Ni-based alloy flux-cored wire

Abstract

Provided is a Ni-based alloy flux-cored wire with which it is possible to obtain a weld metal in which the occurrence of weld defects such as pores and surface pits is suppressed, while having excellent slag stripping properties and bead shapes. A Ni-based alloy flux-cored wire in which a flux is filled in an outer skin comprising a Ni-based alloy, the Ni-based alloy flux-cored wire containing Ni, Cr, Mo, W, Mn, and Fe in prescribed amounts with respect to the total mass of the wire, the Ni-based alloy flux-cored wire containing TiO2: 3.0-10.0 mass%, the SiO2-equivalent value of metal Si and Si oxide: 1.0-3.0 mass%, the SiO2-equivalent value of Si and Si oxide: 1.0-3.0 mass%, and the balance being Fe and unavoidable impurities, with respect to the total mass of the wire, the Ni-based alloy flux-cored wire containing Ni, Cr, Mo, W, Mn, and Fe. The ZrO2 conversion value of the metal Zr and the Zr oxide is less than 1.0 mass%, the Al2O3 content is more than 0.2 mass% and less than 1.2 mass%, the MnO2 content is more than 0.2 mass% and less than 1.6 mass%, and the F content is less than 0.07 mass%.

Description

Technical Field

[0001] The invention relates to a Ni-based alloy flux-cored welding wire. Background Art

[0002] When manufacturing structures exposed to corrosive environments such as chemical plants or seawater, or LNG tanks serving as cryogenic pressure vessels, highly corrosion-resistant austenitic stainless steel or 9% Ni steel are used as structural components. Furthermore, Ni-based alloy welding materials, such as Inconel (registered trademark) 625 and Hastelloy (registered trademark) C276, are generally used for these structural components, rather than common metals. The mainstream welding methods using these Ni-based alloy welding materials are gas tungsten arc welding (GTAW), submerged arc welding (SAW), and shielded metal arc welding (SMAW). However, in recent years, the use of flux-cored arc welding (FCAW), which uses Ni-based alloy flux-cored wire with a Ni-based alloy sheath, has been expanding in pursuit of improved work efficiency.

[0003] For example, Patent Document 1 proposes a Ni-based alloy flux-cored welding wire that offers excellent weldability and thermal crack resistance in a vertical welding position, while also reducing slag adhesion and the occurrence of pitting on the weld bead surface. The flux-cored welding wire described in Patent Document 1 contains Mn, Ni, Cr, Mo, W, and Fe in specified amounts relative to the total mass of the wire. Furthermore, the flux specifies the contents of TiO₂, SiO₂ equivalents, ZrO₂ equivalents, Al₂O₃, MnO₂, and Bi₂O₃ relative to the total mass of the wire, and the values ​​calculated as ([TiO₂] + [ZrO₂]) / ([SiO₂] + [Al₂O₃]).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2021-133422 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] However, the flux-cored welding wire described in Patent Document 1 aims to achieve excellent weldability in the vertical welding position. Therefore, it is designed to increase the melting point and viscosity of the slag, supporting the molten pool during welding and preventing it from sagging. Consequently, gases (oxygen, hydrogen, etc.) generated during welding cannot be fully discharged from the molten pool while the slag solidifies. Furthermore, when this flux-cored welding wire is used in horizontal welding, for example, the upper side of the groove becomes an obstacle, hindering the discharge of gases. If gases generated during welding remain in the molten pool, welding defects such as porosity and surface pitting may occur.

[0009] The present invention has been made in view of the above-mentioned circumstances, and its object is to provide a Ni-based alloy flux-cored welding wire that can appropriately maintain the viscosity of the slag, thereby improving the slag stripping properties and weld bead shape, and can also obtain a weld metal in which the occurrence of welding defects such as porosity and surface pitting is suppressed even in welding postures other than vertical welding.

[0010] Means of solving the problem

[0011] The above-mentioned object of the present invention is achieved by the following structure [1] of the Ni-based alloy flux-cored welding wire.

[0012] [1] A Ni-based alloy flux-cored welding wire, characterized in that the wire is formed by filling a flux in a sheath formed of a Ni-based alloy, wherein:

[0013] Relative to the total mass of welding wire,

[0014] Ni: 39 mass% or more and 59 mass% or less,

[0015] Cr: 5 mass% or more and 20 mass% or less,

[0016] Mo: 10 mass% or more and 20 mass% or less,

[0017] W: 1.0 mass % or more and 5.0 mass % or less,

[0018] Mn: 0.1 mass% or more and 5 mass% or less,

[0019] Fe: 3.0 mass% or more and 10.0 mass% or less,

[0020] TiO2: 3.0% by mass or more and 10.0% by mass or less,

[0021] SiO2 conversion value of metal Si and Si oxide: 1.0 mass% or more and 3.0 mass% or less,

[0022] ZrO2 conversion value of metal Zr and Zr oxide: 1.0 mass % or less,

[0023] Al2O3: 0.2 mass% or more and 1.2 mass% or less,

[0024] MnO2: 0.2 mass% or more and 1.6 mass% or less, and

[0025] F: 0.07 mass % or less.

