Plated Steel Wire

Abstract

To provide a plated steel wire excellent in corrosion resistance and capable of suppressing even the occurrence of cracks in a plating layer during treatment.SOLUTION: A plated steel wire 1 includes a base material steel wire 10 and a plating layer 11. The plating layer 11 including, by mass%, Al:4.5 to less than 15.0%, Mg:0.3-4.0%, 0.01-0.50% of one or more elements selected from a group consisting of Sn, Bi and In and the remainder consisting of Zn and impurities satisfies the formula (1). In a main body area 13 except an alloy layer 12 in the plating layer 11, the area ratio of a α phase is 20 to 70%; the area ratio of an eutectic phase is 10-60%; and a specific concentration area rate having 1.0% or more of the content of one kind of Sn, Bi and In is 0.5-10.0%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a plated steel wire. [Background technology]

[0002] Plated steel wire is used as a material for wire mesh, fences, power transmission wires, etc. The plated steel wire comprises a base steel wire and a plating layer formed on the surface of the base steel wire.

[0003] The plating layer of a plated steel wire is required to have corrosion resistance. For example, zinc plating, zinc alloy plating, etc. are used as the plating layer of a plated steel wire. Zinc plating is a plating made of Zn. Zinc alloy plating is a plating made of an alloy of Zn and other alloying elements. Examples of zinc alloy plating include Zn-Al alloy plating containing Zn and Al, or Zn-Al-Mg alloy plating containing Zn, Al, and Mg. A plated steel wire having a zinc alloy plating layer has higher corrosion resistance than a plated steel wire having a zinc plating layer.

[0004] However, the above-mentioned zinc alloy plating layer tends to be harder than the zinc plating layer. Therefore, in a plated steel wire having a zinc alloy plating layer, cracks are likely to occur in the zinc alloy plating layer during processing, typically bending. In a plated steel wire having a crack in the zinc alloy plating layer, the corrosion resistance of the cracked portion is reduced. Therefore, in a plated steel wire having a zinc alloy plating layer, it is necessary to suppress the occurrence of cracks in the plating layer during processing.

[0005] A technology for suppressing cracks in a plating layer during processing is disclosed, for example, in JP-T-2020-503439 (Patent Document 1).

[0006] The alloy-plated steel material disclosed in Patent Document 1 includes a zinc alloy plating layer. The zinc alloy plating layer contains 0.5 to 2.5% Mg, 0.5 to 3.0% Al, and the remainder Zn and inevitable impurities. The zinc alloy plating layer includes a single Zn phase and a mixed phase of Zn and Mg, and the mixed phase of Zn and Mg has a lamellar structure consisting of a Zn phase and an Mg-Zn alloy phase. The average width of the lamellar structure is 1.5 μm or less. In this document, the average width of the lamellar structure in the zinc alloy plating layer is set to 1.5 μm or less. Patent Document 1 states that this suppresses the occurrence of cracks in the plating layer during processing. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 2020-503439 Summary of the Invention [Problem to be solved by the invention]

[0008] However, it may be possible to suppress the occurrence of cracks in the plating layer during processing by means other than the means disclosed in the above-mentioned Patent Document 1.

[0009] An object of the present invention is to provide a plated steel wire that is excellent in corrosion resistance and can suppress the occurrence of cracks in the plating layer during processing. [Means for solving the problem]

[0010] The plated steel wire according to the present invention has the following configuration.

[0011] A plated steel wire, A base steel wire; a plating layer formed on a surface of the base steel wire, The plating layer is In mass%, Al: 4.5 to less than 15.0% Mg: 0.3 to 4.0%, and One or more elements selected from the group consisting of Sn, Bi, and In: 0.01 to 0.50%; and the balance being Zn and impurities, and satisfying formula (1), In a main body region of the plating layer excluding the alloy layer in a cross section perpendicular to the longitudinal direction of the plated steel wire, The area ratio of the α phase containing Al and Zn is 20 to 70%, the area ratio of the eutectic phase containing the Zn phase and the Zn-Mg phase is 10 to 60%, The area ratio of the specific enriched region in which the content of any one of Sn, Bi, and In is 1.0% or more is 0.5 to 10.0%. Plated steel wire. 4.0≦Mg / (Sn+Bi+In)≦20.0 (1) Here, the content of each element in formula (1) is substituted with the content of the corresponding element in mass %. [Effects of the Invention]

[0012] The plated steel wire of the present invention has excellent corrosion resistance and can suppress the occurrence of cracks in the plated layer during processing. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view perpendicular to the longitudinal direction of the plated steel wire of this embodiment. [Figure 2] 1 is an image of the microstructure of a plating layer 11 in a cross section perpendicular to the longitudinal direction of a plated steel wire 1. [Figure 3] FIG. 3 is a schematic diagram for explaining the intersection method. [Figure 4] FIG. 4 is a diagram showing elemental mapping of Sn when a surface analysis using an electron probe microanalyzer is carried out on the plating layer 11 of this embodiment that satisfies Features 1 to 4. [Figure 5] FIG. 5 is a cross-sectional view perpendicular to the longitudinal direction of a plated steel wire 1 having a different configuration from that shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present inventors have investigated, from the viewpoint of chemical composition, the plating layer of a plated steel wire that has excellent corrosion resistance and can suppress the occurrence of cracks in the plating layer during processing. As a result, they have concluded that by further adding one or more elements selected from the group consisting of Sn, Bi, and In to a Zn-Al-Mg alloy plating that has excellent corrosion resistance, it is possible to achieve both excellent corrosion resistance and suppression of cracks in the plating layer during processing.

[0015] Therefore, the present inventors further investigated the chemical composition of the coating layer, and as a result, they found that if a coated steel wire satisfies the following characteristic 1, it is highly likely that both excellent corrosion resistance and suppression of cracking of the coating layer during processing can be achieved.

[0016] (Feature 1) The chemical composition of the coating layer of the coated steel wire is, in mass %, Al: 4.5 to less than 15.0%, Mg: 0.3 to 4.0%, one or more elements selected from the group consisting of Sn, Bi, and In: 0.01 to 0.50%, Si: 0 to 0.50%, Fe: 0 to 2.00%, Pb: 0 to 0.50%, Sr: 0 to 0.50%, V: 0 to 0.50%, Cr: 0 to 0.50%, Mn: 0 to 0.50%, Ti: 0 to 0.50%, Be: 0 to 0.50%, Na: 0-0.50%, K: 0-0.50%, Ca: 0-0.50%, Cu: 0-0.50%, La: 0-0.50%, Ce: 0-0.50%, Hf: 0-0.50%, Mo: 0-0.50%, W: 0-0.50%, Nb: 0-0.50%, Ta: 0-0.50%, Co: 0-0.50%, Ni: 0-0.50%, and B: 0-0.50%, with the remainder being Zn and impurities.

[0017] However, even in a plated steel wire having a plating layer that satisfies Feature 1, there are still cases in which it is not possible to sufficiently achieve both excellent corrosion resistance and suppression of cracking of the plating layer during processing. Therefore, the present inventors conducted further studies. As a result, the present inventors found that if a plating layer that satisfies Feature 1 also satisfies the following Features 2 to 4, it is possible to achieve both excellent corrosion resistance and suppression of cracking of the plating layer during processing. (Feature 2) In the cross section perpendicular to the longitudinal direction of the plated steel wire, in the main body region excluding the alloy layer, The area ratio of the α phase containing Al and Zn is 20 to 70%, The area ratio of the eutectic phase containing the Zn phase and the Zn-Mg phase is 10 to 60%. (Feature 3) In the cross section perpendicular to the longitudinal direction of the plated steel wire, in the main body region excluding the alloy layer, The area ratio of the specific enriched region in which the content of any one of Sn, Bi, and In is 1.0% or more is 0.5 to 10.0%. (Feature 4) The above chemical composition further satisfies formula (1). 4.0≦Mg / (Sn+Bi+In)≦20.0 (1) Here, the content of each element in formula (1) is substituted with the content of the corresponding element in mass %.

