JP2024086031A - Double shield tig welding method - Google Patents

Abstract

To provide a double shield tig welding method which reduces consumption of inert gas.SOLUTION: A double shield tig welding method uses a weld torch WT having an inner nozzle 4 for jetting inner gas 7 and an outer nozzle 5 for jetting outer gas 9, generates an arc after pre-flow of the inner gas 7 and the outer gas 9 at the time of weld start and is shifted to a stationary welding period, extinguishes the arc at the time of weld end and then performs after flow of the inner gas 7 and the outer gas 9, and ends the welding, wherein the after flow jets only the outer gas 9 and stops jetting of the inner gas 7.SELECTED DRAWING: Figure 1

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 ejects an inner gas and an outer nozzle that ejects 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

In conventional double-shielded TIG welding, the inner and outer gases are pre-flowed at the start of welding, then an arc is generated to transition to a steady-state welding period, and at the end of welding, the arc is extinguished and the inner and outer gases are post-flowed to finish the welding. In double-shielded TIG welding, two inert gases, the inner gas and the outer gas, must be ejected, and inert gases such as argon and helium are expensive, resulting in a problem of higher running costs than with normal single-shielded TIG welding.

The present invention aims to provide a double-shielded TIG welding method that can reduce the consumption of inert gas.

In order to solve the above-mentioned problems, the invention of claim 1 comprises:
A welding torch having an inner nozzle for ejecting an inner gas and an outer nozzle for ejecting an outer gas is used,
At the start of welding, a preflow of the inner gas and the outer gas is performed, and then an arc is generated to transition to a steady welding period;
In a double shield TIG welding method, the welding is completed by performing afterflow of the inner gas and the outer gas after extinguishing the arc at the end of welding,
The afterflow reduces the flow rate of the inner gas to be lower than that during the steady welding period.
This is a double shielded TIG welding method characterized by the above.

The invention of claim 2 is as follows:
The inner gas is reduced by reducing the flow rate to zero.
2. The double shielded TIG welding method according to claim 1 .

The invention of claim 3 is as follows:
The inner gas is reduced by reducing the flow rate from the middle of the afterflow.
2. The double shielded TIG welding method according to claim 1 .

The invention of claim 4 is as follows:
The preflow ejects the inner gas after ejecting the outer gas.
The double shielded TIG welding method according to any one of claims 1 to 3, characterized in that

The double shielded TIG welding method of the present invention can reduce the consumption of inert gas.

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 period determination circuit TP receives the above-mentioned welding start signal On as an input, performs the following processing, and outputs a period determination signal Tp.
1) When welding is completed, a period determination signal Tp=0 is output.
2) When the welding start signal On changes to a high level, a period determination signal Tp=1 (preflow period) is output.
3) When a predetermined preflow period has elapsed, a period determination signal Tp=2 (steady welding period) is output.
4) Thereafter, when the welding start signal On changes to a low level, a period determination signal Tp=3 (afterflow period) is output.
5) When a predetermined after-flow period has elapsed, a period determination signal Tp=0 (welding end state) is output.

The inner gas ejection start circuit TI receives the period discrimination signal Tp as input and outputs an inner gas ejection start signal Ti that goes high for a short period of time when a predetermined delay time Td has elapsed since the period discrimination signal Tp changed to 1. The delay time Td is shorter than the preflow period.

The inner gas flow rate setting circuit FIR receives the above-mentioned period discrimination signal Tp as an input and outputs an inner gas flow rate setting signal Fir which becomes a predetermined preflow inner gas flow rate value when the period discrimination signal Tp=1 (preflow period), a predetermined steady welding period inner gas flow rate value when the period discrimination signal Tp=2 (steady welding period), and an afterflow inner gas flow rate value set by any one of the following 1) to 3) when the period discrimination signal Tp=3 (after-flow period). Here, it is desirable that the preflow inner gas flow rate value is smaller than the steady welding period inner gas flow rate value.
1) The after-flow inner gas flow rate is reduced to a flow rate lower than the steady-state welding period inner gas flow rate, for example, to 50% or less.
2) The after-flow inner gas flow rate value is set to 0.
3) The after-flow inner gas flow rate is reduced from the middle of the after-flow period to a flow rate lower than the inner gas flow rate during the steady welding period, for example, to 50% or less.

The inner gas flow regulator CI is a known mass flow controller or the like, and receives the inner gas ejection start signal Ti, the period discrimination signal Tp, and the inner gas flow rate setting signal Fir as inputs. 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 period discrimination signal Tp changes to 0 (end of welding), it 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.

The outer gas flow rate setting circuit FOR receives the above-mentioned period discrimination signal Tp as an input, and outputs an outer gas flow rate setting signal For which is a predetermined preflow outer gas flow rate value when the period discrimination signal Tp = 1 (preflow period), a predetermined steady-state welding period outer gas flow rate value when the period discrimination signal Tp = 2 (steady-state welding period), and a predetermined afterflow outer gas flow rate value when the period discrimination signal Tp = 3 (afterflow period). Here, it is desirable for the preflow outer gas flow rate value to be greater than the steady-state welding period outer gas flow rate value. The afterflow outer gas flow rate value may be less than or equal to the steady-state welding period outer gas flow rate value.

