wire

Abstract

To provide a wire material that is made into a steel wire to provide a sufficient durability ratio, and demonstrates adequate wire drawing processability.SOLUTION: A wire material disclosed herein includes, in mass%, C: 0.70-1.10% (excluding 1.10%), Si: 0.10-0.40%, Mn: 0.15-0.80%, Cu: 0.10-1.00% (excluding 1.00%), P: 0.015% or less, S: 0.015% or less, N: 0.0005-0.0060%, Al: 0.003% or less, and O: 0.0040% or less, with a balance being Fe and impurities, and satisfies a formula (1) and a formula (2). 0.10≤Si / (C+Ni)≤0.20 (1) and 1.43≤(Cr+Mn+Cu) / (Si+10P+10S+100N)≤1.63 (2).SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to wire rods.

Background Art

[0002] Steel wires are used for bead wires, steel cords, wire ropes, etc. For example, a wire rod is drawn to form a steel wire, and then a plating film is coated on the steel wire and a plating diffusion treatment is performed to manufacture the steel wire.

[0003] The steel wires used for the above applications are required to have an excellent durability ratio (= tensile strength / fatigue strength). Therefore, for wire rods used as materials for steel wires, excellent durability ratio is required when manufacturing steel wires using the wire rods as materials. Furthermore, when manufacturing steel wires, wire drawing may be performed on the wire rods serving as the materials for the steel wires multiple times. Therefore, excellent wire drawing property is also required.

[0004] Techniques related to improving wire drawing property and fatigue characteristics of steel wires are proposed in Japanese Patent Application Laid-Open No. 2011-225990 (Patent Document 1).

[0005] The wire rod disclosed in Patent Document 1 contains, in mass%, C: 0.70 to 1.2%, Si: 0.1 to 1.5%, Mn: 0.1 to 1.5%, P: 0.015% or less (excluding 0%), S: 0.015% or less (excluding 0%), Al: 0.005% or less (excluding 0%), B: 0.0005 to 0.010%, N: 0.002 to 0.005%, the solid solution N is 0.0015% or less (including 0%), the balance is composed of iron and inevitable impurities, the area ratio of the pearlite structure is 90% or more, and in the pearlite structure of 2000 μm There are 100 or less (including 0) BN-based compounds having a circle equivalent diameter of 100 nm or more and less than 1000 nm, and 10 or less (including 0) BN-based compounds having a circle equivalent diameter of 1000 nm or more. In Patent Document 1, by controlling the number of BN-based compounds, the wire drawing property and fatigue characteristics are enhanced.

Prior Art Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2011-225990 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] In the wire rod proposed in Patent Document 1, the drawability and fatigue properties are improved by controlling the BN compound in the steel. However, these properties may be improved by other means.

[0008] The object of the present invention is to provide a wire material that has sufficient drawability and, when used as a material to manufacture steel wire, provides a sufficient durability ratio in the steel wire. [Means for solving the problem]

[0009] The wire material of the present invention is The chemical composition is expressed in mass percent. C: 0.70-1.10% Si: 0.10~0.40%, Mn: 0.15~0.80%, Cu: 0.10 to less than 1.00%, P: 0.015% or less, S: 0.015% or less, N: 0.0005~0.0060%, Al: 0.003% or less, and, It contains O: 0.0040% or less, with the remainder consisting of Fe and impurities. The equations (1) and (2) are satisfied. 0.10 ≤ Si / (C+Ni) ≤ 0.20 (1) 1.43≦(Cr+Mn+Cu) / (Si+10P+10S+100N)≦1.63 (2) Here, the content of each element symbol in Formula (1) and Formula (2) is substituted with the content in mass% of the corresponding element. When an element is not contained, "0" is substituted into the corresponding element symbol.

[0010] The wire rod of the present invention has a chemical composition in mass% of C: 0.70 to less than 1.10%, Si: 0.10 to 0.40%, Mn: 0.15 to 0.80%, Cu: 0.10 to less than 1.00%, P: 0.015% or less, S: 0.015% or less, N: 0.0005 to 0.0060%, Al: 0.003% or less, and O: 0.0040% or less, and contains further contains one or more selected from the group consisting of Group 1 and Group 2, and the balance consists of Fe and impurities, and satisfies Formula (1) and Formula (2). [Group 1] Cr: 0.60% or less, Co: 0.50% or less, Mo: 0.10% or less, B: 0.005% or less, W: 0.20% or less, Ni: 0.50% or less, V: 0.10% or less, Nb: 0.10% or less, Ti: 0.10% or less, and Sn: 0.10% or less, and is one or more selected from the group consisting of [Group 2] Ca: 0.0050% or less, Mg: 0.0050% or less, Zr: 0.010% or less, and rare earth elements: 0.0050% or less, and is one or more selected from the group consisting of 0.10 ≦ Si / (C + Ni) ≦ 0.20 (1) 1.43 ≦ (Cr + Mn + Cu) / (Si + 10P + 10S + 100N) ≦ 1.63 (2) Here, the content in mass % of the corresponding element is substituted for each element symbol in Formula (1) and Formula (2). When an element is not contained, "0" is substituted for the corresponding element symbol.

Advantages of the Invention

[0011] The wire rod of the present invention has sufficient wire drawing workability, and when a steel wire is manufactured using the wire rod as a raw material, a sufficient durability ratio can be obtained in the steel wire.

Embodiments for Carrying Out the Invention

[0012] First, the inventors of the present invention examined from the viewpoint of chemical composition a wire rod that has sufficient wire drawing workability and that can obtain a sufficient durability ratio in a steel wire when the steel wire is manufactured using the wire rod as a raw material. As a result, the chemical composition contains, in mass %, C: 0.70 to less than 1.10%, Si: 0.10 to 0.40%, Mn: 0.15 to 0.80%, P: 0.015% or less, S: 0.015% or less, N: 0.0005 to 0.0060%, Al: 0.003% or less, and O: 0.0040% or less. When any optional element is contained, in addition, instead of a part of Fe, it contains one or more selected from the group consisting of the above-mentioned Group 1 and Group 2, and the balance consists of Fe and impurities. It was considered that if it is a wire rod, sufficient wire drawing workability can be obtained, and when the wire rod is used as a raw material to form a steel wire, there is a possibility of obtaining a sufficient durability ratio.

[0013] However, with the above chemical composition, a sufficient durability ratio could not be obtained when steel wire was produced. Therefore, the inventors further investigated means to obtain a sufficient durability ratio when manufacturing steel wire using wire material. Here, the inventors focused on Cu. When steel wire is manufactured using wire material, Cu precipitates in the steel wire as nanoscale fine Cu particles. In steel wire, high strength is obtained by introducing a large number of dislocations through wire drawing. However, when subjected to repeated fatigue, the dislocations move and disappear, reducing the fatigue strength. As a result, the durability ratio decreases. If fine Cu particles are present, the fine Cu particles can fix the dislocations. Therefore, it is thought that a sufficient durability ratio can be obtained.

