JP2018119190A - Plated steel wire, steel cord and rubber-steel cord complex - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plated steel wire that has excellent adhesion to a rubber free from Co salt without deterioration of productivity or wire drawability, and also prevents degradation of adhesive strength with time, and provide a steel cord and a rubber-steel cord complex.SOLUTION: A plated steel wire has a Cu coat plating layer that is on a steel wire and coats the steel wire, and a second plating layer that is on the Cu coat plating layer and contains at least one element of Fe, Co, Cr, Nb, V or Mo. A coverage of the Cu coat plating layer by the second plating layer is 5% or more and 70% or less.SELECTED DRAWING: Figure 1A

Description

  The present invention relates to a plated steel wire, a steel cord, and a rubber-steel cord composite.

  Brass plating is often formed on the surface of a rubber reinforcing material (for example, a steel cord used as a reinforcing material for a tire). Such a steel cord is embedded in unsulfurized rubber and then vulcanized to bond the steel cord and rubber. Vulcanization is a final step in producing a rubber product, and is a step of applying pressure and heating at a temperature of 150 ° C. to 200 ° C. for 20 minutes to 40 minutes. By such vulcanization, the rubber is crosslinked and an adhesive layer is formed at the interface between the steel cord brass plating and the rubber. Such an adhesive layer mainly includes a sulfide formed by a reaction between Cu and Zn of brass plating and S (sulfur) contained in rubber.

  As described above, the steel cord and the rubber are bonded together by the sulfide generated during vulcanization. Therefore, an organic cobalt salt containing Co may be blended in the rubber as a catalyst for promoting the formation of sulfide. Co is useful for ensuring the initial bond strength between the steel cord and rubber. However, when a tire or the like is used in a high-temperature and high-humidity environment, the reaction between brass and Cu and Zn and S contained in the rubber proceeds. As a result, as the adhesive layer becomes thicker, the sulfide composition changes, and the adhesive strength between the steel cord and rubber decreases.

  Furthermore, the organic cobalt salt has a problem that the double bond of the rubber molecule is cut and the rubber is deteriorated. In addition, Co acting as a catalyst for the vulcanization reaction between Cu and S is a rare metal, and if Co is contained in the rubber, the cost becomes very high. Therefore, it is desired to reduce organic cobalt salts from rubber such as tires.

  In order to solve such a problem, a steel cord provided with brass plating containing Co or Ni has been proposed (for example, see Patent Documents 1 to 3 below).

  Further, as a method for achieving both adhesion and wire drawing workability without incorporating Co or Ni into brass plating, a technique for optimizing the plating composition and plating thickness has been proposed (for example, the following patent documents) 4 and Patent Document 5).

  Furthermore, as a method of suppressing the coarsening of particles due to the reaction of the Cu layer with sulfur in the rubber while bringing the steel wire and rubber into close contact, the unevenness of the ultrafine steel wire is covered in order from the surface of the ultrafine steel wire. Coating Cu plating (first layer) to smooth the surface, diffusion preventing layer (second layer) to prevent the diffusion of Cu from the first layer while ensuring wire drawing workability, aging degradation of adhesive strength A plated steel wire that has an adhesive Cu plating (third layer) with an average thickness of 10 to 50 nm is proposed (see, for example, Patent Document 6 below).

JP-A-1-98632 JP 2003-94108 A JP 2002-13085 A JP 2009-248102 A JP-A-5-278147 Japanese Patent No. 5333331

  However, when Ni or Co is contained in the brass plating as in the techniques disclosed in Patent Documents 1 to 3, there is a problem that the plating layer becomes hard and the wire drawing workability deteriorates. Further, the method of adding Co or Ni only to the surface layer of the brass plating has a complicated manufacturing process, and there is a concern about an increase in cost.

  In addition, as in the technique disclosed in Patent Document 4, it is difficult to control the composition of the brass plating by the method of performing diffusion heat treatment after performing multilayer plating of Cu and Zn with adjusted thickness. In addition, this technique increases the cost because the number of plating steps increases. On the other hand, as in the technique disclosed in the above-mentioned Patent Document 5, it is difficult to ensure the uniformity of the plating thickness by the method of performing the shot blasting after drawing the brass plating wire and reducing the plating thickness.

  Further, the diffusion preventing layer in Patent Document 6 has no defects such as cracks. In such a configuration, if the first layer reacts with the rubber, Cu is depleted, and the supply of Cu from the diffusion prevention layer is almost impossible unless it is used in a high temperature environment, although it depends on the diffusion prevention element. . Therefore, when Cu in the first layer is depleted, the adhesion with the rubber is subsequently lowered.

  On the other hand, when the surface of the steel wire is thinned, the surface of the steel wire before plating has irregularities, so iron is locally exposed on the surface of the steel wire after plating. The part (Fe exposed part) which existed exists. When such an exposed Fe portion becomes large, adhesion to the rubber becomes insufficient, and oxygen and moisture permeate over time, resulting in iron rust. When iron rust occurs, the adhesive strength is significantly reduced due to volume expansion.

  Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to reduce the productivity and wire drawing workability, and to adhere to rubber not containing Co salt. An object of the present invention is to provide a plated steel wire, a steel cord, and a rubber-steel cord composite that are excellent and that can suppress deterioration of adhesive strength with time.

As a result of intensive studies to solve the above problems, the inventors of the present application have found that the second layer capable of suppressing the diffusion of Cu in the upper layer of the Cu plating layer that is a supply source for supplying Cu for vulcanization. By providing a plating layer and controlling the coverage of the Cu plating layer by the second plating layer within a predetermined range, it was possible to obtain knowledge that the above-described problems could be solved.
The gist of the present invention completed based on such findings is as follows.

