WO2019106815A1

WO2019106815A1 - Aluminum-clad steel wire and method of producing same

Info

Publication number: WO2019106815A1
Application number: PCT/JP2017/043197
Authority: WO
Inventors: 俊彦手島; 敏之真鍋
Original assignee: 日本製鉄株式会社
Priority date: 2017-11-30
Filing date: 2017-11-30
Publication date: 2019-06-06
Also published as: JP6825720B2; JPWO2019106815A1

Abstract

Provided is an aluminum-clad steel wire which is used as a core material of an aluminum conductor steel-reinforced cable, and comprises a steel wire and an Al-containing layer that covers at least a portion of the steel wire. A chemical composition of the steel wire is, in mass%, C : 0.60 to 1.10%, Si : 0.01 to 0.10%, Mn : 0.10 to 0.30%, and Al : 0.005 to 0.050% with the remainder comprising Fe and impurities. In a longitudinal section of the steel wire, and when D is used for the diameter of the steel wire, an average aspect ratio of a cementite, in the regions within D/10 from the straight lines residing at a distance of D/4 from the central axis of the steel wire, is 10 to 25. A half width of the (211) plane in a longitudinal section of the steel wire, as measured using an x-ray diffraction instrument that uses a Mo tube, is at least 0.14° and less than 0.30°.

Description

Aluminum coated steel wire and method of manufacturing the same

The present disclosure relates to an aluminum clad steel wire used as a core material of a steel core aluminum stranded wire and a method of manufacturing the same.

A steel core aluminum stranded wire (aluminum conductor steel-reinforced cable, hereinafter sometimes referred to as "ACSR") used for a transmission line or the like is a cable using an aluminum wire or an aluminum alloy wire as a conductor.
Heretofore, as the ACSR, an ACSR having a structure in which an aluminum wire or an aluminum alloy wire is twisted on the outside with a single wire or a stranded wire made of a galvanized steel wire as a core material is used.
Conventionally, various studies have been made on galvanized steel wire as a core material of ACSR.
For example, Patent Document 1 relates to a method of manufacturing a stranded steel wire (ACSSR steel wire) used to mechanically reinforce an Al wire of a power transmission cable, and more specifically, in a corrosive environment. C: 0.75 to 1%, Si: 0.15 to 1.3%, Mn for the purpose of providing a manufacturing method of high strength Zn plated steel wire for ACSR with a tensile strength of 240 kgf / mm ² or more. Al: 2 to 12% containing steel wire containing 0.3 to 1%, optionally Cr: 0.1 to 1%, V: 0.02 to 0.3% of 1 to 2 types Method of producing high strength Zn-plated steel wire for ACSR with excellent corrosion resistance, which is drawn at a layer reduction ratio of 20 to 80% after hot-dip plating using a Zn bath, and then blued at 300 to 370 ° C. It is disclosed.

On the other hand, regarding steel materials, improvement in electrical conductivity may be required.
For example, Patent Document 2 can perform cold forging with good dimensional accuracy, and as a steel material for electrical parts that can ensure excellent electrical conductivity, C: 0.02% or less (0% or less) %, Si: 0.1% or less (not 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 a steel material for electrical parts excellent in cold forgeability and electrical conductivity, in which the metal structure is a ferrite single phase structure.

Patent Document 1: Japanese Patent Application Laid-Open No. 4-236742 Patent Document 2: Japanese Patent Application Laid-Open No. 2003-226938

By the way, in ACSR using zinc-plated steel wire (for example, Zn-plated steel wire described in Patent Document 1) as core material, zinc is used in the contact portion between aluminum and zinc with different electrode potentials by using rainwater etc. as electrolyte. It may corrode, and furthermore, aluminum may corrode due to the contact between the exposed iron and the aluminum. These tendencies are particularly noticeable when ACSR is used in high humidity areas such as coastal areas.
Therefore, instead of galvanized steel wire as an ACSR core material, an aluminum-clad steel wire (aluminum-clad steel wire) comprising a steel wire and an Al-containing layer covering at least a part of the steel wire. Sometimes referred to as "AC line" may be used.

In ACSR using an AC wire as a core, current flows not only to the portion of the aluminum wire twisted around the outside of the core but also to the portion of the AC wire as the core. Therefore, when the electrical resistance of the AC line is large, the electrical resistance of the entire ACSR is also increased, and the power transmission efficiency may be reduced.
In the case of low tensile strength of AC wire in ACSR having AC wire as a core material, it is conceivable to improve the tensile strength of AC wire by increasing the proportion of steel wire in AC wire. However, when the proportion of steel wire in the AC wire is increased, the electrical resistance of the AC wire and thus the electrical resistance of the ACSR may increase.

From the above reasons, it is required to improve the tensile strength and reduce the electrical resistivity of the steel wire in the AC wire.
In this regard, in the Zn-plated steel wire described in Patent Document 1, in order to improve the strength and corrosion resistance, the Si content is 0.15% or more and the Mn content is 0.3% or more. For this reason, when the steel wire in the Zn plated steel wire described in Patent Document 1 is used as a steel wire in an AC wire, the electrical resistivity may be excessively large.
On the other hand, in the steel material of patent document 2, in order to improve cold forgeability, C content is 0.02% or less. For this reason, when the steel material of patent document 2 is used as a steel wire in AC wire, tensile strength may become inadequate.

On the other hand, ductility is required for the steel wire in the AC wire from the viewpoint of suppressing the delamination of the steel wire in the AC wire.

Therefore, an object of the present disclosure is to provide an aluminum coated steel wire provided with a steel wire excellent in tensile strength and ductility and having a reduced electrical resistivity, and a manufacturing method suitable for manufacturing the above-mentioned aluminum coated steel wire. It is to be.

Means for solving the above problems include the following aspects.
<1> Used as core material of steel core aluminum stranded wire,
A steel wire, and an Al-containing layer covering at least a part of the steel wire,
The chemical composition of the steel wire is in mass%,
C: 0.60 to 1.10%,
Si: 0.01 to 0.10%,
Mn: 0.10 to 0.30%,
Al: 0.005 to 0.050%,
N: 0 to 0.0070%,
P: 0 to 0.030%,
S: 0 to 0.030%,
Cr: 0 to 1.00%,
Mo: 0 to 0.20%,
V: 0 to 0.15%,
Ti: 0 to 0.050%,
Nb: 0 to 0.050%,
B: 0 to 0.0030%, and
Remainder: consists of Fe and impurities,
In the longitudinal section of the steel wire, when the diameter of the steel wire is D, the average aspect ratio of cementite in a region within D / 10 from the straight line where the distance from the central axis of the steel wire is D / 4 is 10 or more and 25 or less,
The aluminum coated steel wire whose half value width of (211) plane measured using the X-ray-diffraction apparatus which used Mo tube in the longitudinal cross-section of the said steel wire is 0.14 degrees or more and less than 0.30 degrees.
<2> The steel wire is, by mass%,
The aluminum-coated steel wire according to <1>, containing at least one of Cr: 0% and 1.00% or less and Mo: 0% and 0.20% or less.
<3> The steel wire is, by mass%,
It is described in <1> or <2> containing at least one of V: more than 0% and 0.15% or less, Ti: more than 0% and 0.050% or less, and Nb: more than 0% and 0.050% or less Aluminum coated steel wire.
<4> The steel wire is, by mass%,
B: The aluminum-coated steel wire according to any one of <1> to <3>, containing 0% or more and 0.0030% or less.
<5> The aluminum-coated steel wire according to any one of <1> to <4>, wherein the tensile strength of the steel wire is 1900 MPa or more.
<6> A method of manufacturing the aluminum-coated steel wire according to any one of <1> to <5>,
The chemical composition is in mass%,
C: 0.60 to 1.10%,
Si: 0.01 to 0.10%,
Mn: 0.10 to 0.30%,
Al: 0.005 to 0.050%,
N: 0 to 0.0070%,
P: 0 to 0.030%,
S: 0 to 0.030%,
Cr: 0 to 1.00%,
Mo: 0 to 0.20%,
V: 0 to 0.15%,
Ti: 0 to 0.050%,
Nb: 0 to 0.050%,
B: 0 to 0.0030%, and
Remainder: consists of Fe and impurities,
In the cross section, when the diameter of the wire is d, prepare a wire having a pearlite fraction of 90% or more in the region combining the region within d / 7 from the center and the region within d / 7 from the outer peripheral surface The process to
Obtaining an unannealed steel wire by subjecting the wire to a first wire drawing process;
Obtaining an unannealed steel wire with an Al-containing layer by forming an Al-containing layer covering at least a part of the unannealed steel wire;
Performing a second wire drawing process on the unannealed steel wire with the Al-containing layer;
Obtaining the aluminum-coated steel wire by annealing the non-annealed steel wire with the Al-containing layer subjected to the second wire drawing;
Including
The wire drawing strain represented by the following formula (1) is more than 2.6 and not more than 3.6, and the diameter of the steel wire in the aluminum coated steel wire is not less than 1.0 mm and not more than 3.5 mm,
The manufacturing method of the aluminum coated steel wire whose annealing temperature in the said annealing is 370 degreeC-520 degrees C or less, and the annealing time in the said annealing is 10 to 180 second.
Wire drawing strain = 2 × ln (diameter of the wire (mm) / diameter of the steel wire in the aluminum-coated steel wire (mm)) Formula (1)

According to the present disclosure, an aluminum-coated steel wire provided with a steel wire excellent in tensile strength and ductility and having a reduced electrical resistivity, and a manufacturing method suitable for manufacturing the above-mentioned aluminum-coated steel wire are provided. .

