Flux-cored wire and method for manufacturing welded joint

Abstract

This flux-cored wire for welding includes a steel sheath and a flux filled inside the steel sheath and contains an oxide and an alloy component. The total amount X of Mn oxides in terms of MnO is 0.3-15.0% in mass% with respect to the total mass of the flux-cored wire. The total amount Y of Ti oxides in terms of TiO2 is 0.1-10.0%. The ratio of the total amount X of Mn oxides to the total amount of the total amount X of Mn oxides and the total amount Y of Ti oxides (X / (X+Y)) is 0.65-1.00. The total content of Mn excluding Mn contained as an oxide is 3.0-30.0%.

Description

Method for manufacturing flux-cored wire and welded joints

[0001] This disclosure relates to a method for manufacturing flux-cored wire and welded joints.

[0002] In recent years, due to stricter regulations on carbon dioxide emissions caused by global warming, demand for hydrogen fuel, which emits no carbon dioxide compared to oil and coal, and natural gas, which emits less carbon dioxide, has been increasing. Consequently, the demand for the construction of liquid hydrogen tanks, liquid carbon dioxide tanks, and LNG tanks for use on ships and land has also increased globally. The steel used in liquid hydrogen tanks, liquid carbon dioxide tanks, and LNG tanks is nickel-based low-temperature steel containing 6-9% Ni, in order to ensure toughness at extremely low temperatures of -196°C. Austenitic wires are used for welding these nickel-based low-temperature steels to obtain weld metal with excellent low-temperature toughness.

[0003] For example, Patent Document 1 discloses a stainless steel wire for gas-encased arc welding, in which the surface of a stainless steel core wire is covered with nickel plating having a surface hardness of Hv hardness of 300 to 500 and a thickness of 0.2 to 4 μm, and the free expansion diameter of the coated wire is in the range of 350 to 800 mm.

[0004] Patent Document 1: Japanese Unexamined Patent Publication No. 2002-18587

[0005] When welding in a vertical upward position using flux-cored wire, it is important to raise the solidification temperature of the slag above that of iron (Fe) to support the molten pool with the solidified slag. The solidification temperature of the slag can be increased by adding oxides such as Ti oxide. On the other hand, Mn as an alloying component lowers the solidification temperature of the slag. However, since Mn has the function of improving the low-temperature toughness of the weld metal, it is required to improve weldability in all positions while maintaining the amount of Mn.

[0006] Therefore, the object of this disclosure is to provide an austenitic flux-cored wire with improved weldability in all positions, and a method for manufacturing a welded joint using the flux-cored wire.

[0007] Means for solving the problem include the following embodiments: <1> A flux-cored welding wire comprising a steel outer sheath and flux filled inside the steel outer sheath, wherein the wire contains oxide and alloy components, optionally containing at least one selected from the group consisting of fluorides, nitrides, metal carbonates, and sulfates, optionally containing at least one specific compound selected from the group consisting of Sr compounds, Y compounds, Zr compounds, Ba compounds, and Sc compounds, wherein the total amount X of Mn oxide in terms of MnO equivalent is 0.3% to 15.0% by mass % of the total mass of the flux-cored wire, and Ti oxide is TiO ２Flux-cored wire wherein the total amount Y of the converted value is 0.1% to 10.0%, the ratio of the total amount X of Mn oxide to the total amount Y of Ti oxide (X / (X+Y)) is 0.65 to 1.00, and the total content of Mn excluding the Mn contained as oxide is 3.0% to 30.0%. <2> The content of the alloy components, in mass % of the total mass of the flux-cored wire, is as follows: C: 0.003% to 0.650%, Si: 0.03% to 0.80%, Mn: 3.0% to 30.0%, P: 0.050% or less, S: 0.050% or less, Cu: 0% to 10.00%, Ni: 0% to 30.0%, Cr: 0% to 30.0%, Mo: 0% to 10.0%, Nb: 0% to 5.00%, V: 0% to 5.00%, Co: 0% to 10.00%, Pb: 0% to 1.00%, Sn: 0% to 1.00%, Al: 0% to 0.50%, Ti: 0% to 0.50%. The flux-cored wire according to <1>, wherein the alloy components are: Ta: 0% to 1.00%, Hf: 0% to 1.00%, W: 0% to 30.00%, Mg: 0% to 0.50%, REM: 0% to 0.50%, Zr: 0% to 5.00%, Ca: 0% to 0.50%, B: 0% to 0.1000%, and N: 0% to 0.500%, with the remainder being Fe and impurities. <3> The flux-cored wire according to <2>, wherein the mass ratio ([Mn] / [Ni]) of the Mn content [Mn] and the Ni content [Ni] included as alloy components is 0.30 to 3.00. <4> The flux-cored wire according to any one of <1> to <3>, wherein the oxide contains at least one specific oxide selected from the group consisting of Si oxide, Zr oxide, Al oxide, Na oxide, K oxide, Ba oxide, Ca oxide, Mg oxide, and Fe oxide in the following range in mass% of the total mass of the flux-cored wire, and the total content of the specific oxide is greater than 0% to 10.00% in mass% of the total mass of the flux-cored wire. SiO of Si oxide ２ Total amount of converted value: 0% to 5.00% Zr oxide ZrO ２ Total amount of converted value: 0% to 5.00% Al oxide２ O ３ Total amount of conversion value: 0% to 5.00% Na of Na oxide ２ Total amount of conversion value: 0% to 5.00% K of K oxide ２ Total amount of conversion value: 0% to 5.00% BaO of Ba oxide, total amount of conversion value: 0% to 5.00% CaO of Ca oxide, total amount of conversion value: 0% to 5.00% MgO of Mg oxide, total amount of conversion value: 0% to 5.00% FeO of Fe oxide <5> As the fluoride, K ２ SiF ６ , K ２ ZrF ６ , NaF, Na ３ AlF ６ , CaF ２ , LiF, and MgF ２ containing at least one specific fluoride selected from the group consisting of, and the total content of the specific fluoride being more than 0% to 10.00% by mass based on the total mass of the flux-containing wire, the flux-containing wire according to any one of <1> to <4>. <6> As the metal carbonate, MgCO ３ , Na ２ CO ３ , LiCO ３ , CaCO ３ , K ２ CO ３ , BaCO ３ , FeCO ３ , MnCO ３ , and SrCO ３ containing at least one specific metal carbonate selected from the group consisting of, and the total content of the specific metal carbonate being more than 0% to 10.00% by mass based on the total mass of the flux-containing wire, the flux-containing wire according to any one of <1> to <5>. <7> As the nitride, AlN, BN, Ca ３ N ２ , CeN, CrN, Cu ３ N, Fe ４ N, Fe ３ N, Fe ２ N, Mg ３ N, Mo ２ N, NbN, Si ３ N４ , TiN, VN, ZrN, Mn ２ N and Mn ４ A flux-cored wire according to any one of <1> to <6>, wherein it contains at least one specific nitride selected from the group consisting of N, and the total content of the specific nitride is greater than 0% to 10.00% by mass relative to the total mass of the flux-cored wire. <8> A flux-cored wire according to any one of <1> to <7>, wherein it contains at least one specific compound, and the total content of Sr, Y, Zr, Ba, and Sc elements contained in the specific compound is greater than 0% to 1.0000% by mass relative to the total mass of the flux-cored wire. <9> A flux-cored wire according to any one of <1> to <8>, wherein the steel sheath does not have welded joints at the seams. <10> A flux-cored wire according to any one of <1> to <8>, wherein the steel sheath has welded joints at the seams. <11> A flux-cored wire according to any one of <1> to <10>, wherein the surface of the steel outer sheath is coated with either or both polytetrafluoroethylene oil and perfluoropolyether oil. <12> A method for manufacturing a welded joint, comprising the step of welding steel materials using a flux-cored wire according to any one of <1> to <11>.

[0008] This disclosure provides an austenitic flux-cored wire with improved weldability in all positions, and a method for manufacturing a welded joint using the flux-cored wire.

[0009] Embodiments, which are examples of this disclosure, will now be described. These descriptions and examples are illustrative of embodiments and do not limit the scope of the invention. In this specification, numerical ranges expressed using "~" mean ranges that include the numbers before and after "~" as lower and upper limits, respectively, unless "greater than" or "less than" is attached to the numbers before and after "~". If "greater than" or "less than" is attached to the numbers before and after "~", the numerical range means ranges that do not include those numbers as lower or upper limits. In numerical ranges described in steps in this specification, the upper limit of one step numerical range may be replaced with the upper limit of another step numerical range, or with the value shown in the examples. Similarly, the lower limit of one step numerical range may be replaced with the lower limit of another step numerical range, or with the value shown in the examples. Furthermore, "%" for content means "mass%" unless otherwise specified. "0~" for content (%) means that the component is an optional component and does not need to be included.

[0010] Each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition, if multiple types of the substance corresponding to each component are present in the composition, unless otherwise specified, it means the total amount of those multiple types of substances present in the composition. The term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes, as long as the intended function of that process is achieved.

[0011] <Flux-cored wire> The flux-cored wire according to this disclosure (hereinafter also simply referred to as "wire") is a flux-cored wire for welding comprising a steel sheath (hereinafter also simply referred to as "sheath") and flux filled inside the sheath. The welding wire according to this disclosure contains oxide and alloy components. The wire may optionally contain at least one selected from the group consisting of fluorides, nitrides, metal carbonates, and sulfates, and may contain at least one specific compound selected from the group consisting of Sr compounds, Y compounds, Zr compounds, Ba compounds, and Sc compounds. The wire has a total amount X of Mn oxides converted to MnO (hereinafter also simply referred to as "Mn oxide amount X") in mass % of the total mass of the wire, and Ti oxide TiO ２ The total converted amount Y (hereinafter also simply referred to as "Ti oxide amount Y") is between 0.1% and 10.0%, and the ratio of the amount of Mn oxide X to the total amount of Ti oxide Y (X / (X+Y)) is between 0.65 and 1.00. In addition, the total content of Mn excluding the Mn contained as oxide (hereinafter also simply referred to as "Mn excluding oxide") is between 3.0% and 30.0% by mass relative to the total mass of the flux-cored wire.

