WO2025211031A1 - Wire material, steel wire and twisted wire - Google Patents

Abstract

Provided are: a wire material which has a chemical composition containing, in terms of mass%, 0.50-1.10% of C, 0.10-1.00% of Si, 10.0-18.0% of Mn, 0.050% or less of P, 0.050% or less of S and 0.005-0.035% of N, with the remainder comprising Fe and impurities, includes an austenite structure, has a relative magnetic permeability of 1.100 or less, and is such that in a cross section perpendicular to the length direction of the wire material, the areal ratio of carbides having a maximum length of 0.5 μm or more in a central part is 0.05-2.00% and the degree of segregation of carbon in a center segregation part is 1.20 or less, and in a cross section parallel to the length direction including the center axis of the wire material, the average aspect ratio of austenite grains in the austenite structure is less than 1.40; a steel wire in which the average aspect ratio of austenite grains in the austenite structure is 1.40 or more; and a twisted wire that includes the steel wire.

Description

Wire rods, steel wires and stranded wires

This disclosure relates to wire rods, steel wires, and stranded wires.

The reinforcing steel material for general power transmission lines is carbon steel, which is a ferromagnetic material. During power transmission, the temperature of the power transmission line rises not only due to the electrical resistance of the line but also due to electromagnetic induction from the reinforcing wire. It is known that the temperature rise of the power transmission line ultimately leads to power loss.
Therefore, there is a demand for non-magnetic wires that do not cause electromagnetic induction during power transmission.

Patent Document 1 discloses a non-magnetic, high-strength wire suitable for use as a core wire for power lines, which has high strength, non-magnetic properties, and a low thermal expansion coefficient. The wire contains, by weight, 27-42% manganese (Mn), 0.35% or less (excluding 0%) carbon (C), 0.5% or less silicon (Si), 0.03% or less phosphorus (P), and 0.03% or less sulfur (S), with the balance being Fe and other unavoidable impurities, and has a Neel temperature exceeding 150°C.

Patent Document 2 discloses a non-magnetic steel that achieves high strength, high yield strength, and low magnetic permeability, and has excellent bending workability at room temperature and also at low temperatures. The non-magnetic steel contains 0.8 to 1.2% C (meaning mass %; the same applies hereinafter to chemical components), 0.1 to 0.6% Si, more than 13% but not more than 20% Mn, 0.001% or more but less than 0.02% Al, 0.040% or less P (not including 0%), 0.045% or less S (not including 0%), and 0.025 to 0.05% N, with the balance being iron and unavoidable impurities. The austenite structure accounts for 99.0% or more by area of the microstructure, and the austenite grain size number is 8.0 to 10.5.

Patent Document 3 discloses a non-magnetic steel that exhibits high strength and low magnetic permeability, and further has excellent bending workability, particularly at low temperatures, even when a decarburized layer is present. The composition is, by mass, C: 0.8-1.2%, Si: 0.1-0.6%, Mn: more than 13% but less than 20%, Al: 0.001% or more but less than 0.02%, P: more than 0% but 0.040% or less, S: more than 0% but 0.045% or less, and N: 0.025-0.05%, with the balance being iron and unavoidable impurities, and the hydrogen concentration in the steel being kept to 4.5 ppm by mass or less.

Patent Document 4 discloses a non-magnetic steel wire rod or bar containing C: 0.40-0.8%, Si: 0.50% or less (excluding 0%), Mn: 8-25%, P: 0.03% or less (excluding 0%), S: 0.030% or less (excluding 0%), Al: 0.010-0.10%, N: 0.0010-0.020%, the balance being iron and unavoidable impurities, with the amount of dissolved N being 0.001% or less (including 0%), the structure being an austenite single-phase structure, and the number of austenite crystal grains with a crystal grain size of 30-80 μm being 80% or more of the total austenite crystal grains.

Patent Document 5 discloses a steel material having a component composition containing, by mass%, C: 0.10% to 2.50%, Mn: 8.0% to 45.0%, P: 0.300% or less, S: 0.1000% or less, Ti: 0.10% to 5.00%, Al: 0.001% to 5.000%, N: 0.5000% or less, and O (oxygen): 0.1000% or less, and containing C, Ti, and Mn in ranges that satisfy the following formula (1), with the balance being Fe and unavoidable impurities, and having a structure containing, by area ratio, 90% or more of an austenite phase and 0.2% or more of Ti carbide.
25([C]-12.01[Ti]/47.87)+[Mn]≧25...(1)
Here, [C], [Ti], and [Mn] are the contents (mass%) of each element.

Patent Document 1: JP-T-2022-551861A Patent Document 2: JP-A-2014-177662 Patent Document 3: JP-A-2017-179395 Patent Document 4: JP-A-2013-023743 Patent Document 5: WO 2020-054553

The objective of this disclosure is to provide wire rod, non-magnetic steel wire, and stranded wire using non-magnetic steel wire that can be used to produce non-magnetic steel wire while suppressing wire breakage during wire drawing.

