JP2008207246A - Laser brazing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser brazing method which is suitable for a lap fillet joint of sheet metal. <P>SOLUTION: The brazing material is melted by irradiation of a laser beam having a wave length of near-infrared light or far-infrared light, while a brazing material made of a copper alloy is being supplied, in a state that a backing material is in contact with an area corresponding to a position whose upper surface side is to be irradiated by the laser beam and the lower surface side is the fillet of the lap fillet joint where a top and a bottom steel sheet members are lapped together. The backing material may be a rotatable member, a slidable member or a close contacting member covering the whole bottom surface of the lap fillet joint, depending upon the position to be applied. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser brazing method, and more particularly to a laser brazing method suitable for use in a lap fillet joint of thin steel plates.

  Brazing, which does not melt the material to be joined, but is joined via a brazing material having a melting point lower than that of the material to be joined, is widely used in electronic parts, automobiles, etc. The heat sources include furnace heating, gas flame, arc Or various things, such as a laser, are used.

  Among these, laser brazing is thin like an automobile body because the heat input required for brazing is small and heat distortion does not easily occur and the accuracy of the member is maintained, and a good-looking joint can be efficiently produced. Used for joining lap fillet joints of structural members made of steel plates.

  FIG. 7 is a schematic diagram for explaining the laser brazing of the lap fillet joint. The brazing material wire 3 is supplied to the edge portion of the upper plate 1 in contact with the lower plate 2, and the spot diameter is larger than the wire diameter of the brazing material wire 3. The brazing material wire 3, the edge of the upper plate 1, and the surface of the lower plate 2 are irradiated and heated by the laser beam 4, and brazing is performed by simultaneously moving the wire supply point and the laser beam 4.

  Regarding laser brazing of a lap fillet joint of an automobile body, Patent Documents 1 to 3 have been proposed for the purpose of improving the joining strength and appearance.

  Patent Document 1 describes that a certain gap is provided between an upper plate and a lower plate in a lap fillet joint, and a molten brazing material enters the gap to increase a bonding area.

  Patent Document 2 relates to a laser brazing processing method and apparatus for increasing the bonding strength between a pair of members that are overlapped with each other without increasing the build-up of a bead, and a gap between an upper plate and a lower plate of a lap fillet joint. It is described that a securing roller is inserted to provide a gap and a molten brazing material is inserted to increase the wet area.

Further, Patent Document 3 relates to a method of attaching a laser emitting device called a machining head to an articulated robot and laser brazing the bending portion, and supplying the molten material according to the moving speed of the processing point at the bending portion. It is described that adjustment is made so that the appearance portion does not rise.
JP 2005-59209 A JP 2006-175481 A Japanese Patent No. 3555612

  In order to perform laser brazing properly, it is necessary to heat the upper and lower plates so that the brazing material melted by the laser beam is sufficiently wet and spread on the upper plate edge and the lower plate surface. It is important not to melt the base material so as not to increase strain and deformation.

  FIG. 8 schematically shows a cross-section of the joint of the lap fillet joint after laser brazing, where (a) shows a state in which a weld metal 5 is formed by brazing at the overlapping end portions of the upper plate 1 and the lower plate 2. When the melting of the plate 2 (base material) does not occur, (b) shows the case where the melting part 6 occurs.

  In the case of laser brazing of a steel sheet, a copper alloy (melting point: about 1,000 ° C.), which has a melting point lower than that of steel and can obtain a relatively high strength weld metal, is often used. In the case of a laser with a wavelength of near-infrared light or far-infrared light, such as a gas laser, the absorption rate of steel is higher than that of copper. The part is heated to a temperature exceeding the melting point of the steel sheet.

  In the base steel sheet directly under the laser irradiation, a temperature distribution is formed in which the surface irradiated with the laser reaches the maximum temperature due to the heat conduction in the steel sheet. However, if the base metal is thin, The steel sheet surface is likely to be hotter and the base material is likely to melt.

For example, laser brazing using a silicon bronze wire (wire diameter: 1.2 mm) equivalent to JIS Z 3341 YCuSiB in a lap fillet joint of steel plates with a thickness of 0.8 mm and a tensile strength of 270 N / mm ² Then, under the conditions of a laser output of 3 kW, an irradiation laser beam spot diameter of 2.4 mm, a joining speed of 3 m / min, and a brazing material wire supply speed of 3 m / min, the brazed portion of the lower plate surface has a depth of 0.1 to 0.1 by laser irradiation. Melts about 0.2 mm.

  This is because the thickness of the lower steel plate is thin and heat conduction is unlikely to occur, so the surface temperature of the lower plate became higher than the melting point of the steel plate due to laser irradiation. Even if the laser irradiation conditions were adjusted, the melting of the brazing wire -Conditions that allow sufficient wetting and prevent melting of the lower steel sheet cannot be obtained.

