Cu-zn coated steel wire, stranded wire, method for manufacturing cu-zn coated steel wire, and method for manufacturing stranded wire

Abstract

To provide a plated steel wire and a stranded wire which have excellent corrosion fatigue properties and are easily manufactured, and to provide a method for manufacturing the plated steel wire and a method for manufacturing the stranded wire.SOLUTION: A Cu-Zn plated steel wire comprising a steel wire and a plating layer covering the steel wire and consisting of Cu, Zn and impurities, wherein the plating layer comprises, from the steel wire side, a coating layer A consisting of Cu and impurities and covering at least a part of the outer peripheral surface of the steel wire, a coating layer B consisting of Cu, Zn and impurities, and a coating layer C consisting of Zn and impurities and having a thickness of 0.5 μm or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a Cu-Zn plated steel wire, a stranded wire, a method for manufacturing a Cu-Zn plated steel wire, and a method for manufacturing a stranded wire. [Background technology]

[0002] Rubber products such as tires use reinforcing materials such as steel wire to reinforce the rubber. The reinforcing material exerts its reinforcing effect by adhering to the rubber. For this reason, the surface of reinforcing materials such as steel wire is usually plated with brass (a binary alloy plating made of copper and zinc) which has adhesive properties with rubber.

[0003] Patent Document 1 discloses a steel cord for use in pneumatic tires with improved corrosion fatigue life (corrosion fatigue resistance), which has two inner and outer metal plating layers on the surface of the steel cord, the inner layer of which is a nickel plating layer with a coating amount of 0.02 wt % or more and less than 0.5 wt % relative to the weight of the steel cord, and the outer layer of which is a brass plating layer.

[0004] Patent Document 2 discloses a metal wire for reinforcing rubber that is inexpensive and does not require heat treatment after plating, and that has a core wire, a base layer made of Cu and disposed around the core wire, and a coating layer containing Cu and Zn and disposed around the base layer, with the Cu concentration being discontinuous at the boundary between the base layer and the coating layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-30706 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-214337 Summary of the Invention [Problem to be solved by the invention]

[0006] Truck and bus tires are retreaded, meaning that the tread is replaced and reused. However, corrosion or breakage of the steel cords during retreading often makes retreading impossible, or the number of retreads is limited to one or so. Therefore, in order to increase the number of retreads, it is desirable to improve the corrosion fatigue properties of the steel cords.

[0007] An object of the present disclosure is to provide a Cu-Zn plated steel wire and stranded wire that are excellent in corrosion fatigue properties and easy to manufacture, as well as a method for manufacturing a Cu-Zn plated steel wire and a method for manufacturing a stranded wire. [Means for solving the problem]