[0018] The plated steel wire according to this embodiment, which has been completed based on the above findings, has the following configuration.

[0019] [1] A plated steel wire, A base steel wire; a plating layer formed on a surface of the base steel wire, The plating layer is In mass%, Al: 4.5 to less than 15.0% Mg: 0.3 to 4.0%, and One or more elements selected from the group consisting of Sn, Bi, and In: 0.01 to 0.50%; and the balance being Zn and impurities, and satisfying formula (1), In a main body region of the plating layer excluding the alloy layer in a cross section perpendicular to the longitudinal direction of the plated steel wire, The area ratio of the α phase containing Al and Zn is 20 to 70%, the area ratio of the eutectic phase containing the Zn phase and the Zn-Mg phase is 10 to 60%, The area ratio of the specific enriched region in which the content of any one of Sn, Bi, and In is 1.0% or more is 0.5 to 10.0%. Plated steel wire. 4.0≦Mg / (Sn+Bi+In)≦20.0 (1) Here, the content of each element in formula (1) is substituted with the content of the corresponding element in mass %.

[0020] [2] [1] The plated steel wire according to [1], The plating layer further comprises: In place of a part of the Zn, in mass%, Si: 0.50% or less, Fe: 2.00% or less, Pb: 0.50% or less, Sr: 0.50% or less, V: 0.50% or less, Cr: 0.50% or less, Mn: 0.50% or less, Ti: 0.50% or less, Be: 0.50% or less, Na: 0.50% or less, K: 0.50% or less, Ca: 0.50% or less, Cu: 0.50% or less, La: 0.50% or less, Ce: 0.50% or less, Hf: 0.50% or less, Mo: 0.50% or less W: 0.50% or less, Nb: 0.50% or less, Ta: 0.50% or less, Co: 0.50% or less, Ni: 0.50% or less, and B: 0.50% or less, Contains one or more elements selected from the group consisting of Plated steel wire.

[0021] The plated steel wire of this embodiment will be described in detail below. "%" regarding elements means mass % unless otherwise specified.

[0022] [About plated steel wire 1] Fig. 1 is a cross-sectional view perpendicular to the longitudinal direction of a plated steel wire according to this embodiment. Referring to Fig. 1, the plated steel wire 1 according to this embodiment includes a base steel wire 10 and a plating layer 11. The plating layer 11 is formed on the surface of the base steel wire 10.

[0023] [About base steel wire 10] The base steel wire 10 refers to a wire that has been subjected to wire drawing at least once. The steel type of the base steel wire 10 is not particularly limited. The steel type of the base steel wire 10 may be appropriately selected depending on the mechanical properties (e.g., tensile strength, workability, etc.) required of the plated steel wire 1. The chemical composition of the base steel wire 10 is not particularly limited, but may be, for example, the chemical composition of a soft steel wire specified in JIS G3505 (2017) or the chemical composition of a hard steel wire specified in JIS G3506 (2017).

[0024] [Characteristics of plating layer 11] The plating layer 11 includes an alloy layer 12 and a main body region 13. The plating layer 11 does not necessarily have to include the alloy layer 12. In other words, the plating layer 11 may be a layer made up of the main body region 13.

[0025] When the plating layer 11 includes the alloy layer 12, the alloy layer 12 is formed mainly in the vicinity of the base steel wire 10. The alloy layer 12 contains Zn, Al, and Fe. The alloy layer 12 is composed of an intermetallic compound mainly composed of Zn, Al, and Fe. In other words, the alloy layer 12 is a layer well known to those skilled in the art.

[0026] The plating layer 11 satisfies the following characteristics 1 to 4. (Feature 1) The chemical composition of the coating layer of the coated steel wire is, in mass %, Al: 4.5 to less than 15.0%, Mg: 0.3 to 4.0%, one or more elements selected from the group consisting of Sn, Bi, and In: 0.01 to 0.50%, Si: 0 to 0.50%, Fe: 0 to 2.00%, Pb: 0 to 0.50%, Sr: 0 to 0.50%, V: 0 to 0.50%, Cr: 0 to 0.50%, Mn: 0 to 0.50%, Ti: 0 to 0.50%, Be: 0 to 0.50%, Na: 0-0.50%, K: 0-0.50%, Ca: 0-0.50%, Cu: 0-0.50%, La: 0-0.50%, Ce: 0-0.50%, Hf: 0-0.50%, Mo: 0-0.50%, W: 0-0.50%, Nb: 0-0.50%, Ta: 0-0.50%, Co: 0-0.50%, Ni: 0-0.50%, and B: 0-0.50%, with the remainder being Zn and impurities. (Feature 2) In the cross section perpendicular to the longitudinal direction of the plated steel wire, in the main body region excluding the alloy layer, The area ratio of the α phase containing Al and Zn is 20 to 70%, The area ratio of the eutectic phase containing the Zn phase and the Zn-Mg phase is 10 to 60%. (Feature 3) In the cross section perpendicular to the longitudinal direction of the plated steel wire, in the main body region excluding the alloy layer, The area ratio of the specific enriched region in which the content of any one of Sn, Bi, and In is 1.0% or more is 0.5 to 10.0%. (Feature 4) The above chemical composition further satisfies formula (1). 4.0≦Mg / (Sn+Bi+In)≦20.0 (1) Here, the content of each element in formula (1) is substituted with the content of the corresponding element in mass %.

[0027] Hereinafter, features 1 to 4 of the plating layer 11 will be described.

[0028] [(Feature 1) Chemical composition of plating layer 11] The chemical composition of the plating layer 11 contains the following elements.

[0029] [Essential elements] Al: 4.5 to less than 15.0% Aluminum (Al) enhances the corrosion resistance of the plated steel wire 1 through sacrificial corrosion protection. Furthermore, Al suppresses the formation of Mg oxides in a plating bath containing Mg. If the Al content is less than 4.5%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the ranges of this embodiment. On the other hand, if the Al content is 15.0% or more, the melting point of the coating bath becomes high even if the contents of other elements are within the ranges of this embodiment. In this case, the generation of oxides in the coating bath is promoted. As a result, it becomes necessary to remove the oxides during the manufacturing process, which reduces production efficiency. Therefore, the Al content is 4.5 to less than 15.0%. The lower limit of the Al content is preferably 5.0%, more preferably 5.5%, and even more preferably 6.0%. The upper limit of the Al content is preferably 14.0%, more preferably 13.5%, and even more preferably 13.0%.

