JP3136231B2 - Laser welding method for aluminum alloy members - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for laser welding aluminum alloy members.

[0002]

2. Description of the Related Art In recent years, in the field of transportation such as automobiles, railway vehicles, ships, etc., lightweight aluminum alloy materials have been adopted instead of steel materials in the manufacture thereof in order to cope with low fuel consumption and high speed. It is becoming. Generally, consumable electrode type arc welding is used for joining aluminum alloy members by welding. In the joining of aluminum alloy members by this arc welding, welding joints having a relatively wide groove shape such as Y-type or V-type are often adopted, and due to the properties of the aluminum alloy material, its thermal conductivity is low. High welding requires a relatively large heat input, which results in an unnecessarily large overfill and a large deformation after welding. Is required.

[0003] On the other hand, in laser welding, since the laser beam has the property of a concentrated heat source with a high energy density, it is possible to perform deep penetration welding with low heat input, and to effect heat and deformation on members to be joined. Is very low and high-speed welding is possible. Therefore, penetration penetration of the butt-welded portion or lap-welded portion to be joined formed by the aluminum alloy members from the surface on the laser beam incident side to the reverse surface on the opposite side in one pass. (Full penetration) has been attempted by laser welding.

[0004]

However, in the conventional laser welding method for aluminum alloy members, the laser output and the welding speed are simply adjusted to increase or decrease, so that porosity defects and low viscosity on the back surface are low. There were many burn-through defects in which the molten pool partially burned off along the weld line.

The present invention has been made in view of the above-mentioned circumstances, and a welding portion formed of aluminum alloy members to be joined is formed from the surface on the laser beam incident side to the back surface on the opposite side. When laser welding is performed so as to reach the penetration penetration, the occurrence of porosity defects and burnout defects can be extremely reduced, and a high quality weld having extremely few welding defects can be stably obtained.
An object of the present invention is to provide a laser welding method for an aluminum alloy member.

[0006]

In order to achieve the above object, according to the present invention, a welded portion formed of aluminum alloy members to be joined is formed from the surface on the laser light incident side where the penetration is performed. When performing laser welding so as to achieve penetration penetration reaching the opposite back surface, on the back surface side of the weld to be joined, in contact with the back surface, the width is 1 to 6 mm around the welding line, and The depth in the anti-backside direction is 1 to
A laser welding method for an aluminum alloy member, comprising: forming a cavity having a cross-sectional dimension of 3 mm and extending along a welding line, and performing laser welding while supplying an inert gas as a back shield gas into the cavity. It is. Also,
According to a second aspect of the present invention, there is provided a laser for an aluminum alloy member according to the first aspect, wherein the inert gas is helium gas alone or a mixed gas of helium gas and argon gas containing helium gas at a mixing ratio of 30 vol% or more. It is a welding method.

[0007]

In the laser welding method according to the present invention, the welding portion to be joined formed by the aluminum alloy members is formed so that the penetration becomes a penetration penetration from the surface on the laser beam incident side to the back surface on the opposite side. When performing laser welding, a cavity extending along the welding line is formed on the back surface side, in contact with the back surface, so that metal vapor, hydrogen, and the like are discharged into the cavity during laser welding. The porosity defect (blow hole defect) in the penetration bead (weld metal) generated due to metal vapor, hydrogen, or the like can be extremely reduced. In addition, since an inert gas is supplied as a back shield gas into the cavity, the molten pool serving as a back bead on the back surface of the welded portion is cooled, and the formation of the keyhole is stabilized by cooling the molten pool. Therefore, burn-through of the molten pool on the back surface of the welded portion can be extremely reduced. The inert gas supplied into the cavity also functions to protect a molten pool serving as a back bead and to remove plasma.

