JP2020116597A - Three-electrode single-sided gas shielded arc welding method - Google Patents

Abstract

To provide a three-electrode single-sided gas shielded arc welding method that enables obtaining sound weld metal highly efficiently, the metal that is superior in rear bead and top bead shapes, and reduced in a sputter generation rate without a weld flaw.SOLUTION: An arc welding method is performed as follows: steel granules are filled in a groove to the height of 1/5 to 1/2 of a workpiece plate thickness when performing one side welding by bringing a backing material into abutment with the groove back side of V or Y-shape of groove angles of 30-55°; a gap distance of leading electrode wire, intermediate electrode wire and trailing electrode wire is made 80 to 300 mm, respectively; the welding current density of the leading electrode wire is made 250 A/mmor more, the welding current density of the intermediate electrode wire is made 220A/mmor more, and the welding current density of the trailing electrode wire is made 200A/mmor more; and the welding is made by the swing of the leading electrode wire of 65 to 115 times/m, the swing of the intermediate electrode wire and the trailing electrode wire of 30 to 90 times/m, respectively.SELECTED DRAWING: Figure 1

Description

The present invention relates to a grooved three-electrode single-sided gas shielded arc welding method formed by a material to be welded, and particularly in welding a material to be welded having a plate thickness exceeding 22 mm, a back bead and a front bead shape are good, and spatter is generated. TECHNICAL FIELD The present invention relates to a three-electrode single-sided gas shielded arc welding method capable of highly efficiently obtaining a sound weld metal having a small amount and no welding defects.

Various high-efficiency welding methods are used for rationalization and efficiency in welding of various welded structures during construction. Above all, single-sided welding is applied to shipbuilding and bridges where the ratio of butt welding is high.

As a one-sided welding method, a submerged arc welding method has been widely used as a plate joint welding for shipbuilding. For example, Patent Document 1 discloses a single-sided submerged arc welding device, and Patent Documents 2 and 3 disclose a single-sided submerged arc welding method using three electrodes or four electrodes.

However, the single-sided submerged arc welding device disclosed in Patent Document 1 has a problem in that it requires large-scale equipment and is not applicable to short-length welding because it is complicated.

On the other hand, a single-sided gas shielded arc welding method capable of short length welding has been put into practical use. Patent Documents 4 to 6 disclose a technique in which a backing material is brought into contact with the groove back surface to perform solid-side welding or flux-cored wire for the leading electrode and flux-cored wire for the trailing electrode to perform single-sided welding by gas shield arc welding. There is. These are one-sided gas shielded arc welding of 12 to 25 mm of material to be welded with two electrodes. However, also in the technologies disclosed in Patent Documents 4 to 6, when the plate thickness of the material to be welded exceeds 22 mm, the back bead may not come out or the shape of the back bead may be defective, and the first layer and the second layer In many cases, poor fusion occurs between the eyes and high temperature cracking occurs in the first layer, which causes various problems in actual construction.

JP2012-665A JP-A-5-337651 JP, 2005-246385, A JP, 9-206945, A JP, 10-202368, A JP, 2000-102871, A

Therefore, the present invention has been devised in view of the above-mentioned problems, and particularly in short to long welding in which the plate thickness of the material to be welded exceeds 22 mm, the back bead and front bead shape are good, and spatter An object of the present invention is to provide a three-electrode single-sided gas shielded arc welding method capable of producing a sound weld metal with a small amount of generation and no welding defects with high efficiency.

The gist of the present invention is a three-electrode single-sided gas shielded arc welding method in which a backing material is brought into contact with a V- or Y-shaped grooved rear surface having a groove angle of 30 to 55° in a material to be welded to perform three-electrode single-sided gas shielded arc welding. And filling the inside of the groove with steel particles to a height of 1/5 to 1/2 of the thickness of the material to be welded, the distance between the electrodes of the leading electrode wire and the intermediate electrode wire, and the intermediate electrode wire and the rear electrode wire. The distance between electrodes with the row electrode wire is 80 to 300 mm, the welding current density of the leading electrode wire is 250 A/mm ² or more, the welding current density of the intermediate electrode wire is 220 A/mm ² or more, and the welding current of the trailing electrode wire is The density is 200 A/mm ² or more, and the oscillation of the leading electrode wire is welded at 65 to 115 times/minute, and the oscillation of the intermediate electrode wire and the trailing electrode wire is welded at 30 to 90 times/minute, respectively. To do.

