JP7230669B2 - Steel wire and aluminum-coated steel wire - Google Patents

Description

The present disclosure relates to steel wire and aluminized steel wire.

An aluminum conductor steel-reinforced cable (hereinafter sometimes referred to as "ACSR") used for power transmission lines and the like is a cable using aluminum as a conductor. ACSR generally has a structure in which a galvanized steel wire single or stranded wire is used as a core material and an aluminum wire is twisted on the outside.
When an ACSR with such a structure is used in a high-humidity area such as a coastal area, rainwater or the like is used as an electrolyte, and zinc corrodes at the contact points between zinc and aluminum, which have different electrode potentials. and aluminum come into contact with each other and the aluminum corrodes. Therefore, in these regions, aluminum-clad steel wire (hereinafter sometimes referred to as "AC wire") is used instead of galvanized steel wire.

The AC wire is a JIS standard piano steel wire such as SWRS72B or SWRS82B whose outer circumference is coated with aluminum. Using the AC line as a component of the ACSR improves power transmission efficiency because the current also flows through the AC line. Therefore, it is required to reduce the electrical resistance of the AC line.
For example, Patent Document 1 aims to provide a method for manufacturing an AC wire used to mechanically reinforce an Al conductor of a power transmission cable. Si: 1.0 to 1.5 wt%, Mn: 0.4 to 0.6 wt%, Cr: 0.2 to 0.7 wt%, S: 0.015 wt% or less, P: 0.015 % by weight of the steel wire is first plated in a galvanizing tank and then secondarily plated in a zinc-aluminum plating tank to form an iron-zinc-aluminum alloy layer comprising an iron-zinc-aluminum alloy layer and a zinc-aluminum alloy layer. A method for producing a high-strength plated steel wire for reinforcing overhead power transmission lines which satisfies 40% to 60% of the total thickness of the wire and has low electrical resistance is disclosed.

On the other hand, the current flows not only in the aluminum part but also in the steel wire part. Regarding steel materials, there are cases where an improvement in electrical conductivity is required.
For example, Patent Document 2 describes a steel material for electrical parts that can perform cold forging with good dimensional accuracy and can ensure excellent electrical conductivity. %), Si: 0.1% or less (not including 0%), Mn: 0.1 to 0.5%, P: 0.02% or less (including 0%), S: 0.02 % or less (including 0%), Al: 0.01% or less (including 0%), N: 0.005% or less (including 0%), O: 0.02% or less (including 0%) and has a ferrite single-phase metallographic structure, and is excellent in cold forgeability and electrical conductivity.

JP 2016-076482 A JP 2003-226938 A

However, with the techniques disclosed in Patent Document 1 or Patent Document 2, it is difficult to obtain a steel wire that achieves both a reduction in electrical resistivity and an improvement in tensile strength.

In order to solve such problems, an object of the present disclosure is to provide a steel wire capable of achieving both a reduction in electrical resistivity and an improvement in tensile strength, and an aluminum-coated steel wire comprising the steel wire. It is.

Means for solving the above problems include the following aspects.
[1] The chemical composition is C: 0.40% or more and 1.10% or less in mass%,
Si: 0.005% or more and 0.15% or less,
Mn: 0.10% or more and 0.30% or less,
Cr: 0.003% or more and less than 0.30%,
Mo: 0.01% or more and 0.20% or less,
P: 0.030% or less,
S: 0.030% or less,
N: 0.0060% or less, and the balance: Fe and impurity elements, and the total of Mo content and Cr content is 0.14% or more,
having a perlite structure,
C dissolved in ferrite is 500 ppm or less on a mass basis,
When the diameter of the steel wire is D, the average lamella of the pearlite structure in a cross section parallel to the longitudinal direction of the steel wire and including the central axis in a region within D/10 from the central axis of the steel wire A steel wire having an interval of 50 nm or less and a degree of accumulation of ferrite in the <110> orientation parallel to the longitudinal direction of the steel wire of 2.0 or more.
[2] The chemical composition is Al: 0.070% or less in mass%,
Ti: 0.050% or less,
Nb: 0.050% or less,
V: 0.10% or less,
Cu: 0.50% or less,
Ni: 0.50% or less,
Ca: 0.0040% or less,
Mg: 0.0040% or less, and B: 0.0030% or less,
The steel wire according to [1], further satisfying one or more selected from the group consisting of:
[3] The above [1] or [2], wherein the area ratio of the pearlite structure in a region within D/10 from the central axis in the cross section perpendicular to the longitudinal direction of the steel wire is 90% or more. steel wire.
[4] The chemical composition, in mass %,
Al: 0.005% or more and 0.070% or less, and
Ti: 0.005% or more and 0.050% or less, Nb: 0.002% or more and 0.050% or less, and V: 0.002% or more and 0.10% or less, one or two selected from the group consisting of The steel wire according to [2] or [3] above, which satisfies the above requirements.
[5] The chemical composition, in mass %,
Cu: 0.05% or more and 0.50% or less, and Ni: 0.05% or more and 0.50% or less, any one or two selected from the group consisting of [2] to [4] or the steel wire according to one.
[6] The chemical composition, in mass %,
Ca: 0.0002% or more and 0.0040% or less, and Mg: 0.0002% or more and 0.0040% or less, any one or two selected from the group consisting of [2] to [5] or the steel wire according to one.
[7] The chemical composition, in mass %,
B: The steel wire according to any one of [2] to [6], satisfying 0.0001% or more and 0.0030% or less.
[8] An aluminum-coated steel wire comprising the steel wire according to any one of [1] to [7] and an aluminum-containing layer coating at least part of the steel wire.

ADVANTAGE OF THE INVENTION According to this disclosure, the aluminum coated steel wire provided with the steel wire and the said steel wire which can make both reduction of an electrical resistivity and improvement of tensile strength compatible is provided.

In this specification, a numerical range represented by "to" means a range including the numerical values before and after "to" as lower and upper limits.
In this specification, "%" and "ppm" indicating the contents of components (elements) are based on mass.
In the numerical ranges described stepwise in this specification, the upper limit or lower limit of a certain stepwise numerical range may be replaced with the upper or lower limit of another stepwise numerical range. , may also be replaced by the values shown in the examples.

[Steel wire]
The steel wire of this embodiment is
The chemical composition is C: 0.40% or more and 1.10% or less in mass%,
Si: 0.005% or more and 0.15% or less,
Mn: 0.10% or more and 0.30% or less,
Cr: 0.003% or more and less than 0.30%,
Mo: 0.01% or more and 0.20% or less,
P: 0.030% or less,
S: 0.030% or less,
N: 0.0060% or less, and the balance: Fe and impurity elements, and the total of Mo content and Cr content is 0.14% or more,
having a perlite structure,
C dissolved in ferrite is 500 ppm or less on a mass basis,
When the diameter of the steel wire is D, the average lamella of the pearlite structure in a cross section parallel to the longitudinal direction of the steel wire and including the central axis in a region within D/10 from the central axis of the steel wire The interval is 50 nm or less, and the degree of integration of the <110> orientation parallel to the longitudinal direction of the steel wire of ferrite is 2.0 or more.
In addition, the chemical composition of the steel wire of the present embodiment is Al: 0.070% or less in mass%,
Ti: 0.050% or less,
Nb: 0.050% or less,
V: 0.10% or less,
Cu: 0.50% or less,
Ni: 0.50% or less,
Ca: 0.0040% or less,
Mg: 0.0040% or less, and B: 0.0030% or less,
One or more selected from the group consisting of may be further satisfied.