[0012] The wire described herein can improve weldability in all positions. The reason for this effect is presumed to be as follows.

[0013] When welding in a vertical upward position using flux-cored wire, it is important to suppress the dripping of molten metal in the molten pool. For example, if the solidification temperature of the slag is higher than that of iron (Fe), the molten pool is supported by the slag, which solidifies before the molten metal, making welding in the vertical upward position easier and improving weldability in all positions. One way to increase the solidification temperature of the slag is to add oxides that affect the solidification temperature, such as Ti oxide. On the other hand, increasing the amount of Mn (excluding oxides) in the wire lowers the solidification temperature of the slag and reduces weldability in all positions. However, Mn is an austenite-stabilizing element and can promote the austenitization of the weld metal obtained by welding, improving its low-temperature toughness. Therefore, there is a need for flux-cored wire that improves weldability in all positions while maintaining the amount of Mn that affects the low-temperature toughness of the weld metal.

[0014] In contrast, the wire according to this disclosure has a Mn oxide content X, a Ti oxide content Y, and their ratio (X / (X+Y)) within the above range, and the amount of Mn excluding oxides is within the above range. In other words, the amount of Mn excluding oxides in the wire is suppressed to 30.0% or less, and instead the amount of Mn oxide X is increased to 0.3% or more. Also, since the ratio of the amount of Mn oxide X to the amount of Ti oxide Y (X / (X+Y)) is 0.65 or more, a sufficient amount of Mn oxide is contained. The Mn oxide decomposes into Mn and O in the arc and molten pool, and Mn becomes a component of the weld metal. Therefore, the Mn in the Mn oxide promotes the austenitization of the weld metal, and the low-temperature toughness of the weld metal can be improved. Thus, the wire according to this disclosure can be suitably used when forming an austenitic weld metal. In addition, the Mn oxide has little effect on the solidification temperature of the slag, that is, the lowering of the solidification temperature of the slag is suppressed. Therefore, welding in the vertical upward position becomes easier. As a result, according to this disclosure, a flux-cored wire can be obtained that improves weldability in all positions while maintaining the amount of Mn that affects low-temperature toughness in the weld metal.

[0015] The requirements for flux-cored wires relating to this disclosure are described below.

[0016] The wire according to this disclosure contains at least an oxide as a compound component, and further contains chemical components other than the compound component (also referred to simply as "alloy components" in this specification). Examples of compound components other than oxides include fluorides, metal carbonates, nitrides, and sulfates. The compound components also include Sr compounds, Y compounds, Zr compounds, Ba compounds, and Sc compounds. The wire according to this disclosure melts together with a portion of the steel material during welding and becomes weld metal after solidification.

[0017] The total amount of Mn excluding oxides (Mn content excluding oxides) refers to the total amount of Mn elements in Mn compounds contained in the wire as fluorides, nitrides, metal carbonates, and sulfates, and the total amount of Mn elements contained in the wire as alloying components (i.e., chemical components excluding oxides, fluorides, nitrides, metal carbonates, and sulfates). Examples of Mn excluding oxides include, for example, ferromanganese, silicon manganese, manganese nitride, and Mn in metallic components added to the wire as alloying components (so-called metallic manganese).

[0018] [Amount of Mn excluding oxides] The wire according to this disclosure has a total Mn content (amount of Mn excluding oxides) of 3.0% to 30.0%. Mn is an austenite-stabilizing element and can promote the austenitization of the weld metal obtained by welding and improve low-temperature toughness. For this reason, the lower limit of the amount of Mn excluding oxides is set to 3.0% or more. On the other hand, increasing the amount of Mn excluding oxides in the wire lowers the solidification temperature of the slag and reduces weldability in all positions. For this reason, the upper limit of the amount of Mn excluding oxides is set to 30.0% or less. The lower limit of the amount of Mn excluding oxides in the wire is preferably 3.5%, 4.0%, 4.5%, or 5.0%. The upper limit of the amount of Mn excluding oxides in the wire is preferably 28.0%, 26.0%, 24.0%, 22.0%, 20.0%, 18.0%, 16.0%, or 15.0%.

[0019] [Compound Components] The compound components contained in the wires relating to this disclosure are described below. In the description of compound components, "%" means "mass % of the total mass of the flux-cored wire" unless otherwise specified. Compound components present in the steel sheath are either absent or present in extremely small amounts. Therefore, the compound component content in this specification refers to the compound component content contained in the flux.

[0020] (Ti oxide TiO ２ Total amount of converted value Y: 0.1% to 10.0% Ti oxide is a slag component and has the effect of increasing the solidification temperature of the slag and suppressing the dripping of molten metal when welding in a vertical upward position. In addition, Ti oxide has the effect of uniformly covering the entire bead with slag. Furthermore, Ti oxide has the effect of stabilizing the arc duration and reducing the amount of spatter generated. By including Ti oxide in the wire, welding workability (especially vertical welding performance) can be improved. Therefore, Ti oxide is included in the wire. On the other hand, Ti oxide increases the oxygen content of the weld metal and deteriorates the low-temperature toughness. Therefore, the amount of Ti oxide Y in the wire is set to 0.1 to 10.0%. The lower limit of the amount of Ti oxide Y in the wire is preferably 0.5%, 1.0%, 2.0%, or 3.0%. The upper limit of the Ti oxide content Y in the wire is preferably 8.0%, 7.0%, 6.0%, or 5.0%.

[0021] Ti oxides can mainly exist as rutile, titanium oxide, titanium slag, ilmenite, sodium titanate, and potassium titanate in flux. Ti oxide TiO ２ The total amount of the converted value is the total amount of Ti oxide contained in the wire, plus TiO2. ２ When converted to TiO ２ This is a mass percentage relative to the total mass of the wire. Examples of Ti oxides include TiO, TiO ２ Ti ２ O ３ Ti ３ O ５ These are some examples, and they are added as rutile, titanium dioxide, titanium slag, ilmenite, sodium titanate, potassium titanate, etc.

[0022] -Ti oxide TiO ２ How to calculate the total amount of converted values ​​- TiO2 oxide ２ The total amount of the converted value is determined by analyzing the mass of Ti present as oxide in the wire using an X-ray fluorescence analyzer and an X-ray diffraction (XRD) analyzer. By analyzing the components contained in the flux using X-ray fluorescence analysis and then analyzing the molecular structure of the contained components using X-ray diffraction (XRD), the amount of Ti present as oxide in the wire and the amount of Ti included as alloy components can be determined separately. Although the steel sheath may also contain Ti oxide, the amount is extremely small compared to the Ti oxide contained in the flux, so the Ti oxide that may be contained in the sheath can be ignored. Specifically, first, flux is taken from the wire and this flux is analyzed using the method described above. For example, the analysis may reveal TiO ２ Ti ２ O ３ , and Ti ３ O ５ If detected, the mass % of each Ti oxide is [TiO ２ ] [Ti ２ O ３ ] [Ti ３ O ５ Represented as ], Ti oxide TiO ２ The sum of the converted values ​​is [Converted TiO ２ Expressed as ], it is calculated by the following formula C1. [Converted TiO ２ ]=(0.60×[TiO ２ ] + 0.67 × [Ti ２ O ３ ] + 0.64 × [Ti ３ O ５ ]) × 1.67 Equation C1 The coefficients (0.60, 0.67, 0.64) in Equation C1 are coefficients for calculating the amount of Ti contained in each oxide, and the multiplier at the end (1.67) is calculated from the total amount of Ti present as oxide in the wire to TiO ２ This is a multiplier used to calculate the converted value.

[0023] Here, we will explain how to find the coefficient. M ｘ O ｙ (Example: TiO ２ Ti２ O ３ , and Ti ３ O ５ etc.) are detected, the coefficient for M ｘ O ｙ is calculated by the following formula C2. [Atomic weight of M element] × x / ([Atomic weight of M element] × x + [Atomic weight of oxygen] × y) Formula C2 The 0.60, 0.67, 0.64 in Formula C1 correspond to the coefficients obtained by the above formula C2. Also, the method for obtaining the multiplier for calculating the conversion value will be explained. M ａ O ｂ (e.g., TiO ２ , Ti ２ O ３ , and Ti ３ O ５ etc.) is calculated by the following formula C3. ([Atomic weight of M element] × a + [Atomic weight of oxygen] × b) / ([Atomic weight of M element] × a) Formula C3 The 1.67 in Formula C1 corresponds to the multiplier obtained by the above formula C3. Note that the oxide may also be a compound combined with two metal elements. The method for obtaining the coefficient in that case is for M ｘ O ｙ M ２ ｚ (e.g., TiO ３ ・Fe, that is, M = Ti, M ２ = Fe, x = 1, y = 3, z = 1 oxide, examples of oxides other than Ti oxide are ZrSiO ４ , that is, M = Zr, M ２ = Si, x = 1, y = 4, z = 1 oxide) is detected, it is calculated by the following formula C4. [Atomic weight of M element] × x / ([Atomic weight of M element] × x + [Atomic weight of oxygen] × y + [Atomic weight of M ２ element] × z) Formula C4

[0024] The total amount of MnO conversion value of Mn oxide, the total amount of SiO ２ conversion value of Si oxide, the total amount of ZrO ２ conversion value of Zr oxide, the total amount of Al ２ O ３ conversion value of Al oxide, the total amount of Na ２ O conversion value of Na oxide, the total amount of K ２The total amount of O equivalent values, the total amount of Ba oxide equivalent values, the total amount of Ca oxide equivalent values, the total amount of Mg oxide equivalent values, and the total amount of Fe oxide equivalent values ​​are also calculated using TiO. ２ The total amount of the converted values ​​is obtained by the same calculation as above. That is, the flux collected by a fluorescent X-ray analyzer and an X-ray diffraction (XRD) analyzer is analyzed, and coefficients and multipliers are calculated according to the above formulas C2, C3, and C4 according to the various oxides detected, and the calculation is performed in the same manner as above formula C1. Representative oxides detected by the analysis are listed below. Mn oxides: MnO, Mn ２ O, MnO ２ Si oxides: SiO, SiO ２ Si ２ O ３ Si ２ O ４ Zr oxide: ZrO ２ Al oxides: AlO, Al ２ O ３ Al ３ O ５ Na oxide: Na ２ O, Na ２ O ２ K oxide: K ２ O, KO ２ Ba oxides: BaO, BaO ２ Ca oxide: CaO, CaO ２ Mg oxides: MgO, MgO ２ Mg ２ O Fe oxides: FeO, Fe ２ O ４ FeO ３

[0025] The method for separating the steel sheath from the flux when analyzing various compositions of compound components such as Ti oxide is as follows: Open the steel sheath of the flux-cored wire using pliers or similar tools and collect the flux from inside. Then, remove the flux adhering to the inner surface of the steel sheath, which is the contact point with the flux, using a wire brush and ultrasonic cleaning. This separates the steel sheath from the flux.

