Wire for gas-shielded arc welding, gas-shielded arc welding method, and method for manufacturing weld metal

Abstract

Provided is a wire for gas-shielded arc welding that enables the obtainment of weld metal with excellent tensile strength and low-temperature toughness. In the wire for gas-shielded arc welding, the C content is 0.040 mass% or more and 0.090 mass% or less with respect to the total mass of the wire, the contents of Si, Mn, Ti, Ni, Fe, Cr, Mo, and Cu are specified, and when the content of each element with respect to the total mass of the wire is expressed in mass% by [C], [Si], [Mn], [Ti], [Ni], [Cr], [Mo], and [Cu], the value A1 calculated by the following formula (1) is 4.05 or more, and the value A2 calculated by the following formula (2) is 0.45 or more. Formula (1): A1 = [Mn] + [Ni]; Formula (2): A2 = -[C] + [Si] / 7 + [Mn] / 7 + [Ti] / 4 + [Ni] / 38 + [Cr] / 8 + [Mo] / 5 + [Cu] / 15

Description

Gas-shielded arc welding wire, gas-shielded arc welding method, and method for producing weld metal

[0001] The present invention relates to a gas-shielded arc welding wire used for arc welding of high-tensile steel, a gas-shielded arc welding method using the welding wire, and a method for producing weld metal using the welding wire.

[0002] Welded structures, such as marine structures used in oil and gas drilling and production, offshore wind power generation, and pipelines used in oil and gas transportation, are becoming larger and are increasingly being operated in cold regions. Therefore, the steel plates used in these welded structures are becoming stronger, and therefore the welding materials used are also required to have high strength and excellent toughness at low temperatures.

[0003] Furthermore, in recent years, when manufacturing such welded structures, there has been a trend toward welding under welding conditions of high current and high heat input in order to improve the efficiency of the welding work. Under such high heat input conditions, the strength of the weld metal decreases and the impact properties also deteriorate. Therefore, there is an increasing demand for technology that can obtain welds with excellent properties even when welding is performed under severe welding conditions, and in particular, there is a growing need for welding materials that can improve the properties of welds.

[0004] For example, Patent Document 1 proposes a metal-based flux-cored wire that specifies the contents of C, Si, Mn, S, and P relative to the total mass of the wire, as well as the converted values ​​of metal fluorides, Na oxide, and K oxide in the flux. Patent Document 1 describes that by limiting the above components, it is possible to obtain a metal-based flux-cored wire for welding that is excellent in welding workability, weather defect resistance, and crack resistance, and that produces a weld metal with good mechanical properties.

[0005] Furthermore, Patent Document 2 discloses a gas metal arc welding wire for high-tensile steel, which contains C, Si, Mn, Cu, Ni, Cr, Mo, V, Nb, and Ti relative to the total weight of the wire, limits P, S, Al, N, and O, and regulates the total amount of Ca, Mg, and As. According to Patent Document 2, it is possible to obtain a wire that has yield strength and toughness equal to or greater than those of the high-tensile steel base material, is free from defects due to sulfides, and has good workability.

[0006] Japanese Unexamined Patent Publication No. 2023-114400 Japanese Unexamined Patent Publication No. 8-267273

[0007] However, when welding is performed using the flux-cored wire described in Patent Document 1, the tensile strength of the deposited metal is 540 to 680 MPa, which is insufficient. Furthermore, the gas metal arc welding wire described in Patent Document 2 contains predetermined amounts of Nb and V to improve strength and yield strength, and also contains a large amount of Cr, which results in excessively high tensile strength, raising concerns about hot cracking, and making it difficult to obtain a deposited metal with sufficient toughness.

[0008] The present invention has been made in view of the above-mentioned problems, and has an object to provide a gas-shielded arc welding wire that can be suitably used in gas-shielded arc welding of high-tensile steel and that can produce a weld metal that has good tensile strength and toughness at low temperatures, a gas-shielded arc welding method using the welding wire, and a method for producing a weld metal using the welding wire.

[0009] The above object of the present invention is achieved by the following configuration [1] relating to a wire for gas-shielded arc welding.

[0010] [1] The wire contains, relative to the total mass of the wire, C: 0.040 mass% or more and 0.090 mass% or less, Si: 0.40 mass% or more and 0.90 mass% or less, Mn: 1.35 mass% or more and 2.80 mass% or less, Ti: 0.05 mass% or more and 0.40 mass% or less, Ni: 1.80 mass% or more and 3.70 mass% or less, and Fe: 88.0 mass% or more, Cr: 0.60 mass% or less (including 0 mass%), Mo: 0.90 mass% or less (including 0 mass%), Cu: 0.50 mass% or less (including 0 mass%), 1. A gas-shielded arc welding wire characterized in that, when the C content relative to the total mass of the wire is expressed as [C] in mass%, the Si content relative to the total mass of the wire is expressed as [Si] in mass%, the Mn content relative to the total mass of the wire is expressed as [Mn] in mass%, the Ti content relative to the total mass of the wire is expressed as [Ti] in mass%, the Ni content relative to the total mass of the wire is expressed as [Ni] in mass%, the Cr content relative to the total mass of the wire is expressed as [Cr] in mass%, the Mo content relative to the total mass of the wire is expressed as [Mo], and the Cu content relative to the total mass of the wire is expressed as [Cu] in mass%, wherein the value A1 calculated by the following formula (1) is 4.05 or more, and the value A2 calculated by the following formula (2) is 0.45 or more. A1=[Mn]+[Ni]...Formula (1) A2=-[C]+[Si] / 7+[Mn] / 7+[Ti] / 4+[Ni] / 38+[Cr] / 8+[Mo] / 5+[Cu] / 15...Formula (2)

[0011] Furthermore, preferred embodiments of the present invention relating to the wire for gas-shielded arc welding relate to the following [2] to [6].

