Metal flux-cored wire for welding

Abstract

To provide a metal flux-cored wire for welding which excels in welding operability, is superior in resistance to pore defects and cracking, and ensures favorable mechanical properties of weld metal.SOLUTION: A metal flux-cored wire for welding comprises, in terms of mass% with respect to the total mass of the wire, C: 0.13-0.25%, Si: 0.1-1.2%, Mn: 0.5-2.0%, Cu: 0.1-0.5%, S: 0.020-0.050%, and P: 0.03% or less in the total of a steel sheath and a flux, further comprises, in terms of mass% with respect to the total mass of the wire, within the flux, Si oxides: at most 0.20% in total as SiO2 equivalent value, alloy fluorides: 0.003-0.120% in total as F equivalent value, and one or more of Na oxide and K oxide: 0.02-0.10% in total as Na2O oxide equivalent value and K2O oxide equivalent value, with the balance being Fe and impurities, wherein (10[S]+3[C]) / Mn is 0.25-0.45.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a metal-based flux-cored welding wire, which is excellent in welding workability such as arc stability, amount of spatter generation, amount of slag generation, and bead shape, and which is also excellent in resistance to blowhole defects and cracking, and which produces a weld metal with good mechanical properties. [Background technology]

[0002] Flux-cored wires for gas-shielded arc welding are highly efficient and have excellent welding workability, and are widely used in fields such as architecture, steel frames, and marine structures. Metal-based flux-cored wires in particular produce less slag than rutile-based or basic-based flux-cored wires, which produce a lot of slag, and the slag removal work in continuous multi-pass welding is simple, so they are preferred for use under conditions of continuous multi-pass welding inside a groove.

[0003] In particular, metal-based flux-cored wire for gas-shielded arc welding using Ar-CO2 mixed gas produces smaller droplets than solid wire or metal-based flux-cored wire for gas-shielded arc welding using CO2 gas, making it less likely to generate large spatter. This reduces the amount of spatter adhering to the weld or welding torch nozzle, reducing the amount of spatter removal required. Furthermore, the degree of slag formation due to oxidation of alloying agents such as Mn and Si and deoxidizers is low, reducing the amount of slag generated. Furthermore, reducing the oxygen content of the weld metal effectively improves the low-temperature toughness of the weld metal, making it widely used.

[0004] Various types of metal-based flux-cored wires for gas-shielded arc welding using Ar-CO mixed gas have been developed. For example, Patent Document 1 discloses a flux-cored wire for gas-shielded arc welding using a mixed gas that produces less slag and can produce flat beads in horizontal fillet welding.

[0005] Furthermore, Patent Document 2 discloses a flux-cored wire for gas-shielded arc welding that contains a large amount of alloy powder and uses a mixed gas that has excellent low-temperature toughness.

[0006] Patent Document 3 discloses a flux-cored wire for gas-shielded arc welding that uses a mixed gas that has good arc stability, good welding workability such as a small amount of spatter, and excellent low-temperature toughness.

[0007] Patent Document 4 discloses a metal-based flux-cored wire for gas-shielded arc welding that uses an Ar-CO mixed gas, which produces extremely small amounts of slag and spatter, provides a good bead shape, and also produces a weld metal with good low-temperature toughness. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-197991 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-144516 [Patent Document 3] Japanese Patent Publication No. 2020-203302 [Patent Document 4] Japanese Patent Publication No. 2022-127093 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the flux-cored wires described in Patent Documents 1 and 2 do not specify a specific sulfur content, resulting in a large amount of slag production. Furthermore, the slag spreads thinly over the bead, making slag removal difficult and time-consuming. Furthermore, the bead's appearance is not smooth. Furthermore, if multiple passes are performed without removing the slag, the area of slag covering the bead increases. Therefore, if the consumable electrode (wire) comes into contact with the slag when starting the arc for the next pass, no current flows and no arc occurs. To generate an arc, the slag must be removed from the area where the wire is in contact. In the case of automatic welding, this process results in significant time loss and increases manufacturing costs.

[0010] Furthermore, since the flux-cored wires described in Patent Documents 2 and 3 contain Ti, a large amount of Ti oxide is produced, resulting in a large amount of slag, which takes a long time to remove.

[0011] Furthermore, the alloy components of the flux-cored wire described in Patent Document 4 have the problem that good low-temperature toughness at -60°C cannot be stably obtained.

