Flux-cored wire, welded joint and weld metal

Abstract

Provided is a flux-cored wire which is used for welding a structure in an extremely low temperature region, and which can yield a weld metal that exhibits excellent strength and has a lateral expansion amount that is a prescribed value or higher. The flux-cored wire contains Fe, C, Cr, Ni, and the like, at prescribed quantities relative to the total mass of the wire, and also contains 0.001-0.15 mass% of Nb and 0.005-0.30 mass% of V. In addition, a value A1 derived from formula (1) is 0.02-0.30, and a value A2 derived from formula (2) is 10.0-12.3. Formula (1): A1=[Nb]W+[V]W. Formula (2): A2=1.31×(0.98×[Cr]W+[Mo]Ｗ+0.7×[Nb]Ｗ)-1.1×([Ni]Ｗ+35×[C]Ｗ+20×[N]Ｗ+0.25×[Cu]Ｗ). Here, [element]W is a value that indicates the content of said element in the flux-cored wire in terms of mass%.

Description

Flux-cored wire, welded joints and weld metal

[0001] The present invention relates to a flux-cored wire, a welded joint, and a weld metal.

[0002] Generally, gases are liquefied at low temperatures and stored in tanks to improve the efficiency of transportation and storage, and therefore structural components of storage tanks are required to have low-temperature toughness in the liquefaction temperature range of the gas to be stored. For example, Patent Document 1 discloses an austenitic stainless steel flux-cored wire that can produce weld metal with excellent cryogenic toughness at around −196°C. The flux-cored wire described in Patent Document 1 specifies the contents of C, Si, Mn, P, Ni, Cr, and N, as well as a value obtained by a formula using the contents of Ni, Cr, Mn, Si, and C in the wire.

[0003] Japanese Patent Application Publication No. 2021-7982

[0004] In recent years, with environmental considerations in mind, the use of hydrogen as a fuel for power generation, automobiles, and the like has been considered, and the demand for hydrogen is increasing. Accordingly, there is also a growing demand for storage tanks that can safely store liquefied hydrogen. Specifically, there is a need for storage tanks that can be used in cryogenic temperatures, for example, at temperatures lower than those used in ordinary liquefied storage tanks, such as at cryogenic temperatures of about −253°C or higher. Therefore, there is a need for the development of flux-cored wires that can be used for welding structures in even lower temperature regions. The value of lateral bulge is sometimes required as an indicator of the low-temperature toughness of the weld metal for such low-temperature tanks. However, the flux-cored wire described in Patent Document 1 does not take lateral bulge into consideration.

[0005] The present invention has been made in consideration of the above problems, and has an object to provide a flux-cored wire used for welding structures in a cryogenic temperature range, which has excellent strength and can produce a weld metal having a lateral expansion amount equal to or greater than a desired value, a welded joint obtained by using the flux-cored wire, and a weld metal.

[0006] As a result of extensive research, the inventors have found that in order to obtain weld metal that exhibits excellent strength and lateral expansion in the cryogenic temperature region, it is effective to control the total amount of Nb and V in the wire and to control the amount of ferrite by setting the value obtained by a calculation formula using the Cr equivalent and Ni equivalent within a predetermined range. The present invention was made based on this finding.

[0007] The above object of the present invention is achieved by the following configuration [1] relating to a flux-cored wire.

[0008] [1] A flux-cored wire containing, relative to the total mass of the wire, Fe: 40% by mass or more and 70% by mass or less, C: 0.001% by mass or more and 0.030% by mass or less, Cr: 14.0% by mass or more and 28.0% by mass or less, Ni: 7.0% by mass or more and 20.0% by mass or less, Nb: 0.001% by mass or more and 0.15% by mass or less, and V: 0.005% by mass or more and 0.30% by mass or less, Mo: 4.0% by mass or less, Cu: 0.50% by mass or less, N: 0.020% by mass or less, and a value A1 calculated by the following formula (1): 0.02 to 0.30, and a value A2 calculated by the following formula (2): 10.0 to 12.3. A1 = [Nb] Ｗ + [V] Ｗ ...Formula (1) A2=1.31×(0.98×[Cr] Ｗ + [Mo] Ｗ +0.7 × [Nb] Ｗ )-1.1×([Ni] Ｗ +35 x [C] Ｗ +20×[N] Ｗ +0.25 × [Cu] Ｗ ) ...Equation (2) where [Nb] Ｗ is the Nb content in the flux-cored wire expressed in mass%, [V] Ｗ is the V content in the flux-cored wire expressed in mass%, and [Cr] Ｗ is the Cr content in the flux-cored wire expressed in mass%, and [Mo] Ｗ is the Mo content in the flux-cored wire expressed in mass%, and [Ni] Ｗis the Ni content in the flux-cored wire expressed in mass%, and [C] Ｗ is the C content in the flux-cored wire expressed in mass%, [N] Ｗ is the N content in the flux-cored wire expressed in mass%, and [Cu] Ｗ is the Cu content in the flux-cored wire expressed in mass %.

[0009] Furthermore, preferred embodiments of the present invention relating to the flux-cored wire relate to the following [2] to [3].

[0010] [2] Furthermore, with respect to the total mass of the wire, Si: 0.10 mass% or more and 1.00 mass% or less, F: 0.10 mass% or more and 0.50 mass% or less, Mn: 0.1 mass% or more and 1.60 mass% or less, TiO ２ 4.00% by mass or more and 10.00% by mass or less, ZrO of metal Zr and Zr compound ２ Contains: Converted value: 0.50 mass% or more and 4.00 mass% or less, MgO equivalent value of metal Mg and Mg compound: 0.05 mass% or more and 1.00 mass% or less, Na: 0.01 mass% or more and 0.50 mass% or less, and K: 0.01 mass% or more and 0.50 mass% or less, P: 0.030 mass% or less, S: 0.030 mass% or less, Co: 0.300% by mass or less, W: 0.50% by mass or less, REM: 0.500% by mass or less, Ti: 1.0% by mass or less, Al: 0.3% by mass or less, Al ２ O ３ : 1.00 mass % or less, Li: 0.50 mass % or less.

[0011] [3] The flux-cored wire according to [1] or [2], characterized in that the Ni: 10.0 mass% or more and 13.0 mass% or less, the Cr: 16.5 mass% or more and 18.0 mass% or less, and the Mo: 1.7 mass% or more and 2.2 mass% or less.

[0012] The above object of the present invention is achieved by the following configuration [4] relating to a welded joint.

[0013] [4] A welded joint, characterized by being produced by welding a stainless steel plate as a base material using the flux-cored wire according to any one of [1] to [3].

[0014] The above object of the present invention is achieved by the following configuration [5] relating to the weld metal.

