JP2021070047A - Laser welding method for steel plate - Google Patents

Abstract

To provide a laser welding method for steel plate which can suppress formation of a blow hole without performance of time-consuming adjustment.SOLUTION: A laser welding method for steel plate comprises a groove processing process, an overlapping process, and an irradiation process as follows. In the groove processing process, a groove 7, which has a width larger than that of a molten pool 6 when welding by laser irradiation from an irradiation part, is formed in one steel plate 1 of steel plates which are overlapped in a thickness direction. In the overlapping process, another steel plate is overlapped with the steel plate 1 with the groove 7 formed therein to cover opening of the groove 7. In the irradiation process, laser beam is radiated toward a bottom of the groove 7 from the irradiation part, and at the same time, the irradiation part is moved so that the molten pool 6 when welding by irradiation of the laser beam moves in an extension direction of the groove 7 in the state that the pool has an interval between itself and inside surfaces 7a on both sides in a width direction of the groove 7.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for laser welding a steel sheet.

In laser welding of steel sheets, steel sheets are defined by irradiating steel sheets stacked in the thickness direction with a laser from an irradiation portion in the thickness direction and moving the irradiation portion along the steel plates. It is known to weld at welds of length and width.

By the way, in a steel sheet to be laser welded, the surface of the steel sheet may be coated with zinc to prevent rust, or foreign matter such as oil may adhere to the surface of the steel sheet. In this case, when the steel plates are welded by laser irradiation, the zinc and foreign matter melt and evaporate to generate gas, and the gas mixes with the molten pool at the time of welding and blows to the welded part of the steel plates. Holes may be formed.

Therefore, it is conceivable to weld the steel sheets by laser irradiation in a state where a gap for letting the gas escape is formed between the steel sheets stacked in the thickness direction. In this way, even if zinc or foreign matter on the surface of the steel sheet melts and evaporates during welding to generate gas, the gas is discharged through the gaps between the steel sheets. Therefore, the gas does not mix in the molten pool, and the mixing of the gas into the molten pool suppresses the formation of blow holes in the welded portions of the suppressed steel sheets.

Incidentally, in order to form a gap between the steel plates stacked in the thickness direction, in Patent Document 1, by irradiating one steel plate with a beam before welding, the portion of the steel plate to which the beam hits is thermally expanded. It is made to form a protrusion. As a result, when the steel plates are stacked in the thickness direction, a gap is formed between the steel plates by the protrusions.

Further, in Patent Document 2, a recess is formed in one steel plate by bending, while a protrusion that is fitted into the recess is formed in the other steel plate by bending when the steel plates are stacked in the thickness direction. The amount of protrusion of the portion is set to be larger than the depth of the recessed portion. As a result, when the steel plates are stacked in the thickness direction, a gap having a size corresponding to the difference between the protrusion amount of the protrusion and the depth of the recess is formed between the steel plates. ..

Japanese Unexamined Patent Publication No. 7-167777 Japanese Unexamined Patent Publication No. 2013-237053

The gap between the steel plates stacked in the thickness direction must be accurately and appropriately sized, otherwise there is a problem that the welding between the steel plates is defective, and a blow hole in the welded portion between the steel plates. The problem arises that the formation of the steel cannot be suppressed. Specifically, if the size of the gap is too large, welding at the welded portion between the steel plates may not be properly performed when the laser is irradiated, and there is a possibility that the welding at the welded portion may be defective. On the other hand, if the size of the gap is too small, the gas generated by the melting and evaporation of zinc and foreign matter during welding is not effectively discharged through the gap and is mixed into the molten pool and becomes a welded portion between the steel plates. Blow holes may be formed.

However, when a gap is formed between the steel plates as shown in Patent Documents 1 and 2, it takes a lot of time and effort to make the gap an appropriate size. That is, in Patent Document 1, since the size of the protrusion corresponds to the size of the gap, the protrusion is formed so that the size of the protrusion corresponds to the appropriate size of the gap. The laser irradiation on the steel sheet of the steel sheet must be precisely adjusted. Further, in Patent Document 2, the difference between the depth of the recess and the amount of protrusion of the protrusion corresponds to the size of the gap. Therefore, the depth of the recesses and the protrusions of the protrusions so that the difference between the depth of the recesses in one steel plate and the protrusion amount of the protrusions in the other steel plate corresponds to the appropriate size of the gap. The amount must be finely adjusted.

An object of the present invention is to provide a laser welding method for a steel sheet capable of suppressing the formation of blow holes without performing time-consuming adjustment.

