JP2002035970A - Laser beam welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser beam welding method easily managing plate clearance, having excellent productivity, and capable of forming a high quality weld part. SOLUTION: In this laser beam welding method, two members at least one member of which comprises a coated base material (a galvanized steel plate or the like) coated by a coating material having a lower melting point than the base material, are piled and weld by irradiating a welding prospective position with a laser beam L. At least one of those two members is a member 1 with flange having a flange part 11. The flange part 11 is formed so that the outside from the welding prospective position of the member 1 with flange is bent in a direction separating from the other member 2. Since coating material steam G which is generated by laser beam irradiation is relieved from between the flange part 11 and the other member 2, even though the member 1 with flange is adhered to the other member 2, generation of blowhole or the like can be prevented.

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 welding members to be joined which are covered with a coating material having a lower melting point than a base material, and which overlaps each other or another member to be joined. The laser welding method of the present invention is suitable as a method for welding galvanized steel sheets and the like.

[0002]

2. Description of the Related Art Laser welding (hereinafter, also referred to as "lap welding") of superposed members to be welded, such as galvanized steel sheets and painted steel sheets, coated with a coating material having a lower melting point than the base material, It is known that, during welding, a coating material vapor generated between members to be welded blows away molten metal, so that spatter is generated intensely, and pits and blow holes frequently occur in a weld bead. Further, at a position to be welded (hereinafter, also referred to as a “probable welding position”),
It is also known that by irradiating a laser beam with a gap provided between members to be welded at appropriate intervals, the generated coating material vapor escapes from the gap to perform good lap welding.

[0003]

If the gap for allowing the coating material vapor to escape is too wide, melt-through occurs. If the gap is too narrow, the vapor cannot be sufficiently escaped to solve problems such as generation of blowholes. Can not. Therefore, during welding,
It is necessary to manage the gap between the members to be welded at the expected welding position (hereinafter, also referred to as “plate gap”) within a predetermined range. The range of the plate gap where good welding quality can be obtained depends on the thickness of the member to be welded.
In the case of 0 mm, it is usually about 0.2 to 0.4 mm.

As a method of providing the plate gap, Japanese Patent Application Laid-Open No.
Japanese Unexamined Patent Publication No. 27189 discloses a method in which a plate gap is formed at a position expected to be welded by subjecting a member to be welded to plastic working (pressing or the like) or cutting. Also,
Japanese Patent Application Laid-Open No. 7-32180 discloses that only a member to be welded on a laser irradiation side is first melted using a laser on a constrained side of a prospective welding position, and the contraction of the molten metal during cooling is used. A laser welding method is disclosed in which a member to be welded is warped and deformed to form a gap at a position where welding is expected, and then lap welding is performed.

However, in the method described in Japanese Patent Application Laid-Open No. 61-27189, the number of steps for press working or cutting work is increased, so that manufacturing efficiency is reduced. Further, in the case of press working, it is necessary to build a press die, and especially in a large workpiece to be joined, it may be difficult to manage the plate gap due to press working accuracy, deformation of the member due to its own weight, and the like. . In the method described in Japanese Patent Application Laid-Open No. 7-32180, since the free end of the member to be welded is raised by melting and shrinking of the member to be welded to form a plate gap, it is necessary to manage the plate gap with high precision. It is difficult. In addition, melting and shrinkage of the member to be welded cause unnecessary distortion and deformation of the member to be welded, which is not preferable. Further, since ordinary laser welding is performed after once irradiating a laser to form a plate gap, the welding speed is reduced and productivity is reduced.

[0006] An object of the present invention is to provide a laser welding method which can easily manage a gap between sheets, is excellent in productivity, and can form a high quality welded portion.

[0007]

According to a first aspect of the present invention, there is provided a laser welding method according to the first aspect, wherein two members are overlapped with each other, and a laser beam is irradiated to a welding expected position of the overlapped portion. A laser welding method for welding two members, wherein at least one of the two members is made of a coated base material coated with a coating material having a lower melting point than the base material, and the two members are At least one of the members is a flanged member having a flange portion, the flange portion is formed by bending in a direction away from the other member outside the expected welding position of the one member,
The laser irradiation is performed in a state where the two members are brought into close contact with each other at least at the expected welding position.

[0008] The formation of the flange portion is preferably performed before the flanged member and the other member are overlapped with each other because processing is easy. The method of forming the flange portion is not particularly limited, but according to the method of bending in the step of punching the member to be welded, the flange portion can be formed without adding an extra step to the conventional manufacturing process, and a press die or the like can be formed. Is not required.

The shape of the flange is such that the thickness of the flanged member is t ₁ and the outer radius bending radius of the flange is R.
It is preferable that R is in the range of t ₁ ≦ R ≦ 100 mm, and as described in claim 2, 2t ₁ ≦ R ≦ 5
More preferably, it is within a range of 0 mm. When forming the flange portion by normal bending, it is difficult to reduce than t ₁ to R. On the other hand, R is 100m
If it exceeds m, the space formed between the flanged member and the other member is narrow, so that the coating material vapor cannot be sufficiently released, and a blow hole or the like may be generated.