The outer gas flow regulator CO is a known mass flow controller or the like, and receives the above-mentioned period discrimination signal Tp and the above-mentioned outer gas flow rate setting signal For as input. During the period from when the period discrimination signal Tp changes to 1 (pre-flow period) to when the period discrimination signal Tp changes to 0 (end of welding), 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 rate 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-mentioned period discrimination signal Tp as input, and when the period discrimination signal Tp = 2 (steady welding period), applies a high-frequency high voltage between the electrode 1 and the base material 2, and when an arc 3 is generated, starts outputting the welding current Iw, and when the period discrimination signal Tp = 3 (afterflow period), 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 period discrimination 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 (liters/minute), Figure (E) shows the change over time of the inner gas flow rate Fi (liters/minute), and Figure (F) shows the change over time of the welding current Iw. Below, the operation at the start and 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 period discrimination signal Tp becomes 1 (preflow period). 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.

At time t3, as shown in FIG. 1B, when the period discrimination signal Tp changes to 2 (steady welding period), 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 starts the flow of the welding current Iw as shown in FIG. 1F. At the same time, as shown in FIG. 1D, the outer gas flow rate Fo becomes a predetermined steady welding period outer gas flow rate value determined by the outer gas flow rate setting signal For in FIG. 1. Similarly, as shown in FIG. 1E, the inner gas flow rate Fi becomes a predetermined steady welding period inner gas flow rate value determined by the inner gas flow rate setting signal Fir in FIG. Then, welding starts 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 at the same time. 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, it was necessary to set the preflow period 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 pre-flow time even shorter. As a result, it is possible to further reduce the consumption of expensive inert gas.

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. As a result, the consumption of expensive inert gas can be further reduced.

Furthermore, it is desirable to set the outer gas flow rate Fo higher 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. As a result, the consumption of expensive inert gas can be further reduced.

When the welding operator turns off the torch switch at time t4, the welding start signal On changes to a low level, as shown in (A) of the figure. In response to this, as shown in (F) of the figure, the flow of the welding current Iw stops and the arc is extinguished.

At the same time, at time t4, as shown in Fig. 1B, when the period discrimination signal Tp changes to 3 (after-flow period), as shown in Fig. 1D, the outer gas flow rate Fo becomes a predetermined after-flow outer gas flow rate value determined by the outer gas flow rate setting signal For in Fig. 1. Similarly, as shown in Fig. 1E, the inner gas flow rate Fi becomes the following after-flow inner gas flow rate values 1) to 3) determined by the inner gas flow rate setting signal Fir in Fig. 1. Fig. 1E shows the following case 3).
1) The after-flow inner gas flow rate is reduced to a flow rate lower than the steady-state welding period inner gas flow rate, for example, to 50% or less.
2) The after-flow inner gas flow rate value is set to 0.
3) The after-flow inner gas flow rate is reduced from the middle of the after-flow period to a flow rate lower than the inner gas flow rate during the steady welding period, for example, to 50% or less.

At time t5, as shown in FIG. 1B, when the period discrimination signal Tp changes to 0 (welding end), as shown in FIG. 1D, the outer gas flow rate Fo becomes 0 and the gas ejection stops, and as shown in FIG. 1E, the inner gas flow rate Fi becomes 0 and the gas ejection stops. This ends the welding.

In the conventional technology, both the outer gas and the inner gas are ejected during the after-flow period. In contrast, in this embodiment, the flow rate of the inner gas is reduced during the after-flow period. The effect of the after-flow is to shield the electrode and the molten pool from the air until they are cooled. To achieve this effect, it is sufficient to eject the outer gas and eject the inner gas at a reduced flow rate. 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 Electrode 1: Tungsten electrode with a diameter of 3.2 mm Outer gas and inner gas: 100% argon gas Base material 2: Butt joint of mild steel with a plate thickness of 2.3 mm Welding current Iw: 150 A, welding speed: 30 cm/min
Outer gas flow rate Fo: Pre-flow period 12 l/min, steady welding period 10 l/min, post-flow period 10 l/min
Inner gas flow rate Fi: Pre-flow period 4 l/min, steady welding period 5 l/min, post-flow period 0 l/min
Preflow period: 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)
Afterflow period: 10 seconds

In the above-described embodiment, there are cases where crater treatment is performed before extinguishing the arc, and then afterflow is performed. In such cases, the flow rate of the inner gas may be reduced during the crater treatment period. This is because the main purpose is to shield the electrode and molten pool from the atmosphere during the crater treatment period, and for this purpose, the outer gas is ejected, and the desired effect is achieved even if the inner gas is ejected at a reduced flow rate. In this way, the consumption of inert gas can be further reduced.

REFERENCE SIGNS LIST 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 CI Inner gas flow regulator CO Outer gas flow regulator Fi Inner gas flow rate 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 Period discrimination circuit Tp Period discrimination signal WT Welding torch

Claims (4)

A welding torch having an inner nozzle for ejecting an inner gas and an outer nozzle for ejecting an outer gas is used,
At the start of welding, a preflow of the inner gas and the outer gas is performed, and then an arc is generated to transition to a steady welding period;
In a double shield TIG welding method, the welding is completed by performing afterflow of the inner gas and the outer gas after extinguishing the arc at the end of welding,
The afterflow reduces the flow rate of the inner gas to be lower than that during the steady welding period.
A double shielded TIG welding method. The inner gas is reduced by reducing the flow rate to zero.
The double shield TIG welding method according to claim 1 . The inner gas is reduced by reducing the flow rate from the middle of the afterflow.
The double shield TIG welding method according to claim 1 . The preflow ejects the inner gas after ejecting the outer gas.
The double shielded TIG welding method according to any one of claims 1 to 3.

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