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(11) | EP 2 371 984 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Method for producing a coated metal wire |
| (57) The present invention relates to methods for manufacturing a weldable coated metal
wire comprising a metal core surrounded by a coating, wherein the coating comprises
a zinc inner layer, a passivation layer and a sealing layer comprising silicon compounds.
The present invention further relates to a weldable coated metal wire and structures
comprising one or more weldable coated metal wires according to the present invention. |
FIELD OF THE INVENTION
[0001] The present invention relates to methods for manufacturing a weldable coated metal wire comprising a metal core surrounded by a coating, wherein the coating comprises a zinc inner layer, a passivation layer and a sealing layer comprising silicon compounds. The present invention further relates to a weldable coated metal wire and structures comprising one or more weldable coated metal wires according to the present invention.
BACKGROUND OF THE INVENTION
[0002] Metal wire is an important raw material in industry and construction. Several metals and metallic alloys possess the physical properties necessary to make useful wire. The metals must in the first place be ductile and strong in tension, the quality on which the utility of wire principally depends. The metals suitable for wire, possessing almost equal ductility, are platinum, silver, iron, copper, aluminium, steel and gold; and it is only from these and certain of their alloys with other metals, principally brass and bronze, that metal wire is prepared.
[0003] From the prior art it is known that metal wire may be provided with various metallic coatings in order to add functionalities to the metal wire or in order to enhance its properties. Known metallic coatings on a metal wire are brass for adhesion with rubber, zinc or a zinc-aluminum alloy for corrosion resistance, and nickel for a heat resistance. Zinc coatings are often applied to metal wire by means of a hot dip process. Passivating and sealing coatings are also often used to increase the corrosion resistance of the metal wire.
[0004] Commonly used methods for applying coatings onto metal objects are dipping the objects into a solution coating solution or spraying a coating solution onto the metal object. However, coating an object by dipping it into a bath takes a long time and such a method is not suited for metal wires. Dip coating, in which a metal object is immersed into a bath with the coating solution, is usually performed on large metal objects that require a uniform coating.
[0005] Spraying a coating onto a metal wire, on the other hand, provides a coating which is not uniformly spread on the wire. Also, problems such as the occurrence of foam in the coating solution make the coating procedure difficult as the consistence of the coating would vary.
[0006] Both spray coating and dip coating are also processes which are hard to incorporate in an in-line process. Dip coating requires a step where the process is stopped to apply the coating, whereas spraying affects greatly the speed of the process. Especially when applying a complex coating, comprising different coating layers, onto a metal wire, dip coating as well as spray coating are unsuited to be incorporated into the in-line process where the metal wire is continuously conveyed at a constant velocity through the different process steps.
[0007] In view of the above, there remains a need in the art for a method for applying complex coatings onto metal wires. Especially when the complex coatings comprise several layers with a different chemistry, and when the application of the coating needs to be performed in a continuous in-line operation with a minimum amount of materials and labour and with a constant and predetermined quality of the coatings. The present invention aims to provide a method allowing the manufacturing of a coated metal wire, wherein a metal wire is subjected to at least three coating processes.
[0008] More in particular, the present invention aims to provide a method for producing a coated metal wire with a high quality. Additionally the coating provided onto the metal wire according to the present invention provides the metal wire with specific beneficial characteristics including an improved resistance to corrosion, good welding properties and good ductility.
