Circular process for manufacturing a steel wire intended for reinforcing rubber articles

Abstract

The invention relates to a method for manufacturing a steel wire for reinforcing rubber articles selected from vehicle tires, tracks and conveyor belts obtained from the recycling of metal wires from pneumatic tires.

Description

Title of the invention: Circular process for manufacturing a steel wire for reinforcing rubber articles Technical field of the invention

[0001] The present invention relates to the field of manufacturing processes for steel wires intended for the reinforcement of rubber articles such as pneumatic or non-pneumatic tires, tracks and conveyor belts, in particular to the field of manufacturing processes for steel wires from feedstocks comprising recycled steels from pneumatic tires, giving these processes a so-called "circular" character because they come from the pneumatic and go back to the pneumatic. Previous art

[0002] The steels used to manufacture wires for reinforcing rubber articles such as pneumatic or non-pneumatic tires, tracks, and conveyor belts have very tight tolerances in chemical composition, firstly to allow for severe forming by wire drawing and secondly to ensure sufficient mechanical strength to perform their reinforcing function. Therefore, the residual elements present in the chemical composition must be as low as possible.

[0003] Steel is produced by two main processes, known as the "blast furnace process" and the "electric process".

[0004] The blast furnace process produces very high-quality steel. The raw material used comes from ore, guaranteeing very low residual element content in the steel produced. However, this process generates a significant environmental impact, particularly in terms of CO2 emissions. Partial replacement of the ore with recycled steel (or "scrap") is possible and reduces the environmental impact. However, the constraints of the process are such that the maximum quantity of scrap metal allowed by this process is limited to 30%. These constraints limit the reductions that can be achieved in terms of the environmental footprint of steel produced by the blast furnace process when this steel must meet the requirements for use as reinforcement in rubber products.

[0005] To increase the proportion of recycled steel, and thus further reduce the environmental footprint of the steel produced, steel can be produced using the so-called "electric" process. This process allows for the recycling of a larger proportion of scrap metal, and can even accept a load consisting of 100% scrap metal. However, Increasing the recycling rate also increases the level of residual elements in the steel produced, such as copper, nickel, molybdenum, and chromium. To limit the concentrations of these elements and achieve the desired properties, scrap metal substitutes can be used, such as pre-reduced iron ores ("Direct Reduced Iron" or DRI), which are derived from ore and have low residual element content. The use of these scrap metal substitutes helps guarantee the quality of the steel produced, particularly its wire drawing properties, but limits the environmental benefits of steel produced by the electric arc furnace process, notably by limiting the recycled steel content.

[0006] End-of-life pneumatic tires are composite objects comprising textile fibers, metal wires, and rubber compounds, which makes their recycling particularly complex. After cutting and / or grinding, the textile, metal, and rubber can be separated. The rubber can then, for example, be pyrolyzed to produce chemical compounds that can be reintroduced into the manufacturing cycle of new pneumatic tires.

[0007] Metal wires can be recycled in the steel industry. However, recycling these steels to produce new pneumatic-grade steels, for the purposes of a so-called "circular" economy, faces numerous difficulties. Indeed, the wires resulting from the separation stages, particularly grinding, are very short and therefore volatile and difficult to handle. Furthermore, these metal wires are surface-coated with a brass, bronze, or zinc alloy to improve their adhesion to rubber, which raises issues regarding the management of residual materials in steelmaking processes when these steels are intended for reinforcing rubber articles. Moreover, these wires contain significant proportions of rubber. Due to their flammability, these rubbers can cause problems during the steel melting process.Furthermore, tire rubbers, particularly those in contact with metallic reinforcement elements, contain high levels of sulfur. However, the specifications required for steel intended for reinforcing rubber articles limit the range of solutions available for managing residual sulfur content in castings, especially to guarantee the wire-drawing properties of the steels produced.

[0008] Continuing its research, the applicant discovered a process for recycling steel wires from rubber articles for the manufacture of pneumatic grade steel. Definitions

[0009] The compounds mentioned in the description may be of fossil origin or bio-based. In the latter case, they may be partially or totally derived from biomass or obtained from renewable raw materials derived from biomass. This includes, in particular, polymers, plasticizers, fillers, etc.

[0010] In the present invention, unless expressly stated otherwise, all percentages (%) indicated are percentages (%) by mass.

[0011] On the other hand, any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​going from more than a to less than b (that is to say, bounds a and b excluded) while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​going from a to b (that is to say, including the strict bounds a and b).