[0015] [5] The weld metal contains, relative to the total mass of the weld metal, C: 0.001 mass% or more and 0.040 mass% or less, Cr: 14.0 mass% or more and 22.0 mass% or less, Ni: 7.0 mass% or more and 18.0 mass% or less, Mn: 0.3 mass% or more and 1.5 mass% or less, Nb: 0.001 mass% or more and 0.15 mass% or less, and V: 0.005 mass% or more and 0.30 mass% or less, Si: 1.0 mass% or less, Ti: 1.0 mass% or less, Mo: 4.0 mass% or less, Cu: 0.50 mass% or less, N: 0.020 mass% or less, the balance being Fe and unavoidable impurities, and a value A3 calculated by the following formula (3): 0.02 or more and 0.30 or less, and A weld metal characterized in that the value A4 calculated by the following formula (4) is 10.0 or more and 12.3 or less: A3 = [Nb] Ｍ + "V" Ｍ ...Formula (3) A4=1.18×([Cr] Ｍ + [Mo] Ｍ +0.7 × [Nb] Ｍ )-[Ni] Ｍ -35 x [C] Ｍ -20 x [N] Ｍ −0.25×[Cu] Ｍ ...Equation (4) where [Nb] Ｍ is the Nb content in the weld metal expressed in mass%, [V] Ｍ is the value of the V content in the weld metal expressed in mass%, and [Cr] Ｍ is the Cr content in the weld metal expressed in mass%, and [Mo] Ｍ is the value of the Mo content in the weld metal expressed in mass%, and [Ni] Ｍ is the Ni content in the weld metal expressed in mass%, [C] Ｍ is the value of the C content in the weld metal expressed in mass%, [N] Ｍis the value of the N content in the weld metal expressed in mass%, and [Cu] Ｍ is the Cu content in the weld metal expressed in mass %.

[0016] Furthermore, a preferred embodiment of the present invention relating to the weld metal relates to the following [6].

[0017] [6] The weld metal according to [5], characterized in that P: 0.030 mass% or less, S: 0.030 mass% or less, Co: 0.500 mass% or less, W: 0.50 mass% or less, the Ni: 12.0 mass% or more and 14.0 mass% or less, the Cr: 17.0 mass% or more and 19.0 mass% or less, and the Mo: 1.7 mass% or more and 2.5 mass% or less.

[0018] According to the present invention, a flux-cored wire can be provided that can produce a weld metal having excellent strength and a lateral expansion amount equal to or greater than a desired value. Furthermore, according to the present invention, by using the flux-cored wire, a welded joint that can be suitably used in a cryogenic environment can be provided. Furthermore, according to the present invention, a weld metal having excellent strength and a lateral expansion amount equal to or greater than a desired value can be provided.

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the preferred embodiments. However, the present invention is not limited to the preferred embodiments described below.

[0020] [Flux-cored wire] The flux-cored wire according to this embodiment is a stainless steel flux-cored wire in which a stainless steel sheath is filled with flux. The contents of Fe, C, Cr, Ni, Nb, V, Mo, Cu, and N in the wire are controlled, and the total content of Nb and V and a value calculated by a specific formula using the contents of Cr, Mo, Nb, Ni, C, N, and Cu are also controlled.

[0021] Hereinafter, each component contained in the flux-cored wire according to the present embodiment will be described in detail. In this specification, the flux-cored wire may be simply referred to as a wire.

[0022] <Fe: 40% by mass or more and 70% by mass or less> Fe is a main component constituting the outer sheath of the flux-cored wire according to this embodiment. In relation to the contents of flux components and the like contained in the wire, the Fe content relative to the total mass of the wire is 40% by mass or more, preferably 45% by mass or more, and more preferably 50% by mass or more. On the other hand, the Fe content relative to the total mass of the wire is 70% by mass or less, preferably 65% ​​by mass or less, and more preferably 60% by mass or less.

[0023] <C: 0.001% by mass or more and 0.030% by mass or less> While C is an element that improves the tensile strength of the weld metal, it segregates in the final solidification portion of the weld metal, lowering the melting point of the molten liquid and degrading hot cracking resistance. If the C content in the wire is less than 0.001% by mass, it is impossible to obtain a weld metal with good tensile strength. Therefore, the C content relative to the total mass of the wire is set to 0.001% by mass or more, preferably 0.003% by mass or more, and more preferably 0.005% by mass or more. On the other hand, if the C content in the wire exceeds 0.030% by mass, the hot cracking susceptibility increases. Therefore, the C content relative to the total mass of the wire is set to 0.030% by mass or less, preferably 0.025% by mass or less, and more preferably 0.020% by mass or less.

[0024] <Cr: 14.0% by Mass or More and 28.0% by Mass or Less> Cr is a component that improves the strength of the weld metal and stabilizes the ferrite phase. If the Cr content in the wire is less than 14.0% by mass, a weld metal with sufficient strength cannot be obtained. Therefore, the Cr content relative to the total mass of the wire is set to 14.0% by mass or more, preferably 15.0% by mass or more, and more preferably 16.5% by mass or more. On the other hand, if the Cr content in the wire exceeds 28.0% by mass, the toughness of the weld metal deteriorates and solidification segregation of Cr is promoted, resulting in deterioration of hot cracking resistance. Therefore, the Cr content relative to the total mass of the wire is set to 28.0% by mass or less, preferably 23.0% by mass or less, and more preferably 18.0% by mass or less.

[0025] <Ni: 7.0 mass% or more and 20.0 mass% or less> Ni is a component that has the effect of stabilizing the austenite structure. If the Ni content in the wire is less than 7.0 mass%, the austenite structure becomes unstable. Therefore, the Ni content relative to the total mass of the wire is set to 7.0 mass% or more, preferably 8.5 mass% or more, and more preferably 10.0 mass% or more. On the other hand, if the Ni content in the wire exceeds 20.0 mass%, the solid solubility of C and N decreases, making blowholes more likely to occur. Therefore, the Ni content relative to the total mass of the wire is set to 20.0 mass% or less, preferably 16.5 mass% or less, and more preferably 13.0 mass% or less.

[0026] <Nb: 0.001% by mass or more and 0.15% by mass or less> Nb is a component that forms carbides, reduces the amount of dissolved C, and has the effect of improving the absorbed energy and the amount of lateral expansion. In this embodiment, it is necessary to appropriately control the contents of Nb and V, which will be described later, particularly for the purpose of achieving a desired amount of lateral expansion or more. If the Nb content in the wire is less than 0.001% by mass, the desired amount of lateral expansion cannot be obtained. Therefore, the Nb content relative to the total mass of the wire is set to 0.001% by mass or more, preferably 0.02% by mass or more, and more preferably 0.04% by mass or more. On the other hand, if the Nb content in the wire exceeds 0.15% by mass, the absorbed energy of the weld metal decreases. Therefore, the Nb content relative to the total mass of the wire is set to 0.15% by mass or less, preferably 0.10% by mass or less, and more preferably 0.08% by mass or less.

[0027] <V: 0.005% by Mass or More and 0.30% by Mass or Less> Like Nb, V is a component that forms carbides to reduce the amount of solute C and improve the absorbed energy and lateral expansion amount. In order to achieve a desired lateral expansion amount or more, the V content must be appropriately controlled. If the V content in the wire is less than 0.005% by mass, the desired lateral expansion amount cannot be obtained. Therefore, the V content relative to the total mass of the wire is set to 0.005% by mass or more, preferably 0.03% by mass or more, and more preferably 0.05% by mass or more. On the other hand, if the V content in the wire exceeds 0.30% by mass, the absorbed energy of the weld metal decreases. Therefore, the V content relative to the total mass of the wire is set to 0.30% by mass or less, preferably 0.20% by mass or less, and more preferably 0.10% by mass or less.

