MX2007005565A - Fabric structure comprising silver-germanium-copper alloy - Google Patents

Abstract

A woven, braided or knitted fabric structure comprises wires of silver alloy, preferably a precipitation-hardenable Ag Cu Ge alloy. The process for making a fabric structure may comprise providing silver wire having a temper of more than fully soft but less than half hardness, forming said wire into said structure and heating the structure to precipitation harden the wire.

Description

WOVEN STRUCTURE COMPRISING AN ALLOY OF SILVER-GERMANIUM-COPPER Field of the Invention This invention relates to woven structures based on silver threads, which may comprise all or part of the structures. Background of the Invention The literature on the production of silver threads is relatively scarce. For example, patent US 6627149 (Tayama et al.) Describes the production of silver wire of a relatively large diameter and of high purity for use in recording or image transmission applications. The literature that refers to the silver-based woven structures is also scarce. Such woven structures have been based mainly on braided strips, cords or filaments together, see, US-A-240096 (Crane), US-A-253587 (Crane) and US-A-5203182 (Wiriath). However, US-A-2708788 (Cassman et al) discloses a mesh or sheet of silver through which the material will be evaporated during the manufacture of television tubes, the mesh is stiffened by the deposition of gold over the same and by the alloy of silver and gold to cause shrinkage of the mesh. US-A-5122185 (Hochella) discloses a precious metal mesh used as the so-called "vacuum tuners" in the recovery of platinum from Ref. 182126 from a gas stream from the oxidation of ammonia. The mesh is preferably pure palladium, but may also be a palladium alloy with one or more metals selected from nickel, cobalt, platinum, ruthenium, iridium, gold, silver and copper. Knitting by wire or metal fiber stitches is already known, for example, as in US-A-2274684 (Goodloe), but the existing knitted, metallic knits are predominantly ferrous alloys. US-A-5188813 (Fairey et al., Johnson Matthey) describes woven fabrics of stitches by stitch consisting essentially of interlock loops of precious metal fibers selected from the metals of the group of platinum, gold, and alloys thereof using circular bed or flat bed knitting machines, with platinum or with platinum alloys, for use as metallic catalytic sieves that are preferred. Fairey et al found that strands of platinum alloy or metals with similar mechanical properties could not be knitted effectively and that attempts to do so led to a break in the fiber and clogging of the machine. cause that the tensile strength of the metal fibers was insufficient to withstand the frictional forces in the knitting process. The solution described was to feed the metallic fiber with a supplementary fiber that acted as a lubricant, the supplementary fiber preferably being in the form of multiple cords instead of a monofilament, and the cords surround the metallic wire to minimize contact of the metal with the metal. After knitting, the supplementary fiber can be removed by dissolving in a solvent or by pyrolysis. WO 92/02301 (Heywood) discloses a woven fabric of warp stitches of platinum, palladium or rhodium threads, using for example the knitted fabric of knitting, raschel or jacquard to give metal screens catalysts that are more flexible or open than the knits. woven metal sieves and that are less likely to twist under thermal stress. The knitter by points is facilitated either by the lubrication of the wire with a lubricant such as starch or wax or by feeding a supplementary fiber. A particular structure of the fine mesh warp knitted fabric, based on noble metal threads and for use as a catalyst, is described in US-A-6089051 (Gorywoda et al). None of the above references discloses or suggests the formation of dot-woven structures based on fine silver or silver alloy, and our experience is that standard Sterling silver has insufficient tensile strength for weaving by effective points on the machine.