[0012] The term "wire" refers to an object having a very large length relative to its cross-section, this cross-section being observed in a plane perpendicular to the longest length of the wire. The cross-section of the wire may be circular, oval, or polygonal, for example, square or rectangular, the corners of which may be rounded in the case of a polygonal shape. The shape of the wire cross-section is imparted during the diameter reduction steps by diameter reduction means, these means being, for example, dies or rolling devices. Preferably, the wire cross-section is circular, oval, or rectangular. The term "wire diameter" refers to the longest length of the wire cross-section. Detailed description of the invention

[0013] The invention relates to a method for manufacturing a steel wire for reinforcing rubber articles selected from vehicle tires, tracks and conveyor belts comprising at least:

[0014] a) A step of grinding pneumatic tires and separating metallic fibers so as to obtain metallic fibers comprising at most 15% by weight of non-metallic elements;

[0015] b) A refining step of the metallic fibers obtained during step a) by grinding and separation so as to obtain metallic fibers comprising at most 4% by weight of non-metallic elements;

[0016] c) A compaction step of the metal fibers obtained during step b) so as to obtain briquettes with a density of at least 1.5;

[0017] d) A manufacturing step of a steel wire called "wire rod" of a diameter d ranging from 4.5 to 6.5 mm from a steel charge comprising at least 1% by weight of briquettes obtained during step c).

[0018] Preferably, in the grinding stage, the pneumatic tires are cut into strips with a maximum dimension of 20 cm, preferably 10 cm.

[0019] Preferably, the steel charge feeding the wire rod manufacturing stage also includes at least one scrap metal selected from categories E2, E8, E8E, E6 and E653 defined in standard NF A 08-821.

[0020] Preferably, the briquettes obtained at the end of step c) have a density of at least 2.0, preferably at least 2.5 and preferably at least 2.8.

[0021] Preferably, the steel wire from step d) has the following composition, expressed as a percentage by weight of steel:

[0022] • Carbon: from 0.05% to 1.1%,

[0023] • Manganese: from 0% to 0.7%,

[0024] • Silicon: from 0% to 1%,

[0025] • Chrome: from 0% to 1%,

[0026] • Nitrogen: from 0 ppm to 120 ppm,

[0027] The contents of elements S, P, Mo, Al being each less than 0.02%, the contents of Ni, Cr, Cu being each less than 0.1%, the remainder of the composition of the steel being iron and unavoidable impurities.

[0028] Preferably, the wire rod manufacturing step includes a steelmaking operation in an electric furnace.

[0029] Preferably, the process according to the invention comprises, subsequent to step d), a step e) of reducing the diameter of the wire rod from a diameter d to a diameter dl.

[0030] Preferably, the diameter dl ranges from 0.6 to 3.0 mm.

[0031] Preferably, the process according to the invention comprises, later in step e), a step of forming, on the surface of the wire of diameter dl, a metallic coating chosen from the group formed by copper, zinc, nickel, cobalt, tin, iron, aluminum, manganese, an alloy of two of these metals and an alloy of three of these metals, preferably chosen from the group formed by an alloy of copper and zinc, an alloy of copper and tin, and a ternary alloy formed by copper, zinc, and a metal chosen from nickel, cobalt, tin and iron.

[0032] Preferably, the process according to the invention further comprises a step of drawing the metal wire from diameter dl to a diameter d2.

[0033] Preferably, the diameter d2 ranges from 0.06 to 0.4 mm.

[0034] The invention also relates to a reinforcement rod for bandages vehicle design comprising a metallic wire obtained by the process according to the invention.

[0035] The invention also relates to a cable for reinforcing rubber articles selected from vehicle tires, tracks and conveyor belts comprising an assembly of metal wires obtained by the process according to the invention.

[0036] The invention also relates to the use of the metal wire obtained by the process according to the invention in a rubber article selected from bandages pneumatic tires, non-pneumatic tires, tracks and conveyor belts. Step a) Grinding and separation

[0037] The process according to the invention includes a step a) of grinding pneumatic tires and separating the metallic fibers so as to obtain metallic fibers comprising at most 15% by weight of non-metallic elements.

[0038] The processes for grinding and dehulling pneumatic tires are known to those skilled in the art and are currently being implemented to be able to separate at least roughly a part of the rubber, a part of the textile and a part of the metal.

[0039] The grinding step includes a series of cutting operations allowing the pneumatic band to be reduced to centimeter-sized, or even subcentimeter-sized, chips, thus freeing the metallic part of the band which can be separated by means of, for example, electromagnets.

