Method for manufacturing coated arc welding rods and weld joints

Abstract

The invention comprises a steel core wire and a flux coating the core wire, wherein the chemical composition of the core wire is C: 0 to 0.650%, Si: 0.03 to 0.50%, Mn: 2.1 to 30.0%, P: 0 to 0.050%, S: 0 to 0.050%, 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 1.00%, Al: 0 to 0.10%, Ti: 0 to 0.10%, B: 0 to 0.1000%, N: 0 to A coated arc welding electrode having 0.5000%, remainder: Fe and impurities, with (Mn+Ni) of 5.0% or more, (Mn+Ni+Cr) of 15.0% or more, and an fcc ratio of 70% or more in the core wire.

Description

Technology Field

[0001] The present disclosure relates to a method for manufacturing a coated arc welding rod and a welded joint. Background Technology

[0002] In recent years, due to the tightening of carbon dioxide emission regulations caused by global warming, the demand for hydrogen fuel, which emits no carbon dioxide compared to oil and coal, and natural gas, which emits less carbon dioxide, has been increasing. Consequently, the global demand for the construction of liquid hydrogen tanks, liquid carbon dioxide tanks, and LNG tanks used on ships and land has also been rising. For steel materials used in liquid hydrogen tanks, liquid carbon dioxide tanks, and LNG tanks, Ni-based low-temperature steel containing 6 to 9% Ni is being used to ensure toughness at extremely low temperatures of -196°C.

[0003] In addition, for welding these Ni-based low-temperature steels, austenitic coated arc welding electrodes are used to obtain weld metal with excellent low-temperature toughness. These coated arc welding electrodes are mainly designed with a Ni content of 70%.

[0004] For example, regarding a welding material having a Ni content of 70%, Patent Document 1 describes a Ni-based material having a Ni content of 35 to 70%, containing at least 4.0 mass% of TiO2, SiO2, and ZrO2 in total amount relative to the total mass of the wire in the flux, and also containing 0.6 to 1.2 mass% of Mn oxide in terms of MnO2, and when the contents of TiO2, SiO2, ZrO2, and MnO2 (converted amounts) are expressed in mass% as [TiO2], [SiO2], [ZrO2], and [MnO2], respectively, [TiO2] / [ZrO2] is 2.3 to 3.3, [SiO2] / [ZrO2] is 0.9 to 1.5, and ([TiO2]+[SiO2]+[ZrO2]) / [MnO2] is 5 to 13. A "flux-containing wire having an alloy as the core wire" is disclosed. Prior art literature

[0005] Japanese Patent Publication No. 2008-246507 The problem to be solved

[0006] However, welding materials designed with a Ni content of 70% to ensure low-temperature toughness of the weld metal are very expensive, so there is a demand for cheaper alternatives.

[0007] While expensive Ni is known as an austenite-stabilizing element, inexpensive Mn has the same effect. Therefore, reducing the Ni content and increasing the Mn content yields a weld metal that is inexpensive and has excellent low-temperature toughness. However, increasing Mn alone generates a large amount of fumes. If fumes increase, the visibility of the weld metal or arc deteriorates, becoming a factor in causing welding defects.

[0008] Accordingly, the objective of the present invention is to provide a coated arc welding rod that can obtain a weld metal with low cost and excellent low-temperature toughness, and a method for manufacturing a weld joint using said coated arc welding rod. means of solving the problem

[0009] The means of solving the problem include the following modes.

[0010] <1> A coated arc welding electrode comprising a steel core wire and a flux coating the core wire, wherein the chemical composition of the core wire is, in mass % relative to the total mass of the core wire,

[0011] C: 0 to 0.650%,

[0012] Si: 0.03 to 0.50%,

[0013] Mn: 2.1 to 30.0%,

[0014] P: 0 to 0.050%,

[0015] S: 0 to 0.050%,

[0016] Cu: 0 to 5.0%,

[0017] Ni: 1.0 to 30.0%,

[0018] Cr: 0 to 10.0%,

[0019] Mo: 0 to 10.0%,

[0020] Nb: 0 to 1.00%,

[0021] V: 0 to 1.00%,

[0022] Co: 0 to 1.00%,

[0023] Pb: 0 to 1.00%,

[0024] Sn: 0 to 1.00%,

[0025] Al: 0 to 0.10%,

[0026] Ti: 0 to 0.10%,

[0027] B: 0 to 0.1000%,

[0028] N: 0 to 0.5000%,

[0029] O : 0 to 0.0050%, and

[0030] Remainder: Fe and impurities,

[0031] In addition, the sum of the above Mn content and the above Ni content (Mn+Ni) is 5.0% or more, and

[0032] The sum of the above Mn content, the above Ni content, and the above Cr content (Mn+Ni+Cr) is 15.0% or more, and

[0033] A coated arc welding electrode having an fcc ratio of 70% or more obtained by the magnetic induction method in the above-mentioned core wire.

[0034] <2> A mass ratio (Ni / Mn) of the above Mn content and the above Ni content of 0.10 or more, <1> Coated arc welding rod as described in

[0035] <3> The above mass ratio (Ni / Mn) is 1.00 or higher, <2> Coated arc welding rod as described in

[0036] <4> The above Ti content is Ti: 0.003 to 0.10%, <1> inside <3> Coated arc welding rods as described in any one of the items.

[0037] <5> The chemical composition of the flux in mass % relative to the total mass of the flux,

[0038] Sum of TiO2 equivalent values ​​of Ti oxide: 0 to 25.00%,

[0039] Sum of SiO2 equivalent values ​​of Si oxide: 0 to 25.00%,

[0040] Sum of ZrO2 equivalent values ​​of Zr oxide: 0 to 5.00%,

[0041] Sum of Al2O3 equivalent values ​​of Al oxide: 0 to 5.00%,

[0042] Sum of MgO equivalent values ​​of Mg oxide: 0 to 5.00%,

[0043] Sum of CaO equivalent values ​​of Ca oxide: 0 to 25.00%,

[0044] Sum of Na2O equivalent values ​​of Na oxide: 0 to 5.00%,

[0045] Sum of K2O equivalent values ​​of K oxides: 0 to 5.00%,

[0046] CaF2: 0 to 30.00%,

[0047] CaCO3: 0 to 60.00%,

[0048] BaCO3: 0 to 15.00%,

[0049] MgCO3: 0 to 15.00%, and

[0050] Li2CO3: containing 0 to 15.00%,

[0051] In a mass % relative to the total mass of the flux, the metal component in the chemical composition of the flux is,

[0052] C: 0.020 to 5.000%,

[0053] Si: 0 to 5.00%,

[0054] Mn: 0 to 30.00%,

[0055] P: 0 to 0.050%,

[0056] S: 0 to 0.050%,

[0057] Cu: 0 to 20.0%,

[0058] Ni: 0 to 20.0%,

[0059] Cr: 0 to 20.0%,

[0060] Mo: 0 to 10.0%,

[0061] Nb: 0 to 5.00%,

[0062] V: 0 to 5.0%,

[0063] Co: 0 to 1.00%,

[0064] Pb: 0 to 1.00%,

[0065] Sn: 0 to 1.00%,

[0066] W: 0 to 20.0%,

[0067] Mg: 0 to 5.00%,

[0068] Al: 0 to 5.0%,

[0069] Ca: 0 to 5.00%,

[0070] Ti: 0 to 5.000%,

[0071] B: 0 to 5.0000%,

[0072] REM: 0 to 5.00%,

[0073] Bi: 0 to 5.000%,

[0074] N: 0 to 5.0000%, and

[0075] Remainder: Fe and impurities, and also

[0076] The sum of the contents of the above CaCO3, above BaCO3, above MgCO3 and above Li2CO3 is 5.00% or more, <1> inside <4> Coated arc welding rods as described in any one of the items.

[0077] <6> The sum of the Mn content and the Ni content (Mn+Ni) in the above flux is 1.00% or more, <5> Coated arc welding rod as described in

[0078] <7> The sum of the TiO2 equivalent values ​​of the above Ti oxide, the sum of the SiO2 equivalent values ​​of the above Si oxide, the sum of the ZrO2 equivalent values ​​of the above Zr oxide, the sum of the Al2O3 equivalent values ​​of the above Al oxide, the sum of the MgO equivalent values ​​of the above Mg oxide, the sum of the CaO equivalent values ​​of the above Ca oxide, the sum of the Na2O equivalent values ​​of the above Na oxide, the sum of the K2O equivalent values ​​of the above K oxide, and the sum of the CaF2 content, the CaCO3 content, the BaCO3 content, the MgCO3 content, and the Li2CO3 content, wherein the sum X is 94.98% or less, <5> or <6> Coated arc welding rod as described in

[0079] <8> The average thickness of the above flux is 5.0 mm or less, <1> inside <7> Coated arc welding rods as described in any one of the items.

[0080] <9> <1> inside <8> A method for manufacturing a welded joint comprising a process of welding steel using a coated arc welding rod described in any one of the claims. Effects of the invention

[0081] According to the present disclosure, a coated arc welding rod that can obtain a weld metal with low cost and excellent low-temperature toughness, and can reduce the amount of fumes generated, and a method for manufacturing a weld joint using said coated arc welding rod can be provided. Specific details for implementing the invention

[0082] An exemplary embodiment of the present disclosure will be described.

[0083] Furthermore, within this specification, a numerical range indicated using "to" means a range that includes these figures as lower and upper limits, where "greater than" and "less than" are not indicated in the figures before and after "to". Additionally, a numerical range that does not include these figures as lower or upper limits, where "greater than" or "less than" is indicated in the figures before and after "to".

[0084] In the numerical ranges described stepwise within this specification, the upper limit of any stepwise numerical range may be substituted with the upper limit of another stepwise numerical range or may also be substituted with the value disclosed in the embodiment. Additionally, the lower limit of any stepwise numerical range may be substituted with the lower limit of another stepwise numerical range or may also be substituted with the value disclosed in the embodiment.

[0085] In addition, regarding the content, "%" means "mass%".

[0086] "0 to" as the content (%) means that the component is an optional component and does not need to be included.

[0087] Coated Arc Welding Electrode

[0088] A coated arc welding electrode according to the present disclosure (hereinafter simply referred to as "welding electrode") comprises a steel core wire and a flux that coats the core wire. The coated arc welding electrode according to the present disclosure has a chemical composition of the core wire that is of a predetermined composition.

[0089] The coated arc welding electrode according to the present disclosure is a welding electrode that, by the above composition, can obtain a weld metal with low cost and excellent low-temperature toughness, and can also reduce the amount of fumes generated.

[0090] And, the coated arc welding rod according to the present disclosure was determined by the following findings.

[0091] The inventors examined a technology for obtaining a welding rod capable of improving the low-temperature toughness of the weld metal and reducing the amount of fumes generated, even when the Ni content is reduced and the Mn content is increased. As a result, the following findings were obtained.

[0092] Fumes are formed when metal vapor generated from a molten pool is released into the air by the arc force and solidifies. By controlling this arc force, the amount of fumes generated can be reduced. The arc force depends not only on the welding conditions but also on the composition of the core wire. Specifically, by controlling the content of Ni and Mn, which function as austenite-stabilizing elements contained in the core wire, the Ni content in the entire welding rod can be reduced, and even if the Mn content is increased, the arc force can be mitigated, allowing for the production of a weld metal with excellent low-temperature toughness and a reduction in the amount of fumes generated.

[0093] From the above findings, it has been discovered that the coated arc welding electrode according to the present disclosure is a welding electrode that can obtain a weld metal with low cost and excellent low-temperature toughness, and can also reduce the amount of fumes generated.

[0094] In addition, the inventors examined metal carbonates, oxides, Mn, and Ni in the flux and found that low-temperature toughness is also improved by controlling their amounts.