Further, the leading electrode wire is a solid wire, the intermediate electrode wire is a metal flux-cored wire in which the total amount of the slag forming agent is 1 mass% or less based on the total mass of the wire, and the trailing electrode wire is slag forming against the total mass of the wire. A rutile flux-cored wire containing 4 to 9 mass% of the total amount of the agent is used.

Further, the polarity of the intermediate electrode wire is a wire minus, which is a three-electrode single-sided gas shielded arc welding method.

According to the three-electrode single-sided gas shielded arc welding method of the present invention, particularly in the welding of a short to long plate thickness of the material to be welded exceeding 22 mm, the back bead and the front bead shape are good, and the amount of spatter generation is small, A sound weld metal without welding defects such as poor fusion and slag inclusion can be obtained with high efficiency.

It is a figure which shows the groove part of the to-be-welded material used for the 3 electrode single-sided gas shielded arc welding method of this invention.

In order to solve the above problems, the inventors of the present invention have a three-electrode single-sided gas shielded arc welding method for a material to be welded having a plate thickness of more than 22 mm, the back bead and the front bead shape are good, and the amount of spatter is small, Detailed studies were conducted in order to obtain a sound weld metal with high efficiency without welding defects such as fusion failure and slag inclusion.

FIG. 1 shows a groove portion of a material to be welded used in a three-electrode single-sided gas shielded arc welding method to which the present invention is applied. The backing material 2 is brought into contact with the back surface 1a of the material 1 to be welded, and the material 1 to be welded is used as a groove having a groove angle θ, and the steel grains 3 are filled in the groove bottom portion 4. G indicates a gap.

As a result of various studies using the material to be welded 1, the backing material 2 was brought into contact with the back surface 1a of the material to be welded 1, and the groove angle θ, the filling height of steel grains, the distance between electrodes, the welding current density of each electrode. By limiting the number of swings of each electrode, the shape of the back bead and front bead is good, the amount of spatter is small, and there is no welding defect such as fusion failure or slag entrainment. I found that.

Further, by limiting the types of the leading electrode wire, the intermediate electrode wire and the trailing electrode wire and the amount of the slag forming agent, the shape of the back bead and the front bead, the defect resistance is further improved, and the polarity of the intermediate electrode is set to the wire. It was also found that the amount of spatter generated is further reduced by setting it to a negative value.

Hereinafter, each limitation reason of the three-electrode one-sided gas shielded arc welding method of the present invention will be described in detail.

[V- or Y-shaped groove with a groove angle of 30 to 55°]
By setting the groove angle θ of the material to be welded 1 to 30 to 55°, the back bead is uniform and the shape is also good. If the groove angle θ is less than 30°, no back bead appears or the bead shape is non-uniform, resulting in a defect. Further, when the groove angle θ is less than 30°, hot cracking easily occurs. On the other hand, when the groove angle θ of the material to be welded 1 exceeds 55°, the back bead comes out too much and the melt-through easily occurs. Further, when the groove angle θ of the material to be welded 1 exceeds 55°, the groove cross-sectional area becomes large, so that it becomes difficult to perform single-sided gas shield arc welding by three-electrode one-pass welding. Therefore, the groove angle θ of the workpiece 1 is set to 30 to 55°.

When the gap G is provided at the bottom of the groove, the gap is 5 mm or less. If the gap G exceeds 5 mm, the back bead tends to come out too much, and melt-through tends to occur. In addition, the root face in the case of the Y groove is 3 mm or less. If the root face exceeds 3 mm, the back bead tends to be uneven. Furthermore, when the groove surface is temporarily attached, it is preferable that the distance from the back surface 1a of the material 1 to be welded is 7 mm or less in order to stably expose the back bead.

It is preferable to use a ceramic solid backing material as the backing material 2 because it is not necessary to use a magnet or a restraining jig, but the same applies even if a copper plate backing material or a flux copper backing material used in combination with a glass tape is used. The effect is obtained.

[Filling steel particles to 1/5 to 1/2 of the thickness of the material to be welded]
By filling the groove with 1 to 5 to 1/2 of the material to be welded, the arc is stable, the back bead is uniform, and the shape is good. When the filling of the steel grain 3 into the groove is less than ⅕ of the plate thickness t of the material 1 to be welded, the back bead tends to come out too much and melt-through tends to occur. On the other hand, when the filling of the steel grain 3 into the groove exceeds 1/2 of the plate thickness t of the material to be welded 1, no back bead appears or the back bead shape becomes defective.