[0008] In the laser welding method according to the present invention, the cavity has a cross-sectional dimension of 1 to 6 mm around the welding line and a depth of 1 to 3 mm in the direction opposite to the back surface, and extends along the welding line. It is important to form it so that it extends.
If the depth of the cavity in the direction opposite to the back surface is less than 1 mm, the reflected laser light will be reflected on the back surface of the welded portion, and the shape of the back bead will be poor. If it exceeds 3 mm, the molten pool will be cooled on the back surface of the welded portion. This is because the effect of preventing burnout is insufficient. Also, if the width of the cavity is less than 1 mm, it becomes narrower than the minimum width of the back bead, which prevents the discharge of metal vapor, hydrogen, etc., and if it exceeds 6 mm, the cooling of the molten pool on the back surface of the weld becomes insufficient. This is because the effect of preventing burn-through is small.

In the laser welding method according to the present invention, the inert gas supplied into the cavity is helium gas alone or helium gas in a mixing ratio of 30 vol% or more in view of a cooling effect on the molten pool on the back surface of the welded portion. It is preferable to use a mixed gas containing helium gas and argon gas. Helium gas mixture ratio of 30
If it is less than vol, the cooling of the molten pool is not sufficient, and the effect of preventing burn-through deteriorates, which is not preferable.

In the laser welding method according to the present invention, the welding conditions such as the laser output and the welding speed may be set according to the type of laser, the thickness of the weld to be joined, the shape of the joint, and the like. Is set to 3 kW or more when a carbon dioxide gas laser is used, and is set to 1 kW or more when a YAG laser is used.

[0011]

Embodiments of the present invention will be described below. [Embodiment 1] FIG. 1 is a sectional view for explaining a butt-welded portion and a cavity according to a laser welding method according to Embodiment 1 of the present invention. In this embodiment, as shown in FIG.
By joining the two members 1A and 1B such that the recesses thereof face each other and the ends of the members 1A and 1B to each other, the upper welded portion in the drawing has an I-shaped butted shape. A cavity extending along the welding line having a sectional shape of a rectangular section having a width W around the welding line and a depth D in the direction opposite to the back surface, in contact with the back surface, and in contact with the back surface. The one in which C was formed was produced. And cavity C
A plurality of samples having different widths W and depths D were prepared, and laser welding was performed under the welding conditions described below so that penetration would be penetration penetration, and then the welding results were investigated. In this embodiment, a member 1 having a concave portion having a rectangular section
Extruded profiles are used as A and 1B, and the back shield gas is supplied into the cavity C from the other end while closing one end in the direction of the weld line. .

The welding conditions are as follows: Test material: JIS A6
N01S, weld thickness: 2 mm, welding position: downward welding, carbon dioxide laser output: 4 kW, welding speed: 50 mm
/ S, type of shield gas and its flow rate: Ar gas, 20 liters per minute, type of back shield gas into the cavity and its flow rate: Ar 50% + He 50%, total 20 per minute
Liter, welding length: 500 mm.

Table 1 shows the welding results. In Table 1, the radiation transmission test for knowing the state of occurrence of defects in the penetration bead (in the weld metal) is based on JIS Z 3105, and the burn-through occurrence rate is the number of burn-out defects that can be visually counted. The value obtained by dividing the number by the welding length was converted per unit length, and represents the number of burn-through occurrences per unit length of 100 mm. As shown in FIG. 7, test numbers 17 and 18 as comparative examples
Result of laser welding of the I-shaped butt-shaped welded portion constituted by the three members 1C and 1D to be simply penetrated without supplying a back shield gas to the back side thereof It shows.

[0014]

[Table 1]

From Table 1, two aluminum alloy members 1
The laser welding is performed on the I-shaped butt-welded portion constituted by A and 1B so that the penetration becomes a penetration penetration from the surface on the laser beam incident side to the reverse surface on the opposite side. On the back side of the weld, a cavity having a rectangular cross-section in contact with the back surface and extending along the welding line is formed by the two aluminum alloy members themselves, and the cross-sectional dimension of the cavity has a width centering on the welding line. If the depth is 1 to 6 mm and the depth in the direction opposite to the back surface satisfies the range of 1 to 3 mm, by performing laser welding while supplying an inert gas as a back shield gas into the cavity, It can be seen that the occurrence of porosity defects and burn-through defects can be extremely reduced, and a high-quality weld having extremely few welding defects can be stably obtained.

