Method and electronic device for determining a temperature of a steel wire during air-cooling on a conveyor, related computer program and installation

Abstract

The invention concerns a method for determining a temperature of a steel wire (12) during its cooling by air on a conveyor having a central axis (18) and two lateral edges (20) extending in a conveying direction (X), the steel wire (12) being wound in successive loops (22) comprising each at least one central portion (24) near the central axis (18) and at least one edge portion (26) near a respective lateral edge (20), comprising: - estimating a wire temperature gradient with respect to a radial position within the wire, as a function of a total heat transfer coefficient depending on a convective heat transfer coefficient associated to air convection and on a radiative heat transfer coefficient associated to radiation; and for at least one central portion (24), the radiative heat transfer coefficient being calculated according to a predefined center effective emissivity; - computing the temperature of the steel wire (12) according to the wire temperature gradient; for at least one edge portion (26), the radiative heat transfer coefficient is calculated according to an edge effective emissivity distinct and independent from the center effective emissivity.

Description

[0001] Method and electronic device for determining a temperature of a steel wire during air-cooling on a conveyor, related computer program and installation

[0002] FIELD OF THE INVENTION

[0003] The present invention concerns a determination method for determining a temperature of a steel wire during its cooling by air on a conveyor, the method being implemented by an electronic determination device.

[0004] The invention also relates to a computer program including software instructions which, when executed by a processor, implement such a determination method.

[0005] The invention further concerns such an electronic determination device for determining a temperature of the steel wire during air-cooling on the conveyor.

[0006] The invention also concerns a steel wire production installation for producing the steel wire, comprising inter alia such an electronic determination device.

[0007] TECHNICAL BACKGROUND

[0008] The technical field is that of steel wire production.

[0009] After a steel wire has been rolled, typically in a rolling mill, while very hot, it is cooled, on a conveyor. On the conveyor, the wire is typically looped, and form a series of several successive, partially overlapping loops, the loops being all substantially in the same horizontal plane seen from above, and cooled by air blown by fans. The fans are typically arranged below the conveyor, all along the conveyor. The conveyor extends in a conveying direction and has a central axis and two lateral edges on either side of the central axis, the central axis and the lateral edges extending in the conveying direction.

[0010] The speed of the conveyor may vary locally and is adjustable, and the power of fans may vary from fan to fan, and is adjustable.

[0011] As usual for steel thermal treatments, it is useful to know how to estimate the thermal route followed by the wire during the cooling.

[0012] The article “Effect of Air Temperature on the Thermal Behavior and Mechanical Properties of Wire Rod Steel during Stelmor Cooling" from Joong-ki Hwang, published in ISM International, Vol. 62 (2022), No. 11 , pp. 2343-2354, https: / / doi.org / 10.2355 / isijinternational.ISIJINT-2022-047, describes the effect of air temperature on the thermal behavior and mechanical properties of steel wire rods. In particular, a wire temperature gradient with respect to a radial position within the wire is estimated as a function of a total heat transfer coefficient, and the total heat transfer coefficient depends notably on a convective heat transfer coefficient associated to air convection and on a radiative heat transfer coefficient associated to radiation.

[0013] The total heat transfer coefficient is estimated for a center region of the loop near the central axis, and since the temperature of the wire ring for an edge region near a lateral edge of the conveyor is difficult to predict owing to the geometric complexity of the wire ring, this article further teaches to use a correction factor to predict the temperature for the edge region based on the total heat transfer coefficient estimated for the center region. Accordingly, the total heat transfer coefficient for the edge region is equal to the total heat transfer coefficient for the center region multiplied by said correction factor.

[0014] Nevertheless, this temperature prediction is not always enough accurate.

[0015] SUMMARY OF THE INVENTION

[0016] One objective of the invention is to provide a better method for determining a temperature of a steel wire during its cooling by air on a conveyor.

[0017] For this purpose, the subject-matter of the invention concerns, inter alia, a determination method for determining a temperature of a steel wire during its cooling by air on a conveyor, the conveyor extending in a conveying direction and having a central axis and two lateral edges on either side of the central axis, the central axis and the lateral edges extending in the conveying direction, the steel wire being wound in loops placed successively on the conveyor and spaced from one another in the conveying direction, each loop comprising at least one central portion near the central axis and at least one edge portion near a respective lateral edge of the conveyor, the method being implemented by an electronic determination device and comprising the following steps:

[0018] - estimating a wire temperature gradient with respect to a radial position within the wire, as a function of a total heat transfer coefficient, the total heat transfer coefficient depending on a convective heat transfer coefficient associated to air convection and on a radiative heat transfer coefficient associated to radiation; and for at least one central portion, the radiative heat transfer coefficient being calculated according to a predefined center effective emissivity;

[0019] - computing the temperature of the steel wire according to the estimated wire temperature gradient; wherein for at least one edge portion, the radiative heat transfer coefficient is calculated according to an edge effective emissivity, the edge effective emissivity being distinct and defined independently from the center effective emissivity. Thus, the method according to the invention is more accurate than the prior art method, and in particular estimates the radiative heat transfer coefficient for each edge portion of the wire, independently from the radiative heat transfer coefficient estimated for a respective central portion of the wire.

[0020] In other words, a different effective emissivity is used for computing the heat exchange by radiation at the center, and on the edge, to reflect that there is more wire-overlapping on the edge and so, less radiation losses.

[0021] Advantageously, for each edge portion, the radiative heat transfer coefficient is calculated according to an edge effective emissivity, and said edge effective emissivity depends on a spacing between two successive loops.

[0022] Preferably, the edge effective emissivity increases when the spacing between two successive loops increases, to reflect that the wire-overlapping decreases in this case, and so there are more radiation losses.

[0023] According to other advantageous aspects of the invention, the determination method comprises one or several of the following features, taken individually or according to any technically possible combination:

[0024] - the method further comprises acquiring at least one value among the group comprising: a measured value of an initial temperature, a measured value of a conveying speed, a control value of the conveying speed, a measured value of an air velocity, a measured value of a power of a set of fan(s) blowing air on the steel wire, a control value of the set of fan(s); and during the computing step, the temperature of the steel wire is computed according further to the at least one acquired value;

[0025] - the computed temperature is intended for performing at least one action among the group comprising: controlling the conveyor, controlling the air cooling, determining microstructural and / or mechanical properties of the steel wire that has been cooled down, and modelling an installation for producing the steel wire;

[0026] - the edge effective emissivity depends on a spacing between two successive loops along the conveying direction;

[0027] - the edge effective emissivity increases when the spacing between two successive loops increases; the edge effective emissivity preferably verifying the following equation: where Eedge represents the edge effective emissivity, e represents the spacing between two successive loops, and

[0028] A and B are first and second parameters; A and B preferably depending on a diameter of the wire; the first parameter still preferably verifying the following equation:

[0029] A = Fprl + Fpr2. D where A represents the first parameter,

[0030] D represents the diameter of the wire,

[0031] Fpr1 and Fpr2 are constant coefficients; and the second parameter still preferably verifying the following equation:

[0032] B = Fpr3 + FprA. D where B represents the second parameter,

[0033] D represents the diameter of the wire,

[0034] Fpr3 and Fpr4 are constant coefficients;

[0035] - the spacing between two successive loops is determined depending on a conveying speed.