The means for solving the above problems include the following aspects.
<1> In mass%,
C: 0.50 to 1.10%,
Si: 0.10-1.00%,
Mn: 10.0-18.0%,
P: 0.050% or less,
S: 0.050% or less,
N: 0.005-0.035%,
Cu: 0 to 0.40%,
Ni: 0 to 0.40%,
Cr: 0-2.50%,
Mo: 0-1.00%,
V: 0 to 0.25%,
Ti: 0 to 0.100%,
Al: 0-0.100%,
Nb: 0 to 0.050%,
Sn: 0 to 0.050%,
B: 0 to 0.0050%,
Bi: 0-0.20%,
Pb: 0 to 0.09%,
Ca: 0 to 0.0100%, and Mg: 0 to 0.0100%,
The balance has a chemical composition of Fe and impurities,
Contains austenite structure,
The relative permeability is 1.100 or less,
In a cross section perpendicular to the longitudinal direction of the wire rod, carbides having a maximum length of 0.5 μm or more at the center of the cross section are 0.05 to 2.00% in terms of area ratio, and the degree of carbon segregation in the center segregation portion is 1.20 or less,
A wire rod, wherein in a cross section parallel to the longitudinal direction and including a central axis of the wire rod, the number average aspect ratio of austenite grains in the austenite structure is less than 1.40.
<2> The wire according to <1>, wherein the chemical composition includes, in mass %, one or more elements selected from the group consisting of the following first, second, and third groups:
(Group 1)
Cu: 0.05 to 0.40%, and Ni: 0.05 to 0.40% or less One or two selected from the group consisting of (second group)
Cr: 0.02-2.50%,
Mo: 0.02-1.00%,
V: 0.002-0.25%,
Ti: 0.005-0.100%,
One or more selected from the group consisting of Al: 0.005 to 0.100%, and Nb: 0.002 to 0.050% (Group 3)
Sn: 0.002-0.050%,
B: 0.0001 to 0.0050%,
Bi: 0.002-0.20%,
Pb: 0.002-0.09%,
<3> The wire rod according to <1> or <2>, wherein the maximum thickness of the carbide is 0.50 μm or less.
<4> The wire rod according to any one of <1> to <3>, wherein the grain size of the austenite grains in the austenite structure is 8.0 μm or more and 14.0 μm or less.
<5> In mass%,
C: 0.50 to 1.10%,
Si: 0.10-1.00%,
Mn: 10.0-18.0%,
P: 0.050% or less,
S: 0.050% or less, and
N: 0.005-0.035%,
Cu: 0 to 0.40%,
Ni: 0 to 0.40%,
Cr: 0-2.50%,
Mo: 0-1.00%,
V: 0 to 0.25%,
Ti: 0 to 0.100%,
Al: 0-0.100%,
Nb: 0 to 0.050%,
Sn: 0 to 0.050%,
B: 0 to 0.0050%,
Bi: 0-0.20%,
Pb: 0 to 0.09%,
Ca: 0 to 0.0100%, and Mg: 0 to 0.0100%,
The balance has a chemical composition of Fe and impurities,
Contains austenite structure,
The relative permeability is 1.100 or less,
In a cross section perpendicular to the longitudinal direction of the steel wire, carbides having a maximum length of 0.5 μm or more at the center of the cross section have an area ratio of 0.05 to 2.00%, and the degree of carbon segregation in a central segregation portion is 1.20 or less,
A steel wire, wherein in a cross section parallel to the longitudinal direction and including a central axis of the steel wire, the number average aspect ratio of austenite grains in the austenite structure is 1.40 or more.
<6> The steel wire according to <5>, wherein the chemical composition includes, in mass %, one or more elements selected from the group consisting of the following first, second, and third groups:
(Group 1)
Cu: 0.05 to 0.40%, and Ni: 0.05 to 0.40% or less One or two selected from the group consisting of (second group)
Cr: 0.02-2.50%,
Mo: 0.02-1.00%,
V: 0.002-0.25%,
Ti: 0.005-0.100%,
One or more selected from the group consisting of Al: 0.005 to 0.100%, and Nb: 0.002 to 0.050% (Group 3)
Sn: 0.002-0.050%,
B: 0.0001 to 0.0050%,
Bi: 0.002-0.20%,
Pb: 0.002-0.09%,
<7> The steel wire according to <5> or <6>, which has a plating layer on a surface thereof.
<8> A stranded wire comprising the steel wire according to any one of <5> to <7>.

This disclosure provides wire rod, non-magnetic steel wire, and stranded wire using non-magnetic steel wire that can be manufactured while suppressing wire breakage during wire drawing.

FIG. 1 is a diagram showing an example of carbides that become the starting points of cracks during wire drawing of a wire rod.

An embodiment that is an example of the present disclosure will be described.
In this specification, a numerical range expressed using "to" means a range that includes the numerical values written before and after "to" as the lower and upper limits. Furthermore, when the numerical values written before and after "to" are followed by "greater than" or "less than," the numerical range does not include these numerical values as the lower or upper limit.
In the numerical ranges described in stages in this specification, the upper limit value of a certain numerical range may be replaced by the upper limit value of another numerical range described in stages, or may be replaced by a value shown in an example.
In the numerical ranges described in stages in this specification, the lower limit value of a certain numerical range may be replaced by the lower limit value of another numerical range described in stages, or may be replaced by a value shown in an example.
The content of an element in the chemical composition may be simply expressed as "amount" (for example, C amount, Si amount, etc.).
With respect to the content of elements in the chemical composition, "%" means "mass %."
Furthermore, the term "process" does not only refer to an independent process, but also includes processes that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

The inventors of the present disclosure have conducted extensive research to find a wire rod and a steel wire that are both non-magnetic and suppressed from breaking during wire drawing, and as a result, have discovered the following findings.
(a) The high Mn content can be utilized to create a metastable austenite structure. However, it is known that metastable austenite undergoes strain-induced martensitic transformation during cold working, making it difficult to maintain low magnetic properties in drawn steel wires such as those used in power transmission cables.
(b) We investigated high carbon and high manganese components as components that can maintain low magnetic properties without causing deformation-induced martensitic transformation even after wire drawing and high strength, and arrived at a component system that maintains low magnetic properties even after wire drawing.
(c) On the other hand, with a high carbon content, carbides are formed in the center, which become the starting point for cracks during the wire drawing process, leading to breakage during the wire drawing process and a decrease in the ductility of the wire. It was effective to keep the area ratio of carbides below 2%.
(d) Furthermore, when there is variation in the solute carbon concentration, such as when the solute carbon concentration is high in the center, wire drawability deteriorates. The precipitation of carbides is effective in reducing variation in the solute carbon concentration.
(e) The wire rod, steel wire, and stranded wire according to the present disclosure were developed under the conditions that allowed for wiredrawability and maintaining non-magnetic properties after wiredrawing.

[Wire rod]
The wire rod according to the present disclosure will be described.
The wire rod according to the present disclosure has, in mass%,
C: 0.50 to 1.10%,
Si: 0.10-1.00%,
Mn: 10.0-18.0%,
P: 0.050% or less,
S: 0.050% or less, and N: 0.005 to 0.035%,
and
The balance has a chemical composition of Fe and impurities,
Contains austenite structure,
The relative permeability is 1.100 or less,
In a cross section perpendicular to the longitudinal direction of the wire rod, carbides having a maximum length of 0.5 μm or more at the center of the cross section are 0.05 to 2.00% in terms of area ratio, and the degree of carbon segregation in the center segregation portion is 1.20 or less,
In a cross section of the wire rod that is parallel to the longitudinal direction and includes a central axis of the wire rod, the number average aspect ratio of austenite grains in the austenite structure is less than 1.40.
Furthermore, the wire rod according to the present disclosure may contain optional elements described below in place of a portion of Fe.

<Chemical composition>
The chemical composition (content of each element) of the wire according to the present disclosure will be described.

C: 0.50-1.10%
Carbon (C) stabilizes austenite and suppresses the deformation-induced martensitic transformation after wire drawing. This results in sufficient non-magnetic properties. If the C content is less than 0.50%, the above effect cannot be fully achieved. On the other hand, if the C content exceeds 1.10%, excessive carbides precipitate. The precipitated carbides become the starting point for cracks during processing. As a result, sufficient workability cannot be achieved. Therefore, the C content is 0.50 to 1.10%.
The lower limit of the C content is preferably 0.60%, more preferably 0.70%, and further preferably 0.80%.
The upper limit of the C content is preferably 1.05%, more preferably 1.03%, and further preferably 1.00%.

Si: 0.10-1.00%
Silicon (Si) has the effect of deoxidizing steel. Si also increases the strength of steel through solid solution strengthening. If the Si content is less than 0.10%, the above effect cannot be fully achieved. On the other hand, if the Si content exceeds 1.00%, wire drawability deteriorates. Therefore, the Si content is 0.10 to 1.00%.
The lower limit of the Si content is preferably 0.15%, more preferably 0.18%, and further preferably 0.20%.
The upper limit of the Si content is preferably 0.90%, more preferably 0.80%, and further preferably 0.70%.