[0095] From the above findings, it has been discovered that the coated arc welding electrode according to the present disclosure preferably contains oxide, Mn, and Ni in predetermined amounts, and that this allows for obtaining a weld metal with excellent low-temperature toughness at a low cost, and also enables a welding electrode that can reduce the amount of fumes generated.

[0096] Hereinafter, the reasons for limiting the requirements constituting the coated arc welding electrode according to the present disclosure (including any requirements) will be explained in detail.

[0097] (Chemical composition of the heart wire)

[0098] The chemical composition of the core wire is explained in detail below.

[0099] In addition, regarding the description of the chemical composition of the core wire, "%" means "mass % of the total mass of the chemical composition of the core wire" unless otherwise specified.

[0100] The chemical composition of the core wire is,

[0101] C: 0 to 0.650%,

[0102] Si: 0.03 to 0.50%,

[0103] Mn: 2.1 to 30.0%,

[0104] P: 0 to 0.050%,

[0105] S: 0 to 0.050%,

[0106] Cu: 0 to 5.0%,

[0107] Ni: 1.0 to 30.0%,

[0108] Cr: 0 to 10.0%,

[0109] Mo: 0 to 10.0%,

[0110] Nb: 0 to 1.00%,

[0111] V: 0 to 1.00%,

[0112] Co: 0 to 1.00%,

[0113] Pb: 0 to 1.00%,

[0114] Sn: 0 to 1.00%,

[0115] Al: 0 to 0.10%,

[0116] Ti: 0 to 0.10%,

[0117] B: 0 to 0.1000%,

[0118] N: 0 to 0.5000%,

[0119] O : 0 to 0.0050%, and

[0120] Remainder: Fe and impurities,

[0121] In addition, the sum of the Mn content and Ni content (Mn+Ni) is 5.0% or more, and

[0122] The sum of the Mn content, Ni content, and Cr content (Mn+Ni+Cr) is 15.0% or more, and

[0123] The fcc ratio obtained by the magnetic induction method in the above-mentioned core wire is 70% or more.

[0124] (C: 0 to 0.650%)

[0125] Carbon (C) is an element that causes spatter. For spatter reduction, the lower the carbon content in the core wire, the more advantageous it is. Furthermore, carbon is also an interstitial solid solution strengthening element. If the carbon content in the core wire is excessive, the wire becomes hard, making processing difficult. Additionally, spatter increases.

[0126] Accordingly, the C content of the core wire is set to 0 to 0.650%.

[0127] However, to make the carbon content of the core wire 0%, the cost of decarbonization increases. In addition, there is a concern that the carbon content of the welding rod is insufficient and the strength of the weld metal is insufficient. Therefore, if the carbon content of the core wire is low, the carbon content of the flux must be increased. Accordingly, the lower limit of the carbon content of the core wire may be 0.003%, 0.005%, or 0.008%.

[0128] The upper limit of the C content of the core 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%.

[0129] (Si: 0.03 to 0.50%)

[0130] Si is a deoxidizing element. If the Si content of the core wire is too low, the P content of the core wire increases.

[0131] Meanwhile, Si has low solubility in the austenite phase, and as the amount of Si increases, embrittlement phases such as intermetallic compounds and δ-ferrite are formed at high temperatures, causing high-temperature ductility to deteriorate.

[0132] Accordingly, the Si content of the core wire is set to 0.03 to 0.50%.

[0133] The lower limit of the Si content of the core wire is preferably 0.04%, 0.05%, or 0.08%.

[0134] The upper limit of the Si content of the core wire is preferably less than 0.50%, 0.48%, 0.45%, 0.40%, 0.35%, 0.30%, or 0.20%.

[0135] (Mn: 2.1 to 30.0%)

[0136] Mn is an element that causes an increase in the amount of fumes generated. For reducing the amount of fumes generated, it is advantageous for the Mn content of the core wire to be as low as possible. In addition, if Mn is added in excess, the stacking fault energy decreases, and toughness deteriorates.

[0137] Meanwhile, Mn is an austenite-stabilizing element. If the Mn content of the core wire is too low, the overall Mn content of the welding rod becomes insufficient, making it difficult for the austenitization of the weld metal to proceed and causing a deterioration in low-temperature toughness. Furthermore, to ensure the low-temperature toughness of the weld metal, it becomes necessary to excessively increase the Mn content of the flux.

[0138] Accordingly, the Mn content of the core wire is set to 2.1 to 30.0%.

[0139] The lower limit of the Mn content of the core wire is preferably 3.0%, 5.0%, greater than 5.0%, 5.2%, greater than 6.0%, 6.2%, 7.0%, greater than 7.0%, 7.2%, greater than 10.0%, or 10.2%.

[0140] The upper limit of the Mn content of the core wire is preferably 25.0%, 20.0%, 19.0%, 18.0%, 15.0%, or 12.0%.

[0141] (P: 0 to 0.050%)

[0142] Since P is an impurity element that reduces the toughness of the weld metal, it is desirable to minimize the P content of the core wire. Accordingly, the lower limit of the P content of the core wire is set to 0%. However, from the perspective of reducing the cost of P removal, the P content of the core wire should be 0.003% or higher.

[0143] Meanwhile, if the P content of the core wire is 0.050% or less, the adverse effect on the toughness of P is within an acceptable range.

[0144] Accordingly, the P content of the core wire is set to 0 to 0.050%.

[0145] In order to effectively suppress the decrease in toughness of the weld metal, the P content of the core wire is preferably 0.040% or less, 0.030% or less, 0.020% or less, 0.015% or less, or 0.010% or less.

[0146] (S: 0 to 0.050%)

[0147] Since sulfur is an impurity element that reduces the toughness of the weld metal, it is desirable to minimize the sulfur content of the core wire. Accordingly, the lower limit of the sulfur content of the core wire is set to 0%. However, from the perspective of reducing sulfur removal costs, the sulfur content of the core wire should be 0.003% or higher.

[0148] Meanwhile, if the S content of the core wire is 0.050% or less, the adverse effect of S on toughness is within an acceptable range.

[0149] Accordingly, the S content of the core wire is set to 0 to 0.050%.

[0150] In order to effectively suppress the decrease in toughness of the weld metal, the sulfur content of the core wire is preferably 0.040% or less, 0.030% or less, 0.020% or less, 0.015% or less, or 0.010% or less.

[0151] (Cu: 0 to 5.0%)

[0152] Copper is a precipitation strengthening element and may be included in the core wire to improve the strength of the weld metal. However, if the copper content of the core wire is excessive, the above effect becomes saturated. Furthermore, if the copper content of the core wire is excessive, the wire becomes hard, making wire processing difficult.

[0153] Accordingly, the Cu content of the core wire is set to 0 to 5.0%.

[0154] The lower limit of the Cu content of the core wire is preferably 0.3%, 0.5%, or 0.7%.

[0155] The upper limit of the Cu content of the core wire is preferably 4.5%, 4.0%, or 3.5%.

[0156] (Ni: 1.0 to 30.0%)

[0157] Ni is an austenite-stabilizing element. If the Ni content of the core wire is too low, the overall Ni content of the welding rod becomes insufficient, making it difficult for the austenitization of the weld metal to proceed, which leads to a deterioration in low-temperature toughness. Furthermore, to ensure the low-temperature toughness of the weld metal, it becomes necessary to excessively increase the Ni content of the flux.

[0158] On the other hand, increasing the Ni content of the core wire raises the cost of the welding rod.

[0159] Accordingly, the Ni content of the core wire is set to 1.0 to 30.0%.

[0160] The lower limit of the Ni content of the core wire is preferably 2.0%, 3.0%, 5.0%, greater than 6.0%, 6.2%, 7.0%, greater than 8.0%, or 8.2%.

[0161] The upper limit of the Ni content of the core wire is preferably 28.0%, 26.0%, 24.0%, 22.0%, 20.0%, 19.0%, 18.0%, 15.0%, or 12.0%.

[0162] (Cr: 0 to 10.0%)

[0163] Cr is an austenite-stabilizing element and may be included in the core wire to improve the low-temperature toughness of the weld metal.

[0164] On the other hand, if the Cr content of the core wire is excessive, a martensitic structure forms in the core wire, making core wire processing difficult. Furthermore, if the Cr content of the core wire is excessive, the amount of low-melting point compounds in the molten metal increases, and since the solid-liquid coexistence temperature range of the molten metal widens, it becomes prone to high-temperature cracking.

[0165] Accordingly, the Cr content of the core wire is set to 0 to 10.0%.

[0166] The lower limit of the Cr content of the core wire is preferably 0.01%, 0.02%, 1.0%, 2.0%, or 3.0%.

[0167] The upper limit of the Cr content of the core wire is preferably 9.0%, 8.0%, less than 8.0%, 7.8%, 7.0%, less than 6.0%, or 5.8%.

[0168] (Mo: 0 to 10.0%)

[0169] Mo is a precipitation strengthening element and may be included in the core wire to improve the strength of the weld metal. However, if the Mo content in the core wire is excessive, the wire becomes hard, making processing difficult. Furthermore, if the Mo content is excessive, the strength of the weld metal becomes excessive, leading to a decrease in low-temperature toughness.

[0170] Accordingly, the Mo content of the core wire is set to 0 to 10.0%.

[0171] The lower limit of the Mo content of the core wire is preferably 1.0%, 2.0%, or 3.0%.

[0172] The upper limit of the Mo content of the core wire is preferably 9.0%, 8.0%, or 7.0%.

[0173] (Nb: 0 to 1.00%)

[0174] Since Nb is an element that forms carbides in the weld metal and increases the strength of the weld metal, it may be included in the core wire.

[0175] On the other hand, if the Nb content of the core wire is excessive, the wire becomes hard, making wire processing difficult. In addition, if the Nb content of the core wire is excessive, there is a risk of high-temperature cracking in the weld metal.

[0176] Accordingly, the Nb content of the core wire is set to 0 to 1.00%.

[0177] The lower limit of the Nb content of the core wire is preferably 0.01%, 0.05%, 0.10%, 0.15%, or 0.20%.

[0178] The upper limit of the Nb content of the core wire is preferably 0.95%, 0.90%, 0.85%, or 0.80%.

[0179] (V: 0 to 1.00%)

[0180] Since V is an element that forms carbonitrides in the weld metal and increases the strength of the weld metal, it may be included in the core wire.

[0181] On the other hand, if the V content of the core wire is excessive, the wire becomes hard, making wire processing difficult. Additionally, if the V content of the core wire is excessive, there is a possibility that high-temperature cracking may occur in the weld metal.

[0182] Accordingly, the V content of the core wire is set to 0 to 1.00%.

[0183] The lower limit of the V content of the core wire is preferably 0.01%, 0.05%, 0.10%, 0.15%, or 0.20%.

[0184] The upper limit of the V content of the core wire is preferably 0.95%, 0.90%, 0.85%, or 0.80%.

[0185] (Co: 0 to 1.00%)

[0186] Since Co is an element that increases the strength of the weld metal through solid solution strengthening, it may be included in the core wire.

[0187] On the other hand, if the Co content of the core wire is excessive, the wire becomes hard, making wire processing difficult. Furthermore, if the Co content of the core wire is excessive, the ductility of the weld metal decreases, making it impossible to ensure toughness.

[0188] Accordingly, the Co content of the core wire is set to 0 to 1.00%.

[0189] The lower limit of the Co content of the core wire is preferably 0.01%, 0.05%, 0.10%, 0.15%, or 0.20%.

[0190] The upper limit of the Co content of the core wire is preferably 0.95%, 0.90%, 0.85%, or 0.80%.

[0191] (Pb: 0 to 1.00%)

[0192] Pb may be included in the core wire because it has the effect of improving the machinability of the weld metal by enhancing the toe formability between the base steel and the weld metal.

[0193] On the other hand, if the Pb content of the core wire is excessive, the arc condition deteriorates, increasing spatter.

[0194] Accordingly, the Pb content of the core wire is set to 0 to 1.00%.