[0040] For example, pneumatic tires are cut, in a first coarse grinding stage, into strips ranging from a few centimeters to a few tens of centimeters, typically around 15 to 20 cm, preferably ranging from 4 to 10 cm.

[0041] Thus, in the grinding stage, the pneumatic tires are preferably cut into strips with a maximum dimension of 20 cm, preferably 10 cm.

[0042] These strips are then cut into centimeter-sized chips so as to release the metal fibers which can be separated for example by means of electromagnets.

[0043] At the end of these steps, the metallic fibers comprise at most 15% by weight of non-metallic elements. By non-metallic elements, we mean rubbers and textile fibers. Step b) of refining the metallic fibers

[0044] The process according to the invention includes a step b) of refining the metallic fibers obtained during step a) by grinding and separation so as to obtain metallic fibers comprising at most 4% by weight of non-metallic elements.

[0045] The refining step can be carried out by grinding and / or stirring the metallic fibers so as to separate the non-metallic elements from the metallic fibers, then by separating, for example by means of electromagnets, the refined metallic fibers.

[0046] The refining step is adjusted so as to obtain metallic fibers comprising at most 4% by weight of non-metallic elements, in particular at most 4% by weight of gum.

[0047] This content of non-metallic elements helps to minimize the risks of combustion and fume emissions during subsequent foundry stages, while limiting the input of residuals from gums such as sulfur, the management of which is delicate when the steel is intended for the reinforcement of rubber articles chosen from vehicle tires, tracks and conveyor belts. Step c) of compacting the metallic fibers

[0048] The process according to the invention includes a step c) of compacting the metal fibers obtained during step b) so as to obtain briquettes of a density of at least 1.5.

[0049] The metal fibers obtained at the end of step b) exhibit a wide range of lengths, from a few millimeters to a few centimeters. Compacting these fibers into briquettes significantly reduces fiber volatility and thus minimizes filter clogging during subsequent melting operations. Furthermore, these denser briquettes limit the flotation of the lighter fibers on the surface of the melting baths, thereby improving the mixing of the briquettes with other scrap metal during melting, while also limiting fiber oxidation on the surface of the bath.

[0050] Preferably, the briquettes obtained at the end of step c) have a density of at least 2.0, preferably at least 2.5 and preferably at least 2.8. These densities make it possible to limit the aforementioned phenomena even more.

[0051] Step d) of manufacturing a steel wire called "wire rod"

[0052] The process according to the invention includes a step d) of manufacturing a steel wire called "wire rod" of a diameter d ranging from 4.5 to 6.5 mm from a steel charge comprising at least 1% by weight of briquettes obtained during step c).

[0053] The wire rod manufacturing step includes a melting step in which a steel charge is fed into a furnace where the charge is melted and processed in a manner known to those skilled in the art. The casting is then formed into a wire commonly referred to as "wire rod," as described, for example, in the article "Steel Drawing" in Techniques de l'Ingénieur, M 3 125, with a diameter ranging from 4.5 mm to 6.5 mm. This wire is then stored in the form of a bundle.

[0054] The steel charge comprises at least 1% by weight of briquettes obtained in step c). The steel charge may also comprise scrap metal, iron ore, and metallurgical coke. Preferably, the steel charge comprises at least 2% by weight of briquettes obtained in step c), preferably

[0055] Preferably, the steel feedstock for the wire rod manufacturing stage also includes at least one scrap piece selected from scrap metal described as "new, low-residual, and uncoated" in accordance with standard NF A 08-821, Table 2, namely among the categories E2, E8, E8E, E6 and E653. In particular, a selection of these scraps is made to use only those with very low residuals (Cu, Sn, Cr, Ni, Mo).

[0056] According to a preferred embodiment, the steel at the base of the steel wire obtained by the process according to the invention has, as a percentage by weight of steel, the following composition: • Carbon: from 0.05% to 1.1%, • Manganese: from 0% to 0.7%, • Silicon: from 0% to 1%, • Chrome: from 0% to 1%, • Nitrogen: from 0 ppm to 120 ppm,

[0057] The contents of elements S, P, Mo, Al being each less than 0.02%, the contents of Ni, Cr, Cu being each less than 0.1%, the remainder of the composition of the steel being iron and unavoidable impurities.

[0058] Preferably, this steel is produced by the so-called "electric steelmaking" process using an electric furnace. This process is well known to those skilled in the art and described, for example, in the article "The manufacture and naming of steels" in Techniques de l'Ingénieur, TBA1040. Step e) of reducing the diameter of the wire rod

[0059] Preferably, the process according to the invention comprises, subsequent to step d), a step e) of reducing the diameter of the wire rod from a diameter d to a diameter dl.

