MXPA97002586A - Stainless steel wire to reinforce the corona of the neumat covers - Google Patents

Abstract

The present invention relates to a stainless steel wire to reinforce the crown of tires, this wire is characterized by the following features: a) its diameter is at least 0.05mm and at most 0.6mm, b) its resistance to traction is at least 2400MPa c) its ductility in torsion is at least equal to 30 turns capable of resisting by a length of wire equal to 500 times its diameter, applying a tension equal to 5 percent of an amount that would have broken before applying the torsion, d) the wire steel comprises at least 0.02% and at most 0.2% carbon, at least 6% and maximum 10% nickel, at least 16% and maximum 20% chromium, the molybdenum content of the steel is zero or at most equal to 5%, the total nickel, chromium and molybdenum is at least 23% and maximum 28.5%, all these percentages are% by weight e) the structure of the steel comprises at least 50% by volume of martensite and is Ustenite or comprises less than 50% by volume of the same

Description

STAINLESS STEEL WIRE FOR REINFORCING THE CROWN OF THE TIRE COVERS DESCRIPTION OF THE INVENTION The present invention relates to tires reinforced with metallic threads. The invention relates, in particular, to tires reinforced with stainless steel wires. The patent application FR-A-2 096 405 very generally describes a tire that comprises a reinforcement layer disposed between the layers of the carcass and the rubber tread, the radially outer surface of this layer being reinforced. by stainless steel cables. The wires described for the realization of these cables have insufcient mechanical properties. The object of the present invention is a stainless steel wire to reinforce the crown of the tires, this wire being characterized by the following points: a) its diameter is at least equal to 0.05 mm and at most equal to 0.6 mm; b) its tensile strength is at least 2,400 MPa; c) its torsional ductility is at least 30 turns; REF: 24432 d) the wire steel comprises at least 0.02 * and at most 0.2 * carbon, at least 6 * and at most 10 * nickel, at least 16 * and at most 20 * chrome, being zero or as much equal to 5 * the content of molybdenum steel. the sum of nickel, chromium and molybdenum being at least equal to 23 * and at most equal to 28.5 *. all these values being * percentages by weight; e) the structure of the steel comprises at least 50 * by volume of martensite and is devoid of austenite or comprises less than 50 * of it in volume. The invention also relates to the assemblies intended to be used in the crowns of the tires, these assemblies comprising at least one thread according to the invention. The invention also relates to reinforcing fabrics for tire crowns. said fabrics comprising at least one yarn and / or an assembly according to the invention. The invention also relates to tires whose crowns comprise at least one thread and / or an assembly and / or a reinforcing fabric according to the invention. The invention also relates to a process for preparing the yarn according to the invention, this process being characterized by the following points: a) it is based on a stainless steel wire whose diameter is at least equal to 0.3 mm and at most equal to 3 mm; the steel of the wire comprises at least 0.02 * and at most 0.2 * carbon, at least 6 * and at most 10 * nickel, at least 16 * and at most 20 * chromium, being zero or as much as a 5 * the content of the molybdenum steel at least equal to 23 * and as much equal to a 28.5 *, all these values being * percentages by weight; the structure of this steel is completely austenitic or practically austenitic; b) at least one deformation treatment is carried out. without thermal treatment. the total deformation being at least equal to 1.5. The term "reinforcement" must be taken in a very general sense, whereby reinforcement fabrics may be, for example, fabrics which participate essentially mechanically in the reinforcement of the crown of the tires, particularly in the form of textile fabrics. triangulation, or in the form of protective fabrics arranged between the triangulation fabrics and the tread. I. Definitions and tests 1. Torque measurements The measurements of breaking strength, breaking strength, modulus and elongation after breaking are made in tension according to the AFNOR NF method A 03-151 of June 1978. 2. Deformation By definition, the deformation € is given by the formula: e - Ln (SQ / Sf) where Ln is the Neperian logarithm, SQ is the initial section of the thread before this deformation and S. the section of the thread after this deformation . 3. Torsional ductility By definition. The twisting ductility of a yarn is the number of torsion turns on itself that the yarn can withstand, this measurement is made in a thread length equal to 500 times the diameter. One end of this thread is held inside a fixed jaw, and the other end is held inside a rotating jaw that is rotated in such a way that the axis of rotation is the same as the axis of the thread, the tension being during this torque equal to 5 * of the tensile strength of the thread measured before twisting, and count the number of turns necessary to cause the thread to break. 4. Structure of the steels The identification and quantification of the structure of the steels are carried out in the following manner. An X-ray diffraction method is used. The method used is to determine the total diffracted intensity for each of the phases of the steel, in particular martensite a '. the martensite 6 and the gamma austenite, adding the integrated intensity of all the diffraction peaks of this phase, which allows to calculate the percentages of each of the phases in relation to the set of all the phases of the steel. The X-ray diffraction spectra are determined, in the section of the wire to be studied, with a goniometer, with the help of a chromium antichode. A sweep allows obtaining the characteristic lines of each of the present phases. In the case of the three phases mentioned above (the two martensites and the austenite), the sweep is 50 degrees to 160 degrees. To determine the integrated intensities of the peaks. it is necessary to unscrew the interfering stripes. For each peak of any phase, we have the following relationship: ^ nt "(Lmh x Imax) P with: I. - integrated intensity of peak L. - the width at half height of the peak (in degrees) I "," = the intensity of the peak (in beats per second) P = the measurement step of the peak (0.05 degrees) Are taken. for example. the following characteristic lines: austenite gamma ray (111) 20 - 66.8 line (200) 20 - 79.0 line (220) 20 - 128.7 line rayon (110) 20 - 68.8 line (200) 20 - 106 line (211) 20 - 156.1 martensita € stripe (100) 20 - 65.4 line (002) 20 - 71.1 line (101) 20 - 76.9 line (102) 20 - 105.3 line (110) 20 - 136.2 The angle 20 is the total angle in degrees between beam incident and the beam diffracted. The crystallographic structures of the preceding phases are the following: gamma austenite: cubic with centered faces martensite to 'centered cubic or quadratic centered martensite .6 hexagonal compact.