[0036] - the spacing between two successive loops further depends on a diameter of the loops, a diameter of the wire and a rolling speed; the spacing between two successive loops preferably verifying the following equation:

[0037] Vce = n. ds. - D

[0038] VL where e represents the spacing between two successive loops, ds represents the diameter of the loops,

[0039] Vc represents the conveying speed,

[0040] VL represents the rolling speed, and

[0041] D represents the diameter of the wire;

[0042] - the center effective emissivity is a constant value;

[0043] - the radiative heat transfer coefficient verifies the following equation:

[0044] ( - )

[0045] '1R = £'o'T^Tr where hR represents the radiative heat transfer coefficient,

[0046] E represents the effective emissivity of the respective portion of the wire, o represents the Stefan Boltzmann constant,

[0047] Ts represents a surface temperature of the respective portion of the wire, and

[0048] TA represents an ambient temperature; the surface temperature for a respective central portion being distinct from the surface temperature for a corresponding edge portion, in the same loop than said central portion;

[0049] - the convective heat transfer coefficient verifies the following equation: y hc= ck . — „ c D where he represents the convective heat transfer coefficient, ck represents a multiplying coefficient,

[0050] D represents the diameter of the wire,

[0051] VA represents an air velocity, and a, p are predefined power coefficients; the predefined power coefficient related to the air velocity for a respective central portion being preferably distinct from the predefined power coefficient related to the air velocity for a corresponding edge portion; the corresponding edge portion being in the same loop than said central portion; the predefined power coefficient related to the diameter of the wire for the respective central portion being preferably distinct from the predefined power coefficient related to the diameter of the wire for the corresponding edge portion; and the air velocity for the respective central portion being preferably distinct from the air velocity for the corresponding edge portion.

[0052] - the method further comprises the step of performing at least one action among the group comprising: controlling the conveyor, controlling the air cooling, determining microstructural and / or mechanical properties of the steel wire that has been cooled down, and modelling an installation for producing the steel wire.

[0053] The subject-matter of the invention also concerns a determination method for determining a temperature of a steel wire during its cooling by air on a conveyor, the conveyor extending in a conveying direction and having a central axis and two lateral edges on either side of the central axis, the central axis and the lateral edges extending in the conveying direction, the steel wire being wound in loops placed successively on the conveyor and spaced from one another in the conveying direction, each loop comprising at least one central portion near the central axis and at least one edge portion near a respective lateral edge of the conveyor, the method being implemented by an electronic determination device and comprising the following steps:

[0054] - estimating a wire temperature gradient with respect to a radial position within the wire, as a function of a total heat transfer coefficient, the total heat transfer coefficient depending on a convective heat transfer coefficient associated to air convection and on a radiative heat transfer coefficient associated to radiation;

[0055] - computing the temperature of the steel wire according to the estimated wire temperature gradient; wherein the convective heat transfer coefficient verifies the following equation: where he represents the convective heat transfer coefficient, ck represents a multiplying coefficient,

[0056] D represents the diameter of the wire,

[0057] VA represents an air velocity, and a, p are predefined power coefficients; and wherein:

[0058] - the predefined power coefficient related to the air velocity for a respective central portion is distinct from the predefined power coefficient related to the air velocity for a corresponding edge portion; the corresponding edge portion being in the same loop than said central portion; and / or the predefined power coefficient related to the diameter of the wire for the respective central portion is distinct from the predefined power coefficient related to the diameter of the wire for the corresponding edge portion.

[0059] The subject-matter of the invention is also a computer program including software instructions which, when executed by a processor, implement a determination method as defined above.

[0060] The subject-matter of the invention is also an electronic determination device for determining a temperature of a steel wire during its cooling by air on a conveyor, the conveyor extending in a conveying direction and having a central axis and two lateral edges on either side of the central axis, the central axis and the lateral edges extending in the conveying direction, the steel wire being wound in successive loops spaced from one another in the conveying direction, each loop comprising at least one central portion near the central axis and at least one edge portion near a respective lateral edge of the conveyor, the electronic determination device comprising:

[0061] - an estimation module configured for estimating a wire temperature gradient with respect to a radial position within the wire, as a function of a total heat transfer coefficient, the total heat transfer coefficient depending on a convective heat transfer coefficient associated to air convection and on a radiative heat transfer coefficient associated to radiation; and for at least one central portion, the radiative heat transfer coefficient being calculated according to a predefined center effective emissivity;

[0062] - a computation module configured for computing the temperature of the steel wire according to the estimated wire temperature gradient; wherein for at least one edge portion, the radiative heat transfer coefficient is calculated according to an edge effective emissivity, the edge effective emissivity being distinct and defined independently from the center effective emissivity.

[0063] According to other advantageous aspects of the invention, the electronic determination device comprises one or several of the following features, taken individually or according to any technically possible combination:

[0064] - the electronic determination device further comprises an acquisition module configured for acquiring at least one value among the group comprising: a measured value of an initial temperature, a measured value of a conveying speed, a control value of the conveying speed, a measured value of an air velocity, a measured value of a power of a set of fan(s) blowing air on the steel wire, a control value of the set of fan(s); and the computation module being configured for computing the temperature of the steel wire according further to the at least one acquired value;

[0065] - the computed temperature is intended for performing at least one action among the group comprising: controlling the conveyor, controlling the air cooling, determining microstructural and / or mechanical properties of the steel wire that has been cooled down, and modelling an installation for producing the steel wire.

[0066] The subject-matter of the invention is also an installation for producing a steel wire, comprising:

[0067] - a rolling mill for delivering the steel wire,

[0068] - a conveyor for conveying the steel wire in a conveying direction, the conveyor extending in the conveying direction and having a central axis and two lateral edges on either side of the central axis, the central axis and the lateral edges extending in the conveying direction, the steel wire being wound in successive loops spaced from one another in the conveying direction, each loop comprising at least one central portion near the central axis and at least one edge portion near a respective lateral edge of the conveyor,

[0069] - a set of fan(s) arranged below the conveyor, for blowing air on the conveyed steel wire, and

[0070] - a controller for controlling the conveyor and / or the set of fan(s), wherein the installation further comprises an electronic determination device for determining a temperature of the steel wire during its cooling by air on the conveyor, the electronic determination device being connected to the controller and as defined above.

