JP2010167428A - Laser beam welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform excellent laser beam welding by discharging gas of plating metal simultaneously with forming a bead when welding two plated and lapped metal plates by laser beam. <P>SOLUTION: When a laminated body 10a is welded by the laser beam L1, an irradiation diameter part 18 of the laser beam L1 and a heat-affected zone 20 which is formed on a circumferential edge of the irradiation diameter part 18 and reaches temperature in the range of equal to or higher than that of the evaporation of the plating before completing the annular welding pass through an area during welding, the area is defined as a heat-affected pass 26. The entire area which is heated to the temperature of the evaporation of the plating before completing the annular welding is defined as a heat-affected range 30. The entire range finally surrounded by a weld bead 22 is scanned by the laser beam L1 so as to be heated above the evaporation temperature of the plating before completing the annular welding. The heat-affected range 30 is circular, and its radius R1 is set to be equal to or less than the width W of the heat-affected pass 26. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a laser welding method in which laser beams are irradiated from one surface to two superimposed metal plates and welded in an annular shape.

  Conventionally, surface-treated metal plates such as galvanized steel plates have been widely used as structural members such as automobile bodies.

  When laser welding these plated steel sheets, a sufficient area cannot be obtained when spot welding is performed, and therefore, a method of welding with a circular bead in consideration of strength has been proposed (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 2007-888

  However, it is conceivable that in the initial stage of the work of forming the circular bead, the plating is not melted and remains in the area surrounded by the circular bead. It is conceivable that the surrounding portion that has not melted melts due to heat conduction from the surroundings, and eventually a bead is formed. Since the central portion is already closed by the bead formed in the periphery, it is not discharged, and the internal pressure increases, which may cause explosion.

  In addition, when the bead is formed in a C-shape or the like in order to eliminate the surrounding portion and secure a path through which the metal plating gas is discharged, the area required for welding is unnecessarily widened and is not efficient. It may also cause a decrease in fatigue strength.

  The present invention has been made in consideration of such problems, and before the formation of the molten bead is completed, the gas generated by evaporation of the treatment material in the process of forming the molten bead can be discharged to the outside. An object of the present invention is to provide a laser welding method that makes it possible to reduce the occurrence of explosions as much as possible.

  The laser welding method according to the present invention is a laser welding method in which laser beams are irradiated from one surface to two superimposed metal plates and welded in an annular shape, and at least one of the laminated surfaces of the metal plates is subjected to a surface treatment. And the entire region finally surrounded by the molten bead is heated to a temperature equal to or higher than the evaporation temperature of the surface treatment material before the end of the annular welding.

  Thereby, the gas which the processing material evaporated on the lamination surface of the metal plate can secure the discharge path to the outside, and can suppress the occurrence of explosion.

  On the laminated surface, a laser bead diameter portion and a periphery of the light diameter portion are formed as a heat-affected zone in a range above the temperature at which the treatment material evaporates before the end of the annular welding, The heat-affected zone may be allowed to pass through the entire range that is finally surrounded by the above.

  According to the laser welding method according to the present invention, the gas in which the treatment material has evaporated on the laminated surface of the metal plates can secure a discharge path to the outside and suppress the occurrence of explosion.

It is a partial cross section side view of a laminated body and a laser welding machine. It is a partial cross section side view which shows the state which irradiated the laser from the state shown in FIG. It is a figure explaining the heat influence range. It is a top view which shows the bead formed with the laser welding method which concerns on 1st Embodiment, and a heat influence range. It is a section side view showing the bead formed with the laser welding method concerning a 1st embodiment, and a heat influence range. It is a top view which shows the bead formed with the laser welding method which concerns on 2nd Embodiment, and a heat influence range. It is a partial cross section side view of a layered product and a laser welding machine concerning a modification. It is a partial cross section side view which shows the state which irradiated the laser from the state shown in FIG.

  Hereinafter, the laser welding method according to the present invention will be described with reference to FIGS.

  First, basic means common to the embodiments will be described. In the laser welding method according to each embodiment, as shown in FIG. 1, one surface (hereinafter referred to as a surface on the upper plate 12 side) is formed on the laminated body 10 a in which the upper plate 12 and the lower plate 14 are overlapped. 2), as shown in FIG. 2, laser L1 is irradiated from the laser welding machine 16, and welding is performed while moving the irradiation position. The workpiece to be welded by the laser welding method according to each embodiment may be a laminated body 10b (see FIGS. 7 and 8) described later.

  As a means for moving the irradiation position of the laser L1, the direction of the laser irradiation part of the laser welding machine 16 may be changed, the irradiation direction may be changed via a predetermined optical means, or the work side may be moved. As a means for moving the irradiation position of the laser L1, the laser welding machine 16 may be moved by a robot. The laser L1 is, for example, a YAG laser. The moving speed of the irradiation position of the laser L1 is basically a constant speed.