The volume percentage of any "i" phase can then be calculated by the following relationship: with I. "sum of the integrated intensities of all the peaks of this phase" i "I. - sum of the integrated intensities of all the peaks of all the diffraction phases of the steel Thus, we have in particular: martensite '' I / I * of martensite 6? e /? t * total of martensite ds, +? e) /? t * of gamma austenite Igamma / It. with: • a 'integrated intensity of all martensite peaks' - integrated intensity of all martensite peaks € gamita - integrated intensity of all peaks of gamma austenite. In what follows, the various * that refer to the phases of the steel structure are expressed in volume and the thermal "martensite" or "martensite phase" cover the whole of the phases martensite a 'and martensite 6. representing, therefore, , the term * of martensite * in volume of the total of these two martensitic phases. and the term "austßnita" represents austenite gamma. The * in volume of the various phases, determined by the preceding method, are obtained with a precision of approximately 5 *. II EXAMPLES The invention will be easily understood with the help of the following non-limiting examples and referring, if necessary, to the single figure of the drawing schematically representing, in radial section, a tire according to the invention. . In all these examples, the * that refer to the composition in elements of steels (for example, * *) of carbon, nickel, chromium and molybdenum) are * by weight, * which refer to the structure of steels (for example, the * in martensite and austenite phases) are * in volume, and the values of breaking strength, breaking strength, elongation after breaking and modulus are determined in tensile, in accordance with the Chapter I, section 1 that precedes. Thread according to the invention In the examples a wire according to the invention is used, whose composition is as follows: C - 0.092; Yes - 1.74; Mn - 1.31; Ni - 7.87; Cr - 17.75; Mo - 0.68; N - 0.034; Cu-0.20; S-0.001; P - 0.002. The rest is made up of iron with the usual unavoidable impurities. All the figures that refer to the composition of the steel are * by weight. This thread is prepared in the following manner. It is based on a steel wire whose composition is the same as that given above. This thread has a diameter of 0.9 mm. This thread is coated with a layer of nickel that has a thickness of approximately 0.3 μm and has the following mechanical characteristics: strength at break: 550 N breaking strength: 870 MPa elongation after breakage: 58 *. A copper deposit and then a deposit of zinc by electrolytic route at room temperature is made on this nickel-coated wire, and then it is thermally heated by Joule effect at 540 * C to obtain brass by diffusion of copper and zinc, being the weight ratio (phase) / (phase a + phase ß) approximately equal to 0.85, being phases a and 0 the phases of the brass. This wire is then drawn cold in a humid environment with a grease which is known in the form of an emulsion in water. The total deformation E of this drawing is 2.78. After the brass coating is obtained, no heat treatment is carried out on the yarn. The yarn obtained has a diameter of 0.224 mm. or approximately 0.23 mm, and the surrounding nickel and brass coating has a very small thickness. lower than the micrometer. what is negligible in relation to the diameter of the steel. The characteristics of the yarn according to the invention, thus obtained, are the following: strength at break: 110 N breaking strength: 2.805, MPa modulus: 190 GPa elongation after breakage: 1 * twisting ductility: 60 turns . Structure of the steel of this yarn according to the invention: ensitic sea phase practically equal to 85 * by volume, this phase being, in practice, only martensite a '. the austenite phase being practically 15 * in volume. Naturally, the composition of the yarn steel in its elements (for example, carbon, chromium, nickel, molybdenum) is the same as that of the starting yarn.

