Steel wire with a metal coating added with silver

Abstract

The present invention provides a steel wire, comprising a steel substrate and a metal coating covering said steel substrate for the adhesion with the rubber compound, wherein the metal coating comprises silver (Ag). The present invention also provides a bead bundle and a tire, comprising the steel wire. The present invention further provides a process for improving the fatigue performance of a steel wire, said process comprising adding silver (Ag) into the metal coating of the steel wire.

Description

STEEL WIRE WITH A METAL COATING ADDED WITH SILVERTechnical Field

[0001] The present invention relates to a steel wire for reinforcing a tire, particularly the bead portion of a tire.Background Art

[0002] Bead wire is a metal wire for making the bead bundle for reinforcing the bead of a tire. Normally a bead wire has a metal coating for the adhesion with the rubber compound of a tire after the vulcanization, such as the coating of brass, bronze or zinc. The bead wire has a cross section of round shape or polygonal shape, including a flat, rectangular or square shape. Sometimes the bead wire has a resin layer upon the metal coating. In some cases, the bead wire has a thin raw rubber compound layer upon the resin coating, or the bead wire has a thin raw rubber compound layer directly upon the metal coating.

[0003] WO2014 / 102031 discloses a bead wire having a resin layer, wherein the resin layer comprises a corrosion inhibiting reagent. The corrosion inhibiting reagent is for improving the corrosion resistance of the bead wire.

[0004] LIS5176957 discloses a bead wire having a bronze coating and a rubber compound coating upon the bronze coating, wherein the bronze coating has a specific weight ratio of Cu and Sn for improving the adhesion between the bead wire and the rubber compound coating after the vulcanization. “Adhesion” takes place between metal coating and vulcanized rubber compound which is already reacted via crosslinking into three-dimensional network structures.

[0005] Despite the prior art, there is still needed to further improve the performance of a steel wire (such as a bead wire), in particular providing a bead wire having a longer lifetime.Disclosure of Invention

[0006] The present inventors have surprisingly found that by adding silver (Ag) into the metal coating of a steel wire (such as a bead wire), the steel wire would have improved fatigue performance. As a result, the tire would have a longer life.

[0007] Therefore, in a first aspect, the present invention provides a steel wire for reinforcing rubber, comprising a steel substrate and a metal coating covering said steel substrate for the adhesion with the rubber compound, wherein the metal coating comprises silver (Ag).

[0008] In some embodiments, in the steel wire of the present invention, the metal coating comprises copper (Cu) and tin (Sn), wherein the amount of copper (Cu) is expressed as below: Cu / (Cu+Sn) is in the range of 97.0-99.7 wt%.

[0009] In some embodiments, in the steel wire of the present invention, the metal coating comprises copper (Cu) and tin (Sn), wherein the amount of copper (Cu) is expressed as below: Cu / (Cu+Sn) is in the range of 97.0-98.0 wt%.

[0010] In some embodiments, in the steel wire of the present invention, the metal coating comprises copper (Cu) and tin (Sn), wherein the amount of copper (Cu) is expressed as below: Cu / (Cu+Sn) is more than or equal to 80.0 wt% and less than 97.0 wt%.

[0011] In some embodiments, in the steel wire of the present invention, the metal coating comprises copper (Cu) and tin (Sn), wherein the amount of copper (Cu) is expressed as below: Cu / (Cu+Sn) is in the range of 80.0-94.0 wt%.

[0012] In some embodiments, in the steel wire of the present invention, the amount of silver (Ag) is expressed as below: Ag / (Ag+Cu+Sn) is in the range of 0.1 -5.0 wt%.

[0013] In some embodiments, in the steel wire of the present invention, the amount of silver (Ag) is expressed as below: Ag / (Ag+Cu+Sn) is in the range of 0.2-2.0 wt%.

[0014] In some embodiments, in the steel wire of the present invention, the metal coating comprises copper (Cu) and zinc (Zn), wherein the amount of copper (Cu) is expressed as below: Cu / (Cu+Zn) is in the range of 60-70 wt%.

[0015] In some embodiments, in the steel wire of the present invention, the amount of silver (Ag) is expressed as below: Ag / (Ag+Cu+Zn) is in the range of 0.1 -5.0 wt%.

[0016] In some embodiments, in the steel wire of the present invention, the amount of silver (Ag) is expressed as below: Ag / (Ag+Cu+Zn) is in the range of 0.2-2.0 wt%.