  The upper plate 12 is galvanized as a surface treatment, and a plating layer (treatment material) is provided on the upper surface 12a and the lower surface 12b of the steel plate 12c. Similarly, the lower plate 14 is galvanized, and a plating layer is provided on the upper surface 14a and the lower surface 14b of the steel plate 14c.

  A moderately narrow gap G <b> 1 is secured between the lower surface 12 b of the upper plate 12 and the upper surface 14 a of the lower plate 14 via the spacer 15.

  FIG. 2 is a cross-sectional side view illustrating a state in which the laser L1 irradiated from the upper surface 12a side of the upper plate 12 is irradiated to the upper plate 12 and the lower plate 14. An irradiation diameter portion 18 (see FIG. 3) of the laser L1 and a heat-affected portion 20 formed on the periphery of the irradiation diameter portion 18 and in a range equal to or higher than a temperature at which galvanization evaporates are formed on the upper plate 12 and the lower plate 14. Is formed. The heat-affected zone 20 has a range in which galvanization evaporates before the end of the annular welding.

  The cross sections of the irradiation diameter portion 18 and the heat affected zone 20 of the laser L1 have substantially the same area on the lower surface 12b and the upper surface 14a of the laminated surface. The zinc gas 24 generated by evaporating the galvanizing is discharged from the gap G1, as indicated by the dashed arrow.

  As indicated by the arrows in FIG. 3, when the center O1 of the irradiation diameter portion 18 is moved from the point P1 to the point P2, the range through which the irradiation diameter portion 18 has moved and moved (the double hatched range in FIG. 3) is a weld. The range is defined as a molten bead 22. Further, the region through which the heat affected zone 20 passes during welding (hatched range in FIG. 3) is a region in which galvanization evaporates before the end of the annular welding, and is defined as a heat affected path 26.

  The entire region heated to a temperature at which the plating evaporates before the end of the annular welding is defined as a heat affected range 30 (see FIG. 4). The molten bead 22 is included in the heat affected path 26. Let W be the width of the heat affected path 26. Strictly speaking, the width of the heat-affected path 26 is not necessarily constant, but is assumed to be constant so that the invention can be easily understood.

  In the laser welding method according to the present embodiment, the laser L1 is scanned so that the entire range finally surrounded by the molten bead 22 is heated to the evaporating temperature of the galvanizing before the annular welding is finished. Then, the upper plate 12 and the lower plate 14 are welded. Further, the irradiation position of the laser L1 may be moved along a predetermined route so that a region surrounded by the heat affected path 26 does not occur during the movement.

  Next, individual embodiments will be described.

  As shown in FIG. 4, in the laser welding method according to the first embodiment, the path 32 of the center O1 of the irradiation diameter portion 18 is a closed path that makes a circular loop around the base point (center of gravity) A, and is on the laminated surface. The heat-affected area 30 is formed in a circular shape. At this time, the radius R1 of the heat-affected area 30 that is finally formed is set to be equal to or smaller than the width W of the heat-affected path 26. As a result, the final heat-affected area 30 includes the base point A, and the entire area finally surrounded by the molten bead 22 is heated to the evaporating temperature of the galvanizing or higher before the end of the annular welding. Further, there is no region surrounded by the heat affected path 26 during the movement of the laser L1. In the example shown in FIG. 4, the end of the heat affected zone 20 is matched with the base point A.

  In this welding method, if the irradiation diameter portion 18 is at least partially overlapped at the start point and the end point, the path 32 is substantially annular, and the generation of stress at these start point and end point can be prevented.

  In the laser welding method according to the first embodiment, the laser L1 is scanned, and the cross-sectional side surface of the laminated body 10a after drawing the circular shape in which the center O1 of the irradiation diameter portion 18 is a circular path on the upper plate 12 The figure is shown in FIG. As shown in FIG. 5, simultaneously with the start of the formation of the molten bead 22, the zinc plating melts and evaporates on the laminated surface of the upper plate 12 and the lower plate 14, and the zinc gas 24 is generated. The zinc gas 24 is discharged from the gap G1.

  As described above, according to the laser welding method according to the first embodiment, the entire range finally surrounded by the molten bead 22 is heated to the evaporating temperature of the galvanizing or higher before the annular welding is finished. .

  Thereby, before the molten bead 22 is closed in an annular shape, a discharge path for discharging the zinc gas 24 generated on the laminated surface of the upper plate 12 and the lower plate 14 to the outside is secured. In other words, the molten bead 22 is closed. In this case, the galvanizing inside thereof has already been evaporated and discharged to the outside, and the internal pressure does not increase and the occurrence of explosion can be suppressed.

  Even if gas is generated inside the annular shape, the amount is so small that the internal pressure does not increase, and the occurrence of explosion can be suppressed. Moreover, the path | route 32 is cyclic | annular, Comprising: There is no distinction of a starting point and an end point after welding, and the fall of fatigue strength can be prevented. Furthermore, the area of the molten bead 22 is larger than the irradiation diameter portion 18, and the welding joint strength is increased.