  Accordingly, an object of the present invention is to provide a laser brazing method capable of brazing without melting the base material even if the base material of the lap fillet joint is a thin steel plate.

The object of the present invention can be achieved by the following means.
1. A laser that melts the brazing material by irradiating it with a laser beam while supplying a brazing material made of a copper alloy to the fillet portion of the lap fillet joint where the steel plate-like members of the upper and lower plates are overlapped A brazing method, characterized in that a backing metal is provided on a lower surface side of the lap fillet joint so as to be in contact with a portion of the upper surface side facing a position irradiated with a laser beam.
2. 2. The laser brazing method according to claim 1, wherein the backing metal is movable in synchronism with the progress of the laser beam while in contact with the lower surface side portion opposite to the position irradiated with the laser beam on the upper surface side. .
3. 3. The laser brazing method according to 2, wherein the backing metal is a rotating body or a sliding member.
4). 4. The laser brazing method according to any one of 1 to 3, wherein the laser is a laser having a wavelength of near infrared light or far infrared light.

  According to the present invention, melting of a base steel plate at a position irradiated with a laser is suppressed, and a lap fillet joint with less thermal strain and deformation is obtained, which is extremely useful in industry.

  The present invention is characterized in that a backing metal for heat removal is provided at a position on the lower surface side of the portion irradiated with the laser beam on the lower plate of the lap fillet joint.

  FIG. 1 is a diagram for explaining a laser brazing method for a lap fillet joint according to an embodiment of the present invention. The lap fillet joint is constituted by an upper plate 1 and a lower plate 2, and a laser beam 4 is applied to the fillet portion. Irradiate to supply a wire-like brazing material 3. In the figure, each of the upper plate 1 and the lower plate 2 of the lap fillet joint is fixed by a clamp device 7.

  A backing metal 8 is brought into contact with the lower plate 2 of the lap fillet joint, and heat is extracted from the portion heated by the irradiated laser beam 4 by heat conduction.

FIG. 4 is a view for explaining the irradiation position of the laser beam 4 and shows a cross-sectional view in the width direction of the lap fillet joint. The irradiation position of the laser beam 4 is such that the vicinity of the beam center axis is outside the end portion 1 a of the upper plate 1 and is directly irradiated on the upper surface of the lower plate 2, and the outer edge of the laser beam 4 is applied to a part of the upper plate 1. Then, the brazing material is easily wetted with the upper plate end face and the lower plate surface, which is preferable in forming a sound welded portion.

  In the lower plate 2, the irradiated upper surface portion 2 a exposed to the vicinity of the beam center axis of the laser beam 4 is easily melted. Therefore, the mounting position of the backing metal 8 is the center in the width direction on the back surface side of the lower plate 2. Therefore, it is preferable in view of cooling efficiency to be within a position facing the irradiated upper surface portion 2a.

  The width of the backing metal 8 is preferably equal to or larger than the beam diameter of the laser beam 4 in order to increase the heat removal effect, and is further water-cooled.

  Depending on the desired amount of thermal strain of the lap fillet joint, the backing metal 8 has a dimensional shape such as the width of the joint cross section, the length of the contact portion with respect to the joint length, and the presence or absence of a cooling structure such as material and water cooling. The cooling capacity such as is appropriately selected. Usually, the backing metal 8 is installed so as to contact the lower surface of the lower plate over the entire length of the joint of the lap fillet joint.

  The backing metal 8 is preferably made of metal, and preferably has a thermal conductivity equal to or higher than that of the base material on which laser irradiation is performed from the viewpoint of heat conduction and heat removal.

  Further, in order to efficiently conduct heat by irradiation from the lower plate 2, it is important that the lower plate 2 is in close contact with the lower plate 2. In the present invention, the shape of the backing metal 8 is not particularly defined, and various shapes can be used depending on the use environment.

  FIG. 2 shows another embodiment of the present invention, in which a plate-like backing 9 made of a steel plate or a copper plate is overlapped and brought into contact with the back side of the lower plate, and the lower plate is pressed from the front side by mechanical or pneumatic pressure. An example of the arrangement in which the plate-like backing metal 9 is pressed against the back surface of the lower plate facing the laser irradiation portion is shown.

  Further, a member that can move in synchronization with the progress of the laser beam, for example, rotating, while the backing metal is in contact with the portion opposite to the position irradiated with the laser beam on the lower plate upper surface side on the lower plate rear surface side A rotating body such as a roller or a square member may be used.

  In any case, it is preferable that the material is made of metal having a large heat removal effect, and fins and openings are provided so as to obtain an air cooling effect, and the material is moved while being in contact with the back surface of the lower plate.