[1] A coated Cu plating layer that is located on the surface of the steel wire and covers the steel wire, and an element that is located on the coated Cu plating layer and is at least one of Fe, Co, Cr, Nb, V, or Mo A plated steel wire, wherein the covering ratio of the coated Cu plating layer by the second plating layer is 5% or more and 70% or less.
[2] The second plating layer is made of an alloy containing Fe, Co, Cr, Nb, V, or Mo, an alloy containing two or more elements of Fe, Co, Cr, Nb, V, or Mo, Fe [1], which is a plating layer containing an oxide of at least one of Co, Cr, Nb, V, or Mo, or a hydroxide of at least any of Fe, Co, Cr, Nb, V, or Mo. The plated steel wire described.
[3] The second plating layer is located on the coated Cu plated layer and has a layered plated layer having cracks or pinholes reaching the coated Cu plated layer, or an island located on the coated Cu plated layer The plated steel wire according to [1] or [2], which is a plate-like plating layer.
[4] The plated steel according to any one of [1] to [3], wherein the thickness of the coated Cu plating layer is 20 nm to 500 nm, and the thickness of the second plating layer is 3 nm to 300 nm. line.
[5] The plated steel wire according to any one of [1] to [4], wherein the steel wire is a steel wire having a tensile strength of 3200 MPa or more.
[6]
The steel cord which consists of a plated steel wire as described in any one of [1]-[5].
[7]
A steel cord comprising a stranded wire in which a plurality of the plated steel wires according to any one of [1] to [5] are bundled.
[8]
A rubber-steel cord composite in which the steel cord according to [6] or [7] is embedded in rubber.

  As described above, according to the present invention, productivity and wire drawing workability are not reduced, adhesiveness with a rubber not containing Co salt is excellent, and deterioration of adhesive strength with time is suppressed. Plated steel wires, steel cords and rubber-steel cord composites can be realized.

It is explanatory drawing which showed typically the cross-sectional structure at the time of cut | disconnecting the plated steel wire which concerns on embodiment of this invention to the radial direction of a steel wire. It is explanatory drawing which showed typically the partial cross section structure at the time of cut | disconnecting the plating steel wire which concerns on the same embodiment to the major axis direction of a steel wire. It is explanatory drawing which showed typically an example of the manufacturing process of the plated steel wire which concerns on the same embodiment.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

  The embodiment of the present invention described in detail below relates to a steel wire whose surface is plated for use as a reinforcing material for various rubber products such as tires such as steel cords. It relates to an excellent plated steel wire.

(About the contents examined by the present inventors)
Prior to detailed description of the plated steel wire and rubber-steel cord composite according to the embodiment of the present invention, the contents of the study conducted by the present inventors will be described first.

A steel cord made of a plated steel wire having a surface plated with brass is embedded in the tire. When a tire is used, Cu contained in the brass plating diffuses to the rubber side with the passage of time due to the temperature caused by the heat generated by the tire, and the adhesive layer becomes thick. In addition, since Cu in the adhesive layer diffuses toward the rubber side and the composition of Cu sulfide of Cu sulfide approaches CuS, the adhesive strength decreases. The bond strength depends on the composition of Cu sulfide, and the closer to Cu ₂ S, the higher the bond strength, and the composition close to CuS is considered to decrease the bond strength.

The present inventors examined the influence of the thickness of the steel cord brass plating on the deterioration over time of the adhesive strength with rubber. First, when the brass plating is thin, the adhesive strength between the steel cord and the rubber is high, and the adhesive layer formed at the interface with the rubber is thin and the composition is Cu sulfide close to Cu ₂ S. I understood. On the other hand, when the brass plating was thick, the adhesive strength was low, the adhesive layer was thick, and the composition was close to CuS.

The mechanism by which the thickness and composition of the adhesive layer formed at the interface between the steel cord and rubber changes depending on the thickness of the brass plating is not necessarily clear, but is considered as follows. During vulcanization, Cu in the brass plating reacts with S in the rubber at the interface between the brass plating and the rubber to form Cu ₂ S. When the brass plating is thin, since the supply of Cu from the plating is small, the diffusion of Cu is suppressed, the adhesive layer does not grow, and the composition hardly changes. On the other hand, when the brass plating is thick, the Cu supply from the plating is large, so that the diffusion of Cu is promoted and the adhesive layer grows, and the composition becomes close to CuS due to the diffusion of Cu from the adhesive layer to the rubber. .

Regarding the thickness of the adhesive layer at the interface between the brass plating and the rubber, it is considered that the adhesive strength is saturated when the thickness exceeds a certain value. Therefore, it is considered that the reason why the adhesive strength is prevented from aging by making the brass plating thin is that the composition of the adhesive layer is maintained in a state close to Cu ₂ S. In addition, although Zn sulfide also exhibits adhesive strength, the adhesive strength is about 50 to 70% of Cu sulfide. Furthermore, in brass plating, the Cu concentration decreases and the Zn concentration increases, so that the corrosion resistance decreases, and the adhesive strength between the plating and the adhesive layer also decreases due to oxidative expansion.

Based on these results, the present inventors examined a method for suppressing the aging deterioration of the adhesive strength between an ultrafine plated steel wire such as a steel cord and rubber. First, in order to increase the adhesive strength between the ultrafine plated steel wire and the rubber, it is important that the composition of the adhesive layer is Cu ₂ S. Therefore, the higher the Cu concentration, the better the composition of the plating that comes into contact with the rubber. Also, brass plating is usually formed by performing diffusion heat treatment after performing Cu plating and Zn plating. However, since Zn does not contribute to the improvement of adhesive strength, it is not necessary to contain Zn, and it is preferable to perform wire drawing as it is after performing Cu plating.

