Solid wire and method for producing weld joint

Abstract

This solid wire has a Vickers hardness Hv of 180-500, an fcc ratio of at least 70% as obtained by a magnetic induction method, and a chemical composition, in mass % with respect to the total mass of the solid wire, C: 0-0.650%, Si: 0.03-0.50%, Mn: 4.1-30.0%, P: 0.050% or less, S: 0.050% or less, Cu: 0-5.0%, Ni: 1.0-30.0%, Cr: 0-10.0%, Mo: 0-10.0%, Nb: 0-1.00%, V: 0-1.00%, Co: 0-1.00%, Pb: 0-1.00%, Sn: 0-1.000%, Al: 0-0.10%, Ti: 0-0.10%, Ta: 0-1.00%, Hf: 0-1.00%, W: 0-30.00%, Mg: 0-0.50%, REM: 0-0.50%, Zr: 0-5.00%, B: 0-0.1000%, N: 0-0.500%, and O: 0.0500% or less, with the balance being Fe and impurities.

Description

Method for manufacturing solid wire and welded joint

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to methods for manufacturing solid wire and weld joints.

[0002] In recent years, due to the tightening of carbon dioxide emission regulations in response to the issue of global warming, there has been an increasing demand for hydrogen fuel, which emits no carbon dioxide compared to petroleum and coal, as well as natural gas, which also emits less carbon dioxide. Accordingly, there has been a global increase in demand for the construction of liquid hydrogen tanks, liquid carbon dioxide tanks, LNG tanks, and the like, which are used on ships and on land. Ni-based low-temperature steels containing 6 to 9% Ni are used for the steel materials used in liquid hydrogen tanks, liquid carbon dioxide tanks, LNG tanks, and the like, because they are required to ensure toughness at extremely low temperatures of -196°C. Furthermore, austenitic wires are used to weld these Ni-based low-temperature steels, which can produce weld metal with excellent low-temperature toughness.

[0003] For example, as an austenitic wire, Japanese Patent Application Laid-Open No. 2008-246507 describes a wire having a Ni content of 35 to 70% and a TiO content of 100% relative to the total mass of the wire in the flux. ２ , SiO ２ and ZrO ２ in a total amount of 4.0 mass % or more, and further, Mn oxide is MnO ２ The content is 0.6 to 1.2 mass % in terms of TiO ２ , SiO ２ , ZrO ２ and MnO ２ The contents of (equivalent amounts) are expressed in mass % as [TiO ２ ], [SiO ２ ], [ZrO ２ ] and [MnO ２ ], [TiO ２ ] / [ZrO ２ ] is 2.3 to 3.3, [SiO ２ ] / [ZrO ２ ] is 0.9 to 1.5, and ([TiO ２ ]+[SiO ２ ]+[ZrO ２ ]) / [MnO ２] is 5 to 13." Furthermore, JP 2017-502842 A discloses a wire having an outer sheath made of a Ni-based alloy, "wherein, by weight, C: 0.15 to 0.8%, Si: 0.2 to 1.2%, Mn: 15 to 34%, Cr: 6% or less, Mo: 1.5 to 4%, S: 0.02% or less, P: 0.02% or less, B: 0.01% or less, Ti: 0.09 to 0.5%, N: 0.001 to 0.3%, TiO ２ :4~15%, SiO ２ , ZrO ２ and Al ２ O ３ The document discloses a "flux cored arc welding wire containing: 0.01 to 9% of one or more elements selected from the group consisting of: a total of 0.01 to 9% of one or more elements selected from the group consisting of: a total of 0.5 to 1.7% of one or more elements selected from K, Na and Li, 0.2 to 1.5% of one or more elements selected from F and Ca, and the balance being Fe and other unavoidable impurities."

[0004] Wire feedability is one of the important indicators in various welding methods, such as submerged arc welding (SAW). That is, when a coiled wire is straightened and fed, it is required to be straightened and fed to the desired feeding position. However, if the wire is too hard, straightening is not performed properly, the wire feeding position shifts, the arc generation location becomes unstable, and meandering of the bead occurs. Recently, so-called γ-based steels with an FCC ratio of 70% or more have been used for solid wires. γ-based steels are high-alloy steels, and wire hardness can lead to unstable feedability. Therefore, reducing the amount of alloy in the wire can be considered to soften the wire. However, if the amount of alloy in the wire is reduced too much, the amount of alloy in the weld metal will be insufficient, preventing the desired performance. Another method to obtain soft wire is to draw the wire until it is sufficiently thin and then anneal it. However, annealing the wire after thinning the wire requires a long annealing time, reducing production efficiency. Therefore, it is important to design the alloy amount from the viewpoint of obtaining an appropriate wire hardness while ensuring production efficiency. Therefore, for solid wires with an fcc ratio of 70% or more, there is a demand for wires that are soft without reducing the alloy amount too much and have excellent feedability during welding.

[0005] Therefore, an object of the present disclosure is to provide a solid wire that is excellent in feedability during welding, and a method for manufacturing a welded joint using the solid wire.

[0006] The means for solving the problem include the following aspects. <1> Vickers hardness Hv is 180 or more and 500 or less, fcc proportion determined by magnetic induction method is 70% or more, and chemical composition is, in mass% with respect to the total mass of the solid wire, C: 0% to 0.650%, Si: 0.03% to 0.50%, Mn: 4.1% to 30.0%, P: 0.050% or less, S: 0.050% or less, Cu: 0% to 5.0%, Ni: 1.0% to 30.0%, Cr: 0% to 10.0%, Mo: 0% to 10.0%, Nb: 0% to 1.00%, V: 0% to 1.00%, Co: 0% to 1.00%, Pb: 0% to 1.00%, Sn: 0% to 1.000%, A solid wire comprising: Al: 0% to 0.10%, Ti: 0% to 0.10%, Ta: 0 to 1.00%, Hf: 0 to 1.00%, W: 0 to 30.00%, Mg: 0 to 0.50%, REM: 0 to 0.50%, Zr: 0 to 5.00%, B: 0% to 0.1000%, N: 0% to 0.500%, and O: 0.0500% or less, with the balance being Fe and impurities. <2> The solid wire according to <1>, wherein the area ratio of inclusions having an equivalent circle diameter of 5 μm or more in the solid wire is 3.00% or less. <3> The solid wire according to <1> or <2>, wherein the total content of the Mn and the Ni (Mn + Ni) is 5.0% or more, and the total content of the Mn, the Ni, and the Cr (Mn + Ni + Cr) is 15.0% or more. <4> The solid wire according to any one of <1> to <3>, wherein the mass ratio (Ni / Mn) of the Mn content to the Ni content is 0.10 or more. <5> The solid wire according to <4>, wherein the mass ratio (Ni / Mn) is 1.00 or more. <6> The solid wire according to any one of <1> to <5>, wherein the total content of the Nb, V, Ti, Ta, Hf, and Zr (Nb + V + Ti + Ta + Hf + Zr) is 0.0005% or more and 5.00% or less.<7> A method for manufacturing a welded joint, comprising a step of welding steel materials by at least one welding method selected from the group consisting of a submerged arc welding method, a gas metal arc welding method, and a tungsten inert gas welding method, using the solid wire according to any one of <1> to <6>.