GB-B-2255348 (Rateau, Albert and Johns, Metaleurop Recherche) discloses a novel silver alloy that maintains the hardness and luster properties inherent in Ag-Cu alloys while reducing the resulting problems of the tendency of the copper content to oxidize. The alloys are ternary alloys of Ag-Cu-Ge containing at least 92.5% by weight of Ag, 0.5-3% by weight of Ge and the rest, apart from the impurities, of copper. The alloys are stainless in the air of the environment during the operations of production, transformation and conventional finishing, they are deformable easily when they are cold, they are easily brazed and they do not cause a significant shrinkage during the casting. They also exhibit superior ductility and tensile strength. Germanium is established to exert a protective function that was responsible for the advantageous combination of the properties exhibited by the new alloys, and is in a solid solution in the phases of both silver and copper. The microstructure of the alloy consists of two phases, a solid solution of germanium and copper in silver surrounded by a solid filament solution of germanium and silver in copper that contains by itself a few dispersoids of the intermetallic CuGe phase. Germanium in the copper-rich phase is said to inhibit the surface oxidation of this phase by the formation of a protective coating of GeO and / or thin Ge02 that prevented the appearance of a purple spot during brassizing and annealing by the flame. In addition, the tarnish development was appreciably delayed by the addition of germanium, the surface became slightly yellow instead of black and the tarnish products were easily removed by ordinary tap water. US-A-6168071 (Johns) and EP-B-0729398 (Johns) describe a silver / germanium alloy comprising a silver content of at least 77% by weight and a germanium content of between 0.4 and 7% , the rest is mainly copper apart from some impurities, such alloy contained elemental boron as a grain refiner at a concentration greater than 0 ppm and less than 20 ppm. The boron content of the alloy could be achieved by providing the boron in a master copper-boron alloy having 2% by weight of elemental boron. It was reported that such low boron concentrations surprisingly provided excellent refining of the grain in a silver / germanium alloy, imparting greater strength and ductility to the alloy, compared to a silver / germanium alloy without boron. Silver sterling Argentium (trademark) comprises Ag 92.5% by weight and Ge 1.2% by weight, the rest is copper and approximately 4 ppm of boron as a grain refiner. The Society of the American Goldsmiths maintains a web site for the commercial modalities of the aforementioned alloys known as Argentium (registered trademark) at the address of the network http: // www. silversmithing. com / largent ium. htm US-A-6726877 (Eccles) discloses inter alia a silver alloy composition for jewelry hardenable by mechanical means, resistant to the formation of purple spots, comprising 81-95.409% by weight of Ag, 0.5-6% by weight. Cu weight, 0.05-5% by weight of Zn, 0.02-2% by weight of Si, 0.01-2% by weight of B, 0.01-1.5% by weight of In and 0.01 not greater than 2.0% by weight of Ge . The germanium content is alleged to lead to alloys that have mechanical hardening characteristics of a kind exhibited by conventional 0.925 silver alloys, along with resistance to the formation of a purple stain from alloys that are allegedly resistant to the formation of a purple spot, known prior to June 1994. The amounts of Ge in the alloy from about 0.04 to 2.0% by weight are alleged to provide hardening properties by mechanical means, modified in relation to the alloys of the resistant class to the formation of a purple stain that do not include germanium, but the operation of the hardening is not linear with the increase of the germanium nor the hardening is linear with the degree of the hardening by mechanical means. The Zn content of the alloy has a support in the color of the alloy as well as in the operation as a reducing agent for the silver and copper oxides and is preferably 2.0-4.0% by weight. The Si content of the alloy is preferably adjusted in relation to the proportion of Zn used and is preferably 0.15 to 0.2% by weight. The hardening by precipitation after annealing is not described, and there is no description or suggestion that the problems of distortion and damage to welded joints in the almost finished work made of this alloy can be avoided. By way of background, US-A-4810308 (Eagar et al.; Leach & Garner) describes a hardenable silver alloy comprising not less than 90% silver; not less than 2.0% copper; and at least one metal selected from the group consisting of lithium, tin and antimony. The silver alloy may also contain up to 0.5% by weight of bismuth. Preferably, the metals comprising the alloy are combined and heated to a temperature of not less than 676-760 ° C (1250-1450 ° F) for example for about 2 hours to anneal the alloy in a solid solution, a temperature of 732 ° C. C (1350 ° F) is used in the examples. The annealed alloy is then cooled rapidly to room temperature by quenching. It can then be hardened over time by reheating to 149-371 ° C (300-700 ° F) for a predetermined period of time followed by cooling of the hardened alloy with the passage of time at room temperature. The hardened alloy over time demonstrates a substantially higher hardness than that of traditional sterling silver, typically 100 HVN (Vickers hardness number), and can be returned by elevated temperatures to a state relatively soft. The description of US-A-4869757 (Eagar et al., Leach &Garner) is similar. In both cases, the annealing temperature described is higher than that of Argentium, and no reference describes alloys resistant to the formation of a purple stain or tarnish. The inventor has no knowledge of the process described in these patents that is used for commercial production, and again there is no description or suggestion that the hardening can be achieved in almost completed work. A silver alloy called Steralite is said to be covered by US-A-5817195 (Davitz); 5882441 (Davitz), and exhibiting high resistance to corrosion and tarnish. The alloy of US-A-5817195 (Davitz) contains 90-92.5% by weight of Ag, 5.75-5.5% by weight of Zn, 0.25 to less than 1% by weight of Cu, 0.25-0.5% by weight of Ni, 0.1- 0.25% by weight of Si and 0.0-0.05% by weight of In. The alloy of US-A-5882441 (Davitz) contains 90-94% by weight of Ag, 3.5-7.35% by weight of Zn, 1-3% by weight of Cu and 0.1-2.5% by weight of Si. An alloy of low copper content-high zinc content, like, is described in US-A-4973446 (Bernhard et al) and is said to exhibit reduced purple spot formation, reduced porosity and reduced grain scale . It has now been found that silver wire can be formed by machining into woven structures by processes such as weaving, knitting or braiding and that sufficient strength can be imparted to the wire by the formation itself by machining if the wire is hardened by the hardening by mechanical means from its fully annealed state prior to the formation of the fabric, at the same time that a further hardening by mechanical means is allowed to take place in the fabric forming process and still allowing the development of a hardness additional by hardening by precipitation. Argentium wire and other silver / copper / germanium alloy wires, in particular, have a particularly desirable combination of physical properties that allow them to be knitted or otherwise formed into woven or cable structures or lacing structures braided.