The steel wire of this embodiment has excellent tensile strength and reduced electrical resistivity.
In this specification, the electrical resistivity of the steel wire means the electrical resistivity of the steel wire in the longitudinal direction at room temperature (for example, 20°C).
As used herein, the tensile strength of a steel wire means the longitudinal tensile strength of the steel wire at room temperature (eg, 20°C).

The aforementioned effects of the steel wire of the present embodiment (that is, improvement in tensile strength and reduction in electrical resistivity) are achieved by the combination of the chemical composition and the metallographic structure.
For example, in the chemical composition of the steel wire according to the present embodiment, the contents of Si, Mn, Cr, Mo, etc. are reduced below the upper limits of the contents of each element. This reduces the electrical resistivity. In addition, the tensile strength is improved by containing 0.40% or more of C and having an average lamellar spacing of 50 nm or less in the central portion (the region within D/10 from the central axis). These configurations achieve an improvement in tensile strength and a reduction in electrical resistivity of the steel wire.

<Chemical Composition of Steel Wire>
The chemical composition of the steel wire according to this embodiment will be described below.
In the chemical composition of the steel wire according to the present embodiment, the essential elements are C: 0.40% or more and 1.10% or less, Si: 0.005% or more and 0.15% or less, Mn: 0.10% or more and 0 .30% or less, Cr: 0.003% or more and less than 0.30%, Mo: 0.01% or more and 0.20% or less, and the impurity elements are P: 0.030% or less, S: 0.030% % or less, N: 0.0060% or less, and optional elements are Al: 0.070% or less, Ti: 0.050% or less, Nb: 0.050% or less, V: 0.10% or less, Cu : 0.50% or less, Ni: 0.50% or less, Ca: 0.0040% or less, Mg: 0.0040% or less, B: 0.0030% or less, and the balance is Fe and impurity elements (P , S and N), and the total content of Mo and Cr is 0.14% or more.
Hereinafter, the chemical composition of the steel wire according to this embodiment may be referred to as "the chemical composition in this embodiment". The content of each element in the chemical composition in this embodiment will be described below.

C: 0.40-1.10%
C is an effective element for increasing the tensile strength of steel wire. If the C content is less than 0.40%, the tensile strength of the steel wire may be insufficient. Therefore, the C content is 0.40% or more. The C content is preferably 0.45% or more.
On the other hand, if the C content exceeds 1.10%, the cementite fraction may increase and the electrical resistivity of the steel wire may decrease. Therefore, the C content is 1.10% or less. The C content is preferably 1.05% or less, more preferably 1.00% or less.

Si: 0.005-0.15%
Si is an element effective for increasing the tensile strength of a steel wire through solid-solution strengthening, and is also an element necessary as a deoxidizing agent. However, if the Si content is less than 0.005%, these Si addition effects may not be sufficient. Therefore, the Si content is 0.005% or more. From the viewpoint of more stably receiving these Si addition effects, the Si content is preferably 0.01% or more.
On the other hand, Si is an element that increases the electrical resistivity of the steel wire. If the Si content exceeds 0.15%, the electrical resistivity of the steel wire may become excessively high. Therefore, the Si content is 0.15% or less. The Si content is preferably 0.10% or less, more preferably 0.070% or less.

Mn: 0.10-0.30%
Mn is an element that acts to increase the tensile strength of the steel wire. Mn is also an element that prevents hot embrittlement during wire rod rolling by fixing S in steel as MnS. However, if the Mn content is less than 0.10%, these effects may not be sufficient. Therefore, the Mn content is 0.10% or more. Furthermore, in order to ensure the tensile strength of the steel wire and prevent hot shortness at a higher level, the Mn content is preferably 0.13% or more, more preferably 0.15% or more. be.
On the other hand, Mn has the effect of increasing the electrical resistivity of the steel wire. Therefore, if the Mn content exceeds 0.30%, the electrical resistivity of the steel wire may become excessively high. Therefore, the Mn content is 0.30% or less. The Mn content is preferably 0.25% or less.

Cr: 0.003 to less than 0.30% Cr is an element that improves hardenability. Therefore, it is an element that increases the area ratio of the pearlite structure and improves the tensile strength by combined addition with Mo, which will be described later. Cr is also an element that reduces the lamellar spacing of the pearlite structure and increases the tensile strength of the steel wire. To obtain this effect, the Cr content must be 0.003% or more. Cr content is more preferably 0.01% or more. More preferably, it is 0.05% or more.
If the Cr content exceeds 0.30%, the electrical resistivity of the steel wire may become excessively high. The reason for this is that Cr may reduce the electrical resistivity when manufactured under manufacturing conditions in which Cr is not sufficiently distributed to ferrite during pearlite transformation. The Cr content is 0.30% or less from the viewpoint of suppressing an excessive increase in electrical resistivity of the steel wire. Cr content is more preferably 0.25% or less.

Mo: 0.01-0.20%
Mo is an element that improves hardenability. Therefore, it is an element that increases the area ratio of the pearlite structure and improves the tensile strength by combined addition with Cr described above. In order to obtain this effect, it is necessary to make it 0.01% or more.
On the other hand, if the Mo content exceeds 0.20%, the hardenability of the wire may become excessively high. In this case, the pearlite transformation during patenting may be insufficient, the area ratio of the pearlite structure may decrease, and the torsional properties after wire drawing may decrease. From the viewpoint of steel wire manufacturability, the Mo content is 0.20% or less. More preferably, the Mo content is 0.16% or less.

Mo+Cr: 0.14% or more From the viewpoint of exhibiting the effect of combined addition of Mo and Cr, the total content of Mo and Cr must be 0.14% or more in mass %. The sum of Mo content and Cr content is preferably 0.15% or more, more preferably 0.17% or more.
The upper limit of the sum of Mo content and Cr content is the sum of the upper limits of each element, that is, less than 0.50%. From the viewpoint of pearlite area ratio, the upper limit of the sum of Mo content and Cr content may be 0.40% or less, or 0.35% or less.

P: 0.030% or less P is an element that segregates at grain boundaries of steel to increase electrical resistivity. If the P content exceeds 0.030%, the electrical resistivity of the steel wire may become excessively high. Therefore, the P content is 0.030% or less. From the viewpoint of further reducing the electrical resistivity of the steel wire, the P content is preferably 0.025% or less, more preferably 0.020% or less.
However, from the viewpoint of reducing the production cost (dephosphorization cost), the P content may be more than 0%, may be 0.0005% or more, or may be 0.0010% or more. .