[0026] In addition, preferred embodiments of the present invention of the Ni-based alloy flux-cored welding wire relate to the following [2] to [5].

[0027] [2] The Ni-based alloy flux-cored welding wire according to [1], characterized in that when the wire contains at least one selected from Na, K, and Li, the value A1 calculated by the following formula (1) is 0.70 or less.

[0028] Formula (1): A1=[Na]+[K]+[Li]

[0029] Here, [Na] represents the Na content in the welding wire expressed in mass % relative to the total mass of the welding wire, [K] represents the K content in the welding wire expressed in mass % relative to the total mass of the welding wire, and [Li] represents the Li content in the welding wire expressed in mass % relative to the total mass of the welding wire.

[0030] [3] The Ni-based alloy flux-cored welding wire according to [1] or [2], characterized in that the B conversion value of the metal B and B compounds contained relative to the total mass of the welding wire is: 0.030 mass% or less.

[0031] [4] The Ni-based alloy flux-cored welding wire according to any one of [1] to [3], characterized in that the content of Ti is 0.50 mass % or less, and the content of Al is 0.50 mass % or less, relative to the total mass of the welding wire.

[0032] [5] The Ni-based alloy flux-cored welding wire according to any one of [1] to [4], wherein the value A2 calculated by the following formula (2) is 3.48 or less.

[0033] Formula (2): A2=([Al]+[Al2O3]+[TiO2]) / ([SiO2]+[ZrO2]×0.1)

[0034] Here, [Al] is the Al content in the welding wire expressed in mass % relative to the total mass of the welding wire, [Al2O3] is the Al2O3 content expressed in mass % relative to the total mass of the welding wire, [TiO2] is the TiO2 content expressed in mass % relative to the total mass of the welding wire, [SiO2] is the SiO2 equivalent value expressed in mass % relative to the total mass of the welding wire, and [ZrO2] is the ZrO2 equivalent value expressed in mass % relative to the total mass of the welding wire.

[0035] Effects of the Invention

[0036] According to the present invention, a Ni-based alloy flux-cored welding wire can be provided which has excellent slag detachability and weld bead shape and can produce weld metal in which weld defects such as porosity and surface pitting are suppressed even in welding postures other than vertical welding. DETAILED DESCRIPTION

[0037] The present inventors have conducted intensive research on a flux-cored welding wire that can control the slag viscosity within an appropriate range and reduce welding defects in various welding postures. As a result, they have discovered that adjusting the MnO2 content and the fluoride content in the flux is effective in solving the above-mentioned problems.

[0038] The following describes the Ni-based alloy flux-cored welding wire according to this embodiment. Modes for implementing the present invention will be described in detail. The present invention is not limited to the embodiments described below and can be implemented with various modifications without departing from the spirit of the invention. In this specification, the Ni-based alloy flux-cored welding wire may be referred to simply as "flux-cored welding wire" or "welding wire."

[0039] [Ni-based alloy flux-cored welding wire]

[0040] The Ni-based alloy flux-cored welding wire of this embodiment comprises a Ni-based alloy sheath filled with flux. Specifically, the flux-cored welding wire of this embodiment comprises a cylindrical Ni-based alloy sheath and flux filled within (inside) the sheath. Furthermore, the flux-cored welding wire can be of either a seamless type with no seams in the sheath or a seamed type with a seam in the sheath, formed into a tubular shape such as a C-shaped cross-section or an overlapping cross-section.

[0041] First, the components contained in the entire Ni-based alloy flux-cored welding wire of this embodiment will be described in detail, along with the reasons for their addition and numerical limitations. Throughout this specification, unless otherwise specified, the amounts of each component in the flux-cored welding wire are defined as the total amount of the components contained in the sheath formed of the Ni-based alloy and the flux relative to the total mass of the welding wire (the total amount of the sheath and the flux within the sheath).

[0042] <Ni: 39 mass % or more and 59 mass % or less>

[0043] Nickel is a major component that constitutes the matrix in weld metals containing Ni-based alloys. It also contributes to the weld metal's toughness and ductility, as well as its corrosion resistance. If the Ni content in the welding wire is less than 39% by mass, these effects cannot be achieved, and a weld metal with the desired Ni content cannot be obtained. Therefore, the Ni content in the welding wire is 39% by mass or greater, preferably 43% by mass or greater, and more preferably 45% by mass or greater, relative to the total mass of the welding wire.

[0044] On the other hand, if the Ni content in the welding wire exceeds 59 mass%, the addition of other alloying elements becomes insufficient, and mechanical properties cannot be ensured. Furthermore, a weld metal having the desired Ni content cannot be obtained. Therefore, the Ni content in the welding wire is 59 mass% or less, preferably 57 mass% or less, and more preferably 55 mass% or less, relative to the total mass of the welding wire.

