JP3614062B2 - Lap laser welding method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lap laser welding method for a rust-proof steel plate (for example, a galvanized steel plate, a composite steel plate coated with a resin on a plated layer of a plated steel plate, etc.).
[0002]
[Prior art]
When a rust-proof steel plate, for example, a galvanized steel plate is overlapped and laser-welded, as shown in FIG. 10, the plated portions 11a and 12a between the steel plates 11 and 12 become high-pressure gas 14 by laser heat (the melting point of Fe as a base material). Is about 1500 ° C., whereas, for example, the boiling point of Zn used for galvanizing is about 906 ° C.), and the weld bead 13 may be blown off and blown out. In this case, poor welding and reduced weld strength are caused.
In order to suppress the high-pressure gas blowout through the weld bead, it is effective to provide a minute gap between the steel plates and let the high-pressure gas generated by gasification of the plating metal escape through the minute gap. If this minute gap is about 0.4 mm or more, the welded portion will not be connected, and if it is less than about 0.1 mm, gas escape will be poor and high-pressure gas will be blown out easily through the weld bead. It is necessary to manage within the range of about 0.1 to 0.4 mm (Toyota Technical Disclosure No. 9018).
Conventionally, in order to form a minute gap between two steel plates to be overlapped laser welded, a method for forming a convex portion for forming a gap on one side of a rust-proof steel plate as described below, or the shape of two plates There is a method of using.
(1) Embossing A convex part is formed on one mold, a concave part is formed on the other mold in alignment with the convex part, a steel plate is sandwiched between the molds, and the convex part is formed on the steel plate. .
(2) Laser spot As disclosed in Japanese Patent Application Laid-Open No. 11-47967, a steel plate is irradiated with laser light to form a molten pool, and gas is blown there to extrude the molten metal around the molten pool. Forming part. A portion of the molten pool becomes a recess.
{Circle around (3)} A punching-out of a plate or use of a cross-section R portion A punching-out of a steel plate is used as a convex portion. Alternatively, the gap between the plates generated when the steel plate with the curved cross section and the steel plate with the straight cross section are overlapped is used as the gas escape gap.
[0003]
[Problems to be solved by the invention]
However, the above gap forming method has the following problems.
In the formation of the convex portion by the embossing of the above (1), it is difficult to align the upper and lower concave and convex portions. In addition, it is difficult to create a minute convex portion having a height of about 0.1 to 0.4 mm, and it is difficult to manage the size of the convex portion.
In the above-described convex portion formation by the laser spot (2), the concave and convex portions are formed by laser irradiation, so that the processing cost is high. In addition, it takes time because laser irradiation is performed point by point. Moreover, the process for convex part formation is needed other than the press process of a steel plate. As a result, the cost increases.
In the gap forming method using the punching-out of the plate of (3), it is difficult to manage the height of the beam, and it is difficult to manage the size of the gap. Also, when creating a gap using the shape of the cross-section R, if the laser light irradiation position is shifted even a little, the dimension between the plate gaps changes greatly, making it difficult to manage the dimension of the gap.
An object of the present invention is to provide an overlap laser that can easily form a convex portion for forming a minute gap for gas escape between rust-proof steel plates to be laser welded on one steel plate to be overlap laser welded. It is to provide a welding method.
[0004]
[Means for Solving the Problems]
The present invention for achieving the above object is as follows.
(1) A lap laser welding method for two rust-proof steel plates,
The position of the punch with respect to the steel plate to be subjected to the coining process is set in a direction orthogonal to the longitudinal direction of the site to be laser welded, and the distance between the center of the raised portion formed on the steel plate by the coining and the center of the site to be laser welded Is within about 3 mm, and in the direction parallel to the longitudinal direction of the portion to be laser welded, the center interval of the raised portion is within about 10 mm, the end of the portion to be laser welded and the center of the raised portion Determined so that the interval is within about 5 mm,
Subjected to coining on one surface of one of the steel plate by the convex portion of the punch having a convex portion at the tip to form an upstream portion serving to coining portion around the one side,
One steel plate and the other steel plate are overlapped with a gap due to the raised portion, and laser welding is performed on the overlapped portion.
Lap laser welding method.