[0008] The means for solving the above problems include the following aspects. <1> Steel wire, a plating layer covering the steel wire and comprising Cu, Zn and impurities; The plating layer is formed from the steel wire side as follows: a coating layer A comprising Cu and impurities and coating at least a part of the outer circumferential surface of the steel wire; A coating layer B consisting of Cu, Zn and impurities, and a coating layer C consisting of Zn and impurities and having a thickness of 0.5 μm or more; Cu-Zn plated steel wire. <2> The coating layer A has a coating rate of 30% or more with respect to the outer circumferential surface of the steel wire. <1> The Cu-Zn plated steel wire according to claim 1. <3> The average Cu content in the entire plating layer is 10 to 95 mass%. <1> or <2> The Cu-Zn plated steel wire according to claim 1. <4> The thickness of the coating layer B is 0.05 μm or more. <1> ~ <3> 10. The Cu-Zn plated steel wire according to claim 9, wherein the Cu-Zn plated steel wire is a Cu-Zn plated steel wire having a thickness of 1000 nm or less. <5> the average Cu content in the entire plating layer is 10 to 95 mass%; The thickness of the coating layer B is 0.05 μm or more. <1> ~ <4> 10. The Cu-Zn plated steel wire according to claim 9, wherein the Cu-Zn plated steel wire is a Cu-Zn plated steel wire having a thickness of 1000 nm or less. <6> <1> ~ <5> A stranded wire comprising the Cu-Zn plated steel wire according to any one of the above. <7> a Cu plating step of plating the steel wire with Cu to obtain a first Cu-plated steel wire; a wiredrawing process step of drawing the first Cu-plated steel wire into a second Cu-plated steel wire; a Zn plating step of plating the second Cu-plated steel wire with Zn to obtain a Cu-Zn-plated steel wire; A method for producing a Cu-Zn plated steel wire, comprising: <8> a Cu plating step of plating the steel wire with Cu to obtain a first Cu-plated steel wire; a wiredrawing process step of drawing the first Cu-plated steel wire into a second Cu-plated steel wire; a Zn plating step of plating the second Cu-plated steel wire with Zn to obtain a Cu-Zn-plated steel wire; a stranding process step of bundling a plurality of the Cu-Zn plated steel wires and performing a stranding process to form a stranded wire; A method for manufacturing a stranded wire, comprising: <9> a Cu plating step of plating the steel wire with Cu to obtain a first Cu-plated steel wire; a wiredrawing process step of drawing the first Cu-plated steel wire into a second Cu-plated steel wire; a stranding process step of bundling a plurality of the second Cu-plated steel wires and performing a stranding process to form a stranded wire; a Zn plating step of plating the stranded wire with Zn; A method for manufacturing a stranded wire, comprising: [Effects of the Invention]

[0009] According to the present disclosure, there are provided Cu-Zn plated steel wire and stranded wire that are excellent in corrosion fatigue properties and easy to manufacture, as well as a method for manufacturing a Cu-Zn plated steel wire and a method for manufacturing a stranded wire. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a flow diagram showing an example of a method for producing a Cu-Zn plated steel wire according to the present disclosure. [Figure 2]1 is a flow diagram showing an example (first embodiment) of a method for manufacturing a stranded wire according to the present disclosure. [Figure 3] FIG. 4 is a flow diagram showing an example (second embodiment) of a method for manufacturing a stranded wire according to the present disclosure. [Figure 4] FIG. 2 is a diagram showing an example of an area analysis by SEM-EDS (energy dispersive X-ray spectroscopy) of the plating layer of the Cu-Zn plated steel wire produced in the example. [Figure 5] FIG. 2 is a diagram showing an example of line analysis by SEM-EDS (energy dispersive X-ray spectroscopy) of the plating layer of the Cu-Zn plated steel wire produced in the example. [Figure 6] FIG. 1 is a flow chart showing an example of a conventional general manufacturing process for brass-plated steel wire and stranded wire. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the Cu-Zn plated steel wire and stranded wire, and methods for manufacturing the Cu-Zn plated steel wire and stranded wire according to the present disclosure will be described in detail. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. However, if the lower limit is marked with "over" or the upper limit is marked with "less than," those numerical values ​​are not included. In the numerical ranges described in stages in this specification, the upper limit of a certain numerical range may be replaced by the upper limit of another numerical range described in stages or a value shown in an example, and the lower limit of a certain numerical range may be replaced by the lower limit of another numerical range described in stages or a value shown in an example. "%" indicating the content of an element means "% by mass" unless otherwise specified. The term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved. In this specification, "steel wire" refers to a steel material before plating or a steel material (base steel) as a base material in a plated steel wire, and "plated steel wire" refers to a steel material including a steel wire and a plating layer applied to the steel wire. Note that a steel material obtained by wiredrawing a "steel wire" is also referred to as a "steel wire," and a steel material obtained by wiredrawing a "plated steel wire" is also referred to as a "plated steel wire." In this specification, a "Cu layer" refers to a layer made of Cu and impurities, and a "Zn layer" refers to a layer made of Zn and impurities. The same applies to Cu plating layers and Zn plating layers; a "Cu-Zn plating layer" or a "Cu-Zn layer" refers to a layer made of Cu, Zn, and impurities. A "Cu-Zn plated steel wire" refers to a plated steel wire including a steel wire and a Cu-Zn plating layer (Cu-Zn layer).

