JPH10216974A - Laser beam welding method for plated steel plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct lap joint welding hardly causing a blow hole and a warp after welding by forming the same height projecting parts on two facing plated steel plate faces, irradiating a region of the plated steel plate between the projecting parts and welding. SOLUTION: A projecting part 30 is formed for a first plated steel plate 10 by a half punch device, a second projecting part having a same height (h) is formed at a prescribed interval L. A second plated steel plate 20 is butted/ stacked on the two projecting parts 39 of the first plated steel plate 10. The region formed with the two plated steel plate 10, 20 between the two projecting parts is irradiated with a laser beam 50 from a laser beam irradiation nozzle 51 to be welded. The same height projecting parts are formed to both of two plated steel plate, the two plates can be stacked not to align the projecting parts. By this method, the configuration of weld zone is always kept same, there is no variance in welding strength, stabilized joint welding is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser welding method for performing a so-called lap joint welding in which two plated steel sheets are welded together by irradiating a laser beam.

[0002]

2. Description of the Related Art This type of laser welding method using lap joint welding is applied to various types of O such as copiers, printers and facsimile machines.
It is also used in manufacturing frames for A-device. This is the reason that generally accepted laser welding can perform welding work in a state of non-contact with the member to be welded, and has advantages such as less thermal influence compared to arc welding. .

[0003] In the laser welding method using the lap joint welding method, it is known that blowholes (also referred to as pinholes) are easily generated in a welded portion of a plated steel sheet. In the blow hole, the plating layer exists in the abutting part of the plated steel sheet to be superimposed, so that the components of the plated layer evaporate, especially in the molten pool of the plated steel sheet that appears when it is melted by laser beam irradiation, and bubbles are generated. It is thought that it is formed by doing.

[0004] As a technique for preventing the occurrence of such blow holes, for example, Japanese Patent Application Laid-Open No. 7-155974 has been proposed.
There is a laser welding method as disclosed in Japanese Unexamined Patent Publication (Kokai) No. H10-26095. In this laser welding method, a protrusion is formed on at least one of the two plated steel sheets, and the top of the protrusion is brought into contact with the surface of the other plated steel sheet, from the side opposite to the top of the protrusion. The laser beam is radiated. According to this laser welding method, a gap is formed by the projection between the two plated steel sheets supported in parallel by the jig, and the plating generated at the top contact portion of the projection during welding. It is said that since the metal vapor of the layer component is released through the gap, bubbles causing blowholes do not remain in the molten pool.

[0005]

However, in the above-mentioned proposed laser welding method, first, the area to be irradiated with the laser beam is a very limited narrow area opposite to the top of the protruding portion. There is a major problem that the position opposite to the top of the protruding portion is not correctly irradiated, but is irradiated to a shifted position. The cause of such a shift of the irradiation position of the laser beam is as follows.
When the focusing state of the laser beam, the irradiation angle, the irradiation setting position, etc. are shifted, the formation position of the protrusion formed on the plated steel sheet is shifted, or the shape is varied, the plating when overlapping The case where the (projecting portion) of the steel plate is displaced or inclined in position is exemplified.

In order to prevent the deviation of the irradiation position of the laser beam, which can be caused by the above-mentioned factors, the laser beam must be accurately positioned at the position opposite to the top of the protrusion. In order to irradiate, it is necessary to perform high-precision setting work of the laser beam irradiation device, and for the cause, it is necessary to form the protruding part at the exact position and in the same shape with high accuracy. It is necessary to superimpose (project) the two plated steel sheets at an accurate position and in a parallel state without tilting, and it is necessary to use a high-precision jig corresponding thereto. Therefore, in the conventional laser welding method described above, in order to properly irradiate the laser beam to the side opposite to the top of the protrusion, it is necessary to satisfy all the working conditions that require the above-described accuracy. Due to the necessity of satisfying the conditions, there has been a problem that the efficiency of the entire welding operation is deteriorated and the manufacturing cost is increased.

