Flux and method for manufacturing welded joint

Abstract

A welding flux comprising, as alloy components, C: 0.050% to 5.000%, Cr: 0-20.0%, and at least one oxide selected from the group consisting of a Ba oxide, a Ca oxide, an Mn oxide, an Mg oxide, an Fe oxide, and a Zr oxide, wherein: the basicity BL of BL = 1.3 [BaO] + 0.5 [CaO + MnO + Na2O + K2O] + 0.2 [MgO + FeO] + 0.05 [ZrO2) - 0.05 [Al2O3] - 0.2 [TiO2] - 0.5 [SiO2] +5 ([C] + [Mg] + [Fe]) is 2.0-60.0; and the particle size distributions are such that more than 2.00 mm: 40% or less, more than 1.00 mm and 2.00 mm or less: 5-50%, more than 0.50 mm and 1.00 mm or less: 5-75%, more than 0.25 mm and 0.50 mm or less: 5-50%, and 0.25 mm or less: 40% or less.

Description

Flux and method for manufacturing welded joints

[0001] This disclosure relates to flux and a method for manufacturing welded joints.

[0002] In recent years, due to stricter regulations on carbon dioxide emissions caused by global warming, 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 demand for the construction of liquid hydrogen tanks, liquid carbon dioxide tanks, and LNG tanks for use on ships and land has also increased globally. Steel materials used in liquid hydrogen tanks, liquid carbon dioxide tanks, and LNG tanks are nickel-based low-temperature steels containing 6-9% Ni, in order to ensure toughness at extremely low temperatures of -196°C. Welding of these nickel-based low-temperature steels is performed using welding methods such as submerged arc welding using flux and wire. For example, Patent Document 1 discloses a welding material for austenitic heat-resistant steel used in flux-based welding.

[0003] Patent Document 1: Japanese Unexamined Patent Publication No. 2014-140884

[0004] For example, steel used in liquid hydrogen tanks, liquid carbon dioxide tanks, and LNG tanks requires toughness at low temperatures. Furthermore, not only for steel used at low temperatures, but also for welds (i.e., weld metal) formed by welding steel materials together, both high strength and high toughness are required. And from the perspective of increasing toughness, reducing the oxygen concentration in the weld metal is necessary.

[0005] Therefore, the object of this disclosure is to provide a flux that yields a weld metal having high strength and reduced oxygen concentration, and a method for manufacturing a welded joint using the flux.

[0006] The means for solving the problem include the following aspects: <1> Containing alloy components and oxides, the content of the alloy components in mass % of the total mass of the flux is: C: 0.050% to 5.000%, Si: 0% to 0.50%, Mn: 0% to 30.0%, P: 0% to 0.050%, S: 0% to 0.050%, Cu: 0% to 5.0%, Ni: 0% to 50.0%, Cr: 0% to 20.0%, Mo: 0% to 30.0%, Nb: 0% to 10.00%, V: 0% to 10.00%, Co: 0% to 10.00%, Pb: 0% to 10.00%, Sn: 0% to 10.00%, Al: 0% to 10.00%, Ti: 0% to 10.00% B: 0% to 0.5000%, N: 0% to 5.0000%, Ta: 0% to 1.00%, Hf: 0% to 1.00%, W: 0% to 30.00%, Mg: 0% to 10.00%, REM: 0% to 0.50%, Ca: 0% to 10.00%, Zr: 0% to 5.00%, and Fe: 0% to 5.0%, wherein the oxide includes at least one oxide selected from the group consisting of Ba oxide, Ca oxide, Mn oxide, Na oxide, K oxide, Mg oxide, Fe oxide, Zr oxide, Al oxide, Ti oxide, and Si oxide, and optionally includes at least one selected from the group consisting of fluorides, nitrides, metal carbonates, and sulfates. A welding flux that optionally contains at least one specific compound selected from the group consisting of Sr compounds, Y compounds, Zr compounds, Ba compounds, and Sc compounds, has a basicity BL represented by the following formula 1 to 2.0 to 60.0, and has a particle size distribution measured by a sieve specified in JIS Z8801-1:2000, where: over 2.00 mm: 40% or less, over 1.00 mm and up to 2.00 mm: 5% to 50%, over 0.50 mm and up to 1.00 mm: 5% to 75%, over 0.25 mm and up to 0.50 mm: 5% to 50%, and 0.25 mm and below: 40% or less. BL = 1.3 [BaO] + 0.5 [CaO + MnO + Na ２ O+K ２ O]+0.2[MgO+FeO]+0.05[ZrO ２ ]-0.05[ Al ２ O ３- 0.2 [TiO ２ - 0.5 [SiO ２ + 5([C] + [Mg] + [Fe]) Formula 1 In Formula 1, [BaO] represents the total amount of BaO conversion value of Ba oxide, [CaO + MnO + Na ２ O + K ２ O] represents the total amount of the total amount of CaO conversion value of Ca oxide, the total amount of MnO conversion value of Mn oxide, the total amount of Na ２ O conversion value of O, and the total amount of K ２ O conversion value of oxide, [MgO + FeO] represents the total amount of the total amount of MgO conversion value of Mg oxide and the total amount of FeO conversion value of Fe oxide, [ZrO<​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​３ FeCO ３ MnCO ３ , and SrCO ３ The flux according to <1> or <2>, comprising at least one metal carbonate selected from the group consisting of the following, wherein the total content of the metal carbonates is greater than 0% to 20.00% by mass relative to the total mass of the flux. <4> Total amount of the Ba oxide in terms of BaO equivalent, Total amount of the Ca oxide in terms of CaO equivalent, Total amount of the Mn oxide in terms of MnO equivalent, Na of the Na oxide ２ Total amount of O equivalent value, K of the K oxide ２ Total amount of O equivalent value, total amount of Mg O equivalent value of the Mg oxide, total amount of Fe O equivalent value of the Fe oxide, Zr O equivalent value of the Zr oxide ２ Total amount of the converted value, Al of the Al oxide ２ O ３ Total amount of converted values, TiO of the Ti oxide ２ The total amount of the converted value, and the SiO of the Si oxide. ２ The flux according to any one of <1> to <3>, wherein the total amount of the converted values ​​is greater than 0% to 60.00% by mass relative to the total mass of the flux. <5> The flux according to any one of <1> to <4>, wherein it contains at least one specific compound, and the total content of Sr, Y, Zr, Ba, and Sc elements contained in the specific compound is greater than 0% to 1.000% by mass relative to the total mass of the flux. <6> The nitride is AlN, BN, Ca ３ N ２ , CeN, CrN, Cu ３ N, Fe ４ N, Fe ３ N, Fe ２ N, Mg ３ N, Mo ２ N, NbN, Si ３ N ４ , TiN, VN, ZrN, Mn ２ N and Mn ４A flux according to any one of <1> to <5>, comprising at least one nitride selected from the group consisting of N, wherein the total content of the nitrides is greater than 0% to 40% by mass relative to the total mass of the flux. <7> The composition of the elements constituting the flux, expressed as mass % of the total mass of the flux, is as follows: C: 0.050% to 7.000%, Si: 0% to 10.00%, Mn: 0% to 45.00%, P: 0% to 0.050%, S: 0% to 0.050%, Cu: 0% to 30.000%, Ni: 0% to 50.0%, Cr: 0% to 20.0%, Mo: 0% to 40.0%, Nb: 0% to 10.00%, V: 0% to 10.00%, Co: 0% to 10.00%, Pb: 0% to 10.00%, Sn: 0% to 10.00%, Al: 0% to 25.00%, Ti: 0% to 30.00%. B: 0% to 5.0000%, N: 0% to 15.000%, Ta: 0% to 1.00%, Hf: 0% to 1.00%, W: 0% to 30.00%, Mg: 0% to 30.00%, REM: 0% to 0.50%, Ca: 0% to 40.00%, Zr: 0% to 5.00%, Total of Sr, Y, Ba, and Sc: 0% to 1.00%, O: 0% to 30.00%, F: 0% to 30.00%, Na: 0% to 20.00%, K: 0% to 20.00%, Li: 0% to 10.00%, Ce: 0% to 25.00%, and the remainder: Fe and impurities. The flux described in any one of <1> to <6>.<8> The composition of the elements constituting the flux, expressed as mass % of the total mass of the flux, is as follows: C: 0.300% to 3.000%, Si: 0.50% to 5.00%, Mn: 0% to 10.00%, P: 0.0005% to 0.050%, S: 0.0005% to 0.050%, Cu: 0% to 1.00%, Ni: 0% to 30.0%, Cr: 0% to 10.0%, Mo: 0% to 10.0%, Nb: 0% to 5.00%, V: 0% to 5.00%, Co: 0% to 1.00%, Pb: 0% to 1.00%, Sn: 0% to 1.00%, Al: 0% to 3.00%. Ti: 0% to 3.00%, B: 0% to 0.1000%, N: 0% to 5.000%, Ta: 0% to 0.50%, Hf: 0% to 0.50%, W: 0% to 10.00%, Mg: 0% to 10.00%, REM: 0% to 0.10%, Ca: 15.00% to 40.00%, Zr: 0% to 2.00%, Total of Sr, Y, Ba, and Sc: 0% to 0.30%, O: 5% to 30.00%, F: 15.00% to 30.00%, Na: 0% to 10.00%, K: 0% to 10.00%, Li: 0% to 5.00% A flux according to any one of <1> to <7>, wherein Ce: 0% to 10.00%, and the remainder: Fe and impurities. <9> A flux according to any one of <1> to <8>, wherein the particle size distribution is: over 2.00 mm: 5% or less, over 1.00 mm to 2.00 mm: 10% to 30%, over 0.50 mm to 1.00 mm: 10% to 70%, over 0.25 mm to 0.50 mm: 10% to 50%, and 0.25 mm or less: 5% or less. <10> A flux according to any one of <1> to <9>, wherein D50 is 0.3 mm to 1.5 mm. <11> A method for manufacturing a welded joint, comprising manufacturing a welded joint using the flux according to any one of <1> to <10>.

[0007] This disclosure provides a flux that yields a weld metal having high strength and reduced oxygen concentration, and a method for manufacturing a welded joint using the flux.

[0008] Embodiments, which are examples of this disclosure, will now be described. These descriptions and examples are illustrative of embodiments and do not limit the scope of the invention. In this specification, numerical ranges expressed using "~" mean ranges that include the numbers before and after "~" as lower and upper limits, respectively, unless "greater than" or "less than" is attached to the numbers before and after "~". If "greater than" or "less than" is attached to the numbers before and after "~", the numerical range means ranges that do not include those numbers as lower or upper limits. In numerical ranges described in steps in this specification, the upper limit of one step numerical range may be replaced with the upper limit of another step numerical range, or with the value shown in the examples. Similarly, the lower limit of one step numerical range may be replaced with the lower limit of another step numerical range, or with the value shown in the examples. Furthermore, "%" for content means "mass%" unless otherwise specified. "0~" for content (%) means that the component is an optional component and does not need to be included.

[0009] Each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition, if multiple types of the substance corresponding to each component are present in the composition, unless otherwise specified, it means the total amount of those multiple types of substances present in the composition. The term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes, as long as the intended function of that process is achieved.

[0010] <Flux for welding> The flux for welding according to this disclosure (which may be simply referred to as "flux" in this disclosure) contains alloy components and oxides. The flux for welding according to this disclosure may optionally contain at least one selected from the group consisting of fluorides, nitrides, metal carbonates, and sulfates, and may also contain at least one specific compound selected from the group consisting of Sr compounds, Y compounds, Zr compounds, Ba compounds, and Sc compounds. The flux for welding according to this disclosure may contain 0.050% to 5.000% of C and 20.0% or less of Cr as alloy components, by mass % of the total mass of the flux. The flux for welding according to this disclosure also contains at least one oxide selected from the group consisting of Ba oxide, Ca oxide, Mn oxide, Na oxide, K oxide, Mg oxide, Fe oxide, Zr oxide, Al oxide, Ti oxide, and Si oxide, and has a basicity BL represented by the following formula 1 of 2.0 to 60.0. BL=1.3[BaO]+0.5[CaO+MnO+Na ２ O+K ２ O]+0.2[MgO+FeO]+0.05[ZrO ２ ]-0.05[ Al ２ O ３ ]-0.2[TiO ２ ]-0.5[SiO ２ ] + 5 ([C] + [Mg] + [Fe]) Equation 1 In Equation 1, [BaO] represents the total amount of Ba oxides in BaO equivalent, and [CaO + MnO + Na ２ O+K ２ O] represents the total amount of Ca oxides converted to CaO, the total amount of Mn oxides converted to MnO, and Na oxides. ２ Total amount of O equivalent value and K of K oxide ２ [MgO + FeO] represents the total amount of the sum of the MgO equivalent values ​​of Mg oxides and the FeO equivalent values ​​of Fe oxides, and [ZrO ２ ] is Zr oxide ZrO ２ Represents the total amount of the converted values, [Al ２ O ３ ] is Al oxide Al ２ O ３ Represents the total amount of the converted value, [TiO ２ ] is TiO of Ti oxide２ This represents the total amount of the converted values, [SiO ２ ] is Si oxide SiO ２ The total amount of the converted values ​​is shown, where [C] represents the content of C as an alloying component, [Mg] represents the content of Mg as an alloying component, and [Fe] represents the content of Fe as an alloying component. Furthermore, the welding flux according to this disclosure has a particle size distribution measured by a sieve specified in JIS Z8801-1:2000, which is within the following ranges: over 2.00 mm: 40% or less, over 1.00 mm and up to 2.00 mm: 5% to 50%, over 0.50 mm and up to 1.00 mm: 5% to 75%, over 0.25 mm and up to 0.50 mm: 5% to 50%, and 0.25 mm or less: 40% or less.