[0012] The present invention has been devised in view of the above-mentioned problems, and has as its object to provide a metal-based flux-cored welding wire which is excellent in welding workability such as arc stability, amount of spatter generated, amount of slag generated, and bead shape, and which is also excellent in resistance to blowhole defects and cracking, and which produces a deposited metal with good mechanical properties. [Means for solving the problem]

[0013] The gist of the present invention for solving the above problems is as follows.

[0014] The metal-based flux-cored welding wire according to the present invention is a metal-based flux-cored welding wire including a steel sheath and flux filled in the steel sheath, and contains, in mass % relative to the total mass of the wire, the total of the steel sheath and the flux, C: 0.04 to 0.11%, Si: 0.1 to 1.2%, Mn: 0.5 to 2.0%, Cu: 0.10 to 0.50%, S: 0.020 to 0.050%, and P: 0.03% or less; and The flux contains, in mass % relative to the total amount, Si oxides (SiO2 equivalent) in a total amount of 0.20% or less, metal fluorides (F equivalent) in a total amount of 0.003 to 0.120%, one or more of Na oxides and K oxides (Na2O equivalent and KO equivalent) in a total amount of 0.02 to 0.10%, the value calculated by the following formula (1) being 0.25 to 0.45, and the remainder being Fe and impurities contained in the steel sheath and flux. (10[S]+3[C]) / [Mn]·················································Formula (1) Here, [S], [C], and [Mn] represent the mass % of each element contained in the steel sheath and flux relative to the total mass of the wire.

[0015] The metal-based flux-cored welding wire according to the present invention is further characterized in that it contains, in mass % relative to the total mass of the wire, one or both of Ni: 1.5% or less and B: 0.010% or less in total of the steel sheath and flux.

[0016] The metal-based flux-cored welding wire according to the present invention is further characterized in that it contains, in mass % relative to the total mass of the wire, one or more of Mo: 0.30% or less, Cr: 0.05% or less, and V: 0.05% or less in total of the steel sheath and flux. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a metal-based flux-cored welding wire which is excellent in welding workability such as arc stability, amount of spatter generation, amount of slag generation, and bead shape, and which is also excellent in resistance to blowhole defects and cracking, and which produces a deposited metal with good mechanical properties, particularly low-temperature toughness. DETAILED DESCRIPTION OF THE INVENTION

[0018] The composition and content of the metal-based flux-cored welding wire to which the present invention is applied, and the reasons for limiting each component will be described below. The content of each component is expressed as mass% relative to the total mass of the wire, and is simply expressed as %.

[0019] [Total of steel sheath and flux: C: 0.04~0.11%] Carbon has the effect of improving the strength of the weld metal. In addition, adjusting the amount of carbon added allows a small amount of oxygen, which is released as slag through carbon, to remain in the weld metal, thereby suppressing the amount of slag produced. If the carbon content is less than 0.04%, the strength of the weld metal decreases. On the other hand, if the carbon content exceeds 0.11%, the amount of slag produced increases. Therefore, the carbon content of the steel sheath and flux combined should be 0.04 to 0.11%. In addition to the components contained in the steel sheath, carbon can be added from metal powder and alloy powder from the flux.

[0020] [Si content in total of steel sheath and flux: 0.1 to 1.2%] Silicon improves the strength and low-temperature toughness of the weld metal. It also increases the viscosity of the molten metal, improving the bead appearance and shape. Furthermore, silicon controls the amount of slag produced. If the silicon content is less than 0.1%, the bead appearance and shape deteriorate, and resistance to blowhole defects decreases. On the other hand, if the silicon content exceeds 1.2%, excessive silicon is retained in the weld metal, resulting in excessive weld metal strength and reduced low-temperature toughness. Furthermore, if the silicon content exceeds 1.2%, the amount of slag produced increases. Therefore, the total silicon content of the steel sheath and flux should be 0.1 to 1.2%. In addition to being a component of the steel sheath, silicon can be added from the flux via metallic silicon, Fe-Si, Fe-Si-Mn, and other alloy powders.