In this laser welding method, as shown in FIGS. 9A and 10A, when the irradiation position of the laser beam 100 is shifted from the position opposite to the top of the protrusion 102 of the plated steel sheet 101, FIGS. As shown in 10b, there is a problem that the plated steel plate portion 101a of the protruding portion 102 on the opposite side to the side where the welded portion 103 is present warps in a direction away from the other steel plate 104 (upper side in the drawing).
At this time, the plated steel plate portion 101b on the welded portion 103 side is slightly warped. The dotted line in FIG.
Shows the exact irradiation position of. It is considered that the warpage is caused by welding distortion in which the internal stress generated by shrinkage when the metal of the steel sheet melted by the irradiation of the laser beam is solidified remains. In particular, when welding is performed on an inclined portion deviating from the top of the protruding portion 102 as shown in the illustrated example, the welding strain acts on the surrounding steel plate portion to reduce the gap around the welded portion 103. The steel plate on the side opposite to the fusion zone is warped so as to float up with the top of the fulcrum as a fulcrum. Such a warp is caused even when welding is performed using the holding jig 105 to fix the two superposed plated steel sheets, as indicated by a two-dot chain line in FIGS. 9A and 10A. ,
The same occurs when the jig 105 is removed after welding.

[0008] Therefore, when the irradiation position of the laser beam is shifted, such a warp occurs, and high-precision welding cannot be performed. Moreover, this laser beam 100
Since the irradiation position deviation of fluctuates for each product (plated steel sheet) and can fluctuate even during the same welding,
As illustrated in FIGS. 11A to 11C, the position and form of the welded portion 103 fluctuate due to the change in the irradiation position shift, and the degree of warpage (the distance h between the plated steel plates 101 and 102 in the figure) varies depending on the position of the welded portion 103. _{1 to} h ₃ ) are different from each other,
Depending on the form of the welding portion 103, the joining area of the welding portion is also different from each other. For this reason, there is a problem that the welding accuracy varies and the welding strength also varies.

Further, in the above-described laser welding method, it is assumed that the protruding portion 102 is in line or point contact with the other steel plate 104, but strictly speaking, the protruding portion 102 and the surface of the plated steel plate 104 Because the plating layers slightly overlap with each other, for example, if the top shape of the protrusion 102 is a flat shape such that even a little surface contact is made, the overlapping plating layer area increases and metal vapor is less likely to be released. However, there is a problem that the occurrence of blow holes cannot be reliably prevented.

Incidentally, as a measure for reliably preventing this blow hole, the above-mentioned publication (Japanese Unexamined Patent Application Publication No.
No. 55974), two coated steel sheets 200, 2 as shown in FIG.
01 is arranged in parallel with a predetermined space 202 therebetween, and the laser beam 100 is irradiated from one of the plated steel sheets 200 side. According to this method, a gap 202 is reliably formed between the two plated steel sheets 200 and 201, and there is no overlapping plating layer region. Therefore, metal vapor of a plating layer component can be released through the gap 202. it can. However, in this method, there is a problem that a high-precision holding jig 203 (204 is a spacer) must be used to make the two plated steel sheets 200 and 201 face each other with a predetermined space 202 therebetween. In addition, there is a problem related to warping as described below.

That is, even when welding is performed by this method, the welded portion 205 has a welding strain W for narrowing the gap as described above (FIG. 2B).
When the holding jig 203 is removed after the welding, the spacer 204 interposed between the two plated steel sheets disappears as shown in FIG. 12C, so that the two plated steel sheets 200 and 201 It is warped in the direction of approaching each other at the periphery. Particularly, the periphery of the welded portion 205 of the plated steel sheet 200 irradiated with the laser beam 100 is warped so as to be deformed toward the plated steel sheet 201 side. 200a in the figure indicates the position of the steel plate 200 before welding.

An object of the present invention is to generate blow holes and warpage after welding even if the irradiation accuracy of a laser beam, the accuracy of the shape or formation position of a protruding portion, the overlay accuracy of a plated steel sheet, and the like fluctuate. It is another object of the present invention to provide a laser welding method that can easily and efficiently perform lap joint welding that always provides stable welding accuracy and welding strength.

[0013]

According to a first aspect of the present invention, there is provided a laser welding method comprising: laminating two or more plated steel sheets;
In the laser welding method for a plated steel sheet that performs lap joint welding by irradiating a laser beam, at least two protrusions having the same height are formed on one of the two plated steel sheets facing each other when the lapping is performed. Or at least both of them, at least one protrusion having the same height is formed, and the plated steel sheets are overlapped so that each protrusion contacts the surface of the plated steel sheet on the side where the protrusion is not formed. Thereafter, the welding is performed by irradiating a laser beam to a region of the plated steel sheet located between the projecting portions.