[0011] This disclosure provides a flux that yields a weld metal with high strength and reduced oxygen concentration. The reason for this effect is presumed to be as follows.

[0012] The flux according to this disclosure contains 0.050% or more of carbon (C) as an alloying component. Therefore, carbon is supplied to the weld metal from the flux, enhancing solid solution strengthening by carbon and increasing the strength of the weld metal. However, even if carbon is supplied to the weld metal from the flux, if a large amount precipitates as carbides, the effect of solid solution strengthening in the weld metal cannot be enhanced. In contrast, the flux according to this disclosure has a Cr content of 20.0% or less as an alloying component. In other words, the content of Cr, which is a carbide-precipitating element, is reduced, suppressing the amount of carbon that precipitates as carbides, and increasing the strength of the weld metal through solid solution strengthening. Furthermore, the flux according to this disclosure has a basicity BL represented by formula 1 of 2.0 or higher. By increasing the basicity BL of the flux and supplying carbon, magnesium, or fe to the weld metal from the flux, the deoxidation effect can be enhanced, and the oxygen concentration in the weld metal can be reduced. As a result of the reduction in oxygen concentration, the toughness of the resulting weld metal is increased.

[0013] Furthermore, by ensuring the flux particle size distribution is within the aforementioned range, the slag-metal reaction is promoted, and the oxygen concentration of the weld metal is reduced. If the flux particle size distribution falls outside the aforementioned range and there is too much flux with large particle sizes (specifically, if the proportion of flux with particles larger than 2.00 mm exceeds 40%), the slag-metal reaction is not promoted, and the oxygen concentration of the weld metal becomes high. Also, if the flux particle size distribution falls outside the aforementioned range and there is too much flux with small particle sizes (specifically, if the proportion of flux with particles smaller than 0.25 mm exceeds 40%), the molten metal flow during welding becomes unstable, increasing the amount of oxygen brought in from the outside air and flux, resulting in a higher oxygen concentration.

[0014] As described above, the flux according to this disclosure yields weld metal with high strength and reduced oxygen concentration.

[0015] The flux related to this disclosure will be described in more detail below.

[0016] The flux relating to this disclosure contains oxides as alloying and compounding components. Alloying components refer to chemical components excluding oxides, fluorides, nitrides, metal carbonates, and sulfates, while compounding components refer to components included as oxides, fluorides, nitrides, metal carbonates, or sulfates. Note that compounding components also include Sr compounds, Y compounds, Zr compounds, Ba compounds, and Sc compounds. The flux relating to this disclosure melts together with a portion of the steel material during welding, and a portion of the flux, including the alloying components, becomes the weld metal after solidification, along with a portion of the molten steel material.

[0017] [Alloy Components] The alloy components contained in the flux relating to this disclosure are described below. In the description of alloy components, "%" means "mass % relative to the total mass of the flux" unless otherwise specified.

[0018] The flux contains 0.050% to 5.000% carbon and 0% to 20.0% chromium as alloying components. The reasons for the inclusion of these alloying components are explained below.

[0019] (C: 0.050% to 5.000%) Carbon (C) is an interstitial solid solution strengthening element, and increasing the C content can improve the strength of the weld metal. On the other hand, if the C content is too high, hot cracking will occur in the weld metal. Also, C is an element that generates spatter, and from the viewpoint of reducing spatter, a lower C content in the flux is advantageous. Therefore, the C content of the flux should be 0.050% to 5.000%. The lower limit of the C content of the flux may be 0.100%, 0.200%, 0.300%, 0.400%, or 0.500%. The upper limit of the C content of the flux is preferably 4.500%, 4.000%, 3.300%, 3.000%, 2.500%, or 2.000%.

[0020] (Cr: 0% to 20.0%) Cr is a ferrite-stabilizing element and may be included in the flux to improve the strength of the weld metal. On the other hand, Cr is a carbide-precipitating element, and by reducing the Cr content of the flux, the amount of C precipitated as carbides can be suppressed, and the strength of the weld metal can be increased by solid solution strengthening. Therefore, the Cr content of the flux should be 0 to 20.0%. The lower limit of the Cr content of the flux is preferably 0.01%, 0.02%, 1.0%, 2.0%, or 3.0%. The upper limit of the Cr content of the flux is preferably 18.0%, 16.0%, 14.0%, 12.0%, or 10.0%.

[0021] Next, we will explain the alloying components other than C and Cr that may be included in the flux, that is, the optional alloying components other than Cr.

[0022] The flux relating to this disclosure has alloy component content of: C: 0.050% to 5.000%, Si: 0% to 0.50%, Mn: 0% to 30.0%, P: 0% to 0.050%, S: 0% to 0.050%, Cu: 0% to 5.0%, Ni: 0% to 50.0%, Cr: 0% to 20.0%, Mo: 0% to 30.0%, Nb: 0% to 10.00%, V: 0% to 10.00%, Co: 0% to 10.00%, Pb: 0% to 10.00%, Sn: 0% to 10.00%, Al: 0% to 10.00%, Ti: 0% to 10.00%, B Preferably, the ratios are: N: 0% to 0.5000%, Ta: 0% to 1.00%, Hf: 0% to 1.00%, W: 0% to 30.00%, Mg: 0% to 10.00%, REM: 0% to 0.50%, Ca: 0% to 10.00%, and Zr: 0% to 5.00%.

[0023] (Si: 0% to 0.50%) Si is a deoxidizing element and can reduce the O content of the flux, so it may be included in the flux. On the other hand, Si has low solid solubility in the austenite phase, and by reducing the Si content, the formation of brittle phases such as intermetallic compounds and δ-ferrite at high temperatures can be suppressed, and high-temperature ductility can be improved. Therefore, the Si content of the flux is preferably 0% to 0.50%. The lower limit of the Si content of the flux is preferably 0.01%, 0.03%, 0.05%, 0.08%, or 0.10%. The upper limit of the Si content of the flux is preferably 0.40%, 0.30%, or 0.20%.

[0024] (Mn: 0% to 30.0%) Mn is an austenite-stabilizing element that promotes austenitization of the weld metal and can improve the low-temperature toughness of the weld metal, so it may be included in the flux. On the other hand, Mn is an element that causes an increase in the amount of fume generated. Furthermore, reducing the Mn content can increase the stacking fault energy and improve toughness. Therefore, the Mn content of the flux is preferably 0% to 30.0%. The lower limit of the Mn content of the flux is preferably 0.5%, 1.0%, 2.0%, 3.0%, 4.0%, or 5.0%. The upper limit of the Mn content of the flux is preferably 28.0%, 26.0%, 24.0%, 22.0%, 20.0%, 18.0%, 16.0%, or 15.0%.

[0025] (P: 0% to 0.050%) P is an impurity element that reduces the toughness of the weld metal, so it is preferable to reduce the P content of the flux as much as possible. Therefore, the lower limit of the P content of the flux is set to 0%. However, from the viewpoint of reducing the cost of eliminating P, the P content of the flux should be 0.0005% or more. On the other hand, if the P content of the flux is 0.050% or less, the adverse effect of P on toughness can be reduced. Therefore, it is preferable that the P content of the flux be 0% to 0.050%. In order to effectively suppress the decrease in toughness of the weld metal, it is preferable that the P content of the flux be 0.040% or less, 0.030% or less, 0.020% or less, 0.015% or less, 0.010% or less, or 0.005% or less.

[0026] (S: 0% to 0.050%) S is an impurity element that reduces the toughness of the weld metal, so it is preferable to reduce the S content of the flux as much as possible. Therefore, the lower limit of the S content of the flux is 0%. However, from the viewpoint of reducing the cost of S removal, the S content of the flux should be 0.0005% or more. On the other hand, if the S content of the flux is 0.050% or less, the adverse effect of S on toughness can be reduced. Therefore, it is preferable that the S content of the flux be 0% to 0.050%. In order to effectively suppress the decrease in toughness of the weld metal, it is preferable that the S content of the flux be 0.040% or less, 0.030% or less, 0.020% or less, 0.015% or less, 0.010% or less, or 0.005% or less.

[0027] (Cu: 0% to 5.0%) Cu is a precipitation strengthening element and may be included in the flux to improve the strength of the weld metal. Cu is also an austenite stabilizing element and may be included in the flux to improve the low-temperature toughness of the weld metal. On the other hand, if the Cu content of the flux is excessive, the above effects will saturate. Therefore, it is preferable that the Cu content of the flux be between 0% and 5.0%. The lower limit of the Cu content of the flux is preferably 0.3%, 0.5%, or 0.7%. The upper limit of the Cu content of the flux is preferably 4.5%, 4.0%, 3.5%, 3.0%, 2.5%, or 2.0%.

[0028] (Ni: 0% to 50.0%) Ni is an austenite-stabilizing element. Increasing the Ni content of the flux promotes austenitization of the weld metal and improves low-temperature toughness. Therefore, Ni may be included in the flux. On the other hand, reducing the Ni content of the flux can reduce the cost of the flux. Therefore, it is preferable that the Ni content of the flux be between 0% and 50.0%. The lower limit of the Ni content of the flux is preferably 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, or 9.0%. The upper limit of the Ni content of the flux is preferably 45.0%, 40.0%, 35.0%, 30.0%, 25.0%, 20.0%, 18.0%, or 15.0%.

[0029] (Mo: 0% to 30.0%) Mo is a precipitation strengthening element and may be included in the flux to improve the strength of the weld metal. On the other hand, Mo is a carbide precipitation element, and by reducing the Mo content of the flux, the amount of C that precipitates as carbides can be suppressed, and the strength of the weld metal can be increased by solid solution strengthening. Therefore, it is preferable that the Mo content of the flux be 0% to 30.0%. The lower limit of the Mo content of the flux is preferably 1.0%, 3.0%, or 5.0%. The upper limit of the Mo content of the flux is preferably 25.0%, 20.0%, 15.0%, 10.0%, or 8.0%.

[0030] (Nb: 0% to 10.00%) Nb is an element that increases the strength of the weld metal by solid-solubilizing it in the weld metal, so it may be included in the flux. On the other hand, Nb is an element that promotes hot cracking, and hot cracking can be suppressed by reducing the Nb content of the flux. Therefore, it is preferable that the Nb content of the flux be 0% to 10.00%. The lower limit of the Nb content of the flux is preferably 0.001%, 0.003%, 0.005%, 0.01%, 0.015%, or 0.02%. The upper limit of the Nb content of the flux is preferably 8.00%, 6.00%, 4.00%, 2.00%, or 1.00%.

[0031] (V: 0% to 10.00%) V is an element that increases the strength of the weld metal by solid-solubilizing it in the weld metal, and therefore may be included in the flux. On the other hand, V is a carbonitride precipitation element, and by reducing the V content of the flux, the amount of carbonitride precipitation can be suppressed, and the strength of the weld metal can be increased by solid-solution strengthening. Therefore, it is preferable that the V content of the flux be 0% to 10.00%. The lower limit of the V content of the flux is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the V content of the flux is preferably 8.00%, 6.00%, 4.00%, 2.00%, or 1.00%.

[0032] (Co: 0% to 10.00%) Co is an element that increases the strength of the weld metal through solid solution strengthening, and therefore may be included in the flux. On the other hand, reducing the Co content of the flux can increase the ductility of the weld metal and ensure toughness. Therefore, it is preferable that the Co content of the flux be between 0% and 10.00%. The lower limit of the Co content of the flux is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the Co content of the flux is preferably 8.00%, 5.00%, 3.00%, 1.00%, 0.80%, 0.60%, or 0.50%.

[0033] (Pb: 0% to 10.00%) Pb may be included in the flux because it improves the formability of the weld toe between the base material (steel) and the weld metal, and improves the machinability of the weld metal. On the other hand, reducing the Pb content of the flux stabilizes the arc state and reduces spatter. Therefore, it is preferable that the Pb content of the flux be 0% to 10.00%. The lower limit of the Pb content of the flux is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the Pb content of the flux is preferably 8.00%, 6.00%, 4.00%, 2.00%, 1.00%, or 0.50%.

[0034] (Sn: 0% to 10.00%) Sn is an element that improves the corrosion resistance of the weld metal, so it may be included in the flux. On the other hand, reducing the Sn content of the flux can suppress the occurrence of cracks in the weld metal. Therefore, it is preferable that the Sn content of the flux be between 0% and 10.00%. The lower limit of the Sn content of the flux is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the Sn content of the flux is preferably 8.00%, 6.00%, 4.00%, 2.00%, 1.00%, or 0.50%.

