8, wherein all of the first, second, and third laser beams are pulsed laser beams.   The laser welding method according to claim 9, wherein the first, second, and third laser beams are generated by the same pulse laser oscillation device.   The laser welding method according to claim 9 or 10, wherein the peak powers of the first and second laser beams are held at set values by feedback control.   The laser welding method according to any one of claims 9 to 11, wherein a size of the peeling region is adjusted by an irradiation range of the first laser light.   The laser welding method according to claim 12, wherein the sizes of the first and second peeling regions are adjusted by beam spot diameters of the first and second laser beams, respectively.   The laser welding method according to any one of claims 9 to 11, wherein the sizes of the first and second peeling regions are adjusted by the pulse widths of the first and second laser beams, respectively.   The laser welding method according to claim 1, wherein the film is formed by a surface treatment.   The laser welding method according to claim 15, wherein the film is formed by plating or painting. The laser welding method according to claim 16, wherein the coating is a galvanized coating.

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