JP4506575B2 - Galvanized steel sheet laser brazing device, galvanized steel sheet laser brazing method, brazed galvanized steel sheet manufacturing method. - Google Patents

Description

  The present invention relates to a technique for joining a joint including a galvanized steel sheet by brazing, and more particularly to a technique for melting a brazing material by irradiation with a laser beam.

  Lasers are used as one of heat sources in brazing galvanized steel sheets. In this brazing, zinc having a low boiling point evaporates, thereby causing poor bonding with small pits (blow holes).

  The following Patent Document 1 discloses a technique for preventing the occurrence of blowholes at a joint by brazing a galvanized steel sheet in an argon gas atmosphere using a wire containing 60% or more of copper.

  In addition, the following patent documents 2 and 3 are mentioned as a literature about the laser "welding" of a galvanized steel plate. The technique of the following patent document 2 performs laser welding while moving laser light along a welding track of a galvanized steel sheet. In this technique, laser beam spectroscopy is performed. First, galvanization is evaporated and separated by a laser beam having a low energy density, and immediately thereafter, welding is performed by a laser beam having a high energy density. Moreover, in the technique disclosed in Patent Document 3 below, by providing a fine rough surface on the entire surface of the steel plate, the generation of spatter is suppressed and the zinc vapor pressure is reduced, thereby preventing the occurrence of welding defects such as blow holes. is doing.

Japanese Patent Laid-Open No. 3-165968 JP-A-4-231190 JP 2002-346780 A

  In the technique of Patent Document 1, it is necessary to prepare a working space using argon gas, and the apparatus configuration must be large. In addition, it is possible to prevent brazing bead oxidation by using an argon atmosphere, but it is not possible to suppress the penetration of zinc vapor into the molten pool, which is the main cause of surface pits, and a sufficient effect is not necessarily obtained. . Further, the techniques of Patent Documents 2 and 3 relate to welding, and the effectiveness in brazing is not necessarily clear.

  An object of the present invention is to realize a new technique for suppressing or preventing the generation of pits (blow holes) in laser brazing of a galvanized steel sheet.

  An object of the present invention is to establish a technique for improving the finish of laser brazing of a galvanized steel sheet under a simple apparatus configuration.

  The galvanized steel sheet laser brazing apparatus of the present invention is a supply means for supplying a brazing material from the front side in the brazing progression direction with respect to the laser irradiation position set in the vicinity of the brazing joint location of the joint including the galvanized steel sheet, A laser beam irradiation mechanism that melts a brazing material supplied by irradiating a laser beam to the laser irradiation position while moving the laser irradiation position relatively in the brazing direction, and at the laser irradiation position of the laser beam A laser beam irradiation mechanism in which the energy density is set higher on the front side in the traveling direction than on the rear side in the traveling direction.

  A galvanized steel sheet is a steel sheet whose surface is galvanized. In the brazing joining, joining is performed using a joint including two or three or more galvanized steel sheets as a joint location. The brazing material to be used is not particularly limited, and copper brazing, silver brazing, and the like can be widely used.

  The galvanized steel sheet laser brazing apparatus includes a supply unit and a laser beam irradiation mechanism, and performs brazing by melting a brazing material supplied by the supply unit with a laser beam irradiated by the laser beam irradiation mechanism. The laser beam irradiation is performed by sequentially moving the laser irradiation position. In other words, the laser irradiation is performed by moving the absolute irradiation position of the laser beam using a robot or a mirror, or by moving the galvanized steel sheet to be irradiated by operating the holding device of the galvanized steel sheet. The position moves relative to the galvanized steel sheet. The holding device may be incorporated in the galvanized steel sheet laser brazing apparatus, or may be a separately provided galvanized steel sheet laser brazing apparatus and constitute a laser brazing system.

  The supply means supplies the brazing material to the laser irradiation position from the front side in the brazing direction. That is, the brazing material is supplied so that a new brazing material before melting is disposed at the destination of the laser beam. Typically, the supply means continuously supplies the wire-like brazing material with its tip disposed at the laser irradiation position.

