Basic flux-cored welding wire, weld metal obtained using basic flux-cored welding wire, welding method, and method for manufacturing welded joints.

Abstract

Basic flux-cored welding wire, deposited metal obtained using basic flux-cored welding wire, welding method and welding joint manufacturing method enable all-position welding and obtain deposited metal and weld metal with excellent balance of strength and toughness. In basic flux-cored welding wire containing strong deoxidizing elements, the total amount of strong deoxidizing elements is 1.50–4.0% by mass, REM is 0.03–0.12% by mass, and B is less than 0.02% by mass. Furthermore, the contents of REM, Fe, C, Si, Mn, P, S, Cr, Mo, Al, Zr, Ni, and B, calculated from 32.1×[Si]-40.6×[Mn]-20.1×[Ni]-19.7×[Mo]-172.6×[C]-408.2×[REM]-5824.4×[B]-38.4×[Cr]-9960×[P]+43793×[S], satisfy 48.0% or less.

Description

Technical Field

[0001] This invention relates to an alkaline flux-cored welding wire that can be welded in all postures and has an excellent balance of strength and toughness, the deposited metal obtained using the above-mentioned alkaline flux-cored welding wire, and the welding method and welded joint using the above-mentioned alkaline flux-cored welding wire. Background Technology

[0002] Flux-cored welding wires can be classified into rutile, basic, and metallic types based on the type of flux they contain. They can be used according to their applications, but basic flux-cored wires have the advantage of achieving excellent toughness because they can suppress the oxygen content of the weld metal. However, basic flux-cored wires also have the disadvantage of poor welding operability, particularly making them unsuitable for difficult welding positions such as vertical, horizontal, and overhead welding.

[0003] Patent Document 1 discloses a technology that overcomes the aforementioned shortcomings in alkaline flux-cored welding wire. Specifically, Patent Document 1 describes a flux comprising a strongly deoxidizing metal element containing Mg and Al and a fluorine compound powder. The strongly deoxidizing metal powder and the fluorine compound powder have specific particle sizes, the flux ratio is 10-30% by mass, and it satisfies the following conditions: Al: 1.0-3.5% by mass, Mg: ... ( The specific composition of the wire (0.3-0.9% by mass), the total of the fluorine conversion value F of the fluorine compound (0.30-1.20% by mass), the total of strong deoxidizing metal elements (2.2% or more by mass), strong deoxidizing metal elements (15-35% by mass), and fluorine compound powder (10-45% by mass) enables welding in all postures.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2021-000646 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, the flux-cored welding wire described in Patent Document 1 contains a strong deoxidizing element in order to enable welding in all postures. This strong deoxidizing element plays an excellent deoxidizing role in welding, but it may be discharged with the slag or remain as an inclusion in the weld metal.

[0009] However, inclusions remaining in the weld metal have an adverse effect on mechanical properties, especially toughness. In other words, while Patent Document 1 overcomes the shortcomings of basic flux-cored wires that can be welded in all positions, it fails to maximize the advantages of basic flux-cored wires with excellent toughness.

[0010] Furthermore, toughness depends on the strength value, and there are issues regarding the balance between strength and toughness that vary depending on the target strength. For example, there are cases where a design with high strength produces good toughness, but if the target strength is lowered and the design is repeated, the toughness deteriorates drastically. This is because the addition of elements changes according to the target strength, affecting the microstructure of the deposited metal or weld metal.

[0011] The present invention addresses these problems and aims to provide an alkaline flux-cored wire and welding method capable of welding in all orientations, producing deposited metal and weld metal (hereinafter also referred to as "welded joint") with an excellent balance of strength and toughness, as well as deposited metal and weld joint with an excellent balance of strength and toughness.

[0012] Problem-solving methods

[0013] The above-mentioned objective of the present invention can be achieved by the following [1] configuration of the alkaline flux-cored wire.

[0014] [1] An alkaline flux-cored welding wire, characterized in that it is an alkaline flux-cored welding wire containing a strong deoxidizing element, wherein,

[0015] The total amount of the strong deoxidizing element, relative to the total mass of the welding wire, is 1.50% by mass or more and 4.00% by mass or less, and contains REM: 0.030% by mass or more and 0.120% by mass, and Fe: 85.0% by mass or more, and satisfies the following conditions:

[0016] C: less than 0.050% by mass

[0017] Si: less than 0.60% by mass

[0018] Mn: less than 2.00% by mass

[0019] P: less than 0.0150% by mass

[0020] S: less than 0.0150% by mass

[0021] Cr: less than 1.00% by mass

[0022] Mo: less than 1.00% by mass

[0023] Al: less than 3.00% by mass

[0024] Mg: less than 3.00% by mass

[0025] Zr: less than 3.000% by mass

[0026] Ti: less than 3,000% by mass

[0027] Ca: less than 3.00% by mass

[0028] Ni: less than 5.00% by mass

[0029] B: Less than 0.0200% by mass

[0030] Ba: less than 4.00% by mass

[0031] F: Less than 2.00% by mass

[0032] The value calculated by the following formula (1): below 48.0,

[0033] The value calculated by the following formula (2): below 48.0,

[0034] The value calculated by the following formula (3) is 0.09 or higher.

[0035] The value calculated by the following formula (4) is 0.14 or higher.

[0036] Formula (1): 32.1×[Si]-40.6×[Mn]-20.1×[Ni]-19.7×[Mo]-172.6×[C]-408.2×[REM]-5824.4×[B]-38.4×[Cr]-9960×[P]+43793×[S]

[0037] Formula (2): 33.9×[Si]-47.0×[Mn]-22.2×[Ni]-11.9×[Mo]-203.9×[C]-443.5×[B]-4482.2×[B]-36.1×[Cr]-15281×[P]+47868×[S]

[0038] Formula (3): 0.001×[Fe]-0.71×[Si]+0.08×[Mn]-0.08×[Al]+0.69×[Zr]+0.03×[Ni]+0.01×[Mo]+0.32×[C]+2.27×[REM]+9.57×[B]+0.11×[Cr]

[0039] Formula (4): 0.003×[Fe]-0.35×[Si]+0.09×[Mn]-0.13×[Al]+0.22×[Zr]+0.02×[Ni]-0.02×[Mo]-0.11×[C]+1.17×[REM]+4.30×[B]+0.09×[Cr]

[0040] In formulas (1) to (4), [REM], [Fe], [C], [Si], [Mn], [P], [S], [Cr], [Mo], [Al], [Zr], [Ni], and [B] are the contents of REM, Fe, C, Si, Mn, P, S, Cr, Mo, Al, Zr, Ni, and B, respectively, expressed as a percentage of mass relative to the total mass of the welding wire.

[0041] Furthermore, the preferred embodiments of the present invention of alkaline flux-cored wire relate to the following [2] to

[11] .

[0042] [2] The basic flux-cored welding wire according to [1] is characterized in that, relative to the total mass of the welding wire, it further contains at least one element selected from the following:

[0043] Nb: less than 0.50% by mass

[0044] Cu: less than 2.00% by mass

[0045] W: less than 1.00% by mass

[0046] Ta: less than 1.00% by mass

[0047] V: Less than 1.00% by mass

[0048] Sr: less than 4.00% by mass, and

[0049] Total alkali metal elements: less than 3.00% by mass.

[0050] The balance consists of O, N, and impurities.

[0051] [3] The alkaline flux-cored welding wire according to [1] or [2] is characterized in that the content of B is more than 0.0020% by mass and less than 0.0150% by mass relative to the total mass of the welding wire.

[0052] [4] The basic flux-cored welding wire according to any one of [1] to [3] is characterized in that the content of B includes the B conversion value of B oxide,

[0053] When the B conversion value of the B oxide relative to the total mass of the welding wire is expressed as [B oxide] in mass % and the value calculated by equation (5): [B oxide] / [B] is 0.5 or more.

[0054] [5] The alkaline flux-cored wire according to any one of [1] to [4] is characterized in that,

[0055] Contains at least one selected from Ba: less than 4.00% by mass, Ca: less than 3.00% by mass, and Sr: less than 4.00% by mass.

[0056] The flux contains at least one selected from BaF2, CaF2, and SrF2, which are fluorides of Ba, Ca, and Sr.

[0057] The Ba content includes the Ba conversion value of BaF2, the Ca content includes the Ca conversion value of CaF2, and the Sr content includes the Sr conversion value of SrF2.

[0058] The F content includes the F conversion values ​​of BaF2, CaF2 and SrF2.

[0059] [6] According to the alkaline flux-cored wire described in [5], the content of F is equal to the F conversion value of the total fluoride contained in the flux.

[0060] [7] The basic flux-cored welding wire according to any one of [1] to [6] is characterized in that the content of oxides in the flux is more than 0.005% by mass and less than 0.100% by mass relative to the total mass of the welding wire.

[0061] [8] The alkaline flux-cored welding wire according to any one of [1] to [7] is characterized in that,

[0062] The Cr content, relative to the total mass of the welding wire, is 0.20% by mass or more and 0.90% by mass or less, and...

[0063] The Mo content, relative to the total mass of the welding wire, is less than 0.50% by mass.

[0064] The value calculated by equation (6): [Cr] / ([Cr]+[Mo]) is greater than 0.20.

[0065] [9] The basic flux-cored welding wire according to any one of [1] to [7] is characterized in that,

[0066] The Cr content, relative to the total mass of the welding wire, is less than 0.90% by mass, and,

[0067] The Mo content, relative to the total mass of the welding wire, is 0.10% by mass or more and 0.80% by mass or less.

[0068] The value calculated by equation (7): [Mo] / ([Cr]+[Mo]) is greater than 0.10.

[0069]

[10] The alkaline flux-cored welding wire according to any one of [1] to [9] is characterized in that,

[0070] As the strong deoxidizing element, the content of Al relative to the total mass of the welding wire is 1.00% by mass or more and 2.50% by mass or less, and...

[0071] The Mg content is less than 1.00% by mass.

[0072] When the Mg content in the welding wire is expressed as [Mg] as a percentage of mass relative to the total mass of the welding wire,

[0073] The value calculated by equation (8): [Al] / ([Al]+[Mg]) is greater than 0.5 and less than 1.0.

[0074]

[11] The basic flux-cored wire according to any one of [1] to

[10] is characterized in that the REM contains La and Ce.

[0075] Furthermore, the above-mentioned objectives of the present invention relate to the following

[12] regarding the weld metal.

