Double shield tig welding method

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

[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 aluminum or its alloys (hereinafter simply referred to as aluminum) are welded using the conventional double-shielded TIG welding method, a phenomenon occurs in which the weld state becomes unstable as the temperature of the base metal rises.

[0005] Therefore, an object of the present invention is to provide a double-shielded TIG welding method that can maintain a stable welded state even if the temperature of the base metal rises when the base metal is aluminum. [Means for solving the problem]

[0006] 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.

[0007] 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,

[0008] 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,

[0009] 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, Effect of the Invention

[0010] According to the double shielded TIG welding method of the present invention, when the base metal is aluminum, the welded state can be maintained stably even if the temperature of the base metal rises. [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 main welding inner gas flow rate setting circuit FICR takes the above-mentioned arc occurrence determination signal Ad as input, and when the arc occurrence determination signal Ad is at low level, it becomes a predetermined initial inner gas flow rate value for main welding, and when the arc occurrence determination signal Ad changes to 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 value 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 reduction rate mentioned above. 2) The larger the value of the welding current Iw, the larger the reduction rate is set. 3) The thinner the base material thickness, the greater the reduction rate.

[0020] 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.

[0021] The inner gas flow regulator CI 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 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 during the period from the point 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.

[0022] 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.

[0023] The outer gas flow regulator CO receives as input the welding start signal On, the preflow period signal Tp, and the outer gas flow setting signal For, 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.

[0024] 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 as 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 base material 2 serving as the positive electrode.

[0025] The welding power source PS receives as input the above-mentioned welding start signal On and the above-mentioned preflow period signal Tp, 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.

[0026] 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.

[0027] 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.

[0028] 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. 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.

[0029] When the pre-flow 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 supply of the welding current Iw starts. At time t3, when the supply of the welding current Iw determines that an arc has been generated, 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 value inner gas flow rate value determined by the main welding inner gas flow rate setting signal Ficr in FIG. Then, welding starts at time t3.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] At time t3, as shown in (G) of the same figure, when the arc occurrence determination signal Ad changes to a high level, the main welding inner gas flow rate setting circuit FICR of Figure 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.

[0035] 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 becomes wider, 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 becomes wider, 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 generation of the arc. In this way, as the temperature of the base material rises over time from the generation of the arc, the inner gas flow rate Fi is reduced, and the effect of narrowing the arc becomes weaker. As a result, it is possible to suppress the welding state from becoming unstable.

[0036] Furthermore, according to this embodiment, the greater the temperature rise rate of the base metal, the greater the decrease rate of the flow rate Fi of the inner gas is set. This makes it possible to achieve a good balance between the action of expanding the shape of the arc and the action of the inner gas of constricting it, thereby making the welding state more stable.

[0037] Furthermore, according to this embodiment, the larger the value of the welding current, the larger the reduction rate of the flow rate Fi of the inner gas is made. The larger the value of the welding current, the larger the temperature rise rate of the base metal. By doing so, the balance between the action of expanding the shape of the arc and the action of constricting it by the inner gas can be improved, so that the welding state becomes more stable.

[0038] Furthermore, according to this embodiment, the thinner the base metal is, the greater the reduction rate of the flow rate Fi of the inner gas is. The thinner the base metal is, the greater the temperature rise rate of the base metal is. By doing as described above, the balance between the action of expanding the shape of the arc and the action of constricting the arc by the inner gas can be improved, so that the welding state becomes more stable.

[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. 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.) [Explanation of symbols]

[0043] 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 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 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 blow-out start circuit Ti Inner gas ejection start signal TP Preflow period circuit Tp Preflow period signal WT Welding Torch

Claims

1. 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.

2. 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 .

3. 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 .

4. 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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