Flux-cored wire for self-shielded arc welding

Abstract

To provide a flux-cored wire for self-shielded arc welding which can obtain a weld metal with high strength and excellent toughness, can suppress weld defect, and has good welding workability.SOLUTION: In a flux-cored wire for self-shielded arc welding contains, by mass % to a wire total mass, C: 0.05 to 0.25%, Mn: 0.5 to 1.5%, Al: 1.0 to 3.0%, and Si: 0.8% or less in total of steel outer skin and flux, and contains, in th flux, Mg: 1.0 to 3.0%, total of SiO2 conversion values: 0.1 to 0.5%, total of F conversion values: 1 to 5%, total of one or more kinds of metal carbonate:0.2 to 1.5%, and total of one or more kinds of Na2O conversion values and K2O conversion values: 0.02 to 0.15%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a flux-cored wire for self-shielded arc welding of 590 MPa-class high-tensile steel, which can produce a weld metal with high strength and excellent toughness, is free from welding defects such as pits and blowholes, and provides good welding workability. [Background technology]

[0002] Flux-cored wire for self-shielded arc welding is a welding method in which a gas generating agent such as a metal fluoride or a metal carbonate is added to the welding wire, and the metal fluoride or metal carbonate is decomposed by arc heat during welding to generate a shielding gas that covers the molten pool, allowing welding to be performed while isolating the atmosphere without using a shielding gas. This welding method does not require equipment such as cylinders or piping to deliver the shielding gas, so the welding equipment has a simple structure and is easy to carry, and is widely used in civil engineering and construction fields. For example, Patent Document 1 discloses a flux-cored wire for self-shielded arc welding that is capable of all-position welding.

[0003] However, compared to conventional gas-shielded arc welding, self-shielded arc welding has problems such as an unstable arc, poor welding workability, a tendency to develop porosity defects such as pits and blowholes, and poor mechanical properties of the weld metal.

[0004] As a means for solving this problem, Patent Document 2 discloses a flux-cored wire for self-shielded arc welding in which appropriate amounts of Al, which has the effect of fixing N in the molten metal and improving porosity resistance, Mg, which has the effect of shielding the weld, metal fluorides, and metal carbonates are added to the welding wire, thereby improving shielding resistance and preventing porosity defects such as pits and blowholes, and also achieving good welding workability, such as stabilizing the arc.

[0005] Furthermore, Patent Document 3 discloses a flux-cored wire for self-shield arc welding in which the addition of Al prevents the occurrence of porosity defects such as pits and blowholes, while the simultaneous addition of Al, Mg, and Ba facilitates stabilization of the arc, resulting in good welding workability, and the addition of appropriate amounts of Mn and Ni can improve the toughness of the weld metal.

[0006] If the flux-cored wires for self-shielded arc welding disclosed in Patent Documents 2 and 3 are used, it is possible to suppress porosity defects such as pits and blowholes, stabilize the arc, and obtain good welding workability. However, because a large amount of Al is added, the microstructure of the weld metal is likely to become coarse, making it difficult to obtain a weld metal with excellent mechanical properties, and in particular, it is difficult to obtain a weld metal with sufficient toughness.

[0007] Furthermore, in recent years, the strength of welded structures has been increasing in the civil engineering and architectural fields, and high-strength steels such as 590 MPa-class steels are widely used. When welding such high-strength steels, the weld metal also needs to be quite strong, so elements that improve the strength of the weld metal, such as Mo, are sometimes added to the welding wire used in self-shielded arc welding. However, when Mo or other elements are contained in the weld metal, it becomes even more difficult to obtain the toughness of the weld metal.