[0007] According to the present disclosure, it is possible to provide a solid wire having excellent feedability during welding and a method for manufacturing a welded joint using the solid wire.

[0008] FIG. 2 is a schematic diagram for explaining a feedability test carried out in the examples.

[0009] An embodiment that is an example of the present disclosure will be described. In this specification, when a numerical range expressed using "to" is used, unless the numerical values ​​before and after "to" are followed by "greater than" or "less than," it means a range that includes these numerical values ​​as the lower and upper limits. Furthermore, when the numerical values ​​before and after "to" are followed by "greater than" or "less than," it means a range that does not include these numerical values ​​as the lower or upper limit. In the numerical ranges described in stages in this specification, the upper limit of a certain numerical range may be replaced by the upper limit of another numerical range described in stages, or may be replaced by a value shown in an example. Furthermore, the lower limit of a certain numerical range may be replaced by the lower limit of another numerical range described in stages, or may be replaced by a value shown in an example. Furthermore, with regard to the content, "%" means "mass %." When the content (%) is "0 to," it means that the component is an optional component and may not be included.

[0010] <Solid Wire> The solid wire (hereinafter also simply referred to as "wire") according to the present disclosure has a Vickers hardness Hv of 180 or more and 500 or less, an fcc fraction determined by a magnetic induction method of 70% or more, and a Cr content of 10.0% or less by mass relative to the total mass of the wire. The chemical composition of the solid wire, expressed as mass% relative to the total mass of the solid wire, is within the range described below. The wire according to the present disclosure is used in various welding methods, such as submerged arc welding (SAW), gas metal arc welding (including GMAW, MIG (Metal Inert Gas) welding, and MAG (Metal Active Gas) welding), and tungsten inert gas (TIG) welding.

[0011] The solid wire according to the present disclosure has the above-described configuration, and is excellent in wire feedability during welding. The reason for this effect is presumed to be as follows.

[0012] Wire feedability is one of the important indicators in various welding methods, such as submerged arc welding (SAW). In various welding methods, welding is performed while continuously feeding the wire toward the welding point. During this process, the coiled wire is straightened (i.e., its curl is corrected) while being fed. Therefore, if the wire is too hard, the wire cannot be straightened properly, resulting in a misalignment of the wire feed position, an unstable arc generation location, and a meandering bead. Recently, so-called γ-based steels with an FCC ratio of 70% or more are sometimes used for solid wires. Since high-alloy steels are used in γ-based steels, the wire can harden due to the high alloy content, and excessive hardness can result in unstable feedability. Therefore, reducing the alloy content in the wire can be considered to obtain a softer wire. However, if the alloy content in the wire composition is reduced too much, the alloy content in the weld metal will be insufficient, and the desired performance will not be achieved. Therefore, for solid wires with an fcc ratio of 70% or more, there is a demand for wires that are soft without reducing the alloy content too much, thereby providing excellent feedability during welding (excellent straightening properties during feeding).

[0013] In contrast, the solid wire according to the present disclosure has an fcc ratio of 70% or more, a Cr content controlled to 10.0% or less, and by optimizing the heat treatment conditions and number of wiredrawings of the solid wire in the wiredrawing process during production of the solid wire, the wire has a Vickers hardness Hv of 180 or more and 500 or less. This makes it possible to obtain a soft wire while maintaining an appropriate alloy content, and provides a wire that has excellent feedability during welding (more specifically, straightening ability during feeding).

[0014] The requirements for the solid wire according to the present disclosure will be explained below.

[0015] The wire according to the present disclosure melts together with a part of the steel material to be welded and the flux, and becomes a weld metal after solidification.

[0016] (Vickers hardness Hv) The Vickers hardness Hv of the wire is 180 or more and 500 or less. If the Vickers hardness Hv exceeds 500, the wire becomes too hard and lacks toughness, causing breakage during straightening and poor feedability during welding (straightenability during feeding). On the other hand, if the alloy amount is too small, the Vickers hardness Hv softens to less than 180 and the wire buckles. Furthermore, from the viewpoint of feedability during welding (straightenability during feeding) and buckling, the Vickers hardness Hv is preferably 250 or more and 470 or less, more preferably 300 or more and 450 or less.

[0017] Here, a method for controlling the Vickers hardness Hv of the wire will be described. The hardness of the wire is controlled by optimizing the amount of solid solution strengthening and stacking fault energy by adjusting the amount of alloy and the type of alloy contained in the wire. From the viewpoint of softening the wire (i.e., Hv 500 or less), it is preferable to reduce the amount of solid solution strengthening of the wire and increase the stacking fault energy. On the other hand, from the viewpoint of preventing the wire from becoming too soft (i.e., Hv 180 or more), it is preferable to increase the amount of solid solution strengthening of the wire and decrease the stacking fault energy. Furthermore, in order to control the Vickers hardness Hv of the wire within the above range, it is important to optimize the heat treatment conditions and the number of wiredrawings of the solid wire in the wiredrawing process when manufacturing the solid wire.

[0018] The Vickers hardness Hv of the wire is measured by the following method. The wire is mirror-polished in the direction parallel to the drawing direction (L cross section), and the Vickers hardness is measured at any five points in the center of the wire according to JIS Z 2244 (2009). The test force is 9.8 N. The average of the five Vickers hardness values ​​obtained is taken as the Vickers hardness of the wire.

[0019] (Fcc percentage determined by magnetic induction method) The fcc percentage in the wire is 70% or more. By setting the fcc percentage to 70% or more, the percentage of austenite in the structure of the wire is increased, and the low-temperature toughness of the obtained weld metal can be improved. The fcc percentage is preferably 80% or more, more preferably 90% or more, and may even be 100%. The remainder of the structure is bcc.

[0020] In addition, from the viewpoint of setting the fcc ratio in the wire to 70% or more, the lower limit of the total amount of elements excluding Fe and impurities in the chemical composition of the wire is preferably 10%, 15%, 20%, 25%, or 30%. On the other hand, the upper limit of the total amount of elements excluding Fe and impurities in the chemical composition of the wire is not particularly limited, but is preferably, for example, 60% or 55%. Note that the term "impurities" as used herein refers to components that are mixed in due to raw materials such as ore or scrap, or various factors in the manufacturing process, when industrially manufacturing wire, and are acceptable within a range that does not adversely affect the properties of the wire. For example, these impurities do not include P, S, and O.