S: 0.030% or less S is an element that increases the electrical resistivity of the steel wire. If the S content exceeds 0.030%, the electrical resistivity of the steel wire may become excessively high. Therefore, the S content is 0.030% or less. From the viewpoint of further reducing the electrical resistivity of the steel wire, the S content is preferably 0.020% or less, more preferably 0.015% or less.
However, from the viewpoint of reducing the production cost (desulfurization cost), the S content may be more than 0%, 0.002% or more, or 0.005% or more.

N: 0.0060% or less N is an element that increases the electrical resistivity of the steel wire. Therefore, if the N content exceeds 0.0060%, the electrical resistivity of the steel wire may become excessively high. Therefore, the N content is 0.0060% or less. From the viewpoint of further reducing the electrical resistivity of the steel wire, the N content is preferably 0.0050% or less.
N is also an element that increases the tensile strength of the steel wire by fixing dislocations during cold wire drawing. From the viewpoint of such effects, the N content may be greater than 0%, may be 0.0010% or more, or may be 0.0020% or more.

Al: 0.070% or less Al is an arbitrary element. That is, the Al content may be 0%.
Al is an element that has a deoxidizing action, and Al is an element that forms nitrides in the steel wire and refines the austenite grain size to reduce the pearlite block grain size. Al may be added to reduce the amount of oxygen in the steel wire. From the viewpoint of such action, the Al content may be greater than 0%, may be 0.005% or more, or may be 0.030% or more.
On the other hand, if the Al content exceeds 0.070%, the electrical resistivity of the steel wire may become excessively high. The reason for this is thought to be that when the Al content exceeds 0.070%, coarse oxide-based inclusions are excessively likely to be formed in the steel wire. Therefore, the Al content is 0.070% or less. From the viewpoint of further suppressing the electrical resistivity of the steel wire, the Al content is preferably 0.050% or less, more preferably 0.035% or less.

Ti: 0.050% or less Ti is an arbitrary element. That is, the Ti content may be 0%.
Ti is an element that forms carbides or carbonitrides in the steel wire to refine the austenite grain size, thereby reducing the pearlite block grain size. This improves the ductility of the steel wire. From the viewpoint of such actions, the Ti content may be greater than 0%, may be 0.005% or more, or may be 0.007% or more.
On the other hand, if the Ti content exceeds 0.050%, the amount of carbides or carbonitrides becomes large and the grain size of the austenite becomes too fine, resulting in poor hardenability and low tensile strength. Therefore, the Ti content is 0.050% or less. From the viewpoint of further reducing the electrical resistivity of the steel wire, the Ti content is preferably 0.030% or less.

Nb: 0.050% or less Nb is an arbitrary element. That is, the Nb content may be 0%.
Nb is an element that forms carbides or carbonitrides in the steel wire to refine the austenite grain size, thereby reducing the pearlite block grain size. This improves the ductility of the steel wire. From the viewpoint of such action, the Nb content may be greater than 0%, may be 0.002% or more, or may be 0.005% or more.
On the other hand, if the Nb content exceeds 0.050%, the amount of carbides or carbonitrides becomes large and the grain size of the austenite becomes too fine, resulting in poor hardenability and low tensile strength. Therefore, the Nb content is 0.050% or less. From the viewpoint of further reducing the electrical resistivity of the steel wire, the Nb content is preferably 0.030% or less.

V: 0.10% or less V is an arbitrary element. That is, the V content may be 0%.
V is an element that forms carbides or carbonitrides in the steel wire to refine the austenite grain size, thereby reducing the pearlite block grain size. This improves the ductility of the steel wire. From the viewpoint of such action, the V content may be greater than 0%, may be 0.002% or more, or may be 0.005% or more.
On the other hand, if the V content exceeds 0.10%, the amount of carbides or carbonitrides becomes large and the grain size of the austenite becomes too fine, resulting in poor hardenability and low tensile strength. Therefore, the V content is 0.10% or less. From the viewpoint of further reducing the electrical resistivity of the steel wire, the V content is preferably 0.080% or less.

From the viewpoint of further improving the ductility of the steel wire, the steel wire according to the present embodiment has a chemical composition, in mass%, of Al: 0.005% or more and 0.070% or less, and Ti: 0.005%. % or more and 0.050% or less, Nb: 0.002% or more and 0.05% or less, and V: 0.002% or more and 0.10% or less. is preferred.

Cu: 0.50% or less Cu is an arbitrary element. That is, the Cu content may be 0%.
Cu is an element that improves the hardenability of steel. By increasing the hardenability of steel, the transformation temperature can be stabilized and the strength of the steel wire can be improved. From the viewpoint of such action, the Cu content may be greater than 0%, may be 0.05% or more, may be 0.10% or more, or may be 0.20% or more. good too.
On the other hand, if the Cu content exceeds 0.50%, the electrical resistivity of the steel wire may become excessively high. The Cu content is 0.40% or less from the viewpoint of suppressing an excessive increase in electrical resistivity of the steel wire. Cr content is more preferably 0.35% or less.

Ni: 0.50% or less Ni is an arbitrary element. That is, the Ni content may be 0%.
Ni is an element that improves the hardenability of steel. By increasing the hardenability of steel, the transformation temperature can be stabilized and the strength of the steel wire can be improved. From the viewpoint of such action, the Ni content may be more than 0%, may be 0.05% or more, may be 0.10% or more, or may be 0.20% or more. good too.
On the other hand, if the Ni content exceeds 0.50%, the electrical resistivity of the steel wire may become excessively high. The Ni content is 0.40% or less from the viewpoint of suppressing an excessive increase in electrical resistivity of the steel wire. The Ni content is more preferably 0.35% or less.

From the viewpoint of improving the tensile strength, the steel wire according to the present embodiment has a chemical composition of Cu: 0.05% or more and 0.50% or less and Ni: 0.05% or more and 0.50% by mass. % or less, preferably satisfies one or two selected from the group consisting of

Ca: 0.0040% or less Ca is an arbitrary element. That is, the Ca content may be 0%.
Ca dissolves in MnS and has the effect of finely dispersing MnS. By finely dispersing MnS, cracking during wire drawing can be suppressed, and a steel wire with high strength can be processed. From the viewpoint of such actions, the Ca content may be greater 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 0.0040%, the effect is saturated. In addition, it reduces the ductility of the steel wire due to the formation of oxides. Therefore, the Ca content is 0.0040% or less. From the viewpoint of further improving the ductility of the steel wire, the Ca content is preferably 0.0030% or less.

