Method and device for determining the metallurgical condition of a product

Abstract

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

Description

[Technical Field]

[0001] The present invention relates to a plant for processing metal products, whether in the form of blooms, billets, strips, tubes or any other profile, where knowledge of the metallurgical state of the product is important. [Background technology]

[0002] Problems that the invention aims to solve The mechanical properties of a metal product are closely related to its metallurgical state: for example, the proportion of austenite, ferrite, pearlite, bainite, or martensite in the structure of a steel product determines the mechanical strength of the steel product.

[0003] Plants for processing metal products can be used to modify the metallurgical state of the product, for example to increase its mechanical strength. To operate efficiently, it is necessary to know the metallurgical state of the product at different stages of the transformation process.

[0004] Traditionally, the metallurgical condition of a product is inspected by taking a sample and then analyzing it photomicrographically under a microscope in combination with other tests such as hardness measurements or tensile tests. This control method allows for a detailed analysis of the metallurgical condition of the product, but it is done in a laboratory and requires significant processing time to obtain the information. During this time, the plant may produce a lower quality product.

[0005] It is known to use devices dedicated to the in-line control of the metallurgical condition of the products being processed. Such devices operate, for example, by measuring magnetic values ​​such as residual magnetism, or by ultrasound, or by X-ray transmission. However, these are expensive and complex to use and necessarily require the installation of dedicated equipment for this function in the production line.

[0006] Furthermore, from application 2005188948, it is known to use a device comprising a pair of coils to estimate the hardness of a stainless steel product. The device comprises an excitation coil with two detection coils arranged therein, and the product is placed on one of the detection coils. The hardness of the product is estimated based on the magnetic permeability of the product, which is determined based on the difference in voltage induced in the detection coil when an alternating current is applied to the excitation coil.

[0007] This solution is dedicated to determining the magnetic permeability of the product in order to estimate its hardness. This device is complicated and costly, since it has a coil interlocking system. This method is not particularly suitable for heating products at high temperatures, nor for controlling heat treatment plants for such products.

[0008] The present invention improves these problems. Summary of the Invention

[0009] The present invention provides a low-cost solution for in-line, continuous estimation of the metallurgical state of processed products in order to optimize manufacturing parameters, and in some embodiments does not require additional equipment on the production line dedicated to this function.

[0010] According to a first aspect of the present invention, a method is proposed for in-line and continuous estimation of the metallurgical state of a metal product moving through a plant for the continuous processing of metal products, the method comprising the step of determining the saturation induction (Bsat) of the metal product as it passes through a longitudinal magnetic field oscillator circuit of the plant.

[0011] Preferably, the method includes determining the proportion of austenite in the metal product based on its saturation induction (Bsat) determined when the product passes through a longitudinal magnetic field oscillating circuit.

[0012] According to a second aspect of the present invention, a method is proposed for controlling a plant for the continuous processing of metal products moving through the plant, comprising a step for in-line and continuous estimation of the metallurgical state of metal products moving through the plant for continuous processing according to the first aspect of the invention, or one or more improvements thereof, followed by a step of adjusting the operation of the plant on the basis of the saturation induction (Bsat) of the product determined as the product passes through a longitudinal magnetic field oscillator circuit.

[0013] The method according to the present invention may include a step of comparing the value of the saturation induction (Bsat1) of the product determined when the product passes through the longitudinal magnetic field oscillator circuit with an expected value (Bsat2), and the adjustment step includes modifying at least one operating parameter of the plant when the difference between the estimated value (Bsat1) and the expected value (Bsat2) is greater than a predetermined threshold.

[0014] According to a variant of the invention, the operation of the plant is adjusted according to the change in the saturation induction of the product between a first value (Bsat3) determined when passing through a first longitudinal magnetic field oscillator circuit of the plant and a second value (Bsat4) determined when passing through a second longitudinal magnetic field oscillator circuit of the plant.

[0015] According to a third aspect of the present invention, a plant for the continuous treatment of moving metal products is proposed, which is capable of implementing the method according to the first or second aspect of the present invention, or one or more of their improvements, the plant comprising a longitudinal flow oscillating circuit through which the products pass and a computer program capable of determining the saturation induction (Bsat) of the products circulating in the oscillating circuit.