BRIEF DESCRIPTION OF THE INVENTION The invention provides a woven structure comprising yarns of a silver alloy which may be knitted, woven, braided, woven with hooks or otherwise formed and which may comprise fibers that are total, partial or predominantly silver. The invention also provides a process for manufacturing a woven structure as mentioned above which comprises providing a silver wire having a temper greater than that of the fully softened material but less than the material half the hardness, shaping the wire into the structure woven, and heat the structure for hardening by precipitation of the wire. In a further aspect, the invention provides a woven structure (for example a structure formed by knitted fabric, hooked fabric or other interlock loops of the wire) comprising (as all of the filaments or yarns in the structure) or as some of the filaments or threads in the structure) threads of a silver alloy having a grain structure refined by incorporation into the molten silver alloy from which the wire is formed, of a boron compound that It can decompose. Detailed Description of the Invention Alloys for forming the wire The wire used to form the present structures can be any grade of silver curable by precipitation and by mechanical means, but preferably it is an alloy of silver, copper and germanium, for example an alloy consisting of , apart from impurities and any grain refiner, 80-96% in silver, 0.1-5% germanium and 1-19.9% copper, by weight of the alloy. Sterling grade alloys of the above type may comprise, apart from impurities and the grain refiner, 92.5-98% silver, 0.3-3% germanium, and 1-7.2% copper, by weight of the alloy, together with 1-200 ppm for example 1-40 ppm boron as a grain refiner. A particularly preferred group of such alloys consists, apart from the impurities and the grain refiner, of 92.5-96% silver, 0.5-2% germanium, and 1-7% by weight of copper, by weight of the alloy, together with 1-40 ppm boron as the grain refiner. The alloy may further comprise zinc, preferably in a proportion, by weight, with respect to copper of not more than 1: 1. Accordingly, the alloy may comprise 81-95.49% by weight of Ag, 0.5-6% by weight of Cu, 0.05-5% by weight of Zn, 0.02-2% by weight of Si, 0.01-2% by weight of B, optionally 0.01-1.5% by weight of In, optionally 0.25-6% by weight of Sn and 0.01-not greater than 2.0% by weight of Ge. The alloy from which the present wire is formed may contain one or more incidental ingredients known per se in the production of silver alloys in amounts (for example in total up to 0.5% by weight) which are not detrimental to the strength mechanical, tarnish resistance and other material properties. Cadmium can also be added in similar amounts although its use is not currently preferred. Tin can be beneficial, typically in an amount of 0.5% by weight. The indium can be added in small amounts for example as a grain refiner and to improve the wettability of the alloy. Other elements of possible incidental ingredients, selected from Al, Ba, Be, Co, Cr, Er, Ga, Mg, Ni, Pb, Pd, Pt, Si, Ti, V, Y, Yb, and Zr, provided the effect of germanium in terms of providing resistance to the formation of a purple spot and tarnish so that it is not unduly affected. Refining the grain of the alloys Boron can be incorporated into the silver alloys used to make the wire for the present purposes as a grain refiner. It can be added, for example, to the molten silver alloy as a master alloy of copper / boron, at 2% by weight of B. However, it has recently been found that alloys having improved mechanical properties (including for example tensile strength) can be made by introducing the boron into the alloy as a boron compound selected from the compounds of alkyl boron, boron hydrides, halides of boron, metal hydrides containing boron, metal halides containing boron and mixtures thereof. The use of wire made of molten silver treated with boron compounds that can be decomposed as mentioned above, is advantageous for the present invention since the mechanical properties thereof are more consistent and the strength can be higher both prior to forming of the woven structure as after over-heating the woven structure to effect hardening. In some embodiments, the refined grain silver by means of a decomposable boron compound is detectable for example on an electron micrograph examination because of its