JP7388969B2 - Tandem gas shielded arc welding method and welding equipment - Google Patents

Description

The present invention relates to a tandem gas-shielded arc welding method and a welding device.

In fillet welding of longitudinal materials (reinforcing materials) in the field of shipbuilding, twin tandem one-pool methods and high-speed fillet welding methods using three electrodes have been developed in recent years for the purpose of speeding up welding. The twin tandem 1 pool method is a welding method in which electrodes are placed on both sides of a standing plate, the number of electrodes is 2, and one molten pool is formed by the two electrodes, and the same flux-cored wire is attached to both electrodes. The method used has been widely put into practical use.

On the other hand, as a welding method using such two electrodes, Patent Document 1 discloses a tandem gas shield arc welding method used in fields such as bridges and ships. The above welding method uses a solid wire for the leading electrode and a flux-cored wire for the trailing electrode, and adjusts the shielding gas, torch angle, arc voltage, welding current, wire protrusion length, etc. It is stated that as a result, the amount of spatter generated is small, undercuts do not occur, and deep penetration becomes possible.

Further, Patent Document 2 proposes a two-electrode horizontal fillet gas shield arc welding method used particularly for thick plate members. The welding method described in Patent Document 2 also uses a solid wire for the leading electrode and a flux-cored wire for the trailing electrode, and adjusts the distance between the leading electrode and the trailing electrode, the wire target position, and the wire diameter. It has been adjusted. This makes it possible to efficiently obtain fillet welds with long legs that have excellent porosity resistance, low spatter generation, good slag removability, bead shape, etc., and no welding defects such as insufficient penetration. Are listed.

Patent No. 6025627 Patent No. 6188626

By the way, in the fields of bridges and shipbuilding, a primer, which is an anti-rust paint, is often applied to the surface of a steel plate to be welded in order to prevent the steel plate from rusting. This primer is vaporized by the heat of the arc, and gas is generated that enters the molten pool. At this time, if the gas cannot escape from the molten pool to the outside air, pore defects will occur, the appearance will deteriorate significantly, and a rework process will be required. Therefore, in horizontal fillet gas shielded arc welding applied in the bridge and shipbuilding fields, excellent porosity resistance is also required.

However, the welding method described in Patent Document 1 does not sufficiently consider pore defects caused by the primer. Further, in the above welding method, the torch angle θ _L of the leading electrode is 5≦θ _L <40°, and the welding torch approaches the lower plate during welding. Therefore, for example, when welding longitudinal materials to the outer skin of a ship, if the distance between adjacent longitudinal materials is small, the small angle of the welding torch may interfere with the group of torches used to weld adjacent longitudinal materials. Therefore, there is a problem that it becomes difficult to arrange the welding torch. Furthermore, when this welding method is applied to fillet welding of longitudinal materials in shipbuilding, there is a problem that strike-through is likely to occur if there is a gap of several mm between the upright plate and the lower plate. Therefore, there is a need for a welding method that satisfies the property of not causing welding defects even if a relatively large gap exists (hereinafter, such property is referred to as "gap resistance").

Furthermore, the welding method described in Patent Document 2 is a welding method that assumes welding of plate materials having a thickness of 30 mm or more, and obtains a welded part with a leg length of 8 mm or more. Even when applied to welding, it is not possible to simultaneously achieve an excellent bead shape and a reduction in pore defects. Therefore, no matter which of the welding methods described above is used, pore defects such as blowholes and pits occur due to the primer, and it is necessary to repair the pore defects after welding.

The present invention has been made in view of the above-mentioned circumstances, and provides a fillet welding method that has excellent pore resistance and gap resistance, has a good bead shape, and can be welded at high speed. The object of the present invention is to provide a tandem gas-shielded arc welding method and welding device.

As a result of intensive research, the present inventors found that if it were possible to use a solid wire for the leading electrode, dig deep into the molten pool to reduce the amount of unmelted material on the root surface, and release the primer gas to the outside from directly below the arc, It has been found that pore defects are significantly reduced. In addition, by appropriately determining the aiming position of the wire and appropriately controlling the relationship between the welding current and arc voltage of the leading electrode, the present inventors have ensured gap resistance and welding defects such as undercuts. It was also found that the occurrence of can be suppressed.

