JP2024039483A - flux cored wire - Google Patents

Abstract

The present invention provides a flux-cored wire that can realize stable buried arc welding at low cost. [Solution] A flux-cored wire 1 for buried arc welding has a steel outer sheath 6 and a flux 5 filled in the steel outer sheath 6. Contains 0.40 to 1.20% by mass of a slag forming agent consisting of a substance, 13.70% by mass or more of metal powder, and 0.05 to 0.50% by mass of alkali metal-containing fluorides or oxides in total in terms of alkali metal. Further, the flux 5 contains 0.19 to 1.00% by mass of a gas generating agent made of fluoride based on the total mass of the wire. Furthermore, the flux 5 contains 0.30 to 1.00% by mass of a gas generating agent made of metal carbonate based on the total mass of the wire. Further, the flux 5 contains Ti or a Ti compound in a total amount of 0.30 to 0.75 mass% in terms of Ti based on the total mass of the wire. [Selection diagram] Figure 1

Description

The present invention relates to a flux-cored wire used in arc welding.

As one method of gas arc welding, a method called buried arc welding has been known for a long time, and is disclosed in, for example, Patent Document 1 listed below. In general arc welding, the arc generation position at the tip of the wire is located above the surface of the base metal, resulting in open arc welding, and a molten pool formed by melting the base metal and the wire is formed directly below the arc.

On the other hand, in buried arc welding, the welding voltage is lowered and the welding current is increased to increase the arc pressure. As a result, in buried arc welding, the arc generation position at the wire tip is located below the surface of the base metal, and the penetration depth of the molten pool becomes deeper, making it possible to efficiently weld thick plates with fewer welds. It can be carried out.

Patent No. 6777969

By the way, in buried arc welding, as described above, the arc generation position enters the molten pool and a deep octopus-shaped depression (hereinafter referred to as an arc hole) is formed by the arc. As a result, the arc is extinguished due to contact between the droplets formed at the tip of the wire and the surrounding molten metal, causing a short circuit, and then explosive re-ignition of the arc occurs repeatedly. There is a problem that is not stable.

In contrast, in Patent Document 1, the arc is stably generated by controlling the welding current with high precision. However, in order to control such welding current with high precision, an expensive power supply device is required, which is costly.

The present invention has been made in view of such problems, and an object of the present invention is to provide a flux-cored wire that can realize stable buried arc welding at low cost.

A flux-cored wire according to the present invention for solving the above problems is a flux-cored wire for a buried arc having a steel outer sheath and a flux filled in the steel outer sheath, wherein the flux is Contains 0.40 to 1.20% by mass of a slag forming agent made of metal oxide, 13.70% by mass or more of metal powder, and fluoride or oxide containing an alkali metal, with a total of 0.05 to 0.50 in terms of alkali metal value. It is characterized by containing % by mass.

According to the flux-cored wire of the present invention, stable buried arc welding can be achieved by containing a predetermined amount of a slag forming agent made of a metal oxide, metal powder, and a fluoride or oxide containing an alkali metal. .

FIG. 1 is a schematic cross-sectional view of a flux-cored wire according to an embodiment of the present invention. FIG. 2 is a schematic diagram for explaining buried arc welding according to an embodiment of the present invention.

Embodiments of the present invention will be described below. In this embodiment, buried arc welding is stabilized by adjusting the flux component of the metal flux-cored wire (composite wire). FIG. 1 is a schematic cross-sectional view schematically showing the configuration of a flux-cored wire according to this embodiment. As shown in the figure, the flux-cored wire 1 according to the present embodiment includes a core flux 5 and a steel outer sheath 6 that covers the flux 5 .

In this embodiment, the structure of the flux-cored wire 1 is a wrap type with a seam on the outer skin, but it may be a seamless type without a seam on the outer skin. Plating or the like may be further applied. In addition, in this specification, "~" indicating a numerical range is used to include the numerical values described before and after it as a lower limit value or an upper limit value.

In this embodiment, the steel outer skin 6 includes C (carbon): 0.023 mass%, Si (silicon): 0.01 mass%, Mn (manganese): 0.14 mass%, and P with respect to the total mass of the steel outer skin 6. (phosphorus): 0.008% by mass, S (sulfur): 0.006% by mass, and other components are Fe (iron) and inevitable impurities.