[0060] This step can be carried out according to any method known to a person skilled in the art. For example, this step can be carried out by rolling, by passing the metal wire through a succession of pairs of rollers, each pair being oriented at an angle to the previous pair, for example oriented perpendicularly.

[0061] In a preferred arrangement, this step is carried out by wire drawing. This wire drawing step, well known to those skilled in the art, is often referred to as "dry wire drawing". It typically comprises several operations.

[0062] In a first uncoiling operation, the wire rod with an initial diameter d ranging from 4.5 to 6.5 mm is uncoiled. This wire has a maximum tensile strength between 300 MPa and 1300 MPa. The wire is stored in a bundle on a reel from which it is uncoiled using automated uncoiling means, for example, an uncoiler. The microstructure of the steel is then ferritic-pearlitic.

[0063] Then, in a descaling operation of the wire rod, the wire rod is passed through several successive pulleys and through two straighteners, each formed by several pulleys, the pulleys of each straightener being mounted to rotate about an axis perpendicular to the axis of rotation of the pulleys of the other straightener. This removes a layer of iron oxides, called scale, present on the surface of the wire rod.

[0064] Next, the wire rod is coated with a layer of wire drawing lubricant before starting the actual wire drawing, in n wire drawing operations, n being able for example to vary from 6 to 12.

[0065] The n wire drawing operations are intended to reduce the diameter of the metal wire from the initial diameter d to an intermediate diameter dl.

[0066] Wire drawing operations preferably form an uninterrupted series of dry wire drawing operations from the initial diameter d to the intermediate diameter dl. Each wire drawing operation is a dry wire drawing operation in which the wire is passed through a die with a diameter smaller than the wire diameter upstream of the die. Thus, the wire has a diameter downstream of the die smaller than the diameter upstream of the die. The diameter of each die is smaller than the diameter of the die located upstream. For the uninterrupted series of dry wire drawing steps from the initial diameter d to the intermediate diameter dl, the rational strain e = 2In(d / dl) is defined.

[0067] Wire-pulling means positioned downstream of each die, for example capstans, make it possible to exert sufficient pulling force to draw the wire through each die. A wire-drawing lubricant in powder form is used.

[0068] Dry wire drawing refers to the wire flowing through a gaseous medium, such as ambient air. The wire drawing lubricant used in dry wire drawing is in powder form. During dry wire drawing, the traction devices, such as capstans, are exposed to the gaseous medium, such as ambient air.

[0069] An uninterrupted series of wire drawing steps means that the wire undergoes a series of successive passes through several wire drawing dies, each pass through each wire drawing die corresponding to a wire drawing operation. Apart from the last pass, each pass through a die is directly followed by a pass through the next die. In an uninterrupted series of wire drawing operations, the wire undergoes no other operation, in particular heat treatment or coating, than a wire drawing operation. In other words, the wire undergoes no operation, in particular heat treatment or coating, between two directly successive wire drawing operations in the series.

[0070] After dry wire drawing, the wire may optionally be wound onto a reel during a winding operation, prior to its possible processing in subsequent diameter reduction, coating, or shaping steps. Winding can be used to temporarily store the wire or to transport it to the location where the other steps are carried out. The wire is then subsequently unwound in a winding operation. unwinding before feeding into the next possible step of the process.

[0071] Preferably, the diameter dl ranges from 0.6 to 3.0 mm. By "diameter", we mean the largest dimension in which the cross-section of the metal wire is inscribed, i.e. the diameter of the circle circumscribed about the cross-section of the wire.

[0072] The metal wire of diameter dl preferably has a tensile strength Rm, measured according to ASTM D2969-04, of at least 600 MPa, preferably at least 1000 MPa. Preferably, the metal wire of diameter dl has a tensile strength Rm of at least 1500 MPa for a diameter of 2.0 mm.

[0073] Preferably, the metal wire of diameter dl has a twist value of at least 20 turns, this value being measured according to ASTM E 558-83.

[0074] Preferably, following the reduction step to a diameter dl, the metal wire is subjected to a heat treatment operation. If a winding operation is carried out after the dry drawing operations, the heat treatment operation is carried out after the unwinding operation.