The nickel coating allows a good fixation of the brass coating on the steel, and the brass coating facilitates the deformation of the yarn, during its manufacture, as well as the bonding of the yarn with the rubber, during the use of the yarn inside the rubber. Example 1 The object of this example is to compare the mechanical characteristics of the yarn according to the invention with those of a known yarn. A known stainless steel of type is used 316. according to the application FR-A-2 096 405 before »cited. This steel has the following composition: C-0.029; Yes - 0.45; Mn - 0.66; Ni - 12.62; Cr-17.51; Mo - 2.40; the sum of nickel, chromium and molybdenum is. then, equal to 32.53; Cu - 0.24; S-0.003; P - 0.023. This known steel is in the form of a yarn of 0.8 bread which is coated in the same manner as that described above for the yarn according to the invention, but with deformations ranging from 0 to 4. It is found that the resistance to the thread break thus obtained increases with the value of € but that this is always small, being its maximum value, obtained for € * 3.8 (thread diameter obtained approximately 0.12 mm). less than 2,000 MPa, which is too small for use in tires, the module being then equal to 175 GPa. On the other hand, it is found that the torsional ductility of this known thread is always less than 30 turns. This value is too small to guarantee the realization of sets. The difference in properties between these two yarns can be explained by the fact that the known yarn does not comprise martensite. or comprises only a small portion of martensite. notably less than 50 * in volume of the steel structure, for example of the order of 5 * in volume, even with the high values of € used. Example 2 The object of this example is to compare the characteristics of an assembly according to the invention with those of a known assembly, all of these sets being sets of layers. Sets according to the invention are made of type (1 + 6) 23 unbonded. These identical sets are, each. a set of layers consisting of an untwisted thread that serves as the core around which six threads are wound in the same direction, with a pitch of 12.5 mm.

All threads of this set are identical to the yarn according to the invention described in example 1.