[0028] <Mo: 4.0% by Mass or Less> Like Cr, Mo is a component that has the effect of improving the strength of the weld metal. However, in the flux-cored wire according to this embodiment, Mo does not necessarily need to be contained and may be 0% by mass. However, when Mo is contained in the wire for the purpose of improving the strength of the weld metal, the Mo content relative to the total mass of the wire is preferably 1.0% by mass or more, and more preferably 1.7% by mass or more. On the other hand, if the Mo content in the wire exceeds 4.0% by mass, the toughness of the weld metal deteriorates and solidification segregation of Mo is promoted, resulting in deterioration of hot cracking resistance. Therefore, the Mo content relative to the total mass of the wire is set to 4.0% by mass or less, preferably 3.1% by mass or less, and more preferably 2.2% by mass or less.

[0029] <Cu: 0.50% by mass or less> Cu is a component that has the effect of stabilizing the austenite structure. However, in the flux-cored wire according to the present embodiment, Cu does not necessarily need to be contained, and it may be 0% by mass. However, when Cu is contained in the wire for the purpose of stabilizing the austenite structure, the Cu content relative to the total mass of the wire is preferably 0.001% by mass or more, and more preferably 0.005% by mass or more. On the other hand, if the Cu content in the wire exceeds 0.50% by mass, the hot cracking resistance of the weld metal deteriorates. Therefore, the Cu content relative to the total mass of the wire is set to 0.50% by mass or less, preferably 0.25% by mass or less, and more preferably 0.15% by mass or less.

[0030] <N: 0.020% by mass or less> N is a solid-solution strengthening element and has the effect of improving the strength of the weld metal. However, in the flux-cored wire according to this embodiment, N does not necessarily need to be contained, and it may be 0% by mass. However, when N is contained in the wire for the purpose of improving the strength of the weld metal, the N content relative to the total mass of the wire is preferably 0.002% by mass or more, and more preferably 0.005% by mass or more. On the other hand, if the N content exceeds 0.020% by mass, the absorbed energy of the weld metal decreases. Therefore, the N content relative to the total mass of the wire is set to 0.020% by mass or less, preferably 0.015% by mass or less, and more preferably 0.012% by mass or less.

[0031] <Value A1 Calculated by Formula (1): 0.02 or More and 0.30 or Less> As described above, Nb and V are components that significantly affect the absorbed energy and lateral expansion amount of the weld metal. Therefore, a desired lateral expansion amount can be obtained by controlling the respective contents of Nb and V in the wire and appropriately controlling the total value of the Nb and V contents. If the value A1 calculated by the following formula (1), which is the total value of the Nb and V contents in the wire, is less than 0.02, the desired absorbed energy and lateral expansion amount cannot be obtained. Therefore, the value A1 is set to 0.02 or more, preferably 0.04 or more, and more preferably 0.06 or more. On the other hand, if the value A1 calculated by the following formula (1) exceeds 0.30, the absorbed energy of the weld metal decreases. Therefore, the value A1 is set to 0.30 or less, preferably 0.20 or less, and more preferably 0.12 or less.

[0032] A1 = [Nb] Ｗ + [V] Ｗ ...Formula (1) where [Nb] Ｗ is the Nb content in the flux-cored wire expressed in mass%, [V] Ｗ is the V content in the flux-cored wire expressed in mass %.

[0033] <Value A2 Calculated by Formula (2): 10.0 to 12.3> In this embodiment, the ferrite content of the weld metal can be controlled within a desired range by adjusting parameters using the contents of Cr, Mo, and Nb, which are ferrite stabilizing elements, and the contents of Ni, C, N, and Cu, which are austenite stabilizing elements, in the wire. More specifically, the following formula (2) is a formula for subtracting the Ni equivalent, which is the degree of the austenite stabilizing element converted into the amount of nickel, from the Cr equivalent, which is the degree of the ferrite stabilizing element converted into the amount of chromium. Therefore, by specifying the value A2 calculated by this formula (2), it is possible to prevent an excess or deficiency of ferrite and achieve a balance between strength and toughness.

[0034] If the value A2 calculated by the following formula (2) is less than 10.0, the amount of ferrite will be too small, resulting in a decrease in the strength of the weld metal. Therefore, the value A2 should be 10.0 or greater, preferably 11.0 or greater, and more preferably 11.5 or greater. On the other hand, if the value A2 calculated by the following formula (2) exceeds 12.3, the amount of ferrite will be too large, resulting in a decrease in the low-temperature toughness and lateral expansion of the weld metal. Therefore, the value A2 should be 12.3 or less, preferably 12.1 or less, and more preferably 11.9 or less.

[0035] A2=1.31×(0.98×[Cr] Ｗ + [Mo] Ｗ +0.7 × [Nb] Ｗ )-1.1×([Ni] Ｗ +35 x [C] Ｗ +20×[N] Ｗ +0.25 × [Cu] Ｗ ) ...Equation (2) where [Cr] Ｗ is the Cr content in the flux-cored wire expressed in mass%, and [Mo] Ｗ is the value of the Mo content in the flux-cored wire expressed in mass%, and [Nb] Ｗ is the Nb content in the flux-cored wire expressed in mass%, [Ni] Ｗ is the Ni content in the flux-cored wire expressed in mass%, and [C] Ｗ is the C content in the flux-cored wire expressed in mass%, [N] Ｗ is the N content in the flux-cored wire expressed in mass%, and [Cu] Ｗ is the Cu content in the flux-cored wire expressed in mass %.

[0036] The flux-cored wire according to this embodiment can solve the problems of the present invention if the content of each component is within the above-mentioned range. In order to further improve the welding workability and the mechanical properties of the weld metal, the wire may further contain Si, F, Mn, TiO ２ , metal Zr, Zr compounds, metal Mg, Mg compounds, Na and K. Also, P, S, Co, W, REM, Ti, Al, Al ２O ３ It is also preferable that the content of Li relative to the total mass of the wire is specified. The preferred ranges of these contents will be described below.

[0037] <Si: 0.10% by mass or more and 1.00% by mass or less> Si is a component that has the effects of improving the strength of the weld metal, ensuring low-temperature toughness, and suppressing the occurrence of blowholes. When the Si content in the wire is 0.10% by mass or more, the above effects can be obtained. Therefore, the Si content relative to the total mass of the wire is preferably 0.10% by mass or more, and more preferably 0.40% by mass or more. On the other hand, when the Si content in the wire is 1.00% by mass or less, deterioration of hot cracking resistance can be prevented. Therefore, the Si content relative to the total mass of the wire is preferably 1.00% by mass or less, and more preferably 0.70% by mass or less. The Si content in the wire refers to the total content of all Si contained in elemental Si, Si alloys, and Si compounds in the wire.

[0038] <F: 0.10% by mass or more and 0.50% by mass or less> In this embodiment, F can be contained in the wire for the purpose of suppressing the amount of spatter generated and stabilizing the arc. When the F content in the wire is 0.10% by mass or more, the effect of suppressing the amount of spatter generated and stabilizing the arc can be obtained. Therefore, when F is contained in the wire, the F content relative to the total mass of the wire is preferably 0.10% by mass or more, and more preferably 0.15% by mass or more. On the other hand, when the F content in the wire is 0.50% by mass or less, spatter and fumes can be suppressed. Therefore, the F content relative to the total mass of the wire is preferably 0.50% by mass or less, and more preferably 0.30% by mass or less.