[0017] The metal coating comprises or consists of one, two or more metal components in addition to the silver. Preferably the ratio of the amount of the one, two or more metal components other than the silver to the total amount of metalcomponents of the metal coating is in the range of 95.0-99.9 wt%. More preferably, the ratio of the amount of the one, two or more metal components other than the silver to the total amount of metal components of the metal coating is in the range of 98.0- 99.8 wt%. In some embodiments, in the steel wire of the present invention, the ratio of the amount of silver (Ag) to the total amount of metal components of the metal coating is in the range of 0.1 -5.0 wt%. Preferably, the ratio of the amount of silver (Ag) to the total amount of metal components of the metal coating is in the range of 0.2-2.0 wt%.

[0018] In some embodiments, in the steel wire of the present invention, the metal coating comprises or consists of two or more metal components in addition to the silver. One preferable example is that the two or more metal components are in the form of metal alloy, such as brass which is the alloy of zinc and copper or bronze which is the alloy of zinc and tin. The two or more metal components are selected from the group consisting of copper, zinc, cobalt, nickel, tin, indium, titanium, manganese, iron, bismuth and molybdenum. Preferably the ratio of the amount of the two or more metal components other than the silver to the total amount of metal components of the metal coating is in the range of 95.0-99.9 wt%. More preferably, the ratio of the amount of the two or more metal components other than the silver to the total amount of metal components of the metal coating is in the range of 98.0-99.8 wt%.

[0019] Alternatively, the metal coating comprises or consists of one single metal component in addition to the silver. Preferably the ratio of the amount of the one metal component other than the silver to the total amount of metal components of the metal coating is in the range of 95.0-99.9 wt%. More preferably, the ratio of the amount of the one metal component other than the silver to the total amount of metal components of the metal coating is in the range of 98.0-99.8 wt%. One example of single metal component is zinc, and this means the metal coating comprises or consists of zinc and silver. Preferably, the amount of silver (Ag) is expressed as below: Ag / (Ag+Zn) is in the range of 0.1 -5.0 wt%. More preferably, the amount of silver (Ag) is expressed as below: Ag / (Ag+Zn) is in the range of 0.2-2.0 wt%.

[0020] The steel wire preferably has a diameter of no more than 3mm. As one preferable example, the steel wire has a diameter of 0.15mm-0.55mm, or the steel wire has a diameter of 0.8mm-2.5mm.

[0021] The steel wire of the present invention is used for reinforcing rubber articles, such as tires, conveyor belts or hoses. Especially, the steel wire is used as a bead wire for reinforcing the bead of a tire. In such a case, the steel wire further has a thermoplastic resin coating, such as a coumarone resin coating or a petroleum resin coating, covering the metal coating. Preferably, the bead wire has a thin raw rubber compound layer upon the thermoplastic resin coating. The steel wire for bead wire has a diameter of 0.8mm-1 ,2mm preferably. Preferably, the metal coating of the steel wire comprises or consists of copper (Cu), tin (Sn) and silver (Ag), or the metal coating comprises or consists of zinc (Zn) and silver (Ag).

[0022] The steel wire may be used as monofilament for reinforcing the rubber articles, or two or more steel wires may be twisted to form a steel cord for reinforcing the rubber articles, such as the belt layer, the carcass layer or the tread layer of the tire. The steel wire for monofilament or steel cord preferably has a diameter of 0.15mm-0.55mm preferably. Some preferable examples of the metal coating for the steel wire for monofilament or steel cord are: the metal coating comprising or consisting of copper (Cu), zinc (Zn) and silver (Ag), the metal coating comprising or consisting of zinc (Zn) and silver (Ag), the metal coating comprising or consisting of copper (Cu), zinc (Zn), cobalt (Co) and silver (Ag), the metal coating comprising or consisting of copper (Cu), zinc (Zn), iron (Fe) and silver (Ag), the metal coating comprising or consisting of zinc (Zn), cobalt (Co) and silver (Ag). The ratio of the amount of silver (Ag) to the total amount of metal components of the metal coating is in the range of 0.1 -5.0 wt%. Preferably, the ratio of the amount of silver (Ag) to the total amount of metal components of the metal coating is in the range of 0.2-2.0 wt%. Preferably, the steel wire for monofilament or steel cord has a thermoplastic resin coating covering the metal coating.