The force at breakage of this assembly is 735 N. Moreover, known assemblies of the same type as that of the assemblies according to the invention are realized, (1 + 6) 23 not strapped, but with the difference of than the threads, identical to each other. they are then known cold-drawn pearlitic steel wires. non-rusting, comprising a 0.7 * carbon, these wires having a diameter of approximately 0.23 mm, a breaking force of 115 N. a breaking strength of 2865 MPa, a modulus of 205 GPa. an elongation after breaking a 1 * and a twisting ductility of 180 turns. Each of these known assemblies has a breaking force equal to 766 N. Four identical tires of dimension 175/70 R 13 are produced. The single figure of the drawing schematically represents one of these covers 100 in radial section, ie in cutting by a plane passing through the axis of rotation of this cover, this axis of rotation not being represented in the figure, in order to simplify. This cover 100 comprises a crown 1. two sides 2 and two heels 3 each reinforced in a manner known per se by a rod 4. A known radial carcass 5, made of textile material (rayon), is disposed from one heel 3 to the other, wound around the rods 4. The line yy 'represents the equatorial plane, that is to say the plane perpendicular to the axis of rotation of the cover and passing through the central part of the crown 1. The crown 1 is reinforced by an armature 6 located on top of the carcass ply 5. between the carcass ply 5 and the tread 10. Armor 6 comprises two work fabrics indicated in Figure 61 and 62. the web 61 being closest to the carcass ply 5. and the fabric 62 being located on top of the fabric 61 and below the tread 10. The fabric 61 is constituted by known assemblies 610 of type (3 x 2) 23. Each of these sets, devoid of a band, is made up of three braided cables, each cable being made of twisted wire by two known threads, identical to the known thread described above for this example, twisted together with a pitch of 12.5 mm, the twisting of the threads having been carried out. twisted wire in the opposite direction to that of the wires of the other two braided wires, all these twisted wires being twisted together with a mounting pitch of 12.5 mm, the winding direction of the assembly being the same as the winding direction of the wires in the two braided cables, whose wires are wound in the same direction. These assemblies 610 are parallel to each other and form an angle of 20 degrees with the equatorial plane yy ', the pitch of this fabric being 1.4 mm, the pitch being the interval separating the axes of any two contiguous sets 610, this being measured interval and the aforementioned angle in the vicinity of the equatorial plane yy '. The fabric 62 comprises sets 620 parallel to each other. that they form with the equatorial plane yy 'the same angle (20 degrees) and that they have the same pitch (1.4) mm) as the sets 610, in the vicinity of the equatorial plane, but this angle is oriented in the opposite direction from that of the fabric 61. and thus, the crossed fabrics 61 and 62 are in a known manner. The assemblies 620 of the fabric 62 are those of the type (1 + 6) 23 cited above, or according to the invention, these assemblies then being designated by 620A. or not according to the invention, these sets known by 620B being then designated. The distribution in sets 620A and 620B is carried out according to four zones, two zones 62A comprising the assemblies 620A. and two zones 62B comprising the sets 620B. The length of each of these zones. measured according to the equatorial plane, it represents the fourth part of the circumference of the cloth 62, the four zones of equal dimensions being arranged alternately, that is, in the order: an area 62A. an area 62B. an area 62A, an area 62B. in the longitudinal direction, that is, following the intersection of the web 62 by the equatorial plane yy '. In all these zones the known gum covering the assemblies 620 is identical. By definition, the sub-hollow is the distance between the bottom of the tread pattern 10 and the virtual surface tangent to the top of the sets 620 of the fabric 62, this surface being schematized, which is located between the tread 10 and fabric 62, by line 62L in the drawing. This subhole is equal to 2.5 mm. For simplicity of the drawing, a single groove 11 of the pattern 110 of the tread band 10 is shown, the sub-holed being outlined by the distance between the bottom 12 of the groove 11 and the line 62L, and the references 62A. 62B, 620A and 620B are not indicated in the drawing. These four identical covers are mounted on a touring vehicle (Renault R21). with a load corresponding to the empty load of the vehicle plus four persons, the covers being inflated 100 to 2 bars, and the following test is carried out, without exchanging the covers. The vehicle is pre-rolled (preparatory taxi) for 1,500 km at 40 km / h on a track covered with flint, to cause perforations of the tread and a mechanical stress on the assemblies. and then it is rolled over a circuit of 3.5 km, which comprises a pond full of salt water, thus rolling the vehicle at each turn of the circuit on a dry coating and into the salt water to cause a chemical stress on the sets by corrosion , being the speed of rotation on the circuit of 60 km / h. The test is stopped after 3,800 km (including rolling on the flint), because one of the tires has a deformation of the tread. This cover is debarked to expose the cloth 62. and the following findings are made: the deformation of the tread 10 manifests only in the witness zones 62B. the zones 62A according to the invention not presenting any deformation; in the witness zones 62B. the 620B assemblies have a total of 63 complete breaks; these breaks are due, on the one hand, to the perforations of the tread by the 5 flint pieces, creating these perforations a mechanical solicitation of the assemblies and allowing the migration of salt water towards the assemblies, and. on the other hand, to the corrosion of the sets by the salt water in the zones of contact; In addition, significant corrosion of the assemblies on both sides of the breakage is observed, over a large length (at least 5 cm); - in the witness zones 62B, the adhesion between the rubber of the cloth 62, which serves to coat the assemblies, and the assemblies 620B is practically non-existent as a consequence of the corrosion; in zones 62A according to the invention, not there is no rupture due to corrosion, only breakages remain due to perforations whose number is small (34 for the set of these zones 62A). and the adhesion with the coating rubber is excellent.