(2) A method of lap laser welding of two rust-proof steel plates,
The position of the punch with respect to the steel plate to be subjected to the coining process is set in a direction orthogonal to the longitudinal direction of the site to be laser welded, and the distance between the center of the raised portion formed on the steel plate by the coining and the center of the site to be laser welded Is within about 3 mm, and in the direction parallel to the longitudinal direction of the portion to be laser welded, the center interval of the raised portion is within about 10 mm, the end of the portion to be laser welded and the center of the raised portion Determined so that the interval is within about 5 mm,
Subjected to coining on one surface of one of the steel plate by the convex portion of the punch having a convex portion at the distal end, an annular upsurge portion and / or the mountain-shaped in upsurge on the other surface to the coining portion around the one side Forming part,
One steel plate and the other steel plate are overlapped with a gap due to the raised portion, and laser welding is performed on the overlapped portion.
Lap laser welding method.
(3) In the press apparatus for press-molding the steel sheet to be subjected to the coining process, the punch is placed on one of the two molds sandwiching the portion of the steel plate to which laser welding is applied, and the punch tip is placed on the die surface. Forming a recess recessed from the surface of the mold around the tip of the projecting punch, and incorporating it into the mold, leaving the other mold of the two molds facing the punch as a flat surface, The bulge portion is formed in a portion sandwiched between the two molds of the steel sheet to be subjected to the coining simultaneously with the press forming of the steel sheet to be subjected to the coining. The lap laser welding method as described.
[0005]
In the lap laser welding method of (1) or (2) above, the bulge is formed by coining with a punch, so that the bulge can be formed easily and inexpensively compared to the conventional method.
In addition, since the position of the punch with respect to the steel plate subjected to coining satisfies the above conditions (1) and (2), all the raised parts are effective for escaping the high-pressure gas generated during laser welding. Can work and perform high quality laser welding.
In the overlap laser welding method of ( 3 ) above, since the surface facing the punch of the one of the two molds not incorporating the punch is a flat surface, a recess is formed on the punch facing surface (embossing). Compared to the case where the raised portion is formed by processing), it is not necessary to align the convex portion and the concave portion of the punch, and the raised portion is easily and inexpensively formed .
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Below, the overlap laser welding method of the Example of this invention is demonstrated with reference to FIGS.
As shown in FIGS. 1 and 2, the lap laser welding of the embodiment of the present invention is a lap laser welding method of two rust-proof steel plates 11 and 12. The rust-proof steel plates 11 and 12 are plated steel plates such as zinc (the plated portion is not shown in FIG. 1, and 11a and 12a indicate the plated portions of the steel plates 11 and 12 in FIG. 2), or resin or the like is applied on the plated steel plate. It consists of a painted composite plated steel sheet. The steel plates 11 and 12 are used, for example, as thin steel plates for automobiles.
[0007]
In the lap laser welding of the embodiment of the present invention, the step of forming the raised portion 15 on one of the two rust-proof steel plates 11 and 12 and the two rust-proof steel plates 11 and 12 are stacked. And a step of performing laser welding together.
In the step of forming the raised portion 15, as shown in FIG. 1, one surface of one steel plate 11 is coined by the convex portion 16 of the punch 17 having the convex portion 16 at the tip, and the one side of the convex portion 15 is indented. An annular raised part 15 is formed around the part and / or a mountain-like raised part 15 is formed on the other surface. The tip of the convex portion 16 is flat or convexly curved because it is severely worn when it is acute.
In the laser welding process, as shown in FIG. 2, one steel plate 11 and the other steel plate 12 are overlapped with a gap 18 formed by the raised portion 15, and the overlapping portion 19 is irradiated with laser light 20. Apply laser welding.
[0008]
In the step of forming the swelled portion 15, as shown in FIG. 1, two molds 22 sandwiching a portion where the laser welding of the steel plate 11 is performed in the press device 21 for press-forming the steel plate 11 subjected to the coining process. , 23, the punch 17 on one mold 22, the tip of the convex portion 16 at the tip of the punch protrudes from the mold surface 22 a by a predetermined amount, and the mold 22 has a recess recessed from the mold surface 22 a around the tip of the projecting punch. 24 is formed and assembled, and the surface 23a of the other die 23 out of the two dies 22 and 23 facing the punch 17 is a flat surface, and when the steel plate 11 to be coined is pressed, Simultaneously with the press forming, the raised portion 15 is formed in the portion sandwiched between the two dies 22 and 23 of the steel plate 11 to be subjected to the coining process. By forming the raised portion 15 at the same time as the press molding, it is not necessary to provide a special extra process for forming the raised portion 15, thereby increasing the number of steps and increasing the cost.