[0195] The lower limit of the Pb content of the core wire is preferably 0.01%, 0.05%, 0.10%, 0.15%, or 0.20%.

[0196] The upper limit of the Pb content of the core wire is preferably 0.95%, 0.90%, 0.85%, or 0.80%.

[0197] (Sn: 0 to 1.00%)

[0198] Since Sn is an element that improves the corrosion resistance of weld metal, it may be included in the core wire.

[0199] On the other hand, if the Sn content of the core wire is excessive, there is a risk of cracking in the weld metal.

[0200] Accordingly, the Sn content of the core wire is set to 0 to 1.00%.

[0201] The lower limit of the Sn content of the core wire is preferably 0.01%, 0.05%, 0.10%, 0.15%, or 0.20%.

[0202] The upper limit of the Sn content of the core wire is preferably 0.95%, 0.90%, 0.85%, or 0.80%.

[0203] (Al: 0 to 0.10%)

[0204] Al is a deoxidizing element and may be included in the core wire to suppress welding defects and improve the cleanliness of the weld metal.

[0205] On the other hand, if the Al content of the core wire is excessive, coarse inclusions are formed within the wire, making wire processing difficult. Furthermore, if the Al content is excessive, Al may form nitrides or oxides within the weld metal, potentially reducing the low-temperature toughness of the weld metal.

[0206] Accordingly, the Al content of the core wire is set to 0 to 0.10%.

[0207] The lower limit of the Al content of the core wire is preferably 0.01%, 0.02%, or 0.03%.

[0208] The upper limit of the Al content of the core wire is preferably 0.09%, 0.08%, or 0.07%.

[0209] (Ti: 0 to 0.10%)

[0210] Ti is a deoxidizing element and may be included in the core wire to suppress welding defects and improve the cleanliness of the weld metal.

[0211] On the other hand, if the Ti content of the core wire is excessive, coarse inclusions are formed within the wire, making wire processing difficult. Furthermore, if the Ti content of the core wire is excessive, carbides may form in the weld metal, potentially degrading the toughness of the weld metal.

[0212] Accordingly, the Ti content of the core wire is set to 0 to 0.10%.

[0213] The lower limit of the Ti content of the core wire is preferably 0.003%, 0.01%, 0.02%, or 0.03%.

[0214] The upper limit of the Ti content of the core wire is preferably 0.09%, 0.08%, or 0.07%.

[0215] (B: 0 to 0.1000%)

[0216] B is an austenite-stabilizing element and an interstitial solid solution strengthening element, and may be included in the core wire to improve the low-temperature toughness and strength of the weld metal.

[0217] On the other hand, if the B content of the core wire is excessive, the core wire becomes hard, making core wire processing difficult. In addition, if the B content of the core wire is excessive, M 23 (C, B)6 precipitates and causes toughness deterioration.

[0218] Accordingly, the B content of the core wire is set to 0 to 0.1000%.

[0219] The lower limit of the B content of the core wire is preferably 0.0005%, 0.0010%, or 0.0020%.

[0220] The upper limit of the B content of the core wire is preferably 0.0800%, 0.0500%, or 0.0100%.

[0221] (N: 0 to 0.5000%)

[0222] N is an austenite-stabilizing element and an interstitial solid solution strengthening element, and may be included in the core wire to improve the low-temperature toughness and strength of the weld metal.

[0223] On the other hand, if the N content of the core wire is excessive, the core wire becomes hard, making it difficult to process. In addition, if the N content of the core wire is excessive, the occurrence of blows increases, which causes welding defects.

[0224] Accordingly, the N content of the core wire is set to 0 to 0.5000%.

[0225] The lower limit of the N content of the core wire is preferably 0.0010%, 0.0100%, or 0.0500%.

[0226] The upper limit of the N content of the core wire is preferably 0.4500%, 0.4000%, or 0.3500%.

[0227] (O : 0 to 0.0050%)

[0228] O may be contained in the core wire as an impurity. However, since an excessive amount of O can cause deterioration in toughness and ductility of the weld metal, the upper limit of the O content in the core wire is set to 0.0050% or less.

[0229] The upper limit of the O content of the core wire is preferably 0.0040% or 0.0030%.

[0230] Meanwhile, from the perspective of suppressing the increase in manufacturing costs due to the reduction of the O content, the lower limit of the O content of the core wire is preferably 0.0003% or 0.0005%.

[0231] (Remainder: Fe and impurities)

[0232] The remaining components in the chemical composition of the core wire are Fe and impurities.

[0233] Impurities refer to components that are introduced during the industrial production of core wires due to raw materials such as ore or scrap, or various factors of the manufacturing process, and are permitted within a range that does not adversely affect the characteristics of the welding rod.

[0234] (Sum of Mn and Ni content (Mn+Ni))

[0235] Mn and Ni are each austenite-stabilizing elements that improve the low-temperature toughness of the weld metal. Meanwhile, since Ni is an expensive metal, in order to improve the low-temperature toughness of the weld metal while keeping the cost of the welding rod low, the Mn content and Ni content in the core wire each satisfy the above ranges, and the sum of the Mn content and Ni content (Mn+Ni) is 5.0% or more.

[0236] The sum of the Mn content and Ni content (Mn+Ni) in the core wire is preferably 7.0% or more, 10.0% or more, or 15.0% or more.

[0237] In addition, Mn is an element that causes an increase in the amount of fumes generated. Furthermore, if Mn is added in excess, the stacking fault energy decreases, and toughness deteriorates. Therefore, from the perspective of reducing the amount of fumes generated while suppressing the cost of welding rods and improving the low-temperature toughness of the weld metal, it is desirable that the Mn content and Ni content in the core wire each satisfy the above ranges, and that the sum of the Mn content and Ni content (Mn+Ni) be 37.0% or less.

[0238] The sum of the Mn content and Ni content (Mn+Ni) in the core wire is, more preferably, 35.0% or less, 32.0% or less, or 30.0% or less.

[0239] (Sum of Mn content, Ni content and Cr content (Mn+Ni+Cr))

[0240] Mn, Ni, and Cr are each austenite-stabilizing elements that improve the low-temperature toughness of the weld metal. Meanwhile, since Ni is an expensive metal, in order to improve the low-temperature toughness of the weld metal while keeping the cost of the welding rod low, the Mn content, Ni content, and Cr content in the core wire each satisfy the above ranges, and the sum of the Mn content, Ni content, and Cr content (Mn+Ni+Cr) is 15.0% or more.

[0241] The sum of the Mn content, Ni content, and Cr content (Mn+Ni+Cr) in the core wire is 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.

[0242] Mn is an element that causes an increase in the amount of fumes generated. In addition, if Mn is added in excess, the stacking fault energy decreases, and toughness deteriorates. Cr is an element that forms a martensite structure and affects the workability of the core wire. In addition, Cr causes an increase in the amount of low-melting point compounds in the molten metal. Therefore, from the perspective of reducing the amount of fumes generated, increasing the workability of the core wire, and reducing the amount of low-melting point compounds in the molten metal while improving the low-temperature toughness of the weld metal and suppressing the cost of the welding rod, it is desirable that the Mn content, Ni content, and Cr content in the core wire each satisfy the above ranges, and that the sum of the Mn content, Ni content, and Cr content (Mn+Ni+Cr) be 47.0% or less.

[0243] The sum of the Mn content, Ni content, and Cr content (Mn+Ni+Cr) in the core wire is, more preferably, 45.0% or less, 42.0% or less, or 40.0% or less.

[0244] (Mass ratio of Mn content to Ni content (Ni / Mn))

[0245] Mn and Ni are austenite-stabilizing elements, respectively, and improve the low-temperature toughness of weld metal. On the other hand, Ni is an expensive metal, and Mn is an element that causes an increase in fume generation. Furthermore, adding an excess of Mn lowers the stacking fault energy, leading to a deterioration in toughness. Additionally, Ni improves toughness by increasing the stacking fault energy.

[0246] For this reason, in order to suppress the cost of welding rods, improve the low-temperature toughness of the weld metal, and reduce the amount of fumes generated, it is desirable to set the mass ratio of the Mn content and the Ni content (Ni / Mn) in the core wire to 0.10 or higher.

[0247] The lower limit of the mass ratio (Ni / Mn) of the Mn content and the Ni content in the core wire is, more preferably, 0.20, 0.30, 0.50, 0.70, 1.00, 1.10, or 1.20.

[0248] The upper limit of the mass ratio (Ni / Mn) of the Mn content and Ni content in the core wire is preferably 10.00, 8.00, or 5.00.

[0249] (fcc ratio obtained by self-induction)

[0250] To increase the low-temperature toughness of the weld metal, it is desirable to increase the proportion of austenite in the microstructure of the core wire. For this reason, the fcc ratio in the core wire is set to 70% or more. The fcc ratio is preferably 80% or more, or 90% or more, and may be 100%. In addition, the remainder of the microstructure is bcc.

[0251] The fcc ratio in the tissue of the heart can be determined by the following method.

[0252] A sample is taken from the core wire, and on the surface of the sample, a FERITSCOPE (registered trademark) FMP30 (manufactured by Fisher Instruments Inc.) is used, and a probe manufactured by Fisher Instruments Inc. (FGAB 1.3-Fe) is used with the probe of said measuring instrument to measure the bcc ratio (%) by magnetic induction, and the arithmetic mean value of the measured bcc ratio is calculated. Using the average value of the obtained bcc ratio, the fcc ratio (%) in the tissue of the core wire is calculated by the following formula.

[0253] fcc ratio = 100 - bcc ratio

[0254] (Chemical composition of flux)

[0255] Hereinafter, the preferred chemical composition of the flux according to the present disclosure will be described.

[0256] In addition, in the description of the chemical composition of the flux, "%" means "mass % of the total mass of the flux" unless otherwise specified.

[0257] The chemical composition of the flux according to the present disclosure is,

[0258] Sum of TiO2 equivalent values ​​of Ti oxide: 0 to 25.00%,

[0259] Sum of SiO2 equivalent values ​​of Si oxide: 0 to 25.00%,

[0260] Sum of ZrO2 equivalent values ​​of Zr oxide: 0 to 5.00%,

[0261] Sum of Al2O3 equivalent values ​​of Al oxide: 0 to 5.00%,

[0262] Sum of MgO equivalent values ​​of Mg oxide: 0 to 5.00%,

[0263] Sum of CaO equivalent values ​​of Ca oxide: 0 to 25.00%,

[0264] Sum of Na2O equivalent values ​​of Na oxide: 0 to 5.00%,

[0265] Sum of K2O equivalent values ​​of K oxides: 0 to 5.00%,

[0266] CaF2: 0 to 30.00%,

[0267] CaCO3: 0 to 60.00%,

[0268] BaCO3: 0 to 15.00%,

[0269] MgCO3: 0 to 15.00%, and

[0270] It is preferable to include 0 to 15.00% Li2CO3.

[0271] (Sum of TiO2 equivalent values ​​of Ti oxide: 0 to 25.00%)

[0272] Ti oxide is a slag component that acts to uniformly coat the entire bead with slag. Additionally, Ti oxide stabilizes arc sustainment, thereby reducing spatter generation and improving weldability (especially orientation weldability). For this reason, Ti oxide may be included.

[0273] However, it is preferable that the sum of the TiO2 equivalent values ​​of Ti oxide and the sum of the SiO2 equivalent values ​​of Si oxide be 5.00% or more, that is, it may contain only either Ti oxide or Si oxide. Accordingly, the lower limit of the sum of the TiO2 equivalent values ​​of Ti oxide may be 0%.

[0274] Meanwhile, since the total TiO2 equivalent value of Ti oxide is 25.00% or less, the oxygen content of the weld metal can be suppressed, thereby ensuring low-temperature toughness. In addition, since the total TiO2 equivalent value of Ti oxide is 25.00% or less, the increase in slag viscosity can be suppressed, so the slag does not become too thick, and the bulging shape of the bead's end can be prevented. Furthermore, since the total TiO2 equivalent value of Ti oxide is 25.00% or less, the occurrence of pitting can be suppressed. In addition, the occurrence of slag curling can be suppressed.