  Furthermore, by making the heat-affected area 30 circular, stable welding without strength directivity is possible and the appearance is improved. By setting the irradiation route to a closed route that makes a round, stable and lean welding is possible.

  As shown in FIG. 6, in the laser welding method according to the second embodiment, the path 34 of the center O1 of the irradiation diameter portion 18 is a circular circuit that forms an equilateral triangle with the base point A as a reference, and The distance α from the base point A to the vertex of the regular triangle along the path 34 is set to be equal to or less than the radius β (= W / 2) of the heat affected zone 20. As a result, a triangular molten bead 22 is obtained, and for example, welding can be performed in accordance with the shape of the corner of the plate 36.

  In each of the above-described embodiments, the gap G1 (see FIG. 2) is provided between the upper plate 12 and the lower plate 14, and the gas is discharged from the gap G1. The upper plate 12 and the lower plate 14 may be laminated in contact with each other.

  That is, as shown in FIG. 7, the upper plate 12 and the lower plate 14 are laminated in contact with each other, and there is no gap between them. In this case, the laser L2 has a relatively short focal length by a predetermined optical means, and the cross section of the irradiation diameter portion 18 and the heat-affected zone 20 is such that the upper surface of the upper plate 12 is long and the lower surface 14b side of the lower plate 14 is short. As a side, a trapezoid with a certain inclination angle may be used.

  When the laser L2 is irradiated in this way, a molten bead 22 is formed in the range of the irradiation diameter portion 18 or the heat affected zone 20, and the upper plate 12 and the lower plate are solidified and cooled in the melting bead 22 solidification process. 14 has volume shrinkage. At this time, as shown in FIG. 8, from the shape of the sectional view of the irradiation diameter portion 18 and the heat affected zone 20 of the laser L2, the one closer to the laser welding machine 16 is combined with the irradiation diameter portion 18 and the heat affected zone 20. Since the area is wide, the volume shrinkage is large, and the volume shrinkage is small in the far side. Therefore, a gap G <b> 2 is formed around the difference between the volume shrinkage between the upper plate 12 and the lower plate 14.

  Thus, before the molten bead 22 is formed by a predetermined path, the zinc gas 24 generated in the process of forming the molten bead 22 can be discharged to the outside from the gap G2, and the occurrence of explosions is made as much as possible. The effect of reducing can be achieved.

  In the above-described embodiment, the entire range finally surrounded by the molten beads 22 by the irradiation of the lasers L1 and L2 is heated so as to be equal to or higher than the evaporation temperature of the surface treatment material before the end of the annular welding. However, the heating method is not limited to this, and for example, a heat source other than the welding lasers L1 and L2 may be prepared. The heating by another heat source does not need to be synchronized with the lasers L1 and L2, and may be heated from a reasonably early stage.

  On the other hand, if laser scanning is used for heating as in the present embodiment, the configuration becomes simple, which is preferable.

  In addition, the upper plate 12 and the lower plate 14 are galvanized on both upper and lower surfaces, but not limited thereto, at least one of the overlapping surfaces between the upper plate 12 and the lower plate 14, That is, if at least one of the lower surface 12b of the upper plate 12 or the upper surface 14a of the lower plate 14 is plated, the laser welding method according to the present embodiment can be effectively applied.

  In the above-described embodiment, the galvanized steel sheet is used. However, surface treatment such as an aluminized steel sheet or a chrome plated steel sheet may be used, and the present invention is not limited to the galvanized steel sheet.

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

DESCRIPTION OF SYMBOLS 10a, 10b ... Laminated body 12 ... Upper plate 12a, 14a ... Upper surface 12b, 14b ... Lower surface 14 ... Lower plate 16 ... Laser welding machine 18 ... Irradiation diameter part 20 ... Heat affected zone 22 ... Molten bead 24 ... Zinc gas 26 ... Heat Influence path 30 ... Heat influence range 32, 34, 36 G1, G2 ... Gap L1, L2 ... Laser O1 ... Center of irradiation diameter part

Claims (2)

In a laser welding method in which a laser beam is irradiated from one surface to two stacked metal plates and welded in an annular shape,
Surface treatment is applied to at least one of the laminated surfaces of the metal plate,
A laser welding method characterized in that the entire range finally surrounded by a molten bead is heated to a temperature equal to or higher than the evaporation temperature of the surface-treated material before the end of annular welding. The laser welding method according to claim 1, wherein
On the laminated surface, formed on the periphery of the irradiation diameter portion of the laser and the irradiation diameter portion, a range above the temperature at which the treatment material evaporates before the end of the annular welding is a heat affected zone,
A laser welding method, wherein the heat-affected zone is allowed to pass through an entire range finally surrounded by a molten bead.

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