[0021] [Mn content in steel sheath and flux: 0.5-2.0%] Mn acts as a deoxidizer and also has the effect of improving the strength and low-temperature toughness of the weld metal. If the Mn content is less than 0.5%, the strength and low-temperature toughness of the weld metal will decrease. On the other hand, if the Mn content exceeds 2.0%, excessive Mn will be retained in the weld metal, resulting in excessive weld metal strength, reduced low-temperature toughness, and increased slag production. Therefore, the total Mn content in the steel sheath and flux should be 0.5 to 2.0%. In addition to being a component contained in the steel sheath, Mn can also be added from the flux as metallic Mn, Fe-Mn, Fe-Si-Mn, and other alloy powders.

[0022] [Cu content in steel sheath and flux combined: 0.10 to 0.50% or less] Cu has a precipitation strengthening effect, lowering the transformation temperature and refining the structure of the weld metal, thereby improving low-temperature toughness. Cu also has the effect of suppressing hot cracking in the weld. However, if the Cu content is less than 0.10%, this effect is not obtained and the low-temperature toughness of the weld metal decreases. On the other hand, if the Cu content exceeds 0.50%, precipitation embrittlement occurs and the low-temperature toughness of the weld metal decreases. Therefore, the total Cu content of the steel sheath and flux is set to 0.10 to 0.50%. Cu can be added from the components contained in the steel sheath, the Cu plating applied to the steel sheath surface, metallic Cu from the flux, and alloy powder such as Fe-Si-Cu.

[0023] [Sulfur content in steel sheath and flux: 0.020-0.050%] Sulfur lowers the surface tension of the molten pool during welding, thereby changing the flow of the molten metal and making it easier for the slag to aggregate. Aggregation of slag facilitates its removal after welding, resulting in a good bead appearance and shape after slag removal. If the S content is less than 0.020%, the molten slag does not aggregate and adheres in a fine, sparse dispersion, resulting in poor slag removability and poor bead appearance and shape. On the other hand, if the S content exceeds 0.050%, the low-temperature toughness of the weld metal decreases. Furthermore, if the S content exceeds 0.050%, hot cracking is more likely to occur in the weld. Therefore, the total S content of the steel sheath and flux should be 0.020-0.050%. In addition to being a component of the steel sheath, S can also be added from flux, metal powder, alloy powder, iron sulfide, etc.

[0024] [P: 0.03% or less in total for steel sheath and flux] P is one of the main elements that causes hot cracking in welds, and is an impurity contained in trace amounts in the raw materials of steel sheaths and flux. If P exceeds 0.03%, hot cracking in welds becomes more likely to occur. Therefore, P content is set to 0.03% or less.

[0025] [Si oxides in flux: SiO2 equivalent total of 0.20% or less] Silicon oxides have the effect of improving the conformity of the bead toe and improving the bead appearance and shape. However, they also increase the amount of slag produced and the oxygen content in the weld metal, so the silicon oxide content must be limited. If the total silicon oxides in SiO2 equivalent exceeds 0.20%, the oxygen content in the weld metal increases and low-temperature toughness decreases. Therefore, the total silicon oxides in SiO2 equivalent must be 0.20% or less. Silicon oxides can be added from silica sand, orthoclase, and the solid components of water glass made from sodium silicate and potassium silicate from the flux.

[0026] [Metal fluorides in flux: 0.003 to 0.120% in total F converted value] Metal fluorides have the effect of stabilizing the arc. If the total F-equivalent value of the metal fluorides is less than 0.003%, the arc becomes unstable. On the other hand, if the total F-equivalent value of the metal fluorides exceeds 0.120%, the arc becomes too strong, the arc becomes unstable, and the amount of spatter increases. Therefore, the total F-equivalent value of the metal fluorides is set to 0.003 to 0.120%. Note that metal fluorides can be added from CaF2, NaF, LiF, MgF2, K2SiF6, Na3AlF6, AlF6, etc., and the F-equivalent value is the total F content contained in these.

[0027] [One or more of sodium oxides and potassium oxides in the flux: 0.02 to 0.10% in total of Na2O equivalent and K2O equivalent] Na oxide and K oxide act as arc stabilizers, stabilizing the arc. If the total of the Na2O equivalent and K2O equivalent values of one or more Na oxides and K oxides is less than 0.02%, the arc becomes unstable and the amount of spatter increases. On the other hand, if the total of the Na2O equivalent and K2O equivalent values of one or more Na oxides and K oxides exceeds 0.10%, the arc length becomes longer, the arc becomes unstable, and the amount of spatter increases. Therefore, the total of the Na2O equivalent and K2O equivalent values of one or more Na oxides and K oxides in the flux should be 0.02-0.10%. Na oxide and K oxide can be added from solid components of water glass made from sodium silicate and potassium silicate, potassium feldspar, Na2Ti3O7, etc.