[0012] [2] The wire for gas-shielded arc welding according to [1], characterized in that the value A3 calculated by the following formula (3) is 5.0 or less: A3 = [Ti] / [C] Formula (3)

[0013] [3] The gas-shielded arc welding wire according to [1], characterized in that the value A4 calculated by the following formula (4) is 28.5 or less: A4 = 52.8 × [C] + 26.3 × [Si] + 0.5 × [Mn] + 13.4 × [Ti] + 1.1 × [Ni] + 2.1 × [Cr] + 0.9 × [Mo] + 1.5 × [Cu] ... formula (4)

[0014] [4] The wire for gas-shielded arc welding according to [1], characterized in that the value A3 calculated by the following formula (3) is 5.0 or less, and the value A4 calculated by the following formula (4) is 28.5 or less: A3 = [Ti] / [C] Formula (3) A4 = 52.8 × [C] + 26.3 × [Si] + 0.5 × [Mn] + 13.4 × [Ti] + 1.1 × [Ni] + 2.1 × [Cr] + 0.9 × [Mo] + 1.5 × [Cu] Formula (4)

[0015] [5] The gas-shielded arc welding wire according to any one of [1] to [4], further comprising at least one element selected from Na, K, and Li, wherein the value A5 calculated by the following formula (5) is 0.80 or less, where [Na] is the Na content relative to the total mass of the wire in mass%, [K] is the K content relative to the total mass of the wire in mass%, and [Li] is the Li content relative to the total mass of the wire in mass%. A5: [Na] + [K] + [Li] Formula (5)

[0016] [6] The wire for gas-shielded arc welding according to any one of [1] to [5], further comprising F: 0.30 mass % or less.

[0017] The above object of the present invention is also achieved by the gas-shielded arc welding method according to the following item [7].

[0018] [7] A gas-shielded arc welding method, characterized by welding using the gas-shielded arc welding wire according to any one of [1] to [6].

[0019] The above object of the present invention is also achieved by the following configuration [8] relating to a method for producing a weld metal.

[0020] [8] A method for producing a weld metal, characterized in that the weld metal is produced using the gas-shielded arc welding wire according to any one of [1] to [6].

[0021] According to the present invention, it is possible to provide a gas-shielded arc welding wire that can be suitably used in gas-shielded arc welding of high-tensile steel and that can produce a weld metal that has good tensile strength and toughness at low temperatures, a gas-shielded arc welding method using the welding wire, and a method for producing a weld metal using the welding wire.

[0022] The present inventors conducted extensive research to obtain weld metal with good tensile strength and low-temperature toughness. However, since toughness generally depends on strength, and the higher the strength, the more difficult it is to achieve both strength and low-temperature toughness. Therefore, it was difficult to solve the above problem by simply adjusting the content of specific elements in the wire. Therefore, the present inventors discovered that the desired strength of the weld metal can be maintained by appropriately controlling the value calculated by a specific formula using the content of elements in the wire. Furthermore, the present inventors discovered that the low-temperature toughness of the weld metal can be improved by appropriately controlling the total value of the Mn content and Ni content in the wire. That is, by controlling the value calculated by the below-described formula (1) and the total value of the Mn content and Ni content based on the content of elements in the wire, a weld metal having both high strength and low-temperature toughness can be obtained.

[0023] Hereinafter, an embodiment for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described. Note that the present invention is not limited to the embodiment described below, and can be carried out with any modifications within the scope of the gist of the present invention.

[0024] [Gas-Shielded Arc Welding Wire] The gas-shielded arc welding wire according to the present embodiment may be a flux-cored wire or a solid wire. In this specification, these may be collectively referred to simply as a wire. The flux-cored wire is a steel sheath (hereinafter simply referred to as the sheath) filled with flux, and its outer diameter is preferably, for example, 0.9 mm or more and 1.6 mm or less. The flux filling rate can be set to any value as long as the content of each element in the wire falls within the range of the present invention. However, from the viewpoint of wire drawability and wire feedability, it is preferably, for example, 6 mass % or more and 20 mass % or less with respect to the total mass of the wire. The wire may have a seam in the sheath, or may have no seam, and there are no limitations on the shape of the seam or the cross-sectional shape of the wire.

[0025] The solid wire generally refers to a wire having a solid cross section and a homogeneous cross section, and the wire surface may be copper-plated to improve the electrical conductivity of the wire during welding. In this embodiment, the outer diameter of the solid wire and whether or not the wire surface is plated are not particularly limited, but the outer diameter is preferably, for example, 0.9 mm or more and 1.6 mm or less.

[0026] The elements contained in the wire according to this embodiment and the reasons for limiting the contents thereof will be described in detail below. When the wire according to this embodiment is a flux-cored wire, the elements described below may be contained in either the sheath or the flux, or may be contained in both the steel sheath and the flux. In this case, the content of each element in the wire refers to the content of the element in mass % relative to the total mass of the steel sheath and the flux. When the wire according to this embodiment is a solid wire, the elements described below may be contained in either the bulk of the wire or the copper plating, or may be contained in both the bulk of the wire and the copper plating. In this case, the content of each element in the wire refers to the content of the element in mass % relative to the total mass of the bulk of the wire and the copper plating.

[0027] Furthermore, unless otherwise specified, each element defined in this embodiment may be contained in the wire in the form of a metal, in the form of a compound, or in the form of both a metal and a compound. Therefore, regardless of the form in which each element is contained in the wire, it is defined as a value converted into a single element. For example, in the case of Si, the Si content refers to the sum of the Si-converted values ​​of metal Si and Si compounds. Note that metal Si includes both simple Si and Si alloys.

