JP3084152B2 - Laser welding method - Google Patents

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 in which members to be welded having a predetermined thickness are overlapped and welded by a laser beam.

[0002]

2. Description of the Related Art In general, for example, when plate-like members to be welded are overlapped and welded, Japanese Patent Laid-Open No. 61-212496 is known.
As disclosed in Japanese Patent Application Laid-Open Publication No. H11-260, a method is adopted in which a overlapped portion between members to be welded is sandwiched between two electrode tips of a spot welding gun, and spot welding is performed at predetermined intervals in the longitudinal direction of the overlapped portion.

There is also a laser welding method in which two plate-like members having a low melting point plating layer such as zinc plating are overlapped and welded by a laser beam.
After being cut while melting the member to be welded on the irradiation side by laser beam irradiation, a predetermined gas pressure is set to prevent oxidation of the member to be irradiated on the irradiation side exposed while forming a groove by the cutting. The molten inert gas is supplied to the irradiation-side welded member in the molten state, and the irradiation-side welded member in the molten state is caused to flow into the non-irradiation-side welded member through the groove, and the welded members are connected to each other. (See JP-A-56-62688). In this case, a small gap (for example, with respect to the thickness of the irradiated side member to be welded) is provided between the overlapped portions of the members to be welded in order to provide a relief for the plating material that evaporates at the time of welding to prevent the occurrence of a probe hole. A gap of about 10%) is provided in advance.

[0004]

However, in the welding method using the spot welding gun as described above, since the members to be welded are sandwiched between the overlapped portions at predetermined intervals, the load on the overlapped portions between the members to be welded is increased. Acts on each spot welding portion, that is, each spot welding point, and cannot increase the rigidity of the members to be welded. Also, at the time of welding, since the member to be welded adheres to the two electrode tips of the spot welding gun,
There is a possibility that the resistance between the electrode tips may increase, resulting in poor welding, and the member to be welded needs to be cut off from the electrode tips. Further, since welding is performed in a state where the overlapped portions of the members to be welded are sandwiched by the spot gun, a load is applied to the overlapped portions of the members to be forcibly attracted to the members to be welded. Will be inaccurate.

On the other hand, when the overlapped portion of the members to be welded is welded by using the above-described laser beam welding method, the irradiated member to be welded which has been melted by the irradiation of the laser beam is counter-irradiated through the groove. The heat of fusion is lost while flowing into the member to be welded on the side. Therefore, if there is a large gap due to a production error or the like between the overlapped portions of the members to be welded, the heat of fusion will be further deprived, and the heat of fusion of the members to be irradiated will cause the material to be irradiated to the opposite side. The members to be welded cannot be welded to each other while melting the members to be welded, and the members to be irradiated on the irradiation side flow into the gap to cause welding defects. That is, when the gap between the overlapped portions of the members to be welded becomes 20% of the plate thickness of the member to be irradiated on the irradiation side, an undercut occurs in the member to be irradiated on the irradiation side, and the gap becomes smaller than that of the member to be irradiated on the irradiation side. Plate thickness 40
%, The irradiation-side welded member flows into the gap, and a defect is generated in the irradiation-side welded member.

Therefore, it is conceivable that the gap is made as small as possible by separately using a clamping means or the like in the above-mentioned laser beam welding method. However, continuous welding using a laser beam is restricted in construction. Will be.

In this case, as means for improving the allowable limit of the gap between the overlapped portions of the members to be welded, the irradiated member to be irradiated in the molten state is caused to flow into the member to be irradiated on the non-irradiation side through the groove. At this time, it is conceivable that the filler wire is fed and the filler wire is melted by irradiating the laser beam. However, it is possible to compensate for the defective portion of the member to be irradiated on the irradiation side which flows into the gap by an amount corresponding to the melting of the filler wire. Although it is effective, the gap tolerance cannot be expanded.

The present invention has been made in view of the above points, and an object of the present invention is to focus on the laser welding method using the laser beam, and to use the filler wire to form a member to be welded on the irradiation side and a filler wire. Before the heat of fusion is taken away, by injecting it into the member to be welded on the non-irradiation side, thereby increasing the rigidity of the members to be welded, which is a disadvantage of the welding method using a spot welding gun, from each electrode tip. In addition to eliminating the need for scraping off the material, the precision of the members to be welded is kept good, and the members to be welded are reliably welded without causing welding defects while expanding the allowable gap of the overlap between the overlapping parts. Is to do.