[0012] The inventors of the present disclosure conducted extensive research to find a method for manufacturing a plated steel wire that combines corrosion fatigue properties with ease of manufacturing. As a result, they found that wiredrawing can be easily performed by Cu-plating a steel wire and then drawing it, and that by further plating the wire with Zn after drawing, a Cu-Zn plated steel wire (sometimes simply referred to as "plated steel wire" in the present disclosure) with excellent corrosion fatigue properties can be manufactured.

[0013] Fig. 6 is a flow chart showing an example of a conventional manufacturing process for general brass-plated steel wire and stranded wire. Conventional brass plating generally involves electroplating a steel wire with Cu and then Zn, followed by a diffusion heat treatment. The steel wire is then drawn to produce a brass-plated steel wire, which is then stranded as needed.

[0014] On the one hand, FIG. 1 is a flowchart showing an example of a method for manufacturing a plated steel wire according to the present disclosure. In the method for manufacturing a plated steel wire in the present disclosure, diffusion heat treatment is omitted, and the outermost layer is made of a Zn plating layer to improve corrosion fatigue characteristics. In addition, since the work can be carried out in the same plating order as conventional brass plating, no change to the production line is required. Moreover, since diffusion heat treatment is omitted, reduction of heat treatment cost and reduction of exhaust gas can be achieved. Furthermore, since the Zn plating layer reduces drawability, the drawability can also be made compatible by changing the process of drawing after conventional Zn plating to a process of performing drawing before Zn plating after Cu plating.

[0015] Hereinafter, the Cu-Zn plated steel wire according to the present disclosure that can be manufactured by the method for manufacturing a Cu-Zn plated steel wire according to the present disclosure will be described first.

[0016] <Cu-Zn plated steel wire> The Cu-Zn plated steel wire according to the present disclosure includes a steel wire and a plating layer covering the steel wire and composed of Cu, Zn, and impurities. The plating layer includes, from the steel wire side, a coating layer A composed of Cu and impurities and covering at least a part of the outer peripheral surface of the steel wire, a coating layer B composed of Cu, Zn, and impurities, and a coating layer C composed of Zn and impurities and having a thickness of 0.5 μm or more.

[0017] (Steel wire) The steel wire (base metal) in the present disclosure is composed mainly of Fe and contains C and the like. The steel material components (chemical composition of the steel wire) of the steel wire are not particularly limited and can be selected according to the use, required strength, and the like. For example, when the Cu-Zn plated steel wire according to the present disclosure is used as a steel cord for a tire, in order to reduce weight and enhance the reinforcing effect, it is preferable that the steel wire, which is the base material of the plated steel wire, has a thin wire diameter and high strength. For this purpose, the C content of the steel wire is preferably 0.70% or more, and in order to achieve higher strength, the C content is preferably 0.92% or more. In order to further increase the strength, a steel material component containing 1.02% or more of C is preferable.

[0018] The steel wire may contain components such as Si and Mn in addition to Fe and C, and may contain, for example, about 0.2% of Cr as needed to increase strength. The diameter and metal structure of the steel wire depend on the application of the plated steel wire, but for example, the wire diameter is 0.1 mm to 0.4 mm, and the structure is preferably mainly composed of pearlite.

[0019] (plating layer) The plating layer in the present disclosure is composed of the following coating layer A, coating layer B, and coating layer C from the steel wire side.