[0023] In a second aspect, the present invention provides a steel cord. A steel cord for rubber reinforcement, the steel cord comprises two or more steel wires, each of the steel wires has a diameter of 0.15mm-0.55mm, at least one of the steel wires oreach of the steel wires is the invention steel wire as described above. The steel cord may have any one of the existing construction, such as 1x2, 1x3, 1x4, 1x5, 1x6, 1x7, 1x8, 1 +3, 1 +4, 1 +5, 1 +6, 2+5, 2+5cc, 2+6, 2+7, 2+7cc, 2+8, 3+6, 3+8, 3+8cc, 3+9, 3+9cc, 4+9, 4+10, 1 +3+8, 1 +4+8cc, 1 +4+9, 1 +5+10, 1 +5+10cc, 1 +6+11 , 1 +6+12, 1 +6+12cc, 2+5+10, 2+6+12, 3+8+13, 3+8+13+1 , 3+9+15, 3+9+15+1 , 4+10+16, 4+10+16+1 , 2+2, 2+3, 2+4, 3+2, 3+3, 3+4, 4+3, 4+6; 3x2, 3x3, 3x4, 3x6, 3x7, 4x2, 4x4, 4x7, 7x7, 7x7+1 , 7x(3+9), 7x(3+9)+1 , 7x(1 +18), 7x(1 +18)+1 , 7x(3+9+15) or 7x(3+9+15)+1 . The steel cord may have a twist pitch of 4mm-40mm, or preferably 6mm-38mm.

[0024] In a third aspect, the present invention provides a bead bundle, comprising a bead ring, said bead ring comprising at least one steel wire in accordance with the embodiments of the present invention.

[0025] In a fourth aspect, the present invention provides a tire, comprising at least one belt layer, at least one carcass layer, at least one tread layer and a pair of bead bundles, said bead bundles comprises at least one steel wire in accordance with the embodiments of the present invention, and / or said belt layer, said carcass layer and / or said tread layer comprises at least one steel wire in accordance with the embodiments of the present invention and / or at least one steel cord in accordance with the embodiments of the present invention.

[0026] In a fifth aspect, the present invention provides a process for improving the fatigue performance of a steel wire, said process comprising adding silver (Ag) into the metal coating of the steel wire.

[0027] These and other aspects, features and advantages will become apparent to those of ordinary skill in the art from a reading of the following detailed description and the appended claims. For the avoidance of doubt, any feature of one aspect of the present invention may be utilized in any other aspect of the invention.BRIEF DESCRIPTION OF THE FIGURE

[0028] The foregoing will be apparent from the following more particular description of example embodiments of the invention, as illustrated in the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments of the present invention.

[0029] Figure 1 is a schematic drawing of a steel wire with a metal coating in accordance with the embodiments of the present invention.DETAILED DESCRIPTION

[0030] The contents of any referenced patent, patent application or publication are incorporated by reference in their entirety, especially with respect to the disclosure of definitions (to the extent not inconsistent with any definitions specifically provided in this disclosure) and general knowledge in the art.

[0031] The numerical ranges disclosed herein include all values from, and including, the lower and upper value. For ranges containing explicit values (e.g., 1 to 7), any subrange between any two explicit values is included (e.g., 1 to 2; 2 to 6; 5 to 7; 3 to 7; 5 to 6; etc.).

[0032] Unless stated to the contrary, implicit from the context, or customary in the art, all parts and percentages are based on weight and all test methods are current as of the filing date of this disclosure.

[0033] Unless otherwise explicitly indicated, all numbers in this description indicating amounts of materials, physical properties of materials and / or use are to be understood as modified by the word “about”. Numerical ranges expressed in the format “from x to y” are understood to include x and y. When for a specific feature multiple preferred ranges are described in the format “from x to y”, it is understood that all ranges combining the different endpoints are also contemplated.

[0034] In a first aspect, the present invention provides a steel wire, comprising a steel substrate and a metal coating covering said steel substrate for the adhesion with the rubber compound, wherein the metal coating comprises silver (Ag).

[0035] The steel substrate is usually made from a high carbon wire rod. The wire rod is firstly cleaned by mechanical descaling and / or by chemical pickling in a H2SO4 or HCI solution in order to remove the oxides present on the surface. The wire rod is then rinsed in water and is dried. The dried wire rod is then subjected to a first series of dry drawing operations in order to reduce the diameter until a first intermediate diameter.

[0036] At this first intermediate diameter, e.g. at about 3.0 to 3.5 mm, the dry drawn steel wire is subjected to a first intermediate heat treatment, called patenting.Patenting means first austenitizing until a temperature of about 1000°C followed by a transformation phase from austenite to pearlite at a temperature of about 600 - 650°C. The steel wire is then ready for further mechanical deformation.

[0037] Thereafter the steel wire is further dry drawn from the first intermediate diameter until a final diameter in a second number of diameter reduction steps. The final diameter typically ranges from 0.80 mm to 2.5 mm.

[0038] If the total reduction in the first and second dry drawing step is not too big, a direct drawing operation can be done from wire rod till final diameter. A steel substrate is made thereof.