SUMMARY OF THE INVENTION
[0009] The present invention relates in general to methods for manufacturing a coated metal wire. More specifically, the coated metal wire comprises a metal core (1) surrounded by a coating (2), wherein the coating (2) comprises three layers: an inner layer (3), a central layer (4) and an outer layer (5) as indicated in Figure 1. The different layers of the coating are applied by guiding a metal wire through a series of successive baths comprising coating solutions. By guiding the metal wire through the series of successive baths comprising coating solutions, different coating layers may be applied onto the metal wire, thereby providing the wire with improved characteristics. The inventors have found that the methods of the present invention are methods that only require short contact times with the coating solutions, thereby providing a very fast coating method. Furthermore the methods of the present invention provide a coated metal wire with a high quality. The coated metal wire is characterized by having a high corrosion resistance, thereby increasing the lifetime of the coated metal wire, or constructions comprising the coated metal wire. A further important feature of the coated metal wire according to the present invention is that the coating of the wire does not affect the welding properties of the wire and improves the wear-resistance of the wire. A further important aspect of the methods of the present invention is that the methods allow the introduction of coloring agents into the coating of the wire. The color of coated metal wires in the prior art was restricted to a limited number of colors due to the fact that the introduction of some color, such as for instance a black color, affects the welding characteristics of the coated metal wire. However, in the methods of the present invention coloring agents may be introduced thereby providing coated metal wires with a great variety of colors, including black coated metal wires, and this without affecting the other characteristics of the coated metal wire. Also the coated metal wire according to the present invention remains flexible and deformable without distorting the coating layer.
[0010] The present invention provides methods for producing a coated metal wire, which is preferably weldable, comprising a metal core and a coating comprising a radial inner layer, a radial outer layer and a radial central layer arranged between said inner and outer layer, wherein the methods comprise the steps of:
- (a) conveying in a continuous manner a metal core wire through a galvanization solution comprising zinc, thereby providing a zinc coating layer onto said metal core wire and obtaining a galvanized metal wire;
- (b) conveying in a continuous manner said galvanized metal wire obtained from step (a) through a passivation solution thereby providing a coating layer onto said galvanized metal wire and obtaining a passivated metal wire; and;
- (c) conveying in a continuous manner said passivated metal wire obtained from step (b) through a sealer solution comprising a silicon compound and optionally coloring agents, thereby providing a sealer coating onto said passivated metal wire and obtaining said coated metal wire.
[0011] The present invention also relates to a weldable coated metal wire comprising a metal core and a coating layer comprising a radial inner layer, a radial outer layer and a radial central layer arranged between said inner and outer layer, wherein said radial inner layer is a zinc layer, said radial central layer is a passivation layer and said radial outer layer is a sealer layer comprising silicon compounds and optionally coloring agents.
[0012] The present invention also relates to the use of a one or more weldable coated metal wires according to the present invention in a metal structure.
[0013] These and further aspects and embodiments of the invention are further explained in the following sections and in the claims, as well as illustrated by non-limiting examples.
BRIEF DESCRIPTION OF THE FIGURES
[0014] Figure 1 schematically illustrates a cross-section of the coated metal wire according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0015] Before the present methods and devices used in the invention are described, it is to be understood that this invention is not limited to particular methods, components, or devices described, as such methods, components, and devices may, of course, vary. It is also to be understood that the terminology used herein is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims.
[0016] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein may be used in the practice or testing of the present invention, the preferred methods and materials are now described.
[0017] As used herein, the singular forms "a", "an", and "the" include both singular and plural referents unless the context clearly dictates otherwise.
[0018] The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps.
[0019] The terms "comprising", "comprises" and "comprised of' also include the term "consisting of".
[0020] The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within the respective ranges, as well as the recited endpoints.
[0021] The term "about" as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of +/-10% or less, preferably +/-5% or less, more preferably +/-1 % or less, and still more preferably +/-0.1 % or less of and from the specified value, insofar such variations are appropriate to perform in the disclosed invention. It is to be understood that the value to which the modifier "about" refers is itself also specifically, and preferably, disclosed.
[0022] All documents cited in the present specification are hereby incorporated by reference in their entirety.
[0023] Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, definitions for the terms used in the description are included to better appreciate the teaching of the present invention.
[0026] The term "metal wire" as used herein refers to a single, usually cylindrical, string of metal which is used to bear mechanical loads.