[0021] The fcc percentage in the wire structure can be determined by the following method: A sample is taken from the wire, the bcc percentage (%) is measured on the sample surface by magnetic induction, and the arithmetic mean value of the measured bcc percentages is determined. Using the obtained mean value of the bcc percentages, the fcc percentage (%) in the wire structure is determined by the following formula: fcc percentage = 100 - bcc percentage

[0022] (Chemical Composition of Solid Wire) The chemical composition of the solid wire according to the present disclosure will be described below. In the description of the chemical composition of the solid wire, "%" means "mass % with respect to the total mass of the solid wire" unless otherwise specified. In addition, when the solid wire according to the present disclosure has a plating layer on its outer surface, the chemical composition of the solid wire also includes the chemical composition of the plating layer.

[0023] The chemical composition of the solid wire according to the present disclosure is: C: 0% to 0.650%, Si: 0.03% to 0.50%, Mn: 4.1% to 30.0%, P: 0.050% or less, S: 0.050% or less, Cu: 0% to 5.0%, Ni: 1.0% to 30.0%, Cr: 0% to 10.0%, Mo: 0% to 10.0%, Nb: 0% to 1.00%, V: 0% to 1.00%, Co: 0% to 1.00%, Pb: 0% to 1.00%, Sn: 0% to 1.000%, Al: 0% to 0.10%, Ti: 0% to 0.10%, Ta: 0 to 1.00%, Hf: 0 to 1.00%, W: 0 to 30.00%, Mg: 0 to 0.50%, REM: 0 to 0.50%, Zr: 0 to 5.00%, B: 0% to 0.1000%, N: 0% to 0.500%, and O: 0.500% or less, with the balance being Fe and impurities.

[0024] (C: 0 to 0.650%) C is an element that generates spatter. In order to reduce spatter, the lower the C content of the wire, the more advantageous it is. Furthermore, C is an interstitial solid solution strengthening element, and reducing the C content of the wire softens the wire. Therefore, the C content of the wire is set to 0 to 0.650%. However, reducing the C content of the wire to 0% increases the cost of decarbonization. Furthermore, there is a concern that the C content of the wire will be insufficient, resulting in insufficient strength of the weld metal. Therefore, the lower limit of the C content of the wire may be 0.003%, 0.005%, or 0.008%. The upper limit of the C content of the wire is preferably 0.600%, 0.500%, 0.400%, 0.300%, 0.200%, less than 0.200%, 0.190%, 0.180%, 0.150%, or 0.120%.

[0025] (Si: 0.03 to 0.50%) Si is a deoxidizing element. By increasing the Si content of the wire, the P content of the wire can be reduced. On the other hand, Si has low solid solubility in the austenite phase, and by reducing the Si content, it is possible to suppress the formation of embrittlement phases such as intermetallic compounds and δ ferrite at high temperatures and improve high-temperature ductility. Therefore, the Si content of the wire is set to 0.03 to 0.50%. The lower limit of the Si content of the wire is preferably 0.04%, 0.05%, or 0.08%. The upper limit of the Si content of the wire is preferably less than 0.50%, 0.48%, 0.45%, 0.40%, 0.35%, 0.30%, or 0.20%.

[0026] (Mn: 4.1 to 30.0%) Reducing the Mn content increases stacking fault energy and can improve toughness. On the other hand, Mn is an austenite stabilizing element. Increasing the Mn content of the wire promotes austenitization of the weld metal and can improve low-temperature toughness. Therefore, the Mn content of the wire is set to 4.1 to 30.0%. The lower limit of the Mn content of the wire is preferably 4.2%, 5.0%, more than 5.0%, 5.2%, more than 6.0%, 6.2%, 7.0%, more than 7.0%, 7.2%, more than 10.0%, or 10.2%. The upper limit of the Mn content of the wire is preferably 28.0%, 26.0%, 25.0%, 23.0%, 21.0%, 20.0%, 19.0%, 18.0%, 17.8%, 16.8%, 15.8%, 15.0%, 14.8%, or 12.0%.

[0027] (P: 0.050% or less) P is an impurity element that reduces the toughness of the weld metal, so it is preferable to reduce the P content of the wire as much as possible. For example, the lower limit of the P content of the wire may be 0%. However, from the viewpoint of reducing the deP cost, the P content of the wire is preferably 0.003% or more. On the other hand, if the P content of the wire is 0.050% or less, the adverse effect of P on toughness can be reduced. Therefore, the P content of the wire is set to 0.050% or less. In order to effectively suppress the reduction in toughness of the weld metal, the P content of the wire is preferably 0.040% or less, 0.030% or less, 0.020% or less, 0.015% or less, 0.010% or less, or 0.005% or less.

[0028] (S: 0.050% or less) S is an impurity element that reduces the toughness of the weld metal, so it is preferable to reduce the S content of the wire as much as possible. For example, the lower limit of the S content of the wire may be 0%. However, from the viewpoint of reducing desulfurization costs, the S content of the wire is preferably 0.003% or more. On the other hand, if the S content of the wire is 0.050% or less, the adverse effect of S on toughness can be reduced. Therefore, the S content of the wire is set to 0.050% or less. In order to effectively suppress a decrease in the toughness of the weld metal, the S content of the wire is preferably 0.040% or less, 0.030% or less, 0.020% or less, 0.015% or less, 0.010% or less, or 0.005% or less.

[0029] (Cu: 0 to 5.0%) Cu is a precipitation strengthening element and may be contained in the wire to improve the strength of the weld metal. Cu is also an austenite stabilizing element and may be contained in the wire to improve the low-temperature toughness of the weld metal. On the other hand, if the Cu content of the wire is excessive, the above effects saturate. Furthermore, reducing the Cu content of the wire softens the wire. Therefore, the Cu content of the wire is set to 0 to 5.0%. The lower limit of the Cu content of the wire is preferably 0.3%, 0.5%, or 0.7%. The upper limit of the Cu content of the wire is preferably 4.5%, 4.0%, or 3.5%.

[0030] (Ni: 1.0 to 30.0%) Ni is an austenite stabilizing element. Increasing the Ni content of the wire promotes austenitization of the weld metal and improves low-temperature toughness. On the other hand, reducing the Ni content of the wire can reduce the cost of the wire. Therefore, the Ni content of the wire is set to 1.0 to 30.0%. The lower limit of the Ni content of the wire is preferably 2.0%, 3.0%, 3.2%, 3.6%, 3.7%, 4.2%, 4.7%, 5.0%, 5.2%, more than 6.0%, 6.2%, 7.0%, more than 8.0%, 8.2%, 10.2%, 12.2%, or 13.2%. The upper limit of the Ni content of the wire is preferably 28.0%, 26.0%, 24.0%, 22.0%, 20.0%, 19.0%, 18.0%, or 15.0%.