[0014] Therefore, the inventors further investigated the chemical composition of the wire material used for steel wire. As a result, they concluded that if the chemical composition of the wire material contains less than 0.10 to 1.00% Cu, a sufficient durability ratio can be obtained in the steel wire when it is manufactured using this wire material.

[0015] However, simply setting the chemical composition of the wire within the above range was still insufficient to obtain a sufficient durability ratio in some cases. Therefore, the inventors conducted further investigations. As a result, they found that if the chemical composition of the wire satisfies the above range and also satisfies the following formulas (1) and (2), then when steel wire is manufactured using the wire as a material, sufficient wire drawability can be obtained, and when steel wire is manufactured using the wire as a material, a sufficient durability ratio can be obtained in the steel wire. 0.10 ≤ Si / (C+Ni) ≤ 0.20 (1) 1.43≦(Cr+Mn+Cu) / (Si+10P+10S+100N)≦1.63 (2) Here, the mass percentage content of each element is substituted for the element symbol in equations (1) and (2). If an element is not present, "0" is substituted for the corresponding element symbol.

[0016] The wire material of this embodiment was completed based on the above technical concept and has the following configuration.

[0017] [1] The chemical composition is expressed in mass percent. C: 0.70-1.10% Si: 0.10~0.40%, Mn: 0.15~0.80%, Cu: 0.10 to less than 1.00%, P: 0.015% or less, S: 0.015% or less, N: 0.0005~0.0060%, Al: 0.003% or less, and, It contains O: 0.0040% or less, with the remainder consisting of Fe and impurities. The following conditions satisfy equations (1) and (2): Wire rod. 0.10 ≤ Si / (C+Ni) ≤ 0.20 (1) 1.43≦(Cr+Mn+Cu) / (Si+10P+10S+100N)≦1.63 (2) Here, the mass percentage content of each element is substituted for the element symbol in equations (1) and (2). If an element is not present, "0" is substituted for the corresponding element symbol.

[0018] [2] The chemical composition is expressed in mass percent. C: 0.70-1.10% Si: 0.10~0.40%, Mn: 0.15~0.80%, Cu: 0.10 to less than 1.00%, P: 0.015% or less, S: 0.015% or less, N: 0.0005~0.0060%, Al: 0.003% or less, and, Contains O: 0.0040% or less, Furthermore, it contains one or more elements selected from the groups consisting of Group 1 and Group 2, with the remainder being Fe and impurities. The following conditions satisfy equations (1) and (2): Wire rod. [Group 1] Cr: 0.60% or less, Co: 0.50% or less, Mo: 0.10% or less B: 0.005% or less, W: 0.20% or less, Ni: 0.50% or less, V: 0.10% or less, Nb: 0.10% or less, Ti: 0.10% or less, and, One or more selected from the group consisting of Sn: 0.10% or less. [Group 2] Ca: 0.0050% or less, Mg: 0.0050% or less, Zr: 0.010% or less, and, Rare earth elements: One or more elements selected from the group consisting of 0.0050% or less. 0.10 ≤ Si / (C+Ni) ≤ 0.20 (1) 1.43≦(Cr+Mn+Cu) / (Si+10P+10S+100N)≦1.63 (2) Here, the mass percentage content of each element is substituted for the element symbol in equations (1) and (2). If an element is not present, "0" is substituted for the corresponding element symbol.

[0019] [3] [2] The wire material described above, The above group 1 contains, Wire rod.

[0020] [4] The wire material described in [2] or [3], The following include the second group: Wire rod.

[0021] The wire material according to this embodiment will be described in detail below. Unless otherwise specified, the "%" in relation to elements refers to mass %.

[0022] [Features of the wire material in this embodiment] The wire of this embodiment has the following features: (Feature 1) The chemical composition satisfies the range described in this embodiment. (Feature 2) The above chemical composition further satisfies formula (1). 0.10 ≤ Si / (C+Ni) ≤ 0.20 (1) Here, each element symbol in equation (1) is substituted with the mass percentage content of the corresponding element. If an element is not present, "0" is substituted for the corresponding element symbol. (Feature 3) The above chemical composition further satisfies formula (2). 1.43≦(Cr+Mn+Cu) / (Si+10P+10S+100N)≦1.63 (2) Here, each element symbol in equation (2) is substituted with the mass percentage content of the corresponding element. If an element is not present, "0" is substituted for the corresponding element symbol. The following describes each of its features.

[0023] [(Feature 1) Regarding chemical composition] The chemical composition of the wire in this embodiment contains the following elements:

[0024] C: 0.70-1.10% Carbon (C) increases the strength of wire rods and steel wires manufactured using wire rods as a material. If the C content is less than 0.70%, the above effect cannot be fully obtained, even if the content of other elements is within the range of this embodiment. On the other hand, if the carbon content is 1.10% or more, protereminate cementite will be excessively formed even if the content of other elements is within the range of this embodiment. In this case, the wire's drawability will decrease. Furthermore, the toughness and ductility of the steel wire after drawing will decrease. Therefore, the C content is less than 0.70-1.10%. The preferred lower limit for the C content is 0.74%, more preferably 0.78%, and even more preferably 0.80%. The preferred upper limit for the C content is 1.08%, more preferably 1.05%, and even more preferably 1.03%.

[0025] Si: 0.10~0.40% Silicon (Si) increases the strength of the wire. Furthermore, Si deoxidizes the steel during the steelmaking process in the wire manufacturing process. If the Si content is less than 0.10%, the above effects cannot be fully obtained, even if the content of other elements is within the range of this embodiment. On the other hand, if the Si content exceeds 0.40%, Si oxide will be formed even if the content of other elements is within the range of this embodiment. Si oxide reduces the wire's drawability. Therefore, the Si content is 0.10-0.40%. The preferred lower limit for the Si content is 0.13%, more preferably 0.15%, and even more preferably 0.18%. The preferred upper limit for the Si content is 0.38%, more preferably 0.36%, and even more preferably 0.34%.

[0026] Mn: 0.15~0.80% Manganese (Mn) delays the transformation of protereminate cementite and grain boundary ferrite during cooling from the austenite temperature range in the wire manufacturing process. This results in the formation of fine pearlite lamellae. Consequently, the strength of the steel wire manufactured from the wire is increased while maintaining sufficient wire drawability. If the Mn content is less than 0.15%, the above effect cannot be fully obtained. On the other hand, if the Mn content exceeds 0.80%, Mn will segregate within the wire, even if the content of other elements is within the range of this embodiment. In this case, bainite or martensite will form in the region where Mn has segregated, reducing the wire's drawability. Therefore, the Mn content is 0.15-0.80%. The preferred lower limit of the Mn content is 0.20%, more preferably 0.25%, and even more preferably 0.30%. The preferred upper limit for the Mn content is 0.70%, more preferably 0.60%, and even more preferably 0.50%.

