JP2002331373A - Welding method for aluminum - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding method for alumina capable of conducting stable welding even in the case that the surface of an aluminum alloy, etc., is covered with an alumina oxide film. SOLUTION: In carrying out the welding work by moving a welding torch provided with an insulating material 6 positioned at the fore side of a welding wire 5 toward the welding direction, and mounted so as to approach but not to come into contact with a welding object 2, while emitting a CO2 laser beam on the position P at the fore side of the insulating material 6 toward the welding direction, and parting from the welding position N of the welding object 2 by a fixed distance, the oxide film of the welding object 2 is removed, and the arc welding is applied to the welding position N of the welding object.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy for improving the welding quality of an object to be welded by preventing arc breakage, poor welding, etc. which occur when welding aluminum by consumable electrode AC pulse arc welding. Related to welding method.

[0002]

2. Description of the Related Art The method of welding aluminum and its alloys (hereinafter referred to as aluminum alloys, etc.) is in principle the same as that of steel, but there are great differences in the properties as metals, so the welding conditions are different. It is a metal that cannot be easily welded. The reason that aluminum alloys and the like cannot be easily welded is as follows. (A) Aluminum alloy and the like have a high affinity for oxygen, and an oxide film is formed on the surface in the atmosphere. (B) Since the melting temperature of aluminum oxide of the oxide film on this surface is higher than that of aluminum inside, the inside has fluidity first and the oxide film is involved. (C) Since the specific gravity of the aluminum alloy or the like is small, the floating of the oxide is poor and the oxide is easily caught in the welded portion. (D) It is easy to melt off because the melting temperature is low. (E) Thermal conductivity of iron is about 4
Because it is twice as hot, heat is easily dissipated and local heating is difficult.

The above problems have been solved by the practical use of a gas arc welding method using an inert gas such as argon or helium. FIG. 2 is a schematic front end of a welding torch 1a illustrating a welding method using a conventional welding torch 1a of an AC pulse arc welding machine, which is one of the gas arc welding methods using an inert gas. As shown in FIG. 2, the welding method of the AC pulse arc welding is such that a welding wire 5 is fed from a tip 4 of a welding torch 1a by a wire feeding mechanism (not shown) at a previously set feeding speed, and also shown in the drawing. Welding wire 5 and workpiece 2 by the omitted welding power source
Is a welding method in which an arc 3 is generated between the two to perform welding.

[0004] The AC arc welding method, which is a basic technique of the AC pulse arc welding method described above, employs a method in which a welding wire has a positive polarity and a work to be welded has a negative polarity, and a cathode spot is formed on the work to be formed. Since the work function of aluminum oxide is smaller than that of aluminum, a cathode spot is easily formed on the oxide film, and the oxide film of the cathode spot heated to high temperature is destroyed. This destruction action is called a cleaning action and is indispensable for aluminum welding.

In AC pulse arc welding, a welding wire is fed at a predetermined feeding speed, and an electrode having a positive polarity (hereinafter, referred to as an electrode) in which the welding wire serves as an anode and the workpiece serves as a cathode.
This is a welding method in which an arc generation period of EP polarity) and an arc generation period of electrode minus polarity (hereinafter referred to as EN polarity) in which a welding wire becomes a cathode and an object to be welded becomes an anode are alternately repeated. Therefore, the welding current is conducted from the welding wire toward the work during the EP polarity period,
During the EN polarity period, power is supplied from the workpiece to the welding wire.

[0006] AC pulse arc welding is used for welding aluminum alloys and the like, and is often used particularly when the thickness of the workpiece is several [mm] or less.
The reason why AC pulse arc welding is frequently used for welding thin sheets is as follows. That is, in AC pulse arc welding, the workpiece becomes a cathode during the EP polarity period, and the heat input to the workpiece increases due to the cathode drop voltage. On the other hand, during the EN polarity period, the workpiece becomes an anode and heat is input to the workpiece by the anode drop voltage. However, since the anode drop voltage value is smaller than the above-described cathode drop voltage value, the anode workpiece drops. Heat input becomes smaller. Therefore, in AC pulse arc welding, the magnitude of the heat input to the workpiece can be arbitrarily adjusted by controlling the time ratio between the EP polarity period and the EN polarity period. In the welding of thin plates, if the heat input to the workpiece is too large, burn-through will occur,
Conversely, if the heat input is too small, poor penetration will occur, and in both cases welding defects will result. Therefore, as described above, AC pulse arc welding capable of controlling the heat input to the workpiece is suitable for welding thin plates.