That is, the above object of the present invention is achieved by the following configuration [1] related to the tandem gas shielded arc welding method.
[1] Tandem gas-shielded arc for fillet welding a lower plate having a main surface and a vertical plate arranged in a direction intersecting the main surface of the lower plate using a leading electrode and a trailing electrode. A welding method,
using a solid wire as the leading electrode;
using a solid wire as the leading electrode;
using carbon dioxide gas as a shielding gas for the leading electrode,
The torch angle θ _L of the leading electrode formed by the main surface and the welding torch is 40°≦θ _L ≦60°,
The wire protrusion length E _L of the leading electrode is 10 mm≦E _L ≦20 mm,
A distance H _L from the root portion on the standing plate side to the wire target position of the leading electrode is 1 mm≦H _L ≦3 mm,
The welding current I _L (A) and the arc voltage V _L (V) of the leading electrode satisfy the following formula (1),
using a flux-cored wire as the trailing electrode;
using carbon dioxide gas as a shielding gas for the trailing electrode,
A torch angle θ _T between the welding torch of the main surface and the trailing electrode is 40°≦θ _T ≦60°,
The wire protrusion length E _T of the trailing electrode is 20 mm≦ _ET ≦30 mm,
A distance W _T from the root portion on the lower plate side to the wire target position of the trailing electrode is 1 mm≦W _T ≦5 mm,
An inter-electrode distance D between the leading electrode and the trailing electrode is 25 mm≦D≦45 mm,
A tandem gas shield arc welding method in which the welding speed is 800 mm/min or more.
50≦V _L ×1000/I _L ≦70...Formula (1)

Further, preferred embodiments of the present invention relating to the tandem gas shielded arc welding method relate to the following [2] and [3].
[2] The welding current _IL of the leading electrode is 350A≦ _IL ≦530A,
The tandem gas shield arc welding method according to [1], wherein the arc voltage V _L of the leading electrode is 22V≦V _L ≦33V.
[3] The welding current _IT of the trailing electrode is 250A≦ _IT ≦400A,
The tandem gas shield arc welding method according to [1] or [2], wherein the arc voltage _VT of the trailing electrode is 25V≦ _VT ≦38V.

Further, the above object of the present invention is achieved by the following configuration [4] related to the welding device.
[4] A welding device used in the tandem gas shielded arc welding method according to any one of [1] to [3].

According to the present invention, fillet welding has excellent pore resistance and gap resistance, can reduce the amount of spatter, has a good bead shape, and can be welded at high speed. Tandem gas shielded arc welding method and welding device can be provided.

FIG. 1 is a perspective view showing a tandem gas shield arc welding method according to an embodiment of the present invention. FIG. 2 is a perspective view showing an example of a tandem gas shield arc welding method in which the torch angle of the leading electrode side welding torch is made small. FIG. 3 is a sectional view showing the state of weld metal when fillet welding is performed with the welding torch angle θ _L on the leading electrode side being 45° and the wire aiming position P _L being the root portion. Figure 4 shows the state of the weld metal when fillet welding is performed with the welding torch angle θ _L on the leading electrode side being 45° and the distance H _L from the root part to the wire target position P _L on the standing plate side being 2 mm. FIG. FIG. 5 is a cross-sectional view for explaining the torch angle θ _T of the trailing electrode and the wire aiming position P _T in the tandem gas-shielded arc welding method according to the embodiment of the present invention.

Hereinafter, a tandem gas shield arc welding method according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that for convenience of explanation, the sizes and shapes of members may be exaggerated in the drawings, and depictions of some structures may be omitted.

First, a tandem gas shield arc welding method according to an embodiment of the present invention will be described with reference to FIG.

The tandem gas shielded arc welding method according to the present embodiment is formed between a lower plate 1 having a main surface 1a and a vertical plate 2 disposed in a direction crossing the main surface 1a of the lower plate 1. In this method, fillet welding is performed while injecting shielding gas (not shown) to the root portion 3 that has been welded. In addition, as shown in FIG. 1, in this embodiment, the lower plate 1 disposed horizontally and the standing plate 2 disposed perpendicularly to the main surface 1a of the lower plate 1 will be explained as an example. The vertical plate 2 may be arranged in a direction intersecting the main surface 1a of the lower plate 1, and is not necessarily limited to being perpendicular to the main surface 1a.