[0027] More specifically, the coated metal wire comprises a metal core (1) surrounded by a coating (2), wherein the coating (2) comprises three layers: an inner layer (3), a central layer (4) and an outer layer (5) as indicated in Figure 1. The different layers of the coating are applied by guiding a metal wire through a series of successive baths comprising coating solutions. By guiding the metal wire through the series of successive baths comprising coating solutions, different coating layers may be applied onto the metal wire, thereby providing the wire with improved characteristics. The inventors have found that the methods of the present invention are methods that only require short contact times with the coating solutions, thereby providing a very fast coating method. Furthermore the methods of the present invention provide a coated metal wire with a high quality. The coated metal wire is characterized by having a high corrosion resistance, thereby increasing the lifetime of the coated metal wire, or constructions comprising the coated metal wire. A further important feature of the coated metal wire according to the present invention is that the coating of the wire does not affect the welding properties of the wire and improves the wear-resistance of the wire. A further important aspect of the methods of the present invention is that the methods allow the introduction of coloring agents into the coating of the wire. Whereas the color of coated metal wires in the prior art was restricted to a limited number of colors due to the fact that the introduction of some color, such as for instance a black color, affects the welding characteristics of the coated metal wire. In the methods of the present invention coloring agents may be introduced thereby providing coated metal wires with a great variety of colors, including black coated metal wires, and this without affecting the other characteristics of the coated metal wire. Also the coated metal wire according to the present invention remains flexible and deformable without distorting the coating layer.
[0028] The present invention provides methods for producing a coated metal wire, which is preferably weldable, comprising a metal core and a coating comprising a radial inner layer, a radial outer layer and a radial central layer arranged between said inner and outer layer, wherein the method comprises the steps of:
- (a) conveying in a continuous manner a metal core wire through a galvanization solution comprising zinc, thereby providing a zinc coating layer onto said metal core wire and obtaining a galvanized metal wire;
- (b) conveying in a continuous manner said galvanized metal wire obtained from step (a) through a passivation solution thereby providing a coating layer onto said galvanized metal wire and obtaining a passivated metal wire; and;
- (c) conveying in a continuous manner said passivated metal wire obtained from step (b) through a sealer solution comprising a silicon compound and optionally coloring agents, thereby providing a sealer coating onto said passivated metal wire and obtaining said coated metal wire.
[0029] As used herein the term "coated metal wire" refers to a metal wire comprising a metal core surrounded by a coating. The metal wire refers to a single, string of metal which may be used for a large number of applications. In fact the metal wire is an important raw material in industry and construction.
[0030] The metal wire may have any cross-section such as round, square, rectangular, oval or half oval cross-sections. The metal wires according to the present invention may be chosen within a high diameter range ranging between 0.1 mm and 50 mm, preferably between 0.5 mm and 30 mm and more preferably between 2 mm and 16 mm. The coating according to the present invention has a thickness between 0.1 µm and 50 µm, preferably between 0.5 µm and 30 µm and more preferably between 2 µm and 16 µm.
[0031] The material of the metal core may be any type of metal or metallic alloy such as, platinum, silver, iron, copper, aluminium, gold, steel, brass or bronze. Preferably the material of the metal core is steel or iron. When a steel metal core is used, the steel may provided with either a low or high carbon content.
[0032] According to the present invention the inner layer of the coating refers to the portion of coating at the interface with the metal core. The outer layer of the coating refers to the portion of coating intended to be on the outside of the coated metal wire. The central layer of the coating refers to the portion of the coating arranged between the inner and the outer layer.
[0033] The methods according to the invention comprise at least three steps where a metal wire is guided or conveyed through a bath containing a coating solution. The metal wire is conveyed along a predetermined path in a continuous manner, preferably at a velocity comprised in the range from about 10 to about 500 m/min, more preferably at a velocity comprised in the range from about 25 to about 250 m/min and most preferably at a velocity comprised in the range from about 50 to about 200 m/min. The conveying rate of the metal wire may for instance be about 50, 60, 70, 75, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190 or 200 m/min. Preferably, the conveying rate of the metal wire in the methods according to the present invention remains substantially constant through the entire process. This refers to the continuous manner by which the metal wire is conducted through each of the coating solutions.
[0034] Therefore, in a particular embodiment the methods of the present invention provides that said metal wire is conveyed in at least steps (a), (b) and (c) at a velocity comprised in the range from about 10 to about 500 m/min.
[0035] The methods for conveying the metal wire through the process of the present invention may refer to any type of conveying methods known in the art. For instance the device for conveying the metal wire comprises at least one device for feeding the metal wire into a series of coating baths and a device for receiving the coated metal wire. Depending on the conveying rate of the metal wire and the distance the wire travels through each of the coating solutions, the residence time of the metal wire in each of the coating solutions may be calculated.