Mn: 10.0-18.0%
Manganese (Mn) stabilizes austenite and suppresses strain-induced martensitic transformation, thereby achieving sufficient non-magnetic properties. If the Mn content is less than 10.0%, the above effects are not fully achieved. On the other hand, if the Mn content exceeds 18.0%, even if soaking, as described below, diffuses and reduces the carbides present in large amounts in the center of the cast slab, it is not possible to sufficiently reduce the area ratio and segregation degree of carbides in the center. Therefore, the Mn content is 10.0 to 18.0%.
The lower limit of the Mn content is preferably 11.0%, more preferably 11.5%, and even more preferably 12.0%.
The upper limit of the Mn content is preferably 17.0%, more preferably 16.5%, and even more preferably 16.0%.

P: 0.050% or less Phosphorus (P) is an impurity. P segregates at the grain boundaries of austenite crystal grains, reducing wiredrawability. If the P content of the wire rod is 0.050% or less, the reduction in workability is suppressed, and the target properties can be obtained by satisfying other requirements.
The upper limit of the P content is preferably 0.045%, more preferably 0.040% or less. The lower limit of the P content is not limited and is preferably 0% (i.e., no P is contained), but from the viewpoint of reducing the dephosphorization cost, it may be more than 0% or may be 0.001% or more.

S: 0.050% or less Sulfur (S) reduces workability. If the S content of the wire rod is 0.050% or less, the target properties can be obtained while satisfying other requirements.
The upper limit of the S content is preferably 0.040%. The lower limit of the S content is not limited, but may be more than 0% or may be 0.001% or more from the viewpoint of reducing the desulfurization cost.

N: 0.005-0.035%
Nitrogen (N) stabilizes austenite and suppresses deformation-induced martensitic transformation, thereby achieving sufficient non-magnetic properties. N also increases the strength of steel through solid solution strengthening. If the N content is less than 0.005%, the above effect cannot be fully achieved. On the other hand, if the N content exceeds 0.035%, defects such as blowholes tend to occur in the steel. This reduces the drawability of the wire rod. Therefore, the N content is 0.005 to 0.35%.
The lower limit of the N content is preferably 0.007%, more preferably 0.010%, and further preferably 0.012%.
The upper limit of the N content is preferably 0.030%, more preferably 0.024%, and further preferably 0.020%.

The wire rod according to the present disclosure may contain, in place of a portion of the Fe, one or more of the following optional elements: Cu, Ni, Cr, Mo, V, Ti, Al, Nb, Sn, B, Bi, Pb, Ca, and Mg. These optional elements may not be included, or may be included within the ranges below. When these optional elements are included, the lower limit of the content may be greater than 0%. Furthermore, these optional elements are divided into the following first to third groups from the standpoint of their effects.

[Group 1] Cu and Ni
The chemical composition of the wire rod according to the present disclosure may further contain one or two elements selected from the above-mentioned Group 1 in place of a portion of Fe. These elements are optional elements, and all of them improve the non-magnetic properties of the steel material and increase the toughness of the steel material. Each element will be described below.

Cu: 0.40% or less Copper (Cu) is an optional element. That is, the Cu content may be 0%.
Cu is an element that stabilizes austenite and improves the non-magnetic properties of the steel material. From the viewpoint of this function, the Cu content may be more than 0%, 0.05% or more, 0.10% or more, or 0.20% or more.
On the other hand, if the Cu content exceeds 0.40%, the wire drawability of the wire rod decreases. From the viewpoint of further improving the wire drawability of the wire rod, the Cu content is 0.40% or less. The Cu content is preferably 0.35% or less.

Ni: 0.40% or less Nickel (Ni) is an optional element. That is, the Ni content may be 0%.
Ni is an element that stabilizes austenite and improves the non-magnetic properties of steel. From the viewpoint of this function, the Ni content may be more than 0%, 0.05% or more, 0.10% or more, or 0.20% or more.
On the other hand, if the Ni content exceeds 0.40%, the wire drawability of the wire rod decreases. From the viewpoint of further improving the wire drawability of the wire rod, the Ni content is 0.40% or less, and more preferably 0.35% or less.

[Group 2] Cr, Mo, V, Ti, Al and Nb
The chemical composition of the wire rod according to the present disclosure may further contain, in place of a portion of Fe, one or more elements selected from the above-mentioned Group 2. These elements are optional elements, and all of them increase the strength of the steel material and the steel wire. Each element will be described below.

Cr: 2.50% or less Chromium (Cr) is an optional element. That is, the Cr content may be 0%.
Cr is an element that forms carbides and increases the strength of steel materials through precipitation strengthening. Cr also stabilizes austenite and improves the non-magnetic properties of steel materials. This results in increased strength and improved non-magnetic properties of wire rods and steel wires. In view of this effect, the Cr content may be more than 0%, 0.02% or more, or 0.05% or more.
On the other hand, if the Cr content exceeds 2.50%, coarse Cr carbides are formed, which reduces the wire drawability of the wire rod. Therefore, the Cr content is 2.50% or less. From the viewpoint of further improving the wire drawability of the wire rod, the Cr content is preferably 2.00% or less.

Mo: 1.00% or less Molybdenum (Mo) is an optional element. That is, the Mo content may be 0%.
Mo is an element that forms carbides and increases the strength of steel materials through precipitation strengthening, and also has the effect of increasing the tensile strength of steel wires obtained after wire drawing.
From this viewpoint, the Mo content of the wire rod may be more than 0% or may be 0.02% or more.
On the other hand, if the Mo content of the wire rod exceeds 1.00%, the above effect saturates and the manufacturing cost of the wire rod increases.
Therefore, the Mo content is preferably in the range of 0.02 to 1.00%, and more preferably 0.04 to 0.90%.

V: 0.25% or less Vanadium (V) is an optional element. That is, the V content may be 0%.
V is an element that forms carbides and nitrides and increases the strength of steel materials through precipitation strengthening. This increases the strength of wire rods and steel wires. From the viewpoint of this effect, the V content may be more than 0%, 0.002% or more, or 0.005% or more.
On the other hand, if the V content exceeds 0.25%, the amount of carbides or carbonitrides increases, resulting in a decrease in wiredrawability. Therefore, the V content is 0.25% or less. From the viewpoint of further improving the wiredrawability of the wire rod, the V content is preferably 0.15% or less.

Ti: 0.100% or less Titanium (Ti) is an optional element. That is, the Ti content may be 0%.
Ti is an element that forms carbides and nitrides to increase the strength of steel materials through precipitation strengthening. This increases the strength of wire rods and steel wires. From the viewpoint of this effect, the Ti content may be more than 0%, 0.005% or more, or 0.007% or more.
On the other hand, if the Ti content exceeds 0.100%, the amount of carbides or carbonitrides increases, resulting in a decrease in wiredrawability. Therefore, the Ti content is 0.100% or less. From the viewpoint of further improving the wiredrawability of the wire rod, the Ti content is preferably 0.050% or less.