[0028] <C: 0.040% by Mass or More and 0.090% by Mass or Less> C is an element that has the effect of improving the strength of the weld metal. If the C content is less than 0.040% by mass, the desired strength of the weld metal cannot be obtained. Therefore, the C content relative to the total mass of the wire is set to 0.040% by mass or more, preferably 0.045% by mass or more, and more preferably 0.050% by mass or more. On the other hand, if the C content exceeds 0.090% by mass, coarsening of grain boundary carbides is promoted, and toughness at low temperatures is reduced. Therefore, the C content relative to the total mass of the wire is set to 0.090% by mass or less, preferably 0.080% by mass or less, more preferably 0.075% by mass or less, and even more preferably 0.070% by mass or less.

[0029] <Si: 0.40% by mass or more and 0.90% by mass or less> Si is an element that ensures the toughness of the weld metal and has the effect of improving its strength. If the Si content is less than 0.40% by mass, the desired strength and toughness of the weld metal cannot be obtained. Therefore, the Si content relative to the total mass of the wire is set to 0.40% by mass or more, preferably 0.43% by mass or more, and more preferably 0.48% by mass or more. On the other hand, if the Si content exceeds 0.90% by mass, a coarse ferrite structure is formed, making it impossible to stably obtain the toughness of the weld metal at low temperatures. Therefore, the Si content relative to the total mass of the wire is set to 0.90% by mass or less, preferably 0.80% by mass or less, more preferably 0.75% by mass or less, and even more preferably 0.70% by mass or less.

[0030] <Mn: 1.35% by Mass or More and 2.80% by Mass or Less> Mn is an element that has the effect of improving the strength and toughness at low temperatures of the weld metal. If the Mn content is less than 1.35% by mass, the desired strength of the weld metal cannot be obtained. Therefore, the Mn content relative to the total mass of the wire is set to 1.35% by mass or more, preferably 1.50% by mass or more, more preferably 1.85% by mass or more, and even more preferably 2.00% by mass or more. On the other hand, if the Mn content exceeds 2.80% by mass, the strength of the weld metal increases excessively and the toughness at low temperatures decreases. Therefore, the Mn content relative to the total mass of the wire is set to 2.80% by mass or less. Note that in order to suppress the occurrence of intergranular fracture in a structure mainly composed of the original material region in the weld metal and further improve the toughness at low temperatures, the Mn content relative to the total mass of the wire is preferably 2.70% by mass or less, more preferably 2.60% by mass or less.

[0031] <Ti: 0.05% by Mass or More and 0.40% by Mass or Less> Ti is an element that forms a complex oxide mainly composed of Ti in the weld metal, and acicular ferrite is formed from this complex oxide, thereby promoting the refinement of the weld metal microstructure. Therefore, by including Ti in the wire, the strength of the weld metal can be maintained while improving its toughness. If the Ti content is less than 0.05% by mass, the desired strength of the weld metal cannot be obtained. Therefore, the Ti content relative to the total mass of the wire is set to 0.05% by mass or more, preferably 0.10% by mass or more, and more preferably 0.15% by mass or more. On the other hand, if the Ti content exceeds 0.40% by mass, the grain boundaries become embrittled and the toughness decreases. Therefore, the Ti content relative to the total mass of the wire is set to 0.40% by mass or less, preferably 0.35% by mass or less, and more preferably 0.30% by mass or less.

[0032] <Ni: 1.80 mass% or more and 3.70 mass% or less> When the wire contains Ni, the parent phase is strengthened, thereby improving the toughness of the weld metal at low temperatures. If the Ni content is less than 1.80 mass%, the weld metal cannot achieve the desired toughness at low temperatures. Therefore, the Ni content relative to the total mass of the wire is set to 1.80 mass% or more, preferably 2.00 mass% or more, and more preferably 2.30 mass% or more. On the other hand, if the Ni content exceeds 3.70 mass%, hot cracking is likely to occur. Therefore, the Ni content relative to the total mass of the wire is set to 3.70 mass% or less, preferably 3.50 mass% or less, more preferably 3.10 mass% or less, and even more preferably 2.80 mass% or less.

[0033] <Fe: 88.0 mass% or more> Fe is a main component of the wire according to this embodiment. From the viewpoint of ensuring the deposition amount of the wire, in this embodiment, the Fe content relative to the total mass of the wire is 88.0 mass% or more, preferably 90.0 mass% or more, more preferably 92.0 mass% or more, and even more preferably 93.2 mass% or more.

[0034] <Cr: 0.60 mass% or less (including 0 mass%)> The inclusion of Cr in the wire can enhance hardenability and improve the strength of the weld metal. In this embodiment, Cr need not be contained in the wire, or even 0 mass%, as long as the strength of the weld metal can be ensured by adjusting the contents of other elements and controlling the value A2 calculated by Equation (2) described below. However, since Cr also has the effect of improving the strength of the weld metal, when Cr is contained in the wire for the purpose of improving strength, the Cr content relative to the total mass of the wire is preferably 0.20 mass% or more, and more preferably 0.30 mass% or more. On the other hand, when the Cr content exceeds 0.60 mass%, the strength of the weld metal increases excessively, making it impossible to obtain the desired low-temperature toughness of the weld metal. Therefore, when Cr is contained in the wire according to this embodiment, the Cr content relative to the total mass of the wire is set to 0.60 mass% or less, preferably 0.55 mass% or less, and more preferably 0.50 mass% or less.