[0035] (Al: 0% to 10.00%) Al is a deoxidizing element and may be included in the flux to suppress welding defects and improve the cleanliness of the weld metal. On the other hand, by reducing the Al content of the flux, the formation of nitrides or oxides in the weld metal by Al can be suppressed, and the decrease in the low-temperature toughness of the weld metal can be suppressed. Therefore, it is preferable that the Al content of the flux be 0% to 10.00%. The lower limit of the Al content of the flux is preferably 0.10%, 0.50%, 1.00%, 1.50%, or 2.00%. The upper limit of the Al content of the flux is preferably 8.00%, 6.00%, 5.00%, 4.00%, or 3.00%.

[0036] (Ti: 0% to 10.00%) Ti is a deoxidizing element and may be included in the flux to suppress welding defects and improve the cleanliness of the weld metal. On the other hand, Ti is a carbide precipitation element, and by reducing the Ti content of the flux, the amount of C that precipitates as carbides can be suppressed, and the strength of the weld metal can be increased by solid solution strengthening. Therefore, it is preferable that the Ti content of the flux be 0% to 10.00%. The lower limit of the Ti content of the flux is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the Ti content of the flux is preferably 8.00%, 6.00%, 4.00%, 2.00%, or 1.00%.

[0037] (B: 0% to 0.5000%) B is an interstitial solid solution strengthening element and may be included in the flux to improve the low-temperature toughness and strength of the weld metal. On the other hand, by reducing the B content of the flux, M ２３ (C, B) ６ Precipitation is suppressed, and toughness deterioration can be suppressed. Therefore, the B content of the flux is preferably 0% to 0.5000%. The lower limit of the B content of the flux is preferably 0.0005%, 0.0010%, or 0.0020%. The upper limit of the B content of the flux is preferably 0.4000%, 0.3000%, 0.2000%, 0.1000%, 0.0500%, or 0.0100%.

[0038] (N: 0% to 5.0000%) N is an austenite-stabilizing element and an interstitial solid solution strengthening element, and may be included in the flux to improve the low-temperature toughness and strength of the weld metal. On the other hand, reducing the N content of the flux can suppress blowouts and reduce welding defects. Therefore, the N content of the flux is preferably 0% to 5.0000%. The lower limit of the N content of the flux is preferably 0.0010%, 0.0100%, or 0.0500%. The upper limit of the N content of the flux is preferably 3.0000%, 1.0000%, 0.8000%, 0.6000%, 0.4000%, or 0.2000%.

[0039] (Ta: 0% to 1.00%) Ta may be included in the flux as it contributes to suppressing hot cracking. On the other hand, Ta is a carbide precipitation element, and by reducing the Ta content of the flux, the amount of C that precipitates as carbides can be suppressed, and the strength of the weld metal can be increased by solid solution strengthening. Therefore, it is preferable that the Ta content of the flux be 0% to 1.00%. The lower limit of the Ta content of the flux is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the Ta content of the flux is preferably 0.80%, 0.60%, 0.40%, or 0.20%.

[0040] (Hf: 0% to 1.00%) Hf may be included in the flux as it contributes to suppressing hot cracking. On the other hand, Hf is a carbide precipitation element, and by reducing the Hf content of the flux, the amount of C that precipitates as carbides can be suppressed, and the strength of the weld metal can be increased by solid solution strengthening. Therefore, it is preferable that the Hf content of the flux be 0% to 1.00%. The lower limit of the Hf content of the flux is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the Hf content of the flux is preferably 0.80%, 0.60%, 0.40%, or 0.20%.

[0041] (W: 0% to 30.00%) W is an element that increases the strength of the weld metal through solid solution strengthening, and therefore may be included in the flux. On the other hand, W is a carbide precipitation element, and by reducing the W content of the flux, the amount of C that precipitates as carbides can be suppressed, and the strength of the weld metal can be increased through solid solution strengthening. Therefore, it is preferable that the W content of the flux be 0% to 30.00%. The lower limit of the W content of the flux is preferably 0.50%, 1.00%, 3.00%, or 5.00%. The upper limit of the W content of the flux is preferably 28.00%, 25.00%, 23.00%, 20.00%, 18.00%, 15.00%, 13.00%, or 10.00%.

[0042] (Mg: 0% to 10.00%) Mg may be included in the flux to improve the toughness of the weld metal by reducing the amount of oxygen in the weld metal through its deoxidizing effect. On the other hand, reducing the Mg content of the flux reduces the amount of slag generated and suppresses welding defects such as slag inclusion. Therefore, it is preferable that the Mg content of the flux be between 0% and 10.00%. The lower limit of the Mg content of the flux is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the Mg content of the flux is preferably 8.00%, 6.00%, 4.00%, 2.00%, or 1.00%.

[0043] (REM: 0% to 0.50%) Since REM is a strong deoxidizing element, it may be included in the flux. On the other hand, by reducing the REM content of the flux, the degrading effect of REM combining with oxygen is suppressed, and from this viewpoint as well, hot workability can be improved. Therefore, the REM content of the flux is preferably 0% to 0.50%. The lower limit of the REM content of the flux is preferably 0.01%, 0.03%, or 0.05%. The upper limit of the REM content of the flux is preferably 0.40%, 0.30%, 0.20%, or 0.10%.

[0044] "REM" is a collective term for 17 elements including Sc, Y, and lanthanides, and the REM content refers to the total content of one or more of these REM elements. REM is generally contained in mischmetal. Therefore, for example, it may be added in the form of mischmetal so that the amount of REM falls within the above range.

[0045] (Ca: 0% to 10.00%) Ca alters the structure of sulfides in the weld metal and refines the size of sulfides and oxides in the weld metal, thus effectively improving the ductility and toughness of the weld metal. For this reason, Ca may be included in the flux. On the other hand, reducing the Ca content of the flux can ensure weldability by suppressing deterioration of the weld bead shape and stabilizing the arc. Therefore, it is preferable that the Ca content of the flux be between 0% and 10.00%. The lower limit of the Ca content of the flux is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the Ca content of the flux is preferably 8.00%, 6.00%, 4.00%, 2.00%, or 1.00%.

[0046] (Zr: 0% to 5.00%) Zr may be included in the flux to improve the toughness of the weld metal by reducing the amount of oxygen in the weld metal through its deoxidizing effect. On the other hand, Zr is a carbide precipitation element, and by reducing the Zr content of the flux, the amount of C that precipitates as carbides can be suppressed, and the strength of the weld metal can be increased by solid solution strengthening. Therefore, it is preferable that the Zr content of the flux be 0% to 5.00%. The lower limit of the Zr content of the flux is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the Zr content of the flux is preferably 4.00%, 3.00%, 2.00%, or 1.00%.

[0047] (Remainder of alloy components: Fe and impurities) The remaining components of the components contained in the flux according to the present disclosure (that is, components other than the alloy components described above and the compound components described later) are Fe and impurities. Fe may be contained in the flux as any one or more forms selected from the group consisting of ferroalloy powders such as Fe—Si, Fe—Mn, and Fe—Ti alloys. The content of Fe as an alloy component in the flux is preferably 0% to 5.0%. The lower limit of the Fe content as an alloy component of the flux is preferably 0.10%, 0.20%, 0.30%, 0.50%, or 1.00%. The upper limit of the Fe content as an alloy component of the flux is preferably 3.00%, 2.00%, or 1.50%. Impurities mean components that are mixed in during the industrial production of the flux due to raw materials such as ores or scraps, or various factors in the production process, and are allowed as long as they do not adversely affect the properties of the flux.

[0048] [Basicity BL: 2.0 to 60.0] The flux according to the present disclosure contains at least one oxide selected from the group consisting of Ba oxide, Ca oxide, Mn oxide, Na oxide, K oxide, Mg oxide, Fe oxide, Zr oxide, Al oxide, Ti oxide, and Si oxide, and the basicity BL represented by the following formula 1 is 2.0 to 60.0. BL = 1.3[BaO] + 0.5[CaO + MnO + Na ２ O + K ２ O] + 0.2[MgO + FeO] + 0.05[ZrO ２ - 0.05[Al ２ O ３ - 0.2[TiO ２ - 0.5[SiO ２ + 5([C] + [Mg] + [Fe]) Formula 1 In Formula 1, the meanings of [oxide] and [element symbol] are as described above.

[0049] A basicity BL of 2.0 or higher, as represented by Equation 1, enhances the deoxidation effect and reduces the oxygen concentration in the weld metal. As a result, the toughness of the resulting weld metal is improved by reducing the oxygen concentration. On the other hand, a basicity BL of 60.0 or lower suppresses the decrease in work efficiency due to excessive slag formation.

[0050] The lower limit of the basicity BL in the flux is preferably 3.0, 5.0, 7.0, 9.0, or 10.0. The upper limit of the basicity BL in the flux is preferably 50.0, 40.0, 35.0, 30.0, 28.0, 25.0, 23.0, 20.0, 18.0, or 15.0.

[0051] [Compound Components] The compound components contained in the flux relating to this disclosure are described below. In the description of compound components, "%" means "mass % relative to the total mass of the flux" unless otherwise specified.

[0052] (Oxides) The flux contains at least one oxide selected from the group consisting of Ba oxide, Ca oxide, Mn oxide, Na oxide, K oxide, Mg oxide, Fe oxide, Zr oxide, Al oxide, Ti oxide, and Si oxide (hereinafter also referred to as "specific oxide"). Preferably, the flux contains at least one oxide selected from the group consisting of Ba oxide, Ca oxide, Mn oxide, Na oxide, K oxide, Mg oxide, Fe oxide, Zr oxide, Al oxide, Ti oxide, and Si oxide as the specific oxide.

[0053] The total content of the specific oxides is preferably more than 0% and up to 60.00% by mass based on the total mass of the flux. When the content of the specific oxides is more than 0%, a good bead appearance can be obtained and the amount of oxygen in the weld metal can be reduced. When the content of the specific oxides is 60.00% or less, it is possible to suppress the amount of oxygen in the weld metal from becoming excessive and enhance the toughness. The lower limit of the total content of the specific oxides is preferably 1.00%, 2.00%, 4.00%, 6.00%, 8.00%, or 10.00%. The upper limit of the total content of the specific oxides is preferably 50.00%, 40.00%, 30.00%, or 20.00%.

[0054] The total content of the specific oxides means the total amount of the BaO equivalent of the Ba oxide, the total amount of the CaO equivalent of the Ca oxide, the total amount of the MnO equivalent of the Mn oxide, the total amount of the Na ２ O equivalent of the Na oxide, the total amount of the K ２ O equivalent of the K oxide, the total amount of the MgO equivalent of the Mg oxide, the total amount of the FeO equivalent of the Fe oxide, the total amount of the ZrO ２ equivalent of the Zr oxide, the total amount of the Al ２ O ３ equivalent of the Al oxide, the total amount of the TiO ２ equivalent of the Ti oxide, the total amount of the SiO ２ equivalent of the Si oxide, and represents the total amount.

[0055] - Method for obtaining the total amount of the equivalent of the oxides - Here, the calculation method for the total amount of the equivalent of each oxide will be described.

[0056] First, it will be described by taking the Ti oxide as an example. The Ti oxide may mainly exist as rutile, titanium oxide, titanium slag, ilmenite, sodium titanate, potassium titanate, etc. in the flux. The total amount of the TiO ２ equivalent of the Ti oxide is the mass% of TiO ２ with respect to the total mass of the flux when all the Ti oxides contained in the flux are converted to TiO ２ . As the Ti oxide, for example, TiO, TiO ２ , Ti ２ O３ Ti ３ O ５ These are some examples, and they are added as rutile, titanium dioxide, titanium slag, ilmenite, sodium titanate, potassium titanate, etc.

[0057] Ti oxide TiO ２ The total amount of the converted value is determined by analyzing the mass of Ti present as an oxide in the flux using an X-ray fluorescence analyzer and an X-ray diffraction (XRD) analyzer. By analyzing the components contained in the flux using X-ray fluorescence analysis and then analyzing the molecular structure of the components contained in the flux using X-ray diffraction (XRD), it is possible to separately determine the amount of Ti present as an oxide in the flux and the amount of Ti included as an alloy component. For example, by analysis, TiO ２ Ti ２ O ３ , and Ti ３ O ５ If detected, the mass % of each Ti oxide is [TiO ２ ] [Ti ２ O ３ ] [Ti ３ O ５ Represented as ], Ti oxide TiO ２ The sum of the converted values ​​is [Converted TiO ２ Expressed as ], it is calculated by the following formula C1. [Converted TiO ２ ]=(0.60×[TiO ２ ] + 0.67 × [Ti ２ O ３ ] + 0.64 × [Ti ３ O ５ ]) × 1.67 Equation C1 The coefficients (0.60, 0.67, 0.64) in Equation C1 are coefficients for calculating the amount of Ti contained in each oxide, and the multiplier at the end (1.67) is calculated from the total amount of Ti present as oxide in the flux to TiO ２ This is a multiplier used to calculate the converted value.