The other covers present after the debarking the same characteristics but with a smaller degree. The invention thus allows a very clear improvement of the corrosion resistance, which results in a very small number of breakages of the assemblies and a conservation of the adhesion between the assemblies and the coating rubber. Example 3 The object of this example is to show that the wire according to the invention allows to use assemblies that could not be used up here with known threads. The yarn according to the invention defined above is used for the assemblies according to the invention and the control yarn described in example 2 is used for the witness assemblies. For the tests, two types of assemblies are used: - cable assembly braided; this set devoid of band is of the type (3 x 2) 23 defined in example 2; - set of layers; this set, devoid of hoop. It consists of a twisted wire, which serves as a core, around which five threads are wound according to a pitch of 12.5 mm. thus forming a layer that surrounds the soul, the formula of this set being designated by (1 + 5) 23. With the yarn according to the invention, two kinds of assemblies according to the invention are made, the sets designated by Al. Of the type (3 x 2) 23. and the sets designated by A2. of the type (1 + ) 23. With the control yarn, a single class of sets of type (3 x 2) 23 is made. these assemblies being designated which are not according to the invention by Bl. The characteristics of these sets are indicated in Table 1 below. Table 1 Bl Al A2 Di 0.73 mm 0.72 mn 0.66 mn Fr 668 N 639 N 645 N The abbreviations used are the following: Fr: force at break; Di: diameter of the circle circumscribed to the cross section of the assembly made perpendicular to the longitudinal direction of the assembly. Four series of tire covers are made, the covers of any series being identical to each other. All these series present the same known road pattern. These series are designated by Sl. S2. S3. S4 and the covers of this series are identical to the cover 175/70 R 13 described above in example 2. with the following differences, the reference signs of the cover 100 being preserved for the purpose of simplification: in the fabric 62 of a any deck, all sets 620 are the same and there is no zoning, the angles being 1 & orientation of the assemblies 620 and the steps are the same as in the cover 100 described in example 2; The assemblies of this cloth 62 are the following: - SI Series: Bl sets; - S2 series: Al sets; - series S3 and S4: sets A2 series Sl, S2. S3 differ from each other. and cover 100 of example 2. only on the fabric 62, while the S4 series presents, in addition, the difference that the subhußco is smaller than in the Sl series. S2 and S3, being the sub-nest of the S4 series of 1.9 mm instead of 2.5 mm. which represents a decrease of approximately 24 *. The series Sl consists of known witness covers and the S2 series. S3 and S4 are constituted by covers according to the invention. 3.1 Corrosion tests Four covers of each series are mounted in the same vehicle as in example 2 (vehicle Renault R21) with the same conditions of inflation and loading, and are subjected to the same test conditions as in this example 2, with the following differences: the preparatory taxiing sß performs for 1,600 km; the running on the circuit stops after approximately 4,600 km of total rolling (ie about 3,000 km) on the circuit). This running time is defined as the running time at which a deformation of a witness tire is observed. This filming time is the same for all the series, therefore, each filming test is carried out with four covers of the same series. The covers are then observed at the end of the test and then they are peeled off to examine the fabrics 62. They are studied as well. various parameters. making an average for the covers of each test, on the one hand, for the two covers mounted on the front of the vehicle and. on the other hand, for the two covers mounted on the rear of the vehicle. Due to the conception of the vehicle (front wheel drive). the rear covers are more sensitive to aggression by the pieces of flint than the front covers, for the following reason: the passage of the torque on the front axle in relation to those of the rear axle reduces the cuts of the front covers to favor the ejection of the pieces of flint out of the tread.The following determinations are made: - The drilling of the tread is counted (this number is abbreviated by N--), the length is measured average (in millimeters) of the oxidized sets (in the areas of rupture) in the cloth 62 (this length is briefly represented by Lg2) All the counts Np. N o, n¿ and all the measurements of Lfi2 are made on a half of the cover studied.

The results obtained relative to the rear mounted covers are indicated in table 2. Table 2 YES S2 S3 S4 N 338 (100) 360 (106) 432 (127) 680 (201) 62 98.5 (100) 70 (71) 67 (68) 129 (131) N62 37.0 0 0 0 The results obtained relative to the front mounted covers are indicated in table 3. Table 3 SI SJL S3 S4 N 104 (100) 93 (89) 114 (110) 284 (273) P Nfi2 56.5 (100) 29.5 (71) 40.5 (62) 76 (134) N62 37.5 0 0 0 In tables 2 and 3 the figures in parentheses they refer to the relative values, taking for 100 the values of the witness covers (series Sl). The observation of the tires and the values in Tables 2 and 3 allow the following findings to be made: - the witness covers show a deformation of the tread, which renders them useless; this is due to the fact that in these covers, the assemblies 620 of the fabric 62 are strongly oxidized and have numerous breaks; - the covers according to the invention do not present any deformation of the tread; the assemblies 620 of the fabric 62 do not exhibit corrosion; the covers according to the invention of the series S2 and S3 have practically the same value N P as the control series Sl and a value N0_2_ notably smaller than the SI series; the series S4 according to the invention, with reduced sub-hob, leads to a remarkable increase in the number of perforations N of the tread band and to a notable increase in the number of breaks Ng2 of the sets 620 of the fabric 62 in relation to the other series, but without causing oxidation of the upper fabric 62; - in all cases, the covers according to the invention have a longer life than that of the witness covers. 3.2 Weights of the covers Table 4 gives, in kg, the weight of each one of the covers of each series.