[0009]
The punch 17 is preferably incorporated into the mold 22 by forming the punch 17 separately from the mold 22 and inserting the punch 17 into a punch receiving recess 25 formed in the mold 22. However, the convex portion 16 of the punch 17 and the concave portion 24 around it may be formed integrally with the mold 22. When the punch 17 is formed separately from the mold 22 and inserted into the punch receiving recess 25 formed in the mold 22, the punch 17 has a cylindrical portion 17 a and a convex shape portion 16, and the cylindrical portion 17 a is convex. The outer diameter of the shape portion 16 is larger than the outer diameter of the shape portion 16, and the height of the cylindrical portion 17 a is smaller than the depth of the punch receiving recess portion 25. A recess 24 is formed around.
[0010]
The punch 17 facing part of the other mold 23 may also be inserted into a punch receiving part receiving recess formed in the mold 23 with the punch receiving part formed separately from the mold 23. By doing so, when the flat surface of the opposite portion of the punch 23 of the other mold 23 is worn out and becomes concave as the swelled portion 15 is formed by pressing, only the punch receiving portion is easily replaced. Can be maintained.
[0011]
The press device 21 includes a lower die 22, an upper die curved blade 23, and a pad 26. The punch 17 is incorporated in the lower die 22, and the punch facing surface of the curved blade 23 is a flat surface. . However, the punch 17 may be incorporated in the curved blade 23 and the punch facing surface of the lower mold 22 may be a flat surface.
[0012]
In the laser welding process, as shown in FIG. 2, the two steel plates 11 and 12 are superposed and pressed firmly. F is a presser force. In this case, since the raised portion 15 is formed in advance on one steel plate 11, a gap 18 corresponding to the height of the raised portion 15 is formed between the two steel plates 11 and 12. The gap 18 serves as a passage for releasing high-pressure gas generated between the two steel plates 11 and 12 during laser welding. In this state, laser welding is performed by irradiating the overlapping portion 19 of the two steel plates 11 and 12 with laser light 20. Laser welding is a region in which a gap 18 is formed between the two steel plates 11 and 12 by the raised portion 15 (the steel plates pressed by the molds 21 and 22 when the distance from the raised portion 15 becomes too large. 11 and 12 are brought into contact with each other and the gap is eliminated, so that the distance from the raised portion 15 is within a predetermined distance, and is applied to a region where a gap exists between the steel plates 11 and 12.
When laser welding is performed in this region, even if the plating 11a, 11b of the steel plates 11, 12 is gasified by the heat of laser welding and high pressure gas is generated, it escapes to the outside through the gap 18, so the weld bead is removed. A normal laser welding bead 13 is formed without blowing off to the surface side, and welding strength is ensured.
[0013]
Since the laser welding 20 is applied to the region where the gap 18 is formed between the two steel plates 11 and 12 by the raised portion 15, the position of the punch 17 with respect to the steel plate 11 to be coined is shown in FIG. As shown in FIG. That is, the distance between the center of the raised portion 15 and the center of the portion 27 to be laser welded is within about 3 mm in the direction orthogonal to the longitudinal direction of the portion 27 to be laser welded (the portion that becomes the weld bead 13 after welding). In addition, in the direction parallel to the longitudinal direction of the portion 27 to be laser welded, the center distance of the raised portion 15 is within about 10 mm, and the distance between the end of the portion 27 to be laser welded and the center of the raised portion 15 is about The position of the punch 17 is determined so as to be within 5 mm.
[0014]
【Example】
A test for grasping the forming load of the raised portion 15 was performed.
FIG. 3 shows the test apparatus. The workpiece made of the galvanized steel plate 11 to form the raised portion 15 is sandwiched between the spacer 28 and the punch 17 disposed on the lower die 22 and the upper die 23 to form the raised portion 15 on the workpiece 11. did. The punch 17 has a convex portion 16, a cylindrical portion 17 a, and a base portion 17 b, a spacer 28 is disposed around the cylindrical portion 17 a of the punch 17, and the upper end portion of the convex portion 16 protrudes 0.8 mm from the upper end of the spacer 28. Set. The punch 17 was supported by a base 29, and the base 29 was supported by a urethane cylinder 30 and placed on a lower die 22 (not shown).
[0015]
The test specifications were as follows.
Two types of punches having a taper angle of 90 ° and 60 ° of the convex portion of the punch were used.
Height of cylindrical part and convex part of punch: 10mm
Spacer height: 9.2 mm. The height of the cylindrical portion of the punch and the convex portion-spacer height = 0.8 mm is the amount of protrusion of the punch tip from the spacer.
