JP3088782B2 - TIG arc welding method for aluminum alloy - 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 periodically switching the polarity of a voltage supplied between a non-consumable electrode and a workpiece.
The present invention relates to a TIG arc welding method in which a non-consumable electrode is shielded with an inert gas, and a filler wire is added and welded.

[0002]

2. Description of the Related Art Conventionally, aluminum alloy joints used as structural materials for aircraft are required to have a particularly high quality. Therefore, welding is performed by a TIG arc welding method capable of obtaining stable quality. When horizontal fillet welding is performed by a normal TIG pulse arc welding method, the penetration ratio P / W between the penetration depth P and the weld bead width W is 1 or less as shown in FIG. Recently, even if the plate thickness is increased or horizontal fillet welding is performed, as shown in FIG.
A penetration depth P / W, which is a narrow weld bead width of 6 mm or less and has a depth equal to or greater than the weld bead width, that is, the ratio of the penetration depth P to the weld bead width W.
It is required to reduce the weight by reducing the excess as well as to perform high-strength welding by setting at least one.

[0003] As a welding method corresponding to the above requirements,
Conventionally, the following TIG arc welding method or plasma arc welding method has been adopted. The first method focuses on the fact that a TIG arc welding method of DC positive polarity can obtain deep penetration (however, there is no cleaning action for removing an oxide film of an aluminum alloy by an arc). A method of mechanically or chemically removing an aluminum oxide film and conducting TIG arc welding by applying a positive DC current having a non-consumable electrode with a negative polarity is applied. In the first method, although a certain degree of deep penetration can be obtained, since there is no cleaning action by an arc, an extra step of removing an oxide film before the occurrence of a welding arc is required. Even after a lapse of time, however, the regenerated oxide film often gets caught in the weld metal and causes welding defects.

In a second method, a non-consumable electrode is supplied with a low-frequency AC pulse current of a rectangular wave to supply a positive polarity period in which the polarity of the non-consumable electrode is negative and a reverse polarity period in which the polarity is positive. By applying an AC pulse current in which the time ratio or the energizing current value ratio in each period or both are adjusted, T
An IG arc welding method is employed. In the second method, for example, as shown in FIG.
In [mm], horizontal fillet welding is performed and the above penetration depth P
In order to obtain deep penetration, a welding current of 300 [A] or more is required, and in order to reduce the current value as much as possible, preheating is also required. Aircraft structures are often welded with variously complex inner and outer surfaces, curves, curved surfaces, etc.,
Hand welding is often used. If a current as high as 300 [A] is used during the manual welding as in the case of the welding in FIG. 1 described above, the operator's body is burdened by the radiant heat of the arc, and the work is performed only for a short time. Cannot continue. Further, when such a high current is applied, the amount of melting of the filler wire increases, the amount of welding increases, and the weight of the structure cannot be reduced. Further, the third method employs an AC plasma arc welding method. However, in this method, if the above-mentioned deep penetration is to be obtained, a large current is required. Zurk is likely to occur, and electrodes and nozzles may be burned.
Appropriate welding can be performed only up to the middle thickness plate of [mm] or less.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a TIG arc welding method capable of efficiently joining an aluminum alloy with the most stable quality, to secure a proper cleaning width and to reduce a welding bead width. To reduce the excess volume, increase the penetration depth to secure the bonding strength, reduce the consumption of non-consumable electrodes (hereinafter referred to as electrodes), keep the welding result constant, and reduce the low current. It is intended to reduce the burden on the operator by using it and to stabilize the quality by continuously welding a long welding length without interruption.

[0020]

SUMMARY OF THE INVENTION The present invention is a welding method provided with the following means. This is a TIG arc welding method in which the polarity of a voltage supplied between an electrode and a workpiece is periodically switched to add a filler wire and weld an aluminum alloy. The positive polarity ratio SP / of the positive polarity current of the peak value Is at the energizing time Ts when the electrode is negative and the reverse polarity current of the peak value Ir at the energizing time Tr when the electrode is positive.
(SP + RP) = Is · Ts / (Is · Ts + Ir · T
A non-equilibrium rectangular wave alternating current in which r) is more than 0.6 and less than 0.9 is applied. After the non-equilibrium rectangular wave AC current is supplied for the conduction period Ta, the positive DC current is supplied for the conduction period Td, and the unbalanced rectangular wave AC current and the positive DC current are supplied with the conduction ratio Ta / Td = 2/3. And switching frequency F = 0.4
Switching is performed at a low frequency from 1 Hz to 1 Hz . The electrodes are shielded with a mixed gas of argon gas and helium gas at substantially the same flow rate ratio. The filler wire is added during the period of non-equilibrium square wave alternating current. The penetration ratio P / W between the penetration depth P and the weld bead width W is 1
A welding current for obtaining the above weld metal is applied.

