Method and device for determining the metallurgical state of a product

Abstract

A method for the in-line and continuous estimation of the metallurgical state of a metal product (1) travelling through a plant (2) for the continuous processing of metal products, comprising a step of determining the saturation induction (Bsat) of the metal product as it passes through a longitudinal-field oscillator circuit (3) of the plant.

Description

METHOD AND DEVICE FOR DETERMINING THE METALLURGICAL STATE OF A PRODUCT Designation of the technical field concerned

[0001] The invention relates to installations for processing metal products, whether in the form of slabs, billets, strips, tubes, or any other profile, for which knowledge of the metallurgical state of the products is important.

[0002] Technical problems addressed by the invention and technical background

[0003] The mechanical properties of a metal product are closely linked to its metallurgical state. For example, the proportion of austenite, ferrite, pearlite, bainite, or martensite in the structure of a steel product will determine its mechanical strength.

[0004] Metal processing facilities allow the metallurgical state of a product to be modified, for example to increase its mechanical strength. For them to operate efficiently, it is necessary to know the metallurgical state of the products at different stages of the transformation process.

[0005] Traditionally, the control of the metallurgical state of a product is carried out by taking a sample and then analyzing it under a microscope, combined with other tests such as hardness measurements or tensile tests. This control method allows for a detailed analysis of the metallurgical state of the products, but it is carried out in a laboratory and requires a significant processing time to obtain the information. During this time, the installation may produce poor quality products.

[0006] It is known to use equipment dedicated to the online control of the metallurgical state of a product during processing. This equipment works, for example, by measuring a magnetic value such as remanence, or by ultrasound or X-ray transmission. However, they are expensive, complex to use and necessarily require the installation of equipment dedicated to this function on the production line.

[0007] It is also known from JP2005188948 to use a device comprising a set of coils for estimating the hardness of a stainless steel product. The device comprises an excitation coil inside which two detection coils are placed, the product being positioned in one of the detection coils. The estimation of the hardness of the product is carried out according to the magnetic permeability of the product determined according to the difference between voltages induced in the detection coils when an alternating current is applied to the excitation coil.

[0008] This solution is dedicated to determining the magnetic permeability of a product to estimate its hardness. The device is complex and expensive with a nesting of coils. It is not suitable for heating the product, particularly at high temperatures, nor for controlling a heat treatment installation for said product.

[0009] The invention makes it possible to remedy these problems.

[0010] The invention provides an inexpensive solution for providing an online and continuous estimate of the metallurgical state of a product being processed in order to optimize production parameters. Furthermore, in some of its embodiments, it does not require the addition of equipment dedicated to this function on the production line.

[0011] According to a first aspect of the invention, there is proposed a method for online and continuous estimation of the metallurgical state of a metal product during its passage in an installation for the continuous treatment of metal products, comprising a step of determining the saturation induction (Bsat) of the product during the passage of said metal product in a longitudinal field oscillating circuit equipping said installation.

[0012] Preferably, the method comprises a determination of the proportion of austenite in the product as a function of its saturation induction (Bsat) determined during the passage of the metallic product in the longitudinal field oscillating circuit.

[0013] According to a second aspect of the invention, a method is proposed for controlling an installation for the continuous treatment of a moving metal product, comprising a step of online and continuous estimation of the metallurgical state of a metal product being moved in the continuous treatment installation according to the first aspect of the invention, or one or more of its improvements, followed by a step of adjusting an operation of the installation as a function of the saturation induction (Bsat) of the product determined during its passage in the longitudinal field oscillating circuit.

[0014] The method according to the invention may comprise a step of comparing the value of the saturation induction (Bsat1) of the product determined during its passage through the longitudinal field oscillating circuit with an expected value (Bsat2), the adjustment step comprising a modification of at least one operating parameter of the installation when the difference between the estimated value (Bsat1) and the expected value (Bsat2) is greater than a predetermined threshold.