[Embodiment 2] FIG. 2 is a sectional view for explaining a butt-welded portion and a cavity according to a laser welding method according to Embodiment 2 of the present invention. In this embodiment, as shown in FIG. 2, two members 1E and 1F having a concave portion having a rectangular cross section at an end and made of an aluminum alloy are joined to each other with the concave portions facing each other. Thus, the upper welded portion to be joined and the lower welded portion to be joined in the drawing have an I-shaped butt shape, and further have a rectangular section in contact with the backside of the welded portion to be joined and in contact with the backside. A cavity C having a width W centered on the weld line, a depth D in the direction opposite to the back surface and a cross-sectional dimension D extending along the weld line was formed. Then, a plurality of cavities C having different widths W and depths D are prepared, and laser welding is performed under the welding conditions described below so that penetration becomes penetration penetration.
Thereafter, the welding results were investigated. The laser welding was performed with the butt-welded portion to be joined on the upper side in the figure in a downward posture, and thereafter, the member was turned over and the lower butt-weld part in the figure was performed in the downward posture. In this embodiment, extruded members are used as the members 1E and 1F each having a concave portion having a rectangular cross section at the end, and the inside of the cavity C is closed with one end in the welding line direction. The back shield gas was supplied from the other end.

The welding conditions are as follows: Test material: JIS A6
N01S, weld thickness: 3 mm, welding position: downward welding, carbon dioxide laser output: 5.5 kW, welding speed: 6
6.7 mm / s, type of shielding gas and its flow rate: A
r gas, 20 liters per minute, type and flow rate of back shield gas into the cavity: He, 10 liters per minute, welding length: 300 mm.

Table 2 shows the welding results. In Table 2, the radiation transmission test was performed in the same manner as in Example 1 in accordance with JIS Z31.
05, and the burn-through occurrence rate represents the number of burn-through occurrences per unit length of 100 mm, similarly to Example 1.

[0019]

[Table 2]

From Table 2, two aluminum alloy members 1
At the time of laser welding the two I-shaped butt welds to be joined constituted by E and 1F so that the penetration becomes a penetration penetration from the surface on the laser beam incident side to the back surface on the opposite side. On the back side of the two welds to be formed, that is, a cavity having a rectangular cross section extending between the respective welds and extending along the weld line is formed by the two aluminum alloy members themselves, and the sectional dimension of the cavity is reduced. The width is 1 to 6 mm around the weld line, and the depth in the direction opposite to the back surface is 1 to 3 m
m, if laser welding is performed while supplying an inert gas as a back shield gas into the cavity, the occurrence of porosity defects and burn-out defects can be extremely reduced, It can be seen that a high quality weld having very few welding defects can be stably obtained.

[Embodiment 3] FIG. 3 is a sectional view for explaining a butt-welded portion and a cavity according to a laser welding method according to Embodiment 3 of the present invention. In this embodiment, as shown in FIG. 3, a cavity forming auxiliary plate 2 made of a copper alloy should be used for the case where the cross-sectional dimension of the cavity in the comparative example of the above-mentioned embodiment 2 exceeds the dimension range according to the present invention. so,
On the back surface side of the welded portion to be joined constituted by the two aluminum alloy members 1G and 1H, the width W is 1 to 6 mm around the welding line, and the depth D in the direction opposite to the back surface is 1
A cavity C satisfying the range of ３3 mm was formed, and laser welding was performed. The auxiliary plate 2 for forming a cavity may be made of an aluminum alloy or steel. The welding conditions are the same as in the second embodiment. Table 3 shows the welding results.

[0022]

[Table 3]

From Table 3, two aluminum alloy members 1
G, 1H itself and the cavity forming auxiliary plate 2 have a width of 1 to 6 mm centering on the welding line on the back surface side of the butt weld to be joined formed by the aluminum alloy members 1G, 1H, and The depth in the direction opposite to the back surface is 1-3 mm
By forming a cavity that satisfies the range described above and performing laser welding while supplying an inert gas as a back shield gas into the cavity, the occurrence of burn-through defects can be extremely reduced, and welding defects can be extremely reduced. It can be seen that quality welds can be obtained stably.