[0275] Therefore, it is preferable that the total TiO2 equivalent value of Ti oxide in the flux be 0 to 25.00%.

[0276] The lower limit of the sum of the TiO2 equivalent values ​​of Ti oxide is, more preferably, 1.00%, 2.00%, 3.00%, or 5.00%.

[0277] The upper limit of the sum of the TiO2 equivalent values ​​of Ti oxide is, more preferably, 23.00%, 20.00%, 18.00%, 15.00%, 13.00%, or 10.00%.

[0278] In addition, Ti oxide may exist mainly as rutile, titanium oxide, titanium slag, illuminite, sodium titaniumate, potassium titaniumate, etc., in the flux. Therefore, by mainly controlling the content of Ti oxide in the flux, the content of Ti oxide can be set to the above range.

[0279] Here, the sum of the TiO2 equivalent values ​​of Ti oxides refers to the mass percentage relative to the total mass of the welding rod of TiO2 when all Ti oxides contained in the flux (e.g., TiO, TiO2, Ti2O3, Ti3O5, etc., and added as rutile, titanium oxide, titanium slag, illuminite, sodium titaniumate, potassium titaniumate, etc.) are converted to TiO2.

[0280] Furthermore, the sum of the TiO2 equivalent values ​​of Ti oxide is determined by analyzing the mass of Ti present as an oxide in the flux using a fluorescence X-ray analysis device and an X-ray diffraction (XRD) device. Additionally, after analyzing the components contained in the flux by fluorescence X-ray analysis, the amount of Ti present as an oxide in the flux and the amount of Ti included as a metallic component can be determined by dividing them by interpreting the molecular structure of the contained components using X-ray diffraction (XRD).

[0281] Specifically, first, flux is collected from the welding rod and analyzed by the above method. For example, if TiO2, Ti2O3, and Ti3O5 are detected by analysis, the mass% of each Ti oxide is denoted as [TiO2], [Ti2O3], and [Ti3O5], and the sum of the Ti oxide converted values ​​is denoted as [converted TiO2], then it is calculated by the following Equation 1.

[0282] [Converted TiO2]=(0.60×[TiO2]+0.67×[Ti2O3]+0.64×[Ti3O5])×1.67 … Equation 1

[0283] The coefficients (0.60, 0.67, 0.64) in Equation 1 are coefficients for calculating the amount of Ti contained in each oxide, and the multiplier (1.67) at the end is a multiplier for calculating the TiO2 equivalent value from the total amount of Ti present as an oxide in the flux.

[0284] Here, the method for calculating the coefficients is explained. M x O y If oxides (e.g., TiO2, Ti2O3, Ti3O5) are detected, then M x O y The coefficient applied to is calculated using the following Equation 2.

[0285] [Atomic weight of element M]×x / ([Atomic weight of element M]×x+[Atomic weight of oxygen]×y) … Equation 2

[0286] 0.60, 0.67, and 0.64 in Equation 1 correspond to the coefficients obtained by Equation 2 above.

[0287] In addition, the method for calculating the multiplier to determine the converted value is explained. M a O b The multiplier for conversion to (e.g., TiO2) is calculated using Equation 3 below.

[0288] ([Atomic weight of element M]×a+[Atomic weight of oxygen]×b) / ([Atomic weight of element M]×a) … Equation 3

[0289] The 1.67 in Equation 1 corresponds to the multiplier obtained by Equation 3 above.

[0290] In addition, oxides are also considered to be compounds formed by combining two types of metal elements. The method for calculating the coefficient in that case is M x O y M 2 z (e.g., TiO3·Fe, i.e., M=Ti, M 2 If an oxide of Fe, x=1, y=3, z=1 is detected, calculate using Equation 4 below.

[0291] [Atomic weight of element M]×x / ([Atomic weight of element M]×x+[Atomic weight of oxygen]×y+[M 2 [Atomic weight of an element]×z) … Equation 4

[0292] In addition, the sum of the SiO2 equivalent values ​​of Si oxide, the sum of the ZrO2 equivalent values ​​of Zr oxide, the sum of the Al2O3 equivalent values ​​of Al oxide, the sum of the MgO equivalent values ​​of Mg oxide, the sum of the CaO equivalent values ​​of Ca oxide, the sum of the Na2O equivalent values ​​of Na oxide, the sum of the K2O equivalent values ​​of K oxide, the sum of the MnO2 equivalent values ​​of Mn oxide, and the sum of the FeO equivalent values ​​of Fe oxide are also obtained by calculations similar to the sum of the TiO2 equivalent values ​​of Ti oxide. That is, the flux collected by the fluorescence X-ray analysis device and the X-ray diffraction (XRD) device is analyzed, and depending on the various oxides detected, coefficients and multipliers are calculated based on the above Equations 2, 3, and 4, and calculated in the same way as the above Equation 1.

[0293] Representative oxides detected by analysis are listed below.

[0294] Si oxides; SiO, SiO2, Si2O3, Si2O4

[0295] Zr oxide; ZrO2

[0296] Al oxides; AlO, Al2O3, Al3O5

[0297] Mg oxide; MgO, MgO2, Mg2O

[0298] Ca oxide; CaO, CaO2

[0299] Na oxide; Na2O, Na2O2

[0300] K oxide; K2O, KO2

[0301] Mn oxides; MnO, Mn2O, MnO2

[0302] Fe oxides; FeO, Fe2O4, FeO3

[0303] (Sum of SiO2 equivalent values ​​of Si oxides: 0 to 25.00%)

[0304] Si oxide is a slag component and has the function of improving slag detachability by increasing the viscosity of the molten slag; therefore, from this perspective, it is acceptable to include Si oxide.

[0305] However, it is preferable that the sum of the TiO2 equivalent values ​​of Ti oxide and the sum of the SiO2 equivalent values ​​of Si oxide be 5.00% or more, that is, it may contain only one of Ti oxide and Si oxide. Accordingly, the lower limit of the sum of the SiO2 equivalent values ​​of Si oxide may be 0%.

[0306] In addition, since the total SiO2 equivalent value of Si oxide is 0.10% or more, the slag coating condition is improved, slag detachability is increased, and the bead shape and bead appearance can be improved. In addition, weldability (especially orientation weldability) can be secured.

[0307] Meanwhile, since the total SiO2 equivalent value of Si oxides is 25.00% or less, the oxygen content of the weld metal can be suppressed, thereby ensuring low-temperature toughness. In addition, since the total SiO2 equivalent value of Si oxides is 25.00% or less, the amount of spatter can be suppressed. Furthermore, since the total SiO2 equivalent value of Si oxides is 25.00% or less, the occurrence of pits and gas grooves can be suppressed. In addition, the occurrence of slag entrapment can be suppressed.

[0308] Therefore, it is preferable that the total SiO2 equivalent value of Si oxide in the flux be 0 to 25.00%.

[0309] The lower limit of the total SiO2 equivalent value of Si oxide is, more preferably, 0.05%, 0.10%, 0.15%, 0.20%, or 0.25%.

[0310] The upper limit of the total SiO2 equivalent value of Si oxide is, more preferably, 23.00%, 20.00%, 18.00%, 15.00%, 13.00%, or 10.00%.

[0311] In addition, Si oxides may exist mainly as silica sand, zircon sand, feldspar, sodium silicate, potassium silicate, etc. in the flux.

[0312] (The sum of the TiO2 equivalent values ​​of Ti oxide and the sum of the SiO2 equivalent values ​​of Si oxide is 5.0% or more)

[0313] Ti oxide and Si oxide are slag components, and it is desirable to include at least one of them from the perspective of improving the coating condition of the slag and weldability. In particular, it is desirable to have the sum of the TiO2 equivalent values ​​of Ti oxide and the sum of the SiO2 equivalent values ​​of Si oxide in the flux 5.0% or more.

[0314] The lower limit of the sum of the TiO2 equivalent values ​​of Ti oxide and the sum of the SiO2 equivalent values ​​of Si oxide in the flux is, more preferably, 7.0% or 10.0%.

[0315] The upper limit of the sum of the TiO2 equivalent values ​​of Ti oxide and the sum of the SiO2 equivalent values ​​of Si oxide in the flux is preferably 50.0%, 45.0%, 40.0%, 35.0%, or 30.0%.

[0316] (Sum of ZrO2 equivalent values ​​of Zr oxide: 0 to 5.00%)

[0317] Zr oxide increases the oxygen content of the weld metal, thereby degrading low-temperature toughness. Therefore, from the perspective of low-temperature toughness, it is desirable not to include Zr oxide, and the lower limit of the sum of the ZrO2 equivalent values ​​of Zr oxide is set to 0%.

[0318] However, since Zr oxide is a slag component and has the effect of increasing slag coverage and smoothing the bead shape through horizontal fillet welding, it may be included from this perspective.

[0319] Meanwhile, by keeping the total ZrO2 equivalent value of Zr oxide at 5.00% or less, the bead shape can be suppressed from becoming convex. In addition, the occurrence of slag curling can be suppressed.

[0320] Therefore, it is preferable that the sum of the ZrO2 equivalent values ​​of Zr oxide in the flux be 0 to 5.00%.

[0321] The upper limit of the sum of the ZrO2 equivalent values ​​of Zr oxide is, more preferably, 4.50%, 4.00%, 3.50%, or 3.00%.

[0322] In addition, Zr oxide can exist mainly as zircon sand, zirconium oxide, etc. in the flux, and may also be contained in trace amounts in Ti oxide.

[0323] (Sum of Al2O3 equivalent values ​​of Al oxide: 0 to 5.00%)

[0324] Since Al oxide is an oxygen source, adding Al oxide increases the amount of oxygen in the weld metal, which becomes a factor in the deterioration of toughness. Therefore, from the perspective of low-temperature toughness, it is desirable not to include Al oxide, and the lower limit of the total Al2O3 equivalent value of Al oxide is set to 0%.

[0325] However, since Al oxide has the effect of preventing undercutting on the upper side of the fillet bead by improving slag coverage when it forms molten slag, it may be included from this perspective.

[0326] Meanwhile, by keeping the total Al2O3 equivalent value of Al oxides at 5.00% or less, it is possible to suppress the bead edge on the lower side of the fillet bead from becoming a swollen bead shape. In addition, it is possible to suppress the occurrence of slag ingress.

[0327] Therefore, it is desirable to set the total Al2O3 equivalent value of Al oxide in the flux to 0 to 5.00%.

[0328] The upper limit of the total Al2O3 equivalent value of Al oxide is, more preferably, 4.50%, 4.00%, 3.50%, or 3.00%.

[0329] In addition, Al oxides are often present mainly as components of alumina, feldspar, etc., in the flux.

[0330] (Sum of MgO equivalent values ​​of Mg oxide: 0 to 5.00%)

[0331] Mg oxide acts as a deoxidizer when Mg decomposes during welding, thereby reducing the oxygen content of the weld metal. Since this improves the low-temperature toughness of the weld metal, it may be included. When the total MgO equivalent value of the Mg oxide is 0.10% or more, the oxygen reduction effect of the weld metal is increased, and the low-temperature toughness is further improved.

[0332] Meanwhile, since the total MgO equivalent value of Mg oxide is 5.00% or less, the solidification temperature of the welding slag can be suppressed, thereby improving welding workability (especially grain weldability).

[0333] Therefore, it is preferable that the sum of the MgO equivalent values ​​of Mg oxide in the flux be 0 to 5.00%.

[0334] The lower limit of the sum of the MgO equivalent values ​​of Mg oxide is, more preferably, 0.10%, 0.20%, 0.30%, or 0.40%.

