Double-shield TIG welding method

Abstract

To improve work efficiency by quickly forming a bridge portion between a first work piece and a second work piece by means of a molten pool at the start of welding in a case where a T-shaped fillet joint formed of a first work piece and a second work piece of aluminum is welded by a double-shield TIG welding method.SOLUTION: A double-shield TIG welding method is as follows: a work piece is made of aluminum or its alloy, a joint is a T-shaped fillet joint formed of a first work piece and a second work piece, pre-flowing of inner gas and outer gas is performed when welding is started, then arc is generated and welding current Iw is supplied to perform welding. In the double-shield TIG welding method, a flow rate Fi of the inner gas during an initial period from a time t3 of arc generation to a time t4 is set to a value larger than that during a subsequent steady period. The initial period is set based on a period until a bridge portion is formed between the first work piece and the second work piece by a molten pool.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 for ejecting an inner gas and an outer nozzle for ejecting an outer gas (see, for example, Patent Document 1). As the inner gas and the outer gas, inert gases such as argon and helium are used. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-15048 A Summary of the Invention [Problem to be solved by the invention]

[0004] When a T-shaped fillet joint formed from a first workpiece and a second workpiece made of aluminum or its alloy (hereinafter simply referred to as aluminum) is welded using the conventional double-shielded TIG welding method, there is a problem in that it takes time to form a bridge between the first workpiece and the second workpiece by a molten pool at the start of welding, reducing work efficiency.

[0005] Therefore, the present invention aims to provide a double shielded TIG welding method that can quickly form a bridge between the first workpiece and the second workpiece by a molten pool at the start of welding when welding a T-shaped fillet joint formed of a first and second aluminum workpiece, thereby improving work efficiency. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the invention of claim 1 comprises: The workpiece is aluminum or an alloy thereof, and the joint is a T-shaped fillet joint formed from a first workpiece and a second workpiece; 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, a flow rate of the inner gas is set to a value greater during an initial period from the occurrence of the arc than during a steady period thereafter; This is a double shielded TIG welding method characterized by the above.

[0007] The invention of claim 2 is as follows: The initial period is set based on a period until a bridge portion formed by a molten pool is formed between the first workpiece and the second workpiece. 2. The double shielded TIG welding method according to claim 1,

[0008] The invention of claim 3 is as follows: During the initial period, the welding current is applied in a pulse waveform. 3. The double shield TIG welding method according to claim 1 or 2.

[0009] The invention of claim 4 is as follows: During the initial period, the welding current is applied in a pulse waveform having an amplitude of 50 A or more and a frequency in the range of 10 to 500 Hz. 3. The double shield TIG welding method according to claim 1 or 2. Effect of the Invention

[0010] According to the double shielded TIG welding method of the present invention, when welding a T-shaped fillet joint formed from a first and second aluminum workpiece, a bridge formed by a molten pool can be quickly formed between the first and second workpieces at the start of welding, thereby improving work efficiency. [Brief description 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. [Diagram 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 PREFERRED EMBODIMENTS

[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 to a high level 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 above-mentioned 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 when 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 to High level for a short period of time after a predetermined delay time Td has elapsed since the preflow period signal Tp went to High level. The delay time Td is shorter than the preflow period Tp.

[0018] 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.

[0019] The initial period setting circuit TIPR outputs a predetermined initial period setting signal Tipr.

[0020] The main welding inner gas flow rate setting circuit FICR receives the above arc occurrence determination signal Ad and the above initial period setting signal Tipr as inputs, and outputs a main welding inner gas flow rate setting signal Ficr which has a predetermined initial period inner gas flow rate value during the initial period determined by the initial period setting signal Tipr from the time when the arc occurrence determination signal Ad changes to a high level, and which has a predetermined steady-state period inner gas flow rate value during the steady-state period thereafter. Here, the initial period inner gas flow rate value is set to a value larger than the steady-state period inner gas flow rate value.

[0021] 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 that 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 to set the preflow inner gas flow rate value to a value smaller than the main welding initial value inner gas flow rate value.

[0022] The inner gas flow regulator CI is a well-known mass flow controller that receives as input the above-mentioned welding start signal On, the above-mentioned inner gas jet start signal Ti, and the above-mentioned inner gas flow rate setting signal Fir, and during the period from the time when the inner gas jet 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, 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 jets it out.

[0023] 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 which 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 desirably set to a value larger than the main welding outer gas flow rate value.