It is a figure which shows notionally the longitudinal section in an example of the steel wire of this indication, and field X in this longitudinal section. In an example of the manufacturing method of the steel wire of this indication, it is a figure showing notionally the cross section of a wire, and field Y1 in a cross section, and field Y2.

In the present specification, a numerical range represented using “to” means a range including numerical values described before and after “to” as the lower limit value and the upper limit value.
In the present specification, “%” indicating the content of the component (element) means “mass%”.
In the present specification, the content of C (carbon) may be referred to as "C content". The contents of other elements may be similarly described.
In the present specification, the term "step" is not limited to an independent step but may be included in the term if the intended purpose of the step is achieved even if it can not be clearly distinguished from other steps. Be
In the numerical range described step by step in the present specification, the upper limit or the lower limit of a certain stepwise numerical range may be replaced with the upper limit or the lower limit of the numerical range described in another stepwise. Also, they may be replaced with the values shown in the embodiments.

[Aluminum coated steel wire]
The aluminum clad steel wire of the present disclosure is used as a core material of a steel core aluminum stranded wire, and comprises a steel wire and an Al-containing layer covering at least a part of the steel wire, and the chemical composition of the steel wire is a mass %, C: 0.60 to 1.10%, Si: 0.01 to 0.10%, Mn: 0.10 to 0.30%, Al: 0.005 to 0.050%, N: 0 0.00 0.0070%, P: 0 to 0.030%, S: 0 to 0.030%, Cr: 0 to 1.00%, Mo: 0 to 0.20%, V: 0 to 0.15% , Ti: 0 to 0.050%, Nb: 0 to 0.050%, B: 0 to 0.0030%, and the rest: Fe and impurities, and the diameter of the steel wire in the longitudinal cross section of the steel wire A cementer in a region within D / 10 (hereinafter also referred to as “region X”) from a straight line in which the distance from the central axis of the steel wire is D / 4, where D is And the half value width of the (211) plane measured with an X-ray diffractometer using a Mo tube in the longitudinal section of the steel wire is 0.14 ° or more and 0. Less than 30 °.

The steel wire in the aluminum clad steel wire of the present disclosure is excellent in tensile strength and ductility, and has a reduced electrical resistivity.
In the present specification, the electrical resistivity of a steel wire means the electrical resistivity in the longitudinal direction of the steel wire at room temperature (for example, 20 ° C.).
In the present specification, the tensile strength of a steel wire means the tensile strength in the longitudinal direction of the steel wire at room temperature (for example, 20 ° C.).

The aforementioned effects of the steel wire in the aluminum clad steel wire of the present disclosure (i.e., improvement in tensile strength and ductility, and reduction in electrical resistivity) can be achieved by the above chemical composition and cementite in the region X in the longitudinal section. And the half value width of the (211) plane in the longitudinal section.
For example, in the chemical composition of the steel wire in the present disclosure (that is, the steel wire in the aluminum-coated steel wire of the present disclosure; the same applies hereinafter), the content of Si, Mn, Cr, etc. is the upper limit value of the content of each element The average aspect ratio of cementite is limited to 25 or less in the region X which is reduced below and in the longitudinal section of the steel wire. These configurations reduce the electrical resistivity of the steel wire.
However, when the content of Si, Mn, Cr, etc. is reduced, there is a concern that the tensile strength of the steel wire may be reduced.
In this regard, in the steel wire in the present disclosure, the half value width of the (211) plane having a positive correlation with the dislocation density in the steel wire is 0.14 ° or more, and the C content is 0.60% The above-mentioned, the average aspect ratio of cementite being 10 or more, and the like ensure the excellent tensile strength of the steel wire.

On the other hand, if the dislocation density in the steel wire is too high, the ductility of the steel wire may be reduced.
In this regard, in the steel wire in the present disclosure, when the half width of the (211) plane is less than 0.30 °, the dislocation density in the steel wire is reduced to some extent, and as a result, the steel wire is excellent Ductility is secured.

<Chemical composition of steel wire>
Hereinafter, the chemical composition of the steel wire in the present disclosure will be described.
The chemical composition of the steel wire in the present disclosure is, in mass%, C: 0.60 to 1.10%, Si: 0.01 to 0.10%, Mn: 0.10 to 0.30%, Al: 0 .005 to 0.050%, N: 0 to 0.0070%, P: 0 to 0.030%, S: 0 to 0.030%, Cr: 0 to 1.00%, Mo: 0 to 0.. 20%, V: 0 to 0.15%, Ti: 0 to 0.050%, Nb: 0 to 0.050%, B: 0 to 0.0030%, and the balance: Fe and impurities.

The chemical composition of the steel wire raw material (for example, melted steel, ingot, wire rod, etc. described later) in the present disclosure is also similar to the chemical composition of the steel wire in the present disclosure. The manufacturing process from molten steel, through ingots and wires to steel wires does not affect the chemical composition.
Hereinafter, the chemical composition of the steel wire in the present disclosure may be referred to as "the chemical composition in the present disclosure".
Hereinafter, the content of each element in the chemical composition in the present disclosure will be described.

C: 0.60 to 1.10%
C is an element effective to increase the tensile strength of the steel wire. If the C content is less than 0.60%, the tensile strength of the steel wire may be insufficient. For this reason, the C content is 0.60% or more. The C content is preferably 0.70% or more.

On the other hand, when the C content exceeds 1.10%, the electrical resistivity of the steel wire may become excessively large. This reason is considered to be industrially difficult to suppress the formation of proeutectoid cementite (cementite precipitated along old austenite grain boundaries) when the C content exceeds 1.10%. . 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: 0.01 to 0.10%
Si is an element effective for enhancing the tensile strength of a steel wire by solid solution strengthening, and is also an element necessary as a deoxidizer. However, if the Si content is less than 0.01%, the effect of adding these Si may not be sufficient. For this reason, the Si content is 0.01% or more. The Si content is preferably 0.05% or more from the viewpoint of achieving the effects of the addition of Si more stably.

On the other hand, Si is an element that increases the electrical resistance of the steel wire. If the Si content exceeds 0.10%, the electrical resistivity of the steel wire may become excessively high. Therefore, the Si content is 0.10% or less. The Si content is preferably 0.09% or less, more preferably 0.08% or less.

Mn: 0.10 to 0.30%
Mn is an element having an effect of enhancing the tensile strength of the steel wire. Mn is also an element having the function of preventing hot embrittlement of the steel wire by fixing S in the steel as MnS. However, if the Mn content is less than 0.10%, these effects may not be sufficient. For this reason, the Mn content is 0.10% or more. Furthermore, in order to realize the securing of the tensile strength of the steel wire and the prevention of hot embrittlement at a higher level, the Mn content is preferably 0.15% or more, more preferably 0.20% or more. is there.

On the other hand, Mn has an effect of increasing the electrical resistivity of the steel wire. For this reason, when the Mn content exceeds 0.30%, the electrical resistivity of the steel wire may become excessively large. Therefore, the Mn content is 0.30% or less. The Mn content is preferably 0.26% or less.

Al: 0.005 to 0.050%
Al is an element having a deoxidizing action, and is an element necessary for reducing the amount of oxygen in the steel wire. However, if the Al content is less than 0.005%, it may not be possible to sufficiently obtain the effect (reduction of the amount of oxygen in the steel wire) by containing Al. For this reason, the Al content is 0.005% or more. Furthermore, from the viewpoint of obtaining this effect at a higher level, the Al content is preferably 0.010% or more, more preferably 0.020% or more.

On the other hand, when the Al content exceeds 0.050%, the electrical resistivity of the steel wire may become excessively large. The reason is considered to be that if the Al content exceeds 0.050%, coarse oxide inclusions are easily formed in the steel wire. For this reason, the Al content is 0.050% or less. From the viewpoint of further suppressing the electric resistivity of the steel wire, the Al content is preferably 0.040% or less, more preferably 0.035% or less.