Mg: 0.0040% or less Mg is an arbitrary element. That is, the Mg content may be 0%.
Mg dissolves in MnS and has the effect of finely dispersing MnS. By finely dispersing MnS, cracking during wire drawing can be suppressed, and a steel wire with high strength can be processed. From the viewpoint of such action, the Mg content may be greater than 0%, may be 0.0002% or more, or may be 0.0005% or more.
On the other hand, even if the Mg content exceeds 0.0040%, the effect is saturated. In addition, it reduces the ductility of the steel wire due to the formation of oxides. Therefore, the Mg content is 0.0040% or less. From the viewpoint of further improving the ductility of the steel wire, the Mg content is preferably 0.0030% or less.

From the viewpoint of further improving the ductility of the steel wire, the steel wire according to the present embodiment has a chemical composition of Ca: 0.0002% or more and 0.0040% or less and Mg: 0.0002% or more and 0% by mass. It is preferable to satisfy one or two selected from the group consisting of 0.0040% or less.

B: 0.0030% or less B is an arbitrary element. That is, the B content may be 0%.
If the B content exceeds 0.0030%, coarse carbides or carbonitrides are likely to be formed in the steel wire, which may increase the electrical resistivity of the steel wire. Therefore, the B content is 0.0030% or less. From the viewpoint of further reducing the electrical resistivity of the steel wire, the B content is preferably 0.0025% or less.
On the other hand, B is an element that forms BN in the steel wire and reduces the solute N, thereby reducing the electrical resistivity of the steel wire. From the viewpoint of such action, the B content may be greater than 0%, may be 0.0001% or more, or may be 0.0005% or more.

From the viewpoint of further reducing the electrical resistivity of the steel wire, the steel wire according to the present embodiment preferably has a chemical composition of B: 0.0001% or more and 0.0030% or less in mass%.

Balance: Fe and Impurity Elements In the chemical composition according to the present embodiment, the balance excluding the above-described elements is Fe and impurity elements.
Here, the impurity element refers to a component contained in the raw material or a component mixed in the manufacturing process and not intentionally included in the steel.
Impurity elements include all elements other than the elements described above. Only one element or two or more elements may be used as impurities.

The steel wire according to the present embodiment can achieve both high tensile strength and low electrical resistivity by controlling the composition within the range described above. Furthermore, it is also possible to exhibit excellent ductility by adding arbitrary elements.

<Metal structure of steel wire>
Next, the metal structure of the steel wire according to this embodiment will be described.
The steel wire according to this embodiment has a pearlite structure with lamellar cementite. In the present embodiment, the pearlite structure having lamellar cementite is a structure derived from pearlite or pseudo-pearlite present in the wire before wire drawing, in which a cementite phase (lamellar cementite) and a ferrite phase are alternately repeated in layers. It is an overlapping organization. In other words, the pearlite structure having lamellar cementite in the present embodiment is a structure including linear, curved, or fragmentary cementite and ferrite phase existing between cementite.

The steel wire according to the present embodiment preferably contains 70 area% or more, more preferably 90 area% or more, of the pearlite structure in the metal structure in the cross section of the region within D/10 from the central axis, where D is the diameter. is more preferred. In particular, sufficient tensile strength can be obtained when the pearlite structure is 90 area % or more. The pearlite structure is more preferably 95 area % or more, particularly preferably 97 area % or more, and may be 100 area %.
The steel wire according to the present embodiment may contain a non-pearlite structure (ferrite structure, bainite structure, martensite structure) in addition to the pearlite structure. However, if the non-pearlite structure exceeds 10 area %, the area ratio of the pearlite structure decreases and the tensile strength decreases, so the non-pearlite structure is preferably limited to 10 area % or less. Among the non-pearlite structures, the ferrite structure is distinguished from the ferrite phase contained in the pearlite structure. In addition, the term “ferrite” in this specification means both the ferrite phase in the pearlite structure and the ferrite phase in the non-pearlite structure.

-Method for measuring area ratio of pearlite structure-
After the cross section perpendicular to the longitudinal direction of the steel wire (that is, the cross section of the steel wire) was mirror-polished, it was corroded with picral, and a field emission scanning electron microscope (FE-SEM) was used at a magnification of 2000 times to obtain a D from the center. Observe and photograph 5 points at arbitrary positions in the area within /10. The area per field of view is 2.7×10 ⁻³ mm ² (0.045 mm length, 0.060 mm width).

Then, a transparent sheet such as an OHP (Over Head Projector) sheet is overlaid on each photograph obtained. In this state, the "non-perlite texture" on each transparent sheet is colored. Next, the area ratio of the "colored area" in each transparent sheet is determined by image analysis software (eg, Image-J), and the average value is calculated as the average value of the area ratio of the non-pearlite structure. The area ratio of the pearlite structure is calculated by subtracting the obtained area ratio of the non-pearlite structure from 100%, and the average value of the five fields of view is taken as the average area ratio of the pearlite structure.

(Amount of C dissolved in ferrite)
In the steel wire according to the present embodiment, the amount of C dissolved in ferrite (in this specification, it may be referred to as “solid solution C concentration” or “solid solution C amount”) is 500 ppm or less on a mass basis. be.
A steel wire is obtained by drawing a rolled wire rod (in this specification, it may be simply referred to as a “wire rod”). The wire rod structure for manufacturing the steel wire according to the present embodiment is mainly a pearlite structure in which the lamellar cementite is oriented in random directions, and the lamellar cementite is oriented in various directions with respect to the direction of electricity flow. The electrical resistivity increases due to the presence of As the wire is drawn, the lamellar cementite becomes aligned in the longitudinal direction of the steel wire, that is, parallel to the direction of electric current flow. As a result, the electrical resistivity of the steel wire is much lower than that of the wire. However, when wire drawing is further applied, lamellar cementite is forcibly dissolved in ferrite. C dissolved in ferrite remarkably increases the electrical resistivity of the steel wire, so the dissolved carbon (C) concentration is defined as described above.
When the concentration of C dissolved in ferrite is 500 ppm or less, the electrical resistivity can be lowered. The concentration of C dissolved in ferrite is preferably 400 ppm or less, more preferably 300 ppm or less. Although the lower limit of the solute C concentration is not particularly limited, it may be 10 ppm or more, or 30 ppm or more, from the viewpoint of further improving the strength of the steel wire.

-Method for measuring solid solution C concentration-
The amount of C dissolved in ferrite in the steel wire (dissolved C concentration) can be obtained from the following tensile test, aging treatment, and tensile test.
A steel wire is cut into a length of 340 mm, the top and bottom are fixed by a wedge chuck at 70 mm, and an extensometer is attached at the center of 50 mm to perform a tensile test α. At this time, the test is stopped when the steel wire is deformed by 2%, and the load is removed while being careful not to bend the steel wire. The stress α is calculated by dividing the obtained maximum load by the cross-sectional area.
After that, the steel wire is held in a furnace at 100° C. for 1 hour and subjected to aging treatment. After heating, cool by standing to cool. Again, 70 mm above and below the steel wire is fixed with a wedge chuck, an extensometer is attached to the center 50 mm, a tensile test β is performed, and the wire is broken. The 0.2% proof stress obtained in the tensile test β is obtained and defined as the stress β. The Young's modulus used in calculating the 0.2% yield strength is calculated using strain obtained from an extensometer in the range of 0.4-0.7 TS. TS means tensile strength (MPa). At this time, it is known that the differential stress δ between the stress β and the stress α takes a value dependent on the dissolved C concentration.
In the case of the steel wire according to the present embodiment, the concentration of solid solution C (mass basis, mass %) can be obtained as follows: stress δ (MPa)/5000. The above test is performed 5 times, and the average value is taken as the dissolved C concentration.