[0036] In one of the steps of the methods according to the present invention the metal core wire is conveyed or guided in a continuous manner through a galvanization solution comprising zinc, thereby providing a zinc coating layer onto said metal core wire and obtaining a galvanized metal wire. According to the methods of the present invention this process step is referred to as the galvanization step in which a zinc coating layer is applied onto the metal core wire. This galvanization step may occur using any of the galvanization methods known in the art, including hot-dip galvanization or electrolytic galvanization with zinc. The methods according to the present invention preferably use electrolytic galvanization.
[0037] In hot-dip galvanization the metal core wire is guided through a molten bath of zinc at a temperature of about 460 °C. When exposed to the atmosphere, pure zinc reacts with oxygen to form zinc oxide, which further reacts with carbon dioxide to form zinc carbonate which protect the metal core against corrosion. When using hot-dip galvanization the galvanized metal wire may first be subjected to a polishing step before applying the other coating layers onto the galvanized metal wire. This polishing step may include a wire drawing pass. Wire drawing is a metalworking process used to reduce the diameter of a wire or for polishing purposes by pulling the wire through a single, or series of, drawing die(s). Drawing is preferably performed at room temperature, but it may be performed at elevated temperatures for large wires. Electrolytic galvanization may occur either through an alkaline or acidic electrolytic galvanization process in which the metal wire is first loaded with an electrical charge before guiding the wire through the galvanization solution comprising zinc. Electrolytic galvanization does not require elevated temperatures of the galvanization solution, the temperature of the galvanization solution ranges between 60 and 75 °C. In an alkaline electrolytic galvanization process the electrolyte is an alkaline solution comprising zinc. For example a zinc-containing alkaline solution comprising for instance NaOH and ZnO may be used for this process. For an acidic electrolytic galvanization process the electrolyte is an acidic solution comprising zinc. For example an acidic galvanization solution may comprise zinc sulfide or zinc chloride. Other additives may be added to the electrolytic galvanization solution to improve the quality of the coating.
[0038] Whereas in general a zinc coating forms a physical barrier against corrosion, the inventors have found that an electrolytic galvanization provides additional benefits to the applied zinc coating. The coating is found to be more easily applied onto the metal wire without requiring extensive maintenance of the equipment. Furthermore, the thickness of the zinc coating may be controlled more accurately when using electrolytic galvanization. Also the zinc coating is found to have a greater adherence to the metal core as well as improve the adherence of the next coating layer. Also, the inventors have found that an electrolytic galvanization process provides a high quality galvanized metal wire does not require wire drawing steps.
[0039] As used herein the term "galvanized metal wire" refers to a metal wire comprising a metal core surrounded by a zinc coating. The thickness of the zinc coating layer ranges between 0.1 µm and 50 µm, preferably between 1 µm and 25 µm and more preferably between 2 µm and 15 µm.
[0040] In a particular step of the methods according to the present invention the galvanized metal wire is conveyed or guided in a continuous manner through a passivation solution. This process step provides a coating layer onto said galvanized metal wire thereby obtaining a passivated metal wire. According to the methods of the present invention this process step is referred to as the passivation step in which a coating layer is applied onto the galvanized metal wire. This passivation step may occur using any of the passivation methods known in the art, and preferably by guiding the galvanized metal wire through a passivating solution. The passivation solution typically comprises compounds such as cobalt, trivalent chromium, hexavalent chromium, iron, nickel, molybdenum, manganese, lanthanum, lanthanide, or mixtures thereof dissolved in solutions such as chromates, molybdates, etc. Additionally, the passivating solution may optionally further comprise halide ions including fluoride, chloride and bromide ions as well as one or more compatible wetting agents. Preferably, the passivation solution comprises trivalent chromium ions, cobalt ions and nitrate ions.
