JP2002103041A - Dual-electrode vertical electrogas arc welding method for extra-thick steel member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dual-electrode vertical electrogas arc welding method by which, at the time of welding a thick steel plate, good low temperature toughness and good weldability can be obtained. SOLUTION: In the dual-electrode vertical electrogas arc welding method for extra-thick steel in which a sliding copper backing is applied on either face of the extra-thick material to be welded, a stationary type backing material is applied on the other face, two welding electrodes are inserted side by side into the grooves thereof in the sheet thickness direction, and the material to be welded is subjected to welding, flux cored wire containing metallic fluoride by 0.1 to 0.8% expressed in terms of F, a slag generating agent containing metallic fluoride by 0.3 to 1%, 0.03 to 0.12% C, 0.2 to 0.9% Si, 0.9 to 2.8% Mn, 0.1 to 0.6% Mo, 0.02 to 0.4% Ti and 0.002 to 0.012% B (further, 0.5 to 4% Ni), to the total amount of the wire, is used for the welding electrode 5 on the side of the sliding copper backing 2, and solid wire is used for the welding electrode 6 on the side of the stationary type backing material 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-electrode vertical electrogas arc welding method for extremely thick steel, and more particularly, to a weld metal having good low-temperature toughness.
The present invention relates to a two-electrode vertical electrogas arc welding method for extremely thick steel having good welding workability.

[0002]

2. Description of the Related Art In general, electrogas arc welding is performed in a vertical direction, since the welding efficiency is high because the plate thickness is welded all at once. Therefore, ships and oil storage tanks using mild steel, 490 MPa class high tensile steel, 620 MPa class high tensile steel, etc. Used in the production of bridges and bridges. In recent years, thick steel plates having a thickness of 5 mm or more have been frequently used in shark strake portions and hatch coaming portions of large container ships, bridge girder portions of bridges, and the like.

[0003] In the case of electrogas arc welding of a thick steel plate of such a large structure, the welding speed is extremely reduced by one-pass welding using one electrode. When performing long welding using a flux-cored wire, the welding efficiency is required, such as the need to temporarily suspend welding and replace it with a new welding wire, or to repair the welded seam, because the amount of welding wire is insufficient. There was a problem of lowering.

[0004] Electrogas arc welding methods that can solve these problems and improve welding efficiency include, for example,
A two-electrode vertical electrode in which two welding electrodes are arranged side by side in the plate thickness direction and inserted into a groove disclosed in Japanese Patent Application Laid-Open No. 8-187579, and the material to be welded is welded while oscillating both electrodes. Gas arc welding methods and apparatus have been proposed.

[0005] In the conventional two-electrode vertical electrogas arc welding known in Japanese Patent Application Laid-Open No. 8-187579, etc., a sliding copper metal is used on the front side of a material to be welded and a fixed backing material is used on the back side. Usually, since both welding electrodes are welded by using a flux-cored wire, the slag generated from the welding electrode wire on the fixed backing material side is in particular the slag of the welding electrode wire on the adjacent sliding copper plate side. It is blocked by the arc force and cannot escape from the sliding copper plate side. Therefore, the molten slag on the welding pool is generated between the arc of the welding electrode wire on the sliding copper plate side and the welding electrode wire on the backing material side (slag between the welding electrode wires).
And it becomes easy to accumulate between the arc generated from the wire of the welding electrode on the backing material side and the fixed backing material (fixed backing material side slag).

[0006] When the amount of the retained slag becomes excessive, slag rebounds frequently during welding, and slag adheres to the two welding electrodes. As a result, wire feeding becomes unstable, resulting in an inadequate sound. If the weld metal cannot be obtained, or if the amount of slag adhered to the welding electrode on the fixed backing material side in particular increases, the work efficiency such as welding interruption due to contact with the groove will occur. Also, if the amount of slag accumulated on the welding pool increases, the arc heat generated from the wires of the two welding electrodes will not be sufficiently transmitted to the weld metal or the groove surface, resulting in poor fusion and deterioration of the appearance of the Uranami bead. In addition, the amount of oxygen in the weld metal is extremely reduced and the hardenability becomes excessive, which causes problems such as an increase in the strength of the weld metal and a decrease in the impact performance of the weld metal.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention is directed to a two-electrode vertical electrogas arc capable of obtaining good low-temperature toughness and good workability when welding a thick steel plate. It is intended to provide a welding method.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and in particular, by specifying the component composition of a flux-cored wire for a welding electrode on the side of a sliding copper plate, it is possible to improve welding workability and weld metal. The feature of the invention is to improve low-temperature toughness, and the gist of the invention is as follows.