[0076]

[12] A weld metal, characterized in that, relative to the total mass of the weld metal, it contains

[0077] C: ≥0.020% by mass and ≤0.100% by mass

[0078] Si: ≥0.05% by mass and ≤0.50% by mass

[0079] Mn: ≥0.20% by mass and ≤1.80% by mass

[0080] Al: 0.30% by mass or more, less than 1.50% by mass

[0081] Ce: ≥0.002% by mass, ≤0.010% by mass

[0082] Fe: ≥85.0% by mass

[0083] and satisfy

[0084] La: less than 0.008% by mass

[0085] P: less than 0.0200% by mass

[0086] S: less than 0.0200% by mass

[0087] Cr: less than 1.00% by mass

[0088] Mo: less than 1.00% by mass

[0089] Mg: less than 0.50% by mass

[0090] Zr: less than 0.50% by mass

[0091] Ti: less than 0.05% by mass

[0092] Ca: less than 0.50% by mass

[0093] Ni: less than 3.00% by mass

[0094] B: Less than 0.0090% by mass

[0095] Ba: less than 1.00% by mass

[0096] Nb: less than 0.001% by mass

[0097] Cu: less than 0.1% by mass

[0098] V: less than 0.001% by mass

[0099] W: less than 0.1% by mass

[0100] Ta: less than 0.1% by mass

[0101] Sr: less than 1.00% by mass

[0102] Total alkali metal elements: less than 0.05% by mass

[0103] O: less than 0.0250% by mass

[0104] N: less than 0.0100% by mass

[0105] The remaining amount is impurities.

[0106] In addition, the above-mentioned objectives of the present invention relate to the following

[13] alkaline flux-cored wire.

[0107]

[13] An alkaline flux-cored welding wire, characterized in that the deposited metal described in

[12] is obtained.

[0108] Furthermore, the above-mentioned objectives of the present invention relate to the following

[14] regarding welding methods.

[0109]

[14] A welding method characterized in that gas-shielded arc welding is performed using any one of the basic flux-cored welding wires [1] to

[11] and

[13] .

[0110] Furthermore, the above-mentioned objectives of the present invention relate to the following

[15] regarding welded joints.

[0111]

[15] A welded joint, characterized in that it is manufactured using the welding method described in

[14] .

[0112] Invention Effects

[0113] According to the present invention, an alkaline flux-cored wire capable of welding in all postures and producing deposited metal and weld metal with an excellent balance of strength and toughness, as well as a welding method, are provided, along with deposited metal and weld joints with an excellent balance of strength and toughness. Detailed Implementation

[0114] In this embodiment, by including a strong deoxidizing element in an appropriate amount in the basic flux-cored welding wire, welding operability can be improved, enabling welding in difficult positions. However, depending on the element used for strength adjustment, an imbalance between the strength and toughness of the deposited metal or weld metal may occur.

[0115] Therefore, the inventors further derived parametric formulas based on the relationship between composition and mechanical properties designed within the strength range used in industry. Specifically, the composition and mechanical properties of this embodiment are summarized using a multiple regression equation to represent the relationship between strength, toughness, and brittle fracture ratio. By satisfying the four formulas described below, a welding wire composition with an excellent balance of strength and toughness can be derived.

[0116] The embodiments of the present invention will now be described in detail. However, the present invention is not limited to the embodiments described below, and can be implemented in any way without departing from the spirit of the invention.

[0117] [1. Basic flux-cored welding wire]

[0118] The basic flux-cored welding wire of this embodiment (hereinafter, sometimes simply referred to as "welding wire") includes a flux as the core and a strip steel as the outer sheath. Hereinafter, the preferred range and the reasons for limiting the components and their contents contained in the basic flux-cored welding wire of this embodiment will be specifically explained.

[0119] In this specification, the use of "~" indicates that the values ​​preceding and following it are included as lower and upper limits. Additionally, in this specification, elements followed by "(Wire)" indicate that the element is contained in the welding wire.

[0120] Similarly, elements followed by "(Metal)" indicate that the element is contained in the deposited metal.

[0121] Here, we assume Mn as an example of an element. If Mn is the metal of the welding wire as a whole... (Wire) Then, we can list the Mn contained in the strip steel and the Mn metal powder contained in the flux, etc., and consider the Mn conversion value of the Mn compound as a whole welding wire. ( (Wire), then the Mn conversion values ​​for Mn oxides, etc., can be listed. Additionally, the so-called Mn... (Wire)The content of Mn is the total metallic Mn content of the welding wire. (Wire) Mn conversion values ​​for Mn-related compounds (Wire) The total quantity, as the Mn content of the welding wire as a whole, is expressed as a percentage of mass relative to the total mass of the welding wire. Furthermore, in this total quantity, the total metallic Mn content of the welding wire... (Wire) Mn conversion value of the Mn compound in the welding wire as a whole (Wire) Either of them can be 0.

[0122] <Total amount of strong deoxidizing elements: ≥1.50% by mass and ≤4.00% by mass>

[0123] The alkaline flux-cored welding wire of this embodiment (hereinafter, sometimes simply referred to as "welding wire") comprises a flux as the core and a strip steel as the outer sheath. In this embodiment, by adding an appropriate amount of strong deoxidizing elements, improved welding operability and applicability to difficult welding positions can be achieved. Examples of strong deoxidizing elements include Al, Mg, Ti, Ca, and Zr, and the total amount is specified. Furthermore, this total amount is a percentage by mass relative to the total mass of the welding wire. For example, when the welding wire contains Al, Mg, Ti, Ca, and Zr, it is the total amount of these elements. If the total amount of strong deoxidizing elements is less than 1.50% by mass, it is difficult to apply to difficult welding positions. Therefore, the total amount of strong deoxidizing elements is 1.50% by mass or more, preferably 2.00% by mass or more.

[0124] On the other hand, if the total amount of strong deoxidizing elements exceeds 4.00% by mass, the number of inclusions in the weld metal increases excessively, resulting in a decrease in toughness. Therefore, in the alkaline flux-cored wire of this embodiment, within the composition range of formulas (1) to (4) described later, the total amount of strong deoxidizing elements is 4.00% by mass or less, preferably 3.20% by mass or less. Furthermore, as described later, Al and Mg are preferably included as strong deoxidizing elements.

[0125] <REM (Wire) : ≥0.030% by mass and ≤0.120% by mass >

[0126] REM (Rare Earth Metals) This refers to rare earth elements, such as Ce and La. As mentioned above, by including strong deoxidizing elements in the welding wire, welding in difficult positions can be achieved. However, if the content of strong deoxidizing elements in the welding wire is excessive, inclusions remain in the weld metal, resulting in deteriorated toughness. The inventors discovered, from the relationship between the number density of inclusions in the weld metal and toughness, that by reducing this number density, toughness can be improved. Furthermore, the inventors also discovered that by including REM in the welding wire within a specified range... (Wire) This can reduce the number density.

[0127] Specifically, by making REM (Wire) If the content is 0.030 or higher, REM acts as a binder to agglomerate the oxides of the added strong deoxidizing elements. For example, when welding wire containing Al, Mg, and REM is used to form weld metal, if the microstructure of the weld metal is observed, a composite oxide of REM, Al, and Mg is formed, and it can be confirmed that the number density of inclusions in the weld metal is reduced.

[0128] If REM (Wire) If the content is less than 0.030% by mass, it cannot exert a coagulating effect on the aforementioned oxides. Therefore, REM (Wire) The content of [specific component] is 0.030% by mass or more, preferably 0.040% by mass or more, relative to the total mass of the welding wire.

[0129] On the other hand, if REM (Wire) If the content of REM is higher than 0.120% by mass, the inclusions will coarsen due to agglomeration, which may adversely affect the mechanical properties or cause unacceptable welding defects. Therefore, REM (Wire) The content of [specific component] is less than 0.120% by mass relative to the total mass of the welding wire, preferably less than 0.110% by mass.

[0130] Furthermore, REM is preferably contained in the flux. Its form of addition is irrelevant; it can be in the form of metallic REM, REM-containing alloys, or REM compounds, etc. Here, when REM is included in the flux in the form of a compound, REM... (Wire) The content includes the REM conversion value of the REM compound. Furthermore, it is preferable that the REM is included in the flux in the form of a REM-containing alloy, and more preferably, all the REM added to the welding wire is contained in the flux in the form of a REM-containing alloy. Also, the REM contained in the basic flux-cored wire of this embodiment is preferably La and Ce.

[0131] In this embodiment, to achieve the objectives of the present invention, multiple parameters using the content of specific elements are generated, and the values ​​of these parameters are specified. Furthermore, in this specification, the content of a certain component relative to the total mass of the welding wire is expressed as [(component name)]. Specifically, [REM], [Fe], [C], [Si], [Mn], [P], [S], [Cr], [Mo], [Al], [Zr], [Ni], [B], and [Mg] represent the content of REM in the welding wire, expressed as a percentage of mass relative to the total mass of the welding wire. (Wire) Fe (Wire) C (Wire) Si (Wire) Mn (Wire) P (Wire) S (Wire)Cr (Wire) Mo (Wire) Al (Wire) Zr (Wire) Ni (Wire) B (Wire) and Mg (Wire) The value of the content.

[0132] <Values ​​calculated by the following formula (1): 48.0 and below>

[0133] Equation (1) is used to adjust mechanical properties such as strength and toughness. It is a parameterized formula based on the relationship between elements related to carbon equivalent and cold cracking sensitivity, and the brittle fracture ratio at -46°C, using multiple regression analysis. Based on the content of each element, if the value calculated by Equation (1) is 48.0 or less, the welding wire composition consists of elements with low brittle fracture ratio at extremely low temperatures, which can be described as having excellent toughness at extremely low temperatures. On the other hand, if the value calculated by Equation (1) is higher than 48.0, the brittle fracture ratio is high, which cannot ensure sufficient toughness. In addition, depending on the welding position, the welding wire composition consists of elements with potentially deviated toughness. Therefore, the value calculated by Equation (1) is preferably 48.0 or less, and more preferably 47.0 or less.

[0134] Equation (1):

[0135] 32.1×[Si]-40.6×[Mn]-20.1×[Ni]-19.7×[Mo]-172.6×[C]-408.2×[REM]-5824.4×[B]-38.4×[Cr]-9960×[P]+43793×[S]

[0136] <Values ​​calculated by formula (2): 48.0 and below>

[0137] Equation (2) is used to adjust mechanical properties such as strength and toughness. It is a parameterized formula based on the relationship between elements related to carbon equivalent and cold cracking sensitivity, and the brittle fracture ratio at -20°C, using multiple regression analysis. Based on the content of each element, if the value calculated by Equation (2) is 48.0 or less, the welding wire composition consists of elements with high brittle fracture ratio at low temperature, and thus it can be said that the toughness at low temperature is excellent. On the other hand, if the value calculated by Equation (2) is higher than 48.0, the brittle fracture ratio is high, and sufficient toughness cannot be ensured. In addition, depending on the welding position, the welding wire composition consists of elements with potentially deviated toughness. Therefore, the value calculated by Equation (2) is preferably 48.0 or less, and more preferably 40.0 or less.