[0035] <Mo: 0.90% by Mass or Less (Including 0% by Mass)> The inclusion of Mo in the wire can provide the effect of improving the strength of the weld metal. In this embodiment, Mo need not be contained in the wire, or may be 0% by mass, as long as the strength of the weld metal can be ensured by adjusting the contents of other elements and controlling the value A2 calculated by Equation (2) described below. However, when Mo is contained in the wire for the purpose of improving the strength of the weld metal, the Mo content relative to the total mass of the wire is preferably 0.05% by mass or more, and more preferably 0.10% by mass or more. On the other hand, if the Mo content exceeds 0.90% by mass, the strength of the weld metal increases excessively, making it impossible to obtain the desired low-temperature toughness of the weld metal. Therefore, when Mo is contained in the wire according to this embodiment, the Mo content relative to the total mass of the wire is set to 0.90% by mass or less, preferably 0.80% by mass or less, more preferably 0.40% by mass or less, and even more preferably 0.15% by mass or less.

[0036] <Cu: 0.50% by Mass or Less (Including 0% by Mass)> When the wire contains Cu, the strength of the weld metal can be maintained and the matrix can be strengthened, thereby improving toughness at low temperatures. In this embodiment, Cu need not be contained in the wire, or even 0% by mass, as long as the strength of the weld metal can be ensured by adjusting the contents of other elements and controlling the value A2 calculated by Equation (2) described below. However, when Cu is contained in the wire, the effect of improving electrical conductivity during welding can be obtained. Therefore, when Cu is contained in the wire for the purpose of improving electrical conductivity, the Cu content relative to the total mass of the wire is preferably 0.15% by mass or more, and more preferably 0.20% by mass or more. Note that the presence of Cu in the coating layer further improves the electrical conductivity of the wire. Therefore, when Cu is contained in the wire according to this embodiment, it is preferable that at least a portion of the Cu content is present in the Cu coating layer of the wire. On the other hand, when the Cu content exceeds 0.50% by mass, the risk of cracking the weld metal due to solidification segregation increases. Therefore, when Cu is contained in the wire according to this embodiment, the Cu content relative to the total mass of the wire is 0.50 mass% or less, preferably 0.40 mass% or less, and more preferably 0.15 mass% or less.

[0037] Furthermore, in the wire according to this embodiment, the toughness and strength of the weld metal can be ensured by controlling the values ​​calculated by a predetermined formula based on the contents of the contained elements. The formula for ensuring the toughness and strength of the weld metal and the range of values ​​obtained by this formula will be described in detail below. In this specification, the C content relative to the total mass of the wire is expressed as [C] in mass%, the Si content relative to the total mass of the wire is expressed as [Si] in mass%, the Mn content relative to the total mass of the wire is expressed as [Mn] in mass%, the Ti content relative to the total mass of the wire is expressed as [Ti] in mass%, the Ni content relative to the total mass of the wire is expressed as [Ni] in mass%, the Cr content relative to the total mass of the wire is expressed as [Cr] in mass%, the Mo content relative to the total mass of the wire is expressed as [Mo] in mass%, and the Cu content relative to the total mass of the wire is expressed as [Cu] in mass%. Furthermore, as will be described in detail later, the wire according to this embodiment preferably contains at least one element selected from F, Na, K, and Li in a range that satisfies the predetermined formula or the predetermined content in the wire. Therefore, in this specification, the F content relative to the total mass of the wire will be expressed as [F] in mass%, the Na content relative to the total mass of the wire will be expressed as [Na] in mass%, the K content relative to the total mass of the wire will be expressed as [K] in mass%, and the Li content relative to the total mass of the wire will be expressed as [Li] in mass%.

[0038] <Value A1 calculated by formula (1): 4.05 or more> In the wire according to this embodiment, it is important to specify the total value of the Mn content and the Ni content as well as the contents of the above-mentioned elements. That is, the inventors have found that the toughness of the weld metal at low temperatures can be improved by appropriately controlling the value A1 calculated by formula (1), which is the total value of the Mn content and the Ni content, while controlling the contents of the above-mentioned elements.

[0039] If the value A1 calculated by formula (1) is less than 4.05, the desired low-temperature toughness of the weld metal cannot be obtained; for example, the toughness at −40° C. will be less than the desired value of 62 J. Therefore, the value A1 calculated by formula (1) is set to 4.05 or more, preferably 4.20 or more, more preferably 4.50 or more, and even more preferably 4.70 or more. In the present embodiment, the upper limit of the value A1 calculated by formula (1) is not particularly limited, but if the value A1 is 6.00 or less, the risk of cracking of the weld metal is reduced. Therefore, the value A1 calculated by formula (1) is preferably 6.00 or less, more preferably 5.50 or less, and even more preferably 5.30 or less.

[0040] A1 = [Mn] + [Ni] Formula (1)

[0041] <Value A2 Calculated by Equation (2): 0.45 or More> In the wire according to this embodiment, it is important to specify the contents of the above elements and also to control the value calculated by the equation based on the C content, Si content, Mn content, Ti content, Ni content, Cr content, Mo content, and Cu content in the wire. The inventors have found that there is a good correlation between the value A2 calculated by the following equation (2) based on the contents of the above elements and the strength of the weld metal. That is, equation (2) shown below is an equation obtained by parameterizing the relationship between the elements that affect the strength of the weld metal and the strength of the weld metal through multiple regression analysis.

[0042] A2=-[C]+[Si] / 7+[Mn] / 7+[Ti] / 4+[Ni] / 38+[Cr] / 8+[Mo] / 5+[Cu] / 15...Formula (2)

[0043] If the value A2 calculated by the above formula (2) is less than 0.45, the desired strength of the weld metal cannot be obtained, and for example, the strength will be less than the desired value of 720 MPa. Therefore, the value A2 calculated by the above formula (2) is set to 0.45 or more. Furthermore, by setting the value A2 to 0.49 or more, the strength of the weld metal can be set to 780 MPa or more. Therefore, the value A2 obtained by the above formula (2) is preferably 0.49 or more, and even more preferably 0.51 or more. Meanwhile, in this embodiment, the upper limit of the value A2 calculated by the above formula (2) is not particularly specified, but it is preferably 0.70 or less, taking into consideration the balance between the strength and toughness of the weld metal.