[0020] -Coating layer A- Coating layer A is a Cu layer consisting of Cu and impurities, and coats at least a portion of the outer circumferential surface of the steel wire. Coating layer A is a layer derived from the Cu plating layer when a steel wire (first Cu-plated steel wire) on which the Cu plating layer has been formed is further drawn in the manufacturing method of a Cu-Zn-plated steel wire described later. The Cu plating layer before wiredrawing is provided to facilitate wiredrawing. The thickness of the Cu plating layer before wiredrawing becomes thinner as the area reduction rate during wiredrawing increases, and a portion of the Cu plating layer after wiredrawing, together with Zn from the Zn plating applied thereafter, constitutes coating layer B. Therefore, there is no particular problem if coating layer A (Cu layer) does not remain on a portion of the outer circumferential surface of the steel wire. The coverage rate of coating layer A with respect to the outer circumferential surface of the steel wire is not particularly limited, but it is preferably 30% or more from the viewpoint of adhesion between the steel wire and coating layer B. The thickness of the coating layer A is not particularly limited, but the average thickness of the coating layer A is, for example, 0.2 to 0.5 μm.

[0021] The impurities in coating layer A are elements that are unintentionally contained due to components other than Cu contained in the plating bath, etc. The impurities in coating layer B and coating layer C are elements that are unintentionally contained due to components other than Cu and Zn. That is, the remainder of the chemical composition of each coating layer in the present disclosure other than Cu and Zn is impurities. Here, the term "impurities" refers to substances that are mixed in from the Cu raw material, Zn raw material used as plating raw materials, or the manufacturing environment when each coating layer is formed by Cu plating, wire drawing, or Zn plating, and are acceptable within a range that does not adversely affect the Cu-Zn steel wire and stranded wire according to the present disclosure.

[0022] -Coating layer B- Coating layer B is a Cu-Zn layer consisting of Cu, Zn, and impurities. Coating layer B is formed between coating layer A and coating layer C, or between the surface of the steel wire and coating layer C. Coating layer B is a layer formed from a drawn Cu plating layer and a subsequently formed Zn plating layer in a manufacturing method of a Cu-Zn plated steel wire, which will be described later. The thickness of coating layer B is not particularly limited, but from the viewpoint of adhesion between the steel wire and coating layer C and adhesion between coating layer A and coating layer C, it is preferably 0.05 μm or more, and more preferably 0.10 μm or more.

[0023] The Cu-Zn plated steel wire according to the present disclosure contains Cu in coating layer A and coating layer B. From the viewpoint of adhesion between the steel wire and the plating layer, the average Cu content in the entire Cu-Zn plating layer (coating layer A, coating layer B, and coating layer C) is preferably 10 to 95%, and more preferably 20 to 80%. The average Cu content in the entire plating layer can be calculated by extracting the plating layer with an ammonia solution, quantifying the concentrations of Cu and Zn using ICP (Inductively Coupled Plasma), and using the obtained Cu concentration (mass%) and Zn concentration (mass%) according to the following formula. Average Cu content %=Cu concentration / (Cu concentration+Zn concentration)×100

[0024] -Coating layer C- The coating layer C is a Zn layer containing Zn and impurities. The coating layer C is a layer formed by applying Zn plating to a drawn Cu plating layer in a method for producing a plated steel wire, which will be described later. The Cu-Zn plated steel wire according to the present disclosure can exhibit excellent corrosion fatigue properties by having the coating layer C (Zn layer) as the outermost plating layer. From the viewpoint of corrosion fatigue properties, the thickness of the coating layer C is preferably 0.5 μm or more, and more preferably 0.7 μm or more. There is no particular upper limit to the thickness of the coating layer C, but from the viewpoints of productivity and production costs, it may be 5.0 μm or less, or 2.0 μm or less.

[0025] <Method of manufacturing plated steel wire> Next, a method for producing a Cu-Zn plated steel wire according to the present disclosure will be described. 1, the method for producing a Cu-Zn-plated steel wire according to the present disclosure includes a Cu-plating step of Cu-plating a steel wire to form a first Cu-plated steel wire, a wiredrawing step of drawing the first Cu-plated steel wire to form a second Cu-plated steel wire, and a Zn-plating step of Zn-plating the second Cu-plated steel wire to form a Cu-Zn-plated steel wire. Each step will be described below.