  Next, the thinner the Cu plating that comes into contact with the rubber, the better. However, if the plating is simply made thinner, the portion where the iron is locally exposed (Fe exposed portion) caused by irregularities on the surface of the ultrafine steel wire becomes larger. , The adhesive strength decreases. Therefore, it is important to provide a layer having a thickness that can cover the irregularities and a smooth surface on the surface of the ultra fine steel wire. Further, when the plating is thick, the wire drawing workability is also required for the plating. Therefore, Cu for forming the adhesive layer is preferably soft from the viewpoint of following the wire drawing.

  Therefore, it is preferable to provide Cu plating on the surface of the steel wire. However, if the thickness of the Cu plating is thin, the exposed Fe portion becomes large and the adhesive strength is lowered. Therefore, the present inventors have studied an ultra-fine plated steel wire having a multilayer plating on the surface, and have completed the present invention described in detail below.

(About plated steel wire)
The plated steel wire according to the embodiment of the present invention completed based on the above examination results will be described in detail below with reference to FIGS. 1A and 1B.
FIG. 1A is an explanatory view schematically showing a cross-sectional structure when the plated steel wire according to the present embodiment is cut in the radial direction of the steel wire, and FIG. 1B shows the plated steel wire according to the present embodiment as a steel. It is explanatory drawing which showed typically the partial cross section structure at the time of cut | disconnecting in the major axis direction of a line.

<Outline of plated steel wire>
As schematically shown in FIGS. 1A and 1B, the plated steel wire 1 according to the embodiment of the present invention has at least two layers of multi-layer plating on the surface of a steel wire (for example, an ultrafine steel wire). It is the provided plated steel wire (for example, extra fine plated steel wire). Of the plated steel wire 1 according to the present embodiment, the first layer in contact with the steel wire 11 is a coated Cu plating having an average thickness of 20 to 500 nm, which has a thickness necessary for covering the unevenness of the steel wire 11. is there. In FIG. 1A and FIG. 1B, the unevenness | corrugation which may exist on the surface of the steel wire 11 is not illustrated for convenience of drawing preparation. Hereinafter, the first layer formed by the coated Cu plating is referred to as a coated Cu plated layer 13.

  The upper layer of the coated Cu plating layer 13 is a layer that functions as a diffusion preventing layer for preventing diffusion of Cu during vulcanization and use. This layer is located on the upper layer of the coated Cu plating layer 13 and is a group consisting of Fe, Co, Cr, Nb, V and Mo (hereinafter, elements constituting this group are collectively referred to as “X”. And at least one element selected from. Hereinafter, this plating layer functioning as a diffusion preventing layer is referred to as a second plating layer 15. The element group X contained in the second plating layer 15 is composed of elements that hardly generate Cu and an intermetallic compound. The second plating layer 15 may contain various impurities in addition to at least one element selected from the element group X as described above.

  Here, examples of impurities that can be contained in the second plating layer 15 include B, C, O, F, Al, Si, P, S, Cl, Ti, Co, Ni, Zr, Sn, Ag, and W. , Pb and the like. When the content of the element present in the second plating layer 15 is 0.1% by mass or less with respect to the total plating mass, or the total content of the elements present in the second plating layer 15 is If it is 1.0 mass% or less, it will not affect performance.

  The state of the element group X in the second plating layer 15 is not particularly limited. The second plating layer 15 includes any metal of the element group X, an alloy containing two or more elements of the element group X, at least any oxide of the element group X, or at least any of the element group X. Such hydroxides may be contained. That is, the second plating layer 15 located on the outermost layer of the plated steel wire 1 according to the present embodiment may be any of a single metal layer, an alloy layer, an oxide layer, a hydroxide layer, and a multilayer made of these. Good. The average thickness of the second plating layer 15 is, for example, about 3 nm to 300 nm.

  The method for laminating the second plating layer 15 is not particularly limited, and a known plating method such as electroplating, hot dipping, or vapor deposition plating can be used. Moreover, in the plated steel wire 1 according to the present embodiment, defects such as pinholes and cracks may exist in the second plating layer 15. That is, the second plating layer 15 is preferably a layered plating layer having cracks or pinholes reaching the coated Cu plated layer 13 or an island-shaped plated layer located on the coated Cu plated layer 13. In the plated steel wire 1 according to this embodiment after the wire drawing, the coverage of the coated Cu plated layer 13 by the second plated layer 15 is 5% or more and 70% or less (in other words, the exposure rate of the coated Cu plated layer 13). 30% or more and 95% or less).

  When the steel cord is manufactured using the plated steel wire 1 according to the present embodiment, and the rubber-steel cord composite is manufactured using the steel cord, it is not covered with the second plating layer 15. A portion where the coated Cu plating layer 13 is exposed serves as an adhesion point with the rubber. The presence of defects almost uniformly on the surface of the second plating layer 15 suppresses the diffusion of Cu from the coated Cu plating layer 13 to the rubber, and is effective in suppressing the coarsening of CuS. Further, in the rubber-steel cord composite using the plated steel wire 1, the rubber flows from a defective portion such as a pinhole or a crack, and the adhesion between the plated steel wire 1 (steel cord) and the rubber is achieved by the anchor effect. improves.