N: 0 to 0.0070%
N is an element that raises the electrical resistivity of the steel wire. For this reason, when the N content exceeds 0.0070%, the electrical resistivity of the steel wire may become excessively high. For this reason, the N content is 0.0070% or less. From the viewpoint of further reducing the electrical resistance of the steel wire, the N content is preferably 0.0050% or less.
The N content may be 0%.
However, N is also an element that raises the tensile strength of the steel wire by fixing the dislocation during cold drawing. From the viewpoint of this effect, the N content may be more than 0%, may be 0.0010% or more, and may be 0.0020% or more.

P: 0 to 0.030%
P is an element which segregates in the grain boundaries of steel to increase the electrical resistance. If the P content exceeds 0.030%, the electrical resistivity of the steel wire may become excessively high. For this reason, the P content is 0.030% or less. From the viewpoint of further reducing the electrical resistance of the steel wire, the P content is preferably 0.025% or less, more preferably 0.020% or less.
The P content may be 0%. However, from the viewpoint of reducing the manufacturing cost (dephosphorization cost), the P content may be more than 0%, may be 0.0005% or more, and may be 0.0010% or more. .

S: 0 to 0.030%
S is an element that raises 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. For this reason, the S content is 0.030% or less. From the viewpoint of further reducing the electrical resistance of the steel wire, the S content is preferably 0.015% or less, more preferably 0.010% or less.
The S content may be 0%. However, from the viewpoint of reducing the manufacturing cost (desulfurization cost), the S content may be more than 0%, may be 0.002% or more, and may be 0.005% or more.

Cr: 0 to 1.00%
Cr is an arbitrary element. That is, the Cr content may be 0%.
If the Cr content exceeds 1.00%, the electrical resistivity of the steel wire may become excessively high. The reason is considered that when the Cr content exceeds 1.00%, spheroidization of cementite by annealing is inhibited, and as a result, the average aspect ratio of cementite exceeds 25. Therefore, the Cr content is 1.00% or less. From the viewpoint of further reducing the electrical resistance of the steel wire, the Cr content is preferably 0.95% or less.
On the other hand, Cr has the effect of increasing the tensile strength of the steel wire by reducing the lamella spacing of the pearlite. From the viewpoint of this action, the Cr content may be more than 0%, may be 0.10% or more, and may be 0.20% or more.

In the present specification, spheroidizing of cementite by annealing means that the average aspect ratio of cementite in region X of the longitudinal section of the steel wire is reduced by annealing (specifically, the average aspect ratio is 25 or less). It means that. In the present specification, spheroidization of cementite by annealing does not mean that cementite has a perfect spherical shape.

Mo: 0 to 0.20%
Mo is an arbitrary element. That is, the Mo content may be 0%.
If the Mo content exceeds 0.20%, the electrical resistivity of the steel wire may become excessively high. For this reason, the Mo content is 0.20% or less. From the viewpoint of further reducing the electrical resistance of the steel wire, the Mo content is preferably 0.10% or less.
On the other hand, Mo has the effect of increasing the tensile strength of the steel wire. From the viewpoint of this action, the Mo content may be more than 0%, may be 0.02% or more, and may be 0.05% or more.

V: 0 to 0.15%
V is any element. That is, the V content may be 0%.
When the V content exceeds 0.15%, coarse carbides or carbonitrides are easily formed in the steel wire, and the electrical resistivity of the steel wire may be increased. For this reason, the V content is 0.15% or less. From the viewpoint of further reducing the electrical resistivity of the steel wire, the V content is preferably 0.08% or less.
On the other hand, V is an element which forms carbides or carbonitrides in the steel wire to reduce the pearlite block size. Thereby, the decomposition of cementite is suppressed, and it is possible to achieve both the improvement of the tensile strength of the steel wire and the reduction of the electrical resistivity. From the viewpoint of this action, the V content may be more than 0%, may be 0.02% or more, and may be 0.05% or more.

Ti: 0 to 0.050%
Ti is an optional element. That is, the Ti content may be 0%.
When the Ti content exceeds 0.050%, coarse carbides or carbonitrides are easily formed in the steel wire, and the electrical resistivity of the steel wire may be increased. For this reason, 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.
On the other hand, Ti is an element that forms carbides or carbonitrides in the steel wire to reduce the pearlite block size. Thereby, the decomposition of cementite is suppressed, and it is possible to achieve both the improvement of the tensile strength of the steel wire and the reduction of the electrical resistivity. From the viewpoint of this action, the Ti content may be more than 0%, may be 0.002% or more, and may be 0.005% or more.

Nb: 0 to 0.050%
Nb is an arbitrary element. That is, the Nb content may be 0%.
If the Nb content exceeds 0.050%, coarse carbides or carbonitrides are easily formed in the steel wire, and the electrical resistivity of the steel wire may be increased. For this reason, 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 0.020% or less.
On the other hand, Nb is an element that forms carbides or carbonitrides in the steel wire to reduce the pearlite block size. Thereby, the decomposition of cementite is suppressed, and it is possible to achieve both the improvement of the tensile strength of the steel wire and the reduction of the electrical resistivity. From the viewpoint of the action, the Nb content may be more than 0%, may be 0.002% or more, and may be 0.005% or more.

B: 0 to 0.0030%
B is any 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, and the electrical resistivity of the steel wire may be increased. For this reason, the B content is 0.0030% or less. From the viewpoint of further reducing the electrical resistance of the steel wire, the B content is preferably 0.0025% or less.
On the other hand, B is an element which reduces the electrical resistivity of a steel wire by forming BN in a steel wire and reducing solid solution N. From the viewpoint of this action, the B content may be more than 0%, may be 0.0003% or more, and may be 0.0010% or more.

Remainder: Fe and impurities In the chemical composition in the present disclosure, the remainder excluding the above-described elements is Fe and impurities.
Here, the term "impurity" refers to a component contained in the raw material or a component mixed in the production process and not a component intentionally contained in steel.
As an impurity, all elements other than the elements mentioned above are mentioned. The element as an impurity may be only one or two or more.

The chemical composition of the steel wire in the present disclosure can contain at least one of Cr: more than 0% and 1.00% or less and Mo: 0% and less than 0.20% or less by mass%. The action of each of Cr and Mo in this case and the preferable content of each are as described above.

The chemical composition of the steel wire in the present disclosure is, by mass%, at least one of V: more than 0% and 0.15% or less; It can contain seeds. In this case, the actions of V, Ti and Nb and the preferable contents of each are as described above.

The chemical composition of the steel wire in the present disclosure can contain, in mass%, B: more than 0% and 0.0030% or less. The action and the preferable content of B in this case are as described above.

<Average Aspect Ratio of Cementite in the Longitudinal Section of Steel Wire and Half-Value Width of (211) Plane>
Next, the average aspect ratio of cementite and the half value width of the (211) plane in the longitudinal section of the steel wire in the present disclosure (that is, the steel wire in the aluminum-coated steel wire of the present disclosure) will be described.
In the steel wire according to the present disclosure, in the longitudinal section of the steel wire, the region X (that is, when the diameter of the steel wire is D, the distance from the central axis of the steel wire is D / 10 within a straight line The average aspect ratio of cementite in the region b) is 10 or more and 25 or less, and in the longitudinal section of the steel wire, the half-value width of the (211) plane measured using an X-ray diffractometer using a Mo tube is 0. 14 degrees or more and less than 0.30 degrees.

In the present specification, the longitudinal cross section of the steel wire means a cross section parallel to the longitudinal direction of the steel wire and including the central axis of the steel wire.
In the present specification, the cross section of the steel wire means a cross section perpendicular to the longitudinal direction of the steel wire. In addition, the cross section of a wire is the same meaning.

(Average aspect ratio of cementite)
The steel wire in the present disclosure is a region X in the longitudinal cross section (that is, a region within D / 10 of a straight line in which the distance from the central axis of the steel wire is D / 4, where D is the diameter of the steel wire) The average aspect ratio of cementite in is 10 or more and 25 or less.

Hereinafter, the region X in the vertical cross section of the steel wire will be described with reference to FIG.
FIG. 1: is a figure which shows notionally the longitudinal cross-section in the example of the steel wire of this indication, and the area | region X in this longitudinal cross-section.
As shown in FIG. 1, when the diameter of the steel wire is D, the region X is a straight line (in FIG. 1) having a distance of D / 4 from the central axis of the steel wire (one-dot chain line in FIG. 1). The area within D / 10 from the two broken lines of (2 areas in FIG. 1 with diagonal lines and the sign “X”). Region X is, in other words, a band-shaped region of width D / 5 centered on a straight line whose distance from the central axis of the steel wire is D / 4.

In the present disclosure, the reason for specifying the average aspect ratio of cementite in the region X is because the average aspect ratio of cementite in the region X is considered to be appropriate as a representative value of the aspect ratios of the longitudinal sections of the steel wire. Generally, in a steel wire produced by wire drawing of a wire, the aspect ratio of cementite in the vicinity of the outer peripheral surface of the steel wire tends to be smaller than the aspect ratio of cementite in region X, and the steel wire The aspect ratio of cementite near the central axis of H tends to be larger than the aspect ratio in the region X.