[0045] <Cr: 5 mass % or more and 20 mass % or less>

[0046] Cr is a component necessary for improving corrosion resistance against oxidizing acids. If the Cr content in the welding wire is less than 5 mass%, the aforementioned effects cannot be achieved, and a weld metal having the desired Cr content cannot be obtained. Therefore, the Cr content in the welding wire is 5 mass% or more, preferably 8 mass% or more, and more preferably 12 mass% or more, relative to the total mass of the welding wire.

[0047] On the other hand, if the Cr content in the welding wire exceeds 20 mass%, Cr carbonitrides may precipitate, potentially reducing the mechanical properties of the weld metal. Furthermore, a weld metal having the desired Cr content cannot be obtained. Therefore, the Cr content in the welding wire is 20 mass% or less, preferably 19 mass% or less, and more preferably 18 mass% or less, relative to the total mass of the welding wire.

[0048] <Mo: 10 mass % or more and 20 mass % or less>

[0049] Mo, when included in the welding wire along with Cr, ensures not only corrosion resistance against oxidizing acids but also excellent corrosion resistance against non-oxidizing acids and salts. If the Mo content in the welding wire is less than 10% by mass, the aforementioned effects cannot be achieved, and a weld metal with the desired Mo content cannot be obtained. Therefore, the Mo content in the welding wire is 10% by mass or greater, preferably 11% by mass or greater, and more preferably 12% by mass or greater, relative to the total mass of the welding wire.

[0050] On the other hand, if the Mo content in the welding wire exceeds 20 mass%, precipitation of intermetallic compounds with Ni becomes significant, potentially reducing the mechanical properties of the weld metal. Furthermore, a weld metal having the desired Mo content cannot be obtained. Therefore, the Mo content in the welding wire is 20 mass% or less, preferably 19 mass% or less, and more preferably 18 mass% or less, relative to the total mass of the welding wire.

[0051] <W: 1.0 mass % or more and 5.0 mass % or less>

[0052] W, when added to the weld metal from the welding wire, stabilizes the γ phase through solid solution strengthening, thereby increasing the tensile strength of the weld metal. If the W content in the welding wire is less than 1.0 mass%, these effects cannot be achieved, and a weld metal with the desired W content cannot be obtained. Therefore, the W content in the welding wire is 1.0 mass% or more, preferably 2.0 mass% or more, and more preferably 2.5 mass% or more, relative to the total mass of the welding wire.

[0053] On the other hand, if the W content in the welding wire exceeds 5.0 mass%, W segregation may occur, potentially reducing the toughness of the weld metal. Furthermore, a weld metal having the desired W content may not be obtained. Therefore, the W content in the welding wire is 5.0 mass% or less, preferably 4.0 mass% or less, and more preferably 3.5 mass% or less, relative to the total mass of the welding wire.

[0054] <Mn: 0.1 mass % or more and 5 mass % or less>

[0055] Mn is a γ-phase-forming element and is effective for strengthening the matrix. If the Mn content in the welding wire is less than 0.1% by mass, the aforementioned effects cannot be achieved. Furthermore, a weld metal with the desired Mn content cannot be obtained. Therefore, the Mn content in the welding wire is 0.1% by mass or greater, preferably 0.2% by mass or greater, and more preferably 0.3% by mass or greater, relative to the total mass of the welding wire.

[0056] On the other hand, if the Mn content in the welding wire exceeds 5 mass%, slag removability is reduced, and a weld metal having a desired Ni content cannot be obtained. Therefore, the Mn content in the welding wire is 5 mass% or less, preferably 4 mass% or less, and more preferably 3 mass% or less, relative to the total mass of the welding wire.

[0057] <Fe: 3.0 mass % or more and 10.0 mass % or less>

[0058] Fe, by dissolving in the Ni-based alloy, can improve the tensile strength of the weld metal. If the Fe content in the welding wire is less than 3.0 mass%, this effect cannot be achieved, and a weld metal with the desired Fe content cannot be obtained. Therefore, the Fe content in the welding wire is 3.0 mass% or more, preferably 3.5 mass% or more, and more preferably 4.0 mass% or more, relative to the total mass of the welding wire.

[0059] On the other hand, if the Fe content in the welding wire exceeds 10.0% by mass, a low-melting-point Laves phase precipitates at the grain boundaries and may remelt during reheating of multilayer overlay welding, causing reheating liquid cracking at the grain boundaries. Furthermore, a weld metal with the desired Fe content cannot be obtained. Therefore, the Fe content in the welding wire is 10.0% by mass or less, preferably 9.0% by mass or less, and more preferably 8.0% by mass or less, relative to the total mass of the welding wire.

[0060] Next, the components contained in the flux of the Ni-based alloy flux-cored welding wire of this embodiment will be described in detail, along with the reasons for their addition and numerical limitations. In this specification, the components contained in the flux are specified in terms of their content relative to the total mass of the welding wire (the combined amount of the sheath and the flux within the sheath).

