JP7307025B2 - Multi-electrode gas-shielded arc single-sided welding method and multi-electrode gas-shielded arc single-sided welding apparatus - Google Patents

Description

The present invention relates to a multi-electrode gas-shielded arc single-sided welding method and a multi-electrode gas-shielded arc single-sided welding apparatus.

Single-sided welding is a welding method in which a refractory backing material is pressed against the back side of the groove of the butt joint, which is the material to be welded, and welding is performed from the front side of the groove to produce a back bead on the back side of the groove. . This allows full penetration to be obtained by welding from only one side without reversing the butt joint.
The efficiency of single-sided welding can be improved by increasing the welding current and reducing the cross-sectional area of the groove (narrowing the groove). However, as the current increases and the groove becomes narrower, the bead becomes more susceptible to hot cracks. Therefore, multi-electrode gas-shielded arc single-sided welding using multiple electrodes including a leading electrode and a trailing electrode instead of a single electrode has been proposed.

For example, in Patent Document 1, the polarities of the leading electrode and the trailing electrode are appropriately defined, and the wire projection length of the leading electrode, the welding current, the wire feed amount, etc., and the metal composition of the trailing electrode, etc. are appropriately adjusted. A multi-electrode gas-shielded arc single-sided welding method has been proposed.

Japanese Patent Application Laid-Open No. 2019-13980

By the way, as a method for evaluating hot cracking in a multi-electrode gas-shielded arc single-sided welding method, a C-shaped jig constrained butt weld cracking test method (JIS Z 3155: 1993) is known. In this test method, even if the welding method described in Patent Document 1 is used, cracks may occur at positions other than the crater. Therefore, there is a demand for a welding method that can further suppress the occurrence of hot cracks.
In addition, when welding a V-groove shape having a root gap, final welding is generally performed after tacking. .

The present invention has been made in view of such problems, and an object of the present invention is to provide a multi-electrode gas-shielded arc single-sided welding method capable of suppressing the occurrence of hot cracks while having a favorable back bead shape. .

In the conventional multi-electrode gas-shielded arc single-sided welding method, the inter-electrode distance between the leading electrode and the trailing electrode is set to 50 mm or less, and the molten pool is reheated with the trailing electrode before the molten pool is solidified by the leading electrode. This prevents the molten pool from forming two complete pools and improves hot cracking resistance. That is, it has been recognized that when the inter-electrode distance exceeds 50 mm, the hot cracking resistance deteriorates.
However, as a result of extensive research by the present inventors, the leading electrode weld pool was completely solidified, particularly by setting the inter-electrode distance between the leading electrode and the trailing electrode to 65 mm or more compared to the conventional welding method. It was found that since the trailing electrode melts again later, the melt pool does not become too large and crack resistance is significantly improved. The present inventors also found that the polarity of the trailing electrode, the welding current, and the filling amount of the groove filler affect the occurrence of hot cracks and the shape of the back bead.

Furthermore, the inventors have found that even when the inter-electrode distance between the leading electrode and the trailing electrode is 65 mm or less, the welding current and welding voltage of the leading electrode, and the wire type and polarity of the trailing electrode can be controlled. It has also been found that crack resistance and back bead shape are significantly improved by The present invention has been made based on these findings.

That is, the multi-electrode gas-shielded arc single-sided welding method according to the present invention has the following configuration [1].

[1] A multi-electrode gas-shielded arc single-sided welding method in which a groove formed by abutting a pair of plate materials is filled with a groove filler and welded using a plurality of electrodes arranged in a row in the welding line direction, ,
the plurality of electrodes includes a leading electrode and a trailing electrode following the leading electrode;
Polarity of the preceding electrode: DCEP,
wire type of the preceding electrode: flux-cored wire or solid wire;
Polarity of the trailing electrode: DCEN,
wire type of the trailing electrode: flux-cored wire;
Welding current of the trailing electrode: 180 A or more,
distance between the leading electrode and the trailing electrode: 65 mm or more and 150 mm or less;
Root gap of the groove: 3 mm or more and 8 mm or less,
Area of the portion occupied by the groove filler on the plane orthogonal to the weld line direction: 20 mm ² or more and 50 mm ² or less,
multi-electrode gas-shielded arc single-sided welding method.

Further, another multi-electrode gas-shielded arc single-sided welding method according to the present invention has the configuration of [2] below.

[2] A multi-electrode gas-shielded arc single-sided welding method in which a groove formed by abutting a pair of plate materials is filled with a groove filler and welded using a plurality of electrodes arranged in a row in the welding line direction, ,
the plurality of electrodes includes a leading electrode and a trailing electrode following the leading electrode;
Polarity of the preceding electrode: DCEP,
Wire type of the preceding electrode: solid wire,
Welding current of the preceding electrode: 500 A or less,
Welding voltage of the leading electrode: 40 V or less,
Polarity of the trailing electrode: DCEP,
wire type of the trailing electrode: flux-cored wire;
Welding current of the trailing electrode: 180 A or more,
distance between the leading electrode and the trailing electrode: 65 mm or less;
Plate thickness of the plate material: 16 mm or less,
Root gap of the groove: 2 mm or less,
Area of the portion occupied by the groove filler in the plane perpendicular to the weld line direction: 10 mm ² or less,
multi-electrode gas-shielded arc single-sided welding method.