[0016] A computer program refers to any type of computer program or computational software, whether implemented on a desktop computer or a computer integrated into an electrical cabinet, PLC, electronic computer, or any other control and command system of an industrial plant. Memory refers to any type of "machine-readable storage medium." A "machine-readable storage medium" or "computer-readable storage medium" refers to, 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, as well as any medium involved in providing instructions to a processor for execution. Machine-readable media can include non-transitory media that can store data and do not include carrier waves and / or transient electronic signals propagated wirelessly or over wired connections. Non-volatile media include, for example, optical disks, magnetic disks, or read-only memory. Volatile media include dynamic memory, including cache memory. Transmission media include coaxial cables, copper wire, and optical fibers. Common forms of computer readable media include, but are not limited to, for example, floppy disks, flexible disks, hard disks, magnetic strips, any other magnetic media, CD-ROMs, DVDs, any other optical media, punch cards, other physical media with patterns of holes, RAM, PROMs and EPROMs, FLASH-EPROMs, any other memory chip or cartridge, carrier waves, or any other medium from which a computer can read. Various forms of computer readable media may be involved in supporting one or more sequences of one or more instructions to a processor for execution thereof.

[0017] A computer program product may include machine-executable code and / or instructions, which may represent procedures, functions, subprograms, programs, routines, subprograms, modules, software, classes, or any combination of instructions, data structures, or program instructions. A code segment may be coupled to another code segment or a hardware circuit by sending and / or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be sent, forwarded, or transmitted by any suitable means, such as memory sharing, messaging, token transmission, network transmission, etc., among others.

[0018] According to one embodiment of the present invention, the primary function of the oscillator circuit is to heat the product.

[0019] The oscillator circuit can be used to determine the saturation induction of the product.

[0020] According to the invention, the oscillator circuit is advantageously used to control the plant.

[0021] According to another aspect of the invention, there is proposed a computer program product comprising instructions which, when loaded into a computer memory, cause a system for controlling and commanding a plant according to the third aspect of the invention to carry out the steps of the method according to the first or second aspect of the invention.

[0022] The present invention can be implemented using an oscillator circuit present in a plant whose main function is to heat the product, adding an additional function to the existing device, making it possible to estimate the saturation induction of the product, which depends on its metallurgical state, without the need to modify it.

[0023] The invention can also be implemented by adding an oscillator circuit to the plant, whose function is limited to estimating the metallurgical state of the product. Its function is not to heat the product or to modify its properties. In this way, the oscillator circuit is similar to a sensor that measures the properties of the product.

[0024] In this case, the power of the oscillator circuit is very low and limited to the power required for the circuit to operate, which does not result in overheating of the product or limits it to a strict minimum.

[0025] The oscillator circuit according to the invention comprises in particular a power supply, also known as a converter, an adapter box with a capacitor, and a longitudinal flux inductor.

[0026] The metallurgical condition of the product is determined as it passes through the inductor.

[0027] An oscillator circuit whose function is limited to saturation induction and evaluation of the metallurgical condition of the product can have, for example, the following features: Output: 25~100kW Adapter box capacitance: 1.2 to 20 μF Frequency: 5 to 200 kHz Inductor length in the direction of product movement: 10 to 60 cm Number of turns of inductor: 1

[0028] An oscillator circuit whose main function is to heat the product and which has the additional function of estimating the saturation induction and metallurgical state of the product can have, for example, the following characteristics: Power: 25kW~7000kW Adapter box capacitance: 2.4~50μF Frequency: 5 to 200 kHz Inductor length in the direction of product movement: 10 to 400 cm Number of turns of inductor: 1 to 20

[0029] The metallurgical condition of the product is assessed by measuring in real time the electrical quantities of the oscillator circuit, such as the voltage and frequency at the terminals of the inductor. This requires knowledge of the electrical properties of the oscillator circuit, in particular its impedance and inductance, the inductance of the inductor, and its equivalent capacitance. Furthermore, knowledge of the product's electrical resistance at the temperature within the oscillator circuit, or, if the main function of the oscillator circuit is to heat the product, at the average temperature between the product's inlet and outlet from the oscillator circuit, is also required.