The steel wire in the present disclosure is excellent in tensile strength as compared with the case where the average aspect ratio of cementite in the region X in the longitudinal cross-section is less than 10. Hereinafter, this point will be described in detail.

The average aspect ratio of cementite in the region X in the longitudinal cross-section is 10 or more and 25 or less, the steel wire in the present disclosure is a wire mainly composed of a lamellar pearlite structure (i.e. steel before being drawn). It is indicated that the same is a steel wire formed by drawing and annealing.
Specifically, when a wire mainly composed of a lamellar perlite structure is subjected to wire drawing and annealing, the lamellar cementite in the lamellar perlite structure is divided by the wire drawing, and the divided lamellar cementite is spheroidized by annealing. As a result, cementite having an average aspect ratio of 10 to 25 in the region X in the longitudinal cross section is formed. By drawing a wire mainly having a lamellar perlite structure, work hardening can be promoted, and as a result, a steel wire having excellent tensile strength can be manufactured.
On the other hand, when wire drawing and annealing are performed on a wire mainly composed of a martensitic structure and / or a bainite structure, the tensile strength of the obtained steel wire is insufficient because work hardening is insufficient in the wire drawing. Run out. When wire drawing based on a martensitic structure and / or a bainite structure is carried out and annealing, the average aspect ratio of cementite in the region X in the longitudinal cross section of the obtained steel wire is less than 10.
For the above reasons, the steel wire in the present disclosure has the average aspect ratio of cementite in the region X in the longitudinal cross-section of 10 or more and 25 or less (in particular, the average aspect ratio of 10 or more). Compared with the case where an aspect ratio is less than 10, it is excellent in tensile strength.

From the viewpoint of further improving the tensile strength of the steel wire, the average aspect ratio of cementite in the region X in the longitudinal cross section is preferably 12 or more.

On the other hand, when the average aspect ratio of cementite in region X in the longitudinal cross-section exceeds 25, the electrical resistivity of the steel wire may become excessively large.
In this regard, the steel wire in the present disclosure has an electrical resistivity that is greater than 25 when the average aspect ratio of cementite in the region X in the longitudinal cross-section is 25 or less. Reduced.
From the viewpoint of further reducing the electrical resistivity of the steel wire, the average aspect ratio of cementite in the region X in the longitudinal cross section is preferably less than 25, more preferably 24 or less, and still more preferably 23 or less.

The average aspect ratio of cementite in the region X in the longitudinal section is not only the wire drawing strain but also the wire drawing strain (for example, the wire drawing strain represented by the formula (1) described later), and the annealing time in annealing There is also a correlation with the annealing temperature in annealing.
As the drawing strain is larger, the average aspect ratio of cementite tends to be smaller. The reason for this is considered to be that lamellar cementite in the lamellar perlite structure of the wire is more likely to be divided by the wire drawing as the wire drawing strain is larger.
Also, the larger the annealing time and the annealing temperature, the smaller the average aspect ratio of cementite tends to be. The reason for this is considered to be that the effect of spheroidizing cementite by annealing (that is, the effect of reducing the average aspect ratio of cementite by annealing) is more easily exhibited as the annealing time and the annealing temperature are larger.

-Method of measuring average aspect ratio of cementite-
In the present specification, the average aspect ratio of cementite in the region X in the longitudinal cross section of the steel wire means a value measured as follows.
The longitudinal section of the steel wire is mirror-polished, and the mirror-polished longitudinal section is corroded with picric acid alcohol (picral), and the corroded longitudinal section is observed using a field emission scanning electron microscope (FE-SEM) Then, two different places (that is, two fields of view) are selected from the area X in the longitudinal cross section, and metallographic photographs are taken at a magnification of 10000 times for each part.
On each photograph, a straight line is drawn every 1 μm along two orthogonal directions. Measure the length and width of cementite on the intersection of straight lines (the cementite closest to the intersection if there is no cementite on the intersection) and then measure the ratio of the length to the width (ie, the length / Width ratio) is calculated as the aspect ratio of the cementite. Here, the length of cementite is the length from one end to the other end along the shape of cementite. At this time, cementite which is out of the visual field is excluded from the calculation target of the aspect ratio. The width of cementite is the width of cementite at a position bisecting the length from one end to the other end along the shape of cementite.
For each photograph, cementite is selected at 60 locations (ie, 120 locations in a total of two fields of view), and the aspect ratio is calculated by the method described above for each of the 120 selected cementites. Here, when the aspect ratio of cementite of 60 places can not be calculated per one photo, a photo of another view is substituted.
The obtained 120 values (aspect ratio) are arithmetically averaged, and the obtained arithmetic average value is taken as an average aspect ratio.

(Half-value width of (211) plane)
In the longitudinal section of the steel wire of the present disclosure, the half value width of (211) plane measured using an X-ray diffractometer using a Mo tube (hereinafter, also simply referred to as “half value width of (211) plane”) Is correlated with the dislocation density in the steel wire. As the dislocation density in the steel wire is higher, the half value width of the (211) plane tends to be larger.

In the longitudinal section of the steel wire of the present disclosure, the half value width of the (211) plane is 0.14 ° or more. This improves the tensile strength of the steel wire. From the viewpoint of further improving the tensile strength of the steel wire, the half value width of the (211) plane is preferably 0.15 ° or more.

Moreover, in the longitudinal cross-section of the steel wire of this indication, the half value width of a (211) plane is 0.30 degrees or less. This improves the ductility of the steel wire. When the half width of the (211) plane exceeds 0.30 °, the ductility of the steel wire is reduced, and as a result, delamination may occur. From the viewpoint of further improving the ductility of the steel wire, the half value width of the (211) plane is preferably 0.29 ° or less.

-Method of measuring half width of (211) plane-
In the present specification, the half value width of the (211) plane in the longitudinal cross section of the steel wire (that is, the half value width of the (211) plane measured using an X-ray diffractometer using a Mo tube) is It means the value measured in this way.
The vertical cross section of the steel wire is mirror-polished, and the X-ray diffraction profile is measured on the mirror-polished vertical cross-section under the following conditions using an X-ray diffractometer (for example, "RINT 2200" manufactured by Rigaku Corporation). In the obtained X-ray diffraction profile, the half value width of the diffraction peak of the (211) plane is determined, and the obtained value is taken as the half value width of the (211) plane.

-Measurement conditions of X-ray diffraction profile-
Tube: Mo tube (tube using Mo as target)
Target output: 50 KV, 40 mA
Slit: divergence 1/2 °, scattering 1 °, light reception 0.15 mm
Sampling width: 0.010 °
Measurement range (2θ): 34.2 ° to 36.2 °
Maximum count number: 3000 or more

The dislocation density in the steel wire and the half value width of the (211) plane are the amount of wire drawing strain, the annealing time in annealing, and the annealing when the wire is subjected to wire drawing and annealing to produce a steel wire. There is a correlation with the annealing temperature at
The larger the drawing strain, the higher the dislocation density in the steel wire, and the larger the FWHM of the (211) plane.
The longer the annealing time, the lower the dislocation density in the steel wire (ie, the smaller the half width of the (211) plane), and the higher the annealing temperature, the lower the dislocation density in the steel wire (ie, (211) The half width of the face is reduced). The reason for these is considered to be that the dislocations introduced into the steel wire by drawing strain are recovered by annealing.

(Metallographic structure of cross section)
The steel wire in the present disclosure has a pro-eutectoid ferrite component in a region in which a region within D / 7 from the center and a region within D / 7 from the outer peripheral surface in a cross section when the diameter of the steel wire is D. The rate is preferably 10% or less. This further improves the tensile strength of the steel wire.
The pro-eutectoid ferrite fraction referred to herein means the area ratio of the pro-eutectoid ferrite structure to the whole metal structure in the area combining the area within D / 7 from the center and the area within D / 7 from the outer peripheral surface. .
A steel wire having a pro-eutectoid ferrite fraction of 10% or less can be manufactured by drawing a wire mainly having a lamellar perlite structure.
There is no particular limitation on the lower limit of the pro-eutectoid ferrite fraction, and the pro-eutectoid ferrite fraction may be 0%.
In the area | region which united the area | region within D / 7 from a center, and the area | region within D / 7 from an outer peripheral surface, it is preferable that the remainder except a pro-eutectoid ferrite from metal structure is a lamellar perlite structure.
The pro-eutectoid ferrite fraction in the cross section of the steel wire can be measured by the same method as the measurement of the pearlite fraction in the cross section of the wire described later.

<Tensile strength of steel wire>
As described above, the steel wire in the present disclosure is excellent in tensile strength.
The tensile strength of the steel wire is preferably 1900 MPa or more, more preferably 2100 MPa or more, and particularly preferably 2300 MPa or more.
The upper limit of the tensile strength of the steel wire is not particularly limited. The tensile strength of the steel wire may be 2800 MPa or less or 2600 MPa or less from the viewpoint of production suitability of the steel wire.