Preferred embodiments of the present invention relating to the multi-electrode gas-shielded arc single-sided welding method relate to the following [3] and [4].

[3] The multi-electrode gas-shielded arc single-sided welding method according to [1] or [2], wherein the groove shape of the pair of plate materials is V-shaped and the groove angle is 25° or more.

[4] The multi-electrode gas-shielded arc single-sided welding method according to any one of [1] to [3], wherein the welding current of the trailing electrode is 300 A or less.

Further, the above object of the present invention is achieved by the following configuration [5] relating to a multi-electrode gas-shielded arc single-sided welding apparatus.

[5] A multi-electrode gas-shielded arc single-sided welding apparatus for use in the multi-electrode gas-shielded arc single-sided welding method according to any one of [1] to [4].

Advantageous Effects of Invention According to the present invention, it is possible to provide a multi-electrode gas-shielded arc single-sided welding method capable of effectively preventing the occurrence of hot cracks while providing a favorable back bead shape.

FIG. 1 is a top view schematically showing a test steel sheet for evaluation test of hot cracking and back bead shape. FIG. 2 is a schematic explanatory diagram of a cross section taken along line AA of FIG. FIG. 3 shows invention example No. 14 is a cross-sectional photograph of the weld metal. FIG. 4 shows comparative example no. 7 is a cross-sectional photograph of the weld metal of No. 7. FIG. 5 shows Comparative Example No. 9 is a cross-sectional photograph of the weld metal of No. 9.

DETAILED DESCRIPTION OF THE INVENTION Embodiments for carrying out the present invention will be described in detail below. In addition, this invention is not limited to embodiment described below. Further, in this specification, the term "to" indicating a numerical range is used to include the numerical values before and after it as lower and upper limits.
First, a multi-electrode gas-shielded arc single-sided welding method (hereinafter sometimes simply referred to as "first welding method") according to the first invention will be described in detail.

[First welding method]
The multi-electrode gas-shielded arc single-sided welding method according to the first invention fills a groove formed by abutting a pair of plate materials with a groove filler, and uses a plurality of electrodes arranged in a row in the weld line direction. A multi-electrode gas-shielded arc single-sided welding method for welding, comprising:
the plurality of electrodes includes a leading electrode and a trailing electrode following the leading electrode;
Polarity of Leading Electrode: DCEP,
leading pole wire: flux cored wire or solid wire,
Polarity of trailing electrode: DCEN,
trailing pole wire: flux cored wire,
Welding current of trailing electrode: 180 A or more,
distance between leading and trailing electrodes: 65 mm or more and 150 mm or less;
Groove root gap: 3 mm or more and 8 mm or less,
Area of the portion occupied by the groove filler in the plane orthogonal to the weld line direction: 20 mm ² or more and 50 mm ² or less,
Weld as
In this embodiment, the plate material is a steel plate, for example, a mild steel plate. Further, the multi-electrode gas-shielded arc single-sided welding method according to the present embodiment is first-layer welding when welding materials to be welded together.

[Leading electrode]
<Polarity of Leading Electrode>
The polarity of the leading electrode in the first welding method is a DCEP (Direct Current Electrode Positive) consumable electrode.

<Wire type of leading electrode>
A flux-cored wire or a solid wire (hereinafter sometimes simply referred to as "wire") is used as the leading electrode wire. An iron-based flux-cored wire is preferably used as the flux-cored wire of the leading electrode. A flux-cored wire is a wire in which flux is filled inside a cylindrical steel sheath. Either wire (seam type) structure with gaps left in the gap can be adopted. Also, the outer skin may be plated with copper.

<Wire composition of leading electrode>
When a flux-cored wire is used as the leading electrode, its composition varies depending on the type of material to be welded and welding conditions, and is not particularly limited. For example, a wire having an Fe content of 80 to 95% by mass with respect to the entire wire can be used. Elements other than Fe that can be contained in the wire include, for example, C, Mn, Ti, P, S, Ni, Si, Cr, Cu, Mo, Mg, B, F, Na, K, Nb, V, Zr, Al etc. are mentioned. These may be intentionally added or may be included as unavoidable impurities.
In addition, the wire composition when a solid wire is used as the leading electrode is not limited, but as an example, C: 0.01 to 0.18% by mass, Si: 0 to 1.00% by mass, Mn: 0.50 to 2.80% by mass, P: 0.030% by mass or less, S: 0.030% by mass or less, and Cu: 0.50% by mass or less, the balance being Fe and unavoidable impurities composition. In addition, Ti, Ni, Cr, Al, Zr, Mg, etc. may be included.

<Wire diameter of leading electrode>
The wire diameter of the flux-cored wire or solid wire of the leading electrode is not particularly limited, but is preferably 1.0 mm or more, more preferably 1.2 mm or more, from the viewpoint of welding workability. From the viewpoint of welding workability, it is preferably 2.0 mm or less, more preferably 1.6 mm or less.