[0039] <Mn: 0.1% by mass or more and 1.60% by mass or less> Mn has a deoxidizing effect to suppress blowholes caused by oxygen-based gases and also has the effect of stabilizing the austenite structure. Therefore, in this embodiment, Mn may be contained in the wire. When the Mn content in the wire is 0.1% by mass or more, a sufficient deoxidizing effect can be obtained. Therefore, the amount of Mn added relative to the total mass of the wire is preferably 0.1% by mass or more, and more preferably 0.50% by mass or more. On the other hand, when the Mn content is 1.60% by mass or less, a decrease in the amount of lateral expansion can be suppressed. Therefore, the Mn content relative to the total mass of the wire is preferably 1.60% by mass or less, and more preferably 1.50% by mass or less.

[0040] <TiO ２ :4.00 mass% or more and 10.00 mass% or less>TiO ２ is the main component of the slag forming agent, and is a component that has the effect of forming a uniform slag with good encapsulation properties and improving arc stability. ２ It also has the effect of increasing the melting point of the slag and flattening the bead shape in all-position welding. ２ When the content is 4.00 mass % or more, the above-mentioned effects can be sufficiently obtained. ２ The content is preferably 4.00 mass% or more, and more preferably 5.00 mass% or more. ２ When the content is 10.00 mass % or less, the flux becomes easily soluble, and the occurrence of slag winding can be suppressed. ２ The content is preferably 10.00 mass % or less, and more preferably 7.0 mass % or less. ２ The content is the TiO of the Ti compound contained in the wire. ２ The Ti compounds used herein refer to Ti oxides, Ti nitrides, and the like.

[0041] Metallic Zr and Zr compound ZrO ２ Converted value: 0.50 mass% or more and 4.00 mass% or less > ZrO２ is a component that has the effect of accelerating slag solidification and forming a flat bead shape in both the vertical and upward positions. ２ When the converted value is 0.50 mass % or more, the above-mentioned effect can be sufficiently obtained. ２ The converted value is preferably 0.50 mass % or more, and more preferably 1.00 mass % or more. ２ When the converted value is 4.00 mass % or less, good slag encapsulation and slag removability can be obtained. ２ The converted value is preferably 4.00 mass % or less, and more preferably 2.00 mass % or less. ２ The converted value is calculated by dividing all Zr contained in metallic Zr and Zr compounds by ZrO ２ Here, "metallic Zr" refers to the total amount of Zr contained in simple Zr and Zr alloys, and "Zr compounds" refers to Zr oxides and the like.

[0042] <Metallic Mg and Mg Compounds in MgO Equivalent: 0.05% by Mass or More and 1.00% by Mass or Less> Metallic Mg and Mg compounds are components that increase the slag solidification point and improve arc stability. When the MgO equivalent is 0.05% by mass or more, the above effects can be sufficiently obtained. Therefore, the MgO equivalent in the wire is preferably 0.05% by mass or more, and more preferably 0.15% by mass or more, based on the total mass of the wire. On the other hand, when the MgO equivalent is 1.00% by mass or less, deterioration of the bead shape can be prevented. Therefore, the MgO equivalent is preferably 1.00% by mass or less, and more preferably 0.30% by mass or less. In this embodiment, the MgO equivalent is the value obtained by converting all Mg contained in metallic Mg and Mg compounds into MgO. Here, metallic Mg refers to the total amount of Mg contained in Mg alone and Mg alloys. Furthermore, Mg compounds refers to Mg oxides and the like.

[0043] <Na: 0.01% by mass or more and 0.50% by mass or less> Alkali metals such as Na are components that have the effect of improving arc stability, and can be contained in the wire as fluorides or composite oxides. When the Na content in the wire is 0.01% by mass or more, the effect of improving arc stability can be obtained. Therefore, the Na content relative to the total mass of the wire is preferably 0.01% by mass or more, and more preferably 0.10% by mass or more. On the other hand, when the Na content in the wire is 0.50% by mass or less, a decrease in the slag melting point can be suppressed and a good bead shape can be achieved in all-position welding. Therefore, the Na content relative to the total mass of the wire is preferably 0.50% by mass or less, and more preferably 0.20% by mass or less. Note that Na can be, for example, Na ２ O and the like are present in the wire.

[0044] <K: 0.01% by mass or more and 0.50% by mass or less> Like Na, alkali metals such as K are components that have the effect of improving arc stability, and can be contained in the wire as fluorides or composite oxides. When the K content in the wire is 0.01% by mass or more, the effect of improving arc stability can be obtained. Therefore, the K content relative to the total mass of the wire is preferably 0.01% by mass or more, and more preferably 0.10% by mass or more. On the other hand, when the K content in the wire is 0.50% by mass or less, a decrease in the slag melting point can be suppressed and a good bead shape can be achieved in all-position welding. Therefore, the K content relative to the total mass of the wire is preferably 0.50% by mass or less, and more preferably 0.20% by mass or less. Note that K can be, for example, K ２ O and K ２ SiF ６ etc., are present in the wire.

[0045] <P: 0.030% by mass or less> P is an unavoidable impurity in the wire. Since the cryogenic toughness decreases as the P content in the weld metal increases, the P content in the welding wire is preferably low. Therefore, the P content relative to the total mass of the wire is preferably 0.030% by mass or less, and more preferably 0.020% by mass or less.

[0046] <S: 0.030% by mass or less> S, like P, is an unavoidable impurity in the wire. Since the cryogenic toughness decreases as the S content in the weld metal increases, the smaller the S content in the welding wire, the better. Therefore, the S content relative to the total mass of the wire is preferably 0.030% by mass or less, and more preferably 0.010% by mass or less.

[0047] <Co: 0.300% by mass or less> Co is a component that has the effect of adjusting the toughness of the weld metal, so Co can be contained in the wire as necessary. If the Co content in the wire is 0.300% by mass or less, a decrease in the strength of the weld metal can be suppressed. Therefore, the Co content relative to the total mass of the wire is preferably 0.300% by mass or less, and more preferably 0.200% by mass or less.

[0048] <W: 0.50% by mass or less> W is a solid-solution strengthening element in steel and is a component that dissolves in the weld metal and has the effect of improving the strength of the weld metal. Therefore, W can be contained in the wire as needed. If the W content in the wire is 0.50% by mass or less, deterioration of toughness can be suppressed. Therefore, the W content relative to the total mass of the wire is preferably 0.50% by mass or less, and more preferably 0.20% by mass or less.

[0049] <REM: 0.500% by mass or less> Since REM (rare earth element) is a deoxidizing element, REM can be contained in the wire as needed. However, if the REM content in the wire is 0.500% by mass or less, deterioration of welding workability can be suppressed. Therefore, the REM content relative to the total mass of the wire is preferably 0.500% by mass or less, and more preferably 0.400% by mass or less. Note that REM refers to the 15 lanthanoid series rare earth elements from La to Lu in the periodic table. These elements may be added alone or in combination of two or more.