[0026] (Cu plating process) The steel wire is plated with Cu to form a first Cu-plated steel wire. For example, a hot rolled wire rod is subjected to primary wire drawing to form a primary steel wire having a wire diameter of about 1.0 mm to 2.0 mm, and then isothermally transformed by heat treatment to form a steel wire with a pearlite structure. Next, the steel wire is electroplated with Cu to form a Cu plating layer on the surface of the base steel (steel wire), to obtain a first Cu-plated steel wire. The thickness of the Cu plating layer is, for example, 1.0 to 5.0 μm. In the Cu plating step, it is preferable to perform Cu plating so that the average Cu content in the entire plating layer, including the Zn plating layer described below, is 10 to 95 mass %.

[0027] (Wire drawing process) After the Cu plating step, the first Cu-plated steel wire is drawn to form a second Cu-plated steel wire. For example, the first Cu-plated steel wire is wet drawn without heating to a wire diameter in the range of 0.1 mm to 0.4 mm.

[0028] (Zn plating process) After wire drawing, the second Cu-plated steel wire is plated with Zn to form a Cu-Zn-plated steel wire. For example, the surface of the second Cu-plated steel wire is electroplated with Zn to form a Zn-plated layer. The thickness of the Zn plating layer is preferably 0.5 μm or more from the viewpoint of corrosion resistance, and the upper limit of the thickness of the Zn plating layer may be 5.0 μm or less, or may be 2.0 μm or less from the viewpoint of productivity and production costs.

[0029] <Stranded wire> The stranded wire according to the present disclosure is a stranded wire including the Cu-Zn-plated steel wire according to the present disclosure. The Cu-Zn-plated steel wire according to the present disclosure has excellent corrosion fatigue properties and is easy to manufacture, and therefore a stranded wire using the Cu-Zn-plated steel wire according to the present disclosure also has excellent corrosion fatigue properties and is easy to manufacture. Note that the stranded wire according to the present disclosure may be configured to include the Cu-Zn-plated steel wire according to the present disclosure and other plated steel wires, but from the viewpoints of corrosion fatigue properties and ease of manufacture, it is preferable to configure the stranded wire solely using the Cu-Zn-plated steel wire according to the present disclosure.

[0030] <Stranded wire manufacturing method> 2 is a flow diagram showing an example (first embodiment) of a method for manufacturing a stranded wire according to the present disclosure. a Cu plating process for plating the steel wire with Cu to obtain a Cu-plated steel wire; a wiredrawing process step of drawing the first Cu-plated steel wire into a second Cu-plated steel wire; a Zn plating step of plating the second Cu-plated steel wire with Zn to obtain a Cu-Zn-plated steel wire; a stranding process step of bundling a plurality of the Cu-Zn plated steel wires and performing a stranding process to form a stranded wire; The method includes: The Cu plating step, wire drawing step, and Zn plating step are the same as those in the method for producing a Cu-Zn plated steel wire according to the present disclosure, and a plurality of the obtained Cu-Zn plated steel wires are bundled together and subjected to a wire twisting process to form a twisted wire.

[0031] The Zn plating of the surface layer formed on the first Cu-plated steel wire of the present disclosure can be performed not only on the single wire but also after the wire has been made into a stranded wire. Fig. 3 is a flow chart showing an example (second embodiment) of a method for manufacturing a stranded wire according to the present disclosure. The method for manufacturing a stranded wire according to the second embodiment of the present disclosure includes the following steps: a Cu plating step of plating the steel wire with Cu to obtain a first Cu-plated steel wire; a wiredrawing process step of drawing the first Cu-plated steel wire into a second Cu-plated steel wire; a stranding process step of bundling a plurality of the second Cu-plated steel wires and performing a stranding process to form a stranded wire; a Zn plating step of plating the stranded wire with Zn; The method includes:

[0032] The stranded wire manufactured by this method also has a Zn-plated layer formed on the exposed surface of the stranded wire, similar to that of the Cu-Zn-plated steel wire according to the present disclosure, and has excellent corrosion fatigue properties. Furthermore, since the first Cu-plated steel wire is drawn to form a second Cu-plated steel wire, and a plurality of the second Cu-plated steel wires are bundled together to form a stranded wire and then Zn-plated, Zn plating can be performed efficiently, thereby reducing manufacturing costs. [Example]

[0033] The Cu-Zn plated steel wire, the stranded wire, and the manufacturing method thereof according to the present disclosure will be specifically described below with reference to examples. Note that the examples shown below are merely examples, and the Cu-Zn plated steel wire, the manufacturing method thereof, and the stranded wire, and the manufacturing method thereof according to the present disclosure are not limited to the examples below.