fine grain structure. The boron compound can be introduced into the molten silver alloy in the gas phase, advantageously mixed with a carrier gas which helps to create a stirring action in the molten alloy and to disperse the boron content of the gas mixture within said alloy . Suitable carrier gases include, for example, hydrogen, nitrogen and argon. The gaseous boron compound and the carrier gas can be introduced from above into a container containing the molten silver, for example a crucible in a silver melting furnace, a casting boiler or a tundish using a metallurgical lancet. which may be an elongated tubular body of refractory material for example of graphite or may be a metallic tube lining in the refractory material and is immersed in its lower end in the molten metal. The lancet is preferably of sufficient length to allow the injection of the gaseous boron compound and the carrier gas deep into the molten silver alloy. Alternatively, the gas containing the boron can be introduced into the molten silver from one side or from below using for example a permeable gas bubble cap or a submerged injection nozzle. For example, Rautomead International of Dundee, Scotland, manufactures continuous casting machines, horizontal, in the RMK series for the continuous casting of semi-finished products in silver. The alloy to be heated is placed in a solid graphite crucible, protected by an inert gas atmosphere which can be, for example, oxygen-free nitrogen containing <; 5 ppm of oxygen and < 2 ppm moisture and is heated by heating with an electrical resistance using graphite blocks. Such furnaces have an integrated facility for the bubbling of inert gas through the molten material. The addition of small amounts of the gas that contains the thermally decomposable boron to the inert gas that is bubbled through the mixture easily provides a boron content of some ppm or a few tenths of a ppm, desired. The introduction of the boron compound into the alloy as a stream of gas diluted over a period of time, the carrier gas of the gas stream serving to stir the molten metal or alloy, rather than in one or more relatively large amounts , it is believed that it will be favorable from the point of view of avoiding the development in the metal or the alloy of boron hard points. Compounds that can be introduced into the molten silver or alloys thereof in this manner, include boron trifluoride, diborane or trimethylboro which are available in pressurized cylinders diluted with hydrogen, argon, nitrogen or helium, diborane is preferred to Because apart from boron, the only other element that is introduced into the alloy is hydrogen. A still further possibility is to bubble the carrier gas through the molten silver to effect agitation thereof and to add a solid boron compound, for example, NaBH4 or aBF4 in the fluidized gas stream as a finely divided powder forming a aerosol. A boron compound can also be introduced into the molten silver alloy in the liquid phase, either as such or in an inert organic solvent. Compounds which can be introduced in this manner include alkylborane or alkoxy alkyl borane such as triethylborane, tripropylborane, tri-n-butyl-imborane and methoxydiethylborane which by their safe handling can be dissolved in hexane or THF. The liquid boron compound can be filled and sealed in silver or copper foil containers that resemble a capsule or envelope using the known envelope / liquid or capsule / liquid filling machinery and using a protective atmosphere to provide the envelopes with filled capsules or other small containers typically of 0.5-5 ml capacity, more typically approximately 1-1.5 ml. Capsules or envelopes filled in an appropriate number can then be submerged individually or as one or more groups in the molten silver or an alloy thereof. A still further possibility is to atomize the liquid boron-containing compound into a stream of a carrier gas which is used to stir the molten silver as described above. The droplets may take the form of an aerosol in the stream of the carrier gas, or they may become evaporated therein. Preferably, the boron compound is introduced into the molten silver alloy in the solid phase, using for example a solid borane eg decaborane Bi0H14 (mp 100 ° C, e.g. 213 ° C). However, boron is preferably added in the form of either a metal hydride containing boron or a boron containing metal fluoride.