[0027] Cu: Less than 0.10-1.00% Copper (Cu) forms nanoscale fine Cu particles within steel wires manufactured from wire rods, thereby increasing the fatigue strength of the steel wires and, as a result, improving the durability ratio of the steel wires. If the Cu content is less than 0.10%, the above effect cannot be fully obtained, even if the content of other elements is within the range of this embodiment. On the other hand, if the Cu content is 1.00% or more, even if the content of other elements is within the range of this embodiment, Cu will segregate at the grain boundaries and red-hot embrittlement will occur. In this case, the hot workability of the wire will decrease. Therefore, the copper content is less than 0.10-1.00%. The preferred lower limit for the Cu content is 0.15%, more preferably 0.20%, and even more preferably 0.30%. The preferred upper limit for the Cu content is 0.90%, more preferably 0.80%, and even more preferably 0.70%.

[0028] P:0.015% or less Phosphorus (P) is an impurity. That is, the lower limit of P content is greater than 0%. If the P content exceeds 0.015%, even if the content of other elements is within the range of this embodiment, P will segregate at the grain boundaries, causing the grain boundaries to become brittle. Therefore, when manufacturing steel wire using wire rod as a material, the strength of the steel wire will decrease. Furthermore, the drawability of the wire rod will decrease. Therefore, the P content is 0.015% or less. A low phosphorus (P) content is preferable. However, excessive reduction of the P content increases manufacturing costs. Therefore, considering normal industrial production, the preferred lower limit of the P content is greater than 0%, more preferably 0.001%, even more preferably 0.003%, and even more preferably 0.004%. The preferred upper limit for the P content is 0.014%, more preferably 0.012%, and even more preferably 0.010%.

[0029] S: 0.015% or less Sulfur (S) is an impurity. That is, the lower limit of S content is greater than 0%. If the S content exceeds 0.015%, even if the content of other elements is within the range of this embodiment, S will segregate at the grain boundaries, causing the grain boundaries to become brittle. Therefore, when manufacturing steel wire using wire rod as a material, the strength of the steel wire will decrease. Furthermore, the drawability of the wire rod will decrease. Therefore, the sulfur content is 0.015% or less. A low sulfur (S) content is preferable. However, excessive reduction of the S content increases manufacturing costs. Therefore, considering normal industrial production, the preferred lower limit of the S content is greater than 0%, more preferably 0.001%, even more preferably 0.002%, and even more preferably 0.003%. The preferred upper limit for the S content is 0.014%, more preferably 0.012%, and even more preferably 0.010%.

[0030] N: 0.0005~0.0060% Nitrogen (N) forms nitrides with Al and other elements in the wire. These nitrides suppress the coarsening of austenite grains by pinning during heating in the wire manufacturing process. If the N content is less than 0.0005%, the above effect cannot be fully obtained, even if the content of other elements is within the range of this embodiment. On the other hand, if the N content exceeds 0.0060%, the solid-solution N accelerates age hardening when the wire is drawn. Therefore, even if the content of other elements is within the range of this embodiment, the wire drawability decreases. Therefore, the N content is between 0.0005% and 0.0060%. The preferred lower limit of the N content is 0.0006%, more preferably 0.0008%, even more preferably 0.0015%, and even more preferably 0.0030%. The preferred upper limit for the N content is 0.0055%, more preferably 0.0050%, and even more preferably 0.0045%.

[0031] Al: 0.003% or less Aluminum (Al) is an impurity. If the Al content exceeds 0.003%, even if the content of other elements is within the range of this embodiment, an excess of oxide will be formed. In this case, the wire drawing processability of the wire will decrease. Therefore, the Al content is 0.003% or less. A low Al content is preferable. However, excessive reduction of the Al content increases manufacturing costs. Therefore, considering normal industrial production, the preferred lower limit of the Al content is greater than 0%, and more preferably 0.001%.

[0032] O: 0.0040% or less Oxygen (O) is an impurity. If the O content exceeds 0.0040%, coarse oxides will form in the wire, even if the content of other elements is within the range of this embodiment. As a result, the wire's drawability will decrease. Therefore, the O content is 0.0040% or less. A low oxygen content is preferable. However, excessive reduction of the oxygen content increases manufacturing costs. Therefore, considering normal industrial production, the preferred lower limit of the oxygen content is greater than 0%, more preferably 0.0001%, and even more preferably 0.0003%. The preferred upper limit for the O content is 0.0038%, and more preferably 0.0036%.

[0033] The remainder of the chemical composition of the wire according to this embodiment consists of Fe and impurities. Here, impurities in the chemical composition refer to substances that are unintentionally included during the industrial manufacture of the wire from raw materials such as ore, scrap, or the manufacturing environment, and are acceptable as long as they do not adversely affect the wire according to this embodiment.

[0034] [About Optional Elements] The chemical composition of the wire in this embodiment may further include one or more elements selected from the group consisting of Group 1 and Group 2, in place of a portion of Fe. [Group 1] Cr: 0.60% or less, Co: 0.50% or less, Mo: 0.10% or less B: 0.005% or less, W: 0.20% or less, Ni: 0.50% or less, V: 0.10% or less, Nb: 0.10% or less, Ti: 0.10% or less, and, One or more selected from the group consisting of Sn: 0.10% or less. [Group 2] Ca: 0.0050% or less, Mg: 0.0050% or less, Zr: 0.010% or less, and, Rare earth elements: One or more elements selected from the group consisting of 0.0050% or less. The following describes these arbitrary elements.

[0035] [Group 1: Cr, Co, Mo, B, W, Ni, V, Nb, Ti, and Sn] The chemical composition of the wire in this embodiment may further include the elements of the first group described above, in place of some of the Fe. These elements are arbitrary and all enhance the strength of the steel wire manufactured using the wire as a material. The elements of the first group will be described below.

[0036] Cr:0.60% or less Chromium (Cr) is an optional element and does not need to be included. In other words, the Cr content may be 0%. When chromium is present, i.e., when the chromium content is greater than 0%, chromium enhances the hardenability of the wire rod and increases the strength of the steel wire manufactured from it. Even a small amount of chromium will provide some degree of the above effect. However, if the Cr content exceeds 0.60%, Cr will segregate within the wire, even if the content of other elements is within the range of this embodiment. In this case, bainite or martensite will form in the region where Cr has segregated. As a result, the wire's drawability will decrease. Therefore, the Cr content is between 0 and 0.60%, and if present, it is 0.60% or less. The preferred lower limit for the Cr content is 0.01%, more preferably 0.05%, and even more preferably 0.08%. The preferred upper limit for the Cr content is 0.55%, more preferably 0.50%, and even more preferably 0.45%.