According to this laser welding method, at least two protrusions having the same height are formed on one of the two plated steel sheets facing each other when they are overlapped,
Alternatively, at least one protrusion having the same height is formed on both of them. That is, a total of at least two protrusions are formed in the two facing plated steel sheets. Next, the plated steel sheets are overlapped such that the tops of the protruding portions are in contact with the surfaces of the plated steel sheets on which the protruding portions are not formed. As a result, at least two plated steel sheets that face each other and are kept in a parallel state with a certain gap formed by at least two protrusions without using a high-precision jig. Then, the laser beam is applied to the region of the plated steel sheet between the protrusions. At this time, the irradiation position of the laser beam only needs to be in the region between the projecting portions, and is not influenced by the shape or the forming position of the projecting portion, the accuracy of the superposed state of the plated steel sheets, or the like. Further, the metal vapor of the plating layer component in the plated steel sheet irradiated with the laser beam is released from the gap. Furthermore, the welding strain generated when the molten metal in the laser beam irradiated part solidifies is due to the internal stress that tries to narrow the gap between the two plated steel sheets due to the presence of protrusions on both sides of the welded part. As a result, the plated steel sheet is not warped.

According to a second aspect of the invention, there is provided a laser welding method.
In the laser welding method according to claim 1, the plated steel sheet is plated with a plating material having a boiling point lower than the melting point of the steel sheet metal. As such a plated steel sheet, for example, there is an iron steel sheet plated with zinc.

According to this laser welding method, the metal vapor of the plating component is apt to be generated at the time of welding. However, as described above, the two plated steel sheets facing each other are parallel with at least two protruding portions having a gap. Since laser welding is performed in this state, the plating layers do not overlap with each other, and the metal vapor is reliably released through the voids.
Thus, blow holes do not occur.

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIGS. 1 and 2 show a working state of a laser welding method according to an embodiment of the present invention. FIG. 1 is a perspective view thereof, and FIG. 2 is a sectional view taken along line AA. In the laser welding method of this embodiment, the first plated steel sheet 10 and the second plated steel sheet 20 are overlapped, and a laser beam is linearly irradiated to perform lap joint welding. Each of the first and second plated steel plates 10 and 20 is formed by forming plated layers 12 and 22 on both surfaces of the steel plates 11 and 21, respectively.
In this embodiment, the two plated steel sheets 10 and 20 are made of iron steel sheets having both surfaces plated with zinc.

In this laser welding method, first, as shown in FIG. 2 and FIG. 4, a half-punch device (not shown) is formed on the first plated steel sheet 10 without punching a punched hole. (A punch device set to execute a half-punching process halfway)
The two protrusions 30 and 31 are formed. These two protrusions 3
0 and 31 have the same protruding height h and are formed with a predetermined interval L therebetween. In this embodiment, as the protruding portions 30, 31, the apex portions 30a, 31a are formed in a substantially columnar cylindrical shape and the protruding portions have a protruding height h of several hundred microns. The distance L between the protruding portions 30 and 31 varies depending on the type and output of the laser, the thickness of the steel plate, and the like. .

Next, the first plated steel sheet 10 is set on the welding work table 40 and the second plated steel sheet 20
On the other hand, the two projections 30 and 31 are overlapped so as to abut on the surface of the second plated steel sheet 20, and pressed and fixed by a holding jig 41 from the side opposite to the projection. The holding jig 41 has such a simple structure that it can be held down by a small air cylinder (not shown) or fixed by a magnet.

At this time, since the two projections 30 and 31 of the first plated steel sheet 10 are in contact with the surface of the second plated steel sheet 20, the two steel sheets 10 and 20 are at the height of the projections 30 and 31. h is maintained in a parallel state in which a gap S having the same interval as h is formed. That is, the two plated steel sheets 10, 2
No. 0 does not need to be supported in a parallel state where the gap S is formed by using a special jig, and the surface 10 a opposite to the protruding portion of the first plated steel sheet 10 is pressed by the pressing jig 41. With only this, the parallel state as described above can be easily and reliably held.

Then, after the two plated steel sheets 10 and 20 are overlapped in such a state, the first plated steel sheet 10
In the region R between the protrusions 30 and 31 of
Welding is performed by irradiating a laser beam 50 output from a laser generator (not shown). The laser beam 50 is irradiated as a defocused minute spot through a lens 52 held by a beam irradiation nozzle 51. Then, the irradiation position is usually performed at an intermediate point between the protruding portions 30 and 31, but excluding the protruding portions, the protruding portions 30 and the protruding portions 3 are provided.
The distance may be shifted from the intermediate point as long as it is within the region R between 1. Therefore, it is not required that the irradiation accuracy of the laser beam be so high. As the laser generator, a gas laser such as a CO ₂ laser is usually used, but a solid-state laser such as a YAG laser can also be used. In particular, since the YAG laser can easily transmit its laser light through an optical fiber, there is no need to install dedicated transmission equipment such as a CO ₂ laser, which is excellent in versatility, and has many types of welding patterns. High practical value in some cases.