[0026] (Total amount of Mn oxide in MnO equivalent X: 0.3% to 15.0%) Mn oxide promotes austenitization of the weld metal due to the influence of Mn contained in the oxide, improving the low-temperature toughness of the weld metal. Furthermore, Mn oxide has little effect on the solidification temperature of the slag, and even if Mn oxide is included in the wire, the lowering of the solidification temperature of the slag is suppressed. Therefore, Mn oxide is included in the wire. On the other hand, if there is an excess of Mn oxide, a large amount of fumes will be generated. Therefore, the amount of Mn oxide X in the wire should be 0.3 to 15.0%. The lower limit of the amount of Mn oxide X in the wire is preferably 0.5%, 1.0%, 2.0%, or 3.0%. The upper limit of the amount of Mn oxide X in the wire is preferably 14.0%, 13.0%, 12.0%, or 10.0%. Mn oxide can mainly exist as manganese oxide in the flux and pyrolusite, etc.

[0027] (Total amount of Mn oxide X and Ti oxide Y (X + Y)) The total amount of Mn oxide X and Ti oxide Y (X + Y) is preferably 1.0% or more, and more preferably 3.0% or more. The upper limit of the total amount (X + Y) is 25.0%. Both Mn oxide and Ti oxide are oxides that form slag, and having the total amount (X + Y) within the above range improves workability in vertical welding and overhead welding.

[0028] (Ratio of amount X to total amount Y of Mn oxide and Ti oxide (X / (X+Y))) The ratio of the total amount X of Mn oxide to the total amount Y of Ti oxide (X / (X+Y)) is 0.65 to 1.00. When the ratio (X / (X+Y)) is 0.65 or higher, a sufficient amount of Mn oxide is contained in the wire, and vertical workability can be improved by raising the solidification temperature of the slag. The lower limit of the ratio (X / (X+Y)) is preferably 0.70, 0.75, or 0.80 from the viewpoint of increasing the amount X of Mn oxide and suppressing the lowering of the solidification temperature of the slag. The upper limit of the ratio (X / (X+Y)) is substantially 0.993, but from the viewpoint of bead shape, it is preferably 0.95, 0.90, or 0.85.

[0029] Next, I will explain the compound components that may be included in the wire, that is, the optional compound components.

[0030] (Specific Oxides) The wire may contain oxides other than Mn oxide and Ti oxide. Specifically, it may contain at least one specific oxide selected from the group consisting of Si oxide, Zr oxide, Al oxide, Na oxide, K oxide, Ba oxide, Ca oxide, Mg oxide, and Fe oxide. When specific oxides are included, it is preferable that their total content is greater than 0% to 10.00%. A total content of specific oxides of 10.00% or less suppresses excessive slag formation and stabilizes the arc. The total content of specific oxides refers to the SiO2 content of Si oxide. ２ Total amount of converted values, Zr oxide ZrO ２ Total amount of converted value, Al oxide ２ O ３ Total amount of converted values, Na of Na oxide ２ Total amount of O equivalent value, K of K oxide ２ This refers to the sum of the total amount of O equivalent values, the total amount of Ba oxide equivalent values ​​(BaO equivalent values), the total amount of Ca oxide equivalent values ​​(CaO equivalent values), the total amount of Mg oxide equivalent values ​​(MgO equivalent values), and the total amount of Fe oxide equivalent values ​​(FeO equivalent values).

[0031] SiO of Si oxide ２ Total amount of converted value: 0% to 5.00% Si oxide is a slag component and has the effect of increasing slag flow and improving slag detachability. By including Si oxide in the wire, welding workability (especially vertical welding performance) can be improved. Therefore, Si oxide may be included in the wire. On the other hand, by reducing the Si oxide content, the oxygen content of the weld metal can be suppressed, and the deterioration of low-temperature toughness can be suppressed. Therefore, the Si oxide content of the wire is SiO ２The total amount of converted values ​​(Si oxide content) is preferably 0 to 5.00%. The lower limit of the Si oxide content in the wire is preferably 0.10%, 0.20%, 0.50%, 0.80%, or 1.00%. The upper limit of the Si oxide content in the wire is preferably 4.80%, 4.50%, 4.20%, or 4.00%. Si oxide can mainly exist as silica sand, zircon sand, feldspar, sodium silicate, and potassium silicate in the flux.

[0032] Zr oxides ZrO ２ Total amount of converted value: 0% to 5.00% Zr oxide is a slag component and has the effect of improving slag coverage and smoothing the bead shape in horizontal fillet welding. Therefore, Zr oxide may be included in the wire. On the other hand, by reducing the Zr oxide content, the oxygen content of the weld metal can be suppressed, and the deterioration of low-temperature toughness can be suppressed. Therefore, ZrO ２ The total amount of converted values ​​(Zr oxide amount) is preferably 0 to 5.00%. The lower limit of the Zr oxide amount in the wire is preferably 0.10%, 0.20%, 0.50%, 0.80%, or 1.00%. The upper limit of the Zr oxide amount in the wire is preferably 4.80%, 4.50%, 4.20%, or 4.00%. Zr oxide can mainly exist as zircon sand in the flux and zirconium oxide, and may also be present in trace amounts in Ti oxide.

[0033] Al oxide ２ O ３ Total amount of converted value: 0% to 5.00% When Al oxide constitutes molten slag, it has the effect of preventing undercuts on the upper leg side of the fillet bead by improving slag coverage. Therefore, Al oxide may be included in the wire. On the other hand, by reducing the Al oxide content, the oxygen content of the weld metal can be suppressed, and the deterioration of low-temperature toughness can be suppressed. Therefore, the Al oxide content of the wire ２ O ３The total amount of converted values ​​(amount of Al oxide) is preferably 0 to 5.00%. The lower limit of the amount of Al oxide in the wire is preferably 0.10%, 0.20%, 0.50%, 0.80%, or 1.00%. The upper limit of the amount of Al oxide in the wire is preferably 4.80%, 4.50%, 4.20%, or 4.00%. Al oxide is often present mainly as alumina and feldspar components in the flux.

[0034] Na oxide ２ Total amount of O equivalent: 0% to 5.00% Na oxide has the effect of reducing the oxygen content of the weld metal and improving low-temperature toughness, as the Na that decomposes during welding acts as a deoxidizing agent. Therefore, it is possible to include Na oxide in the wire. On the other hand, since Na oxide lowers the solidification temperature of the welding slag, it is preferable to suppress its content in the wire. Therefore, the amount of Na oxide in the wire is ２ The total amount of O equivalent (Na oxide amount) is preferably 0 to 5.00%. The lower limit of the Na oxide amount in the wire is preferably 0.01%, 0.02%, or 0.03%. The upper limit of the Na oxide amount in the wire is preferably 4.00%, 3.00%, 2.00%, 1.00%, 0.50%, 0.20%, or 0.10%.

[0035] K of K oxide ２ Total amount of O equivalent: 0% to 5.00% K oxide has the effect of reducing the oxygen content of the weld metal and improving low-temperature toughness, as the K that decomposes during welding acts as a deoxidizing agent. Therefore, K oxide may be included in the wire. On the other hand, since K oxide lowers the solidification temperature of the welding slag, it is preferable to suppress its content in the wire. Therefore, the K oxide content of the wire ２ The total amount of O equivalent (K oxide amount) is preferably 0 to 5.00%. The lower limit of the K oxide amount in the wire is preferably 0.01%, 0.02%, or 0.03%. The upper limit of the K oxide amount in the wire is preferably 4.00%, 3.00%, 2.00%, 1.00%, 0.50%, 0.20%, or 0.10%.

[0036] - Total amount of Ba oxide in BaO equivalent: 0% to 5.00% Ba oxide has the effect of reducing the oxygen content of the weld metal and improving low-temperature toughness. Therefore, Ba oxide may be included in the wire. On the other hand, the arc can be stabilized by reducing the Ba oxide content. Therefore, the total amount of Ba oxide in BaO equivalent (Ba oxide amount) in the wire is preferably 0 to 5.00%. The lower limit of the Ba oxide amount in the wire is preferably 0.02%, 0.05%, 0.08%, or 0.10%. The upper limit of the Ba oxide amount in the wire is preferably 4.00%, 3.00%, 2.00%, 1.00%, 0.50%, or 0.30%.

[0037] - Total amount of Ca oxide in CaO equivalent: 0% to 5.00% Ca oxide has the effect of maintaining the weld bead shape well and improving vertical weldability. Therefore, Ca oxide may be included in the wire. On the other hand, by reducing the amount of Ca oxide, the occurrence of slag inclusion is suppressed and a sound joint can be easily produced. Therefore, the total amount of Ca oxide in CaO equivalent (amount of Ca oxide) in the wire is preferably 0 to 5.00%. The lower limit of the amount of Ca oxide in the wire is preferably 0.02%, 0.05%, 0.08%, 0.10%, 0.15%, or 0.20%. The upper limit of the amount of Ca oxide in the wire is preferably 4.00%, 3.00%, 2.00%, 1.00%, or 0.50%.