Al: 0.100% or less Aluminum (Al) is an optional element. That is, the Al content may be 0%.
Al is an element that forms nitrides and refines austenite grains through a pinning effect. Refining the austenite grains increases the strength of the steel material and the steel wire. Al may be added to reduce the amount of oxygen in the steel wire. In view of this effect, the Al content may be more than 0%, 0.005% or more, or 0.030% or more.
On the other hand, if the Al content exceeds 0.100%, Al nitrides are excessively formed. In this case, the amount of solute N in the steel material decreases, the stability of austenite decreases, and the nonmagnetic properties deteriorate. For this reason, the Al content is 0.100% or less. From the viewpoint of further improving the nonmagnetic properties of the wire rod and steel wire, the Al content is preferably 0.050% or less, and more preferably 0.035% or less.

Nb: 0.050% or less Niobium (Nb) is an optional element. That is, the Nb content may be 0%.
Nb is an element that forms nitrides and refines austenite grains through a pinning effect. Refining austenite grains increases the strength of the steel material. This increases the strength of wire rods and steel wires. In view of this effect, the Nb content may be more than 0%, 0.002% or more, or 0.005% or more.
On the other hand, if the Nb content exceeds 0.050%, the amount of carbides or carbonitrides increases, resulting in a decrease in wire drawability. Therefore, the Nb content is 0.050% or less. From the viewpoint of further improving the wire drawability of the wire rod, the Nb content is preferably 0.030% or less.

[Third Group] Sn, B, Bi, Pb, Ca, and Mg
The chemical composition of the wire rod according to the present disclosure may further contain, in place of a portion of Fe, one or more elements selected from the above-mentioned Group 3. These elements are optional elements, and all of them improve the wire drawability of the wire rod. Each element will be described below.

Sn: 0.050% or less Tin (Sn) is an optional element. That is, the Sn content may be 0%.
Sn is an element that improves wire drawability. From the viewpoint of this function, the Sn content may be more than 0%, 0.002% or more, or 0.005% or more.
On the other hand, if the Sn content exceeds 0.050%, the hot workability deteriorates. Therefore, the Sn content is 0.050% or less. From the viewpoint of further improving the hot workability, the Sn content is preferably 0.030% or less.

B: 0.0050% or less Boron (B) is an optional element. That is, the B content may be 0%.
B is an element that segregates at grain boundaries to increase grain boundary strength, thereby improving the wiredrawability of the steel material. From the viewpoint of this effect, the B content may be more than 0%, 0.0001% or more, or 0.0005% or more.
If the B content exceeds 0.0050%, coarse carbonitrides are likely to be formed in the wire rod, which may deteriorate the non-magnetic properties of the wire rod and steel wire. Therefore, the B content is 0.0050% or less. From the viewpoint of further reducing the electrical resistivity of the steel wire, the B content is preferably 0.0040% or less.

Bi: 0.20% or less Bismuth (Bi) is an optional element. That is, the Bi content may be 0%.
Bi is an element that refines the dendritic structure during solidification. This refines inclusions and improves the wire drawability of the wire rod. From the viewpoint of this effect, the Bi content may be more than 0%, 0.002% or more, or 0.005% or more.
On the other hand, if the Bi content exceeds 0.20%, the hot workability of the steel material decreases. Therefore, the Bi content is 0.20% or less. From the viewpoint of further improving the hot workability, the Bi content is preferably 0.10% or less.

Pb: 0.09% or less Lead (Pb) is an optional element. That is, the Pb content may be 0%.
Pb is an element that improves the wiredrawability of steel. From the viewpoint of this function, the Pb content may be more than 0%, 0.002% or more, or 0.005% or more.
On the other hand, if the Pb content exceeds 0.09%, the hot workability deteriorates. Therefore, the Pb content is 0.09% or less. From the viewpoint of further improving the hot workability, the Pb content is preferably 0.05% or less.

Ca: 0.0100% or less Calcium (Ca) is an optional element. That is, the Ca content may be 0%.
Ca forms Ca sulfides and has the effect of suppressing the coarsening of MnS. By suppressing the coarsening of MnS, cracking during wire drawing can be suppressed, and high-strength steel wire can be produced. From the viewpoint of this effect, the Ca content may be more than 0%, may be 0.0002% or more, or may be 0.0005% or more.
On the other hand, even if the Ca content exceeds 0.0100%, the effect saturates. Furthermore, since a large amount of coarse Ca-based oxides is formed, wire drawability is actually reduced. For this reason, the Ca content is 0.0100% or less. From the viewpoint of further improving the wire drawability of the wire rod, the Ca content is preferably 0.0050% or less.

Mg: 0.0100% or less Magnesium (Mg) is an optional element. That is, the Mg content may be 0%.
Mg dissolves in MnS and has the effect of finely dispersing the MnS. By finely dispersing the MnS, cracking during wire drawing can be suppressed, and high-strength steel wire can be produced. From the viewpoint of this effect, the Mg content may be more than 0%, 0.0002% or more, or 0.0005% or more.
On the other hand, even if the Mg content exceeds 0.0100%, the effect saturates. Furthermore, the formation of oxides actually reduces the wiredrawability. For this reason, the Mg content is 0.0100% or less. From the viewpoint of further improving the wiredrawability of the wire rod, the Mg content is preferably 0.0050% or less.

<Magnetic properties>
Relative magnetic permeability: 1.100 or less The wire according to the present disclosure has a relative magnetic permeability of 1.100 or less. The relative magnetic permeability represents the ratio of the magnetic permeability of a substance to the magnetic permeability of a vacuum μ0 (= 4π × 10-7 [H/m]) as a reference, and is calculated by the following formula.
μr=μ/μ0
(μr: relative magnetic permeability, μ: magnetic permeability, μ0: vacuum magnetic permeability)
The closer the relative magnetic permeability is to 1, the less likely it is to be magnetized, and in the present disclosure, a wire having a relative magnetic permeability of 1.100 or less is considered to be "non-magnetic." The relative magnetic permeability of the wire according to the present disclosure is measured and calculated by the method described in the examples below.

<Metal structure>
Next, the metallographic structure of the wire rod according to the present disclosure will be described. Regarding the parameters described below regarding the metallographic structure of the wire rod, the number-average aspect ratio of austenite grains is a value in a cross section (sometimes referred to as a "longitudinal cross section") parallel to the longitudinal direction of the wire rod, including the central axis of the wire rod, and the other parameters mean values in a cross section (sometimes referred to as a "transverse cross section") perpendicular to the longitudinal direction of the wire rod, unless otherwise specified. The same applies to the parameters regarding the metallographic structure of the steel wire described below.