[0039] And then the steel substrate is provided with a coating, such as brass coating by electroplating, bronze coating by electroless plating (i.e. , chemical plating) or zinc coating by electroplating. In case the coating is brass coating, silver (Ag) is applied by electroplating in a silver plating bath after the application of copper coating and prior to the application of zinc coating, wherein the silver plating bath can be the bath of a dilute nitric acid solution of silver nitrate AgNO3at a concentration of 0.01 - 0.5g / L or the bath of a dilute sulfuric acid solution of silver sulphate Ag2SO4at a concentration of 0.01 -0.5g / L. In case the coating is bronze coating, silver (Ag) is applied by electroless plating together with the electroless plating of copper and tin (i.e. copper, tin and silver are in one electroless plating bath including silver solution such as the dilute nitric acid solution of silver nitrate AgNO3at a concentration of 0.01 - 0.5g / L or the dilute sulfuric acid solution of silver sulphate Ag2SO4at a concentration of 0.01 -0.5g / L). In case the coating is zinc coating, silver (Ag) is applied by electroplating in a silver plating bath prior to the application of zinc coating, wherein the silver plating bath can be the bath of a dilute nitric acid solution of silver nitrate AgNO3at a concentration of 0.01 -0.5g / L or the bath of a dilute sulfuric acid solution of silver sulphate Ag2SO4at a concentration of 0.01 -0.5g / L. In this way, the steel wire having a metal coating comprising silver (Ag) is obtained. In the metal coating, silver (Ag) is distributed in the metal coating, in which silver (Ag) may be alloyed with other metals, or silver (Ag) may exist separately.

[0040] The steel wire with a diameter of 0.80 mm to 2.5 mm can be further coated with a thermoplastic resin coating upon the metal coating, such as a coumarone resincoating or a petroleum resin coating. The thermoplastic resin coating can be applied by extrusion. The steel wire with a diameter of 0.80 mm to 2.5 mm may be used for reinforcing the bead portion of the tire.

[0041] The cross-section of the steel wire is preferably round. Alternatively, the cross-section of the steel wire is a shaped cross section, such as a flat, rectangular or square shape, which is shaped by being subjected to rollers or dies for shaping the cross section.

[0042] The steel wire with a diameter of 0.80 mm to 2.5 mm may be further subjected to a series of cross-section reductions by means of wet drawing machines, up to a diameter of 0.15mm-0.55mm. Wet drawing process includes a series of drawing passes by various drawing dies. The steel wire with a diameter of 0.15mm- 0.55mm may be used solely or be twisted with one or more steel wires to make a steel cord for reinforcing the rubber article such as tire. The steel cord can be made by any of the existing methods, i.e. , cabling or bunching, to twist the two or more steel wires.

[0043] The tensile strength of the steel wire can be any of existing tensile strength levels, such as normal standard tensile NT, high tensile HT, super tensile ST, ultra- tensile UT or mega tensile MT.

[0044] The steel composition of the steel wire can be any of existing steel composition in the field. The steel wire can be made of the steel with at least 50wt% or even at least 70wt% recycled steel.

[0045] Figure 1 shows a schematic drawing of a steel wire with a metal coating in accordance with the embodiments of the present invention.

[0046] In some embodiments, in the steel wire, the metal coating comprises copper (Cu) and tin (Sn), wherein the amount of copper (Cu) is expressed as below: Cu / (Cu+Sn) is in the range of 97.0-99.7 wt%, and more preferably 97.0-98.0 wt%. In some embodiments, Cu / (Cu+Sn) is 97.0 wt% or more, 97.1 wt% or more, 97.2 wt% or more, 97.3 wt% or more, 97.4 wt% or more, 97.5 wt% or more, 97.6 wt% or more, or 97.7 wt% or more. In some embodiments, the metal coating comprises copper (Cu) and tin (Sn), wherein the amount of copper (Cu) is expressed as below: Cu / (Cu+Sn) is 99.7 wt% or less, 99.5 wt% or less, 99.2 wt% or less, 99.0 wt% or less, 98.8 wt% orless, 98.6 wt% or less, 98.4 wt% or less, 98.2 wt% or less, 98.0 wt% or less, or 97.8 wt% or less.