[0061] <TiO2: 3.0% by mass or more and 10.0% by mass or less>

[0062] TiO2 forms a uniform, well-coated slag, effectively improving arc stability. Therefore, it is included in the flux as a primary slag former. Furthermore, TiO2 is a high-melting-point oxide, and its inclusion in the flux can improve welding workability. If the TiO2 content in the flux is less than 3.0% by mass, its slag former properties are not fully realized, and the weld bead tends to sag. Therefore, the TiO2 content in the flux should be at least 3.0% by mass, preferably at least 3.5% by mass, and more preferably at least 4.0% by mass, relative to the total mass of the welding wire.

[0063] On the other hand, if the TiO2 content in the flux exceeds 10.0% by mass, the slag component in the welding wire becomes excessive, resulting in excessive slag generation during welding, and slag tends to droop from the weld. Furthermore, slag inclusions are more likely to occur, and pitting resistance is reduced. Therefore, the TiO2 content in the flux should be 10.0% by mass or less, preferably 9.0% by mass or less, and more preferably 8.0% by mass or less, relative to the total mass of the welding wire.

[0064] <SiO2 conversion value of metallic Si and Si oxide: 1.0 mass % or more and 3.0 mass % or less>

[0065] Like TiO2, metallic Si and Si oxides are components that increase slag viscosity and are included in the flux as a slag-forming agent to achieve a good weld bead shape. If the SiO2 equivalent value in the flux is less than 1.0 mass%, the aforementioned effect as a slag-forming agent may not be fully achieved, and welding workability may be reduced. Therefore, the SiO2 equivalent value in the flux should be 1.0 mass% or more, preferably 1.2 mass% or more, and more preferably 1.5 mass% or more, relative to the total mass of the welding wire.

[0066] On the other hand, if the SiO2 conversion value in the flux exceeds 3.0 mass%, slag removability decreases. Therefore, the SiO2 conversion value in the flux is 3.0 mass% or less, preferably 2.8 mass% or less, and more preferably 2.5 mass% or less, relative to the total mass of the welding wire.

[0067] The SiO2 equivalent value of metallic Si and Si oxide is the total value of elemental Si, Si alloys, and Si oxides contained in the flux converted into SiO2.

[0068] <ZrO2 equivalent value of metallic Zr and Zr oxide: 1.0 mass % or less>

[0069] Metallic Zr and Zr oxides are components that enhance arc jettability and improve arc stability even in low current ranges. They also accelerate slag solidification, improving welding workability. If the ZrO2 equivalent content in the flux exceeds 1.0 mass%, the slag solidification temperature rises, causing the slag to solidify rapidly. Consequently, gases generated by the solidifying weld metal cannot escape through the solidifying slag, making it more likely that craters will form in the weld. Therefore, the ZrO2 equivalent content in the flux should be 1.0 mass% or less, preferably 0.9 mass% or less, and more preferably 0.8 mass% or less, relative to the total mass of the welding wire.

[0070] The ZrO2 equivalent value of metal Zr and Zr oxide is the total value of metal Zr, Zr alloy and Zr oxide contained in the flux converted into ZrO2.

[0071] <Al2O3: 0.2 mass% or more and 1.2 mass% or less>

[0072] Like TiO, Al2O3 is a slag-forming agent that shapes the weld bead and improves its compatibility with the base metal. Al2O3 is also effective in adjusting slag viscosity and preventing weld bead sagging. If the Al2O3 content in the flux is less than 0.2% by mass, these effects cannot be fully achieved, and slag viscosity cannot be properly controlled. Therefore, the Al2O3 content in the flux should be at least 0.2% by mass, preferably at least 0.4% by mass, and more preferably at least 0.5% by mass, relative to the total mass of the welding wire.

[0073] On the other hand, if the Al2O3 content in the flux exceeds 1.2% by mass, the slag viscosity becomes too high, slag inclusions are more likely to occur, and slag removability is also deteriorated. Therefore, the Al2O3 content in the flux is 1.2% by mass or less, preferably 1.1% by mass or less, and more preferably 1.0% by mass or less, relative to the total mass of the welding wire.

[0074] <MnO2: 0.2 mass% or more and 1.6 mass% or less>

[0075] MnO2 has a low melting point and, when added to the flux, lowers the solidification temperature of the molten slag. Therefore, by including a specified amount of MnO2 in the flux, the viscosity of the slag can be appropriately maintained. During welding other than in the vertical position, gases generated from the solidifying weld metal can be discharged, thereby suppressing the occurrence of porosity and other problems. If the MnO2 content in the flux is less than 0.8% by mass, the above effects cannot be fully achieved, and welding defects are more likely to occur. Therefore, the MnO2 content in the flux is 0.2% by mass or more, preferably 0.3% by mass or more, and more preferably 0.4% by mass or more, relative to the total mass of the welding wire.