[0008] As a means for solving these problems, Patent Document 4 discloses a flux-cored wire for self-shielded arc welding that contains appropriate amounts of Al, BaF2, and Sr composite oxide to stabilize the arc and thereby improve welding workability by suppressing porosity defects such as pits and blowholes, and that contains appropriate amounts of C, Mn, Ni, and Mo to improve the strength and toughness of the weld metal. However, although the flux-cored wire for self-shielded arc welding disclosed in Patent Document 4 achieves good welding workability by stabilizing the arc and suppressing porosity defects such as pits and blowholes, it has the problem of excessively high strength of the weld metal due to the increased amounts of C, Mn, Ni, and Mo added. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 62-238097 [Patent Document 2] Japanese Patent Application Publication No. 3-118993 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-301382 [Patent Document 4] Japanese Patent Application Laid-Open No. 2009-119497 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been devised in view of the above-mentioned problems, and an object of the present invention is to provide a flux-cored wire for self-shielded arc welding of 590 MPa class high-tensile steel, which can provide a weld metal with high strength and excellent toughness, can suppress porosity defects such as pits and blowholes, and has good welding workability. [Means for solving the problem]

[0011] The gist of the present invention is a flux-cored wire for self-shielded arc welding, which is made by filling a steel sheath with flux, and which contains, in mass % relative to the total mass of the wire, a total of the steel sheath and flux, C: 0.05 to 0.25%, Mn: 0.5 to 1.5%, Al: 1.0 to 3.0%, and Si: 0.8% or less; and further, in mass % relative to the total mass of the wire, the flux contains Mg: 1.0 to 3.0%, a total of Si oxides in terms of SiO2: 0.1 to 0.5%, a total of metal fluorides in terms of F: 1.3 (excluding 1.3) to 5%, Calcium carbonate, barium carbonate, lithium carbonate One or more of the following Metal carbonate total: 0.5The composition is characterized by containing 0.02 to 0.11% of iron in the steel outer shell, iron powder, iron in the iron alloy powder, and impurities, and a total of 0.02 to 0.11% of one or two of sodium oxides and potassium oxides in terms of Na2O and K2O, respectively.

[0012] The wire is also characterized in that the total mass of the steel sheath and flux contains 0.5% or less Mo, expressed as a percentage by mass relative to the total mass of the wire.

[0013] Furthermore, the present invention provides a flux-cored wire for self-shield arc welding, characterized in that the total mass of the steel sheath and flux contains 1.0% or less Ni, in terms of mass % relative to the total mass of the wire. [Effects of the Invention]

[0014] According to the flux-cored wire for self-shielded arc welding to which the present invention is applied, it is possible to provide a flux-cored wire for self-shielded arc welding that can obtain a weld metal having a high strength of 590 MPa or more and excellent toughness, and that is free from porosity defects such as pits and blowholes and has good welding workability. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view of a flux-cored ear for self-shielded arc welding fabricated in an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] In order to solve the above-mentioned problems, the present inventors have conducted detailed studies on the component composition of a flux-cored wire for self-shielded arc welding that can produce a weld metal with a high strength of 590 MPa or more and excellent toughness, that is free from porosity defects such as pits and blowholes, that produces a stable arc, and that provides excellent welding workability.

[0017] As a result, it was found that adding an appropriate amount of Al to flux-cored wire for self-shielded arc welding can fix N in the molten metal as AlN and suppress the occurrence of porosity defects such as pits and blowholes, but Al coarsens the microstructure of the weld metal, reducing the toughness of the weld metal. Therefore, various methods were investigated to improve the strength of the weld metal while suppressing the coarsening of the microstructure. As a result, it was found that adding large amounts of gas-generating metal fluorides, metal carbonates, and Mg to flux-cored wire for self-shielded arc welding can improve shielding properties and reduce the amount of Al added, thereby suppressing the coarsening of the microstructure. Furthermore, it was found that adding appropriate amounts of C and Mn can improve the strength and toughness of the weld metal. Furthermore, it was found that increasing the amount of Mn added to obtain the required toughness of the weld metal results in an excessively high strength of the weld metal.

[0018] Therefore, further investigation was conducted to obtain a weld metal that suppresses the occurrence of porosity defects such as pits and blowholes, has a strength of 590 MPa, and has good toughness.As a result, it was found that by reducing the amount of metal carbonate added to suppress the amount of slag generation, by minimizing the amount of Al added and increasing the amounts of Mg and metal fluoride added, high shielding properties are ensured and the occurrence of porosity defects such as pits and blowholes is suppressed, and by keeping the amount of Mn added low and adjusting the amount of C added, a weld metal with a strength of 590 MPa and good toughness can be obtained.Furthermore, it was found that the strength of the weld metal can be improved without reducing the toughness of the weld metal by adding appropriate amounts of Mo and Ni.