[0047] In some embodiments, in the steel wire, the metal coating comprises copper (Cu) and tin (Sn), wherein the amount of tin (Sn) is expressed as below: Sn / (Cu+Sn) is in the range of 0.3-3.0 wt%, and more preferably 2.0-3.0 wt%. In some embodiments, the metal coating comprises copper (Cu) and tin (Sn), wherein the amount of tin (Sn) is expressed as below: Sn / (Cu+Sn) is 0.3 wt% or more, 0.5 wt% or more, 0.8 wt% or more, 1 .0 wt% or more, 1 .2 wt% or more, 1 .5 wt% or more, 1 .8 wt% or more, 2.0 wt% or more, 2.1 wt% or more, 2.2 wt% or more, or 2.3 wt% or more. In some embodiments, the metal coating comprises copper (Cu) and tin (Sn), wherein the amount of tin (Sn) is expressed as below: Sn / (Cu+Sn) is 3.0 wt% or less, 2.9 wt% or less, 2.8 wt% or less, 2.7 wt% or less, 2.6 wt% or less, 2.5 wt% or less, 2.4 wt% or less, or 2.3 wt% or less.

[0048] In some other embodiments, in the steel wire, the metal coating comprises copper (Cu) and tin (Sn), wherein the amount of copper (Cu) is expressed as below: Cu / (Cu+Sn) is more than or equal to 80.0 wt% and less than 97.0 wt%, preferably in the range of 80.0-94.0 wt%. In some embodiments, the metal coating comprises copper (Cu) and tin (Sn), wherein the amount of copper (Cu) is expressed as below: Cu / (Cu+Sn) is 80.0 wt% or more, 82.0 wt% or more, 84.0 wt% or more, 86.0 wt% or more, 88.0 wt% or more, 90.0 wt% or more, 92.0 wt% or more, 94.0 wt% or more, 95.0 wt% or more, 95.5 wt% or more, 96.0 wt% or more, 96.1 wt% or more, 96.2 wt% or more, 96.3 wt% or more, 96.4 wt% or more, 96.5 wt% or more, or 96.6 wt% or more. In some embodiments, the metal coating comprises copper (Cu) and tin (Sn), wherein the amount of copper (Cu) is expressed as below: Cu / (Cu+Sn) is less than 97.0 wt%, 96.9 wt% or less, 96.8 wt% or less, 96.7 wt% or less, 96.6 wt% or less, 96.5 wt% or less, 96.4 wt% or less, 96.2 wt% or less, 96.0 wt% or less, 95.5 wt% or less, 95.0 wt% or less, 94.5 wt% or less, or 94.0 wt% or less.

[0049] In some other embodiments, in the steel wire, the metal coating comprises copper (Cu) and tin (Sn), wherein the amount of tin (Sn) is expressed as below: Sn / (Cu+Sn) is in more than 3 wt% and less than or equal to 20 wt%, preferably in the range of 6.0-20.0 wt%. In some embodiments, the metal coating comprises copper(Cu) and tin (Sn), wherein the amount of tin (Sn) is expressed as below: Sn / (Cu+Sn) is more than 3 wt%, 4 wt% or more, 5 wt% or more, 6 wt% or more, 7 wt% or more, 8 wt% or more, 9 wt% or more, or 10 wt% or more. In some embodiments, the metal coating comprises copper (Cu) and tin (Sn), wherein the amount of tin (Sn) is expressed as below: Sn / (Cu+Sn) is 20 wt% or less, 18 wt% or less, 16 wt% or less, 14 wt% or less, 12 wt% or less, or 10 wt% or less.

[0050] In accordance with the present invention, the metal coating of the steel wire is added with silver (Ag). In some embodiments, in the steel wire, the amount of silver (Ag) is expressed as below: Ag / (Ag+Cu+Sn) is in the range of 0.1 -5.0 wt%, preferably 0.2-2.0 wt%, and more preferably 0.6-1 . wt%. In some embodiments, in the steel wire, Ag / (Ag+Cu+Sn) is 0.1 % or more, 0.2% or more, 0.3% or more, 0.4% or more, 0.5% or more, 0.6% or more, 0.7% or more, 0.8% or more, 0.9% or more, 1.0% or more, 1.1 % or more, or 1.2% or more, in wt%. In some embodiments, in the steel wire, Ag / (Ag+Cu+Sn) is 5.0% or less, 4.0% or less, 3.0% or less, 2.5% or less, 2.0% or less, 1.8% or less, 1.6% or less, 1.5% or less, 1.4% or less, 1.3% or less, 1.2% or less, 1.1 % or less, or 1 .0% or less, in wt%.