  In addition, as mentioned above, the metal of the element group X contained in the 2nd plating layer 15 which concerns on this embodiment cannot make an intermetallic compound with Cu easily. Therefore, peeling due to the formation of an intermetallic compound with Cu when heat is generated by wire drawing hardly occurs. Plating peeling resulting from the formation of an intermetallic compound containing Cu causes exposure of the base iron and reduction of the amount of Cu, resulting in a decrease in adhesion. Therefore, in the plated steel wire 1 which concerns on this embodiment, since generation | occurrence | production of this plating peeling is suppressed, the adhesiveness of a plating layer improves. Further, by using a metal that is baser than Fe among the metals of element group X, it is possible to realize sacrificial anticorrosive ability in addition to the above effects.

  Moreover, in the general manufacturing process of a plated steel wire, the steel wire used as a base material is plated after annealing and further drawn. However, in the plated steel wire 1 according to the present embodiment, thermal diffusion is performed between the steel wire 11 and the coated Cu plated layer 13 and between the coated Cu plated layer 13 and the second plated layer 15. Therefore, plating may be performed before annealing the steel wire.

  Note that the oxide or hydroxide of the element group X may be present on the surface of the plated steel wire 1 according to the present embodiment, but the plating containing the oxide or hydroxide of the element group X If the wire drawing process is performed after the plating, the plating is easily peeled off. In addition, the oxide or hydroxide remains in the wire drawing device, thereby causing the ground iron of the plated steel wire to be exposed. Therefore, when plating containing a large amount of at least one of oxide and hydroxide, it is desirable to perform the plating treatment after drawing or after twisting.

<Details of plated steel wire>
Hereinafter, the plated steel wire 1 according to the present embodiment will be described in more detail.

  The diameter of the plated steel wire 1 according to the present embodiment is preferably 0.4 mm or less in order to obtain flexibility. This is because when the wire diameter is thicker than 0.4 mm and the flexibility is lowered, the ride comfort of the automobile is lowered when used as a rubber reinforcing material for a tire. Therefore, the upper limit of the wire diameter of the plated steel wire 1 is 0.4 mm. On the other hand, if the wire diameter is made too thin, the manufacturing process becomes longer and the productivity of the final product is also lowered, which requires time and cost for manufacturing. For this reason, it is preferable that the lower limit of the wire diameter of the plated steel wire 1 is 0.1 mm or more. The wire diameter of the plated steel wire 1 is more preferably 0.17 mm to 0.34 mm.

  In addition, the strength of the plated steel wire 1 according to the present embodiment (in other words, the strength of the steel wire 11 as a material) preferably has a tensile strength of 3200 MPa or more in order to obtain a reinforcing effect. Although the component of a steel wire is not specifically limited, In order to ensure intensity | strength, it is preferable that C content is 0.7 mass%-1.1 mass%. The metal structure of the steel wire 11 is preferably pearlite that has been drawn to ensure strength. In addition, in the case of a filament, the tensile strength of a steel wire can be measured by a tensile test based on JIS Z2241 (1998).

  As schematically shown in FIGS. 1A and 1B, a multilayer plating layer composed of two or more layers is provided on the surface of the steel wire 11 (for example, an ultrafine steel wire). The coating Cu plating layer 13 of the first layer located on the surface of the steel wire 11 improves the adhesion between the steel wire 11 and the ground iron, smoothes the unevenness of the surface of the steel wire 11, and in particular, the convex portion. In this case, local exposure of iron is suppressed, and formation of coarse Fe exposed portions is prevented. Further, a portion of the coated Cu plating layer 13 that is not covered by the second plating layer 15 corresponding to the second layer (that is, a defective portion such as a pinhole or a crack existing in the second plating layer 15) is in contact with the rubber. Cu sulfide is formed by vulcanization.

  The second plating layer 15, which is a second layer existing on the coated Cu plating layer 13 and functions as a diffusion preventing layer, suppresses the diffusion of Cu present in the coated Cu plating layer 13 that is the first layer. is there. The second plating layer 15 has defects uniformly on the entire surface thereof, so that Cu diffuses gradually from the defects and suppresses the formation of coarse grains of CuS. Also, by having irregularities due to pinholes, cracks, etc., when manufacturing a composite with rubber, the rubber flows into the defective part, an anchor effect is obtained after curing, and contributes to physical adhesion . In addition, a defect part arises in the 2nd plating layer 15 because the hard 2nd plating layer 15 cannot follow the wire drawing of the foundation | substrate (namely, the steel wire 11 or the comparatively soft coating Cu plating layer 13). This is because a crack is generated or a part of the second plating layer 15 is detached from the base. However, if Cu and the second plating layer 15 are alloyed when cracks occur, the exposure of the base iron and the reduction of the Cu amount occur, which adversely affects the adhesion. Therefore, in the plated steel wire 1 which concerns on this embodiment, the element group X contained in the 2nd plating layer 15 is comprised from the element which is hard to produce | generate Cu and an intermetallic compound.

  The coated Cu plating layer 13 of the first layer preferably has an average thickness of 20 nm or more in order to prevent the formation of Fe exposed portions and suppress the generation of coarse Fe exposed portions. On the other hand, if the coated Cu plating layer 13 is too thick, the plating adhesion is lowered, so that the upper limit of the average thickness is preferably 500 nm or less. The thickness (average thickness) of the coated Cu plating layer 13 is more preferably 50 nm to 300 nm.

  The plated steel wire 1 which concerns on this embodiment has the 2nd plating layer 15 which is a 2nd layer which functions as a diffusion prevention layer in the outer side of the coating Cu plating layer 13 of the 1st layer. The second plating layer 15 is a plating layer that suppresses diffusion of Cu. In particular, it is important to prevent the diffusion of Cu in order to suppress aged deterioration of the adhesive strength. Therefore, it is important that the second plating layer 15 which is a diffusion preventing layer is difficult to react with Cu in an environment where heat is generated by wire drawing and thereafter used as a product, and formation of an alloy layer is suppressed. . In addition, when providing a plating process before annealing a steel wire, the 2nd plating layer 15 is a metal of element group X (Fe, Co, Cr, Nb, V, Mo) which does not form an intermetallic compound with Cu. It is preferably composed of a single element or an alloy mainly composed of at least two elements of element group X.