[0034] <Production of plated steel wire> A hot-rolled wire rod having a diameter of 5.5 mm and having the steel composition shown in Table 1 (the balance being Fe and impurities) was prepared, pickled, lime-coated, and dry-drawn to a diameter of 1.39 mm.

[0035] [Table 1]

[0036] After dry drawing, the wire was heated at 1000°C for 36 seconds, and then subjected to heat treatment for isothermal transformation in the range of 580 to 620°C for 6 seconds.

[0037] Thereafter, the obtained steel wire was subjected to Cu electroplating, Zn electroplating, diffusion heat treatment, and wet wire drawing according to the procedures shown in Table 2 to obtain plated steel wire. The diffusion heat treatment was carried out at 450°C for 9 seconds. The wire was wet drawn at a drawing speed of 100 m / min to a wire diameter of 0.2 mm.

[0038] <Stranded wire manufacturing> The plated steel wire was twisted using a tubular twisting machine to twist the wire into a 7-strand configuration (1 wire + 6 wires) at a twisting pitch of 10 mm and a speed of 2 m / min.

[0039] <Observation of the plating / steel wire interface> The state of the interface between the plating and the steel wire (base steel) in the plated steel wire or stranded wire was observed as follows. Plated steel wire or stranded wire was cut perpendicular to the length using a CP (cross section polisher: registered trademark, manufactured by JEOL Ltd.) to obtain a C-section (a cross section perpendicular to the length), which was then observed using a FE-SEM (field emission scanning electron microscope) at 20,000x magnification. The plating layer and base steel (steel wire) were identified using backscattered electron images.

[0040] The plating coverage was determined by performing surface analysis using SEM-EDS (energy dispersive X-ray spectroscopy), drawing a line at the boundary between the base steel and coating layer A, and calculating the ratio of the length of contact with coating layer A to the length of the line drawn. Figure 4 shows an example of surface analysis. Using SEM-EDS, the amounts of Fe, Cu, and Zn were quantified by line analysis, and the thickness of each plating layer was measured. Figure 5 shows an example of line analysis.

[0041] <Calculation of average Cu content> The plated steel wire was immersed in a 70% ammonia solution to extract the plating layer, and the concentrations of Cu and Zn were quantified using ICP (Inductively Coupled Plasma). The obtained Cu concentration (mass%) and Zn concentration (mass%) were used to calculate the average Cu content (%) according to the following formula. Average Cu content %=Cu concentration / (Cu concentration+Zn concentration)×100

[0042] <Fatigue test> The fatigue test was carried out by rotary bending according to the following procedure. Both ends of a plated steel wire or stranded wire are fixed to a rotating shaft (chuck), and one of the chucks is rotated by a motor while the other chuck is allowed to rotate freely. The bending stress is adjusted by changing the curvature of the steel wire through the length of the steel wire, the distance between the chucks, and the chuck angle. The chucks are arranged in a straight line, and the angle of zero is defined as when the tips are facing each other. When changing the chuck angle, both chucks are moved the same angle. For example, if the distance between the chucks is narrowed or the chuck angle is increased, the curvature of the steel wire increases, and the bending stress also increases. The rotation speed is 3,000 rpm, and the wire is rotated in one direction to evaluate the fracture life. The fatigue test was carried out with the plated steel wire or stranded wire immersed in distilled water, and the corrosion fatigue life was evaluated.

[0043] Table 2 shows the steel type, manufacturing method, and plating composition.