[0037] Co:0.50% or less Cobalt (Co) is an optional element and does not need to be included. In other words, the Co content may be 0%. When present, i.e., when the Co content is greater than 0%, Co suppresses the precipitation of proteroclastic cementite and increases the strength of steel wire manufactured using wire material. Even a small amount of Co will provide some degree of the above effect. However, if the Co content exceeds 0.50%, even if the content of other elements is within the range of this embodiment, the hardness of the wire becomes excessively hard, and the wire drawing processability of the wire decreases. Therefore, the Co content is 0-0.50%, and if present, it is 0.50% or less. The preferred lower limit for the Co content is 0.01%, more preferably 0.05%, and even more preferably 0.08%. The preferred upper limit for the Co content is 0.45%, more preferably 0.40%, and even more preferably 0.35%.

[0038] Mo: 0.10% or less Molybdenum (Mo) is an optional element and does not need to be included. In other words, the Mo content may be 0%. When Mo is present, i.e., when the Mo content is greater than 0%, Mo delays the transformation of protereminate cementite and grain boundary ferrite during cooling from the austenite temperature range in the wire manufacturing process. This results in the formation of fine pearlite lamellae. Consequently, the strength of the steel wire manufactured from the wire is increased while maintaining sufficient wire drawability. Even a small amount of Mo can provide the above effect to some extent. However, if the Mo content exceeds 0.10%, the hardenability of the wire becomes excessively high. In this case, even if the content of other elements is within the range of this embodiment, bainite will form in the wire, reducing the wire's drawability. Therefore, the Mo content is 0-0.10%, and if present, it is 0.10% or less. The preferred lower limit for the Mo content is 0.01%, more preferably 0.03%, and even more preferably 0.05%. The preferred upper limit for the Mo content is 0.08%, more preferably 0.07%, and even more preferably 0.06%.

[0039] B: 0.005% or less Boron (B) is an optional element and does not need to be included. In other words, the B content may be 0%. If B is present, that is, if the B content is greater than 0%, B enhances the hardenability and strength of the wire. Even if only a small amount of B is present, the above effects can be obtained to some extent. However, if the B content exceeds 0.005%, even if the content of other elements is within the range of this embodiment, the hot workability of the steel material will decrease during the wire rod manufacturing process. Therefore, the B content is 0-0.005%, and if present, it is 0.005% or less. The preferred lower limit for the B content is 0.001%, and more preferably 0.002%. The preferred upper limit for the B content is 0.004%, and more preferably 0.003%.

[0040] W: 0.20% or less Tungsten (W) is an optional element and does not need to be included. In other words, the W content may be 0%. When present, i.e., when the W content is greater than 0%, W enhances the hardenability of the wire rod and increases the strength of the steel wire manufactured from that wire rod. Even a small amount of W content will provide some degree of the above effect. However, if the W content exceeds 0.20%, even if the content of other elements is within the range of this embodiment, the hot workability of the steel material will decrease during the wire rod manufacturing process. Therefore, the W content is 0-0.20%, and if present, it is 0.20% or less. The preferred lower limit of the W content is 0.01%, more preferably 0.03%, and even more preferably 0.05%. The preferred upper limit for the W content is 0.18%, more preferably 0.16%, and even more preferably 0.14%.

[0041] Ni: 0.50% or less Nickel (Ni) is an optional element and does not need to be included. In other words, the Ni content may be 0%. When Ni is present, i.e., when the Ni content is greater than 0%, Ni delays the transformation of protereminate cementite and grain boundary ferrite during cooling from the austenite temperature range in the wire manufacturing process. This results in the formation of fine pearlite lamellae. Consequently, the strength of the steel wire manufactured from the wire is increased while maintaining sufficient wire drawability. Even a small amount of Ni can provide the above effect to some extent. However, if the Ni content exceeds 0.50%, the hardenability of the wire becomes excessively high. In this case, even if the content of other elements is within the range of this embodiment, bainite will form in the wire, reducing the wire's drawability. Therefore, the Ni content is 0-0.50%, and if present, it is 0.50% or less. The preferred lower limit for the Ni content is 0.01%, more preferably 0.03%, and even more preferably 0.10%. The preferred upper limit for the Ni content is 0.48%, more preferably 0.45%, and even more preferably 0.40%.

[0042] V: 0.10% or less Vanadium (V) is an optional element and does not need to be present. In other words, the V content may be 0%. If present, i.e., if the V content is greater than 0%, V forms precipitates that are carbides and / or carbonitrides, thereby increasing the strength of the wire and the steel wire manufactured from the wire. Even a small amount present will provide some degree of the above effect. However, if the V content exceeds 0.10%, excessive precipitates will form. In this case, even if the content of other elements is within the range of this embodiment, the wire's drawability will decrease. Therefore, the V content is 0-0.10%, and if present, it is 0.10% or less. The preferred lower limit for the V content is 0.01%, more preferably 0.02%, and even more preferably 0.03%. The preferred upper limit for the V content is 0.09%, more preferably 0.08%, and even more preferably 0.07%.

[0043] Nb: 0.10% or less Niobium (Nb) is an optional element and does not need to be included. In other words, the Nb content may be 0%. When Nb is present, i.e., when the Nb content is greater than 0%, Nb forms precipitates that are carbides and / or carbonitrides, thereby increasing the strength of the wire and the steel wire manufactured from the wire. Even a small amount of Nb present will provide some degree of the above effect. However, if the Nb content exceeds 0.10%, excessive precipitates will form. In this case, even if the content of other elements is within the range of this embodiment, the wire's drawability will decrease. Therefore, the Nb content is 0-0.10%, and if present, it is 0.10% or less. The preferred lower limit for the Nb content is 0.01%, more preferably 0.02%, and even more preferably 0.03%. The preferred upper limit for the Nb content is 0.09%, more preferably 0.08%, and even more preferably 0.07%.

[0044] Ti: 0.10% or less Titanium (Ti) is an optional element and does not need to be included. In other words, the Ti content may be 0%. When present, i.e., when the Ti content is greater than 0%, Ti forms precipitates that are carbides / nitrides, increasing the strength of wire rods and steel wires manufactured from them. Even a small amount of Ti present will provide some degree of the above effect. However, if the Ti content exceeds 0.10%, excessive precipitates will form. In this case, even if the content of other elements is within the range of this embodiment, the wire's drawability will decrease. Therefore, the Ti content is 0-0.10%, and if present, it is 0.10% or less. The preferred lower limit for the Ti content is 0.01%, and more preferably 0.02%. The preferred upper limit for the Ti content is 0.09%, and more preferably 0.08%.