[0038] - Total amount of Mg oxide in MgO equivalent: 0% to 5.00% Mg oxide has the effect of improving low-temperature toughness by reducing the oxygen content of the weld metal, as the Mg decomposed during welding acts as a deoxidizing agent. Mg oxide also has the effect of stabilizing the arc. Therefore, it is acceptable to include Mg oxide in the wire. On the other hand, since Mg oxide lowers the solidification temperature of the welding slag, it is preferable to suppress its content in the wire. Therefore, the total amount of Mg oxide in MgO equivalent (Mg oxide amount) in the wire is preferably 0 to 5.00%. The lower limit of the Mg oxide amount in the wire is preferably 0.01%, 0.02%, 0.03%, or 0.05%. The upper limit of the Mg oxide amount in the wire is preferably 4.00%, 3.00%, 2.00%, 1.00%, 0.50%, or 0.20%.

[0039] - Total amount of Fe oxide in FeO equivalent: 0% to 5.00% Fe oxide has the effect of maintaining the weld bead shape well and improving vertical weldability. Fe oxide also has the effect of stabilizing the arc. Therefore, Fe oxide may be included in the wire. On the other hand, by reducing the Fe oxide content, the occurrence of slag inclusion is suppressed and a sound joint can be easily produced. Therefore, the total amount of Fe oxide in FeO equivalent (Fe oxide amount) of the wire is preferably 0 to 5.00%. The lower limit of the Fe oxide amount of the wire is preferably 0.01%, 0.02%, or 0.03%. The upper limit of the Fe oxide amount of the wire is preferably 4.00%, 3.00%, 2.00%, 1.00%, 0.50%, 0.30%, or 0.20%.

[0040] (Total content of specific fluorides: more than 0% to 10.00%) The wire may contain fluorides. Specifically, K ２ SiF ６ _K ２ ZrF ６ NaF, Na ３ AlF ６ CaF ２ LiF, and MgF ２Examples include at least one specific fluoride selected from the group consisting of the following. Specific fluorides have the effect of reducing the oxygen content of the weld metal. On the other hand, reducing the total amount of specific fluorides suppresses the generation of welding fumes and reduces welding defects. Therefore, the total content of specific fluorides in the wire (specific fluoride amount) is preferably between 0% and 5.00%. The lower limit of the specific fluoride amount in the wire is preferably 0.10%, 0.20%, 0.30%, or 0.50%. The upper limit of the specific fluoride amount in the wire is preferably 9.00%, 8.00%, 7.00%, or 5.00%.

[0041] (Total content of specific metal carbonates: more than 0% to 10.00%) The wire may contain metal carbonates. Specifically, MgCO ３ Na ２ CO ３ LiCO ３ CaCO ３ _K ２ CO ３ BaCO ３ FeCO ３ MnCO ３ , and SrCO ３ A specific metal carbonate is selected from the group consisting of the following. The specific metal carbonate is ionized by an arc to form CO ２ This CO generates gas, ２ The gas lowers the partial pressure of hydrogen in the welding atmosphere, reducing the amount of diffusible hydrogen in the weld metal. On the other hand, by reducing the total content of specific metal carbonates, it is possible to suppress the retention of carbon (C) from the decomposition of carbonates in the weld metal. Therefore, the total content of specific metal carbonates in the wire (specific metal carbonate amount) is preferably between 0% and 10.00%. The lower limit of the specific metal carbonate amount in the wire is preferably 0.10%, 0.20%, 0.30%, or 0.50%. The upper limit of the specific metal carbonate amount in the wire is preferably 9.00%, 8.00%, 7.00%, or 5.00%.

[0042] (Total content of specific nitrides: more than 0% to 10.00%) The wire may contain nitrides. Specifically, AlN, BN, Ca ３ N２ , CeN, CrN, Cu ３ N, Fe ４ N, Fe ３ N, Fe ２ N, Mg ３ N, Mo ２ N, NbN, Si ３ N ４ , TiN, VN, ZrN, Mn ２ N and Mn ４ At least one specific nitride selected from the group consisting of N is mentioned. The specific nitride has the effect of reducing the amount of diffusible hydrogen in the weld metal and significantly improving the low-temperature crack resistance of the weld metal. On the other hand, by reducing the total content of the specific nitride, it is possible to suppress the excess N yield in the weld metal. Therefore, the total content of the specific nitride in the wire (specific nitride amount) is preferably more than 0% to 10.00%. The lower limit of the specific nitride amount in the wire is preferably 0.10%, 0.20%, 0.30%, or 0.50%. The upper limit of the specific nitride amount in the wire is preferably 9.00%, 8.00%, 7.00%, or 5.00%. The specific nitride in the wire is AlN, CeN, CrN, Cu ３ N, Fe ３ N, NbN, Si ３ N ４ VN, Mn ２ N and Mn ４ It may also be at least one nitride selected from the group consisting of N.

[0043] (Total content of Sr, Y, Zr, Ba, and Sc elements in the specific compound: greater than 0% to 1.0000%) The wire may contain at least one specific compound selected from the group consisting of Sr compounds, Y compounds, Zr compounds, Ba compounds, and Sc compounds. The specific compound is a compound of at least one element from Sr, Y, Zr, Ba, and Sc with another element, such as oxides, fluorides, nitrides, metal carbonates, and sulfates. Specifically, as an Sr compound, SrSO ４ , and SrCO ３ However, as a Y compound, it is YF ３ , and Y ２ O３ However, as a Zr compound, ZrO ２ , and ZrSiO ４ However, as a Ba compound, it is BaSO ４ , and BaF ２ However, as an Sc compound, it is ScO ３ , and ScF ３ These are some examples. However, the specific compound is not particularly limited as long as it contains at least Sr, Y, Zr, Ba, or Sc.

[0044] The elements Sr, Y, Zr, Ba, and Sc contained in the specific compound have the effect of reducing the amount of oxygen. Therefore, the specific compound may be included in the wire. On the other hand, high-temperature cracking can be suppressed by reducing the total content of each of the above elements contained in the specific compound. Therefore, the total content of Sr, Y, Zr, Ba, and Sc contained in the specific compound in the wire (amount of specific compound elements) is preferably more than 0% to 1.0000%. The lower limit of the amount of specific compound elements in the wire is preferably 0.0100%, 0.0200%, or 0.0300%. The upper limit of the amount of specific compound elements in the wire is preferably 0.9700%, 0.9500%, 0.9000%, 0.800%, or 0.6000%.

[0045] For example, ZrO ２ It belongs to the category of specific compounds and specific oxides, SrCO ３ These belong to specific compounds and specific metal carbonates. The content of compounds belonging to multiple classifications is included in the content of each classification. For example, if the wire relating to this disclosure is ZrO ２ If it contains ZrO ２ The content of this substance is included in the total content of specific oxides, as well as in the total content of specific compounds.

[0046] [Alloy Components] The alloy components that may be included in the wire according to this disclosure, i.e., chemical components other than oxides, fluorides, nitrides, metal carbonates, and sulfates, are described below. In the description of alloy components, "%" means "mass % of the total mass of the flux-cored wire" unless otherwise specified.

[0047] The wire relating to this disclosure has an alloy content of C: 0.003% to 0.650%, Si: 0.03% to 0.80%, Mn: 3.0% to 30.0%, P: 0.050% or less, S: 0.050% or less, Cu: 0% to 10.00%, Ni: 0% to 30.0%, Cr: 0% to 30.0%, Mo: 0% to 10.0%, Nb: 0% to 5.00%, V: 0% to 5.00%, Co: 0% to 10.00%, Pb: 0% to 1.00%, Sn: 0% to 1.00%, Al: 0% to 0.50%, Ti: 0% to 0.50%, Ta: 0% to 1.00%. Preferably, the alloy consists of Hf: 0% to 1.00%, W: 0% to 30.00%, Mg: 0% to 0.50%, REM: 0% to 0.50%, Zr: 0% to 5.00%, Ca: 0% to 0.50%, B: 0% to 0.1000%, and N: 0% to 0.500%, with the remainder being Fe and impurities. The alloy components may be contained in the steel shell or as flux.

[0048] (C: 0.003 to 0.650%) Carbon (C) is an element that generates spatter. To reduce spatter, the lower the carbon content of the wire, the more advantageous it is. Also, carbon is an interstitial solid solution strengthening element, and reducing the carbon content of the wire makes the wire softer. Therefore, it is preferable that the carbon content of the wire be 0.650% or less. However, reducing the carbon content of the wire to 0% increases the cost of carbon removal. Also, increasing the carbon content of the wire can improve the strength of the weld metal. Therefore, the lower limit of the carbon content of the wire is 0.003%, and it may also be 0.005% or 0.008%. The upper limit of the carbon content of the wire may be 0.600%, 0.500%, 0.400%, 0.300%, 0.200%, 0.190%, 0.180%, 0.150%, or 0.120%.

[0049] (Si: 0.03-0.80%) Si is a deoxidizing element. By increasing the Si content of the wire, the O content of the wire can be reduced. On the other hand, Si has low solid solubility in the austenite phase, and by reducing the Si content, the formation of brittle phases such as intermetallic compounds and δ-ferrite at high temperatures can be suppressed, thereby improving high-temperature ductility. Therefore, the Si content of the wire is preferably 0.03-0.80%. The lower limit of the Si content of the wire is preferably 0.04%, 0.05%, or 0.08%. The upper limit of the Si content of the wire is preferably 0.70%, 0.60%, 0.50%, 0.40%, 0.30%, or 0.20%.