(1) A sliding copper plate is applied to one surface of an extremely thick material to be welded, and a fixed backing plate is applied to the other surface, and two welding electrodes are placed in the groove. In a two-electrode vertical electrogas arc welding method for a very thick steel material, which is inserted side by side in the thickness direction and welds a material to be welded, the metal electrode is attached to the welding electrode on the sliding copper abutment side in a mass% with respect to the total amount of the wire. Of fluoride: 0.1 to 0.8%, slag forming agent containing metal fluoride: 0.3 to 1%, C: 0.03 to 0.12%, S
i: 0.2 to 0.9%, Mn: 0.9 to 2.8%, M
o: 0.1 to 0.6%, Ti: 0.02 to 0.4%, B
Using a flux-cored wire containing 0.002 to 0.012%, and using a solid wire as a welding electrode on the fixed backing material side; two-electrode vertical electrogas arc welding of extremely thick steel material. Method. (2) In the flux-cored wire used for the welding electrode on the side of the sliding copper plate, mass% with respect to the total amount of the wire,
Ni: containing 0.5 to 4% (1)
2. A two-electrode vertical electrogas arc welding method for an extremely thick steel material according to item 1.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In general, a two-electrode vertical electrogas arc welding method can greatly increase the welding speed as compared with a conventional one-electrode one-pass welding method. FIG. 1 is a schematic view for explaining a two-electrode vertical electrogas arc welding method. In the drawings, reference numerals 5 and 6 denote wires of respective welding electrodes, reference numeral 2 denotes a sliding copper plate, reference numeral 8 denotes a fixed backing material, and reference numeral 9 denotes a backing material. Is a molten pool,
Reference numeral 10 denotes a weld metal. As the fixed backing material 8, a material in which one or several glass tapes are stacked on a solid flux backing material in which refractory material powder is solidified is usually used.
The shielding gas is blown into the groove by CO ₂ by a nozzle (not shown) provided on or adjacent to the sliding copper metal.

As a result of studies conducted by the present inventors through experiments and the like, in the conventional two-electrode vertical electrogas arc welding method, slag mainly generated from the welding electrode wire during welding accumulates on the molten pool, and the sliding copper contact is formed. The gold side slag 1 can escape from the sliding copper abutment 2 side through the groove of the slag escape 11, but the slag 3 between the welding electrode wires and the fixed backing material side slag 4 easily accumulates. It turned out that such a problem arises.

(1) The fixed backing material side slag 4 is mainly generated from the fixed backing material side electrode wire 6 and the fixed backing material 8. The slag jumps up during welding, in particular, the slag adheres to the fixed backing material side electrode wire 6, and the wire feeding becomes unstable, so that not only a healthy weld metal cannot be obtained, but also the groove surface of the material to be welded. In some cases, making welding impossible. (2) As means for solving the above problem (1),
As a welding electrode on the fixed backing material side, a solid wire that generates much less slag than a flux-cored wire is used. Some improvement can be achieved by using wires. However, in actual welding work, the cross-sectional area is not always constant due to variations in groove processing accuracy. appear. (3) Also, if the slag is excessively accumulated on the molten pool,
The deoxidizing action of the molten metal is excessively promoted, and the weld metal has an excessively hardened structure, so that sound weld metal properties cannot be obtained.

The present inventors have intensively studied the wire of a welding electrode used for welding in order to solve the problems in using the above-described two-electrode vertical electrogas arc welding method. As a result, by using a flux-cored wire that regulates the slag generating agent and alloying agent for the welding electrode on the sliding copper contact side and using a solid wire for the welding electrode on the fixed backing material side, the groove processing accuracy can be improved. It has been found that even when the groove cross-sectional area increases due to variation, a weld metal having good welding workability and good low-temperature toughness can be obtained stably.

The details of the present invention will be described below. According to the present invention, a sliding copper metal is applied to one surface of a material to be welded, and a fixed backing material is applied to the other surface, and two welding electrodes are formed in a groove formed by the material to be welded. This is a two-electrode vertical electrogas arc welding method in which a thick material to be welded is inserted by arranging in the thickness direction, and a flux in which the following slag forming agent and alloying agent are regulated in the welding electrode on the side of the sliding copper. A solid wire is used for the welding electrode on the fixed backing material side using a cored wire. Also, in this case, each welding electrode
Oscillation may be performed at the time of welding to achieve uniform penetration into the groove wall.