[0030]

The operation of the present invention will be described below. (Description of Table 1)

[Table 1] B. when TIG arc welding of an aluminum alloy was welded with an AC square wave current. Welding current when the electrode is negative (positive current)
Peak value Is C. Energization time when the electrode is negative Ts D. The peak value of the welding current (reverse polarity current) when the electrode is positive IrE. It describes the effect of the four parameters of the energization time Tr when the electrode is positive on the width of the cleaning width, the width of the welding bead, the width of the welding bead, the penetration depth, and the shallowness of the electrode.

From Table 1, as the peak value Is of the welding current when the electrode is negative and the conduction time Ts are longer,
Although the penetration depth is large and the consumption of the electrode can be reduced, it is necessary to supply a reverse polarity current when the electrode is positive in order to obtain an appropriate or minimum required cleaning width. The peak value Ir of the reverse polarity current and the conduction time Tr
When the value is large, the consumption of the electrode becomes large. Therefore, a low value that can obtain a proper or necessary minimum cleaning width and a welding bead width is selected.

(Explanation of FIG. 3) FIG. 3 is a diagram showing a waveform of a welding current applied in the welding method of the present invention. In the same figure, the positive polarity ratio SP / (SP + RP) of the positive polarity current of the peak value Is at the conduction time Ts when the electrode is negative and the reverse polarity current of the peak value Ir at the conduction time Tr when the electrode is positive. Is · Ts / (Is · Ts + Ir · Tr) (1) A non-equilibrium rectangular wave AC current exceeding 0.5 is applied to the conduction period Ta.
After the energization, a positive DC current is applied for an energization period Td.

(Description of FIG. 4) FIG. 4 shows the positive polarity ratio SP / (SP + R) in the above equation (1 ).
It is a figure which shows the relationship between (horizontal axis) and the penetration ratio P / W (vertical axis). In FIG. 5, the penetration ratio P / W is shown in FIG.
As shown in, on a flat plate of aluminum alloy material A5083 having a thickness of 10 [mm], at a welding speed 20 [cm / min] in the average value 250 of the full-wave rectification of the welding current [A], the positive polarity ratio
FIG. 6 shows the relationship between the penetration depth P and the weld bead width W shown in FIG. 5 when TIG arc welding is performed using argon gas as a shielding gas while changing SP / (SP + RP) . As shown in the figure, the positive polarity ratio SP / (SP + R)
Exceeds 0.6, the penetration ratio P / W becomes large. However, in the TIG arc welding of an aluminum alloy, when the positive polarity ratio SP / (SP + RP) is 0.9 or more, it becomes difficult to secure a cleaning width for obtaining the welding bead width W, and an oxide film is formed on the welding bead. Is formed, the positive polarity ratio SP / (SP + R
P) is suitably in the range of more than 0.6 and less than 0.9.

(Explanation of FIG. 6) In FIG. 4 described above, as long as argon gas is used as the shielding gas, the positive polarity ratio SP / (SP + RP) becomes
The welding method of the present invention cannot exceed the target value of 1. Therefore, it is necessary to use a shielding gas in which helium gas having a high potential gradient is mixed with argon gas. FIG.
FIG. 3 is a diagram showing a change in penetration ratio P / W (horizontal axis) when TIG arc welding is performed while changing a flow rate mixing ratio [%] (horizontal axis) of argon gas and helium gas.
In the same figure, the penetration ratio P / W is the same as that of FIG. 5 described above, and the positive polarity ratio SP / (SP + R
Instead of fixing P) to 0.7, the mixing ratio of argon gas and helium gas is changed. As shown in the figure, when the mixing ratio of the helium gas becomes 45% or more, the penetration ratio P / W can be made 1 or more.

(Description of FIGS. 7 and 8) However, when the mixing ratio of helium gas becomes 60% or more, FIG.
As shown in FIG. 7, oxides (MgO, SiO, Al2 O3) of black aluminum alloy elements adhere to the surface of the weld bead, and as shown in FIG. 7B, these oxides are contained in the weld metal. Or get caught. Therefore, the mixing ratio of the flow rates of the argon gas and the helium gas is 45 to 55 [%].
When a mixed gas having approximately the same flow rate ratio is used, no black oxide is generated on the surface of the weld bead as shown in FIG. 8 (A), and as shown in FIG. Oxide is not entrained in the material. As shown in FIG. 8A, the cleaning width Y is slightly larger than the welding bead width W.
Has been obtained.