[0050] (Mn: 3.0-30.0%) Mn is an austenite-stabilizing element. Increasing the Mn content of the wire promotes austenitization of the weld metal, improving its low-temperature toughness. On the other hand, Mn as an alloying component lowers the solidification temperature of the slag, resulting in reduced weldability in all positions. Mn is also an element that causes increased fume generation. Furthermore, reducing the Mn content increases the stacking fault energy, thereby improving toughness. Therefore, the Mn content of the wire is preferably 3.0-30.0%. The lower limit of the Mn content of the wire is preferably 3.5%, 4.0%, 4.5%, or 5.0%. The upper limit of the Mn content of the wire is preferably 28.0%, 26.0%, 24.0%, 22.0%, 20.0%, 18.0%, 16.0%, or 15.0%.

[0051] (P: 0.050% or less) P is an impurity element that reduces the toughness of the weld metal, so it is preferable to reduce the P content of the wire as much as possible. However, from the viewpoint of reducing the cost of eliminating P, the P content of the wire may be 0.003% or more. On the other hand, if the P content of the wire is 0.050% or less, the adverse effect of P on toughness can be reduced. Therefore, it is preferable that the P content of the wire be 0.050% or less. In order to effectively suppress the decrease in toughness of the weld metal, it is preferable that the P content of the wire be 0.040% or less, 0.030% or less, 0.020% or less, 0.015% or less, 0.010% or less, or 0.005% or less.

[0052] (S: 0.050% or less) S is an impurity element that reduces the toughness of the weld metal, so it is preferable to reduce the S content of the wire as much as possible. However, from the viewpoint of reducing the cost of S removal, the S content of the wire may be 0.0003% or more. On the other hand, if the S content of the wire is 0.050% or less, the adverse effect of S on toughness can be reduced. Therefore, it is preferable that the S content of the wire be 0.050% or less. In order to effectively suppress the decrease in toughness of the weld metal, it is preferable that the S content of the wire be 0.040% or less, 0.030% or less, 0.020% or less, 0.015% or less, 0.010% or less, or 0.005% or less.

[0053] (Cu: 0-10.00%) Cu is a precipitation strengthening element and may be included in the wire to improve the strength of the weld metal. Cu is also an austenite stabilizing element and may be included in the wire to improve the low-temperature toughness of the weld metal. On the other hand, if the Cu content of the wire is excessive, the above effects will saturate. Also, reducing the Cu content of the wire will make the wire softer. Therefore, it is preferable that the Cu content of the wire be between 0 and 10.00%. The lower limit of the Cu content of the wire is preferably 0.30%, 0.50%, or 0.70%. The upper limit of the Cu content of the wire is preferably 9.00%, 8.00%, 7.00%, or 5.00%.

[0054] (Ni: 0-30.0%) Ni is an austenite-stabilizing element. Increasing the Ni content of the wire increases the overall Ni content of the wire, promoting austenitization of the weld metal and improving low-temperature toughness. Therefore, Ni may be included in the wire. On the other hand, reducing the Ni content of the wire can reduce the cost of the wire. Therefore, the Ni content of the wire is preferably 0-30.0%. The lower limit of the Ni content of the wire is preferably 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, or 9.0%. The upper limit of the Ni content of the wire is preferably 28.0%, 26.0%, 24.0%, 22.0%, 20.0%, 19.0%, 18.0%, or 15.0%.

[0055] (Cr: 0-30.0%) Cr is a ferrite-stabilizing element and may be included in the wire to improve the strength of the weld metal. On the other hand, reducing the Cr content of the wire suppresses the amount of low-melting-point compounds in the molten metal and further narrows the temperature range in which the solid and liquid coexistence of the molten metal is narrowed, thereby suppressing hot cracking. Therefore, the Cr content of the wire is preferably 0-30.0%. The lower limit of the Cr content of the wire is preferably 0.01%, 0.02%, 1.0%, 2.0%, or 3.0%. The upper limit of the Cr content of the wire is preferably 28.0%, 25.0%, 23.0%, 20.0%, 18.0%, 15.0%, 13.0%, or 10.0%.

[0056] (Mo: 0-10.0%) Mo is a precipitation strengthening element and may be included in the wire to improve the strength of the weld metal. On the other hand, reducing the Mo content of the wire can suppress the strength of the weld metal and increase its low-temperature toughness. Also, reducing the Mo content of the wire makes the wire softer. Therefore, the Mo content of the wire is preferably 0-10.0%. The lower limit of the Mo content of the wire is preferably 1.0%, 2.0%, or 3.0%. The upper limit of the Mo content of the wire is preferably 9.0%, 8.0%, or 7.0%.

[0057] (Nb: 0-5.00%) Nb is an element that forms carbides in the weld metal and increases the strength of the weld metal, so it may be included in the wire. On the other hand, reducing the Nb content of the wire can suppress the occurrence of hot cracking in the weld metal. Therefore, the Nb content of the wire is preferably 0-1.00%. The lower limit of the Nb content of the wire is preferably 0.001%, 0.002%, 0.005%, 0.01%, or 0.015%. The upper limit of the Nb content of the wire is preferably 4.00%, 3.00%, 2.00%, or 1.00%.

[0058] (V: 0-5.00%) V is an element that forms carbonitrides in the weld metal and increases the strength of the weld metal, so it may be included in the wire. On the other hand, reducing the V content of the wire can suppress the occurrence of hot cracking in the weld metal. Therefore, the V content of the wire is preferably 0-5.00%. The lower limit of the V content of the wire is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the V content of the wire is preferably 4.00%, 3.00%, 2.00%, 1.00%, 0.95%, or 0.90%.

[0059] (Co: 0-10.00%) Co is an element that increases the strength of the weld metal through solid solution strengthening, and therefore may be included in the wire. On the other hand, reducing the Co content of the wire can increase the ductility of the weld metal and ensure toughness. Therefore, the Co content of the wire is preferably 0-10.00%. The lower limit of the Co content of the wire is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the Co content of the wire is preferably 8.00%, 5.00%, 3.00%, 1.00%, 0.90%, 0.80%, 0.70%, 0.60%, or 0.50%.

[0060] (Pb: 0-1.00%) Pb may be included in the wire because it has the effect of improving the formability of the toe shape between the base material (steel) and the weld metal, and improving the machinability of the weld metal. On the other hand, reducing the Pb content of the wire can stabilize the arc state and reduce spatter. Therefore, it is preferable that the Pb content of the wire be 0-1.00%. The lower limit of the Pb content of the wire is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the Pb content of the wire is preferably 0.90%, 0.80%, 0.70%, 0.60%, or 0.50%.

[0061] (Sn: 0-1.00%) Sn is an element that improves the corrosion resistance of the weld metal, so it may be included in the wire. On the other hand, reducing the Sn content of the wire can suppress the occurrence of cracks in the weld metal. Therefore, it is preferable that the Sn content of the wire be 0-1.00%. The lower limit of the Sn content of the wire is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the Sn content of the wire is preferably 0.90%, 0.80%, 0.70%, 0.60%, or 0.50%.

[0062] (Al: 0-0.50%) Al is a deoxidizing element and may be included in the wire to suppress welding defects and improve the cleanliness of the weld metal. On the other hand, by reducing the Al content of the wire, the formation of nitrides or oxides in the weld metal by Al is suppressed, and the decrease in the low-temperature toughness of the weld metal can be suppressed. Therefore, the Al content of the wire is preferably 0-0.10%. The lower limit of the Al content of the wire is preferably 0.01%, 0.02%, or 0.03%. The upper limit of the Al content of the wire is preferably 0.40%, 0.30%, 0.20%, 0.10%, 0.08%, or 0.07%.

[0063] (Ti: 0-0.50%) Ti is a deoxidizing element and may be included in the wire to suppress welding defects and improve the cleanliness of the weld metal. On the other hand, reducing the Ti content of the wire can suppress the formation of carbides in the weld metal and suppress the deterioration of the toughness of the weld metal. Therefore, the Ti content of the wire is preferably 0-0.10%. The lower limit of the Ti content of the wire is preferably 0.003%, 0.01%, 0.02%, or 0.03%. The upper limit of the Ti content of the wire is preferably 0.40%, 0.30%, 0.20%, 0.10%, 0.08%, or 0.07%.

[0064] (Ta: 0-1.00%) Ta may be included in the wire as it contributes to suppressing high-temperature cracking. On the other hand, reducing the Ta content of the wire can suppress the coarsening of inclusions. Therefore, it is preferable that the Ta content of the wire be 0-1.00%. The lower limit of the Ta content of the wire is preferably 0.0001%, 0.0003%, 0.0005%, or 0.0007%. The upper limit of the Ta content of the wire is preferably 0.90%, 0.80%, 0.70%, or 0.60%.

[0065] (Hf: 0-1.00%) Hf may be included in the wire as it contributes to suppressing high-temperature cracking. On the other hand, reducing the Hf content of the wire can suppress the coarsening of inclusions. Therefore, it is preferable that the Hf content of the wire be 0-1.00%. The lower limit of the Hf content of the wire is preferably 0.0001%, 0.0003%, 0.0005%, or 0.0007%. The upper limit of the Hf content of the wire is preferably 0.90%, 0.80%, 0.70%, or 0.60%.

[0066] (W: 0-30.00%) W is an element that increases the strength of the weld metal through solid solution strengthening, and therefore may be included in the wire. On the other hand, reducing the W content of the wire can increase the ductility of the weld metal and ensure toughness. Therefore, the W content of the wire is preferably 0-30.00%. The lower limit of the W content of the wire is preferably 0.50%, 1.00%, 3.00%, or 5.00%. The upper limit of the W content of the wire is preferably 28.00%, 25.00%, 23.00%, or 20.00%.

[0067] (Mg: 0-0.50%) Mg may be included in the wire to reduce the oxygen content of the weld metal through its deoxidizing effect and improve the toughness of the weld metal. On the other hand, reducing the Mg content of the wire reduces the amount of slag generated and suppresses welding defects such as slag inclusion. Therefore, the Mg content of the wire is preferably 0-0.50%. The lower limit of the Mg content of the wire is preferably 0.0001%, 0.0005%, 0.0010%, 0.0020%, or 0.0030%. The upper limit of the Mg content of the wire is preferably 0.40% or 0.30%.