[0030] The present invention allows for automatic in-line control of the metallurgical condition of a product at a point in a plant by determining the value of the saturation induction of the product as it passes through an oscillating circuit and comparing it to a reference value.

[0031] This standard corresponds to the standard for a product having the desired quality, especially with regard to metallurgical structure and mechanical properties.

[0032] Thus, implementation of the present invention allows for continuous monitoring of the production quality of the plant.

[0033] Control can be exercised at some points in the plant by adding dedicated oscillator circuits at points where knowledge of the metallurgical state of the product is useful to optimize the production parameters of the plant.

[0034] The present invention allows for adjustment of operating parameters to maintain the metallurgical condition of the product at an expected level by maintaining the saturation induction of the product at a desired level.

[0035] The invention further allows for traceability of the characteristics of the products processed in the plant by recording average data for each product and data relating to its length.

[0036] An oscillator circuit has a quality factor Q which can be expressed in the form of the following equation:

[0037]

number

[0038] The inductance of the oscillator circuit is determined by the sum of the inductances of the devices that make up the oscillator circuit, the inductance L1 of the converter, and the inductance Lind of the inductor.

[0039] Depending on the plant configuration, if the system comprises upstream and downstream transformers, they can be expressed as follows:

[0040]

number

[0041] The inductance of an inductor can also be expressed by the following equation:

[0042]

number

[0043] The electrical resistivity of the product varies depending on the temperature, as shown for example in Figure 5. To implement the method according to the invention, it is necessary to know this value as a function of temperature.

[0044] The quality factor Q of an oscillator circuit can also be expressed according to the following formula:

[0045]

number

[0046] Therefore, for a given temperature, the magnetic permeability of a product can be expressed with the following resolution:

[0047]

number

[0048] The quality factor Q of an oscillator circuit can also be expressed according to the following formula:

[0049]

number

[0050] The current strength in the inductor is estimated from the following relationship:

[0051]

number

[0052] The electrical resistance of the product is expressed as follows:

[0053]

number

[0054] The saturation induction (Bsat) is determined using the following formula:

[0055]

number

[0056] The k value is determined from the curve shown in FIG. 6, where the vertical axis is the k value and the horizontal axis is the ratio between the thickness of the product and the penetration depth of the current in the product.

[0057] The strength of the magnetic field H is expressed by the following equation:

[0058]

number

[0059] Numerical application Numerical example of application of the invention to a metal strip moving on a continuous processing line equipped with an induction heating inductor. In this example, we use an existing inductor to heat the strip and estimate its metallurgical state by adding this functionality according to the invention.

[0060] Input data Strip: Carbon steel according to Bisra 1 Diagram relating the austenite content of carbon steel strip to its saturation induction according to Bisra 1 (Fig. 7) Thickness Ep Strip: 1.3mm Strip width: 1200mm Strip surface area: 3.36m 2 Average temperature of the strip cross section in the inductor: 612.5°C Inductor length: 3.360m Inductor turns N: 1 Equivalent capacitance of the oscillator circuit: C: 18.48 μF Oscillator circuit inductance L: 0.069 μH Inductor inductance Lind: 0.169 μH Measured oscillator frequency: 89.8.10 3 Hz Diagram (Figure 6) relating the value of the quantity k based on the thickness ep of the product and the penetration depth p of the current in it. For this example, the value of k is 1.29

[0061] Determining the quality factor Q of an oscillator circuit

[0062]

number

[0063]

number

[0064] Determination of the electrical resistance of the product R

[0065]

number

[0066] Determination of the electrical resistivity of the product ρ:

[0067]

number

[0068] Determining the product's magnetic permeability μr

[0069]

number

[0070] Determination of magnetic field H

[0071]

number

[0072] Determination of the saturation induction Bsat:

[0073]

number

[0074] Determination of austenite content by saturation induction Bsat: This is done using the diagram shown in Figure 7, which relates the austenite content of a carbon steel product according to Bisra 1 to its saturation induction.