[0031] (Cr: 0 to 10.0%) Cr is a ferrite stabilizing element and may be contained in the wire to improve the strength of the weld metal. On the other hand, if the Cr content of the wire is excessive, the wire becomes too hard due to excessive solid solution strengthening or precipitation of Cr carbides, resulting in poor feedability during welding (straightening during feeding). Furthermore, if the Cr content of the wire is excessive, the amount of low-melting-point compounds in the molten metal increases, and the solid-liquid coexistence temperature range of the molten metal widens, making hot cracking more likely to occur. Therefore, the Cr content of the wire is set to 0 to 10.0%. The lower limit of the Cr content of the wire is preferably 0.01%, 0.02%, 1.0%, 2.0%, or 3.0%. The upper limit of the Cr content of the wire is preferably 9.8%, 9.0%, 8.0%, less than 8.0%, 7.8%, 7.0%, less than 6.0%, 5.8%, or 4.8%.

[0032] (Mo: 0 to 10.0%) Mo is a precipitation strengthening element and may be contained in the wire to improve the strength of the weld metal. On the other hand, by reducing the Mo content of the wire, the strength of the weld metal can be suppressed and low-temperature toughness can be increased. Furthermore, by reducing the Mo content of the wire, the wire becomes softer. Therefore, the Mo content of the wire is set to 0 to 10.0%. The lower limit of the Mo content of the wire is preferably 1.0%, 2.0%, or 3.0%. The upper limit of the Mo content of the wire is preferably 9.0%, 8.0%, or 7.0%.

[0033] (Nb: 0 to 1.00%) Nb is an element that forms carbides in the weld metal and increases the strength of the weld metal, so it may be contained in the wire. On the other hand, by reducing the Nb content of the wire, it is possible to suppress the occurrence of hot cracking in the weld metal. Furthermore, by reducing the Nb content of the wire, the wire becomes softer. Therefore, the Nb content of the wire is set to 0 to 1.00%. The lower limit of the Nb content of the wire is preferably 0.001%, 0.002%, 0.005%, 0.010%, or 0.015%. The upper limit of the Nb content of the wire is preferably 0.95%, 0.90%, 0.85%, or 0.80%.

[0034] (V: 0 to 1.00%) V is an element that forms carbonitrides in the weld metal and increases the strength of the weld metal, so it may be contained in the wire. On the other hand, by reducing the V content of the wire, it is possible to suppress the occurrence of hot cracking in the weld metal. Furthermore, by reducing the V content of the wire, the wire becomes softer. Therefore, the V content of the wire is set to 0 to 1.00%. The lower limit of the V content of the wire is preferably 0.01%, 0.05%, 0.10%, 0.15%, or 0.20%. The upper limit of the V content of the wire is preferably 0.95%, 0.90%, 0.85%, or 0.80%.

[0035] (Co: 0 to 1.00%) Co is an element that increases the strength of the weld metal through solid solution strengthening, and therefore may be contained in the wire. On the other hand, by reducing the Co content of the wire, the ductility of the weld metal can be increased and toughness can be ensured. Furthermore, by reducing the Co content of the wire, the wire becomes softer. Therefore, the Co content of the wire is set to 0 to 1.00%. The lower limit of the Co content of the wire is preferably 0.01%, 0.05%, 0.10%, 0.15%, or 0.20%. The upper limit of the Co content of the wire is preferably 0.95%, 0.90%, 0.85%, or 0.80%.

[0036] (Pb: 0 to 1.00%) Pb may be contained in the wire because it has the effect of improving the shape of the toe between the base steel material and the weld metal and improving the machinability of the weld metal. On the other hand, by reducing the Pb content of the wire, the arc state can be stabilized and spatter can be reduced. Therefore, the Pb content of the wire is set to 0 to 1.00%. The lower limit of the Pb content of the wire is preferably 0.01%, 0.05%, 0.10%, 0.15%, or 0.20%. The upper limit of the Pb content of the wire is preferably 0.95%, 0.90%, 0.85%, or 0.80%.

[0037] (Sn: 0 to 1.000%) Sn is an element that improves the corrosion resistance of the weld metal, and therefore may be contained in the wire. On the other hand, by reducing the Sn content of the wire, it is possible to suppress the occurrence of cracks in the weld metal. Therefore, the Sn content of the wire is set to 0 to 1.000%. The lower limit of the Sn content of the wire is preferably 0.010%, 0.050%, 0.100%, 0.150%, or 0.200%. The upper limit of the Sn content of the wire is preferably 0.950%, 0.900%, 0.850%, or 0.800%.

[0038] The wire preferably contains at least one selected from the group consisting of Co, Pd, and Sn in the above-mentioned content. That is, the content of at least one selected from the group consisting of Co, Pd, and Sn is preferably more than 0%.

[0039] (Al: 0 to 0.10%) Al is a deoxidizing element and may be contained in the wire to suppress welding defects and improve the cleanliness of the weld metal. On the other hand, reducing the Al content of the wire suppresses the generation of coarse inclusions in the wire (e.g., inclusions with an equivalent circle diameter of 5 μm or more), thereby softening the wire. Furthermore, reducing the Al content of the wire suppresses the formation of nitrides or oxides in the weld metal due to Al, thereby suppressing a decrease in the low-temperature toughness of the weld metal. Therefore, the Al content of the wire is set to 0 to 0.10%. The lower limit of the Al content of the wire is preferably 0.01%, 0.02%, or 0.03%. The upper limit of the Al content of the wire is preferably 0.09%, 0.08%, or 0.07%.

[0040] (Ti: 0 to 0.10%) Ti is a deoxidizing element and may be contained in the wire to suppress welding defects and improve the cleanliness of the weld metal. On the other hand, reducing the Ti content of the wire suppresses the formation of coarse inclusions (e.g., inclusions with an equivalent circle diameter of 5 μm or more) in the wire, thereby softening the wire. Furthermore, reducing the Ti content of the wire suppresses the formation of carbides in the weld metal, thereby suppressing deterioration in the toughness of the weld metal. Therefore, the Ti content of the wire is set to 0 to 0.10%. The lower limit of the Ti content of the wire is preferably 0.003%, 0.01%, 0.02%, or 0.03%. The upper limit of the Ti content of the wire is preferably 0.09%, 0.08%, 0.07%, or 0.05%.