A leading electrode side welding torch 4a and a trailing electrode side welding torch 5a are arranged on one surface (principal surface) 2a side of the vertical plate 2. Further, a leading electrode side welding torch 4b and a trailing electrode side welding torch 5b are similarly arranged on the other surface 2b side of the vertical plate 2. The leading electrode side welding torches 4a, 4b and the trailing electrode side welding torches 5a, 5b are each connected to a welding power source (not shown), and are held at a predetermined torch angle. Then, by supplying electric power at a predetermined arc voltage and welding current to a predetermined target position between the lower plate 1 and the standing plate 2, which are the base materials, the wires 6a, 6b, 7a and An arc is formed between 7b and the wire aiming position.

Here, the torch angle θ _L is the angle formed by the main surface 1a of the lower plate 1 and the center line of the leading electrode side welding torches 4a, 4b, that is, the center line of the protruding portions that are the tips of the wires 6a, 6b. It is. Similarly, the torch angle θ _T is the angle formed by the main surface 1a of the lower plate 1 and the center line of the trailing electrode side welding torches 5a, 5b, that is, the center line of the protruding portions that are the tips of the wires 7a, 7b. It's an angle.

The lower plate 1 and the upright plate 2, which are base materials, are melted by the arc, and the wires 6a, 6b, 7a, and 7b are melted by Joule heat generated by the arc heat of the arc and the welding current flowing through the wires 6a, 6b, 7a, and 7b. is melted by Then, the molten wires 6a, 6b, 7a, and 7b are fused with the molten weld metal to form a welded portion.

Here, as a result of intensive studies, the present inventors have found that in tandem gas shielded arc welding for fillet welding, in order to obtain a welding method that has excellent pore resistance and gap resistance, and provides a good bead shape. teeth,
(a) Reducing the unwelded portion in the region S where the end surface 2c of the upright plate 2 and the main surface 1a of the lower plate 1 face each other,
(b) Set the distance H _L from the root part on the upright board side to the wire target position P _L to 1 to 3 mm, so that even if there is a gap between the upright board and the lower board, there will be no strike-through;
(c) Adjusting the arc voltage and welding current range in which undercut does not occur even if the target position _PL of the welding torch is set above the root part;
(d) optimizing the target position and distance between electrodes in order to shape the bead with the trailing electrode;
found that it is extremely important.

First, each condition in the leading electrode will be explained in detail.
[Leading pole]

<Solid wire using carbon dioxide gas as shielding gas>
The leading electrode wires 6a and 6b are made of inexpensive solid wires that do not contain expensive elements such as rare earth elements, and 100% carbon dioxide gas that does not contain expensive inert gases such as argon gas is used as the shielding gas. In the tandem welding method, two electrodes share the role of ensuring the depth of penetration with the leading electrode and adjusting the bead shape with the trailing electrode. Therefore, in this embodiment, a solid wire that can achieve deep penetration is used as the leading electrode. In fillet welding, deep or shallow penetration refers to penetration in the horizontal direction, that is, in the thickness direction of the standing plate 2, unless otherwise specified.

Furthermore, as will be explained in detail later, in this embodiment, the relationship between the arc voltage of the leading electrode and the welding current and other welding conditions are appropriately controlled, so even if 100% carbon dioxide gas welding is used. It can be spray-transferred, achieving low spatter without causing undercuts.

<Torch angle θ _L : 40°≦θ _L ≦60°, distance H _{L from the root part on the standing board side to the wire aiming position PL: 1 mm≦H L ≦} 3 mm>
The reasons for limiting the torch angle θ _L of the leading electrode and the wire aiming position P _L in the tandem gas shielded arc welding method will be explained with reference to FIGS. 2 to 4. Note that in FIGS. 2 to 4, the same content as in FIG. 1 is denoted by the same reference numeral, and detailed explanation thereof will be omitted.
FIG. 2 is a perspective view showing an example of a tandem gas shield arc welding method in which the torch angles of the leading electrode side welding torches 4a and 4b are made small. FIG. 3 is a cross-sectional view showing the state of weld metal when fillet welding is performed with the welding torch angle θ _L on the leading electrode side being 45 degrees and the wire aiming position P _L being the root part (distance H _L : 0 mm). . Figure 4 shows the state of the weld metal when fillet welding is performed with the welding torch angle θ _L on the leading electrode side being 45° and the distance H _L from the root part to the wire target position P _L on the standing plate side being 2 mm. FIG.