<Electric resistivity of steel wire>
As mentioned above, the steel wire in the present disclosure has a reduced electrical resistivity.
The electrical resistivity of the steel wire is preferably 0.175 μΩm or less.
The lower limit of the electrical resistivity of the steel wire is not particularly limited. The electrical resistivity of the steel wire may be 0.140 μΩm or more from the viewpoint of production suitability of the steel wire.

<Diameter of steel wire>
The diameter of the steel wire is preferably 1.0 mm or more and 3.5 mm or less.
When the diameter of the steel wire is 1.0 mm or more, wire drawing in the case of obtaining an aluminum coated steel wire by wire drawing can be performed more stably.
When the diameter of the steel wire is 3.5 mm or less, decomposition of cementite during wire drawing and an increase in electrical resistance due to this decomposition can be further suppressed.

<Al-containing layer>
The aluminum clad steel wire of the present disclosure includes an Al-containing layer covering at least a part of the above-described steel wire.
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 a component having the largest content (% by mass).
50 mass% or more is preferable, as for content of Al in an Al containing layer, 80 mass% or more is still more preferable, and 90 mass% or more is especially preferable.
As the Al-containing layer, an Al layer composed of Al (that is, pure Al) or an Al alloy layer composed 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. 50 mass% or more is preferable, 80 mass% or more is still more preferable, and, as for content of Al in Al alloy, 90 mass% or more is especially preferable. Specifically, preferred examples of the Al alloy include the 3000 series to 7000 series Al alloys in the international aluminum alloy name.
The Al layer made of Al here may contain impurities in addition to Al. Similarly, the Al alloy layer made of an Al alloy as referred to herein may contain impurities in addition to the Al alloy.

The area ratio of the Al-containing layer to the entire cross section of the aluminum-coated steel wire of the present disclosure is preferably 10% to 64%.
When the area ratio of the Al-containing layer is 10% or more, the electrical resistance (in detail, the electrical resistance in the longitudinal direction) of the entire aluminum clad steel wire is further reduced.
When the area ratio of the Al-containing layer is 64% or less, the tensile strength of the entire aluminum clad steel wire is further improved.
The area ratio of the Al-containing layer is more preferably 10% to 50%, still more preferably 10% to 40%, and still more preferably 15% to 35%.

The aluminum clad steel wire of the present disclosure described above is used as a core material of a steel core aluminum stranded wire.
As the steel core aluminum stranded wire referred to herein, a general steel core aluminum stranded wire having a structure in which the aluminum clad steel wire of the present disclosure is used as a core material and an aluminum wire or an aluminum alloy wire is twisted on the outside of this core material. There is no particular limitation.

[Example of production method of aluminum coated steel wire (production method A)]
The following manufacturing method A is mentioned as an example of the method of manufacturing the aluminum clad steel wire of this indication.
Production method A is
The chemical composition is the chemical composition in the present disclosure described above, and in the cross section, when the diameter of the wire is d, a region within d / 7 from the center and a region within d / 7 from the outer peripheral surface are combined. Preparing a wire having a pearlite fraction of 90% or more in the region (hereinafter, also referred to as “wire preparation step”);
A step of obtaining an unannealed steel wire by subjecting the wire to a first wire drawing process (hereinafter, also referred to as a “first wire drawing step”);
Forming an Al-containing layer covering at least a part of the unannealed steel wire to obtain an Al-containing layer-containing unannealed steel wire (hereinafter, also referred to as an “Al-containing layer forming step”);
A step of subjecting the aluminum-containing unannealed steel wire to a second wire drawing process (hereinafter, also referred to as a “second wire drawing step”);
A step of obtaining an aluminum-coated steel wire (hereinafter, also referred to as an “annealing step”) by annealing the second wire-drawn non-annealed steel wire with an Al-containing layer;
Including
The wire drawing strain represented by the following formula (1) is more than 2.6 and not more than 3.6, and the diameter of the steel wire in the aluminum clad steel wire is not less than 1.0 mm and not more than 3.5 mm,
The annealing temperature in the annealing is over 370 ° C. and 520 ° C. or less, and the annealing time in the annealing is 10 seconds or more and 180 seconds or less.

Wire drawing strain = 2 × ln (diameter of wire (mm) / diameter of steel wire in aluminum coated steel wire (mm)) Formula (1)

The production method A may include other steps as necessary.

<Wire preparation process>
The wire preparing step has the chemical composition according to the present disclosure described above, and in the cross section, when the diameter of the wire is d, a region within d / 7 from the center (hereinafter also referred to as “region Y1”) and the outer periphery This is a step of preparing a wire having a pearlite fraction of 90% or more in a region obtained by combining a region within d / 7 from the surface (hereinafter also referred to as “region Y2”).

Hereinafter, the region Y1 and the region Y2 in the cross section of the wire will be described with reference to FIG.
FIG. 2: is a figure which shows notionally the cross section of a wire, and area | region Y1 in this cross section, and area | region Y2 in an example of the manufacturing method of the steel wire of this indication.
As shown in FIG. 2, assuming that the diameter of the wire is d, the region Y1 is a region within d / 7 from the center P of the wire (a region indicated by hatching and “Y1” in FIG. 2) The region Y2 is a region within d / 7 from the outer peripheral surface (a region indicated by oblique lines and a symbol "Y2" in FIG. 2).

The reason for specifying the pearlite fraction in the area obtained by combining the area Y1 and the area Y2 in the cross section of the wire in the manufacturing method A is that the pearlite fraction in the area obtained by combining the area Y1 and the area Y2 is the cross section of the wire Because it is considered to be appropriate as a representative value of the perlite fraction in

In the manufacturing method A, a wire having a pearlite fraction of 90% or more in a region obtained by combining the region Y1 and the region Y2 is used as a wire which is a steel material before wire drawing, and the first wire drawing is performed on this wire Work hardening can be promoted by applying the second wire drawing process. Therefore, the tensile strength of the wire can be efficiently improved. That is, the steel wire excellent in tensile strength can be manufactured.

The pearlite fraction of the wire means the area ratio of the lamellar perlite structure in the entire metallographic structure in the combined area of the area Y1 and the area Y2.
The pearlite fraction of the wire is preferably 95% or more.
The pearlite fraction of the wire may be 100%, less than 100%, or 99% or less.
In the area | region which united the area | region Y1 and the area | region Y2, it is preferable that the remainder (namely, non-perlite structure) which remove | eliminated the lamellar perlite structure from metal structure is a proeutectoid ferrite structure.

In the present specification, the pearlite fraction in the combined area of the area Y1 and the area Y2 means a value measured as follows.
The cross section of the wire is mirror-polished, the mirror-polished cross-section is corroded with picral, and the corroded cross-section is observed using an FE-SEM. From each of the area Y1 and the area Y2, the observation view is 10 Select each place (ie, a total of 20 views). In each of the 20 selected fields of view, metallographic photographs are taken at a magnification of 2000 ×. The area per view is 2.7 × 10 ^-3 mm ² (0.045 mm in length, 0.060 mm in width).
Next, a transparent sheet (for example, an OHP (Over Head Projector) sheet) is overlaid on each metallographic photograph, and in this state, color is applied to the non-perlite structure (that is, a structure other than the lamellar perlite structure) in each transparent sheet. Paint.
Next, for each transparent sheet, the area ratio of the “colored area” is determined by image analysis software. The obtained area ratio (20 values) is arithmetically averaged, and the obtained value is taken as the area ratio of non-perlite structure. Let the value which deducted the area rate of non-pearlite structure from 100% be the pearlite fraction in the field which combined field Y1 and field Y2 in the cross section of a wire.

The diameter of the wire is preferably 6 mm or more and 12 mm or less.
When the diameter of the wire is 6 mm or more, it is easier to make the drawing strain more than 2.6.
When the diameter of the wire is 12 mm or less, the first wire drawing is easier.

The wire preparation step may be a step of merely preparing a pre-manufactured wire, or may be a step of manufacturing the wire.

(Preferred method of manufacturing wire rod)
Hereinafter, the preferable manufacturing method of a wire in the case where a wire preparation process is a process of manufacturing a wire is demonstrated.
The preferred method of producing the wire is
A step of melting an steel having the chemical composition in the present disclosure described above and then casting to obtain an ingot (hereinafter also referred to as a “casting step”);
A step of heating the ingot and then hot rolling to obtain a wire rod (hereinafter also referred to as a “hot rolling step”);
including.

Melting of steel in the casting step can be performed by a usual method using a melting furnace such as a vacuum melting furnace.