  When each plating is performed before the wire drawing process, in order to suppress alloying with Cu, it is preferable that the second plating layer 15 as the diffusion preventing layer does not melt due to heat generated during the wire drawing process. Although the processing heat generated during wire drawing varies greatly depending on the wire drawing speed, die shape, lubrication performance, etc., it may reach about 500 ° C. Therefore, it is preferable that the 2nd plating layer 15 which is a diffusion prevention layer is metal plating whose melting | fusing point is 600 degreeC or more.

  The method for forming the second plating layer 15 that is the diffusion preventing layer is not particularly limited, and a known plating method such as hot dipping, electroplating, or vapor deposition plating can be used. Since the Cu plating on the steel wire is generally often performed by electroplating, the formation of the second plating layer 15 is also preferably performed by electroplating.

  The element group X constituting the second plating layer 15 hardly forms an alloy with Cu in a solid phase below the melting point, and Cu hardly diffuses. Therefore, the supply of Cu to the rubber through the second plating layer 15 from the coated Cu plating layer 13 as the first layer is prevented, and the supply (diffusion) of Cu to the rubber is prevented in the second plating layer 15. It becomes only from the part (namely, defective part) which the covering Cu plating layer 13 exposed. Therefore, in the plated steel wire 1 according to the present embodiment, the diffusion reaction of Cu is suppressed.

  In the second plating layer 15, Cu exposed after a crack or the like is generated by the wire drawing process and the rubber to be poured after that must contact each other. Therefore, the average thickness of the second plating layer 15 is preferably 300 nm or less. Moreover, in order to prevent unnecessary diffusion of Cu, the average thickness of the second plating layer 15 is preferably 3 nm or more. The average thickness of the second plating layer 15 is more preferably 10 nm to 100 nm.

  The second plating layer 15 which is a diffusion preventing layer exposes the Cu of the coating Cu plating layer 13 located in the lower layer by, for example, forming the second plating layer 15 in a mottled manner due to wire drawing. Must be. If the exposure rate of the coated Cu plating layer 13 is too high, an effect of suppressing the diffusion of Cu is hardly obtained, so it is necessary to set the exposure rate to 95% or less. In other words, the coverage of the coated Cu plated layer 13 by the second plated layer 15 needs to be 5% or more. On the other hand, when the exposure rate of the coated Cu plating layer 13 is too high, the adhesion point with the rubber is reduced, so that sufficient adhesion cannot be obtained at the initial stage after the rubber is cured. Therefore, the exposure rate of covering Cu plating layer 13 needs to be 30% or more. In other words, the coverage of the coated Cu plated layer 13 by the second plated layer 15 needs to be 70% or less. The exposure rate of the coated Cu plating layer 13 is preferably 50% or more and 70% or less. In other words, the coverage of the covering Cu plating layer 13 by the second plating layer 15 is preferably 30% or more and 50% or less.

  When the plated steel wire 1 according to the present embodiment is manufactured, when the plating is performed before the wire drawing process, the second plated layer 15 after the wire drawing has fine cracks in a direction perpendicular to the wire drawing direction. Is preferably generated uniformly throughout. There is no problem if the plating is separated from the steel wire by drawing, but as mentioned earlier, the Cu exposure rate should not exceed 95% after the final drawing. Moreover, the 2nd plating layer 15 will follow a wire drawing process too much, and Cu exposure rate must not be 30% or less after the final wire drawing. When the metal of the second plating layer 15 is hard, or when the second plating layer 15 is a layer mainly composed of an alloy, cracks are likely to occur. In order to satisfy such conditions, it is important to determine the composition and thickness of the second plating layer 15 before wire drawing, and the wire drawing conditions. In addition, since a defect portion such as a crack is generated in the second plating layer 15 which is a diffusion prevention layer, rubber flows into the defect portion, and the effect of improving the adhesion between the rubber and the steel wire by the anchor effect is also achieved. can get.

  In addition, in the plated steel wire 1 according to the present embodiment, a crack or the like reaches not only the second plated layer 15 but also the coated Cu plated layer 13 or a part of the coated Cu plated layer 13 by the wire drawing process. There may be a portion where the Fe of the steel wire 11 has been exposed due to, for example, peeling off.

  Here, the average thickness of the coating Cu plating layer 13 and the average thickness of the second plating layer 15 in the plated steel wire 1 according to this embodiment can be measured from the cross-sectional SEM image or TEM image of the plated steel wire 1. Is possible. More specifically, the plated steel wire 1 is embedded and polished, and the resulting cross section is measured at a magnification of about 30,000 to 100,000 times. The crack state is observed from the cross-sectional image, and if Cu and X are distinguished from the contrast, the thickness of each layer is determined together. In addition, when each layer is not known by contrast, or when the plating type is unknown, point analysis or mapping analysis is performed. At this time, the spot diameter is preferably 2 nm to 10 nm. In addition, let the thickness of each layer be the average value of the values measured at three or more locations.

Furthermore, the coverage of the element group X is determined from the EDS mapping data in the SEM image or TEM image of the steel wire surface, and the thickness of the element group X is obtained from the residual amount of the element group X, the density and the coverage in the metal species. It is possible. At this time, the spot diameter is preferably 1.5 μm to 0.5 μm. Moreover, the total of the mapping measurement area of EDS shall be 10000 micrometers ² or more, and the average value in this range is determined as the coverage of X.