[0030] Mg: 0.3 to 4.0% Magnesium (Mg) sacrificially protects the plated steel wire 1, thereby increasing its corrosion resistance. If the Mg content is less than 0.3%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the ranges of this embodiment. On the other hand, if the Mg content exceeds 4.0%, an excessive amount of the Zn-Mg phase, an intermetallic compound consisting of Zn and Mg, is generated in the microstructure of the coating layer. In this case, even if the contents of other elements are within the ranges of this embodiment, the coating layer 11 becomes excessively hard. As a result, cracks in the coating layer are more likely to occur during processing. Therefore, the Mg content is 0.3 to 4.0%. The lower limit of the Mg content is preferably 0.5%, more preferably 0.7%, and even more preferably 0.9%. The upper limit of the Mg content is preferably 3.5%, more preferably 3.0%, and even more preferably 2.5%.

[0031] One or more elements selected from the group consisting of Sn, Bi, and In: 0.01 to 0.50% Tin (Sn), bismuth (Bi), and indium (In) all combine with Mg to form the intermetallic compound Mg-(Sn, Bi, In) phase. The formation of the Mg-(Sn, Bi, In) phase suppresses the formation of the Zn-Mg phase, thereby improving the workability of the plating layer 11. If the total content of one or more elements selected from the group consisting of Sn, Bi, and In is less than 0.01%, the above-mentioned effects cannot be sufficiently obtained, even if the contents of the other elements are within the ranges of this embodiment. On the other hand, if the total content of one or more elements selected from the group consisting of Sn, Bi, and In exceeds 0.50%, the corrosion resistance may decrease even if the contents of other elements are within the ranges of this embodiment. Therefore, the total content of one or more elements selected from the group consisting of Sn, Bi, and In is 0.01 to 0.50%. The lower limit of the total content of one or more elements selected from the group consisting of Sn, Bi, and In is preferably 0.05%, and more preferably 0.10%. The upper limit of the total content of one or more elements selected from the group consisting of Sn, Bi, and In is preferably 0.40%, and more preferably 0.30%. The significant figures for the Sn content, Bi content, and In content are all rounded to one decimal place.

[0032] The balance of the chemical composition of the plating layer 11 is composed of Zn and impurities. Here, the impurities refer to substances that are mixed in from raw materials or the manufacturing environment when the plating layer 11 is industrially manufactured, and are acceptable within a range that does not adversely affect the plating layer 11 according to this embodiment.

[0033] [Optional elements] The chemical composition of the plating layer 11 further includes, in place of a portion of Zn, Si: 0.50% or less, Fe: 2.00% or less, Pb: 0.50% or less, Sr: 0.50% or less, V: 0.50% or less, Cr: 0.50% or less, Mn: 0.50% or less, Ti: 0.50% or less, Be: 0.50% or less, Na: 0.50% or less, K: 0.50% or less, Ca: 0.50% or less, Cu: 0.50% or less, La: 0.50% or less, Ce: 0.50% or less, Hf: 0.50% or less, Mo: 0.50% or less W: 0.50% or less, Nb: 0.50% or less, Ta: 0.50% or less, Co: 0.50% or less, Ni: 0.50% or less, and B: 0.50% or less, The optional elements may be contained in the composition of the present invention. The optional elements will be described below.

[0034] [About Si] Si:0.50% or less Si is an optional element and may not be contained, that is, the Si content may be 0%. When contained, Si bonds with Mg to form an Mg-Si phase. The Mg-Si phase improves the corrosion resistance of plated steel wire. The formation of an Mg-Sn phase further suppresses the formation of an Fe-Al phase and suppresses the formation of an Mg-Zn phase. This improves the workability of the plated steel wire. Even if only a small amount of Si is contained, the above effects can be achieved to some extent. However, if the Si content exceeds 0.50%, the Mg—Si phase becomes excessively coarse, which may result in a decrease in the workability of the plated steel wire. Therefore, the Si content is 0 to 0.50%, and when Si is contained, it is 0.50% or less (more than 0 to 0.50%). The lower limit of the Si content is preferably 0.01%, more preferably 0.05%, even more preferably 0.10%, and still more preferably 0.15%. The upper limit of the Si content is preferably 0.48%, more preferably 0.45%, and even more preferably 0.40%.

[0035] [About Fe] Fe:2.00% or less Fe is an optional element and may not be contained, that is, the Fe content may be 0%. During the manufacturing process of plated steel wire, Fe in the steel wire may be contained in the plating layer. In this case, Fe forms an alloy layer. The alloy layer improves the corrosion resistance of the plated steel wire. Even if even a small amount of Fe is contained, the above effects can be obtained to some extent. However, if the Fe content exceeds 2.00%, an excessive alloy layer is formed, which reduces the workability of the plated steel wire. Therefore, the Fe content is 0 to 2.00%, and when contained, it is 2.00% or less (more than 0 to 2.00%). The lower limit of the Fe content is preferably 0.01%, more preferably 0.05%, even more preferably 0.10%, and still more preferably 0.15%. The upper limit of the Fe content is preferably 1.90%, more preferably 1.75%, and even more preferably 1.50%.

[0036] [About Pb, Sr, V, Cr, Mn, Ti, Be, Na, K, Ca, Cu, La, Ce, Hf, Mo, W, Nb, Ta, Co, Ni, and B] Lead (Pb), strontium (Sr), vanadium (V), chromium (Cr), manganese (Mn), titanium (Ti), beryllium (Be), sodium (Na), potassium (K), calcium (Ca), copper (Cu), lanthanum (La), cerium (Ce), hafnium (Hf), molybdenum (Mo), tungsten (W), niobium (Nb), tantalum (Ta), cobalt (Co), nickel (Ni), and boron (B) are all optional elements and may not be included. If included, these elements substitute for part of the Mg-(Sn, Bi, In) phase, further improving the workability of the plated steel wire. The inclusion of even a small amount of any one or more of these elements can achieve the above-mentioned effects to some extent. However, if the content of each of the above elements exceeds 0.50%, the workability of the plated steel wire is deteriorated. Furthermore, the formation of the Zn-Mg phase is suppressed, and the corrosion resistance of the plated steel wire is deteriorated. Therefore, the content of each of the elements Pb, Sr, V, Cr, Mn, Ti, Be, Na, K, Ca, Cu, La, Ce, Hf, Mo, W, Nb, Ta, Co, Ni, and B is 0 to 0.50%, and if contained, it is 0.50% or less (more than 0 to 0.50%).

[0037] The lower limit of each of the elements Pb, Sr, V, Cr, Mn, Ti, Be, Na, K, Ca, Cu, La, Ce, Hf, Mo, W, Nb, Ta, Co, Ni, and B is preferably 0.01%, more preferably 0.05%, and even more preferably 0.10%. The upper limit of each of the elements Pb, Sr, V, Cr, Mn, Ti, Be, Na, K, Ca, Cu, La, Ce, Hf, Mo, W, Nb, Ta, Co, Ni, and B is preferably 0.48%, more preferably 0.45%, and even more preferably 0.40%.

[0038] [Method for analyzing the chemical composition of the plating layer 11] The chemical composition of the plating layer 11 is determined by the following method. In accordance with JIS H0401:1999 "Test Method for Hot-Dip Galvanizing," the plated steel wire is immersed in a hydrochloric acid solution to dissolve the plating layer, and a solution is obtained. The obtained solution is subjected to ICP (Inductively Coupled Plasma) emission spectroscopy to perform elemental analysis of the chemical composition of the plating layer.

[0039] The content of each element is determined by rounding off the measured value to the nearest significant digit based on the significant digits specified in this embodiment. For example, the Al content of the plating layer 11 is determined to one decimal place. Therefore, the Al content is determined to one decimal place by rounding off the measured value to one decimal place.