Regarding the size of the flux wire 1, the outer diameter of the steel outer skin 6 is φ1.6 mm. Of course, the size of the flux-cored wire 1 and the size and composition of the steel outer sheath 6 can be changed as appropriate.

As shown in Figure 2, in buried arc welding, the molten metal is pushed down by the arc force caused by the high-current electromagnetic pinch force, and welding progresses as an octopus-shaped space (arc hole) is formed. When a deep arc hole is formed with the aim of increasing penetration, the molten part of the wire tip often comes into contact with the molten metal, causing a short circuit, which extinguishes the arc and closes the arc hole, followed by an explosive arc. A series of unstable phenomena is repeated, resulting in the restriking of . This makes the welding unstable and the bead shape deteriorates.

Carbon dioxide gas, which is used as a shielding gas, has a large cooling effect due to gas dissociation, so the potential gradient of the arc is large and there is a strong tendency for it to occur in a concentrated manner.If a buried arc occurs and a deep arc hole is formed, the arc will be concentrated at the bottom of the arc hole. As a result, the arc force no longer acts on the entire area inside the arc hole, and the upper part of the arc hole where no arc is generated loses its support and tries to shrink, causing a short circuit between the droplet formed at the tip of the wire and the surrounding molten metal. However, the arc is extinguished.

This phenomenon occurs because there is a constant force acting on the arc hole due to the hydrostatic pressure and surface tension of the molten metal that tries to close it, and the arc hole is maintained by the arc force that resists this. This is because as the arc hole becomes deeper, it becomes difficult to apply arc force to the entire arc hole.

As a result of intensive studies on methods to avoid this phenomenon and to suppress the unstable phenomenon even if a deep arc hole is formed, it was found that an appropriate amount of fluoride or oxide containing an alkali metal was added to the flux 5 of the flux-cored wire 1. We have newly discovered that it is effective. Due to the addition of alkali metals, during buried arc welding, the arc is generated over a wide area within the octopus-shaped arc hole without being excessively concentrated at the bottom of the arc hole, thereby resisting hydrostatic pressure and surface tension. This is because the arc hole can be maintained.

In addition, we have newly found that by adding an appropriate amount of a gas generating agent made of fluoride or metal carbonate to Flux 5, it is possible to maintain arc holes more stably. This is because in an octopus-shaped arc hole with an opening in only one direction, if more gas is generated from the tip of the flux-cored wire located inside the arc hole than the amount of gas escaping from the opening, the internal pressure inside the arc hole will increase. This is because the clogging of the arc hole can be more stably prevented.

The above effects lead to good penetration and bead appearance in buried arc welding. These phenomena and effects occur only in an arc that occurs in a unique closed space called a buried arc surrounded by molten metal, and provide completely new knowledge that has not been obtained with conventional open arcs where the surrounding area is open. It is.

On the other hand, new findings have been made regarding penetration inhibiting factors in buried arc welding. In other words, when the amount of slag forming agent made of metal oxide in the flux-cored wire becomes excessive, it becomes molten slag and stays at the bottom of the arc hole, but the electrical conductivity of molten slag of metal oxide is low. As a result, arc generation and heating at the bottom of the arc hole are delayed, and as the amount of slag increases, the penetration depth becomes shallower.

In order to prevent this, it was found that it was necessary to limit the amount of slag forming agent in the flux 5 of the flux-cored wire 1 to an appropriate amount, and instead increase the ratio of metal powder with excellent electrical conductivity. did.

It was also discovered that among metal oxides, titanium oxide has better electrical conductivity than other metal oxides, and does not become a factor inhibiting penetration in buried arc welding. Therefore, depending on the required toughness level of the weld metal, if necessary, it can be added in the form of metallic titanium or a titanium compound in combination with boron addition to refine the microstructure.

Table 1 below shows specific Examples A1 to 20 and Comparative Examples B1 to B5 regarding the components of the flux 5 of this embodiment. In Table 1, the component ratio of the flux 5 is the mass ratio of each component to the total mass of the flux-cored wire 1 as a percentage (mass %).

In Table 1, "F.R." indicates the filling rate of flux 5 in flux-cored wire 1. Example A and Comparative Example B of Flux 5 contain "metal", "metal carbonate", "slag forming agent (alkali metal oxide)", "fluoride", and "slag forming agent (metal oxide)". )" and "slag remover" at predetermined component ratios (including the case of 0% by mass).

