Method for operating an annealing surface

Abstract

The invention relates to a method for operating an annealing furnace (200) for annealing a metal strip (100). According to the method, at first at least one desired target material property ME Soll is specified for a point or a section of the metal strip (100) after it has passed through the annealing furnace (200). Additionally, information E regarding the metal strip is provided upstream of or in the annealing furnace. A target temperature distribution T Soll and / or a target speed V Soll for the metal strip in the annealing furnace is then calculated with the aid of a computer-assisted model as a function of the target material property and said information. The target temperature distribution and / or target speed thus calculated are / is then set in the annealing furnace (200) in order to change the material property of the metal strip downstream of the annealing furnace into the desired target material property ME Soll.

Description

[0001] The control of the material properties of a metal strip to a desired target material property, as claimed in EP patent EP 2 742 158 B1, including the simulation of actual material properties of a metal strip using a computer-aided model, requires significant computing power and processing time. The control is achieved through an interactive modification of process parameters, temperature, and / or speed to produce the desired material properties for the metal strip. The increased processing time is a disadvantage because it results in a reduction of the possible calculation scenarios or iteration steps.

[0002] Der Aufsatz Yahiro K et al: "Development of strip temperature control system for a continuous annealing line", Plenary Session, Emerging Technologies, and Factory Automation. MAUl, Nov. 15 - 19, 1993; [Proceedings of the International Conference on Industrial Electronics, Control, and Instrumentation (IECON)], New York, IEEE, Us, Bd. 1, 15.November 1993 (1993-11-15, pages 481-486, XP000451844) discloses a method for operating an annealing furnace for annealing a metal strip, comprising the following steps: According to claim 1: specifying at least one desired target material property that a point or section of the metal strip is to have after passing through the annealing furnace; providing at least one piece of information (E) about the metal strip before or in the annealing furnace; calculating a target temperature distribution and / or a target velocity of the metal strip in the annealing furnace using a computer-aided model as a function of the desired target material property and the information about the metal strip; and setting the target temperature distribution and / or the target velocity of the metal strip in the annealing furnace using a furnace control as an actuator.

[0003] The article by Vallee G et al: "Ligne de recuit tout asynchrone pour ugine gueugnon", Revue de Metallurgie - Cahiers d'Informations Techniques, Revue de Metallurgie. Paris, FR, Vol. 90, No. 6, June 1, 1993 (1993-06-01), pages 843-847, XP000393745, ISSN: 0035-1563 discloses a similar process to the previously mentioned article by Yahiro, but using the properties of the metal strip to be treated and the actual properties of the process in a model to determine the speed and temperature to be used for the furnace.

[0004] US patent application US 5,673,368 A also discloses a method for operating an annealing furnace using a computer-generated model. According to the US patent application, this model is adjusted after each complete heat treatment cycle.

[0005] The paper by Smith MA et al: "Application of distributed control on UPI'S KM / CAL", Aise Steel Technology, Aise, Pittsburgh, PA, US, Vol. 70, No. 6, June 1, 1993 (1993-06-01), pages 17-22, XP000387767, ISSN: 0021-1559 discloses a method for operating an annealing furnace for annealing a metal strip according to the preamble of claim 1.

[0006] The invention is based on the objective of further developing a known method for operating an annealing furnace for annealing a metal strip with a view to improving product quality and increasing output.

[0007] This problem is solved by the method claimed in claim 1.

[0008] The method claimed in claim 1 constitutes a control system, but not a regulation system. Within the framework of this control system, a target temperature distribution and / or a target speed of the metal strip in the annealing furnace are calculated and specified such that the metal strip exhibits a desired target material property upon exiting the annealing furnace. Unlike a regulation system, the presence of this desired target material property is not monitored within the framework of the method claimed in claim 1; in particular, the desired target material property is not compared with a measured actual material property of the metal strip after exiting the annealing furnace to establish a material property control deviation, and this control deviation is not reduced to zero.