<Shield gas during welding with leading electrode>
The shielding gas used during welding with the leading electrode is not particularly limited, but for example, Ar gas, carbon dioxide gas, a mixed gas of Ar gas and carbon dioxide gas, and a mixed gas of Ar gas and oxygen gas can be used. The gas flow rate is also not particularly limited, but can be, for example, 15 to 30 L/min.

<Wire protruding length of leading electrode>
Although the length of wire protrusion of the leading electrode is not particularly limited, a length of 15 mm or more is preferable because the stability of the back bead is improved and burn-through can be prevented. The wire projection length is more preferably 17 mm or longer, and even more preferably 19 mm or longer. Further, it is preferable to set the wire projection length to 35 mm or less, because it facilitates formation of the back bead. The wire projection length is more preferably 33 mm or less, and even more preferably 31 mm or less.

<Welding current of leading electrode>
When a single electrode is used and welding is performed with a large current of, for example, about 400 A, cracks are likely to occur in the weld metal. In the first welding method, a plurality of electrodes including a leading electrode and a trailing electrode following the leading electrode are used, and the polarities of the leading and trailing electrodes, the distance between the electrodes, the filling amount of the filler, etc. are appropriately adjusted. By controlling this, it is possible to prevent cracks in the weld metal even with large currents. The welding current of the leading electrode is not particularly limited, but it is preferable to set it to 350 A or more because it facilitates the formation of the back bead. A welding current of 370 A or more is more preferable, and a welding current of 400 A or more is even more preferable. A welding current of 550 A or less is preferable because the stability of the bead is improved and burn-through can be prevented. A welding current of 530 A or less is more preferable, and 500 A or less is even more preferable.

<Welding voltage of leading electrode>
The welding voltage of the leading electrode is also not particularly limited, but is preferably 25 V or higher, more preferably 27 V or higher, from the viewpoint of arc stability. From the viewpoint of arc stability, the welding voltage is preferably 40 V or less, more preferably 35 V or less.

<Wire feeding amount of leading electrode>
The wire feeding rate of the leading electrode is not particularly limited, but it is preferable to set it at 5.0 m/min or more because it facilitates formation of the back bead. The wire feed rate is more preferably 5.5 m/min or more, and even more preferably 6.0 m/min or more. A wire feed rate of 14.0 m/min or less is preferable because the stability of the back bead is improved and burn-through can be prevented. The wire feed rate is more preferably 13.0 m/min or less, and even more preferably 12.0 m/min or less.

<Weaving width of leading electrode>
Although the weaving width of the leading electrode is not particularly limited, it is preferably from 0 to 7 mm because the formation of the back bead is improved, more preferably 1 mm or more, and more preferably 5 mm or less.

[Successor electrode]
<Polarity of trailing electrode>
The trailing electrode in the first welding method is an electrode following the leading electrode, and is a consumable electrode having a DCEN (Direct Current Electrode Negative) polarity.

<Wire type of trailing electrode>
A flux-cored wire is used as the wire of the trailing electrode. As with the flux-cored wire of the leading electrode, the flux-cored wire of the trailing electrode also has a cylindrical steel sheath filled with flux, and the seams of the steel sheath are welded. It is possible to adopt both a structure of a wire (seamless type) and a wire (seam type) in which gaps are left without welding joints. Also, the outer skin may be plated with copper.

<Welding current of trailing electrode>
In the first welding method, by appropriately controlling the welding current of the trailing electrode and the inter-electrode distance between the leading and trailing electrodes, the molten pool is maintained at an appropriate size and strain in the weld metal is reduced. is reduced to prevent the occurrence of hot cracks. By setting the inter-electrode distance between the leading electrode and the trailing electrode described later to 150 mm or less and setting the welding current of the trailing electrode to 180 A or more, the slag formed during welding by the leading electrode is completely solidified. Since arcing can be prevented and an arc can be reliably generated, a favorable back bead shape can be formed. Therefore, the welding current of the trailing electrode is set to 180 A or more, preferably 200 A or more, more preferably 220 A or more.
On the other hand, when the welding current of the trailing electrode is 320 A or less, welding workability is improved, which is preferable. Further, the welding current of the trailing electrode is more preferably 300 A or less, and even more preferably 280 A or less.
In addition, in this embodiment, the number of electrodes can be multi-electrode such as three electrodes or four electrodes.

<Wire composition of trailing electrode>
The composition of the flux-cored wire used as the trailing electrode varies depending on the type of material to be welded and welding conditions, and is not particularly limited. For example, a wire having an Fe content of 80 to 95% by mass with respect to the entire wire can be used. Elements other than Fe that can be contained in the wire include, for example, C, Mn, Ti, P, S, Ni, Si, Cr, Cu, Mo, Mg, B, F, Na, K, Nb, V, Zr, Al, N, O and the like can be mentioned. These may be intentionally added or may be included as unavoidable impurities.