The grain size of the steel grains 3 is preferably 1.5 mm or less in order to improve the stability of the arc and the shape of the back bead. In addition, although the component is mainly Fe, C is preferably 0.10% by mass or less, S and P are preferably 0.020% by mass or less in mass% based on the total mass of the steel grains 3 due to cracking resistance, and other components. In consideration of the strength and toughness of the weld metal, Si, Mn, Mo, and other deoxidizing agent or alloying agent can be added. Granules obtained by cutting steel wires of various sizes may be used as long as they satisfy the above grain sizes and components.

[The electrode distance between the leading electrode wire and the intermediate electrode wire and the electrode distance between the intermediate electrode wire and the trailing electrode wire are 80 to 300 mm, respectively]
When the distance between the electrodes of the preceding electrode wire (hereinafter referred to as the L pole) and the intermediate electrode wire (hereinafter referred to as the T1 pole) is 80 to 300 mm, the arcs of the L pole and the T1 pole are stable and the amount of spatter generation is small. In addition, the back bead is uniform and the shape is good. If the distance between the electrodes of the L pole and the T1 pole is less than 80 mm, the arc of the L pole and the T1 pole becomes unstable, and the amount of spatter generated increases. On the other hand, if the distance between the electrodes of the L pole and the T1 pole exceeds 300 mm, the welding device becomes large, which is not preferable. Therefore, the inter-electrode distance between the leading electrode wire and the intermediate electrode wire is 80 to 300 mm.

When the electrode distance between the T1 pole and the trailing electrode wire (hereinafter referred to as the T2 pole) is 80 to 300 mm, the arc of the T1 pole is particularly stable and the amount of spatter is reduced. If the distance between the electrodes of the T1 pole and the T2 pole is less than 80 mm, the arc of the T1 pole becomes unstable and the amount of spatter generated increases. On the other hand, if the distance between the electrodes of the T1 pole and the T2 pole exceeds 300 mm, the welding apparatus becomes large, which is not preferable. Therefore, the inter-electrode distance between the intermediate electrode wire and the trailing electrode wire is 80 to 300 mm.

[Current density of the leading electrode wire: 250 A/mm ² or more]
By setting the current density of the L pole to 250 A/mm ² or more, the back bead is uniform and the bead shape is good. If the current density of the L pole is less than 250 A/mm ² , the back bead shape becomes defective. The upper limit of the current density of the L pole is preferably 350 A/mm ² in terms of crack resistance. Further, the wire diameter of the L pole is preferably 1.4 to 1.6 mm from the viewpoint of high welding current density per wire cross-sectional area and crack resistance.

[Current density of intermediate pole wire: 220 A/mm ² or more]
By setting the current density of the T1 electrode to 220 A/mm ² or more, it is possible to prevent the groove toe portion of the weld metal of the L electrode from being completely melted and causing fusion failure. If the current density of the T1 pole is less than 220 A/mm ² , fusion failure easily occurs at the groove toe of the weld metal of the L pole.

The upper limit of the current density of the T1 pole is preferably 320 A/mm ² or less in order to suppress the spatter generation amount. Further, the wire diameter of the T1 pole is preferably 1.2 to 1.6 mm so that the welding current density per wire sectional area is relatively high and the arc is stabilized.

[Current density of trailing electrode wire: 200 A/mm ² or more]
By setting the current density of the T2 pole to 200 A/mm ² or more, it is possible to prevent the groove toe of the weld metal of the T1 pole from being completely melted and causing fusion failure. If the current density of the T2 pole is less than 200 A/mm ² , fusion failure is likely to occur at the groove toe of the weld metal of the T1 pole.

The upper limit of the current density of the T2 pole is preferably 300 A/mm ² or less in order to improve the shape of the front bead. The wire diameter of the T2 pole is preferably 1.2 to 1.6 mm in order to improve the shape of the front bead.

[Pulsating of the preceding electrode wire: 65 to 115 times/minute]
By setting the swing of the L pole to 65 to 115 times/minute, the back bead is uniformly exposed and the bead shape is also improved. If the oscillation of the L pole is less than 65 times/minute, the waveform of the back bead becomes rough and a good back bead cannot be obtained. On the other hand, when the swing of the L pole exceeds 115 times/minute, the arc becomes unstable and a good back bead cannot be obtained.

The number of times of rocking is one reciprocating motion of the L pole. The swing width (oscillate width) of the L pole is preferably 3 to 5 mm in order to obtain a good back bead.