[0009]

Means for Solving the Problems To achieve the above object, the present invention provides a laser welding method in which members to be welded having a predetermined thickness are overlapped and welded by a laser beam. After cutting the member to be welded on the irradiation side while melting it, a filler wire is fed into the groove formed by the cutting, and the filler wire is melted by the laser beam irradiation. The gas pressure was set such that the irradiated member to be irradiated and the filler wire in the molten state were pushed into the non-irradiated member to be welded through the groove to the member to be welded and the filler wire in the state. The inert gas is supplied.

[0010]

According to the present invention, in the present invention, the member to be welded and the filler wire on the irradiation side, which are melted by the laser beam irradiation, are supplied through the groove formed by cutting when the laser beam is irradiated. Due to the inert gas set to a gas pressure such that the welded member and filler wire in the molten state are pushed into the welded member on the non-irradiated side, production errors may occur between the overlapped parts of the welded members. Even if there is a gap, it will be pushed into the member to be welded on the non-irradiation side before the heat of fusion is taken away.

Therefore, the members to be welded can be welded to each other while melting the members to be irradiated on the opposite side by the heat of fusion of the member to be irradiated and the filler wire. The irradiation-side welded member flowing into the gap between them does not cause an undercut or a missing portion in the irradiation-side welded member. In addition, a clamping means or the like, which was necessary for making the gap as small as possible, becomes unnecessary, and there is no restriction on laser welding.

In addition, as described above, since the melted irradiation-side welded member and filler wire are pushed into the non-irradiation-side welded member before the heat of fusion is deprived, the filler wire melts and flows into the gap. The allowable limit of the gap can be increased while compensating for the missing portion of the member to be welded on the irradiation side.

Further, according to the laser welding method as described above, it is not necessary to cut off the material from each electrode tip without reducing the rigidity of the members to be welded, which is a disadvantage of the welding method using the spot welding gun. In addition, the accuracy of the member to be welded after welding is kept good.

[0014]

As described above, according to the laser welding method of the present invention, the member to be irradiated and the filler wire which are in a molten state by the irradiation of the laser beam are filled with the gas pressure of the inert gas through the groove. Since the welding heat is pushed into the non-irradiation-side welded member before heat is taken away, the gap between the irradiation-side welded member and the filler wire is compensated for by using the heat of fusion of the filler wire to compensate for the missing part of the irradiation-side welded member. And the members to be welded can be reliably welded together while melting the members to be welded on the non-irradiation side. In addition, there is no need for clamping means and the like, thereby eliminating restrictions on laser welding.

Further, it is possible to improve the rigidity of the members to be welded while eliminating the necessity of shaving off the material from each electrode tip, thereby keeping the accuracy of the members to be welded good.

[0016]

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

As shown in FIGS. 1 to 3, reference numeral 1 denotes a part of a side sill extending in the front-rear direction at the lower end of the side end of the vehicle. The side sill 1 includes an inner panel 2 having a substantially hat-shaped cross section, The outer panel 3 having a substantially hat-shaped cross section is formed in a closed cross section. The inner panel 2 and the outer panel 3 are linearly welded by laser welding in the direction in which the side sill 1 extends in the overlapping portion 4 where the flanges 2a and 3a provided at the side end portions overlap each other. The inner panel 2 and the outer panel 3 are each made of a cold-rolled steel plate having a thickness of 0.8 mm.

Here, as shown in FIG. 5, in order to measure the welding strength at the overlapped portion 4 of the inner panel 2 and the outer panel 3, plate thicknesses corresponding to the flange 2a of the inner panel 2 and the flange 3a of the outer panel 3, respectively. A description will be given of a welding method by laser welding when two plate-like members A and B made of a 0.8 mm cold-rolled steel plate are used.