<Wire diameter of trailing electrode>
Although the wire diameter of the flux-cored wire used as the trailing electrode is not particularly limited, it is preferably 1.0 mm or more, more preferably 1.2 mm or more, from the viewpoint of welding workability. From the viewpoint of welding workability, it is preferably 2.0 mm or less, more preferably 1.6 mm or less.

<Shield gas during welding with the trailing electrode>
The shielding gas used during welding with the trailing electrode is not particularly limited, but for example, Ar gas, carbon dioxide, a mixed gas of Ar gas and carbon dioxide gas, or a mixed gas of Ar gas and oxygen gas can be used. The gas flow rate is also not particularly limited, but can be, for example, 15 to 30 L/min.

<Wire protruding length of trailing electrode>
The length of wire projection of the trailing electrode is not particularly limited, but if it is 15 mm or more, the arc force becomes sufficient and the ghost lines indicating the segregation of impurities can be completely eliminated, which is preferable. The wire projection length is more preferably 17 mm or longer, and even more preferably 19 mm or longer. In addition, by setting the wire projection length to 35 mm or less, the arc force is sufficient to completely eliminate the ghost line, the arc is stabilized, and the amount of spatter generation can be reduced, which is preferable. The wire projection length is more preferably 33 mm or less, and even more preferably 31 mm or less.

<Wire feeding amount of the trailing electrode>
The amount of wire feeding to the trailing electrode is also not particularly limited, but if it is 1.0 m/min or more, the arc force becomes sufficient and the ghost line can be completely eliminated, so it is preferable. The wire feed rate is more preferably 1.2 m/min or more, and still more preferably 1.4 m/min or more. Further, when the wire feeding rate is 10.0 m/min or less, the arc force becomes sufficient and the ghost lines can be completely eliminated. In addition, the arc is stabilized and the amount of spatter generation can be reduced. preferable. The wire feed rate is more preferably 9.8 m/min or less, and even more preferably 9.6 m/min or less.

<Welding voltage of trailing electrode>
Although the welding voltage of the trailing electrode is not particularly limited, it is preferably 15 V or higher, more preferably 20 V or higher, from the viewpoint of arc stability. From the viewpoint of arc stability, the welding voltage is preferably 40 V or less, more preferably 35 V or less.

<Weaving width of trailing electrode>
Although the weaving width of the trailing electrode is not particularly limited, it is preferably 0 to 10 mm because the state of front bead formation is improved, and is more preferably 8 mm or less.

[Welding conditions]
<Distance between Leading Electrode and Trailing Electrode>
In the first welding method, the inter-electrode distance between the leading electrode and the trailing electrode is made longer than the conventional distance to keep the molten pool at an appropriate size, reduce strain in the weld metal, It prevents the occurrence of hot cracks. Even when the various conditions of the leading and trailing electrodes are adjusted to the conditions described in the first welding method, if the inter-electrode distance between the leading and trailing electrodes is less than 65 mm, a molten pool is formed. becomes too large, strain occurs on the surface of the weld metal, and cracking cannot be effectively prevented. Therefore, the inter-electrode distance between the leading electrode and the trailing electrode is set to 65 mm or more. The inter-electrode distance between the leading electrode and the trailing electrode is preferably 70 mm or more, more preferably 80 mm or more.
On the other hand, as described above, by setting the welding current of the trailing electrode to 180 A or more and setting the inter-electrode distance between the leading electrode and the trailing electrode to 150 mm or less, the slag formed during welding by the leading electrode is completely removed. Since solidification can be prevented and an arc can be reliably generated, a favorable back bead shape can be formed. Therefore, the inter-electrode distance between the leading electrode and the trailing electrode is set to 150 mm or less, preferably 120 mm or less, and even more preferably 100 mm or less.

<Groove root gap>
If the root gap is less than 3 mm, a good back bead shape cannot be obtained. Therefore, the root gap should be 3 mm or more, preferably 5 mm or more.
On the other hand, if the root gap exceeds 8 mm, the arc becomes unstable. Therefore, the root gap should be 8 mm or less, preferably 7 mm or less.

<Filling amount of groove filler>
In the first welding method, since the root gap is 3 mm or more and 8 mm or less as described above, it is necessary to fill an appropriate amount of groove filler. As the groove filler, there are powders, chips, and the like, and the specific gravity varies depending on the form. Define quantity. Here, the groove filler is provided so as to have a substantially uniform height after filling the groove (see the portion 6 occupied by the groove filler in FIG. 2). A gap between the groove filler and the groove filler is formed in the portion occupied by the groove filler.
If the area is less than 20 mm ² , a good back bead shape cannot be stably obtained. Therefore, the area occupied by the groove filler should be 20 mm ² or more, preferably 30 mm ² or more.
On the other hand, even if the area exceeds 50 mm ² , a good back bead shape cannot be stably obtained. Therefore, the area occupied by the groove filler should be 50 mm ² or less, preferably 45 mm ² or less.
In the first welding method, since the pair of plate materials have a root gap, the cross section of the groove filler in the plane perpendicular to the weld line direction is trapezoidal when the V groove shape is used. Therefore, by measuring the depth of the filled groove filler, the area can be determined based on the root gap and the groove angle.