[0044] Furthermore, with the wire according to this embodiment, a weld metal having an excellent balance between strength and toughness can be obtained by controlling the values ​​calculated by the following formulas (3) and (4) based on the content of each element. The weld metal having an excellent balance between strength and toughness preferably has a strength of 750 to 900 MPa and a toughness of 70 to 120 J, for example.

[0045] <Value A3 calculated by Equation (3): 5.0 or less> By appropriately controlling the Ti content and C content in the wire, the structure in the weld metal is refined, thereby improving the toughness while maintaining the strength of the weld metal. When the value calculated by the following Equation (3) is 5.0 or less, a weld metal can be obtained in which the toughness of the weld metal falls within a particularly preferable range. Therefore, the value A3 calculated by Equation (3) is preferably 5.0 or less, and more preferably 4.0 or less. Meanwhile, in the present embodiment, the lower limit of the value A3 calculated by the following Equation (3) is not specified, but is preferably 0.556 or more, taking into account the Ti content and C content in the wire according to the present embodiment.

[0046] A3=[Ti] / [C]...Formula (3)

[0047] <Value A4 calculated by Formula (4): 28.5 or less> When the value A4 calculated by the following formula (4) is 28.5 or less, it is possible to obtain a weld metal that falls within the above-mentioned preferred range, particularly without excessively increasing the strength of the weld metal. Therefore, the value A4 calculated by Formula (4) is preferably 28.5 or less, and more preferably 27.0 or less. Meanwhile, in the present embodiment, the lower limit of the value A4 calculated by the following formula (4) is not particularly specified, but is preferably 18.0 or more, taking into consideration the balance between the strength and toughness of the weld metal.

[0048] A4=52.8×[C]+26.3×[Si]+0.5×[Mn]+13.4×[Ti]+1.1×[Ni]+2.1×[Cr]+0.9×[Mo]+1.5×[Cu]...Formula (4)

[0049] The present invention aims to achieve desired strength and toughness, but toughness depends on the strength value, and the balance between strength and toughness may vary depending on the target strength. For example, when designed to a certain strength, toughness may be good, but when the target strength is increased and the design is remade, toughness may become extremely poor. This is because the elements contained in the wire and the balance of the contents of each element change depending on the target strength, which affects the weld metal structure. In this embodiment, the ratio of the desired strength (720 MPa) to the desired toughness value (62 J) of the weld metal at −40° C. is used as an indicator of the balance between strength and toughness. That is, when the tensile strength (TS) of the weld metal is represented as [TS] (MPa) and the impact value (IV) indicating the toughness at −40° C. is represented as [IV] (J), if [TS] / [IV] is 11.6 or less, it is possible to ensure excellent toughness relative to strength, and it can be determined that the balance between strength and toughness is extremely excellent.

[0050] When the value A3 calculated by the above formula (3) is 5.0 or less and the value A4 calculated by the formula (4) is 28.5 or less, [TS] / [IV] can be controlled to 11.6 or less, and a weld metal having an even better balance between strength and toughness while maintaining the desired strength and toughness can be obtained.

[0051] The wire according to the present embodiment preferably further contains at least one element selected from F, Na, K, and Li. The preferred contents of these elements and the reasons for limiting them will be described in detail below. In this specification, when the wire contains at least one element selected from Na, K, and Li, the Na content relative to the total mass of the wire will be expressed as [Na] in mass%, the K content relative to the total mass of the wire will be expressed as [K] in mass%, and the Li content relative to the total mass of the wire will be expressed as [Li] in mass%.

[0052] <F: 0.30% by mass or less> Including F in the wire can reduce diffusible hydrogen in the weld metal and suppress the amount of spatter generated, thereby improving arc stability. The F content in the wire may be 0% by mass. However, when F is included in the wire to improve arc stability, the F content relative to the total mass of the wire is preferably 0.005% by mass or more, and more preferably 0.010% by mass or more. Note that, depending on the elements contained in the wire, if the F content is too high, the arc may become unstable and spatter may increase. Therefore, the F content relative to the total mass of the wire is preferably 0.30% by mass or less, and more preferably 0.15% by mass or less.

[0053] <Value A5 Calculated by Formula (5): 0.80 or Less> Alkali metals such as Na, K, and Li, like F, are elements that have the effect of stabilizing the arc. Therefore, in this embodiment, in order to improve arc stability, it is preferable that the wire contains at least one element selected from F, Na, K, and Li. The preferred content of F when contained in the wire is as described above. However, for Na, K, and Li, specifying the total amount thereof can further improve arc stability. The contents of Na, K, and Li in the wire may each be 0 mass%. However, when at least one of Na, K, and Li is contained in the wire to improve arc stability, the total amount thereof, i.e., the value A5 calculated by the following formula (5), is preferably 0.005 or more, more preferably 0.010 or more. Note that, depending on the elements contained in the wire, if the total content of Na, K, and Li is too high, the arc may become unstable and spatter may increase. Therefore, the value A5 calculated by the formula (5) is preferably 0.80 or less, and more preferably 0.40 or less.

[0054] A5=[Na]+[K]+[Li]...Formula (5)

[0055] In addition to the above elements, the wire according to the present embodiment may contain Al, Mg, Zr, etc., within a range that does not impair the effects of the present invention. The preferred ranges of the contents of these elements and the reasons for their limitations will be further explained below.