However, in the welding method of aluminum alloy or the like by the AC pulse arc welding shown in FIG. 2, arc breakage frequently occurs at the time of electrode polarity switching and after the polarity switching.
As a method of preventing the arc break, there is a method of irradiating a diode laser (Diode laser) light to the fusion site N during welding work of AC pulse arc welding.
As a laser light source, other laser light sources such as a YAG laser light may be used in addition to the diode laser light. However, the absorptivity of the beam on the surface of an aluminum alloy or the like is determined by the diode having a wavelength of 808 [nm]. The laser light is much higher than the YAG laser light having a wavelength of 1064 [nm], and the diode laser light is two times the YAG laser light.
Absorption rate more than double. Therefore, the use of diode laser light can be used with lower power than the use of other laser light sources, for example, YAG laser light. FIG. 3 is a schematic front end view of a welding torch 1a in which a welding portion N is irradiated with a diode laser beam when welding is performed by a conventional welding torch 1a in the AC pulse arc welding machine shown in FIG. Hereinafter, a welding method combining an AC pulse arc welding machine and a diode laser beam will be described with reference to FIG.

In the same figure, during the EP polarity period, the welding current flows from the welding wire 5 toward the workpiece 2 and EN
During the polarity period, current flows from the workpiece 2 toward the welding wire 5. At this time, the arc 3 is applied to the welding portion N of the workpiece 2.
Formed on top and welded. As described above, welding is performed without any problem during the EP polarity period or the EN polarity period. However, arc breakage may occur during and after the polarity switching of the electrodes. When such an arc break occurs, as shown in FIG. 3, the arc break is prevented by a welding method of irradiating a diode laser beam oscillated from an oscillation source (not shown) onto a welding portion N of the workpiece 2. I do.

In FIG. 1, when a diode laser beam is irradiated on the welding portion N, aluminum on the welding portion N of the workpiece 2 evaporates. The state in which the aluminum is evaporated is a state in which electricity flows very easily, and the arc is easily converged. Therefore, the welding portion N of the workpiece 2 is
By irradiating the diode laser light on the upper side, it is possible to prevent an arc break occurring at the time of switching the polarity of the electrode and after the polarity switching.

[0010]

As described above, aluminum alloys and the like are metals which cannot be easily welded. However, they are generated when aluminum is welded by irradiating a diode laser beam to a molten portion of AC pulse arc welding. It is possible to prevent arc breaks, poor welding, and the like, thereby improving the welding quality of the workpiece.

However, welding conditions for aluminum alloy and the like differ depending on the material of the aluminum alloy and the like, the state of the oxide film on the surface, the type of shielding gas, the shielding state, and the like. In particular, aluminum alloys and the like are very easily oxidized, react with oxygen in the air even at room temperature, and their surfaces are covered with hard and thin glassy aluminum oxide. Hereinafter, this aluminum oxide film is referred to as alumina (Al ₂ O ₃ ). When a surface treatment for coloring the surface of an aluminum alloy or the like is performed, an alumina layer is intentionally formed on the surface to color the alumina. When welding an aluminum alloy or the like covered with a layer of alumina as described above, the arc generated between the aluminum alloy or the like and the welding wire is hindered by the alumina. It is very difficult to set the condition of the welding power source omitting the above. Therefore, when the surface of the aluminum alloy or the like is covered with the oxide film of alumina as described above, it has been extremely difficult to perform stable welding. Therefore, the present invention provides a method for welding aluminum capable of performing stable welding even when the surface of an aluminum alloy or the like is covered with the alumina oxide film as described above.

[0012]

A method for welding aluminum according to the present invention comprises a welding torch and a welding wire 5 fed from a welding torch tip 4, and a workpiece 2 and a welding wire 5 are provided.
Between the welding torch 1 and the welding torch 1 in the welding direction.

The invention of claim 1 at the time of filing is shown in FIG.
As shown in the figure, the welding torch 1 provided with the insulator 6 attached in front of the welding wire 5 in the welding direction so as not to be in close contact with the workpiece 2 is moved in the welding direction. When performing a welding operation, a position P which is located in front of the insulator 6 in the welding direction and a predetermined distance L from the welding portion N of the object 2 to be welded is irradiated with a CO ₂ laser beam while being irradiated. This is a method of welding aluminum by removing an oxide film of the article 2 and performing arc welding on the welding portion N of the workpiece 2 from which the oxide film has been removed.