[0076] On the other hand, if the MnO2 content in the flux exceeds 1.6% by mass, slag adheres and the peelability decreases. Therefore, the MnO2 content in the flux is 1.6% by mass or less, preferably 1.5% by mass or less, and more preferably 1.4% by mass or less, relative to the total mass of the welding wire.

[0077] <F: 0.07 mass % or less>

[0078] Fluorides improve arc stability and slag fluidity, but the present inventors have discovered that reducing the amount of fluoride in the welding wire is effective in suppressing the occurrence of pores. If the fluorine content in the flux exceeds 0.07% by mass, significant pores may occur, for example, during transverse welding. Therefore, the fluorine content in the flux should be 0.07% by mass or less, preferably 0.04% by mass or less, and more preferably 0.02% by mass or less, relative to the total mass of the welding wire. Examples of fluorine sources in the flux include LiF, NaF, Na3AlF6, and K2SiF6.

[0079] <Value A1 calculated by formula (1): 0.70 or less>

[0080] In this embodiment, when the welding wire contains at least one selected from Na, K, and Li, it is preferable to specify the total value of their contents. Alkaline compounds represented by Na, K, and Li in the welding wire act as arc stabilizers and are components that have effects such as suppressing the occurrence of sputtering. However, the welding wire does not necessarily contain Na, K, and Li. However, when the welding wire contains at least one of these, if the value A1 calculated by the following formula (1) representing the total value of the Na, K, and Li contents is 0.05 or greater, the effect of the arc stabilizer can be achieved. Therefore, the value A1 calculated by the following formula (1) is preferably 0.05 or greater, more preferably 0.08 or greater, further preferably 0.10 or greater, and particularly preferably 0.15 or greater.

[0081] On the other hand, if the value A1 calculated by the following formula (1) is 0.70 or less, arc stability is improved and the amount of sputtering can be reduced. Therefore, the value A1 calculated by the following formula (1) is preferably 0.70 or less, more preferably 0.65 or less, further preferably 0.60 or less, and particularly preferably 0.55 or less.

[0082] Here, formula (1): A1=[Na]+[K]+[Li]

[0083] Here, [Na] represents the Na content in the welding wire as a percentage by mass relative to the total mass of the welding wire, [K] represents the K content in the welding wire as a percentage by mass relative to the total mass of the welding wire, and [Li] represents the Li content in the welding wire as a percentage by mass relative to the total mass of the welding wire. In this embodiment, the Na content, K content, and Li content represent the Na-converted value of Na compounds, the K-converted value of K compounds, and the Li-converted value of Li compounds, respectively.

[0084] <B conversion value of metal B and B compound: 0.030 mass % or less (including 0 mass %)>

[0085] Metal B and B compounds are components that degrade the hot cracking resistance of the weld metal, so it is preferable to limit the content of metal B and B compounds in the welding wire. If the B-converted value in the welding wire is 0.030 mass% or less, the occurrence of hot cracks can be prevented. Therefore, the B-converted value of metal B and B compounds in the welding wire is preferably 0.030 mass% or less, more preferably 0.020 mass% or less, even more preferably 0.010 mass% or less, relative to the total mass of the welding wire, and may be 0 mass%.

[0086] However, B has the effect of preventing a decrease in weld metal elongation caused by hydrogen. Therefore, when B is contained in the welding wire to achieve this effect, the B-converted value of metallic B and B compounds in the welding wire is preferably 0.005% by mass or more relative to the total mass of the welding wire.

[0087] The B conversion value is the total conversion value of elemental B, B alloys, and B compounds contained in the welding wire converted into B. Examples of B compounds include oxides such as B2O3, and examples of B alloys include Fe—B alloys.

[0088] <Ti: 0.50 mass % or less (including 0 mass %)>

[0089] Ti, as a deoxidizing component, reduces the amount of dissolved oxygen in the molten metal, inhibits the "C + O = CO (gas)" reaction, and reduces the amount of pores. However, excessive addition can degrade hot cracking resistance. A Ti content of 0.50% by mass or less in the welding wire relative to the total mass of the wire can reduce the amount of pores and maintain excellent hot cracking resistance. Therefore, the Ti content in the welding wire is preferably 0.50% by mass or less, more preferably 0.40% by mass or less, and even more preferably 0.30% by mass or less, and may be 0% by mass. Examples of Ti sources include metallic Ti and Ti alloys (such as Fe-Ti alloys). In this embodiment, the Ti content refers to the Ti content of these metallic Ti and Ti alloys. Specifically, the Ti content refers to the Ti content derived from metallic Ti and Ti alloys that dissolve in sulfuric acid and does not include Ti in the form of oxides such as TiO2 that are insoluble in sulfuric acid.

