Double shield TIG welding method

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

[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 a welding torch equipped with an inner nozzle for ejecting an inner gas and an outer nozzle for ejecting an outer gas is used to perform welding while generating an arc on a welding line (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] 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 vary. When the weld line section is a straight section and when it is 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 of multiple straight sections, the same problem as above occurs when the inner gas ejection state changes from the state around the weld line.

[0005] Therefore, an object of the present invention is to provide a double shielded TIG welding method that can maintain good bead shape and penetration shape even if the inner gas ejection condition changes in some sections of the weld line. [Means for solving the problem]

[0006] 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 an arc is generated along the weld line while welding, 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.

[0007] 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,

[0008] 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 shield TIG welding method according to claim 1 or 2. Effect of the Invention

[0009] According to the double shielded TIG welding method of the present invention, even if the ejection state of the inner gas changes in a portion of the weld line, the bead shape and the penetration shape can be maintained favorably. [Brief description of the drawings]

[0010] [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

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] 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.

[0013] 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.

[0014] 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 an operation control signal Rc, which will be described later.

[0015] 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 a welding start position Ps, a first path position P1, a second path position P2, and a 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 a high level when the welding robot RM moves and reaches the welding start position Ps, and becomes a 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 a main welding inner gas flow rate setting signal Ficr. Therefore, the value of the main welding inner gas flow rate setting signal Ficr becomes the pre-stored first welding inner gas flow rate value during the first section Ps-p1, becomes the pre-stored second welding inner gas flow rate value during the second section P1-p2, and becomes the pre-stored third welding inner gas flow rate value during the third section P2-pe.

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

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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: a first section Ps-P1, a second section P1-P2, and a third section P2-Pe. The first section Ps-P1 is a straight line section, the second section P1-P2 is an arc section, and the third section P2-Pe is a straight line section.

[0027] 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 changes to 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.

[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. 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.

[0029] When the pre-flow 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 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 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 weld line, and welding starts.

[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] 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 that the inner gas ejection state is different from that in the straight section. For this reason, the bead shape and penetration shape can be maintained well 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. Here, the second welding inner gas flow rate value is set to a value larger than that in the other sections.

[0035] At time t6, when the tip position of the welding torch WT in Fig. 1 mounted on the welding robot RM in Fig. 1 reaches the welding end position Pe, 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 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.

[0036] At time t7 when a predetermined after-flow time has elapsed from time t6, 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.

[0037] 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.

[0038] 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: 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, 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.)

[0039] 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, and also on various welding conditions such as plate thickness, welding position, and distance between the electrode tip and the base material. If 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.

[0040] 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 ejection state of the inner gas 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 in the straight section, good welding quality can be maintained.

[0041] 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 stored as teaching data for the welding robot. In this way, when the welding robot moves along the welding line and enters each section, the inner gas flow rate is automatically set to an appropriate value, so that the welding work can be made more efficient and good welding quality can be maintained. [Explanation of symbols]

[0042] 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 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 signal PS Welding Power Source RC robot controller Rc Operation control signal RM Welding Robot 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. 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.

2. 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 .

3. 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.

Images