[0040] Similarly, the content of other elements other than the Al content of the plating layer 11 is determined by rounding off the measured value to the smallest digit specified in this embodiment, and the value obtained is the content of the element.

[0041] Rounding off means rounding down if the fraction is less than 5, and rounding up if the fraction is 5 or more.

[0042] [(Feature 2) Area ratio of α phase and eutectic phase in the main body region 13] Figure 2 is an image of the microstructure of the main body region 13 of the plating layer 11, excluding the alloy layer 12, in a cross section perpendicular to the longitudinal direction of the plated steel wire 1 in Figure 1. The T direction in Figure 2 means the thickness direction of the plating layer 11. The L direction means the longitudinal direction of the plated steel wire 1. The C direction means the direction perpendicular to the T direction and the L direction.

[0043] Referring to FIG. 2, the microstructure of the main body region 13 of the plating layer 11 contains at least the following phases. (1)α phase (2) Eutectic phase

[0044] In the plating layer 11 in a cross section perpendicular to the longitudinal direction of the plated steel wire, in the main body region 13 excluding the alloy layer 12, the area ratio of the α phase containing Al and Zn is 20 to 70%, and the area ratio of the eutectic phase containing the Zn phase and the Zn-Mg phase is 10 to 60%.

[0045] [Definition of α phase 11A] The α phase 11A is composed of Al and Zn. As shown in FIG. 2, the α phase can be identified as a region that is less bright than the eutectic phase 11B in the backscattered electron image. In FIG. 2, the gray and black regions that are less bright than the eutectic phase 11B correspond to the α phase 11A. More specifically, the region that is less bright than the eutectic phase 11B in the backscattered electron image and in which Al and Zn are detected by energy dispersive X-ray analysis (EDS) is defined as the α phase 11A.

[0046] [Definition of eutectic phase 11B] The eutectic phase 11B contains at least a Zn phase and a Zn-Mg phase. The eutectic phase 11B may further contain an Al phase and / or an Mg-(Sn, Bi, In) phase. As shown in FIG. 2, the eutectic phase 11B is a mixture of at least a Zn phase, which has a higher brightness than the α phase 11A, and a Zn-Mg phase, which has a brightness similar to that of the α phase 11A. In the eutectic phase 11B, at least the Zn phase and the Zn-Mg phase are mixed in a layered or granular form.

[0047] The Zn phase is brighter than the α-phase 11A and the Zn-Mg phase in a backscattered electron image, and Zn is detected in EDS, while Mg is hardly detected. In a backscattered electron image, the Zn phase can be easily distinguished from the α-phase 11A and the Zn-Mg phase by contrast.

[0048] The Zn-Mg phase is a phase that is less bright than the Zn phase in a backscattered electron image, and in which Zn and Mg are detected by EDS.

[0049] As described above, the eutectic phase 11B may further contain an Al phase and / or an Mg-(Sn, Bi, In) phase. The Al phase has lower brightness than the α phase 11A and the eutectic phase 11B in a backscattered electron image, and is a phase in which Al is detected by EDS.

[0050] The Mg-(Sn, Bi, In) phase is an intermetallic compound containing Mg and one or more elements selected from the group consisting of Sn, Bi, and In. The Mg-(Sn, Bi, In) phase has lower brightness than the Zn phase in a backscattered electron image, and Mg and one or more elements selected from the group consisting of Sn, Bi, and In are detected in EDS. However, because it is difficult to identify the Mg-(Sn, Bi, In) phase in a backscattered electron image, the Mg-(Sn, Bi, In) phase is recognized as a specific enrichment region, as described in Feature 3 below.

[0051] [Area ratio of α phase 11A] The area ratio of the α phase 11A in the coating layer 11 affects the corrosion resistance and workability of the plated steel wire 1. If the area ratio of the α phase 11A is less than 20%, the plated steel wire 1 cannot obtain sufficient corrosion resistance and workability. On the other hand, if the area ratio of the α phase 11A exceeds 70%, the area ratio of the eutectic phase decreases. In this case, the plated steel wire 1 cannot obtain sufficient corrosion resistance. Therefore, the area ratio of the α phase 11A is 20 to 70%. The lower limit of the area ratio of the α phase 11A is preferably 25%, more preferably 30%, and even more preferably 35%. The upper limit of the area ratio of the α phase 11A is preferably 67%, more preferably 65%, and even more preferably 60%.

[0052] [Regarding the area ratio of eutectic phase 11B] The area ratio of the eutectic phase 11B in the plating layer 11 affects the corrosion resistance and workability of the plated steel wire 1. If the area ratio of the eutectic phase 11B is less than 10%, sufficient corrosion resistance cannot be obtained in the plated steel wire 1. On the other hand, the eutectic phase 11B is harder than the α phase 11A. Therefore, if the area ratio of the eutectic phase 11B exceeds 60%, the workability of the plated steel wire 1 decreases. In other words, cracks are more likely to occur in the plating layer 11 when the plated steel wire 1 is worked. Therefore, the area ratio of the eutectic phase 11B is 10 to 60%. The lower limit of the area ratio of the eutectic phase 11B is preferably 15%, more preferably 20%, and even more preferably 25%. The upper limit of the area ratio of the eutectic phase 11B is preferably 58%, more preferably 55%, and even more preferably 53%.

[0053] [Method for measuring the area ratio of the α phase 11A and the area ratio of the eutectic phase 11B in the main body region 13] The area ratio of the α phase 11A and the area ratio of the eutectic phase 11B in the main body region 13 excluding the alloy layer 12 of the plating layer 11 in a cross section perpendicular to the longitudinal direction of the plated steel wire 1 can be determined by the following method.

[0054] A sample including the plating layer 11 is taken from the plated steel wire 1. Of the surface of the sample, a cross section including the plating layer 11 and perpendicular to the longitudinal direction of the plated steel wire 1 is defined as the observation surface. The observation surface is mirror-polished. Of the plating layer 11 on the observation surface after mirror polishing, in the main body region 13 excluding the alloy layer 12, a region of 20 μm in the thickness direction of the plating layer 11 and 40 μm in the direction perpendicular to the thickness direction of the plating layer 11 and the longitudinal direction of the plated steel wire 1 (width direction) is defined as the observation region. Four observation regions are arbitrarily selected.

[0055] In an SEM backscattered electron image of a cross section perpendicular to the longitudinal direction of the plated steel wire 1, the base steel wire 10, the alloy layer 12, and the main body region 13 have different contrasts. Specifically, the alloy layer 12 has a darker brightness than the main body region 13. Therefore, a person skilled in the art would be able to distinguish the base steel wire 10, the alloy layer 12, and the main body region 13 from the contrast of the backscattered electron image.

[0056] A scanning electron microscope (SEM) equipped with an energy dispersive X-ray analyzer (EDS) was used to generate backscattered electron images of each observation area. As mentioned above, the α phase and the eutectic phase contain different elements. Therefore, in the backscattered electron images, the α phase and the eutectic phase can be clearly distinguished based on their contrast.

[0057] The α phase and the eutectic phase can also be clearly distinguished by performing point analysis using EDS. When performing point analysis using EDS, the current value of the electron beam is set to 70 to 80 nA, and the analysis time is set to 30 seconds. By using the above method, the α phase 11A and the eutectic phase 11B are identified in the observation area. The point analysis is performed at the observation point CP.

[0058] The area ratios of the α phase 11A and the eutectic phase 11B are determined using the following intersection method.