[0068] (REM: 0-0.50%) REM may be included in the wire because it has the effect of improving the hot workability during the manufacturing of the wire. On the other hand, by reducing the REM content of the wire, the reduction in cleanliness due to REM combining with oxygen is suppressed, and from this viewpoint as well, the hot workability can be improved. Therefore, the REM content of the wire is preferably 0-0.50%. The lower limit of the REM content of the wire is preferably 0.001%, 0.003%, 0.005%, or 0.010%. The upper limit of the REM content of the wire is preferably 0.40%, or 0.30%.

[0069] "REM" is a collective term for 17 elements including Sc, Y, and lanthanides, and the REM content refers to the total content of one or more of these REM elements. REM is generally contained in mischmetal. Therefore, for example, it may be added in the form of mischmetal so that the amount of REM falls within the above range.

[0070] (Zr: 0-5.00%) Zr may be included in the wire to improve the toughness of the weld metal by reducing the amount of oxygen in the weld metal through its deoxidizing effect. On the other hand, reducing the Zr content of the wire suppresses the formation of coarse inclusions, making the wire softer and suppressing wire breakage. Therefore, the Zr content of the wire is preferably 0-5.00%. The lower limit of the Zr content of the wire is preferably 0.0005%, 0.0010%, 0.0020%, or 0.0050%. The upper limit of the Zr content of the wire is preferably 4.00%, 3.00%, 2.00%, or 1.00%.

[0071] (Ca: 0-0.50%) Ca may be included in the wire to improve the toughness of the weld metal by reducing the amount of oxygen in the weld metal through its deoxidizing effect. On the other hand, reducing the Ca content of the wire reduces the amount of slag generated and suppresses welding defects such as slag inclusion. Therefore, the Ca content of the wire is preferably 0-0.50%. The lower limit of the Ca content of the wire is preferably 0.0001%, 0.0005%, 0.0010%, 0.0020%, or 0.0030%. The upper limit of the Ca content of the wire is preferably 0.40% or 0.30%.

[0072] (B: 0-0.1000%) B is an interstitial solid solution strengthening element and may be included in the wire to improve the low-temperature toughness and strength of the weld metal. On the other hand, by reducing the B content of the wire, M ２３ (C, B) ６The precipitation of ions is suppressed, and the deterioration of toughness can be suppressed. Therefore, the B content of the wire is preferably 0 to 0.1000%. The lower limit of the B content of the wire is preferably 0.0005%, 0.0010%, or 0.0020%. The upper limit of the B content of the wire is preferably 0.0800%, 0.0500%, or 0.0100%.

[0073] (N: 0-0.500%) N is an austenite-stabilizing element and an interstitial solid solution strengthening element, and may be included in the wire to improve the low-temperature toughness and strength of the weld metal. On the other hand, reducing the N content of the wire can suppress blowouts and reduce welding defects. Therefore, the N content of the wire is preferably 0-0.500%. The lower limit of the N content of the wire is preferably 0.001%, 0.010%, or 0.050%. The upper limit of the N content of the wire is preferably 0.450%, 0.400%, or 0.350%.

[0074] (Mass ratio of Mn content to Ni content (Mn / Ni)) Mn and Ni are austenite-stabilizing elements, respectively, and improve the low-temperature toughness of the weld metal. On the other hand, Ni is an expensive metal, and Mn is an element that causes an increase in the amount of fumes generated. In addition, Mn is an element that causes a decrease in toughness by lowering the stacking fault energy when added in excess. Ni improves toughness by increasing the stacking fault energy. Therefore, from the viewpoint of improving the low-temperature toughness of the weld metal and reducing the amount of fumes generated while keeping wire costs down, it is preferable to set the mass ratio of Mn content to Ni content (Mn / Ni) in the wire to 0.30 or higher. The lower limit of the mass ratio of Mn content to Ni content (Mn / Ni) in the wire is more preferably 0.50, 0.70, 1.00, or 1.20. The upper limit of the mass ratio (Mn / Ni) of Mn content to Ni content in the wire is preferably 3.00, 2.80, 2.50, 2.30, or 2.00. In this disclosure, the mass ratio of Mn content to Ni content may be expressed as "[Mn] / [Ni]".

[0075] [Remainder: Fe and Impurities] The remainder of the components contained in the flux-cored wire according to this disclosure (i.e., components other than the compound components and the alloy components) are Fe and impurities. Fe may be included in the flux-cored wire in one or more forms selected from the group consisting of a steel sheath, iron powder for adjusting the filling density, and iron alloy powders such as Fe-Si, Fe-Mn, and Fe-Ti alloys. Impurities are components that are mixed in during the industrial manufacture of the wire due to raw materials such as ore or scrap, or various factors in the manufacturing process, and are acceptable as long as they do not adversely affect the properties of the wire. Examples of impurities include O (oxygen).

[0076] [Component Analysis] The components of the wire relating to this disclosure shall be analyzed separately for the steel sheath and the flux. The analysis of the flux shall conform to JIS Z 3352:2017.

[0077] (Wire Shape) Next, the shape (wire structure) of the flux-cored wire according to this disclosure will be described. Generally, flux-cored wires are classified into two types: wires having a seamless shape (wires with welded joints at the seams of the outer sheath) because the seams of the outer sheath are welded and therefore have no slit-shaped gaps, and wires having a seam shape (wires with slit-shaped gaps at the seams of the outer sheath) because the seams of the outer sheath are not welded and therefore have no welded joints at the seams of the outer sheath.

[0078] Any shape can be used for the flux-cored wire according to this disclosure. However, in order to suppress the occurrence of cold cracking in the weld metal, it is preferable that there are no slit-like gaps in the outer sheath. Hydrogen (H) that enters the weld area during welding diffuses into the weld metal and the workpiece, and accumulates at stress concentration points, causing cold cracking. There are various sources of H, but when welding is performed under conditions where the cleanliness of the weld area and gas shielding conditions are strictly controlled, moisture (H) contained in the wire can cause cold cracking. ２ O) is the main source of H, and the amount of this moisture strongly influences the amount of diffusible hydrogen in welded joints.

[0079] If the outer sheath has seams, moisture from the atmosphere can easily penetrate into the flux through the seams. Therefore, it is desirable to remove the seams from the outer sheath to suppress the penetration of moisture from the atmosphere into the flux through the outer sheath between wire manufacturing and wire use. If the outer sheath has seams and the period between wire manufacturing and wire use is long, it is desirable to vacuum-pack the entire flux-cored wire or store the flux-cored wire in a container that can maintain a dry state in order to prevent the penetration of H sources such as moisture.

[0080] (Wire diameter) The diameter of the flux-cored wire according to this disclosure is not particularly limited, but can be, for example, φ1.0 to φ2.0 mm, and can be further φ1.2 to φ1.6 mm.

[0081] (Sheath Thickness) The thickness of the sheath is preferably 150 μm or more and 450 μm or less. A thickness of 150 μm or more allows for the maintenance of appropriate strength in the wire, further improving feeding performance during welding. A thickness of 450 μm or less prevents the wire from becoming too strong, further improving feeding performance during welding. The thickness of the sheath is preferably 200 μm or more and 400 μm or less, and more preferably 250 μm or more and 350 μm or less.

[0082] The thickness of the outer shell shall be the arithmetic mean of the thicknesses measured at any five points on the outer shell. However, the crimped parts (i.e., the parts where the ends of the outer shell are overlapped and welded together when forming the outer shell into a cylinder) shall not be included in the measurement points (the five arbitrary points mentioned above) used to measure the thickness of the outer shell.

[0083] (Filling Rate) The filling rate of flux in the flux-cored wire according to this disclosure is not particularly limited, as long as the above-mentioned conditions are met. In view of the filling rates of general flux-cored wires, the lower limit of the filling rate of the flux-cored wire according to this disclosure may be, for example, 8%, 10%, or 12%. The upper limit of the filling rate of the flux-cored wire according to this disclosure may be, for example, 28%, 25%, 22%, 20%, or 17%. When calculating the filling rate, the mass of the sheath and the flux are measured separately.

[0084] (Lubricant) The flux-cored wire according to this disclosure may further comprise a lubricant applied to the wire surface (the surface of the steel sheath). The lubricant applied to the wire surface has the effect of improving the wire feeding performance during welding. Various types of lubricants (e.g., vegetable oils such as palm oil) can be used for welding wires, but in order to suppress low-temperature cracking of the weld metal, it is preferable to use one or both of H-free polytetrafluoroethylene oil (PTFE oil) and perfluoropolyether oil (PFPE oil). The flux-cored wire according to this disclosure may further comprise a plating formed on the wire surface. In this case, the lubricant is applied to the surface of the plating.

[0085] <Method for manufacturing flux-cored wire> Next, a method for manufacturing flux-cored wire according to this disclosure will be described.

[0086] (In the case of flux-cored wire having a seamless shape) A flux-cored wire having a seamless shape is manufactured by, for example, a step of preparing flux, a step of forming a U-shaped open tube using a forming roll while feeding a steel strip in the longitudinal direction, a step of supplying flux into the open tube through the opening of the open tube, a step of butt welding the opposing edges (both ends in the circumferential direction) of the opening of the open tube to obtain a seamless tube, a step of annealing the obtained seamless tube before starting the wire drawing process, and a step of drawing the seamless tube to obtain a flux-cored wire having a predetermined wire diameter.

[0087] Specifically, the flux-cored wire according to this disclosure is obtained by manufacturing it as follows: (1) A steel strip is continuously fed into a forming machine, and both ends of the steel strip in the width direction are processed to form a U-shape in the longitudinal direction to obtain an open tube. (2) Flux is supplied and filled through the U-shaped opening in the open tube. (3) The opposing edges (both ends in the circumferential direction) of the opening of the open tube are butt-welded to form an O-shaped tube with a longitudinal direction, to obtain a seamless tube. The outer diameter of the seamless tube is 2.0 mm to 6.0 mm (preferably 4.0 mm to 5.0 mm). (4) The seamless tube is annealed to solution. (5) The annealed seamless tube is drawn until its outer diameter is φ1.0 to φ2.0 mm.