[0050] <Ti: 1.0 mass% or less> Ti is a component that has the effect of improving the toughness of the weld metal, so Ti can be contained in the wire as necessary. When the Ti content in the wire is 1.0 mass% or less, the oxygen content in the weld metal can be reduced, and the toughness of the weld metal can be adjusted to a desired range. Therefore, the Ti content relative to the total mass of the wire is preferably 1.0 mass% or less, and more preferably 0.8 mass% or less. Note that the Ti content in the wire refers to the content of all metallic Ti contained in the Ti alloy and elemental Ti contained in the wire.

[0051] <Al: 0.3 mass% or less> Al is a component that has a deoxidizing effect and has the effect of stabilizing the toughness of the weld metal, so Al can be contained in the wire as necessary. When the Al content in the wire is 0.3 mass% or less, it is possible to appropriately adjust the yield of alloy elements in the weld metal and to suppress excessive strength increase. Therefore, the Al content relative to the total mass of the wire is preferably 0.3 mass% or less, and more preferably 0.1 mass% or less. Note that the Al content in the wire refers to the content of elemental Al and all metallic Al contained in the Al alloy contained in the wire.

[0052] <Al ２ O ３ : 1.00% by mass or less> Al ２ O ３ is a slag forming agent and a component that has the effect of improving the bead shape. Therefore, if necessary, Al is added to the wire. ２ O ３ The wire may contain Al. ２ O ３ When the content of Al relative to the total mass of the wire is 1.00 mass % or less, good slag removability can be obtained. ２ O ３ The content is preferably 1.00 mass % or less, and more preferably 0.20 mass % or less. ２ O ３ The content is the amount of Al in Al compounds such as Al oxides contained in the wire. ２ O ３This represents the value converted into

[0053] <Li: 0.50% by mass or less> Like the above-mentioned Na and K, alkali metals such as Li are components that have the effect of improving arc stability, and can be contained in the wire as a fluoride or composite oxide. Furthermore, when the Li content in the wire is 0.50% by mass or less, a decrease in the slag melting point can be suppressed and a good bead shape can be achieved in all-position welding. Therefore, the Li content relative to the total mass of the wire is preferably 0.50% by mass or less, and more preferably 0.20% by mass or less.

[0054] <Remainder of Flux-Cored Wire> The flux-cored wire of this embodiment contains, as essential components, Fe, C, Cr, Ni, Nb, and V, and may contain Mo, Cu, and N. The total content of these components is preferably 80 mass % or more, more preferably 83 mass % or more, and even more preferably 85 mass % or more, based on the total mass of the wire. The wire may further contain Si, F, Mn, TiO ２ , ZrO ２ , MgO, Na, K, P, S, Co, W, REM, Ti, Al, Al ２ O ３ , Li, etc. Furthermore, the balance of these components may include, for example, Ca, Ba, Ta, Bi, etc.

[0055] The method for manufacturing the flux-cored wire according to the present embodiment is not particularly limited, and the wire can be manufactured by a general manufacturing process, for example, by forming a stainless steel hoop into a U-shape, filling the U-shaped hoop with flux, molding the hoop into a cylindrical shape with the flux filled inside, and drawing the wire to a target diameter.

[0056] The material of the outer sheath may be any type of stainless steel or the like without any particular limitation, as long as the content of each component in the total mass of the flux-cored wire is controlled within the above range.

[0057] The flux-cored wire according to this embodiment can be suitably used for welding low-temperature steels such as 5% Ni steel and various austenitic stainless steels. The shielding gas used is not particularly limited. For example, Ar gas, carbon dioxide gas (CO ), etc. ２ ), oxygen gas (O ２ ) and mixtures thereof, etc. These may contain oxygen, nitrogen, hydrogen, etc. as inevitable impurities.

[0058] [Welded Joint] The welded joint according to this embodiment is produced by welding a stainless steel plate as a base material using the flux-cored wire.

[0059] [Weld Metal] The weld metal according to this embodiment is formed, for example, by welding using the above-mentioned flux-cored wire, and has excellent strength and lateral expansion. The components and their contents contained in the weld metal according to this embodiment will be described in detail below. Each element is defined as the total amount of the component contained in a predetermined region of the weld metal that is not affected by the composition of the base metal, expressed as a value per total mass of the weld metal. The content of each component in the weld metal according to this embodiment will be described below.

[0060] <C: 0.001% by Mass or More and 0.040% by Mass or Less> C is a component that stabilizes the austenite phase in the weld metal, making it less likely to transform to the martensite phase. C also contributes to increasing the strength of the weld metal. If the C content in the weld metal is less than 0.001% by mass, it is difficult to obtain a weld metal with good tensile strength. Therefore, the C content relative to the total mass of the weld metal is set to 0.001% by mass or more, preferably 0.005% by mass or more, and more preferably 0.008% by mass or more. On the other hand, if the C content in the weld metal exceeds 0.040% by mass, the strength increases excessively, making it difficult to obtain excellent cryogenic toughness. Therefore, the C content relative to the total mass of the weld metal is set to 0.040% by mass or less, preferably 0.030% by mass or less, and more preferably 0.025% by mass or less.

[0061] <Cr: 14.0% by Mass or More and 22.0% by Mass or Less> Cr is a component that stabilizes the ferrite phase in the weld metal and makes it difficult for transformation to martensite to occur. If the Cr content in the weld metal is less than 14.0% by mass, the ferrite phase becomes unstable, making it difficult to obtain excellent cryogenic toughness. Therefore, the Cr content relative to the total mass of the weld metal is set to 14.0% by mass or more, preferably 16.0% by mass or more, and more preferably 17.0% by mass or more. On the other hand, if the Cr content in the weld metal exceeds 22.0% by mass, the ferrite phase becomes excessively stabilized, resulting in a decrease in cryogenic toughness. Therefore, the Cr content relative to the total mass of the weld metal is set to 22.0% by mass or less, preferably 20.0% by mass or less, and more preferably 19.0% by mass or less.

[0062] <Ni: 7.0% by Mass or More and 18.0% by Mass or Less> Ni is a component that stabilizes the austenite phase in the weld metal and makes it less likely to transform to martensite. If the Ni content in the weld metal is less than 7.0% by mass, the austenite phase becomes unstable, resulting in reduced cryogenic toughness. Therefore, the Ni content relative to the total mass of the weld metal is set to 7.0% by mass or more, preferably 11.0% by mass or more, and more preferably 12.0% by mass or more. On the other hand, if the Ni content in the weld metal exceeds 18.0% by mass, the austenite phase becomes excessively stabilized, making it impossible to obtain excellent cryogenic toughness. Therefore, the Ni content in the weld metal is set to 18.0% by mass or less, preferably 15.0% by mass or less, and more preferably 14.0% by mass or less.

[0063] <Mn: 0.3% by mass or more and 1.5% by mass or less> Mn is an austenite stabilizing element and also a deoxidizing agent that removes oxygen in the weld metal as slag and improves mechanical strength. If the Mn content in the weld metal is less than 0.3% by mass, the deoxidizing effect is insufficient, increasing the oxygen content in the weld metal, making it impossible to obtain excellent cryogenic toughness. Therefore, the Mn content relative to the total mass of the weld metal is set to 0.3% by mass or more, preferably 0.4% by mass or more, and more preferably 0.5% by mass or more. On the other hand, if the Mn content in the weld metal exceeds 1.5% by mass, the strength of the weld metal increases excessively, resulting in a decrease in cryogenic toughness. Therefore, the Mn content relative to the total mass of the weld metal is set to 1.5% by mass or less, preferably 1.0% by mass or less, and more preferably 0.9% by mass or less.