[0075] The heat treatment operation modifies the metallographic structure of the wire of diameter dl to regenerate the wire rod structure. Those skilled in the art know how to determine the various parameters of this step, for example, in "The Basic Principles of Heat Treatment of Steels," André Constant and Guy Henry, ISBN 2-85330-083-8.

[0076] During this operation, the metal wire of diameter dl is heated to a temperature greater than or equal to the austenitizing temperature of the steel, here greater than or equal to 850°C. Depending on the chemical composition of the steel, those skilled in the art know, notably as described in "Précis de métallurgie", ISBN 2-12-260121-6, what austenitizing temperature must be reached. Thus, if the austenitizing is insufficient, unrecrystallized bands remain, and the resulting austenite is not homogeneous, which hinders subsequent wire drawing. If the austenitizing is too extensive, the microstructure obtained upon subsequent cooling is an acicular ferrite (known as Windmanstätten ferrite) for low-carbon steel or a bainte-martensitic ferrite for high-carbon steel, and not a ferritic-pearlitic structure.

[0077] The metal wire of diameter dl is then cooled to impart a pearlitic or ferritic-pearlitic microstructure to the steel. As is well known to those skilled in the art, the metal wire is cooled to prevent the formation of any microstructure other than a pearlitic, ferritic, or ferritic-pearlitic structure. Too rapid a cooling rate would lead to an acicular ferritic, bainitic, or martensitic microstructure. Those skilled in the art know how to determine the cooling rate based on the chemical composition of the steel and the austenitizing temperature using charts available, in particular, in the document "Atlas of Curves of "Transformation of French-made steels", IRDIS, 1974. Stage of formation of a metallic coating

[0078] Preferably, the process according to the invention comprises, later in step e), a step of forming, on the surface of the wire of diameter dl, a metallic coating chosen from the group formed by copper, zinc, nickel, cobalt, tin, iron, aluminum, manganese, an alloy of two of these metals and an alloy of three of these metals, preferably chosen from the group formed by an alloy of copper and zinc, an alloy of copper and tin, and a ternary alloy formed by copper, zinc, and a metal chosen from nickel, cobalt, tin and iron.

[0079] This step is well known to those skilled in the art and can be carried out, for example and when the coating is brass, by successive operations of depositing copper, depositing zinc, and then thermal diffusion.

[0080] Wire drawing step of the metal wire to a diameter d2

[0081] Preferably, the process according to the invention further comprises a step of drawing the metal wire from diameter dl to a diameter d2.

[0082] The wire drawing step to a diameter d2 is carried out by passing the wire successively through several dies with progressively decreasing diameters. The number of dies, and consequently the number of successive diameter reductions, depends on the ductility of the wire and the diameter d2 to be achieved. The smaller the diameter d2, the greater the number of dies that can be used.

[0083] Wire-pulling means positioned downstream of each die, for example, multi-stage capstans, make it possible to exert sufficient pulling force to draw the wire through each die. The pulling means and the dies are immersed in a liquid bath of wire-drawing lubricant, for example as described in document WO 2008 / 113481.

[0084] Wet wire drawing refers to the wire flowing through a liquid medium, for example, an aqueous solution. Preferably, the wire drawing lubricant used in wet wire drawing is in liquid form. During wet wire drawing, the traction means, for example, capstans, are exposed to the liquid medium, for example, the aqueous solution.

[0085] Thus, the metal wire undergoes 1 to m wire drawing operations (m varying for example from 8 to 23) allowing the diameter of the metal wire to be reduced from a diameter dl to the diameter d2 as well as increasing the maximum breaking stress of the metal wire.

[0086] Preferably, the diameter d2 ranges from 0.06 to 0.4 mm.

[0087] Preferably, the wire drawing operations form an uninterrupted series of wet wire drawing operations from the wire diameter d1 to the diameter d2. Each operation 1 to m is a wet wire drawing operation in which The wire is passed through a die with a diameter smaller than the wire diameter upstream of the die. Thus, the wire has a diameter downstream of the die smaller than the diameter upstream of the die. The diameter of each downstream die is smaller than the diameter of the die located upstream. For the uninterrupted series of wire drawing operations in a wet environment, drawing the wire from diameter dl to diameter d2, the rational deformation is defined as e' = 2.In(dl / d2).