[0058] Here, we will explain how to find the coefficient. M ｘ O ｙ (Example: TiO ２ Ti ２ O ３ , and Ti ３O ５ If oxides such as the above are detected, M ｘ O ｙ The coefficients involved are calculated using the following formula C2: [Atomic weight of element M] × x / ([Atomic weight of element M] × x + [Atomic weight of oxygen] × y) Formula C2 The values ​​0.60, 0.67, and 0.64 in formula C1 correspond to the coefficients obtained using the above formula C2. Furthermore, the method for determining the multipliers used to calculate the conversion value will be explained. M ａ O ｂ (Example: TiO ２ Ti ２ O ３ , and Ti ３ O ５ The multiplier for conversion to (etc.) is calculated using the following formula C3: ([atomic weight of element M] × a + [atomic weight of oxygen] × b) / ([atomic weight of element M] × a) Formula C3 The 1.67 in formula C1 corresponds to the multiplier obtained using the above formula C3. Note that oxides may also be compounds bonded with two metal elements. In that case, the coefficient is calculated as follows: ｘ O ｙ M ２ ｚ (Example: TiO ３ Fe, that is, M = Ti, M ２ An example of an oxide other than a Ti oxide is ZrSiO, where x=1, y=3, and z=1. ４ , in other words, M = Zr, M ２ If an oxide of Si (x=1, y=4, z=1) is detected, the calculation is performed using the following formula C4: [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 C4

[0059] Total amount of Ba oxides in BaO equivalent, total amount of Ca oxides in CaO equivalent, total amount of Mn oxides in MnO equivalent, Na oxides in Na ２ Total amount of O equivalent value, K of K oxide ２ Total amount of O equivalent, total amount of Mg oxide equivalent to MgO, total amount of Fe oxide equivalent to FeO, Zr oxide equivalent to ZrO ２ Total amount of converted value, Al oxide ２ O ３ The total amount of the converted value, and the SiO of Si oxide.２ The total amount of the converted value is also TiO2, a Ti oxide. ２ The sum of the converted values ​​is obtained by the same calculation. That is, the flux is analyzed using an X-ray fluorescence analyzer and an X-ray diffraction (XRD) analyzer, and coefficients and multipliers are calculated according to the above formulas C2, C3, and C4 according to the various oxides detected, and the calculation is performed in the same manner as the above formula C1. Representative oxides detected by the analysis are listed below. Ba oxide; BaO, BaO ２ Ca oxide; CaO, CaO ２ Mn oxides; MnO, Mn ２ O, MnO ２ Na oxide; Na ２ O, Na ２ O ２ K oxide; K ２ O, KO ２ Mg oxide; MgO, MgO ２ Mg ２ O Fe oxide; FeO, Fe ２ O ４ FeO ３ Zr oxide; ZrO ２ Al oxides; AlO, Al ２ O ３ Al ３ O ５ Si oxide; SiO, SiO ２ Si ２ O ３ Si ２ O ４

[0060] (Fluoride) The flux may contain fluoride. Specifically, K ２ SiF ６ _K ２ ZrF ６ NaF, Na ３ AlF ６ CaF ２ LiF, and MgF ２ It is preferable to contain at least one fluoride selected from the group consisting of (hereinafter also referred to as "specific fluoride").

[0061] The total content of specific fluorides is preferably between 0% and 70.0% by mass relative to the total mass of the flux. A specific fluoride content of over 0% reduces the hydrogen partial pressure in the arc, thereby reducing dissolved hydrogen in the weld metal and suppressing hydrogen embrittlement. A specific fluoride content of 70.0% or less suppresses the increase in hydrogen content associated with hygroscopic fluorides. The lower limit of the total content of specific fluorides is preferably 1.0%, 2.0%, 4.0%, 6.0%, 8.0%, or 10.0%. The upper limit of the total content of specific fluorides is preferably 60.0%, 50.0%, 40.0%, 30.0%, or 20.0%.

[0062] (Metal carbonates) The flux may contain metal carbonates. Specifically, MgCO ３ Na ２ CO ３ Li ２ CO ３ CaCO ３ _K ２ CO ３ BaCO ３ FeCO ３ MnCO ３ , and SrCO ３ It is preferable to contain at least one metal carbonate selected from the group consisting of (hereinafter also referred to as "specific metal carbonate").

[0063] The total content of specific metal carbonates is preferably between 0% and 20.00% by mass relative to the total mass of the flux. When the content of specific metal carbonates is greater than 0%, CO is generated when the metal carbonates are ionized by the arc. ２ The gas suppresses the increase of hydrogen, nitrogen, and oxygen in the weld metal. A specific metal carbonate content of 20.00% or less suppresses an excess of carbon in the weld metal, thereby increasing toughness. The lower limit of the total specific metal carbonate content is preferably 1.0%, 2.0%, 3.0%, 4.0%, or 5.0%. The upper limit of the total specific metal carbonate content is preferably 18.0%, 16.0%, 14.0%, 12.0%, or 10.0%.

[0064] (Nitrides) The flux may contain nitrides. Specifically, AlN, BN, Ca ３ N ２ , CeN, CrN, Cu ３ N, Fe ４ N, Fe ３ N, Fe ２ N, Mg ３ N, Mo ２ N, NbN, Si ３ N ４ , TiN, VN, ZrN, Mn ２ N and Mn ４ It is preferable to contain at least one nitride selected from the group consisting of N (hereinafter also referred to as "specific nitride").

[0065] The total content of specific nitrides is preferably greater than 0% to 40% by mass relative to the total mass of the flux. When the content of specific nitrides is greater than 0%, the nitrogen generated by the ionization of nitrides by the arc dissolves into the weld metal, improving the strength of the weld metal. When the content of specific nitrides is 40% or less, the decrease in toughness due to the effect of nitrogen is suppressed, and the occurrence of welding defects is suppressed. The lower limit of the total content of specific nitrides is preferably 1%, 2%, 3%, 4%, or 5%. The upper limit of the total content of specific nitrides is preferably 35%, 30%, 25%, 20%, or 15%.

[0066] (Specific Compounds) The flux may contain at least one specific compound selected from the group consisting of Sr compounds, Y compounds, Zr compounds, Ba compounds, and Sc compounds. The specific compound is a compound of at least one element from the elements Sr, Y, Zr, Ba, and Sc (which may be referred to as the "specific compound element" in this disclosure) and another element, and is such as an oxide, fluoride, nitride, metal carbonate, or sulfate. For example, an Sr compound may be SrSO ４ and SrCO ３ Examples include YF. ３ and Y ２ O ３ Examples include ZrO ２ and ZrSiO ４Examples include BaSO4. Ba-compounds include BaSO4. ４ and BaF ２ Examples include ScO ３ and ScF ３ These are some examples. However, the specific compound is not particularly limited as long as it contains at least Sr, Y, Zr, Ba, or Sc.

[0067] The total content of Sr, Y, Zr, Ba, and Sc elements in the specific compound is preferably between 0% and 1.000% by mass relative to the total mass of the flux. A total content of the above elements in the specific compound exceeding 0% allows for a good bead appearance and reduces the amount of oxygen in the weld metal. A total content of the above elements in the specific compound of 1.000% or less suppresses the occurrence of hot cracking. The lower limit of the total content of the above elements in the specific compound is preferably 0.010%, 0.020%, 0.030%, 0.050%, or 0.100%. The upper limit of the total content of the above elements in the specific compound is preferably 0.800%, 0.600%, 0.500%, 0.400%, or 0.300%.

[0068] For example, ZrO ２ It belongs to the category of specific compounds and oxides, SrCO ３ It belongs to specific compounds and metal carbonates. The content of compounds belonging to multiple classifications is included in the content of each classification. For example, if the flux relating to this disclosure is ZrO ２ If it contains ZrO ２ The content of this compound is included in the total amount as an oxide, as well as in the total amount as a specific compound.

[0069] [Specific Elements] It is preferable that the composition of all elements constituting the flux relating to this disclosure, that is, all elements consisting of elements included as compound components and elements included as alloy components (which may be referred to as "specific elements" in this disclosure), is within the following range. In the description of specific elements, "%" means "mass % of the total mass of the flux" unless otherwise specified.

[0070] The flux relating to this disclosure contains the following specific elements: C: 0.050% to 7.000%, Si: 0% to 10.00%, Mn: 0% to 45.00%, P: 0% to 0.050%, S: 0% to 0.050%, Cu: 0% to 30.000%, Ni: 0% to 50.0%, Cr: 0% to 20.0%, Mo: 0% to 40.0%, Nb: 0% to 10.00%, V: 0% to 10.00%, Co: 0% to 10.00%, Pb: 0% to 10.00%, Sn: 0% to 10.00%, Al: 0% to 25.00%, Ti: 0% to 30.00%, B Preferably, the mixture contains: 0% to 5.0000%, N: 0% to 15.000%, Ta: 0% to 1.00%, Hf: 0% to 1.00%, W: 0% to 30.00%, Mg: 0% to 30.00%, REM: 0% to 0.50%, Ca: 0% to 40.00%, Zr: 0% to 5.00%, total of Sr, Y, Ba, and Sc: 0% to 1.00%, O: 0% to 30.00%, F: 0% to 30.00%, Na: 0% to 20.00%, K: 0% to 20.00%, Li: 0% to 10.00%, and Ce: 0% to 25.00%, with the remainder of the specific elements consisting of Fe and impurities.

[0071] Furthermore, the flux relating to this disclosure contains the following specific elements: C: 0.300% to 3.000%, Si: 0.5% to 5.00%, Mn: 0% to 10.00%, P: 0.0005% to 0.050%, S: 0.0005% to 0.050%, Cu: 0% to 1.000%, Ni: 0% to 30.0%, Cr: 0% to 10.0%, Mo: 0% to 10.0%, Nb: 0% to 5.00%, V: 0% to 5.00%, Co: 0% to 1.00%, Pb: 0% to 1.00%, Sn: 0% to 1.00%, Al: 0% to 3.00%, Ti: 0% to 3.00%, B Contains: 0% to 0.1000%, N: 0% to 5.000%, Ta: 0% to 0.50%, Hf: 0% to 0.50%, W: 0% to 10.00%, Mg: 0% to 10.00%, REM: 0% to 0.10%, Ca: 15% to 40.00%, Zr: 0% to 2.00%, Total of Sr, Y, Ba, and Sc: 0% to 0.30%, O: 5% to 30.00%, N: 0% to 5.000%, F: 15% to 30.00%, Na: 0% to 10.00%, K: 0% to 10.00%, Li: 0% to 5.00%, Ce: 0% to 10.00%. It is more preferable that the remainder of the specific element consists of Fe and impurities.

[0072] The form of the specific elements contained in the flux is not particularly limited and may be included as alloying components or as compound components (i.e., oxides, fluorides, nitrides, metal carbonates, sulfates, Sr compounds, Y compounds, Zr compounds, Ba compounds, or Sc compounds).

[0073] The following explains why certain elements are included.

[0074] -C: 0.050% to 7.000%- Carbon (C) is an interstitial solid solution strengthening element, and increasing the C content can improve the strength of the weld metal. On the other hand, if the C content is too high, hot cracking will occur in the weld metal. Also, C is an element that generates spatter, and from the viewpoint of reducing spatter, a lower C content in the flux is advantageous. Therefore, it is preferable that the C content as a specific element in the flux be between 0.050% and 7.000%. The lower limit of the C content as a specific element in the flux is more preferably 0.100%, 0.200%, 0.300%, 0.400%, or 0.500%. The upper limit of the C content as a specific element in the flux is more preferably 4.500%, 4.000%, 3.300%, 3.000%, 2.500%, or 2.000%. The carbon content as a specific element in the flux is more preferably between 0.300% and 3.000%.

[0075] -Si: 0% to 10.00%- Si is a deoxidizing element and can reduce the O content of the flux, so it may be included in the flux as a specific element. On the other hand, Si has low solid solubility in the austenite phase, and by reducing the Si content, the formation of brittle phases such as intermetallic compounds and δ-ferrite at high temperatures can be suppressed, and high-temperature ductility can be improved. Therefore, the Si content as a specific element in the flux is preferably 0% to 10.00%. The lower limit of the Si content as a specific element in the flux is preferably 0.01%, 0.03%, 0.05%, 0.08%, 0.10%, 0.20%, 0.30%, or 0.50%. The upper limit of the Si content as a specific element in the flux is preferably 8.00%, 6.00%, 4.00%, 5.00%, or 2.00%. The Si content as a specific element in the flux is more preferably 0.50% to 5.00%.

[0076] -Mn: 0% to 45.00%- Mn is an austenite-stabilizing element that promotes austenitization of the weld metal and can improve the low-temperature toughness of the weld metal, so it may be included in the flux as a specific element. On the other hand, Mn is an element that causes an increase in the amount of fumes generated. Furthermore, reducing the Mn content can increase the stacking fault energy and improve toughness. Therefore, it is preferable that the Mn content as a specific element in the flux be between 0% and 45.00%. The lower limit of the Mn content as a specific element in the flux is preferably 0.50%, 1.00%, 2.00%, 3.00%, 4.00%, or 5.00%. The upper limit of the Mn content as a specific element in the flux is preferably 40.00%, 35.00%, 30.00%, 25.00%, 20.00%, 15.00%, or 10.00%. The Mn content as a specific element in the flux is more preferably between 0% and 10.00%.