[0064] <Nb: 0.001% by mass or more and 0.15% by mass or less> Nb is a component that forms carbides in the weld metal, reduces the amount of solute C, and improves the absorbed energy and the amount of lateral expansion. If the Nb content in the weld metal is less than 0.001% by mass, the desired amount of lateral expansion cannot be obtained. Therefore, the Nb content relative to the total mass of the weld metal is set to 0.001% by mass or more, preferably 0.02% by mass or more, and more preferably 0.04% by mass or more. On the other hand, if the Nb content in the weld metal exceeds 0.15% by mass, the absorbed energy of the weld metal decreases. Therefore, the Nb content relative to the total mass of the weld metal is set to 0.15% by mass or less, preferably 0.10% by mass or less, and more preferably 0.08% by mass or less.

[0065] <V: 0.005% by Mass or More and 0.30% by Mass or Less> Like Nb, V is a component that forms carbides in the weld metal, reduces the amount of solute C, and improves the absorbed energy and lateral expansion. If the V content in the weld metal is less than 0.005% by mass, the desired lateral expansion cannot be obtained. Therefore, the V content relative to the total mass of the weld metal is set to 0.005% by mass or more, preferably 0.02% by mass or more, and more preferably 0.04% by mass or more. On the other hand, if the V content in the weld metal exceeds 0.30% by mass, the absorbed energy of the weld metal decreases. Therefore, the V content relative to the total mass of the weld metal is set to 0.30% by mass or less, preferably 0.20% by mass or less, and more preferably 0.10% by mass or less.

[0066] <Si: 1.0 Mass% or Less> Si is a component that has the effect of promoting deoxidation, but in the weld metal according to this embodiment, Si need not be contained, and may be 0 mass%. When Si is contained in the weld metal for the purpose of ensuring the strength and low-temperature toughness of the weld metal, the Si content in the weld metal is preferably 0.2 mass% or more, and more preferably 0.3 mass% or more, relative to the total mass of the weld metal. On the other hand, if the Si content in the weld metal exceeds 1.0 mass%, the crystal strength of the weld metal decreases, and excellent cryogenic toughness cannot be obtained. Therefore, the Si content relative to the total mass of the weld metal is set to 1.0 mass% or less, preferably 0.6 mass% or less, and more preferably 0.5 mass% or less.

[0067] <Ti: 1.0 mass% or less> Ti is a component that has the effect of improving the toughness of the weld metal, but if its content in the weld metal exceeds a certain amount, the strength increases excessively, resulting in a decrease in toughness. Therefore, the Ti content relative to the total mass of the weld metal is set to 1.0 mass% or less, preferably 0.2 mass% or less, and more preferably 0.1 mass% or less.

[0068] <Mo: 4.0 mass% or less> Mo is a component that has the effect of improving the strength of the weld metal, but if its content in the weld metal exceeds a certain amount, the strength increases excessively, resulting in a decrease in toughness. Therefore, the Mo content relative to the total mass of the weld metal is set to 4.0 mass% or less, preferably 3.0 mass% or less, and more preferably 2.5 mass% or less. Furthermore, the Mo content relative to the total mass of the weld metal is preferably 1.7 mass% or more.

[0069] <Cu: 0.50 mass% or less> Cu is a component that has the effect of improving the strength of the weld metal, but if its content in the weld metal exceeds a certain amount, the strength increases excessively, resulting in a decrease in toughness. Therefore, the Cu content relative to the total mass of the weld metal is set to 0.50 mass% or less, preferably 0.20 mass% or less, and more preferably 0.10 mass% or less.

[0070] <N: 0.020% by mass or less> N is a component that stabilizes the austenite phase in the weld metal, making it less likely to transform into the martensite phase. N is also a component that contributes to increasing the strength of the weld metal. If the N content in the weld metal exceeds 0.020% by mass, the strength increases excessively, making it difficult to obtain excellent cryogenic toughness. Therefore, the N content relative to the total mass of the weld metal is set to 0.020% by mass or less, preferably 0.018% by mass or less, and more preferably 0.015% by mass or less.

[0071] <Value A3 calculated by the following formula (3): 0.02 or more and 0.30 or less> As described above, Nb and V are components that significantly affect the absorbed energy and lateral expansion amount of the weld metal. Therefore, a desired lateral expansion amount can be obtained by controlling the respective contents of Nb and V in the weld metal and appropriately controlling the total value of the Nb and V contents. If the value A3 calculated by the following formula (3), which is the total value of the Nb and V contents in the weld metal, is less than 0.02, the desired absorbed energy and lateral expansion amount cannot be obtained. Therefore, the value A3 is set to 0.02 or more, preferably 0.04 or more, and more preferably 0.06 or more. On the other hand, if the value A3 calculated by the following formula (3) exceeds 0.30, the absorbed energy of the weld metal decreases. Therefore, the value A3 is set to 0.30 or less, preferably 0.20 or less, and more preferably 0.15 or less. A3 = [Nb] Ｍ + "V" Ｍ ...Equation (3) where [Nb] Ｍ is the Nb content in the weld metal expressed in mass%, [V] Ｍ is the V content in the weld metal expressed in mass %.

[0072] <Value A4 Calculated by Formula (4): 7.6 to 10.3> In this embodiment, the ferrite content of the weld metal can be controlled within a desired range by adjusting parameters that use the contents of Cr, Mo, and Nb, which are ferrite stabilizing elements, and the contents of Ni, C, N, and Cu, which are austenite stabilizing elements, in the weld metal. More specifically, Formula (4) below is a formula for subtracting the Ni equivalent, which is obtained by converting the level of the ferrite stabilizing element into the amount of nickel, from the Cr equivalent, which is obtained by converting the level of the ferrite stabilizing element into the amount of chromium. Therefore, by specifying the value A4 calculated by Formula (4), it is possible to prevent an excess or deficiency of ferrite and achieve a balance between strength and toughness.

[0073] If the value A4 calculated by the following formula (4) is less than 7.6, the amount of ferrite will be too small, resulting in a decrease in the strength of the weld metal. Therefore, the value A4 should be 7.6 or more, preferably 8.0 or more, and more preferably 8.5 or more. On the other hand, if the value A4 calculated by the following formula (4) exceeds 10.3, the amount of ferrite will be too large, resulting in a decrease in the low-temperature toughness and lateral expansion of the weld metal. Therefore, the value A4 should be 10.3 or less, preferably 10.0 or less, and more preferably 9.5 or less.

[0074] A4=1.18×([Cr] Ｍ + [Mo] Ｍ +0.7 × [Nb] Ｍ )-[Ni] Ｍ -35 x [C] Ｍ -20 x [N] Ｍ −0.25×[Cu] Ｍ ) ...Equation (4) where [Cr] Ｍ is the Cr content in the weld metal expressed in mass%, and [Mo] Ｍ is the value of the Mo content in the weld metal expressed in mass%, [Nb] Ｍ is the Nb content in the weld metal expressed in mass%, [Ni] Ｍ is the Ni content in the weld metal expressed in mass%, [C] Ｍ is the value of the C content in the weld metal expressed in mass%, [N] Ｍ is the value of the N content in the weld metal expressed in mass%, and [Cu] Ｍ is the Cu content in the weld metal expressed in mass %.