[0028] [(10[S] + 3[C]) / [Mn]··· the value calculated by formula (1) is 0.25 to 0.45] By adjusting the values calculated by the following formula 1 for the above-mentioned S, C, and Mn, the slag removability can be improved.

[0029] In formula (1), [S], [C], and [Mn] represent the mass% of each element contained in the steel sheath and flux relative to the total mass of the wire. If the value calculated by formula (1) is less than 0.25, slag removability will be poor. On the other hand, if the value calculated by formula (1) exceeds 0.45, the bead appearance and shape will be deteriorated. Therefore, the value calculated by formula (1) should be between 0.25 and 0.45.

[0030] [Ni: 1.5% or less in total for steel sheath and flux] Ni has the effect of further improving the low-temperature toughness of the weld metal. However, if Ni exceeds 1.5%, the strength of the weld metal becomes excessive and hot cracking becomes more likely to occur in the weld. Therefore, the total Ni content of the steel sheath and flux should be 1.5% or less. In addition to being a component contained in the steel sheath, Ni can also be added from metallic Ni from the flux or alloy powder such as Fe-Ni.

[0031] [B: 0.010% or less in total for steel sheath and flux] B has the effect of further improving the low-temperature toughness of the weld metal. However, if B exceeds 0.010%, the strength of the weld metal becomes excessive and hot cracking becomes more likely to occur in the weld. Therefore, the total B content of the steel sheath and flux should be 0.010% or less. B can be added from alloy powders made from Fe-B, borax, colemanite, etc., or oxides.

[0032] [Mo: 0.30% or less in total for steel sheath and flux] Mo has the effect of improving the strength of the weld metal. However, if Mo exceeds 0.30%, the strength of the weld metal becomes excessive and the low-temperature toughness decreases. Therefore, the Mo content should be 0.30% or less. Mo can be added from the components contained in the steel sheath, as well as from the alloy powder of metallic Mo from the flux.

[0033] [Cr: 0.05% or less in total for steel sheath and flux] Cr has the effect of improving the strength of the weld metal. However, if the Cr content exceeds 0.05%, the low-temperature toughness of the weld metal decreases. Therefore, the Cr content should be 0.05% or less. Cr can be added from the components contained in the steel sheath, as well as from metallic Cr from the flux and alloy powder such as Fe-Cr.

[0034] [V: 0.05% or less in total for steel sheath and flux] V has the effect of improving the strength of the weld metal. If V exceeds 0.05%, the low-temperature toughness of the weld metal decreases. Therefore, the V content should be 0.05% or less. V can be added as a component contained in the steel sheath, as well as from metallic V from the flux, or alloy powder such as Fe-V.

[0035] The metal-based flux-cored welding wire of the present invention may contain other components, such as Mg: 0.05% or less, Ti: 0.05% or less, and Al: 0.05% or less, within ranges that do not affect the effects of the present invention. The remainder is Fe and impurities, such as Fe in the steel sheath, iron powder in the flux, and the Fe content and impurities in iron alloy powder such as Fe-Mn, Fe-Si-Mn, and Fe-Ni alloys.

[0036] The flux filling rate is not particularly specified, but is preferably 8 to 20 mass % with respect to the total mass of the wire from the viewpoint of productivity. [Example]

[0037] The effects of the present invention will be described in more detail below with reference to examples.

[0038] First, JIS G3141:2017 SPCC strip steel was used for the steel sheath, which was formed into a U-shape and filled with flux that had been dried to thoroughly remove moisture. The seams of the steel sheath were then welded to form a seamless wire, which was then pipe-formed and drawn to produce prototype flux-cored wires with various main components and a wire diameter of 1.2 mm, as shown in Table 1. In this case, a wire with a seam in which the steel sheaths are crimped together may also be produced. The flux filling rate was set to 10 to 18 mass%.

[0039] [Table 1]

[0040] [evaluation] Using the wire produced as described above, flat welding workability and mechanical properties of the weld metal were evaluated.