[0077] -P: 0% to 0.050%- Since phosphorus (P) is an impurity element that reduces the toughness of the weld metal, it is preferable to reduce the P content of the flux as much as possible. Therefore, the lower limit of the P content as a specific element in the flux is set to 0%. However, from the viewpoint of reducing the cost of eliminating P, it is preferable that the P content as a specific element in the flux be 0.0005% or more. On the other hand, if the P content as a specific element in the flux is 0.050% or less, the adverse effect of P on toughness can be reduced. Therefore, it is preferable that the P content as a specific element in the flux be 0% to 0.050%. In order to effectively suppress the reduction in the toughness of the weld metal, it is preferable that the P content as a specific element in the flux be 0.040% or less, 0.030% or less, 0.020% or less, 0.015% or less, 0.010% or less, or 0.005% or less. The phosphorus (P) content in the flux is more preferably 0.0005% to 0.050%.

[0078] -S: 0% to 0.050%- S is an impurity element that reduces the toughness of the weld metal, so it is preferable to reduce the S content of the flux as much as possible. Therefore, the lower limit of the S content as a specific element in the flux is set to 0%. However, from the viewpoint of reducing the cost of removing S, it is preferable that the S content as a specific element in the flux be 0.0005% or more. On the other hand, if the S content as a specific element in the flux is 0.050% or less, the adverse effect of S on toughness can be reduced. Therefore, it is preferable that the S content as a specific element in the flux be 0% to 0.050%. In order to effectively suppress the decrease in toughness of the weld metal, it is preferable that the S content as a specific element in the flux be 0.040% or less, 0.030% or less, 0.020% or less, 0.015% or less, 0.010% or less, or 0.005% or less. The sulfur content as a specific element in the flux is more preferably 0.0005% to 0.050%.

[0079] -Cu: 0% to 30.000%- Cu is a precipitation strengthening element and may be included in the flux as a specific element to improve the strength of the weld metal. Cu is also an austenite stabilizing element and may be included in the flux as a specific element to improve the low-temperature toughness of the weld metal. On the other hand, if the Cu content of the flux is excessive, the above effects will saturate. Therefore, it is preferable that the Cu content as a specific element in the flux be between 0% and 30.000%. The lower limit of the Cu content as a specific element in the flux is preferably 0.300%, 0.500%, or 0.700%. The upper limit of the Cu content as a specific element in the flux is preferably 5.000%, 4.500%, 4.000%, 3.500%, 3.000%, 2.500%, 2.000%, 1.500%, or 1.000%. The Cu content as a specific element in the flux is more preferably between 0% and 1,000%.

[0080] -Ni: 0% to 50.0%- Ni is an austenite-stabilizing element. Increasing the Ni content of the flux promotes austenitization of the weld metal and improves low-temperature toughness. Therefore, Ni may be included in the flux as a specific element. On the other hand, reducing the Ni content of the flux can reduce the cost of the flux. Therefore, it is preferable that the Ni content as a specific element in the flux be between 0% and 50.0%. The lower limit of the Ni content as a specific element in the flux is preferably 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, or 9.0%. The upper limit of the Ni content as a specific element in the flux is preferably 45.0%, 40.0%, 35.0%, 30.0%, 25.0%, 20.0%, 18.0%, or 15.0%. The Ni content as a specific element in the flux is more preferably between 0% and 30.0%.

[0081] -Cr: 0% to 20.0%- Cr is a ferrite-stabilizing element and may be included in the flux as a specific element to improve the strength of the weld metal. On the other hand, Cr is a carbide-precipitating element, and by reducing the Cr content of the flux, the amount of C precipitated as carbides can be suppressed, and the strength of the weld metal can be increased by solid solution strengthening. Therefore, it is preferable that the Cr content as a specific element in the flux be 0% to 20.0%. The lower limit of the Cr content as a specific element in the flux is preferably 0.01%, 0.02%, 1.0%, 2.0%, or 3.0%. The upper limit of the Cr content as a specific element in the flux is preferably 18.0%, 16.0%, 14.0%, 12.0%, or 10.0%. It is more preferable that the Cr content as a specific element in the flux be 0% to 10.0%.

[0082] -Mo: 0% to 40.0%- Mo is a precipitation strengthening element and may be included in the flux as a specific element to improve the strength of the weld metal. On the other hand, Mo is a carbide precipitation element, and by reducing the Mo content of the flux, the amount of C that precipitates as carbides can be suppressed, and the strength of the weld metal can be increased by solid solution strengthening. Therefore, it is preferable that the Mo content as a specific element in the flux be 0% to 40.0%. The lower limit of the Mo content as a specific element in the flux is preferably 1.0%, 3.0%, or 5.0%. The upper limit of the Mo content as a specific element in the flux is preferably 35.0%, 30.0%, 25.0%, 20.0%, 15.0%, or 10.0%. It is more preferable that the Mo content as a specific element in the flux be 0% to 10.0%.

[0083] -Nb: 0% to 10.00%- Since Nb is a solid solution strengthening element, it may be included in the flux as a specific element. On the other hand, Nb is a carbide precipitation element, and by reducing the Nb content of the flux, the amount of C that precipitates as carbides can be suppressed, and the strength of the weld metal can be increased by solid solution strengthening. Therefore, it is preferable that the Nb content as a specific element in the flux be 0% to 10.00%. The lower limit of the Nb content as a specific element in the flux is preferably 0.001%, 0.003%, 0.005%, 0.01%, 0.015%, or 0.02%. The upper limit of the Nb content as a specific element in the flux is preferably 8.00%, 6.00%, 5.00%, 4.00%, 2.00%, or 1.00%. It is more preferable that the Nb content as a specific element in the flux be 0% to 5.00%.

[0084] -V: 0% to 10.00%- Since V is a solid solution strengthening element, it may be included in the flux as a specific element. On the other hand, V is a carbonitride precipitation element, and by reducing the V content of the flux, the amount of C that precipitates as carbonitride can be suppressed, and the strength of the weld metal can be increased by solid solution strengthening. Therefore, it is preferable that the V content as a specific element in the flux be 0% to 10.00%. The lower limit of the V content as a specific element in the flux is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the V content as a specific element in the flux is preferably 8.00%, 6.00%, 5.00%, 4.00%, 2.00%, or 1.00%. It is more preferable that the V content as a specific element in the flux be 0% to 5.00%.

[0085] -Co: 0% to 10.00%- Co is an element that increases the strength of the weld metal through solid solution strengthening, and therefore may be included in the flux as a specific element. On the other hand, reducing the Co content of the flux can increase the ductility of the weld metal and ensure toughness. Therefore, it is preferable that the Co content as a specific element in the flux be between 0% and 10.00%. The lower limit of the Co content as a specific element in the flux is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the Co content as a specific element in the flux is preferably 8.00%, 5.00%, 3.00%, 1.00%, 0.80%, 0.60%, or 0.50%. It is more preferable that the Co content as a specific element in the flux be between 0% and 1.00%.

[0086] -Pb: 0% to 10.00%- Pb may be included in the flux because it improves the formability of the weld toe between the base material (steel) and the weld metal, and improves the machinability of the weld metal. On the other hand, reducing the Pb content of the flux stabilizes the arc state and reduces spatter. Therefore, it is preferable that the Pb content as a specific element in the flux be between 0% and 10.00%. The lower limit of the Pb content as a specific element in the flux is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the Pb content as a specific element in the flux is preferably 8.00%, 6.00%, 4.00%, 2.00%, 1.00%, or 0.50%. It is more preferable that the Pb content as a specific element in the flux be between 0% and 1.00%.

[0087] -Sn: 0% to 10.00%- Sn is an element that improves the corrosion resistance of the weld metal, so it may be included in the flux as a specific element. On the other hand, reducing the Sn content of the flux can suppress the occurrence of cracks in the weld metal. Therefore, it is preferable that the Sn content as a specific element in the flux be between 0% and 10.00%. The lower limit of the Sn content as a specific element in the flux is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the Sn content as a specific element in the flux is preferably 8.00%, 6.00%, 4.00%, 2.00%, 1.00%, or 0.50%. It is more preferable that the Sn content as a specific element in the flux be between 0% and 1.00%.

[0088] -Al: 0% to 25.00%- Al is a deoxidizing element and may be included in the flux as a specific element to suppress welding defects and improve the cleanliness of the weld metal. On the other hand, by reducing the Al content of the flux, the formation of nitrides or oxides in the weld metal by Al can be suppressed, and the decrease in the low-temperature toughness of the weld metal can be suppressed. Therefore, it is preferable that the Al content as a specific element in the flux be 0% to 25.00%. The lower limit of the Al content as a specific element in the flux is preferably 0.10%, 0.50%, 1.00%, 1.50%, or 2.00%. The upper limit of the Al content as a specific element in the flux is preferably 20.00%, 15.00%, 10.00%, 8.00%, 6.00%, 4.00%, or 3.00%. It is more preferable that the Al content as a specific element in the flux be 0% to 3.00%.

[0089] -Ti: 0% to 30.00%- Ti is a deoxidizing element and may be included in the flux as a specific element to suppress welding defects and improve the cleanliness of the weld metal. On the other hand, Ti is a carbide precipitation element, and by reducing the Ti content of the flux, the amount of C that precipitates as carbides can be suppressed, and the strength of the weld metal can be increased by solid solution strengthening. Therefore, it is preferable that the Ti content as a specific element in the flux be 0% to 30.00%. The lower limit of the Ti content as a specific element in the flux is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the Ti content as a specific element in the flux is preferably 25.00%, 20.00%, 15.00%, 10.00%, 8.00%, 6.00%, 4.00%, 3.00%, or 1.00%. The Ti content as a specific element in the flux is more preferably between 0% and 3.00%.

[0090] -B: 0% to 5.0000%- B is an interstitial solid solution strengthening element and may be included in the flux as a specific element to improve the low-temperature toughness and strength of the weld metal. On the other hand, by reducing the B content of the flux, M ２３ (C, B)６ Precipitation is suppressed, and toughness deterioration can be suppressed. Therefore, it is preferable that the B content as a specific element in the flux be 0% to 5.0000%. The lower limit of the B content as a specific element in the flux is preferably 0.0005%, 0.0010%, or 0.0020%. The upper limit of the B content as a specific element in the flux is preferably 4.000%, 3.000%, 2.000%, 1.000%, 0.8000%, 0.6000%, 0.4000%, 0.2000%, 0.1000%, 0.0500%, or 0.0100%. It is more preferable that the B content as a specific element in the flux be 0% to 0.1000%.

[0091] -N: 0% to 15.000%- N is an austenite-stabilizing element and an interstitial solid solution strengthening element, and may be included in the flux as a specific element to improve the low-temperature toughness and strength of the weld metal. On the other hand, reducing the N content of the flux can suppress blowouts and reduce welding defects. Therefore, it is preferable that the N content as a specific element in the flux be 0% to 15.000%. The lower limit of the N content as a specific element in the flux is preferably 0.001%, 0.010%, or 0.050%. The upper limit of the N content as a specific element in the flux is preferably 13.000%, 10.000%, 8.000%, 5.000%, 3.000%, 1.000%, 0.800%, 0.600%, 0.400%, or 0.200%. The nitrogen content as a specific element in the flux is more preferably between 0% and 5,000%.

[0092] -Ta: 0% to 1.00%- Ta may be included in the flux as a specific element because it contributes to suppressing hot cracking. On the other hand, Ta is a carbide precipitation element, and by reducing the Ta content of the flux, the amount of C that precipitates as carbides can be suppressed, and the strength of the weld metal can be increased by solid solution strengthening. Therefore, it is preferable that the Ta content as a specific element in the flux be 0% to 1.00%. The lower limit of the Ta content as a specific element in the flux is preferably 0.0001%, 0.0002%, 0.0003%, 0.0005%, or 0.0010%. The upper limit of the Ta content as a specific element in the flux is preferably 0.80%, 0.60%, 0.50%, 0.40%, or 0.20%. It is more preferable that the Ta content as a specific element in the flux be 0% to 0.50%.

[0093] -Hf: 0% to 1.00%- Hf may be included in the flux as a specific element because it contributes to suppressing hot cracking. On the other hand, Hf is a carbide precipitation element, and by reducing the Hf content of the flux, the amount of C that precipitates as carbides can be suppressed, and the strength of the weld metal can be increased by solid solution strengthening. Therefore, it is preferable that the Hf content as a specific element in the flux be 0% to 1.00%. The lower limit of the Hf content as a specific element in the flux is preferably 0.0001%, 0.0002%, 0.0003%, 0.0005%, or 0.0010%. The upper limit of the Hf content as a specific element in the flux is preferably 0.80%, 0.60%, 0.50%, 0.40%, or 0.20%. It is more preferable that the Hf content as a specific element in the flux be 0% to 0.50%.

[0094] -W: 0% to 30.00%- W is an element that increases the strength of the weld metal through solid solution strengthening, and therefore may be included in the flux as a specific element. On the other hand, W is a carbide precipitation element, and by reducing the W content of the flux, the amount of C that precipitates as carbides can be suppressed, and the strength of the weld metal can be increased through solid solution strengthening. Therefore, it is preferable that the W content as a specific element in the flux be 0% to 30.00%. The lower limit of the W content as a specific element in the flux is preferably 0.50%, 1.00%, 3.00%, or 5.00%. The upper limit of the W content as a specific element in the flux is preferably 28.00%, 25.00%, 23.00%, 20.00%, 18.00%, 15.00%, 13.00%, or 10.00%. The W content as a specific element in the flux is more preferably between 0% and 10.00%.