[0015] According to an alternative embodiment of the invention, the operation of the installation is adjusted according to the evolution of the saturation induction of the product between a first value (Bsat3) determined during its passage in a first longitudinal field oscillating circuit equipping the installation and a second value (Bsat4) determined during its passage in a second longitudinal field oscillating circuit equipping the installation.

[0016] According to a third aspect of the invention, there is provided an installation for the continuous treatment of a moving metal product capable of implementing a method according to the first or second aspect of the invention, or one or more of their improvements, comprising an oscillating circuit with longitudinal flow traversed by said product and a computer program capable of determining the saturation induction (Bsat) of the product circulating in the oscillating circuit.

[0017] A computer program means any type of computer program or calculation software, whether implemented on a desktop computer or a computer embedded in an electrical cabinet, a PLC, an electronic calculator or any other control and command system of an industrial installation. Memory means all types of "machine-readable storage medium / media". "Machine-readable storage medium / media" or "computer-readable storage medium / media" means, but is not limited to, portable or non-portable storage devices, optical storage devices and various other media capable of storing, containing or supporting instructions and / or data, and any medium that participates in the provision of instructions to a processor for their execution.A machine-readable medium may include a non-transitory medium in which data may be stored and which does not include carrier waves and / or transient electronic signals propagating wirelessly or over wired connections. Non-volatile media include, for example, optical disks, magnetic disks, or read-only memories. Volatile media include dynamic memory, including cache memory. Transmission media include coaxial cables, copper wires, and optical fibers.Common forms of computer-readable media include, for example, but are not limited to, a floppy disk, a floppy disk, a hard disk, a magnetic tape, any other magnetic media, a CD-ROM, a DVD, any other optical media, punched cards, other physical media with patterns of holes, RAM, PROM and EPROM, FLASH-EPROM, any other memory chip or cartridge, a carrier wave, or any other medium from which a computer can read. Various forms of computer-readable media may be involved in carrying one or more sequences of one or more instructions to a processor for execution.

[0018] A computer program product may include machine-executable code and / or instructions that may represent a procedure, function, subroutine, program, routine, subprogram, module, software, class, or any combination of instructions, data structures, or program instructions. A code segment may be coupled to another code segment or hardware circuit by transmitting and / or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc., may be transmitted, passed, or conveyed by any suitable means, including memory sharing, message passing, token passing, network transmission, etc.

[0019] According to an exemplary embodiment of the invention, the oscillating circuit has the primary function of heating the product.

[0020] The oscillating circuit can have the function of determining the saturation induction of the product.

[0021] Advantageously according to the invention, the oscillating circuit is used for controlling the installation.

[0022] According to another aspect of the invention, there is provided a computer program product comprising instructions which when loaded into a memory of a computer, cause a system for monitoring and controlling an installation according to the third aspect of the invention to execute the steps of the method according to the first or second aspect of the invention.

[0023] The invention can be implemented using an oscillating circuit present on the installation whose main function is to heat the product. An additional function is added to the existing equipment allowing the saturation induction of the product to be estimated, which depends on its metallurgical state, without it being necessary to modify it.

[0024] The invention can also be implemented by adding an oscillating circuit to the installation. Its function is then limited to estimating the metallurgical state of the product. Its function is not to heat the product or modify its properties. The oscillating circuit is thus similar to a sensor for measuring a property of the product.

[0025] The power of the oscillating circuit is then very low, being limited to that necessary for the circuit to operate. This does not cause the product to heat up, or limits it to the strict minimum.

[0026] An oscillating circuit according to the invention notably comprises a power source, also called a converter, an adaptation box comprising capacitors, and a longitudinal flux inductor.

[0027] The metallurgical state of the product is determined as it passes through the inductor.