[0045] Sn: 0.10% or less Tin (Sn) is an optional element and does not need to be included. In other words, the Sn content may be 0%. If Sn is present, that is, if the Sn content is greater than 0%, Sn suppresses ferrite decarburization that occurs during hot working, thereby suppressing the decrease in wire strength. Even if only a small amount of Sn is present, the above effect can be obtained to some extent. However, if the Sn content exceeds 0.10%, even if the content of other elements is within the range of this embodiment, Sn will segregate at the grain boundaries, causing red-hot embrittlement. In this case, the hot workability of the wire will decrease. Therefore, the Sn content is 0-0.10%, and if present, it is 0.10% or less. The preferred lower limit for the Sn content is 0.01%, more preferably 0.02%, and even more preferably 0.03%. The preferred upper limit for the Sn content is 0.09%, more preferably 0.08%, and even more preferably 0.07%.

[0046] [Group 2: Ca, Mg, Zr, and rare earth elements (REM)] The chemical composition of the wire rod in this embodiment may further include the elements of the second group described above in place of some of the Fe. These elements are arbitrary and all maintain the drawability of the wire rod and the steel wire manufactured using the wire rod as a material.

[0047] Ca:0.0050% or less Calcium (Ca) does not need to be present. In other words, the Ca content may be 0%. If the Ca content is 0.0050% or less, the decrease in the drawability of wire rods and steel wires is suppressed. Therefore, a Ca content of 0.0050% or less is acceptable. If the Ca content exceeds 0.0050%, excess oxides will be generated. In this case, the drawability of wire rods and steel wires will decrease. Therefore, the Ca content is between 0 and 0.0050%, and if present, it is 0.0050% or less. The lower limit of the Ca content may be 0.0001%, 0.0002%, or 0.0005%. The preferred upper limit for the Ca content is 0.0040%, more preferably 0.0030%, and even more preferably 0.0020%.

[0048] Mg: 0.0050% or less Magnesium (Mg) does not need to be present. In other words, the Mg content may be 0%. If the Mg content is 0.0050% or less, the decrease in the drawability of wire rods and steel wires is suppressed. Therefore, the presence of Mg at 0.0050% or less is acceptable. If the Mg content exceeds 0.0050%, excess oxides will be generated. In this case, the drawability of wire rods and steel wires will decrease. Therefore, the Mg content is between 0 and 0.0050%, and if present, it is 0.0050% or less. The lower limit of the Mg content may be 0.0001%, 0.0002%, or 0.0005%. The preferred upper limit for the Mg content is 0.0040%, more preferably 0.0030%, and even more preferably 0.0020%.

[0049] Zr: 0.010% or less Zirconium (Zr) does not need to be included. In other words, the Zr content may be 0%. If the Zr content is 0.010% or less, the decrease in the drawability of wire rods and steel wires is suppressed. Therefore, a Zr content of 0.010% or less is acceptable. If the Zr content exceeds 0.010%, excess oxides will be generated. In this case, the drawability of wire rods and steel wires will decrease. Therefore, the Zr content is 0-0.010%, and if present, it is 0.010% or less. The lower limit of the Zr content may be 0.001%, 0.002%, or 0.005%. The preferred upper limit for the Zr content is 0.009%, more preferably 0.008%, and even more preferably 0.007%.

[0050] Rare earth elements: 0.0050% or less Rare earth elements (REMs) are optional elements and do not need to be included. In other words, the REM content may be 0%. When present, REM fixes S. This suppresses the decrease in the drawability of wire rods and steel wires. Even a small amount of REM present can provide some of the above effect. However, if the REM content exceeds 0.0050%, coarse inclusions are formed, reducing the drawability of wire rods and steel wires. Therefore, the REM content is between 0 and 0.0050%, and if present, it is 0.0050% or less. The preferred lower limit for the REM content is 0.0001%, more preferably 0.0002%, and even more preferably 0.0005%. The preferred upper limit for the REM content is 0.0045%, more preferably 0.0040%, and even more preferably 0.0035%.

[0051] In this specification, REM refers to one or more elements selected from the group consisting of scandium (Sc) with atomic number 21, yttrium (Y) with atomic number 39, and lanthanides from lanthanum (La) with atomic number 57 to lutetium (Lu) with atomic number 71. In this specification, REM content refers to the total content of these elements.

[0052] [Method for measuring the chemical composition of wire] The chemical composition of the wire in this embodiment can be measured by a well-known component analysis method in accordance with JIS G0321:2017. Specifically, chips are collected from the inside of the wire after removing the oxide scale using a drill. The collected chips are dissolved in acid to obtain a solution. Elemental analysis of the chemical composition is performed on the solution using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry). The C and S content is determined by a well-known high-frequency combustion method (combustion-infrared absorption method). The N content is determined using a well-known inert gas fusion-thermal conductivity method. The O content is determined using a well-known inert gas fusion-infrared absorption method.

[0053] Furthermore, the content of each element shall be rounded to the minimum digit of the element content specified in this embodiment, based on the significant figures defined in this embodiment. For example, the carbon content of the steel material in this embodiment is defined to two decimal places. Therefore, the carbon content shall be the value obtained by rounding the third decimal place of the measured value to two decimal places.

[0054] Similarly, for the carbon content of the steel material in this embodiment, the content of other elements is determined by rounding the measured value to the minimum digit specified in this embodiment.

[0055] Rounding means that if the fractional part is less than 5, it is rounded down, and if the fractional part is 5 or greater, it is rounded up.

[0056] [Regarding (Feature 2) Equation (1)] The wire of this embodiment further satisfies formula (1), provided that its chemical composition satisfies feature 1. 0.10 ≤ Si / (C+Ni) ≤ 0.20 (1) Here, each element symbol in equation (1) is substituted with the mass percentage content of the corresponding element. If an element is not present, "0" is substituted for the corresponding element symbol. In other words, if the arbitrary element Ni is not present, equation (1) becomes as follows: 0.10 ≤ Si / C ≤ 0.20 (1)

[0057] F1 is defined as follows: F1 = Si / (C + Ni) Furthermore, if the element Ni is not present, F1 will be as follows: F1 = Si / C

[0058] In steel wire manufactured using the wire material of this embodiment, nanoscale fine Cu particles may precipitate at the interface between ferrite and cementite in pearlite (hereinafter referred to as the ferrite / cementite interface) or within the ferrite in pearlite. Fine Cu particles precipitated within the ferrite contribute more to improving the durability ratio than fine Cu particles precipitated at the ferrite / cementite interface. Therefore, precipitation of fine Cu particles within the ferrite between lamellar cementite in pearlite is effective in improving the durability ratio.