[0041] (Ta: 0 to 1.00%) Ta may be contained in the wire because it contributes to suppressing hot cracking. On the other hand, by reducing the Ta content of the wire, it is possible to suppress the generation of coarse inclusions (for example, inclusions with an equivalent circle diameter of 5 μm or more). Therefore, the Ta content of the wire is set to 0 to 1.00%. The lower limit of the Ta content of the wire is preferably 0.0001%, 0.0003%, 0.0005%, or 0.0007%. The upper limit of the Ta content of the wire is preferably 0.90%, 0.80%, 0.70%, or 0.60%.

[0042] (Hf: 0 to 1.00%) Hf may be contained in the wire because it contributes to suppressing hot cracking. On the other hand, by reducing the Hf content of the wire, it is possible to suppress the generation of coarse inclusions (for example, inclusions with an equivalent circle diameter of 5 μm or more). Therefore, the Hf content of the wire is set to 0 to 1.00%. The lower limit of the Hf content of the wire is preferably 0.0001%, 0.0003%, 0.0005%, or 0.0007%. The upper limit of the Hf content of the wire is preferably 0.90%, 0.80%, 0.70%, or 0.60%.

[0043] (W: 0 to 30.00%) W may be contained in the wire because it is an element that increases the strength of the weld metal through solid solution strengthening. On the other hand, by reducing the W content of the wire, the ductility of the weld metal can be increased and toughness can be ensured. Furthermore, by reducing the W content of the wire, the wire becomes softer. Therefore, the W content of the wire is set to 0 to 30.00%. The lower limit of the W content of the wire is preferably 0.20%, 0.50%, 0.80%, or 1.00%. The upper limit of the W content of the wire is preferably 25.00%, 20.00%, 15.00%, or 10.00%.

[0044] (Mg: 0 to 0.50%) Mg may be contained in the wire because it has a deoxidizing effect, reducing the oxygen content in the weld metal and improving the toughness of the weld metal. On the other hand, reducing the Mg content of the wire reduces the amount of slag produced and suppresses welding defects such as slag inclusion. Therefore, the Mg content of the wire is set to 0 to 0.50%. The lower limit of the Mg content of the wire is preferably 0.0001%, 0.0005%, 0.0010%, 0.0020%, or 0.0030%. The upper limit of the Mg content of the wire is preferably 0.40% or 0.30%.

[0045] (REM: 0 to 0.50%) REM has the effect of improving hot workability during the production of solid wire, and therefore may be contained in the wire. On the other hand, if the REM content of the wire is excessive, the REM combines with oxygen, significantly reducing cleanliness and instead deteriorating hot workability. Therefore, the REM content of the wire is set to 0 to 0.50%. The lower limit of the REM content of the wire is preferably 0.001%, 0.003%, 0.005%, or 0.010%. The upper limit of the REM content of the wire is preferably 0.40% or 0.30%.

[0046] Note that "REM" is a collective term for 17 elements, including Sc, Y, and lanthanides, and the REM content refers to the total content of one or more REM elements. REM is generally contained in misch metal. Therefore, for example, REM may be added in the form of misch metal so that the amount of REM falls within the above range.

[0047] (Zr: 0 to 5.00%) Zr may be contained in the wire because it has a deoxidizing effect, reducing the oxygen content in the weld metal and improving the toughness of the weld metal. On the other hand, reducing the Zr content of the wire can suppress the generation of coarse inclusions (e.g., inclusions with an equivalent circle diameter of 5 μm or more). Therefore, the Zr content of the wire is set to 0 to 10.00%. The lower limit of the Zr content of the wire is preferably 0.0005%, 0.0010%, 0.0020%, or 0.0050%. The upper limit of the Zr content of the wire is preferably 4.00%, 3.00%, 2.00%, or 1.00%.

[0048] (B: 0 to 0.1000%) B is an interstitial solid solution strengthening element, and may be contained in the wire to improve the low temperature toughness and strength of the weld metal. On the other hand, by reducing the B content of the wire, M ２３ (C, B) ６The precipitation of B is suppressed, and deterioration of toughness can be suppressed. Furthermore, reducing the B content of the wire makes the wire softer. Therefore, the B content of the wire is set to 0 to 0.1000%. The lower limit of the B content of the wire is preferably 0.0005%, 0.0010%, or 0.0020%. The upper limit of the B content of the wire is preferably 0.0800%, 0.0500%, or 0.0100%.

[0049] (N: 0 to 0.500%) N is an austenite stabilizing element and an interstitial solid solution strengthening element, and may be contained in the wire to improve the low-temperature toughness and strength of the weld metal. On the other hand, by reducing the N content of the wire, the occurrence of blowouts can be suppressed and welding defects can be reduced. Furthermore, by reducing the N content of the wire, the wire becomes softer. Therefore, the N content of the wire is set to 0 to 0.500%. The lower limit of the N content of the wire is preferably 0.0001%, 0.0002%, or 0.0004%. The upper limit of the N content of the wire is preferably 0.400%, 0.200%, 0.100%, 0.050%, or 0.020%.

[0050] (O: 0.0500% or less) O ​​may be contained in the wire as an impurity. However, an excessive O content leads to deterioration of the toughness and ductility of the weld metal, so it is preferable to reduce the O content of the wire, with the upper limit being 0.0500% or less. The upper limit of the O content of the wire is preferably 0.0400%, 0.0300%, 0.0200%, 0.0100%, or 0.0050%. On the other hand, the lower limit of the O content of the wire may be 0%, but from the viewpoint of suppressing an increase in manufacturing costs due to the reduction of the O content, it is preferably 0.0003% or 0.0005%.

[0051] (Balance: Fe and impurities) The balance components in the chemical composition of the wire are Fe and impurities. The impurities refer to components that are mixed in due to raw materials such as ores or scraps or various factors in the manufacturing process when industrially manufacturing the wire, and are acceptable within a range that does not adversely affect the properties of the wire.

[0052] (Mass ratio (Cr / Mn) of Cr content to Mn content) The mass ratio (Cr / Mn) of the Cr content to the Mn content is preferably 10.00 or less. In other words, by ensuring that the Cr content is not too large relative to the Mn content, solid solution strengthening is not excessive, and stacking fault energy is not too low, preventing the wire from becoming hard, thereby improving feedability during welding (straightening ability during feeding). The lower limit of the mass ratio (Cr / Mn) is 0. The upper limit of the mass ratio (Cr / Mn) in the wire is more preferably 9.00, 8.00, 7.00, 6.00, or 5.00. The lower limit of the mass ratio (Cr / Mn) in the wire is more preferably 0.50, 1.00, 1.50, or 2.00.