[0028] An oscillating circuit whose function is limited to estimating the saturation induction and the metallurgical state of the product may, for example, have the following characteristics:

[0029] . Power: 25 to 100 kW

[0030] . Adapter box capacity: 1.2 to 20 µF

[0031] . Frequency: 5 to 200 kHz

[0032] . Length of the inductor, in the direction of product movement: 10 to 60 cm

[0033] . Number of turns of the inductor: 1

[0034] An oscillating circuit whose main function is to heat the product, and which includes an additional function of estimating the saturation induction and the metallurgical state of the product, may, for example, have the following characteristics:

[0035] . Power: 25 kW to 7000 kW

[0036] . Adapter box capacity: 2.4 to 50 µF

[0037] . Frequency: 5 to 200 kHz

[0038] . Length of the inductor, in the direction of product movement: 10 to 400 cm

[0039] . Number of turns of the inductor: 1 to 20

[0040] The assessment of the metallurgical state of the product is obtained from measurements of electrical quantities of the oscillating circuit carried out in real time, for example the voltage and frequency at the terminals of the inductor. It requires knowledge of the electrical properties of the oscillating circuit, in particular the impedance and inductance of the oscillating circuit, the inductance of the inductor, and the equivalent capacitance of the oscillating circuit. It also requires knowledge of the electrical resistivity of the product at the temperature at which it is in the oscillating circuit, or at its average temperature between the inlet and the outlet of the product from the oscillating circuit if the primary function of the oscillating circuit is to heat the product.

[0041] The invention allows automatic and online control of the metallurgical state of the product at a point in the installation by determining the value of the saturation induction of the product during its passage through the oscillating circuit and by comparing this with a reference value.

[0042] This reference value corresponds to that of a product having the desired quality, particularly in terms of metallurgical structure and mechanical properties.

[0043] The implementation of the invention thus makes it possible to ensure continuous monitoring of the production quality of the installation.

[0044] A check can be carried out at several points on an installation by adding oscillating circuits dedicated to the points where knowledge of the metallurgical state of the product is useful for optimizing the production parameters of the installation.

[0045] The invention makes it possible to adjust the operating parameters of the installation to maintain the metallurgical state of the product at the expected level, while maintaining the value of the saturation induction of the product at the desired level.

[0046] The invention also allows traceability of the properties of the products treated on the installation by recording average data for each product, and data on its length.

[0047] An oscillating circuit has a quality factor Q which can be expressed in the form of the following equation:

[0048] (1)

[0049] With :

[0050] (H): inductance of the oscillating circuit,

[0051] (Hz): oscillation frequency of the oscillating circuit,

[0052] (ohm): electrical resistivity of the product.

[0053] The inductance of the oscillating circuit is determined by the sum of the inductances of the equipment constituting the oscillating circuit, that of the converter, L1, and that of the inductor, Lind.

[0054] Depending on the construction of the installation, when the system includes an upstream transformer and a downstream transformer, they can be expressed by:

[0055]

[0056]

[0057] The inductance of the inductor is also expressed according to the expression:

[0058]

[0059] The electrical resistivity of the product varies depending on the temperature, as illustrated for example by the. It is necessary to know this according to the temperature to implement the method according to the invention.

[0060] The quality factor Q of the oscillating circuit can also be expressed according to the following equation:

[0061]

[0062] With :

[0063] (H): inductance of the oscillating circuit,

[0064] (H): inductance of the inductor,

[0065] (mm): thickness of the product to be heated,

[0066] (mm): width of the product to be heated,

[0067] (Hz): oscillation frequency of the oscillating circuit,

[0068] (μH.m -1 ): absolute magnetic permeability of vacuum (1.256 μH / m),

[0069] (μH.m -1 ): magnetic permeability of the product which varies according to the temperature,

[0070] ρ (μΩ.m -1 ): electrical resistivity of the product which varies according to the temperature.

[0071] For a given temperature, we can thus express the magnetic permeability of the product by the following resolution:

[0072]

[0073]

[0074]

[0075] (2)

[0076] The quality factor Q of the oscillating circuit can also be expressed according to the following equation:

[0077] (3)

[0078] With :

[0079] (V): voltage measured across the inductor terminals,

[0080] (I): current intensity in the inductor,

[0081] (W): active power measured at the terminals of the power source's supply network.

