JP2025000075A - Double shield tig welding method - Google Patents

Abstract

To provide a double shield tig welding method which stably maintains a weld state even if a temperature of a base material rises when the base material is composed of aluminum or its alloy.SOLUTION: In a double shield tig welding method using a welding torch containing a base material composed of aluminum or its alloy and including inner nozzles for jetting inner gas and outer nozzles for jetting outer gas, generating an arc at a time t3 after preflow of the inner gas and the outer gas is performed at the time of start of welding, applying welding current Iw and performing welding, a flow rate Fi of the inner gas is decreased with time from the time of arc generation at the time t3.SELECTED DRAWING: Figure 2

Description

The present invention relates to a double shielded TIG welding method.

A double-shielded TIG welding method is commonly used, in which welding is performed using a welding torch equipped with an inner nozzle that sprays an inner gas and an outer nozzle that sprays an outer gas (see, for example, Patent Document 1). Inert gases such as argon and helium are used as the inner and outer gases.

JP 2020-15048 A

When welding aluminum or its alloys (hereafter simply referred to as aluminum) using the conventional double-shielded TIG welding method, the weld condition becomes unstable as the temperature of the base material rises.

The present invention aims to provide a double-shielded TIG welding method that can stably maintain the welded state even if the temperature of the base metal rises when the base metal is aluminum.

In order to solve the above-mentioned problems, the invention of claim 1 comprises:
The base material is aluminum or its alloy,
A welding torch having an inner nozzle for ejecting an inner gas and an outer nozzle for ejecting an outer gas is used,
In a double shield TIG welding method, an arc is generated after preflowing the inner gas and the outer gas at the start of welding, and a welding current is applied to weld the material,
The flow rate of the inner gas is decreased over time from the occurrence of the arc.
This is a double shielded TIG welding method characterized by the above.

The invention of claim 2 is as follows:
The greater the temperature rise rate of the base material, the greater the reduction rate of the flow rate of the inner gas.
2. The double shielded TIG welding method according to claim 1 .

The invention of claim 3 is as follows:
The larger the value of the welding current, the larger the reduction rate of the flow rate of the inner gas.
2. The double shielded TIG welding method according to claim 1 .

The invention of claim 4 is as follows:
The thinner the plate thickness of the base material, the greater the reduction rate of the flow rate of the inner gas.
2. The double shielded TIG welding method according to claim 1 .

The double-shielded TIG welding method of the present invention allows the welded state to be maintained stably even if the temperature of the base material rises when the base material is aluminum.

1 is a block diagram of a welding apparatus for carrying out a double shielded TIG welding method according to an embodiment of the present invention. 2 is a timing chart of each signal in the welding apparatus of FIG. 1 , illustrating a double-shielded TIG welding method according to an embodiment of the present invention.

The following describes an embodiment of the present invention with reference to the drawings.

Figure 1 is a block diagram of a welding device for carrying out a double-shielded TIG welding method according to an embodiment of the present invention. Each block will be described below with reference to the figure.

The welding torch WT mainly comprises an electrode 1, an inner nozzle 4 surrounding it, and an outer nozzle 5 surrounding the inner nozzle 4. A tungsten electrode or the like is used for the electrode 1.

The welding start circuit ON outputs a welding start signal ON that goes to a high level when welding begins. This welding start circuit ON is a torch switch provided on the welding torch WT. The welding start circuit ON may also be provided within the robot control device.

The preflow period circuit TP receives the above-mentioned welding start signal On as input and outputs a preflow period signal Tp that remains at a high level until a predetermined preflow time has elapsed from the time the welding start signal On changes to a high level.

The inner gas ejection start circuit TI receives the preflow period signal Tp as input and outputs an inner gas ejection start signal Ti that goes to high level for a short period of time a predetermined delay time Td has elapsed since the preflow period signal Tp changed to high level. The delay time Td is shorter than the preflow period Tp.

The arc occurrence determination circuit AD is provided in the current path of the welding current Iw, and outputs an arc occurrence determination signal ad that is at a high level when the welding current Iw is flowing. When the welding current iw is flowing, an arc is generated.