<Welding speed>
The welding speed is preferably 200 mm/min or more and 400 mm/min or less. By setting the welding speed to 200 mm/min or more, an appropriate heat input can be obtained, so that a favorable back bead shape can be obtained, and problems such as peeling of the backing material do not occur. The welding speed is more preferably 230 mm/min or higher, still more preferably 250 mm/min or higher.
Also, by setting the welding speed to 400 mm/min or less, the cooling speed of the weld metal does not become too fast, and the occurrence of hot cracks can be further suppressed. The welding speed is more preferably 380 mm/min or less, still more preferably 350 mm/min or less.

<Thickness of plate material>
When the plate thickness of the plate material to be welded is 40 mm or less, the occurrence of angular deformation due to welding heat input can be suppressed, and the occurrence of hot cracks can be further prevented. Therefore, the plate thickness of the plate material is preferably 40 mm or less, more preferably 35 mm or less. In addition, in this embodiment, a board|plate material is a steel plate.

<Groove shape, groove angle>
The first welding method can be used for a pair of plate members having various groove shapes such as V-shape, I-shape, L-shape, U-shape, X-shape, and H-shape. A V-shaped groove is preferable because a good back bead shape can be obtained. Further, when the groove angle is 25° or more, the occurrence of hot cracks can be further prevented, which is preferable, and 35° or more is more preferable.

Next, a multi-electrode gas-shielded arc single-sided welding method (hereinafter sometimes simply referred to as "second welding method") according to the second invention will be described in detail.

[Second welding method]
The multi-electrode gas-shielded arc single-sided welding method according to the second invention fills a groove formed by abutting a pair of plate materials with a groove filler, and uses a plurality of electrodes arranged in a row in the welding line direction. A multi-electrode gas-shielded arc single-sided welding method for welding, comprising:
the plurality of electrodes includes a leading electrode and a trailing electrode following the leading electrode;
Polarity of Leading Electrode: DCEP,
Lead electrode wire type: solid wire,
Welding current of leading electrode: 500 A or less,
Welding voltage of leading electrode: 40 V or less,
Polarity of trailing electrode: DCEP,
Wire type of trailing electrode: Flux cored wire,
Welding current of trailing electrode: 180 A or more,
Inter-electrode distance between the leading electrode and the trailing electrode: 65 mm or less,
Plate thickness: 16 mm or less,
Groove root gap: 2 mm or less,
Area of the portion occupied by the groove filler in the plane orthogonal to the weld line direction: 10 mm ² or less,
Weld as
In this embodiment, the plate material is a steel plate, for example, a mild steel plate. Further, the multi-electrode gas-shielded arc single-sided welding method according to the present embodiment is first-layer welding when welding materials to be welded together.

[Leading electrode]
<Polarity of Leading Electrode>
The polarity of the leading electrode in the second welding method is a DCEP (Direct Current Electrode Positive) consumable electrode.

<Wire type of leading electrode>
A solid wire (hereinafter sometimes simply referred to as "wire") is used as the leading electrode wire. In the second welding method, since welding is performed with a root gap of 2 mm or less, a solid wire with a deep penetration depth is used.

<Wire composition of leading electrode>
The composition of the solid wire of the leading electrode varies depending on the type of material to be welded and welding conditions, and is not particularly limited. For example, C: 0.01 to 0.18% by mass, Si: 0 to 1.00% by mass, Mn: 0.50 to 2.80% by mass, P: 0.030% by mass or less, S: 0.030% by mass % or less, and Cu: 0.50 mass % or less, with the balance being Fe and unavoidable impurities. In addition, Ti, Ni, Cr, Al, Zr, Mg, etc. may be included.

<Welding current of leading electrode>
In the second welding method, when welding a pair of plate materials with a plate thickness of 16 mm or less with a root gap of 2 mm or less, the welding current and welding voltage of the leading electrode are appropriately adjusted to Cracking of the weld metal is prevented by keeping the molten pool at an appropriate size and adjusting the distance between the electrodes. By setting the welding voltage of the leading electrode, which will be described later, to 40 V or less and the welding current of the leading electrode to 500 A or less, as described above, cracking of the weld metal can be prevented. The welding current of the leading electrode is preferably 480 A or less.
On the other hand, the lower limit of the welding current of the leading electrode is not particularly limited, but if it is set to 350 A or more, the formation of the back bead is facilitated, which is preferable. A welding current of 400 A or more is more preferable.

<Welding voltage of leading electrode>
As described above, the back bead shape can be improved by appropriately adjusting the thickness of the plate material, the root gap and the welding current of the leading electrode, and setting the welding voltage of the leading electrode to 40 V or less. Therefore, the welding voltage of the leading electrode is 40 V or less, preferably 36 V or less, more preferably 33 V or less.
On the other hand, the lower limit of the welding voltage of the leading electrode is not particularly limited.