[0071] According to an advantageous aspect of the invention, the installation comprises the following feature: - the controller is configured for controlling the conveyor and / or the set of fan(s) according to the temperature of the steel wire determined by the electronic determination device.

[0072] BRIEF DESCRIPTION OF THE DRAWINGS

[0073] The invention will be better understood upon reading of the following description, which is given solely by way of example and with reference to the appended drawings, wherein:

[0074] - Figure 1 is a schematic view of an installation for producing a steel wire, comprising inter alia a conveyor for conveying the steel wire in a conveying direction and an electronic determination device for determining a temperature of the steel wire during its cooling by air on the conveyor;

[0075] - Figure 2 is a top view of a steel wire wound in successive loops spaced apart in the conveying direction, each loop comprising at least one central portion close to a central axis of the conveyor and at least one edge portion close to a respective side edge of the conveyor;

[0076] - Figure 3 is a flowchart of a method for determining the temperature of the steel wire during its cooling by air on the conveyor of Figure 1 , the method being implemented by the electronic determination device of Figure 1 ; and

[0077] - Figure 4 shows first and second curves of the temperature of the steel wire with respect to a distance along the conveying direction; the first, and respectively second, curves concerning corresponding central portion(s), and respectively corresponding edge portion(s).

[0078] DETAILED DESCRIPTION

[0079] The expression “substantially equal to” defines a relationship of equality at plus or minus 10%, preferably at plus or minus 5%, still preferably at plus or minus 2%.

[0080] In Figure 1 , a production installation 10 for producing a steel wire 12 comprises a rolling mill 14 for delivering the steel wire 12, a conveyor 16 for conveying the steel wire 12 in a conveying direction X, and a set of fan(s) (not shown) arranged below the conveyor 16.

[0081] The conveyor 16 extends in the conveying direction X and has a central axis 18 and two lateral edges 20 on either side of the central axis 18, the central axis 18 and the lateral edges 20 extending in the conveying direction X.

[0082] The steel wire 12 is wound in successive loops 22 spaced from one another in the conveying direction X, each loop 22 comprising at least one central portion 24 near the central axis 18 and at least one edge portion 26 near a respective lateral edge 20 of the conveyor 16. A portion, whether a central portion 24 or an edge portion 26, means a small section of wire, i.e. a small length of wire. Each central portion 24 is closer to the central axis 18 than to a respective lateral edge 20, and for example straddles the central axis 18. Each edge portion 26 is closer to a respective lateral edge 20 than to the central axis 18. Each loop 22 typically comprises two central portions 24 which are approximately diametrically opposed to each other, and two edge portions 26 which are also approximately diametrically opposed to each other. Each central portion 24 is advantageously separate from the edge portion(s) 26 included in the same loop 22. The loops 22 are slightly overlapping each other and are substantially all in the same horizontal plane, seen from above in Figure 2. Said horizontal plane includes the conveying direction X and is substantially parallel to the conveyor 16.

[0083] The steel wire 12 extends locally along an extension direction corresponding to a tangent of a respective loop 22, and the determination of a temperature T of the steel wire 12 depends on a radial variation of temperature, i.e. a variation of the temperature T as a function of a radial position r within the wire along a radial direction, perpendicular to the extension direction, the radial direction then also being perpendicular to the tangent of the loop 22. The variation of temperature is also called wire temperature gradient <5T / 6r, and said gradient is with respect to the radial position r.

[0084] The steel wire 12 has a diameter D which is typically of the order of a few millimeters, the diameter D being for example between 1 mm (millimeter) and 30 mm, preferably between 3 mm and 15 mm, and even more preferably substantially equal to 7 mm.

[0085] The production installation 10 further comprises a controller 28 and an electronic determination device 30.

[0086] As known per se, the wire rolling mill 14 is a machine used to produce steel wire from a continuous metal stock. The rolling process involves passing the metal through multiple passes, reducing its cross-sectional area. The rolling mill 14 is for example a set of stands composed of two, three or four rolls, each roll with a different diameter and groove design; or else a block milling passing the metal through multiple blocks of varying shape to produce the desired size of the wire 12.

[0087] The conveyor 16 comprises rollers 32 each extending in a transverse direction Y perpendicular to the conveying direction X, the rollers 32 being arranged successively, i.e. one after the other, in the conveying direction X, as shown in Figure 1. The conveyor 16 also comprises two lateral guide rails 34, each one extending in the conveying direction X, the two lateral guide rails 34 being arranged on either side of the rollers 32, and perpendicular to the rollers 32. The conveyor 16 further comprises a drive system (not shown) powering the conveyor elements and optionally wiper blades or guides (not shown), that are used to keep dust and debris from accumulating on the conveyor 16 and to maintain a smooth path for the wire 12. The rollers 32 and associated bearings (not shown) support the weight of the wire 12 and facilitate smooth movement along the conveyor 16. The lateral guide rails 34 provide support and alignment for the conveyor 16, ensuring that the wire 12 remains on course.

[0088] The set of fan(s) comprises at least one fan arranged below the conveyor 16 for blowing air on the conveyed steel wire 12. The set of fan(s) comprises advantageously several fans, typically about thirty fans, arranged successively in the conveying direction X, all along the conveyor 16.

[0089] Each loop 22 has a diameter ds, shown in Figure 2, which is typically of the order of a few decimeters, the diameter ds being for example between 0.5 m (meter) and 2 m, preferably between 0.7 m and 1.5 m, and even more preferably substantially equal to 1.1 m.

[0090] A spacing between two successive loops 22 along the conveying direction X is denoted e, as shown in Figure 2. The spacing e is typically of the order of a few centimeters, the spacing e is for example between 1 cm (centimeter) and 50 cm, preferably between 2 cm and 10 cm.

[0091] The controller 28 is configured for controlling the conveyor 16 and / or the set of fan(s). In particular, the controller 28 is configured for controlling the operation of the conveyor 16 and / or the set of fan(s), and notably operation parameters of the conveyor 16 and / or the set of fan(s).

[0092] The operation parameters controlled by the controller 28 are for example: a conveying speed Vc which is the speed of displacement of steel wire 12 along the conveying direction X; an air velocity VA which is the speed of the air blown by the set of fan(s) on the conveyed steel wire 12; a power of the set of fan(s) blowing air on the steel wire 12.

[0093] The electronic determination device 30 is configured for determining the temperature T of the steel wire 12 during its cooling by air on the conveyor 16.

[0094] Optionally, the electronic determination device 30 is advantageously connected to the controller 28 for transmitting control signal(s) to the controller 28 and / or acquiring control information from the controller 28.

[0095] Further optionally, the electronic determination device 30 is advantageously connected to the rolling mill 14 for acquiring information from the rolling mill 14.

[0096] To determine the temperature T of a steel wire 12 during its cooling by air on a conveyor 16, the electronic determination device 30 comprises an estimation module 40 and a computation module 42.