[0009] Strictly speaking, the term "temperature distribution" refers to a section of the metal strip. However, in the context of this description, the term "temperature distribution" also implies a singular temperature value at a specific point on the metal strip.

[0010] The term "annealing furnace" as used in this description includes not only heating equipment but also cooling equipment downstream of the heating equipment in the direction of flow.

[0011] Calculating and specifying a target temperature distribution and / or a target speed of the metal strip in the annealing furnace is less computationally intensive than simulating material properties. Furthermore, the control system does not require feedback of a process parameter. Overall, this allows for increased output.

[0012] The claimed method is designed to perform a desired self-correction or self-adaptation. For this purpose, the actual material properties of the metal strip are measured after passing through the annealing furnace, and a comparative temperature distribution and / or a comparative velocity of the metal strip in the annealing furnace are calculated using the computer-aided model of the annealing furnace, depending on the measured actual material properties and information provided about the metal strip before or in the annealing furnace. The temperature distribution and / or the velocity of the metal strip in the annealing furnace are then adjusted to the previously determined comparative temperature distribution and / or velocity by appropriately adapting the computer-aided model.

[0013] In other words, the self-correction or self-adaptation process involves performing the method according to claim 1 for specifying a temperature distribution and / or the speed of the metal strip in the annealing furnace, with the sole difference being that the computer model receives the actual measured material properties of the metal strip after passing through the annealing furnace as its input, instead of the target material properties. For clarity, the output variables of the computer-aided model are referred to as reference variables in this case, specifically the reference temperature distribution and / or the reference speed. The actual temperature distribution and / or the actual speed of the metal strip in the annealing furnace are recorded as actual values ​​and compared with the previously calculated reference variables.This comparison can reveal a non-zero deviation in the temperature distribution and / or the velocity of the metal strip in the annealing furnace. In an adaptation value calculation unit, at least one suitable adaptation value is then calculated based on these deviations. The computer-aided model is subsequently adapted using the calculated adaptation value. The inventive method for operating an annealing furnace described above is then preferably carried out for future metal strips using the adapted computer-aided model. This results in optimized target temperature distributions and / or target velocities for the metal strip, which are set in the annealing furnace using a furnace control system as an actuator.

[0014] According to one embodiment of the invention, the computer-aided model can, for example, work with an experience database, a statistical model, or stored annealing curves, and is therefore applicable to any type of steel. This model can be used immediately, especially for newly developed steel grades. Unlike a physical model, which must be implemented for each new steel grade, the statistical model used according to the invention is easier to generate.

[0015] According to a further preferred embodiment, the adaptation of the computer-aided model does not take place during the passage of the metal strip through the annealing furnace, the strip whose measured or simulated actual material properties formed the basis for calculating the at least one adaptation value or for adapting the computer-aided model. Instead, the adaptation preferably takes place only for metal strips to be annealed in the future.

[0016] The term "material property of the metal strip", whether target or actual value, refers in the context of this description to, for example, the yield strength, the tensile strength, the elongation at break or the uniform elongation of the metal strip after it has passed through the annealing furnace.

[0017] Further advantageous embodiments of the method according to the invention are the subject of the dependent claims.

[0018] The description includes two figures, whereby Figure 1 the inventive method; and Figure 2 illustrates the adaptation of the computer-aided model according to the invention.

[0019] The invention is described in detail below with reference to the figures mentioned, in the form of exemplary embodiments. In all figures, identical technical elements are designated by the same reference numerals.

[0020] Figure 1Figure 1 illustrates the inventive method for operating an annealing furnace 200. In the annealing furnace 200, metal strip 100 is annealed as it passes through the furnace in the direction of the arrow. The core element of the inventive method is the calculation of a target temperature distribution Ttarget and / or a target velocity Vtarget for the metal strip in the annealing furnace. This calculation is performed using a computer-aided model 220 of the annealing furnace, depending on a predetermined desired target material property MEtarget of the metal strip and depending on information E about the metal strip. The information relates to properties of the metal strip before or in the annealing furnace 200, or it relates to information about previous processing steps in the production of the metal strip. Regarding a broader meaning of the term "material property," reference is made here to the definition given above in the general part of the description.