In the hot rolling step, prior to hot rolling, it is preferable to heat the ingot at a temperature of 1150 ° C. or more and 1350 ° C. or less for 30 minutes or more and 90 minutes or less.
When the heating temperature of the ingot is 1150 ° C. or more and the heating time of the ingot is 30 minutes or more, the ingot center can be sufficiently heated, and segregation of the center can be suppressed. As a result, it is possible to suppress breakage of the wire or steel wire during wire drawing after hot rolling.
Further, by setting the ingot heating temperature to 1350 ° C. or less and the ingot heating time to be 90 minutes or less, the progress of decarburization in the steel can be suppressed, and as a result, the steel wire resulting from decarburization It is possible to suppress the decrease in tensile strength of

In the hot rolling step, the finishing temperature of the hot rolling is preferably 800 ° C. or more and 1000 ° C. or less.
The resistance reaction force during hot rolling can be reduced as the finishing temperature of hot rolling is 800 ° C. or higher, and the shape can be easily formed.
The fall of the ductility of a wire can be controlled as the finish temperature of hot rolling is 1100 ° C or less, and the fracture during wire drawing can be controlled.

The cooling method after hot rolling is preferably air cooling (including blast cooling) or water cooling. Thereby, a wire rod having a pearlite fraction of 90% or more is easily obtained.
The preferred range of the diameter of the wire obtained by hot rolling is as described above.

<First wire drawing process>
The first wire drawing step is a step of obtaining a non-annealed steel wire by subjecting the above-described wire to a first wire drawing process.
In the production method A, the first wire drawing step is provided before the later-described second wire drawing step (that is, the step of performing a second wire drawing process after the formation of the Al-containing layer), whereby the roundness of the steel wire is obtained. An effect is obtained that it is easy to manufacture an aluminum coated steel wire which is excellent in the thickness of the Al-containing layer and reduced in thickness.
The first wire drawing process can be performed using a wire drawing machine commonly used in the field (for example, a wire drawing machine including dies and rolls).
The diameter of the unannealed steel wire obtained by the first wire drawing is preferably 3 mm or more and 10 mm or less.
As the diameter of the unannealed steel wire is 3 mm or more, the amount of processing in wire drawing after forming the Al-containing layer (that is, second wire drawing described later) can be increased, so The adhesion between the steel wire and the Al-containing layer in the steel wire can be further improved.
When the diameter of the unannealed steel wire is 10 mm or less, wire drawing after forming the Al-containing layer (that is, second wire drawing described later) becomes easier.

<Al-containing layer forming step>
The Al-containing layer forming step is a step of obtaining an Al-containing layer-containing non-annealed steel wire by forming an Al-containing layer covering at least a part of the unannealed steel wire.
There is no restriction | limiting in particular as a formation method of Al containing layer, The method normally used in this field is applicable.
As a method of forming an Al-containing layer, for example, a method of forming an Al-containing layer by extruding an unannealed steel wire in a tube containing Al; applying a powder containing Al to an unannealed steel wire And a method of forming an Al-containing layer by subsequent sintering; and the like.
As a material of a tube containing Al and a material of a powder containing Al, Al or an Al alloy is preferable, respectively. About the preferable aspect of Al alloy, it is as above-mentioned.
In the Al-containing layer forming step, the Al-containing layer is applied to at least a part of the unannealed steel wire, preferably to the entire outer peripheral surface of the unannealed steel wire, It is preferable to form so that the area ratio of 10% to 64%.

<2nd wire drawing process>
The second wire drawing step is a step of subjecting the Al-containing layer-containing unannealed steel wire to a second wire drawing process.
In the manufacturing method A, by providing the second wire drawing step after the Al-containing layer forming step, the effect of being able to improve the adhesion between the Al-containing layer and the steel wire is exhibited.
The second wire drawing process can also be performed using a wire drawing machine commonly used in the field (for example, a wire drawing machine including dies and rolls).
The diameter of the second non-annealed steel wire after wire drawing (that is, the non-annealed steel wire in the non-annealed steel wire with an Al-containing layer) is preferably 1.0 mm or more and 3.5 mm or less.
When the diameter of the unannealed steel wire after the second wire drawing is 1.0 mm or more, the second wire drawing can be performed more stably, so the tensile strength of the steel wire is more than that. improves.
When the diameter of the unannealed steel wire after the second wire drawing is 3.5 mm or less, decomposition of cementite during the second wire drawing and an increase in electrical resistance due to the decomposition can be further suppressed.

<Annealing process>
The annealing step is a step of obtaining an aluminum-coated steel wire by performing annealing on the second wire-drawing uncoated steel wire with Al-containing layer.
Annealing can be performed using the annealing machine normally used in this field | area.
There is no restriction | limiting in particular in the cooling method in annealing (namely, the cooling method after heat treatment in the following annealing temperature and the following annealing time), Any of air cooling, water cooling, and furnace cooling can be applied.

(Annealing temperature)
The annealing temperature in annealing is more than 370 ° C. and less than or equal to 520 ° C.
When the annealing temperature in the annealing is over 370 ° C., solid solution carbon can be reprecipitated as cementite, and since spheroidization of cementite can be promoted, the average aspect ratio of cementite of the obtained steel wire is 25 or less Easy to adjust. For this reason, the electrical resistivity of the steel wire can be reduced.
Also, if the annealing temperature in the annealing is over 370 ° C., it is easy to recover the dislocations introduced by the strain in the first wire drawing process and / or the second wire drawing process by annealing (ie, it is easy to reduce the dislocation density) Because of this, it is easy to adjust the half value width of the (211) plane of the obtained steel wire to less than 0.30 °. Therefore, the ductility of the steel wire can be improved.
The annealing temperature in the annealing is preferably 380 ° C. or more, more preferably 400 ° C. or more.

When the annealing temperature in the annealing is 520 ° C. or less, an excessive decrease in dislocation density due to the annealing can be suppressed, so the half width of the (211) plane of the obtained steel wire can be easily adjusted to 0.14 ° or more. For this reason, the fall of the tensile strength of the steel wire by annealing can be suppressed.
The annealing temperature in the annealing is preferably 500 ° C. or less, more preferably 480 ° C. or less.

(Annealing time)
The annealing time in annealing is 10 seconds or more and 180 seconds or less.
Since the dislocation introduced by the strain in the first wire drawing step and / or the second wire drawing step is easily recovered by annealing if the annealing time in the annealing is 10 seconds or more (that is, the dislocation density is easily reduced). The half width of the (211) plane of the obtained steel wire can be easily adjusted to less than 0.30 °. Therefore, the ductility of the steel wire can be improved.
The annealing time is preferably 20 seconds or more, more preferably 25 seconds or more.

On the other hand, if the annealing time in the annealing is 180 seconds or less, an excessive decrease in dislocation density due to the annealing can be suppressed, so the half width of the (211) plane of the obtained steel wire can be easily adjusted to 0.14 ° or more . For this reason, the fall of the tensile strength of the steel wire by annealing can be suppressed.
The annealing time in annealing is preferably 120 seconds or less.

(Wire drawing strain)
In the production method A, the drawing strain represented by the following formula (1) is more than 2.6 and not more than 3.6, and the diameter of the steel wire in the aluminum coated steel wire is not less than 1.0 mm and not more than 3.5 mm .

The wire drawing strain represented by the formula (1) is a numerical value of the amount of strain introduced by the first wire drawing process and the second wire drawing process.
In Formula (1), "ln" means a natural logarithm (namely, "log _e ").

It is easy to increase the dislocation density of the steel by the strain in the first wire drawing and the second wire drawing if the wire drawing strain represented by the formula (1) is more than 2.6, so it is obtained It is easy to adjust the half value width of the (211) plane of the steel wire to 0.14 ° or more. Moreover, work hardening is fully performed as the wire-drawing process distortion represented by Formula (1) is more than 2.6. For these reasons, the tensile strength of the steel wire is improved.
Furthermore, since it is easy to divide cementite by the first wire drawing and the second wire drawing when the wire drawing strain represented by the formula (1) is more than 2.6, the cementite of the obtained steel wire It is easy to adjust the average aspect ratio of to 25 or less. For this reason, the electrical resistivity of the steel wire can be reduced.
The wire drawing strain represented by the formula (1) is preferably 2.7 or more, more preferably more than 2.7.

When the wire drawing strain represented by the formula (1) is 3.6 or less, the diameter of the wire to be subjected to the first wire drawing process can be reduced to some extent. For this reason, it is easy to perform the first wire drawing process because the wire drawing process strain represented by the formula (1) is 3.6 or less. From the viewpoint of facilitating the first wire drawing process, the wire drawing process strain represented by the formula (1) is preferably 3.4 or less, more preferably 3.2 or less.

In the production method A, the diameter of the steel wire in the finally obtained aluminum clad steel wire is 1.0 mm or more and 3.5 mm or less.
When the diameter of the steel wire is 1.0 mm or more, the first wire drawing and / or the second wire drawing can be performed more stably.
Since the diameter of the steel wire is 3.5 mm or less, the decomposition of cementite can be suppressed during the first wire drawing and / or the second wire drawing, thereby increasing the electrical resistivity of the steel wire. It can suppress more.