In the present specification, the root portion refers to the tangent between the main surface 1a of the lower plate 1 and the main surface 2a of the upright plate 2 or the surface 2b opposite to the main surface, and the root portion extends in the welding direction. There is. In addition, if there is a root gap between the lower plate 1 and the standing plate 2, the lower plate 1 will be A tangent to the principal surface 1a is defined as a root portion.

In the welding shown in FIG. 2, the torch angles θ _L of the leading electrode side welding torches 4a and 4b are both 20°, the torch angles θ _T of the trailing electrode side welding torches 5a and 5b are both 45°, and the wire aiming position Both P _L and P _T are root parts.
Here, this embodiment assumes tandem gas-shielded arc welding, which is suitable for fillet welding of longitudinal materials in the field of shipbuilding. Therefore, if the torch angle θ _L of the leading electrode side welding torches 4a, 4b is less than 40°, for example, 20°, and the distance between adjacent longitudinal members (corresponding to the standing plates 2 in FIG. 2) is small, This will interfere with the group of torches used to weld adjacent longitudinal materials, making it difficult to arrange the welding torches. In addition, when a gap of several mm is created between the upright plate 2 and the lower plate 1, strike-through is likely to occur.

On the other hand, if the torch angle θ _L of the leading electrode exceeds 60°, deep penetration cannot be obtained regardless of the aiming position P _L of the wire. Therefore, in the welding method according to the present embodiment, the torch angle θ _L of the leading electrode is set to 40° or more and 60° or less.

As shown in FIG. 3, even when the torch angle θ _L of the leading electrode is set to 45 degrees, for example, the target position P _L of the wires 6 a and 6 b is set to the root portion 3 in order to obtain deep penetration. When set, unmelted residue is generated in the region S where the end surface 2c of the vertical plate 2 and the main surface 1a of the lower plate 1 face each other, and the primer present in this region S is vaporized, causing pore defects 9 in the weld metal 8. will occur.

Therefore, in this embodiment, it is further necessary to appropriately select the wire aiming position _PL . That is, as shown in FIG. 4, the torch angle θ _L is set as described above, and the distance (height) H _L from the root portion on the upright plate side to the wire aiming position P _L is set to 1 mm or more and 3 mm or less. As a result, it is possible to reduce the amount of unmelted material remaining in the region S where the end surface 2c of the vertical plate 2 and the main surface 1a of the lower plate 1 face each other, and it is possible to prevent the occurrence of pore defects in the weld metal 8. can.

Note that the inclination angle of the leading electrode side welding torches 4a, 4b with respect to the welding direction, that is, the angle φ _L formed by the center line of the leading electrode side welding torches 4a, 4b and a plane normal to the welding direction is particularly limited. Although it is not a specific matter, it is preferable to set the receding angle to 0° or more and 15° or less, taking into consideration the amount of spatter generated and the bead shape.

<Relationship between welding current I _L (A) and arc voltage V _L (V): satisfy formula (1)>
Generally, in welding using 100% carbon dioxide gas, an arc is generated from below the droplet formed at the tip of the molten wire, so the droplet is difficult to separate from the wire and becomes coarse. This results in a globular transition in which the molten metal moves while oscillating. When globule transfer occurs, a large amount of spatter is generated, and the welding current _IL also varies greatly depending on the droplet transfer, so the arc force also varies from moment to moment. Further, if the wire aiming position _PL is set above the root portion, undercuts are likely to occur on the surface of the upright plate 2 when welding is performed under normal welding conditions.