The invention of claim 2 at the time of filing is shown in FIG.
As shown in the figure, the welding torch 1 provided with the insulator 6 attached in front of the welding wire 5 in the welding direction so as not to be in close contact with the workpiece 2 is moved in the welding direction. When performing a welding operation, a position P which is located in front of the insulator 6 in the welding direction and a predetermined distance L from the welding portion N of the object 2 to be welded is irradiated with a CO ₂ laser beam while being irradiated. This is an aluminum welding method in which arc welding and diode laser light are hybridized to a welding portion N of the workpiece 2 from which the oxide film has been removed and the oxide film has been removed.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram that best illustrates the features of the invention according to the present application. FIG. 1 is the same as FIG. 4 described later, and the description will be given later with reference to FIG. FIG. 4 is a schematic front end of a welding torch 1 for explaining a method of welding aluminum according to a first embodiment of the present invention. FIG. 5 is a schematic side view of the welding torch 1 viewed from the arrow V in FIG. 4, and FIG.
FIG. 6 is a schematic sectional view taken along line VI-VI of FIG. 4. Hereinafter, a method for welding aluminum according to the first embodiment of the present invention will be described with reference to FIGS.

In FIGS. 4 to 6, the welding wire 5 is fed from the tip 4 of the welding torch 1 by a wire feeding mechanism (not shown) at a preset feeding speed, as in the description of FIG. 2 described above. At the same time, welding is performed by generating an arc 3 between the welding wire 5 and the workpiece 2 by a welding power source (not shown). As shown in FIGS. 4 to 6, the welding torch 1 of the present invention is attached to the welding torch 1 in front of the tip 4 of the welding torch in the welding direction so that the welding torch 1 does not come into close contact with the workpiece 2. The insulator 6 is provided. The insulator 6 is a material made of a heat-resistant substance, such as ceramics or copper, and is attached to a position where the arc 3 generated between the welding wire 5 and the workpiece 2 is not normally touched. I have.

When welding is performed using the welding torch 1 having the above configuration, an arc generated between the welding wire 5 and the workpiece 2 in front of the welding portion N in the welding direction. A position P which is not affected by 3 and does not irradiate the insulator 6 is irradiated with a CO ₂ laser beam.
At this time, the distance L between the welding portion N and the irradiation position P of the CO ₂ laser beam is a distance that is not affected by the arc 3 and does not irradiate the insulator 6 as described above, and is usually covered. The optimum value is appropriately set according to welding conditions such as the thickness of the workpiece 2 and the set value of the welding power source.

When the CO ₂ laser beam is irradiated close to the arc 3, the CO ₂ laser beam is absorbed by the arc 3. However, the CO ₂ laser beam is provided between the welding portion N and the irradiation position P of the CO ₂ laser beam. By setting the distance L to the optimum value as described above, welding can be performed without the CO ₂ laser beam being absorbed by the arc 3. In the first embodiment of the present invention and a second embodiment described later, the distance L is set to a value smaller than 10 [mm] and larger than 0 [mm].

The CO ₂ laser can emit a large output power at a lower cost than other lasers. Among them, the CO ₂ laser used in the present invention is a high peak power T laser.
EA (Transversely Excited A
A tmospheric pressure laser is used. (TEA laser is a kind of a CO ₂ laser is simply means that TEA laser is a kind of a CO ₂ laser, even if that TEA laser. Hereinafter, TEA
It is called a laser. Although a commonly used CO ₂ laser can emit an output of a level of 10 kW, a TEA laser can obtain an output of 1 GW even if the peak power is relatively small. Therefore, when a TEA laser is used at the time of welding an aluminum alloy or the like, the alumina covering the surface of the aluminum alloy or the like can be instantaneously removed.
In addition, the TEA laser light is subjected to steady-state pulse control by a TEA laser power supply device (not shown), and is irradiated with the laser light in conjunction with a power supply device (not shown) of the welding torch 1.

As described above, TEA laser light is applied to the position P in front of the welding portion N in the welding direction. Although the surface at the position P irradiated with the TEA laser light is covered with the alumina layer, the irradiation with the TEA laser light removes the alumina layer covered with the surface. That is, while the welding torch 1 is moving in the welding direction, the position P in front of the welding portion N is irradiated with the TEA laser beam as described above, and after a predetermined time T has elapsed, the alumina layer is removed. When the welding portion N reaches the position P, the alumina layer adhering to the surface of the workpiece 2 has been removed. Therefore, welding can be performed by the arc 3 generated between the welding wire 5 and the workpiece 2 without being hindered by the layer of alumina.

Here, the time T set after the TEA laser beam is irradiated to the position P in front of the welding portion N is TEA laser light.
The surface to be a welding portion N of an aluminum alloy or the like from which the alumina layer has been removed by the laser light is oxidized again without forming an oxide film on the surface, and until the arc is generated in the welding portion N by the welding torch 1. Time
The time suitable for the welding conditions such as the thickness of the workpiece 2 and the set value of the welding power source is set in advance.

