Double shielded TIG welding method

Abstract

To secure sufficient shielding performance even if a pre-flow time at the start of welding is set short in a double shield tig welding method.SOLUTION: In a double shield tig welding method, a welding torch, including an inner nozzle for jetting an inner gas and an outer nozzle for jetting an outer gas, is used and pre-flow of the inner gas and the outer gas is performed at the start of welding and then an arc is generated to perform welding at time t3. In the pre-flow of time t1 to t3, jetting of the outer gas Fo is started at the time t1 and jetting of the inner gas Fi is started at a time t2. The pre-flow is set so that a time period from the time t1 to t2 during which only the outer gas Fo is jetted is longer than a time period from the time t2 to t3 during which the inner gas Fi is jetted.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a double-shielded TIG welding method. [Background technology]

[0002] 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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-15048 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional double-shielded TIG welding methods, the inner and outer gases are simultaneously ejected to initiate preflow before generating an arc. Because the inner gas entrains surrounding air during the ejection, it takes a long time, approximately 6 to 10 seconds, for the gas to reach a steady state. Therefore, if sufficient preflow time is not provided, welding begins with air entrained, resulting in reduced shielding and potential for poor welding. However, setting a long preflow time reduces work efficiency and consumes a large amount of expensive inert gas.

[0005] Therefore, an object of the present invention is to provide a double-shielded TIG welding method that can ensure sufficient shielding even if the preflow time at the start of welding is set to be short. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the invention of claim 1 is as follows: A welding torch having an inner nozzle for ejecting inner gas and an outer nozzle for ejecting outer gas is used, In a double-shielded TIG welding method, at the start of welding, an arc is generated after preflowing the inner gas and the outer gas, The pre-flow ejects the inner gas after ejecting the outer gas. This is a double-shielded TIG welding method characterized by the above.

[0007] The invention of claim 2 is as follows: The pre-flow is set so that the time during which only the outer gas is ejected is longer than the time during which the inner gas is ejected. 2. The double-shielded TIG welding method according to claim 1, wherein:

[0008] The invention of claim 3 is as follows: The flow rate of the inner gas is set to be smaller during the preflow than after the preflow has ended. 3. The double-shielded TIG welding method according to claim 1 or 2.

[0009] The invention of claim 4 is as follows: The flow rate of the outer gas is set to be larger during the preflow than after the preflow has ended. 3. The double-shielded TIG welding method according to claim 1 or 2. [Effects of the Invention]

[0010] The double-shielded TIG welding method of the present invention ensures sufficient shielding even when the preflow time at the start of welding is set short, thereby improving work efficiency and reducing the consumption of expensive inert gas. [Brief explanation of the drawings]

[0011] [Figure 1] 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. [Figure 2] 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. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] 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. Each block will be described below with reference to the diagram.

[0014] The welding torch WT mainly includes an electrode 1, an inner nozzle 4 surrounding the electrode 1, and an outer nozzle 5 surrounding the inner nozzle 4. The electrode 1 is a tungsten electrode or the like.

[0015] The welding start circuit ON outputs a welding start signal ON that goes high when welding starts. This welding start circuit ON is a torch switch provided on the welding torch WT. The welding start circuit ON may also be provided in the robot control device.

[0016] The preflow period circuit TP receives the welding start signal On as an 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.

[0017] 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 high for a short period of time after a predetermined delay time Td has elapsed since the preflow period signal Tp went high. The delay time Td is shorter than the preflow period Tp.

[0018] The inner gas flow rate setting circuit FIR receives the preflow period signal Tp as input and outputs an inner gas flow rate setting signal Fir that is a predetermined preflow inner gas flow rate when the preflow period signal Tp is at a high level and a predetermined main welding inner gas flow rate when the preflow period signal Tp is at a low level. Here, it is desirable that the preflow inner gas flow rate be set to a value smaller than the main welding inner gas flow rate.

[0019] The inner gas flow regulator CI receives the welding start signal On, the inner gas ejection start signal Ti, and the 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 the time 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.

[0020] The outer gas flow rate setting circuit FOR receives the preflow period signal Tp as an input, and outputs an outer gas flow rate setting signal For that becomes a predetermined preflow outer gas flow rate value when the preflow period signal Tp is at a high level, and becomes a predetermined main welding outer gas flow rate value when the preflow period signal Tp is at a low level. Here, the preflow outer gas flow rate value is preferably set to a value greater than the main welding outer gas flow rate value.

[0021] The outer gas flow regulator CO receives the welding start signal On, the preflow period signal Tp, and the outer gas flow setting signal For as inputs, and 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 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.

[0022] An inner gas 7 flows through a passage inside the inner nozzle 4. An outer gas 9 flows through a 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.

[0023] The welding power source PS receives the above-mentioned welding start signal On and the above-mentioned preflow period signal Tp as inputs, and when the welding start signal On goes high and the preflow period signal Tp goes low, 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 low, it stops outputting the welding current Iw.