[0041] The passivation methods refers to methods of making the galvanized metal wire "passive" thereby reducing the reactivity of a chemically active metal surface by immersion in a passivating solution. The passivation solution oxidizes and dissolves any impurities on the surface of the galvanized metal wire thereby removing any impurities. Passivation leads to the spontaneous formation of a hard non-reactive surface film that inhibits further corrosion.
[0042] As used herein the term "passivated metal wire" refers to a metal wire comprising a metal core surrounded by a zinc inner coating layer, which is surrounded by a passivation coating layer. The thickness of the passivation coating layer ranges between 50 nm and 750 nm, preferably between 100 nm and 600 nm, more preferably between 150 nm and 500 nm and more preferably between about 200 nm and 400 nm.
[0043] In a particular step of the methods according to the present invention the passivated metal wire is conveyed or guided in a continuous manner through a sealer solution comprising a silicon compound and optionally coloring agents, thereby providing a sealer coating onto said passivated metal wire and obtaining the coated metal wire according to the present invention. According to the methods of the present invention this process step is referred to as the sealing step in which a coating layer is applied onto the passivated metal wire. This sealing step may occur using any of the sealing methods known in the art, and preferably by guiding the passivated metal wire through a sealing solution.
[0044] The sealing methods refer to methods of providing the coated metal wire with an outer coating layer for withstanding aggressive environments. The sealing coating is giving the coated metal wire a further coating layer for corrosion resistance. This can be explained by the closed structure of the sealing coating and by the intrinsic inert properties of the sealer.
[0045] In a particular embodiment the present invention provides methods for producing a weldable coated metal wire wherein the residence time of said passivated metal wire in said sealer solution according to step (c) ranges between 15 and 60 seconds and preferably between 25 and 35 seconds and more preferably 30 seconds.
[0046] In contrary to the methods of the prior art where coating with a typical sealer solution requires typical contact times of more that 2 minutes, the methods according to the present invention provides a high quality sealer coating on the passivated metal wire, and this only after a short contact time between the sealer solution and the passivated metal wire.
[0047] In a particular embodiment, the present invention refers to methods according to the invention, wherein the temperature of said sealer solution is at room temperature or preferably ranges between 15°C and 35°C. The temperature of said sealer solution may for instance be about 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34 or 35°C. The pH of said sealer solution ranges between 8.0 and 10.0, more preferably between 8.5 and 9.5 and most preferably between 8.9 and 9.3. In a particular embodiment the present invention provides methods for producing a weldable coated metal wire wherein said sealer solution comprises silicon compounds. Said silicon compounds are preferably organic and/or inorganic silicon compound wherein said inorganic silicon compound is preferably chosen from the group comprising a silicate such as sodium silicate, potassium silicate, magnesium silicate, cobalt silicate, sodium metasilicate, potassium metasilicate, calcium metasilicate, silicic acid or metasilicic acid, and wherein said organic silicon compound is chosen from the group comprising silicon compound containing carbon silicon bonds such as organosilanes, siloxides, silyl halides, silyl hydrides, silenes, siloles and/or hypercoordinated silicon and preferably C1 to C6 alkyl silanes, silicon oil, ethyl silicate, silyl acetals, silanols, siloxanes, polysiloxanes, silyl ethers, trimethylsilyl chloride, dichloromethylphenylsilane, dimethyldichlorosilane, methyltrichlorosilane, (4-aminobutyl)diethoxymethylsilane, trichloro(chloromethyl)silane, trichloro(dichlorophenyl)silane, trichloroethylsilane, trichlorophenylsilane and/or trimethylchlorosilane.
[0048] More preferably said sealer solution is SurTec 556 RTTM (Suretec), PLUS® L, VL, ML, M or XL seal coatings (Dacral), Sealer 300 W (Atotech) or Sealer 350 W (Atotech). More preferably, according to a particular embodiment, the present invention relates to methods according to the present invention wherein said sealer solution comprises silicon compounds in a concentration ranging between 0.01 g/L and 10 g/L, preferably between 0.05 g/L and 5 g/L, more preferably between 0.1 g/L and 5 g/L.
