Method for operating an annealing furnace

Abstract

A method for operating an annealing furnace to anneal a metal strip provides that, initially, at least one target material property (MP.sub.Target) is specified for a point or a section of the metal strip after passing through the annealing furnace. In addition, information (E) on the metal strip is provided before or in the annealing furnace. A calculation of a target temperature distribution (T.sub.Target) and/or a target speed (V.sub.Target) of the metal strip in the annealing furnace is then carried out with the assistance of a computer-aided model as a function of the target material properties and the specified information. The target temperature distribution and/or target speed calculated in this manner is/are subsequently set in the annealing furnace in order to transfer the material property of the metal strip behind the annealing furnace to the desired target material property MP.sub.Target.

Claims

1. A method for operating an annealing furnace (200) for annealing a metal strip, comprising the following steps: selecting a desired target material property (MP.sub.Target), to be assumed by a point or section of the metal strip (100) after passing through the annealing furnace (200), the target material property (MP.sub.Target) being one of a yield strength, a tensile strength, an elongation at break and a uniform elongation; providing information (E) relating to the metal strip in front of or in the annealing furnace (200); calculating a target temperature distribution (T.sub.Target) and/or a target speed (V.sub.Target) of the metal strip (100) in the annealing furnace (200) by a computer-aided model (220) as a function of the desired target material property (MP.sub.Target) and the information (E) relating to the metal strip; setting the target temperature distribution (T.sub.Target) and/or the target speed (V.sub.Target) of the metal strip (100) in the annealing furnace (200) by a furnace control system (230) as a control element; measuring an actual material property (MP.sub.Actual) of the metal strip (100) after passing through the annealing furnace (200); calculating a comparative temperature distribution (T.sub.Comp) and/or a comparative speed (V.sub.Comp) of the metal strip (100) in the annealing furnace (200) with by the computer-aided model (220) as a function of the measured actual material property (MP.sub.Actual) of the metal strip (100) after passing through the annealing furnace (200) and the information (E) relating to the metal strip in front of or in the annealing furnace (200); and adjusting the temperature distribution and/or the speed of the metal strip (100) in the annealing furnace (200) to the comparative temperature distribution (T.sub.Comp) and/or the comparative speed (V.sub.Comp) through adapting of the computer-aided model; wherein the adapting of the computer-aided model takes place only after the passing of at least the entire metal strip through the annealing furnace (200), and wherein the adapting of the computer-aided model comprises the sub-steps of measuring an actual temperature distribution (T.sub.Actual) and/or an actual speed (V.sub.Actual) of the metal strip (100) in the annealing furnace (200), comparing the actual temperature distribution (T.sub.Actual) with the calculated comparative temperature distribution (T.sub.Comp) and determining a temperature deviation (ΔT); and/or comparing the actual speed (V.sub.Actual) of the metal strip (100) in the annealing furnace (200) with the comparative speed (V.sub.Comp) and determining a speed deviation (ΔV); calculating at least one adaptation value (a) for adjustment of the computer-aided model (220) based on the temperature deviation (ΔT) and/or the speed deviation (ΔV); adapting the computer-aided model (220) based on the adaptation value (a); and recalculating the target temperature distribution (T.sub.Target) and/or the target speed (V.sub.Target) of a new metal strip (100) by the adapted computer-aided model (220), and wherein the information (E) relating to the metal strip (100) before or in the annealing furnace (200) is selected from the group consisting of a tensile strength and/or a yield strength before a continuous galvanizing line (CGL), before a continuous annealing line (CAL), in a pickling line, or before a reel, a reel temperature, a final rolling temperature of the metal strip upon exiting a finishing roll train, an input temperature of a slab from which the metal strip is produced, at the input of the finishing roll train, a strip speed of the metal strip upon exiting a last stand of the finishing roll train, a rolling force in a skin pass mill, rolling forces during cold rolling, rolling forces during hot rolling, an input temperature of the slab into a roughing stand in front of the finishing roll train, a cold rolling grade, a composition of a material of the metal strip, a carbon content of the metal strip; and a straightening force at a flattener in front of the CGL/CAL.

2. The method according to claim 1, wherein measuring the actual material property (MP.sub.Actual) of the metal strip (100) after passing through the annealing furnace (200) is performed at the point or section of the metal strip for which the desired target material property is specified.

3. The method according to claim 1, wherein the adaptation of the computer-aided model takes place only after the passing of a plurality of metal strips through the annealing furnace (200).

4. The method according to claim 1, wherein calculating the target temperature distribution and/or the target speed of the metal strip takes place as long as the at least one point or section of the metal strip to which the desired target material property (MP.sub.Target) of the metal strip refers is still located before or in the annealing furnace (200).

5. The method according to claim 1, wherein the computer-aided model (220) uses an experience database, a statistical model, or stored annealing curves when calculating the target temperature distribution (T.sub.Target) and/or the target speed (V.sub.Target).

6. The method according to claim 1, wherein the actual material property of the metal strip is measured directly online or on a sample taken from the metal strip after the metal strip (100) has passed through the annealing furnace.