As described above, the positive polarity ratio is determined using a mixed gas of argon gas and helium gas at substantially the same flow ratio.
Even when a non-equilibrium rectangular wave AC current of SP / (SP + RP) = 0.7 is applied, the current application period Td of the positive DC current of the welding current shown in FIG. 3 used in the TIG arc welding method of the present invention.
Exceeds a predetermined ratio as compared with the energizing period Ta of the non-equilibrium rectangular wave AC current, there is no longer any area that has been cleaned during the energizing period Td. Therefore, if the conduction ratio Ta / Td between Ta and Td is set to 2/3,
The cleaning action remains even during the positive direct current energizing period Td. In addition, it is necessary to add the filler wire during the AC current supply period Ta in order to perform the cleaning action of the filler wire to be added. Further, in order to secure time for adding the filler wire, It is necessary to switch at a low frequency of 1 [Hz] or less, which is the switching frequency between the current supply period Ta and the positive polarity DC current supply period Td. Also, the AC energization period Ta
No matter how long the cleaning region obtained during the period of the positive polarity DC conduction period Td remains, the cleaning region is 1.5 times or less.
When the positive direct current conduction period Td is longer than 2 seconds, an oxide film is involved, and a sound weld cannot be obtained. Therefore, 1 / (1 + 1.5) = 0.4 Hz or more (If Td = 1.5 seconds, Ta / Td = 2/3 and Ta = 1
Second) switching frequency.

[0040]

【Example】

(Description of FIG. 9) FIGS. 9A and 9B are views showing the appearance and cross section of a weld bead when horizontal fillet welding is performed by the TIG arc welding method of the present invention. . The welding conditions of the embodiment of the present invention are as follows. Aluminum / magnesium alloy A508 with a plate thickness of 20 [mm]
3 is a welding current (Is = 170 [A]) having a waveform shown in FIG.
Ts = 10 [ms], Ir = 500 [A], Tr = 1 [m]
s], Ta / Td = ２, switching frequency F = 1 [H
z], an average value of 200 [A]), and horizontal fillet welding is performed at a welding speed of 15 [cm / min] using a mixed gas of argon gas and helium gas at substantially the same mixing ratio. When TIG arc welding is performed under these welding conditions, the current value is lower than the average value of the welding current of the ordinary TIG pulse arc welding method aimed at by the present invention, as shown in FIGS. 9A and 9B. Thus, a molten bridge portion 3 between the web 1 and the flange 2 having a penetration ratio P / W = 1.1 can be obtained.

The normal TIG pulse pulse shown in FIG.
When horizontal fillet welding is performed by the welding method, the weld bead width W is wide and the penetration depth P is shallow, and the penetration ratio P / W is small.
= 0.5 only. This normal TIG pulse alarm
The welding conditions were a square wave alternating current with a positive polarity ratio of 0.7,
The average value of the full-wave rectification of the welding current is 300 [A], argon gas is used, and the welding speed is 10 [cm / min].

(Explanation of FIG. 10) FIGS. 10A to 10C show an arc 5 generated between the electrode 4 and the workpiece consisting of the web 1 and the flange 2 by the TIG arc welding method of the present invention. Let the electrode tip 4
distance Lt when the distance Lt between a and the workpiece is changed
FIG. 9 is an explanatory diagram for determining an appropriate value of. Distance Lt is 3 [m
m], as shown in FIG. 3A, a one-sided melted portion 1a is formed in the web 1, and when the distance Lt becomes less than 1 [mm], the electrode is caused by camera shake as shown in FIG. Since the tip 4a and the workpiece 2 may come into contact with each other,
As shown in (C) , the distance Lt needs to be 1 to 2 [mm].