[0097] According to an optional addition, the electronic determination device 30 further comprises an acquisition module 44 and / or a transmission module 46. In the example of Figure 1 , the electronic determination device 30 includes a processing unit 50 formed for example of a memory 52 and of a processor 54 coupled to the memory 52. In this example, the electronic determination device 30 also includes a display screen and input / output means, not shown, such as a keyboard and a mouse or pointer, each being connected to the processing unit 50.

[0098] In the example of Figure 1 , the estimation module 40 and the computation module 42, and optionally the acquisition module 44 and / or the transmission module 46, are for example each realized, i.e. implemented, as a software executable by the processor 54. Accordingly, the memory 52 of the processing unit 50 is adapted to store an estimation software and a computation software, and optionally an acquisition software and / or a transmission software. The processor 54 of the processing unit 50 is then configured to execute the estimation software and the computation software, and optionally the acquisition software and / or the transmission software. The skilled person will understand that by software is generally meant a set of computer-executable software instruction(s), corresponding to a binary executable or a portion of a binary executable. Each of the aforementioned software is therefore, for example, a sub-program, such as a routine, a software function, or a computer module of a global prevention software corresponding the determination device 30.

[0099] As a variant not shown, the estimation module 40 and the computation module 42, and optionally the acquisition module 44 and / or the transmission module 46, are each in the form of a programmable logic component, such as a Field Programmable Gate Array or FPGA, or in the form of a portion of such a programmable logic component, or else in the form of a dedicated integrated circuit, such as an Application Specific integrated Circuit or ASIC.

[0100] When the electronic determination device 30 is in the form of one or more software programs, i.e. in the form of a computer program, it is also capable of being recorded on a computer-readable medium, not shown. The computer-readable medium is, for example, a medium capable of storing electronic instructions and being coupled to a bus of a computer system. For example, the readable medium is an optical disk, a magneto-optical disk, a ROM memory, a RAM memory, any type of non-volatile memory (for example EPROM, EEPROM, FLASH, NVRAM), a magnetic card or an optical card. A computer program with software instructions is then stored on the readable medium.

[0101] The estimation module 40 is configured for estimating a wire temperature gradient <5T / 6r with respect to a radial position r as a function of a total heat transfer coefficient hi-.

[0102] The estimation module 40 is for example configured for estimating the wire temperature gradient <5T / 6r according to the following equations: [1] dT

[0103] — = 0 at r = 0 dr

[0104] [2] where 6T / 6r represents the wire temperature gradient, r represents the radial position, and R is wire radius , namely the half of the diameter D of the wire 12, k(T) represents the thermal conductivity,

[0105] Ts represents a surface temperature of the wire 12, and

[0106] TA represents an ambient temperature.

[0107] The total heat transfer coefficient hT(expressed for instance in Watt per Kelvin and per square meter) depends on a convective heat transfer coefficient he associated to air convection and on a radiative heat transfer coefficient hR associated to radiation.

[0108] The total heat transfer coefficient hTis for example equal to the sum of the convective heat transfer coefficient he associated to air convection and the radiative heat transfer coefficient hR associated to radiation. Accordingly, the estimation module 40 is configured for calculating the total heat transfer coefficient hTaccording to the following equation:

[0109] [3] hT= hc+ hR

[0110] For at least one central portion 24, the radiative heat transfer coefficient hR is calculated according to a predefined center effective emissivity EC. The center effective emissivity ECis advantageously a constant value, for example determined according to preliminary measure(s).

[0111] According to the invention, for at least one edge portion 26, the radiative heat transfer coefficient hR is calculated according to an edge effective emissivity Eedge, the edge effective emissivity Eedge being distinct and defined independently from the center effective emissivity Ec.

[0112] The skilled person will observe that the effective emissivity, denoted E in a general manner, is equal to the product of a form factor and an emissivity. This applies both for the center effective emissivity ECand for the edge effective emissivity Eedge, which are each one the product of respective form factor and emissivity.

[0113] Further, it is typically the form factor that varies between the center effective emissivity Ec and the edge effective emissivity Eedge. In other words, an edge form factor involved in the edge effective emissivity Eedge is typically distinct and defined independently from a center form factor involved in the center effective emissivity EC.

[0114] Advantageously, the edge effective emissivity Eedge is strictly smaller than the center effective emissivity EC. For example, in given operation conditions, the edge effective emissivity Eedge may be substantially equal to 0.4, while the center effective emissivity ECis substantially equal to 0.6.

[0115] Optionally, the edge effective emissivity Eedge depends on the spacing e between two successive loops 22 along the conveying direction X.

[0116] Further optionally, the edge effective emissivity Eedge increases when the spacing e between two successive loops 22 increases.

[0117] The edge effective emissivity Eedge verifies for example the following equation:

[0118] [4]

[0119] £eage= A.10B ewhere Eedge represents the edge effective emissivity, e represents the spacing between two successive loops 22, and A and B are first and second parameters.

[0120] The first A and second B parameters advantageously depend on the diameter D of the wire 12.

[0121] The first parameter A verifies for example the following equation:

[0122] [5]

[0123] A = Fprl + Fpr2. D where A represents the first parameter, D represents the diameter of the wire 12, Fpr1 and Fpr2 are constant coefficients.

[0124] The second parameter B verifies for example the following equation:

[0125] [6]

[0126] B = Fpr3 + FprA. D where B represents the second parameter, D represents the diameter of the wire 12, Fpr3 and Fpr4 are constant coefficients.

[0127] Optionally, the spacing e between two successive loops 22 is determined depending on the conveying speed Vc.

[0128] Further optionally, the spacing e between two successive loops 22 further depends on the diameter ds of the loops 22, the diameter D of the wire 12 and the rolling speed VL.

[0129] The spacing e between two successive loops 22 verifies for example the following equation:

[0130] [7] where e represents the spacing between two successive loops 22, ds represents the diameter of the loops 22, Vc represents the conveying speed, VL represents the rolling speed, and D represents the diameter of the wire 12.

[0131] The radiative heat transfer coefficient hR verifies for example the following equation:

[0132] [8] where hR represents the radiative heat transfer coefficient, E represents the effective emissivity of the respective portion of the wire 12, o represents the Stefan Boltzmann constant, Ts represents a surface temperature of the respective portion of the wire 12, and TA represents an ambient temperature.

[0133] The surface temperature for a respective central portion 24 is advantageously distinct from the surface temperature for a corresponding edge portion 26.

[0134] The corresponding edge portion 26 is in the same loop 22 than the respective central portion 24.

[0135] The convective heat transfer coefficient he verifies the following equation:

[0136] [9] y hc= ck . — „ c D where he represents the convective heat transfer coefficient, ck represents a multiplying coefficient, D represents the diameter of the wire 12, VA represents an air velocity, and a, p are predefined power coefficients.