When a metal hydride containing boron is used, suitable metals include sodium, lithium, potassium, calcium, zinc and mixtures thereof. When a boron containing metal fluoride is used, sodium is the preferred metal. Sodium borohydride, NaBH 4 which has a molecular weight of 37.85 and contains 28.75% boron, is even more preferred. The boron can be bonded to the molten silver alloy both in the first casting and at intervals during the storage of the alloy in the molten state and subsequently to compensate for the loss of boron if the alloy is kept in the molten state for a period of time. time, as in a continuous casting process by grain. Surprisingly it has been found that when a decomposable boron compound such as a borane or a borohydride is added, more than 20 ppm can be incorporated into a silver alloy without the development of boron hard spots. This is advantageous because boron is rapidly lost from the molten silver: according to one experiment, the boron content in the molten silver decomposes with a half-life of about 2 minutes. The mechanism of this decomposition is not clear, but it can be an oxidizing process. It is therefore desirable to incorporate more than 20 ppm of boron in an alloy as a first cast, and amounts for example up to 50 ppm, typically up to 80 ppm, and in some cases up to 800 or even 1000 ppm can be incorporated. Thus, a grain from the silver melt containing approximately 40 ppm boron could be produced. Due to the loss of boron during subsequent re-melting and wire formation, the boron content of the finished wire may be closer to 1-20 ppm, but the ability to achieve relatively high initial boron concentrations means that It can achieve improved consistency and improved mechanical properties. Formation of the wire from the alloys The formation of the germanium-containing silver in a wire for the formation of a fabric according to the invention can be carried out using conventional wire-making processes. In certain embodiments of the invention, the metal is cast to form ingots that are wound on a roller mill to form a wire rod. The resulting bar is stretched successively through a series of diameter dies that are progressively reduced to give the required size. Stretching may be in single block machines, or the wire may be stretched over continuous wire stretching machines having a series of guides through which the wire passes in a continuous manner. Lubrication can be provided when necessary. In the final stage, and when required in the intermediate stages, the wire can be annealed to restore ductility. Preferably this step is carried out in an atmosphere that is not too reductive or that is mildly oxidizing. The corrosion resistance of the present AgCuCe alloys depends on the presence of the oxide films, and these are reduced for example by an atmosphere of 50% hydrogen, 50% nitrogen with some loss of tarnish resistance. In each step, it is desirable that the annealing atmosphere should be an inert gas, generally nitrogen, with less than 10% hydrogen, typically 3-10%, preferably about 3-5%. If the atmosphere of the furnace is thermofractioned ammonia, it is preferred that the hydrogen content should not be greater than the range indicated above. It has been found that it is possible to have mildly oxidizing conditions during annealing, that is, partial temperatures and pressures of oxygen, which allow the Ag-Cu- (Zn) -Ge alloys to be processed in such a way that the Ge will react to form Ge02 without Cu forming CuC > 2. However, the restrictions on the maximum processing temperature and time on the temperature rise from the normal commercial annealing temperature and the time used for the production of silver-copper alloys such as Sterling Silver., typically approximately 625 ° C or 650 ° C. It has been established that the Ag-Cu- (Zn) -Ge alloys can be processed even at annealing temperatures such as 625 ° C and 650 ° C to selectively oxidize the Ge to Ge02, using a controlled atmosphere. Preferably, the annealing atmosphere is a selectively oxidizing, wet atmosphere. By "wet" is this context is meant an atmosphere containing moisture (H20), such that the atmosphere exhibits a dew point of at least +1 ° C, preferably at least +25 ° C, more preferably at minus +40 ° C. Preferably, the dew point is considered to be within the range of +1 ° C to +80 ° C, more preferably in the range of +2 ° C to +50 ° C. The dew point can be defined as the temperature at which an atmosphere containing water vapor must be cooled so that saturation occurs, whereby an additional cooling below the dew point temperature leads to dew formation. A more comprehensive definition is given in "Handbook of Chemistry and Physics," 65th Ed. (1985-85), CRC Press Inc., USA, page F-75. It is preferred that the selectively oxidizing atmosphere comprises hydrogen and moisture, for example an atmosphere of nitrogen, hydrogen and water vapor, such as a gaseous mixture of 95% nitrogen / 5% hydrogen (v / v) containing water vapor , or a furnace atmosphere of nitrogen, hydrogen, carbon monoxide, carbon dioxide, methane, and water vapor. In practice, it is preferred to produce the selectively oxidizing, wet annealing atmosphere by controlling the addition of water vapor to a dry, or inert, substantially dry kiln atmosphere, for example to a furnace atmosphere predominantly nitrogen or nitrogen and hydrogen, and which typically comprises nitrogen, hydrogen, carbon monoxide, carbon dioxide and methane. The dew point in the furnace can be measured by conventional means such as a dew point meter or a probe in the furnace, and the mixing ratios of the gas are adjusted accordingly to control the selectively oxidizing atmosphere. As explained above, in some embodiments of the invention, the annealing of the wire is carried out under the selectively oxidizing atmosphere. If, as