[0075] <P: 0.030 mass% or less> P is an unavoidable impurity in the weld metal. Since the cryogenic toughness decreases as the P content in the weld metal increases, a smaller P content in the weld metal is preferable. Therefore, the P content relative to the total mass of the weld metal is preferably 0.030 mass% or less, and more preferably 0.020 mass% or less.

[0076] <S: 0.030% by mass or less> S, like P, is an unavoidable impurity in the weld metal. Since the cryogenic toughness decreases as the S content in the weld metal increases, it is preferable that the S content in the weld metal be small. Therefore, the S content relative to the total mass of the weld metal is preferably 0.030% by mass or less, and more preferably 0.010% by mass or less.

[0077] <Co: 0.500 mass% or less> Co is a component that has the effect of adjusting the toughness of the weld metal, so Co can be contained in the weld metal as necessary. If the Co content in the weld metal is 0.500 mass% or less, a decrease in strength can be suppressed. Therefore, when Co is contained in the weld metal, the Co content relative to the total mass of the weld metal is preferably 0.500 mass% or less, and more preferably 0.200 mass% or less.

[0078] <W: 0.50% by mass or less> W is a component that has the effect of improving the strength of the weld metal, so W can be contained in the weld metal as necessary. However, if the W content in the weld metal exceeds a predetermined amount, the strength increases excessively, resulting in a decrease in toughness. Therefore, the W content relative to the total mass of the weld metal is preferably 0.50% by mass or less, and more preferably 0.20% by mass or less.

[0079] <Balance: Fe and Inevitable Impurities> In the weld metal according to this embodiment, the balance excluding the above-mentioned components is Fe and unavoidable impurities. Fe is the main component constituting the outer sheath of the flux-cored wire according to this embodiment and is retained in the weld metal. The Fe content relative to the total mass of the weld metal is, for example, preferably 40 mass% or more, more preferably 50 mass% or more, and even more preferably 60 mass% or more. On the other hand, the Fe content relative to the total mass of the weld metal is preferably 70 mass% or less, more preferably 68 mass% or less, and even more preferably 66 mass% or less. In addition to the P and S mentioned above, examples of unavoidable impurities include O, As, Sb, Sn, Bi, and S. The O content in the weld metal is preferably less than 0.100 mass% relative to the total mass of the weld metal. Furthermore, the total amount of unavoidable impurities in the weld metal excluding P, S, and O is preferably 0.10 mass% or less relative to the total mass of the weld metal.

[0080] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to these examples and can be practiced with modifications within the scope of the spirit of the present invention, and all such modifications are included in the technical scope of the present invention.

[0081] [Preparation of Flux-Cored Wire] Flux-cored wires having the compositions shown in Tables 1 to 3 below were prepared using sheaths and fluxes of various compositions. The flux ratios were 18 to 26.5 mass%. In Table 3, "-" indicates that the corresponding component was not intentionally added. In Table 1, Formula (1): A1 indicates the value A1 calculated by Formula (1), and Formula (2): A2 indicates the value A2 calculated by Formula (2). Formulas (1) and (2) are as follows:

[0082] A1 = [Nb] Ｗ + [V] Ｗ ...Formula (1) A2=1.31×(0.98×[Cr] Ｗ + [Mo] Ｗ +0.7 × [Nb] Ｗ )-1.1×([Ni] Ｗ +35 x [C]Ｗ +20×[N] Ｗ +0.25 × [Cu] Ｗ ) ...Equation (2) where [Nb] Ｗ is the Nb content in the flux-cored wire expressed in mass%, [V] Ｗ is the V content in the flux-cored wire expressed in mass%, and [Cr] Ｗ is the Cr content in the flux-cored wire expressed in mass%, and [Mo] Ｗ is the Mo content in the flux-cored wire expressed in mass%, and [Ni] Ｗ is the Ni content in the flux-cored wire expressed in mass%, and [C] Ｗ is the C content in the flux-cored wire expressed in mass%, [N] Ｗ is the N content in the flux-cored wire expressed in mass%, and [Cu] Ｗ is the Cu content in the flux-cored wire expressed in mass %.

[0083] [Gas-shielded arc welding] Two carbon steel plates with a thickness of 20 mm were prepared and processed to have a groove angle of 45°. Then, using the prepared flux-cored wire, two to three layers of buttering were formed on the surface of the groove and the surface of the backing material, and the carbon steel plates were arranged to form a V-groove. Then, gas-shielded arc welding was performed on the groove using each flux-cored wire. The welding conditions were 100% CO ２ The shielding gas was 190A-28V, and the welding was performed in a downward position with 6 layers and 12 passes.

[0084] [Measurement of weld metal composition] The obtained weld metals were subjected to solid-state emission spectroscopy analysis in accordance with JIS G 1253:2002 at the same positions as those for collecting tensile test specimens, as described below, to measure the composition of each weld metal. The contents of chemical components in the weld metals are shown in Tables 4 and 5. In Table 4, Equation (3): A3 indicates the value A3 calculated by Equation (3), and Equation (4): A4 indicates the value A4 calculated by Equation (4). Equations (3) and (4) are as follows: The balance of the weld metal is Fe and unavoidable impurities.

[0085] A3 = [Nb Ｍ + "V" Ｍ ...Formula (3) A4=1.18×([Cr] Ｍ + [Mo] Ｍ +0.7 × [Nb] Ｍ )-[Ni] Ｍ -35 x [C] Ｍ -20 x [N] Ｍ −0.25×[Cu] Ｍ ) ...Equation (4) where [Nb] Ｍ is the Nb content in the weld metal expressed in mass%, [V] Ｍ is the value of the V content in the weld metal expressed in mass%, and [Cr] Ｍ is the Cr content in the weld metal expressed in mass%, and [Mo] Ｍ is the value of the Mo content in the weld metal expressed in mass%, and [Ni] Ｍ is the Ni content in the weld metal expressed in mass%, [C] Ｍ is the value of the C content in the weld metal expressed in mass%, [N] Ｍ is the value of the N content in the weld metal expressed in mass%, and [Cu] Ｍ is the Cu content in the weld metal expressed in mass %.

[0086] [Mechanical Performance Evaluation Test] (Charpy Impact Test) Standard V-notch test pieces were taken from the obtained weld metals in accordance with JIS Z 2242:2023, and a Charpy impact test was performed. The test temperature for the Charpy impact test was -196°C, and the Charpy impact value (vE-196°C) and the amount of lateral expansion LE (mm) were measured. Five test pieces for measuring the Charpy impact value and five test pieces for measuring the amount of lateral expansion were taken from each weld metal. The average value of the measured values ​​was evaluated for the Charpy impact value. The minimum value of the five test results was evaluated for the amount of lateral expansion.

[0087] (Tensile test) A0 test piece was taken from the obtained weld metal at a position where the center of the test piece was the weld center line, and a tensile test was performed in accordance with JIS Z 3111: 2005. The test temperature for the tensile test was room temperature (20°C).