[0059] The ratios of C content, Ni content, and Si content in the chemical composition of Feature 1 affect the area of ​​the ferrite / cementite interface in pearlite. Specifically, if the ratio of Si content to the total C and Ni content (i.e., F1) is too low, the precipitation of fine Cu particles at the ferrite / cementite interface is suppressed. As a result, a sufficient durability ratio cannot be obtained.

[0060] If F1 is 0.10 or higher, fine Cu particles are more likely to form in the ferrite between lamellar cementites rather than at the ferrite / cementite interface within the pearlite of the steel wire manufactured using the wire material of this embodiment. Therefore, assuming that features 1 and 3 are satisfied, the durability ratio of the steel wire can be sufficiently increased.

[0061] On the other hand, if F1 is 0.20 or less, sufficient wire drawing processability can be obtained in the wire material.

[0062] Therefore, F1 is between 0.10 and 0.20. A preferred lower limit for F1 is 0.12, and more preferably 0.14. The preferred upper limit for F1 is 0.19.

[0063] [Regarding (Feature 3) Equation (2)] The wire of this embodiment further satisfies formula (2), provided that its chemical composition satisfies feature 1. 1.43≦(Cr+Mn+Cu) / (Si+10P+10S+100N)≦1.63 (2) Here, each element symbol in equation (2) is substituted with the mass percentage content of the corresponding element. If an element is not present, "0" is substituted for the corresponding element symbol. In other words, if the arbitrary element Cr is not present, equation (2) becomes as follows: 1.43≦(Mn+Cu) / (Si+10P+10S+100N)≦1.63 (2)

[0064] We define F2 as F2 = (Cr + Mn + Cu) / (Si + 10P + 10S + 100N). Furthermore, if the element Cr is not present, F2 will be as follows: F2 = (Mn + Cu) / (Si + 10P + 10S + 100N) F2 is an index relating to the durability ratio of steel wire manufactured using wire rod as a material, and the drawability of the wire rod used as the material.

[0065] Of the molecules in F2, Cr and Mn contribute to the tensile strength of steel wire manufactured from wire material, while Cu contributes to fatigue strength as described above. Therefore, the molecules in F2 increase the durability ratio of the steel wire. On the other hand, the denominators Si, P, S, and N in F2 decrease the durability ratio.

[0066] If F2 is 1.43 or higher, the Cr, Mn, and Cu content is sufficiently high compared to the Si, P, S, and N content. Therefore, a sufficient durability ratio can be obtained in steel wire manufactured using wire rod as the raw material.

[0067] On the other hand, if F2 is too high, the Cr, Mn, and Cu content may be too high relative to the Si, P, S, and N content. In this case, the microstructure may not be sufficiently stable. This can lead to a decrease in durability ratio and reduced wire drawing processability. Conversely, if F2 is 1.63 or less, the Cr, Mn, and Cu content is within an appropriate range relative to the Si, P, S, and N content. Therefore, the microstructure is sufficiently stable. As a result, sufficient wire drawing processability is obtained, and a sufficient durability ratio is achieved in steel wire manufactured using wire rod as the raw material.

[0068] Therefore, F2 is between 1.43 and 1.63. A preferred lower limit for F2 is 1.44, more preferably 1.45, and even more preferably 1.46. A preferred upper limit for F2 is 1.62, more preferably 1.61, and even more preferably 1.60.

[0069] [Effects of the wire material in this embodiment] The wire of this embodiment satisfies features 1 to 3. Therefore, with the wire of this embodiment, a sufficient durability ratio can be obtained in steel wire manufactured using the wire as a material. Furthermore, the wire of this embodiment provides sufficient wire drawing processability.

[0070] [Microstructure of the wire in this embodiment] The microstructure of the wire in this embodiment consists substantially of a pearlite structure. Here, "consistently of a pearlite structure" means that the pearlite area ratio is 90% or more.

[0071] [Method for observing the microstructure of wire] The microstructure of the wire in this embodiment and the area ratio of perlite are measured by the following method.

[0072] A specimen is taken from the wire. The cross section of the specimen perpendicular to the wire's axis is designated as the observation surface. The observation surface is polished to a mirror finish. The polished observation surface is etched with Nital to reveal the microstructure. Four fields of view in the 4 / D area of ​​the etched observation surface are observed at 200x magnification using an optical microscope. Here, the 4 / D area refers to the central part of the radius (i.e., the part at a depth of D / 4 radially from the wire's surface) when D is the diameter passing through the center of a circular observation surface. Photographs are generated for each field of view. The size of each field of view is, for example, 0.60 mm × 0.48 mm.

[0073] Based on the contrast of the photographic images in each field of view, each tissue (ferrite, pearlite, bainite, and martensite) is identified. The total area of ​​pearlite identified in the four fields of view (μm²) 2 ) is calculated. Based on the total area of ​​the four fields of view and the total area of ​​the perlite, the perlite area ratio (%) is calculated.

[0074] It is also well known that the microstructure of wire materials used for applications such as bead wire, steel cord, bridge wire, and wire rope is substantially pearlite.

[0075] [Applications of the wire material of this embodiment] The wire material of this embodiment can be widely applied, for example, as a material for steel wire manufactured by wire drawing. The steel wire can be applied to bead wire, steel cord, bridge wire, wire rope, and the like.

[0076] [An example of a method for manufacturing wire according to this embodiment] An example of a method for manufacturing the wire of this embodiment will be described. The method for manufacturing the wire described below is just one example for manufacturing the wire of this embodiment. Therefore, the wire having the above-described configuration may be manufactured by other manufacturing methods other than the method described below. However, the manufacturing method described below is a preferred example of a method for manufacturing the wire of this embodiment.

[0077] An example of the wire manufacturing method of this embodiment includes the following steps. (Process 1) Material preparation process (Process 2) Blooming rolling process (Process 3) Finish rolling process The following describes each step.

[0078] [(Process 1) Material preparation process] In the material preparation process, the material for the wire rod of this embodiment is prepared. Specifically, molten steel satisfying Feature 1 in chemical composition is produced. The refining method is not particularly limited, and any well-known method may be used. For example, molten iron produced by a well-known method is refined in a converter (primary refining). A well-known secondary refining method is performed on the molten steel tapped from the converter. Through the above process, molten steel with a chemical composition satisfying Feature 1 is produced.

[0079] The material is manufactured using the molten steel produced by a well-known casting method. For example, an ingot may be manufactured using the ingot-making method with the molten steel. Alternatively, a bloom may be manufactured using the continuous casting method with the molten steel. The material (ingot or bloom) is manufactured by the above method.