[0059] Fig. 3 is a schematic diagram for explaining the intersection method. As shown in Fig. 3, in a rectangular observation area 20 of 40 μm × 20 μm, the thickness direction of the plating layer 11 is defined as the T direction, and the direction perpendicular to the T direction is defined as the C direction. Of the four sides of the observation area 20, a pair of sides parallel to the C direction are defined as C-direction sides 20C, and a pair of sides parallel to the T direction are defined as T-direction sides 20T. The C-direction sides 20C are 40 μm long, and the T-direction sides 20T are 20 μm long.

[0060] A plurality of C-direction line segments CS are arranged in parallel with the C-direction side 20C at a pitch of 5 μm in the T direction. Similarly, a plurality of T-direction line segments TS are arranged in parallel with the T-direction side 20T at a pitch of 5 μm in the C direction. The four vertices of the observation area, the intersection of the C-direction side 20C and the T-direction line segment TS, the intersection of the T-direction side 20T and the C-direction line segment CS, and the intersection of the T-direction line segment TS and the C-direction line segment CS are defined as observation points CP.

[0061] The phase overlapping each observation point CP is identified using the method described above. The ratio (%) of the total number of observation points CP that overlap with the α phase 11A to the total number of observation points CP is defined as the area ratio (%) of the α phase 11A. Similarly, the ratio (%) of the total number of observation points CP that overlap with the eutectic phase 11B to the total number of observation points CP is defined as the area ratio (%) of the eutectic phase 11B. The arithmetic mean value of the area ratios of the α phase 11A obtained in the four observation regions is defined as the area ratio (%) of the α phase 11A of the plated steel wire 1. Similarly, the arithmetic mean value of the area ratios of the eutectic phase 11B obtained in the four observation regions is defined as the area ratio (%) of the eutectic phase 11B of the plated steel wire 1.

[0062] [(Feature 3) Area ratio of specific enriched areas in coated steel wire 1] Furthermore, in the plated steel wire 1, in the cross section perpendicular to the longitudinal direction of the plated steel wire 1, in the main body region 13 of the plating layer 11 excluding the alloy layer 12, the area ratio of the specific enriched region in which the content of any one of Sn, Bi, and In is 1.0% or more is 0.5 to 10.0%.

[0063] Fig. 4 is a diagram showing elemental mapping of Sn when area analysis using an electron probe microanalyzer is performed on main body region 13 in plating layer 11 of this embodiment that satisfies Features 1 to 4. Fig. 4 was obtained by a method for measuring the area ratio of a specific enriched region, which will be described later.

[0064] Referring to Figure 4, the white area in the figure is a specific enrichment region where 1.0% or more Sn was detected by mass %. In this way, the specific enrichment region is defined as a region where the content of any one of Sn, Bi, and In is 1.0% or more. The specific enrichment region corresponds to the Mg-(Sn, Bi, In) phase. The Mg-(Sn, Bi, In) phase is often very fine and is extremely difficult to identify by microstructural observation. Therefore, the Mg-(Sn, Bi, In) phase is substituted for the specific enrichment region. The area ratio of the specific enrichment region is then used as an index of the area ratio of the Mg-(Sn, Bi, In) phase.

[0065] The specific enriched region suppresses cracking of the coating layer 11 during processing. If the area ratio of the specific enriched region is less than 0.5%, the above effect cannot be sufficiently achieved. On the other hand, if the specific enriched region exceeds 10.0%, the Zn-Mg phase is excessively reduced. In this case, even if the coating layer 11 satisfies Features 1, 2, and 4, the corrosion resistance is reduced. Therefore, the area ratio of the specific enriched region is 0.5 to 10.0%.

[0066] The lower limit of the area ratio of the specific enriched region is preferably 1.0%, more preferably 1.5%, and even more preferably 2.0%. The upper limit of the area ratio of the specific enriched region is preferably 9.5%, more preferably 9.0%, and even more preferably 8.5%.

[0067] [Method for measuring the area ratio of specific enriched regions] The area ratio of the specific enriched region in the main region 13 can be determined by the following method. A sample including the plating layer 11 is taken from the plated steel wire 1. A cross section of the sample surface that includes the plating layer 11 and is perpendicular to the longitudinal direction of the plated steel wire 1 is defined as the observation surface. The observation surface is mirror-polished. In the main body region 13 of the plating layer 11 on the mirror-polished observation surface, excluding the alloy layer 12, an area of ​​20 μm in the thickness direction (T direction) of the plating layer 11 and 80 μm in the direction (C direction) perpendicular to the thickness direction (T direction) of the plating layer 11 and the longitudinal direction (L direction) of the plated steel wire 1 is defined as the observation area. Four observation areas are arbitrarily selected.

[0068] Each observation area is subjected to area analysis using an electron beam microanalyzer. The pixel size for area analysis is 0.4 μm × 0.4 μm. The beam voltage for the EPMA is 15.0 kV. The analysis time is 50 ms per point.

[0069] If the content of any one of Sn, Bi, and In in each pixel is 1.0% or more, the area of ​​that pixel is designated as a "specific enrichment area." The ratio (%) of the total area of ​​the pixel areas recognized as specific enrichment areas to the area of ​​each observation area where area analysis was performed is defined as the area ratio (%) of the specific enrichment area. The arithmetic mean value of the area ratios of the specific enrichment areas determined in the four observation areas is defined as the area ratio (%) of the specific enrichment area of ​​the plated steel wire 1.

[0070] [(Feature 4) About parameter formulas] The chemical composition of the plating layer 11 further satisfies formula (1). 4.0≦Mg / (Sn+Bi+In)≦20.0 (1) Here, the content of each element in formula (1) is substituted with the content of the corresponding element in mass %.

[0071] Define F1 as follows: F1 = Mg / (Sn+Bi+In) F1 is an index relating to the corrosion resistance and workability of the plating layer 11. Among the elements contained in the plating layer 11, Mg significantly improves the corrosion resistance. However, Mg increases the hardness of the plating layer 11 and reduces the workability of the plating layer 11.

[0072] On the other hand, among the elements contained in the plating layer 11, Sn, Bi, and In improve the workability of the plating layer 11. However, if Sn, Bi, and In are contained in excess, the corrosion resistance of the plating layer 11 decreases.

[0073] Therefore, in order to achieve both corrosion resistance and workability of the plating layer 11 that satisfies the features 1 to 3, it is necessary to adjust F1 within an appropriate range.

[0074] If F1 is less than 4.0, the total content of Sn, Bi, and In relative to the Mg content is high, which reduces the corrosion resistance of the plated steel wire 1. When F1 exceeds 20.0, the total content of Sn, Bi, and In relative to the Mg content is low. In this case, the workability of the plating layer 11 is low, and cracks are likely to occur in the plating layer 11 when the plated steel wire 1 is processed.

[0075] In the plating layer 11 that satisfies Features 1 to 3, if F1 is 4.0 to 20.0, the plated steel wire 1 has excellent corrosion resistance, and the occurrence of cracks in the plating layer 11 during processing can be suppressed.

[0076] The lower limit of F1 is preferably 4.5, more preferably 5.0, and even more preferably 5.5. The upper limit of F1 is preferably 19.5, more preferably 19.0, and even more preferably 18.5.