Therefore, in this embodiment, by controlling the ratio of the arc voltage V _L (V) to the welding current I _L (A) to a range that satisfies the following formula (1), it is possible to ensure deep penetration while reducing the welding current I L (A). To realize a welding method that enables sputter welding and does not cause undercuts. In other words, by satisfying formula (1), it is possible to form an arc around the droplet rather than under it, resulting in spray transfer even with 100% carbon dioxide welding, achieving extremely low spatter welding. and no undercuts occur.
50≦V _L ×1000/I _L ≦70...Formula (1)

The following relationship exists between each parameter in the above formula (1) and the welding characteristics.
(A) If the arc voltage _VL is too high, spray transfer cannot be maintained and globular transfer occurs, resulting in a large amount of spatter. Also, undercuts are more likely to occur.
(B) If the welding current _IL is too low, the arc force of the leading electrode becomes weak and the penetration becomes shallow.
(C) If the arc voltage _VL is too low, the arc cannot be maintained stably, making it difficult to obtain a good bead shape.
(D) If the welding current _IL is too high, the arc force becomes too large, making it difficult to obtain a good bead shape.
Therefore, in this embodiment, the value obtained by the above formula (1) is set to 70 or less, preferably 65 or less. Further, the value obtained by the above formula (1) is set to be 50 or more. As a result, it is possible to maintain spray transfer, reduce spatter, suppress the occurrence of undercuts, maintain a good bead shape, and obtain deep penetration.

<Wire protrusion length _EL : 10mm≦ _EL ≦20mm>
The wire protrusion length E _L affects the welding current I _L and the wire melting rate. Here, the wire protrusion length E _L is, for example, the length from the contact tip 11a for supplying current to the wire 6a to the base metal at the tip of the leading electrode side welding torch 4a shown in FIG. .
For example, when the welding current I _L is constant, the shorter the wire protrusion length E _L , the lower the wire melting rate, which is advantageous for deep penetration. However, when the welding current I _L is made variable, if the wire protrusion length E _L is less than 10 mm, the arc force of the leading electrode becomes too strong, resulting in poor bead shape. On the other hand, when the wire protrusion length E _L exceeds 20 mm, the wire melting rate becomes excessive and the penetration becomes shallow. Therefore, the wire protrusion length E _L of the leading electrode is set to 10 mm or more and 20 mm or less. Note that it is preferably 12 mm or more and 18 mm or less.

<Welding current _IL : 350A≦ _IL ≦530A, arc voltage _VL : 22V≦ _VL ≦33V>
In this embodiment, the desired effect can be obtained by setting the ratio between the arc voltage V _L (V) of the leading electrode and the welding current I _L (A) to a range that satisfies the above formula (1). , arc voltage V _L (V), and welding current I _L (A), it is possible to obtain even better pore resistance and bead shape.

When the welding current _IL is 350 A or more, the penetration becomes deeper and the effect of suppressing the occurrence of unmelted material or pore defects becomes higher. Further, when the welding current _IL is 530 A or less, the arc force of the leading electrode can be appropriately adjusted, and a better bead shape can be obtained. Therefore, it is preferable that the welding current _IL is 350 A or more and 530 A or less.

Further, when the arc voltage V _L is 22 V or more, an even better bead shape can be obtained, and when the arc voltage V _L is 33 V or less, the amount of spatter generated can be appropriately suppressed, and undercuts etc. The effect of preventing occurrence is increased. Therefore, it is preferable that the arc voltage _VL is 22V or more and 33V or less.

Next, each condition at the trailing pole will be explained in detail.
[Posterior pole]

<Flux-cored wire using carbon dioxide as shielding gas>
As shown in FIG. 1, in this embodiment, flux-cored wires are used as the trailing electrode wires 7a and 7b, and 100% carbon dioxide gas is used as the shielding gas. Welding with a trailing electrode using a flux-cored wire has the effect of adjusting the bead shape of the weld metal obtained with the leading electrode.

<Torch angle _θT : 40°≦ _θT ≦60°, distance from the root part on the lower plate side to the wire target position _PT : 1mm≦ _WT ≦5mm _>
Referring to FIG. 5, the torch angle θ _T of the trailing electrode and the wire aiming position P _T in the tandem gas shielded arc welding method will be described. In FIG. 5, the same content as in FIG. 1 is given the same reference numeral, and detailed explanation thereof will be omitted.
In this embodiment, the torch angle θ _T of the trailing electrode side welding torches 5a and 5b is set to an angle of 40° or more and 60° or less, preferably 45° or more and 55° or less. Thereby, the bead formed by the leading electrode can be flattened and shaped into a good bead shape.