[0335] The upper limit of the sum of the MgO equivalent values ​​of Mg oxide is, more preferably, 4.50%, 4.00%, 3.50%, or 3.00%.

[0336] (Sum of CaO equivalent values ​​of Ca oxide: 0 to 25.00%)

[0337] Ca oxide may be included as it improves the shape of the slag, facilitates slag stripping after welding, and stabilizes the arc.

[0338] Meanwhile, since the total CaO equivalent value of Ca oxide is 25.00% or less, the oxygen contained in the Ca oxide enters the molten pool, so the increase in the amount of oxygen in the weld metal can be suppressed and the decrease in the toughness of the weld metal can be suppressed.

[0339] Therefore, it is preferable that the total CaO2 equivalent value of Ca oxide in the flux be 0 to 25.00%.

[0340] The lower limit of the sum of the CaO2 equivalent values ​​of Ca oxide is, more preferably, 0.10%, 0.20%, 0.30%, or 0.40%.

[0341] The upper limit of the total CaO2 equivalent value of Ca oxide is, more preferably, 23.00%, 20.00%, 18.00%, 15.00%, 13.00%, or 10.00%.

[0342] (Sum of Na2O equivalent values ​​of Na oxide: 0 to 5.00%)

[0343] Na oxide acts as a deoxidizer when Na decomposes during welding, and reduces the oxygen content of the weld metal. Since this improves the low-temperature toughness of the weld metal, it may be included. When the total Na2O equivalent value of the Na oxide is 0.10% or more, the oxygen reduction effect of the weld metal is increased, and the low-temperature toughness is further improved.

[0344] Meanwhile, since the total Na2O equivalent value of Na oxide is 5.00% or less, the solidification temperature of the welding slag can be suppressed, thereby improving welding workability (especially grain weldability).

[0345] Therefore, it is preferable that the total Na2O equivalent value of Na oxide in the flux be 0 to 5.00%.

[0346] The lower limit of the sum of the Na2O equivalent values ​​of Na oxide is, more preferably, 0.10%, 0.20%, 0.30%, or 0.40%.

[0347] The upper limit of the sum of the Na2O equivalent values ​​of Na oxide is, more preferably, 4.50%, 4.00%, 3.50%, or 3.00%.

[0348] (Sum of K2O equivalent values ​​of K oxides: 0 to 5.00%)

[0349] K oxides act as a deoxidizer when K decomposes during welding, thereby reducing the oxygen content of the weld metal. Since this improves the low-temperature toughness of the weld metal, they may be included. When the total K2O equivalent value of the K oxides is 0.10% or more, the oxygen reduction effect of the weld metal is increased, and the low-temperature toughness is further improved.

[0350] Meanwhile, since the total K2O equivalent value of K oxides is 5.00% or less, the solidification temperature of the welding slag can be suppressed, thereby improving welding workability (especially grain weldability).

[0351] Therefore, it is preferable that the sum of the K2O equivalent values ​​of K oxides in the flux be 0 to 5.00%.

[0352] The lower limit of the sum of the K2O equivalent values ​​of K oxides is, more preferably, 0.10%, 0.20%, 0.30%, or 0.40%.

[0353] The upper limit of the sum of the K2O equivalent values ​​of K oxides is, more preferably, 4.50%, 4.00%, 3.50%, or 3.00%.

[0354] (Other oxides)

[0355] The flux according to the present disclosure may include, as other oxides, oxides such as Fe oxide and Mn oxide.

[0356] In addition, the Fe oxide content refers to the sum of the FeO equivalent values ​​of Fe oxide, and the Mn oxide content refers to the sum of the MnO equivalent values ​​of Mn oxide.

[0357] (CaF2: 0 to 30.00%)

[0358] CaF2 may be included as it has the effect of reducing the oxygen content of the weld metal. By having a CaF2 content of 0.10% or more, the effect of reducing the oxygen content of the weld metal is increased, and low-temperature toughness is further improved.

[0359] Meanwhile, by having a CaF2 content of 30.00% or less, the generation of fumes can be reduced and the occurrence of welding defects can be suppressed.

[0360] Therefore, it is preferable that the CaF2 content in the flux be 0 to 30.00%.

[0361] The lower limit of the CaF2 content is, more preferably, 0.10%, 0.20%, 0.30%, or 0.40%.

[0362] The upper limit of the CaF2 content is, more preferably, 28.00%, 25.00%, 23.00%, 20.00%, 18.00%, or 15.00%.

[0363] (Other fluorides)

[0364] The flux according to the present disclosure may include, as other fluorides, fluorides such as K2SiF6, K2ZrF6, NaF, Na3AlF6, and MgF2.

[0365] In addition, the content of CaF2 and other fluorides is measured by fluorescence X-ray analysis and X-ray diffraction (XRD), just like the content of the aforementioned Ti oxide.

[0366] (CaCO3: 0 to 60.00%)

[0367] (BaCO3: 0 to 15.00%)

[0368] (MgCO3: 0 to 15.00%)

[0369] (Li2CO3: 0 to 15.00%)

[0370] Metal carbonates are ionized by an arc and generate CO2 gas. CO2 gas lowers the partial pressure of hydrogen in the welding atmosphere and reduces the amount of diffusible hydrogen in the weld metal. Therefore, the flux according to the present disclosure may include one or more types selected from the group consisting of CaCO3, BaCO3, MgCO3, and Li2CO3 as metal carbonates.

[0371] Meanwhile, by reducing the content of metal carbonates, the amount of spatter generated can be suppressed.

[0372] Therefore, it is preferable that the CaCO3 content in the flux be 0 to 60.00%.

[0373] The lower limit of the CaCO3 content is, more preferably, 0.10%, 0.20%, 0.30%, or 0.40%.

[0374] The upper limit of the CaCO3 content is, more preferably, 55.00%, 50.00%, 45.00%, 40.00%, 35.00%, or 30.00%.

[0375] In addition, it is preferable that the BaCO3 content in the flux be 0 to 15.00%.

[0376] The lower limit of the BaCO3 content is, more preferably, 0.10%, 0.20%, 0.30%, or 0.40%.

[0377] The upper limit of the BaCO3 content is, more preferably, 14.00%, 12.00%, 10.00%, 8.00%, 7.00%, or 5.00%.

[0378] In addition, it is preferable that the MgCO3 content in the flux be 0 to 15.00%.

[0379] The lower limit of the MgCO3 content is, more preferably, 0.10%, 0.20%, 0.30%, or 0.40%.

[0380] The upper limit of the MgCO3 content is, more preferably, 14.00%, 12.00%, 10.00%, 8.00%, 7.00%, or 5.00%.

[0381] In addition, it is preferable that the Li2CO3 content in the flux be 0 to 15.00%.

[0382] The lower limit of the Li2CO3 content is, more preferably, 0.10%, 0.20%, 0.30%, or 0.40%.

[0383] The upper limit of the Li2CO3 content is, more preferably, 14.00%, 12.00%, 10.00%, 8.00%, 7.00%, or 5.00%.

[0384] (The sum of the contents of CaCO3, BaCO3, MgCO3, and Li2CO3 is 5.00% or more)

[0385] CaCO3, BaCO3, MgCO3, and Li2CO3 are sources of shield gas, and it is desirable to include at least one of them from the perspective of ensuring good mechanical properties. In particular, it is desirable to have a total content of CaCO3, BaCO3, MgCO3, and Li2CO3 in the flux of 5.00% or more.

[0386] In addition, the lower limit of the total content of CaCO3, BaCO3, MgCO3, and Li2CO3 in the flux is, more preferably, 7.00% or 10.00%.

[0387] The upper limit of the total content of CaCO3, BaCO3, MgCO3, and Li2CO3 in the flux is preferably 90.00%, 80.00%, 70.00%, 65.00%, or 60.00%.

[0388] (Other metal carbonates)

[0389] The flux according to the present disclosure may include, as other metal carbonates, metal carbonates such as Na2CO3, K2CO3, FeCO3, MnCO3, and SrCO3.

[0390] In addition, the content of CaCO3, BaCO3, MgCO3, Li2CO3, and other metal carbonates is measured by fluorescence X-ray analysis and X-ray diffraction (XRD), just like the content of the aforementioned Ti oxide.

[0391] (Sum of Ti oxide, Si oxide, Zr oxide, Al oxide, Mg oxide, Ca oxide, Na oxide, K oxide, CaF2, CaCO3, BaCO3, MgCO3 and Li2CO3 X)

[0392] The chemical composition of the flux according to the present disclosure is preferably such that, in mass % relative to the total mass of the coated arc welding rod, the sum of the TiO2 equivalent values ​​of Ti oxide, the sum of the SiO2 equivalent values ​​of Si oxide, the sum of the ZrO2 equivalent values ​​of Zr oxide, the sum of the Al2O3 equivalent values ​​of Al oxide, the sum of the MgO equivalent values ​​of Mg oxide, the sum of the CaO equivalent values ​​of Ca oxide, the sum of the Na2O equivalent values ​​of Na oxide, the sum of the K2O equivalent values ​​of K oxide, the CaF2 content, the CaCO3 content, the BaCO3 content, the MgCO3 content, and the Li2CO3 content X (hereinafter simply referred to as “sum of specific additives X”) is 94.98% or less.

[0393] By keeping the sum of specific additives X at 94.98% or less, slag ingress can be prevented.

[0394] The sum X of specific additives is, more preferably, 90.00% or less, 85.00% or less, 80.00% or less, 75.00% or less, or 70.00% or less.

[0395] (Nitride)

[0396] The flux according to the present disclosure may further include nitrides.

[0397] Nitrides have the effect of significantly improving the weld metal's resistance to low-temperature cracking by reducing the amount of diffusible hydrogen in the weld metal. Although the reason for this is not clear, it is speculated that one reason is that the nitrogen (N) in the nitride combines with hydrogen (H) during welding to form ammonia (NH3), and this NH3 is released outside the weld metal.

[0398] The flux according to the present disclosure may include, as a nitride, one or more selected from the group consisting of, for example, AlN, BN, Ca3N2, CeN, CrN, Cu3N, Fe4N, Fe3N, Fe2N, Mg3N, Mo2N, NbN, Si3N4, TiN, VN, ZrN, Mn2N and Mn4N.

[0399] In addition, the nitride content is measured by fluorescence X-ray analysis and X-ray diffraction (XRD), just like the aforementioned Ti oxide content.

[0400] (Metal component in the chemical composition of flux-containing wire)

[0401] Next, the metal component in the preferred chemical composition of the flux according to the present disclosure will be described.

[0402] In addition, regarding the description of the metal components of the flux, "%" means "mass % of the total mass of the flux" unless otherwise specified.

[0403] Here, the term "metal component in the chemical composition" of the flux refers to the component included in the flux excluding oxides, fluorides, nitrides, and metal carbonates.

[0404] The flux according to the present disclosure, in mass % relative to the total mass of the coated arc welding electrode, the metal component in the chemical composition of the flux,

[0405] C: 0.020 to 5.000%,

[0406] Si: 0 to 5.00%,

[0407] Mn: 0 to 30.00%,

[0408] P: 0 to 0.050%,

[0409] S: 0 to 0.050%,

[0410] Cu: 0 to 20.0%,

[0411] Ni: 0 to 20.0%,

[0412] Cr: 0 to 20.0%,

[0413] Mo: 0 to 10.0%,

[0414] Nb: 0 to 5.00%,

[0415] V: 0 to 5.0%,

[0416] Co: 0 to 1.00%,

[0417] Pb: 0 to 1.00%,

[0418] Sn: 0 to 1.00%,

[0419] W: 0 to 20.0%,

[0420] Mg: 0 to 5.00%,

[0421] Al: 0 to 5.0%,

[0422] Ca: 0 to 5.00%,

[0423] Ti: 0 to 5.000%,

[0424] B: 0 to 5.0000%,

[0425] REM: 0 to 5.00%,

[0426] Bi: 0 to 5.000%,

[0427] N: 0 to 5.0000%, and

[0428] Remainder: It is preferable that it be Fe and impurities.