In order to perform the above test, it is preferable to perform the tensile test α within one day after the wire drawing process to obtain the final wire diameter. If more than one day has passed, the steel wire is bent with a roller or the like to a curvature of 10 times the steel wire diameter D, and further bent with a roller or the like to 10 times the steel wire diameter D so that the wire is wound in the opposite direction. The process has to be done twice. As a result, the C fixed to the dislocation can be dissolved again, and the dissolved carbon concentration can be measured by the above test.

The dissolved C concentration is often calculated at a stress of about δ/500 to 1000, but in the steel wire according to the present embodiment, compared with the measured value with the 3D-atom probe, the dissolved C concentration is A stress of δ/5000 was determined to be appropriate. This method is used because the 3D-atom probe has large variations depending on the location.

(average lamellar spacing)
As described above, the steel wire according to the present embodiment has a pearlite structure in which ferrite and cementite form a layered lamellar structure. The tensile strength can be improved by reducing the average pearlite lamellar spacing (average lamellar spacing) of the steel wire. Since the average lamellar spacing does not significantly affect the electrical resistivity, it is preferable to reduce the average lamellar spacing in order to improve the balance between the improvement in tensile strength and the reduction in electrical resistivity. From this point of view, the average lamellar spacing (average lamellar spacing) in a region within D/10 from the central axis when the diameter of the steel wire is D in a cross section (longitudinal cross section) parallel to the longitudinal direction of the steel wire is 50 nm or less. , more preferably 45 nm or less, and still more preferably 40 nm or less. This further improves the tensile strength of the steel wire.
There is no particular lower limit because the narrower the average lamellar spacing, the better the tensile strength.

-Method for measuring lamellar spacing-
A cross section parallel to the longitudinal direction of the steel wire and containing the central axis (that is, a vertical cross section of the steel wire) is mirror-polished, then corroded with picral, and a field emission scanning electron microscope (FE-SEM) is used. At a magnification of 10,000 times, observations are made at 5 arbitrary positions in an area within D/10 from the central axis, and photographs are taken. Specifically, in the range where the orientation of the perlite lamellae is aligned in the field of view using photographs of each field of view, 5 lamella intervals can be measured, and the location where the lamella interval is the smallest, and the second lamella interval For a small area, a straight line is drawn perpendicular to the lamella to find the length of 5 lamella intervals, and by dividing it by 5, the perlite lamella interval at each location can be obtained. The average value of the lamellar spacings at 10 locations in each visual field thus obtained can be used as the "average lamellar spacing" (average lamellar spacing) of the sample.

(<110> integration)
The steel wire according to the present embodiment is parallel to the longitudinal direction of the steel wire in a region within D/10 from the center where D is the diameter of the steel wire in a cross section (cross section) perpendicular to the longitudinal direction. The degree of integration of the <110> orientation (hereinafter sometimes simply referred to as “the degree of integration of <110>”) is 2.0 or more. Here, the degree of accumulation of <110> means how many times the frequency of existence of crystal grains having an orientation of <110> with respect to a structure having a completely random orientation distribution (in this case, the degree of accumulation is 1). It is an index that indicates whether
In the steel wire of the present embodiment, the degree of accumulation of <110> parallel to the longitudinal direction of the steel wire in a region within D/10 from the central axis is 2.0 or more, so that the strength of the steel wire is increased. can be improved enough. From this point of view, the steel wire of the present embodiment preferably has a <110> accumulation degree of 2.1 or more, more preferably 2.2 or more, in a region within D/10 from the central axis.

The degree of accumulation of <110> is correlated with the wire drawing strain. gets worse. On the other hand, when the degree of accumulation is high, wire drawing strain is large, a large amount of cementite is decomposed, and carbon is forcibly dissolved in ferrite.
The upper limit of the <110> accumulation degree in the area within D/10 from the central axis is not particularly limited, but from the viewpoint of suppressing wire breakage during wire drawing, it is preferably 4.0 or less, and 3.8. The following are more preferable.

-<110>Method for measuring integration-
The degree of accumulation of <110> parallel to the longitudinal direction of the steel wire in the region within D/10 from the central axis is obtained by measuring as follows.
A cross section perpendicular to the longitudinal direction of the steel wire (that is, a cross section of the steel wire) is mirror-polished, then polished with colloidal silica, and a field emission scanning electron microscope (FE-SEM) is used at a magnification of 1000 times or more. EBSD measurements (measurements by electron beam backscatter diffraction) are performed by observing each of the four fields of view at arbitrary positions within a radius of D/10 from the axis. The step at the time of measurement shall be 0.1 μm.
Next, the degree of accumulation of <110> viewed from the longitudinal direction of the steel wire is calculated. For example, an integration degree of <110> can be obtained by using OIM analysis (EBSD analysis software of TSL Solutions Co., Ltd., OIM: Orientation Imaging Microscopy). When using OIM analysis, pixels with a CI value of 0.1 or less and clusters of pixels of 9 or less are considered noise and excluded.

-Method of measuring electrical resistivity-
The steel wire according to the present embodiment is a steel wire with reduced electrical resistivity, and the electrical resistivity of the steel wire can be measured by the following procedure.
After removing the lubricant from the surface layer of the steel wire and straightening it into a straight rod, the electrical resistance value in the longitudinal direction of the steel wire is measured at a temperature of 20° C. by the four-probe method. The obtained electrical resistance value is multiplied by the area of the cross section of the test piece (that is, the cross section perpendicular to the longitudinal direction of the test piece), and the obtained value is divided by the voltage drop distance of the test piece. Calculate the electrical resistivity (μΩm) in the longitudinal direction. Here, the voltage drop distance is the distance between the inner two terminals among the four terminals. The lubricant on the surface layer may be removed mechanically by sandblasting, sandpaper, or the like, or chemically by hydrochloric acid or the like.