In Example A and Comparative Example B, the "metals" were Fe (iron), Mn (manganese), Mg (magnesium), Al (aluminum), Fe-Si alloy, Fe-Ti alloy, Contains powders of Fe-B alloy, Fe-Mn alloy, and Si-Mn alloy.

Further, Example A and Comparative Example B contain CaCO ₃ (calcium carbonate) as a “metal carbonate”. Metal carbonates can also include, for example, magnesium carbonate, dolomite, and the like.

Further, Example A and Comparative Example B contain a metal oxide including an alkali metal oxide as a slag forming agent, and the alkali metal oxide slag forming agent is Na ₂ O・Al ₂ O ₃・Contains 6SiO ₂ (soda feldspar) and KAlSi ₃ O ₈ (potassium feldspar). Further, Example A and Comparative Example B contain TiO ₂ (titanium oxide) and ZrO ₂ (zirconia) as metal oxide slag forming agents. Metal oxide slag formers can also include, for example, Fe ₂ O ₃ (iron oxide).

Furthermore, in Example A and Comparative Example B, NaF ₂ (sodium fluoride), K ₂ SiF ₆ (potassium silicofluoride), CaF ₂ (calcium fluoride), Na ₃ AlF ₆ (ice crystals) were used as “fluorides”. (sodium hexafluoroaluminate). The fluoride may also include, for example, potassium fluoride, aluminum fluoride, magnesium fluoride, and the like. Further, Example A and Comparative Example B contain Bi ₂ O ₃ (bismuth oxide) as a slag remover.

Next, the evaluation results of Example A and Comparative Example B will be explained using Tables 2 and 3. In this embodiment, for Example A and Comparative Example B, buried arc welding is performed under a CO ₂ gas shield to improve "penetration", "bead appearance", "bead shape", and "stability of current/voltage". The "comprehensive evaluation" (Table 2 above) and toughness evaluation (Table 3) were performed.

Regarding Table 2, the evaluation of "penetration" and "bead shape" was performed by etching the cross section of the plate material that was bead-on-plate welded using flux-cored wire 1 of Example A and Comparative Example B. Processed so that the shape can be observed, the penetration depth (mm), bead width (mm), and excess height (mm) are determined by image processing from the photographed etched cross-sectional image, and evaluation is performed based on these calculated values. went.

The evaluation results for "melt-in" were as follows: Examples A1, 2, 4, 6-10, 12-17, and 19 were evaluated as "○ (11.0 or higher)," and Examples A3, 5, 11, 18, and 20 and Comparative Example B1 were evaluated as "○ (11.0 or higher)." "△ (10.0 to 10.9)" and Comparative Examples B2 to 5 were "× (9.9 or less)".

The evaluation results for "bead shape (bead width)" are "○ (19.0 to 23.9)" for Examples A1 to 6, 8 to 16, 18 to 20 and Comparative Examples B1 and 3, and "○ (19.0 to 23.9)" for Examples A7 and 17 and Comparative Example B4 was “△ (24.0 or more)” and Comparative Examples B2 and 5 were “× (18.9 or less)”.

The evaluation results for "bead shape (excess height)" were "〇 (6.0 or less)" for Examples A2 to 6, 8, 9, 13, 14, 19, and 20 and Comparative Examples B1, 3 to 5; Examples A1, 7, 10 to 12, and 15 to 18 were rated "△ (6.1 to 6.9)", and Comparative Example B2 was rated "× (7.0 or more)".

The "bead appearance" was evaluated visually. The evaluation results for "bead appearance" were as follows: Examples A1, 3, 4, 6, 11, 14, 15, 17 to 20 and Comparative Examples B2, 3, and 5 were evaluated as "○ (good)"; Samples 7 to 10, 12, 13, and 16 were graded "△ (some problems)" and Comparative Examples B1 and 4 were graded "x (defective)."

The evaluation results of "stability of current and voltage" were evaluated by recording the current value and voltage value during welding on a data logger, and calculating the standard deviation during each welding. The evaluation results of "voltage stability" are "○ (1.50 or less)" for Examples A2 to 6, 10 to 12, 14, 16 to 20 and Comparative Examples B1 and 3, and "○ (1.50 or less)" for Examples A1, 7 to 9, and 13. , 15 was "△ (1.51 to 1.69)", and Comparative Example B4 was "× (1.70 or more)".