usual, the annealing is carried out as successive annealing steps, for example with interleaved stretching steps, then at least the final annealing step must be carried out under a selectively oxidizing atmosphere. In the further embodiments of the invention, one or more of the annealing steps preceding the final annealing step are carried out under a reducing atmosphere. However, in other embodiments of the invention, all of the annealing steps are carried out under a selectively oxidizing atmosphere. In the embodiments of the invention, the annealing of the wire is carried out at a temperature in the range from 400 ° C to 750 ° C, typically in the range from 400 ° C to 700 ° C, preferably in the range from 500 ° C. C up to 675 ° C, more preferably in the range from 600 ° C to 650 ° C, and in particular at about 625 ° C. In the embodiments of the invention, the annealing is carried out for a total period in the range from 5 minutes, at the highest annealing temperatures, up to 5 hours, at the lower annealing temperatures, and preferably in the range of 15 minutes. minutes up to 2 hours. A further improvement in tarnishing resistance can be obtained by heating the post-production of the wire, ie after the alloy has been stretched and annealed to provide a finished wire. The heating may be in an atmosphere of air or steam at a temperature in the range from 40 ° C to 220 ° C, preferably in the range of 50 ° C to 200 ° C, more preferably in the range of 60 ° C to 180 ° C. Preferably, postproduction heat treatment is carried out for a period in the range from 1 minute to 24 hours, preferably in the range of 10 minutes to 4 hours. Accordingly, the protective coating of germanium oxide can be further developed within the surface of the alloy. Advantageously, this post-production treatment also covers the protection of the alloy against tarnishing, which is particularly important for the fine wire because of its high surface area in relation to its mass. The structures of the invention may consist wholly or mainly of silver threads, or the silver wire may be a minor component, for example when incorporated in bandages to take advantage of the bacterial properties of silver. The wire is a solid section different from the strip, and can be provided in a reel or in a reel or in a roll. The wire used to manufacture the present woven structures may be circular in cross section, but other sections may be employed, for example, oval, polygonal, strip or flat wire depending on the desired appearance for the finished chain. The wire will typically be circular in section. It may be of diameter or size of 0.05-2.0 mm, typically 0.1-1 mm. The wire may be a single cord or may comprise a plurality of twisted cords together. Hardness of the wire to form the woven structures Prior to the formation of the present structures, the wire of the invention should preferably be more than fully softened but less than half the hardness. These expressions have well understood meanings in the jewelry trade. In the jewelery wire, the hardness or malleability is graduated as soft or extra soft, of a quarter of hardness, half hardness, hard, and flexible hardness. The numbers instead of the names can also designate the hardness of the wire. The numbering system, which ranges from zero to 10 or greater, is based on the number of times the wire has been stretched through progressively smaller holes in a drawing plate. Each increase in the number designates a duplication of the preceding number. The soft or extra-soft wire is as it was annealed, has not been subsequently stretched through a plate and has a zero number. It is malleable and can easily be bent by hand in a large number of ways but does not retain its shape under tension. The wire that is hard to a quarter has been stretched through a single plate, the medium hard wire has been stretched twice and the hard wire has been stretched four times. The wire used to form the present structures is preferably a quarter-hardness wire, which imparts the necessary bending and breaking strength required for the fabric in the machine or the knitted fabric in the machine, but leaves sufficient material in the solid solution for both hardening by mechanical means during weaving or spot weaving and for subsequent hardening by precipitation. Structures that can be formed from the wire The wire can be knitted in the weft on a circular or flat bed knitting machine to produce for example a knitted structure in single layer knit stitches, or layer structures doubles, or more structures similar to a network, open, which can be tubular or can be flat sheets. In particular, wire-like, tubular, single-layer structures, based on a single layer or two layers, can be used as a substitute for conventional chains in the manufacture of jewelry such as bracelets and necklaces, and have the advantage of an attractive appearance and luminosity. The wire can also be warp knitted. The wire can be further shaped into braided cable structures, for example by twisting together a plurality of single silver filaments to form pleated yarns which are then braided, see for example US-A-4170921 and US-A-6070434 (Figure 6) for example to form a braided silver shirt surrounding the core that can be made of silver, of another metal or for example of plastic filaments. An additional possibility is to form the wire in a hook-woven structure. "Crochet" as used herein, means a manufacturing process of a needlework comprising loop stitches formed from a single strand or filament, for example a silver / copper / germanium alloy using a needle with Hook shape and includes both the formation of a base row that may be useful per se as a chain of jewelry and the manufacture of a flat woven structure or open work from successive rows of knitted fabrics. You can make structures of the type of band and