[0082] The current intensity in the inductor is deduced from the following relationship:

[0083]

[0084] With :

[0085] (f): capacitance of the oscillating circuit, given by construction,

[0086] (Hz): oscillation frequency of the oscillating circuit.

[0087] The electrical resistance of the product is expressed in the form:

[0088] (4)

[0089] (ohm.m): electrical resistivity of the product

[0090] L (H): inductance of the oscillating circuit

[0091] S (m 2) : product surface

[0092] The determination of the saturation induction (Bsat) is obtained via the following equation:

[0093] (5)

[0094] Either :

[0095]

[0096] With :

[0097] (μH.m -1 ): magnetic permeability of the product,

[0098] (μH.m -1 ): absolute magnetic permeability of vacuum,

[0099] (Am -1 ): magnetic field intensity in amperes per meter of inductor length,

[0100] (unitless): value depending on the thickness of the product and the depth of penetration current in it.

[0101] The value k is determined from the curve shown in, with the value of k on the ordinate and the ratio between the thickness of the product and the depth of penetration of the current into the product on the abscissa.

[0102] The intensity of the magnetic field H is expressed by the following equation:

[0103] (6)

[0104] With :

[0105] N: number of turns of the inductor,

[0106] Iind (A): intensity of the electric current in the inductor,

[0107] Lg (m): length of the inductor. Digital application

[0108] Example of numerical application of the invention for a metal strip moving on a continuous processing line comprising an induction heating inductor. In this example, the existing inductor ensuring the heating of the strip is used to estimate its metallurgical state by adding this function according to the invention. Input data

[0109] . Band: carbon steel according to Bisra 1

[0110] . Diagram () relating the austenite content of a carbon steel strip according to Bisra 1 to its saturation induction

[0111] . Thickness of the band: 1.3 mm

[0112] . Width of the band: 1200 mm

[0113] . Strip area: 3.36 m²

[0114] Average temperature of the section of the strip located in the inductor: 612.5°C

[0115] . Inductor length: 3.360 m

[0116] . Number number of turns of the inductor: 1

[0117] . Equivalent capacitance C of the oscillating circuit: 18.48 µF

[0118] . Inductance of the oscillating circuit: 0.069 µH

[0119] . Inductance of the inductor: 0.169 µH

[0120] . Measured oscillating circuit frequency: 89.8.10 3 Hz

[0121] . Diagram (Figure 6) relating the value of the quantity depending on the thickness of the product and the depth of penetration of the current in it. Value of for this example: 1.29

[0122] Determination of the quality factor of the oscillating circuit:

[0123] (3)

[0124] . Tension measured at the terminals of the inductor: 2336 V

[0125] . Intensity measured current in the inductor: 25000 A

[0126] . Active power measured inductor: 3201 kW

[0127]

[0128] Determination of electrical resistance of the product

[0129] (1)

[0130]

[0131] Determination of electrical resistivity of the product:

[0132] (4)

[0133] 0.99

[0134] → = 0.99 μΩ.m

[0135] Determination of magnetic permeability of the product

[0136] (2)

[0137]

[0138] 212 μH.m -1 Determination of the magnetic field H

[0139] (6)

[0140] Hm -1

[0141] Determination of saturation induction Bsat:

[0142] (5)

[0143]

[0144] →

[0145] Determination of austenite content according to saturation induction :

[0146] It is carried out using the diagram shown relating the austenite content of a carbon steel product according to Bisra 1 to its saturation induction.

[0147] For an ordinate value of of 1.53 T, we obtain an austenite content of 16%.