[0075] For a Bsat of 1.53T on the vertical axis, an austenite content of 16% is obtained.

[0076] In practice, the relationship between the austenite content of the strip and its saturation induction is represented by a mathematical equation that is entered into a computer program implementing the method according to the invention, so that the austenite content is determined automatically by calculation. [Brief explanation of the drawings]

[0077] Other features and advantages of the present invention will become apparent during the course of the following detailed description, which should be read in conjunction with the accompanying drawings. [Figure 1] 1 is a schematic partial longitudinal section of a plant for the continuous treatment of metal products according to a first embodiment of the invention; [Figure 2] 1 is a schematic partial longitudinal section of a plant for the continuous treatment of metal products according to a second embodiment of the invention; [Figure 3] 1 is a schematic partial longitudinal section of a plant for the continuous treatment of metal products according to a third embodiment of the invention; [Figure 4] 10 is a schematic partial longitudinal section of a plant for the continuous treatment of metal products according to a fourth embodiment of the invention; FIG. [Figure 5] FIG. 1 illustrates the change in product resistance R based on product temperature. [Figure 6] FIG. 1 shows the variation of k-value depending on the thickness of the product and the current penetration depth therein. [Figure 7] FIG. 1 shows the change in austenite content of a product due to saturation induction.

[0078] 1 shows a schematic diagram of a plant 2 for the continuous treatment of metal products according to a first exemplary embodiment of the invention, in which the products 1 circulate. The plant comprises a furnace 5 for modifying the metallurgical state of the products and thereby the mechanical properties of the products. In this example, a longitudinal flux oscillator circuit 3 is installed in the furnace and heats the products.

[0079] The main function of this oscillator circuit is therefore to heat the product. According to the invention, the oscillator circuit is provided with the additional function of determining the saturation induction of the product as it passes through the oscillator circuit.

[0080] To perform this function, the computer program product 4 includes instructions for determining the saturation induction Bsat of the product from information originating from the oscillator circuit, such as current or voltage values ​​measured in real time in the oscillator circuit, information originating from the system for controlling and commanding the furnace, such as the format and chemical composition of the product circulating in the oscillator circuit, the temperature of the product at the inlet and outlet of the oscillator circuit, and pre-recorded reference data such as the structural characteristics of the oscillator circuit or the electromagnetic characteristics of the product depending on the nature and temperature of the product.

[0081] 2 shows a schematic diagram of a plant 2 for the continuous processing of metal products according to a second exemplary embodiment of the invention, in which the product 1 circulates. In this example, a longitudinal flux oscillator circuit 3 is added downstream of the furnace 5 in the direction of product movement. This oscillator circuit only determines the saturation induction of the product at the furnace outlet.

[0082] In this embodiment, the oscillator circuit is small and low capacitance. It is sized to minimize heating of the product and ensure sufficient coupling with the product so that electrical measurements can be made on the oscillator circuit. Ideally, there would be no heating of the product, but it is not possible to ensure coupling between the oscillator circuit and the product without some heating occurring.

[0083] 3 shows a schematic diagram of a plant 2 for the continuous treatment of metal products according to a third exemplary embodiment of the invention, in which the products 1 circulate. In this example, a first longitudinal flux oscillator circuit 31 is arranged upstream of the furnace 5, and a second longitudinal flux oscillator circuit 32 is present inside the furnace.

[0084] The first oscillator circuit 31 simply determines the saturation induction of the product at the inlet of the furnace. Its only function is to heat the product.

[0085] The main function of the second oscillator circuit 32 is to heat the product, with the additional function of determining the saturation induction of the product added to it.

[0086] In this example, the computer program 4 determines and compares the saturated induction values ​​of the products for the two oscillator circuits.

[0087] For example, a system for controlling and directing a furnace may modify the furnace settings according to the product saturation induction determined from the first oscillator circuit. This value represents the metallurgical state of the product at the furnace inlet. It is therefore possible to adjust the furnace settings, and thus the thermal cycle followed by the product therein, according to the initial state of the product upstream of the furnace.