Note that the inclination angle of the trailing electrode with respect to the welding direction, that is, the angle _φT formed by the center line of the trailing electrode and the plane normal to the welding direction, is not particularly limited, but it depends on the amount of spatter generated and In consideration of the bead shape, it is preferable to set the advancing angle to 0° or more and 25° or less.

In this embodiment, it is further necessary to appropriately select the wire target position _PT of the trailing pole. That is, as shown in FIG. 5, the distance W _T from the root portion 3 on the lower plate side to the wire target position P _T is set to be 1 mm or more and 5 mm or less. Thereby, the bead formed in the leading electrode can be flattened and formed into a good bead shape.

<Wire protrusion length _ET : 20mm≦ _ET ≦30mm>
The wire protrusion length E _T influences the welding current I _T and the wire melting rate. Similar to the leading electrode, the wire protrusion length _ET of the trailing electrode is defined as the wire protrusion length ET of the trailing electrode from the contact tip 12a for supplying current to the wire 7a to the base metal at the tip of the trailing electrode side welding torch 5a shown in FIG. The length is up to.
If the wire protrusion length _ET of the trailing electrode is less than 20 mm, the amount of wire melting will be insufficient.
Furthermore, if the wire protrusion length _ET of the trailing electrode exceeds 30 mm, the arc tends to become unstable.
Therefore, the wire protrusion length _ET should be 20 mm or more and 30 mm or less, preferably 23 mm or more and 28 mm or less.

<Welding current I _T :250A≦I _T ≦400A, arc voltage V _T :25V≦V _T ≦38V>
For the trailing electrode as well, by appropriately controlling the arc voltage V _T (V) and welding current I _T (A), it is possible to form a bead with an even better shape and to suppress the occurrence of welding defects. can do.
When the welding current _IT is 250 A or more and 400 A or less, the arc can be further stabilized and an excellent bead shape can be obtained. Further, when the arc voltage V _T is 25 V or more, an even better bead shape can be obtained, and when it is 38 V or less, the amount of spatter generation can be appropriately suppressed, and welding defects can be prevented. be able to. Therefore, the welding current _IT is preferably 250 A or more and 400 A or less, and the arc voltage V _T is preferably 25 V or more and 38 V or less.
[Interelectrode distance D between leading electrode and trailing electrode: 25mm≦D≦45mm]
In this embodiment, it is further necessary to appropriately set the distance between the electrodes. In other words, when the distance between the electrodes is as small as less than 25 mm, and the leading electrode satisfies formula (1), the shape of the pool formed between each arc will change, and the final bead shape will also vary. It becomes stable and no deep penetration effect can be obtained. Furthermore, if the distance between the electrodes exceeds 45 mm, the arc of the trailing electrode will pass through after the molten pool of the leading electrode has solidified, so that the molten pools of the two arcs will separate. As a result, the shaping effect of the bead shape by the trailing electrode is lost, making high-speed welding impossible.
Therefore, the inter-electrode distance D between the leading electrode and the trailing electrode is set to 25 mm or more and 45 mm or less.

[Welding speed: 800mm/min or more]
In this embodiment, since fillet welding is performed using two electrodes on one side, welding can be performed at a high welding speed of 800 mm/min or more, and excellent construction efficiency can be obtained. Note that if the welding speed is less than 800 mm/min, the amount of weld metal increases excessively, the bead appearance deteriorates, and deep penetration effect cannot be obtained. Therefore, the welding speed is set to 800 mm/min or more.

In this embodiment, the welding power source is not particularly limited, and may be either a DC power source or an AC power source. However, from a general-purpose point of view, a DC power supply with constant voltage characteristics is preferable. Further, the materials of the lower plate and the upright plate are not limited, and they may be coated with paint such as a primer. Further, the thickness of the vertical plate is not particularly limited, but since the commonly used plate thickness ranges from 6 to 16 mm, it is preferable that the upper limit is 16 mm and the lower limit is 6 mm. Furthermore, the diameter of the welding wire is also not particularly limited, but in this embodiment, preferably, the upper limit is 1.6 mm and the lower limit is 1.2 mm.