(Description of FIG. 11) FIG. 11 shows changes in the average value I [A] (horizontal axis) of the full-wave rectification of the welding current and the thickness t [mm] (vertical axis) of the flat plate shown in FIG. It is a figure which shows the penetration ratio P / W at the time of performing TIG arc welding without adding a filler wire. The dotted line ZZ shown in the figure shows P / W when welding is performed by the ordinary TIG pulse arc welding method, and the solid line AA shows P / W when welding is performed by the TIG arc welding method of the present invention.
/ W. The welding conditions of the normal TIG pulse arc welding method indicated by the dotted line ZZ are as follows: the positive polarity ratio SP / (SP + RP) =
A non-equilibrium square wave alternating current of 0.7 , argon gas is used, and the welding speed is 20 [cm / min]. Also, the solid line AA
According to the present invention, the welding conditions of the TIG arc welding method are positive polarity.
When the ratio SP / (SP + RP) = 0.7 , the energization ratio Ta / T
A mixed gas of argon gas and helium gas having substantially the same mixing ratio at d = is used, and the welding speed is 20 [cm / min].

In the figure, the numerical value in parentheses indicates the penetration ratio P / W, and the average value of the full-wave rectification of the welding current is 2
In the case of 00 [A], in the ordinary TIG pulse arc welding method indicated by the dotted line ZZ, it is possible to melt only up to a plate thickness of 10 [mm], and the penetration ratio is 0.7.
In contrast, the TIG arc of the present invention shown by the solid line AA
In the welding method, it can be melted to a plate thickness of 20 [mm] and the penetration ratio can be 1.3.

(Description of FIGS. 12 and 13) FIG. 12 is a block diagram of a welding apparatus for carrying out a normal TIG pulse arc welding method. In the figure, 1 and 2 are workpieces, 4 is an electrode, 10 is a DC power supply circuit obtained by rectifying a commercial AC power supply, for example, L1 is a DC reactor, C1 is a rectifying capacitor, and TR1 and TR2 are reverse polarities. The current conducting transistors, TS1 and TS2, are positive polarity current conducting transistors. PC1 is a polarity switching circuit for controlling conduction and cutoff of these transistors, and NT1 receives the polarity switching signal Pc1 as input and outputs an inverted reverse polarity energizing signal Sr. 13 (A) to 13 (C) show the waveform of the polarity switching signal Pc1 (= positive polarity energizing signal Ss), the waveform of the reverse polarity energizing signal Sr, and the work to be welded shown in FIG. 12, respectively. It is a figure showing the waveform of welding current I of the direction of an electrode. Transistors TS1 and TS2 and transistors TR1 and TR2 are generated by a positive polarity conduction signal Ss shown in FIG. 4A and a reverse polarity conduction signal Sr shown in FIG.
Are turned on and off, respectively, and a rectangular wave alternating current shown in FIG.

(Explanation of FIGS. 14 and 15) FIG. 14 is a block diagram of a welding apparatus for carrying out the TIG arc welding method of the present invention. In FIG. The description is omitted because it is the same as the description, and only the differences will be described. In FIG. 14, NT2 is a NOT circuit for inverting the polarity switching signal Pc1 shown in FIG. 15A and outputting an inverted signal Nt2 shown in FIG. 15B, and MM1 is a monomultivibrator circuit. A low-frequency signal Mm1 shown in FIG. 15 (C), which determines the energization ratio Ta / Td between the energization period Ta of the rectangular wave AC current and the energization period Td of the positive DC current by the switching frequency F [Hz]. ND
1, when the inverted signal Nt2 of the NOT circuit NT2 and the low frequency signal Mm1 are input and both signals are at the low level L,
NA for outputting positive conduction signal Ss shown in FIG.
This is an ND circuit. FIG. 15D shows the same positive conduction signal Ss as in FIG. 13A, which turns on and off the transistors TS1 and TS2, and FIG.
Similarly to (B), it is a reverse polarity current supply signal Sr, which turns on and off the transistors TR1 and TR2. By turning on and off these transistors, the square wave AC current and the positive DC current shown in FIG. Is turned on.

[0070]

According to the present invention, even if the plate thickness is increased or horizontal fillet welding is performed, the weld bead width is as small as 6 mm or less. By making the penetration equal to or greater than that, it is possible to reduce the weight by reducing the excess, and to weld a high-strength aluminum alloy, and to reduce the arc heat due to the lower welding current. Since the electrode can be used continuously for a long time because the electrode is less worn, it is possible to continuously weld a long object, and furthermore, during a predetermined AC current conduction period. Since a reliable welding result can be obtained by reliably adding the filler wire, it is indispensable for an aircraft structure, a nuclear structure and the like where safety is important.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a penetration depth P and a weld bead width W in horizontal fillet welding by a normal TIG pulse arc welding method.

FIG. 2 is a diagram showing a relationship between a penetration depth P of horizontal fillet welding and a weld bead width W required for recent aircraft structures.