  Note that the thickness and composition of each plating layer after being embedded in the rubber is determined by using a means such as Cryo-CP (Cross-section Polishing) that does not easily damage each plating layer (perpendicular to the drawing direction). Cross section in the direction), and elemental analysis with FE-SEM-EDX (field emission scanning electron microscope with energy dispersive X-ray analyzer) and FE-EPMA (field emission electron beam microanalyzer) It is possible to measure.

  The average thickness of the coated Cu plated layer 13 and the second plated layer 15 of the plated steel wire (for example, ultrafine plated steel wire) 1 according to the present embodiment is the same as that of the coated Cu plated layer 13 before wire drawing and It can be controlled by the average thickness of the two plating layers 15 and the degree of processing. In addition, in the case of electroplating, the average thickness of the coated Cu plating layer 13 and the second plating layer 15 before wire drawing can be adjusted by the current density of the electroplating and the wire speed, etc. In the case of a method, it can adjust with immersion time, wiping conditions, etc. Moreover, the average thickness of the coating Cu plating layer 13 before the wire drawing and the second plating layer 15 can be adjusted by the degree of vacuum, the heating conditions of the evaporation source, and the like in the case of the evaporation plating method.

  In the conventional brass plating, it is important to reduce the Cu concentration and suppress the supply of Cu in order to suppress the aging deterioration of the adhesive strength. On the other hand, in this invention, since Cu is supplied from the defect part of the 2nd plating layer 15, and spreading | diffusion of Cu is suppressed in parts other than a defect part, in the 1st layer which exists on the steel wire 11, It is possible to use a material plated with pure Cu. Furthermore, since the rubber flows into the defective portion of the second plating layer 15, it is possible to improve the adhesion with the rubber due to the anchor effect.

In the case of brass plating, since Zn suppresses the reaction between Cu and S, it is important to promote the formation of Cu sulfide during vulcanization, and an organic cobalt salt is blended in the rubber as a catalyst. However, in the present invention, there is no element that inhibits the reaction between Cu and S at the time of vulcanization at the place where Cu and rubber are in contact with each other. Is sufficient, and an adhesive layer having a composition close to that of Cu ₂ S is formed, and the adhesive strength can be ensured. Furthermore, since the rubber flows into the defective portion of the second plating layer 15, the adhesion strength can be ensured also by the anchor effect.

  As described above, when the plated steel wire according to the present embodiment is used to produce a composite with rubber using such a plated steel wire, the bond strength between the ultrafine plated steel wire such as a steel cord and rubber is as follows. It is good immediately after vulcanization, and even when time passes in a high temperature and high humidity environment such as when a tire is used, the deterioration of the adhesive strength is small, and excellent adhesion to rubber can be ensured. Furthermore, when producing a composite with rubber using the plated steel wire according to the present embodiment, it is not necessary to contain an organic Co salt in the rubber, and a diffusion treatment for alloying the plating becomes unnecessary. Thus, depletion due to diffusion of Cu and generation of coarse grains of Cu and sulfur are suppressed even for a long period of time. Therefore, in the plated steel wire according to the present embodiment, it is possible to extend the life of the plated steel wire, and the industrial contribution is extremely remarkable.

(About manufacturing method of plated steel wire)
Next, a method for manufacturing a plated steel wire (for example, ultra-fine plated steel wire) 1 according to the present embodiment will be described with reference to FIG. FIG. 2 is an explanatory view schematically showing an example of a manufacturing process of the plated steel wire according to the present embodiment.

  In the method for producing a plated steel wire according to the present embodiment, first, a steel wire having a wire diameter of about 3 mm to 5.5 mm is manufactured by hot rolling, and after descaling, the steel wire is obtained with a wire diameter of 1 mm. The wire is drawn to 3 mm (dry wire drawing) and wound into a coil. Next, while feeding a steel wire having a wire diameter of 1 to 3 mm wound in a coil shape, the steel wire is subjected to a patenting heat treatment as necessary, and then subjected to a plating treatment. As will be described later, the electroplating includes Cu plating for forming the covering Cu plating layer 13, second plating using an element included in the element group X for forming the second plating layer 15, and including. The steel wire that has been subjected to the plating treatment is again wound into a coil shape. Subsequently, wire drawing (wet wire drawing) is performed so that the wire diameter of the plated steel wire is about 0.1 mm to 0.4 mm while feeding the steel wire wound in a coil shape. The tensile strength of the plated steel wire is adjusted according to the degree of drawing.

  The plating process is mainly performed by electroplating. Heat treatment is performed on a steel wire having a wire diameter of 1 to 3 mm to remove the influence of wire drawing and the like, and then pretreatment such as pickling and degreasing is performed as shown in detail in FIG. Thereafter, the coated Cu plating is performed by electroplating to form the coated Cu plating layer 13, and then the second plating layer 15 which is a diffusion preventing layer is formed. The second plating layer 15 is composed of an element group X (a combination of one or more of Fe, Co, Cr, Nb, V, and Mo). The electric Cu plating is preferably performed by copper pyrophosphate plating in order to ensure safety and plating adhesion. The average thicknesses of the coated Cu plating layer 13 and the second plating layer 15 before the wire drawing can be adjusted by the current density and the wire speed of electroplating.

  Here, in order to ensure plating adhesion, it is preferable that the average thickness of the coated Cu plating layer 13 before wire drawing is 30 nm or more. In order to prevent plating peeling in wet wire drawing, the upper limit of the average thickness of the coated Cu plating layer 13 before wire drawing is preferably 1 μm.