In the present invention, the component composition of the flux-cored wire used as the wire of the welding electrode on the sliding copper plate side is defined as follows in terms of mass% with respect to the total amount of the wire. Metal fluorides: Metal fluorides are effective for effectively reducing the amount of oxygen in the weld metal. However, if the content is less than 0.1%, the effect cannot be sufficiently exhibited, and good low-temperature toughness is obtained. I can't get it. On the other hand, if the content exceeds 0.8%, the amount of oxygen is extremely reduced and the hardenability becomes excessive, so that the strength of the weld metal is increased, and the impact value is decreased, and The melting point of the slag decreases and the weld metal cannot be held, causing metal dripping. Therefore, in the present invention, the content of metal fluoride is 0.1% to 0.8% in terms of F.
And Metal fluorides include CaF ₂ and NaF.

Slag forming agent containing metal fluoride: In the present invention, the content of the slag forming agent containing metal fluoride which determines the amount of slag in the molten pool is defined as 0.3 to 1%.
If it is less than 0.3%, the slag holdability is degraded, and metal dripping occurs. On the other hand, if it exceeds 1%, the amount of slag generated in the molten pool becomes excessive, causing slag splashing. The components of the slag forming agent include SiO ₂ , ZrO ₂ ,
Na ₂ O and the like.

The elements C, Si and Mn are components which mainly act as deoxidizing agents for the molten metal, and their contents are defined as follows. C: If the C content in the wire of the welding electrode is less than 0.03%, deoxidation becomes insufficient, nonmetallic inclusions remain in the weld metal, and the toughness of the weld metal deteriorates. On the other hand, when the C content is 0.1.
If it exceeds 12%, the strength of the weld metal will be excessive, and solidification cracks will easily occur. Therefore, C
The content was set to 0.03 to 0.12%.

Si: When the Si content in the wire of the welding electrode is less than 0.2%, deoxidation is insufficient, nonmetallic inclusions remain in the weld metal, and the toughness of the weld metal deteriorates. On the other hand, S
When the i content exceeds 0.9%, the strength of the weld metal becomes excessive, and the generation of spatters increases.
The welding workability deteriorates. Therefore, the Si content is set to 0.2 to 0.9%.

Mn: Mn acts as a deoxidizing agent similarly to C and Si, and affects the fluidity of slag by balance with Si. If the Mn content is less than 0.9%, deoxidation becomes insufficient, nonmetallic inclusions remain in the weld metal, and the toughness of the weld metal deteriorates, and the slag fluidity deteriorates, causing slag splashing. On the other hand, if the Mn content exceeds 2.8%, the welding strength becomes excessive and good low-temperature toughness cannot be obtained. Therefore, the Mn content is set to 0.9 to 2.8%.

Mo: Mo has the effect of enhancing the hardenability of the weld metal, and is added to ensure the strength of the weld metal in large heat input welding such as electrogas arc welding. If the Mo content in the wire is less than 0.1%, such effects cannot be obtained. Conversely, if the Mo content exceeds 0.6%, the strength of the weld metal becomes excessive and the toughness deteriorates due to precipitation of carbides. cause. Therefore, the Mo content is set to 0.1 to 0.6%.

Ti: Ti acts as a strong deoxidizing agent, forms nuclei for the formation of ferrite in the weld metal structure, and has the effect of refining crystal grains. If the content of Ti in the wire is less than 0.02%, the effect of improving the toughness by refining the crystal grains is not recognized, and if the content exceeds 0.4%, the strength of the deposited metal becomes excessive and the toughness increases. Deteriorates.
Therefore, the Ti content is set to 0.02 to 0.4%.

B: B refines pro-eutectoid ferrite and, in a two-electrode electrogas arc weld metal,
In particular, it acts to improve the toughness of the granular crystal part formed in the final solidified part. If the B content in the wire is less than 0.002%, the effect of refining crystal grains and improving toughness cannot be obtained, and if the content exceeds 0.012%, weld cracks are likely to occur. Therefore, the range of the B content is 0.002 to 0.0
It was set to 12.

The above are the basic components of the present invention. By adding Ni in the range of 0.5 to 4%, it is possible to obtain a welded joint capable of obtaining stable toughness up to a low temperature range by solid solution strengthening. Therefore, in the present invention, particularly in large heat input welding, Ni is added in the range of 0.5 to 4% when good low-temperature toughness is required. Ni content is 0.5%
Below, the effect of solid solution strengthening cannot be obtained, and if the content exceeds 4%, welding cracks occur.