Although the tandem gas shield arc welding method according to the embodiment of the present invention has been described above, the present invention is also applied to a welding device used in the tandem gas shield arc welding method according to each embodiment described above.

The present invention will be described in detail below with reference to invention examples and comparative examples, but the present invention is not limited thereto.

[Tandem gas shield arc welding]
As shown in FIG. 1, the vertical plate 2 is installed vertically to the main surface 1a of the lower plate 1 arranged horizontally, and the leading electrode side welding torches 4a, 4b and the trailing electrode side welding torches 5a, 5b are installed vertically. Fillet welding was performed under various welding conditions while injecting shielding gas. For the leading electrode and the trailing electrode, the torch advancing angle and receding angle were both 7°, the wire diameter was 1.6 mm, and 100% CO ₂ gas was used as the shielding gas. Further, as the solid wire, a wire satisfying the chemical components of C≦0.10% by mass, P≦0.025% by mass, and S≦0.025% by mass was used. Further, as the flux-cored wire, a wire satisfying the chemical components of 3.5% by mass≦TiO ₂ ≦9.0% by mass and 0.1% by mass≦ZrO ₂ ≦2.5% by mass was used. Furthermore, the thickness of the base materials (lower board 1 and upright board 2) was 12 mm, and the material used was SM490A. Further, a primer was applied to the surface of the base material to an average thickness of 30 μm.

The welding conditions, interelectrode distance, and welding speed for each of the leading electrode and trailing electrode are shown in Tables 1 to 4 below. In addition, in Table 1 below, FCW described in the "Type of Wire" column indicates a flux-cored wire (Flux Cored Wire). In addition, the standing board side described in the item of distance from the root part to the target position indicates the distance H _L from the root part to the wire aiming position P _L on the standing board side, and the lower board side refers to the lower board side. The distance W _T from the root portion to the wire target position P _T in is shown.

[Evaluation test]
Comparative example no. 1 to 25 and invention example No. Evaluation tests for pore defects, gap resistance, and bead shape were conducted for Nos. 26 to 50. The test methods and evaluation criteria for each evaluation test are shown below, and the evaluation results are shown in Tables 5 and 6 below.

<Stomatal defects>
Pore defects were evaluated by taking a transmission photograph in accordance with the radiographic transmission test specified in Japanese Industrial Standards JIS Z 3104-1995 and checking whether bubbles were generated in the molten metal. As for the evaluation criteria, a case where no defect was confirmed was rated as ◯ (good), and a case where bubbles were generated and a defect was confirmed was graded as × (poor).

<Gap resistance>
Gap resistance was evaluated by arranging the lower plate 1 and the upright plate 2 with a gap of 2 mm, welding them under the tandem gas shield arc welding conditions described above, and observing the obtained weld metal. The evaluation criteria is 0 (good) if there is no bleed-through or sufficient cross-linking between the base materials, and if there is bleed-through or the base materials are not sufficiently cross-linked. was rated as × (defective).

<Bead shape>
The bead shape is determined by visually checking the surface appearance after peeling off the slag, and if there are no welding defects and the bead shape is good, it is marked as ○ (good), and if welding defects occur or the bead shape is unstable, it is rated as ○ (good). Those that were rated as × (defective).

As shown in Tables 2, 4 and 6 above, invention example No. 26 to 50, the type of wire, torch angle, target position, and wire protrusion length of the leading electrode and trailing electrode are within the scope of the present invention, and the relationship between the welding current and arc voltage of the leading electrode is expressed by the formula (1) is satisfied, and the distance between the electrodes and welding speed are within the range of the present invention, so welding can be performed at high speed, excellent pore resistance and gap resistance are obtained, and the bead shape is It was good.

On the other hand, as shown in Tables 1, 3, and 5, Comparative Example No. In Nos. 1 and 2, the value of formula (1) was large and the target position of the leading electrode was 5 to 6 mm on the lower plate side, so the unmelted area in region S was extremely large and a large amount of pore defects occurred. In addition, since the distance D between the electrodes is as large as 100 mm, the molten pools caused by the two arcs are separated from each other. As a result, high-speed welding became impossible, and comparative example No. In No. 2, since the welding speed was high, not only a large number of pore defects occurred, but also a normal bead was not formed.