  The laser beam irradiation is set such that the energy density for the side receiving the laser beam is higher on the front side in the traveling direction than on the rear side in the traveling direction. This energy density may be set by setting the density distribution of the laser beam itself non-uniformly, or by setting the angle of the irradiated side with respect to the laser beam and the distance of the irradiated side with respect to the laser source non-uniformly. It may be done by doing.

  According to this configuration, relatively high energy is absorbed from the laser beam on the front side in the traveling direction. Therefore, the brazing material supplied to the front side in the traveling direction is rapidly heated to melt. On the other hand, relatively low energy is absorbed from the laser beam on the rear side in the traveling direction. Therefore, the molten pool of the brazing material spreading to the rear side in the traveling direction is not so heated. Zinc on the surface of the galvanized steel sheet is vaporized in the laser irradiation process and the contact process with the molten pool, and enters the molten pool of brazing material. However, since the molten pool is kept at a relatively low temperature, it is considered that the amount of zinc gas generated and the amount of zinc gas entering during the contact process with the molten pool decreases. Moreover, since it solidifies comparatively quickly, it is thought that zinc gas becomes difficult to escape from the surface of a molten pool. This can be expected to suppress or prevent the occurrence of bonding defects such as pits.

  It should be noted that how to set the magnitude and distribution of the energy density of the laser beam specifically is arbitrary. This is because, for example, the finish of brazing varies depending on various factors such as the composition, shape or amount of the brazing material, the heat conduction characteristics or galvanizing amount of the galvanized steel sheet, and the traveling speed of laser irradiation. Therefore, it is only necessary to conduct experiments to find a good setting. In any case, it is not always necessary to give the required energy at the same energy density to the brazing material, but it is better to first give a high energy density and later at a low energy density in order to improve the brazing finish. preferable. It can be said that one of the characteristic points of the present invention is that this non-uniform energy density setting is realized by changing the energy density on the front side and the rear side of the moving laser beam.

In one aspect of the galvanized steel sheet laser brazing apparatus of the present invention, the laser beam irradiation mechanism irradiates a laser beam in a divergent manner with respect to the laser irradiation position from the laser irradiation direction inclined forward in the traveling direction. The energy density at the laser irradiation position of the laser beam is set higher on the front side in the traveling direction than on the rear side in the traveling direction. The divergent laser beam is obtained by using a diverging lens after focusing once using a convex lens that is focused on the front side (laser irradiation source side) of the irradiation position, or by a concave lens provided on the front side of the irradiation position. It can be obtained by using the spread. Since the laser density increases toward the front side of the laser beam that spreads toward the end, it is possible to relatively increase the energy density on the front side in the traveling direction at the laser irradiation position by irradiating from the front side in the traveling direction.
Laser irradiation from the front side in the traveling direction can be realized by adjusting the irradiation direction of the laser beam with respect to the laser irradiation position using a mirror or the like. The laser irradiation angle may be fixed or variable. If it is variable, it may be adjusted manually or automatically. As an example of automatic adjustment, there is a mode in which an optimum angle is calculated based on the temperature monitoring result.

  In one aspect of the galvanized steel sheet laser brazing apparatus of the present invention, the supplying means supplies the brazing material to the laser beam at a relatively large angle, thereby increasing the density of the laser beam irradiated to the brazing material. It may be allowed. A relatively large angle means that the angle is not nearly parallel, for example, about 40 degrees or more. Further, it may be supplied at an angle substantially orthogonal, that is, at least about 60 degrees or more, or about 70 to 80 degrees or more. When the laser irradiation angle can be changed in the laser beam irradiation mechanism, it is also effective to change the supply angle of the brazing material in conjunction with it. It is also effective to make the brazing material to be supplied a planar shape and increase the laser irradiation area as compared with its volume.