[0051] In some embodiments, in the steel wire, the metal coating comprises copper (Cu) and zinc (Zn), wherein the amount of copper (Cu) is expressed as below: Cu / (Cu+Zn) is in the range of 60-70 wt%. In some embodiments, in the steel wire, the metal coating comprises copper (Cu) and zinc (Zn), wherein the amount of copper (Cu) is expressed as below: Cu / (Cu+Zn) is in the range of 60-77 wt%. In some embodiments, in the steel wire, the amount of silver (Ag) is expressed as below: Ag / (Ag+Cu+Zn) is in the range of 0.1 %-5.0% in wt%, preferably 0.2%-2.0% in wt%, and more preferably 0.6%-1.2% in wt%. In some embodiments, in the steel wire, Ag / (Ag+Cu+Zn) is 0.1 % or more, 0.2% or more, 0.3% or more, 0.4% or more, 0.5% or more, 0.6% or more, 0.7% or more, 0.8% or more, 0.9% or more, 1.0% or more, 1.1 % or more, or 1.2% or more, in wt%. In some embodiments, in the steel wire, Ag / (Ag+Cu+Zn) is 5.0% or less, 4.0% or less, 3.0% or less, 2.5% or less, 2.0% or less, 1.8% or less, 1.6% or less, 1.5% or less, 1.4% or less, 1.3% or less, 1.2% or less, 1.1 % or less, or 1 .0% or less, in wt%.

[0052] In some embodiments, in the steel wire, the metal coating comprises zinc (Zn). In some embodiments, in the steel wire, the amount of silver (Ag) is expressed as below: Ag / (Ag+Zn) is in the range of 0.1 -5.0 wt%, preferably 0.2-2.0 wt%, and more preferably 0.6-1 .2 wt%. In some embodiments, in the steel wire, Ag / (Ag+Zn) is 0.1 % or more, 0.2% or more, 0.3% or more, 0.4% or more, 0.5% or more, 0.6% or more, 0.7% or more, 0.8% or more, 0.9% or more, 1 .0% or more, 1.1 % or more, or 1 .2% or more, in wt%. In some embodiments, in the steel wire, Ag / (Ag+Zn) is 5.0% or less, 4.0% or less, 3.0% or less, 2.5% or less, 2.0% or less, 1.8% or less, 1.6% or less, 1 .5% or less, 1 .4% or less, 1 .3% or less, 1 .2% or less, 1.1 % or less, or 1 .0% or less, in wt%.

[0053] In some embodiments, in the steel wire, the metal coating comprises zinc (Zn) and Cobalt (Co), wherein the amount of Zinc (Zn) is expressed as below: Zn / (Co+Zn) is in the range of 80-98 wt%. In some embodiments, in the steel wire, the amount of silver (Ag) is expressed as below: Ag / (Ag+Zn+Co) is in the range of 0.1 -5.0 wt%, preferably 0.2-2.0 wt%, and more preferably 0.6-1 .2 wt%. In some embodiments, in the steel wire, Ag / (Ag+Zn+Co) is 0.1 % or more, 0.2% or more, 0.3% or more, 0.4% or more, 0.5% or more, 0.6% or more, 0.7% or more, 0.8% or more, 0.9% or more, 1.0% or more, 1.1 % or more, or 1.2% or more, in wt%. In some embodiments, in the steel wire, Ag / (Ag+Zn+Co) is 5.0% or less, 4.0% or less, 3.0% or less, 2.5% or less, 2.0% or less, 1.8% or less, 1.6% or less, 1.5% or less, 1.4% or less, 1.3% or less, 1 .2% or less, 1.1 % or less, or 1 .0% or less, in wt%.

[0054] In some embodiments, in the steel wire, the metal coating comprises a metal alloy composed of two or more metal components. In some embodiments, in the steel wire, the ratio of the amount of silver (Ag) to the total amount of metal components of the metal coating is in the range of 0.1 %-5.0% in wt%. In some embodiments, in the steel wire, the ratio of the amount of silver (Ag) to the total amount of metal components of the metal coating is 0.1 % or more, 0.2% or more, 0.3% or more, 0.4% or more, 0.5% or more, 0.6% or more, 0.7% or more, 0.8% or more, 0.9% or more, 1.0% or more, 1.1 % or more, or 1.2% or more, in wt%. In some embodiments, in the steel wire, the ratio of the amount of silver (Ag) to the total amount of metal components of the metal coating is 5.0% or less, 4.0% or less, 3.0% or less, 2.5% orless, 2.0% or less, 1.8% or less, 1.6% or less, 1.5% or less, 1.4% or less, 1.3% or less, 1 .2% or less, 1.1 % or less, or 1 .0% or less, in wt%.

[0055] The steel wire preferably has a diameter of no more than 3mm. As one preferable example, the steel wire has a diameter of 0.15mm-0.55mm, or the steel wire has a diameter of 0.8mm-2.5mm.