[0137] The predefined power coefficient a related to the air velocity VA for a respective central portion 24, denoted ac, is advantageously distinct from the predefined power coefficient a related to the air velocity A for a corresponding edge portion 26, denoted aedge. More preferably, said predefined power coefficient acfor the respective central portion 24 is greater than said predefined power coefficient aedge for the corresponding edge portion 26, i.e. Oc > Qedge; with further each one typically between 0 and 1 , or even from 0.1 to 1 .

[0138] The predefined power coefficient related to the diameter D of the wire 12 for a respective central portion 24, denoted pc, is still advantageously distinct from the predefined power coefficient p related to the diameter D of the wire 12 for a corresponding edge portion 26, denoted pedge. More preferably, said predefined power coefficient pcfor the respective central portion 24 is lower than said predefined power coefficient Pedge for the corresponding edge portion 26, i.e. pc< Pedge; with further each one typically between 0 and 1 , or even from 0.05 to 0.5 The air velocity for a respective central portion 24, denoted VA_C, is further advantageously distinct from the air velocity for a corresponding edge portion 26, denoted VA_edge. Advantageously, the air velocity VA_edge for a respective edge portion 26 is generally chosen higher than the air velocity VA_Cfor a corresponding central portion 24, for example substantially 20 m / s at the edge, and substantially 15m / s on the central axis. This allows for a more homogeneous cooling of the wire 12, despite the greater heat exchange coefficients at the center.

[0139] Optionally, in practice (e.g. for line control, or a-posteriori characterization), the air velocity A is not measured directly; it is deduced from a fan power factor (or supply power, or other fan control variable), and from an initial calibration of a relation between the air velocity VA and the fan power factor. In other words, the quantity received or measured is rather the power factor used to control the set of fan(s).

[0140] Further, the multiplying coefficient ck for a respective central portion 24, denoted ckc, is advantageously distinct from the multiplying coefficient ck for a corresponding edge portion 26, denoted ckedge. The value of the multiplying coefficient ck is for example adjusted experimentally and empirically for each new installation 10, notably because the free space between the rollers 34 for the passage of air varies from one installation 10 to another.

[0141] According to the aforementioned options, the convective heat transfer coefficient he advantageously verifies the following equation for a respective central portion 24:

[0142]

[0010] yacf 1ir 1A- C.rc — CKrc . —Dcp“cwhere hc,crepresents the convective heat transfer coefficient, ckcrepresents a multiplying coefficient, D represents the diameter of the wire 12, VA_Crepresents an air velocity, and ac, pcare predefined power coefficients, all respectively for said central portion 24; and the convective heat transfer coefficient he advantageously verifies the following equation for a corresponding edge portion 26:

[0143]

[0011] where he, edge represents the convective heat transfer coefficient, ckedge represents a multiplying coefficient, D represents the diameter of the wire 12, A_edge represents an air velocity, and aedge, Pedge are predefined power coefficients, all respectively for said edge portion 26; and preferably with at least one, several or all difference(s) among the following differences. Ckc ckedge, VA_C V A_edge, C(c Oedge and Pc Pedge- Alternatively, the convective heat transfer coefficient he is calculated both for a respective central portion 24 and for a corresponding edge portion 26 with the same single value of air velocity, denoted VA in this case. This value of air velocity A is typically an average velocity, for example averaged over the area covered by the fan flow. According to this variant, it is also possible to proceed in this way, even if the edge air velocity VA_edge is actually different from the center air velocity VA_C, by using in this case a multiplying coefficient different from the multiplying coefficient ck referred to in aforementioned equations

[0010] and

[0011] , In other words, said multiplying coefficient will ingest the edge / center air velocity dissymmetry, and the same average air velocity will be used to calculate the convective heat transfer coefficient hc,cfor the central portion 24 and the convective heat transfer coefficient he, edge for the edge portion 26.

[0144] Further advantageously, the sum of the predefined power coefficients a, p is substantially equal to 1 , both for the central portion 24 and respectively the edge portion 26. In other words, the predefined power coefficients a, preferably verify the following equation:

[0145]

[0012] a + / 3 « 1 and in particular, the following equations

[0146]

[0013] ac + Pc ~ 1

[0147]

[0014] aedge T edge ~ 1

[0148] The computation module 42 is configured for computing the temperature T of the steel wire 12 according to the estimated wire temperature gradient 5T / br.

[0149] The computation module 42 is configured to solve the heat diffusion equation in one dimension, namely as a function of the radial position r, and also as a function of time, with the edge condition of equation [2] and a given initial condition for the temperature field in the wire section at the start of conveyor 16, i.e. at the start of cooling. The computation module 42 is then configured to calculate the evolution over time t (i.e. during cooling) of a temperature field T(r,t) in the wire section.

[0150] The computation module 42 is typically configured to calculate the evolution of the temperature, in particular of the temperature field T(r,t), time step by time step.

[0151] At each time step, the computation module 42 is typically configured to also calculate the evolution of microstructure properties (e.g. phase fractions, for austenite and pearlite, and possibly also for ferrite, bainite and / or martensite), taking into account the current temperature. In fact, it may be a field of phase fractions (i.e. values as a function of r), as in the case of temperature. At each time step, depending on the temperature T(r,t), the computation module 42 is configured, for example, to determine whether a phase transformation is starting (and if so, which one), and with what transformation rate, or whether a phase transformation is already underway, and then to update the corresponding transformation rate, and the current phase fraction values.

[0152] An interlamellar spacing between perlite plates can also be determined, in particular as a function of a perlite transformation temperature for the thermal route considered.

[0153] Alternatively, some microstructure properties may be calculated by a calculator (not shown), external to the electronic determination device 30 and to which the computed temperature T has been transmitted by the transmission module 46.

[0154] It should be noted that the evolution of the temperature, in particular of the temperature field T(r,t), and the evolution of microstructure properties are coupled. The phase transitions in question can be exothermic; and when a phase (e.g. bainite, from austenite, or perlite from austenite) starts to be formed, this can release heat into the wire. The hump visible on curves in Figure 4 is due to such a heat release.

[0155] The temperature T, computed by the determination device 30, and in particular by the computation module 42, is intended for performing at least one action among the group comprising: controlling the conveyor 16, controlling the air cooling, determining microstructural and / or mechanical properties of the steel wire 12 that has been cooled down, and modelling an installation for producing the steel wire 12.

[0156] The computed temperature, which is used for said controlling, may designate the current temperature; or the final temperature at the end of conveyor 16, i.e. at the end of cooling; or else the entire time evolution of temperature.

[0157] Various control options are available for controlling the conveyor 16 and / or the set of fan(s).

[0158] If a temperature computed at the current instant (taking into account an initial temperature measurement and the process parameters used up to that point) is different from a target temperature for that instant, then the conveyor speed and / or the power of subsequent fan(s) is corrected according to this difference.