[0088] By uninterrupted series of wire drawing operations, it is understood that the wire makes a series of successive passes through several wire drawing dies, each pass through each wire drawing die corresponding to a wire drawing operation. Apart from the last pass, each pass through a die is directly followed by a pass through the next die. In an uninterrupted series of wire drawing operations, the wire does not undergo any operation, in particular heat treatment or coating, other than a wire drawing operation. In other words, the wire does not undergo any operation, in particular heat treatment or coating, between two directly successive wire drawing operations in the series. Rod

[0089] The metal wire obtained by the process according to the invention can be shaped into a rod. The invention therefore also relates to a reinforcement rod for tires intended for vehicles, comprising a metal wire obtained by the process according to the invention with a diameter dl.

[0090] The rod can be any type of rod used in vehicle tires, for example a so-called braided rod, a package type rod or a conical rectangular wire rod.

[0091] A bundled curtain rod is a rod comprising several windings of at least one metal wire of diameter dl, optionally coated with a metallic coating, for example galvanized, arranged axially next to each other in several layers radially superimposed on each other. The metal wire of diameter dl may have a round, square, or rectangular cross-section.

[0092] A braided rod is a rod comprising several windings of at least one metal wire of diameter dl, possibly coated with a metallic coating, for example galvanized, the wire being wound helically around a central wire, called the core wire, in one or more layers.

[0093] A conical rectangular wire rod, an example of which is illustrated [Fig. 1], is an annular structure of revolution whose axis of revolution coincides with that of the vehicle tire, comprising several windings of at least one rectangular cross-section metal wire (1), for example with a cross-section of 2 mm by 1.3 mm, optionally coated with a metallic coating, for example galvanized, these windings being arranged side by side in a direction (2) forming a small angle per relative to the axial direction (3), for example, 6 windings arranged side by side in a direction forming an angle of 15° with the axial direction, the longest length of the rectangular cross-section wire being aligned with this direction, in several layers radially superimposed on one another, for example, 6 layers (6x6 rod), or for example, 8 windings arranged side by side in a direction forming an angle of 15° with the axial direction, the longest length of the rectangular cross-section wire being aligned with this direction, in several layers radially superimposed on one another, for example, 5 layers (8x5 rod). Such a rod is obtained by winding the wire around a form that gives the rod a conical shape. Reinforcement cable

[0094] A pneumatic tire generally comprises a crown including a crown reinforcement surmounted by a tread, two sidewalls extending radially inward from the crown, two radially internal beads within the sidewalls and each comprising an annular reinforcing structure, and a carcass layer anchored in the beads, extending through the sidewalls and the crown. The annular reinforcing structure includes a substantially rotating bead about an axis. The crown reinforcement, the bead, and the carcass layer may contain steel reinforcements comprising a wire according to the invention.

[0095] Thus, the yarn obtained by the process according to the invention is intended for reinforcing rubber articles selected from pneumatic tires, non-pneumatic tires, tracks, and conveyor belts. For these uses, such yarn can be used as is, or as an assembly of several yarns. The assembly can be carried out by any method known to those skilled in the art, such as cabling, twisting, winding, or other.

[0096] The metal wire according to the invention, particularly when drawn to a diameter d2, can be formed into an assembly of metal wires in the form of cables used for reinforcing rubber articles, for example in the crown reinforcements or carcass plies of vehicle tires. Among these assemblies, one can mention classically used assemblies of wires of diameter d2, such as the so-called "2.30" assemblies consisting of the assembly by helical winding of two wires of 30 hundredths of a millimeter in diameter or the so-called "9.28" assemblies consisting of a cable comprising a first layer of 2 wires wound helically around each other, and a layer of 7 wires wound helically around the first layer with wires of diameter 0.28 mm or the so-called "19.18" consisting of a cable comprising a core wire, a first layer of 6 wires of diameter 0.18 mm wound helically around the core wire and a layer of 12 wires of diameter 0.18 mm wound helically around the first layer or called "6.35. Elastic » consisting of a cable comprising three strands, one strand being made up of 2 0.35 wires wound helically around each other, the three strands also being wound helically so as to form the cable. Use of metal wire

[0097] The invention also relates to the use of the metal wire obtained by the process according to the invention in a rubber article selected from pneumatic tires, non-pneumatic tires, tracks and conveyor belts. Examples

[0098] End-of-life tires are cut into chips approximately ten centimeters long. These chips are then further ground into a powder with a size on the order of one centimeter. The metal fibers are separated using magnetic means. In this way, more than 95% by weight of the metallic elements present in the end-of-life tires is recovered.

[0099] These metallic fibers, which contain 10 to 20% by weight of gum, here 15% by weight, feed a refining stage in which the fibers are filtered and separated by magnetic means, the elements of too large a size, on the order of a centimeter, being ground again in order to separate the non-metallic part from the metallic part.