[0024] 2 is a timing chart of signals in the welding apparatus of FIG. 1, illustrating a double-shielded TIG welding method according to an embodiment of the present invention. (A) in FIG. 2 shows the change over time of the welding start signal On, (B) in FIG. 2 shows the change over time of the preflow period signal Tp, (C) in FIG. 2 shows the change over time of the inner gas ejection start signal Ti, (D) in FIG. 2 shows the change over time of the outer gas flow rate Fo (liters / minute), (E) in FIG. 2 shows the change over time of the inner gas flow rate Fi (liters / minute), and (F) in FIG. 2 shows the change over time of the welding current Iw. Operations at the start and end of welding will be described below with reference to the figures.

[0025] At time t1, when the welding operator turns on the torch switch provided on the welding torch WT shown in FIG. 1, the welding start signal On changes to high level, as shown in FIG. 1(A). In response to this, the preflow period signal Tp changes to high level, as shown in FIG. 1(B). At the same time, the outer gas flow regulator CO shown in FIG. 1 starts to eject outer gas. 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 shown in FIG.

[0026] At time t2, a predetermined delay time Td after time t1, the inner gas ejection start signal Ti goes high for a short time, as shown in (B) of the figure. In response to this, the inner gas flow regulator CI of Fig. 1 starts ejecting the inner gas. As shown in (E) of the figure, 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 of Fig. 1.

[0027] 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 starts the flow of the welding current Iw, as shown in FIG. 1(F). 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 outer gas flow rate value determined by the inner gas flow rate setting signal Fir in FIG. Then, welding starts at time t3.

[0028] As described above, during the preflow period, the inner gas is ejected after the outer gas is ejected. In this manner, the inner gas is started to be ejected while the surrounding area is shielded by the outer gas, so the inner gas does not entrain the surrounding air, and the steady state can be quickly reached. Therefore, in this embodiment, the preflow time can be shortened by about 50% compared to the conventional technology in which the outer gas and inner gas are simultaneously ejected. Therefore, in this embodiment, sufficient shielding can be ensured even if the preflow time at the start of welding is set short, thereby improving work efficiency and reducing the consumption of expensive inert gas. For example, while the conventional technology required the preflow period to be set to about 6 seconds, this embodiment can be set to about 3 seconds.

[0029] 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 the pre-flow time can be set even shorter.

[0030] Furthermore, it is desirable to set the inner gas flow rate Fi smaller during the pre-flow period than during the main welding period after the pre-flow period has ended. This allows the inner gas ejection state to reach a steady state more quickly, making it possible to set an even shorter pre-flow time.

[0031] Furthermore, it is desirable to set the outer gas flow rate Fo higher during the pre-flow period than during the main welding period after the pre-flow period has ended. This allows the inner gas to be ejected in a steady state more quickly, making it possible to set the pre-flow time even shorter.

[0032] Numerical examples of the above parameters are shown below. Welding torch WT: A 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: 3.2 mm diameter tungsten electrode Outer gas and inner gas: 100% argon gas Base material 2: 2.3mm thick mild steel butt joint Welding current Iw: 150A, welding speed: 30cm / min Outer gas flow rate Fo: Pre-flow period 12 l / min, main welding period 10 l / min Inner gas flow rate Fi: Pre-flow period 4 l / min, main welding period 5 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.)

[0033] At time t4, when the welding operator turns off the torch switch, the welding start signal On changes to low level, as shown in (A) of the figure. In response to this, the flow of welding current Iw stops, as shown in (F) of the figure. At the same time, the outer gas flow rate Fo becomes 0, as shown in (D) of the figure, and the outer gas stops being ejected.

[0034] At time t5, when a predetermined after-flow time has elapsed since time t4, the inner gas flow rate Fi becomes 0, and the injection of the inner gas stops, as shown in (E) of the same figure. The after-flow time is set to about 7 seconds.

[0035] In the prior art, both outer and inner gases are ejected during the after-flow period. In contrast, in this embodiment, only inner gas is ejected. The function of the after-flow is to shield the electrode and molten pool from air until they cool. To achieve this function, it is sufficient to eject only inner gas. This reduces the consumption of expensive inert gas. [Explanation of symbols]

[0036] 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 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 injection start circuit Ti inner gas ejection start signal TP preflow period circuit Tp Preflow period signal WT welding torch

Claims

1. A welding torch having an inner nozzle for ejecting inner gas and an outer nozzle for ejecting outer gas is used, In a double-shielded TIG welding method, at the start of welding, an arc is generated after preflowing the inner gas and the outer gas, The pre-flow ejects the inner gas after ejecting the outer gas. A double shielded TIG welding method characterized by the above.

2. The pre-flow is set so that the time during which only the outer gas is ejected is longer than the time during which the inner gas is ejected. The double shield TIG welding method according to claim 1 .

3. The flow rate of the inner gas is set to be smaller during the preflow than after the preflow has ended.

3. The double-shielded TIG welding method according to claim 1 or 2.

4. The flow rate of the outer gas is set to be larger during the preflow than after the preflow has ended.

3. The double-shielded TIG welding method according to claim 1 or 2.

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