[0429] That is, in the flux according to the present disclosure, the above component is the content of a component included in addition to oxides, fluorides, nitrides, and metal carbonates.

[0430] In addition, it is desirable that the sum of the Mn content and Ni content (Mn+Ni) in the flux be 1.00% or more.

[0431] (C: 0.020 to 5.000%)

[0432] C is an element that improves the strength of the weld metal and is an element for ensuring the strength of the weld metal.

[0433] Meanwhile, by reducing the carbon content of the flux, the effect of deteriorating toughness caused by the increase in strength of the weld metal can be suppressed, thereby ensuring low-temperature toughness of the weld metal.

[0434] Therefore, it is preferable that the C content of the flux be 0.020 to 5.000%.

[0435] The lower limit of the C content of the flux is, more preferably, 0.050%, 0.100%, or 0.200%.

[0436] The upper limit of the C content of the flux is, more preferably, 4.500%, 4.000%, 3.500%, or 3.000%.

[0437] (Si: 0 to 5.00%)

[0438] Si may be included in the flux to improve the cleanliness of the weld metal and suppress the occurrence of welding defects such as blowholes.

[0439] Meanwhile, by reducing the Si content of the flux, micro-segregation in the weld metal can be suppressed during the welding of Ni steel and Ni-based alloy steel, and embrittlement in the segregated area can be suppressed.

[0440] Therefore, it is preferable to set the Si content of the flux to 0 to 5.00%.

[0441] The lower limit of the Si content of the flux is, more preferably, 0.10%, 0.20%, 0.25%, 0.30%, or 0.35%.

[0442] The upper limit of the Si content of the flux is, more preferably, 4.50%, 4.00%, 3.50%, or 3.00%.

[0443] (Mn: 0 to 30.00%)

[0444] Mn is an austenite-stabilizing element that can promote the austenitization of the weld metal, thereby ensuring low-temperature toughness. Furthermore, to secure low-temperature toughness of the weld metal, it is not necessary to excessively increase the Mn content added to the core wire.

[0445] Furthermore, Mn is an element that functions as a deoxidizer to improve the cleanliness of the weld metal. Additionally, by forming MnS, Mn neutralizes sulfur in the weld metal and improves the low-temperature toughness of the weld metal. Moreover, Mn has the effect of preventing high-temperature cracking. For this reason, Mn may be included in the flux.

[0446] However, it is preferable that the sum of the Mn content and the Ni content (Mn+Ni) be 1.00% or more, that is, the flux may contain only one of Mn and Ni. Accordingly, the lower limit of the Mn content may be 0%.

[0447] Meanwhile, by reducing the Mn content of the flux, micro-segregation in the weld metal can be suppressed during the welding of Ni steel and Ni-based alloy steel, thereby suppressing embrittlement in the segregated area.

[0448] Therefore, it is preferable to have a Mn content of 0 to 30.00% of the flux.

[0449] The lower limit of the Mn content of the flux is, more preferably, 0.10%, 0.50%, 1.00%, 2.00%, 5.00%, 7.00%, or 9.00%.

[0450] The upper limit of the Mn content of the flux is, more preferably, 28.00%, 25.00%, 22.00%, or 20.00%.

[0451] (P: 0 to 0.050%)

[0452] Since phosphorus is an impurity element that reduces the toughness of the weld metal, it is desirable to minimize the phosphorus content of the flux. Accordingly, the lower limit of the phosphorus content in the flux is set to 0%. However, from the perspective of reducing phosphorus removal costs, the phosphorus content should be 0.003% or higher.

[0453] Meanwhile, if the P content of the flux is 0.050% or less, the adverse effect of P on toughness can be suppressed.

[0454] Therefore, it is preferable to set the P content of the flux to 0 to 0.050%.

[0455] In order to effectively suppress the decrease in toughness of the weld metal, the P content of the flux is more preferably 0.040% or less, 0.030% or less, 0.020% or less, 0.015% or less, or 0.010% or less.

[0456] (S: 0 to 0.050%)

[0457] Since sulfur is an impurity element that reduces the toughness of the weld metal, it is desirable to minimize the sulfur content of the flux. Accordingly, the lower limit of the sulfur content in the flux is set to 0%. However, from the perspective of reducing sulfur removal costs, the sulfur content of the flux should be 0.003% or higher.

[0458] Meanwhile, if the S content of the flux is 0.050% or less, the adverse effect of S on toughness can be suppressed.

[0459] Therefore, it is preferable to set the S content of the flux to 0 to 0.050%.

[0460] In order to effectively suppress the decrease in toughness of the weld metal, the S content of the flux is more preferably 0.040% or less, 0.030% or less, 0.020% or less, 0.015% or less, or 0.010% or less.

[0461] (Cu: 0 to 20.0%)

[0462] Cu is a precipitation strengthening element and may be included in the flux to improve the strength of the weld metal. Additionally, Cu is an austenite stabilizing element and may be included in the flux to improve the low-temperature toughness of the weld metal.

[0463] On the other hand, if the Cu content of the flux is excessive, the above effect becomes saturated.

[0464] Therefore, it is preferable that the Cu content of the flux be 0 to 20.0%.

[0465] The lower limit of the Cu content of the flux is, more preferably, 0.5%, 0.7%, or 1.0%.

[0466] The upper limit of the Cu content of the flux is, more preferably, 19.0%, 18.0%, 17.0%, or 15.0%.

[0467] (Ni: 0 to 20.0%)

[0468] Ni is an austenite-stabilizing element that can accelerate the austenitization of the weld metal, thereby ensuring low-temperature toughness. Furthermore, to secure low-temperature toughness of the weld metal, it is not necessary to excessively increase the Ni content added to the core wire. Therefore, Ni may be incorporated into the flux.

[0469] However, it is preferable that the sum of the Mn content and the Ni content (Mn+Ni) be 1.00% or more, that is, the flux may contain only one of Mn and Ni. Accordingly, the lower limit of the Ni content may be 0%.

[0470] Meanwhile, by reducing the Ni content of the flux, the cost of the flux can be reduced.

[0471] Therefore, it is preferable that the Ni content of the flux be 0 to 20.0%.

[0472] The lower limit of the Ni content of the flux is, more preferably, 0.1%, 0.5%, 1.0%, 2.0%, 3.0%, 5.0%, 7.0%, 10.0%, or 12.0%.

[0473] The upper limit of the Ni content of the flux is, more preferably, 19.0%, 18.0%, 17.0%, or 15.0%.

[0474] (Cr: 0 to 20.0%)

[0475] Cr is an austenite-stabilizing element that can accelerate the austenitization of the weld metal, thereby ensuring low-temperature toughness. Furthermore, to secure low-temperature toughness of the weld metal, it is not necessary to excessively increase the Ni content added to the core wire. Therefore, Cr may be included in the flux.

[0476] Meanwhile, by reducing the Cr content of the flux, the amount of low-melting point compounds in the molten metal can be reduced, and since the solid-liquid coexistence temperature range of the molten metal is narrowed, the occurrence of high-temperature cracking can be suppressed.

[0477] Therefore, it is preferable that the Cr content of the flux be 0 to 20.0%.

[0478] The lower limit of the Cr content of the flux is, more preferably, 0.1%, 0.5%, 1.0%, 2.0%, 2.5%, 3.0%, or 3.5%.

[0479] The upper limit of the Cr content of the flux is, more preferably, 19.0%, 18.0%, 17.0%, or 15.0%.

[0480] (Mo: 0 to 10.0%)

[0481] Mo is a solid solution strengthening element and also a precipitation strengthening element, and may be included in flux to improve the strength of the weld metal.

[0482] Meanwhile, by reducing the Mo content of the flux, the excessive strength of the weld metal can be prevented, thereby ensuring low-temperature toughness.

[0483] Therefore, it is preferable to have a Mo content of 0 to 10.0% in the flux.

[0484] The lower limit of the Mo content of the flux is, more preferably, 0.1%, 0.5%, 1.0%, 2.0%, 2.5%, 3.0%, or 3.5%.

[0485] The upper limit of the Mo content of the flux is, more preferably, 9.8%, 9.5%, 9.0%, 8.5%, or 8.0%.

[0486] (Nb: 0 to 5.00%)

[0487] Since Nb is an element that forms carbides in the weld metal and increases the strength of the weld metal, it may be included in the flux.

[0488] Meanwhile, by reducing the Nb content of the flux, the occurrence of high-temperature cracking in the weld metal can be suppressed.

[0489] Therefore, it is preferable that the Nb content of the flux be 0 to 5.00%.

[0490] The lower limit of the Nb content of the flux is, more preferably, 0.10%, 0.50%, 1.00%, or 1.50%.

[0491] The upper limit of the Nb content of the flux is, more preferably, 4.50%, 4.00%, or 3.50%.

[0492] (V: 0 to 5.0%)

[0493] Since V is an element that forms carbonitrides in the weld metal and increases the strength of the weld metal, it may be included in the flux.

[0494] Meanwhile, by reducing the V content of the flux, the occurrence of high-temperature cracking in the weld metal can be suppressed.

[0495] Therefore, it is preferable to have a V content of 0 to 5.0% of the flux.

[0496] The lower limit of the V content of the flux is, more preferably, 0.1%, 0.5%, 1.0%, or 1.5%.

[0497] The upper limit of the V content of the flux is, more preferably, 4.5%, 4.0%, or 3.5%.

[0498] (Co: 0 to 1.00%)

[0499] Since Co is an element that increases the strength of the weld metal through solid solution strengthening, it may be included in the flux.

[0500] Meanwhile, by reducing the Co content of the flux, the decrease in ductility of the weld metal can be suppressed and toughness can be secured.

[0501] Therefore, it is preferable to have a Co content of 0 to 1.00% in the flux.

[0502] The lower limit of the Co content of the flux is, more preferably, 0.01%, 0.05%, 0.10%, 0.15%, or 0.20%.

[0503] The upper limit of the Co content of the flux is, more preferably, 0.90%, 0.80%, 0.70%, 0.60%, or 0.30%.

[0504] (Pb: 0 to 1.00%)

[0505] Since Pb has the effect of improving the machinability of the weld metal, it may be included in the flux.

[0506] Meanwhile, by reducing the Pb content of the flux, the arc state can be maintained well and the generation of spatter can be suppressed.

[0507] Therefore, it is preferable to have a Pb content of 0 to 1.00% in the flux.

[0508] The lower limit of the Pb content of the flux is, more preferably, 0.01%, 0.05%, 0.10%, 0.15%, or 0.20%.

[0509] The upper limit of the Pb content of the flux is, more preferably, 0.90%, 0.80%, 0.70%, 0.60%, or 0.30%.

[0510] (Sn: 0 to 1.00%)

[0511] Since Sn is an element that improves the corrosion resistance of weld metal, it may be included in the flux.

[0512] Meanwhile, by reducing the Sn content of the flux, the occurrence of cracks in the weld metal can be suppressed.

[0513] Therefore, it is preferable to set the Sn content of the flux to 0 to 1.00%.

[0514] The lower limit of the Sn content of the flux is, more preferably, 0.01%, 0.05%, 0.10%, 0.15%, or 0.20%.

[0515] The upper limit of the Sn content of the flux is, more preferably, 0.90%, 0.80%, 0.70%, 0.60%, or 0.30%.

[0516] (W: 0 to 20.0%)

[0517] W is a solid solution strengthening element and may be included in the flux to improve the strength of the weld metal.

[0518] Meanwhile, by reducing the W content of the flux, the excessive strength of the weld metal can be prevented, thereby ensuring toughness.

[0519] Therefore, it is preferable that the W content of the flux be 0 to 20.0%.

[0520] The lower limit of the W content of the flux is, more preferably, 0.1%, 0.5%, 1.0%, or 2.0%.