FIG. 4 shows the structure of the laser welding apparatus 10.
In this figure, reference numeral 11 denotes a laser welding torch of a laser oscillator R, and a focusing lens 12 for focusing a laser beam is provided at the tip of the laser welding torch 11. A bracket is provided near the tip of the laser welding torch 11 so that the leading end of the linear filler wire 14 led out of the storage portion 13 wound and stored is supplied to the tip of the condenser lens 12. 15 and is supported so as to be freely inserted. The filler wire 14 has a diameter of 0.8
mm carbon dioxide welding material is used and filler wire 1
The feeding speed to the tip of the condenser lens 12 is 1.86 m / min.
Is set to

First, as shown in FIG.
2 Irradiation of the laser beam from the tip cuts the welded member A on the irradiation side (upper side in the figure) while melting it.
Next, the leading end of the filler wire 14 is fed to the groove 21 formed by the cutting, and the filler wire 14 is melted by the irradiation of the laser beam. Simultaneously with the irradiation, the welded member on the irradiation side in the molten state is irradiated. A gas which pushes the irradiation-side welded member A and the filler wire 14 in the molten state into the non-irradiation-side welded member B (the lower side in the figure) through the groove 21 into the A and the filler wire 14. Pressure, here gas pressure of 3.0 kg / cm ² (twice the gas pressure of 1.5 kg / cm ² by the conventional laser welding method)
Is supplied as an inert gas set as described above, and a welded portion 22 is formed over a welding length of 30 mm. In this case, the argon gas G is supplied on the irradiation axis of the laser beam. In addition, argon gas G
Is 45 l / min, whereas the supply of argon gas by the conventional laser welding method is 30 l / min.

Next, in Table 1 below, laser welding conditions according to the present invention and conventional laser welding conditions are compared.
In the laser welding conditions according to the present invention, the filler wire 1
No. 4 was fed, whereas no filler wire was fed under the conventional laser welding conditions, and the above conditions were used for argon gas. The output of the laser beam was set to 2.4 kw, the welding speed was set to 2.0 m / min, and the defocus amount was set to -1 mm.

[0022]

[Table 1] Then, as shown in FIG. 6, in the welded portion created by the laser welding conditions according to the present invention method in Table 1 above and the laser welding conditions according to the conventional method, there exists between the overlapping portions 4 between the members A and B to be welded. When the gap amount does not exist, the tensile strength (kN) with respect to the gap amount (in this case, simply shown in dimensional units) is almost the same between the method of the present invention and the conventional method, but the gap amount is 0. When the gap becomes 0.4 mm (gap of 50% with respect to the thickness of the member A to be welded on the laser beam irradiation side), the limit is reached in the conventional method, whereas in the present invention, the gap amount is 0.7 mm (gap in the laser beam irradiation side). (A gap of about 90% with respect to the plate thickness of the member A to be welded) does not reach the limit.

This is because, as shown in the sectional view of the welded portion 22 for each gap amount (%) in Table 2 below, in the conventional method, when the gap amount is 0% where no gap exists, the welded member A melts. The member B to be welded to the member B
Is welded while melting smoothly, whereas in the case of a gap amount of 40%, the molten heat of the welded member A is lost due to the gap between the welded member A and the welded member B. This is because B could not be melted and flowed into the gap, causing an undercut or a missing portion in the groove 21. And the gap amount is 90
% Could not be measured.

On the other hand, according to the method of the present invention, the welded member A and the filler wire 14 are pushed into the welded member B by the gas pressure of the argon gas G when the gap amount is 0% and the gap amount is 0%. The member B is welded by swelling up and down while melting smoothly. When the gap amount is 40%, the melted member A and the filler wire 14 are pushed into the member B by the gas pressure of the argon gas G without flowing into the gap, and the member B is melted smoothly. Weld up and down while welding. Even when the gap amount becomes 90%, the melted member A and the filler wire 14 are pushed into the member B by the gas pressure of the argon gas G without flowing into the gap.
Is melted smoothly and welded up and down.