In the laser welding method of steel plates that solves the above problems, the steel plates stacked in the thickness direction are irradiated with a laser from the irradiation portion in the thickness direction, and the irradiation portions are moved along the steel plates to move the steel plates to each other. Weld at a weld with a specified length and width. Further, the welding method includes the following grooving step, stacking step, and irradiation step. In the grooving process, one of the steel plates stacked in the thickness direction extends in the same direction as the welded portion and has a width larger than that of the molten pool at the time of welding by irradiating the laser from the irradiated portion. To form. In the laminating step, another steel sheet is superposed on the steel sheet on which the groove is formed in the thickness direction to cover the opening of the groove. In the irradiation step, while irradiating the laser from the irradiation portion toward the bottom of the groove, the molten pool at the time of welding by the irradiation of the laser has a space between the inner surfaces on both sides in the width direction of the groove. The irradiation unit is moved so as to move in the extending direction of the groove in the state.

An enlarged plan view schematically showing a state in which one of the steel plates in which grooves are formed is viewed from the other steel plate side among the steel plates stacked in the thickness direction. The cross-sectional view which shows the state at the time of welding of steel plates. The cross-sectional view which shows the processing mode of the groove with respect to the steel plate in the grooving process. The plan view which shows the processing mode of the groove in the steel sheet. The cross-sectional view which shows the welding mode of steel plates in an irradiation process. The plan view which shows the state which one steel plate in the irradiation process is seen from the other steel plate side. The plan view which shows the state which one steel plate after welding is seen from the other steel plate side. FIG. 5 is a cross-sectional view showing a state in which the welded steel plates are viewed from the direction of arrows AA in FIG. FIG. 5 is a cross-sectional view showing another example of a groove formed in one steel plate. The plan view which shows the groove. The plan view which shows the other example of the groove formed in one steel plate. FIG. 5 is a plan view schematically showing another example of a laser irradiation mode on a steel plate.

Hereinafter, an embodiment of the laser welding method for a steel sheet will be described with reference to FIGS. 1 to 8.
1 and 2 each show an embodiment of laser welding of the present embodiment. As shown in FIG. 2, in the laser welding of the steel plates 1 and 2 stacked in the thickness direction, the steel plates 1 and 2 are welded to each other in the thickness direction (vertical direction of FIG. 2) from the irradiation unit 3. Irradiate the laser. Then, while irradiating the laser from the irradiation unit 3 as described above, the irradiation unit 3 is moved along the steel plates 1 and 2, that is, in the left-right direction of FIG. 2, so that the steel plates 1 and 2 are moved to each other. Weld at the welded portion 4 (FIG. 1) having the specified length and width. Note that FIG. 1 shows a state in which one of the steel plates 1 and 2 stacked in the thickness direction, the steel plate 1, is viewed from above in FIG.

When the steel plates 1 and 2 are welded to each other by laser irradiation, keyholes 5 are generated in the laser-irradiated portions of the steel plates 1 and 2 by melting and evaporating the steel plates 1 and 2. Further, a molten pool 6 is formed around the keyhole 5 in the steel plates 1 and 2 by melting the steel plates 1 and 2. Further, during such welding, gas is generated due to the evaporation of zinc coating the steel plates 1 and 2 and the evaporation of foreign substances such as oil adhering to the surfaces of the steel plates 1 and 2. In the laser welding of the present embodiment, the grooving step, the stacking step, and the laminating step are as follows so that the gas generated as described above is not mixed in the molten pool 6 and a blow hole is not formed in the welded portion 4. The irradiation step is carried out.

In the grooving process, one of the steel plates 1 and 2 stacked in the thickness direction extends in the same direction as the welded portion 4 and the molten pool at the time of welding by irradiating the laser from the irradiation portion 3. A groove 7 having a width larger than 6 (distance in the vertical direction in FIG. 1) is formed. The welded portion 4 is formed so as to extend in the left-right direction of FIG. In the stacking step, another steel plate 2 is superposed on the steel plate 1 on which the groove 7 is formed in the thickness direction to cover the opening of the groove 7. In the irradiation step, while irradiating a laser from the irradiation unit 3 toward the bottom of the groove 7, the molten pool 6 at the time of welding by the irradiation of the laser is between the inner side surfaces 7a on both sides of the groove 7 in the width direction. The irradiation unit 3 is moved so as to move in the extending direction of the groove 7 with a gap between the two.

Next, the grooving process, the stacking process, and the irradiation process will be described in detail individually.
[Grooving process]
3 and 4 show a processing mode of the groove 7 with respect to the steel plate 1. The groove 7 is formed by using a laser processing facility for performing laser welding on the steel plates 1 and 2.