[0148] In practice, the relationship between the austenite content of the strip and its saturation induction is expressed by a mathematical equation entered into the computer program implementing the method according to the invention so that the determination of the austenite content is done automatically by calculation. Brief description of the figures

[0149] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

[0150] is a schematically and partially represented view, in longitudinal view, of an installation for continuous treatment of a metal product according to a first exemplary embodiment of the invention.

[0151] is a schematically and partially represented view, in longitudinal view, of an installation for continuous treatment of a metal product according to a second exemplary embodiment of the invention.

[0152] is a schematically and partially represented view, in longitudinal view, of an installation for continuous treatment of a metal product according to a third exemplary embodiment of the invention.

[0153] is a schematically and partially represented view, in longitudinal view, of an installation for continuous treatment of a metal product according to a fourth exemplary embodiment of the invention.

[0154] is a diagram illustrating the evolution of the resistance R of a product as a function of its temperature.

[0155] is a diagram illustrating the evolution of a value k dependent on the thickness of the product and the depth of penetration of the current into it.

[0156] is a diagram illustrating the evolution of the austenite content of the product according to its saturation induction.

[0157] A schematic representation of an installation 2 for the continuous treatment of metal products according to a first embodiment of the invention can be seen, in which a product 1 circulates. The installation comprises a furnace 5 for modifying the mechanical properties of the product by modifying its metallurgical state. In this example, an oscillating circuit 3 with longitudinal flow is arranged in the furnace to ensure heating of the product.

[0158] The primary function of this oscillating circuit is thus to heat the product. According to the invention, the oscillating circuit includes an additional function of determining the saturation induction of the product as it passes through the oscillating circuit.

[0159] To ensure this function, a computer program product 4 comprises the instructions for determining the saturation induction Bsat of the product from information coming from the oscillating circuit, such as current or voltage values ​​measured in real time on the oscillating circuit, information coming from the control and command system of the furnace, such as the format and chemical composition of the product circulating in the oscillating circuit, the temperature of the product at the inlet and outlet of the oscillating circuit, and pre-recorded reference data, such as structural characteristics of the oscillating circuit or electromagnetic properties of the product according to its nature and temperature.

[0160] A schematic representation of an installation 2 for the continuous treatment of metal products according to a second embodiment of the invention can be seen, in which a product 1 circulates. In this example, an oscillating circuit 3 with longitudinal flow is added downstream of a furnace 5 in the direction of travel of the product. This oscillating circuit only makes it possible to determine the saturation induction of the product at the outlet of the furnace.

[0161] In this embodiment, the oscillating circuit is small and has low capacitance. It is sized to ensure sufficient coupling with the product so that electrical measurements can be made on the oscillating circuit, with minimal heating of the product. Ideally, there would be no heating of the product at all, but it is not possible to ensure coupling of the oscillating circuit with the product without slight heating occurring.

[0162] A schematic representation of an installation 2 for the continuous treatment of metal products can be seen according to a third embodiment of the invention, in which a product 1 circulates. In this example, a first oscillating circuit 31 with longitudinal flow is arranged upstream of a furnace 5 and a second oscillating circuit 32 with longitudinal flow is present in the furnace.

[0163] The first oscillating circuit 31 only determines the saturation induction of the product at the entrance to the oven. Its function is not to heat the product.

[0164] The second oscillating circuit 32 has the main function of heating the product. An additional function of determining the saturation induction of the product has been added to it.

[0165] In this example, computer program 4 determines and compares the saturation induction values ​​of the product at the two oscillating circuits.

[0166] For example, the furnace control and command system modifies the furnace setpoints according to the saturation induction of the product determined from the first oscillating circuit. This value is representative of the metallurgical state of the product at the furnace inlet. It is thus possible to adjust the furnace settings, and thus the thermal cycle followed by the product in it, according to the initial state of the product upstream of the furnace.

[0167] In another example, the furnace control and command system modifies the furnace setpoints according to the evolution of the saturation induction of the product between the two oscillating circuits.