[0049] In a particular embodiment, the present invention relates to methods according to the present invention wherein said coated metal wire obtained from step (c) is submitted to a heat treatment. The heat treatment refers to any type of treatment considered by the skilled person that would increase the temperature of the coated metal wire, such as exposing the coated metal wire to an external heat source such as a furnace, oven or flame, or any other heat treatment such as for instance induction, electrical heating or heat treatment using a laser beam.
[0050] In a preferred embodiment of the present invention the sealer solution according to the present invention is a solution comprising silicon compounds and coloring agents. By adding one or more coloring agents such as pigments to the sealer solution, the coated metal wire according to the invention may be colored in any desired color. This results in a coated metal wire which is colored and which holds at the same time the specific characteristics of the coated metal wire such as corrosion resistance, weldability, wear resistance and ductility.
[0051] As coloring agents either inorganic or organic pigments may be used. The colored metal wires obtained according to the present invention may pertain to the whole visible spectrum, from violet till red. Also luminescent pigments can be added.
[0052] With the addition of coloring agents colors such as black, silver, blue, yellow, olive, green and red may be obtained.
[0053] Colored coated metal wires according to the present invention are also very suitable to be used for fences since they are giving a nice decorative aspect and at the same time an improved corrosion resistance. They can for example be used as barbed wire, for knotted fences, for welded fences,...
[0054] Depending on the desired color the coloring agents may also be applied in a separate coloring solution through which the passivated metal wire is conveyed.
[0055] In a specific embodiment the present invention provides methods according to the present invention wherein the residence time of said passivated metal wire in said sealer solution ranges between 0.5 and 10 seconds, preferably between 0.75 and 5 seconds and preferably between 1 and 2 seconds.
[0056] After applying the sealing coating layer the coated metal wire according to the invention is obtained. As used herein the term "coated metal wire" refers to a metal wire comprising a metal core surrounded by a zinc inner coating layer, which is surrounded by a passivation central coating layer comprising trivalent chromium and cobalt, said central coating layer being surrounded with a sealing coating layer. The thickness of the sealing coating layer ranges between 50 nm and 750 nm, preferably between 100 nm and 600 nm, more preferably between 150 nm and 500 nm and more preferably between about 200 nm and 400 nm.
[0057] In a further specific embodiment, the present invention refers to methods according to the present invention wherein the metal core wire is conveyed, from an initial position where a role of said metal core wire is unwinded, along a predetermined path through several treatment baths containing treatment solutions, to a final receiving position where said coated metal wire is rolled up.
[0058] By guiding the metal wire from the initial position to the final receiving position through the different treatment steps according to the present invention, an in-line process is generated providing fast and low-cost methods of coating a metal wire. With the methods according to the present invention additional process steps of the metal wire such as defatting, rinsing, pickling, wire drawing and/or drying may be included. The methods according to the present invention result in a simplified process. The application of the coating according to the present invention can be performed in a continuous, in-line process with other process steps such as defatting, rinsing, pickling, wire drawing and/or drying. By using a continuous process, the manufacturing costs are considerably reduced.
[0059] A defatting process typically occurs at the beginning of the method, after unwinding the metal wire. Defatting may be performed using methods commonly known in the art and for instance by using a solution of sodium hydroxide and surfactants. Rinsing may be performed prior to and after the galvanization process, and after the passivation process. Rinsing may be performed using methods commonly known in the art and for instance by using an aqueous solution. Pickling refers to a process step where the wire is submitted to an acidic solution just prior to the passivation step. Pickling may be performed using methods commonly known in the art and for instance by using an acidic solution of nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, boric acid, hydrofluoric acid, hydrobromic acid or any other acid known in the art. The drying process may be conducted at the end of the coating process, just prior to rolling up the coated metal wire. Drying of the metal wire may be performed using may be performed using methods commonly known in the art.
[0060] In a specific embodiment of the present invention, the methods for producing a coated metal wire according to the present invention comprises the subsequent steps of:
- (1) unwinding a metal core wire from a role;
- (2) defatting said metal core wire;
- (3) rinsing said metal core wire;
- (4) galvanizing said metal core wire, thereby providing a galvanized metal wire;
- (5) rinsing said galvanized metal wire;
- (6) pickling said galvanized metal wire;
- (7) passivating said galvanized metal wire, thereby providing a passivated metal wire;
- (8) rinsing said passivated metal wire;
- (9) sealing said passivated metal wire, thereby providing a coated metal wire; and;
- (10) drying said coated metal wire.