[0088] Butt welding is performed by electric resistance welding, laser welding, or TIG welding, etc. Furthermore, the flux-cored wire may be further annealed (post-annealed) during or after the wire drawing process to remove moisture from the wire and soften the outer sheath.

[0089] The cross-section of a flux-cored wire that has been butt-seam welded and has no slit-like gaps will show weld marks if polished and etched, but will not show weld marks if not etched. For this reason, it is sometimes called seamless, as described above. For example, in "Introduction to Welding and Joining Technology, New Edition" (2008), edited by the Japan Welding Society, published by Sanpo Shuppan, p. 111, a flux-cored wire that has been butt-seam welded and has no slit-like gaps is described as a seamless type wire. Even if the gaps in the outer sheath of the flux-cored wire are brazed, a flux-cored wire without slit-like gaps can be obtained.

[0090] (In the case of flux-cored wire with slit-shaped gaps) The method for manufacturing flux-cored wire with slit-shaped gaps is the same as the method for manufacturing flux-cored wire with a seamless shape, except that instead of the step of butt welding the circumferential ends of an open tube to obtain a seamless tube, it includes a step of forming an open tube and butting the ends of the open tube to obtain a tube with slit-shaped gaps. The method for manufacturing flux-cored wire with slit-shaped gaps may further include a step of crimping the ends of the butted open tubes. In the method for manufacturing flux-cored wire with slit-shaped gaps, the tube with slit-shaped gaps is drawn.

[0091] <Method for Manufacturing Welded Joints> Next, the method for manufacturing welded joints (welding method) according to this disclosure will be described. The method for manufacturing welded joints according to this disclosure comprises a step of welding steel materials using the flux-cored wire according to this disclosure described above.

[0092] In the method for manufacturing a welded joint according to this disclosure, gas shielded arc welding is preferred as the welding method. In the method for manufacturing a welded joint according to this disclosure, the type of steel material (workpiece) that forms the base material of the welded joint is not particularly limited, but for example, P ＣＭ Examples include steel materials with high susceptibility to low-temperature cracking having a (weld crack susceptibility composition) of 0.24% or more (especially high-strength steel plates with a tensile strength of 590 MPa to 1700 MPa and a plate thickness of 20 mm or more), and Ni-based low-temperature steel plates containing 6% to 9% Ni with a plate thickness of 20 mm or more. Among these, Ni-based low-temperature steel plates containing 6% to 9% Ni with a plate thickness of 20 mm or more can be preferably used.

[0093] The method for manufacturing a welded joint according to the present disclosure preferably includes a step of welding a steel material using a flux-cored wire according to the present disclosure in one or more passes from the first pass to the final pass. If welding is performed in only one pass, the flux-cored wire according to the present disclosure is used in that one pass. The polarity of the flux-cored wire may be positive or negative, but is preferred, as its effect on the amount of diffusible hydrogen and spatter generated in the weld metal is negligibly small.

[0094] The type of shielding gas used in the method for manufacturing welded joints according to this disclosure is not particularly limited. Commonly used shielding gases in the method for manufacturing welded joints according to this disclosure include 100% by volume carbon dioxide and Ar and 3-30% by volume CO2. ２ A mixed gas with the above can preferably be used. Furthermore, the shielding gas used when welding with flux-cored wire according to this disclosure is 5 volume% or less of O ２ They may contain gases. Since these gases are inexpensive, welding using them is advantageous for industrial applications.

[0095] The welding position in the method for manufacturing a welded joint according to this disclosure is not particularly limited. The method for manufacturing a welded joint according to this disclosure can exhibit good welding workability (especially vertical welding performance) regardless of whether the welding position is downward, horizontal, vertical, or upward.

[0096] The welded joint obtained by the manufacturing method of the welded joint according to this disclosure comprises a base material steel and a welded joint composed of weld metal and a heat-affected zone. The tensile strength of the obtained weld metal is preferably high, for example, 590 to 1200 MPa.

[0097] Next, the feasibility and effectiveness of this disclosure will be explained in more detail using the examples and comparative examples provided below. However, the examples below are not limiting to this disclosure, and any design modifications made in accordance with the spirit of the preceding and following descriptions are all within the technical scope of this disclosure.

[0098] (Manufacturing of Flux-Cored Wire) The flux-cored wires of the disclosed examples and comparative examples were manufactured by the method described below. First, a U-shaped open tube was obtained by forming a steel strip using a forming roll while feeding it longitudinally. Flux was supplied into the open tube through the opening, and the opposing edges of the opening of the open tube were butt-welded to obtain a seamless tube. This seamless tube was annealed, and the annealed seamless tube was drawn to obtain a flux-cored wire without slit-like gaps.

[0099] Specifically, the product was manufactured as follows: (1) A steel strip was continuously fed into a forming machine, and both ends of the strip in the width direction were processed to form a U-shape in the longitudinal direction to obtain an open tube. (2) Flux was supplied and filled through the U-shaped opening of the open tube. (3) The opposing edges (both ends in the circumferential direction) of the opening of the open tube were butt-welded to form an O-shaped tube with a longitudinal direction, obtaining a seamless tube. The outer diameter of the seamless tube was 4.5 mm. (4) The seamless tube was annealed to solution. (5) The annealed seamless tube was drawn until its outer diameter was 1.2 mm. In this way, a flux-cored wire with a final wire diameter of φ1.2 mm was prototyped. After prototyping, a lubricant was applied to the wire surface.

[0100] The composition of the obtained flux-cored wire was analyzed using an X-ray fluorescence analyzer and an X-ray diffraction (XRD) analyzer. The composition of the alloy components and compound components were as shown in Tables 1-1, 1-2, and 2-5. The remainder of the alloy and compound component compositions shown in Tables 1-1, 1-2, and 2-5 (i.e., components other than those shown in Tables 1-1 to 5) consisted of iron and impurities. The units of the compositions shown in Tables 1-1, 1-2, and 2-5 are mass percent of the total mass of the flux-cored wire.

[0101] In Table 2, SiO ２ SiO ２ The total amount of the converted value is ZrO ２ Zr oxide ZrO ２ The sum of the converted values, Al ２ O ３ Al oxide is Al ２ O ３ The total amount of the converted values, Na ２ O is Na of Na oxide ２ The total amount of the O equivalent is K ２ O is the K of K oxide ２The total amount of O equivalent values ​​is shown as follows: BaO represents the total amount of Ba oxide equivalent values ​​of Ba, CaO represents the total amount of Ca oxide equivalent values ​​of Ca, MgO represents the total amount of Mg oxide equivalent values ​​of Mg, and FeO represents the total amount of Fe oxide equivalent values ​​of Fe. Some of the wires in this disclosure contain at least one of the following as specific compounds (i.e., Sr compounds, Y compounds, Zr compounds, Ba compounds, and Sc compounds): Sr compounds, Y compounds, and Sc compounds. The total content of Sr, Y, and Sc elements contained in these specific compounds is shown in the "Sr, Y, and Sc" column of Table 5.

[0102] In Tables 1-1, 1-2, and 2-5, values ​​outside the scope defined in this disclosure are underlined. In Tables 1-1, 1-2, and 2-5, blank spaces in the tables relating to compositional content indicate that the content of that alloying or compounding component is less than the number of significant figures. These alloying and compounding components may also be inevitably mixed in or formed in less than the number of significant figures.

[0103]

[0104]

[0105]

[0106]

[0107]

[0108]

[0109] [Evaluation / Vertical Weldability] To evaluate the weldability of vertical welding using flux-cored wires in the disclosed and comparative examples, vertical upward fillet welding and vertical upward bead-on-plate welding were performed on 9% Ni steel. The welding conditions were 180A-23V-10cm / min, and the shielding gas was Ar-20% CO2. ２The workability of vertical welding was evaluated sensorily based on the presence or absence of metal drip. The evaluation was performed for both vertical upward fillet welding and vertical upward bead-on-plate welding. If no drip of molten metal occurred in either vertical upward fillet welding or vertical upward bead-on-plate welding, it was rated as excellent (A); if no drip occurred in only one, it was rated as good (B); and if drip occurred in both, it was rated as poor (C). A or B was considered a pass, and C was considered a fail.

[0110]

[0111] As shown in Table 6, the flux-cored wires of this disclosure, where the amount of Mn oxide X, the amount of Ti oxide Y, the ratio of X to Y (X / (X+Y)), and the total content of Mn excluding Mn contained as oxide are all within the specified range, received an A or B rating in the vertical weldability evaluation. Wire number 21 (comparative example) did not contain MnO and the amount of Mn oxide X was less than 0.3%, resulting in sagging in all welding methods in the vertical weldability evaluation and a C rating. Wire numbers 22 and 24 (comparative examples) had a ratio of X to Y (X / (X+Y)) of less than 0.65, resulting in sagging in all welding methods in the vertical weldability evaluation and a C rating. Wire number 23 (comparative example) had a total content of Mn excluding Mn contained as oxide exceeding 30.0%, resulting in sagging in all welding methods in the vertical weldability evaluation and a C rating.