[0090] <Al: 0.50 mass % or less (including 0 mass %)>

[0091] Al, as a deoxidizing component, reduces the amount of dissolved oxygen in the molten metal, inhibits the "C + O = CO (gas)" reaction, and reduces the amount of pores. However, excessive addition can degrade hot cracking resistance. An Al content of 0.50% by mass or less in the welding wire relative to the total mass of the wire can reduce pores and maintain excellent hot cracking resistance. Therefore, the Al content in the welding wire is preferably 0.50% by mass or less, more preferably 0.40% by mass or less, even more preferably 0.30% by mass or less, and particularly preferably 0.20% by mass or less. It can also be 0% by mass.

[0092] Examples of Al sources include metallic Al and Al alloys (e.g., Fe-Al alloys). In this embodiment, the Al content refers to the value obtained by converting the contents of the aforementioned metallic Al and Al alloys into Al. Specifically, the Al content refers to the Al content derived from metallic Al and Al alloys that dissolve in sulfuric acid and does not include Al in the form of oxides such as Al2O3 that are insoluble in sulfuric acid.

[0093] <Value A2 calculated by formula (2): 3.48 or less>

[0094] In this embodiment, by setting the value A2 calculated using the following formula (2) using the above components to 3.48 or less, slag removability and weld bead shape can be further improved, and the occurrence of weld defects such as pores and surface pits can be further suppressed. Therefore, the value A2 calculated using the following formula (2) is preferably 3.48 or less, more preferably 3.45 or less, and even more preferably 3.40 or less.

[0095] Formula (2): A2=([Al]+[Al2O3]+[TiO2]) / ([SiO2]+[ZrO2]×0.1)

[0096] Here, [Al] is the Al content in the welding wire expressed in mass % relative to the total mass of the welding wire, [Al2O3] is the Al2O3 content in the flux expressed in mass % relative to the total mass of the welding wire, [TiO2] is the TiO2 content in the flux expressed in mass % relative to the total mass of the welding wire, [SiO2] is the SiO2 equivalent value in the flux expressed in mass % relative to the total mass of the welding wire, and [ZrO2] is the ZrO2 equivalent value in the flux expressed in mass % relative to the total mass of the welding wire.

[0097] <Other ingredients and inevitable impurities>

[0098] The Ni-based alloy flux-cored welding wire of this embodiment preferably contains a total of 90% by mass or more of Mn, Ni, Cr, Mo, W, Fe, TiO2, SiO2 conversion value, ZrO2 conversion value, Al2O3, MnO2, and F, more preferably 93% by mass or more, even more preferably 95% by mass or more, and particularly preferably 98% by mass or more. Other components mentioned above, in addition to the preferred ranges of Na, K, Li, B, Ti, and Al mentioned above in this embodiment, also include C, Si, and Cu. Among these components, C is preferably limited to 0.10% by mass or less, Si is preferably limited to 1.0% by mass or less, and Cu is preferably limited to 0.5% by mass or less. Inevitable impurities include P, S, Co, and moisture. Among these inevitable impurities, P is preferably limited to 0.010% by mass or less, S is preferably limited to 0.010% by mass or less, Co is preferably limited to 1.0% by mass or less, and moisture is preferably limited to 0.10% by mass or less.

[0099] <Flux filling rate: 20% to 30% by mass>

[0100] Flux contains compounds such as oxides and fluorides in addition to metals and alloys. In this embodiment, the flux content relative to the total mass of the welding wire, i.e., the flux filling ratio, is not particularly limited. However, a flux filling ratio of 20% by mass or greater can suppress sagging of the molten metal and slag, improving welding workability. Therefore, the flux filling ratio is preferably 20% by mass or greater, and more preferably 21% by mass or greater. Furthermore, a flux filling ratio of 30% by mass or less can appropriately manage moisture absorption by the welding wire, achieving good resistance to porosity defects. Therefore, the flux filling ratio is preferably 30% by mass or less, and more preferably 28% by mass or less.

[0101] <Shell thickness, wire diameter, and shielding gas composition>

[0102] The sheath thickness and wire diameter of the Ni-based alloy flux-cored welding wire of this embodiment are not particularly limited, but are applicable to wires having diameters specified in welding material standards such as AWS and JIS, for example, 0.8 mm, 0.9 mm, 1.0 mm, 1.2 mm, 1.4 mm, and 1.6 mm.

[0103] In addition, as the protective gas composition, 100% CO 2 can be applied, but the effect of this embodiment can also be obtained by using a mixed gas of Ar and CO 2.

[0104] <Welding posture>

[0105] In this embodiment, there is no particular limitation on the welding posture when using the flux-cored wire. However, in this embodiment, since the viscosity of the molten pool is appropriately controlled, the flux-cored wire of this embodiment is particularly suitable for downward welding, horizontal welding, and horizontal fillet welding.

[0106] [Manufacturing method of flux-cored welding wire]

[0107] The method for producing the flux-cored welding wire of the present embodiment is not particularly limited, and the flux-cored welding wire can be produced, for example, by the method described below.