[0053] (Total of Mn Content and Ni Content (Mn+Ni)) Mn and Ni are each an austenite stabilizing element and improve the low-temperature toughness of the weld metal. On the other hand, Ni is an expensive metal, so in order to improve the low-temperature toughness of the weld metal while suppressing the cost of the wire, it is preferable that the Mn content and Ni content in the wire each satisfy the above-mentioned ranges and that the total of the Mn content and Ni content (Mn+Ni) in the wire is 5.0% or more. The total of the Mn content and Ni content (Mn+Ni) in the wire is more preferably 5.4% or more, 5.6% or more, 5.7% or more, 6.0% or more, 6.2% or more, 6.7% or more, 6.9% or more, 7.0% or more, 7.2% or more, 10.0% or more, or 15.0% or more.

[0054] Furthermore, by reducing the Mn content, a decrease in stacking fault energy is suppressed, and a decrease in toughness can be suppressed. Therefore, from the viewpoint of suppressing the cost of the wire and improving the low-temperature toughness of the weld metal, it is preferable that the Mn content and Ni content in the wire each satisfy the above range, and that the total of the Mn content and Ni content (Mn + Ni) in the wire is 37.0% or less. The total of the Mn content and Ni content (Mn + Ni) in the wire is more preferably 35.0% or less, 32.0% or less, or 30.0% or less.

[0055] (Total of Mn Content, Ni Content, and Cr Content (Mn+Ni+Cr)) Mn, Ni, and Cr are each an austenite stabilizing element and improve the low-temperature toughness of the weld metal. On the other hand, Ni is an expensive metal, so in order to improve the low-temperature toughness of the weld metal while suppressing the cost of the wire, it is preferable that the Mn content, Ni content, and Cr content in the wire each satisfy the above-mentioned ranges, and that the total of the Mn content, Ni content, and Cr content (Mn+Ni+Cr) in the wire is 15.0% or more. The total of the Mn content, Ni content, and Cr content (Mn+Ni+Cr) in the wire is more preferably 17.0% or more, 19.0% or more, 20.0% or more, 22.0% or more, 24.0% or more, 26.0% or more, 28.0% or more, or 30.0% or more.

[0056] Furthermore, reducing the Mn content suppresses a decrease in stacking fault energy, thereby suppressing a decrease in toughness. Reducing the Cr content suppresses the formation of martensite structures, softening the wire. Cr also causes an increase in the amount of low-melting-point compounds in the molten metal. Therefore, from the viewpoints of reducing wire costs, improving the low-temperature toughness of the weld metal, enhancing core wire workability, and reducing the amount of low-melting-point compounds generated in the molten metal, it is preferable that the Mn content, Ni content, and Cr content in the wire each satisfy the above-mentioned ranges, and that the total of the Mn content, Ni content, and Cr content (Mn + Ni + Cr) in the wire is 47.0% or less. The total of the Mn content, Ni content, and Cr content (Mn + Ni + Cr) in the wire is more preferably 45.0% or less, 42.0% or less, or 40.0% or less.

[0057] (Mass ratio of Mn content to Ni content (Ni / Mn)) Mn and Ni are each an austenite stabilizing element and improve the low-temperature toughness of the weld metal. On the other hand, Ni is an expensive metal, and an excessive addition of Mn reduces stacking fault energy, thereby causing a decrease in toughness. Ni improves toughness by increasing stacking fault energy. Therefore, from the viewpoint of improving the low-temperature toughness of the weld metal while suppressing the cost of the wire, it is preferable that the mass ratio of Mn content to Ni content (Ni / Mn) in the wire be 0.10 or more. The lower limit of the mass ratio of Mn content to Ni content (Ni / Mn) in the wire is more preferably 0.20, 0.30, 0.50, 0.60, 0.68, 0.70, 0.80, 0.90, 1.00, 1.10, or 1.20. The upper limit of the mass ratio (Ni / Mn) of the Mn content to the Ni content in the wire is preferably 25.00, 20.00, 15.00, 10.00, 8.00, or 5.00.

[0058] (Total Content of Nb, V, Ti, Ta, Hf, and Zr (Nb + V + Ti + Ta + Hf + Zr)) Nb, V, Ti, Ta, Hf, and Zr each contribute to suppressing hot cracking. On the other hand, by reducing the contents of Nb, V, Ti, Ta, Hf, and Zr, the formation of coarse precipitates can be suppressed and toughness can be improved. Therefore, the total content of Nb, V, Ti, Ta, Hf, and Zr in the wire (Nb + V + Ti + Ta + Hf + Zr) is preferably 0.0005% or more and 5.00% or less. The lower limit of the total content of these elements in the wire is preferably 0.0007%, 0.0010%, 0.0015%, 0.0020%, 0.0025%, or 0.0030%. The upper limit of the Zr content of the wire is preferably 4.00%, 3.50%, 3.00%, or 2.50%.

[0059] (Area Ratio of Coarse Inclusions) The solid wire according to the present disclosure preferably has an area ratio of inclusions having an equivalent circle diameter of 5 μm or more (referred to as "coarse inclusions" in the present disclosure) of 3.00% or less. By making the area ratio of coarse inclusions in the solid wire 3.00% or less, that is, by reducing the amount of precipitated coarse inclusions, a soft wire can be obtained while maintaining an appropriate alloy content, and a wire with excellent feedability during welding (more specifically, straightening ability during feeding) can be easily obtained.

[0060] From the viewpoint of the manufacturability of the solid wire, the area ratio of inclusions having an equivalent circle diameter of 5 μm or more is preferably 2.50% or less, more preferably 2.00% or less, even more preferably 1.50% or less, and even more preferably 1.00% or less. The lower limit of the area ratio of inclusions having an equivalent circle diameter of 5 μm or more may be 0%.

[0061] From the viewpoint of manufacturability of the solid wire, the area ratio of inclusions having an equivalent circle diameter of 1 μm or more is preferably 3.00% or less, more preferably 2.00% or less, and even more preferably 1.00% or less. The lower limit of the area ratio of inclusions having an equivalent circle diameter of 1 μm or more may be 0%.

[0062] In the present disclosure, inclusions refer to oxides, carbides, nitrides, carbonitrides, and sulfides, and among these inclusions, those with a circle equivalent diameter of 5 μm or more and those with a circle equivalent diameter of 1 μm or more are subject to measurement.