[0021] After the target temperature distribution Ttarget and / or the target velocity Vtarget have been calculated by the computer-aided model 220, the corresponding values ​​are output to a furnace control unit 230 as an actuator and implemented or set by this unit in the annealing furnace 200. This setting of the target temperature distribution and / or the target velocity Vtarget of the metal strip in the annealing furnace is carried out with the aim of converting the actual material property MEactual of the metal strip downstream of the annealing furnace into the specified desired target material property MEtarget, also downstream of the annealing furnace.

[0022] The calculation of the target temperature distribution Ttarget and / or the target velocity Vtarget of the metal strip in the annealing furnace is carried out as long as at least one point or section of the metal strip to which the said target material property MEtarget of the metal strip refers is located in front of or inside the annealing furnace.

[0023] The computer-aided model 220 can, when calculating the target temperature distribution T target in the annealing furnace 200 and / or when calculating the target speed V target at which the metal strip passes through the annealing furnace 200, draw on an experience database, a statistical model and / or stored annealing curves.

[0024] In order to continuously improve the quality of the inventive method for operating the annealing furnace 200, the inventive method optionally provides for an occasional adaptation of the computer-aided model 220, see Figure 2The inventive method provides the following steps for this adaptation: Measuring the actual material property ME of the metal strip 100 after passing through the annealing furnace 200, see Figure 1 The measurement is preferably performed at the point or section of the metal strip for which the desired target material property has been specified. A comparative temperature distribution TVgl and / or a comparative velocity VVgl of the metal strip 100 in the annealing furnace are calculated using the computer-aided model 220, depending on the measured actual material property MEIst of the metal strip 100 and depending on the provided information E about the metal strip before or in the annealing furnace 200.

[0025] The comparative temperature distribution TVgl and comparative velocity VVgl are calculated using the same computer model 220, taking into account the same information E about the metal strip as the first input variable as the target temperature distribution and the target velocity of the metal strip in the annealing furnace according to Figure 1 However, for calculating the comparative parameters, the computer model 220 does not consider the desired target material property MEtarget as the second input parameter, but rather the actual material property MEactual of the metal strip measured behind the annealing furnace. The temperature distribution and / or the velocity of the metal strip in the annealing furnace are then adjusted to the calculated corresponding comparative parameters, i.e., the comparative temperature distribution Tcf and / or the comparative velocity Vcf, by appropriately adapting the computer model 220.

[0026] Specifically, the aforementioned adjustment comprises the following sub-steps; see Figure 2 The actual temperature distribution Tactual and / or actual velocity Vactual of the metal strip 100 in the annealing furnace 200 is / are measured; see Figure 1 and 2 These measured quantities are compared in a comparison device 250 with the previously calculated corresponding reference quantities; i.e., a temperature deviation ΔT and / or a velocity deviation ΔV are determined, if applicable: ΔT = Tcf - Tactual , ΔV = Vcf - Vactual .

[0027] At least one of these deviations is fed into an adaptation value calculation device 240, which calculates at least one suitable adaptation value a from these input variables for adjusting or adapting the computer-aided model 220. The computer-aided model 220 is then adapted with this adaptation value. According to the invention, this adaptation of the computer model 220 does not take place while a metal strip is passing through the annealing furnace, but preferably only after a complete metal strip has passed through. Therefore, the adaptation of the computer-aided model 220 only affects future metal strips. The adjustment to the reference value is thus extremely slow. Advantageously, the adaptation and the associated measurement data acquisition enable good documentation and thus also conclusive proof of past production conditions; this is valuable quality documentation for downstream processors.