[0108] First, a metal strip forming a steel outer sheath is prepared and formed into a U-shaped open tube by forming rollers while being fed longitudinally. Next, a flux containing various raw materials blended to a predetermined composition is filled into the Ni-based alloy outer sheath, and then processed to form a circular cross-section. Afterwards, the wire is drawn through cold working to obtain a flux-cored wire of the desired diameter.

[0109] In addition, annealing can also be implemented during cold working. In addition, any of the following structures can be adopted: a seamless welding wire in which the seams of the Ni-based alloy outer skin formed during the manufacturing process are welded, and a welding wire in which the seams are not welded but the gaps are retained.

[0110] Example

[0111] Hereinafter, the present invention will be described in more detail with reference to inventive examples and comparative examples, but the present invention is not limited thereto.

[0112] [Manufacturing of Flux-Cored Wire]

[0113] First, a metal strip made of a Ni-based alloy with a thickness of 0.4 mm and a width of 9.0 mm was bent to form a Ni-based alloy sheath. This sheath was coated with a flux containing a metal raw material and slag components, and then drawn to a diameter of 1.2 mm to produce a flux-cored welding wire having the compositions shown in Tables 1 and 2 below. The flux ratio was 23% by mass.

[0114] In Table 2, the formula (1) represents A1 = [Na] + [K] + [Li]. [Na] represents the Na content in the welding wire expressed in mass % relative to the total mass of the welding wire, [K] represents the K content in the welding wire expressed in mass % relative to the total mass of the welding wire, and [Li] represents the Li content in the welding wire expressed in mass % relative to the total mass of the welding wire.

[0115] In addition, the so-called formula (2) represents A2=([Al]+[Al2O3]+[TiO2]) / ([SiO2]+[ZrO2]×0.1).

[0116] Here, [Al] is the Al content in the welding wire expressed in mass % relative to the total mass of the welding wire, [Al2O3] is the Al2O3 content in the flux expressed in mass % relative to the total mass of the welding wire, [TiO2] is the TiO2 content in the flux expressed in mass % relative to the total mass of the welding wire, [SiO2] is the SiO2 equivalent value in the flux expressed in mass % relative to the total mass of the welding wire, and [ZrO2] is the ZrO2 equivalent value in the flux expressed in mass % relative to the total mass of the welding wire.

[0117] [Gas shielded arc welding]

[0118] Next, horizontal fillet welding and transverse welding were performed using the obtained flux-cored wire under the following conditions.

[0119] (Horizontal fillet weld)

[0120] A pair of 9% Ni steel plates with a thickness of 12 mm, a width of 80 mm, and a length of 300 mm were prepared. One plate was placed horizontally, with the end surface of the other plate butting against the top surface of the other plate. A T-joint was then produced by horizontal fillet welding the fillet weld formed between the two plates using an automated welding machine (PICOMAX (registered trademark)). The welding current was 200 A, the voltage was 30 V, the welding speed was 30 cm / min, and the shielding gas was 100% CO2 at a flow rate of 25 L / min.

[0121] (Horizontal welding)

[0122] A 20mm thick, 75mm wide, and 300mm long carbon steel (SM490A) steel plate was machined with a groove groove angled 35° upward and 25° downward from the surface, with a depth of 7mm and a bottom radius of curvature of 5mm. The groove was then semi-automatically filled with transverse groove filler welds (two layers and four passes). The welding current was 180A, the voltage was 28V, the welding speed was 15-65cm / min, and the shielding gas was 100% CO2 at a flow rate of 25L / min.

[0123] [Evaluation test]

[0124] The welded joints were subjected to various evaluation tests shown below. The evaluation results are shown in Table 2 below.

[0125] (Slag peeling properties)

[0126] The slag removability of T-joints produced by horizontal fillet welding was evaluated by observing the resulting welds. The evaluation criteria for slag removability were "◎" (Excellent) if the entire weld bead was covered with slag and easily removable. "○" (Good) if the weld could be used without any problems during normal removal. "X" (Poor) if the weld was difficult to remove.

[0127] (weld bead shape)

[0128] For T-joints produced by horizontal fillet welding, the weld bead shape on the joint surface was visually inspected. The weld bead shape was evaluated as "◎" (Excellent). A slightly convex weld bead was rated "○" (Good). Furthermore, welds with undercut or underfill were rated "X" (Poor).

[0129] (Surface pits)

[0130] For T-joints made with horizontal fillet welds, the weld bead surface was observed for pitting within a 300mm radius of the fixed area. The evaluation criteria for surface pitting were ◎ for no visible pitting, ○ for less than 10 pits (pass), and × for 10 or more pits (fail).

[0131] (Anti-porosity)

[0132] For joints created by transverse welding, the weld reinforcement was ground flat to the plate surface, and then the weld was evaluated for porosity resistance using an X-ray transmission test. The evaluation criteria for porosity resistance were: a weld with fewer than 15 pores of 0.6 mm or larger in diameter was rated "Excellent" (◎), a weld with 15 or more and fewer than 30 pores was rated "Good", and a weld with 30 or more pores was rated "Poor" (X).