In addition, the evaluation results of "current stability" were as follows: Examples A3, 9, 11 to 20 and Comparative Examples B1 and 3 were "○ (40.0 or less)", and Examples A1, 2, 4 to 8, and 10 were " △ (40.1 to 59.9))”, and Comparative Example B4 was “× (60.0 or more)”.

Above, in order to comprehensively evaluate each evaluation of "penetration", "bead appearance", "bead shape", and "current/voltage stability" in Table 2, "〇" is 5 as "overall evaluation". If there are more than 1, mark "◎", if there are 3 or 4 "〇", mark "〇", if there are 1 or 2 "〇", mark "△", if there is even 1 "×", mark "×" Table 2 shows the overall evaluation results.

As the evaluation results of “Comprehensive evaluation”, Examples A3, 4, 6, 14, 19, and 20 are “◎”, and Examples A1, 2, 5, 8, 9, 11-13, 15-18 are “〇” , Examples A7 and 10 were rated "Δ", and Comparative Examples B1 to B5 were rated "x".

Regarding Table 3, toughness evaluation was performed by taking impact test pieces from test plates that were butt welded using flux-cored wire 1 of Example A and Comparative Example B, and performing a Charpy impact test three times at a test temperature of 0°C. The evaluation was made based on the average value of the impact values. Toughness evaluation was performed only on Examples 2, 4, and 6 and Comparative Example B3. The results of the toughness evaluation were that Examples A2 and 6 were ``Good'' (60 or higher), Example A4 was ``B'', and Comparative Example B3 was rated poor ``X'' (less than 60).

Next, based on the evaluation results of Example A and Comparative Example B, the characteristics of the numerical range of the flux component according to the present embodiment will be explained in order with reference to Table 4. Table 4 lists the numerical values of each Example A and Comparative Example B with respect to the following numerical ranges (1) to (8).

(1) Slag forming agent consisting of metal oxide: 0.40 to 1.20% by mass
Flux 5 contains a slag forming agent (Na ₂ O・Al ₂ O ₃・6SiO ₂ , KAlSi ₃ O ₈ , TiO ₂ , ZrO ₂ ) made of metal oxides including alkali metal oxides based on the total mass of the wire. It is desirable to contain 0.40 to 1.20% by mass in total. Regarding numerical range (1), all of Examples A1 to 20 satisfy it, and all of Comparative Examples B1 to B5 do not satisfy it.

If the content of the slag forming agent is less than 0.40% by mass, the amount of slag generated that covers the bead surface during welding will be small, and the bead appearance will become unstable. Furthermore, when the content of the slag forming agent exceeds 1.20% by mass, the amount of slag retained and accumulated at the bottom of the arc hole increases, inhibiting arc generation and reducing the penetration depth. Moreover, when the content of the slag forming agent increases, the content of the metal powder mentioned above cannot be increased.

(2) Metal powder: 13.70% by mass or more Flux 5 contains metal powders of metals including alloys (Fe, Mn, Si, Ti, B, Mg, Al) in a total of 13.70% by mass or more based on the total mass of the wire. It is desirable to include. Regarding numerical range (2), all of Examples A1 to 20 satisfy it, and Comparative Examples B2 to B5 do not satisfy it.

If the metal powder content is less than 13.70% by mass, the amount of metal necessary to fill the groove melted by the arc will not be secured due to the insufficient amount of metal powder, so the arc hole will shrink and the bead shape etc. becomes worse.

(3) Alkali metal equivalent value of fluoride or oxide containing alkali metal: 0.05 to 0.50% by mass
The flux 5 is composed of fluorides (NaF ₂ , K ₂ SiF ₆ , Na ₃ AlF ₆ ) or oxides (Na ₂ O・Al ₂ O ₃・6SiO ₂ , KAlSi ₃ O) containing alkali metals based on the total mass of the wire. ₈ ) in a total amount of 0.05 to 0.50 mass% in terms of alkali metal. It may contain only fluoride, only oxide, or both fluoride and oxide. Numerical range (3) is satisfied by all of Examples A1 to 20, but not by Comparative Example B5.

When an alkali metal is added from the center of the wire, the arc generated from the tip of the wire spreads over the entire inner wall of the arc hole and applies arc pressure, thereby stabilizing the arc hole. When the alkali metal content is less than 0.05% by mass, the spread of the arc becomes small and the arc hole becomes unstable. Furthermore, if the alkali metal content exceeds 0.50% by mass, the arc hole will expand too much, resulting in welding with shallow penetration.