[0041] For welding workability, welding was performed in accordance with JIS Z3111:2005 using 20mm thick steel plate specified in JIS G3126:2015 SLA365, under the welding conditions shown in Table 2. Arc stability, amount of spatter generated, amount of slag generated, and bead appearance and shape were visually inspected, and the presence or absence of porosity defects and hot cracking was also inspected.

[0042] [Table 2]

[0043] (Arc stability) The arc stability was determined to be stable when there was little fluctuation in the length of the arc generated between the wire tip and the steel sheet.

[0044] (amount of spatter generated) The amount of spatter generated was determined by collecting the spatter generated when welding was performed for 1 minute on a JIS G 3106:2017 SM490A steel plate (plate thickness 12 mm) using the current, voltage, welding speed, and shielding gas shown in Table 2 in a copper collection box and measuring its weight. The amount of spatter generated was measured five times, and an average value of 1.5 g or less was considered good. Low: spatter generation is 1.5g or less High: The amount of spatter generated exceeds 1.5g

[0045] (Amount of slag produced) The amount of slag generated was evaluated based on the area ratio of the slag on the bead after measuring the amount of spatter generated. Low: Slag area ratio is 10% or less High: Slag area ratio is over 10%

[0046] (Slag removability) After welding, when the slag formed on the bead surface was struck with a chipping hammer, if the slag cracked and could then be easily removed, it was judged to be good.

[0047] (Bead appearance and shape) The bead appearance and shape were judged to be good if the bead was beautiful and uniform.

[0048] (Porosity defect resistance) The bead surface was visually inspected for the presence or absence of porosity defects such as pits. If even one porosity defect appeared after each welding pass, it was rated as "present."

[0049] <Weld metal test> The weld metal test was performed using 20mm thick steel plates specified in JIS G3126:2015 SLA365, welding in accordance with JIS Z3111:2005, and the test was conducted based on the method of "JIS Z 2343-1:2017 Non-destructive testing - Penetrant testing - Part 1."

[0050] (crack resistance) If even one crack was found on the bead surface in the weld metal test, it was marked as "present." After each welding pass, the presence or absence of hot cracks was visually inspected.

[0051] (mechanical properties) Tensile test (A0 type) and impact test (V-notch test piece) specimens were taken from the center of the weld metal in the thickness direction, and mechanical tests were conducted.

[0052] In the evaluation of the tensile test, a tensile strength of 570 to 680 MPa was considered good.

[0053] The impact test was evaluated by a Charpy impact test (vE-60) at -60°C, and a specimen with an average absorbed energy of 75J or more for three repeated tests was considered good.

[0054] These results are summarized in Table 3. If all evaluation items were good or better, the overall evaluation was marked with a circle, and if even one item was not good, it was marked with an X.

[0055] [Table 3]

[0056] In Table 3, wires W1 to W22 are examples of the present invention, and wires W23 to W35 are comparative examples. The wires W1 to W22, which are examples of the present invention, had appropriate amounts of C, Si, Mn, Cu, S, and P in the steel sheath and flux of the metal-based flux-cored welding wires, and the (10[S] + 3[C]) / [Mn] ratio was appropriate. The total SiO2 equivalent value of Si oxides, the total F equivalent value of metal fluorides, and the total Na2O equivalent value and KO2O equivalent value of one or more sodium oxides and potassium oxides in the flux were appropriate. Therefore, the arc was stable, the amount of spatter generation was small, the amount of slag generation was small, the bead appearance and shape were good, and neither porosity nor hot cracking occurred. Furthermore, the tensile strength and absorbed energy of the weld metal were good, resulting in satisfactory results. Additionally, W4, W6, W8, and W15 had extremely satisfactory results, with the average absorbed energy of the weld metal being 95 J or more, due to the appropriate amounts of Ni and B. Furthermore, W2, W6, W10, W12, W16, W19, and W22 had extremely satisfactory results, with the tensile strength of the weld metal being 650 MPa or more, due to the appropriate amounts of Mo, Cr, and V.

[0057] The wire symbol W23 in the comparative examples had low strength of the weld metal due to the low content of C. Also, the total F-equivalent value of the metal fluorides was low, resulting in an unstable arc.