Austenite structure The wire rod according to the present disclosure includes an austenite structure. The austenite phase is non-magnetic. From the viewpoint of having sufficient non-magnetic properties, the wire rod according to the present disclosure preferably has a high area ratio of the austenite structure, particularly preferably 98.00% or more. However, if the area ratio of the austenite structure is 100.00%, workability will be reduced, so the area ratio of the austenite structure is preferably less than 100.00%.
Other structures (preferably 2.00% or less in total) other than the austenite structure include, for example, ferrite and cementite, which are ferromagnetic at room temperature.

Carbon segregation degree in the central segregation region: 1.20 or less If the carbon segregation degree is high in the central region where the cooling rate is slow during the wire manufacturing process, carbides will precipitate excessively at the grain boundaries. Carbides will become the starting point for cracks during wire drawing. Therefore, if the carbon segregation degree in the central segregation region is high, sufficient wiredrawability will not be obtained. Therefore, the carbon segregation degree in the central segregation region in the cross section of the wire is 1.20 or less.

Area ratio of carbides having a maximum length of 0.5 μm or more in the center (sometimes simply referred to as "carbides" in this disclosure): 0.05 to 2.00%
The center is representative of the carbides that precipitate in the wire manufacturing process because they are most abundant in the center where the cooling rate is slow. When a large amount of carbides precipitate in the center, they often cover the grain boundaries. In this case, the carbides tend to be thick and easily become the starting point of cracks during processing, resulting in insufficient workability. Figure 1 shows an example of carbides (white area) that can become the starting point of cracks during wire drawing. The presence of such plate-like carbides in the center of the wire makes them prone to become the starting point of cracks during wire drawing.
On the other hand, if the area ratio of carbides is less than 0.05%, workability decreases. This is thought to be because the precipitation of part of the solute carbon in the center reduces the variation in solute carbon, improving workability. To obtain sufficient workability, the area ratio of carbides in the center of the cross section of the wire is 0.05 to 2.00%. The area ratio of carbides in the center is preferably 0.07 to 1.90%, and more preferably 0.10 to 1.80%.

Number average aspect ratio of austenite grains: less than 1.40
If the number average aspect ratio of the austenite grains in the longitudinal section of the wire is less than 1.40, it can be said that the wire is in a state where it has not been subjected to processing during the production of the wire, and the wiredrawability can be further improved.

Maximum thickness of carbide: preferably 0.50 μm or less Among carbides, thick cementite precipitated at grain boundaries is particularly the starting point for cracks during processing. By making the maximum thickness of carbide in the cross section of the wire rod preferably 0.50 μm or less, workability can be further improved.

Grain size of austenite grains in the austenite structure: preferably 8.0 μm or more and 14.0 μm or less The grain size of austenite affects strength. In the cross section of the wire rod, if the grain size of the austenite grains in the austenite structure is 8.0 μm or more, an increase in the frequency of nucleation of grain boundary carbides is suppressed, making it difficult for grain boundary carbides to form, and improving workability. If the grain size of the austenite grains in the austenite structure is 14.0 μm or less, coarse grains are not formed, and workability is improved. Therefore, the grain size of the austenite grains in the austenite structure is preferably 8.0 to 14.0 μm.

[Steel wire]
Next, the steel wire according to the present disclosure will be described.
The steel wire according to the present disclosure comprises, in mass %,
C: 0.50 to 1.10%,
Si: 0.10-1.00%,
Mn: 10.0-18.0%,
P: 0.050% or less,
S: 0.050% or less, and
N: 0.005 to 0.035%;
The balance has a chemical composition of Fe and impurities,
Contains austenite structure,
The relative permeability is 1.100 or less,
In a cross section perpendicular to the longitudinal direction of the steel wire, carbides having a maximum length of 0.5 μm or more at the center of the cross section have an area ratio of 0.05 to 2.00%, and the degree of carbon segregation in a central segregation portion is 1.20 or less,
In a cross section of the steel wire that is parallel to the longitudinal direction and includes a central axis thereof, the number average aspect ratio of austenite grains in the austenite structure is 1.40 or more.

The chemical composition of the steel wire according to the present disclosure is the same as that of the wire rod, including any optional elements that may be contained other than the above elements and the contents of each element, and therefore description thereof will be omitted here.
Furthermore, the magnetic properties of the steel wire according to the present disclosure are also the same as those of the wire rod, that is, the relative permeability is 1.100 or less.

The metal structure of the steel wire according to the present disclosure is the same as that of the wire rod, except that the number-average aspect ratio of the austenite grains in the austenite structure in the longitudinal cross section is 1.40 or more.

Number average aspect ratio of austenite grains in the austenite structure of the steel wire: 1.40 or more The steel wire according to the present disclosure has high strength because the number average aspect ratio of the austenite grains is 1.40 or more due to the wiredrawing process.
A high-strength, non-magnetic steel wire can be obtained by satisfying the same requirements as those for the wire rod described above, namely, that in a cross section (transverse section) perpendicular to the longitudinal direction of the steel wire, the area fraction of carbides in the center is 0.05 to 2.00% and the degree of carbon segregation in the central segregation portion is 1.20 or less, except that the number-average aspect ratio of the austenite grains in the austenite structure in the longitudinal section of the steel wire is 1.40 or more. Note that, like the wire rod, the area fraction of the austenite structure of the steel wire is preferably 98.00% or more and less than 100.00%.

Plated wire (alloy-coated) and stranded wire The steel wire of the present disclosure can be coated with a metal such as zinc, a zinc alloy, aluminum, an aluminum alloy, etc. Furthermore, the steel wire of the present disclosure and the alloy-coated steel wire can be bundled or stranded.
Since the steel wire according to the present disclosure has non-magnetic properties, for example, if a stranded wire including the steel wire according to the present disclosure is applied to a power transmission line, the temperature rise of the power transmission line due to electromagnetic induction can be suppressed, and power loss can be reduced.

<Measurement method>
Next, the method for measuring the metal structure will be described.

(carbon segregation degree in the central segregation region)
The degree of carbon segregation is determined using an electron probe microanalyzer (EPMA). The EPMA measures a D/2 mm x D/2 mm area, with a beam diameter of 10 μm and a measurement interval of 10 μm, with D being the wire diameter of the wire, centered at a point within 0.5 mm from the center position of the wire cross section. The carbon concentration of a 50 μm x 50 μm area with a high carbon concentration is calculated from the obtained data. The ratio of the carbon concentration of the 50 μm x 50 μm area to the carbon concentration (average carbon concentration) of the entire D/2 mm x D/2 mm area is defined as the segregation degree. Five locations with high carbon concentrations are selected, and the average value of these segregations is defined as the carbon segregation degree of the central segregation region. The five 50 μm square areas are selected in descending order of carbon concentration, starting with the area with the highest carbon concentration within the measurement range. However, if there are contaminations or pinholes on the measurement surface, a very high carbon concentration will be indicated. In order to exclude such regions, regions where the carbon concentration is three times or more the carbon concentration in the entire range of D/2 mm x D/2 mm are excluded.