[0056] <Al: 0.10% by mass or less (including 0% by mass)> Al is an element that may be contained in the wire as an inevitable impurity. However, since Al is also an element that has the effect of suppressing deterioration in the toughness of the weld metal, Al may be intentionally contained in the wire in this embodiment. If the effect of Al is to be obtained, the Al content relative to the total mass of the wire is preferably 0.005% by mass or more. However, because Al is a strong deoxidizing element, if the Al content in the wire increases, it may combine with oxygen in the weld metal to form coarse oxides, which may deteriorate the toughness. Therefore, when Al is contained in the wire, the Al content relative to the total mass of the wire is preferably suppressed to 0.10% by mass or less.

[0057] <Mg: 0.10% by mass or less (including 0% by mass)> Mg is an element that may be contained in the wire as an inevitable impurity. However, since Mg is also an element that has the effect of suppressing deterioration of the toughness of the weld metal, in this embodiment, Mg may be intentionally contained in the wire. If the effect of Mg is to be obtained, the Mg content relative to the total mass of the wire is preferably 0.005% by mass or more. However, because Mg is a strong deoxidizing element, if the Mg content in the wire increases, Mg may combine with oxygen in the weld metal to form coarse oxides, which may deteriorate the toughness. Therefore, when Mg is contained in the wire, the Mg content relative to the total mass of the wire is preferably suppressed to 0.10% by mass or less.

[0058] <Zr: 0.10% by mass or less (including 0% by mass)> Zr is an element that may be contained in the wire as an inevitable impurity. However, since Zr is also an element that has the effect of suppressing deterioration of the toughness of the weld metal, Zr may be intentionally contained in the wire in this embodiment. If the effect of Zr is to be obtained, the Zr content relative to the total mass of the wire is preferably 0.005% by mass or more. However, because Zr is a strong deoxidizing element, if the Zr content in the wire increases, Zr may combine with oxygen in the weld metal to form coarse oxides, which may deteriorate the toughness. Therefore, when Zr is contained in the wire, the Zr content relative to the total mass of the wire is preferably suppressed to 0.10% by mass or less.

[0059] <Other Elements> In the wire according to this embodiment, the remainder excluding the above elements is preferably unavoidable impurities. Examples of the unavoidable impurities include Al, Mg, Zr, Nb, V, W, Sn, Ca, B, P, S, O, and N. The content of each of these unavoidable impurities is preferably 0.0200 mass% or less, and more preferably 0.0100 mass% or less, relative to the total mass of the wire. Furthermore, the total content of these unavoidable impurities is preferably 0.5 mass% or less, relative to the total mass of the wire.

[0060] [Method for Manufacturing Gas-Shielded Arc Welding Wire] <Method for Manufacturing Flux-Cored Wire> When the wire according to the present embodiment is a flux-cored wire, the flux-cored wire can be manufactured, for example, by the following method. First, a steel strip constituting the outer sheath is formed by a forming roll while being fed in the longitudinal direction to form a U-shaped open tube. Next, the outer sheath is filled with a flux containing a metal or alloy, a compound, Fe powder, etc., so as to have a predetermined chemical composition, and then processed to have a circular cross section. The outer sheath can also be seamless by welding or the like. The wire is then drawn by cold working to a wire diameter of, for example, 1.0 mm or more and 2.0 mm or less. Annealing may be performed during the cold working. The problem of the present invention can be solved as long as the content of each element in the wire falls within the range specified in the present invention. Therefore, the mass fraction of the flux relative to the total mass of the wire, i.e., the flux filling rate, is not particularly limited. However, from the viewpoint of improving the stability of the wire components, the flux filling rate is preferably 6 mass% or more, and more preferably 7 mass% or more. Furthermore, since a high flux filling rate makes the wire more susceptible to breakage, the flux filling rate is preferably set to 20 mass % or less, and more preferably set to 15 mass % or less.

[0061] <Method for Manufacturing Solid Wire> When the wire according to this embodiment is a solid wire, the solid wire can be manufactured, for example, by the method described below. First, molten steel having a specified composition is produced using a converter, an electric furnace, or the like. The method for producing this molten steel is not limited to a specific technique. Next, a steel material such as a billet is produced from the obtained molten steel by a continuous casting method, an ingot casting method, or the like. Thereafter, the obtained steel material is heated, subjected to hot rolling, and further subjected to dry cold rolling and wire drawing to produce a steel strand. The operating conditions for the hot rolling and cold rolling are not limited to specific conditions, and may be any conditions that produce a steel strand having a desired size and shape. Furthermore, the steel strand is subjected to steps of annealing, pickling, wire drawing, and plating to obtain a desired product, i.e., a solid wire.

[0062] [Wire Type] In this embodiment, the type of wire is not limited as long as the contents of C, Si, Mn, Ti, Ni, Fe, Cr, Mo, and Cu in the wire are controlled within the specified ranges, and the value A1 calculated by formula (1) and the value A2 calculated by formula (2) are controlled within the specified ranges. However, since steel plates used in welded structures such as marine structures and pipelines are generally thick plates with thicknesses of approximately 50 to 200 mm and multi-layer welding is the norm, from the viewpoint of improving work efficiency, a welding material that produces very little welding slag and can reduce the work required for slag removal is required. Therefore, a low oxide content in the wire is preferable. Specifically, when the wire used in this embodiment is a flux-cored wire, it is preferable to use a metal-based flux-cored wire rather than a titania-based flux-cored wire. Furthermore, from the viewpoint of increasing the deposition rate and improving welding work efficiency, it is preferable to use a metal-based flux-cored wire rather than a solid wire. When the wire used in this embodiment is a metal-based flux-cored wire, the amount of oxygen relative to the total mass of the wire is preferably at the impurity level, for example, preferably 0.03 mass% or less, and more preferably 0.01 mass% or less.