[0058] Wire W24 produced a large amount of slag due to its high C content. Also, due to its high Mo content, the strength of the weld metal was excessive, resulting in low absorbed energy.

[0059] Wire symbol W25 had a low silicon content, resulting in poor bead appearance and shape. Because of the low silicon content, pits (porosity defects) occurred on the bead surface. In addition, because of the high nickel content, the strength of the weld metal was high. In addition, because of the high nickel content, high-temperature cracking occurred in the weld.

[0060] Wire symbol W26 has a high Si content, which resulted in excessive weld metal strength and low absorbed energy. The high Si content also resulted in a large amount of slag generation.

[0061] Wire symbol W27 had a low S content, which resulted in poor slag removability and poor bead appearance and shape. Also, because the total of the Na2O equivalent value and K2O equivalent value was low, the arc became unstable and a large amount of spatter was generated. Furthermore, because it contained a large amount of B, the strength of the weld metal was high. Because it contained a large amount of B, high-temperature cracking occurred in the weld metal.

[0062] Wire symbol W28 had a high S content, so the absorbed energy of the weld metal was low. Because of the high S content, high-temperature cracking occurred in the weld metal. Also, because the total F-equivalent value of the metal fluorides was high, the arc became unstable and a large amount of spatter was generated.

[0063] Wire symbol W29 had a low Mn content, resulting in low weld metal strength and low absorbed energy. Also, the total of the Na2O equivalent value and K2O equivalent value was high, resulting in an unstable arc and a large amount of spatter. Furthermore, the value of (10[S]+3[C]) / [Mn] was high, resulting in poor bead appearance and shape. Although the amount of Mo was appropriate, it did not have the effect of improving the strength of the weld metal.

[0064] Wire W30 contained a large amount of manganese, which resulted in excessive weld metal strength and low absorbed energy. Because of the large amount of manganese, a large amount of slag was generated. Furthermore, the value of (10[S] + 3[C]) / [Mn] was small, resulting in poor slag removability.

[0065] Wire symbol W31 had a high total F-equivalent value of metal fluorides, which resulted in an unstable arc and a large amount of spatter. In addition, because it contained a lot of V, the absorbed energy of the weld metal was low.

[0066] Wire symbol W32 had a low Cu content, so the absorbed energy of the weld metal was low.

[0067] Wire symbol W33 has a high Cu content, so the absorbed energy of the weld metal was low.

[0068] Wire W34 had a high total SiO2 equivalent value, so the absorbed energy of the weld metal was low. Although the amount of Ni was appropriate, it did not have the effect of improving the absorbed energy of the weld metal.

[0069] Wire W35 had high P content, which caused hot cracking in the weld metal. In addition, because it had high Cr content, the absorbed energy of the weld metal was low.

Claims

1. A metal-based flux-cored welding wire including a steel sheath and a flux filled in the steel sheath, The total mass of the steel sheath and flux is expressed as a percentage by mass of the total wire mass. C: 0.04-0.11%, Si: 0.1-1.2%, Mn: 0.5-2.0%, Cu: 0.10-0.50%, S: 0.020 to 0.050%; P: 0.03% or less, Furthermore, in the flux, in mass % relative to the total mass of the wire, Si oxide: SiO 2 The total converted value is 0.20% or less, Metal fluorides: 0.003 to 0.120% in total F converted value, One or more of sodium oxide and potassium oxide: Na 2 O conversion value and K 2 Contains 0.02 to 0.10% in total converted to O, A metal-based flux-cored welding wire, characterized in that the value calculated by the following formula (1) is 0.25 to 0.45, and the remainder is Fe and impurities contained in the steel sheath and flux. (10[S]+3[C]) / [Mn]...Formula (1) Here, [S], [C], and [Mn] represent the mass % of each element contained in the steel sheath and flux relative to the total mass of the wire.

2. 2. The metal-based flux-cored welding wire according to claim 1, characterized in that the wire contains, in mass % relative to the total mass of the wire, one or both of Ni: 1.5% or less and B: 0.010% or less in total of the steel sheath and the flux.

3. 3. The metal-based flux-cored welding wire according to claim 1 or 2, characterized in that the wire contains, in mass % relative to the total mass of the wire, one or more of Mo: 0.30% or less, Cr: 0.05% or less, and V: 0.05% or less in total of the steel sheath and flux.

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