[0063] The area ratio of inclusions with an equivalent circle diameter of 5 μm or more and inclusions with an equivalent circle diameter of 1 μm or more in a solid wire is measured by the following method. A cross section (C section) perpendicular to the wire drawing direction is stained with Murakami's reagent (an alkaline solution of prussiate; see page 250 of the Metal Data Book, 2nd edition, by Nippon Kinzoku). The stained cross section is observed under an optical microscope at 500x magnification, and inclusions (i.e., oxides, carbides, nitrides, carbonitrides, and sulfides) with an equivalent circle diameter of 5 μm or more and 1 μm or more are targeted based on the area of ​​the inclusions. The area ratio can be determined by calculating the total area of ​​the target inclusions within the observation field. Note that when staining with Murakami's reagent, cleaning is performed after immersion etching.

[0064] The area ratio of inclusions having an equivalent circle diameter of 5 μm or more and inclusions having an equivalent circle diameter of 1 μm or more in a solid wire can be controlled by adjusting the contents of elements that contribute to the precipitation of inclusions, specifically, (1) a method of reducing the contents of carbon (C), nitrogen (N), and sulfur (S), (2) a method of reducing the contents of the elements shown in (1) above and elements that form inclusions (specifically, Al, Ti, Cr, Mo, Nb, V, Ti, Ta, Hf, and Zr), and (3) a method of reducing both the elements shown in (1) above and the elements shown in (2) above.

[0065] The solid wire according to the present disclosure may further include a lubricant applied to the wire surface. The lubricant applied to the wire surface has the effect of improving wire feedability during welding. Various types of lubricants for the wire (e.g., vegetable oils such as palm oil) can be used, but in order to suppress welding defects, it is preferable to use one or both of H-free polytetrafluoroethylene oil (PTFE oil) and perfluoropolyether oil (PFPE oil). Furthermore, as described above, the solid wire according to the present disclosure may further include a plating layer formed on the wire surface. In this case, the lubricant is applied to the surface of the plating layer.

[0066] (Wire Diameter) The diameter of the solid wire according to the present disclosure is not particularly limited, but may be, for example, φ1.6 to φ6.4 mm, or φ1.6 to φ2.4 mm.

[0067] <Method for Manufacturing Solid Wire> Next, a method for manufacturing solid wire according to the present disclosure will be described. First, steel having the above-described chemical composition is melted, and then forged if necessary. This steel is then rolled into a rod. This rod-shaped steel is then drawn to obtain solid wire. Note that in order to improve feedability, i.e., to prevent the wire from hardening, the solid wire is appropriately heat-treated and then drawn. It is important to optimize the number of times of heat treatment and drawing.

[0068] Specifically, the solid wire according to the present disclosure can be obtained by drawing the steel rod (wire rod) as follows: (1) Prepare a steel rod (wire rod) having an outer diameter of 10.0 mm. (2) Heat treat the wire rod at 1100°C for 1 hour in a bright annealing furnace, and then draw it to an outer diameter of 9.0 mm. (3) Continue repeating the same heat treatment and wiredrawing process as in (2) above, and wiredrawing without heat treatment, until the outer diameter φ reaches 1.6 mm to 2.4 mm. Note that when drawing from φ10.0 mm to φ2.4 mm, the number of wiredrawing steps is eight in total, as described below. φ10mm - (no heat treatment, wiredrawing 1) → φ9mm - (heat treatment, wiredrawing 2) → φ8mm - (no heat treatment, wiredrawing 3) → φ7mm - (heat treatment, wiredrawing 4) → φ6mm - (no heat treatment, wiredrawing 5) → φ5mm - (heat treatment, wiredrawing 6) → φ4mm - (no heat treatment, wiredrawing 7) → φ3mm - (no heat treatment, wiredrawing 8) → φ2.4mm By the above manufacturing method, a solid wire according to the present disclosure having a specific Vickers hardness Hv can be obtained.

[0069] Furthermore, a plating layer may be formed on the surface of the solid wire. In this case, the average chemical composition of the entire solid wire, including the chemical composition of the plating layer, must be within the above-mentioned range. Furthermore, a lubricant may be applied to the surface of the solid wire.

[0070] <Method for Manufacturing Welded Joint> Next, a method for manufacturing a welded joint (welding method) according to the present disclosure will be described. The method for manufacturing a welded joint according to the present disclosure includes a step of welding steel materials using the solid wire according to the present disclosure described above by at least one welding method selected from the group consisting of a submerged arc welding (SAW) method, a gas metal arc welding (including GMAW, MIG (Metal Inert Gas) welding, and MAG (Metal Active Gas) welding) method, and a tungsten inert gas welding (TIG) method. The solid wire according to the present disclosure melts together with a portion of the steel materials to be welded and the flux, and after solidification, becomes a weld metal.

[0071] For example, in submerged arc welding, a general submerged arc welding machine can be used, in which granular flux is dispersed on the weld line in advance, the solid wire according to the present disclosure is fed into the flux, and welding is performed using the arc heat generated between the wire and the steel material in the flux. The submerged arc welding conditions may be those of a general method. Furthermore, the welding conditions for gas metal arc welding (including GMAW, MIG welding, and MAG welding) and TIG welding may also be those of a general method.

[0072] In the method for manufacturing a welded joint according to the present disclosure, the type of steel material (material to be welded) that serves as the base material of the welded joint is not particularly limited, but for example, Ni-based low-temperature steel containing 6% to 9% Ni and having a plate thickness of 20 mm or more can be suitably used.

[0073] The method for manufacturing a welded joint according to the present disclosure may include a step of welding steel materials using a solid wire according to the present disclosure in one or more of the first through final passes. When the welding is performed in only one pass, the solid wire according to the present disclosure is used in that one pass. The polarity of the solid wire may be either positive or negative, but positive polarity is preferred, since the effect on the amount of diffusible hydrogen in the weld metal and the amount of spatter generation is negligibly small.

[0074] The welded joint obtained by the method for manufacturing a welded joint according to the present disclosure includes a base steel material and a welded portion composed of a weld metal and a weld heat-affected zone. The tensile strength of the welded metal obtained is preferably high, for example, 590 to 900 MPa.

[0075] Next, the feasibility and effects of the present disclosure will be explained in more detail using examples and comparative examples of the present disclosure. However, the following examples do not limit the present disclosure, and any design changes that are made in accordance with the above and below spirit are all included in the technical scope of the present disclosure.