By this laser beam irradiation, the irradiated portions of the first plated steel sheet 10 and the second plated steel sheet 20 are sequentially melted, and a molten pool 60 is formed in a region shown by a dotted line in FIG. At this time, the plating layers 12 and 22 of each steel sheet are also melted and metal vapor is generated. Among these plating layers, the metal vapor generated from the plating layers 12a and 22a on the side facing the plated steel sheets 10 and 20 is plated. The gas is released into the atmosphere through the gap S formed between the steel plates 10 and 20. Thus, no bubbles remain in the molten pool 60. Therefore, the molten pool 60 has a smooth surface without blow holes at the time of completion of welding, and has a constant welding strength.

Finally, the welding is completed when the molten pool 60 solidifies by natural cooling after melting to form a welded portion. The plated steel sheet 10, which is thus welded,
As shown in FIG. 3, 20 is connected by a welding portion 61 formed between the protruding portion 30 and the protruding portion 31, and after the welding is completed, the fixing by the holding jig 41 is released. It is taken out from the work table 40.

In particular, when the molten pool 60 is solidified by natural cooling, two molten steel plates 1
A force for narrowing the gap S of 0, 20 is generated.
The force for narrowing remains as an internal stress in the welded portion 61 even after solidification. That is, it remains as welding strain W. However, in the welding method of this embodiment, since the projections 30 and 31 exist on both sides of the welded portion 61 to prevent the internal stress caused by the welding strain W, the holding jig 41 is removed. , Two plated steel sheets 10,
20 can be prevented from warping. That is, the plated steel sheets 10 and 20 do not warp in the direction in which the gap S can be narrowed. Therefore, according to this welding method, since the warp of the plated steel sheet due to welding strain does not occur, the first plated steel sheet 10 and the second plated steel sheet 20 can be welded with high accuracy.

In this welding method, the laser beam 5
0 is applied to a position shifted from the intermediate point between the protrusions 30 and 31, the irradiation position is at least
In the region R between 0 and 31, no warpage occurs in the two plated steel sheets 10 and 20 for the same reason. This is because when the irradiation angle of the laser beam 50 is shifted (for example, when the irradiation is performed obliquely), when the shape or formation position of the protruding portion is shifted, or when the superposed state of the plated steel sheets is slightly shifted. It is the same even when there is. As a result, the laser beam irradiation accuracy, the accuracy of the shape or formation position of the projecting portion, and the superposition accuracy of the plated steel sheet, etc., are not required to be so high. Can be simply, efficiently, and inexpensively performed.

The number, shape, formation position, and the like of the projecting portions formed on the plated steel sheet are not limited to the contents of the above-described embodiment, and can be appropriately selected.

For example, in the case of the above-mentioned projections 30, 31, the number thereof may be three or more. Also,
The shape may be a long shape that continuously protrudes as illustrated in FIG. 5, or may be a sharp-pointed shape as illustrated in FIGS. 6 and 7. .
The shape of the top of the protruding portion is desirably a planar shape that can make surface contact with the surface of the plated steel sheet, from the viewpoint of good stability when the steel sheets are stacked. If the shape of the top of the protruding part is flat, the stability at the time of overlapping the steel sheets will be good, so a simpler jig will be used as a jig for fixing the plated steel sheet It is possible to do. Further, the protrusion having the shape as shown in FIG. 5 can be formed by press molding.

As for the formation position, as shown in FIG. 6, one protrusion 30 is formed on the first plated steel sheet 10 and another protrusion 31 is formed on the second plated steel sheet 20. Alternatively, as shown in FIG. 7, the protruding portions 30, 31 may be collectively formed on the second plated steel sheet 20 side. The protruding portion may be formed on the plated steel sheet side where the protruding portion is easily formed. In addition, it is advantageous in terms of manufacturing cost and work efficiency that the protruding portion is formed collectively on one of the plated steel sheets, rather than separately formed on two plated steel sheets as illustrated in FIG. .