[0024]

The present invention will be described in more detail with reference to the following examples. Flux-cored wire Nos. Having different components shown in Table 1. Prototypes Nos. 1 to 14 were used, and these wires were used as welding electrodes on the sliding copper abutment side. Two-electrode vertical electrogas arc welding was performed in one pass. The solid wire used for the welding electrode on the fixed backing material side at that time is JIS Z 3325 YGL1-4.
G The corresponding wire was used. Table 5 shows the test results as test results. No. 1 to No. The evaluation results of the welding workability and the mechanical properties of the weld metal when welding was performed under the conditions of No. 14 were shown. In addition, regarding the mechanical properties of the weld metal, the strength of the weld metal: 560 to 660 MPa, and the impact value at −40 ° C. of 50 J or more was accepted.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

[0029]

[Table 5]

In Table 5, No. 1 of the present invention example. In all of Nos. 1 to 5, good welding workability and mechanical properties of the weld metal were obtained.

The comparative example No. 6 has low C and Mo
And the hardenability was insufficient, and the weld metal strength and impact value were reduced. No. of Comparative Example. In No. 7, since the slag forming agent was small, metal sagging occurred during welding, and the bead appearance was deteriorated. In addition, the strength of the weld metal was increased due to the high Si, and the amount of oxygen in the weld metal was increased due to the low F conversion amount of metal fluoride, and the impact value of the weld metal was reduced. No. of Comparative Example. In No. 8, since the Mn was high, the strength of the weld metal was increased, and since B was low, the microstructure could not be refined and the impact performance of the weld metal was deteriorated.

The comparative example No. In No. 9, the strength of the weld metal was increased due to the high Ti, and the impact performance of the weld metal was deteriorated. No. of Comparative Example. In No. 10, slag splashing occurred frequently, particularly at a gap of 15 mm, because of a large amount of the slag forming agent.
In addition, since C was high, cracks occurred after welding, and the mechanical properties of the weld metal could not be measured. No. of Comparative Example. 11
The slag fluidity deteriorated due to low Mn, and slag splashing occurred. In addition, since B was high, cracks occurred after welding, so that the mechanical properties of the weld metal could not be measured.

The comparative example No. In No. 12, since the Mo content was high, the strength of the weld metal was increased, and the toughness was deteriorated. No. of Comparative Example. 13 is a large amount of metal fluoride in terms of F,
Metal sagging occurred and the appearance of the bead deteriorated, and the amount of oxygen in the weld metal decreased extremely, resulting in excessive quenching, increasing the strength of the weld metal and deteriorating the impact value of the weld metal. No. of Comparative Example. In No. 14, the slag forming agent was large, and slag splashing occurred frequently. In addition, since Ni was high, cracks occurred after welding, so that the mechanical properties of the weld metal could not be measured.

[0034]

According to the present invention, in a two-electrode vertical electrogas arc welding of a very thick steel plate, a flux-cored wire of a specific component is placed on the side of the sliding copper and the solid wire is placed on the fixed backing side. Since the two electrodes used are used, good welding workability and good mechanical properties of the weld metal can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a configuration of a welding method using the wire of the present invention.

[Explanation of Signs] 1 Sliding copper contact side slag 2 Sliding copper contact 3 Slag between welding electrode wires 4 Fixed backing material side slag 5 Sliding copper contacting side welding electrode wire 6 Backing material side welding electrode Wire 8 Fixed backing material 9 Weld pool 10 Weld metal 11 Slag relief

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B23K 37/06 B23K 37/06 P (72) Inventor Shigeru Ohkita 20-1 Shintomi, Futtsu-shi, Chiba New Japan F-term in Technical Development Division of Steel Corporation (reference) 4E001 AA03 BB10 CA01 DA03 DB01 EA05 4E081 AA06 AA09 BA37 BA40 CA17 DA05 DA20 DA39 EA05 EA38 4E084 AA17 BA03 BA04 BA05 BA06 BA09 BA11 BA12 CA03 CA26 DA13 FA03 GA03

Claims (2)

[Claims] 1. An extremely thick material to be welded is provided with a sliding copper abutment on one side and a fixed backing abutment on the other side, and two welding electrodes are provided in the groove. In a two-electrode vertical electrode electrogas arc welding method for welding a material to be welded by arranging the metal fluorides in a direction parallel to each other, the metal fluoride is added to the welding electrode on the sliding copper abutment side by mass% with respect to the total amount of the wire. In terms of F: 0.1 to 0.8%, slag forming agent containing metal fluoride: 0.3 to 1%, C: 0.03 to 0.12%, Si: 0.2 to 0.9 %, Mn: 0.9-2.8%, Mo: 0.1-0.6%, Ti: 0.02-0.4%, B: 0.002-0.012% A solid electrode is used as a welding electrode on the fixed backing material side using a wire, and a two-electrode vertical electrogas electrode of a very thick steel material is used. Click welding method. 2. In a flux-cored wire used for a welding electrode on the sliding copper plate side, mass% with respect to the total amount of the wire.
The two-electrode vertical electrogas arc welding method according to claim 1, further comprising 0.5 to 4% of Ni.