[0088] The measurement results of the Charpy impact value, the amount of lateral expansion, and the tensile strength by the Charpy impact test are shown in Table 6 below. In each of the above evaluation tests, the average value of the Charpy impact value was 35.0 (J / cm ２ ) or more, the amount of lateral expansion was 0.53 mm or more, and the tensile strength was 498 MPa or more, they were judged to have passed. In addition, those that did not achieve the standard value in any of the items were judged to have failed. In addition, the average Charpy impact value was 38.0 (J / cm ２ ) or more, a lateral expansion amount of 0.60 mm or more, and a tensile strength of 503 MPa or more were evaluated as more preferable.

[0089]

[0090]

[0091]

[0092]

[0093]

[0094]

[0095] As shown in Tables 1 to 6, in Examples 1 to 21, the contents of specific components in the wire were appropriately controlled, and the values ​​A1 and A2 calculated using Equations (1) and (2) were within the ranges specified by the present invention. Furthermore, in the obtained weld metal, the contents of each component and the values ​​A3 and A4 calculated using Equations (3) and (4) were within the ranges specified by the present invention. Therefore, weld metals with excellent mechanical properties, particularly lateral expansion values ​​greater than the desired values, were obtained. Example 20 had lower A2 and A4 values ​​than the other Examples, and therefore had a lower tensile strength value than the other Examples. Furthermore, Example 21 had higher Cr and Ni contents than the other Examples, and therefore had lower Charpy impact absorption value and lateral expansion value than the other Examples.

[0096] On the other hand, the wires of Comparative Examples 1 and 2 had low Charpy impact values ​​and lateral expansion values ​​because the A2 and A4 values ​​exceeded the upper limits specified in the present invention. Also, the wires of Comparative Examples 3 and 4 had low tensile strength because the A2 and A4 values ​​were below the lower limits specified in the present invention.

[0097] Although various embodiments have been described above, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above embodiments may be combined in any manner as long as they do not deviate from the spirit of the invention.

[0098] This application is based on a Japanese patent application (Patent Application No. 2023-214737) filed on December 20, 2023, the contents of which are incorporated herein by reference.

Claims

1. A flux-cored wire containing, relative to the total mass of the wire, Fe: 40% by mass or more and 70% by mass or less, C: 0.001% by mass or more and 0.030% by mass or less, Cr: 14.0% by mass or more and 28.0% by mass or less, Ni: 7.0% by mass or more and 20.0% by mass or less, Nb: 0.001% by mass or more and 0.15% by mass or less, and V: 0.005% by mass or more and 0.30% by mass or less, Mo: 4.0% by mass or less, Cu: 0.50% by mass or less, N: 0.020% by mass or less, and a value A1 calculated by the following formula (1): 0.02 to 0.30, and a value A2 calculated by the following formula (2): 10.0 to 12.

3. A1=[Nb] Ｗ + [V] Ｗ ...Formula (1) A2=1.31×(0.98×[Cr] Ｗ + [Mo] Ｗ + 0.7 × [Nb] Ｗ )-1.1×([Ni] Ｗ +35×[C] Ｗ +20×[N] Ｗ + 0.25 × [Cu] Ｗ ) ...Equation (2) where [Nb] Ｗ is the Nb content in the flux-cored wire expressed in mass%, [V] Ｗ is the V content in the flux-cored wire expressed in mass%, and [Cr] Ｗ is the Cr content in the flux-cored wire expressed in mass%, and [Mo] Ｗ is the Mo content in the flux-cored wire expressed in mass%, and [Ni] Ｗ is the Ni content in the flux-cored wire expressed in mass%, [C] Ｗ is the C content in the flux-cored wire expressed in mass%, [N] Ｗ is the N content in the flux-cored wire expressed in mass%, and [Cu] Ｗ is the Cu content in the flux-cored wire expressed in mass %.

2. Furthermore, with respect to the total mass of the wire, Si: 0.10 mass% or more and 1.00 mass% or less, F: 0.10 mass% or more and 0.50 mass% or less, Mn: 0.1 mass% or more and 1.60 mass% or less, TiO ２ 4.00% by mass or more and 10.00% by mass or less, ZrO ２ Contains: Converted value: 0.50 mass% or more and 4.00 mass% or less, MgO equivalent value of metal Mg and Mg compound: 0.05 mass% or more and 1.00 mass% or less, Na: 0.01 mass% or more and 0.50 mass% or less, and K: 0.01 mass% or more and 0.50 mass% or less, P: 0.030 mass% or less, S: 0.030 mass% or less, Co: 0.300% by mass or less, W: 0.50% by mass or less, REM: 0.500% by mass or less, Ti: 1.0% by mass or less, Al: 0.3% by mass or less, Al ２ O ３ 2. The flux-cored wire according to claim 1, characterized in that: Si: 1.00 mass % or less; and Li: 0.50 mass % or less.

3. The flux-cored wire according to claim 1, characterized in that the Ni is 10.0 mass% or more and 13.0 mass% or less, the Cr is 16.5 mass% or more and 18.0 mass% or less, and the Mo is 1.7 mass% or more and 2.2 mass% or less.

4. A welded joint, characterized in that it is produced by welding a stainless steel plate as a base material using the flux-cored wire according to any one of claims 1 to 3.

5. The weld metal contains, based on the total mass of the weld metal, C: 0.001 mass% or more and 0.040 mass% or less, Cr: 14.0 mass% or more and 22.0 mass% or less, Ni: 7.0 mass% or more and 18.0 mass% or less, Mn: 0.3 mass% or more and 1.5 mass% or less, Nb: 0.001 mass% or more and 0.15 mass% or less, and V: 0.005 mass% or more and 0.30 mass% or less, Si: 1.0 mass% or less, Ti: 1.0 mass% or less, Mo: 4.0 mass% or less, Cu: 0.50 mass% or less, N: 0.020 mass% or less, with the balance being Fe and unavoidable impurities, and a value A3 calculated by the following formula (3): 0.02 or more and 0.30 or less, and A weld metal characterized in that the value A4 calculated by the following formula (4) is 7.6 or more and 10.3 or less. A3 = [Nb] Ｍ + "V" Ｍ ...Formula (3) A4=1.18×([Cr] Ｍ + [Mo] Ｍ + 0.7 × [Nb] Ｍ )-[Ni] Ｍ -35 x [C] Ｍ -20 x [N] Ｍ −0.25×[Cu] Ｍ ... Formula (4) where [Nb] Ｍ is the Nb content in the weld metal expressed in mass%, [V] Ｍ is the V content in the weld metal expressed in mass%, [Cr] Ｍ is the Cr content in the weld metal expressed in mass%, [Mo] Ｍ is the value of the Mo content in the weld metal expressed in mass%, and [Ni] Ｍ is the Ni content in the weld metal expressed in mass%, [C] Ｍ is the C content in the weld metal expressed in mass%, [N] Ｍ is the N content in the weld metal expressed in mass%, [Cu] Ｍ is the Cu content in the weld metal expressed in mass%.

6. The weld metal described in claim 5, characterized in that P: 0.030 mass% or less, S: 0.030 mass% or less, Co: 0.500 mass% or less, W: 0.50 mass% or less, the Ni: 12.0 mass% or more and 14.0 mass% or less, the Cr: 17.0 mass% or more and 19.0 mass% or less, and the Mo: 1.7 mass% or more and 2.5 mass% or less.

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