  In one aspect of the galvanized steel sheet laser brazing apparatus of the present invention, the laser beam irradiation mechanism has a function of optically adjusting the laser beam to be non-uniform at least on the front side and the rear side in the traveling direction. Thereby, the energy density at the laser irradiation position of the laser beam is set higher on the front side in the traveling direction than on the rear side in the traveling direction. Optical adjustment is control using physical phenomena such as refraction, diffraction, reflection, and shielding, and can be performed by a lens, a diffraction grating, a mirror, a shield, or the like. This adjustment may be performed manually or automatically by a technique such as an optimization operation corresponding to the temperature monitoring result.

  In one aspect of the galvanized steel sheet laser brazing apparatus of the present invention, in the laser beam irradiation mechanism, the width of the laser beam at the laser irradiation position is set wider than the width of the brazing material. A laser beam is also applied to the steel plate. Therefore, the laser beam directly reaches the galvanized steel sheet, and the surface galvanizing is melted and vaporized. In particular, when the energy density of the laser beam is set high on the front side in the traveling direction, the zinc plating is actively evaporated prior to the melting of the brazing material, so that the zinc vapor entering the melting value after the melting of the brazing material. Is expected to decrease. For this reason, it can be expected that the generation of pits can be suppressed or prevented.

  The galvanized steel sheet laser brazing method of the present invention is a supply step of supplying a brazing material from the front side in the brazing progression direction to a laser irradiation position set in the vicinity of a brazing joint location of a joint including a galvanized steel sheet, A laser beam irradiation step of melting the supplied brazing material by irradiating the laser irradiation position to the laser irradiation position while relatively moving the laser irradiation position in the brazing direction, and is irradiated in the laser irradiation step. The energy density at the laser irradiation position of the laser beam is set higher on the front side in the traveling direction than on the rear side in the traveling direction.

  The method for producing a brazed galvanized steel sheet according to the present invention is a method for producing a galvanized steel sheet brazed using the galvanized steel sheet laser brazing method.

  FIG. 1 is a diagram showing a schematic configuration of a laser brazing system 10 according to the present embodiment. In the illustrated laser brazing system 10, two galvanized steel plates 12 and 14 are set and the joint portions are overlapped. The laser brazing system 10 is a system for producing a joined galvanized steel sheet by brazing the joint to form a joint 16.

  Joining is performed by passing the wire 18 made of a brazing material to the vicinity of the joining location and irradiating the laser beam 20 near the tip to melt the brazing material. The molten brazing material flows into the joint and is firmly bonded to both the galvanized steel plates 12 and 14 in the course of cooling to form the joint 16. The irradiation position of the laser beam 20 and the supply destination of the wire 18 are sequentially moved in the brazing direction 22 along the shape of the joint, and thereby the long joint 16 is formed.

  The laser brazing system 10 includes a control unit 30, a laser oscillator 32, an optical member 34, an optical member driving unit 36, a wire supply device 38, and a steel plate holding device 42 as main components. The control unit 30 is a device having a computer function, and controls the operation of the entire system according to a program. The laser oscillator 32 generates a laser beam, and the optical member 34 includes a mirror and a lens, and guides the laser beam to a laser irradiation position. The optical member driving unit 36 is a device that drives the optical member 34 to move the irradiation position of the laser beam and adjust the irradiation angle. And the steel plate holding | maintenance apparatus 42 is an apparatus which sets the galvanized steel plate before joining to the predetermined position for laser irradiation, and carries it to a downstream process after joining.

  FIG. 2 is a schematic diagram depicting the laser brazing system 10 shown in FIG. 1 from a direction orthogonal to the traveling direction 22. The same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be simplified or omitted. The figure shows a convex lens 50 as a part of the optical member 34 shown in FIG. The convex lens 50 is installed so that the focal point 52 is on the upper side of the joint 16. That is, the laser beam 20 that has passed through the convex lens 50 is once narrowed down at the focal point 52 and then expanded again, and is irradiated onto the laser irradiation range 54 including the vicinity of the tip of the wire 18. In this laser irradiation range 54, the galvanized steel plates 12 and 14 have a flat shape, and the reference perpendicular line 56 indicates a perpendicular line drawn around this area. The optical axis 58 of the laser beam 20 is inclined forward in the traveling direction 22 with respect to the reference perpendicular. The magnitude of the inclination, that is, the magnitude of the torch angle 60 is set by the optical member including the convex lens 50.