[0168] As a variant of this embodiment, the first oscillating circuit placed upstream of the furnace can be replaced by a mathematical model producing an estimate of what the saturation induction of the product should be based on data available on it, in particular during the production stages preceding its entry into the installation. The estimate thus obtained is less precise than with an oscillating circuit but it can be suitable for less demanding applications.

[0169] We can see schematically represented an installation 2 for continuous treatment of a metal product in which a product 1 circulates according to a fourth exemplary embodiment of the invention.

[0170] In this example, a first longitudinal flow oscillating circuit 32 is arranged in a heating section of an oven 5. This first oscillating circuit 31 has the main function of heating the product but it also includes an additional function of determining the saturation induction of the product during its passage through the oscillating circuit.

[0171] A second oscillating circuit 33 is arranged in the furnace at the outlet of a second section, for example a rapid cooling section. This second oscillating circuit 33 only makes it possible to determine the saturation induction of the product at the outlet of the first section. Its function is not to heat the product.

[0172] For example, the furnace control and command system modifies the cooling slope of the product in the cooling section of the furnace according to the saturation induction determined from the first oscillating circuit 32. This saturation induction being representative of the metallurgical state of the product at the end of heating, it is thus possible to modify the cooling slope according to the state of the product at the end of heating.

[0173] In this example, the furnace control and command system verifies that the saturation induction of the product determined from the second oscillating circuit 33 is indeed the expected one. If this is not the case, it adjusts the furnace operating parameters so that the determined value coincides with the expected one.

Claims

Method for online and continuous estimation of the metallurgical state of a metallic product (1) during movement in an installation (2) for continuous treatment of metallic products, characterized in that it comprises a step of determining the saturation induction (Bsat) of the product during the passage of said metallic product in an oscillating circuit (3) with longitudinal field equipping said installation. Method according to the preceding claim, comprising a step of determining the proportion of austenite in the product (1) as a function of its saturation induction (Bsat) determined during the passage of the metallic product in the oscillating circuit (3) with longitudinal field. Method for controlling an installation (2) for continuous processing of a moving metal product (1), comprising a step of online and continuous estimation of the metallurgical state of a metal product (1) during processing in the continuous processing installation (2) according to one of the preceding claims, followed by a step of adjusting an operation of the installation as a function of the saturation induction (Bsat) of the product determined during its passage in the oscillating circuit (3) with longitudinal field. Method according to the preceding claim, comprising a step of comparing the value of the saturation induction (Bsat1) of the product determined during its passage through the oscillating circuit (3) with longitudinal field with a predetermined expected value (Bsat2), in which the adjustment step comprises a modification of at least one operating parameter of the installation when the difference between the estimated value (Bsat1) and the expected value (Bsat2) is greater than a predetermined threshold. Method according to claim 3, in which the step of adjusting the operation of the installation is carried out according to the evolution of the saturation induction (Bsat) of the product between a first value (Bsat3) determined during its passage in a first oscillating circuit (31) with longitudinal field equipping the installation and a second value (Bsat4) determined during its passage in a second oscillating circuit (32) with longitudinal field equipping the installation. Installation (2) for continuous treatment of a moving metal product (1) capable of implementing a method according to one of the preceding claims, characterized in that it comprises an oscillating circuit (3) with longitudinal flow crossed by said product and a computer program (4) capable of determining the saturation induction (Bsat) of the product circulating in the oscillating circuit. Installation according to the preceding claim, in which the oscillating circuit (3) has the primary function of heating the product. Installation according to one of the two preceding claims, in which the oscillating circuit (3) is intended for determining the saturation induction (Bast) of the product. Installation according to the preceding claim, in which the oscillating circuit (3) is used for controlling the installation (2). Computer program product (4) comprising instructions which, when loaded into a memory of a desktop computer or a computer embedded in an electrical cabinet, an automaton, an electronic calculator or any other control and command system of an industrial installation, lead a control system of an installation according to any one of claims 6 to 9 to execute the steps of a method according to one of claims 1 to 5.

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