[0159] If a thermal route T(t) computed between the initial time and the current time differs from a target thermal route for this first time period, then the conveyor speed and / or the power of subsequent fan(s) is corrected according to this difference.

[0160] If the computed thermal route from the initial instant to the end of cooling (calculated as a function of an initial temperature measurement, as a function of process parameters used up to the current instant, and as a function of process parameters forecast for the remainder of the cooling process) differs from a target thermal route, then the conveyor and / or the remaining fan(s) are controlled to approach the target thermal route.

[0161] If one or more final mechanical propertie(s) (deduced from one or more microstructure properties evaluated as explained above, for instance the interlamellar spacing) deviate from one or more target mechanical properties, setpoint(s) for the conveyor and / or the remaining fan(s) are corrected so as to approach the target mechanical properties. The one or more mechanical propertie(s) may comprise one or more of: a tensile strength, a yield strength, a total elongation at break.

[0162] If the thermal route followed, as evaluated after wire cooling, or - and preferably - if one or more final mechanical properties, as evaluated after wire cooling, as a function of the values of the process parameters (conveyor speed, fan power, initial temperature), recorded during cooling, differs from one or more target mechanical properties, then, for the next wire coil, one or more of the process parameters is adjusted to get closer to said the one or more target mechanical properties. Indeed, it is preferable to have a coil of wire with homogeneous propertie(s) along the coil (even if it differs from the target), and to correct only for the next coil of wire. In other words, the wire is then processed coil by coil.

[0163] The thermal evolution for the wire, determined as above explained, can also be used for a posteriori characterization of the wire, which enables to know one or more mechanical properties of the wire, at the end of the manufacturing process, without having to carry out direct mechanical measurements on the wire. Furthermore, it allows to know the wire's properties meter by meter (instead of having a single value for the sample taken from the wire). In this case, the computation is based on a set of measurements (conveyor speed, fan speed, rolling speed, initial temperature, etc.) recorded during the cooling operation.

[0164] For the modelling, this makes it possible to dimension the installation for producing the steel wire 12 (fan power, number of fans, range of conveyor speeds, and conveyor length...), by using this temperature computation to check that the dimensioning in question enables the desired thermal routes to be obtained; then to manufacture (or upgrade) the production installation in accordance with the results of this modelling.

[0165] According to the optional addition, the acquisition module 44 is configured for acquiring at least one value among the group comprising: a measured value of an initial temperature Tmi, a measured value of the conveying speed Vc, a control value of the conveying speed Vc, a measured value of an air velocity VA, a measured value of a power of a set of fan(s) blowing air on the steel wire 12, a control value of the set of fan(s).

[0166] According to said optional addition, the computation module 42 is advantageously configured for computing the temperature T of the steel wire 12 according further to the at least one acquired value. According to the optional addition, the transmission module 46 is configured for transmitting the computed temperature T for performing at least one action among the group comprising: controlling the conveyor 16, controlling the air cooling, determining microstructural and / or mechanical properties of the steel wire 12 that has been cooled down, and modelling an installation for producing the steel wire 12. For example, the transmission module 46 is configured for transmitting the computed temperature T to the controller 28, for controlling the conveyor 16 and / or the set of fan(s).

[0167] The operation of the production installation 10, and in particular of the electronic determination device 30, according to the invention will now be explained in view of Figure 3 representing a flowchart of a determination method according to the invention for determining the temperature T of the steel wire 12 during its cooling by air on the conveyor 16, the method being implemented by the electronic determination device 30.

[0168] Optionally and initially, during an acquiring step 100, the electronic determination device 30 acquires, via its acquisition module 44, at least one value among the group comprising: a measured value of an initial temperature T mi, a measured value of a conveying speed Vc, a control value of the conveying speed Vc, a measured value of an air velocity VA, a measured value of a power of a set of fan(s) blowing air on the steel wire 12, a control value of the set of fan(s).

[0169] After the optional acquiring step 100, the electronic determination device 30 estimates, via its estimation module 40 and during an estimating step 110, the wire temperature gradient <5T / 6r with respect to the radial position r as a function of the total heat transfer coefficient hi-.

[0170] The wire temperature gradient <5T / 6r is for example estimated according to above equations [1] and [2],

[0171] The total heat transfer coefficient hTdepends on the convective heat transfer coefficient he associated to air convection and on the radiative heat transfer coefficient hR associated to radiation, and is for example calculated according to above equation [3],

[0172] The convective heat transfer coefficient he is for example calculated according to above equation [9], and optionally in particular according above equations

[0010] for a respective central portion 24 and respectively

[0011] for a corresponding edge portion 26.

[0173] The radiative heat transfer coefficient hR is for example calculated according to above equation [8], which applies for both central portion 24 and edge portion 26.

[0174] The center effective emissivity ECused for calculating, for example according to equation [8], the radiative heat transfer coefficient hR for at least one central portion 24 is typically a predefined value, and preferably a fixed value. The edge effective emissivity Eedge used for calculating, for example according to equation [8], the radiative heat transfer coefficient hR for at least one edge portion 26 is distinct from the center effective emissivity ECand also defined independently from said center effective emissivity EC.

[0175] The edge effective emissivity Eedge is for example calculated according to above equation [4], and further optionally according to related equations [5] to [7],

[0176] After the estimating step 110, the electronic determination device 30 computes, via its computation module 42 and during a computing step 120, the temperature T of the steel wire 12, according to the wire temperature gradient 5T / 5r estimated during the estimating step 110.

[0177] The estimated wire temperature gradient 5T / 5r is for example used to solve the heat diffusion equation, as described above.

[0178] When at least one value has been acquired during the optional acquiring step 100, the temperature T of the steel wire 12 is advantageously computed according further to said at least one acquired value during the computing step 120.

[0179] The temperature T, during the computing step 120, is intended for performing one or several actions among: controlling the conveyor 16, controlling the air cooling, determining microstructural and / or mechanical properties of the steel wire 12 that has been cooled down, and modelling an installation for producing the steel wire 12.

[0180] Optionally and after the computing step 120, during a performing step 130, the electronic determination device 30 transmits, via its transmission module 46, the computed temperature T for performing at least one action among the group comprising: controlling the conveyor 16, controlling the air cooling, determining microstructural and / or mechanical properties of the steel wire 12 that has been cooled down, and modelling an installation for producing the steel wire 12.

[0181] During said optional performing step 130, the temperature T, previously computed during the computing step 120, is typically transmitted - via the transmission module 46 - to the controller 28 for controlling the conveyor 16 and / or the set of fan(s).

[0182] After the computing step 120, the determination method goes back to the estimating step 110, or else optionally to the acquiring step 100, for iterating the estimating step 110 and then the computing step 120 - or else the acquiring step 100, the estimating step 110 and then the computing step 120, on a new part of the steel wire 12, i.e. on a subsequent part of the steel wire 12.