[0100] At the end of this step, metallic fibers are obtained comprising at most 4% by weight of non-metallic elements, here 3% by weight of rubber, whose density is approximately 1.

[0101] The metal fibers are then compacted into cylindrical briquettes with a density of approximately 3, 20 cm in diameter and 20 cm in length. These dimensions result in briquettes that are easy to handle and compact, meaning they do not crumble during handling. Furthermore, these dimensions ensure proper melting in the steelmaking process.

[0102] A wire rod, which is a circular cross-section steel wire with a diameter ranging from 4.5 to 6.5 mm, here 5.5 mm, is manufactured from a casting from an electric furnace. Two wire rods are thus produced. One wire, called "3% Wire", from a steel charge comprising 3% by mass of briquettes and 59% by mass of recycled scrap metal chosen from categories E2, E8, E8E, E6 and E653 defined in standard NF A 08-821, and a second, called "test wire", produced in the usual way from a steel charge comprising 37% by mass of recycled scrap metal chosen from categories E2, E8, E8E, E6 and E653 defined in standard NF A 08-821, the remainder being pig iron from ore.

[0103] The briquettes remain compact until they are loaded into the kiln. Very few metallic fibers are detected in the filters. The non-volatility of the fibers The presence of rubber from end-of-life tires is thus observed. Furthermore, due to the low rubber content of the briquettes, no fumes from the rubber are observed.

[0104] The steels obtained have the following compositions (in % by weight):

[0105] [Tables 1] ELEMENTS (% by weight) Wire 3% Control Wire Carbon 0.7 0.7 Manganese 0.6 0.5 Silicon 0.2 0.2 Nitrogen 50 ppm 45 ppm Chromium <0.02 <0.02 Sulfur <0.01 <0.01 Phosphorus <0.01 <0.01 Nickel <0.1 <0.1 Copper <0.1 <0.1 Molybdenum <0.01 <0.01 Aluminum <0.01 <0.01 Tin <0.01 <0.01 Iron Qsp.100 Qsp.100

[0106] From these wire rods, metal wires with a circular cross-section and a diameter of 2 mm are produced.

[0107] The 2 mm diameter wire is obtained by drawing in a dry environment a 5.5 mm diameter wire rod using 8 successive dies allowing a progressive reduction of the wire diameter. Measurement methods

[0108] For each of these wires, the mechanical strength Rm, its elongation at break At, and its torsional strength expressed as the number of turns before break are measured. These measurements are carried out in accordance with ASTM D4975-14. They are performed on an unaged sample in accordance with the instructions given in the standard.

[0109] The results are presented on a base of 100 based on the control. A value greater than 100 means a value greater than that of the control.

[0110] A rotary bending test is also performed in a dry atmosphere. This test makes it possible to measure the maximum endurance stress in rotary bending in a dry environment. (oD) of each wire tested.

[0111] The rotating bending test ("Hunter fatigue test") is a known fatigue test; it was described in US-A-2,435,772 patent and used, for example, in EP-A-220,766 patent application to test the fatigue-corrosion resistance of metal wires intended for reinforcing tire casings.

[0112] The principle of the test is as follows: a sample of the wire to be tested, of a determined length, is held at each of its two ends by two parallel jaws. In one of the jaws, the wire can rotate freely while it remains fixed in the second jaw, which is motorized. Bending the wire allows a given bending stress to be applied, the intensity of which varies with the imposed radius of curvature, itself a function of the useful sample length (for example, from 70 to 250 mm) and the distance between the two jaws (for example, from 30 to 115 mm).

[0113] To test the endurance of the wire thus pre-stressed, it is then subjected, by actuating the motorized jaw, to a large number of rotation cycles around its own axis, so as to stress each point of the circumference of its cross-section alternately in extension and in compression (+ o ; - o).

[0114] In practice, the test is conducted as follows: a first stress θ is chosen, and the fatigue test is run for a maximum of 10⁵ cycles at 3000 rotations per minute. Depending on the result obtained—i.e., breakage or non-breakage of the cable after these 10⁵ cycles—a new stress θ (lower or higher than the previous one, respectively) is applied to a new specimen, varying this stress θ according to the so-called staircase method (Dixon & Mood; Journal of the American Statistical Association, 43, 1948, 109–126). A total of 17 iterations are performed. The statistical analysis of the tests, as defined by this staircase method, leads to the determination of an endurance limit—denoted Δd—which corresponds to a 50% probability of wire breakage after the 10⁵ fatigue cycles.