lace. The embodiments of the invention for knitting or knitting with hooks also employ a sacrificial thread mounted substantially parallel and adjacent to the silver alloy wire during the operations involved in knitting or knitting with a hook and fed simultaneously with the same. The sacrificial strand can be formed of any suitable material that can be removed after the knitted structure has been formed. For example, suitable materials for the sacrificial strand may include cotton, an easily soluble metal, and polymers, natural or synthetic, including polyamides, polyesters, cellulosic fibers, acrylic styrene polymers, PVA and other vinyl polymers, alginate, and the like . Multiple strand fibers or cords and monofilament fibers or cords can be used. One of the advantages of a sacrificial strand is to provide a spacer to control the spacing in the structure of the knitted fiber. Accordingly, the thickness of the sacrificial strand can be used as a way to increase or decrease the volume of space between the adjacent portions of the knitted wire. Typically, the sacrificial strand may have a diameter that is approximately the same as the wire. As mentioned above, it may be desirable to decompose or dissolve the sacrificial strand, and the selection of the sacrificial strand is conveniently made to allow decomposition or facilitated dissolution after the woven structure has been formed. Most organic fibers, for example, can be pyrolyzed and / or oxidized to leave a small residue or no waste, or a strong acid such as sulfuric acid or nitric acid can be used. Additionally or as an alternative to a sacrificial strand, a lubricant, for example starch, may be used to reduce friction in the knitting or knitting process with a hook. After the formation of a knitted, braided, woven with hook or woven structure, it may be subjected to a curing treatment by heating in an oven for example at about 300 ° C for about 30-45 minutes followed by gradual cooling. A surprising difference in properties exists between conventional Sterling silver alloys and other binary alloys of Ag-Cu on the one hand and silver alloys of Ag-Cu-Ge on the other hand, on which the gradual cooling of the alloys of the Sterling binary type leads to coarse or coarse precipitates and a small hardening by precipitation, while the gradual cooling of the Ag-Cu-Ge alloys leads to fine precipitates and a hardening by useful precipitation, particularly where the silver alloy contains a effective amount of the grain refiner. further, the addition of germanium to Sterling silver changes the thermal conductivity of the silver alloy, compared to standard Sterling silver. The International Annealed Copper Scale (IACS) is a measure of conductivity in metals. On this scale, the copper value is 100%, pure silver is 106%, and standard Sterling silver is 96%, while a Sterling alloy containing 1.1% germanium has a conductivity of 56%. The significance of this is that sterling argentium alloys and other germanium-containing silver alloys do not dissipate heat as rapidly as standard sterling silver or its germanium-free equivalents, a piece will take a longer time to cool, and the Precipitation hardening to a commercially useful level (preferably up to a Vickers hardness of 110 or greater, more preferably up to 115 or greater) can be carried out during cooling with natural air or during cooling with controlled, slow air. A number of Ag-Cu-Ge-Zn alloys of the boron refined grain using a copper-boron master alloy or using a decomposable boron compound also exhibits a precipitation hardening under the conditions indicated above. The present structures can be used to make articles that can be used, for example chains, bracelets, necklaces, earrings, key rings and the like. The silver wire can be incorporated, in the embodiments of the invention, into a variety of additional structures for example for use in catalysis or a water treatment. Accordingly, it can be incorporated into a backing material for example for carpets, as a minor component in woven or knitted garments, for example for protective clothing or in fashionable garments, in textile fabrics general, knitted, circular or flat fabrics, warp knitted fabrics, sleeves, ribbons, felts perforated with needles or other felts, and twisted or braided cords or cords. The silver wire, either alone or mixed with other metallic or natural or synthetic organic fibers or filaments, can be formed in a porous medium, for example three-dimensional non-woven structures, for example for filtration (for example of water where the anti-aging properties). -bacterial silver can be an advantage) or in catalyst support applications. It can be incorporated as a component of a bandage taking into account its antibacterial properties. In the further embodiments, the silver wire can be formed into a high porosity, non-woven matrix of sintered metal fibers, which exhibits high gas permeability, or a layer that can be folded. The sintered metal fibers can be formed into a medium having a plurality of layers, for example 1-3 layers optionally with an internal or surface support mesh or screen for a variety of filtration applications and other applications including catalysts, filtration gas-solid and / or gas / liquid and / or odor removal and liquid / solid filtration. Because of the high porosity that can be achieved, filter media made using the fibers according to the invention can exhibit a relatively low pressure drop. They can be used as such or incorporated as minor components in textile products, for example in bandages to provide antibacterial properties. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (34)

1. Claims Having described the invention as above, the content of the following claims is claimed as property. A woven structure, characterized in that it comprises silver alloy wires.