[0521] The upper limit of the W content of the flux is, more preferably, 19.0%, 180%, 17.0%, or 15.0%.

[0522] (Mg: 0 to 5.00%)

[0523] Mg is a deoxidizing element and is effective in reducing oxygen in the weld metal and improving its toughness, so it may be included in the flux.

[0524] Meanwhile, by reducing the Mg content of the flux, the arc can be stabilized and spatter and blowholes can be reduced, thereby ensuring welding workability.

[0525] Therefore, it is preferable to have an Mg content of 0 to 5.00% of the flux.

[0526] The lower limit of the Mg content of the flux is, more preferably, 0.02%, 0.05%, 0.10%, 0.20%, or 0.50%.

[0527] The upper limit of the Mg content of the flux is, more preferably, 4.50%, 4.00%, or 3.50%.

[0528] (Al: 0 to 5.0%)

[0529] Al is a deoxidizing element and is effective in suppressing the occurrence of welding defects such as blowholes and improving the cleanliness of the weld metal, so it may be included in the flux.

[0530] Meanwhile, by reducing the Al content of the flux, the formation of nitrides or oxides by Al in the weld metal can be reduced, thereby ensuring low-temperature toughness of the weld metal.

[0531] Therefore, it is preferable that the Al content of the flux be 0 to 5.0%.

[0532] The lower limit of the Al content of the flux is, more preferably, 0.01%, 0.02%, 0.05%, 0.1%, 0.2%, or 0.5%.

[0533] The upper limit of the Al content of the flux is, more preferably, 4.5%, 4.0%, or 3.5%.

[0534] (Ca: 0 to 5.00%)

[0535] Ca alters the structure of sulfides in the weld metal and also refines the size of sulfides and oxides within the weld metal, making it effective for improving the ductility and toughness of the weld metal. For this reason, it is acceptable to include Ca in the flux.

[0536] Meanwhile, by reducing the Ca content of the flux, the coarsening of sulfides and oxides can be suppressed, thereby ensuring low-temperature toughness of the weld metal. In addition, weldability can be secured by suppressing the deterioration of the weld bead shape and stabilizing the arc.

[0537] Therefore, it is preferable to have a Ca content of 0 to 5.00% in the flux.

[0538] The lower limit of the Ca content of the flux is, more preferably, 0.01%, 0.02%, 0.03%, 0.05%, 0.10%, 0.20%, 0.30%, or 0.50%.

[0539] The upper limit of the Ca content of the flux is, more preferably, 4.50%, 4.00%, or 3.50%.

[0540] (Ti: 0 to 5.000%)

[0541] Ti is a deoxidizing element and is effective in suppressing the occurrence of welding defects such as blowholes and improving cleanliness, so it may be included in the flux.

[0542] Meanwhile, by reducing the Ti content of the flux, the formation of carbides in the weld metal can be suppressed, thereby ensuring the toughness of the weld metal.

[0543] Therefore, it is preferable to set the Ti content of the flux to 0 to 5.000%.

[0544] The lower limit of the Ti content of the flux is, more preferably, 0.020%, 0.050%, 0.100%, 0.200%, 0.300%, or 0.500%.

[0545] The upper limit of the Ti content of the flux is, more preferably, 4.500%, 4.000%, or 3.500%.

[0546] (B: 0 to 5.0000%)

[0547] B may be included in the flux because it has the effect of strengthening the grain boundaries of the weld metal and further increasing the tensile strength of the weld metal.

[0548] Meanwhile, by reducing the B content of the flux, the amount of B in the weld metal can also be reduced, and coarse BN or Fe 23 The formation of B compounds such as (C, B)6 is suppressed, thereby ensuring low-temperature toughness of the weld metal.

[0549] Therefore, it is preferable to have a B content of the flux of 0 to 5.0000%.

[0550] The lower limit of the B content of the flux is, more preferably, 0.0010%, 0.0050%, 0.0100%, 0.0500%, 0.1000%, 0.2000%, or 0.5000%.

[0551] The upper limit of the B content of the flux is, more preferably, 4.5000%, 4.0000%, or 3.5000%.

[0552] (REM: 0 to 5.00%)

[0553] Since REM is an element that stabilizes the arc, it may be included in the flux.

[0554] Meanwhile, by reducing the REM content of the flux, the occurrence of spatter can be reduced, thereby ensuring welding workability.

[0555] Therefore, it is preferable that the REM content of the flux be 0 to 5.00%.

[0556] The lower limit of the REM content of the flux is, more preferably, 0.001%, 0.005%, 0.01%, 0.05%, 0.10%, 0.20%, or 0.50%.

[0557] The upper limit of the REM content of the flux is, more preferably, 4.50%, 4.00%, or 3.50%.

[0558] In addition, “REM” refers to a total of 17 elements consisting of Sc, Y, and lanthanides, and the “REM content” refers to the total content of these 17 elements. When lanthanides are used as REM, industrially, REM is contained in the form of misch metal.

[0559] (Bi: 0 to 5.000%)

[0560] Since Bi is an element that improves the detachability of slag, it may be included in the flux.

[0561] Meanwhile, by reducing the Bi content of the flux, the occurrence of solidification cracks in the weld metal can be suppressed.

[0562] Therefore, it is preferable to set the Bi content of the flux to 0 to 5.000%.

[0563] The lower limit of the Bi content of the flux is, more preferably, 0.005%, 0.010%, 0.050%, 0.100%, 0.200%, or 0.500%.

[0564] The upper limit of the Bi content of the flux is, more preferably, 4.500%, 4.000%, or 3.500%.

[0565] (N: 0 to 5.0000%)

[0566] N is an austenite-stabilizing element and also an interstitial solid solution strengthening element. Furthermore, compared to C, N has less adverse effect on the toughness of the weld metal due to the increase in weld metal strength. Therefore, it is acceptable to include N in the flux.

[0567] Meanwhile, by reducing the N content of the flux, the occurrence of blows can be reduced, thereby suppressing the occurrence of welding defects.

[0568] Therefore, it is preferable to set the N content of the flux to 0 to 5.0000%.

[0569] The lower limit of the N content of the flux is, more preferably, 0.0050%, 0.0070%, 0.0100%, 0.0150%, 0.0200%, 0.0300%, 0.0500%, 0.0700%, 0.1000%, or 0.1500%.

[0570] The upper limit of the N content of the flux is, more preferably, 4.5000%, 4.0000%, or 3.5000%.

[0571] (Remainder: Fe and impurities)

[0572] The remaining components in the chemical composition of the flux are Fe and impurities.

[0573] In addition, impurities refer to components that originate from raw materials or are incorporated due to various factors in the manufacturing process when industrially producing flux, and are permitted within a range that does not adversely affect the flux.

[0574] (The sum of Mn content and Ni content (Mn+Ni) is 1.00% or more)

[0575] Mn and Ni are each austenite-stabilizing elements that improve the low-temperature toughness of the weld metal. Meanwhile, since Ni is an expensive metal, in order to improve the low-temperature toughness of the weld metal while keeping the cost of the welding rod low, it is desirable to have the Mn content and Ni content in the flux each meet the above ranges, and the sum of the Mn content and Ni content (Mn+Ni) is 1.00% or more.

[0576] The sum of the Mn content and Ni content (Mn+Ni) in the flux is preferably 2.00% or more, 3.00% or more, or 5.00% or more.

[0577] In addition, Mn is an element that causes an increase in the amount of fumes generated. Furthermore, if Mn is added in excess, the stacking fault energy decreases, and toughness deteriorates. Therefore, from the perspective of reducing the amount of fumes generated while suppressing the cost of welding rods and improving the low-temperature toughness of the weld metal, it is desirable that the Mn content and Ni content in the flux each satisfy the above ranges, and that the sum of the Mn content and Ni content (Mn+Ni) be 50.00% or less.

[0578] The sum of the Mn content and Ni content (Mn+Ni) in the flux is, more preferably, 45.00% or less, 40.00% or less, 35.00% or less, 32.00% or less, 30.00% or less, or 25.00% or less.

[0579] The coated arc welding electrode according to the present disclosure may further comprise a plating formed on the surface of the core wire.

[0580] Although the amount of hydrogen contained in the coated arc welding electrode according to the present disclosure is not particularly limited, it is preferable that it be 12 ppm or less relative to the total mass of the coated arc welding electrode in order to reduce the amount of diffusible hydrogen in the weld metal. There is a risk that the amount of hydrogen in the coated arc welding electrode may increase because moisture may enter the coated arc welding electrode during storage. Therefore, when the period from manufacturing the welding electrode to using the electrode is long, it is preferable to vacuum pack the entire coated arc welding electrode or store the coated arc welding electrode in a container that can hold and support it in a dry state in order to prevent the entry of H sources such as moisture.

[0581] (Welding rod diameter)

[0582] The diameter of the coated arc welding electrode according to the present disclosure is not particularly limited, but is, for example, Φ3.2 to Φ6.0 mm. In addition, the diameter of a general coated arc welding electrode is Φ2.6 to Φ7.0 mm.

[0583] (thickness)

[0584] The average thickness of the flux in the coated arc welding electrode according to the present disclosure is not particularly limited. Taking into account the thickness of the flux in a general coated arc welding electrode, the upper limit of the average thickness of the flux in the coated arc welding electrode according to the present disclosure may be, for example, 5.0 mm, 4.0 mm, or 3.0 mm. In addition, the lower limit of the average thickness of the flux in the coated arc welding electrode according to the present disclosure may be, for example, 0.2 mm, 0.5 mm, 0.8 mm, or 1.0 mm.

[0585] In addition, the average thickness of the flux was determined by measuring the outer diameter of the coated arc welding rod at five random locations, calculating half the value obtained by subtracting the diameter of the core wire from the outer diameter, and taking the arithmetic mean of the result as the average thickness.

[0586] Expressed as a formula, the flux thickness is = ((outer diameter of the coated arc welding rod) - (diameter of the core wire)) / 2.

[0587] Method for manufacturing coated arc welding electrodes

[0588] Next, a method for manufacturing a coated arc welding rod according to the present disclosure will be described.

[0589] In addition, the manufacturing method described below is an example, and the method for manufacturing a coated arc welding electrode according to the present disclosure is not limited to the following method.

[0590] A coated arc welding electrode according to the present disclosure can be manufactured, for example, by undergoing a process of preparing a core wire, a process of applying flux to the core wire, and a process of firing the core wire and the flux.

[0591] In the process of preparing the core wire, steel having the chemical composition described above is melted, for example, and then forged if necessary. Afterward, the steel is processed into a rod shape through rolling. The core wire is obtained by drawing this rod-shaped steel. Additionally, heat treatment may be performed as appropriate.

[0592] Next, a flux is applied to the core wire, and then the core wire and the flux are fired. The firing conditions are not particularly limited, but for example, the firing temperature may be about 150 to 450°C and the firing time may be about 0.1 to 3 hours. In addition, a binder (for example, an aqueous solution of potassium silicate and sodium silicate) may be added to the flux.

[0593] Method for manufacturing welded joints

[0594] Next, a method for manufacturing a welded joint (welding method) according to the present disclosure will be described.

[0595] The method for manufacturing a welded joint according to the present disclosure comprises a process of welding steel using a coated arc welding rod according to the present disclosure described above.

[0596] A welded joint manufactured by the method for manufacturing a welded joint according to the present disclosure has high strength and high toughness. In addition, a welded structure having a welded joint manufactured by the method for manufacturing a welded joint according to the present disclosure also has high strength and high toughness in the welded joint.

[0597] In the method for manufacturing a welded joint according to the present disclosure, gas shielded arc welding is suitable as the welding method.

[0598] 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, a Ni-based low-temperature steel plate containing 6% to 9% Ni with a plate thickness of 20 mm or more can be suitably used.