(4) Fluoride as a gas generating agent: 0.19 to 1.00% by mass
It is desirable that the flux 5 contains a total of 0.19 to 1.00% by mass of fluoride (NaF ₂ , K ₂ SiF ₆ , CaF ₂ , Na ₃ AlF ₆ ) as a gas generating agent based on the total mass of the wire. Numerical range (4) is satisfied by Examples A2 to 6, 8 to 10, 13 to 17, 19, and 20, and not satisfied by Comparative Examples B2 to B5.

Conventionally, adding fluoride has the effect of reducing hydrogen, which causes pore defects and cold cracking, but this time it was added to Flux 5 as a gas generating agent.

By adding a gas generating agent made of fluoride to the flux 5, gas is generated from the tip of the flux-cored wire 1, increasing the internal pressure of the arc hole, and preventing arc hole clogging more stably. I can do it. This effect can only be obtained due to the unique arc generation form of buried arcs, in which the tip of the wire that has entered the inside of the arc hole becomes the arc generation position.

In order to obtain this effect, it is desirable to add 0.19% by mass or more of fluoride as a gas generating agent. Furthermore, if the content of fluoride as a gas generating agent exceeds 1.00% by mass, the internal pressure of the arc hole will become too high, resulting in open arc welding, resulting in shallow welding and large spatter particles. This results in deterioration of welding workability.

(5) Metal carbonate as gas generating agent: 0.30 to 1.00% by mass
The flux 5 desirably contains 0.30 to 1.00% by mass of metal carbonate (Ca ₂ CO ₃ ) as a gas generating agent based on the total mass of the wire. Numerical range (5) is satisfied by Examples A3, 4, 6, 13, 14, 19, and 20, and is not satisfied by Comparative Examples B2 to B5.

Conventional knowledge has it that adding metal carbonates has the effect of reducing hydrogen in welded joints, just like fluorides, and also has the effect of increasing the stability and concentration of the arc. This time, however, it was added to Flux 5 as a gas generating agent, just like fluorides.

By adding metal carbonate as a gas generating agent to the flux 5, carbon dioxide (CO ₂ ) gas is generated from the tip of the flux-cored wire 1, and has the same effect as the fluoride gas generating agent described above. play.

In order to effectively obtain these effects, it is desirable to contain 0.3% by mass or more of metal carbonate as a gas generating agent, but if it is added in excess of 1.00% by mass, excessive CO ₂ gas will be generated. , which is undesirable because it causes melting and deterioration of bead appearance.

(6) Ti equivalent value of Ti or Ti compound: 0.30 to 0.75 mass%
It is desirable that the flux 5 contains Ti or a Ti compound (Fe-Ti, TiO ₂ ) in a total amount of 0.30 to 0.75 mass% in terms of Ti, based on the total mass of the wire. It may contain only Ti, only a Ti compound, or both Ti and a Ti compound. Regarding numerical range (6), all Examples A1 to 20 satisfy it, but Comparative Examples B1 and B3 to 5 do not satisfy it.

Ti is a strong deoxidizing agent and has the effect of reducing the oxygen content of the weld metal and improving the toughness value. In addition, the formed Ti oxide floats away as slag, but the fine grained Ti oxide left behind in the weld metal forms transformation nucleation during the phase transformation from austenite to ferrite during the cooling of the weld metal. It has the effect of becoming a site and making the microstructure finer after the metamorphosis, increasing toughness.

In order to effectively obtain these effects, it is desirable to contain Ti or a Ti compound at a total Ti equivalent value of 0.30 mass% or more, but if it is added in excess of 0.75 mass%, the amount of solid solution titanium increases. Therefore, it is preferable that the content is 0.75% by mass or less, since it may actually deteriorate the toughness.

Additionally, slag made of metal oxides generally has poor electrical conductivity, so if slag stays at the bottom of the octopus-shaped arc hole during buried arc welding, it will inhibit the generation of an arc to the bottom of the arc hole and reduce penetration. Although this may be a factor, slag made of TiO ₂ has superior electrical conductivity compared to other oxides, so it does not inhibit arc generation.

(7) B conversion value of B compound: 0.0010 to 0.0085 mass%
It is desirable that the flux 5 contains a B compound (Fe-B) in an amount of 0.0010 to 0.0085 mass% in terms of B based on the total mass of the wire. Numerical range (7) is satisfied by Examples A1, 2, 6 to 12, and 15 to 18, and is not satisfied by Comparative Examples B1, 3, and 5.