[Embodiment 4] FIG. 4 is a sectional view for explaining a lap welding portion and a cavity according to a laser welding method according to Embodiment 4 of the present invention. In this embodiment, as shown in FIG. 4, two members 1I, 1A, which have a concave portion having a rectangular cross section at an end and are made of an aluminum alloy and have mutually different total thicknesses.
1J are joined with their ends wrapped, so that the upper welded portion and the lower welded portion in the figure have a superimposed shape, and A cavity extending along the welding line having a sectional shape of a rectangular section having a width W around the welding line and a depth D in the direction opposite to the back surface, in contact with the back surface, and in contact with the back surface. The one in which C was formed was produced. And the width W of the cavity C
And depth D were prepared, and laser welding was performed under the welding conditions described below so that penetration would be penetration penetration, and then the welding results were investigated. The laser welding was performed with the lap weld to be joined on the upper side in the figure in a downward posture, and thereafter, the member was turned over and the lower lap weld in the figure in a downward posture. In this embodiment, extruded members are used as the members 1I and 1J each having a concave portion having a rectangular cross section at the end, and the inside of the cavity C is closed with one end in the welding line direction. The back shield gas was supplied from the other end.

The welding conditions are as follows: Test material: JIS A6
N01S, weld thickness: 2 mm, welding position: downward welding, carbon dioxide laser output: 6 kW, welding speed: 33.3
mm / s, type and flow rate of shield gas: Ar gas, 20 liters / minute, type and flow rate of back shield gas into the cavity: He, 10 liters / minute, welding length: 1000 mm. Table 4 shows the welding results.

[0026]

[Table 4]

From Table 4, two aluminum alloy members 1
When the two lap welds to be joined formed by I and 1J are laser-welded so that the penetration becomes a penetration penetration from the surface on the laser beam incident side to the opposite back surface, The two aluminum alloy members themselves form a cavity on the back side of the two welds, i.e., having a rectangular cross section between each of the welds and extending along the weld line, wherein the cross section of the cavity has a width 1 through the line
If it is 6 mm and the depth in the direction opposite to the back surface satisfies the range of 1 to 3 mm, laser burnout is performed by supplying an inert gas as a back shield gas into the cavity, thereby performing burn-through. It can be seen that the generation of defects can be extremely reduced, and a high quality weld having extremely few welding defects can be stably obtained. When the cross-sectional dimension of the cavity in the comparative example of Example 4 exceeds the dimension range according to the present invention, the occurrence of burn-through defects can be extremely reduced by using the cavity forming auxiliary plate described above. It is possible.

[Embodiment 5] FIG. 5 is a sectional view for explaining a butt-welded portion and a cavity according to a laser welding method according to Embodiment 5 of the present invention. In this embodiment, as shown in FIG. 5, the ends of two members 1K and 1L forming a flat plate made of an aluminum alloy are butted to each other to form an I-shaped butt joint to be joined, and furthermore, the joining is performed. A grooved backing plate 3 made of aluminum alloy is fixed to the back surface side of the welded portion to be welded, so that the back surface side of the welded portion is in contact with the back surface and has a rectangular cross section. And a cavity C having a width W around the welding line, a depth D in the direction opposite to the back surface, and a cross section D extending along the welding line was produced. And the plate thickness of the members 1K and 1L,
A plurality of the cavities C having different widths W and different depths D are prepared, and laser welding is performed under the welding conditions described below so that the penetration becomes a penetration penetration. investigated. In this embodiment, the back shield gas is supplied into the cavity C from the other end while the one end in the welding line direction is closed.
The grooved backing plate 3 having a concave groove for forming a cavity may be made of copper or steel.

The welding conditions are as follows: Test material: JIS A5
052P, welding position: downward welding, carbon dioxide gas laser output: 3 to 12 kW, welding speed: 83.3 mm / s, type of shielding gas and its flow rate: Ar gas, 20 liters per minute, type of back shielding gas into the cavity And its flow rate: He, 10 liters per minute, welding length: 500 mm. Table 5 shows the welding results.