[0024] The outer gas flow regulator CO is a known mass flow controller that receives as input the welding start signal On, the preflow period signal Tp, and the outer gas flow setting signal For, 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.

[0025] 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. An inert gas such as argon or helium is used for the inner gas 7 and the outer gas 9. The arc 3 is generated with the electrode 1 serving as the negative electrode and the workpiece 2 serving as the positive electrode.

[0026] The current setting circuit IR outputs a predetermined current setting signal Ir.

[0027] The current control setting circuit ICR receives as input the arc occurrence determination signal Ad, the initial period setting signal Tipr, and the current setting signal Ir, and outputs a current control setting signal Icr which has an amplitude of 50 A or more and a pulse waveform with a frequency in the range of 10 to 500 Hz, with the current setting signal Ir as a center value, during the initial period determined by the initial period setting signal Tipr from the point when the arc occurrence determination signal Ad changes to a High level, and during the steady period thereafter, outputs the value of the current setting signal Ir as the current control setting signal Icr.

[0028] The welding power source PS receives as input the above-mentioned welding start signal On, the above-mentioned preflow period signal Tp, and the above-mentioned current control setting signal Icr, 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 workpiece 2, and when an arc 3 is generated, it begins outputting the welding current Iw set by the current control setting signal Icr, and when the welding start signal On goes to low level, it stops outputting the welding current Iw.

[0029] Fig. 2 is a timing chart of each signal in the welding device of Fig. 1 showing the double shielded TIG welding method according to the embodiment of the present invention. Fig. 2(A) shows the change over time of the welding start signal On, Fig. 2(B) shows the change over time of the preflow period signal Tp, Fig. 2(C) shows the change over time of the inner gas ejection start signal Ti, Fig. 2(D) shows the change over time of the outer gas flow rate Fo (l / min), Fig. 2(E) shows the change over time of the inner gas flow rate Fi (l / min), Fig. 2(F) shows the change over time of the welding current Iw, and Fig. 2(G) shows the change over time of the arc generation determination signal Ad. Hereinafter, the operations at the start of welding, during main welding, and at the end of welding will be described with reference to the figures.

[0030] 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, the preflow period signal Tp changes to a high level as shown in Fig. 1(B). 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.

[0031] 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 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.

[0032] When the preflow period signal Tp changes to a low level at time t3, the welding power source PS in FIG. 1 applies a high frequency high voltage between the electrode 1 and the workpiece 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 actual welding outer gas flow rate value determined by the outer gas flow rate setting signal For in FIG. Then, welding begins at time t3.

[0033] As shown in FIG. 1(G), the initial period is the period from time t3 to t4 from when the arc generation determination signal Ad changes to a high level until the period determined by the initial period setting signal Tipr in FIG. 1 has elapsed. As shown in FIG. 1(E), the inner gas flow rate Fi during the initial period is a predetermined initial period inner gas flow rate value determined by the main welding inner gas flow rate setting signal Ficr in FIG. 1. The initial period inner gas flow rate value is set to a value larger than the steady period inner gas flow rate value. As shown in FIG. 1(F), the welding current Iw during the initial period is a pulse waveform set by the current control setting signal Icr in FIG. 1. The welding current Iw is a pulse waveform with an amplitude of 50A or more and a frequency in the range of 10 to 500Hz, with the current setting signal Ir in FIG. 1 as the center value.

[0034] When the initial period ends at time t4, the steady period begins. As shown in FIG. 1(E), the inner gas flow rate Fi during the steady period is a predetermined steady-period inner gas flow rate value determined by the main welding inner gas flow rate setting signal Ficr in FIG. 1. As shown in FIG. 1(F), the welding current Iw during the steady period is a direct current with a value set by the current setting signal Ir in FIG.

[0035] As described above, during the preflow period, the inner gas is ejected after the outer gas is ejected. In this way, the ejection of the inner gas is started in a state where the surroundings are shielded by the ejection of the outer gas, so that the inner gas does not entrain the surrounding air, and the steady state can be quickly converged. 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, the preflow period had to be set to about 6 seconds, but in this embodiment, it can be set to about 3 seconds.

[0036] Furthermore, it is preferable 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, the inner gas can be more reliably prevented from entraining air, and the pre-flow time can be set even shorter.

[0037] Furthermore, it is desirable to set the inner gas flow rate Fi smaller during the preflow period than during the main welding period after the end of the preflow period. In this way, the ejection state of the inner gas can be brought into a steady state more quickly, and the preflow time can be set even shorter.