[Another example of manufacturing method of aluminum coated steel wire (Process B)]
As a method of manufacturing the aluminum-coated steel wire of the present disclosure, the following manufacturing method B can also be mentioned as an example different from the manufacturing method A.
Process B is
Preparing a wire having a chemical composition according to the present disclosure as described above, and having a pearlite fraction of 90% or more in a region obtained by combining the region Y1 and the region Y2 in the cross section;
Obtaining an Al-containing layered wire by forming an Al-containing layer covering at least a part of the wire;
Drawing a wire with an Al-containing layer;
A process of obtaining an aluminum coated steel wire by annealing the wire rod with Al containing layer subjected to wire drawing;
Including
The wire drawing strain represented by the above-mentioned formula (1) is more than 2.6 and not more than 3.6, and the diameter of the steel wire in the aluminum clad steel wire is not less than 1.0 mm and not more than 3.5 mm,
The annealing temperature in the annealing is over 370 ° C. and 520 ° C. or less, and the annealing time in the annealing is 10 seconds or more and 180 seconds or less.
Manufacturing method B is substantially the same as Manufacturing method A except that the first wire drawing step is not included.

Examples of the present disclosure will be shown below, but the present disclosure is not limited to the following examples.

[Examples 1 to 23, Comparative Examples 1 to 18]
<Production of aluminum coated steel wire>
An aluminum coated steel wire was manufactured by the following steps.

(Wire rod preparation process)
Ingots were obtained by melting 50 kg of each of steels A to T having the chemical compositions shown in Table 1 in a vacuum melting furnace and then casting.

In Examples 1 to 23 and Comparative Examples 1 to 16 and 18, the ingot is heated at 1250 ° C. for 1 hour, then subjected to hot rolling with a finishing temperature of 950 ° C. or higher, and then cooled by blast to obtain lamellae. A wire having a diameter of 10 mm mainly composed of pearlite was obtained.
In Comparative Example 17, the ingot is heated at 1250 ° C. for 1 hour, then subjected to hot rolling with a finishing temperature of 950 ° C. or higher, and then immersed in a salt bath at 480 ° C. to obtain a bainite structure as a main component. A wire of 10 mm in diameter was obtained.

In each steel in Table 1, the numerical values shown in the column of each element mean mass% of the corresponding element.
In each steel in Table 1, "-" means that the corresponding element is not contained.
In each steel in Table 1, the balance excluding the element group described in Table 1 is Fe and impurities.
The underline in Table 1 indicates that it is outside the scope of the present disclosure (the same applies to Table 2 described later).

(Measurement of pearlite fraction and confirmation of the remaining part in the area obtained by combining the area Y1 and the area Y2 in the cross section of the wire rod)
With respect to the wire rod obtained above, the pearlite fraction in the region obtained by combining the region Y1 and the region Y2 in the cross section was measured by the method described above. Moreover, based on the metallographic structure photograph used for the measurement of the perlite fraction, the remaining parts other than perlite were confirmed.
The results are shown in Table 2.
In the "remaining" column in Table 2, "F" means a pro-eutectoid ferrite structure, and "B" means a bainite structure.

(First wire drawing process)
The first wire drawing was performed on the obtained wire rod to obtain an unannealed steel wire having a diameter of 3.8 mm or more and 8.8 mm or less.

(Al-containing layer forming step)
An unannealed steel wire is coated with an Al layer (ie, pure aluminum layer) as an Al-containing layer by extruding the unannealed steel wire obtained above through an Al tube (ie, a pure aluminum tube) did. Thus, an unannealed steel wire with an Al-containing layer was obtained.

(2nd wire drawing process)
The second wire drawing was performed on the unannealed steel wire with an Al-containing layer obtained above until the diameter of the steel wire was in the range of 1.5 mm to 3.0 mm.

(Annealing process)
An aluminum coated steel wire is subjected to the annealing shown in Table 2 (that is, the annealing temperature, the annealing time, and the cooling method) on the second wire-drawn unalloyed steel wire with Al-containing layer. I got
The area ratio of the Al-containing layer to the entire cross section of the obtained aluminum coated steel wire was 23%.

(Calculation of wire drawing strain)
A steel wire was obtained from the obtained aluminum coated steel wire by peeling an Al-containing layer by a mechanical method. The diameter (mm) of the obtained steel wire was measured, and the obtained result was made the diameter (mm) of the steel wire in the aluminum coated steel wire.
The wire drawing strain was calculated by the following formula (1) based on the diameter (mm) of the steel wire in the aluminum-coated steel wire and the diameter (i.e. 10 mm) of the wire rod.
The results are shown in Table 2.

(Calculation of average aspect ratio of cementite in longitudinal section of steel wire in aluminum coated steel wire)
A steel wire was obtained from the obtained aluminum coated steel wire by peeling an Al-containing layer by a mechanical method. Using the obtained steel wire, the average aspect ratio of cementite in the region X in the longitudinal section was calculated by the method described above.
The results are shown in Table 2.

(Measurement of Half-Value Width of (211) Plane in Longitudinal Section of Steel Wire in Aluminum Coated Steel Wire)
A steel wire was obtained from the obtained aluminum coated steel wire by peeling an Al-containing layer by a mechanical method. The half value width of the (211) plane in the longitudinal section was measured by the method described above using the obtained steel wire and an X-ray diffractometer ("RINT 2200" manufactured by RIGAKU Co., Ltd.).
The results are shown in Table 2.

(Observation of metallographic structure in cross section of steel wire in aluminum coated steel wire)
The metal structure in the cross section of the steel wire in the aluminum clad steel wire of Examples 1 to 23 was observed.
Specifically, in each of Examples 1 to 23, a steel wire was obtained by mechanically peeling an Al-containing layer from the aluminum clad steel wire. Regarding the obtained steel wire, in the cross section of the steel wire in the aluminum coated steel wire, by the same method as the measurement of the pearlite fraction in the region where the region Y1 and the region Y2 in the cross section of the wire are combined The metallographic structure was observed.
As a result, in any of the embodiments, in the cross section of the steel wire, the region within D / 7 from the center and the region within D / 7 from the outer peripheral surface (D is the diameter of the steel wire) In the above, the area ratio of the pro-eutectoid ferrite structure was 10% or less, and the balance was the lamellar perlite structure.

(Measurement of tensile strength of steel wire in aluminum coated steel wire)
A steel wire was obtained from the obtained aluminum coated steel wire by peeling an Al-containing layer by a mechanical method.
Two tensile test pieces having a length of 200 mm were taken from the obtained steel wire.
Each of the two tensile test specimens collected was subjected to a tensile test under a temperature condition of 20 ° C. according to the method according to JIS Z 2241 (2011), and the tensile strength (in detail, the length of the tensile test specimen) Tensile strength in the direction was measured.
The average value of the tensile strengths of the two tensile test pieces was taken as the tensile strength of the steel wire in the aluminum clad steel wire.
The results are shown in Table 2.

(Measurement of electrical resistivity of steel wire in aluminum coated steel wire)
A steel wire was obtained from the obtained aluminum coated steel wire by peeling an Al-containing layer by a mechanical method.
From the center of the obtained steel wire, a cylindrical test piece 1.0 mm in diameter × 60 mm in length was collected. The electrical resistance value in the longitudinal direction of the collected test pieces was measured by a four-terminal method at a temperature of 20 ° C. By multiplying the obtained electrical resistance value by the area of the cross section of the test piece (that is, the cross section orthogonal to the longitudinal direction of the test piece) and dividing the obtained value by the length of the test piece in the longitudinal direction The electrical resistivity (μΩm) in the longitudinal direction of the test piece was calculated.

(Evaluation of ductility of steel wire in aluminum coated steel wire)
A steel wire was obtained from the obtained aluminum coated steel wire by peeling an Al-containing layer by a mechanical method. From the obtained steel wire, ten steel wires having a length of 100 times the diameter (hereinafter referred to as "sample") were cut out. The ductility of the steel wire in the aluminum clad steel wire was evaluated by performing a torsion test according to JIS Z 3541 (1991) for each of the ten samples.
In detail, the sample was twisted at 15 rpm (round per minute) until broken, and a torque (resistance to twist) curve was created. In the torque curve, it was determined that delamination occurred when the torque decreased sharply before the disconnection.
The ductility was judged to be good (in Table 2, ductility "A") in the case where none of the 10 samples had delamination occurred.
It was judged that the ductility was insufficient when one or more of the samples in which delamination occurred was present among ten samples (in Table 2, ductility "B").
The results are shown in Table 2.