Comparative example no. In Comparative Example Nos. 3 to 6, the torch angle of the leading electrode is less than the lower limit of the range of the present invention, and the wire aiming position of the leading electrode is the root portion (0 mm). Regarding No. 3, since the wire aiming position of the trailing electrode was also the root portion (0 mm), the gap resistance was poor in all cases.

Comparative example no. In Nos. 7 and 8, the torch angle of the leading electrode was less than the lower limit of the range of the present invention, and because it was aimed at 2 to 3 mm on the vertical plate side, there was a large amount of unmelted material in the region S, and a large number of pore defects occurred. In this case, the shape of the pool between the electrodes was not maintained stably, and the shape of the bead also deteriorated.

Comparative example no. In samples Nos. 9 and 10, since the wire target position of the leading electrode was the root portion (0 mm), the unmelted area in the region S became large and a pore defect occurred.

Comparative example no. In Comparative Example Nos. 11 and 12, the wire protrusion length of the leading electrode is outside the range of the present invention. Comparative Example Nos. 13 and 14 have inter-electrode distances outside the range of the present invention. In No. 15, the welding speed was less than the lower limit of the range of the present invention, so the bead shape was poor in all cases.

Comparative example no. In Nos. 16 to 18, the value of formula (1) is larger than the range of the present invention, and the undissolved area in the region S becomes large, which causes pore defects and undercuts, resulting in the bead shape changing. It became defective.

Comparative example no. In Nos. 19 to 25, the torch aiming position of the leading electrode is the root part (0 mm), and the wire protrusion length exceeds the upper limit of the range of the present invention, and the value obtained by formula (1) is also within the range of the present invention. exceeds the upper limit. Among them, Comparative Example No. In Comparative Example Nos. 19, 20, and 23, the wire aiming position of the trailing electrode is the root portion (0 mm). 23 to 25, the type of wire of the leading electrode is a flux-cored wire. Therefore, in both cases, the undissolved portion of the region S became large, and pore defects occurred.

1 Lower plate 2 Upright plate 3 Root part 4a, 4b Leading electrode side welding torch 5a, 5b Trailing electrode side welding torch 6a, 6b, 7a, 7b Wire 8 Weld metal 9 Pore defect

Claims (4)

A tandem gas shielded arc welding method in which a lower plate having a main surface and a vertical plate arranged in a direction intersecting the main surface of the lower plate are fillet welded using a leading electrode and a trailing electrode. There it is,
using a solid wire as the leading electrode;
using carbon dioxide gas as a shielding gas for the leading electrode,
The torch angle θ _L of the leading electrode formed by the main surface and the welding torch is 40°≦θ _L ≦60°,
The wire protrusion length E _L of the leading electrode is 10 mm≦E _L ≦20 mm,
A distance H _L from the root portion on the standing plate side to the wire target position of the leading electrode is 1 mm≦H _L ≦3 mm,
The welding current I _L (A) and the arc voltage V _L (V) of the leading electrode satisfy the following formula (1),
using a flux-cored wire as the trailing electrode;
using carbon dioxide gas as a shielding gas for the trailing electrode,
A torch angle θ _T between the welding torch of the main surface and the trailing electrode is 40°≦θ _T ≦60°,
The wire protrusion length E _T of the trailing electrode is 20 mm≦ _ET ≦30 mm,
A distance W _T from the root portion on the lower plate side to the wire target position of the trailing electrode is 1 mm≦W _T ≦5 mm,
An inter-electrode distance D between the leading electrode and the trailing electrode is 25 mm≦D≦45 mm,
A tandem gas shield arc welding method in which the welding speed is 800 mm/min or more.
50≦V _L ×1000/I _L ≦70...Formula (1) The welding current _IL of the leading electrode is 350A≦ _IL ≦530A,
The tandem gas shield arc welding method according to claim 1, wherein the arc voltage _VL of the leading electrode is 22V≦ _VL ≦33V. The welding current _IT of the trailing electrode is 250A≦ _IT ≦400A,
The tandem gas shield arc welding method according to claim 1 or 2, wherein the arc voltage _VT of the trailing electrode is 25V≦ _VT ≦38V. A welding device used in the tandem gas shielded arc welding method according to any one of claims 1 to 3.

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