JP2025014652A - Double shielded TIG welding method - Google Patents

Abstract

To stably maintain a weld state even if a temperature of a base material rises when the base material is aluminum or an alloy thereof in a double shield TIG welding method.SOLUTION: In a double shield TIG welding method that uses a welding torch comprising an inner nozzle for ejecting an inner gas and an outer nozzle for ejecting an outer gas, and performs welding while generating an arc on a weld line, the weld line is divided into a plurality of sections, a flow rate Fi of the inner gas is set for each of a first section from time t3 to t4, a second section from time t4 to t5, and a third section from time t5 to t6.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 a welding torch equipped with an inner nozzle for spraying an inner gas and an outer nozzle for spraying an outer gas is used to generate an arc on the weld line while welding (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

A weld line may include multiple sections, such as straight sections and arc sections. When the inner gas ejection state changes, the rigidity of the arc changes, causing the bead shape and penetration shape to fluctuate. When the weld line section is a straight section or an arc section, the inner gas ejection state changes, causing the bead shape and penetration shape to change. Even when the weld line is formed from multiple straight sections, the same problem as above can occur if the inner gas ejection state changes from the state around the weld line.

The present invention aims to provide a double-shielded TIG welding method that can maintain good bead and penetration shapes even if the state of inner gas ejection changes in some sections of the weld line.

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,
In a double shielded TIG welding method in which welding is performed while generating an arc on the weld line,
Dividing the weld line into a plurality of sections;
The flow rate of the inner gas is set for each section.
This is a double shielded TIG welding method characterized by the above.

The invention of claim 2 is as follows:
a flow rate of the inner gas is set to a value different from that when the section is a circular arc section and when the section is a straight line section;
2. The double shielded TIG welding method according to claim 1 .

The invention of claim 3 is as follows:
Welding is done using a welding robot.
The flow rate of the inner gas for each section is stored as teaching data for the welding robot.
3. The double shielded TIG welding method according to claim 1 or 2.

The double-shielded TIG welding method of the present invention can maintain good bead and penetration shapes even if the inner gas ejection state changes in some sections of the weld line.

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 robot RM is equipped with the above-mentioned welding torch WT, and moves the tip of the welding torch WT along the weld line in accordance with the operation control signal Rc described below.

The robot control device RC outputs an operation control signal Rc for moving the above-mentioned welding robot RM according to the stored teaching data, and outputs a welding start signal On and a main welding inner gas flow rate setting signal Ficr according to the teaching data. For example, assume that the path data of the welding line included in the teaching data is formed from the welding start position Ps, the first path position P1, the second path position P2, and the welding end position Pe. In this case, the welding line is divided into three sections, with Ps-P1 being the first section, P1-P2 being the second section, and P2-Pe being the third section. The welding start signal On becomes High level when the welding robot RM moves and reaches the welding start position Ps, and becomes Low level when it reaches the welding end position. Furthermore, an inner gas flow rate value is stored for each section as one of the teaching data. Then, when the welding robot RM moves through each section, the inner gas flow rate value stored corresponding to that section is output as the main welding inner gas flow rate setting signal Ficr. Therefore, the value of the main welding inner gas flow rate setting signal Ficr is the pre-stored first main welding inner gas flow rate value during the first section Ps-p1, the pre-stored second main welding inner gas flow rate value during the second section P1-p2, and the pre-stored third main welding inner gas flow rate value during the third section P2-pe.

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 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 value of the main welding inner gas flow rate setting signal Ficr.

The inner gas flow regulator CI is a known mass flow controller that receives the above-mentioned welding start signal On, the above-mentioned inner gas ejection start signal Ti, and the above-mentioned 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 is a known mass flow controller that receives the above-mentioned welding start signal On, the above-mentioned preflow period signal Tp, and the above-mentioned 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.

In the figure, the weld line is formed from teaching data for the welding start position Ps, the first path position P1, the second path position P2, and the welding end position Pe. Therefore, the weld line is divided into three sections: the first section Ps-P1, the second section P1-P2, and the third section P2-Pe. The first section Ps-P1 is a straight section, the second section P1-P2 is an arc section, and the third section P2-Pe is a straight section.

