JPH0796379A - Carbon dioxide laser welding method for metallic material and welding and joining material - Google Patents

Abstract

PURPOSE:To efficiently obtain a CO2 laser weld zone having decreased blowhole (porosity) defects without requiring intricate welding parameter management even with metallic materials with which the blowhole (porosity) defects are liable to arise. CONSTITUTION:The plural metallic materials are subjected to CO2 laser welding by controlling the irradiation angle of a CO2 laser to an advance angle 10 to 60 deg. or retreat angle 20 to 60 deg. with the welding direction in the method for welding and joining the plural metallic materials by the CO2 laser. The CO2 laser welding is executed by controlling the irradiation angle of the CO2 laser to the advance angle 10 to 60 deg. or retreat angle 20 to 60 deg. with the welding direction in at least the final pass in the case of executing of the welding by superposing the joint parts of the metallic materials with >=2 passes by the CO2 laser. A good effect is obtd. when this method is applied to welding of aluminum or aluminum alloys (sheets, extrudates, etc.) in particular in addition to steel materials.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon dioxide laser welding technique for metallic materials, and more particularly to a carbon dioxide laser welding method and a welding method obtained by the carbon dioxide laser welding of metallic materials, by which a weld portion having few blowhole defects can be obtained. Regarding a joining member.

[0002]

2. Description of the Related Art Conventionally, arc welding such as TIG and MIG, electron beam (EB) welding, and the like have been performed as welding methods for metallic materials. However, there is a problem that welding deformation becomes large when performing arc welding on a thin plate, and it is necessary to perform EB welding in a vacuum, which requires work such as putting a work material in and out of a vacuum chamber. was there. Therefore,
In recent years, a laser welding method capable of performing high-speed / low-distortion welding processing in the atmosphere (including the case of using a processing gas) has been implemented or attempted for each metal material.

However, it is known that blowhole (porosity) defects are likely to occur in laser welded portions of metallic materials.

That is, in laser welding, the aspect ratio
Blowhole (porosity) defects are mainly generated in the welding root part of steel-based materials, etc., where a high penetration depth / surface bead width can be obtained. It is considered that the formed keyhole becomes unstable for some reason, the metal vapor or the shield gas at the bottom of the keyhole is caught in the molten metal, and remains at the time of solidification (when the solidification rate is high). And as a factor that destabilizes the keyhole, sputtering generated in the keyhole during welding,
It is considered that the fluctuation of the metal vapor ejected from the keyhole, the shape of the keyhole (which changes depending on the welding parameters) and the stability of the surrounding molten metal are considered.

On the other hand, aluminum and aluminum alloys, which are non-ferrous materials and have recently attracted attention as a substitute material for steel materials from the viewpoint of weight reduction of structures, have a low viscosity of molten metal, and magnesium, zinc, etc. as additional elements. Including the low melting point and high vapor pressure elements, the tendency of sputtering to occur during laser welding, the high thermal conductivity and fast solidification rate, and many other factors that destabilize the keyhole. It is known that the shield gas is entrapped in the molten metal at the laser welded portion, and blowhole (porosity) defects that remain and solidify remarkably occur.

Therefore, in laser welding of steel-based materials, the following welding methods have been conventionally implemented or proposed as a welding method for suppressing the above-mentioned blowhole (porosity) defects.

First, an appropriate amount of defocusing is performed to enlarge the diameter of the focal spot on the surface of the material to be welded, that is, lower the power density on the surface of the workpiece.
There is a welding method that keeps the stability of the keyhole against the molten metal by increasing the volume of the keyhole at the same time (decreasing the aspect ratio: smaller). However, it is necessary to secure a power density for causing melting.

Also, in order to facilitate the discharge of the gas entrained in the molten metal, the solidification rate is reduced, that is, welding in combination with the remaining heat of the work piece and other heat sources for post-heating the molten pool. There is a way.

On the other hand, in laser welding of aluminum and aluminum alloys, as a welding method for suppressing the above-mentioned blowhole (porosity) defects, an appropriate amount of defocusing is performed as in the case of steel-based materials. Welding methods have been used in the past.

However, in laser welding of steel-based materials and aluminum and aluminum alloys, when defocusing is performed, proper control of the defocusing amount for each material is required, and since the penetration decreases, the welding speed is reduced. Had to lower. Furthermore, when devising an optical system, there is a problem that the optical device, the laser light transmission path, and the periphery of the welding nozzle become complicated.