The main welding inner gas flow rate setting circuit FICR receives the above-mentioned arc occurrence determination signal Ad as an input, and when the arc occurrence determination signal Ad is at a low level, it sets a predetermined initial inner gas flow rate for main welding, and when the arc occurrence determination signal Ad changes to a high level, it outputs a main welding inner gas flow rate setting signal Ficr that decreases over time from the initial inner gas flow rate for main welding to a predetermined lower limit value at a predetermined decrease rate.
1) The greater the rate of temperature rise of the base material, the greater the rate of decrease mentioned above.
2) The greater the value of the welding current Iw, the greater the decrease rate.
3) The thinner the base material is, the greater the reduction rate.

The inner gas flow rate setting circuit FIR receives the preflow period signal Tp and the main welding inner gas flow rate setting signal Ficr as inputs, and outputs an inner gas flow rate setting signal Fir that is a predetermined preflow inner gas flow rate value when the preflow period signal Tp is at a high level, and is the value of the main welding inner gas flow rate setting signal Ficr when the preflow period signal Tp is at a low level. Here, it is desirable that the preflow inner gas flow rate value be set to a value smaller than the main welding initial value inner gas flow rate value.

The inner gas flow regulator CI receives the above welding start signal On, the above inner gas ejection start signal Ti, and the above inner gas flow rate setting signal Fir as inputs, and adjusts the flow rate Fi of the inner gas 7 from the inner gas cylinder 6 to a value determined by the inner gas flow rate setting signal Fir and ejects it during the period from when the inner gas ejection start signal To changes to a high level for a short period of time until the welding start signal On changes to a low level and a predetermined after-flow time has elapsed.

The outer gas flow rate setting circuit FOR receives the preflow period signal Tp as input, and outputs an outer gas flow rate setting signal For that is a predetermined preflow outer gas flow rate value when the preflow period signal Tp is at a high level, and is a predetermined main welding outer gas flow rate value when the preflow period signal Tp is at a low level. Here, it is desirable to set the preflow outer gas flow rate value to a value greater than the main welding outer gas flow rate value.

The outer gas flow regulator CO receives the above welding start signal On, the above preflow period signal Tp, and the above outer gas flow setting signal For as inputs, and during the period from when the welding start signal On changes to a high level to when the welding start signal On changes to a low level, it adjusts the flow rate Fo of the outer gas 9 from the outer gas cylinder 8 to a value determined by the outer gas flow setting signal For and sprays it.

An inner gas 7 flows through the passage inside the inner nozzle 4. An outer gas 9 flows through the passage outside the inner nozzle 4 and inside the outer nozzle 5. Inert gases such as argon and helium are used for the inner gas 7 and outer gas 9. The arc 3 is generated with the electrode 1 serving as the negative electrode and the base material 2 serving as the positive electrode.

The welding power source PS receives the above welding start signal On and the above preflow period signal Tp as inputs, and when the welding start signal On goes to high level and the preflow period signal Tp goes to low level, it applies a high-frequency high voltage between the electrode 1 and the base material 2, and when an arc 3 is generated, it starts outputting the welding current Iw, and when the welding start signal On goes to low level, it stops outputting the welding current Iw.

Figure 2 is a timing chart of each signal in the welding device of Figure 1, which shows a double-shielded TIG welding method according to an embodiment of the present invention. Figure (A) shows the change over time of the welding start signal On, Figure (B) shows the change over time of the preflow period signal Tp, Figure (C) shows the change over time of the inner gas ejection start signal Ti, Figure (D) shows the change over time of the outer gas flow rate Fo (l/min), Figure (E) shows the change over time of the inner gas flow rate Fi (l/min), Figure (F) shows the change over time of the welding current Iw, and Figure (G) shows the change over time of the arc generation determination signal Ad. Below, the operations at the start of welding, during main welding, and at the end of welding will be explained with reference to the figures.

At time t1, when the welding operator turns on the torch switch provided on the welding torch WT in FIG. 1, the welding start signal On changes to a high level, as shown in FIG. 1 (A). In response to this, as shown in FIG. 1 (B), the preflow period signal Tp becomes a high level. At the same time, the outer gas starts to be ejected by the outer gas flow regulator CO in FIG. 1. As shown in FIG. 1 (D), the outer gas flow rate Fo becomes a predetermined preflow outer gas flow rate value determined by the outer gas flow rate setting signal For in FIG. 1.