2. 2. The structure according to claim 1, characterized in that the alloy is an alloy of silver, copper and germanium.
3. 3. The structure according to claim 2, characterized in that the alloy consists, apart from the impurities and any grain refiner, of 80-96% silver, 0.1-5% germanium and 1-19.9% copper, in Alloy weight. .
4. The structure according to claim 3, characterized in that the alloy comprises, apart from the impurities and the grain refiner, 92.5-98% silver, 0.3-3% germanium, and 1-7.2% copper, by weight of the alloy, together with 1-40 ppm boron as the grain refiner.
5. 5. The structure according to claim 4, characterized in that the alloy consists, apart from the impurities and the grain refiner, of 92.5-96% silver, 0.5-2% germanium, and 1-7% copper, by weight of the alloy, together with 1-40 ppm of boron as the grain refiner.
6. 6. The structure according to any preceding claim, characterized in that the alloy further comprises zinc.
7. 7. The structure according to claim 6, characterized in that the zinc is present in a proportion, by weight, with respect to copper of not more than 1: 1.
8. The structure according to any preceding claim, characterized in that the alloy comprises 81-95,409% by weight of Ag, 0.5-6% by weight of Cu, 0.05-5% by weight of Zn, 0.02-2% by weight of Yes, 0.01-2% by weight of B, optionally 0.01-1.5% by weight of In, optionally 0.25-6% by weight of Sn and 0.01-not more than 2.0% by weight of Ge.
9. The structure according to any preceding claim, characterized in that it consists essentially of silver wire.
10. 10. The structure according to any preceding claim, characterized in that the wire is of a diameter of 0.05-2.0 mm.
11. The structure according to claim 10, characterized in that the wire is of a diameter of 0.1-1 mm.
12. 12. The structure according to any preceding claim, characterized in that the silver wire is of a single cord.
13. The structure according to any of claims 1-12, characterized in that the silver wire comprises a plurality of cords.
14. 14. The structure according to any preceding claim, characterized in that it is woven.
15. 15. The structure according to any of claims 1-13, characterized in that it is knitted by stitches.
16. 16. The structure according to claim 15, characterized in that it comprises a single layer.
17. 17. The structure according to claim 15, characterized in that it comprises two or more layers of loops knitted together.
18. 18. The structure according to claims 15, 16 or 17, characterized in that it is knitted from stitches per frame.
19. 19. The structure according to claims 15, 16 or 17, characterized in that it is woven of warp stitches.
20. 20. The structure according to any of claims 15-19, characterized in that it is tubular or similar to a cable.
21. 21. The structure according to any of claims 15-19, characterized in that it is a flat sheet.
22. 22. The structure according to any preceding claim, characterized in that it can be obtained by the formation of a quarter-hardness wire.
23. 23. The structure according to any preceding claim, characterized in that it is hardened by precipitation after the structure has been formed.
24. 24. The structure according to claim 23, characterized in that it is hardened by precipitation by heating to about 300 ° C for about 30 minutes.
25. 25. A process for manufacturing a woven structure, characterized in that it comprises providing a silver wire having a greater temper than fully softened but less than half the hardness, forming the wire within the structure and heating the structure to harden the wire by precipitation.
26. 26. The process according to claim 25, characterized in that the wire before dot weaving is one quarter hard.
27. 27. The process according to claim 25 or 26, characterized in that the woven structure is formed by the knitting of the wire.
28. 28. The process according to claim 27, characterized in that the structure is formed by the fabric of stitches per frame.
29. 29. The process according to claim 27, characterized in that the structure is formed by the knitting of warp stitches.
30. 30. The process according to any of claims 25-29, characterized in that the wire is of a precipitation-curable Ag Cu Ge alloy, containing at least 80% by weight of Ag.
31. 31. The process in accordance with the claim 30, characterized in that the alloy has an effective amount of boron as a grain refiner and up to 20 ppm.
32. 32. A woven structure, characterized in that it comprises silver alloy yarns having a grain structure refined by incorporation into the molten silver alloy from which the wire is formed of a decomposable boron compound.
33. 33. The structure according to claim 32, characterized in that the decomposable boron compound is sodium borohydride.
34. 34. The structure according to claim 32 or 33, characterized in that it is formed by knitting in a machine.