[0095] -Mg: 0% to 30.00%- Mg may be included in the flux as a specific element because it reduces the oxygen content of the weld metal through its deoxidizing effect, thereby improving the toughness of the weld metal. On the other hand, reducing the Mg content of the flux reduces the amount of slag produced, suppressing welding defects such as slag inclusion. Therefore, it is preferable that the Mg content as a specific element in the flux be between 0% and 30.00%. The lower limit of the Mg content as a specific element in the flux is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the Mg content as a specific element in the flux is preferably 25.00%, 20.00%, 15.00%, 10.00%, 8.00%, 6.00%, 4.00%, 2.00%, or 1.00%. The Mg content as a specific element in the flux is more preferably between 0% and 10.00%.

[0096] -REM: 0% to 0.50%- REM may be included in the flux as a specific element because it reduces the oxygen content of the weld metal through its deoxidizing effect, thereby improving the toughness of the weld metal. On the other hand, reducing the REM content of the flux reduces the amount of slag generated, suppressing welding defects such as slag inclusion. Therefore, it is preferable that the REM content as a specific element in the flux be 0% to 0.50%. The lower limit of the REM content as a specific element in the flux is preferably 0.01%, 0.03%, or 0.05%. The upper limit of the REM content as a specific element in the flux is preferably 0.40%, 0.30%, 0.20%, or 0.10%. It is more preferable that the REM content as a specific element in the flux be 0% to 0.10%.

[0097] "REM" is a collective term for 17 elements including Sc, Y, and lanthanides, and the REM content refers to the total content of one or more of these REM elements. REM is generally contained in mischmetal. Therefore, for example, it may be added in the form of mischmetal so that the amount of REM falls within the above range.

[0098] -Ca: 0% to 40.00%- Ca alters the structure of sulfides in the weld metal and refines the size of sulfides and oxides in the weld metal, thus effectively improving the ductility and toughness of the weld metal. For this reason, Ca may be included in the flux as a specific element. On the other hand, reducing the Ca content of the flux can ensure weldability by suppressing deterioration of the weld bead shape and stabilizing the arc. Therefore, it is preferable that the Ca content as a specific element in the flux be between 0% and 40.00%. The lower limit of the Ca content as a specific element in the flux is preferably 1.00%, 2.00%, 4.00%, 6.00%, 8.00%, 10.00%, 12.00%, or 15.00%. The upper limit of the Ca content as a specific element in the flux is preferably 35.00%, 30.00%, 25.00%, or 20.00%. The Ca content as a specific element in the flux is more preferably 15.00% to 40.00%.

[0099] -Zr: 0% to 5.00%- Zr may be included in the flux as a specific element because it reduces the oxygen content of the weld metal through its deoxidizing effect, thereby improving the toughness of the weld metal. On the other hand, Zr is a carbide precipitation element, and by reducing the Zr content of the flux, the amount of C that precipitates as carbides can be suppressed, and the strength of the weld metal can be increased by solid solution strengthening. Therefore, it is preferable that the Zr content as a specific element in the flux be between 0% and 5.00%. The lower limit of the Zr content as a specific element in the flux is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the Zr content as a specific element in the flux is preferably 4.00%, 3.00%, 2.00%, or 1.00%. It is more preferable that the Zr content as a specific element in the flux be between 0% and 2.00%.

[0100] -Total content of Sr, Y, Ba, and Sc: 0% to 1.00%- Sr, Y, Ba, and Sc may be included in the flux as specific elements because they can provide a good bead appearance and reduce the amount of oxygen in the weld metal. On the other hand, reducing the content of Sr, Y, Ba, and Sc suppresses the occurrence of hot cracking. Therefore, it is preferable that the total content of Sr, Y, Ba, and Sc as specific elements in the flux be between 0% and 1.00%. The lower limit of the total content of Sr, Y, Ba, and Sc as specific elements in the flux is preferably 0.01%, 0.02%, 0.03%, 0.05%, or 0.10%. The upper limit of the total content of Sr, Y, Ba, and Sc as specific elements in the flux is preferably 0.80%, 0.60%, 0.50%, 0.40%, or 0.30%. The total content of Sr, Y, Ba, and Sc as specific elements in the flux is more preferably 0% to 0.30%.

[0101] -O: 0% to 30.00%- O can be contained in the flux as an impurity element, oxide, or metal carbonate. O may be included in the flux as a specific element to bring the basicity BL within an appropriate range. On the other hand, reducing the O content suppresses the deterioration of toughness and ductility in the weld metal. Therefore, it is preferable that the O content as a specific element in the flux be between 0% and 30.00%. The lower limit of the O content as a specific element in the flux is preferably 1.00%, 2.00%, 3.00%, 4.00%, or 5.00%. The upper limit of the O content as a specific element in the flux is preferably 25.00%, 20.00%, 15.00%, or 10.00%. It is more preferable that the O content as a specific element in the flux be between 5% and 30.00%.

[0102] -F: 0% to 30.00%- F can be included in the flux, for example, as fluoride. Since F is contained in fluoride, which promotes deoxidation of low-oxygen flux, it may be included in the flux as a specific element. On the other hand, by reducing the F content of the flux, moisture absorption of the flux can be suppressed. Therefore, it is preferable that the F content as a specific element in the flux be between 0% and 30.00%. The lower limit of the F content as a specific element in the flux is preferably 1.00%, 2.00%, 4.00%, 6.00%, 8.00%, 10.00%, 12.00%, or 15.00%. The upper limit of the F content as a specific element in the flux is preferably 28.00%, 26.00%, 24.00%, 22.00%, or 20.00%. The fluorine (F) content in the flux is more preferably between 15.00% and 30.00%.

[0103] -Na: 0% to 20.00%- Na can be included in the flux, for example, as an oxide, fluoride, or metal carbonate. Since Na is a deoxidizing element, it may be included in the flux as a specific element. On the other hand, reducing the Na content of the flux can improve slag detachability. Therefore, it is preferable that the Na content as a specific element in the flux be 0% to 20.00%. The lower limit of the Na content as a specific element in the flux is preferably 0.001%. The upper limit of the Na content as a specific element in the flux is preferably 15.00%. It is more preferable that the Na content as a specific element in the flux be 0% to 10.00%.

[0104] -K: 0% to 20.00%- K can be contained in the flux, for example, as an oxide, fluoride, or metal carbonate. Since K is an arc stabilizer, it may be included in the flux as a specific element. On the other hand, reducing the K content of the flux can improve slag detachability. Therefore, it is preferable that the K content as a specific element in the flux be 0% to 20.00%. The lower limit of the K content as a specific element in the flux is preferably 0.001%. The upper limit of the K content as a specific element in the flux is preferably 20.00%. It is more preferable that the K content as a specific element in the flux be 0% to 10.00%.

[0105] -Li: 0% to 10.00%- Li can be included in the flux, for example, as a fluoride or metal carbonate. Since Li is a deoxidizing element, it may be included in the flux as a specific element. On the other hand, the arc can be stabilized by reducing the Li content of the flux. Therefore, it is preferable that the Li content as a specific element in the flux be 0% to 10.00%. The lower limit of the Li content as a specific element in the flux is preferably 0.0001%. The upper limit of the Li content as a specific element in the flux is preferably 8.00%. It is more preferable that the Li content as a specific element in the flux be 0% to 5.00%.

[0106] -Ce: 0% to 25.00%- Ce can be included in the flux, for example, as a nitride. Since Ce is a deoxidizing element, it may be included in the flux as a specific element. On the other hand, reducing the Ce content of the flux stabilizes the arc. Therefore, it is preferable that the Ce content as a specific element in the flux be 0% to 25.00%. The lower limit of the Ce content as a specific element in the flux is preferably 0.0001%. The upper limit of the Ce content as a specific element in the flux is preferably 15.00%. It is more preferable that the Ce content as a specific element in the flux be 0% to 10.00%.

[0107] -Remainder of the specified element: Fe and impurities- The remaining components of the flux from the specified element are Fe and impurities. Impurities refer to components that are mixed in during the industrial production of flux due to raw materials such as ore or scrap, or various factors in the manufacturing process, and are acceptable as long as they do not adversely affect the properties of the flux. Note that Fe as the remainder of the specified element refers to all Fe, including Fe as an alloy component as well as Fe derived from oxides, etc.

[0108] -Analysis method for the content of specific elements- The content of each of the above elements included as specific elements in the flux shall be measured in accordance with JIS Z 3352:2017.

[0109] [Particle Size Distribution, Particle Size] The flux relating to this disclosure has a particle size distribution measured using a sieve as specified in JIS Z8801-1:2000, which is within the range of the following (Particle Size Distribution 1): (Particle Size Distribution 1) Over 2.00 mm: 40% or less, Over 1.00 mm and up to 2.00 mm: 5% to 50%, Over 0.50 mm and up to 1.00 mm: 5% to 75%, Over 0.25 mm and up to 0.50 mm: 5% to 50%, 0.25 mm and up: 40% or less

[0110] When the particle size distribution of the flux is within the range of (particle size distribution 1), the slag-metal reaction is promoted, and the oxygen concentration of the weld metal is reduced. If the particle size distribution of the flux is outside the range and there is too much flux with large particle sizes (specifically, when the proportion of flux with particles larger than 2.00 mm exceeds 40%), the slag-metal reaction is not promoted, and the oxygen concentration of the weld metal becomes high. Also, if the particle size distribution of the flux is outside the range and there is too much flux with small particle sizes (specifically, when the proportion of flux with particles of 0.25 mm or less exceeds 40%), the molten metal flow during welding becomes unstable, increasing the amount of oxygen brought in from the outside air and flux, resulting in a high oxygen concentration.

[0111] Furthermore, if the particle size distribution is within the range of (particle size distribution 1), it is possible to form weld metal with an excellent bead appearance. If the particle size distribution of the flux falls outside the range and there is too much flux with large particle sizes (specifically, if the proportion of flux with particles larger than 2.00 mm exceeds 40%), the slag-metal reaction may not be promoted, meaning that the slag-metal reaction may not occur, resulting in unstable molten metal flow during welding and deterioration of the bead appearance. Also, if the particle size distribution of the flux falls outside the range and there is too much flux with small particle sizes (specifically, if the proportion of flux with particles of 0.25 mm or less exceeds 40%), the molten metal flow during welding may become unstable and deterioration of the bead appearance.

[0112] The flux relating to this disclosure is preferably further specified in the following particle size distribution range (Particle Size Distribution 2) from the viewpoint of reducing the oxygen concentration of the weld metal and the appearance of the weld bead. (Particle Size Distribution 2) Over 2.00 mm: 5% or less Over 1.00 mm and up to 2.00 mm: 10% to 30% Over 0.50 mm and up to 1.00 mm: 10% to 70% Over 0.25 mm and up to 0.50 mm: 10% to 50% 0.25 mm and up: 5% or less

[0113] The flux according to this disclosure preferably has a D50 of 0.3 mm to 1.5 mm. "D50" refers to the particle size corresponding to the cumulative frequency of 50% in the particle size distribution; that is, the particle size that is 50% of the smallest particle when the particles are arranged in order from smallest to largest. A D50 of 1.5 mm or less allows for the formation of a weld metal with reduced oxygen concentration and an excellent bead appearance. A D50 of 0.3 mm or more prevents scattering due to wind, etc.

[0114] The D50 of flux can be measured by the following method: The particle size distribution is measured based on the particle size analysis method – image analysis method – Part 2: dynamic image analysis method (ISO 13322-2:2021). The D50 can then be measured from this distribution.

[0115] Methods for controlling the particle size distribution and particle size of flux include, for example, using a sieve to select flux with the appropriate particle size.

[0116] <Method for Manufacturing Flux> The method for manufacturing flux according to this disclosure is not particularly limited, as long as it can produce flux having the aforementioned component amounts, basicity, and particle size distribution. For example, predetermined amounts of the aforementioned components are blended, a binder is added to granulate the mixture, and then sieve it to produce flux having the aforementioned component amounts, basicity, and particle size distribution. For example, alloy components may be added as powder and may be integrated with granulated powder such as oxides, or they may remain as powder.

[0117] <Method for Manufacturing Welded Joints> Next, the method for manufacturing welded joints (welding method) according to this disclosure will be described. The method for manufacturing welded joints according to this disclosure comprises a step of welding steel materials using the flux according to this disclosure described above.

[0118] In the method for manufacturing a welded joint according to the present disclosure, submerged arc welding is preferred as the welding method. In the method for manufacturing a welded joint according to the present disclosure, the type of steel material (workpiece) that forms the base material of the welded joint is not particularly limited, but for example, P ＣＭ Examples include steel materials with high susceptibility to low-temperature cracking having a (weld crack susceptibility composition) of 0.24% or more (especially high-strength steel plates with a tensile strength of 590 MPa to 1700 MPa and a plate thickness of 20 mm or more), and Ni-based low-temperature steel plates containing 6% to 9% Ni with a plate thickness of 20 mm or more. Among these, Ni-based low-temperature steel plates containing 6% to 9% Ni with a plate thickness of 20 mm or more can be preferably used.