[0115] This test uses a Bekaert rotary bending machine, model type RBT, equipped with an electrical break detector. Here, cable breakage is defined as the breakage of at least one strand of the cable.

[0116] The formula for calculating the stress o is as follows:

[0117] o=l,198E <p / C

[0118] E being the Young's modulus of the material (in MPa), q> being the diameter of the broken wire (in mm), and C being the distance (in mm) between the two jaws (C = Lo / 2.19; with Lo: useful length of the sample).

[0119] The results are expressed according to the ratio oD / Rm, with Rm being the breaking strength determined as specified above.

[0120] These values ​​are determined on unaged wire as specified in the ASTM standard D4975-14. These values ​​are expressed in MPa / MPa. Results of wire tests

[0121] The results are presented in the table below.

[0122] [Tables2] Wire 2.00 mm Base 100 Control Wire 3% Rm 100 98 At 100 122 Twist 100 100 Rotational bending oD / Rm 0.31 0.36

[0123] It is observed that the metal wire obtained by means of the process according to the invention has characteristics entirely similar to the control wire, with in particular comparable torsion values.

Claims

Claims

1. A method of manufacturing a steel wire intended for reinforcing rubber articles chosen from vehicle tires, caterpillars and conveyor belts comprising at least: a. A step of grinding tires and separating the metal fibers so as to obtain metal fibers comprising at most 15% by weight of non-metallic elements; b. A step of refining the metal fibers obtained during step a) by grinding and separating so as to obtain metal fibers comprising at most 4% by weight of non-metallic elements; c. A step of compacting the metal fibers obtained during step b) so as to obtain briquettes with a density at least equal to 1.5; d. A step of manufacturing a steel wire called "rod wire" with a diameter d ranging from 4.5 to 6.5 mm from a steel charge comprising at least 1% by weight of briquettes obtained during step c).

2. Method according to the preceding claim in which, in the grinding step, the pneumatic tires are cut into strips whose maximum dimension is 20 cm, preferably 10 cm.

3. Method according to any one of the preceding claims in which the steel load feeding the wire rod manufacturing step also comprises at least one scrap metal chosen from categories E2, E8, E8E, E6 and E653 defined in standard NF A 08-821.

4. Method according to any one of the preceding claims in which the briquettes obtained at the end of step c) have a density at least equal to 2.0, preferably at least equal to 2.5 and more preferably at least equal to 2.

8.

5. Method according to any one of the preceding claims in which the steel wire resulting from step d) has, in % by weight of steel, the following composition: • Carbon: from 0.05% to 1.1%, • Manganese: from 0% to 0.7%, • Silicon: from 0% to 1%, • Chromium: from 0% to 1%, • Nitrogen: from 0 ppm to 120 ppm, The contents of elements S, P, Mo, Al being each less than 0.02%, the contents of Ni, Cr, Cu being each less than 0.1%, the rest of the composition of the steel being iron and unavoidable impurities.

6. Method according to the preceding claim in which the step of manufacturing the wire rod comprises an operation of manufacturing the steel in an electric furnace.

7. Method according to any one of the preceding claims comprising, after step d), a step e) of reducing the diameter of the wire rod from a diameter d to a diameter dl.

8. Method according to the preceding claim in which the diameter dl ranges from 0.6 to 3.0 mm.

9. Method according to any one of claims 7 to 8 comprising, subsequently to step e), a step of forming, on the surface of the wire of diameter dl, a metallic coating chosen from the group formed by copper, zinc, nickel, cobalt, tin, iron, aluminum, manganese, an alloy of two of these metals and an alloy of three of these metals, preferentially chosen from the group formed by an alloy of copper and zinc, an alloy of copper and tin, and a ternary alloy formed by copper, zinc, and a metal chosen from nickel, cobalt, tin and iron.

10. A method according to any one of claims 7 to 9 further comprising a step of drawing the metal wire from diameter d1 to diameter d2.

11. Method according to the preceding claim in which the diameter d2 ranges from 0.06 to 0.4 mm.

12. Reinforcing rod for a tire intended for vehicles comprising a metal wire obtained by the method according to any one of claims 7 to 9.

13. Cable for reinforcing rubber articles chosen from vehicle tires, caterpillars and conveyor belts comprising an assembly of metal wires obtained by the method according to any one of claims 10 to 11.

14. Use of the metal wire obtained by the process according to one of any of claims 7 to 11 in a rubber article selected from pneumatic tires, non-pneumatic tires, tracks and conveyor belts.

Images