The angle between the flange portion and the other portion of the flanged member is preferably in a range of 90 ± 30 °, more preferably 90 ± 15 °. Most preferably, it is in the range of 90 ± 5 °. When this angle is 90 ± 5 °, it is advantageous when mechanical tracking is performed using a flange portion, as in an embodiment described later. Further, it is preferable that the laser irradiation is performed while applying a pressing force to the other end of the flange portion at the end end of the flange portion. The “start end of the flange portion” refers to a position at which the surface (outer diameter side surface) of the flanged member that comes into contact with the other member starts to bend in a direction away from the other member. Further, the "end end of the flange portion" refers to a plate end (edge) of the flanged member in the flange portion.

At least one of the members to be welded by the method of the present invention comprises a coated base material whose surface is coated with a coating material having a lower melting point than the base material. Examples of such a coated base material include a galvanized steel sheet, a tin-plated steel sheet, and a painted steel sheet. When both of the members to be joined are made of the coated base material, the amount of the coating material vapor generated is larger than when only one of the members to be joined is made of the coated base material. The effect by is exhibited well. The flange portion may be provided on one of the members to be joined, or may be provided on both.
Usually, it is preferable that the flange portion is provided only on the member on the side irradiated with the laser. The width of the flange is not particularly limited, and may be, for example, 1 to 5 mm, and preferably 1 to 2 mm. If the width of the flange portion is too small, bending may be difficult.

Although the thickness of the member to be welded by the method of the present invention is not particularly limited, it is usually 0.2 to 5.0 m.
m, more preferably 0.4
3.0 mm, more preferably 0.6 to 2.0 mm.

It is preferable that the expected welding position is usually the starting end of the flange portion. At the time of actual welding, there is a possibility that the laser may be irradiated to a position different from the expected welding position due to a manufacturing error of the member, deflection due to its own weight, a control error of the laser irradiation unit, or the like. At this time, as shown in FIG. 6, on a plane perpendicular to the irradiation direction of the laser L, the distance a from the expected welding position W to the welding position X where the laser is actually irradiated is 0 ≦ a ≦ 2 (R− t ₁ ) t ₁ / R
(However, it is preferable to perform control so that the direction from the expected welding position W to the outside of the flanged member is positive.) Here, t ₁ is the thickness of the flanged member, and R is the outer radius bending radius of the flange portion. 6, reference numeral 1 denotes a flanged member, and reference numeral 11 denotes a flanged member.
The reference numeral 2 indicates the other member.
If a is less than 0 (for example, welding position X1), the coating material vapor cannot be sufficiently released, and a blow hole may be generated. On the other hand, a is 2 (R-t ₁₎ exceeds t ₁ / R (for example, welding position X2), flanged member 1 and the other member 2
May be so wide that burn through may occur.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically by way of examples. As shown in FIG. 2, the member to be welded used in the welding method of this embodiment is an upper member (flanged member) which is disposed on the laser irradiation side and has a flange 11 formed thereon.
1 and a lower member 2 which is arranged on the opposite side of the upper member 1 on the side opposite to the laser irradiation side. The upper member 1 and the lower member 2 are each made of a galvanized steel sheet (GA60 / 60) having a thickness of 0.8 mm and a galvanized steel sheet (GA60 / 60) having a plating weight of 60 g / m ^{2 on} one side thereof. It was punched out. In this punching step, a portion having a width of 3.0 mm from the plate end of the upper member 1 is shown in FIG.
Is bent upward to form a flange portion 11. The outer radius bending radius R of the flange portion 11 is 1.6 mm, and the angle between the other portion of the upper member 1 and the flange portion 11 is 90 °. As shown in FIG. 2, welding is performed by irradiating a laser to an expected welding position W corresponding to the start end of the flange portion 11 in the overlapping portion 12 of the upper member 1 and the lower member 2.

FIG. 1 schematically shows a state at the time of welding. The roller 3 attached to a laser torch (not shown) captures the end surface 11a of the flange portion 11 by a concave portion 3a having a width of 0.8 mm formed on the outer peripheral surface thereof, and can roll using the end surface 11a as a guide. By this rolling movement, the laser torch can be moved along the flange portion 11. The laser torch has laser irradiation means for irradiating the laser L to a fixed relative position with respect to the width center of the roller 3. In the present embodiment, the laser irradiating means is adjusted so that the start end of the flange portion 11 is irradiated with the laser L. In this embodiment, by performing the mechanical tracking using the flange portion 11 as described above, the irradiation position of the laser L can be controlled without using a sensor or the like for detecting the flange portion 11.