[0112] (Note) This disclosure includes the following aspects: <1> A flux-cored welding wire comprising a steel sheath and flux filled inside the steel sheath, wherein the total amount X of Mn oxide in MnO equivalent is 0.3% to 15.0% by mass of the total mass of the flux-cored wire, and Ti oxide is TiO ２Flux-cored wire wherein the total amount Y of the converted value is 0.1% to 10.0%, the ratio of the total amount X of Mn oxide to the total amount Y of Ti oxide (X / (X+Y)) is 0.65 to 1.00, and the total content of Mn excluding Mn contained as oxide is 3.0% to 30.0%. <2> As chemical components excluding oxides, fluorides, nitrides, metal carbonates, and sulfates, in mass % of the total mass of the flux-cored wire, C: 0% to 0.650%, Si: 0.03% to 0.80%, Mn: 3.0% to 30.0%, P: 0% to 0.050%, S: 0% to 0.050%, Cu: 0% to 10.00%, Ni: 0% to 30.0%, Cr: 0% to 30.0%, Mo: 0% to 10.0%, Nb: 0% to 5.00%, V: 0% to 5.00%, Co: 0% to 10.00%, Pb: 0% to 1.00%, Sn: 0% to 1.00%, Al: 0% to 0.50% <1> A flux-cored wire according to <1>, comprising Ti: 0% to 0.50%, Ta: 0% to 1.00%, Hf: 0% to 1.00%, W: 0% to 30.00%, Mg: 0% to 0.50%, REM: 0% to 0.50%, Zr: 0% to 5.00%, Ca: 0% to 0.50%, B: 0% to 0.1000%, and N: 0% to 0.500%. <3> A flux-cored wire according to <2>, wherein the mass ratio ([Mn] / [Ni]) of the amount of Mn [Mn] and the amount of Ni [Ni] included as the chemical components is 0.30 to 3.00. <4> A flux-cored wire according to any one of <1> to <3>, wherein at least one specific oxide selected from the group consisting of Si oxide, Zr oxide, Al oxide, Na oxide, K oxide, Ba oxide, Ca oxide, Mg oxide, and Fe oxide is contained in the following range in mass % of the total mass of the flux-cored wire, and the total content of the specific oxide is greater than 0% to 10.00% in mass % of the total mass of the flux-cored wire. SiO of Si oxide ２ Total converted value: 0% to 5.00% Zr oxide ZrO ２ The total amount of the converted value is 0% to 5.00% of Al oxide.２ O ３ Total converted value: 0% to 5.00% Na oxide ２ Total amount of O equivalent value: 0% to 5.00% K oxide ２ Total amount of O equivalent value: 0% to 5.00% Total amount of Ba oxide equivalent value: 0% to 5.00% Total amount of Ca oxide equivalent value: 0% to 5.00% Total amount of Mg oxide equivalent value: 0% to 5.00% Total amount of Fe oxide equivalent value: 0% to 5.00% <5> K ２ SiF ６ _K ２ ZrF ６ NaF, Na ３ AlF ６ CaF ２ LiF, and MgF ２ A flux-cored wire according to any one of claims <1> to <4>, which contains at least one specific fluoride selected from the group consisting of the above, and the total content of the specific fluoride is greater than 0% to 10.00% by mass relative to the total mass of the flux-cored wire. <6> MgCO ３ Na ２ CO ３ LiCO ３ CaCO ３ _K ２ CO ３ BaCO ３ FeCO ３ MnCO ３ , and SrCO ３ A flux-cored wire according to any one of <1> to <5>, comprising at least one specific metal carbonate selected from the group consisting of the following, wherein the total content of the specific metal carbonates is greater than 0% to 10.00% by mass relative to the total mass of the flux-cored wire. <7> AlN, BN, Ca ３ N ２ , CeN, CrN, Cu ３ N, Fe ４ N, Fe ３ N, Fe ２ N, Mg ３ N, Mo ２ N, NbN, Si ３ N ４, TiN, VN, ZrN, Mn ２ N and Mn ４ A flux-cored wire according to any one of <1> to <6>, wherein it contains at least one specific nitride selected from the group consisting of N, and the total content of the specific nitride is greater than 0% to 10.00% by mass relative to the total mass of the flux-cored wire. <8> A flux-cored wire according to any one of <1> to <7>, wherein it contains at least one specific compound selected from the group consisting of Sr compounds, Y compounds, Zr compounds, Ba compounds, and Sc compounds, and the total content of Sr, Y, Zr, Ba, and Sc elements contained in the specific compound is greater than 0% to 1.0000% by mass relative to the total mass of the flux-cored wire. <9> A flux-cored wire according to any one of <1> to <8>, wherein the steel sheath does not have welded joints at the seams. <10> A flux-cored wire according to any one of <1> to <8>, wherein the steel sheath has welded joints at the seams. <11> A flux-cored wire according to any one of <1> to <10>, wherein one or both of polytetrafluoroethylene oil and perfluoropolyether oil are applied to the surface. <12> A method for manufacturing a welded joint, comprising the step of welding steel materials using a flux-cored wire according to any one of <1> to <11>.

[0113] The disclosure of Japanese Patent Application No. 2024-161478, filed on 18 September 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were described specifically and individually.

Claims

A flux-cored welding wire comprising a steel outer sheath and flux filled inside the steel outer sheath, Contains oxide and alloy components, It optionally contains at least one selected from the group consisting of fluorides, nitrides, metal carbonates, and sulfates. It optionally contains at least one specific compound selected from the group consisting of Sr compounds, Y compounds, Zr compounds, Ba compounds, and Sc compounds. In terms of mass % of the total mass of the flux-cored wire, The total amount X of Mn oxides in MnO equivalent is between 0.3% and 15.0%. Ti oxide TiO ２ The total amount Y of the converted values ​​is between 0.1% and 10.0%. The ratio of the total amount of Mn oxide X to the total amount of Ti oxide Y (X / (X+Y)) is 0.65 to 1.

00. Flux-cored wire having a total Mn content of 3.0% to 30.0%, excluding the Mn contained as the aforementioned oxide. 　 The content of the alloy component is, in mass % of the total mass of the flux-cored wire, C: 0.003% to 0.650%, Si: 0.03% to 0.80%, Mn: 3.0% to 30.0%, P: 0.050% or less, S: 0.050% or less, Cu: 0% to 10.00%, Ni: 0% to 30.0%, Cr: 0% to 30.0%, Mo: 0% to 10.0%, Nb: 0% to 5.00%, V: 0% to 5.00%, Co: 0% to 10.00%, Pb: 0% to 1.00%, Sn: 0% to 1.00%, Al: 0% to 0.50%, Ti: 0% to 0.50%, Ta: 0% to 1.00%, Hf: 0% to 1.00%, W: 0% to 30.00%, Mg: 0% to 0.50%, REM: 0% to 0.50%, Zr: 0% to 5.00%, Ca: 0% to 0.50%, B: 0% to 0.1000%, and N: 0% to 0.500%, The remainder consists of Fe and impurities. The flux-cored wire according to claim 1. 　 The flux-cored wire according to claim 2, wherein the mass ratio ([Mn] / [Ni]) of the amount of Mn [Mn] and the amount of Ni [Ni] included in the alloy component is 0.30 to 3.

00. The aforementioned oxide contains at least one specific oxide selected from the group consisting of Si oxide, Zr oxide, Al oxide, Na oxide, K oxide, Ba oxide, Ca oxide, Mg oxide, and Fe oxide, in the following range in mass % relative to the total mass of the flux-cored wire: The flux-cored wire according to any one of claims 1 to 3, wherein the total content of the specified oxides is greater than 0% to 10.00% by mass relative to the total mass of the flux-cored wire. SiO ２ Total amount of converted value: 0% to 5.00% Zr oxide ZrO ２ Total amount of converted value: 0% to 5.00% Al oxide ２ O ３ Total amount of converted value: 0% to 5.00% Na oxide ２ Total amount of O equivalent: 0% to 5.00% K of K oxide ２ Total amount of O equivalent: 0% to 5.00% Total amount of Ba oxide in BaO equivalent: 0% to 5.00% Total amount of Ca oxides in CaO equivalent: 0% to 5.00% Total amount of Mg oxides in MgO equivalent: 0% to 5.00% Total amount of Fe oxide in FeO equivalent: 0% to 5.00% As the fluoride, K ２ SiF ６ , K ２ ZrF ６ , NaF, Na ３ AlF ６ , CaF ２ , LiF, and MgF ２ contains at least one specific fluoride selected from the group consisting of The flux-cored wire according to any one of claims 1 to 4, wherein the total content of the specified fluoride is greater than 0% to 10.00% by mass relative to the total mass of the flux-cored wire. 　 As the aforementioned metal carbonate, MgCO ３ Na ２ CO ３ LiCO ３ CaCO ３ _K ２ CO ３ BaCO ３ FeCO ３ MnCO ３ , and SrCO ３ It contains at least one specific metal carbonate selected from the group consisting of the following, The flux-cored wire according to any one of claims 1 to 5, wherein the total content of the specified metal carbonates is greater than 0% to 10.00% by mass relative to the total mass of the flux-cored wire. 　 As the nitride, AlN, BN, Ca ３ N ２ , CeN, CrN, Cu ３ N, Fe ４ N, Fe ３ N, Fe ２ N, Mg ３ N, Mo ２ N, NbN, Si ３ N ４ , TiN, VN, ZrN, Mn ２ N and Mn ４ It contains at least one specific nitride selected from the group consisting of N, The flux-cored wire according to any one of claims 1 to 6, wherein the total content of the specified nitride is greater than 0% to 10.00% by mass relative to the total mass of the flux-cored wire. 　 It contains at least one of the specified compounds, The flux-cored wire according to any one of claims 1 to 7, wherein the total content of Sr, Y, Zr, Ba, and Sc elements contained in the specified compound is greater than 0% to 1.0000% by mass relative to the total mass of the flux-cored wire. 　 The flux-cored wire according to any one of claims 1 to 8, wherein the steel outer sheath does not have welded joints. 　 The flux-cored wire according to any one of claims 1 to 8, wherein the steel outer sheath has welded joints at the seams. 　 The flux-cored wire according to any one of claims 1 to 10, wherein the surface of the steel outer sheath is coated with either or both polytetrafluoroethylene oil and perfluoropolyether oil. 　 A method for manufacturing a welded joint, comprising the step of welding steel materials using a flux-cored wire according to any one of claims 1 to 11.

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