Reducing the welding speed not only makes it impossible to make use of the high-speed workability that is a characteristic of laser welding, but also causes a large amount of underfill in the welding bead due to the intense sputtering of the aluminum alloy, and the sputtering causes the condensing optical system. There was a problem that it adversely affected the.

Further, in the case of steel-based materials, the number of blowhole (porosity) defects generated can be reduced by the above-mentioned conventional method, but in the case of materials such as aluminum and aluminum alloys which are particularly prone to blowhole (porosity) defects. No significant effect was obtained.

The present invention solves the above-mentioned drawbacks of the prior art, and does not require complicated welding parameter management even for a metal material that is prone to generate blowhole (porosity) defects, and does not require blowhole (porosity). It is an object of the present invention to provide a welding technique capable of efficiently obtaining a carbon dioxide laser welded portion with few defects.

[0014]

As a means for solving the above problems, the present invention is a method for welding and joining a plurality of metal materials by a carbon dioxide gas laser, in which the irradiation angle of the carbon dioxide gas laser is advanced with respect to the welding direction. Angle 20 ° -60 °
Alternatively, the gist is a carbon dioxide laser welding method for a metal material, which is characterized in that the carbon dioxide laser welding is performed by controlling the receding angle to 20 ° to 60 °.

[0015]

The present invention will be described in more detail below.

The laser welding method is classified into various laser welding methods according to the type of heat source (solid-state laser, gas laser, etc.), but in the present invention, a carbon dioxide gas laser with a large output and deep penetration can be obtained. Target.

In the carbon dioxide laser welding method according to the present invention,
By setting the laser irradiation angle relative to the welding direction at a predetermined angle (whether it is an advancing angle or a receding angle), the keyhole is formed to be inclined with respect to the vertical direction with respect to the workpiece surface, and the beam on the workpiece surface is formed. The spot shape becomes elliptical, the ejection holes for metal vapor become large, and even if sputtering occurs during welding, the direction of the generation can be kept constant, which increases the stability of the keyhole and shields it. Entrainment of gas in the molten metal is reduced, and it becomes possible to obtain a laser welded portion with few blowhole (porosity) defects.

In particular, when the advancing angle is adopted as the laser light irradiation angle, the solidification rate of the molten metal is slowed by the post-heating effect of the laser-induced plasma generated directly above the laser irradiation portion on the molten pool, that is, , The discharge of gas in the molten pool is promoted, and further reduction of blowhole (porosity) defects can be expected.

In order to obtain such an effect of reducing blowhole (porosity) defects, it is necessary to set the advancing angle or the receding angle to 20 ° or more. For this effect, the larger the advancing angle or the receding angle, the better. However, as the size is increased, the power density on the surface of the sample is reduced, and the penetration depth is shallower because the penetration direction is inclined from the direction perpendicular to the workpiece, though not as much as when defocusing. The advancing or receding angle must be limited to 60 ° or less. A practical irradiation angle is 30 for both forward and backward angles.
It is desirable that the angle is between about 50 ° and 50 °.

Here, the advancing angle and the receding angle, as shown in FIG. 1, where the laser irradiation angle with respect to the welding direction is θ, the laser irradiation angle when θ is positive is the advancing angle and is negative. The laser irradiation angle is called the receding angle. When θ = 0 °, it is vertical incidence. The laser irradiation angle with respect to the direction perpendicular to the welding direction may be referred to as the advancing angle or the receding angle, but the advancing angle or the receding angle in this case is different from the advancing angle or the receding angle in the present invention.

It goes without saying that the present invention can be applied not only to the welding execution method of only one pass but also to the welding execution method of superposing two or more passes.

In the case of the latter welding method in which two or more passes are superposed, there is a mode in which all or a part of the passes are laser-welded at the laser irradiation angle described above, and the advancing angle is 20 ° to 60 ° at least in the final pass. ° or receding angle 20 ° to 60
It is desirable to use a construction method in which carbon dioxide laser welding is performed at a controlled temperature.

As such a construction method, for example, 1
A desired penetration depth is ensured by the irradiation angle such as vertical incidence at the pass, and the penetration depth is made shallower for each pass after the second pass. (Porosity) defects are sequentially transferred to the upper part, and the generation of defects is suppressed by irradiation at the above-mentioned inclination angle in the final pass to obtain a weld portion with few blowhole (porosity) defects. FIG. 2 shows a schematic diagram of two-pass superposition laser welding.