[0025]

[Table 2] Therefore, in the above-described embodiment, the welded member A and the filler wire 14 on the irradiation side melted by the irradiation of the laser beam from the tip of the condenser lens 12 pass through the groove 21 formed by cutting when the laser beam is irradiated. The argon gas G set at a gas pressure of 3.0 kg / cm ² , which is supplied so as to push the irradiation-side welded member A and the filler wire 14 in the molten state against the non-irradiation-side welded member B.
Accordingly, even if there is a gap due to a production error or the like between the overlapping portions 4 of the members A and B to be welded, the members A and B are pushed into the member B to be irradiated on the non-irradiation side before the heat of fusion is deprived. For this reason, it becomes possible to weld the members A and B by raising and lowering the member B on the non-irradiation side while melting the member B on the non-irradiation side using the heat of fusion of the member A on the irradiation side and the filler wire 14. It is prevented from flowing into the gap between the overlapped portions 4 of the members A and B to be welded, so that the undercut A or the defective portion does not occur in the member A on the irradiation side. In addition, as described above, the irradiation-side welded member A and the filler wire 14 in the molten state are pushed into the non-irradiation-side welded member B before the heat of fusion is taken away. It is possible to increase the allowable limit of the gap to 90% while compensating for the missing portion of the member A to be irradiated on the irradiation side that flows in.

As a result, the allowable limit of the gap can be increased to 90% while making up for the defective portion of the irradiation side welded member A by the heat of fusion of the irradiation side welded member A and the filler wire 14, and The members to be welded A and B can be reliably welded to each other while melting the member to be welded B on the non-irradiation side.

In addition, the need for a clamping means or the like, which is necessary for making the gap as small as possible, is eliminated, and restrictions on laser welding can be eliminated.

Further, according to the laser welding method as described above, the material is removed from each electrode tip without reducing the rigidity of the members A and B to be welded, which is a disadvantage of the welding method using the spot welding gun. Can be eliminated, and the accuracy of the member to be welded after welding can be kept good.

It should be noted that the present invention is not limited to the above-described embodiment, but includes various other modifications.
For example, in the above-described embodiment, the welding method by laser welding when the members A and B made of cold-rolled steel plates are used has been described. However, two plate-shaped members having a low melting point plating layer such as zinc plating are described. The welding member may be welded by laser welding. In this case, undercutting may be caused even if an escape space for a plating material that evaporates due to a gap provided intentionally is provided to prevent occurrence of a blowhole. There is no. Further, two plate-shaped members to be welded made of synthetic resin such as plastic may be welded by laser welding. In this case, a plastic wire is used as the filler wire.

Further, not only continuous welding by laser welding but also spot welding in a spot-like manner as in the present invention, a through-hole is formed in the member to be welded on the irradiation side by laser beam irradiation, and melting is performed. In this state, the irradiation-side welded member and the filler wire in the state are supplied through the through-holes by an inert gas set to a gas pressure such that the filler wire is pushed into the non-irradiation-side welded member so that a gap allowable limit is provided. It is needless to say that the size of the image can be expanded.

[Brief description of the drawings]

FIG. 1 is a sectional view of a state where a welded portion is cut in a longitudinal direction.

FIG. 2 is a perspective view of the vicinity of a superposed portion showing a welding state.

FIG. 3 is a sectional view of a side sill.

FIG. 4 is a side view of the laser welding apparatus.

FIG. 5 is a perspective view of a state where members to be welded whose welding strength is to be measured are welded to each other.

FIG. 6 is a characteristic diagram showing a tensile strength characteristic with respect to a gap amount.

[Explanation of symbols]

 14 Filler wire 21 Groove A Irradiated side member to be welded B Non-irradiated side member to be welded G Argon gas (inert gas)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B23K 26/00-26/14

Claims (1)

(57) [Claims] 1. A laser welding method in which members to be welded having a predetermined thickness are overlapped and welded by a laser beam, wherein the member to be irradiated on the irradiation side is melted and cut by irradiation with a laser beam, and then the cutting is performed. The filler wire is fed into the groove formed by the above, and the filler wire is melted by the irradiation of the laser beam. Simultaneously with the irradiation, the irradiation of the welded member and the filler wire on the irradiation side in the melted state and the irradiation of the melted state are performed. The inert gas set to a gas pressure such that the workpiece to be welded and the filler wire are pushed into the workpiece to be welded on the non-irradiation side via the groove.