  FIG. 3 is a schematic cross-sectional view showing a state near the laser irradiation range 54 shown in FIG. The same components as those in FIG. 2 are denoted by the same reference numerals to simplify the description. The galvanized steel plate 12 is a steel plate having a thickness of about 1 mm, and the surface thereof is thinly galvanized 72. In the vicinity of the joint, a brazing wire 18 is supplied from the front side in the traveling direction 22 and irradiated with a laser beam 20. The wire 18 is melted by the energy received from the laser beam. As a result, a brazing bead 74 is formed on the rear side in the traveling direction 22 of the laser beam 20. The brazing bead 74 is composed of a solidified portion 76 and a liquid molten pool 78 that have cooled and solidified over time. The molten pool 78 extends from the irradiation range of the laser beam 20 to the rear side in the traveling direction 22.

  The laser beam 20 extends radially from the focal point 52. Further, the optical axis 58 of the laser beam 20 is inclined forward of the traveling direction 22, that is, toward the wire 18. Therefore, the energy per unit area (energy density) irradiated to the wire 18 is larger than the energy density irradiated to the molten pool 78. This situation is supported by the experimental data shown in FIG. FIG. 4 is a diagram showing the instantaneous value of the energy density of the laser beam actually measured in the situation as shown in FIG. The horizontal axis represents the traveling direction, and the vertical axis represents the energy density of the laser beam. As is clear from this figure, the energy density is higher on the front side in the traveling direction than on the optical axis 58 as compared with the rear side in the traveling direction on the optical axis 58.

  Therefore, in the situation shown in FIG. 3, the wire 18 is rapidly heated and melted by the laser beam 20 having a high energy density. The molten pool 78 is provided with preliminary thermal energy for completely proceeding with the melting by the laser beam 20 having a low energy density. As a result, the brazing material having fluidity enters the joining portion and joins the galvanized steel sheets 12 and 14.

  In this process, vaporization of the zinc plating 72 having a low boiling point occurs. Vaporization can occur when the laser beam 20 is directly applied to the zinc plating 72 or when the molten brazing material heats the zinc plating 72. A part of the zinc gas enters the molten pool from the lower side of the wire 18. However, since the molten pool 78 is kept at a relatively low temperature, the amount of zinc gas entering the interior is relatively small. Moreover, the flow inside the molten pool 78 is also relatively gentle, and it is rare that zinc gas jumps out of the surface across the molten pool 78 until the brazing material is solidified. Therefore, most of the invading zinc gas is taken into the brazed bead 74 as in the case of the zinc gas 80 shown in FIG. 3, for example, and forms a space or is crushed as it cools and solidifies. It is done. Further, since the energy density of the laser beam 20 is high on the front side in the traveling direction, much of the galvanizing 72 is evaporated in advance, and there is an effect that generation of zinc gas that can be taken into the brazing material is suppressed. Conceivable.

  FIG. 5 shows a drawing prepared by measuring the surface temperature distribution in the brazing process shown in FIG. 3 using a measuring instrument and sketching from the obtained image. The temperature distribution 90 is indicated by an isoline for every 300 degrees. The brazing material supply position is located near the tip on the front side in the traveling direction. The brazing material extends from this vicinity to the rear side in the traveling direction by forming a brazed velvet, and the temperature distribution region of high temperature is correspondingly expanded. The molten pool extends in the vicinity of the high temperature distribution region, and the maximum temperature reaches 1200 ° C. or more, but the high temperature region is small as a whole. This situation becomes clear when compared with FIG. 9 obtained later from other experimental results.

  FIG. 6 shows a pit inspection diagram obtained by taking a photograph of the galvanized steel sheets 12 and 14 and the formed brazing bead 74 shown in FIG. 3 and sketching the results. The surface of the brazing bead 74 is flat and there are no pits.