[0077] [Summary of plated steel wire 1] As described above, the plated steel wire 1 of this embodiment includes the base steel wire 10 and the plating layer 11. The plating layer 11 satisfies the following features 1 to 4. [Feature 1] The content of each element in the chemical composition of the plating layer 11 is within the range of this embodiment. [Feature 2] In the main body region 13, the area ratio of the α phase 11A is 20 to 70%, and the area ratio of the eutectic phase 11B is 10 to 60%. [Feature 3] In the main body region 13, the area ratio of the specific enrichment region is 0.5 to 10.0%. [Feature 4] The chemical composition of the plating layer 11 further satisfies formula (1). 4.0≦Mg / (Sn+Bi+In)≦20.0 (1)

[0078] In the plated steel wire 1 of this embodiment, the plating layer 11 has Features 1 to 4, and therefore has excellent corrosion resistance and can suppress the occurrence of cracks in the plating layer 11 during processing.

[0079] [Other configurations of plated steel wire 1] Fig. 5 is a cross-sectional view perpendicular to the longitudinal direction of a plated steel wire 1 having a configuration different from that shown in Fig. 1. Referring to Fig. 5, as described above, the plated layer 11 does not necessarily have to include the alloy layer 12. In this case, the plated layer 11 is made up of a main body region 13.

[0080] [Method of manufacturing plated steel wire 1] An example of a method for manufacturing the plated steel wire 1 of this embodiment will be described. The method for manufacturing the plated steel wire 1 described below is one example for manufacturing the plated steel wire 1. Therefore, the plated steel wire 1 satisfying the above-mentioned features 1 to 4 may be manufactured by a manufacturing method other than the manufacturing method described below.

[0081] The manufacturing process of the plated steel wire 1 includes the following steps. (Process 1) Steel wire preparation process (Process 2) First plating process (Step 3) Second plating step In the cooling step of the second plating process, the following three stages of cooling are carried out. (1st cooling) Average cooling rate CR1 from plating bath temperature to 340°C: 5.0 to 30.0°C / sec (Second cooling) Average cooling rate from 340℃ to 300℃: 5.0 to 20.0℃ / sec. (Third cooling) Average cooling rate from 300℃ to 200℃: CR3: 5.0 to 1500.0℃ / sec Steps 1 to 3 will be explained below.

[0082] [(Process 1) Steel wire preparation process] In the steel wire preparation step, a steel wire manufactured by a known method is prepared. The steel wire may be supplied by a third party. The steel wire may be manufactured by a manufacturer of plated steel wire. The steel wire is manufactured by drawing a wire rod. The drawn wire rod may be annealed as known to manufacture the steel wire. The annealing may or may not be performed.

[0083] [(Process 2) First plating process] In the first plating step, a well-known galvanizing process is performed on the steel wire prepared in the steel wire preparation step. In the first plating step, a galvanized layer that serves as a base for the alloy layer 12 is formed on the surface of the base steel wire 10. This improves the adhesion of the alloy layer 12, which will be formed in the next second plating step, to the base steel wire 10. The method of the galvanizing process is not particularly limited. The galvanizing process may be a well-known hot-dip galvanizing process or a well-known electrogalvanizing process.

[0084] The steel wire before the galvanizing treatment may be subjected to a well-known pickling treatment and / or a well-known flux treatment. The pickling treatment and / or the flux treatment are optional treatments and may not be performed. The pickling treatment and the flux treatment can improve the adhesion of the galvanized layer to the base steel wire 10.

[0085] [(Step 3) Second plating step] In the second plating step, a hot-dip plating process is performed on the base steel wire 10 on which the zinc plating layer has been formed. The second plating step includes the following steps. (Step 31) Pretreatment step (Step 32) Hot-dip plating process (Step 33) Cooling step Each step will be described below.

[0086] [(Step 31) Pretreatment step] The pretreatment step is an optional step and may not be performed. When the pretreatment step is carried out, in the pretreatment step, the base steel wire 10 on which the zinc plating layer is formed after the first plating step is subjected to a known pickling and / or a known flux treatment.

[0087] [(Step 32) Hot-dip plating process] In the immersion step, a hot-dip galvanizing treatment is performed on the base steel wire 10 on which the zinc-plated layer has been formed. Specifically, the base steel wire 10 is immersed in a galvanizing bath.

[0088] The chemical composition of the plating bath is adjusted so that the chemical composition of the plating layer 11 formed after the second plating step satisfies Features 1 and 4. The temperature (bath temperature) of the plating bath and the immersion time during the hot dip plating step may be within known ranges. The bath temperature is, for example, 400 to 500°C. The immersion time is, for example, 3 to 60 seconds.

[0089] [(Step 33) Cooling step] In the cooling step, the base steel wire 10 is pulled out of the coating bath and cooled. As described above, the cooling step involves the following three-stage cooling. By performing the three-stage cooling, a coating layer 11 that satisfies Features 2 and 3 is formed on the surface of the base steel wire 10. (1st cooling) Average cooling rate CR1 from plating bath temperature to 340°C: 5.0 to 30.0°C / sec (Second cooling) Average cooling rate from 340℃ to 300℃: 5.0 to 20.0℃ / sec. (Third cooling) Average cooling rate from 300℃ to 200℃: CR3: 5.0 to 1500.0℃ / sec

[0090] The first cooling crystallizes the α phase 11A, and the second cooling crystallizes the eutectic phase 11B and the specific enriched region. Then, the third cooling forms the plating layer 11 so that the α phase 11A, the eutectic phase 11B, and the specific enriched region satisfy Features 2 and 3. The first to third cooling steps will be described below.

[0091] [1st cooling] In the temperature range from the temperature of the plating bath (bath temperature) to 340°C, solidification begins from the liquid phase of the plating, and the α phase 11A crystallizes. Therefore, the average cooling rate CR1 in the temperature range from the bath temperature to 340°C is set to 5.0 to 30.0°C / sec.

[0092] If the average cooling rate CR1 is less than 5.0°C / sec, the α phase 11A may become coarse and the amount of crystallization may increase. In this case, the area ratio of the α phase 11A in the plating layer 11 may exceed 70%. On the other hand, if the average cooling rate CR1 exceeds 30.0°C / sec, the temperature of the plating layer 11 may fall below the crystallization temperature range of the α phase 11A before the α phase 11A has sufficiently crystallized. In this case, the area ratio of the α phase 11A will be less than 20%.

[0093] If the average cooling rate CR1 is 5.0 to 30.0°C / sec, the area ratio of the α phase 11A in the coating layer 11 will be 20 to 70%, provided that other cooling conditions are met.

[0094] The average cooling rate CR1 has a lower limit of preferably 6.0° C. / sec, more preferably 7.0° C. / sec, and a higher limit of preferably 25.0° C. / sec, more preferably 20.0° C. / sec.

[0095] The average cooling rate CR1 can be determined by the following method. The temperature of the base steel wire 10 pulled out of the coating bath is measured with a thermometer. The thermometer is, for example, a thermograph. The time it takes for the temperature of the base steel wire 10 to rise from the bath temperature to 340°C is measured. The average cooling rate CR1 (°C / sec) is determined based on the temperature range and the measured time.

[0096] [Second cooling] In the temperature range of 340 to 300° C., the eutectic phase 11B crystallizes. Furthermore, a specific enriched region is also formed along with the crystallization of the eutectic phase 11B. Therefore, the average cooling rate CR2 in the temperature range of 340 to 300° C. is set to 5.0 to 20.0° C. / second.