[0030]

[Table 5]

As shown in Table 5, the aluminum alloy members 1K, 1
A welding line having a rectangular cross-section in contact with the back surface using a cavity-forming grooved backing plate 3 having a concave groove on the back surface side of the I-shaped butt weld to be joined constituted by L If the cross section dimension of the cavity is 1 to 6 mm around the welding line and the depth in the direction opposite to the back surface satisfies the range of 1 to 3 mm, By performing laser welding while supplying an inert gas as a back shield gas into the cavity, the occurrence of porosity defects and burn-through defects can be extremely reduced, and high quality welds with extremely few welding defects can be stabilized. It can be seen that it can be obtained.

Embodiment 6 In this embodiment, in the embodiment shown in FIG. 5, the back shield gas to be supplied into the cavity (groove of the backing plate 3) is a mixture of helium and argon. Laser welding was performed while changing the values, and the welding results were investigated.

The welding conditions are as follows: Test material: JIS A5
052P, thickness: 3 mm, welding posture: downward welding, carbon dioxide laser output: 5 kW, welding speed: 40 mm / s, type of shielding gas and its flow rate: Ar gas, 20 liters per minute, welding length: 500 mm, cavity: width 6mm, depth 2
mm. The total flow rate of the back shield gas was 20 liters per minute. FIG. 6 shows the results.

As shown in FIG. 6, when the mixture ratio of helium in the back shield gas is 30 vol% or more, the incidence of burn-out defects is drastically reduced. This is considered to be due to the effect of cooling the molten pool by the helium gas and the fact that the formation of the keyhole is stabilized by cooling the molten pool.

[0035]

As described above, according to the laser welding method for an aluminum alloy member according to the present invention, the welded portion formed by the aluminum alloy members is welded from the surface on the laser beam incident side. At the time of laser welding so as to achieve penetration penetration reaching the opposite back surface, a cavity extending along the welding line having a predetermined cross-sectional dimension, in contact with the back surface, on the back surface side of the welded portion to be joined. Is formed, and laser welding is performed while supplying an inert gas as a back shield gas into the cavity.Therefore, the occurrence of porosity defects and burnout defects can be extremely reduced, and welding defects can be reduced. Very few high quality welds can be stably obtained. This enables deep penetration welding with low heat input, and contributes to the expansion of the application of laser welding to aluminum alloy members, which has the advantage that thermal effects and thermal deformation on members to be joined are extremely small. Can be.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a butt weld and a cavity according to a laser welding method according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a butt weld and a cavity according to a laser welding method according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a butt weld and a cavity according to a laser welding method according to a third embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a lap weld and a cavity according to a laser welding method according to a fourth embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a butt weld and a cavity according to a laser welding method according to a fifth embodiment of the present invention.

FIG. 6 is a diagram according to a sixth embodiment of the present invention, showing a relationship between a mixing ratio of a helium gas and an argon gas and a burn-out occurrence ratio.

FIG. 7 is a cross-sectional view for explaining a comparative example according to the first embodiment of the present invention.

[Explanation of symbols]

1A to 1L: Aluminum alloy member 2: Cavity forming auxiliary plate 3: Cavity forming grooved backing plate C: Cavity W:
Cavity width D ... Cavity depth

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-5-161989 (JP, A) JP-A-5-208285 (JP, A) JP-A-60-33882 (JP, A) JP-A-53-1983 2365 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 26/00 B23K 26/12 B23K 9/035 B23K 103: 10

Claims (2)

(57) [Claims] 1. A laser welding method for welding a welded portion formed of aluminum alloy members so that the penetration is a penetration penetration from a surface on a laser beam incident side to a rear surface on the opposite side. The width of the welded portion to be welded is in contact with the back surface and the width thereof is 1 around the weld line.
Forming a cavity extending along the weld line with a cross-sectional dimension of 1 to 6 mm and a depth of 1 to 3 mm in the direction opposite to the back surface, and supplying an inert gas as a back shield gas into the cavity to form a laser. A laser welding method for an aluminum alloy member, characterized by performing welding. 2. The laser welding method for an aluminum alloy member according to claim 1, wherein the inert gas is helium gas alone or a mixed gas of helium gas and argon gas containing helium gas at a mixing ratio of 30 vol% or more.