[0044] [Table 2]

[0045] The thickness of each plating layer, the coverage of coating layer A, the average Cu content, wiredrawability, and fatigue life are shown in Table 3. Wiredrawability was marked "×" when wires broke during drawing, and marked "○" when wires could be drawn without breaking. The fatigue life was evaluated as O if the fatigue life was longer than that of ordinary brass-plated steel wire and stranded wire (C1 in Table 3), and X if the fatigue life was equal to or shorter than that of C1.

[0046] [Table 3]

[0047] A1 to A8 are plated steel wires and stranded wires of the present disclosure, and B1 to B8 are stranded wires of the present disclosure. C1 is a typical brass-plated steel wire and stranded wire. The entire plating layer is made of brass, an alloy of Cu and Zn, and has a different layer structure. Since it does not have the coating layer C, which is made of Zn and impurities, it has a short corrosion fatigue life. C2 is a brass-plated steel wire like C1, but has a lower average Cu content. Because of the low average Cu content, wiredrawability was poor and wire breakage occurred. C3 is a plated steel wire and stranded wire whose entire plating layer is composed of Cu. Cu plating has poor corrosion resistance and does not have a coating layer C made of Zn and impurities, so its corrosion fatigue life is short. C4 is a plated steel wire whose entire plating layer is made of Zn. Zn plating has high corrosion resistance but poor workability. The wire was drawn after Zn plating, which caused the wire to break. C5 and C6 have plating layers corresponding to coating layer A and coating layer B, but do not have coating layer C. The outermost layer is Zn plating, which has poor workability, and wire drawing was performed after Zn plating, which resulted in wire breakage.

Claims

1. Steel wire, a plating layer covering the steel wire and comprising Cu, Zn and impurities; The plating layer is formed from the steel wire side as follows: a coating layer A comprising Cu and impurities and coating at least a part of the outer circumferential surface of the steel wire; A coating layer B consisting of Cu, Zn and impurities, and a coating layer C consisting of Zn and impurities and having a thickness of 0.5 μm or more; A Cu-Zn plated steel wire comprising:

2. The coating layer A has a coverage of 30% or more with respect to the outer peripheral surface of the steel wire. The Cu-Zn plated steel wire according to claim 1.

3. The average Cu content in the entire plating layer is 10 to 95 mass%. The Cu-Zn plated steel wire according to claim 1 or 2.

4. The thickness of the coating layer B is 0.05 μm or more. The Cu-Zn plated steel wire according to claim 1 or 2.

5. the average Cu content in the entire plating layer is 10 to 95 mass%; The thickness of the coating layer B is 0.05 μm or more. The Cu-Zn plated steel wire according to claim 1 or 2.

6. A stranded wire comprising the Cu-Zn plated steel wire according to claim 1 or 2.

7. a Cu plating step of plating the steel wire with Cu to obtain a first Cu-plated steel wire; a wiredrawing process step of drawing the first Cu-plated steel wire into a second Cu-plated steel wire; a Zn plating step of plating the second Cu-plated steel wire with Zn to obtain a Cu-Zn-plated steel wire; A method for producing a Cu-Zn plated steel wire, comprising:

8. a Cu plating step of plating the steel wire with Cu to obtain a first Cu-plated steel wire; a wiredrawing process step of drawing the first Cu-plated steel wire into a second Cu-plated steel wire; a Zn plating step of plating the second Cu-plated steel wire with Zn to obtain a Cu-Zn-plated steel wire; a stranding process step of bundling a plurality of the Cu-Zn plated steel wires and performing a stranding process to form a stranded wire; A method for manufacturing a stranded wire, comprising:

9. a Cu plating step of plating the steel wire with Cu to obtain a first Cu-plated steel wire; a wiredrawing process step of drawing the first Cu-plated steel wire into a second Cu-plated steel wire; a stranding process step of bundling a plurality of the second Cu-plated steel wires and performing a stranding process to form a stranded wire; a Zn plating step of plating the stranded wire with Zn; A method for manufacturing a stranded wire, comprising:

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