(Carbide in the center)
The cross section of steel (wire rod or steel wire) is polished. After polishing, it is washed with alcohol and immediately etched with picral. If the polishing is followed by washing with water or if time passes, etching will become impossible. Etching with picral allows carbides to be more clearly distinguished. Etching with picral varies in the conditions for revealing the structure depending on the number of times the solution is used and the polishing conditions, so the conditions are adjusted each time. For example, the etching is carried out at room temperature for about 60 seconds, and while checking to see if the structure is revealed, the process is carried out by determining whether to return to the polishing process or extend the etching time, depending on the situation.
An image is taken with an SEM at 100x magnification (1.1 mm x 0.8 mm) centered on an area within a radius of 0.5 mm from the center position. The carbides are binarized using image analysis software (e.g., Image-J), and the carbide area ratio is calculated from the ratio to the total number of pixels. Five cross sections are observed, and the average is taken as the carbide area ratio. Note that the measurement of the carbide area ratio targets carbides with a maximum length of 0.5 μm or more.

(area ratio of austenite structure)
The cross section of steel (wire rod or steel wire) is polished. After polishing, it is washed with alcohol and immediately etched with picral. If the polished surface is washed with water or if time passes, etching will become impossible. The austenite structure ratio (area ratio) is measured by observing five cross sections at 100x magnification using an SEM, one field of view each, centered on the surface layer (within 1.5 mm from the surface), the middle layer (within 1 mm from the center at 1/4 D from the surface, assuming the wire diameter is D), and the center (within 1 mm from the center at 1/2 D from the surface). The area ratio of carbide, as well as the area ratios of ferrite, pearlite, bainite, and martensite, are determined in the same manner as above, and these are subtracted from 100% to calculate the area ratio of the austenite structure. In this observation, the ferrite phase is judged as a recessed portion relative to the majority of the austenite phase. Furthermore, the cementite phase is judged as a portion that appears white due to charging up, since it is convex and dispersed relative to the austenite and ferrite phases. Bainite and martensite structures are considered to be structures in which cementite phases are dispersed within ferrite phases.

(Maximum thickness of carbide)
The area within a radius of 0.5 mm from the center of the cross section is observed with an SEM at 100x magnification to identify the location where the carbide is thickest, and the carbide is then photographed at 10,000x magnification. The thickness of the carbide is measured using image analysis software (e.g., Image-J).

(Austenite grain size)
Polish the cross section of steel (wire rod or steel wire). After polishing, clean with alcohol etc. and immediately etch with picral. If you wash with water after polishing or if time passes, etching will no longer be possible.
The region within a radius of 0.5 mm from the center position of the cross section is observed at 500x magnification using an SEM, and the particle size is calculated by quadrature.

(number average aspect ratio of austenite grains)
Polish the longitudinal cross section of steel (wire rod or steel wire). After polishing, clean with alcohol etc. and immediately etch with picral. If you wash with water after polishing or if time passes, etching will no longer be possible.
When the austenite grain size appearing in the longitudinal section is measured in all directions, the largest diameter obtained is defined as the "major diameter," and the direction in which the "major diameter" is obtained is defined as the "major diameter direction." The length of a line segment perpendicular to the major diameter direction that is separated (cut off) by the austenite grain boundary is defined as the "minor diameter." The aspect ratio is defined as "major diameter/minor diameter." An area within a radius of 0.5 mm from the center position of the longitudinal section is observed at 500x magnification using an SEM, and the total aspect ratio of each austenite grain is divided by the number of austenite grains measured to calculate the number-average aspect ratio of the austenite grains.

<Method of manufacturing wire rod and steel wire>
The method for producing the wire rod and steel wire according to the present disclosure is not particularly limited, but an example of a suitable production method will be described below.

(Soaking treatment)
Molten steel having the above-described chemical composition is produced in a steelmaking process, and the molten steel is poured into a mold of a billet caster (continuous casting device) to produce a slab (bloom). After casting, in order to suppress the remaining coarse carbides that could cause breakage during wiredrawing, a soaking treatment is performed, for example, by holding the slab in an atmosphere at 1250°C for 10 hours or more. The soaking treatment is a heat treatment in which the center of the slab is held at a high temperature for a long period of time, for example, about 10 hours, in order to diffuse the carbon that is segregated in large amounts in the center and reduce the degree of segregation. This heating method has a fundamentally different purpose from the heating performed to shape the slab in a typical hot rolling process or to reduce the rolling reaction force (for example, an atmosphere temperature of about 1300°C for thick plates).

(slabbing rolling)
The slab is heated to 1000-1250°C, and then bloomed into a billet, after which it is allowed to cool. By heating the slab to a relatively high temperature of 1000-1250°C, it is possible to reduce the amount of carbide in the center.

(Wire rod rolling)
The steel slab is rolled to obtain a rolled wire rod. The heating temperature of the steel slab before rolling is 1000°C to 1250°C, and the holding time is more than 10 to 150 minutes. If the heating temperature of the steel slab before rolling is less than 1000°C, the carbides generated in the center during casting of the slab (bloom) are not sufficiently dissolved, and many coarse carbides that could cause breakage during wire drawing remain in the center. In addition, by increasing the reheating temperature before wire rolling, the austenite grain size becomes coarse, which has the effect of suppressing the remaining coarse carbides that could cause breakage during wire drawing.

The finish rolling temperature should be 800°C or higher. If the finish rolling temperature is less than 800°C, the number-average aspect ratio of the austenite grains is likely to exceed 1.40. Furthermore, if finish rolling is performed at an even lower temperature, the amount of carbides that precipitate in the center is likely to increase.

By cooling the central portion after finish rolling at 5.0°C/sec or more, the carbide content in the central portion can be reduced to 0.05 to 2.00%. To achieve a cooling rate of 5.0°C/sec or more in the central portion, the cooling rate in the surface layer is set to 7.0°C/sec or more. If the cooling rate in the surface layer is less than 7.0°C/sec, the amount of carbide precipitated in the central portion tends to be high.
If the cooling rate in the surface layer exceeds 25.0° C./second, the amount of carbide precipitated in the center tends to be excessively low.
Each temperature is measured using a radiation thermometer.

Through the above process, it is possible to produce the wire rod according to the present disclosure in which carbide segregation in the center is suppressed. Furthermore, when producing steel billets by continuous casting, center segregation may be suppressed by soft reduction.

The wire diameter (diameter) of the wire rod according to the present disclosure is not particularly limited, but by making the diameter smaller, it is possible to ensure a sufficient hot rolling area reduction rate from the billet to the wire rod, and by dissolving and promoting the dispersion of coarse carbides formed in the center during the casting of the bloom, it is possible to reduce the coarse carbides that could cause breakage during the subsequent wire drawing process. For example, when hot rolling a 122 mm square billet, the upper limit of the wire diameter that is effective for ensuring a sufficient area reduction rate and dispersing the coarse carbides in the center is approximately 10 mm. Hot rolling to a diameter of 3.5 mm or less to achieve this effect increases rolling costs, so the lower limit of the wire diameter is approximately 3.5 mm.