[0076] (Manufacturing of Solid Wire) The solid wires of the present disclosure and comparative examples were manufactured by the method described below. First, steels having the chemical compositions shown in Tables 1-1 to 1-3 and Tables 2-1 to 2-3 were melted and then forged. Next, the steels were rolled into rods, and the rod-shaped steel (wire rods) were drawn to obtain solid wires. Specifically, wire drawing from the rod-shaped steel (wire rods) was performed as follows: (1) A rod-shaped steel (wire rods) having an outer diameter of 10.0 mm was prepared. (2) The wire rods were heat-treated at 1100°C for 1 hour in a bright annealing furnace, and then drawn to an outer diameter of 9.0 mm. (3) Subsequently, the following heat treatment and wiredrawing steps were performed until the outer diameter reached 2.4 mm. φ10 mm - (no heat treatment, wiredrawing 1) → φ9 mm - (heat treatment, wiredrawing 2) → φ8 mm - (no heat treatment, wiredrawing 3) → φ7 mm - (heat treatment, wiredrawing 4) → φ6 mm - (no heat treatment, wiredrawing 5) → φ5 mm - (heat treatment, wiredrawing 6) → φ4 mm - (no heat treatment, wiredrawing 7) → φ3 mm - (no heat treatment, wiredrawing 8) → φ2.4 mm (Note that "heat treatment, wiredrawing" refers to a process of performing heat treatment at 1100°C for 1 hour in a bright annealing furnace, followed by wiredrawing. "wiredrawing without heat treatment" refers to a process of performing wiredrawing without the above heat treatment.) In this way, a solid wire with a final wire diameter of φ2.4 mm was prototyped.

[0077] However, in Wire No. 33 (Comparative Example), the steps (heat treatment, wiredrawing 4) and (heat treatment, wiredrawing 6) in the above step (3) were both changed to (no heat treatment, wiredrawing 4) and (no heat treatment, wiredrawing 6). Also, in Wire No. 34 (Comparative Example), the step (no heat treatment, wiredrawing 7) in the above step (3) was changed to (heat treatment, wiredrawing 7).

[0078] The chemical composition of the solid wire thus obtained was analyzed and found to be as shown in Tables 1-1 to 1-3 and Tables 2-1 to 2-3.

[0079] The units of the contents of the chemical compositions of the wires shown in Tables 1-1 to 1-3 and Tables 2-1 to 2-3 are mass % relative to the total mass of the solid wire.

[0080] The remainder of the wires shown in Tables 1-1 to 1-3 and Tables 2-1 to 2-3 (i.e., components other than those shown in the tables) is iron and impurities. Note that in Tables 1-1 to 1-3 and Tables 2-1 to 2-3, numerical values ​​outside the ranges specified in this disclosure are underlined. Also, in Tables 1-1 to 1-3 and Tables 2-1 to 2-3, blank spaces in the tables relating to the content of a chemical component mean that the content of that chemical component is less than the significant digits. These chemical components may be unavoidably mixed in or produced in amounts less than the significant digits.

[0081] The fcc ratio in the wire structure was determined by the following method. A sample was taken from the wire, and the bcc ratio (%) was measured on the sample surface by a magnetic induction method using a FERITSCOPE (registered trademark) FMP30 (manufactured by Fischer Instruments Inc.) and a Fischer Instruments Inc. probe (FGAB 1.3-Fe) as the probe of the measuring instrument, and the arithmetic mean value of the measured bcc ratios was calculated. Using the obtained mean value of the bcc ratios, the fcc ratio (%) in the wire structure was calculated by the following formula: fcc ratio = 100 - bcc ratio

[0082]

[0083]

[0084]

[0085]

[0086]

[0087]

[0088] [Evaluation / Feedability Test (Straightening Degree)] Using the solid wires of the present disclosure and comparative examples, a feedability test was conducted using a LINCOLN submerged arc welding device. FIG. 1 shows a schematic diagram of the wire protruding from the tip end of a straightener. When a NITTETSU FILLER 196 manufactured by Nippon Steel Welding Industries Co., Ltd. was used as the reference wire, the length of the deviation (L) of the feed position at a distance of 50 mm from the tip end 4 was adjusted to 1 mm or less. The wire 2 was fed downward in the direction of gravity at a wire feed rate of 300 cm / min, and the length of the deviation (L) of the feed position at a distance of 50 mm from the tip end 4 was measured and evaluated as the straightening degree based on the following evaluation criteria. -Evaluation Criteria- A (◎): Deviation (L) is 1 mm or less B (◯): Deviation (L) is more than 1 mm and 2 mm or less C (△): Deviation (L) is more than 2 mm and 3 mm or less D (×): Deviation (L) is more than 3 mm

[0089]

[0090] The results shown in the table indicate that the solid wires of the present disclosure have a Vickers hardness Hv in the range of 180 to 500, and are excellent in the degree of straightening. On the other hand, the solid wires of the comparative examples do not satisfy any of the requirements defined in the present disclosure, and have a Vickers hardness Hv outside the range of 180 to 500, and are therefore evaluated as inferior in the degree of straightening.

[0091] 2 Wire 4 Tip end

Claims

1. Vickers hardness Hv is 180 or more and 500 or less, fcc ratio determined by magnetic induction method is 70% or more, and chemical composition is, in mass% with respect to the total mass of the solid wire, C: 0% to 0.650%, Si: 0.03% to 0.50%, Mn: 4.1% to 30.0%, P: 0.050% or less, S: 0.050% or less, Cu: 0% to 5.0%, Ni: 1.0% to 30.0%, Cr: 0% to 10.0%, Mo: 0% to 10.0%, Nb: 0% to 1.00%, V: 0% to 1.00%, Co: 0% to 1.00%, Pb: 0% to 1.00%, Sn: 0% to 1.000%, A solid wire comprising: Al: 0% to 0.10%, Ti: 0% to 0.10%, Ta: 0 to 1.00%, Hf: 0 to 1.00%, W: 0 to 30.00%, Mg: 0 to 0.50%, REM: 0 to 0.50%, Zr: 0 to 5.00%, B: 0% to 0.1000%, N: 0% to 0.500%, and O: 0.0500% or less, with the balance being Fe and impurities.

2. A solid wire as set forth in claim 1, wherein the area ratio of inclusions having a circle equivalent diameter of 5 μm or more in said solid wire is 3.00% or less.

3. A solid wire according to claim 1, wherein the sum of the Mn content and the Ni content (Mn + Ni) is 5.0% or more, and the sum of the Mn content, the Ni content and the Cr content (Mn + Ni + Cr) is 15.0% or more.

4. A solid wire according to claim 1, wherein the mass ratio of the Mn content to the Ni content (Ni / Mn) is 0.10 or more.

5. The solid wire according to claim 4, wherein the mass ratio (Ni / Mn) is 1.00 or more.

6. A solid wire according to claim 1, wherein the total content of Nb, V, Ti, Ta, Hf, and Zr (Nb + V + Ti + Ta + Hf + Zr) is 0.0005% or more and 5.00% or less.

7. A method for manufacturing a welded joint, comprising a step of welding steel materials using the solid wire according to any one of claims 1 to 6 by at least one welding method selected from the group consisting of submerged arc welding, gas metal arc welding, and tungsten inert gas welding.

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