[Aluminum coated steel wire]
The aluminum-coated steel wire has an Al-containing layer that coats at least part of the steel wire described above.
Although the diameter of the steel wire used for the aluminum-coated steel wire is not particularly limited, it is preferably 1.0 mm or more and 5.0 mm or less.
When the steel wire used for the aluminum-coated steel wire has a diameter of 1.0 mm or more, wire drawing can be performed more stably when obtaining the aluminum-coated steel wire by wire drawing.
When the steel wire used for the aluminum-coated steel wire has a diameter of 5.0 mm or less, the decomposition of cementite during wire drawing and the increase in electric resistance due to this decomposition can be further suppressed.
The Al-containing layer is preferably a layer containing Al as a main component.
Here, the layer containing Al as a main component means a layer containing Al as the component with the highest content (% by mass).
The Al content in the Al-containing layer is preferably 50% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more.
As the Al-containing layer, an Al layer made of Al (that is, pure Al) or an Al alloy layer made of an Al alloy is preferable.
As the Al alloy, an Al alloy containing Al and at least one selected from the group consisting of Mg, Si, Zn, and Mn is preferable. The content of Al in the Al alloy is preferably 50% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more. Preferred Al alloys specifically include Al alloys in the 3000s to 7000s international aluminum alloy names.
The Al layer made of Al as used herein may contain impurities other than Al. Similarly, the Al alloy layer made of Al alloy referred to herein may contain an impurity element other than the Al alloy.

[Manufacturing method of steel wire and aluminum-coated steel wire]
Next, a method for manufacturing a steel wire according to this embodiment will be described. The steel wire manufacturing method according to the present embodiment is not particularly limited, but a preferable manufacturing method includes, for example, a step of casting a slab having the composition; a step of heating the slab; a step of hot-rolling a cast slab to obtain a hot-rolled steel; a step of water-cooling the hot-rolled steel and winding it; a step of cooling the hot-rolled steel after the winding; and patenting the hot-rolled steel. a step of cooling the hot rolled steel after patenting to form a wire; a step of applying a lubricating coating to the wire; and a step of drawing the lubricating coated wire. method.
Moreover, when manufacturing an aluminum-coated steel wire using the steel wire according to the present embodiment, a step of coating at least a part of the steel wire manufactured through the above steps with an Al-containing layer may be performed.
Preferred manufacturing conditions for the steel wire and the aluminum-coated steel wire according to this embodiment will be described in detail below. In addition, the process from casting the slab to the process of applying the lubricating coating to the wire will be described as a rolling process.

<Rolling process>
(casting)
In the steel wire manufacturing method according to the present embodiment, first, steel is melted, and then a slab having the chemical composition of the steel wire according to the present embodiment is manufactured by continuous casting or the like. A steel slab may be obtained by subjecting the cast slab to blooming before hot rolling, which will be described later.

(heating)
The slab is preferably heated to a heating temperature at which the average temperature of its cross section is within the range of 1150 to 1250° C. before hot rolling. In addition, the maximum temperature of the slab in heating is called heating temperature. This is because if the heating temperature is less than 1150° C., the reaction force during hot rolling increases, and if it exceeds 1250° C., decarburization proceeds greatly in a short time.

(hot rolling)
A steel slab that has been cooled once after slab rolling and then heated and held again is hot-rolled into a hot-rolled steel. In hot rolling, it is preferable to set the temperature on the delivery side of the finish rolling to over 950°C. This is because if the temperature on the delivery side of the finish rolling is 950° C. or less, the reaction force during hot rolling increases. Moreover, the upper limit of the temperature on the delivery side of the finish rolling is preferably 1100° C. or less. This is because if the temperature exceeds 1100° C., it may not be possible to cool to the target temperature in the next water cooling.

(water cooling and winding)
Next, the hot-rolled steel after finish rolling is water-cooled and coiled. The water cooling stop temperature and winding temperature are set at 800° C. or higher. The upper limits of the water cooling stop temperature and the winding temperature are preferably 900°C or less. If the water cooling stop temperature and the coiling temperature are less than 800° C., the growth of the austenite grain size is suppressed, and hardenability may be deteriorated in order to keep the austenite grain size fine. When the hardenability deteriorates, the lamellar spacing of the steel wire increases and the strength of the steel wire decreases, which may reduce the strength of the steel wire. When the water cooling stop temperature and the coiling temperature exceed 900°C, ferrite and cementite precipitate, so the temperature is preferably 900°C or less. Water cooling is started immediately after hot rolling is completed.

(cooling and patenting)
Then, the coiled hot-rolled steel is preferably cooled to a temperature in the range of 700-750° C. after coiling and before immersion in the molten salt.
If the ultimate cooling temperature is less than 700°C, ferrite transformation proceeds, so it is preferable to control the temperature to 700°C or higher. On the other hand, if the cooling ultimate temperature exceeds 750°C, the temperature of the steel material becomes high when immersed in the molten salt, which may increase the temperature of the molten salt.
After cooling to the range of 700 to 750° C., patenting is performed by immersing in molten salt at a temperature of 600° C. or less. The lower limit of the molten salt temperature is preferably 480°C or higher. The immersion time of the molten salt is generally 10 to 60 seconds.
When the molten salt temperature is lower than 480° C., the formation of bainite structure becomes dominant, so the pearlite structure ratio decreases. Therefore, the molten salt temperature is preferably 480° C. or higher. On the other hand, the upper limit of the molten salt temperature is 600° C. or lower. This is because if the temperature exceeds 600° C., the lamellar spacing of the steel wire increases, the strength of the steel wire decreases, and the strength of the steel wire may decrease.

(water cooling)
It is preferable to cool with water after the patenting treatment with the molten salt is completed. This is because the remaining molten salt can be removed by water cooling. A wire having a pearlite structure can be obtained through the above steps.

(Lubricating film treatment)
In order to increase the lubricating effect during processing during wire drawing, it is preferable that the wire is previously treated with a lubricating film. The lubricating film treatment method may be a physical coating such as a lime coating or a borax coating, or a chemical reaction with iron such as a phosphate coating.

<Wire drawing process>
Next, the wire is drawn to obtain a steel wire. Wire drawing is a process in which a wire is passed through a die with a die hole smaller than the diameter of the wire to reduce the diameter of the wire and lengthen the length of the wire. It is a process that makes it thinner. Here, one wire drawing process is called a pass, and the amount of change in cross-sectional area in one pass is called an area reduction rate. The area reduction rate R can be calculated as follows: R=(S ₀ −S ₁ )/S ₀ ×100, where S ₀ is the cross-sectional area before machining and S ₁ is the cross-sectional area after machining.
Also, strain accumulated in multiple passes is called wire drawing strain. The wire drawing strain ε can be obtained by ε=2×ln (D/d), where d is the diameter of the wire and D is the diameter of the steel wire. The reason why the area reduction rate and wire drawing strain are used separately is that the area reduction rate is an amount of change in cross-sectional area, which is intuitively understandable, but cannot be added. Therefore, the accumulated strain is expressed as a wire drawing strain that can be added.