FIG. 7 shows the welding portion N of the welding torch 1 described in the welding method of FIGS.
FIG. 9 is a schematic diagram for explaining a second embodiment of the present invention in which a diode laser beam is irradiated similarly to FIG. Hereinafter, a second embodiment of the present invention will be described with reference to FIG. In this figure, a TEA laser beam is applied to the front of the welded portion as in the first embodiment shown in FIGS. When the welding portion N reaches the position P to which the laser beam has been irradiated, the alumina layer adhering to the surface of the workpiece 2 has been removed. At this time, in the first embodiment, as described with reference to FIG. 2 described above, arc breakage frequently occurs at the time of electrode switching and after polarity switching. Therefore, as shown in FIG. 7, the welding portion N from which the alumina layer has been removed by the TEA laser beam is irradiated with the arc welding and the diode laser beam in a hybrid manner, thereby achieving a more stable welding than in the first embodiment. It can be carried out.

When welding is performed according to the above-described second embodiment, when the welding operation is started, the TEA laser beam pulse-controlled in a steady state is applied to the front position P of the welding portion N.
Irradiated. Thereafter, after a predetermined time T has elapsed, the welding torch moves in the welding direction and the position P where the alumina layer has been removed by the TEA laser beam becomes the welding portion N and the welding supplied from the tip 4 of the welding torch 1. Wire 5
An arc 3 is generated between the workpiece 2 and the workpiece 2. At this time,
By irradiating the welding portion N with the arc 3 and the diode laser beam in a hybrid manner, it is possible to further prevent arc breakage that frequently occurs at the time of electrode switching and after the polarity switching.

[0024]

The first aspect of the aluminum welding method of the present invention.
In this embodiment, a layer of alumina such as an aluminum alloy covered on the surface is removed by irradiating a CO ₂ laser beam to a position P in front of a welding portion N in a welding direction. Therefore, welding can be performed without the arc 3 generated between the welding wire 5 and the workpiece 2 being hindered by the alumina layer, and good welding quality of the workpiece can always be ensured.

A second embodiment of the method for welding aluminum according to the present invention employs a method in which arc welding and a diode laser beam are hybridized and applied to a welding site N from which an alumina layer has been removed by a CO ₂ laser beam. The same effect as that obtained in the first embodiment can be obtained.
Further, by irradiating the arc welding and the diode laser light in a hybrid manner, it is possible to prevent the arc breaking frequently occurring at the time of electrode switching and polarity switching occurring in the first embodiment, thereby further stabilizing. Welding can be performed.

Further, by using a high peak power TEA laser for the CO ₂ laser of the first and second embodiments of the present invention, an output of 1 GW can be obtained even if the peak power is relatively small. Since the alumina covering the surface of the aluminum alloy or the like can be instantaneously removed, efficient aluminum welding can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram that best represents the features of the invention according to the present application.

FIG. 2 is a schematic front end view of a welding torch 1a for explaining a conventional welding method.

FIG. 3 is a schematic view of the tip of a welding torch when a laser beam is applied to a fusion site when welding is performed with a conventional welding torch.

FIG. 4 is a schematic front end of a welding torch 1 illustrating a method for welding aluminum according to a first embodiment of the present invention.

FIG. 5 is a schematic side view of the welding torch 1 viewed from the arrow V in FIG. 4;

FIG. 6 is a schematic sectional view taken along the line VI-VI of FIG. 4;

FIG. 7 is a schematic diagram for explaining a second embodiment of the present invention.

[Explanation of symbols]

 1, 1a Welding wire 2 Workpiece 3 Arc 4 Welding torch tip 5 Welding wire 6 Insulator

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B23K 9/23 B23K 9 / 23F // B23K 103: 10 103: 10

Claims (2)

[Claims] 1. A welding torch comprising: a welding torch; and a welding wire fed from a tip of the welding torch, wherein an arc is generated between an object to be welded and the welding wire to move the welding torch in a welding direction. In the method of welding aluminum, a welding torch provided with an insulator mounted in front of the welding wire in the welding direction and so as not to be in close contact with the workpiece is moved in the welding direction. when performing the welding operation Te, the a front side of the insulator toward the welding direction, wherein the welded while irradiating CO ₂ laser beam to a position apart a predetermined distance from the welding site of the weldment A method for welding aluminum, comprising removing an oxide film on an object and performing arc welding on a welded portion of the workpiece from which the oxide film has been removed. 2. A welding torch comprising: a welding torch; and a welding wire fed from a tip of the welding torch. An arc is generated between the workpiece and the welding wire to move the welding torch in a welding direction. In the method of welding aluminum, a welding torch provided with an insulator mounted in front of the welding wire in the welding direction and so as not to be in close contact with the workpiece is moved in the welding direction. when performing the welding operation Te, the a front side of the insulator toward the welding direction, wherein the welded while irradiating CO ₂ laser beam to a position apart a predetermined distance from the welding site of the weldment A method for welding aluminum by removing an oxide film of an object and performing welding by hybridizing arc welding and diode laser light on a welded portion of the workpiece from which the oxide film has been removed.