[0019] Regarding other welding workability, we also found that adding appropriate amounts of sodium oxide and potassium oxide is effective in stabilizing the arc.

[0020] Furthermore, it was discovered that by adding an appropriate amount of silicon oxide, the viscosity of the molten slag can be adjusted, and the slag encapsulation of the weld bead and the bead shape can be improved.

[0021] The flux-cored wire for self-shielded arc welding of the present invention is made possible by the synergistic effects of the individual components and the coexistence of the components, and the reasons for adding and limiting each component will be described below. Note that, in the following, the chemical components of the flux-cored wire for self-shielded arc welding will be expressed in mass %, which is the ratio to the total mass of the wire, and descriptions relating to mass % will be simply written as %.

[0022] [Total of steel sheath and flux: C: 0.05 to 0.25%] Carbon (C) has the effect of improving the strength of the weld metal through solid solution strengthening. Furthermore, CO and CO2 generated during welding block the atmosphere from the molten pool, improving shielding and suppressing the occurrence of porosity defects such as pits and blowholes. If the C content is less than 0.05%, this effect is not fully achieved, and the weld metal strength is not sufficient. Furthermore, if the C content is less than 0.05%, the shielding performance is not sufficient, and porosity defects such as pits and blowholes are more likely to occur. On the other hand, if the C content exceeds 0.25%, the strength of the weld metal becomes excessively high and its toughness decreases. Therefore, the total C content of the steel sheath and flux is set to 0.05 to 0.25%. In addition to being a component contained in the steel sheath, C can also be added from the flux as metal powder, alloy powder, etc.

[0023] [Mn content in steel sheath and flux: 0.5-1.5%] Mn acts as a deoxidizer for the weld metal and has the effect of improving the strength and toughness of the weld metal. If the Mn content is less than 0.5%, this effect is not fully achieved, and the strength and toughness of the weld metal decrease. On the other hand, if the Mn content exceeds 1.5%, the strength of the weld metal becomes excessively high and the toughness decreases. Therefore, the total Mn content in the steel sheath and flux is set to 0.5 to 1.5%. In addition to being a component contained in the steel sheath, Mn can also be added to the flux as alloy powder such as metallic Mn, Fe-Mn, or Fe-Si-Mn.

[0024] [Al: 1.0-3.0% in total for steel sheath and flux] Al acts as a deoxidizer to improve the toughness of the weld metal, and also fixes N that penetrates into the molten metal as AlN, thereby suppressing the occurrence of porosity defects such as pits and blowholes. If the Al content is less than 1.0%, this effect is not fully achieved, and porosity defects such as pits and blowholes are more likely to occur. On the other hand, if the Al content exceeds 3.0%, excessive Al is retained in the weld metal, causing the microstructure to coarsen, and reducing the toughness of the weld metal. Therefore, the total Al content of the steel sheath and flux is set to 1.0 to 3.0%. In addition to being a component contained in the steel sheath, Al can also be added to the flux as alloy powder such as metallic Al, Fe-Al, or Al-Mg.

[0025] [Si: 0.8% or less in total for steel sheath and flux] If excessive Si remains in the weld metal, it will cause a decrease in the toughness of the weld metal, so the total content of the steel sheath and flux must be 0.8% or less. In addition to being a component contained in the steel sheath, Si can also be added from the flux in the form of alloy powders such as metallic Si, Fe-Si, and Fe-Si-Mn.

[0026] [Mg in flux: 1.0-3.0%] Mg acts as a deoxidizer, promoting deoxidation of the weld metal and suppressing the occurrence of porosity defects such as pits and blowholes, while also improving the toughness of the weld metal. If the Mg content is less than 1.0%, this effect is not fully achieved, and porosity defects such as pits and blowholes are more likely to occur, while the toughness of the weld metal decreases. On the other hand, if the Mg content exceeds 3.0%, the arc becomes excessively strong and unstable. Therefore, the total Mg content in the steel sheath and flux should be 1.0 to 3.0%. Mg can be added to the flux as metallic Mg or alloy powder such as Al-Mg.