In the wire drawing process, the wire is drawn so as to apply a drawing strain of 1.5 to 3.5 to the wire. Preferably, the wire drawing strain is 1.7 to 3.0.
Wire drawing aligns the lamellar cementite in the longitudinal direction of the steel wire, so the electrical resistivity decreases. Since the electric resistivity becomes the minimum value at a wire drawing strain of 1.0 to 1.5, it is preferable to set the wire drawing strain to 1.5 or more. When the drawing strain is 1.5 or more, the <110> density of ferrite in the region within D/10 from the central axis is 2.0 or more, and the average lamellar spacing is 50 nm or less.
On the other hand, when wire drawing strain is 1.5 or more, cementite is decomposed and C dissolves into ferrite, so the electric resistivity gradually increases. Therefore, it is possible to achieve both strength and electrical resistivity by performing a wire drawing method in which the wire drawing strain is set to 1.5 or more and the decomposition of cementite is suppressed during wire drawing of 1.5 or more. However, if the wire drawing strain exceeds 3.5, the electrical resistivity is greatly reduced even if the wire drawing is performed to suppress the decomposition of cementite, so the wire drawing strain is preferably 3.5 or less.

During the wire drawing process, the temperature of the steel wire rises due to the heat generated during the drawing process. When the steel wire temperature is high, the diffusion of carbon is promoted, so that the decomposition of cementite and the solid solution of C in ferrite are promoted, and the electrical resistivity is greatly increased. Therefore, in order to suppress the decomposition of cementite, that is, the increase in solute carbon, wire drawing conditions that suppress heat generation during wire drawing are important. Specifically, it is effective to combine the suppression of the heat generated by the working of the steel wire with the method of physically cooling the die and the steel wire.

The area reduction rate of each pass is 19% to 28% for wire drawing strain up to 1.0, and the area reduction rate between each pass for wire drawing strain 1.0 to 2.0. is 14% to 23%, and the area reduction rate between each pass is preferably 10% to 18% for wire drawing strains of 2.0 to 3.5. Work heat generation can be suppressed by reducing the area reduction rate corresponding to the work hardening of the steel wire.
Furthermore, the wire drawing speed is preferably 20 m/min or less. A cooling time of 20 m/min or less can be lengthened.
Cooling water used for cooling the die is preferably 5°C to 15°C. If the temperature of the cooling water used for cooling the die is 5°C or higher, freezing can be prevented, and if it is 15°C or lower, the die can be sufficiently cooled.
The cooling water used for water-cooling the steel wire on the exit side of the die is preferably 5°C to 15°C. If the temperature of the cooling water used for water-cooling the steel wire is 5°C or higher, freezing can be prevented, and if the temperature is 15°C or lower, the steel wire can be sufficiently cooled. For water cooling of the steel wire, it is preferable to immerse the steel wire for 1 second or more immediately after the exit side of the die, or to apply cooling water at a flow rate of 10 L/min or more to the center portion of the steel wire immediately after the exit side of the die.

Furthermore, if the wire drawing strain is 1.5 or more, rebending may be performed between passes. The rebending process is a process that gives the steel wire a curvature of 20 times or less the wire diameter of the steel wire in each pass. By performing re-bending, it is possible to move the dislocations accumulated in the cementite during the wire drawing process, thereby suppressing the decomposition of the cementite. Rebending may be performed once or more at a drawing strain of 1.5 to 3.5, and may be performed between each pass.
According to the manufacturing method including the above steps, the steel wire according to the present embodiment is preferably manufactured.

<Coating process>
Next, an Al-containing layer is formed on the obtained steel wire. A step of coating an Al-containing layer on at least a portion of the steel wire manufactured through the above steps may be performed. Means for forming the Al-containing layer may be any of an electroplating method, a hot-dip plating method, and a clad method. The thickness of the Al-containing layer at this point is preferably about 0.7% to 50% of the diameter of the steel wire.
Thereby, the aluminum-coated steel wire according to the present embodiment is manufactured.
This covering step may be performed between the cooling step and the wire drawing step, or may be performed during the wire drawing step. That is, the aluminum-coated steel wire according to the present embodiment can be obtained even if the wire is drawn after the Al-containing layer is formed on the wire.

Examples of the present disclosure will be specifically described below with reference to examples, but the present invention is not limited to the following examples.
First, (Steel A) having the chemical composition shown in Table 1 was smelted in a converter and then bloomed by a normal method to obtain a billet of 122 mm square. The content of each element in Table 1 is mass %, and the balance is Fe and impurity elements. The same applies to Table 3, which will be described later. In Table 3, "-" means that the element is not included.

Thereafter, a step of heating, a step of hot rolling to obtain a hot rolled steel, a step of cooling the hot rolled steel with water and winding it, a step of cooling the hot rolled steel after winding, and applying a patent to the hot rolled steel. The step of drawing and the step of wire drawing were performed under the conditions shown in (1) to (22) in Table 2, respectively, to manufacture steel wires of test levels (A1) to (A22).
The meaning of each item related to wire drawing in Table 2 is as follows.
(Reduction rate design)
○: The area reduction rate of each pass is 19% to 28% up to a wire drawing strain of 1.0, and the area reduction rate between each pass is 14% to 23% up to a wire drawing strain of 1.0 to 2.0. %, and the area reduction rate between each pass was set to 10% to 18% for wire drawing strains of 2.0 to 3.5.
x: Area reduction rate of all passes was within 19 to 23%.
(Wire drawing speed)
Wire drawing speed (water cooling flow rate) based on the length of the drawn steel wire (steel wire that has passed through the die)
Amount of water supplied to the die outlet to cool the steel wire at the die outlet (rebending)
Good: The steel wire was given a curvature of 18 times the diameter of the steel wire before the final pass.
x: No re-bending process was performed.

Using steels (B) to (AF) having the chemical compositions shown in Table 3, steel wires of test levels (B1) to (AF1) were produced in the same manner as for test level (A1). The underlines shown in Table 3 indicate that any of the chemical compositions of the steel are outside the scope of this disclosure.

For the steel wires of test levels (A1) to (A22) and test standards (B1) to (AF1) obtained as described above, the total content of Mo and Cr, the concentration of dissolved C, and the central axis <110> accumulation degree of ferrite, area ratio of pearlite structure, lamellar spacing (average value), tensile strength and electrical resistivity in a region within D/10 from . The results are shown in Tables 4 and 5 below. In Tables 4 and 5, the underlines indicate that the properties are out of the desired range.

The total content of Mo and Cr in the steel wire, the concentration of dissolved C, the <110> accumulation degree of ferrite in the area within D / 10 from the central axis, the area ratio of the pearlite structure, and the average lamellar spacing are Each was measured by the method described above. Also, the tensile strength and electrical resistivity of the steel wire were investigated by the methods described below.

－Tensile strength of steel wire－
A steel wire was cut into a length of 340 mm, and a tensile test was performed by fixing the upper and lower portions of 70 mm with a wedge chuck. The tensile strength (MPa) was calculated by dividing the obtained maximum load by the cross-sectional area.