[0061] According to a particular embodiment the present invention relates to a weldable coated metal wire obtained by or obtainable by any of the methods according to the present invention.
[0062] The present invention also relates to a weldable coated metal wire comprising a metal core and a coating layer comprising a radial inner layer, a radial outer layer and a radial central layer arranged between said inner and outer layer, wherein said radial inner layer is a zinc layer, said radial central layer is a passivation layer and said radial outer layer is a sealer layer comprising silicon compounds and optionally coloring agents.
[0063] In a particular embodiment, the present invention relates to a weldable coated metal wire according to the present invention, wherein the thickness of said radial inner layer ranges between 0.1 and 50 µm, preferably between 1 µm and 30 pm, preferably between 1 µm and 25 µm and more preferably between 2 µm and 15 µm, wherein the thickness of said radial central layer ranges between 50 and 750 nm, preferably between 100 nm and 600 nm, more preferably between 150 nm and 500 nm and more preferably between about 200 nm and 400 nm, and/or wherein the thickness of said radial outer layer ranges between 50 and 750 nm, preferably between 100 nm and 600 nm, more preferably between 150 nm and 500 nm and more preferably between about 200 nm and 400 nm. The weldable coated metal wire according to the present invention may be provided in any color, depending on the coloring agents or pigments in the outer layer. The inventors have also observed for the weldable coated metal wire according to the present invention that the applied coating also provides an improved UV resistance to the metal wire. Where typically passivated objects gradually loose their color when exposed to light, the coated metal wire according to the present invention has been found to maintain the color. It is for instance commonly known that black passivated objects gradually loose their color and turn olive in time. This effect has not been observed for the coated metal wire according to the present invention.
[0064] In a particular embodiment, the present invention relates to a weldable coated metal wire according to the present invention, wherein said radial inner layer comprises zinc and/or wherein said radial outer layer has a silicon content ranging between 93.00% and 100% and optionally a coloring agent content of less than 7.00%.
[0065] In a particular embodiment, the present invention relates to weldable a coated metal wire according to the present invention, wherein said radial outer layer comprises a silicon compound.
[0066] In a particular embodiment, the present invention relates to a weldable coated metal wire according to the present invention, wherein said metal core is made of steel. The present invention also relates to a structure comprising one or more weldable coated metal wires according to the present invention. Said structure comprising one or more weldable coated metal wires according to the present invention refers to a structure that may be used in construction, automotive industry, presentation displays, food industry, medical and/or laboratory products, horticulture, ventilation, lighting and other industries. Non limiting examples of such structures include a fencing structures, gates, woven-wire fabrics, auto bodies and other auto components, U-bolts, towing eyes, fixing eyes and rings, guide tubes, exhaust brackets, head restraints, operating rods, and other metal wire products such as displays, racks, grids, lampshades, frames, hooks, brackets, clips, rings and springs. The weldable coated metal wire according to the present invention may also be used for making a multistranded wire comprising a bundle of such coated metal wires. The multistranded wire is also referred to as a wire rope.
[0067] The weldable coated metal wires according to the present invention have shown to require very short contact times between the metal wire and the coating solutions. Furthermore, the coating provides the metal wire with an increased corrosion resistance, wear resistance and flexibility while still maintaining a good weldability. The weldability of a material refers to its ability to be welded. Many metals can be welded, but some are easier to weld than others. Weldability greatly influences weld quality and is an important factor in choosing which welding process to use. Coated metal wires of the prior art often show that by providing a coating onto the metal wire the weldability decreases. With the coated metal wire according to the present invention the weldability is not affected by the presence of the coating.
[0068] Also, coloring agents may be added to the sealer layer allowing the coated wires to have a specific color, and this without affecting the other characteristics of the weldable coated metal wire.
[0069] The present invention also relates to the use of a one or more weldable coated metal wires according to the present invention in a metal structure.
[0070] The present invention more preferably relates to the use of a one or more weldable coated metal wires according to the present invention in a metal structure for use in construction and/or automotive industry.