[0080] [(Process 2) Blossom rolling process] In the bract rolling process, bract rolling is performed on the material (ingot or bloom) prepared in the material preparation process to produce a billet. In the bract rolling process, the material is first heated using a heating furnace in a well-known manner. The heating temperature is not particularly limited; any known temperature is sufficient. For example, the heating temperature is 1000 to 1200°C.

[0081] The heated material is rolled using a bloc mill, or a bloc mill and a continuous mill, to produce a billet. Specifically, the heated material is reverse-rolled using a bloc mill to produce a billet. If a well-known continuous mill is located downstream of the bloc mill, the billet after bloc rolling may be further tandem-rolled using the continuous mill to produce an even smaller billet. The produced billets are allowed to cool to room temperature (air-cooled) before the finish rolling process.

[0082] [(Process 3) Finish Rolling Process] In the finish rolling process, wire rods are produced by performing finish rolling on the billets manufactured in the bract rolling process. In the finish rolling process, the billets are first heated in a heating furnace using a well-known method. The heating temperature is not particularly limited; any known temperature is sufficient. For example, the heating temperature is 950 to 1150°C.

[0083] Wire rod is manufactured by performing finish rolling (continuous rolling) on ​​a heated billet using a continuous rolling mill. The continuous rolling mill includes multiple rolling stands arranged in a line from upstream to downstream. Each rolling stand includes a pair of work rolls. Calibers are formed on each work roll, and the calibers of the pair of work rolls form a hole. The wire rod after finish rolling is cooled by a well-known method. The winding temperature of the wire rod is within a well-known temperature range, for example, 750 to 940°C.

[0084] Hot-rolled wire undergoes a transformation from austenite to pearlite during cooling after winding. The cooling rate after winding can be determined by well-known methods. For example, the cooling rate up to 650°C after winding can be 5.0°C to 40.0°C / second, the cooling rate from below 650°C (649°C) to 590°C can be 2.0 to 10.0°C / second, and the cooling rate from below 590°C (589°C) to 400°C can be 5.0°C / second or higher. The cooling rate below 400°C (399°C or lower) is not particularly limited. If the wire satisfies characteristics 1 to 3, cooling at the above-mentioned cooling rates will result in a microstructure that is substantially pearlite.

[0085] The wire material of this embodiment is manufactured through the above process.

[0086] [Method of manufacturing steel wire] The method for manufacturing steel wire using the wire material of this embodiment is a well-known manufacturing method. The steel wire is, for example, bead wire. The method for manufacturing steel wire using the wire material of this embodiment is, for example, as follows.

[0087] A method for manufacturing steel wire using the wire rod of this embodiment is as follows: After removing the oxide scale from the wire rod by mechanical descaling, a lubrication treatment is performed. The lubricated wire rod is then drawn to manufacture steel wire. The drawing process may be performed multiple times. The reduction ratio per pass in the drawing process is not particularly limited, but for example, it is set to 17-23%.

[0088] After drawing, the steel wire is subjected to a plating process. Specifically, a well-known electroplating process is performed to coat the surface of the steel wire with a Cu-Zn alloy film. After electroplating, a well-known plating diffusion process is performed on the steel wire. The heat treatment temperature for the plating diffusion process is, for example, 300 to 500°C. During the plating diffusion process, the aforementioned fine Cu particles are generated. Through these steps, steel wire is manufactured as a product.

[0089] In the manufacturing method described above, plating was performed on the steel wire after wire drawing. However, plating may be performed on the wire material before wire drawing, and then wire drawing may be carried out. In this case, the fine Cu particles described above will be generated by the heat generated during the wire drawing process. [Examples]

[0090] The effects of the wire material of this embodiment will be further explained in detail by the following examples. The conditions in the following examples are just one example of conditions adopted to confirm the feasibility and effects of the wire material of this embodiment. Therefore, the wire material of this embodiment is not limited to this one example of conditions.

[0091] [Material preparation process] Wire rods having the chemical compositions shown in Tables 1-1 to 1-3 were manufactured by the following method.

[0092] [Table 1-1]

[0093] [Table 1-2]

[0094] [Table 1-3]

[0095] [Bulking rolling process] The manufactured bloom was subjected to a bloc rolling process to produce billets. Specifically, the bloom was heated to 1100°C using a heating furnace. The heated bloom was then rolled using a bloc rolling mill and a continuous rolling mill to produce billets. The billets produced in the bloc rolling process were allowed to cool to room temperature.

[0096] [Finishing Rolling Process] The manufactured billets underwent a finish rolling process. Specifically, each billet with a test number was heated to 950-1150°C using a heating furnace.

[0097] A heated billet was subjected to finish rolling (continuous rolling) using a continuous rolling mill to produce wire rod. The wire rod after finish rolling was wound at a winding temperature of 800 to 940°C. After winding, the cooling rate was set to 5.0°C to 40.0°C / second up to 650°C, to 2.0 to 10.0°C / second up to 649 to 590°C, and then to 5.0°C / second or higher up to 589 to 400°C. Through the above manufacturing process, wire rod with a diameter of 5.5 mm was produced.

[0098] [About the evaluation test] The following wire evaluation tests (Test 1 to Test 3) were performed on each wire with the corresponding test number that was manufactured. (Test 1) Test to measure the chemical composition of the wire (Test 2) Durability Ratio Evaluation Test (Test 3) Wire drawing processability evaluation test The following describes each test.

[0099] [(Test 1) Chemical composition measurement test of wire material] The chemical composition of each wire was analyzed based on the [Method for Measuring the Chemical Composition of Wire] described above. As a result, the chemical composition of each wire was as shown in Tables 1-1 to 1-3. Furthermore, the perlite area ratio was determined for each wire based on the [Method for Observing the Microstructure of Wire] described above. As a result, the perlite area ratio for all wires except test number 36 was 90% or higher, indicating that they were essentially perlite structures.

[0100] [(Test 2) Durability Ratio Evaluation Test] The durability ratio of steel wires made from the wire material of each test number was determined by the following method. First, the tensile strength of the steel wires made from the wires of each test number was determined by the following method. Steel wires were manufactured using the wires of each test number. Specifically, the oxide scale of the wires was removed by mechanical descaling, and then lubrication was performed. Steel wires were manufactured by drawing the lubricated wires. The reduction ratio per pass in each drawing process was 17-23%.

[0101] Brass plating was performed on the steel wire after drawing. Specifically, a well-known electroplating process was carried out to coat the surface of the steel wire with a well-known Cu-Zn alloy film. A well-known plating diffusion treatment was then performed on the steel wire after electroplating. The heat treatment temperature for the plating diffusion treatment was 450°C. Through the above manufacturing process, a steel wire with a diameter of 1.5 mm including the plating film was manufactured.