[0119] The method for manufacturing a welded joint according to the present disclosure preferably includes a step of welding the steel material using the flux according to the present disclosure in one or more passes from the first pass to the final pass. If welding is performed in only one pass, the flux according to the present disclosure is used in that one pass.

[0120] The welded joint obtained by the manufacturing method of the welded joint according to this disclosure comprises a base material steel and a welded joint composed of weld metal and a heat-affected zone. The tensile strength of the obtained weld metal is preferably high, for example, 590 to 1200 MPa.

[0121] Next, the feasibility and effectiveness of this disclosure will be explained in more detail using the examples and comparative examples provided below. However, the examples below are not limiting to this disclosure, and any design modifications made in accordance with the spirit of the preceding and following descriptions are all within the technical scope of this disclosure.

[0122] <Preparation of Flux> Fluxes having the compositions shown in Tables 1-1 and 1-2, Tables 3 and 4, Tables 5-1 and 5-2, and Tables 6-1 and 6-2 were prepared as the fluxes for the examples and comparative examples of this disclosure. Tables 1-1 and 1-2 show the compositions of oxides, fluorides, nitrides, metal carbonates, sulfates, and chemical components other than specific compounds (i.e., alloy components). Table 2 shows the composition of oxides. Table 3 shows the composition of fluorides. Table 4 shows the composition of metal carbonates. Tables 5-1 and 5-2 show the total content of Sr, Y, Zr, Ba, and Sc elements contained in specific compounds (i.e., Sr compounds, Y compounds, Zr compounds, Ba compounds, and Sc compounds), as well as the composition of nitrides. Tables 6-1 and 6-2 show the composition of all elements (specific elements) constituting the flux, regardless of the form in which they are contained. The remainder of the composition of the specific elements shown in Tables 6-1 and 6-2 (i.e., elements other than those shown in Tables 6-1 and 6-2) is iron and impurities. In Table 2, "BaO" represents the total amount of Ba oxide converted to BaO, "CaO" represents the total amount of Ca oxide converted to CaO, "MnO" represents the total amount of Mn oxide converted to MnO, and "Na ２ "O" is Na of Na oxide ２ The total amount of the O equivalent value is "K ２ "O" is the K of K oxide. ２ The total amount of O equivalent values, "MgO" is the total amount of Mg oxide equivalent values, "FeO" is the total amount of Fe oxide equivalent values, "ZrO ２ " is Zr oxide ZrO ２ The sum of the converted values ​​is "Al ２ O ３ " is Al oxide ２ O ３ The sum of the converted values ​​is "TiO ２ " is Ti oxide TiO ２ The sum of the converted values ​​is "SiO ２" is Si oxide SiO ２ The total amount of each converted value is shown. The total oxide content (total oxide amount) represents the sum of the total amounts of each converted value of these oxides. The compositions shown in Tables 1-1 and 1-2, 3 and 4, 5-1 and 5-2, 6-1 and 6-2 all represent mass % of the total mass of the flux.

[0123] In Tables 1-1, 1-2, and 2, values ​​outside the scope defined in this disclosure are underlined. In Tables 1-1, 1-2, 3, and 4, 5-1 and 5-2, and 6-1 and 6-2, blank spaces in the tables relating to compositional content indicate that the content of that alloying component, compounding component, or specific element is less than the number of significant figures. These alloying components, compounding components, and specific elements may inevitably be mixed in or formed in less than the number of significant figures.

[0124] For fluxes No. 1 to No. 35 shown in Tables 1-1, 1-2, 3, 4, 5-1, 5-2, 6-1, and 6-2, the particle size distribution was controlled by sieving.

[0125] [Measurement of Particle Size Distribution and Particle Size] For each flux in the disclosed example and comparative example, the particle size distribution was measured using a sieve specified in JIS Z8801-1:2000. In addition, D50 was measured for each flux using the measurement method described above. The following criteria were used for evaluation. Note that if particle size distribution condition 2 is met, particle size distribution condition 1 is also met. The results are shown in Table 7. A: Satisfies particle size distribution condition 2 B: Satisfies particle size distribution condition 1, but does not satisfy particle size distribution condition 2 C: Does not satisfy particle size distribution condition 1 (Particle size distribution condition 1) Over 2.00 mm: 40% or less Over 1.00 mm to 2.00 mm: 5% to 50% Over 0.50 mm to 1.00 mm: 5% to 75% Over 0.25 mm to 0.50 mm: 5% to 50% 0.25 mm or less: 40% or less (Particle size distribution condition 2) Over 2.00 mm: 5% or less Over 1.00 mm to 2.00 mm: 10% to 30% Over 0.50 mm to 1.00 mm: 10% to 70% Over 0.25 mm to 0.50 mm: 10% to 50% 0.25 mm or less: 5% or less

[0126]

[0127]

[0128]

[0129]

[0130]

[0131]

[0132]

[0133]

[0134]

[0135] <Submerged Arc Welding (SAW) Using Flux and Solid Wire> A welded joint was manufactured by submerged arc welding two steel plates (base materials) using fluxes No. 1 to No. 35 shown in Tables 1-1, 1-2, 3, 4, 5-1, 5-2, 6-1, and 6-2, and NITTETSU FILLER 196 (φ2.4 mm) manufactured by Nippon Steel Welding Industries as the solid wire. Steel plates (size: 30 mm (t) x 120 mm (w) x 500 mm (l)) were used as the steel plates (base materials) to be welded. Two steel plates (base materials) were butted together, and a Y-shaped groove was formed to half the thickness of the plates so that the groove angle X was 60°. The base materials were butted together with a gap of 1 mm between them. A single bead weld was performed on these base materials in one pass. The weld length was 500 mm. The welding conditions were a current of 360 A, a voltage of 30 V, a wire travel speed of 350 mm / min, and a heat input of 1.9 kJ / mm. In this way, a welded joint with weld metal was manufactured.

[0136] [Evaluation / Oxygen Content of Weld Metal] The oxygen content of the weld metal of weld joints manufactured using the fluxes of this disclosure and comparative example was evaluated. The oxygen content of the weld metal was measured by cutting a pin of the analytical sample for oxygen measurement of the weld metal from the center of the plate thickness and the center of the width of the weld metal in the longitudinal direction of the weld joint, and measuring by inert gas dissolved infrared absorption spectroscopy. The results were evaluated according to the following criteria: A: Oxygen content of 300 ppm or less B: Oxygen content of more than 300 ppm and 500 ppm or less C: Oxygen content of more than 500 ppm

[0137] [Evaluation / Strength of Weld Metal (Tensile Strength)] The tensile strength of the weld metal of welded joints manufactured using the fluxes of this disclosure and comparative example was evaluated using the following procedure. A No. A0 tensile test specimen for tensile testing was cut from the center of the weld metal plate thickness and the center of the weld metal width in the longitudinal direction of the welded joint, and the tensile strength was measured by performing a tensile test in accordance with JIS Z3111:2005. The results were evaluated according to the following criteria: A: 690 MPa or more B: 610 MPa or more and less than 690 MPa C: Less than 610 MPa

[0138] [Evaluation / Bead Appearance] The surface irregularities of the welded joint beads produced using the fluxes of the disclosed examples and comparative examples were measured and evaluated according to the following criteria based on the control tolerances and limit tolerances specified in the Building Construction Standards Specification JASS 6: A: Within control tolerance B: Exceeds control tolerance, within limit tolerance C: Exceeds limit tolerance

[0139] [Overall Judgment] Welds that meet the following criteria were judged as "acceptable": those with an oxygen content rating of A or B and a strength rating of A or B, and those that meet at least one of the following criteria: an oxygen content rating of C and a strength rating of C, or those that exhibited hot cracking.

[0140]

[0141] As shown in Table 7, in the disclosed examples (No. 1 to No. 30) using flux with a carbon content of 0.050% to 5.000% and a Cr content of 0% to 20.0% as alloy components, containing specific oxides, a basicity BL in the range of 2.0 to 60.0, and satisfying particle size distribution condition 1, the strength of the weld metal was ensured and the oxygen content was reduced. Comparative examples No. 31 and No. 32 had a basicity BL of less than 2.0, and the reduction of oxygen content in the weld metal was not achieved. Comparative example No. 33 had a carbon content of over 5.000% as an alloy component, and hot cracking occurred in the weld metal, making it impossible to evaluate the oxygen content, strength, and bead appearance. Comparative examples No. 34 to No. In No. 35, the flux particle size distribution did not meet the aforementioned (particle size distribution condition 1), and there was too much flux with large particle sizes (i.e., the proportion of flux with particle sizes larger than 2.00 mm exceeded 40%), resulting in a failure to reduce the amount of oxygen in the weld metal and a poor bead appearance. In comparative example No. 36, the flux particle size distribution did not meet the aforementioned particle size distribution condition 1, and there was too much flux with small particle sizes (i.e., the proportion of flux with particle sizes smaller than 0.25 mm exceeded 40%), resulting in a failure to reduce the amount of oxygen in the weld metal and a poor bead appearance.