[0056] Figure 1 illustrates the cross-section of one example of the invention steel wire, the invention steel wire has a steel substrate 105 and a metal coating 110 covering the steel substrate 105.

[0057] In a second aspect, the present invention provides a bead bundle, comprising a bead ring, said bead ring comprising at least one steel wire in accordance with the embodiments of the present invention.

[0058] In a third aspect, the present invention provides a tire, comprising at least a pair of bead bundles, said bead bundles comprise at least one steel wire in accordance with the embodiments of the present invention, and / or said belt layer, said carcass layer and / or said tread layer comprises at least one steel wire in accordance with the embodiments of the present invention and / or at least one steel cord in accordance with the embodiments of the present invention.

[0059] In a fourth aspect, the present invention provides a process for improving the fatigue performance of a steel wire, the process comprises adding silver (Ag) into the metal coating of the steel wire.

[0060] Therefore, the invention relates to a steel wire with a metal coating comprising bronze and silver (Ag).

[0061] By way of example, and not limitation, some embodiments of the present disclosure will now be described in detail in the following Examples.EXAMPLES

[0062] Samples

[0063] The starting materials are commercially available from sources that are well known in the art.

[0064] The silver (Ag) content is measured with Inductively Coupled Plasma - Optical Emission Spectroscopy (ICP-OES) by the following measuring method:(a) Cut a length of steel wire about 10g, immerse the length of steel wire in a 10ml of HNO3 (65%) solution, make sure that the metal coating of steel wire is completely dissolved in the HNO3 (65%) solution, transfer the solution with the dissolved metal coating into a 50ml volumetric flask, and dilute it with demi-water to the mark as the sample solution. In case the steel wire has a thermoplastic resin coating, the thermoplastic resin is removed completely before the dissolution of the metal coating, wherein the termoplastic resin can be removed by any existing method, such as dissolving it in ethyl acetate solution;(b) Measure the ion concentration of each metal component of the metal coating in the sample solution by ICP-OES; for example, measure copper, zinc and silver in case the metal coating comprises copper, zinc and silver, or measure copper, tin and silver in case the metal coating comprises copper, tin and silver, or measure zinc and silver in case the metal coating comprises zinc and silver; and then calculate the weight of each metal component by multiplying the ion concentration of the metal component by the volume of sample solution; and(c) Calculate the ratio of the weight of silver (Ag) to the total weight of all metal components of the metal coating, for example, the ratio of Ag / (Ag+Cu+Sn) when the metal coating comprises copper, tin and silver, or the ratio of Ag / (Ag+Cu+Zn) when the metal coating comprises copper, zinc and silver, or the ratio of Ag / (Ag+Zn) when the metal coating comprises zinc and silver.

[0065] Various samples were prepared and reported in Table 1. The weight of metal coating (in g / Kg) indicates the weight ratio of the metal coating and the wire.Table 1s | 1.83 | Cu, Sn, Ag | Yes | 0.251 | 1.20 | 9.30 |Fatigue Performance

[0066] The present inventors have surprisingly found that by adding silver (Ag) into the metal coating of a steel wire, the steel wire would have an improved fatigue performance. As a result, the tire would have an extended life. The improvement of fatigue performance can be demonstrated in the torsion test. Test Procedure is according to Chinese national Standard GB / T239.1.

[0067] The results are reported in Table 2, wherein the comparison data are reported as average values.Table 2Comparing with Reference 1 , Invention 1 shows 2.78% improvement on torsion performance. Comparing with Reference 2, Invention 2 shows 2.70% improvement on torsion performance. Comparing with Reference 3, Invention 3 shows 2.86% improvement on torsion performance.

[0068] The improvement of fatigue performance can also be demonstrated in the bending test. Test Procedure is according to Chinese national Standard GB / T 238.

[0069] The results are reported in Table 3, wherein the comparison data are reported as average values.Table 3Comparing with Reference 1 , Invention 1 shows 7.14% improvement on bending performance. Comparing with Reference 2, Invention 2 shows 8.33% improvement on bending performance. Comparing with Reference 3, Invention 3 shows 22.22% improvement on bending performance.Aged Adhesion Performance

[0070] An extra advantage brought by the addition of Ag is the improved aged adhesion performance of the steel wire. The improvement of aged adhesion performance is indicated in Tables 4 and 5. The first row of Table 5 indicates various aging conditions, wherein “RC” = regular cure, “HA7d”= heat aging for 7 days (at 100°C), “SA2d”=steam aging for 2 days, “CH14d” = cured humidity aging for 14 days, and “SWA7d”= salt water aging for 7 days. Test Procedure is according to ASTM D1871.Table 4Table 5

[0071] Invention 4 and Invention 5 have better adhesion performance than Reference 4. The bronze coating is porous. Without wishing to be bound by theory, inventors believe that the addition of Silver (Ag) can reduce the porosity of the bronzecoating. The adhesion degradation speed is reduced, and the aged adhesion performance is improved.