  FIG. 7 shows results obtained by performing measurements as described with reference to FIG. 6 for various torch angles and tabulating them. The horizontal axis of the figure is the torch angle, the receding angle (the tilt angle of the laser beam toward the front in the traveling direction) increases toward the right side, and the advancing angle angle (the tilt angle of the laser beam toward the rear side in the traveling direction) increases toward the left side. . The number of pits on the vertical axis is indicated by the number per appropriate length. The illustrated results are summarized for the case where the laser beam is moved at a speed of 3 m / min with an output of 3.5 kW. The spot diameter of the laser beam at the irradiation position is about 3 mm. The brazing material is a general copper brazing containing Cu as a main component and containing about 3% of Si. The wire diameter is 1.2 mm, and the wire feeding speed is 5.5 m / min. It can be seen that the number of pits increases rapidly when the advance angle increases, and the number of pits decreases and disappears when the receding angle is increased. Specifically, the number of pits per unit length is 0 to 4 when the advancing angle is 10 degrees, 0 to 2 when the advancing angle is 0 degrees, and 0 when the advancing angle is 10 degrees. It has become. The sketch shown in FIG. 6 is a diagram in the case where the receding angle is 10 degrees, and there is no pit.

  Here, for reference, an example in which the torch angle is changed is shown in FIGS.

  FIG. 8 is a cross-sectional view when the torch angle is 0 degree. This figure corresponds to FIG. 3, and the same or corresponding components are denoted by the same reference numerals as in FIG. 3, and the description thereof is omitted or simplified. In this example, the optical axis 58 of the laser beam 20 is perpendicular to the galvanized steel sheet 12. And the molten pool 78 is receiving high energy compared with the case of FIG. For this reason, more zinc gas enters the molten pool 78. In addition, the brazing material moves relatively rapidly in the molten pool 78, and the zinc gas generated by the vaporization of the zinc plating 72 also moves violently. The figure shows the zinc gas 100 dissolved in the molten pool 78, the zinc gas 102 reaching the vicinity of the surface of the molten pool 78, and the pits 104 formed by the zinc gas jumping out of the surface immediately before solidification. Has been.

  In this example, the brazing wire 18 is supplied to the galvanized steel sheet 12 at a relatively large crossing angle. In contrast, in the example of FIG. 3, the brazing wire 18 is supplied to the galvanized steel sheet 12 at a small crossing angle. This difference is due to the fact that in the example of FIG. 3, the wire 18 is supplied at an angle close to a right angle with respect to the laser beam, and the laser beam 20 irradiated to the wire 18 is enlarged. In other words, in the example of FIG. 3, the supply angle of the wire 18 increases the laser beam density by bringing it closer to the irradiation source side of the laser beam 20, and increases the irradiated area closer to the laser beam 20. It is determined in consideration of the effect of increasing the laser beam density due to.

  9 and 10 are a temperature distribution diagram and a pit inspection diagram when the torch angle is 10 degrees, respectively. 9 is a diagram corresponding to FIG. 5, and FIG. 10 is a diagram corresponding to FIG. In FIG. 9, the temperature distribution 110 is shown by an isoline for every 300 degrees as in FIG. Here, a high temperature region of 1200 degrees or more is widely distributed on the rear side of the brazing filler metal supply position 112 located near the front end in the traveling direction. In the example of FIG. 5, the laser beam on the front side in the traveling direction having a high energy density was irradiated not only on the brazing material but also on the galvanized steel plate in the back, and the heat diffusion through the galvanized steel plate was performed quickly. The thermal energy supplied to the material has become relatively small. On the other hand, in the example of FIG. 9, since the brazing material after melting and spreading is irradiated with a laser beam having a relatively high energy density, the total energy received by the brazing material also increases, and a high temperature molten pool is formed. It is thought that it was formed. For this reason, the zinc gas which penetrate | invaded the molten pool can jump out of the surface of a molten pool easily. As a result, as shown in FIG. 10, a large number of pits 120, 122, 124, 126,. . . Will be formed.