[0028] Following the adaptation of computer model 220, future calculations of the target temperature distribution Ttarget and / or the target velocity Vtarget of the metal strip will be performed using the adapted computer-aided model. The annealing furnace 200 will then be operated with the newly calculated target values ​​for the temperature distribution or the velocity distribution. Reference symbol list

[0029] 100 Metal strip 200 Annealing furnace 220 Computer-aided model 230 Furnace control as actuator 240 Adaptation value calculation device Information about the metal strip ME Actual actual material property of the metal strip ME Target target material property of the metal strip T Actual actual temperature distribution of the metal strip in the annealing furnace T Target target temperature distribution of the metal strip in the annealing furnace T Comparison reference temperature distribution for the metal strip V Actual actual speed of the metal strip in the annealing furnace V Target reference speed of the metal strip in the annealing furnace V Comparison reference speed for the metal strip in the annealing furnace ΔT temperature deviation ΔV speed deviation

Claims

1. Method of operating an annealing furnace (200) for annealing a metal strip, comprising the following steps: - predetermining at least one desired target material characteristic (MESoll), such as, for example, the yield point, the tensile strength, the elongation at fracture and / or the uniform elongation, which a point or section of the metal strip (100) is to have after transiting the annealing furnace (200); - providing at least one item of information (E) about the metal strip before or in the annealing furnace (200); - calculating a target temperature distribution (TSoll) and / or a target speed (VSoll) of the metal strip (100) in the annealing furnace (200) with the help of a computer-supported model (220) in dependence on the desired target material characteristic (MESoll) and the item of information (E) about the metal strip; and - setting the target temperature distribution (TSoll) and / or the target speed (VSoll) of the metal strip (100) in the annealing furnace (200) with the help of a furnace control (230) as setting element; characterised by measuring the actual material characteristic (MEIst) of the metal strip (100) after transit through the annealing furnace (200), preferably at the point or section of the metal strip for which the target material characteristic is predetermined; calculating a comparative temperature distribution (TVgl) and / or a comparative speed (VVgl) of the metal strip (100) in the annealing furnace (200) with the help of the computer-supported model (220) in dependence on the measured actual material characteristic (MEIst) after the transit and the provided item of information (E) about the metal strip before or in the annealing furnace (200); and adapting the temperature distribution and / or the speed of the metal strip (100) in the annealing furnace (200) to the comparative temperature distribution (TVgl) and / or the comparative speed (VVgl) by suitable adaptation of the computer-supported model, wherein the adaptation of the computer-supported model is carried out only after transit of at least the entire metal strip, optionally also several metal strips, through the annealing furnace (200); characterised in that the step of adaptation of the computer-supported model comprises the following substeps: measuring an actual temperature distribution (TIst) and / or an actual speed (VIst) of the metal strip (100) in the annealing furnace (200); comparing the actual temperature distribution (TIst) with the calculated comparative temperature distribution (TVgl) and determining a temperature difference (ΔT); comparing the actual speed (VIst) of the metal strip (100) in the annealing furnace (200) with the comparative speed (VVgl) and determining a speed difference (ΔV); calculating at least one suitable adaptation value (a) for adaptation of the computer-supported model (220) on the basis of the temperature difference (ΔT) and / or the speed difference (ΔV); adapting the computer-supported model (220) on the basis of the adaptation value (a); and recalculation of the target temperature distribution (TSoll) and / or the target speed (VSoll) of a new metal strip (100) with the help of the adapted computer-supported model (220).

2. Method according to claim 1, characterised in that the calculation of the target temperature distribution and / or the target speed of the metal strip is carried out as long as the at least one point or section of the metal strip to which the desired target value characteristic (MESoll) of the metal strip relates is still in front of or in the annealing furnace (200).

3. Method according to claim 1 or 2, characterised in that for calculation of the target temperature distribution (TSoll) and / or the target speed (VSoll) the computer-supported model (220) has resort to an empirical databank, a statistical model or filed annealing plots.

4. Method according to claim 1, characterised in that the actual material characteristic of the metal strip is measured directly on-line or at a sample, which is removed from the metal strip, after the transit of the metal strip (100) through the annealing furnace.

5. Method according to claim 1, characterised by repetition of the steps according to any one of the preceding claims with the adapted computer-supported model for the annealing of a future metal strip (100).

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