Table 4 Sl S2 S3 S4 6.850 6.800 6.810 6.610 Thus, it is noted that the cover S4 with reduced sub-pocket has the smallest weight and allows a weight reduction of approximately 4 * with respect to the control cover Sl. This weight gain can reach or even exceed 5 * for covers that have important and thick drawings such as snow drawings. 3.3 Rolling resistance On a steering wheel having a circumference of approximately 5.36 m, a tire of each of the series Sl, S2 is rolled. S3 and S4. Pressure of each of the covers: 2.1 bars. Load of each of these covers: 373 daN. Table 5 gives, for various speeds, the rolling resistance measured for each of the covers, this resistance being expressed, usually, in kg per ton of cargo. The figures in parentheses give the relative values of rolling resistance, taking the values of the witness cover Sl equal to 100. Table 5 Sl S2 S3 S4 50 km / h 9.7 9.6 9.5 9.2 (100) (99) (98) ( 95) 90 km / h 9.8 9.6 9.5 9.2 (100) (98) (98) (94) 120 km / h 10.3 10.1 10.1 9.8 (100) (98) (98) (95) 160 km / h 12.7 13.1 12.5 12.3 (100) (103) (98) (97) It is found that the subway S4 with reduced sub-hollow presents the smallest rolling resistance. 3.4 Limiting speed On a flywheel whose circumference is approximately 8.5 m sß rolls a cover of each of the series Sl to S4. Pressure of each cover: 2.5 bars Load of each cover: 466 daN. Filming is continued until the studied cover is made useless by cutting off the reliefs of the drawing and by tearing off the reliefs of the pattern and by appearance of the upper crown fabric 62. The speeds measured during the destruction of the covers are indicated in km / h in table 6. The figures in parentheses give the relative values taking as a base 100 the speed of the witness cover Sl.

Table 6 Sl S2 S3 S4 219.2 213.2 217.2 224.0 (100) (97) (99) (102) It is noted that the figures are very approximate for all series Sl to S4. 3.5 Separation of the crown fabrics A cover of one of the series Sl to S4 is dried in a stove for approximately one month at about 60 ° C and these sub-passes are rolled on a wheel having a circumference of approximately 5 m. semi-spherical protuberances are arranged on the steering wheel to cause stresses on the side edges of the fabrics 62. Tire pressure: 2.5 bar; Loading of covers: 466 daN. It is sought, thus, to cause the formation of separation bags between the fabrics 61 and 62. All the covers are rolled for approximately 25,000 km and they are decoked to determine the dimension of the separation bags, measuring the dimensions (in mm) of the rectangles in which these bags are inscribed, the sides of the rectangles being oriented, either in the longitudinal direction (parallel to the equatorial plane of the cover). or in the radial direction (in a plane that contains the axis of rotation of the cover). The results are indicated in table 7. In this table, the first figure is the dimension of the rectangle in the longitudinal direction and the second figure is the dimension of the rectangle in the radial direction, given the area of the rectangles in parentheses. Table 7 Sl S2 S3 S4 480 x 90 500 x 51 380 x 35 Without (43,200) (25,500) (13,300) bags Table 7 shows that the covers S2. S3 and S4 according to the invention allow to reduce the size of the bags, or even to avoid the formation of the bags. In example 3, for the sets 620 of the witness covers, sets Bl of the type (3 x 2) were used. that is, sets of twisted cables, because the sets of layers, for example of formula (1 + 5) or (1 + 6) gave too bad results as a result of corrosion, as seen, on the other hand, in the example 2. The braided cable assemblies, for example of the type (3 x 2) described, allow a penetration of the rubber in the assembly y. consequently, they limit corrosion.