This construction method is a welding method utilizing the fact that blowhole (porosity) defects are generated in the relatively upper part of the weld metal, and it has a relatively low thermal conductivity of Al-Mg system and Al-Zn-Mg. It is effective when applied to a series of aluminum alloys. In the case of Al-Mg system and Al-Zn-Mg system, the blowhole (porosity) defect is located relatively above the laser welding bead because the shield gas caught in the molten pool is the surface of the molten pool as welding progresses. It tends to float in the direction of the molten pool and is released to the outside of the molten pool. This is probably because the solidification rate of the molten pool is high and the gas is trapped in the weld metal before it reaches the surface of the molten pool.

However, since other aluminum alloys have high thermal conductivity and a high solidification rate, defects are likely to occur relatively below the welded portion (root portion), and the application effect is relatively small. The same applies to steel materials.

Further, in the case of superposition welding of two or more passes, even if the second and subsequent passes are welded in tandem, or after welding in the previous pass and welding is performed by changing the welding conditions with the same nozzle, a welded portion with few defects will be obtained. can get.

The other welding conditions for carbon dioxide laser welding are not particularly limited. Assist gas, shield gas, filler material, etc. can be used appropriately.

In particular, with regard to defocusing, there is an effect that the surface size of the keyhole is increased to facilitate discharge of gas inside the keyhole, but on the other hand, since the penetration depth becomes shallow, the welding speed When trying to obtain a deep penetration depth by lowering the welding temperature, there is also a drawback in that, particularly in the case of aluminum alloys, a large underfill is likely to occur in the welding bead due to sputtering due to the lowering of the welding speed. . In addition, in the present invention in which the predetermined advance angle or retreat angle is set, if defocusing is also performed, there arises such a disadvantage that the penetration depth is significantly reduced.
It is desirable not to perform defocusing substantially. If defocusing is performed, consider the forward or backward angle, and
Defocus less than 3 mm is desirable.

In the present invention, since the laser irradiation angle is set to a predetermined advancing angle or receding angle without defocusing as a blowhole defect suppressing means as in the prior art, it is possible to reduce the blowhole defect, and therefore the welding is performed. A high welding speed of 1.5 m / min or more is possible without lowering the speed.

As the material of the metal material, various steel materials such as low alloy steel such as carbon steel and stainless steel, high alloy steel, aluminum and aluminum alloys, other metals and alloys thereof can be used. Besides plates, shapes such as molds and tubes are also possible. Also, the weld joint shape is a butt shape,
Lap joint shapes, fillet shapes, etc. are possible.

Next, examples of the present invention will be described.

[0032]

[Example 1] A steel material (SUS30) as a material to be welded
4), Al alloy (A5083) and pure Al (A1050) plate materials were used, and one pass carbon dioxide laser welding was performed at the laser irradiation angle shown in Table 1 (see FIG. 1). Other welding conditions were: SUS304, A5083, low-order multimode output: 4500 W, A1050: phase matching mode output: 4000 W, welding speed: 2 m / min. The joint shape is a butt shape. No defocusing was done.

The blowhole defects are evaluated by SUS304.
In the case of, the evaluation is performed by the radiation transmission test of JISZ3104, and in the case of aluminum material, the radiation transmission test of JISZ3105 is performed (the penetration depth is taken as the target plate thickness), and grade 1 or higher is marked ◎, grade 2 or higher is marked ○, Grades 3 and below were marked with x. Table 1 shows the evaluation results of penetration depth and blowhole (porosity) defects.

As is clear from Table 1, in any of the materials to be welded, the example of the present invention provides a laser welded portion having extremely few blowhole (porosity) defects.

3 to 4 are aluminum alloys according to the present invention.
(A5083) is a longitudinal cross-sectional photograph of a laser welding bead. FIG. 3 shows no blowhole defects when the advancing angle is 40 °, and FIG. 4 shows some blowholes when the advancing angle is 20 °. On the other hand, FIGS. 5 to 6 show aluminum alloys (A
5083) is a longitudinal cross-sectional photograph of a laser welding bead of FIG.
There are many blowhole defects both when the advancing angle is 15 ° and when vertical incidence is shown in FIG. FIG. 7 shows the relationship between the laser irradiation angle and the number of blowhole defects in the case of A5083.