[0183] Thus, the determination method according to the invention is accurate, and in particular estimates the radiative heat transfer coefficient hR for each edge portion 26 of the wire 12, independently from the radiative heat transfer coefficient hR estimated for a respective central portion 24 of the wire 12.

[0184] Estimating the radiative heat transfer coefficient hR and the convective heat transfer coefficient he according to the invention allows being robust and continuing to give correct values with respect to a change in operating conditions of the production installation 10, and even when moving from one installation 10 to another, provided that the values of the multiplying coefficients ck are adjusted for the new installation 10.

[0185] Further, according to advantageous embodiments, the equations used for the radiative heat transfer coefficient hR and the convective heat transfer coefficient he incorporate the influence of the main operating conditions impacting cooling (and more precisely impacting edge / center cooling asymmetry): wire diameter D, spacing e between successive loops 22, and possibly conveying speed Vc and / or rolling speed VL.

[0186] Thus, the method according to the invention is far better than the prior art method, in particular than the method disclosed in the aforementioned article from Joong-ki Hwang, in which equation (23) recites a simple global coefficient (p for the total heat transfer coefficient h-r, which is constant. In the prior art method, the global coefficient (p therefore does not depend from the wire diameter D and / or from the spacing e, whereas the edge / center dissymmetry varies with the wire diameter D and the spacing e, in practice for both the radiative heat transfer coefficient hR and the convective heat transfer coefficient he. Preferential embodiments of the invention take into account these influences of the wire diameter D and / or the spacing e.

[0187] In other words, a different effective emissivity E is used for computing the heat exchange by radiation at the center, namely the center effective emissivity EC, and on the edge, namely the edge effective emissivity Eedge, with the edge effective emissivity Eedge distinct and independently defined from the center effective emissivity EC, to reflect that there is more wire-overlapping on the edge portions 26 and so, less radiation losses.

[0188] Accordingly, the temperature T of the steel wire 12 is determined for the edge portions 26 independently from the central portions 24 of the wire 12, as illustrated in Figure 4. Indeed, Figure 4 shows several curves of the temperature T of the steel wire 12 with respect to a time expressed in seconds (s), said time corresponding in fact to a longitudinal distance Dx along the conveying direction X. Figure 4 shows in particular curves related to the central portions 24 of the wire 12 along the conveying direction X, said curves being labelled “centre” in Figure 4; and other curves related to the edge portions 26 of the wire 12 along said conveying direction X, said other curves being labelled “edge” in Figure 4. The longitudinal distance Dx is defined from the beginning of the conveyor 16, corresponding to a null value of said distance Dx, and also to a null value of time, up to the end of the conveyor 16 along the conveying direction X. The beginning of the conveyor 16 corresponds to the location where the steel wire 12 is delivered from the rolling mill 14, i.e. to the junction between the rolling mill 14 and the conveyor 16. Figure 4 shows curves of both a measured temperature and a calculated temperature of the steel wire 12; the curves of measured temperature being labelled “Meas” in Figure 4, and the curves of calculated temperature, i.e. determined with the determination method and the electronic determination device 30 according to the invention, being labelled “Calc” in Figure 4. Further, the temperature T of the steel wire 12 is determined, i.e. calculated, for two hypotheses on the initial austenitic grain size (representative respectively of a minimum and maximum values for the austenite grain size, as obtained during industrial production of such steel wires), denoted “dg” in Figure 4, namely 10 pm and 30 m.

[0189] The accuracy obtained is good, having in mind the confidence interval to be expected from industrial measurements. In fact, outside of the difficulty to perform measurements, there is a scattering of the evolutions themselves, due to the geometry of the pile of wire loops 22.

[0190] The results obtained with the determination method and the electronic determination device 30 according to the invention are also illustrated in below Tables 1 and 2.

[0191] Table 1 gives interlamellar spacings, denoted Sp; and tensile strengths, denoted Rm; which are on one hand measured values on the installation and on the other hand calculated values with the invention, for two hypotheses on the initial austenitic grain size (representative respectively of a minimum and maximum values for the austenite grain size, as obtained during industrial production of such steel wires), denoted dy, namely 10 pm (10 microns) and 30 pm. These values are given for diameters 5,5 mm and 7 mm in grade FM70, and for diameters 13 mm and 16 mm in grade FMP82Cr.

[0192] [Table 1]

[0193] Table 2 provides steel compositions (in 10'3%wt), for aforementioned grades FM70 and FMP82Cr.

[0194] [Table 2]

[0195] Advantageously, for each edge portion 26, the radiative heat transfer coefficient hR is calculated according to the edge effective emissivity Eedge depending on the spacing e between two successive loops 22.

[0196] Further advantageously, the edge effective emissivity Eedge increases when the spacing e increases, to reflect that the wire-overlapping decreases in this case, and so there are more radiation losses.

[0197] Also advantageously, the surface temperature Ts used for calculating the radiative heat transfer coefficient hR, for example according to equation [8], is distinct for a respective central portion 24 than for a corresponding edge portion 26, in the same loop 22 than said central portion 24. In other words, the surface temperature Ts used for calculating the radiative heat transfer coefficient hR varies from the central portion 24 to the corresponding edge portion 26.

Claims

CLAIMS1. Method for determining a temperature (T) of a steel wire (12) during its cooling by air on a conveyor (16), the conveyor (16) extending in a conveying direction (X) and having a central axis (18) and two lateral edges (20) on either side of the central axis (18), the central axis (18) and the lateral edges (20) extending in the conveying direction (X), the steel wire (12) being wound in loops (22) placed successively on the conveyor (16) and spaced from one another in the conveying direction (X), each loop (22) comprising at least one central portion (24) near the central axis (18) and at least one edge portion (26) near a respective lateral edge (20) of the conveyor (16), the method being implemented by an electronic determination device (30) and comprising the following steps:- estimating (110) a wire temperature gradient (6T / 6r) with respect to a radial position (r) within the wire, as a function of a total heat transfer coefficient (h-j-), the total heat transfer coefficient (h-r) depending on a convective heat transfer coefficient (he) associated to air convection and on a radiative heat transfer coefficient (hp) associated to radiation; and for at least one central portion (24), the radiative heat transfer coefficient (hp) being calculated according to a predefined center effective emissivity (EC);- computing (120) the temperature (T) of the steel wire (12) according to the estimated wire temperature gradient (5T / br); wherein for at least one edge portion (26), the radiative heat transfer coefficient (IIR) is calculated according to an edge effective emissivity (Eedge), the edge effective emissivity (£edge) being distinct and defined independently from the center effective emissivity (EC).

2. Method according to claim 1 , wherein the method further comprises:- acquiring (100) at least one value among the group comprising: a measured value of an initial temperature (Tmi), a measured value of a conveying speed (Vc), a control value of the conveying speed (Vc), a measured value of an air velocity (VA), a measured value of a power of a set of fan(s) blowing air on the steel wire (12), a control value of the set of fan(s); and during the computing step (120), the temperature (T) of the steel wire (12) is computed according further to the at least one acquired value.