At time t2, when a predetermined delay time Td has elapsed from time t1, the inner gas ejection start signal Ti goes to high level for a short period of time, as shown in FIG. 1B. In response to this, the ejection of the inner gas is started by the inner gas flow regulator CI in FIG. 1. As shown in FIG. 1E, the inner gas flow rate Fi becomes a predetermined pre-flow inner gas flow rate value determined by the inner gas flow rate setting signal Fir in FIG. 1.

When the preflow period signal Tp changes to a low level at time t3, the welding power source S in FIG. 1 applies a high-frequency high voltage between the electrode 1 and the base material 2 in FIG. 1 to generate the arc 3 in FIG. 1, and as shown in FIG. 1 (F), the flow of the welding current Iw begins. At time t3, when the generation of an arc is determined by the flow of the welding current Iw, the arc generation determination signal Ad changes to a high level as shown in FIG. 1 (G). At the same time, as shown in FIG. 1 (D), the outer gas flow rate Fo becomes a predetermined main welding outer gas flow rate value determined by the outer gas flow rate setting signal For in FIG. 1. Similarly, as shown in FIG. 1 (E), the inner gas flow rate Fi becomes a predetermined main welding initial inner gas flow rate value determined by the main welding inner gas flow rate setting signal Ficr in FIG. Then, welding begins at time t3.

As described above, during the preflow period, the outer gas is ejected, followed by the inner gas. In this way, the ejection of the inner gas is started while the surroundings are shielded by the ejection of the outer gas, so that the inner gas does not draw in the surrounding air, and the steady state can be quickly converged to. For this reason, in this embodiment, the preflow time can be shortened to about 50% compared to the conventional technology in which the ejection of the outer gas and the inner gas is started simultaneously. Therefore, in this embodiment, sufficient shielding can be ensured even if the preflow time at the start of welding is set short, so that the work efficiency can be improved and the consumption of expensive inert gas can be reduced. For example, in the conventional technology, the preflow period had to be set to about 6 seconds, but in this embodiment, it can be set to about 3 seconds.

Furthermore, it is desirable to set the time during which only the outer gas is ejected from time t1 to t2 to be longer than the time during which the inner gas is ejected from time t2 to t3. In this way, it is possible to more reliably prevent the inner gas from entraining air, and therefore it is possible to set the preflow time even shorter.

Furthermore, it is desirable to set the inner gas flow rate Fi smaller during the preflow period than during the actual welding period after the end of the preflow period. In this way, the inner gas ejection state can be brought to a steady state more quickly, so that the preflow time can be set even shorter.

Furthermore, it is desirable to set the outer gas flow rate Fo to be greater during the preflow period than during the actual welding period after the end of the preflow period. In this way, the inner gas ejection state can be brought to a steady state more quickly, so that the preflow time can be set even shorter.

At time t3, as shown in FIG. 1(G), when the arc generation determination signal Ad changes to a high level, the main welding inner gas flow rate setting circuit FICR in FIG. 1 causes the inner gas flow rate Fi to decrease over time from the main welding initial inner gas flow rate value at a predetermined decrease rate, and when it reaches a predetermined lower limit value at time t4, it maintains that value.

When the base material is aluminum, the temperature of the base material gradually rises as time passes from the generation of the arc. As the temperature of the base material rises, the cleaning width widens and the arc becomes wider. The larger the inner gas flow rate Fi, the greater the effect of narrowing the shape of the arc. When the temperature of the base material rises and the cleaning width widens, the shape of the arc tends to widen. On the other hand, when the inner gas flow rate Fi is large, the effect of narrowing the arc becomes greater. Then, the action of widening and the action of narrowing repel each other, causing the welding state to become unstable. Therefore, according to the present embodiment, the flow rate Fi of the inner gas is reduced over time from the time of the generation of the arc. In this way, as time passes from the generation of the arc and the temperature of the base material rises, the inner gas flow rate Fi is reduced, so the effect of narrowing the arc becomes weaker. As a result, it is possible to suppress the welding state from becoming unstable.

Furthermore, according to this embodiment, the rate of decrease in the flow rate Fi of the inner gas is increased as the temperature rise rate of the base metal increases. In this way, a good balance can be achieved between the action of expanding the shape of the arc and the action of the inner gas to narrow it, making the welding state more stable.