[0097] If the average cooling rate CR2 is less than 5.0°C / sec, the Zn-Mg phase may become coarse. In this case, the amount of crystallization of the eutectic phase 11B increases. As a result, the workability of the plated steel wire decreases. In this case, the area ratio of the eutectic phase 11B in the plating layer 11 exceeds 60%. On the other hand, if the average cooling rate CR2 exceeds 20.0°C / sec, the amount of crystallization of the Mg-(Sn, Bi, In) phase decreases, and the specific enrichment region may become smaller.

[0098] If the average cooling rate CR2 is 5.0 to 20.0°C / sec, the area ratio of the eutectic phase 11B in the coating layer 11 will be 10 to 60%, and the specific enrichment region will be 0.5 to 10.0%, provided that other cooling conditions are met.

[0099] The lower limit of the average cooling rate CR2 is preferably 6.0° C. / sec, more preferably 7.0° C. / sec, and the upper limit of the average cooling rate CR2 is preferably 18.0° C. / sec, more preferably 16.0° C. / sec.

[0100] The average cooling rate CR2 can be determined by the following method. Using a thermometer, the time required for the temperature of the base steel wire 10 to reach 340°C to 300°C is measured. Based on the temperature range and the measured time, the average cooling rate CR2 (°C / sec) is determined.

[0101] [Third cooling] In the temperature range of 300° C. to 200° C., the α phase 11A, the eutectic phase 11B, and the specific enriched region coarsen or decompose and shrink. Therefore, the average cooling rate CR3 in the temperature range of 300 to 200° C. is set to 5.0 to 1500.0° C. / sec.

[0102] If the average cooling rate CR3 is less than 5.0°C / sec, the area ratio of the α phase 11A, the eutectic phase 11B, or the specific enrichment region 13 changes due to element diffusion, etc. In this case, the corrosion resistance or workability of the plated steel wire may be reduced. Therefore, the average cooling rate CR3 is set to 5.0°C / sec or more.

[0103] The preferred lower limit of the average cooling rate CR3 is 10.0°C / sec, more preferably 15.0°C / sec, even more preferably 20.0°C / sec, even more preferably 25.0°C / sec, even more preferably 30.0°C / sec, even more preferably 35.0°C / sec, and even more preferably 40.0°C / sec.

[0104] There is no particular upper limit to the average cooling rate CR3, but taking into consideration the facility capacity, the upper limit to the average cooling rate CR3 is, for example, 1500.0°C / sec.

[0105] The average cooling rate CR3 can be determined by the following method. Using a thermometer, the time required for the temperature of the base steel wire 10 to reach 300°C to 200°C is measured. Based on the temperature range and the measured time, the average cooling rate CR3 (°C / sec) is determined.

[0106] The plated steel wire according to this embodiment is manufactured by the above manufacturing steps. [Example]

[0107] The effects of the plated steel wire of this embodiment will be described more specifically with reference to examples. The conditions in the following examples are examples adopted to confirm the feasibility and effects of the plated steel wire of this embodiment. Therefore, the plated steel wire of this embodiment is not limited to these examples.

[0108] [Manufacturing of plated steel wire] Plated steel wires were produced by the following method. First, a steel wire having the chemical composition of mild steel wire specified in JIS G3505 (2017) was prepared. Specifically, a wire rod with a wire diameter of 5.5 mm was prepared. The wire rod was subjected to wire drawing and then annealed to produce a steel wire with a wire diameter of 2.0 mm. The steel wire was prepared through the above process.

[0109] The first plating step was carried out on the prepared steel wire. First, the steel wire was pickled and fluxed by a known method. After the flux treatment, the steel wire was hot-dip galvanized by a known method to form a zinc-plated layer on the surface of the steel wire.

[0110] The steel wires on which the zinc-plated layer was formed were subjected to a second plating process. A plating bath for each test number was prepared so that the plating layer of the manufactured plated steel wires would have the chemical composition shown in Tables 1-1 and 1-2. A known flux treatment was performed under the same conditions on the steel wires on which the zinc-plated layer was formed for each test number. Thereafter, the steel wires were immersed in the prepared plating bath to perform a hot-dip plating treatment. At this time, the bath temperature of the plating bath was 440 to 470°C, and the immersion time was 5 to 30 seconds.

[0111] [Table 1-1]

[0112] [Table 1-2]

[0113] The "-" portion in Tables 1-1 and 1-2 means that the content of the corresponding element is 0% in the number of digits specified in the embodiment. In other words, when the corresponding element content is rounded to the specified number of digits in the above-mentioned embodiment, it means that it is 0%. For example, the Bi content in this embodiment is specified as a numerical value to two decimal places. Therefore, in test number 1 in Table 1, when the measured Bi content is rounded to two decimal places, it means that it was 0%. Note that rounding means that if the digit (fraction) to the last digit of the specified digit is less than 5, it is rounded down, and if it is 5 or more, it is rounded up. The remainder other than the elements listed in Table 1 was Zn and impurities.

[0114] The plated steel wire was drawn out of the plating bath and cooled. The average cooling rates for the first, second, and third cooling stages are shown in Table 2.

[0115] [Table 2]

[0116] According to the above manufacturing process, plated steel wires with each test number were manufactured.

[0117] [Evaluation test] The plated steel wires with each test number were subjected to the following evaluation tests. (Test 1) Measurement test of the area ratio of the α phase and eutectic phase of the coating layer (Test 2) Measurement test of the area ratio of specific enriched areas (Test 3) Corrosion resistance evaluation test (Test 4) Workability evaluation test Tests 1 to 4 will be explained below.

[0118] [(Test 1) Measurement test of the area ratio of the α phase and eutectic phase of the plating layer] The area ratios of the α phase and the eutectic phase in the plating layer of the plated steel wire of each test number were determined by the method described above in "Method for measuring the area ratio of the α phase 11A and the area ratio of the eutectic phase 11B in the main body region 13." The obtained area ratios (%) of the α phase and the eutectic phase are shown in Table 2.

[0119] [(Test 2) Measurement test of the area ratio of specific enriched regions] The area ratio of the specific enriched region in the coating layer of the plated steel wire of each test number was determined by the method described in the above-mentioned "Method for measuring the area ratio of the specific enriched region." The obtained area ratios (%) of the specific enriched region are shown in Table 2.

[0120] [(Test 3) Corrosion resistance evaluation test] The corrosion resistance evaluation test of the plated steel wires of each test number was carried out in the following manner. Each plated steel wire with each test number was cut perpendicular to its longitudinal direction to obtain 200 mm long test pieces. The test pieces were subjected to a neutral salt spray cycle test in accordance with JIS H 8052:1999. The neutral salt spray cycle test was conducted under the conditions specified in JASO M609. Specifically, the following steps were carried out under the conditions specified in JASO M609. (Step 1: Salt spray process) The test specimen is placed in the test chamber. The temperature inside the test chamber is set to 35±1℃, and the spray solution is a 5% NaCl aqueous solution, and the spray solution is sprayed continuously inside the test chamber for 2 hours. (Step 2: Drying process) The spraying of the spray solution is stopped, and the test specimen is left in the test chamber, with the temperature set to 60±1°C and the relative humidity RH set to 20-30% or higher, and maintained for 4 hours. (Step 3: Wetting process) With the test specimens stored inside, the temperature in the test chamber is maintained at 50±1°C and the relative humidity at 95% or higher for 2 hours. Steps 1, 2, and 3 were carried out in this order, and steps 1 to 3 constitute one cycle, which was repeated 30 times. The ends of the test specimens (plated steel wires) were covered with resin or the like to prevent corrosion from occurring or progressing from the ends of the test specimens.