[0063] Next, a gas-shielded arc welding method according to this embodiment will be described.

[0064] [Gas-Shielded Arc Welding Method] The gas-shielded arc welding method according to the present embodiment is a welding method using the gas-shielded arc welding wire described above. The welding conditions are not particularly limited except for the use of the wire according to the present embodiment, and the method can be used for welding a general type of base metal. For example, the base metal is preferably high-tensile steel used in large equipment or operation in cold climates. Furthermore, the welding voltage, welding current, welding position, and other conditions generally used in welding methods using gas-shielded arc welding wire can be used. The welding position is also not particularly limited. However, since the wire according to the present embodiment contains Ti, a strong deoxidizing element, the deoxidization of the molten metal progresses, forming an oxide film on the surface of the molten metal and reducing the drooping of the weld bead. Therefore, the gas-shielded arc welding method according to the present embodiment is particularly suitable for use in a horizontal welding position.

[0065] There is no particular limitation on the type of shielding gas. Generally, the mechanical properties of the weld metal are improved by adding CO to the shielding gas. ２ Or O ２ The more CO2 is contained, the more likely it is to deteriorate. ２ If weld metal with the desired mechanical properties can be formed in the gas, 80% Ar-20% CO ２ It is possible to produce weld metal with the desired mechanical properties even when using gas. On the other hand, since steel plates used in welded structures such as marine structures and pipelines are generally thick plates, from the viewpoint of obtaining deep penetration, it is preferable to use CO ２ In this embodiment, by using the above wire, it is possible to produce a weld metal that satisfies the desired mechanical properties, and in consideration of the penetration during welding, it is preferable that the content of CO in the shielding gas is high. ２ The content of CO is preferably high, and 100% CO ２ It is more preferable to use a gas.

[0066] Next, a method for producing a weld metal according to this embodiment will be described.

[0067] [Method for producing weld metal] The method for producing weld metal according to this embodiment is a method for producing weld metal using the gas-shielded arc welding wire according to the embodiment described above. In the method for producing weld metal according to this embodiment, the gas-shielded arc welding method is not particularly limited, and the gas-shielded arc welding method according to the embodiment described above can be applied.

[0068] The effects of the present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0069] [Wire Production] <Flux-cored Wire Production> A tubular sheath having a diameter of 1.2 mm was formed from carbon steel, and flux-cored wires of the invention examples and comparative examples having various compositions were produced by filling the sheath with flux. The mass fraction of the flux (flux filling rate) relative to the total mass of the wire was set to be in the range of 6 mass % to 10 mass %.

[0070] <Production of Solid Wire> Steel materials were produced from molten steel having various compositions, and the resulting steel materials were heated and then subjected to hot rolling, cold rolling, and wire drawing to produce steel strands. The steel strands were then subjected to processes such as annealing, pickling, wire drawing, and plating to produce solid wires having various compositions.

[0071] [Gas-shielded arc welding] Next, gas-shielded arc welding was carried out using the wires of the invention example and the comparative example, under the following welding conditions.

[0072] Base material: JIS G 3106:2017 SM490A Shielding gas type and flow rate: 100% CO ２ , 25 liters / min. Wire diameter: 1.2 mm Welding position: Downward Groove shape: V-shaped Groove angle: 20° Groove gap: 16 mm Welding current: 280 A ± 20 A Arc voltage: 29 V Welding speed: 250 to 450 mm / min. Preheat temperature: 140 to 160°C Interpass temperature: 140 to 160°C

[0073] [Evaluation of Weld Metal] The mechanical properties of the weld metal obtained by the above gas-shielded arc welding were evaluated in accordance with "Tensile and impact test methods for weld metal" specified in JIS Z 3111:2005, by taking tensile test pieces and impact test pieces from the as-welded weld metal and measuring the tensile strength and Charpy absorbed energy.

[0074] <Measurement and Evaluation of Tensile Strength> A tensile test was performed on each test piece at room temperature to measure the tensile strength. As the evaluation criteria for tensile strength, a tensile strength of 780 MPa or more was rated as A, which means excellent. A tensile strength of 720 MPa or more but less than 780 MPa was rated as B, which means good. Furthermore, a tensile strength of less than 720 MPa was rated as C, which means poor.

[0075] <Measurement of Toughness> An impact test was performed on each test piece at a test temperature of -40°C, and the Charpy absorbed energy was measured. Three test pieces were taken so that the notch position was at the center of the as-welded weld metal, and the Charpy absorbed energy was measured for each and the average was calculated. As a criterion for evaluating toughness, a Charpy absorbed energy of 90 J or more was rated as A, indicating that the toughness was excellent. A Charpy absorbed energy of 62 J or more but less than 90 J was rated as B, indicating that the toughness was good. Furthermore, a Charpy absorbed energy of less than 62 J was rated as C, indicating that the toughness was poor.

[0076] In this example, a wire having a tensile strength rating of A or B and a toughness rating of A or B was deemed to have passed, and a wire having either a rating of C was deemed to have failed. The types of wires and the elements and their contents contained in each wire of the invention examples and comparative examples are shown in Table 1 below, and the values ​​A1 to A5 calculated by formulas (1) to (5) and the evaluation results are shown in Table 2 below.

[0077] The remainder other than the wire elements shown in Table 1 below are inevitable impurities, and none of the wires in the invention examples and comparative examples contain K or Li. In Table 1 below, "-" indicates that the corresponding element is not intentionally included or is below the detection limit. In Table 2, "-" in formula (5) indicates that the element used to calculate formula (5) is not intentionally included or is below the detection limit, making it impossible to calculate.