  When the second plating layer 15 is an element group X (one or a combination of two or more of Fe, Co, Cr, Nb, V, and Mo), the deterioration of the adhesive strength between the plated steel wire and the rubber is prevented. Therefore, it is preferable that the average thickness of the second plating by the element group X before the wire drawing is 10 nm or more. On the other hand, the element group X is often hard, and it is preferable not to make it too thick in order to leave the second plating after the wire drawing. Therefore, the preferable upper limit of the average thickness of the second plating layer 15 before the wire drawing is 800 nm.

  When the second plating layer 15 made of the element group X has a laminated structure of a plurality of elements, when the element group X is plated in the step before wire drawing, the elements in the second plating layer 15 are subjected to subsequent heat treatment and processing. Each other can diffuse. Even if the conditions are changed depending on the usage, the element in the second plating layer 15 and Cu are not alloyed. Therefore, if the coverage of the second plating layer 15 after wire drawing does not change, rubber and There is no change in adhesion.

  The process for manufacturing the plated steel wire 1 as described above is merely an example. For example, as briefly mentioned above, as shown in FIG. 2, the second plating may be performed after the wet drawing instead of performing the second plating before the wet drawing. In particular, when the second plating layer of the element group X is easily peeled off by wire drawing, or when the element of the element group X is one that lowers the wire drawing efficiency, the step before twisting the steel wire or twisting is performed. It is preferable to perform the second plating at a later stage. In this case, in order to control the exposure rate of the coating Cu plating layer 13 within a predetermined range, the second plating must be performed by a method that does not cover the entire coating Cu plating layer 13. For example, the second plated layer 15 may be intentionally formed sparsely by masking a part of the coated Cu plated layer 13 or adopting a plating method having a variation in coverage in the initial stage of plating. is important.

  In the above, the manufacturing method of the plated steel wire 1 which concerns on this embodiment was demonstrated easily.

(About steel cord)
When the plated steel wire 1 according to the present embodiment as described above is applied to a tire or the like, the plated steel wire 1 according to the present embodiment is used singly or in accordance with the running performance of the tire. Twist them together to make a steel cord. By twisting a plurality of plated steel wires 1, the strength can be increased as compared with the case where a single plated steel wire 1 is used, and further toughness against bending and deformation can be provided.

(About rubber-steel cord composite)
The steel cord described above is sandwiched between rubber and carbon black, sulfur, zinc oxide and other raw material blended with various additives to form a reinforced belt structure. After that, the tire constituent members are bonded together to form a green tire, set in a vulcanizer, pressed and heated, and the rubber and the plated steel wire are bonded simultaneously with crosslinking for expressing the strength of the rubber. Thereby, it becomes possible to manufacture a rubber-steel cord composite as represented by a tire.

  The type of rubber composition in which the above-described plated steel wire 1 or the above-described steel cord is embedded is not particularly limited, and for example, generally known natural rubber or synthetic rubber is used alone, or two or more types are used. Can be used in combination. Synthetic rubbers include, for example, diene rubbers such as butadiene rubber, styrene-butadiene rubber, isoprene rubber, chloroprene rubber, acrylonitrile-butadiene rubber, butyl rubber, ethylene-propylene rubber, ethylene-vinyl acetate rubber, chlorosulphonated polyethylene, acrylic rubber. For example, olefin rubber such as urethane rubber, fluorine rubber, polysulfide rubber, and the like can be used.

  In the rubber composition, a compounding agent usually used in the rubber industry for improving and adjusting the performance of the rubber can be appropriately blended in a usual compounding amount. Specifically, examples of the compounding agent include fillers such as carbon black and silica, softeners such as aroma oil, guanidines such as diphenylguanidine, thiazoles such as mercaptobenzothiazole, and N, N′-dicyclohexane. Vulcanization accelerators such as sulfenamides such as xyl-2-benzothiazolylsulfenamide, thiurams such as tetramethylthiuram disulfide, vulcanization accelerators such as zinc oxide, poly (2,2,4- And anti-aging agents such as amines such as trimethyl-1,2-dihydroquinoline) and phenyl-α-naphthylamine. In the present embodiment, even when such a compounding agent normally used in the rubber industry coexists in the rubber, the corrosion prevention of the steel wire 11 and the corrosion of the second plating layer 15 are suppressed. Can be made compatible.

  Furthermore, in the above-described plated steel wire 1 or the above-described steel cord, another coating for further improving the corrosion resistance and wire drawing workability between the second plating layer 15 and the rubber, or the plated steel wire 1 or another film for improving the adhesion between the steel cord and the rubber may be present. Such a film is not particularly limited as long as it has a desired characteristic. For example, Cu film, Sn film, Cr film and alloys thereof, phosphate film, chromate film, silane coupling agent, An organic resin film etc. can be mentioned. Moreover, not only these films but also other known films can be applied. Moreover, it is also possible to apply the multilayer film which combined 2 or more types of films | membranes as needed.

  Examples of the resin component of the organic resin film include an epoxy resin, a urethane resin, a polyester resin, a phenol resin, a polyether sulfone resin, a melamine alkyd resin, an acrylic resin, a polyamide resin, and a polyimide resin. Resins, silicone resins, polyvinyl acetate resins, polyolefin resins, polystyrene resins, vinyl chloride resins, vinyl acetate resins, natural rubber resins, synthetic rubber resins, and the like can be used. At this time, in order to improve the adhesion to the second plating layer 15 and the like, silanol groups and the like may be introduced into the various resins. Moreover, for the formation of the resin layer, these resins may be used alone, a mixture of these resins may be used, or a laminated structure of these resins may be formed. Furthermore, pigments and the like may be included to improve the properties of these resins.