Furthermore, by subjecting the obtained wire rod to wire drawing, the steel wire according to the present disclosure can be manufactured.
The wire diameter (diameter) of the steel wire is not particularly limited and is, for example, 2.0 mm or more and 5.0 mm or less. When the diameter of the steel wire is 3.0 mm or more, the wire drawing process can be performed more stably when the steel wire is obtained by wire drawing.

Furthermore, by forming a stranded wire using the steel wire according to the present disclosure, the stranded wire according to the present disclosure can be manufactured.

<Application>
The applications of the wire rod and steel wire according to the present disclosure are not particularly limited. Because the steel wire according to the present disclosure is high-strength and non-magnetic, by applying a stranded wire including the steel wire according to the present disclosure as a reinforcing wire for a power transmission line, for example, the temperature rise of the power transmission line due to electromagnetic induction can be suppressed, which can contribute to suppressing power loss (power transmission loss).

The wire rod, steel wire, and stranded wire of the present disclosure will be explained in more detail below using examples. However, these examples do not limit the wire rod, steel wire, and stranded wire of the present disclosure.

Example 1
Steel materials having the chemical compositions (unit: mass%) shown in Table 1 were prepared, and wire rods and steel wires were manufactured by the methods (conditions) shown in Table 2. The notation "-" in Table 1 indicates that the content of the element in question is at the impurity level, and it can be determined that the element is not substantially contained. The same applies to the notation "-" in Table 4 described below. The remainder of the chemical compositions in Tables 1 and 4 is Fe and impurities.

 

After casting, the slab was subjected to a soaking heat treatment at 1250°C for 12 hours.

The metal structure of the manufactured wire rod and steel wire was measured using the method described above.

If the wire material could be drawn to the steel wire diameter shown in Table 2 and the tensile strength was obtained in the subsequent tensile test, it was rated as "Y". If it could not be drawn to the steel wire diameter shown in Table 2 or the wire broke during the subsequent tensile test, it was rated as "N".

Furthermore, the magnetic properties of the wire rod and steel wire were evaluated based on their relative magnetic permeability. Relative magnetic permeability was measured using a vibrating sample type automatic magnetization measuring device (BHV-50, manufactured by Riken Denshi Co., Ltd.). At room temperature in the air, the wire was magnetized from a demagnetized state to a maximum magnetic field of 15 kOe, then magnetized negatively to a maximum magnetic field of -15 kOe, and then further magnetized to a maximum magnetic field of 15 kOe. Relative magnetic permeability was calculated using the magnetic field strength and magnetic polarization in the range of 5 kOe or above. In this disclosure, a relative magnetic permeability of 1.100 or less is considered "non-magnetic."

The results are shown in Tables 3A and 3B. Note that the γ fraction refers to the area fraction of austenite structure, and the γ grain size refers to the grain size of the austenite grains. Underlined values indicate values outside the scope of this disclosure.

 

The wire rods Nos. 1-1A to 1-5A satisfy the requirements of the present disclosure, and are both non-magnetic and prevent breakage during wire drawing.
The wire rods Nos. 1-1B to 1-4B had excessive or insufficient amounts of carbides, and were broken during wire drawing.
The wire rod No. 1-5B had an austenite grain number average aspect ratio of more than 1.40, and was broken during wire drawing.

Steels 2 to 18 with the chemical compositions shown in Table 4 were used to manufacture wire rods and steel wires using the same method as manufacturing condition A, and evaluations were carried out in the same manner as described above. The results are shown in Table 5. The underlines in Tables 4 and 5 indicate results outside the scope of this disclosure.

 

 

 

The wire rods Nos. 2A to 11A and 19A to 21A satisfy the requirements of the present disclosure, and are both non-magnetic and prevent breakage during wire drawing.
No. 12B had an excessively high C content, which resulted in a large amount of carbide precipitation, poor workability, and wire breakage during wire drawing.
In No. 13B, the C content was too low, the austenite was not stable, and the steel wire after wiredrawing did not become nonmagnetic. In addition, the steel wire broke before the transition from uniform elongation to local elongation occurred during the tensile test, so the tensile strength could not be measured.
No. 14B had an excessively high Si content, which resulted in poor workability and wire breakage during wire drawing.
In No. 16B, the Mn content was too low, the austenite stability of the wire rod was low, and the steel wire after wire drawing did not become nonmagnetic. In addition, the steel wire broke during the tensile test, so the tensile strength could not be measured.
No. 17B had an excessively high N content, which resulted in poor workability and wire breakage during wire drawing.
In No. 18B, the N content was too low, the austenite was not stable, and the steel wire after wiredrawing did not become nonmagnetic. In addition, the steel wire broke before the transition from uniform elongation to local elongation occurred during the tensile test, so the tensile strength could not be measured.

[Note]
<1> In mass%,
C: 0.50 to 1.10%,
Si: 0.10-1.00%,
Mn: 10.0-18.0%,
P: 0.050% or less,
S: 0.050% or less, and
N: 0.005 to 0.035%;
The balance has a chemical composition of Fe and impurities,
In a cross section perpendicular to the longitudinal direction of the wire rod, the austenite structure has an area ratio of 98.00% or more and less than 100.00%, the carbide in the central portion has an area ratio of 0.05 to 2.00%, and the degree of carbon segregation in the central segregation portion is 1.20 or less,
A wire rod, wherein an average aspect ratio of austenite grains in the austenite structure is less than 1.40 in a cross section parallel to the longitudinal direction and including a central axis of the wire rod.
<2> In mass%,
C: 0.50 to 1.10%,
Si: 0.10-1.00%,
Mn: 10.0-18.0%,
P: 0.050% or less,
S: 0.050% or less, and
N: 0.005 to 0.035%;
Furthermore, it contains one or more selected from the group consisting of the following first, second, and third groups:
The balance has a chemical composition of Fe and impurities,
(Group 1)
Cu: 0.40% or less, and Ni: 0.40% or less One or two selected from the group consisting of (second group)
Cr: 2.50% or less,
Mo: 1.00% or less,
V: 0.25% or less,
Ti: 0.100% or less,
Al: 0.100% or less, and Nb: 0.050% or less One or more selected from the group consisting of (Group 3)
Sn: 0.050% or less,
B: 0.0050% or less,
Bi: 0.20% or less,
one or more elements selected from the group consisting of Pb: 0.09% or less, and Ca: 0.0100% or less. In a cross section perpendicular to the longitudinal direction of the wire rod, the austenite structure has an area ratio of 98.00% or more and less than 100.00%, the carbide in the center portion has an area ratio of 0.05 to 2.00%, and the degree of carbon segregation in the center segregation portion is 1.20 or less,
A wire rod, wherein an average aspect ratio of austenite grains in the austenite structure is less than 1.40 in a cross section parallel to the longitudinal direction and including a central axis of the wire rod.
<3> The wire according to <1> or <2>, wherein the maximum thickness of the carbide is 0.50 μm or less.
<4> The wire rod according to any one of <1> to <3>, wherein the grain size of the austenite grains in the austenite structure is 8.0 μm or more and 14.0 μm or less.
<5> In mass%,
C: 0.50 to 1.10%,
Si: 0.10-1.00%,
Mn: 10.0-18.0%,
P: 0.050% or less,
S: 0.050% or less, and
N: 0.005 to 0.035%;
The balance has a chemical composition of Fe and impurities,
In a cross section perpendicular to the longitudinal direction of the steel wire, the austenite structure has an area ratio of 98.00% or more and less than 100.00%, the carbide in the central portion has an area ratio of 0.05 to 2.00%, and the degree of carbon segregation in the central segregation portion is 1.20 or less,
A steel wire, wherein in a cross section parallel to the longitudinal direction and including a central axis of the steel wire, the average aspect ratio of austenite grains in the austenite structure is 1.40 or more.
<6> In mass%,
C: 0.50 to 1.10%,
Si: 0.10-1.00%,
Mn: 10.0-18.0%,
P: 0.050% or less,
S: 0.050% or less, and
N: 0.005 to 0.035%;
Furthermore, it contains one or more selected from the group consisting of the following first, second, and third groups:
The balance has a chemical composition of Fe and impurities,
(Group 1)
Cu: 0.40% or less, and Ni: 0.40% or less One or two selected from the group consisting of (second group)
Cr: 2.50% or less,
Mo: 1.00% or less,
V: 0.25% or less,
Ti: 0.100% or less,
Al: 0.100% or less, and Nb: 0.050% or less One or more selected from the group consisting of (Group 3)
Sn: 0.050% or less,
B: 0.0050% or less,
Bi: 0.20% or less,
Pb: 0.09% or less, and one or more elements selected from the group consisting of Ca: 0.0100% or less, with the balance being Fe and impurities,
In a cross section perpendicular to the longitudinal direction of the steel wire, the austenite structure has an area ratio of 98.00% or more and less than 100.00%, the carbide in the central portion has an area ratio of 0.05 to 2.00%, and the degree of carbon segregation in the central segregation portion is 1.20 or less,
A steel wire, wherein in a cross section parallel to the longitudinal direction and including a central axis of the steel wire, the average aspect ratio of austenite grains in the austenite structure is 1.40 or more.
<7> The steel wire according to <5> or <6>, having a plating layer on the surface.
<8> A stranded wire comprising the steel wire according to any one of <5> to <7>.