[Wobble of intermediate electrode wire: 30 to 90 times/minute]
By setting the oscillation of the T1 pole to 30 to 90 times/minute, it is possible to prevent the groove toe of the weld metal of the L pole from being completely melted and causing a fusion failure. When the swing of the T1 pole is less than 30 times/minute, fusion failure easily occurs at the groove toe of the weld metal of the L pole. On the other hand, when the oscillation of the T1 pole exceeds 90 times/minute, the arc becomes unstable and the amount of spatter generated increases.

The swing width of the T1 pole is preferably 6 to 10 mm in order to completely melt the groove toe of the weld metal of the L pole.

[Following electrode wire swing: 30 to 90 times/minute]
By setting the oscillation of the T2 pole at 30 to 90 times/minute, the shape of the front bead becomes good. If the oscillation of the T2 pole is less than 30 times/minute, the waveform of the front bead becomes rough and the bead shape becomes defective. On the other hand, when the oscillation of the T2 pole exceeds 90 times/minute, the arc becomes unstable and the shape of the front bead becomes defective.

The swing width of the T2 pole is preferably 6 to 10 mm in order to completely melt the groove toe of the weld metal of the T1 pole.

[Leading electrode wire: solid wire]
It is more preferable to use a solid wire for the L pole because the back bead is likely to come out and the bead shape is stabilized. When a metal-based flux-cored wire is used for the L pole, the range of conditions for obtaining a good back bead shape is somewhat narrowed. In addition, when a rutile flux-cored wire is used for the L pole, the back bead is not likely to come out or the bead shape tends to be defective. Therefore, the leading electrode wire is preferably a solid wire, but is not limited to this.

In the solid wire component, C is 0.10 mass% or less from the crack resistance, Si is 0.5 to 1.5 mass% from the improvement of the deoxidizing agent and the bead shape, and Mn is based on the total mass of the wire. It is preferable that the deoxidizer, crack resistance and mechanical performance are contained in an amount of 1.5 to 2.5% by mass, and that Ti is contained in an amount of 0.1 to 0.5% by mass in order to secure the toughness of the weld metal. Further, it is also preferable that Mo is contained in an amount of 1.5% by mass or less in order to secure the strength of the weld metal, and that B is contained in an amount of 0.01% by mass or less in order to secure the toughness of the weld metal.

[Intermediate electrode wire: Metal-based flux-cored wire in which the total amount of slag forming agent is 1% by mass or less based on the total mass of the wire]
Since the arc is most likely to become unstable at the T1 pole, it is preferable to use a metal-based flux-cored wire in which the total amount of the slag forming agent composed of an oxide and a fluorine compound is 1% by mass or less based on the total mass of the wire. If the total amount of the slag forming agent composed of an oxide and a fluorine compound exceeds 1%, the amount of slag produced increases, and the slag may not be completely melted at the T2 pole, and slag entrainment defects are likely to occur. On the other hand, when a solid wire is used for the T1 pole, the arc becomes unstable and the amount of spatter generated increases. Therefore, the intermediate electrode wire is preferably a metal-based flux-cored wire in which the total amount of the slag forming agent is 1% by mass or less with respect to the total mass of the wire, but the present invention is not limited to this.

The slag forming agent includes oxides such as SiO ₂ , TiO ₂ , Al ₂ O ₃ , Na ₂ O and K ₂ O and fluorine compounds such as NaF, AlF ₃ , Na ₃ AlF ₆ and Na ₂ SiF ₆ . It means the total. Others of the metal-based flux-cored wire are metal Si, Fe-Si, metal Mn, Fe-Mn, Fe-Si-Mn, Fe-Ti, Fe-Al, Al-Mg, iron powder and other metal and alloy powders. is there.

[Subsequent electrode wire: rutile flux-cored wire containing 4 to 9 mass% of the total amount of slag-forming agent with respect to the total mass of the wire]
For the T2 pole, it is preferable to use a rutile-based flux-cored wire containing the total amount of the slag forming agent in an amount of 4 to 9 mass% with respect to the total mass of the wire in order to improve the shape of the surface bead. If the total amount of the slag forming agent is less than 4% by mass, the slag encapsulation property will be poor and the shape of the surface bead will be poor. On the other hand, when the total amount of the slag forming agent exceeds 9% by mass, the amount of slag produced increases and the slag entrapment defect is likely to occur. Therefore, it is preferable that the trailing electrode wire is a rutile-based flux-cored wire containing the total amount of the slag forming agent in an amount of 4 to 9 mass% with respect to the total mass of the wire, but is not limited thereto.