[0138] Equation (2):

[0139] 33.9×[Si]-47.0×[Mn]-22.2×[Ni]-11.9×[Mo]-203.9×[C]-443.5×[REM]-4482.2×[B]-36.1×[Cr]-15281×[P]+47868×[S]

[0140] <Values ​​calculated by the following formula (3): 0.09 and above>

[0141] Equation (3) is used to adjust mechanical properties such as strength and toughness. It is based on multiple regression analysis and the elements related to carbon equivalent and cold cracking sensitivity, as well as the "balance between strength and toughness at -46℃".

[0142] The parameterized formula for the relationship between (CVN(-46℃) / TS) is given. Here, CVN refers to the pendulum impact absorption energy (J), and TS refers to the tensile strength (MPa). Based on the content of each element, if the value calculated by the following formula (3) is 0.09 or more, then the welding wire composition is composed of elements that have a good balance between strength and toughness. On the other hand, if the value calculated by the following formula (3) is less than 0.09, then the welding wire composition is composed of elements that have a poor balance between strength and toughness. Therefore, the value calculated by the following formula (3) is preferably 0.09 or more, and more preferably 0.10 or more.

[0143] Equation (3):

[0144] 0.001×[Fe]-0.71×[Si]+0.08×[Mn]-0.08×[Al]+0.69×[Zr]+0.03×[Ni]+0.01×[Mo]+0.32×[C]+2.27×[REM]+9.57×[B]+0.11×[Cr]

[0145] <Value calculated by the following formula (4): 0.14 or higher>

[0146] Equation (4) is used to adjust mechanical properties such as strength and toughness. It is based on multiple regression analysis and the elements related to carbon equivalent and cold cracking sensitivity, and the "balance between strength and toughness at -20℃".

[0147] The parameterized formula for the relationship between (CVN(-20℃) / TS) is given. Here, CVN refers to the absorbed energy (J) of the pendulum impact, and TS refers to the tensile strength (MPa). Based on the content of each element, if the value calculated by the following formula (4) is 0.14 or higher, it is a welding wire composition composed of elements with a good balance between strength and toughness. On the other hand, if the value calculated by the following formula (4) is lower than 0.14, it is a welding wire composition composed of elements with a poor balance between strength and toughness.

[0148] Equation (4):

[0149] 0.003×[Fe]-0.35×[Si]+0.09×[Mn]-0.13×[Al]+0.22×[Zr]+0.02×[Ni]-0.02×[Mo]-0.11×[C]+1.17×[REM]+4.30×[B]+0.09×[Cr]

[0150] Next, the various elements included for the purpose of improving operability and adjusting mechanical properties will be explained. The elements described below, if satisfying equations (1) to (4) above, can achieve a good balance between strength and toughness. However, from a technical point of view, if any element other than Fe is added in excess, welding cracks may occur. Therefore, upper limits are specified for each element. Furthermore, for the purpose of improving operability and adjusting mechanical properties, they can be included as needed. Therefore, the following provisions for elements without lower limits include 0% by mass.

[0151] <Fe (Wire) 85.0% or more in mass >

[0152] In widely used steel grades such as mild steel, high-tensile steel, and low-temperature steel, Fe is the main element among the elements contained to meet the required mechanical properties. If Fe... (Wire) If the Fe content is below 85% by mass, the influence of the remaining elements becomes greater, and the mechanical properties may deteriorate. Therefore, Fe (Wire) The Fe content is 85% by mass or more, preferably 87.0% by mass or more, relative to the total mass of the welding wire. Furthermore, examples of Fe sources in the welding wire include Fe metal powder added to the flux, Fe alloy metal powder, Fe compounds, and Fe contained in the strip steel. When Fe is included in the flux, from the viewpoint of improving the deposition rate, it is preferable to include it in the form of Fe metal powder or Fe alloy metal powder.

[0153] <C (Wire) Less than 0.050% by mass >

[0154] Carbon (C) is a component that affects the strength of both weld metal and weld metal. Increased C content in either the weld metal or weld metal results in higher strength. In commonly used steel grades such as mild steel, high-tensile steel, and low-temperature steel, it is preferable to include C in the welding wire to meet the required strength range. However, if C... (Wire) An increase in the content of carbides makes it easier for carbides to precipitate in the weld metal or weld metal, resulting in a decrease in toughness relative to the target strength, and potentially an imbalance between strength and toughness. Therefore, C (Wire) The content of [specific component] is less than 0.050% by mass relative to the total mass of the welding wire, preferably less than 0.040% by mass.

[0155] On the other hand, in order to adjust the intensity, C (Wire) The content of [C] is preferably 0.001% by mass or more relative to the total mass of the welding wire. Other sources of C in the welding wire include graphite and carbides added to the flux, and C contained in the strip steel. However, from the viewpoint of suppressing carbides, [C]... (Wire) The lower the content of C, the better; it is preferable that the flux does not contain C.

[0156] <Si (Wire) : Less than 0.60% by mass >

[0157] Si (silicon) is a component that affects the strength and toughness of weld metal. In commonly used steel grades such as mild steel, high-tensile steel, and low-temperature steel, the presence of Si in the welding wire is preferred to meet the required mechanical properties. Si has a deoxidizing effect; if the welding wire contains excessive Si, inclusions increase, and the balance between strength and toughness may be disrupted. Therefore, Si... (Wire) The content of [specific component] is less than 0.60% by mass relative to the total mass of the welding wire, preferably less than 0.50% by mass.

[0158] On the other hand, in order to adjust the strength, Si (Wire) The Si content is preferably 0.01% by mass or more relative to the total mass of the welding wire. Furthermore, Si sources in the welding wire can include Si metal powder added to the flux, Si alloy metal powder, Si compounds, and Si contained in the strip steel. When Si is included in the flux for the purpose of suppressing inclusions, it is preferable that it is contained in the form of Si metal powder or Si alloy metal powder.

[0159] <B (Wire) : Less than 0.0200% by mass >

[0160] B is an element that prevents a decrease in the toughness of the deposited and welded metals, and on the other hand, it increases the resistance to cracking. Therefore, B (Wire) The content of B is preferably 0.0150% by mass or less, relative to the total mass of the welding wire. Furthermore, by including B in the welding wire of this embodiment, a reduction in brittle fracture ratio was observed. This is because by including B in the welding wire, the formation of coarse ferrite or bainite phases at grain boundaries can be suppressed. Therefore, from the viewpoint of reducing brittle fracture ratio, B... (Wire) The content of Zr is preferably 0.0020% by mass or more relative to the total mass of the welding wire. Additionally, Zr... (Wire) Content and B (Wire) The content of B will cause an alteration in the balance between strength and toughness, therefore, B (Wire) The preferred range of content is based on Zr (Wire) The change in Zr content. That is, if Zr (Wire)If the content of B is less than 0.045% by mass, then as mentioned above, it is preferable to use B. (Wire) The content is less than 0.0150% by mass, but if Zr (Wire) If the content of B is higher than 0.045% by mass, then it is more preferable to make B (Wire) The content is less than 0.0045% by mass.

[0161] Furthermore, sources of B in welding wire include metal powder added to flux, metal powder of B alloys, compounds of B, and B contained in strip steel.

[0162] Furthermore, if B is contained in the flux in the form of an oxide, the oxide of B is easily and uniformly mixed in the flux, which is advantageous from a manufacturing point of view. Therefore, it is preferable for B to be contained in the flux in the form of an oxide, rather than in the form of metal powder. In this case, B... (Wire) The content includes the B conversion value of B oxide, and the value calculated by the following formula (5) is preferably 0.5 or more, more preferably 0.7 or more, and even more preferably 1.0. When the value calculated by the following formula (5) is 1.0, B (Wire) The content of B is entirely expressed as the B conversion value of B oxide. In other words, when B is present in the welding wire, it is preferable that it is entirely contained in the flux in the form of B oxide.

[0163] Equation (5): [B oxide] / [B]

[0164] In the above formula (5), the so-called [B oxide] is expressed as the B conversion value of B oxide relative to the total mass of the welding wire, expressed as a mass percentage relative to the total mass of the welding wire. (Wire) The value of .

[0165] <Mn (Wire) Less than 2.00% by mass >

[0166] Like silicon (Si), manganese (Mn) is a component that affects the strength and toughness of weld metal. In commonly used steel grades such as mild steel, high-tensile steel, and low-temperature steel, the presence of Mn in the welding wire is preferred to meet the required mechanical properties. Mn has a deoxidizing effect; if the welding wire contains excessive Mn, inclusions increase, and the balance between strength and toughness may be disrupted. Therefore, Mn... (Wire) The content of [specific component] is less than 2.00% by mass relative to the total mass of the welding wire, preferably less than 1.80% by mass.

[0167] On the other hand, in order to adjust the intensity, Mn (Wire)The content of Mn is preferably 0.01% by mass or more relative to the total mass of the welding wire. Furthermore, examples of Mn sources in the welding wire include Mn metal powder added to the flux, Mn alloy metal powder, Mn compounds, and Mn contained in the strip steel. When Mn is included in the flux for the purpose of suppressing inclusions, it is preferable that it is contained in the flux in the form of Mn metal powder or Mn alloy metal powder.

[0168] <P (Wire) : Less than 0.0150% by mass >

[0169] P is an element that reduces crack resistance and the mechanical properties of weld metals. Therefore, P (Wire) The content of P is suppressed to less than 0.0150% by mass relative to the total mass of the welding wire, preferably less than 0.0100% by mass. Furthermore, it is preferable that P is not forcibly added to the welding wire.

[0170] <S (Wire) : Less than 0.0150% by mass >

[0171] S is an element that reduces crack resistance. Therefore, S (Wire) The content of [specific component] is less than 0.0150% by mass relative to the total mass of the welding wire, preferably less than 0.010% by mass.

[0172] On the other hand, S (Wire) By reducing the viscosity and surface tension of the molten welding wire droplets, the droplet transition becomes smoother, resulting in smaller spatter particles and improved welding operability. Therefore, from the perspective of welding operability, S (Wire) The content of S is preferably 0.0005% by mass or more relative to the total mass of the welding wire. Furthermore, it is not important whether S is a source of sulfur in the welding wire; it can be contained in the flux as sulfur monomer powder or sulfur compound, or it can be contained in the strip steel. More preferably, S is not forcibly added to the welding wire.

[0173] <Cr (Wire) Less than 1.00% by mass >

[0174] Cr (Cr) is a component that affects the strength and toughness of both weld metal and deposited metal. In commonly used steel grades such as mild steel, high-tensile steel, and low-temperature steel, Cr is preferred in the welding wire to meet required mechanical properties. However, excessive Cr in the welding wire can easily precipitate as carbides at grain boundaries, potentially disrupting the balance between strength and toughness. Therefore, Cr... (Wire) The content of [specific component] is preferably 1.00% by mass or less and 0.90% by mass or less relative to the total mass of the welding wire.