[0142] (Note) This disclosure includes the following aspects: <1> The chemical components, excluding oxides, fluorides, nitrides, metal carbonates, and sulfates, in mass percent of the total mass of the flux, include: C: 0.050% to 5.000%, and Cr: 0% to 20.0%, and include at least one oxide selected from the group consisting of Ba oxide, Ca oxide, Mn oxide, Mg oxide, Fe oxide, and Zr oxide, and the basicity BL represented by the following formula 1 is 2.0 to 30.0, and the particle size distribution measured with a sieve specified in JIS Z8801-1 (2000) is: greater than 2.00 mm: 40% or less, greater than 1.00 mm and less than or equal to 2.00 mm: 5% to 50%, greater than 0.50 mm and less than or equal to 1.00 mm: 5% to 75%, greater than 0.25 mm and less than or equal to 0.50 mm: 5% to 50%, and A welding flux with a thickness of 0.25 mm or less: 40% or less. BL = 1.3 [BaO] + 0.5 [CaO + MnO + Na ２O+K ２ O]+0.2[MgO+FeO]+0.05[ZrO ２ ]-0.05[ Al ２ O ３ ]-0.2[TiO ２ ]-0.5[SiO ２ ] + 5[C] ... Equation 1 (In Equation 1, [BaO] is the total amount of Ba oxides converted to BaO, [CaO + MnO + Na ２ O+K ２ O] represents the total amount of Ca oxides converted to CaO, the total amount of Mn oxides converted to MnO, and Na oxides. ２ Total amount of O equivalent value and K of K oxide ２ The total amount of the equivalent value of O is [MgO + FeO], which is the total amount of the equivalent value of Mg oxides (MgO) and the equivalent value of Fe oxides (FeO), [ZrO ２ ] is Zr oxide ZrO ２ The sum of the converted values, [Al ２ O ３ ] is Al oxide Al ２ O ３ The sum of the converted values ​​is [TiO ２ ] is TiO of Ti oxide ２ The total amount of the converted values ​​is [SiO ２ ] is Si oxide SiO ２ The total amount of the converted values, and [C] represents the amount of C.) <2> K ２ SiF ６ _K ２ ZrF ６ NaF, Na ３ AlF ６ CaF ２ LiF, and MgF ２ The flux according to <1>, which contains at least one fluoride selected from the group consisting of the following, wherein the total content of the fluorides is greater than 0% to 70.0% by mass relative to the total mass of the flux. <3> MgCO ３ Na ２ CO ３ Li ２ CO ３ CaCO ３ _K ２ CO ３ BaCO ３ FeCO３ MnCO ３ , and SrCO ３ The flux according to <1> or <2>, comprising at least one metal carbonate selected from the group consisting of the following, wherein the total content of the metal carbonate is greater than 0% to 20.00% by mass relative to the total mass of the flux. <4> The flux according to any one of <1> to <3>, comprising at least one oxide selected from the group consisting of Ba oxide, Ca oxide, Mn oxide, Na oxide, K oxide, Mg oxide, Fe oxide, Zr oxide, Al oxide, Ti oxide, and Si oxide, wherein the total content of the oxide is greater than 0% to 60.00% by mass relative to the total mass of the flux. (The total content of the oxide refers to the total amount of Ba oxide in terms of BaO equivalent, the total amount of Ca oxide in terms of CaO equivalent, the total amount of Mn oxide in terms of MnO equivalent, and Na oxide in terms of Na ２ The total amount of O equivalent values ​​and the K of K oxide ２ The total amount of O equivalent values, the total amount of Mg oxide equivalent values ​​for Mg oxide, the total amount of Fe oxide equivalent values ​​for FeO, and the Zr oxide equivalent values ​​for ZrO ２ The total amount of the converted value and the Al oxide ２ O ３ The total amount of the converted value and the TiO of Ti oxide ２ The total amount of the converted value and the SiO of Si oxide ２ (This represents the total amount of the converted values.) <5> A flux according to any one of <1> to <4>, which contains at least one specific compound selected from the group consisting of Sr compounds, Y compounds, Zr compounds, Ba compounds, and Sc compounds, wherein the total content of Sr, Y, Zr, Ba, and Sc elements contained in the specific compound is greater than 0% to 1.000% by mass relative to the total mass of the flux. <6> AlN, BN, Ca ３ N ２ , CeN, CrN, Cu ３ N, Fe ４ N, Fe ３ N, Fe ２ N, Mg ３ N, Mo ２ N, NbN, Si ３ N ４, TiN, VN, ZrN, Mn ２ N and Mn ４The flux according to any one of claims <1> to <5>, comprising at least one nitride selected from the group consisting of N, wherein the total content of the nitrides is greater than 0% to 40% by mass relative to the total mass of the flux. <7> Chemical components as mass percent of the total mass of the flux, excluding oxides, fluorides, nitrides, metal carbonates, and sulfates: C: 0.050% to 5.000%, Si: 0% to 0.50%, Mn: 0% to 30.0%, P: 0% to 0.050%, S: 0% to 0.050%, Cu: 0% to 5.0%, Ni: 0% to 50.0%, Cr: 0% to 20.0%, Mo: 0% to 30.0%, Nb: 0% to 10.00%, V: 0% to 10.00%, Co: 0% to 10.00%, Pb: 0% to 10.00%, Sn: 0% to 10.00%, Al: 0% to 10.00% A flux according to any one of items <1> to <6>, comprising Ti: 0% to 10.00%, B: 0% to 0.5000%, N: 0% to 5.0000%, Ta: 0% to 1.00%, Hf: 0% to 1.00%, W: 0% to 30.00%, Mg: 0% to 10.00%, REM: 0% to 0.50%, Ca: 0% to 10.00%, and Zr: 0% to 5.00%.<8> In mass percent of the total mass of the flux, the following specific elements are included: elements contained as oxides, fluorides, nitrides, metal carbonates, sulfates, Sr compounds, Y compounds, Zr compounds, Ba compounds, or Sc compounds, and elements contained as chemical components other than oxides, fluorides, nitrides, metal carbonates, sulfates, Sr compounds, Y compounds, Zr compounds, Ba compounds, and Sc compounds: C: 0.050% to 7.000%, Si: 0% to 10.00%, Mn: 0% to 45.00%, P: 0% to 0.050%, S: 0% to 0.050%, Cu: 0% to 5.000%, Ni: 0% to 50.0%, Cr: 0% to 20.0%, Mo: 0% to 40.0%, Nb: 0% to 10.00% V: 0% to 10.00%, Co: 0% to 10.00%, Pb: 0% to 10.00%, Sn: 0% to 10.00%, Al: 0% to 25.00%, Ti: 0% to 30.00%, B: 0% to 5.0000%, N: 0% to 15.000%, Ta: 0% to 1.00%, Hf: 0% to 1.00%, W: 0% to 30.00%, Mg: 0% to 30.00%, REM: 0% to 0.50%, Ca: 0% to 40.00%, Zr: 0% to 5.00%, Sr, Y, Ba, and Sc total: 0% to 1.00%, O: 0% to 30.00%, and A flux according to any one of items <1> to <7>, comprising F: 0% to 30.00%, with the remainder of the specified element consisting of Fe and impurities.<9> In mass percent relative to the total mass of the flux, the specified elements are as follows: C: 0.300% to 3.000%, Si: 0.50% to 5.00%, Mn: 0% to 10.00%, P: 0.0005% to 0.050%, S: 0.0005% to 0.050%, Cu: 0% to 1.000%, Ni: 0% to 30.0%, Cr: 0% to 10.0%, Mo: 0% to 10.0%, Nb: 0% to 5.00%, V: 0% to 5.00%, Co: 0% to 1.00%, Pb: 0% to 1.00%, Sn: 0% to 1.00%, Al: 0% to 3.00%, Ti: 0% to 3.00%. The flux according to <8>, comprising B: 0% to 0.1000%, N: 0% to 5.000%, Ta: 0% to 0.50%, Hf: 0% to 0.50%, W: 0% to 10.00%, Mg: 0% to 10.00%, REM: 0% to 0.10%, Ca: 15.00% to 40.00%, Zr: 0% to 2.00%, total of Sr, Y, Ba, and Sc: 0% to 0.30%, O: 5% to 30.00%, and F: 15.00% to 30.00%, with the remainder of the specified elements consisting of Fe and impurities. <10> The flux according to any one of <1> to <9>, wherein the particle size distribution is: over 2.00 mm: 5% or less, over 1.00 mm and 2.00 mm: 10% to 30%, over 0.50 mm and 1.00 mm: 10% to 70%, over 0.25 mm and 0.50 mm: 10% to 50%, and 0.25 mm or less: 5% or less. <11> The flux according to any one of <1> to <10>, wherein D50 is 0.3 mm to 1.5 mm. <12> A method for manufacturing a welded joint, comprising manufacturing a welded joint using the flux according to any one of <1> to <11>.

[0143] The disclosure of Japanese Patent Application No. 2024-161477, filed on 18 September 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were described specifically and individually.

Claims

1. Containing alloying components and oxides, the content of the alloying components, expressed as mass % of the total mass of the flux, is as follows: C: 0.050% to 5.000%, Si: 0% to 0.50%, Mn: 0% to 30.0%, P: 0% to 0.050%, S: 0% to 0.050%, Cu: 0% to 5.0%, Ni: 0% to 50.0%, Cr: 0% to 20.0%, Mo: 0% to 30.0%, Nb: 0% to 10.00%, V: 0% to 10.00%, Co: 0% to 10.00%, Pb: 0% to 10.00%, Sn: 0% to 10.00%, Al: 0% to 10.00%, Ti: 0% to 10.00%. B: 0% to 0.5000%, N: 0% to 5.0000%, Ta: 0% to 1.00%, Hf: 0% to 1.00%, W: 0% to 30.00%, Mg: 0% to 10.00%, REM: 0% to 0.50%, Ca: 0% to 10.00%, Zr: 0% to 5.00%, and Fe: 0% to 5.0%, wherein the oxide includes at least one oxide selected from the group consisting of Ba oxide, Ca oxide, Mn oxide, Na oxide, K oxide, Mg oxide, Fe oxide, Zr oxide, Al oxide, Ti oxide, and Si oxide, and optionally includes at least one selected from the group consisting of fluorides, nitrides, metal carbonates, and sulfates. A welding flux that optionally contains at least one specific compound selected from the group consisting of Sr compounds, Y compounds, Zr compounds, Ba compounds, and Sc compounds, has a basicity BL represented by the following formula 1 to 2.0 to 60.0, and has a particle size distribution measured by a sieve specified in JIS Z8801-1:2000, where: over 2.00 mm: 40% or less, over 1.00 mm and up to 2.00 mm: 5% to 50%, over 0.50 mm and up to 1.00 mm: 5% to 75%, over 0.25 mm and up to 0.50 mm: 5% to 50%, and 0.25 mm and below: 40% or less. BL = 1.3 [BaO] + 0.5 [CaO + MnO + Na ２ O+K ２ O]+0.2[MgO+FeO]+0.05[ZrO ２ ]-0.05[ Al ２ O ３ ]-0.2[TiO ２ - 0.5[SiO ２ + 5([C] + [Mg] + [Fe]) Formula 1 In Formula 1, [BaO] represents the total amount of the BaO conversion value of the Ba oxide, [CaO + MnO + Na ２ O + K ２ O] represents the total amount of the CaO conversion value of the Ca oxide, the total amount of the MnO conversion value of the Mn oxide, the Na ２ O conversion value of the Na oxide, and the total amount of the K ２ O conversion value of the K oxide. [MgO + FeO] represents the total amount of the MgO conversion value of the Mg oxide and the total amount of the FeO conversion value of the Fe oxide. [ZrO ２ represents the total amount of the ZrO ２ conversion value of the Zr oxide. [Al ２ O ３ represents the total amount of the Al ２ O ３ conversion value of the Al oxide. [TiO ２ represents the total amount of the TiO ２ conversion value of the Ti oxide. [SiO ２ represents the total amount of the SiO ２ conversion value of the Si oxide. [C] represents the content of C as an alloy component, [Mg] represents the content of Mg as an alloy component, and [Fe] represents the content of Fe as an alloy component.

2. As the fluoride, K ２ SiF ６ _K ２ ZrF ６ NaF, Na ３ AlF ６ CaF ２ LiF, and MgF ２ The flux according to claim 1, comprising at least one fluoride selected from the group consisting of, wherein the total content of the fluorides is greater than 0% to 70.0% by mass relative to the total mass of the flux.

3. As the metal carbonate, MgCO ３ Na ２ CO ３ Li ２ CO ３ CaCO ３ _K ２ CO ３ BaCO ３ FeCO ３ MnCO ３ , and SrCO ３ The flux according to claim 1 or claim 2, comprising at least one metal carbonate selected from the group consisting of the following, wherein the total content of the metal carbonates is greater than 0% to 20.00% by mass relative to the total mass of the flux.

4. The total amount of the Ba oxide in terms of BaO equivalent, the total amount of the Ca oxide in terms of CaO equivalent, the total amount of the Mn oxide in terms of MnO equivalent, the Na of the Na oxide ２ Total amount of O equivalent value, K of the K oxide ２ Total amount of O equivalent value, total amount of Mg O equivalent value of the Mg oxide, total amount of Fe O equivalent value of the Fe oxide, Zr O equivalent value of the Zr oxide ２ Total amount of the converted value, Al of the Al oxide ２ O ３ Total amount of converted values, TiO of the Ti oxide ２ The total amount of the converted value, and the SiO of the Si oxide. ２ The flux according to any one of claims 1 to 3, wherein the total amount of the converted values ​​is greater than 0% to 60.00% by mass relative to the total mass of the flux.

5. The flux according to any one of claims 1 to 4, wherein the flux contains at least one specific compound, and the total content of Sr, Y, Zr, Ba, and Sc elements contained in the specific compound is greater than 0% to 1.000% by mass relative to the total mass of the flux.

6. As the nitride, AlN, BN, Ca ３ N ２ , CeN, CrN, Cu ３ N, Fe ４ N, Fe ３ N, Fe ２ N, Mg ３ N, Mo ２ N, NbN, Si ３ N ４ , TiN, VN, ZrN, Mn ２ N and Mn ４ The flux according to any one of claims 1 to 5, comprising at least one nitride selected from the group consisting of N, wherein the total content of the nitrides is greater than 0% to 40% by mass relative to the total mass of the flux.

7. The composition of the elements constituting the flux, expressed as mass % of the total mass of the flux, is as follows: C: 0.050% to 7.000%, Si: 0% to 10.00%, Mn: 0% to 45.00%, P: 0% to 0.050%, S: 0% to 0.050%, Cu: 0% to 30.000%, Ni: 0% to 50.0%, Cr: 0% to 20.0%, Mo: 0% to 40.0%, Nb: 0% to 10.00%, V: 0% to 10.00%, Co: 0% to 10.00%, Pb: 0% to 10.00%, Sn: 0% to 10.00%, Al: 0% to 25.00%, Ti: 0% to 30.00%. B: 0% to 5.0000%, N: 0% to 15.000%, Ta: 0% to 1.00%, Hf: 0% to 1.00%, W: 0% to 30.00%, Mg: 0% to 30.00%, REM: 0% to 0.50%, Ca: 0% to 40.00%, Zr: 0% to 5.00%, Total of Sr, Y, Ba, and Sc: 0% to 1.00%, O: 0% to 30.00%, F: 0% to 30.00%, Na: 0% to 20.00%, K: 0% to 20.00%, Li: 0% to 10.00%, Ce: 0% to 25.00%, and the remainder: Fe and impurities. The flux according to any one of claims 1 to 6.

8. The composition of the elements constituting the flux, expressed as mass % of the total mass of the flux, is as follows: C: 0.300% to 3.000%, Si: 0.50% to 5.00%, Mn: 0% to 10.00%, P: 0.0005% to 0.050%, S: 0.0005% to 0.050%, Cu: 0% to 1.00%, Ni: 0% to 30.0%, Cr: 0% to 10.0%, Mo: 0% to 10.0%, Nb: 0% to 5.00%, V: 0% to 5.00%, Co: 0% to 1.00%, Pb: 0% to 1.00%, Sn: 0% to 1.00%, Al: 0% to 3.00%. Ti: 0% to 3.00%, B: 0% to 0.1000%, N: 0% to 5.000%, Ta: 0% to 0.50%, Hf: 0% to 0.50%, W: 0% to 10.00%, Mg: 0% to 10.00%, REM: 0% to 0.10%, Ca: 15.00% to 40.00%, Zr: 0% to 2.00%, Total of Sr, Y, Ba, and Sc: 0% to 0.30%, O: 5% to 30.00%, F: 15.00% to 30.00%, Na: 0% to 10.00%, K: 0% to 10.00%, Li: 0% to 5.00% The flux according to claim 7, wherein the content is Ce: 0% to 10.00%, and the remainder is Fe and impurities.

9. The flux according to any one of claims 1 to 8, wherein the particle size distribution is: over 2.00 mm: 5% or less, over 1.00 mm and 2.00 mm or less: 10% to 30%, over 0.50 mm and 1.00 mm or less: 10% to 70%, over 0.25 mm and 0.50 mm or less: 10% to 50%, and 0.25 mm or less: 5% or less.

10. The flux according to any one of claims 1 to 9, wherein D50 is 0.3 mm to 1.5 mm.

11. A method for manufacturing a welded joint, comprising manufacturing a welded joint using the flux described in any one of claims 1 to 10.

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