The preceding examples show that the invention allows the use of sets of layers (series S3 and S4) that present the following advantages over braided cable assemblies: - they are easier to manufacture and, therefore, of lower cost; they diminish the risks of separation of the fabrics of crown, as sonsequence of its greater compactness; - The compassion of the sets of sapas allows to reduce the thickness of the sagging and elastic gums. consequently, decrease the weight of the subsides. The sompacity c of a set can be defined by the following relationship: C - Sm / St with: Sm - area of the metal surface of the set; St - total surface area of the whole. Sm and St are determined in sections of the set by planes perpendicular to the longitudinal direction of the set, with Sm being the sum of the areas of the surfaces of all the sections of the metal wires and being St the area of the total surface of the sirsunssrito all the sessions of the metallic threads. The value of C is the average of ten measurements of the set considered effected at equidistant intervals, each interval being approximately 30 cm. Preferably, the agreement sets are the invention have a C sompasity at least equal to 65 *. For example, the values of C for the formulas of the sets described above are the following: (3 x 2) 23 (1 + 5) 23 (1 + 6) 23 49 * 67.2 * 78.4 * In the examples of the procedure of agreement with the invention, the starting yarn used comprised a nickel coating and a brass coating was made prior to performing the deformation, but other embodiments are possible, for example, by replacing the nickel with another metallic material. especially copper, or by performing the deformation on a starting yarn devoid of metallic coating, the final yarn therefore being able to be made of only stainless steel.

Preferred, there is at least one of the following characteristics for the thread of agreement are the invention: the diameter of the wire is at least equal to 0.12 mm and as much equal to 0.5 mm; - the resistance to breakage in transssion is at least equal to 2,500 MPa; the module is at least equal to 150 GPa; - the sieve in the sarbone of the asero is at least equal to 0.04 and is much equal to 0.15 * in weight; - the nickel content of the steel is between 7.5 and 9.5 * by weight, the chromium content of the steel is between 17 and 19 * by weight and the molybdenum content of the steel is less than 1 * by weight; - the sulfur content and the phosphorus content are each less than 0.05 * by weight; - the torsional ductility is at least equal to 50 turns; - the structure of the steel is constituted practically, either solely by martensite, or only by martensite and austenite.

Preferably, in the improvement of agreement are the invention. there is at least one of the following characteristics: the starting yarn has a diameter at least equal to 0.5 mm; - the carbon content of the steel is at least equal to 0.05 * and at most equal to 0.15 * by weight; the nickel content of the steel is between 7.5 and 9.5 * by weight, the chromium content of the steel is between 17 and 19 * by weight and the molybdenum content of the steel is less than 1 * by weight; - the sulfur content and the phosphorus content of the steel are each less than 0.05 * by weight; the starting yarn is coated with nickel or copper; - a brass coating is made before deformation; - the deformation is carried out by wet drawing with a grease emulsion in water; the total deformation E is at least equal to 2. The assemblies according to the invention described in the examples were all entirely made up of stainless steel wires according to the invention, but the invention applies to cases where the assemblies do not are constituted more than in part with threads of agreement are the invention. It's like that. for example. the assemblies according to the invention can be pairs of braided sapas or sabers in which only a part of the threads are in accordance with the invention, for example a set of the type 3 x 2 described above in which one of the braided cables has threads of agreement is the invention, the other two braided swords being made are non-stainless threads, this realization may have the advantage of redressing the ties . In the examples described above, the acquisition threads are the invention were used in the form of sets within the cross fabrics, but the invention applies to the case where the threads according to the invention are used as they are, without forming sets, to the cases in which the threads do not form layers, and to the cases in which they are arranged as such or in the form of assemblies, for example, by winding, practically in the longitudinal direction of the covers, thus forming, or not. fabrics, in the crown of these covers. Of course, the invention is not limited to the embodiments described above.

It is noted that in relation to this date, the best method conosido by the solisitante to put into practice the aforementioned invention, is the one that is slaro of the present division of the invssion. Having described the invention as antecedent, the content of the following is claimed as property.