The slag forming agent contains TiO ₂ in an amount of 3 to 6% by mass, and the others include oxides such as SiO ₂ , Al ₂ O ₃ , Na ₂ O and K ₂ O, NaF, AlF ₃ , Na ₃ AlF ₆ , The total of fluorine compounds such as Na ₂ SiF ₆ . In addition, in order to adjust the strength and toughness of the weld metal, the rutile-based flux-cored wire may be made of metal Si, Fe-Si, metal Mn, Fe-Mn, Fe-Si-Mn in addition to the oxide and fluorine compound. , Fe-Ti, Fe-Al, Al-Mg, iron powder and other metal and alloy powders.

[The polarity of the intermediate electrode wire is minus wire]
The polarity of the electrode of gas shielded arc welding is generally wire plus (hereinafter referred to as DCEP), which has good welding workability and provides a penetration depth. The three-electrode single-sided gas shielded arc welding method of the present invention is used. In the above, since the arc is unstable at the T1 pole and the amount of spatter is increased, it is preferable that the polarity of the T1 is wire minus (hereinafter referred to as DCEN) to stabilize the arc and suppress the amount of spatter.

The shield gas used in the three-electrode one-sided gas shielded arc welding method to which the present invention is applied is CO ₂ gas or the like.

Hereinafter, the effects of the present invention will be specifically described with reference to examples.

The steel plate having the composition shown in Table 1 is processed into the V or Y groove shown in Tables 6 and 7, and the ceramic solid backing material is brought into contact with the groove back surface, and the steel particles of the composition shown in Table 2 are filled in the groove. Then, using the solid wire shown in Table 3, the metal flux-cored wire shown in Table 4 and the rutile flux-cored wire shown in Table 5, three-electrode single-sided gas shielded arc welding under various conditions shown in Table 6 and Table 7. Was carried out. Carbon dioxide was used as the shield gas, and the flow rate was 50 l/min for each electrode. The length of the test body was 1500 mm. In Tables 6 and 7, the inter-electrode distance between the leading electrode wire (L) and the intermediate electrode wire (T1) is shown in the column of T1 between the intermediate electrode wire (T1) and the trailing electrode wire (T2). The distance between each is described in the column of T1.

The items investigated were the stability of the arc of each electrode, the amount of spatter, the shape of the back bead, and the shape of the front bead, and then an X-ray transmission test was conducted to examine the presence or absence of welding defects. In the test with a defect, the defect location was cut and the defect occurrence position and the defect type were investigated. The results are shown in Table 8.

Test Nos. in Tables 6 and 8 1-test No. Test No. 9 in the invention example, Table 7 and Table 8. 10-Test No. 20 is a comparative example. Test No. which is an example of the present invention. 1, test No. 2 and test No. 6-test No. 9 is the groove angle, the height of filling of steel grains, the distance between the electrodes of the L pole and the T1 pole, the distance between the electrodes of the T1 pole and the T2 pole, the current density of the L pole and the number of oscillations, the current density of the T1 pole and the oscillation. The number of movements, the current density and the number of oscillations of the T2 pole are within the ranges specified in the present invention, the L pole is a solid wire, the T1 pole is a metal-based flux-cored wire containing an appropriate amount of a slag forming agent, and the T2 pole is a slag. Using a rutile flux cored wire with an appropriate amount of forming agent, and the polarity of the T1 pole is DCEN, the arc is stable at each electrode, the amount of spatter is small, and the shapes of the back bead and front bead are good and welded. There were no defects and the results were extremely satisfactory.

The test No. In No. 3, since the metal-based flux-cored wire having the wire symbol M2 was used for the L pole, the back bead shape was somewhat unstable. In addition, the test No. In No. 4, since the solid wire with the wire symbol S2 was used for the T1 pole, the amount of spatter generated in the T1 pole was rather large. Furthermore, the test No. In No. 5, since the polarity of the T1 pole was DCEP, the arc of the T1 pole was rather unstable and the amount of spatter generated was rather large.

In addition, the test No. 1-test No. As a result of separately investigating the mechanical performance of the weld metal for No. 9, the tensile test (JIS Z 2201 A2) has a tensile strength of 550 to 620 MPa in the central portion of the plate thickness, and the impact test (JIS Z 22024 No.) has a front surface. The absorbed energy of 2 mm below was 100 to 140 J at a test temperature of 0° C., and the absorbed energy of 2 mm below the back surface was 60 to 100 J at 0° C.