FIG. 3 is a diagram showing a waveform of a welding current applied in the welding method of the present invention.

FIG. 4 shows the positive polarity when using argon gas.
Ratio SP / (SP + RP) (horizontal axis) and penetration ratio P /
It is a figure showing relation with W (vertical axis).

FIG. 5 is a diagram showing a relationship between a penetration depth P and a weld bead width W when welding is performed on a flat plate.

FIG. 6 is a diagram showing a change in a penetration ratio P / W (vertical axis) when performing TIG arc welding while changing a flow rate ratio [%] (horizontal axis) between argon gas and helium gas. It is.

FIGS. 7A and 7B show the weld bead surface when performing TIG arc welding using a mixed gas of argon gas 40% and helium gas 60%, respectively. FIG. 3 is a view showing the appearance of a weld bead and the appearance of a cross section of a weld bead.

FIGS. 8A and 8B show the weld bead surface when performing TIG arc welding using a mixed gas of argon gas 50% and helium gas 50%, respectively. FIG. 3 is a view showing the appearance of a weld bead and the appearance of a cross section of a weld bead.

FIGS. 9A and 9B are views showing the appearance and cross section of a weld bead when horizontal fillet welding is performed by the TIG arc welding method of the present invention.

FIGS. 10A to 10C show TIG of the present invention.
The distance L between the electrode tip and the work to be welded is determined by the arc welding method.
FIG. 9 is an explanatory diagram for determining an appropriate value of a distance Lt when t is changed.

FIG. 11 shows an average value I of full-wave rectification of a welding current.
It is a figure which shows the penetration ratio P / W when changing [A] (horizontal axis) and plate thickness t [mm] (vertical axis).

FIG. 12 is a block diagram of a welding apparatus for performing a normal TIG pulse arc welding method.

FIGS. 13A to 13C respectively show FIGS.
FIG. 4 is a diagram showing waveforms of output signals of respective circuits in the block diagram of FIG.

FIG. 14 is a block diagram of a welding apparatus for performing the TIG arc welding method of the present invention.

FIGS. 15A to 15F are FIGS.
FIG. 4 is a diagram showing waveforms of output signals of respective circuits in the block diagram of FIG.

[Explanation of symbols]

P: penetration depth W: weld bead width P / W: penetration ratio I: welding current (average value of full-wave rectification) Is: welding current when the electrode is negative (positive current)
Ts: energizing period when electrode is negative Ir: peak value of welding current (reverse polarity current) when electrode is positive Tr: energizing period SP / (SP + RP) when electrode is positive Positive ratio = Is · Ts / (I
s · Ts + Ir · Tr) Ta: energizing period of non-equilibrium rectangular wave AC current Td: energizing period of positive DC current Ta / Td: energizing ratio F: switching frequency Y: cleaning width t: plate thickness

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-361873 (JP, A) JP-A-63-13677 (JP, A) JP-A-3-473 (JP, A) JP-A 52-361 28442 (JP, A) JP-A-56-109172 (JP, A) JP-A-2-97966 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 9/167 B23K 9 / 09 B23K 9/23 H02M 9/00 B23K 103: 10

Claims (1)

(57) [Claims] 1. A method of periodically switching the polarity of a voltage supplied between a non-consumable electrode and a workpiece to shield the non-consumable electrode with an inert gas, adding a filler wire and welding an aluminum alloy. Time Ts when the non-consumable electrode is negative.
Ratio SP / (SP + RP) = Is of the positive polarity current of the peak value Is of the welding current and the reverse polarity current of the peak value Ir of the welding current during the energization time Tr when the non-consumable electrode is positive.
After applying a non-equilibrium rectangular wave alternating current in which Ts / (Is · Ts + Ir · Tr) is more than 0.6 and less than 0.9 for a period Ta, a positive DC current is applied for a period Td, and the non-equilibrium rectangular wave is applied. The alternating current and the positive direct current are supplied with a conduction ratio Ta /
When Td = 2/3 and switching frequency is 0.4 [Hz] or more, 1
[Hz] or less , the non-consumable electrode is shielded with a mixed gas of argon gas and helium gas at substantially the same flow rate ratio, and during the energizing period of the non-equilibrium rectangular wave alternating current. A TIG arc welding method for an aluminum alloy, in which a filler wire is added and an aluminum alloy is welded by applying a welding current to obtain a weld metal having a penetration ratio P / W of 1 or more between a penetration depth P and a weld bead width W.