The preferable conditions for the wire diameter of the leading electrode, the shielding gas during welding by the leading electrode, the wire projection length of the leading electrode, the wire feeding amount of the leading electrode, and the weaving width of the leading electrode in the second welding method are described in the second welding method. Each condition of the leading electrode in the welding method of No. 1 shall be the same.

[Successor electrode]
<Polarity of trailing electrode>
The trailing electrode in the second welding method is an electrode following the leading electrode, and the polarity is a DCEP (Direct Current Electrode Positive) consumable electrode.
In this embodiment, multiple electrodes such as three electrodes and four electrodes can be used.

<Wire type of trailing electrode>
A flux-cored wire is used as the wire of the trailing electrode. The flux-cored wire of the trailing electrode has a tubular steel sheath filled with flux inside. A wire (seam type) structure in which gaps are left without welding can also be adopted. Also, the outer skin may be plated with copper.

<Welding current of trailing electrode>
By setting the welding current of the trailing electrode to 180 A or more, the slag formed during welding by the leading electrode can be prevented from completely solidifying, and the arc of the trailing electrode can be reliably generated. A back bead shape can be formed. Therefore, the welding current of the trailing electrode is set to 180A or more, preferably 240A or more.
On the other hand, when the welding current of the trailing electrode is 350 A or less, the welding workability is improved, which is preferable. Also, the welding voltage of the trailing electrode is preferably 300 A or less.

<Wire composition of trailing electrode>
The composition of the flux-cored wire used as the trailing electrode varies depending on the type of material to be welded and welding conditions, and is not particularly limited. For example, a wire having an Fe content of 80 to 95% by mass with respect to the entire wire can be used. Elements other than Fe that can be contained in the wire include, for example, C, Mn, Ti, P, S, Ni, Si, Cr, Cu, Mo, Mg, B, F, Na, K, Nb, V, Zr, Al etc. are mentioned. These may be intentionally added or may be included as unavoidable impurities.

Wire diameter of the trailing electrode in the second welding method, shield gas during welding by the trailing electrode, wire projection length of the trailing electrode, wire feed amount of the trailing electrode, welding voltage of the trailing electrode and trailing The preferable conditions for the weaving width of the pole are the same as the conditions for the trailing electrode in the first welding method.

[Welding conditions]
<Distance between Leading Electrode and Trailing Electrode>
In the second welding method, the distance between the leading and trailing electrodes can be set to 65 mm or less by appropriately adjusting the various conditions of the leading and trailing electrodes, the thickness of the plate material, and the root gap. , completely preventing the occurrence of cracks in the weld metal. Even when the various conditions of the leading and trailing electrodes, the thickness of the plate material, and the root gap are adjusted to the conditions described in the second welding method, the inter-electrode distance between the leading and trailing electrodes is 65 mm. , cracks may occur in the upper part of the leading pole. Therefore, the inter-electrode distance between the leading electrode and the trailing electrode is set to 65 mm or less. The inter-electrode distance between the leading electrode and the trailing electrode is preferably 50 mm or less, more preferably 40 mm or less.
On the other hand, the lower limit of the inter-electrode distance between the leading electrode and the trailing electrode is not particularly limited, but it is preferably 20 mm or more for arc stability.

<Groove root gap>
In the second welding method, a good back bead shape can be obtained by setting the root gap of the groove to 2 mm or less under the condition that the plate thickness is 16 mm or less, which will be described later, and cracking of the weld metal occurs. can be prevented. It should be noted that the groove root gap of 0 mm is preferable because cracking of the weld metal can be prevented.

<Filling amount of groove filler>
In the second welding method, since the root gap is set to 2 mm or less as described above, it is necessary to fill an appropriate amount of groove filler in order to form a stable back bead shape. As the groove filler, there are powders, chips, and the like, and the specific gravity varies depending on the form. Define quantity. Here, the groove filler is provided so as to have a substantially uniform height after filling the groove (see the portion 6 occupied by the groove filler in FIG. 2). A gap between the groove filler and the groove filler is formed in the portion occupied by the groove filler.
By setting the area to 10 mm ² or less, a favorable back bead shape can be stably obtained. Therefore, the area occupied by the groove filler should be 10 mm ² or less, preferably 8 mm ² or less.
On the other hand, the above area is preferably 3 mm ² or more for arc stability.
In the second welding method, since the root gap between the pair of plate materials is 2 mm or less, when the V groove shape is used, the cross section of the portion occupied by the groove filler in the plane orthogonal to the weld line direction becomes a triangle. Therefore, by measuring the depth of the filled groove filler, the area can be obtained based on the groove angle.

<Welding speed>
The welding speed is not particularly limited, but if the welding speed is 300 mm/min or more, an appropriate heat input can be obtained, so a good back bead shape can be obtained, and problems such as peeling of the backing material occur. never do. Therefore, the welding speed is preferably 300 mm/min or higher, more preferably 320 mm/min or higher.
Also, when the welding speed is 600 mm/min or less, the cooling speed of the weld metal does not become too fast, and the occurrence of hot cracks can be further suppressed. Therefore, the welding speed is preferably 600 mm/min or less.