[0121] After 30 cycles, the corrosion weight loss of each test piece was measured. 2 If the corrosion loss is less than 50g / m, the plated steel wire is judged to have high corrosion resistance (shown as "E" (Excellent) in the "Corrosion Resistance" column in Table 2). 2 In the above cases, the corrosion resistance of the plated steel wire was judged to be low (indicated as "B" (Bad) in the "Corrosion Resistance" column in Table 2).

[0122] [(Test 4) Workability evaluation test] The plated steel wire of each test number was cut perpendicular to the longitudinal direction to obtain a 400 mm long test piece, the diameter of which was the same as that of the plated steel wire. The test piece was wound five times around a core material with a diameter of 6.0 mm. The winding direction was adjusted to be as perpendicular as possible to the longitudinal direction of the core material. The test piece was wound spirally around the core material so that the test pieces did not overlap and the gap between adjacent test piece portions was as small as possible. After winding, the surface of the test piece (i.e., the surface of the coating layer) was visually inspected for cracks. If cracks of 100 μm or more in width in the longitudinal direction of the steel wire were found on the surface of the coating layer, it was determined that cracks had occurred in the coating layer during processing (denoted by "B" (Bad) in the "Processability" column in Table 2). On the other hand, if no such cracks were found on the surface of the coating layer, it was determined that cracks in the coating layer had been suppressed during processing (denoted by "E" (Excellent) in the "Processability" column in Table 2).

[0123] [Test Results] The test results are shown in Table 2. Referring to Tables 1-1, 1-2, and 2, the plated steel wires with test numbers 1 to 45 had appropriate chemical compositions and were also manufactured by appropriate methods. Therefore, the plated steel wires with these test numbers satisfied Features 1 to 4. As a result, they had excellent corrosion resistance and were able to sufficiently suppress the occurrence of cracks in the plating layer during processing.

[0124] On the other hand, in Test No. 46, the Al content in the coating layer was too low, and therefore the corrosion resistance of the coated steel wire was low.

[0125] In test number 47, the Al content in the coating layer was too high. Therefore, the area ratio of the α phase in the coating layer was too high. As a result, the corrosion resistance of the plated steel wire was low.

[0126] In test number 48, the Mg content in the coating layer was too low. Therefore, the area ratio of the eutectic phase in the coating layer was too low. As a result, the corrosion resistance of the plated steel wire was low.

[0127] In Test No. 49, the Mg content in the coating layer was too low. Therefore, the area ratio of the eutectic phase in the coating layer was too high. As a result, the occurrence of cracks in the coating layer during processing of the plated steel wire could not be sufficiently suppressed.

[0128] In test number 50, the total content of Sn, Bi, and In in the coating layer was too low. Therefore, the area ratio of the specific enriched region was too low. As a result, cracks in the coating layer could not be sufficiently suppressed during processing of the coated steel wire.

[0129] In test numbers 51 to 54, the total content of Sn, Bi, and In in the coating layer was too high. Therefore, the area ratio of the specific enriched region was too high. As a result, the corrosion resistance of the coated steel wire was low.

[0130] In test numbers 55 and 56, F1 was below the lower limit of formula (1), and therefore the corrosion resistance of the plated steel wire was low.

[0131] In test numbers 57 and 58, F1 exceeded the upper limit of formula (1), and therefore, the occurrence of cracks in the coating layer could not be sufficiently suppressed during processing of the coated steel wire.

[0132] In Test No. 59, the average cooling rate CR1 was too slow. As a result, the area ratio of the α phase in the coating layer was too high. As a result, the corrosion resistance of the coated steel wire was low.

[0133] In test number 60, the average cooling rate CR1 was too fast. As a result, the area ratio of the α phase in the coating layer was too low and the area ratio of the eutectic phase was too high. As a result, cracks in the coating layer could not be sufficiently suppressed during processing of the coated steel wire.

[0134] In Test No. 61, the average cooling rate CR2 was too slow. Therefore, the area ratio of the eutectic phase in the coating layer was too high. As a result, cracks in the coating layer could not be sufficiently suppressed during processing of the coated steel wire.

[0135] In Test No. 62, the average cooling rate CR2 was too fast. Therefore, the area ratio of the specific enriched region was low. As a result, cracks in the coating layer could not be sufficiently suppressed during processing of the coated steel wire.

[0136] In Test No. 63, the average cooling rate CR3 was too slow, which resulted in a low area ratio of the specific enriched region, resulting in a decrease in the corrosion resistance of the plated steel wire.

[0137] The embodiments of the present disclosure have been described above. However, the above-described embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and can be implemented by appropriately modifying the above-described embodiments within the scope of the present disclosure. [Explanation of symbols]

[0138] 1. Plated steel wire 10 Base steel wire 11 Plating layer 11A α phase 11B eutectic phase 12 alloy layers 13 Ontology Domain

Claims

1. A plated steel wire, A base steel wire; a plating layer formed on a surface of the base steel wire, The plating layer is In mass%, Al: 4.5 to less than 15.0% Mg: 0.3 to 4.0%, and One or more elements selected from the group consisting of Sn, Bi, and In: 0.01 to 0.50% in total; and the balance being Zn and impurities, and satisfying formula (1), In a cross section perpendicular to the longitudinal direction of the plated steel wire, in a main body region of the plating layer excluding the alloy layer, the area ratio of the α phase containing Al and Zn is 20 to 70%, the area ratio of the eutectic phase containing the Zn phase and the Zn-Mg phase is 10 to 60%, The area ratio of the specific enriched region in which the content of any one of Sn, Bi, and In is 1.0% or more is 0.5 to 10.0%; Plated steel wire. 4.0≦Mg / (Sn+Bi+In)≦20.0 (1) Here, the content of each element in formula (1) is substituted with the content of the corresponding element in mass %.

2. A plated steel wire, A base steel wire; a plating layer formed on a surface of the base steel wire, The plating layer is In mass%, Al: 4.5 to less than 15.0% Mg: 0.3 to 4.0%, and One or more elements selected from the group consisting of Sn, Bi, and In: 0.01 to 0.50% in total; and Si: 0.50% or less, Fe: 2.00% or less, Pb: 0.50% or less, Sr: 0.50% or less, V: 0.50% or less, Cr: 0.50% or less, Mn: 0.50% or less, Ti: 0.50% or less, Be: 0.50% or less, Na: 0.50% or less, K: 0.50% or less, Ca: 0.50% or less, Cu: 0.50% or less, La: 0.50% or less, Ce: 0.50% or less, Hf: 0.50% or less, Mo: 0.50% or less, W: 0.50% or less, Nb: 0.50% or less, Ta: 0.50% or less, Co: 0.50% or less, Ni: 0.50% or less, and B: 0.50% or less, Contains one or more elements selected from the group consisting of the balance being Zn and impurities, satisfying formula (1); In a cross section perpendicular to the longitudinal direction of the plated steel wire, in a main body region of the plating layer excluding the alloy layer, the area ratio of the α phase containing Al and Zn is 20 to 70%, the area ratio of the eutectic phase containing the Zn phase and the Zn-Mg phase is 10 to 60%; The area ratio of the specific enriched region in which the content of any one of Sn, Bi, and In is 1.0% or more is 0.5 to 10.0%; Plated steel wire. 4.0≦Mg / (Sn+Bi+In)≦20.0 (1) Here, the content of each element in formula (1) is substituted with the content of the corresponding element in mass %.

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