[0027] [Total SiO2 equivalent value of silicon oxide in flux: 0.1 to 0.5%] Silicon oxides have the effect of adjusting the viscosity and melting point of molten slag and improving slag encapsulation. If the total SiO2 equivalent of silicon oxides is less than 0.1%, this effect is not fully achieved, resulting in poor slag encapsulation. On the other hand, if the total SiO2 equivalent of silicon oxides exceeds 0.5%, the basicity of the molten slag decreases, the oxygen content of the weld metal increases, and the toughness of the weld metal decreases. Therefore, the total SiO2 equivalent of silicon oxides in the flux should be 0.1 to 0.5%. Silicon oxides can be added to the flux as silica sand, potash glass, fluorite, etc.

[0028] [Metal fluorides contained in flux: 1 to 5% in total in terms of F] Metal fluorides act as gas generators and improve the shielding of the molten pool from the atmosphere. If the total F-equivalent content of the metal fluorides is less than 1%, this effect is insufficient, resulting in insufficient shielding, porosity defects such as pits and blowholes, and an unstable arc. On the other hand, if the total F-equivalent content of the metal fluorides exceeds 5%, the arc becomes excessively strong and unstable. Therefore, the total F-equivalent content of the metal fluorides contained in the flux should be 1-5%. Metal fluorides can be added to the flux as fluorite, sodium fluoride, lithium fluoride, magnesium fluoride, potassium silicofluoride, cryolite, aluminum fluoride, etc., and the F-equivalent content is the sum of the F content of these substances.

[0029] [Total of one or more metal carbonates contained in the flux: 0.5 ~1.5%] Metal carbonates act as gas generators, decomposing with arc heat during welding to generate CO and CO2 gases, which isolate the molten pool from the atmosphere, improving shielding and suppressing the occurrence of porosity defects such as pits and blowholes. If the total content of one or more metal carbonates is less than 0.5%, this effect is insufficient, and porosity defects such as pits and blowholes are more likely to occur. Furthermore, if the total content of one or more metal carbonates is less than 0.5%, the toughness of the weld metal decreases. On the other hand, if the total content of one or more metal carbonates exceeds 1.5%, the arc becomes excessively strong and unstable, resulting in slag entrapment in the weld. Therefore, the total content of one or more metal carbonates in the flux should be 0.5-1.5%. Metal carbonates can be added to the flux as calcium carbonate, barium carbonate, lithium carbonate, etc.

[0030] [The total of one or both of the Na2O equivalent value and K2O equivalent value of Na oxide and K oxide contained in the flux: 0.02 0.11% ] Na oxide and K oxide have the effect of stabilizing the arc state. If the total of one or both of the Na2O equivalent values ​​and K2O equivalent values ​​of Na oxide and K oxide is less than 0.02%, the arc becomes unstable. On the other hand, if the total of one or both of the Na2O equivalent values ​​and K2O equivalent values ​​of Na oxide and K oxide is less than 0.02%, the arc becomes unstable. 0.11% If it exceeds this value, the toe of the bead will not conform well and the bead shape will be poor. Therefore, the total of the Na2O equivalent value and the K2O equivalent value of type 1 or type 2 of the Na oxide and K oxide contained in the flux should be 0.02 to 1.02. 0.11% Na oxide and K oxide can be added from the flux as powders of potash glass, soda glass, etc.

[0031] [Mo: 0.5% or less in total for steel sheath and flux] Mo has the effect of increasing the strength of the weld metal. However, if Mo exceeds 0.5%, the strength of the weld metal becomes excessively high and the toughness decreases. Therefore, the total Mo content of the steel sheath and flux is set to 0.5% or less. In order to obtain the effect of increasing the strength of the weld metal, Mo is preferably 0.1% or more. In addition to being a component contained in the steel sheath, Mo can be added from the flux as metallic Mo powder or alloy powder such as Fe-Mo.

[0032] [Ni: 1.0% or less in total for steel sheath and flux] Ni has the effect of improving the strength and toughness of the weld metal. However, if Ni exceeds 1.0%, the strength of the weld metal becomes excessively high and the toughness decreases. Therefore, Ni content is set to 1.0% or less. In order to obtain the effect of improving the strength and toughness of the weld metal, Ni content is preferably 0.1% or more. In addition to being a component contained in the steel sheath, Ni can also be added from the flux as metallic Ni, Fe-Ni, or other alloy powders.