Comparative Example Medium Test No. In No. 10, since the groove angle θ was narrow, the shape of the back bead was not uniform and hot cracking occurred. Further, since the polarity of the T1 pole is DCEP, the arc of the T1 pole was rather unstable and the amount of spatter generated was rather large.

Test No. For No. 11, since the groove angle θ was wide, the back bead came out too much and melted down, so welding was stopped.

Test No. In No. 12, since the filling height of the steel grains was low, the back bead came out too much and melted down. Therefore, welding was stopped.

Test No. In No. 13, since the filling height of the steel particles was high, the back bead did not come out. Further, since the total amount of the slag forming agent of the rutile flux-cored wire having the wire symbol F6 of the T2 pole was large, a slag inclusion defect was generated in the groove portion of the final layer.

Test No. In No. 14, since the distance between the electrodes of the L pole and the T1 pole was short, the arc of the L pole and the T1 pole was unstable, and the amount of spatter generated was large. Further, since the metal flux-cored wire containing a large amount of the slag forming agent with the wire symbol M4 was used for the T1 pole, a slag inclusion defect was generated in the groove portion of the final layer.

Test No. In No. 15, since the electrode distance between the T1 pole and the T2 pole was short, the arc of the T1 pole was unstable and the amount of spatter generated was large. Further, since the rutile flux-cored wire having the wire symbol F1 was used for the L pole, the shape of the back bead was poor. Further, since the rutile flux-cored wire with a small slag forming agent having the wire symbol F5 was used for the T2 pole, the shape of the front bead was poor.

Test No. In No. 16, since the current density of the L pole was low, the back bead did not appear. Further, since the number of times the T1 pole rocked was small, fusion failure occurred in the groove portion of the second layer. Furthermore, since the polarity of the T1 pole is DCEP, the arc of the T1 pole was rather unstable and the amount of spatter generated was rather large.

Test No. In No. 17, since the current density of the T1 pole was low, fusion failure occurred in the groove portion of the second layer. Moreover, since the metal flux cored wire with the wire symbol M2 was used for the L pole, the back bead was not stable.

Test No. In No. 18, since the current density of the T2 pole was low, fusion failure occurred in the groove portion of the final layer. Further, since the T1 pole oscillates frequently, the arc is unstable and the amount of spatter is large.

Test No. In No. 19, the number of oscillations of the L pole was small, so the waveform of the back bead became rough. Further, since the number of times the T2 pole rocked was small, the waveform of the front bead became rough.

Test No. In No. 20, since the L pole oscillated many times, the arc of the L pole was unstable and the shape of the back bead was poor. In addition, since the T2 pole was oscillated many times, the arc of the T2 pole was unstable and the shape of the front bead was poor.

1 Welded material 2 Backing material 3 Steel grain 4 Groove bottom

Claims (3)

A three-electrode single-sided gas shielded arc welding method, in which a backing material is brought into contact with a V- or Y-shaped grooved rear surface having a groove angle of 30 to 55° in a welded material to perform three-electrode single-sided gas shielded arc welding,
Filling the groove with steel grains to a height of 1/5 to 1/2 of the thickness of the material to be welded,
The electrode distance between the leading electrode wire and the intermediate electrode wire, and the electrode distance between the intermediate electrode wire and the trailing electrode wire are each 80 to 300 mm,
The welding current density of the leading electrode wire is 250 A/mm ² or more, the welding current density of the intermediate electrode wire is 220 A/mm ² or more, and the welding current density of the trailing electrode wire is 200 A/mm ² or more,
And a three-electrode single-sided gas shielded arc welding method, characterized in that the oscillation of the leading electrode wire is welded at 65 to 115 times/minute and the oscillation of the intermediate electrode wire and the trailing electrode wire are welded at 30 to 90 times/minute, respectively. .. The leading electrode wire is a solid wire, the intermediate electrode wire is a metal flux-cored wire in which the total amount of the slag forming agent is 1% by mass or less based on the total weight of the wire, and the trailing electrode wire is the slag forming agent based on the total weight of the wire. The three-electrode single-sided gas shielded arc welding method according to claim 1, wherein a rutile flux-cored wire containing a total of 4 to 9 mass% is used. The three-electrode single-sided gas shielded arc welding method according to claim 1 or 2, wherein the polarity of the intermediate electrode wire is negative.

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