At time t1, the tip position of the welding torch WT of FIG. 1 mounted on the welding robot RM of FIG. 1 moves and reaches the welding start position Ps, where it stops, and as shown in FIG. 1(A), the welding start signal On changes to high level. In response to this, as shown in FIG. 1(B), the preflow period signal Tp becomes high level. At the same time, the outer gas starts to be ejected by the outer gas flow regulator CO of 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 of FIG. 1.

At time t2, a predetermined delay time Td after time t1, the inner gas ejection start signal Ti goes to high level for a short period of time, as shown in FIG. 1C. 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 PS of FIG. 1 applies a high-frequency high voltage between the electrode 1 and the base material 2 of FIG. 1 to generate the arc 3 of FIG. 1, and as shown in FIG. 1 (F), the flow of the welding current Iw begins. At time t3, when the generation of the 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 of FIG. 1. Similarly, as shown in FIG. 1 (E), the inner gas flow rate Fi becomes a value set by the main welding inner gas flow rate setting signal Ficr of FIG. 1. Then, from time t3, the tip position of the welding torch WT of FIG. 1 mounted on the welding robot RM of FIG. 1 starts moving along the welding line, and welding begins.

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.

As shown in FIG. 1E, the inner gas flow rate Fi is the first welding inner gas flow rate value set by the main welding inner gas flow rate setting signal Ficr in FIG. 1 during the first section Ps-P1 from time t3 to t4, the second welding inner gas flow rate value during the second section P1-P2 from time t4 to t5, and the third welding inner gas flow rate value during the third section P2-Pe from time t5 to t6. Here, the first section Ps-P1 and the third section P2-Pe are straight sections, and the second section P1-P2 is an arc section. In the arc section, the welding position of the welding torch WT in FIG. 1 changes from moment to moment, so the inner gas ejection state is different from that of the straight section. For this reason, by setting the second welding inner gas flow rate value in the arc section to a value different from the first and third welding inner gas flow rate values, the bead shape and penetration shape can be maintained well. Here, the second welding inner gas flow rate value is set to a value larger than the other sections.

When the tip position of the welding torch WT of FIG. 1 mounted on the welding robot RM of FIG. 1 reaches the welding end position Pe at time t6, it stops again, and 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 the welding current Iw stops and the arc is extinguished. In response to this, as shown in FIG. 1 (G), the arc generation 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 the outer gas stops.

At time t7, when a predetermined after-flow time has elapsed since time t6, 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 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: 4 l/min during preflow period, 5 l/min in the first and third sections of the main welding period, and 6 l/min in the second section
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.)

The effects of this embodiment will be described below.
According to this embodiment, the weld line is divided into a plurality of sections, and the flow rate of the inner gas is set for each section. The state of ejection of the inner gas changes depending on whether the section is a straight line or an arc, as well as on various welding conditions such as plate thickness, welding position, and distance between the electrode tip and the base material. When the state of ejection of the inner gas changes, the bead shape and penetration shape change. In this embodiment, the flow rate of each section can be optimized according to the state of ejection of the inner gas, so that the bead shape and penetration shape can be maintained well.

More preferably, according to this embodiment, the flow rate of the inner gas is set to a different value when the section is an arc section than when it is a straight section. When the section is an arc section, the welding position changes from moment to moment compared to when it is a straight section, so the inner gas ejection state is different from that of the straight section. For this reason, by setting the inner gas flow rate in the arc section to an appropriate value different from that of the straight section, good welding quality can be maintained.

More preferably, according to this embodiment, welding is performed using a welding robot, and the flow rate of the inner gas for each section is saved as teaching data for the welding robot. In this way, the inner gas flow rate is automatically set to an appropriate value as the welding robot moves along the welding line and enters each section, making it possible to make the welding work more efficient and maintain good welding quality.

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 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 signal PS Welding power source RC Robot control device Rc Operation control signal RM Welding robot TI Inner gas jet start circuit Ti Inner gas jet start signal TP Preflow period circuit Tp Preflow period signal WT Welding torch

Claims (3)

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 shielded TIG welding method in which welding is performed while generating an arc on the weld line,
Dividing the weld line into a plurality of sections;
The flow rate of the inner gas is set for each section.
A double shielded TIG welding method. a flow rate of the inner gas is set to a value different from that when the section is a circular arc section and when the section is a straight line section;
The double shielded TIG welding method according to claim 1 . Welding is done using a welding robot.
The flow rate of the inner gas for each section is stored as teaching data for the welding robot.
3. The double shielded TIG welding method according to claim 1 or 2.

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