At the time of welding, the lower member 2 side (FIG. 2) is attached to the end face 11a of the flange portion 11 from the laser torch via the roller 3.
Is applied to the upper member 1.
While bringing the lower member 2 and the lower member 2 into close contact with each other, the start end of the flange portion 11 is irradiated with the laser L to melt the upper member 1 and the lower member 2 to form a fusion part 4. Since the zinc vapor G generated at this time is released from between the flange portion 11 and the lower member 2, the occurrence of blow holes and the like is prevented. Further, since the plate gap between the upper member 1 and the lower member 2 at the expected welding position W is substantially zero, no burn-through occurs.

In FIG. 1, the upper member 1 and the lower member 2 are in close contact with each other at the overlapping portion 12, but the design shapes of the upper member 1 and the lower member 2, the positions for holding these members,
Alternatively, as shown in FIG. 3A, due to a manufacturing error of the members, a gap 13 is provided between the two members when no external force is applied.
May be present. Even in such a case, the pressing force applied from the roller 3 to the end face 11a causes, for example,
As shown in (b), the upper member 1 and the lower member 2 are brought into close contact with each other at least at the expected welding position W (that is, the plate gap is set to 0), and the welding method of the present invention can be performed. The pressing force at this time can bring the upper member 1 and the lower member 2 into contact with each other at least at the expected welding position W,
In addition, it is only necessary that the defect such as deformation of the member does not occur, and it is not necessary to control the temperature so strictly.

In the above embodiment, the laser irradiation position is controlled by mechanical tracking using the flange portion. However, the laser irradiation position may be controlled by a sensor for detecting the flange position. In the above embodiment, the pressing force is applied to the end face 11a of the flange portion 11 using the roller 3 for performing the mechanical tracking. The pressing force may be applied to For example, upper member 1
The lower member 2 and the lower member 2 may be fixed in advance with a clamp, and the laser irradiation may be performed after the gap at the welding expected position W is set to 0 over the entire range of the welding length. Since the rigidity of the upper member 1 is improved by forming the flange portion 11, the interval between the pressed portions can be increased as compared with the case where the flange portion is not provided.

Further, in the above embodiment, the flange portion 11 is provided only on the upper member 1 (the member to be irradiated on the side irradiated with the laser). However, as shown in FIG. Instead, the flange portion 21 may be formed on the lower member 2 (the member to be welded on the side opposite to the side where the laser is irradiated). Further, as shown in FIG. 5, a flange 11 and a flange 21 may be provided on both the upper member 1 and the lower member 2, respectively.

[0020]

According to the prior art in which a predetermined gap is intentionally formed between the upper member and the lower member at the expected welding position, the shape, holding position, pressing force, etc. of the member are strictly determined. Must be adjusted. In addition, it is difficult to control the size of the plate gap to be within a predetermined range due to a manufacturing error or the like of the member. According to the present invention, by forming a flange portion in advance on a member to be welded and irradiating a laser to the start end of the flange portion, the coating material vapor can be released even if the plate gap at the expected welding position is zero. Therefore, instead of managing the gap to a predetermined size as in the related art, the upper member and the lower member are simply brought into close contact with each other (that is, such that the gap is substantially zero). If the welding is performed (managed), a good welded portion can be obtained without causing burn-through, blowholes, etc., so that the management of the sheet gap is easy.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a state during welding in a welding method according to an embodiment.

FIG. 2 is a perspective view showing a member to be welded used in the welding method according to the embodiment.

FIGS. 3A and 3B are cross-sectional views showing another embodiment, in which FIG. 3A schematically shows a state in which no external force is applied to a member to be welded, and FIG. Shown in

FIG. 4 is a cross-sectional view schematically showing a state at the time of welding in another embodiment.

FIG. 5 is a sectional view schematically showing a state at the time of welding in another embodiment.

FIG. 6 is a cross-sectional view showing a relationship between an expected welding position and a welding position.

[Explanation of symbols]

1: upper member (flanged member) 11: flange portion, 11
a; end face (end end of flange portion); 12; overlapped portion; 2; lower member (the other member); 21 flange portion;
Roller, 4; melting part, G: zinc vapor (coating material vapor),
L: laser, W: expected welding position.

Claims (4)

[Claims] 1. A laser welding method for superposing two members and irradiating a laser to a welding expected position of the superposed portion to weld the two members, wherein at least one of the two members is provided. Is composed of a coated base material in which the base material is coated with a coating material having a lower melting point than the base material, and at least one of the two members is a flanged member having a flange portion. One of the members is formed by bending an outer side of the expected welding position in a direction away from the other member, and the laser irradiation is performed in a state where the two members are brought into close contact with each other at least at the expected welding position. A laser welding method characterized by the above-mentioned. 2. Assuming that the thickness of the flanged member is t ₁ and the outer bending radius of the flange portion is R, R is t ₁ ≦
The laser welding method according to claim 1, wherein R ≦ 100 mm. 3. The angle between the flange portion and the other portion of the flanged member is 90 ± 5 °.
The laser irradiation method according to the above. 4. The laser irradiation method according to claim 1, wherein the laser irradiation is performed while applying a pressing force to an end end of the flange portion toward the other member.