[0072] While this invention has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.

[0073] It is specifically intended that the present disclosure not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.

Claims

Claims:1 . A steel wire for reinforcing rubber, comprising a steel substrate and a metal coating covering said steel substrate for the adhesion with the rubber compound, wherein the metal coating comprises silver (Ag).

2. The steel wire as claimed in claim 1 , wherein the metal coating comprises copper (Cu) and tin (Sn), wherein the amount of copper (Cu) is expressed as below: Cu / (Cu+Sn) is in the range of 97.0-99.7 wt%.

3. The steel wire as claimed in claim 2, wherein the metal coating comprises copper (Cu) and tin (Sn), wherein the amount of copper (Cu) is expressed as below: Cu / (Cu+Sn) is in the range of 97.0-98.0 wt%.

4. The steel wire as claimed in claim 1 , wherein the metal coating comprises copper (Cu) and tin (Sn), wherein the amount of copper (Cu) is expressed as below: Cu / (Cu+Sn) is more than or equal to 80.0 wt% and less than 97.0 wt%.

5. The steel wire as claimed in claim 4, wherein the metal coating comprises copper (Cu) and tin (Sn), wherein the amount of copper (Cu) is expressed as below: Cu / (Cu+Sn) is in the range of 80.0-94.0 wt%.

6. The steel wire as claimed in any one of claims 2 to 5, wherein the amount of silver (Ag) is expressed as below: Ag / (Ag+Cu+Sn) is in the range of 0.1 -5.0 wt%.

7. The steel wire as claimed in claim 6, wherein the amount of silver (Ag) is expressed as below: Ag / (Ag+Cu+Sn) is in the range of 0.2-2.0 wt%.

8. The steel wire as claimed in claim 1 , wherein the metal coating comprises copper (Cu) and zinc (Zn), wherein the amount of copper (Cu) is expressed as below: Cu / (Cu+Zn) is in the range of 60-70 wt%.

9. The steel wire as claimed in claim 8, wherein the amount of silver (Ag) is expressed as below: Ag / (Ag+Cu+Zn) is in the range of 0.1 -5.0 wt%.

10. The steel wire as claimed in claim 9, wherein the amount of silver (Ag) is expressed as below: Ag / (Ag+Cu+Zn) is in the range of 0.2-2.0 wt%.

11. The steel wire as claimed in claim 1 , wherein said metal coating comprises one, two or more metal components in addition to silver.

12. The steel wire as claimed in claim 11 , wherein the ratio of the amount of silver (Ag) to the total amount of metal components of the metal coating is in the rangeof 0.1 -5.0 wt% or in the range of 0.2-2.0 wt%, the ratio of the amount of the one, two or more metal components other than the silver to the total amount of metal components of the metal coating is in the range of 95.0-99.9 wt% or in the range of 98-99.8 wt%.13 The steel wire as claimed in claim 11 or 12, wherein the metal coating comprises two or more metal components in addition to silver, the two or more metal components are selected from the group consisting of copper, zinc, cobalt, nickel, tin, indium, titanium, manganese, iron, bismuth and molybdenum.14 The steel wire as claimed in claim 1 , 11 or 12, wherein the metal coating comprises zinc (Zn), the amount of silver (Ag) is expressed as below: Ag / (Ag+Zn) is in the range of 0.1 -5.0 wt% or in the range of 0.2-2.0 wt%.

15. The steel wire as claimed in any one of claims 1 to 14, wherein the steel wire has a thermoplastic resin coating covering said metal coating.

16. A bead bundle, comprising a bead ring, said bead ring comprising at least one steel wire as claimed in any of the preceding claims.

17. A steel cord for rubber reinforcement, said steel cord comprises two or more steel wires, each of said steel wires has a diameter of 0.15mm-0.55mm, at least one of said steel wires or each of said steel wires is as claimed in any one of claims 1 to 15.

18. A tire, comprising at least one belt layer, at least one carcass layer, at least one tread layer and a pair of bead portions, characterized in that said bead bundles comprising at least one steel wire as claimed in any one of claims 1 to 15, and / or said belt layer, said carcass layer and / or said tread layer comprises at least one steel wire as claimed in any one of claims 1 to 15 and / or at least one steel cord as claimed in claim 17.

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