[0033] The remainder of the flux-cored wire for self-shielded arc welding of the present invention is the Fe content of the steel sheath, iron powder, the Fe content of iron alloy powder such as Fe-Si, Fe-Mn, Fe-Si-Mn, and Fe-Al alloy, and impurities. The iron powder is contained in the flux to adjust the flux filling rate. Furthermore, there are no particular restrictions on the impurities, but from the viewpoint of preventing hot cracking, it is preferable that the P content be 0.010% or less.

[0034] The flux-cored wire for self-shielded arc welding of the present invention is a so-called E-section wire, which is formed by forming a steel sheath into a U shape, filling the inside with flux, and then weaving the sheath into the inside to form a wire.

[0035] The flux filling rate is not particularly limited, but from the viewpoint of productivity, it is preferably 10 to 30% of the total mass of the wire. [Example]

[0036] The effects of the present invention will be specifically explained below with reference to examples.

[0037] A steel sheath (C: 0.001-0.10%, Si: 0.05% or less, Mn: 0.1-0.6%, P: 0.05% or less, S: 0.05% or less) was used, and the steel sheath was formed into a U-shape and filled with various fluxes shown in Table 1 at a filling rate of 15-25%. The sheath was then woven inside and shaped to produce a flux-cored wire with the cross section shown in Figure 1. The wire diameter was 3.2 mm. The flux used was dried before filling.

[0038] [Table 1]

[0039] Using the prototype flux-cored wire for self-shielded arc welding, self-shielded arc welding was carried out, and a weld metal test and welding workability evaluation were carried out.

[0040] The weld metal tests were conducted in accordance with JIS Z 3111 and JIS Z 3313 under the welding conditions shown in Table 2. The steel plate used was JIS G 3106 SM570 (plate thickness: 20 mm). A0 tensile test pieces and V-notch impact test pieces were taken from the center of the plate thickness of the weld metal of the obtained test specimens and subjected to tensile tests and impact tests, respectively.

[0041] The criteria for evaluating the tensile properties of the weld metal were as follows: a tensile strength in the range of 590 to 770 MPa was considered good, and an average absorbed energy of 27 J or more for three samples at 20°C was considered good.

[0042] After preparing the specimens for the weld metal test, the excess metal and backing metal were ground down to the steel plate surface to make it smooth, and then an X-ray examination was carried out in accordance with JIS Z 3104 to check for the presence or absence of welding defects. The results are summarized in Table 3.

[0043] The welding workability was evaluated based on the arc stability, slag coverage, and bead shape during welding in the weld metal test.

[0044] Arc stability was evaluated by measuring voltage fluctuations for 10 seconds during welding and measuring the magnitude of the voltage. Using a threshold of ±4V relative to the average voltage, the arc was deemed stable when the voltage fluctuation exceeded the threshold 80% or less over the 10 seconds, and unstable when the voltage fluctuation exceeded the threshold 20% or more over the 10 seconds. Slag coverage was estimated by estimating the area of ​​the bead that was visually free of slag, and a bead with a slag-free area of ​​10% or less was deemed good. Bead shape was deemed good when the weld bead was sound and free of undercuts or overlaps that required rework.

[0045] [Table 2]

[0046] [Table 3]

[0047] Wire symbols in Tables 1 and 3 1、4、7、11、12 The wire symbols 13 to 24 are examples of the present invention, and comparative examples. 1、4、7、11、12 The C, Mn, Al and Si in the flux-cored wire for self-shielded arc welding were appropriate, and the total of the SiO2 equivalent values ​​of Mg and Si oxides, the total F equivalent values ​​of metal fluorides, the total metal carbonates, and the total Na2O equivalent values ​​and K2O equivalent values ​​of Na oxides and K oxides in the flux were appropriate, so the arc was stable, the slag coverage and bead shape were good, no welding defects such as pits, blowholes and slag entrapment occurred, and the tensile strength and absorbed energy of the deposited metal were both good.

[0048] In addition, Wire symbols 1 and 12 have an appropriate amount of Ni added, so high strength weld metal of 700 MPa or more was obtained, and absorbed energy of 50 J or more was obtained. 11Since the amount of Mo and Ni added was appropriate, a high strength weld metal of over 750 MPa was obtained, and an absorbed energy of over 50 J was obtained.