[0088] According to another example, a system for controlling and commanding a furnace modifies the setpoint of the furnace according to changes in product saturation induction between two oscillator circuits.

[0089] As an alternative to this exemplary embodiment, the first oscillator circuit upstream of the furnace can be replaced by a mathematical model that estimates the saturation induction of the product according to data available about the product, in particular during the manufacturing process prior to its introduction into the plant. The resulting estimate is less accurate than with an oscillator circuit, but may be suitable for less demanding applications.

[0090] FIG. 4 shows diagrammatically a plant 2 for the continuous treatment of metal products in which the products 1 are circulated according to a fourth exemplary embodiment of the invention.

[0091] In this example, a first longitudinal flux oscillator circuit 32 is arranged in the heating section of the furnace 5. The main function of this first oscillator circuit 31 is to heat the product, but it also includes the additional function of determining the saturation induction of the product as it passes through the oscillator circuit.

[0092] A second oscillator circuit 33 is placed in the furnace at the outlet of the second section, e.g., the quenching section. This second oscillator circuit 33 determines the saturation induction of the product at the outlet of the first section. Its only function is to heat the product.

[0093] For example, the system for controlling and commanding the furnace modifies the cooling rate of the product in the cooling section of the furnace according to the saturation induction determined from the first oscillating circuit 32. Since this saturation induction represents the metallurgical state of the product at the end of heating, it is possible to modify the cooling rate according to the state of the product at the end of heating.

[0094] In this example, the system for controlling and commanding the furnace checks that the saturation induction of the product determined from the second oscillator circuit 33 is an expected value, and if not, adjusts the operating parameters of the furnace so that the determined value matches the expected value.

Claims

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

2. 2. The method of claim 1, further comprising determining the percentage of austenite in the metal product (1) based on the saturation induction (Bsat) of the product (1) determined when the product passes through the longitudinal magnetic field oscillator circuit (3).

3. 1. A method for controlling a plant (2) for the continuous processing of moving metal products (1), comprising the steps of: continuously estimating in-line the metallurgical state of a metal product (1) moving through the plant (2) for continuous processing according to any one of claims 1 to 2; and subsequently adjusting the operation of the plant based on the saturation induction (Bsat) of the product determined as the product passes through the longitudinal magnetic field oscillator circuit (3).

4. 4. The method according to claim 3, further comprising a step of comparing the value of the saturation induction (Bsat1) of the product determined when passing through the longitudinal magnetic field oscillator circuit (3) with a predetermined expected value (Bsat2), and the adjustment step comprises modifying at least one operating parameter of the plant if the difference between the estimated value (Bsat1) and the expected value (Bsat2) is greater than a predetermined threshold.

5. 4. The method according to claim 3, wherein the step of adjusting the operation of the plant is carried out according to the change in the saturation induction (Bsat) of the product between a first value (Bsat3) determined when passing through a first longitudinal magnetic field oscillator circuit (31) of the plant and a second value (Bsat4) determined when passing through a second longitudinal magnetic field oscillator circuit (32) of the plant.

6. A plant (2) for the continuous treatment of moving metal products (1) capable of implementing the method according to any one of claims 1 to 5, characterized in that it comprises a longitudinal flow oscillating circuit (3) through which the products pass, and a computer program (4) capable of determining the saturation induction (Bsat) of the products circulating in the oscillating circuit.

7. 7. A plant according to claim 6, wherein the main function of the oscillating circuit (3) is to heat the product.

8. 8. Plant according to any one of claims 6 and 7, wherein the oscillator circuit (3) is designed to determine the saturation induction (Bast) of the product.

9. 9. The plant according to claim 8, wherein the oscillator circuit (3) is used to control the plant (2).

10. A computer program product (4) comprising instructions which, when loaded into the memory of a desktop computer, or a computer embedded in an electrical cabinet, a PLC, an electronic computer, or any other system for controlling and commanding an industrial plant, cause a plant control and command system according to any one of claims 6 to 9 to carry out the steps of the method according to any one of claims 1 to 5.

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