<Thickness of plate material>
When the plate thickness of the plate material to be welded is 16 mm or less, the occurrence of angular deformation due to welding heat input can be suppressed, and the occurrence of hot cracks can be further prevented. Therefore, the plate thickness of the plate material is 16 mm or less, and more preferably 12 mm or less.

Preferred conditions for the groove shape and groove angle in the second welding method are the same as those in the first welding method.

In the first and second welding methods described above, the leading electrode and the trailing electrode following the leading electrode are described, but the present invention is not limited to two electrodes, and can also be applied to welding with three or more electrodes. be able to. In this case, electrodes other than the leading electrode and the trailing electrode following the leading electrode are not particularly limited.

[Multi-electrode gas-shielded arc single-sided welding equipment]
The present invention also relates to a multi-electrode gas-shielded arc single-sided welding method according to the first invention and a multi-electrode gas-shielded arc single-sided welding apparatus used in the multi-electrode gas-shielded arc single-sided welding method according to the second invention. .

The present embodiment will be described in more detail below with reference to examples, but the present invention is not limited to these examples, and can be implemented with modifications within the scope of the gist of the present invention. are possible, and they are all included in the technical scope of the present invention.

<Invention Example No. 1 to 21 and Comparative Example No. 1 to 27>
Gas-shielded arc single-sided welding was performed on mild steel sheets under various welding conditions, and hot cracks and back bead shapes were evaluated. The evaluation of hot cracking was not based on the general C-type jig constrained butt weld cracking test method, but was evaluated by the following evaluation method, which is a stricter condition for cracking.
FIG. 1 is a top view schematically showing a test steel plate for evaluation test of hot cracking and back bead shape, and FIG. However, in FIG. 1, illustration of the groove filler is omitted.
As shown in FIGS. 1 and 2, a pair of plate members 1a and 1b processed to form a V-shaped groove are arranged with a predetermined root gap, and the plate member 1a is placed at the welding start and end portions, respectively. and tab plates 2a and 2b processed in the same shape as 1b were installed. In addition, backing materials 3 are arranged on the back surfaces of the plate members 1a and 1b and the tab plates 2a and 2b, and constraining plates 4 having a U-shaped cross section are arranged at three locations on the back surfaces of the plate members 1a and 1b to support them. Then, the back surfaces of the plate members 1a and 1b and the upper surface of the restraint plate 4 were joined by welding.
Further, two-layer constraining beads 7 were formed at the ends of the tab plates 2a and 2b, and temporary attachment beads 10 were formed at both longitudinal ends and longitudinal central portions of the plate members 1a and 1b. After that, the V-shaped grooves 5 formed between the plate material 1a and the plate material 1b and between the tab plate 2a and the tab plate 2b are filled with groove filler to level the height, and the weld line direction is adjusted. The area of the portion 6 occupied by the groove filler in the orthogonal plane was adjusted.

The plate members 1a and 1b had a length of 600 mm in the direction of the weld line, and a width of 300 mm in a direction orthogonal to the weld line when the plate members 1a and 1b were placed against each other. The tab plates 2a and 2b had a length of 150 mm in the direction of the weld line, and a width of 300 mm in the direction perpendicular to the weld line when they were placed facing each other. Further, the restraint plate 4 had a length in the weld line direction of 20 mm, a width of 300 mm, a height of 200 mm, and a recess width of 80 mm and a recess depth of 35 mm.
The constraining bead 7 had a length of 50 mm in the weld line direction and a thickness of 10 mm, and the temporary bead had a length of 50 mm in the weld line direction and a thickness of 5 mm.

After that, multi-electrode gas-shielded arc single-sided welding was performed by the first welding method and the second welding method under various conditions. Welding conditions are shown in Tables 1 and 2 below, and conditions other than those shown in the tables are shown below.

<Leading electrode>
Wire diameter: 1.6mm
Shield gas and flow rate: carbon dioxide gas, 25 L/min Flux-cored wire: Flux-cored wire conforming to JIS Z 3313: 2009 Solid wire: Fe: 90% by mass, Mn: 2.5% by mass, Si: 0.5% by mass Solid wire conforming to JIS Z 3312: 2009 Wire protrusion length: 30 mm
Wire feed rate: 10m/min Weaving width: 3mm

<Succeeding electrode>
Wire diameter: 1.4mm
Shield gas and flow rate: Carbon dioxide gas, 25 L/min Flux-cored wire: Flux-cored wire conforming to JIS Z 3313:2009 Wire projection length: 25 mm
Wire feed rate: 4m/min Weaving width: 8mm

<Evaluation>
The crack resistance and back bead shape of the welded product after welding were evaluated. The evaluation methods for each evaluation are shown below, and the evaluation results are also shown in Tables 1 and 2. In Tables 1 and 2, FCW indicates flux-cored wire, DCEP indicates Direct Current Electrode Positive, and DCEN indicates Direct Current Electrode Negative.

(Back bead shape)
The state of formation of the back bead on the welded product was visually evaluated. As the evaluation criteria, a sample with a good back bead shape was rated as "O" (good), and a sample with a bad back bead shape or no back bead was rated as "X" (bad).