B (boron) segregates at the austenite grain boundaries of the weld metal, increases the hardenability of the grain boundaries, suppresses the transformation from the austenite grain boundaries to grain boundary ferrite and upper bainite, and remains within the austenite grains. It contributes to the formation of a microstructure mainly consisting of acicular ferrite that undergoes multiple simultaneous transformations from Ti oxide.

However, if it is added in an amount exceeding 0.0085% by mass, the hardenability of the entire weld metal is increased too much, which may actually deteriorate the toughness. Therefore, in the metal flux-cored wire 1 in which the amount of slag forming agent is reduced and the amount of metal powder is increased, as in this embodiment, it is desirable to add the B compound in the above numerical range (7).

(8) Flux filling rate: 17.5 to 19.5 mass%
The flux-cored wire 1 preferably contains 17.5 to 19.5% by mass of flux 5 based on the total mass of the wire. Regarding numerical range (8), all Examples A1 to 20 satisfy it, but Comparative Examples B3 to B5 do not satisfy it.

The flux filling rate of a conventional general welding wire is 10 to 15% by mass, but in this embodiment, the filling rate of flux 5 is increased to achieve deep penetration and high welding. By increasing the filling rate of the flux 5, the cross-sectional area of the steel outer sheath 6 becomes smaller than that of a conventional general welding wire, and the density of the current flowing only through the steel outer sheath 6 becomes higher.

As a result, the resistance heat generation of the protruding portion increases, so that the flux-cored wire 1 melts quickly and the amount of metal per unit time increases.

If the filling rate of the flux 5 is less than 17.5% by mass, the penetration becomes shallow and defects such as waving appear on the bead appearance occur. Further, if the filling rate of the flux 5 exceeds 19.5% by mass, a problem arises in that the steel outer skin 6 cannot be stably filled with the flux 5. Therefore, it is desirable that the filling rate of the flux 5 be within the above numerical range (8).

The embodiments of the present invention have been described in detail above. According to the present embodiment, the slag forming agent made of a metal oxide, metal powder, and a stable slag by containing a predetermined amount of a fluoride or oxide containing an alkali metal. Buried arc welding can be realized.

The embodiments of the present invention are not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the shape and size of the flux-cored wire can be changed as appropriate.

1 Flux-cored wire 5 Flux 6 Steel outer sheath

A flux-cored wire according to the present invention for solving the above problems is a flux-cored wire for buried arc welding having a steel outer sheath and a flux filled in the steel outer sheath, wherein the flux is Contains 0.40 to 1.20% by mass of a slag forming agent made of a metal oxide, 13.70% by mass or more of metal powder, and fluoride or oxide containing an alkali metal, with a total of 0.05 to 1.20% by mass of a slag forming agent made of a metal oxide, based on the mass The flux is characterized in that it contains 0.50% by mass, and the filling rate of the flux is 17.5 to 19.5% by mass relative to the total mass of the wire .

Claims (6)

A flux-cored wire for buried arc welding having a steel outer sheath and a flux filled in the steel outer sheath,
The flux is based on the total mass of the wire,
Contains 0.40 to 1.20% by mass of a slag forming agent made of metal oxide,
Contains 13.70% by mass or more of metal powder,
A flux-cored wire characterized by containing a fluoride or oxide containing an alkali metal in a total amount of 0.05 to 0.50% by mass in terms of alkali metal. The flux-cored wire according to claim 1, wherein the flux contains 0.19 to 1.00% by mass of a gas generating agent made of fluoride based on the total mass of the wire. 3. The flux-cored wire according to claim 1, wherein the flux contains 0.30 to 1.00% by mass of a gas generating agent made of metal carbonate based on the total mass of the wire. The flux-cored wire according to claim 1, wherein the flux contains Ti or a Ti compound in a total amount of 0.30 to 0.75 mass% in terms of Ti, based on the total mass of the wire. The flux-cored wire according to claim 1, wherein the flux contains a B compound in an amount of 0.0010 to 0.0085 mass% in terms of B based on the total mass of the wire. The flux-cored wire according to claim 1, characterized in that the flux filling rate is 17.5 to 19.5 mass% in terms of mass ratio to the total mass of the wire.

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