[0175] On the other hand, in order to adjust the strength, Cr (Wire)The content of Cr, relative to the total mass of the welding wire, is preferably 0.20% by mass or more. Furthermore, examples of Cr sources in the welding wire include Cr metal powder added to the flux, Cr alloy metal powder, Cr compounds, and Cr contained in the strip steel. When Cr is present in the flux, it is preferable that it is present in the flux in the form of Cr metal powder or Cr alloy metal powder.

[0176] <Mo (Wire) Less than 1.00% by mass >

[0177] Mo (Mo) is a component that increases high-temperature strength. In commonly used steel grades such as mild steel, high-tensile steel, and low-temperature steel, Mo is preferred in welding wire to meet required mechanical properties. However, excessive Mo content in the welding wire can lead to an overemphasis on strength, potentially disrupting the balance between strength and toughness. Therefore, Mo... (Wire) The content of [specific component] relative to the total mass of the welding wire is preferably less than 1.00% by mass and less than 0.90% by mass.

[0178] On the other hand, in order to adjust the intensity, Mo (Wire) The content of Mo is preferably 0.10% by mass or more relative to the total mass of the welding wire. Furthermore, examples of Mo sources in the welding wire include Mo metal powder added to the flux, Mo alloy metal powder, Mo compounds, and Mo contained in the strip steel. When Mo is present in the flux, it is preferable that it is present in the flux in the form of Mo metal powder or Mo alloy metal powder.

[0179] In addition, the combination of Cr, which contributes to strength and toughness, and Mo, which is a common element for improving high-temperature strength, is as follows. In order to achieve a balance between strength and toughness, the content is preferably determined according to the application.

[0180] (Design to improve resilience)

[0181] For example, to further improve toughness, it is preferable to have a higher Cr content than Mo content, which contributes to both strength and toughness. That is, to make Cr... (Wire) The content of [Mo] is 0.20% by mass or more and 0.90% by mass relative to the total mass of the welding wire, and [the content of Mo] is [not specified]. (Wire) The content of is less than 0.50% by mass relative to the total mass of the welding wire, preferably 0.20% or more calculated by the following formula (6), more preferably 0.50% or more, further preferably 0.75% or more, and most preferably 1.00%.

[0182] Equation (6): [Cr] / ([Cr]+[Mo])

[0183] (Design for improved high-temperature strength)

[0184] On the other hand, when used in heat-resistant steel applications, it is preferable to have a higher content of Mo, a common element for improving high-temperature strength, than of Cr; that is, to have a higher content of Cr. (Wire) The content of [Mo] is less than 0.90% by mass relative to the total mass of the welding wire, and [the content of Mo] is [not specified]. (Wire) The content of is 0.10% by mass or more and 0.80% by mass or less relative to the total mass of the welding wire, and the value calculated by the following formula (7) is preferably 0.10% by mass or more and 0.45% by mass, more preferably 0.70% by mass or more, and most preferably 1.00%.

[0185] Equation (7): [Mo] / ([Cr]+[Mo])

[0186] <Al (Wire) Less than 3.00% by mass >

[0187] Al is a strong deoxidizing component. Through oxidation in the weld metal, it forms oxides (hereinafter referred to as "slag") on the molten pool. In all-position welding, including difficult positions such as vertical and overhead welding, it can improve weld bead shape and enhance burn-through resistance. However, if the welding wire contains excessive Al, the number of inclusions remaining in the weld metal increases, adversely affecting toughness. Therefore, Al... (Wire) The content of [specific component] is 3.00% by mass or less relative to the total mass of the welding wire, preferably 2.50% by mass or less, and more preferably 1.70% by mass or less.

[0188] On the other hand, Al (Wire) The content of Al relative to the total mass of the welding wire is preferably 0.50% by mass or more, more preferably 1.00% by mass or more. Furthermore, Al sources in the welding wire can include Al metal powder added to the flux, Al alloy metal powder, Al compounds, and Al contained in the strip steel. When Al is included in the flux to further reduce the oxygen content in the weld metal, it is preferable that it is contained in the flux in the form of Al metal powder or Al alloy metal powder.

[0189] <Mg (Wire) Less than 3.00% by mass >

[0190] Like Al, Mg is a strong deoxidizing component. Through oxidation in the weld metal, it forms slag in the molten pool, improving burn-through resistance in all welding positions, including vertical and overhead welding. However, excessive Mg in the welding wire increases the number of inclusions remaining in the weld metal, negatively impacting toughness. Therefore, Mg... (Wire) The content of [specific component] is 3.0% by mass or less relative to the total mass of the welding wire, preferably 1.50% by mass or less, and more preferably 1.00% by mass or less.

[0191] On the other hand, Mg (Wire)The content of Mg, relative to the total mass of the welding wire, is preferably 0.30% by mass or more, more preferably 0.50% by mass or more. Furthermore, examples of Mg sources in the welding wire include Mg metal powder added to the flux, Mg alloy metal powder, Mg compounds, and Mg contained in the strip steel. When Mg is included in the flux with the aim of further reducing the oxygen content in the weld metal, it is preferable that it is contained in the flux in the form of Mg metal powder or Mg alloy metal powder.

[0192] <Zr (Wire) Less than 3,000% by mass >

[0193] Like Al, Zr is a strong deoxidizing component. Through oxidation in the weld metal, it forms slag in the molten pool, improving burn-through resistance in all welding positions, including vertical and overhead welding. However, excessive Zr content in the welding wire increases inclusions in the weld metal, negatively impacting toughness. Therefore, Zr... (Wire) The content of [specific component] is less than 3.000% by mass relative to the total mass of the welding wire, preferably less than 0.500% by mass. If B is considered... (Wire) The content of [substance name] is more preferably 0.045% by mass or less.

[0194] On the other hand, Zr is specified (Wire) The lower limit value is not particularly significant. Furthermore, as a strong deoxidizing element, Zr is preferred when the welding wire mainly contains Mg and Al. (Wire) The content is 0. Furthermore, Zr sources in welding wire can include Zr metal powder added to the flux, Zr alloy metal powder, Zr compounds, and Ti contained in the strip. To further reduce the oxygen content in the weld metal, when Zr is included in the flux, it is preferable to include it in the form of Zr metal powder or Zr alloy metal powder.

[0195] <Ti (Wire) Less than 3,000% by mass >

[0196] Like Al, Ti is a strong deoxidizing component. Through oxidation in the weld metal, it forms oxides (slag) in the molten pool, improving burn-through resistance in all welding positions, including vertical and overhead welding. However, excessive Ti content in the welding wire increases inclusions in the weld metal, negatively impacting toughness. Therefore, Ti... (Wire) The content of [the substance] is less than 3.000% by mass relative to the total mass of the welding wire, preferably less than 0.500% by mass, and more preferably less than 0.010% by mass.

[0197] On the other hand, compared with Mg and Al, Ti has a weaker effect as a deoxidizing component and may even generate precipitates such as TiC, which degrades toughness. Therefore, it is specified that Ti...(Wire) The lower limit value has no particular significance, so when the welding wire mainly contains Mg and Al, Ti (Wire) The content of Ti is preferably 0. Furthermore, Ti sources in the welding wire can include Ti metal powder added to the flux, Ti alloy metal powder, Ti compounds, and Ti contained in the strip steel. To further reduce the oxygen content in the weld metal, when Ti is included in the flux, it is preferably contained in the form of Ti metal powder or Ti alloy metal powder.

[0198] <Ca (Wire) Less than 3.00% by mass >

[0199] Like Al, Ca is a strong deoxidizing component. Through oxidation in the weld metal, it forms oxides (slag) in the molten pool, improving burn-through resistance in all welding positions, including vertical and overhead welding. However, excessive Ca content in the welding wire increases inclusions in the weld metal, negatively impacting toughness. Therefore, Ca... (Wire) The content of [the substance] is 3.0% by mass or less relative to the total mass of the welding wire, preferably 1.00% by mass or less, and more preferably 0.30% by mass or less.

[0200] On the other hand, Ca, by being included in the flux as a fluoride CaF2, contributes to the deoxidation of the weld metal and improves weldability. The aforementioned Ca... (Wire) The content includes the Ca conversion value of CaF2 in the flux, but as a fluoride in the flux, it is not limited to CaF2; for example, fluorides such as BaF2 and SrF2 can be used, so there is no need to set a lower limit for the Ca content. Furthermore, as a strong deoxidizing component, when Mg and Al are mainly added to the welding wire, it is preferable to use Ca... (Wire) The content is 0% by mass.

[0201] Furthermore, examples of sources of Ca in the welding wire include Ca metal powder added to the flux, Ca alloy metal powder, Ca compounds, and Ca contained in the strip steel. In this embodiment, when the welding wire contains Ca, if this Ca is also contained in the flux, the oxygen content in the weld metal can be further reduced. Therefore, all the Ca contained in the welding wire is preferably contained in the flux in the form of fluoride powder, i.e., CaF2.

[0202] In addition to Al, Mg, Zr, Ti, and Ca listed above, various other elements are also known as strong deoxidizing elements. In this embodiment, the five elements mentioned above, which are usually contained in the welding wire in the form of metal powder, are preferred as strong deoxidizing elements for the alkaline flux-cored welding wire.

[0203] Of the five elements mentioned above, Al and Mg, in particular, readily agglomerate slag, forming early and throughout the entire surface of the molten pool. Therefore, they are useful elements for welding in difficult positions using basic flux-cored wire. On the other hand, Zr, Ti, and Ca tend to disperse slag, and due to the flow of the molten pool, they also tend to concentrate slag formation over time. Compared to Al and Mg, their effects are less pronounced.

[0204] Therefore, it is preferable to include at least one strong deoxidizing element among Al, Mg, Ti, Ca, and Zr in the welding wire. Furthermore, regarding the content of each element, Al... (Wire) Mg is 1.00% by mass or more and 2.50% by mass or less. (Wire) Ti is 0.30% by mass or more and 0.50% by mass or less. (Wire) Zr is 0.10% by mass or less (including 0% by mass). (Wire) For amounts of Ca below 0.20% by mass (inclusive), (Wire) The total amount of strong deoxidizing elements contained in the welding wire is 1.50% to 4.00% by mass or less (including 0% by mass) or less.

[0205] Furthermore, in this embodiment, it is more preferable to contain at least one of Al and Mg, and even more preferably, it is more preferable to contain at least Al. In this case, it is particularly preferable that Al is present relative to the total mass of the welding wire. (Wire) Containing 1.00% by mass or more and 2.50% by mass, Mg (Wire) The value is 1.00% by mass or less, and the value calculated by the following formula (8) is 0.5 or more and 1.0 or less.