3. Method according to claim 1 or 2, wherein the computed temperature (T) is intended for performing at least one action among the group comprising: controlling the conveyor (16), controlling the air cooling, determining microstructural and / or mechanicalproperties of the steel wire (12) that has been cooled down, and modelling an installation (10) for producing the steel wire (12).

4. Method according to any one of the preceding claims, wherein the edge effective emissivity (Eedge) depends on a spacing (e) between two successive loops (22) along the conveying direction (X).

5. Method according to claim 4, wherein the edge effective emissivity (Eedge) increases when the spacing (e) between two successive loops (22) increases; the edge effective emissivity (Eedge) preferably verifying the following equation:£eage= A.10B ewhere Eedge represents the edge effective emissivity, e represents the spacing between two successive loops (22), andA and B are first and second parameters;A and B preferably depending on a diameter (D) of the wire (12); the first parameter (A) still preferably verifying the following equation:A = Fprl + Fpr2. D where A represents the first parameter,D represents the diameter of the wire (12),Fpr1 and Fpr2 are constant coefficients; and the second parameter (B) still preferably verifying the following equation:B = Fpr3 + FprA. D where B represents the second parameter,D represents the diameter of the wire (12),Fpr3 and Fpr4 are constant coefficients.

6. Method according to claim 4 or 5, wherein the spacing (e) between two successive loops (22) is determined depending on a conveying speed (Vc).

7. Method according to claim 6, wherein the spacing (e) between two successive loops (22) further depends on a diameter (ds) of the loops (22), a diameter (D) of the wire (12) and a rolling speed (VL); the spacing (e) between two successive loops (22) preferably verifying the following equation:where e represents the spacing between two successive loops (22), ds represents the diameter of the loops (22), Vc represents the conveying speed,VL represents the rolling speed, andD represents the diameter of the wire (12).

8. Method according to any one of the preceding claims, wherein the center effective emissivity (EC) is a constant value.

9. Method according to any one of the preceding claims, wherein the radiative heat transfer coefficient (hp) verifies the following equation:where hR represents the radiative heat transfer coefficient,E represents the effective emissivity of the respective portion of the wire (12), o represents the Stefan Boltzmann constant,Ts represents a surface temperature of the respective portion of the wire (12), andTA represents an ambient temperature; the surface temperature for a respective central portion (24) being distinct from the surface temperature for a corresponding edge portion (26), in the same loop (22) than said central portion (24).

10. Method according to any one of the preceding claims, wherein the convective heat transfer coefficient (he) verifies the following equation: y hc= ck . — „ c D where he represents the convective heat transfer coefficient, ck represents a multiplying coefficient,D represents the diameter of the wire (12),VA represents an air velocity, and a, p are predefined power coefficients; the predefined power coefficient related to the air velocity (VA) for a respective central portion (24) being preferably distinct from the predefined power coefficient related to the air velocity ( A) for a corresponding edge portion (26); the corresponding edge portion (26) being in the same loop (22) than said central portion (24);the predefined power coefficient related to the diameter (D) of the wire (12) for the respective central portion (24) being preferably distinct from the predefined power coefficient related to the diameter (D) of the wire (12) for the corresponding edge portion (26); and the air velocity for the respective central portion (24) being preferably distinct from the air velocity for the corresponding edge portion (26).

11. Computer program comprising software instructions which, when executed by a processor, implement a method according to any one of the preceding claims.

12. Electronic determination device (30) for determining a temperature (T) of a steel wire (12) during its cooling by air on a conveyor (16), the conveyor (16) extending in a conveying direction (X) and having a central axis (18) and two lateral edges (20) on either side of the central axis (18), the central axis (18) and the lateral edges (20) extending in the conveying direction (X), the steel wire (12) being wound in successive loops (22) spaced from one another in the conveying direction (X), each loop (22) comprising at least one central portion (24) near the central axis (18) and at least one edge portion (26) near a respective lateral edge (20) of the conveyor (16), the electronic determination device (30) comprising:- an estimation module (40) configured for estimating a wire temperature gradient (<5T / <5r) with respect to a radial position (r) within the wire, as a function of a total heat transfer coefficient (h-j-), the total heat transfer coefficient (h-r) depending on a convective heat transfer coefficient (he) associated to air convection and on a radiative heat transfer coefficient (IIR) associated to radiation; and for at least one central portion (24), the radiative heat transfer coefficient (hp) being calculated according to a predefined center effective emissivity (EC);- a computation module (42) configured for computing the temperature (T) of the steel wire (12) according to the estimated wire temperature gradient (5T / br); wherein for at least one edge portion (26), the radiative heat transfer coefficient (IIR) is calculated according to an edge effective emissivity (Eedge), the edge effective emissivity (£edge) being distinct and defined independently from the center effective emissivity (EC).

13. Electronic determination device (30) according to claim 12, wherein the electronic determination device (30) further comprises:- an acquisition module (44) configured for acquiring at least one value among the group comprising: a measured value of an initial temperature (Tmi), a measured value of aconveying speed (Vc), a control value of the conveying speed (Vc), a measured value of an air velocity (VA), a measured value of a power of a set of fan(s) blowing air on the steel wire (12), a control value of the set of fan(s); and the computation module (42) being configured for computing the temperature (T) of the steel wire (12) according further to the at least one acquired value.

14. Electronic determination device (30) according to claim 12 or 13, wherein the computed temperature (T) is intended for performing at least one action among the group comprising: controlling the conveyor (16), controlling the air cooling, determining microstructural and / or mechanical properties of the steel wire (12) that has been cooled down, and modelling an installation for producing the steel wire (12).

15. Installation (10) for producing a steel wire (12), comprising:- a rolling mill (14) for delivering the steel wire (12),- a conveyor (16) for conveying the steel wire (12) in a conveying direction (X), the conveyor (16) extending in the conveying direction (X) and having a central axis (18) and two lateral edges (20) on either side of the central axis (18), the central axis (18) and the lateral edges (20) extending in the conveying direction (X), the steel wire (12) being wound in successive loops (22) spaced from one another in the conveying direction (X), each loop (22) comprising at least one central portion (24) near the central axis (18) and at least one edge portion (26) near a respective lateral edge (20) of the conveyor (16),- a set of fan(s) arranged below the conveyor (16), for blowing air on the conveyed steel wire (12), and- a controller (28) for controlling the conveyor (16) and / or the set of fan(s), wherein the installation (10) further comprises an electronic determination device (30) for determining a temperature (T) of the steel wire (12) during its cooling by air on the conveyor (16), the electronic determination device (30) being connected to the controller (28) and according to any one of claims 12 to 14.

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