Load = 600kg
Steel plate thickness = 1.0mm
Number of punches n = 1
[0016]
The test results are shown in FIG. In FIG. 4, the vertical axis indicates the plate thickness after the test (the original plate thickness 1 mm + the height of the raised portion on the punch contact side a + the height b of the raised portion on the opposite side), and the horizontal axis indicates the applied load up to 600 kg. Shown at 100 kg intervals. FIG. 4 shows the results of plotting the test results when the punch angle is 60 ° and 90 ° and connecting them with a solid line of broken lines. The broken line indicates the average of each broken line as a linear straight line. It is a thing.
5 and 6 show the results of measuring the shape of the front and back surfaces of the workpiece at a 0.2 mm pitch when the punch angle is 90 ° and the load F is 600 kg. FIG. 6 shows the surface on the side opposite to the punch contact side, and it can be seen that a mountain-shaped raised portion of 0.1 mm or more is formed. FIG. 5 shows the surface on the punch contact side, and it can be seen that the portion pressed by the punch is a crater-like unevenness that is recessed about 0.8 mm and the periphery thereof is raised. The height of the raised portion of the crater-like unevenness was lower than the height of the raised portion on the surface opposite to the punch contact side.
[0017]
4, 5, and 6, the plate thickness increase amount (the sum of the heights of the raised portions on the front and back surfaces of the workpiece) is 0.06 to 0.15 mm, and the height on the front and back surfaces of the workpiece of about 0.1 mm. It has been found that forming the sum of the heights of the ascending portions is possible by coining, and in that case, a load of about 300 kg or more is required for each swelled portion. Since the load capacity of the pressing device for forming a steel sheet is several tens of times larger than that, it has also been found that a coining process can be performed simultaneously with press forming by incorporating a punch into a conventional pressing device.
[0018]
In addition, when the sum of the heights of the raised parts on the front and back surfaces of the workpiece is about 0.1 mm, there is a difference in the height of the raised parts on the front and back of the workpiece, so that the raised parts of about 0.07 mm or more on one side Can be obtained. When a 1 mm thick galvanized steel sheet with a raised portion of 0.07 mm on one side is overlapped with a flat galvanized steel sheet and laser welding is performed, a good weld bead without blowing off the weld bead is obtained. It was. From this, it was found that the condition of “0.1 mm or more”, which was conventionally considered necessary as a gap between two rust-proof steel plates for escape of high-pressure plating gas, should be “0.07 mm or more”. .
[0019]
Next, a test was performed on the positional relationship between the swelled portion 15 and the portion 27 to be laser welded in order to obtain a good weld bead 13 (with no bead blown off by high-pressure gas). Ten test pieces of the galvanized steel sheet 11 on which the raised portion 15 was formed were selected at random, and the height of the raised portion (the sum of the raised portion heights of the work front and back surfaces) was measured. It was in the range of 13 mm, and was a simple average of 0.12 mm.
[0020]
FIG. 7 shows the result of superposition laser welding when the raised portion 15 is formed so as to be located at the center of the bead at a distance of 1 mm, 2 mm, 3 mm, and 4 mm from the center of the weld bead 13, and FIG. The result of the superposition laser welding when the raised portion 15 is formed at positions 7.5 mm and 12.5 mm from the center at a distance of 13 to 2 mm is shown. The shaded part is the part where the weld bead is rough.
From FIG. 7 and FIG. 8, the bulging portion 15 formation region effective for preventing the roughening of the weld bead 13 is within about 3 mm from the center of the weld bead 13 (site 27 to be welded), and bulges in the longitudinal direction of the weld bead. It was found that the effect of the rising portion 15 is about 5 mm from the rising portion 15. FIG. 9 shows the range of the effective area. However, the above-mentioned 3 mm and 5 mm are data on the limited plate thickness of the flat plate, and are only a guideline number, and the experiment merely proves that there is an effect.
[0021]
【The invention's effect】
According to the lap laser welding method of the first or second aspect , since the bulge portion is formed by coining with a punch, the bulge can be formed easily and inexpensively as compared with the conventional method.
Further, in the direction orthogonal to the longitudinal direction of the part to be laser welded, the distance between the center of the raised portion and the center of the part to be laser welded is within about 3 mm and parallel to the longitudinal direction of the part to be laser welded. The position of the punch with respect to the steel plate to be coined is adjusted so that the center distance of the raised portion is within about 10 mm and the distance between the end of the part to be laser welded and the center of the raised portion is within about 5 mm. As a result, all the raised portions work effectively to escape the high-pressure gas generated during laser welding, and high-quality laser welding can be performed.