As shown in Table 2, the chemical composition of the steel wire is the chemical composition in the present disclosure, and in the region X in the longitudinal cross section of the steel wire, the average aspect ratio of cementite is 10 to 25 and the longitudinal cross section of the steel wire In Examples 1 to 23, in which the half value width of the (211) plane is 0.14 ° or more and less than 0.30 °, the tensile strength and ductility of the steel wire are excellent, and the electrical resistivity of the steel wire is reduced. It was

For each example, the results of each comparative example were as follows.
In Comparative Example 1 in which the C content is too small, the half value width of the (211) plane is less than 0.14 °, and the tensile strength of the steel wire is insufficient. The reason is considered to be that the accumulation of dislocations due to the first wire drawing and the second wire drawing was insufficient due to the C content being too low.
In Comparative Example 2 in which the C content is too large, the electrical resistivity of the steel wire was too high.
In Comparative Example 3 in which the Si content is too large, the electrical resistivity of the steel wire was too high.
In Comparative Example 4 in which the Mn content is too high, the electrical resistivity of the steel wire was too high.
In Comparative Example 5 in which the Cr content was too high, the average aspect ratio of cementite was over 25 and the electrical resistivity of the steel wire was too high. The reason for this is considered to be that the progress of spheroidization due to annealing was impeded due to the Cr content being too high.
In Comparative Example 6 in which the Mo content is too high, the electrical resistivity of the steel wire was too high.
In Comparative Example 7 in which the Nb content is too large, the electrical resistivity of the steel wire was too high.
In Comparative Example 8 in which the Ti content is too high, the electrical resistivity of the steel wire was too high.
In Comparative Example 9 in which the V content was too high, the electrical resistivity of the steel wire was too high.

The tensile strength of the steel wire was insufficient in Comparative Example 10 having the chemical composition in the present disclosure but the half value width of the (211) plane is less than 0.14 °.
The reason for the half value width of the (211) plane being less than 0.14 ° in the comparative example 10 is that the wire drawing strain due to the first wire drawing and the second wire drawing was too small, It is considered that the accumulation of dislocations was insufficient.

In Comparative Example 11 in which the average aspect ratio of cementite is more than 25 and the half value width of the (211) plane is 0.30 ° or more, the electrical resistivity of the steel wire is too high, although it has the chemical composition in the present disclosure. And the ductility of the steel wire was insufficient.
In Comparative Example 11, the reason why the average aspect ratio of cementite is more than 25 is that the annealing temperature is too low, so the effect of spheroidizing cementite by annealing (ie, the effect of reducing the average aspect ratio) is insufficient. It is thought that there was.
The reason why the half value width of the (211) plane is 0.30 ° or more in Comparative Example 11 is considered to be that the effect of recovery of dislocations by annealing is insufficient because the annealing temperature is too low. .

The tensile strength of the steel wire was insufficient in Comparative Example 12 which has the chemical composition in the present disclosure but the half value width of the (211) plane is less than 0.14 °.
The reason for the half value width of the (211) plane being less than 0.14 ° in Comparative Example 12 is that the annealing temperature was too high, so the recovery of dislocations due to annealing became excessive and the dislocation density of the steel wire decreased. It is believed that

The ductility of the steel wire was insufficient in Comparative Example 13 which has the chemical composition in the present disclosure but the half value width of the (211) plane is 0.30 ° or more.
The reason why the half value width of the (211) plane is 0.30 ° or more in Comparative Example 13 is considered to be that the effect of recovery of dislocations by annealing was insufficient because the annealing time was too short. .

The tensile strength of the steel wire was insufficient in Comparative Example 14 having the chemical composition in the present disclosure but the half value width of the (211) plane is less than 0.14 °.
The reason why the half width of the (211) plane is less than 0.14 ° in Comparative Example 14 is considered to be that the recovery of dislocation was excessive and the dislocation density of the steel wire was lowered because the annealing time was too long. Be

In Comparative Example 15 in which the average aspect ratio of cementite is more than 25 and the half value width of the (211) plane is less than 0.14 ° while having the chemical composition in the present disclosure, the electrical resistivity of the steel wire is too high. And the tensile strength of the steel wire was insufficient.
In Comparative Example 15, the reason why the average aspect ratio of cementite is more than 25 is that the wire drawing strain by the first wire drawing and the second wire drawing was too small. It is considered that the effect of dividing cementite was insufficient.
The reason for the half value width of the (211) plane being less than 0.14 ° in the comparative example 15 is that the wire drawing strain due to the first wire drawing and the second wire drawing was too small, so the dislocation was It is considered that the accumulation of

The tensile strength of the steel wire was insufficient in Comparative Example 16 which has the chemical composition in the present disclosure but the half value width of the (211) plane is less than 0.14 °.
The reason for the half value width of the (211) plane being less than 0.14 ° in Comparative Example 16 is that the annealing temperature was too high, so the recovery of dislocations by annealing became excessive and the dislocation density of the steel wire was lowered It is believed that

In Comparative Example 17 having the chemical composition in the present disclosure but having an average aspect ratio of cementite of less than 10, the tensile strength of the steel wire was insufficient. The reason for this is that work hardening by the first wire drawing and the second wire drawing is due to the average aspect ratio of cementite being less than 10 (that is, the structure of the wire rod is bainite-based structure). It is thought that it is because it ran short.

In Comparative Example 18 in which the Al content was too high, the electrical resistivity of the steel wire was too high.

Claims

Used as core material of steel core aluminum stranded wire,
A steel wire, and an Al-containing layer covering at least a part of the steel wire,
The chemical composition of the steel wire is in mass%,
C: 0.60 to 1.10%,
Si: 0.01 to 0.10%,
Mn: 0.10 to 0.30%,
Al: 0.005 to 0.050%,
N: 0 to 0.0070%,
P: 0 to 0.030%,
S: 0 to 0.030%,
Cr: 0 to 1.00%,
Mo: 0 to 0.20%,
V: 0 to 0.15%,
Ti: 0 to 0.050%,
Nb: 0 to 0.050%,
B: 0 to 0.0030%, and
Remainder: consists of Fe and impurities,
In the longitudinal section of the steel wire, when the diameter of the steel wire is D, the average aspect ratio of cementite in a region within D / 10 from the straight line where the distance from the central axis of the steel wire is D / 4 is 10 or more and 25 or less,
The aluminum coated steel wire whose half value width of (211) plane measured using the X-ray-diffraction apparatus which used Mo tube in the longitudinal cross-section of the said steel wire is 0.14 degrees or more and less than 0.30 degrees.
The steel wire is, by mass%,
The aluminum-coated steel wire according to claim 1, containing at least one of Cr: more than 0% and 1.00% or less and Mo: more than 0% and 0.20% or less.
The steel wire is, by mass%,
The method according to claim 1 or claim 2, containing at least one of V: more than 0% and 0.15% or less, Ti: more than 0% and 0.050% or less, and Nb: more than 0% and 0.050% or less. Aluminum coated steel wire.
The steel wire is, by mass%,
The aluminum-coated steel wire according to any one of claims 1 to 3, which contains B: more than 0% and 0.0030% or less.
The aluminum-coated steel wire according to any one of claims 1 to 4, wherein a tensile strength of the steel wire is 1900 MPa or more.
A method of manufacturing the aluminum clad steel wire according to any one of claims 1 to 5,
The chemical composition is in mass%,
C: 0.60 to 1.10%,
Si: 0.01 to 0.10%,
Mn: 0.10 to 0.30%,
Al: 0.005 to 0.050%,
N: 0 to 0.0070%,
P: 0 to 0.030%,
S: 0 to 0.030%,
Cr: 0 to 1.00%,
Mo: 0 to 0.20%,
V: 0 to 0.15%,
Ti: 0 to 0.050%,
Nb: 0 to 0.050%,
B: 0 to 0.0030%, and
Remainder: consists of Fe and impurities
In the cross section, when the diameter of the wire is d, prepare a wire having a pearlite fraction of 90% or more in the region combining the region within d / 7 from the center and the region within d / 7 from the outer peripheral surface The process to
Obtaining an unannealed steel wire by subjecting the wire to a first wire drawing process;
Obtaining an unannealed steel wire with an Al-containing layer by forming an Al-containing layer covering at least a part of the unannealed steel wire;
Performing a second wire drawing process on the unannealed steel wire with the Al-containing layer;
Obtaining the aluminum-coated steel wire by annealing the non-annealed steel wire with the Al-containing layer subjected to the second wire drawing;
Including
The wire drawing strain represented by the following formula (1) is more than 2.6 and not more than 3.6, and the diameter of the steel wire in the aluminum coated steel wire is not less than 1.0 mm and not more than 3.5 mm,
The manufacturing method of the aluminum coated steel wire whose annealing temperature in the said annealing is 370 degreeC-520 degrees C or less, and the annealing time in the said annealing is 10 to 180 second.
Wire drawing strain = 2 × ln (diameter of the wire (mm) / diameter of the steel wire in the aluminum-coated steel wire (mm)) Formula (1)