[0133] The contents of the components shown in Tables 1 and 2 are expressed as mass % relative to the total mass of the welding wire, with the remainder consisting of C, metallic Si and Cu, and unavoidable impurities.

[0134]

Table 1

[0135]

[0136]

Table 2

[0137]

[0138] As shown in Tables 1 and 2 above, Inventive Examples Nos. 1 to 8 all achieved good or excellent evaluation results for slag removability, weld bead shape, surface pitting, and anti-porosity properties, as the components of the welding wire and flux were within the ranges specified by the present invention. In particular, Inventive Examples Nos. 1, 2, 3, 7, and 8 achieved excellent evaluation results for slag removability and weld bead shape, as the value A2 calculated using Equation (2) was within the preferred range.

[0139] On the other hand, in Comparative Example No. 1, since the MnO2 content in the flux was below the lower limit value specified in the present invention, the weld bead shape and surface pitting were poor.

[0140] In Comparative Examples No. 2 and 3, the MnO₂ content in the welding wire was below the lower limit specified by the present invention, resulting in poor weld bead shape and surface pitting. Furthermore, the F content exceeded the upper limit specified by the present invention, resulting in a significant amount of porosity.

[0141] In Comparative Example No. 4, the MnO2 content in the flux was lower than the lower limit specified in the present invention, and the slag peeling properties and surface pitting were poor.

[0142] In Comparative Example No. 5, the MnO2 content in the flux was lower than the lower limit specified in the present invention, and the slag removability was poor.

[0143] In Comparative Example No. 6, since the SiO2 content and the MnO2 content in the flux were below the lower limits specified in the present invention, the slag peeling property, the weld bead shape, and the surface pitting were poor.

[0144] In Comparative Example No. 7, the slag detachability was poor because the MnO2 content in the flux exceeded the upper limit specified in the present invention.

[0145] As described in detail above, according to the present invention, by adjusting the flux composition to a specific range, the viscosity of the molten pool and slag can be appropriately maintained, particularly in horizontal welding, downward welding, and fillet welding postures. This results in a Ni-based alloy flux-cored welding wire that produces a weld metal with excellent slag stripping properties and weld bead shape, while suppressing the occurrence of weld defects such as porosity and surface pitting.

Claims

1. A Ni-based alloy flux-cored welding wire, characterized in that: It is a Ni-based alloy flux-cored wire with a Ni-based alloy sheath filled with flux. Relative to the total mass of welding wire, Ni: 39 mass% or more and 59 mass% or less, Cr: 5 mass% or more and 20 mass% or less, Mo: 10 mass% or more and 20 mass% or less, W: 1.0 mass % or more and 5.0 mass % or less, Mn: 0.1 mass% or more and 5 mass% or less, Fe: 3.0 mass% or more and 10.0 mass% or less, TiO2: 3.0% by mass or more and 10.0% by mass or less, SiO2 conversion value of metal Si and Si oxide: 1.0 mass% or more and 3.0 mass% or less, ZrO2 conversion value of metal Zr and Zr oxide: 1.0 mass % or less, Al2O3: 0.2 mass% or more and 1.2 mass% or less, MnO2: 0.2 mass% or more and 1.6 mass% or less, Furthermore, F: 0.07 mass % or less.

2. The Ni-based alloy flux-cored welding wire according to claim 1, characterized in that: When at least one selected from Na, K and Li is contained, the value A1 calculated by the following formula (1) is 0.70 or less, Formula (1): A1=[Na]+[K]+[Li] Here, [Na] represents the Na content in the welding wire expressed in mass % relative to the total mass of the welding wire, [K] represents the K content in the welding wire expressed in mass % relative to the total mass of the welding wire, and [Li] represents the Li content in the welding wire expressed in mass % relative to the total mass of the welding wire.

3. The Ni-based alloy flux-cored welding wire according to claim 1, characterized in that: The B conversion value of the metal B and B compounds contained relative to the total mass of the welding wire is: 0.030 mass % or less.

4. The Ni-based alloy flux-cored welding wire according to claim 1, characterized in that: The welding wire contains 0.50 mass % or less of Ti and 0.50 mass % or less of Al relative to the total mass of the welding wire.

5. The Ni-based alloy flux-cored welding wire according to claim 1, characterized in that: The value A2 calculated by the following formula (2) is 3.48 or less, Formula (2): A2=([Al]+[Al2O3]+[TiO2]) / ([SiO2]+[ZrO2]×0.1) Here, [Al] is the Al content in the welding wire expressed in mass % relative to the total mass of the welding wire, [Al2O3] is the Al2O3 content expressed in mass % relative to the total mass of the welding wire, [TiO2] is the TiO2 content expressed in mass % relative to the total mass of the welding wire, [SiO2] is the SiO2 equivalent value expressed in mass % relative to the total mass of the welding wire, and [ZrO2] is the ZrO2 equivalent value expressed in mass % relative to the total mass of the welding wire.

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