The disclosure of Japanese Patent Application No. 2024-059232, filed April 1, 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated.

Claims (8)

In mass%,
C: 0.50 to 1.10%,
Si: 0.10-1.00%,
Mn: 10.0-18.0%,
P: 0.050% or less,
S: 0.050% or less,
N: 0.005-0.035%,
Cu: 0 to 0.40%,
Ni: 0 to 0.40%,
Cr: 0-2.50%,
Mo: 0-1.00%,
V: 0 to 0.25%,
Ti: 0 to 0.100%,
Al: 0-0.100%,
Nb: 0 to 0.050%,
Sn: 0 to 0.050%,
B: 0 to 0.0050%,
Bi: 0-0.20%,
Pb: 0 to 0.09%,
Ca: 0 to 0.0100%, and Mg: 0 to 0.0100%,
The balance has a chemical composition of Fe and impurities,
Contains austenite structure,
The relative permeability is 1.100 or less,
In a cross section perpendicular to the longitudinal direction of the wire rod, carbides having a maximum length of 0.5 μm or more at the center of the cross section are 0.05 to 2.00% in terms of area ratio, and the degree of carbon segregation in the center segregation portion is 1.20 or less,
A wire rod, wherein in a cross section parallel to the longitudinal direction and including a central axis of the wire rod, the number average aspect ratio of austenite grains in the austenite structure is less than 1.40. 2. The wire according to claim 1, wherein the chemical composition includes, in mass %, one or more elements selected from the group consisting of the following first, second, and third groups:
(Group 1)
Cu: 0.05 to 0.40%, and Ni: 0.05 to 0.40% or less One or two selected from the group consisting of (second group)
Cr: 0.02-2.50%,
Mo: 0.02-1.00%,
V: 0.002-0.25%,
Ti: 0.005-0.100%,
One or more selected from the group consisting of Al: 0.005 to 0.100%, and Nb: 0.002 to 0.050% (Group 3)
Sn: 0.002-0.050%,
B: 0.0001 to 0.0050%,
Bi: 0.002-0.20%,
Pb: 0.002-0.09%,
One or more selected from the group consisting of Ca: 0.0002 to 0.0100%, and Mg: 0.0002 to 0.0100% Wire rod according to claim 1 or claim 2, wherein the maximum thickness of the carbide is 0.50 μm or less. The wire rod according to any one of claims 1 to 3, wherein the grain size of the austenite grains in the austenite structure is 8.0 μm or more and 14.0 μm or less. In mass%,
C: 0.50 to 1.10%,
Si: 0.10-1.00%,
Mn: 10.0-18.0%,
P: 0.050% or less,
S: 0.050% or less, and
N: 0.005-0.035%,
Cu: 0 to 0.40%,
Ni: 0 to 0.40%,
Cr: 0-2.50%,
Mo: 0-1.00%,
V: 0 to 0.25%,
Ti: 0 to 0.100%,
Al: 0-0.100%,
Nb: 0 to 0.050%,
Sn: 0 to 0.050%,
B: 0 to 0.0050%,
Bi: 0-0.20%,
Pb: 0 to 0.09%,
Ca: 0 to 0.0100%, and Mg: 0 to 0.0100%,
The balance has a chemical composition of Fe and impurities,
Contains austenite structure,
The relative permeability is 1.100 or less,
In a cross section perpendicular to the longitudinal direction of the steel wire, carbides having a maximum length of 0.5 μm or more at the center of the cross section have an area ratio of 0.05 to 2.00%, and the degree of carbon segregation in a central segregation portion is 1.20 or less,
A steel wire, wherein in a cross section parallel to the longitudinal direction and including a central axis of the steel wire, the number average aspect ratio of austenite grains in the austenite structure is 1.40 or more. The steel wire according to claim 5, wherein the chemical composition includes, in mass %, one or more elements selected from the group consisting of the following first, second, and third groups:
(Group 1)
Cu: 0.05 to 0.40%, and Ni: 0.05 to 0.40% or less One or two selected from the group consisting of (second group)
Cr: 0.02-2.50%,
Mo: 0.02-1.00%,
V: 0.002-0.25%,
Ti: 0.005-0.100%,
One or more selected from the group consisting of Al: 0.005 to 0.100%, and Nb: 0.002 to 0.050% (Group 3)
Sn: 0.002-0.050%,
B: 0.0001 to 0.0050%,
Bi: 0.002-0.20%,
Pb: 0.002-0.09%,
One or more selected from the group consisting of Ca: 0.0002 to 0.0100%, and Mg: 0.0002 to 0.0100% The steel wire according to claim 5 or claim 6, which has a plating layer on its surface. A stranded wire comprising the steel wire described in any one of claims 5 to 7.