According to the lap laser welding method of claim 3 , since the surface facing the punch of the one of the two molds not incorporating the punch is a flat surface, a recess is formed on the punch facing surface ( Compared with the case where the raised portion is formed by embossing), it is not necessary to align the convex portion and the concave portion of the punch, and the raised portion is easily and inexpensively formed .
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a swelled part forming step of a lap laser welding method according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a laser welding process of a lap laser welding method according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view of an apparatus used for a coining process test.
FIG. 4 is a graph showing the relationship between plate thickness and load in the coining process.
FIG. 5 is a concavo-convex view of the surface on the punch contact side of the work when the work surface is measured with a roughness meter after coining.
FIG. 6 is a concavo-convex view of the surface of the workpiece on the side opposite to the punch contact side when the workpiece surface is measured with a roughness meter after coining.
FIGS. 7A and 7B are diagrams showing a state in which the weld bead is rough when the positional relationship between the swelled portion and the portion to be laser welded (the portion that becomes the weld bead) is changed.
FIGS. 8A and 8B are diagrams showing a state in which the weld bead is rough when the positional relationship between the swelled portion and the portion to be laser welded (the portion that becomes the weld bead) is changed.
FIG. 9 is a diagram illustrating a condition of a positional relationship between a raised portion and a portion to be laser welded in order to obtain a good weld bead.
FIG. 10 is a cross-sectional view in the vicinity of a weld bead in a conventional lap laser welding method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Rust prevention steel plate 11a Plating part 12 Rust prevention steel plate 12a Plating part 13 Welding bead 14 High pressure gas 15 Swelling part 16 Convex part 17 Punch 17a Cylindrical part 17b Base part 18 Gap 19 Overlapping part 20 Laser beam 21 Press device 22 Bottom Mold 23 Upper mold 24 Recess 25 Punch receiving recess 26 Pad 27 Site to be laser welded 28 Spacer 29 Stand 30 Urethane cylinder

Claims (3)

A method of lap laser welding of two rust-proof steel plates,
The position of the punch with respect to the steel plate to be subjected to the coining process is set in a direction perpendicular to the longitudinal direction of the site to be laser welded, and the distance between the center of the raised portion formed on the steel plate by the coining and the center of the site to be laser welded Is within about 3 mm, and in the direction parallel to the longitudinal direction of the portion to be laser welded, the center interval of the raised portion is within about 10 mm, the end of the portion to be laser welded and the center of the raised portion Determined to be within about 5 mm,
Subjected to coining on one surface of one of the steel plate by the convex portion of the punch having a convex portion at the tip to form an upstream portion serving to coining portion around the one side,
One steel plate and the other steel plate are overlapped with a gap due to the raised portion, and laser welding is performed on the overlapped portion,
Lap laser welding method. A method of lap laser welding of two rust-proof steel plates,
The position of the punch with respect to the steel plate to be subjected to the coining process is set in a direction perpendicular to the longitudinal direction of the site to be laser welded, and the distance between the center of the raised portion formed on the steel plate by the coining and the center of the site to be laser welded Is within about 3 mm, and in the direction parallel to the longitudinal direction of the portion to be laser welded, the center interval of the raised portion is within about 10 mm, the end of the portion to be laser welded and the center of the raised portion Determined to be within about 5 mm,
Subjected to coining on one surface of one of the steel plate by the convex portion of the punch having a convex portion at the distal end, an annular upsurge portion and / or the mountain-shaped in upsurge on the other surface to the coining portion around the one side Forming part,
One steel plate and the other steel plate are overlapped with a gap due to the raised portion, and laser welding is performed on the overlapped portion,
Lap laser welding method. In the press apparatus for press-forming the steel plate to be subjected to the coining process, the punch is projected from one of the two molds sandwiching the portion of the steel plate to be laser-welded, and the punch tip protrudes from the mold surface. A recess recessed from the mold surface is formed around the tip of the projecting punch in the mold and assembled, and the surface of the other mold facing the punch is set as a flat surface, and the coining process is performed. 3. The overlap according to claim 1, wherein the raised portion is formed in a portion sandwiched between the two molds of the steel plate to be subjected to the coining simultaneously with the press forming of the steel plate to be subjected to press forming. Laser welding method.

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