Furthermore, according to this embodiment, the rate of decrease in the flow rate Fi of the inner gas is increased as the value of the welding current increases. The rate of increase in temperature of the base metal increases as the value of the welding current increases. Therefore, by doing as described above, a good balance can be achieved between the action of expanding the shape of the arc and the action of the inner gas trying to narrow it, so the welding state becomes more stable.

Furthermore, according to this embodiment, the thinner the base metal is, the greater the reduction rate of the inner gas flow rate Fi is. The thinner the base metal is, the greater the rate of temperature rise of the base metal. Therefore, by doing as described above, a good balance can be achieved between the action of expanding the shape of the arc and the action of the inner gas trying to narrow it, making the welding state more stable.

When the welding operator turns off the torch switch at time t5, the welding start signal On changes to low level, as shown in FIG. 1(A). In response to this, as shown in FIG. 1(F), the flow of welding current Iw stops and the arc is extinguished. In response to this, as shown in FIG. 1(G), the arc occurrence determination signal Ad changes to low level. At the same time, as shown in FIG. 1(D), the outer gas flow rate Fo becomes 0 and the ejection of outer gas stops.

At time t6, when a predetermined after-flow time has elapsed from time t5, the inner gas flow rate Fi becomes 0, as shown in FIG. 1(E), and the ejection of the inner gas stops. The after-flow time is set to about 7 seconds.

In the conventional technology, both the outer gas and the inner gas are ejected during the afterflow period. In contrast, in this embodiment, only the inner gas is ejected. The function of the afterflow is to shield the electrode and molten pool from the air until they are cooled. To achieve this function, it is sufficient to eject only the inner gas. In this way, the consumption of expensive inert gas can be reduced.

Numerical examples of the above parameters are shown below.
Welding torch WT: Welding torch equipped with a double shield nozzle with an inner nozzle inner diameter of 5 mm and an outer nozzle inner diameter of 13 mm Base material 2: Aluminum or its alloy Electrode 1: Tungsten electrode Outer gas and inner gas: 100% argon gas Outer gas flow rate Fo: Preflow period 12 l/min, main welding period 10 l/min
Inner gas flow rate Fi: Preflow period 4 l/min, initial value during main welding period 5 l/min, decrease rate 0.2 l/min per second, lower limit 3 l/min
Preflow time: 3 seconds (The inner gas starts to jet 2 seconds after the outer gas starts to jet, and the arc occurs 1 second after that.)

1 Electrode 2 Base material 3 Arc 4 Inner nozzle 5 Outer nozzle 6 Inner gas cylinder 7 Inner gas 8 Outer gas cylinder 9 Outer gas AD Arc occurrence determination circuit Ad Arc occurrence determination signal CI Inner gas flow regulator CO Outer gas flow regulator Fi Inner gas flow rate FICR Main welding inner gas flow rate setting circuit Ficr Main welding inner gas flow rate setting signal FIR Inner gas flow rate setting circuit Fir Inner gas flow rate setting signal Fo Outer gas flow rate FOR Outer gas flow rate setting circuit For Outer gas flow rate setting signal Iw Welding current ON Welding start circuit On Welding start signal PS Welding power source TI Inner gas jet start circuit Ti Inner gas jet start signal TP Preflow period circuit Tp Preflow period signal WT Welding torch

Claims (4)

The base material is aluminum or its alloy,
A welding torch having an inner nozzle for ejecting an inner gas and an outer nozzle for ejecting an outer gas is used,
In a double shield TIG welding method, an arc is generated after preflowing the inner gas and the outer gas at the start of welding, and a welding current is applied to weld the material,
The flow rate of the inner gas is decreased over time from the occurrence of the arc.
A double shielded TIG welding method. The greater the temperature rise rate of the base material, the greater the reduction rate of the flow rate of the inner gas.
The double shielded TIG welding method according to claim 1 . The larger the value of the welding current, the larger the reduction rate of the flow rate of the inner gas.
The double shielded TIG welding method according to claim 1 . The thinner the plate thickness of the base material, the greater the reduction rate of the flow rate of the inner gas.
The double shielded TIG welding method according to claim 1 .

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