[0599] In the method for manufacturing a welded joint according to the present disclosure, it is preferable to include a process of welding steel using a coated arc welding electrode according to the present disclosure in one or more of the first pass to the final pass. When welding is performed in only one pass, a coated arc welding electrode according to the present disclosure is used in that one pass.

[0600] Since the polarity of the shielded arc welding electrode has a negligible effect on the amount of spatter generated, it may be either AC or DC, but AC is preferred. In addition, in the case of DC, it is preferred to be positive.

[0601] The welding position in the method for manufacturing a welded joint according to the present disclosure is not particularly limited. The method for manufacturing a welded joint according to the present disclosure can exhibit good weldability (especially vertical weldability) regardless of whether the welding position is a downward position, a sideways position, an upright position, or an upward position.

[0602] A welded joint obtained by the method for manufacturing a welded joint according to the present disclosure comprises a welded joint composed of a base material steel, a weld metal, and a weld heat-affected zone. Since the welded joint according to the present disclosure is manufactured using a coated arc welding electrode according to the present disclosure, it comprises a weld metal having a good bead shape. Accordingly, a welded structure having a welded joint manufactured by the method for manufacturing a welded joint according to the present disclosure also comprises a weld metal having a good bead shape. It is preferable that the tensile strength of the obtained weld metal be high, for example, 590 to 1200 MPa.

[0603] Examples

[0604] Next, the feasibility and effects of the present disclosure will be explained in more detail through the embodiments and comparative examples of the present disclosure; however, the following embodiments are not intended to limit the present disclosure, and any design modifications based on the intent described above are included within the technical scope of the present disclosure.

[0605] (Manufacture of coated arc welding rods)

[0606] The coated arc welding rods of the present disclosure example and comparative example were manufactured by the method described below.

[0607] First, coated arc welding electrodes were produced by applying flux having the chemical compositions shown in Tables 2-A, 2-B, 2-C, and 2-D to core wires having the chemical compositions shown in Tables 1-A and 1-B, and firing them for 1 to 3 hours within a temperature range of 300 to 500°C. The final electrode diameter of the obtained coated arc welding electrodes was Φ6.0 mm, and the average thickness of the flux was 1.0 mm. The composition of these coated arc welding electrodes is shown in Tables 1-A, 1-B, 2-A, 2-B, 2-C, and 2-D.

[0608] The unit of the content of the chemical components of the core wire shown in Tables 1-A, 1-B, 2-A, 2-B, 2-C, and 2-D is mass% relative to the total mass of the core wire. In addition, the unit of the content of the chemical components of the flux, the content of oxides, the content of fluorides, the content of metal carbonates, and the content of iron is mass% relative to the total mass of the flux. In the tables, "mass% relative to the total mass of the core wire" and "mass% relative to the total mass of the flux" are both abbreviated as "mass%", and "metal components in the chemical components of the flux" is abbreviated as "chemical components of the flux".

[0609] In addition, as shown in Table 2-C, “TiO2” represents the sum of the TiO2 equivalent values ​​of Ti oxide, “SiO2” represents the sum of the SiO2 equivalent values ​​of Si oxide, “ZrO2” represents the sum of the ZrO2 equivalent values ​​of Zr oxide, “Al2O3” represents the sum of the Al2O3 equivalent values ​​of Al oxide, “MgO” represents the sum of the MgO equivalent values ​​of Mg oxide, “CaO” represents the sum of the CaO equivalent values ​​of Ca oxide, “Na2O” represents the sum of the Na2O equivalent values ​​of Na oxide, and “K2O” represents the sum of the K2O equivalent values ​​of K oxide.

[0610] "Sum X" shown in Table 2-D represents the sum of the TiO2 equivalent values ​​of Ti oxide, the sum of the SiO2 equivalent values ​​of Si oxide, the sum of the ZrO2 equivalent values ​​of Zr oxide, the sum of the Al2O3 equivalent values ​​of Al oxide, the sum of the MgO equivalent values ​​of Mg oxide, the sum of the CaO equivalent values ​​of Ca oxide, the sum of the Na2O equivalent values ​​of Na oxide, the sum of the K2O equivalent values ​​of K oxide, the CaF2 content, the CaCO3 content, the BaCO3 content, the MgCO3 content, and the Li2CO3 content.

[0611] [Table 1-A]

[0612]

[0613] [Table 1-B]

[0614]

[0615] [Table 2-A]

[0616]

[0617] [Table 2-B]

[0618]

[0619] [Table 2-C]

[0620]

[0621] [Table 2-D]

[0622]

[0623] The remainder of the core wires shown in Tables 1-A and 1-B (i.e., components other than those shown in the tables), and the remainder of the coated arc welding rods shown in Tables 2-A, 2-B, 2-C, and 2-D (i.e., components other than those shown in the tables) are iron and impurities.

[0624] In addition, in Tables 1-A and 1-B, figures outside the range defined in the present disclosure are underlined.

[0625] In addition, in Tables 1-A, 1-B, 2-A, 2-B, 2-C, and 2-D, a blank space in the table regarding the content of chemical components or compounds, etc., indicates that the content of such chemical components or compounds, etc. is less than a significant number of places. These chemical components or compounds, etc. may inevitably be mixed in or generated in amounts less than a significant number of places.

[0626] [evaluation]

[0627] Evaluation was performed by gas shielded arc welding using the shielded arc welding electrodes of the present disclosure example and comparative example, with an upward-facing welding direction. Specifically, the evaluation was performed by the method described below.

[0628] As the steel plate for welding, 9% Ni steel with a plate thickness of 50 mm (steel plate conforming to JIS G 3127:2013 SL9N590) was used. In addition, during the evaluation, the welding current was all AC.

[0629] In addition, the welding conditions for evaluation were set to the conditions listed in Table 3.

[0630] [Table 3]

[0631]

[0632] (Evaluation of fume amount)

[0633] The amount of fumes produced when gas shielded arc welding was performed using the coated arc welding rods of the present disclosure example and comparative example was evaluated.

[0634] The amount of fumes generated by welding was measured using a total collection method with a high-volume air sampler in accordance with JIS Z3930:2013 (Method for measuring the amount of fumes generated by arc welding). Coated arc welding rods with a fume amount of 1000 mg / min or less were deemed "acceptable" with respect to the fume amount, and those with a fume amount exceeding 1000 mg / min were deemed "unacceptable."

[0635] (Evaluation of low-temperature toughness)

[0636] Using the shielded arc welding rods of the present disclosure example and comparative example, a steel plate was gas shielded arc welded, and three impact test specimens (V-notch test specimens with a notch depth of 2 mm) were taken from the center of the plate thickness direction of the weld metal.

[0637] A Charpy impact test was performed on three impact test specimens at -196℃ in accordance with JIS Z2242:2005.

[0638] In addition, for the three impact test specimens, if the average Charpy absorbed energy at -196℃ was 34J or higher, it was classified as “Excellent”; if it was 27J or higher but less than 34J, it was classified as “Pass”; and if it was less than 27J, it was classified as “Fail”.

[0639] (Overall Evaluation)

[0640] When both the evaluation of fume content and the evaluation of low-temperature toughness were "excellent" or "pass," it was evaluated as "pass," and when either one was "fail," it was evaluated as "fail."

[0641] [Table 4]

[0642]

[0643] It can be seen that the coated arc welding electrode of the present disclosure has a low fume amount and excellent low-temperature toughness of the weld metal obtained.

[0644] Meanwhile, the comparative example failed in one or more evaluation criteria because it did not satisfy any of the requirements stipulated in the present disclosure.

Claims

Claim 1 A coated arc welding electrode comprising a steel core wire and a flux coating the core wire, wherein, in mass % relative to the total mass of the core wire, the chemical composition of the core wire is, C: 0 to 0.650%, Si: 0.03 to 0.50%, Mn: 2.1 to 30.0%, P: 0 to 0.050%, S: 0 to 0.050%, Cu: 0 to 5.0%, Ni: 3.0 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 1.00%, Al: 0 to 0.10%, Ti: 0 to A coated arc welding electrode comprising 0.10%, B: 0 to 0.1000%, N: 0 to 0.5000%, O: 0 to 0.0050%, and remainder: Fe and impurities, wherein the sum of the Mn content and the Ni content (Mn+Ni) is 5.0% or more, the sum of the Mn content, the Ni content, and the Cr content (Mn+Ni+Cr) is 15.0% or more, and the fcc ratio obtained by magnetic induction in the core wire is 70% or more. Claim 2 A coated arc welding rod according to claim 1, wherein the mass ratio (Ni / Mn) of the Mn content and the Ni content is 0.10 or higher. Claim 3 In paragraph 2, a coated arc welding rod having a mass ratio (Ni / Mn) of 1.00 or more. Claim 4 A coated arc welding rod according to claim 1, wherein the Ti content is Ti: 0.003 to 0.10%. Claim 5 In claim 1, in mass % relative to the total mass of the flux, the chemical composition of the flux comprises: sum of TiO2 equivalent values ​​of Ti oxide: 0 to 25.00%, sum of SiO2 equivalent values ​​of Si oxide: 0 to 25.00%, sum of ZrO2 equivalent values ​​of Zr oxide: 0 to 5.00%, sum of Al2O3 equivalent values ​​of Al oxide: 0 to 5.00%, sum of MgO equivalent values ​​of Mg oxide: 0 to 5.00%, sum of CaO equivalent values ​​of Ca oxide: 0 to 25.00%, sum of Na2O equivalent values ​​of Na oxide: 0 to 5.00%, sum of K2O equivalent values ​​of K oxide: 0 to 5.00%, CaF2: 0 to 30.00%, CaCO3: 0 to 60.00%, BaCO3: 0 to 15.00%, MgCO3: 0 to 15.00%, and Li2CO3: 0 to 15.00%, wherein the metal components in the chemical composition of the flux, in mass% relative to the total mass of the flux, comprise C: 0.020 to 5.000%, Si: 0 to 5.00%, Mn: 0 to 30.00%, P: 0 to 0.050%, S: 0 to 0.050%, Cu: 0 to 20.0%, Ni: 0 to 20.0%, Cr: 0 to 20.0%, Mo: 0 to 10.0%, Nb: 0 to 5.00%, V: 0 to 5.0%, Co: 0 to 1.00%, Pb: 0 to 1.00%, Sn: 0 to A coated arc welding electrode comprising 1.00%, W: 0 to 20.0%, Mg: 0 to 5.00%, Al: 0 to 5.0%, Ca: 0 to 5.00%, Ti: 0 to 5.000%, B: 0 to 5.0000%, REM: 0 to 5.00%, Bi: 0 to 5.000%, N: 0 to 5.0000%, and the remainder being Fe and impurities, wherein the sum of the contents of CaCO3, BaCO3, MgCO3, and Li2CO3 is 5.00% or more. Claim 6 A coated arc welding rod according to claim 5, wherein the sum of the Mn content and the Ni content (Mn+Ni) in the flux is 1.00% or more. Claim 7 A coated arc welding electrode according to claim 5, wherein the sum X of the TiO2 equivalent values ​​of the Ti oxide, the sum of the SiO2 equivalent values ​​of the Si oxide, the sum of the ZrO2 equivalent values ​​of the Zr oxide, the sum of the Al2O3 equivalent values ​​of the Al oxide, the sum of the MgO equivalent values ​​of the Mg oxide, the sum of the CaO equivalent values ​​of the Ca oxide, the sum of the Na2O equivalent values ​​of the Na oxide, the sum of the K2O equivalent values ​​of the K oxide, the CaF2 content, the CaCO3 content, the BaCO3 content, the MgCO3 content, and the Li2CO3 content is 94.98% or less. Claim 8 A coated arc welding rod according to any one of claims 1 to 7, wherein the average thickness of the flux is 5.0 mm or less. Claim 9 A method for manufacturing a welded joint comprising a process of welding steel using a coated arc welding rod described in any one of claims 1 to 7.

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