[0206] Equation (8): [Al] / ([Al]+[Mg])

[0207] <Ni (Wire) : Less than 5.00% by mass >

[0208] Ni stabilizes the austenitic structure of the weld metal, improves toughness at low temperatures, and adjusts the crystallinity of ferrite. In commonly used steel grades such as mild steel, high-tensile steel, and low-temperature steel, Ni is preferred in the welding wire to meet required mechanical properties. However, excessive Ni content in the welding wire can lead to an overemphasis on strength, potentially disrupting the balance between strength and toughness. Therefore, Ni... (Wire) The content of [specific component] is less than 5.0% by mass relative to the total mass of the welding wire, preferably less than 3.0% by mass.

[0209] On the other hand, when used for welding low-temperature steel, Ni (Wire)The content of Ni relative to the total mass of the welding wire is preferably 0.20% by mass or more. Furthermore, Ni sources in the welding wire can include Ni metal powder added to the flux, Ni alloy metal powder, Ni compounds, and Ni contained in the strip steel. When Ni is included in the flux to further reduce the oxygen content in the weld metal, it is preferable that it is contained in the flux in the form of Ni metal powder or Ni alloy metal powder.

[0210] <Ba (Wire) : Less than 4.00% by mass >

[0211] Ba is mainly contained in the flux in the form of the fluoride BaF2, which helps to deoxidize the weld metal and improve weld operability. Fluorides are generally added to the flux of basic flux-cored wires, and BaF2 is the most commonly used among various fluorides. However, if the welding wire contains excessive Ba, arc deflection will occur, and weld operability may deteriorate. Therefore, Ba... (Wire) The content is 4.00% by mass or less, preferably 3.00% by mass or less.

[0212] Also, the aforementioned Ba (Wire) The content includes the Ba conversion value of BaF2 in the flux, but as a fluoride in the flux, it is not limited to BaF2; for example, fluorides such as CaF2 and SrF2 can be used, so there is no need to set a lower limit for the Ba content. However, when the flux contains Ba compounds such as BaF2 or BaCO3, the Ba content... (Wire) The content of Ba relative to the total mass of the welding wire is preferably 1.75% by mass or more. Examples of Ba sources in the welding wire include Ba metal powder added to the flux, Ba alloy metal powder, Ba compounds, and Ba contained in the strip steel. In this embodiment, when Ba is included in the welding wire, it is preferable that all Ba is contained in the flux in the form of the fluoride BaF2.

[0213] <F (Wire) Less than 2.00% by mass >

[0214] F (Wire) Primarily derived from fluorides. Fluorides are contained in the flux of flux-cored wires in the form of fluorides such as Ca, Ba, or Sr. Fluorides are commonly added to basic flux-cored wires, contributing to improved welding operability. However, F... (Wire) If the content of Fe exceeds 2.00% by mass relative to the total mass of the welding wire, excessive Fe vaporization will occur inside the welding wire, potentially leading to increased spatter and deterioration of welding operability. Therefore, Ba (Wire) The content of [specific component] is 2.00% by mass or less relative to the total mass of the welding wire, preferably 1.00% by mass or less, and more preferably 0.80% by mass or less.

[0215] On the other hand, when the welding wire contains F in order to improve welding operability, F (Wire) The content of [specific element] is preferably 0.40% by mass or more relative to the total mass of the welding wire. Furthermore, the F source in the welding wire is preferably entirely derived from fluorides, such as BaF2, SrF2, Na3AlF6, NaF, CaF2, AlF3, MgF2, etc., and may contain one or more of these. Among these fluorides, it is preferable that at least one fluoride selected from the group consisting of BaF2, SrF2, and CaF2 is included in the welding wire at the content described in the Ba, Sr, and Ca columns above, which is preferred from the perspective of welding operability. In addition, Ba has a low work function, which further stabilizes the cathode point and contributes to improved welding operability; therefore, in this embodiment, it is more preferable that BaF2, as a Ba fluoride, is mainly included in the welding wire. Furthermore, in this embodiment, it is preferable that all Ba [specific element] is included in the welding wire. (Wire) The source is BaF2, and the above F (Wire) Of the content, excluding the F conversion value of BaF2, the F content is... (Wire) The remaining amount of [the substance] is preferably supplied by CaF2.

[0216] Furthermore, the following elements can be added, either in addition to or as a substitute for, commonly used steel types such as mild steel, high-tensile steel, and low-temperature steel, within the general technical range, for purposes such as adjusting mechanical properties and improving weldability. The elements Nb, Cu, W, Ta, V, Sr, and alkali elements listed below were not added in this embodiment. Although their special addition is not required, it is preferable to add them within the optimal range described below when various commonly known effects are desired.

[0217] <Nb (Wire) Less than 0.50% by mass >

[0218] Nitrogen (Nb) is a component that affects mechanical properties such as strength. In commonly used steel grades such as mild steel, high-tensile steel, and low-temperature steel, Nb can be included in the welding wire to meet required mechanical properties. In this case, Nb... (Wire) The content of Nb relative to the total mass of the welding wire is preferably 0.50% by mass or less, more preferably 0.30% by mass or less. Furthermore, Nb sources in the welding wire can include Nb metal powder added to the flux, Nb alloy metal powder, Nb compounds, and Nb contained in the strip steel.

[0219] <Cu (Wire) : Less than 2.0% by mass >

[0220] Cu (Cu) is an element that contributes to improving the strength and weather resistance of weld metals. In commonly used steel grades such as mild steel, high-tensile steel, and low-temperature steel, Cu can be included in the welding wire to meet the required strength and weather resistance. In this case, Cu... (Wire) The content of [specific component] relative to the total mass of the welding wire is preferably 2.0% by mass or less, more preferably 1.0% by mass or less.

[0221] On the other hand, when Cu is included in the welding wire to ensure the strength and weather resistance of the weld metal, Cu... (Wire) The content of Cu in the welding wire is preferably 0.01% by mass or more relative to the total mass of the welding wire. Furthermore, Cu sources in the welding wire include Cu metal powder added to the flux, Cu alloy metal powder, Cu compounds, Cu contained in the strip steel, and Cu plating on the surface of the welding wire.

[0222] <W (Wire) Less than 1.00% by mass >

[0223] W is a component that improves high-temperature strength and resistance to pitting corrosion. In commonly used steel grades such as mild steel, high-tensile steel, and low-temperature steel, W can be added to the welding wire to meet the required mechanical properties. In this case, W... (Wire) The content of W, relative to the total mass of the welding wire, is preferably 1.00% by mass or less, more preferably 0.5% by mass or less. Furthermore, sources of W in the welding wire include W metal powder added to the flux, W alloy metal powder, W compounds, and W contained in the strip steel.

[0224] <Ta (Wire) Less than 1.00% by mass >

[0225] Ta is an element that affects mechanical properties such as strength. In commonly used steel grades such as mild steel, high-tensile steel, and low-temperature steel, Ta can be included in the welding wire to meet required mechanical properties. In this case, Ta... (Wire) The content of Ta relative to the total mass of the welding wire is preferably 1.00% by mass or less, more preferably 0.50% by mass or less. Furthermore, Ta sources in the welding wire can include Ta metal powder added to the flux, Ta alloy metal powder, Ta compounds, and Ta contained in the strip steel.

[0226] <V (Wire) Less than 1.00% by mass >

[0227] V (V) plays a role in increasing the strength of weld metal, but on the other hand, it is an element that reduces toughness and crack resistance. Therefore, V in welding wire... (Wire)The content of V, relative to the total mass of the welding wire, is preferably 1.00% by mass or less, more preferably 0.50% by mass or less. Furthermore, V sources in the welding wire can include metal powders of V added to the flux, alloy metal powders of V, compounds of V, and V contained in the strip steel.

[0228] <Sr (Wire) : Less than 4.00% by mass >

[0229] Sr is primarily contained in the flux as the fluoride SrF2, thereby contributing to the deoxidation of the weld metal and improving weld operability. However, if the Sr content in the welding wire is below 4.00% by mass, arc deflection can be suppressed, resulting in good weld operability. Therefore, Sr (Wire) The content of [specific component] relative to the total mass of the welding wire is preferably 4.00% by mass or less, more preferably 3.00% by mass or less.

[0230] Also, the aforementioned Sr (Wire) The content includes the Sr conversion value of SrF2 in the flux, but as a fluoride in the flux, it is not limited to SrF2; for example, fluorides such as CaF2 and BaF2 can also be used. Therefore, there is no need to set a lower limit for the Sr content. However, when the flux contains Sr compounds such as SrF2 or SrCO3, the Sr content... (Wire) The content of Sr relative to the total mass of the welding wire is preferably 0.05% by mass or more. Examples of Sr sources in the welding wire include Sr metal powder added to the flux, Sr alloy metal powder, Sr compounds, and Sr contained in the strip steel. In this embodiment, when the welding wire contains Sr, it is preferable that all the Sr is contained in the flux in the form of the fluoride SrF2.

[0231] As described above, in the alkaline flux-cored wire of this embodiment, the flux preferably contains at least one selected from the fluorides of Ba, Ca, and Sr: BaF2, CaF2, and SrF2. In this case, the Ba content includes the Ba equivalent of BaF2, the Ca content includes the Ca equivalent of CaF2, the Sr content includes the Sr equivalent of SrF2, and the F content includes the F equivalents of BaF2, CaF2, and SrF2. Furthermore, it is preferable that all the F sources in the wire originate from fluorides; that is, the F content in the wire is equal to the F equivalent of the total fluorides contained in the flux.

[0232] <Total alkali metals: less than 3.00% by mass>

[0233] Alkali metal elements act as arc stabilizers. In this embodiment, the alkali metal is based on metal powder and compounds containing one or more alkali metal elements. Examples of alkali metal elements include K, Li, and Na. The total alkali metal content in the welding wire refers to the total alkali metal content in the welding wire, calculated from the metal powder and compounds composed of alkali metal elements. That is, K... (Wire) Li (Wire) Na (Wire) The total amount of alkali metals in the welding wire is preferably 3.00% by mass or less, more preferably 2.00% by mass or less, relative to the total mass of the welding wire, from the viewpoint that the melting characteristics are preferred for easy adjustment to improve the weld bead shape.

[0234] (Oxides in the welding wire: ≥0.005% by mass and ≤0.100% by mass)

[0235] Oxides form the basis of coarse inclusions and affect toughness; therefore, it is preferable to avoid adding them to the flux in the form of oxides. Thus, the total amount of oxides of each element added to the flux is preferably kept below 0.100% by mass, expressed as a percentage of the total mass of the welding wire. Furthermore, from a manufacturing point of view, B and REM can be added in the form of oxides, and it is more preferable to include 0.005% by mass or more of oxides.