  As described above, by irradiating the laser beam from the front side in the traveling direction, the energy density on the front side in the traveling direction of the laser beam can be relatively increased, and brazing with few or no pits can be easily performed. it can. However, the operation of relatively increasing the energy density on the front side in the traveling direction of the laser beam can be performed in other modes. For example, such an energy density difference can be created by making a laser beam homogeneous in the width direction optically non-homogeneous using a lens or a mirror.

It is a figure which shows schematic structure of a laser brazing system. It is a figure which shows the mode of brazing when a torch angle is set to a receding angle. It is a figure which shows the mode of the cross section in a brazing process. It is a figure which shows energy density distribution of a laser beam. It is a figure which shows the temperature distribution measured during laser brazing. It is a figure which shows the pit distribution in a brazing bead. It is a figure which shows the measurement result about the relationship between a torch angle and the number of pits. It is a reference view showing a cross section of brazing when the torch angle is 0 degree. It is a reference figure which shows temperature distribution at the time of setting a torch angle to 10 degrees of advance angles. It is a reference figure showing pit distribution when a torch angle is set to a forward angle of 10 degrees.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Galvanized steel plate laser brazing system, 12, 14 Galvanized steel plate, 16 joint part, 18 wires, 20 laser beam, 22 traveling direction, 30 control part, 32 laser oscillator, 34 optical member, 36 optical member drive part, 38 Wire feeding device, 42 Steel plate holding device, 50 convex lens, 52 focal point, 54 laser irradiation range, 56 reference perpendicular, 58 optical axis, 60 torch angle, 72 galvanizing, 74 brazing bead, 76 solidification part, 78 molten pool, 80 , 100, 102 Zinc gas, 90, 110 Temperature distribution, 92, 112 Brazing material supply position, 104, 120, 122, 124, 126 pits.

Claims (6)

Supply means for supplying a brazing material from the front side in the brazing progression direction to the laser irradiation position set in the vicinity of the brazing joint location of the joint including the galvanized steel sheet,
A laser beam irradiation mechanism that melts a brazing material supplied by irradiating a laser beam to the laser irradiation position while moving the laser irradiation position relatively in the brazing direction, and at the laser irradiation position of the laser beam A laser beam irradiation mechanism in which the energy density is set higher on the front side in the traveling direction than on the rear side in the traveling direction;
A galvanized steel sheet laser brazing apparatus comprising: The galvanized steel sheet laser brazing device according to claim 1,
In the laser beam irradiation mechanism, the laser beam is irradiated from the laser irradiation direction tilted forward in the traveling direction toward the laser irradiation position, so that the energy density of the laser beam at the laser irradiation position is the forward direction in the traveling direction. A galvanized steel sheet laser brazing device, which is set higher than the rear side. The galvanized steel sheet laser brazing device according to claim 1,
The laser beam irradiation mechanism has a function of optically adjusting the laser beam so that it is non-uniform at least on the front side and the rear side in the traveling direction, so that the energy density at the laser irradiation position of the laser beam is forward in the traveling direction. A galvanized steel sheet laser brazing apparatus characterized in that the side is set higher than the rear side in the traveling direction. The galvanized steel sheet laser brazing device according to claim 1,
In the laser beam irradiation mechanism, the width of the laser beam at the laser irradiation position is set wider than the width of the brazing material, whereby the galvanized steel plate around the brazing material is also irradiated with the laser beam. Galvanized steel sheet laser brazing equipment. A supply step of supplying a brazing material from the front side in the brazing progression direction to the laser irradiation position set in the vicinity of the brazing joint location of the joint including the galvanized steel sheet,
A laser beam irradiation step of melting the brazing material supplied by irradiating a laser beam to the laser irradiation position while moving the laser irradiation position relatively in the brazing progression direction;
Including
A galvanized steel sheet laser brazing method, wherein the energy density at the laser irradiation position of the laser beam irradiated in the laser irradiation step is set higher on the front side in the traveling direction than on the rear side in the traveling direction.   A galvanized steel sheet that is brazed using the galvanized steel sheet laser brazing method according to claim 5 is manufactured.

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