  Examples of the present invention will be described below. In addition, the content of this invention is not restrict | limited by the content as described in the Example shown below.

  Steel having the components shown in Table 1 below was hot-rolled to produce a steel wire having a wire diameter of 5.5 mm. The obtained steel wire was pickled to remove the scale, and then subjected to lime treatment, and was drawn to a wire diameter of 1.0 to 3.0 mm using a dry lubricant mainly composed of Na stearate. The obtained steel wire was heated to 950 ° C. and held for 75 seconds to convert the metal structure to austenite, and then subjected to a patenting treatment in which the steel wire was immersed in a 570 ° C. lead bath for 20 seconds.

  The steel wire subjected to the patenting treatment was successively subjected to electrolytic pickling with sulfuric acid and electrolytic degreasing with an alkaline solution to perform copper pyrophosphate plating. Then, any plating which combined 1 type, or 2 or more types of Fe, Co, Cr, Nb, V, and Mo contained in the element group X was performed, and it wound up after wire drawing. The wire drawing was performed so that the wire diameter was about 0.2 mm by wire drawing.

  A sample was collected from the obtained plated steel wire, and the wire diameter of the plated steel wire was measured with a laser-type non-contact wire diameter measuring device. Moreover, the average thickness of the coating Cu plating layer 13 and the 2nd plating layer 15 was measured from the cross-sectional SEM image. Moreover, the thing whose plating was too thin was computed by said method using TEM.

  Table 2 shows the wire diameter of the plated steel wire after wire drawing, the type of the second plating layer, the average thickness of the coated Cu plating layer and the second plating layer.

  Next, a tensile test of the plated steel wire was performed, and an evaluation was performed with an index where the tensile strength of the conventional brass-plated steel wire was 100.

  Further, four plated steel wires shown in Table 2 were twisted at a pitch of 5 mm to form steel cords. The steel cord is set in a mold, embedded in the rubber composition shown in Table 3, and vulcanized by a hot press heated at 160 ° C. for 30 minutes to produce a rubber-steel cord composite, and evaluation of adhesiveness A sample was prepared.

  Using these samples, initial adhesive strength (initial adhesive strength) and deterioration of adhesive strength over time (aging deterioration) were evaluated. The initial adhesive strength was evaluated by measuring the pulling force when the cord was pulled out of the rubber with a tensile test device and measuring the maximum pulling force. Further, the aging deterioration of the adhesive strength was evaluated as the maximum pulling force when the cord was pulled out from the rubber in the same manner as the initial bonding strength after the sample was immersed in pure water at 80 ° C. for 0 to 7 days. The initial bond strength and aging degradation were evaluated by using an index for the initial bond strength of a brass-plated steel wire manufactured for comparison as 100. Specifically, in this test, aged deterioration was an index of 40 or more on 3 days or an index of 20 or more on 7 days.

  Table 2 below also shows the presence or absence of the Co salt in the rubber composition (rubber type), the initial adhesion strength between the plated steel wire and the rubber, and the evaluation results of the aging degradation by 0-7 days immersion.

  As is apparent from Table 2 above, the plated steel wire according to the present invention ensures sufficient initial adhesive strength even under conditions where no cobalt naphthenate is blended, and is less deteriorated over time than brass plating. I understand that. On the other hand, it can be seen that the plated steel wire corresponding to the comparative example of the present invention is greatly deteriorated over time.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

  When a plated steel wire according to the present invention is used to produce a composite with rubber using such a plated steel wire, the rubber and the reinforcing material are firmly bonded, and the adhesive strength is reduced even after a lapse of time. Since it is remarkably small, the strength of the rubber product can be maintained high. Therefore, the plated steel wire according to the present invention can be used not only as a tire cord and a bead wire, but also as a reinforcing material for rubber hoses and belts, and has very high industrial applicability.

DESCRIPTION OF SYMBOLS 1 Plated steel wire 11 Steel wire 13 Coated Cu plating layer 15 2nd plating layer

Claims (8)

A coating Cu plating layer located on the surface of the steel wire and covering the steel wire;
A second plating layer located on the coated Cu plating layer and containing at least one element of Fe, Co, Cr, Nb, V or Mo;
With
The coating rate of the said covering Cu plating layer by the said 2nd plating layer is a plated steel wire which is 5% or more and 70% or less.   The second plating layer is made of any one of Fe, Co, Cr, Nb, V, or Mo, an alloy containing two or more elements of Fe, Co, Cr, Nb, V, or Mo, Fe, Co, The plating according to claim 1, which is a plating layer containing an oxide of at least one of Cr, Nb, V or Mo, or a hydroxide of at least one of Fe, Co, Cr, Nb, V or Mo. Steel wire.   The second plating layer is located on the coated Cu plating layer and has a layered plating layer having a crack or pinhole reaching the coated Cu plating layer, or an island-shaped plating located on the coated Cu plating layer The plated steel wire according to claim 1 or 2, which is a layer. The thickness of the coated Cu plating layer is 20 nm to 500 nm,
The thickness of the said 2nd plating layer is a plated steel wire of any one of Claims 1-3 which are 3 nm-300 nm.   The plated steel wire according to any one of claims 1 to 4, wherein the steel wire is a steel wire having a tensile strength of 3200 MPa or more.   A steel cord comprising the plated steel wire according to any one of claims 1 to 5.   A steel cord comprising a stranded wire in which a plurality of the plated steel wires according to any one of claims 1 to 5 are bundled. A rubber-steel cord composite in which the steel cord according to claim 6 or 7 is embedded in rubber.

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