  FIG. 5 shows a case where the backing metal is the rotating roller 9, and FIG. 6 shows a case where the backing metal is the sliding member 10. In the case of the sliding member 10, it is easy to slide while being in surface contact with the lower surface and the contact surface is flat so that the heat removal effect is large, and the corner has a surface roughness equal to or less than that of the base material to be joined. It should be made of metal with a mold appearance.

  The laser brazing method according to the present invention is particularly effective for a lap fillet joint of steel plates having a thickness of 1 mm or less, which hardly removes heat due to heat conduction in the thickness direction.

  As described above, the backing metal is brought into close contact with the back surface of the lower steel sheet, and the lower steel sheet is removed by heat conduction to the backing metal, thereby preventing the steel sheet from melting in the laser irradiated part during laser brazing of the thin steel sheet. This makes it possible to maintain advantages and quality such as low thermal distortion of laser brazing.

  Cold-rolled steel plate (equivalent to JIS G 3141 SPCC) with a thickness of 0.8 mm × width 150 mm × length 300 mm is used for the lower and upper plates, and a copper alloy wire (Cu-3.5% Si-1% Mn) with a wire diameter of 1.2 mm , JIS Z 3341 YCuSiB equivalent) was used for brazing, and laser brazing was performed on a lap fillet joint with a lap of 15 mm.

  The lap fillet joint is: 1. A 25mm x 25mm x 300mm square bar-shaped copper piece placed and adhered to the back of the lower plate facing the laser irradiation part (Fig. 1). 2. A steel plate (SPCC) of the same size as the lower plate steel plate (plate thickness 0.8mm x width 150mm x length 300mm) is placed on the back side of the lower plate and clamped together with the lower plate steel plate (Fig. 2). 3. A copper plate instead of the steel plate (SPCC) (FIG. 2). 4. A movable copper roller disposed on the back side of the lower steel plate (FIG. 5) and 5. 5. Five examples of a movable copper block arranged as a sliding member on the back side of the lower plate steel plate (FIG. 6); Only the upper plate and the lower plate were clamped, and nothing was arranged on the back surface of the lower plate of the laser irradiation part (FIG. 3).

  In each lap fillet joint, the upper plate and the lower plate (including the backing metal in the case of FIG. 2) were fixed at a position 20 mm away from the laser irradiation portion by a clamping mechanism operated by pneumatic pressure.

  The Nd: YAG laser was used as the laser, laser irradiation was performed with a laser output of 3 kW and a beam spot diameter of 2.4 mm, and a brazing joint was fabricated with a bonding speed of 3 m / min and a wire supply speed of 3 m / min.

  The joint was evaluated by observing the joint cross-section at three locations: 300 mm from the brazing start end, 30 mm from the brazing start end, 30 mm from the brazing end end, and 30 mm from the brazing end end. did.

  Table 1 shows the test results. In the joints of Nos. 1 to 5 which are the embodiments of the present invention, the upper plate steel sheet can be prevented from melting by the heat removal effect of the copper piece, the steel plate, and the copper plate, and the lower plate is judged as acceptable. In Comparative Example No. 6 in which nothing is arranged on the back surface of the steel plate, the state in which the upper plate steel plate surface is melted by laser irradiation was observed, and the determination was rejected.

Example of the present invention. Another embodiment of the present invention. Conventional example. FIG. 2 is a detailed view of the example of the present invention shown in FIG. 1. Example of the present invention (backing metal: rotating roll) Example of the present invention (backing metal: sliding member) Schematic diagram explaining laser brazing of lap fillet joints In the joint section of a lap fillet joint, (a) is a case where the base material is not melted, and (b) is a view showing a case where the base material is melted.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper plate 2 Lower plate 3 Brazing material 4 Laser 5 Weld metal 6 Melting part 7 Clamping device 8 Backing metal 9 Rotating roll 10 Sliding member

Claims (4)

  A laser that melts the brazing material by irradiating a laser beam while supplying a brazing material made of a copper alloy to the fillet portion of the lap fillet joint in which the steel plate-like members of the upper and lower plates are overlapped A brazing method, characterized in that a backing metal is provided on a lower surface side of the lap fillet joint so as to be in contact with a portion of the upper surface side facing a position irradiated with a laser beam.   2. The laser according to claim 1, wherein the backing metal is movable in synchronism with the progress of the laser beam while in contact with the lower surface portion corresponding to the position irradiated with the laser beam on the upper surface side. Brazing method.   The laser brazing method according to claim 2, wherein the backing metal is a rotating body or a sliding member.   The laser brazing method according to any one of claims 1 to 3, wherein the laser is a laser having a wavelength of near infrared light or far infrared light.

Images