Claims (25)

1. CLAIMS 1. Stainless steel wire to reinforce the crown of the tire covers. This thread is characterized by the following points: a) its diameter is at least equal to 0.05 mm and is much equal to 0.6 mm; b) its tensile strength is at least 2,400 MPa; c) its twisting dust is at least 30 turns; d) the yarn steel comprises at least 0.02 * and at most 0.2 * of sarbono. at least 6 * and at most 10 * of nickel, at least 16 * and at most 20 * of chromium, being zero or as musho equal to 5 * the content of the molybdenum inlet at least equal to 23 * and we are much the same as a 28.5 *. all these values being * percentages by weight; e) the structure of the steel comprises at least 50 * by volume of martensite and is devoid of austenite or comprises less than 50 * of it in volume.
2. 2. Thread according to claim 1, characterized in that the diameter of the wire is at least equal to 0.12 mm and at most equal to 0.5 mm.
3. 3. Thread according to any one of claims 1 or 2 »costerized because the tensile strength is at least 2,500 MPa.
4. 4. Thread according to any one of claims 1 to 3, characterized in that the module is at least equal to 150 GPa.
5. 5. Thread according to any one of claims 1 to 4, sarasterized because the carbon content of the aser is at least equal to 0.05 and is equal to 0.15 * by weight.
6. 6. Thread according to any one of claims 1 to 5, characterized in that the nickel content of the steel is between 7.5 * and ßl 9.5 * by weight, the chromium content of the steel is between 17 and 19 * by weight and the molybdenum content of the steel is less than 1 * by weight.
7. 7. Thread according to any one of claims 1 to 6, characterized in that the sulfur content and the phosphorus content are each less than 0.05 * by weight.
8. 8. Wire according to any one of claims 1 to 7, characterized in that the torsional ductility is at least 50 turns.
9. 9. Wire according to any one of claims 1 to 8, characterized in that the structure of the steel is constituted practically, either solely by martensite, or only by martensite and austenite.
10. 10. A set intended to be used in the crown of a tire, said at least one thread of agreement being any of any of claims 1 to 9.
11. 11. Assembly according to claim 10. cosmetically because its compactness C is less equal to 65 *.
12. 12. Set according to claim 11, characterized in that it is a set of layers.
13. Assembly according to claim 12, characterized in that it is of formula (1 + 5) or (1 + 6).
14. 14. Fabric for reinforcement of the sorona of a tire sub-tire, characterized in that it comprises at least one thread according to any one of the claims 1 to 9 and / or at least one assembly according to any one of claims 10 to 13.
15. Tire cover whose crown is reinforced by at least one thread according to any one of claims 1 to 9 and / or by at least one set according to any one of claims 10 to 13 and / or by at least one fabric according to claim 14.
16. 16. A tire according to claim 15. characterized in that it comprises at least two reinforcing fabrics located on the crown, the single upper layer being reinforced by at least one thread according to the invention are a sucker of claims 1 to 9 and / or at least a set according to any one of claims 10 to 13.
17. 17. Procuring to prepare the yarn of asußrdo are any of claims 1 to 9, characterized by the following points: a) part of a stainless steel wire his diameter is at least equal to 0.3 ram and somo musho equal to 3 mm; the steel of the wire comprises at least 0.02 * and at most 0.2 * carbon, at least 6 * and at most 10 * nickel, at least 16 * and we are much 20 * chromium, being zero or as much as 5 * the content of steel in molybdenum, the sum of nickel, chromium and molybdenum being at least equal to 23 * and at most equal to 28.5 *, all these values being * percentages by weight; the structure of this steel is completely austissitic or practically austenitic; b) at least one deformation treatment is carried out, without heat treatment, the total deformation being at least equal to 1.5.
18. 18. Procurement according to the claim 17. Sarasterized because the starting yarn has a diameter at least equal to 0.5 mm.
19. 19. Process according to any one of claims 17 or 18. characterized in that the content of sarbone of the asero is at least equal to 0.05 * and somo musho equal to 0.15 * by weight.
20. 20. Procurement according to any one of claims 17 to 19. Sarasterized because the nickel content of the steel is between 17 and 19 * by weight and the molybdenum content of the steel is less than 1 * by weight.
21. 21. Process according to any one of claims 17 to 20, characterized in that the sulfur content and the phosphorus content are each less than 0.05 * by weight.
22. 22. Process according to any one of claims 17 to 22, characterized in that the starting yarn is coated with nickel or copper. Method according to any one of claims 17 to 22, characterized in that a brass coating is carried out before deformation. Method according to any one of claims 17 to 23, characterized in that the deformation is carried out by wet drawing, which is a grease emulsion in water. 25. Prosecution according to any one of claims 17 to 24. Sarasterized because the total deformation € is at least equal to 2.