[0236] (Balance: O, N, and unavoidable impurities)

[0237] In this embodiment, the balance other than the aforementioned elements is preferably O, N, and unavoidable impurities, and this balance is preferably totaled to 0.50% by mass or less. Impurities refer to unintentionally added elements other than those mentioned above, such as Sn, Co, Sb, and As. The total impurity content in the welding wire is preferably 0.45% by mass or less, more preferably 0.30% by mass or less.

[0238] Furthermore, when the aforementioned elements are contained in the flux as oxides or nitrides, or dissolved in the strip steel, O and N are also included in the balance. In flux-cored wire, since O and N cannot be clearly analyzed, they are included as a balance. However, in this embodiment, based on the amount of oxides added to the flux-cored wire or the amount of O and N added to the strip steel, it is possible to estimate that the total amount of O and N is 0.05% by mass or less relative to the total mass of the wire. Also, in basic flux-cored wire, it is technically impossible for O and N to exceed 0.05% by mass from the viewpoint of mechanical properties.

[0239] [Strip steel]

[0240] The flux-cored welding wire of this embodiment is a welding wire filled with flux in a strip steel, which is preferably formed from cold-rolled steel strip from the viewpoint of availability and economy. As cold-rolled steel strip, for example, steel strip of type numbers SPCC, SPCD, SPCE, SPCF, SPCG, etc., as described in JIS G 3141:2017 is preferred.

[0241] Another embodiment of the alkaline flux-cored welding wire of the present invention is a welding wire that yields the deposited metal as shown below. Furthermore, the term "deposited metal" refers to the metal transitioning from the weld repair material to the welded portion; by specifying the composition of the deposited metal obtained under generally used welding conditions, the welding wire can be defined. The term "generally used welding conditions" can, for example, be the welding conditions according to the method for preparing the deposited metal as described in JIS Z 3184. For example, conditions such as welding current: 200–220 A, welding voltage: 0–23 V, shielding gas: 100% CO2 gas, and welding heat input: 0.8–1.1 kJ / mm can be used.

[0242] [2. Deposited Metal]

[0243] As described above, the alkaline flux-cored welding wire of this embodiment, by containing strong deoxidizing elements and REM, can perform welding under difficult postures and achieve a good balance between strength and toughness. Similarly, the deposited metal of this embodiment appropriately specifies B... (Metal) The content of La, as appropriately specified by REM, is... (Metal) and Ce (Metal) The content of [specific element] can further enhance the above-mentioned effects. The composition and reasons for limiting the weld metal in this embodiment will be explained in detail below.

[0244] <C (Metal) : ≥0.020% by mass and ≤0.100% by mass >

[0245] Carbon (C) is a component that affects the strength of the weld metal; if the C content in the weld metal increases, the strength increases. Therefore, C... (Metal) The content of [substance name] is 0.020% by mass or more, preferably 0.040% by mass or more, relative to the total mass of the deposited metal.

[0246] On the other hand, if C (Metal) An increase in the content of C makes it easier for carbides to precipitate in the weld metal, resulting in a decrease in toughness relative to the target strength, and potentially an imbalance between strength and toughness. Therefore, C (Metal) The content of [the substance] is less than 0.100% by mass relative to the total mass of the deposited metal, preferably less than 0.095% by mass.

[0247] <Si (Metal): 0.05% by mass or more and 0.50% by mass or less >

[0248] Si is a component that affects the strength and toughness of the weld metal. By including Si in the weld metal at a specified content, the required mechanical properties can be met. Therefore, Si (Metal) The content of [specific component] relative to the total mass of the deposited metal is preferably 0.05% by mass or more, and more preferably 0.10% by mass or more.

[0249] On the other hand, Si has a deoxidizing effect. If there is an excessive amount of Si, it is highly likely that Si will remain as an inclusion in the weld metal, potentially causing an imbalance between strength and toughness. Therefore, Si... (Metal) The content of [the substance] is less than 0.50% by mass relative to the total mass of the deposited metal, preferably less than 0.45% by mass.

[0250] <Mn (Metal) : 0.20% by mass or more and 1.80% by mass or less >

[0251] Like Si, Mn is a component that affects the strength and toughness of the weld metal. By including Mn in the weld metal at a specified content, the required mechanical properties can be achieved. Therefore, Mn (Metal) The content of [specific component] relative to the total mass of the deposited metal is preferably 0.20% by mass or more, and more preferably 0.50% by mass or more.

[0252] On the other hand, Mn has a deoxidizing effect. If the Mn content is excessive, there is a high probability that Mn will remain as an inclusion in the weld metal, potentially causing an imbalance between strength and toughness. Therefore, Mn... (Metal) The content of [substance name] is 1.80% by mass or less, preferably 1.65% by mass or less, relative to the total mass of the deposited metal.

[0253] <Al (Metal) : 0.30% by mass or more and 1.50% by mass or less >

[0254] Al is a strong deoxidizing component. Through oxidation in the deposited metal, it forms oxides (slag) in the molten pool. This improves burn-through resistance in all welding positions, including difficult positions such as vertical and overhead welding. Therefore, it is considered a preferred element for inclusion in welding wire. Thus, Al... (Metal) The content of [specific component] is preferably 0.30% by mass or more, and more preferably 0.40% by mass or more, relative to the total mass of the deposited metal.

[0255] On the other hand, if there is an excessive amount of Al, it is highly likely that Al will remain as an inclusion in the weld metal, negatively impacting toughness. Therefore, Al... (Metal)The content of [specific component] is 1.50% by mass or less, preferably 1.10% by mass or less, and more preferably 1.00% by mass, relative to the total mass of the deposited metal.

[0256] <La (Metal) Less than 0.008% by mass >

[0257] La is a type of REM contained in the welding wire, and it acts as a binder in the deposited metal, causing the oxides of strong deoxidizing elements to coalesce. In this embodiment, the lower limit of the La content in the deposited metal is not specifically set, but in order to obtain the above-mentioned effect, La... (Metal) The content of [specific component] is preferably 0.001% by mass or more relative to the total mass of the deposited metal.

[0258] On the other hand, if La (Metal) If the content of La exceeds 0.008% by mass, the inclusions will coarsen due to agglomeration, which will adversely affect the mechanical properties or may cause unacceptable welding defects. Therefore, La (Metal) The content of [substance name] is less than 0.008% by mass relative to the total mass of the deposited metal, preferably less than 0.006% by mass.

[0259] <Ce (Metal) : ≥0.002% by mass and ≤0.010% by mass >

[0260] Like La, Ce is a type of REM contained in welding wire, acting as a binder within the deposited metal to coagulate oxides of strong deoxidizing elements. Therefore, Ce... (Metal) The content of [the substance] is 0.002% by mass or more, preferably 0.003% by mass or more, relative to the total mass of the deposited metal.

[0261] On the other hand, if Ce (Metal) If the Ce content exceeds 0.010% by mass, the inclusions will coarsen due to agglomeration, adversely affecting mechanical properties or potentially causing unacceptable welding defects. Therefore, Ce (Metal) The content of [substance name] is less than 0.010% by mass relative to the total mass of the deposited metal, preferably less than 0.009% by mass.

[0262] <Fe (Metal) 85.0% or more in mass >

[0263] In widely used steel grades such as mild steel, high-tensile steel, and low-temperature steel, Fe is the main element among the elements contained to meet the required mechanical properties. If Fe... (Metal) If the Fe content is below 85% by mass, the influence of the remaining elements becomes greater, and the mechanical properties may deteriorate. Therefore, Fe (Metal)The content of [amount] is 85% by mass or more, preferably 87.0% by mass or more, relative to the total mass of the deposited metal.

[0264] <P (Metal) : Less than 0.0200% by mass >

[0265] P is an element that reduces the crack resistance and mechanical properties of the weld metal. Therefore, P (Metal) The content of [substance name] is less than 0.020% by mass relative to the total mass of the deposited metal, preferably less than 0.0100% by mass.

[0266] <S (Metal) : Less than 0.0200% by mass >

[0267] S is an element that reduces crack resistance. Therefore, S (Metal) The content of [substance name] is less than 0.0200% by mass relative to the total mass of the deposited metal, preferably less than 0.0100% by mass.

[0268] <Cr (Metal) Less than 1.00% by mass >

[0269] Cr (Cr) is a component that affects the strength and toughness of weld metal. However, if the weld metal contains excessive Cr, it is prone to precipitate as carbides at grain boundaries, potentially disrupting the balance between strength and toughness. Therefore, Cr... (Metal) The content of [amount] is less than 1.00% by mass relative to the total mass of the deposited metal.

[0270] <Mo (Metal) Less than 1.00% by mass >

[0271] Mo is a component that increases high-temperature strength, but if there is an excessive amount of Mo in the weld metal, the strength will increase excessively, and the balance between strength and toughness may be lost. Therefore, Mo... (Metal) The content of [amount] is less than 1.00% by mass relative to the total mass of the deposited metal.

[0272] <Mg (Metal) Less than 0.50% by mass >

[0273] Like Al, Mg is a strong deoxidizing component. If Mg is present in excess, it is highly likely to remain as an inclusion in the weld metal, negatively impacting toughness. Therefore, Mg... (Metal) The content of [the substance] is 0.50% by mass or less relative to the total mass of the deposited metal, preferably 0.30% by mass or less, and more preferably 0.20% by mass or less.

[0274] <Zr (Metal) Less than 0.50% by mass >

[0275] Like Al, Zr is a strong deoxidizing component. If Zr is excessively present, it is highly likely to remain as an inclusion in the weld metal, negatively impacting toughness. Therefore, Zr... (Metal) The content of [the substance] is less than 0.50% by mass relative to the total mass of the deposited metal, preferably less than 0.45% by mass.

[0276] <Ti (Metal) Less than 0.05% by mass >

[0277] Like Al, Ti is a strong deoxidizing component. If Ti is excessively present, it is highly likely to remain as an inclusion in the weld metal, negatively impacting toughness. Therefore, Ti... (Metal) The content of [the substance] is 0.05% by mass or less relative to the total mass of the deposited metal, preferably 0.03% by mass or less, and more preferably 0.01% by mass or less.

[0278] <Ca (Metal) Less than 0.50% by mass >

[0279] Like Al, Ca is a strong deoxidizing component. If Ca is present in excess, it is highly likely to remain as an inclusion in the weld metal, negatively impacting toughness. Therefore, Ca... (Metal) The content of [the substance] is less than 0.50% by mass relative to the total mass of the deposited metal, preferably less than 0.45% by mass.

[0280] <Ni (Metal) Less than 3.00% by mass >

[0281] Ni stabilizes the austenitic structure of the weld metal, improves toughness at low temperatures, and adjusts the crystallinity of the ferrite structure. However, excessive Ni in the weld metal can lead to an excessive increase in strength, potentially disrupting the balance between strength and toughness. Therefore, Ni... (Metal) The content of [substance name] is 3.0% by mass or less, preferably 2.5% by mass or less, relative to the total mass of the deposited metal.