[0038] Furthermore, it is desirable to set the outer gas flow rate Fo larger during the preflow period than during the main welding period after the end of the preflow period. In this way, the ejection state of the inner gas can be brought to a steady state earlier, so that the preflow time can be set even shorter.

[0039] 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 the 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 the outer gas stops.

[0040] At time t6 when a predetermined after-flow time has elapsed from time t5, as shown in (E) of the figure, the inner gas flow rate Fi becomes 0, and the ejection of the inner gas stops. The after-flow time is set to about 7 seconds.

[0041] In the prior art, both the outer gas and the inner gas are ejected during the afterflow period. In contrast, in the present embodiment, only the inner gas is ejected. The function of the afterflow is to shield the electrode and the 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.

[0042] 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. Material of workpiece 2: Aluminum or its alloy Joint: T-joint 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 period 7 l / min, steady 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.)

[0043] The effects of this embodiment will be described below. According to this embodiment, the flow rate of the inner gas is set to a value greater during the initial period from the occurrence of the arc than during the subsequent steady period. When a T-shaped fillet joint formed of a first workpiece and a second workpiece made of aluminum or its alloy is welded using the conventional double-shielded TIG welding method, there is a problem that it takes time to form a bridge between the first workpiece and the second workpiece by a molten pool at the start of welding, which reduces the work efficiency. In contrast, in this embodiment, the flow rate of the inner gas is set to be greater during a predetermined initial period from the occurrence of the arc than during the steady period. The greater the flow rate of the inner gas, the stronger the rigidity of the arc. When the rigidity of the arc becomes stronger, the concentrated heat source promotes melting of the workpieces, and the molten pool is formed quickly. As a result, a bridge between the first workpiece and the second workpiece can be quickly formed by the molten pool, thereby improving work efficiency.

[0044] More preferably, according to this embodiment, the initial period is set based on the period until a bridge is formed by the molten pool between the first workpiece and the second workpiece. If the flow rate of the inner gas remains high for a long time after the bridge is formed, the bead width during the steady period will be narrowed due to the concentration of the arc. For this reason, after the bridge is formed, the flow rate of the inner gas is reduced to a value suitable for the steady period, so that a good bead can be formed.

[0045] More preferably, according to this embodiment, a pulsed welding current is applied during the initial period. When the welding current has a pulsed waveform, the rigidity of the arc becomes stronger than when it is a direct current. Therefore, during the initial period, the rigidity of the arc can be made stronger by increasing the flow rate of the inner gas and applying a pulsed welding current. As a result, the bridge can be formed more quickly, and the work efficiency can be improved.

[0046] More preferably, according to this embodiment, a welding current having a pulse waveform with an amplitude of 50A or more and a frequency in the range of 10 to 500Hz is applied during the initial period. When the pulse waveform is within the above condition range, the rigidity of the arc is stronger than when it is outside the range. Therefore, in this embodiment, the bridge can be formed more quickly, and the working efficiency can be further improved. [Explanation of symbols]

[0047] 1 electrode 2 Work 3. Arc 4 Inner nozzle 5 Outer nozzle 6 Inner gas cylinder 7. Inner Gas 8 Outer gas cylinder 9. Outer Gas AD Arc generation detection circuit Ad Arc occurrence detection signal CI Inner Gas Flow Regulator CO outer gas flow regulator Fi Inner gas flow rate FICR welding inner gas flow rate setting circuit Ficr 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 ICR Current control setting circuit Icr Current control setting signal IR current setting circuit Ir Current setting signal Iw Welding current ON Welding start circuit On Welding start signal PS Welding Power Source TI Inner gas blow-out start circuit Ti Inner gas ejection start signal TIPR Initial Period Setting Circuit Tipr Initial period setting signal TP Preflow period circuit Tp Preflow period signal WT Welding Torch

Claims

1. The workpiece is aluminum or an alloy thereof, and the joint is a T-fillet joint formed from a first workpiece and a second workpiece; 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, a flow rate of the inner gas is set to a value greater during an initial period from the occurrence of the arc than during a steady period thereafter; A double shielded TIG welding method.

2. The initial period is set based on a period until a bridge portion is formed between the first workpiece and the second workpiece by a molten pool. The double shielded TIG welding method according to claim 1 .

3. During the initial period, the welding current is applied in a pulse waveform.

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

4. During the initial period, the welding current is applied in a pulse waveform having an amplitude of 50 A or more and a frequency in the range of 10 to 500 Hz.

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

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