[0078] In Table 2 below, formulas (1) to (5) are as follows: A1 = [Mn] + [Ni] (1) A2 = - [C] + [Si] / 7 + [Mn] / 7 + [Ti] / 4 + [Ni] / 38 + [Cr] / 8 + [Mo] / 5 + [Cu] / 15 (2) A3 = [Ti] / [C] (3) A4 = 52.8 x [C] + 26.3 x [Si] + 0.5 x [Mn] + 13.4 x [Ti] + 1.1 x [Ni] + 2.1 x [Cr] + 0.9 x [Mo] + 1.5 x [Cu] (4) A5: [Na] + [K] + [Li] (5)

[0079]

[0080]

[0081] As shown in Tables 1 and 2 above, in Invention Examples 1 to 14, the contents of each element in the wire were within the ranges specified by the present invention, and the values ​​A1 and A2 calculated by Formulas (1) and (2) were within the ranges specified by the present invention, so weld metals with good tensile strength and low-temperature toughness were obtained. In particular, in Invention Examples 1 to 12 and 14, the value A3 calculated by Formula (3) was within the preferred range specified by the present invention, so the weld metal toughness was even better. In addition, in Invention Examples 1 to 13, the value A4 calculated by Formula (4) was within the preferred range specified by the present invention, so excessively high tensile strength was prevented. Furthermore, in Invention Examples 1 to 12, the value A3 calculated by Formula (3) and the value A4 calculated by Formula (4) were both within the preferred ranges specified by the present invention, so the [TS] / [IV] value was 11.6 or less, and weld metals with an even better balance between strength and toughness were obtained.

[0082] On the other hand, in Comparative Examples 1 and 2, the value A2 calculated by formula (2) was less than the lower limit of the range specified in the present invention, and therefore the strength of the weld metal was reduced. In Comparative Example 3, the value A1 calculated by formula (1) was less than the lower limit of the range specified in the present invention, and therefore the Ni content in the wire was less than the lower limit of the range specified in the present invention, and therefore the toughness of the weld metal was reduced.

[0083] Although various embodiments have been described above, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above embodiments may be combined in any manner as long as they do not deviate from the spirit of the invention.

[0084] This application is based on a Japanese patent application (Patent Application No. 2023-196731) filed on November 20, 2023, the contents of which are incorporated herein by reference.

Claims

1. The wire contains, with respect to the total mass, C: 0.040 mass% or more and 0.090 mass% or less, Si: 0.40 mass% or more and 0.90 mass% or less, Mn: 1.35 mass% or more and 2.80 mass% or less, Ti: 0.05 mass% or more and 0.40 mass% or less, Ni: 1.80 mass% or more and 3.70 mass% or less, and Fe: 88.0 mass% or more, Cr: 0.60 mass% or less (including 0 mass%), Mo: 0.90 mass% or less (including 0 mass%), Cu: 0.50 mass% or less (including 0 mass%), A gas-shielded arc welding wire, characterized in that, when the C content relative to the total mass of the wire is expressed as [C] in mass%, the Si content relative to the total mass of the wire is expressed as [Si] in mass%, the Mn content relative to the total mass of the wire is expressed as [Mn] in mass%, the Ti content relative to the total mass of the wire is expressed as [Ti] in mass%, the Ni content relative to the total mass of the wire is expressed as [Ni] in mass%, the Cr content relative to the total mass of the wire is expressed as [Cr] in mass%, the Mo content relative to the total mass of the wire is expressed as [Mo] in mass%, and the Cu content relative to the total mass of the wire is expressed as [Cu] in mass%, the value A1 calculated by the following formula (1) is 4.05 or more, and the value A2 calculated by the following formula (2) is 0.45 or more. A1=[Mn]+[Ni]...Formula (1) A2=-[C]+[Si] / 7+[Mn] / 7+[Ti] / 4+[Ni] / 38+[Cr] / 8+[Mo] / 5+[Cu] / 15...Formula (2) 2. The wire for gas-shielded arc welding according to claim 1, characterized in that the value A3 calculated by the following formula (3) is 5.0 or less: A3 = [Ti] / [C] ... formula (3) 3. The wire for gas-shielded arc welding according to claim 1, characterized in that the value A4 calculated by the following formula (4) is 28.5 or less: A4 = 52.8 x [C] + 26.3 x [Si] + 0.5 x [Mn] + 13.4 x [Ti] + 1.1 x [Ni] + 2.1 x [Cr] + 0.9 x [Mo] + 1.5 x [Cu] ... formula (4) 4. The wire for gas-shielded arc welding according to claim 1, characterized in that the value A3 calculated by the following formula (3) is 5.0 or less, and the value A4 calculated by the following formula (4) is 28.5 or less: A3 = [Ti] / [C] ... formula (3) A4 = 52.8 x [C] + 26.3 x [Si] + 0.5 x [Mn] + 13.4 x [Ti] + 1.1 x [Ni] + 2.1 x [Cr] + 0.9 x [Mo] + 1.5 x [Cu] ... formula (4) 5. The wire for gas-shielded arc welding according to claim 1, further comprising at least one selected from Na, K and Li, wherein the value A5 calculated by the following formula (5) is 0.80 or less, where the Na content relative to the total mass of the wire is expressed as [Na] in mass%, the K content relative to the total mass of the wire is expressed as [K] in mass%, and the Li content relative to the total mass of the wire is expressed as [Li] in mass%. A5: [Na] + [K] + [Li] ... formula (5) 6. A gas-shielded arc welding wire according to claim 1, further comprising F: 0.30 mass % or less.

7. A gas-shielded arc welding method, comprising welding using the gas-shielded arc welding wire according to any one of claims 1 to 6.

8. A method for producing weld metal, comprising producing weld metal using the gas-shielded arc welding wire according to any one of claims 1 to 6.

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