[0282] <B (Metal) : Less than 0.0090% by mass >

[0283] B prevents a decrease in the toughness of the deposited metal; however, it is also an element that reduces crack resistance. Therefore, B (Metal) The content of B is 0.0090% by mass or less relative to the total mass of the deposited metal, preferably 0.0050% by mass or less. In addition, B has the effect of reducing the brittle fracture ratio, and is preferably 0.0010% by mass or more, more preferably 0.0020% by mass or more.

[0284] <Ba (Metal) Less than 1.00% by mass >

[0285] Ba (Ba) is an element that contributes to the deoxidation of the weld metal and improves weld operability. However, excessive Ba in the weld metal can cause arc deflection, potentially deteriorating weld operability. Therefore, Ba... (Metal) The content is 1.00% by mass or less, preferably 0.90% by mass or less.

[0286] <Nb (Metal) Less than 0.001% by mass >

[0287] Nitrogen (Nb) is a component that affects mechanical properties such as strength. In commonly used steel grades such as mild steel, high-tensile steel, and low-temperature steel, Nb can be included in the weld metal to meet required mechanical properties. In this case, Nb... (Metal) The content of [substance name] is less than 0.001% by mass relative to the total mass of the deposited metal, preferably less than 0.0008% by mass.

[0288] <Cu (Metal) Less than 0.1% by mass >

[0289] Cu (Cu) is an element that contributes to improving the strength and weather resistance of weld metal. In commonly used steel grades such as mild steel, high-tensile steel, and low-temperature steel, Cu can be included in the weld metal to meet the required strength and weather resistance. In this case, Cu... (Metal) The content of [substance name] is less than 0.1% by mass relative to the total mass of the deposited metal, preferably less than 0.08% by mass.

[0290] <V (Metal) Less than 0.001% by mass >

[0291] V (V) plays a role in increasing the strength of weld metal, but on the other hand, it is an element that reduces toughness and crack resistance. Therefore, V in the weld metal... (Metal) The content of [substance name] is less than 0.001% by mass relative to the total mass of the deposited metal, preferably less than 0.0006% by mass.

[0292] <W (Metal) Less than 0.1% by mass >

[0293] W is a component that improves high-temperature strength and pitting corrosion resistance. In commonly used steel grades such as mild steel, high-tensile steel, and low-temperature steel, W can be added to the weld metal to meet required mechanical properties. In this case, W... (Metal) The content of [substance name] is less than 0.1% by mass relative to the total mass of the deposited metal, preferably less than 0.08% by mass.

[0294] <Ta (Metal) Less than 0.1% by mass >

[0295] Ta is an element that affects mechanical properties such as strength. In commonly used steel grades such as mild steel, high-tensile steel, and low-temperature steel, Ta can be included in the weld metal to meet required mechanical properties. In this case, Ta... (Metal) The content of [substance name] is less than 0.1% by mass relative to the total mass of the deposited metal, preferably less than 0.08% by mass.

[0296] <Sr (Metal) Less than 1.00% by mass >

[0297] Sr contributes to the deoxidation of weld metal and improves weldability, thus making it a preferred element for inclusion in flux, thereby allowing the weld metal to contain Sr. In this case, Sr... (Metal) The content of [substance name] is 1.00% by mass or less relative to the total mass of the deposited metal, preferably 0.90% by mass or less.

[0298] <O (Metal) : Less than 0.0250% by mass >

[0299] O (oxide) is dissolved in the weld metal or exists in the form of oxides. If O is present in excess, there is a high probability of residual oxide inclusions in the weld metal, which negatively impacts toughness. Therefore, O... (Metal) The content of [substance name] is less than 0.0250% by mass relative to the total mass of the deposited metal, preferably less than 0.0200% by mass.

[0300] <N (Metal) : Less than 0.0100% by mass >

[0301] Nitrogen (N) exists in the weld metal either in solid solution or as nitrides. If N is present in excess, this solid solution strengthening leads to an excessive increase in strength, potentially causing an imbalance between strength and toughness. Therefore, N... (Metal) The content of [substance name] is less than 0.0100% by mass relative to the total mass of the deposited metal, preferably less than 0.0050% by mass.

[0302] (Balance: Impurities)

[0303] In this embodiment, the balance other than the elements mentioned above is preferably considered as impurities. Impurities refer to unintentionally added elements other than those mentioned above, such as Sn, Co, Sb, and As. The total impurity content in the deposited metal is preferably 0.010% by mass or less, more preferably 0.005% by mass or less.

[0304] Furthermore, the deposited metal of this embodiment can be manufactured, for example, using the above-described [1. basic flux-cored welding wire] by gas-shielded arc welding.

[0305] [3. Welding Method]

[0306] The welding method of this embodiment is a gas shielded arc welding method using the basic flux-cored welding wire described in [1. Basic flux-cored welding wire] above.

[0307] Specifically, among various gas-shielded arc welding methods, it is preferable to use a positive polarity gas-shielded arc welding method with the electrode side being - (negative) and the base metal side being + (positive). There are no particular restrictions on the type of gas used for welding; for example, 100% by volume Ar, 100% by volume CO2, and 100% by volume O2, as well as mixtures thereof, are examples. When using Ar, it is preferable to use a shielding gas containing 70% by volume or more Ar; when using CO2, it is preferable to use a shielding gas containing 70% by volume or more CO2, and more preferably 100% by volume CO2 (hereinafter also referred to as "carbon dioxide"). Furthermore, when using a mixture of Ar and CO2, a mixture of 80% by volume Ar and 20% by volume CO2 is preferred. There are no particular restrictions on the gas flow rate; for example, it can be around 15 to 30 L / min.

[0308] The shape of the welding current waveform can be either straight or pulsed. "Straight" here means there is no specific waveform shape. The welding current range is not particularly limited; for example, 200–300A for flat welding, 150–250A for vertical and horizontal welding, and it can also be used within a range that combines these conditions for circumferential welding of fixed pipes, etc. Furthermore, the arc voltage is not particularly limited; for example, it can be 15–35V. The welding speed is also not particularly limited; for example, it can be 10–50 cm / min. Additionally, there are no particular restrictions on the wire extension length; for example, it can be set to 10–30 mm. However, all welding conditions are not limited to the above ranges and can be determined appropriately according to the application.

[0309] [4. Welded Joint]

[0310] The welded joint of this embodiment is manufactured using the welding method described in [3. Welding Method] above. In the welded joint of this embodiment, the portion of the deposited metal preferably has the composition described in [2. Deposited Metal] above.

[0311] Example

[0312] The present invention will be described in more detail below with examples of invention and comparative examples. However, the present invention is not limited to these embodiments and can be modified and implemented within the scope that conforms to the spirit of the present invention, all of which are included within the technical scope of the present invention. In addition, the welding conditions described herein are one example, and this embodiment is not limited to the following welding conditions.

[0313] Using welding wires with the various compositions shown in Tables 1 to 4 below, weld metal is prepared under the welding conditions shown below. Strength (TS) is measured by tensile test, and impact energy (CVN) is measured at -20°C and -46°C by impact test.

[0314] <Welding Conditions>

[0315] Welding current: 210A

[0316] Arc voltage: 21V

[0317] Polarity: DCEN

[0318] Protective gas: 100% CO2 (by volume)

[0319] Stacking method: 7 layers, 14 steps

[0320] Linear energy: 0.8~1.0kJ / mm

[0321] <Measurement Method>

[0322] (Tension test)

[0323] Tensile test specimens of JIS Z 3111:2005 A1 were extracted from the obtained weld metal. The tensile strength (TS) and 0.2% yield strength (yield stress: PS) of the weld metal were measured by tensile testing according to the method for tensile and impact testing of weld metal specified in JIS Z 3111:2005.

[0324] (Impact test)

[0325] From the obtained weld metal, a 2mm V-notch impact test piece according to JIS Z 3111:2005 was extracted. The absorbed energy (CVN) of the weld metal at -20℃ and -46℃ was measured by impact test according to the "Tension and Impact Test Method of Weld Metal" specified in JIS Z 3111:2005. The average value was used as the CVN (-46℃) and CVN (-20℃) values.

[0326] <Evaluation Methods>

[0327] Next, the balance between strength and toughness, and the brittle fracture ratio are evaluated. Specifically, the values ​​obtained from equations (a) and (b) below are calculated to evaluate the balance between strength and toughness.

[0328] Equation (a): CVN(-46℃) / TS

[0329] Formula (b): CVN(-20℃) / TS

[0330] The closer the values ​​obtained from equations (a) and (b) are to 1, the better the balance between strength and toughness. Specifically, in equation (a), a value above 0.100 indicates a good balance between strength and toughness, above 0.150 is better, above 0.180 is excellent, and above good is considered acceptable. Similarly, in equation (b), a value above 0.150 indicates a good balance between strength and toughness, above 0.200 is better, above 0.220 is excellent, and above good is considered acceptable.

[0331] In addition, the brittle fracture ratio at -20℃ and -46℃ was also evaluated. The brittle fracture ratio is calculated by observing the fracture surface of the test piece after the pendulum impact test and calculating the proportion of the area exhibiting a brittle fracture relative to the specified cross-sectional area before the test. At -20℃ and -46℃, a brittle fracture ratio of less than 40% is considered good, less than 30% is considered excellent, and above good is considered acceptable. The composition of the obtained weld metal is shown in Tables 5 and 6 below, and the evaluation results are shown in Tables 7 and 8 below. Furthermore, in Tables 1, 3, 5, and 6 below, a "-" indicates below the detection limit. Additionally, a "-" in Table 4 indicates that it could not be calculated. Furthermore, the balance of the welding wire composition shown in Tables 1 and 3 below represents O, N, and impurities, and the balance of the weld metal composition shown in Tables 5 and 6 below represents Fe and impurities.

[0332] In addition, in Tables 2 and 4, equations (1) to (8) represent the following equations.