[0036]

[Table 1]

[0037]

[Example 2] A plate material of Al alloy (A5083) was used as a material to be welded, a target penetration depth was set to 4 mm, and carbon dioxide laser welding was performed twice with overlapping welding. At that time, the first pass had a low-order multimode laser output of 4000 W and a welding speed of 2 m / min, and the second pass had a low-order multimode laser output of 4000 W, a welding speed of 2 m / min, and an advancing angle of 35 ° (Fig. 2). The joint shape was a butt shape, and defocusing was not performed.

The method for evaluating blowhole defects is JISZ.
The evaluation was performed by the radiation transmission test of 3105 (the target penetration depth was defined as the target plate thickness). FIG. 8 is a vertical cross-sectional photograph of the laser weld bead, and the blowhole defect was grade 1 (⊚).

[0039]

As described in detail above, according to the present invention,
Efficiently obtain a laser weld with few blowhole (porosity) defects without complication of welding parameters such as proper management of defocus amount, change of optical device, laser light transmission path, and modification of welding nozzle periphery. The remarkable effect of being able to do is obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating the procedure of carbon dioxide laser welding.

FIG. 2 is a schematic diagram illustrating the procedure of 2-pass superposition welding in carbon dioxide laser welding.

FIG. 3 is a photograph showing a vertical cross section (metal structure) of a laser welding bead of an aluminum alloy (A5083), in the case of an advance angle of 40 °.

FIG. 4 is a photograph showing a vertical cross section (metal structure) of a laser welding bead of an aluminum alloy (A5083), in the case of an advancing angle of 20 °.

FIG. 5 is a photograph showing a vertical cross section (metal structure) of a laser weld bead of an aluminum alloy (A5083) in the case of an advance angle of 15 °.

FIG. 6 is a photograph showing a vertical cross section (metal structure) of a laser weld bead of an aluminum alloy (A5083), in the case of vertical incidence.

FIG. 7 is a diagram showing a relationship between a laser irradiation angle and the number of blowhole defects.

FIG. 8 is a photograph showing a vertical cross section (metal structure) of a laser welding bead of an aluminum alloy (A5083) in the case of two-pass superposition welding.

[Explanation of symbols]

a Laser irradiation angle (advancing angle when θ is positive, receding angle when negative) b Welding material c Weld metal part c'Welding metal part (2nd pass) d Machining nozzle e Parabolic mirror (focusing) Lens is acceptable) f Blowhole (porosity) defect

Claims (7)

[Claims] 1. A method of welding and joining a plurality of metal materials by a carbon dioxide laser, wherein the irradiation angle of the carbon dioxide laser is controlled to an advancing angle of 20 ° to 60 ° or a receding angle of 20 ° to 60 ° with respect to the welding direction. And a carbon dioxide laser welding method for a metal material, which comprises performing carbon dioxide laser welding. 2. When performing welding by superposing two or more passes of the joint portion of the metallic material by a carbon dioxide gas laser, at least in the final pass thereof, the irradiation angle of the carbon dioxide gas laser is an advance angle of 20 ° to 60 ° with respect to the welding direction. 2. The method according to claim 1, wherein the carbon dioxide laser welding is performed by controlling the angle or the receding angle to be 20 to 60 degrees. 3. The method according to claim 2, wherein the laser irradiation angle is controlled to secure a desired penetration depth in the first pass, and the penetration depth is successively reduced in the second and subsequent passes. 4. The method according to claim 1, 2 or 3, wherein carbon dioxide laser welding is carried out at a welding speed of 1.5 m / min or more without substantially defocusing. 5. The carbon dioxide gas laser welding of extruded die members made of aluminum or an aluminum alloy,
The method according to 3 or 4. 6. The method according to claim 1, 2, 3 or 4 in which plate materials made of aluminum or an aluminum alloy are laser-welded together with carbon dioxide gas. 7. An extruded die or plate made of aluminum or an aluminum alloy obtained by the carbon dioxide laser welding according to claim 5 or 6, wherein J at the welded portion.
A welded joint member made of aluminum or an aluminum alloy for automobiles, characterized in that the evaluation of blowhole defects by a radiation transmission test prescribed by IS3105 is 2 or higher.