[0102] The tensile strength of each test number was determined using steel wire manufactured from the wire material of the respective test number. Two tensile test specimens were taken from arbitrary positions on the steel wire. The wire diameter of the tensile test specimens was 1.5 mm and the length was 250 mm. A tensile test was performed on the tensile test specimens at room temperature in air, in accordance with JIS Z 2241:2011. In the tensile test, the crosshead speed was set to 10 mm / min, the chuck distance to 150 mm, and the distance between the extensometers to 100 mm. The arithmetic mean of the tensile strengths obtained from the two tensile test specimens was defined as the tensile strength (MPa) for that test number.

[0103] Next, the fatigue strength was determined using the steel wires manufactured from the wire materials of each test number, as described above, by the following method. A sample with a wire diameter of 1.5 mm and a length of 400 mm was taken from an arbitrary position on the steel wire of each test number. The fatigue strength (MPa) was determined using a Nakamura rotary bending fatigue testing machine. The span distance (length of the evaluation section) was set to 100 mm, the rotation speed to 3000 rpm, and the maximum number of cycles to 1.0 × 10⁻⁶. 7 The number of cycles was set to 10. Among the samples that withstood the maximum number of cycles, the maximum stress was defined as the fatigue strength (MPa). Using the obtained fatigue strength and the tensile strength described above, the durability ratio was calculated using the following formula. Durability ratio = Fatigue strength / Tensile strength If the durability ratio was 0.30 or higher, it was determined that a sufficient durability ratio had been obtained (indicated by "○" in the "Durability Ratio" column of Table 2). On the other hand, if the durability ratio was less than 0.30, it was determined that a sufficient durability ratio had not been obtained (indicated by "×" in the "Durability Ratio" column of Table 2).

[0104] [Table 2]

[0105] [(Test 3) Wire drawing processability evaluation test] The reduction of area was determined using steel wires manufactured from the wire material of each test number by the following method. One tensile test specimen was taken from an arbitrary position on the steel wire. The wire diameter of the tensile test specimen was 1.5 mm and the length was 250 mm. A tensile test was performed on the tensile test specimen at room temperature in air, in accordance with JIS Z 2241:2011, to obtain the reduction of area. In the tensile test, the crosshead speed was set to 10 mm / min, the chuck distance to 150 mm, and the distance between the elongators to 100 mm. The arithmetic mean of the reduction of area obtained from two tensile test specimens was taken as the reduction of area (%) for that test number. If the reduction of area was 10% or more, it was judged that sufficient wire drawing workability was obtained (indicated as "○" in the "Wire Drawing Workability" column in Table 2). On the other hand, if the reduction of area was less than 10%, it was judged that sufficient wire drawing workability was not obtained (indicated as "×" in the "Wire Drawing Workability" column in Table 2). Furthermore, if sufficient wire drawing processability can be obtained with steel wire, it is self-evident that sufficient wire drawing processability can also be obtained with wire rod.

[0106] [Test Results] Table 2 shows the test results. Referring to Tables 1-1 to 1-3 and Table 2, the wires from test numbers 1 to 24 met characteristics 1 to 3. As a result, the durability ratio was 0.30 or higher, indicating sufficient durability. Furthermore, the reduction in diameter was 10% or higher, indicating sufficient wire drawing processability.

[0107] On the other hand, in test numbers 25 and 26, the Cu content was too low. As a result, the durability ratio was less than 0.30, and a sufficient durability ratio could not be obtained.

[0108] In test numbers 27 and 28, the F1 value was too low. As a result, the durability ratio was less than 0.30, and a sufficient durability ratio could not be obtained.

[0109] In tests 29 and 30, F1 was too high. As a result, the reduction in diameter was less than 10%, and sufficient wire drawing processability could not be obtained.

[0110] In tests 31 and 32, the F2 value was too low. As a result, the durability ratio was less than 0.30, and a sufficient durability ratio was not achieved.

[0111] In test numbers 33-36, F2 was too high. As a result, the microstructure became unstable, with the pearlite area ratio falling below 90% in test number 36, and the strength becoming too high in test numbers 33-35. Consequently, in these test numbers, a sufficient durability ratio and sufficient wire drawing processability could not be obtained.

[0112] The embodiments of this disclosure have been described above. However, the embodiments described above are merely examples for implementing this disclosure. Therefore, this disclosure is not limited to the embodiments described above, and the embodiments described above can be modified as appropriate without departing from the spirit of this disclosure.

Claims

1. The chemical composition is expressed in mass percent. C: 0.70-1.10% Si: 0.10-0.40%, Mn: 0.15-0.80%, Cu: 0.10 to less than 1.00%, P: 0.015% or less, S: 0.015% or less, N: 0.0005-0.0060%, Al: 0.003% or less, It contains O: 0.0040% or less, with the remainder consisting of Fe and impurities. The following conditions satisfy equations (1) and (2): Wire rod. 0.10≦Si / (C+Ni)≦0.20 (1) 1.43≦(Cr+Mn+Cu) / (Si+10P+10S+100N)≦1.63 (2) Here, the mass percentage content of each element is substituted for the elemental symbol in equations (1) and (2). If an element is not present, the corresponding element symbol is replaced with "0".

2. The chemical composition is expressed in mass percent. C: 0.70-1.10% Si: 0.10-0.40%, Mn: 0.15-0.80%, Cu: 0.30 to less than 1.00%, P: 0.015% or less, S: 0.015% or less, N: 0.0005-0.0060%, Al: 0.003% or less, O: Contains 0.0040% or less, Furthermore, it contains one or more elements selected from the groups consisting of Group 1 and Group 2, with the remainder being Fe and impurities. The following conditions satisfy equations (1) and (2): Wire rod. [Group 1] Cr: 0.60% or less, Co: 0.50% or less, Mo: 0.10% or less B: 0.005% or less, W: 0.20% or less, Ni: 0.50% or less, V: 0.10% or less, Nb: 0.10% or less, Ti: 0.10% or less, One or more selected from the group consisting of Sn: 0.10% or less. [Group 2] Ca: 0.0050% or less, Mg: 0.0050% or less, Zr: 0.010% or less, Rare earth elements: One or more selected from the group consisting of 0.0050% or less. 0.10≦Si / (C+Ni)≦0.20 (1) 1.43≦(Cr+Mn+Cu) / (Si+10P+10S+100N)≦1.63 (2) Here, the mass percentage content of each element is substituted for the elemental symbol in equations (1) and (2). If an element is not present, the corresponding element symbol is replaced with "0".

3. The wire material according to claim 2, The first group contains, Wire rod.

4. The wire material according to claim 2, The following include the second group: Wire rod.

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