EXAMPLES
[0071] Coated metal wires were manufactured according to the methods of the present invention and various characteristics were measured. A weldable coated metal wire having a zinc coating of 15 µm, a passivation coating with a thickness of 300 nm and a sealing coating with a thickness of 300 nm was used to test the corrosion resistance, heat resistance and climate resistance.
[0072] The corrosion resistance of the coated metal wire according to the present invention was measured using a neutral salt spray test (ISO 9227). The coated metal wire according to the present invention showed a corrosion resistance in this test of about 200 hours.
[0073] The heat resistance of the coated metal wire according to the present invention was measured by submitting the coated metal wire to 200°C for 30 minutes and subsequently cooling the metal wire in water of 20°C. This test showed that the coating was highly resistant and no breaks or cracks were observed in the coating. The climate resistance of the coated metal wire according to the present invention was measured by submitting the coated metal wire to continuously changing temperature and water saturation conditions. During this test no breaks or cracks were observed in the coating.
1. Method for producing a coated metal wire comprising a metal core and a coating comprising
a radial inner layer, a radial outer layer and a radial central layer arranged between
said inner and outer layer, wherein the method comprises the steps of:
(a) conveying in a continuous manner a metal core wire through a galvanization solution comprising zinc, thereby providing a zinc coating layer onto said metal core wire and obtaining a galvanized metal wire;
(b) conveying in a continuous manner said galvanized metal wire obtained from step (a) through a passivation solution thereby providing a coating layer onto said galvanized metal wire and obtaining a passivated metal wire;
(c) conveying in a continuous manner said passivated metal wire obtained from step (b) through a sealer solution comprising a silicon compound and optionally coloring agents, thereby providing a sealer coating onto said passivated metal wire and obtaining said coated metal wire.
2. Method according to claim 1, wherein the residence time of said passivated metal wire
in said sealer solution according to step (c) ranges between 15 and 60 seconds and
preferably between 25 and 35 seconds and more preferably 30 seconds.
3. Method according to claim 1 or 2, wherein the temperature of said sealer solution
ranges between 15°C and 35°C and the pH of said sealer solution ranges between 7.5
and 9.5.
4. Method according to any of claims 1 to 3, wherein said silicon compound is an organic
or inorganic silicon compound.
5. Method according to any of claims 1 to 4, wherein said sealer solution comprises silicon
compounds in a concentration ranging between 0.01 g/L and 10 g/L.
6. Method according to any of claims 1 to 5, wherein said coated metal wire obtained
from step (c) is submitted to a heat treatment.
7. Method according to any of claims 1 to 6, wherein said metal wire is conveyed in at
least steps (a), (b) and (c) at a velocity comprised in the range from about 10 to
about 500 m/min.
8. A weldable coated metal wire comprising a metal core and a coating layer comprising
a radial inner layer, a radial outer layer and a radial central layer arranged between
said inner and outer layer, wherein said radial inner layer is a zinc layer, said
radial central layer is a passivation layer and said radial outer layer is a sealer
layer comprising silicon compounds and optionally coloring agents.
9. A weldable coated metal wire according to claim 8, wherein the thickness of said radial
inner layer ranges between 1 and 30 µm, wherein the thickness of said radial central
layer ranges between 100 and 500 nm, and/or wherein the thickness of said radial outer
layer ranges between 100 and 500 nm.
10. A weldable coated metal wire according to claim 8 or 9, wherein said radial inner
layer comprises zinc and/or wherein said radial outer layer has a silicon content
ranging between 93.00% and 100% and optionally a coloring agent content of less than
7.00%.
11. A coated metal wire according to any of claims 9 to 10, wherein said radial outer
layer comprises a silicon compound.
12. A coated metal wire according to any of claims 9 to 11, wherein said metal core is
made of steel.
13. A metal structure comprising one or more coated metal wires according to any of claims
9 to 12.
14. Use of a one or more coated metal wires according to any of claims 9 to 12 in a metal
structure.
15. Use of a one or more coated metal wires according to claim 14 in a metal structure
for use in construction and/or automotive industry.