That is, as shown in FIG. 3, the steel plate 1 is installed at a position corresponding to the irradiation unit 3 of the laser processing facility, and the steel plate 1 is irradiated with the laser from the irradiation unit 3 while irradiating the steel plate 1 with the irradiation unit 3. Move at a speed faster than the moving speed when performing laser welding along. As a result, the laser-irradiated portion of the steel sheet 1 moves, and the groove 7 is formed corresponding to the movement locus.

As shown in FIG. 4, in this example, the welded portion 4 extends so as to be annular in the steel plate 1. Then, the groove 7 is formed so as to be similarly annular along the welded portion 4 and not to overlap with the outer edge of the steel plate 1. Further, the width of the groove 7 is larger than the width of the welded portion 4, and the welded portion 4 is provided inside the groove 7 at intervals from the inner side surfaces 7a on both sides in the width direction of the groove 7. The groove 7 is formed so as to be located.

[Layering process]
As shown in FIG. 5, another steel plate 2 is superposed on the steel plate 1 on which the groove 7 is formed in the thickness direction to cover the opening of the groove 7 (the opening upward in FIG. 5). The inside of the groove 7 between the steel plates 1 and 2 functions as a gap for discharging the gas generated during welding.

[Irradiation process]
As shown in FIG. 5, by irradiating the laser from the irradiation portion 3 toward the bottom of the groove 7, the welded portion 4 of the steel plates 1 and 2 becomes a molten pool 6 at the time of welding by irradiating the laser. .. Further, as shown in FIG. 6, the irradiating portion 3 (FIG. 6) moves the molten pool 6 in the extending direction of the groove 7 with a space between the molten pool 6 and the inner side surfaces 7a on both sides in the width direction of the groove 7. 5) is moved. The distance between one inner surface 7a and the molten pool 6 is preferably equal to the distance between the other inner surface 7a and the molten pool 6, and in this example, the width direction of the groove 7 in the above distance. The length of is 1 mm or more.

Through such movement of the irradiation portion 3, the molten pool 6 is made to go around along the groove 7 (welded portion 4) so as to form an annular shape, so that the steel plates 1 and 2 are joined to each other by laser welding. As described above, the moving speed when moving the irradiation unit 3 is set to be slower than the moving speed of the irradiation unit 3 when forming the groove 7 with the laser on the steel plate 1.

7 and 8 show a state in which the portion of the steel plate 1 after laser welding on the groove 7 side and the welded portion 4 between the steel plates 1 and 2 are viewed from the steel plate 2 side, and the joined steel plates 1 and 2 are joined to each other. Is shown in the direction of arrows AA in FIG. 7. As can be seen from FIG. 7, the welded portions 4 between the steel plates 1 and 2 form an annular shape along the groove 7, and between the welded portion 4 and the inner side surfaces 7a on both sides in the width direction of the groove 7, as can be seen from FIG. A gap 8 is formed in the space.

Next, the operation of the laser welding method for the steel sheet in the present embodiment will be described.
As shown in FIGS. 1 and 2, when the steel plates 1 and 2 are welded to each other by laser irradiation, a keyhole 5 is generated in the portion of the steel plates 1 and 2 that is irradiated with the laser, and the periphery of the keyhole 5 is formed. A molten pool 6 is formed in. Then, the irradiation unit 3 is moved so that the keyhole 5 and the molten pool 6 move in the extending direction of the groove 7 (to the right in FIGS. 1 and 2), so that the steel plates 1 and 2 are laser-welded to each other. Joined to each other.

When the steel plates 1 and 2 are welded to each other by the laser irradiation described above, the gas is caused by the melting and evaporation of foreign substances such as zinc covering the surfaces of the steel plates 1 and 2 and oil adhering to the surfaces of the steel plates 1 and 2. Occurs. As shown by the arrow Y1 in FIG. 1, the gas generated in this way passes through the portion between the molten pool 6 and the inner side surfaces on both sides in the width direction of the groove 7, and the moving direction of the molten pool 6 in the groove 7. Wrap around to the front side of. Since the thickness of the front portion of the molten pool 6 in the moving direction with the key hole 5 becomes thin, the gas penetrates the portion as shown by the arrow Y2 in FIG. 1 and is external through the key hole 5. Is discharged to.

By discharging the gas in this way, it is possible to prevent the gas from being mixed into the molten pool 6 and forming blow holes in the welded portions 4 between the steel plates 1 and 2. Further, the groove 7 formed in one of the steel plates 1 functions as a gap for discharging the gas, and the depth of the groove 7 is a value corresponding to the size of the gap. Therefore, a groove 7 having a depth (for example, 50 μm) corresponding to an appropriate size as the gap is formed in one steel plate 1, and the steel plates 1 and 2 are overlapped with each other in the thickness direction to open the opening of the groove 7 in the other. A gap of an appropriate size can be formed between the steel plates 1 and 2 simply by closing the steel plate 2 of the above.