－Electrical resistivity of steel wire－
A steel wire was cut into a length of 100 mm as a test piece, and oxide scale was removed using sandblasting.
The electrical resistance value in the longitudinal direction of the sampled test piece was measured at a temperature of 20° C. by the four-probe method. The distance between current terminals was 50 mm, and the voltage drop distance was 20 mm. By multiplying the obtained electrical resistance value by the area of the cross section of the test piece (that is, the cross section perpendicular to the longitudinal direction of the test piece) and dividing the obtained value by the voltage drop distance of the test piece, the test The electrical resistivity (μΩm) in the longitudinal direction of the piece was calculated.

When the relationship between the tensile strength σ and the electrical resistivity ρ of the steel wire satisfies σ > 41000 × ρ - 5350 and σ > 1500 MPa, it is judged that both are compatible at a high level. The "strength/conductivity balance" was rated as "○", and when either one was not satisfied, it was rated as "x". Furthermore, it was determined that the higher compatible levels were σ: 1700 MPa or more and ρ: 0.172 μΩm or less.

Tables 4 and 5 collectively describe the results of the respective evaluations described above.
From Table 4, the samples of Examples (A1) to (A14) all satisfy the requirements of the present disclosure. was a line.
On the other hand, the sample (A15) had a large lamellar spacing due to the high temperature of the molten salt, and the tensile strength was poor, failing to achieve both tensile strength and electrical resistivity.
The sample (A16) had a low drawing strain, so the lamellar spacing was large and the <110> density was low, and both tensile strength and electrical resistivity could not be achieved.
In the sample (A17), since wire drawing strain was high, a large amount of carbon dissolved in the ferrite, and both tensile strength and electrical resistivity could not be achieved.
In the sample (A18), since the area reduction rate of each pass was large, a large amount of carbon dissolved in the ferrite, and both tensile strength and electrical resistivity could not be achieved.
In the sample (A19), since the coiling temperature was low, the austenite grains were fine, the hardenability was poor, the lamellar spacing was large, and both tensile strength and electrical resistivity could not be achieved.
In the sample (A20), since the wire drawing speed was high, a large amount of carbon dissolved in the ferrite, and both tensile strength and electrical resistivity could not be achieved.
In the sample (A21), since the temperature of the cooling water was high, a large amount of carbon dissolved in the ferrite, and both tensile strength and electrical resistivity could not be achieved.
In the sample (A22), since the amount of cooling water was insufficient, a large amount of carbon dissolved in the ferrite, and both tensile strength and electrical resistivity could not be achieved.

Among the samples of (A1) to (A14), the pearlite area ratio is 90% or more when observing the range of D/10 with SEM with D/2 as the axis when the diameter is D. (A1) and (A3) to (A14) had a high tensile strength of 2100 MPa or more.
In addition, in (A3) to (A6) and (A9), in which rebending was performed once before the final pass, the amount of dissolved carbon could be controlled to 200 ppm or less, and the electrical resistivity was 0.181 to 0.183 μΩm. , and the electrical resistivity was stably low.

In addition, from the results shown in Table 5, all the samples of test levels (B1) to (Y1), which are examples, satisfy the requirements of the present disclosure, so they have excellent tensile strength and reduced electrical resistivity. It was a steel wire with no problems.
On the other hand, the sample of test number (Z1) had a large lamellar spacing due to the low C content, and could not achieve both tensile strength and electrical resistivity.
The sample of test number (AA1) had a high C content and could not achieve both tensile strength and electrical resistivity.
The sample of test number (AB1) had a high Si content and could not achieve both tensile strength and electrical resistivity.
The sample of test number (AC1) had a high Mn content and could not achieve both tensile strength and electrical resistivity.
The sample of test number (AD1) had a high Cr content and could not achieve both tensile strength and electrical resistivity.
Since the sample of test number (AE1) had a high Mo content, it was not possible to achieve both tensile strength and electrical resistivity.
In the sample of test number (AF1), the total content of Cr and Mo was less than 0.14%, so both tensile strength and electrical resistivity could not be achieved.
Among the samples (B1) to (Y1), the area ratio of pearlite is 90 when a range within D/10 with D/2 as the central axis from the surface of the steel wire when the diameter is D is observed with an SEM. % or more (B1), (E1) ~ (K1), (M1) ~ (O1), (Q1) ~ (S1), (U1) ~ (W1) and (Y1) tensile strength has a high tensile strength of 1700 MPa or more, and the alloy components are controlled within a preferable range (B1), (G1), (H1), (N1), (Q1) to (S1), ( In U1) to (W1) and (Y1), both high tensile strength and low electrical resistivity of 1700 MPa or more and 0.172 μΩm or less were achieved.

Claims (8)

The chemical composition is C: 0.40% or more and 1.10% or less in mass%,
Si: 0.005% or more and 0.15% or less,
Mn: 0.10% or more and 0.30% or less,
Cr: 0.003% or more and less than 0.30%,
Mo: 0.01% or more and 0.20% or less,
P: 0.030% or less,
S: 0.030% or less,
N: 0.0060% or less, and the balance: Fe and impurity elements, and the total of Mo content and Cr content is 0.14% or more,
having a perlite structure,
C dissolved in ferrite is 500 ppm or less on a mass basis,
When the diameter of the steel wire is D, the average lamella of the pearlite structure in a cross section parallel to the longitudinal direction of the steel wire and including the central axis in a region within D/10 from the central axis of the steel wire A steel wire having an interval of 50 nm or less and a degree of accumulation of ferrite in the <110> orientation parallel to the longitudinal direction of the steel wire of 2.0 or more. The chemical composition, in mass %,
Al: 0.070% or less,
Ti: 0.050% or less,
Nb: 0.050% or less,
V: 0.10% or less,
Cu: 0.50% or less,
Ni: 0.50% or less,
Ca: 0.0040% or less,
Mg: 0.0040% or less, and B: 0.0030% or less,
2. The steel wire according to claim 1, further satisfying one or more selected from the group consisting of: 3. The steel wire according to claim 1, wherein an area ratio of said pearlite structure in a region within D/10 from said central axis in a cross section perpendicular to the longitudinal direction of said steel wire is 90% or more. The chemical composition, in mass %,
Al: 0.005% or more and 0.070% or less,
moreover,
Ti: 0.005% or more and 0.050% or less, Nb: 0.002% or more and 0.050% or less,
and V: 0.002% or more and 0.10% or less. The chemical composition, in mass %,
Any one of claims 2 to 4, satisfying one or two selected from the group consisting of Cu: 0.05% to 0.50% and Ni: 0.05% to 0.50% The steel wire according to item 1. The chemical composition, in mass %,
Ca: 0.0002% or more and 0.0040% or less, and Mg: 0.0002% or more and 0.0040% or less, satisfying one or two selected from the group consisting of Any one of claims 2 to 5 The steel wire according to item 1. The chemical composition, in mass %,
B: The steel wire according to any one of claims 2 to 6, satisfying 0.0001% or more and 0.0030% or less. An aluminum-coated steel wire, comprising: the steel wire according to any one of claims 1 to 7; and an aluminum-containing layer that coats at least part of the steel wire.