(Hot crack resistance)
The portions other than the crater of the weld metal after welding by one pass were evaluated by an X-ray transmission test. As the evaluation criteria, "O" (good) was given when no cracks occurred, and "X" (bad) was given when cracks were observed.

FIG. 3 shows invention example No. It is the photograph which image|photographed 14 weld metals. As shown in FIG. 3, a weld metal 8 is formed between the plate material 1a and the plate material 1b by the weld metal 8a of the leading electrode and the weld metal 8b of the trailing electrode, and cracks occur even by a severe evaluation method. It was possible to obtain an excellent back bead shape. Further, as shown in Tables 1 and 2, in the first welding method and the second welding method, the welding conditions were all within the scope of the present invention. 1 to 21 are invention example Nos. shown in FIG. As with No. 14, good crack resistance and an excellent back bead shape could be obtained. In particular, invention example No. 1 to 18 and No. In Nos. 20 and 21, the welding current of the trailing electrode was within the preferred range of the present invention, so the welding workability was also excellent.

On the other hand, Comparative Example No. Nos. 1, 7, and 13 did not use the trailing electrode, so the resistance to cracking was poor. FIG. 4 shows comparative example no. 7 is a photograph of the weld metal of No. 7. As shown in FIG. 7 shows crack 9 in weld metal 8 .

Comparative example no. In Nos. 2-6, 8-12 and 14-18, the inter-electrode distance was out of the range specified in the first welding method, so the crack resistance was poor. FIG. 5 shows Comparative Example No. 9 is a photograph of the weld metal of No. 9. As shown in FIG. For No. 9, cracks 9 also occurred in the weld metal 8.

Comparative example no. 19 to 21, the root gap and the amount of groove filler are out of the range specified in the first welding method, and comparative example No. Comparative Example No. 19 showed no back bead and poor cracking resistance. Comparative Example No. 20 was inferior in back bead shape and crack resistance. 21 became unweldable.

Comparative example no. In 22 to 24, the inter-electrode distance between the leading electrode and the trailing electrode, the welding current of the trailing electrode, and the polarity of the trailing electrode are out of the range specified in the first welding method. Crackability was poor.

Comparative example no. In No. 25, the groove filler amount was out of the range specified in the first welding method, so the back bead was not formed and the crack resistance was poor.

Comparative example no. In Nos. 26 and 27, the inter-electrode distance between the leading electrode and the trailing electrode was out of the range specified in the second welding method, so crack resistance was poor.

1a, 1b Plate materials 2a, 2b Tab plate 3 Backing material 4 Constraining plate 5 V-groove 6 Location occupied by groove filler 7 Constraining bead 8, 8a, 8b Weld metal 9 Crack

Claims (5)

A multi-electrode gas-shielded arc single-sided welding method in which a groove formed by abutting a pair of plate materials is filled with a groove filler and welded using a plurality of electrodes arranged in a row in the welding line direction,
the plurality of electrodes includes a leading electrode and a trailing electrode following the leading electrode;
Polarity of the preceding electrode: DCEP,
wire type of the preceding electrode: flux-cored wire or solid wire;
Polarity of the trailing electrode: DCEN,
wire type of the trailing electrode: flux-cored wire;
Welding current of the trailing electrode: 180 A or more,
distance between the leading electrode and the trailing electrode: 65 mm or more and 150 mm or less;
Root gap of the groove: 3 mm or more and 8 mm or less,
Area of the portion occupied by the groove filler on the plane orthogonal to the weld line direction: 20 mm ² or more and 50 mm ² or less,
multi-electrode gas-shielded arc single-sided welding method. A multi-electrode gas-shielded arc single-sided welding method in which a groove formed by abutting a pair of plate materials is filled with a groove filler and welded using a plurality of electrodes arranged in a row in the welding line direction,
the plurality of electrodes includes a leading electrode and a trailing electrode following the leading electrode;
Polarity of the preceding electrode: DCEP,
Wire type of the preceding electrode: solid wire,
Welding current of the preceding electrode: 500 A or less,
Welding voltage of the leading electrode: 40 V or less,
Polarity of the trailing electrode: DCEP,
wire type of the trailing electrode: flux-cored wire;
Welding current of the trailing electrode: 180 A or more,
distance between the leading electrode and the trailing electrode: 65 mm or less;
Plate thickness of the plate material: 16 mm or less,
Root gap of the groove: 2 mm or less,
Area of the portion occupied by the groove filler in the plane perpendicular to the weld line direction: 10 mm ² or less,
multi-electrode gas-shielded arc single-sided welding method. The multi-electrode gas-shielded arc single-sided welding method according to claim 1 or 2, wherein the pair of plate members have a V-shaped groove and a groove angle of 25° or more. The multi-electrode gas-shielded arc single-sided welding method according to any one of claims 1 to 3, wherein the welding current of said trailing electrode is 300 A or less. A multi-electrode gas-shielded arc single-sided welding apparatus for use in the multi-electrode gas-shielded arc single-sided welding method according to any one of claims 1 to 4.

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