According to the present embodiment described in detail above, the following effects can be obtained.
(1) As a gap for discharging the gas generated during welding, a gap having an appropriate size is easily formed between the steel plates 1 and 2 stacked in the thickness direction through the formation of the groove 7. be able to. Therefore, it is possible to suppress the formation of blow holes without performing time-consuming adjustment.

(2) The groove 7 in the steel plate 1 is formed so as to extend in an annular shape and not to overlap with the outer edge of the steel plate 1. In this case, when the steel plates 1 and 2 are stacked in the thickness direction, the inside of the groove 7 is not opened to the outside. Even in this case, the gas generated by the evaporation of zinc and foreign matter is discharged from the groove 7 to the outside through the keyhole 5, so that the gas is mixed in the molten pool 6 and the steel plates 1 and 2 are welded to each other. It becomes possible to suppress the formation of blow holes in the portion 4.

(3) The groove processing step for forming the groove 7 and the irradiation step for welding the steel plates 1 and 2 can be performed with the same laser processing equipment. Therefore, since it is not necessary to bring the steel plate 1 to another equipment in order to form the groove 7 in the steel plate 1, the steel plate 1 is moved from the equipment for forming the groove 7 to the laser processing equipment for welding. You can save the trouble of making it.

The above embodiment can be changed as follows, for example. The above embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
-The groove 7 does not necessarily have to be formed in an annular shape. For example, as shown in FIGS. 9 and 10, the groove 7 is formed so as to extend linearly, and both ends of the groove 7 in the longitudinal direction do not reach the outer edge of the steel plate 1 (. It may be non-overlapping).

As shown in FIG. 11, the groove 7 is formed so as to form a groove 7 extending linearly and both ends of the groove 7 in the longitudinal direction overlap the outer edge of the steel plate 1 (reach the outer edge of the steel plate 1). It may be formed. In this case, when the steel plates 1 and 2 are stacked in the thickness direction, both ends of the groove 7 in the longitudinal direction are opened to the atmosphere, so that the gas generated during welding is also discharged from both ends of the groove 7. Therefore, it becomes more difficult for the gas to mix with the molten pool 6.

-In the grooving process, the groove 7 is formed by irradiating a laser, but the groove 7 may be formed by cutting, pressing, or the like.
-The distance between one inner surface 7a and the molten pool 6 and the distance between the other inner surface 7a and the molten pool 6 in the irradiation step can be appropriately changed to a value other than 1 mm. is there.

-The distance between one inner surface 7a and the molten pool 6 in the irradiation step does not necessarily have to be equal to the distance between the other inner surface 7a and the molten pool 6.
As shown in FIG. 12, regarding the irradiation of the laser from the irradiation unit 3, the center beam 9 having a circular projection shape on the steel plates 1 and 2 and the ring beam 10 concentrically surrounding the center beam 9 are arranged. It may have a shape to have.

1 ... Steel plate, 2 ... Steel plate, 3 ... Irradiation part, 4 ... Welded part, 5 ... Keyhole, 6 ... Molten pond, 7 ... Groove, 7a ... Inner surface, 8 ... Gap, 9 ... Center beam, 10 ... Ring beam ..

Claims (3)

By irradiating the steel plates stacked in the thickness direction with a laser from the irradiation portion in the thickness direction and moving the irradiation portion along the steel plates, the steel plates are welded to each other with a predetermined length and width. In the laser welding method of steel sheets to be welded at the part,
Grooving that extends in the same direction as the welded portion and forms a groove with a width larger than the molten pool at the time of welding by irradiating the laser from the irradiated portion on one of the steel plates stacked in the thickness direction. Process and
A stacking step of stacking another steel plate on the steel plate on which the groove is formed in the thickness direction to cover the opening of the groove.
While irradiating a laser from the irradiation portion toward the bottom of the groove, the molten pool at the time of welding by the irradiation of the laser is in a state where there is a space between the inner side surfaces on both sides in the width direction of the groove. The irradiation step of moving the irradiation unit so as to move in the extending direction of
A method for laser welding a steel sheet, which comprises. The laser welding of the steel plate according to claim 1, wherein in the grooving step, a groove having both ends in the longitudinal direction is formed as the groove, and the groove is formed so that both ends do not overlap with the outer edge of the one steel plate. Method. The laser welding method for a steel sheet according to claim 1, wherein in the grooving step, the groove is formed so as to extend in an annular shape and not to overlap with the outer edge of one of the steel sheets.

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