[0333] Equation (1):

[0334] 32.1×[Si]-40.6×[Mn]-20.1×[Ni]-19.7×[Mo]-172.6×[C]-408.2×[REM]-5824.4×[B]-38.4×[Cr]-9960×[P]+43793×[S]

[0335] Equation (2):

[0336] 33.9×[Si]-47.0×[Mn]-22.2×[Ni]-11.9×[Mo]-203.9×[C]-443.5×[REM]-4482.2×[B]-36.1×[Cr]-15281×[P]+47868×[S]

[0337] Equation (3):

[0338] 0.001×[Fe]-0.71×[Si]+0.08×[Mn]-0.08×[Al]+0.69×[Zr]+0.03×[Ni]+0.01×[Mo]+0.32×[C]+2.27×[REM]+9.57×[B]+0.11×[Cr]

[0339] Equation (4):

[0340] 0.003×[Fe]-0.35×[Si]+0.09×[Mn]-0.13×[Al]+0.22×[Zr]+0.02×[Ni]-0.02×[Mo]-0.11×[C]+1.17×[REM]+4.30×[B]+0.09×[Cr]

[0341] Equation (5): [B oxide] / [B]

[0342] Equation (6): [Cr] / ([Cr]+[Mo])

[0343] Equation (7): [Mo] / ([Cr]+[Mo])

[0344] Equation (8): [Al] / ([Al]+[Mg])

[0345] Where [REM], [Fe], [C], [Si], [Mn], [P], [S], [Cr], [Mo], [Al], [Zr], [Ni], [B], and [Mg] represent REM as a percentage of mass relative to the total mass of the welding wire. (Wire) Fe (Wire) C (Wire) Si (Wire) Mn (Wire) P (Wire) S (Wire) Cr (Wire) Mo (Wire) Al (Wire) Zr (Wire) Ni (Wire) B (Wire) and Mg (Wire)The value of the content. Additionally, [B oxide] is a B conversion value, expressed as a percentage of mass relative to the total mass of the welding wire. In this embodiment, only B is added in the form of oxides. In other words, the amount of oxides in the welding wire of this embodiment is B. (Wire) The conversion value of B2O3.

[0346] Table 1

[0347]

[0348] Table 2

[0349]

[0350] Table 3

[0351]

[0352] Table 4

[0353]

[0354] Table 5

[0355]

[0356] Table 6

[0357]

[0358] Table 7

[0359]

[0360] Table 8

[0361]

[0362] As shown in Tables 1-4, 7, and 8, in Invention Examples No. 1-16, the components contained in the basic flux-cored welding wire and the values ​​obtained from formulas (1) to (8) are within the range specified in this invention, thus improving burn-through properties, enabling all-position welding, and producing deposited metal with an excellent balance between strength and toughness. Furthermore, comparing Invention Examples No. 5-7, when the Zr content in the welding wire is 0.045% by mass or less, the balance between strength and toughness becomes excellent as the B content increases. Additionally, comparing Invention Examples No. 5, 11, and 14, when the B content is 0.0046-0.0055% by mass, if the Zr content in the welding wire is increased to more than 0.045% by mass, at least one of formulas (a) and (b) representing the balance between strength and toughness tends to decrease as the Zr content increases. That is, it can be seen that both the B content and the Zr content are such that the closer they are to the upper limit of the range specified in this invention, the lower the balance between strength and toughness.

[0363] In particular, in Invention Examples No. 9, 10, 12, 13, 15 and 16, the Zr and B content in the welding wire are within the preferred range specified in this invention, resulting in excellent brittle fracture ratio and balance between strength and toughness.

[0364] On the other hand, in Comparative Examples No. 1 to 19, at least one of the following is undesirable: the REM content, C content, and at least one of the values ​​obtained from Equations (1) to (4) in the welding wire deviates from the range specified in this invention. Therefore, at least one of the brittle fracture ratio and the balance between strength and toughness is undesirable.

[0365] Furthermore, as shown in Tables 5 to 8, in Invention Examples No. 1 to 16, because the content of each component contained in the weld metal is within the range specified in this invention, a weld metal with an excellent balance of strength and toughness can be obtained.

[0366] Thus, according to the alkaline flux-cored wire, welding method, and welding joint manufacturing method of the present invention, all-position welding can be performed, and deposited metal and welding joint with excellent balance of strength and toughness can be obtained.

Claims

1. An alkaline flux-cored welding wire, characterized in that, It is an alkaline flux-cored welding wire containing at least one of the following strong deoxidizing elements: Al, Mg, Ti, Ca, and Zr. The total amount of the strong deoxidizing element relative to the total mass of the welding wire is more than 1.50% by mass and less than 4.00% by mass, and Contains REM: ≥0.030% by mass and ≤0.120% by mass, Fe: ≥85.0% by mass, and meets the following requirements: C: Less than 0.050% by mass Si: less than 0.60% by mass Mn: less than 2.00% by mass P: less than 0.0150% by mass S: less than 0.0150% by mass Cr: less than 1.00% by mass Mo: less than 1.00% by mass Al: less than 3.00% by mass Mg: less than 3.00% by mass Zr: less than 3.000% by mass Ti: less than 3.000% by mass Ca: less than 3.00% by mass Ni: less than 5.00% by mass B: Less than 0.0200% by mass Ba: less than 4.00% by mass F: Less than 2.00% by mass The value calculated by the following formula (1): below 48.0, The value calculated by the following formula (2): below 48.0, The value calculated by the following formula (3) is 0.09 or higher. The value calculated by the following formula (4) is: 0.14 or higher. Equation (1): 32.1×[Si]-40.6×[Mn]-20.1×[Ni]-19.7×[Mo]-172.6×[C]-408.2×[REM]-5824.4×[B]-38.4×[Cr]-9960×[P]+43793×[S] Equation (2): 33.9×[Si]-47.0×[Mn]-22.2×[Ni]-11.9×[Mo]-203.9×[C]-443.5×[REM]-4482.2×[B]-36.1×[Cr]-15281×[P]+47868×[S] Equation (3): 0.001×[Fe]-0.71×[Si]+0.08×[Mn]-0.08×[Al]+0.69×[Zr]+0.0 3×[Ni]+0.01×[Mo]+0.32×[C]+2.27×[REM]+9.57×[B]+0.11×[Cr] Equation (4): 0.003×[Fe]-0.35×[Si]+0.09×[Mn]-0.13×[Al]+0.22×[Zr]+0.02×[Ni]-0.02×[Mo]-0.11×[C]+1.17×[REM]+4.30×[B]+0.09×[Cr] In formulas (1) to (4), [REM], [Fe], [C], [Si], [Mn], [P], [S], [Cr], [Mo], [Al], [Zr], [Ni] and [B] are the contents of REM, Fe, C, Si, Mn, P, S, Cr, Mo, Al, Zr, Ni and B, respectively, expressed as a percentage of mass relative to the total mass of the welding wire.

2. The alkaline flux-cored welding wire according to claim 1, characterized in that, Relative to the total mass of the welding wire, it also contains at least one selected from Nb: less than 0.50% by mass, Cu: less than 2.00% by mass, W: less than 1.00% by mass, Ta: less than 1.00% by mass, V: less than 1.00% by mass, Sr: less than 4.00% by mass, and the total of alkali metal elements: less than 3.00% by mass, with the balance being O, N, and impurities.

3. The alkaline flux-cored welding wire according to claim 1, characterized in that, The content of B is more than 0.0020% by mass and less than 0.0150% by mass relative to the total mass of the welding wire.

4. The alkaline flux-cored welding wire according to claim 1, characterized in that, The content of B includes the B conversion value of B oxide. When the B-conversion value of the B oxide relative to the total mass of the welding wire is expressed as [B oxide] in mass percentage, The value calculated from equation (5): [B oxide] / [B] is greater than 0.

5.

5. The alkaline flux-cored welding wire according to claim 1, characterized in that, Contains at least one selected from Ba: less than 4.00% by mass, Ca: less than 3.00% by mass, and Sr: less than 4.00% by mass. The flux contains at least one selected from BaF2, CaF2, and SrF2, which are fluorides of Ba, Ca, and Sr. The Ba content includes the Ba conversion value of BaF2. The Ca content includes the Ca conversion value of CaF2. The Sr content includes the Sr conversion value of SrF2. The F content includes the F conversion values ​​of BaF2, CaF2 and SrF2.

6. The alkaline flux-cored welding wire according to claim 5, characterized in that, The content of F is equal to the F conversion value of the total fluoride contained in the flux.

7. The basic flux-cored welding wire according to claim 1, characterized in that, The oxide content in the welding wire is more than 0.005% by mass and less than 0.100% by mass relative to the total mass of the welding wire.

8. The basic flux-cored welding wire according to any one of claims 1 to 7, characterized in that, The Cr content is 0.20% by mass and less than 0.90% by mass relative to the total mass of the welding wire, and... The Mo content is less than 0.50% by mass relative to the total mass of the welding wire. The value calculated by equation (6): [Cr] / ([Cr]+[Mo]) is greater than 0.

20.

9. The basic flux-cored welding wire according to any one of claims 1 to 7, characterized in that, The Cr content is less than 0.90% by mass relative to the total mass of the welding wire, and, The Mo content relative to the total mass of the welding wire is 0.10% by mass or more and 0.80% by mass or less. The value calculated by equation (7): [Mo] / ([Cr]+[Mo]) is greater than 0.

10.

10. The basic flux-cored welding wire according to any one of claims 1 to 7, characterized in that, The content of the strong deoxidizing element relative to the total mass of the welding wire, specifically Al, is 1.00% by mass or more and 2.50% by mass or less, and... The Mg content is less than 1.00% by mass. When the content of Mg in the welding wire is expressed as [Mg] as a percentage of mass relative to the total mass of the welding wire, The value calculated by equation (8): [Al] / ([Al]+[Mg]) is greater than 0.5 and less than 1.

0.

11. The basic flux-cored welding wire according to any one of claims 1 to 7, characterized in that, The REM contains La and Ce.

12. A weld metal, characterized in that, It is a weld metal formed using the basic flux-cored wire according to any one of claims 1 to 11, wherein, relative to the total mass of the weld metal, it contains C: ≥0.020% by mass and ≤0.100% by mass Si: ≥0.05% by mass and ≤0.50% by mass Mn: ≥0.20% by mass and ≤1.80% by mass Al: ≥0.30% by mass and ≤1.50% by mass Ce: ≥0.002% by mass and ≤0.010% by mass Fe: ≥85.0% by mass and satisfy La: less than 0.008% by mass P: less than 0.0200% by mass S: less than 0.0200% by mass Cr: less than 1.00% by mass Mo: less than 1.00% by mass Mg: less than 0.50% by mass Zr: less than 0.50% by mass Ti: less than 0.05% by mass Ca: less than 0.50% by mass Ni: less than 2.5% by mass B: Less than 0.0090% by mass Ba: less than 1.00% by mass Nb: less than 0.001% by mass Cu: less than 0.1% by mass V: less than 0.001% by mass W: less than 0.1% by mass Ta: less than 0.1% by mass Sr: less than 1.00% by mass Total alkali metal elements: less than 0.05% by mass O: less than 0.0250% by mass N: less than 0.0100% by mass The remaining amount is impurities.

13. A welding method, characterized in that, Gas-shielded arc welding is performed using the basic flux-cored welding wire according to any one of claims 1 to 11.

14. A welded joint, characterized in that, Manufactured using the welding method described in claim 13.

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