Further, the lap joint welding can be performed by superposing three or more plated steel sheets. FIG.
The case where three plated steel sheets 70, 71, 72 are overlapped and welded is shown. In this case, two plated steel sheets facing each other, that is, a plated steel sheet 70 and a plated steel sheet 71
During this period, a total of two or more projections may be formed between the plated steel sheet 71 and the plated steel sheet 72, respectively. In the example shown in FIG. 8, two protrusions 32 and 33
And two projecting portions 34 and 35 are formed on the plated steel plate 71. In this case, for example, welding may be performed by irradiating the laser beam 50 between the projecting portions 32 and 33 where the interval L between the projecting portions is the smallest.

[0031]

As described above, according to the laser welding method of the present invention, the two plated steel sheets facing each other at the time of superposition are subjected to plating in which at least two or more projections are formed without the projections in total. Since the laser beam is applied to the area of the plated steel sheet between the protruding parts after being overlapped so as to contact the steel sheet, even if the irradiation accuracy of the laser beam, the shape or formation of the protruding part Even if the position accuracy, the overlay accuracy of plated steel sheet, etc. fluctuate,
Lap joint welding that does not generate blow holes or warpage after welding can be performed. Further, even after the jig for fixing the plated steel sheet is removed, the warpage after the welding does not occur. Further, since the plated steel sheet can be reliably supported in a parallel state with a predetermined gap by at least two projections, it is not necessary to use a high-precision jig, and the plated steel sheets can be efficiently overlapped.

Therefore, in this laser welding method, high-precision lap joint welding free of blowholes and warpage can be varied between products by irradiating at least a laser beam into a region between the projecting portions. It can always be performed stably. In addition, as long as the weld is formed at least in the region between the protrusions, the form of the weld is always the same, so that the welding strength is stable without variation. In addition, the laser beam irradiation accuracy, as well as the accuracy of the shape or formation position of the protruding portion and the overlay accuracy of the plated steel sheet, are not required to be so strictly accurate. It can be performed efficiently. Furthermore, since there is no factor that causes an increase in manufacturing cost, the welding unit price and thus the product unit price can be reduced.

When a plated steel sheet plated with a plating material having a boiling point lower than the melting point of the steel sheet metal is used, a metal vapor of a plating component is easily generated at the time of welding. Since voids are reliably formed between the plated steel sheets that overlap, the metal vapor can be released, and the accuracy of the laser beam irradiation, the shape or formation position of the protrusions, the accuracy of the superposition of the plated steel sheets, etc. Regardless, the occurrence of blow holes can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a working state of a laser welding method (lap joint welding) according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a cross-sectional view showing a situation after welding is completed in the embodiment.

FIG. 4 is a perspective view showing a configuration of a protruding portion in the embodiment.

FIG. 5 is a perspective view showing another configuration example of the protruding portion.

FIG. 6 is a perspective view showing another configuration example of the protruding portion.

FIG. 7 is a perspective view showing another configuration example of the protruding portion.

FIG. 8 is a cross-sectional view showing an example of a configuration in a case where three plated steel sheets are lap joint welded.

9 (a) is a cross-sectional view illustrating an example of a laser beam irradiation state, and FIG. 9 (b) is a cross-sectional view illustrating a warp state occurring after welding. It is.

10 (a) is a cross-sectional view illustrating another example of a laser beam irradiation state, and FIG. 10 (b) is a cross-sectional view illustrating a warp state occurring after welding. FIG.

FIG. 11 is an explanatory diagram for explaining a variation in welding accuracy and the like caused by a displacement of a laser beam irradiation position in the laser welding method shown in FIG. 10;

FIG. 12 is an explanatory view showing a process of occurrence of warpage in a conventional laser welding method.

[Explanation of symbols]

10, 20: plated steel sheet, 12, 22: plated layer, 30
-35: protrusion, h: height of protrusion, R: area between protrusions.

Claims (2)

[Claims] 1. A laser welding method for a plated steel sheet in which two or more plated steel sheets are overlapped and lap joint welding is performed by irradiating a laser beam, wherein any one of the two plated steel sheets facing each other when the overlapping is performed. At least one protrusion having the same height is formed on one side, or at least one protrusion having the same height is formed on both of the protrusions, and each of the protrusions is plated on the side where the protrusion is not formed. Plating characterized by superimposing plated steel sheets so as to contact the surface of the steel sheet, and then performing welding by irradiating the laser beam to the area of the plated steel sheet between the protrusions Laser welding method for steel sheet. 2. The laser welding method according to claim 1, wherein the plated steel sheet is plated with a plating material having a boiling point lower than the melting point of the steel sheet metal.