[0049] In the comparative example, wire No. 13 had a low carbon content, which resulted in blowholes in the weld. Also, because of the low carbon content, the tensile strength of the deposited metal was low. Furthermore, because of the high magnesium content, the arc became excessively strong and unstable. Furthermore, because of the low nickel content, the effect of improving the tensile strength and absorbed energy of the deposited metal was not achieved.

[0050] Wire No. 14 had a high carbon content, resulting in high tensile strength and low absorbed energy of the deposited metal. In addition, the total SiO2 equivalent value of silicon oxide was low, resulting in poor slag encapsulation.

[0051] Wire No. 15 had a low Mn content, so the tensile strength and absorbed energy of the deposited metal were low. Also, the total F-equivalent value of the metal fluorides was low, so the arc became unstable. Also, the total F-equivalent value of the metal fluorides was low, so blowholes occurred in the weld. Furthermore, the low Mo content did not have the effect of improving the tensile strength of the deposited metal.

[0052] Wire No. 16 had a high Mn content, which resulted in high tensile strength of the deposited metal and low absorbed energy. Also, the total F-equivalent value of the metal fluorides was high, which resulted in an excessively strong and unstable arc.

[0053] Wire No. 17 had a low Al content, so blowholes occurred in the weld.

[0054] Wire No. 18 had a high Al content, so the absorbed energy of the deposited metal was low. Also, the total Na2O equivalent value and K2O equivalent value of Na oxide and K oxide was low, so the arc became unstable.

[0055] Wire No. 19 had a low Mg content, which caused blowholes in the weld. Also, because of the low Mg content, the absorbed energy of the weld metal was low.

[0056] Wire No. 20 had a high Si content, which resulted in low absorbed energy in the weld metal. Also, the total Na2O equivalent and K2O equivalent values ​​of sodium oxide and potassium oxide were high, which resulted in poor conformity at the toe of the bead and a poor bead shape.

[0057] Wire No. 21 had a high total SiO2 equivalent of silicon oxides, which resulted in low absorbed energy in the weld metal. Also, because it had a high total of metal carbonates, the arc was excessively strong and unstable, causing slag inclusion in the weld.

[0058] Wire No. 22 had a low total metal carbonate content, which resulted in low absorbed energy in the weld metal. Also, because the total metal carbonate content was low, blowholes occurred in the weld.

[0059] Wire No. 23 had a high total F-equivalent value of metal fluorides, which resulted in an excessively strong and unstable arc. Also, because it contained a lot of Mo, the tensile strength of the deposited metal was high and the absorbed energy was low.

[0060] Wire No. 24 had a low total Na2O equivalent value and K2O equivalent value of Na oxide and K oxide, which resulted in an unstable arc. In addition, because it contained a large amount of Ni, the tensile strength of the deposited metal was high and the absorbed energy was low.

Claims

1. In a flux-cored wire for self-shield arc welding, which is made by filling a steel sheath with flux, the total mass of the steel sheath and flux is, in mass %, C: 0.05-0.25%, Mn: 0.5-1.5%, Al: 1.0-3.0%, Si: 0.8% or less; Furthermore, in the flux, in mass % relative to the total mass of the wire, Mg: 1.0-3.0%, Si oxide SiO 2 Total conversion value: 0.1-0.5%, Total F-equivalent value of metal fluorides: 1.3 (excluding 1.3) to 5%, Total of one or more metal carbonates of calcium carbonate, barium carbonate, and lithium carbonate: 0.5 to 1.5%, Na in Na oxide and K oxide 2 O equivalent value and K 2 The total of one or two types of O equivalent: 0.02 to 0.11%; 1. A flux-cored wire for self-shield arc welding, the balance of which consists of the iron content of the steel sheath, iron powder, the iron content of the iron alloy powder, and impurities.

2. 2. The flux-cored wire for self-shielded arc welding according to claim 1, wherein the total mass of the steel sheath and the flux is 0.5% or less by mass % relative to the total mass of the wire.

3. 3. The flux-cored wire for self-shielded arc welding according to claim 1, wherein the total of the steel sheath and the flux contains 1.0% or less Ni, in mass % relative to the total mass of the wire.

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