7. The method according to claim 1, further comprising repeating the steps according to claim 1 with the adapted computer-aided model when annealing a future metal strip (100).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrated a method for operating an annealing furnace.

(2) FIG. 2 illustrated the adapting of a computer-aided model.

DETAILED DESCRIPTION

(3) Exemplary embodiments are described in detail below with reference to the specified figures. In all figures, the same technical elements are designated with the same reference signs.

(4) FIG. 1 illustrates the method for operating an annealing furnace 200. In the annealing furnace 200, a metal strip 100 is annealed while passing through the annealing furnace in the direction of the arrow. The core element of the method is the calculation of a target temperature distribution T.sub.Target and/or a target speed V.sub.Target for the metal strip in the annealing furnace. This calculation is carried out with the assistance of a computer-aided model 220 of the annealing furnace as a function of a specified desired target material property MP.sub.Target of the metal strip and as a function of information E relating to the metal strip. The information relates to properties of the metal strip before or in the annealing furnace 200 or it relates to information on previous processing steps in the manufacture of the metal strip. With regard to a broader meaning of the terms “material property” and “information,” reference is made at this point to the definitions of such terms given above in the general part of the description.

(5) After the calculation of the target temperature distribution T.sub.Target and/or the target speed V.sub.Target by the computer-aided model 220, the corresponding values are output to a furnace control system 230 as control elements and implemented or set by this in the annealing furnace 200. The specified setting of the target temperature distribution T.sub.Target and/or the target speed V.sub.Target of the metal strip in the annealing furnace is carried out with the aim of transferring the actual material property MP.sub.Actual of the metal strip behind the annealing furnace to the specified desired target material property MP.sub.Target, likewise behind the annealing furnace.

(6) The calculation of the target temperature distribution T.sub.Target and/or the target speed V.sub.Target 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 specified target material property MP.sub.Target of the metal strip refers is still in front of or in the annealing furnace.

(7) The computer-aided model 220 can use an experience database, a statistical model and/or stored annealing curves when calculating the target temperature distribution T.sub.Target in the annealing furnace 200 and/or when calculating the target speed V.sub.Target with which the metal strip passes through the annealing furnace 200.

(8) In order to continuously improve the quality of the method for operating the annealing furnace 200, the method optionally provides for an occasional adaptation of the computer-aided model 220, see FIG. 2. For this adaptation, the method provides the following sub-steps: Measurement of the actual material property MP.sub.Actual of the metal strip 100 after passing through the annealing furnace 200, see FIG. 1. The measurement preferably takes place at the point or section of the metal strip for which the desired target material property has been specified. Calculation of a comparative temperature distribution T.sub.Comp and/or a comparative speed V.sub.Comp of the metal strip 100 in the annealing furnace with the assistance of the computer-aided model 220 as a function of the measured actual material property MP.sub.Actual of the metal strip 100 and as a function of the provided information E on the metal strip before or in the annealing furnace 200.

(9) The comparative temperature distribution T.sub.Comp and comparative speed V.sub.Comp are calculated with the same computer model 220, taking into account the same information E on the metal strip as the first input variable, such as the target temperature distribution and the target speed of the metal strip in the annealing furnace as shown in FIG. 1. However, for the calculation of the comparative variables as the second input variable, the computer model 220 does not take into account the desired target material property MP.sub.Target, but the actual material property MP.sub.Actual of the metal strip actually measured behind the annealing furnace. The temperature distribution and/or the speed of the metal strip in the annealing furnace are then adjusted to the calculated corresponding comparative variables, i.e. the comparative temperature distribution T.sub.Comp and/or the comparative speed V.sub.Comp through an appropriate adaptation of the computer-aided model 220.

(10) Specifically, the specified adjustment comprises the following sub-steps; see FIG. 2:

(11) The actual temperature distribution T.sub.Actual and/or actual speed V.sub.Actual of the metal strip 100 in the annealing furnace 200 is/are measured; see FIGS. 1 and 2. Such measured variables are compared in a comparison device 250 with the previously calculated associated comparative variables; i.e. a temperature deviation ΔT and/or a speed deviation ΔV are determined if necessary: ΔT=T.sub.Comp T.sub.Actual, ΔV=V.sub.Comp−V.sub.Actual.

(12) At least one of these deviations is included in an adaptation value calculation device 240, which calculates from these input variables at least one suitable adaptation value a for adjusting or adapting the computer-aided model 220. The computer-aided model 220 is then adapted with such adaptation value. Such adaptation of the computer model 220 does not take place during the passing of a metal strip through the annealing furnace, but preferably only after the passing through of a complete metal strip. For this reason, the adaptation of the computer-aided model 220 will only have an effect on future metal strips. In this respect, the adjustment to the comparative value is extremely slow. Advantageously, the adaptation and the measured value acquisition carried out for it enables good documentation and thus also conclusive proof of the production conditions in the past; this is valuable quality documentation for further processors.

(13) After the computer model 220 has been adapted, future calculations of the target temperature distribution T.sub.Target and/or the target speed V.sub.Target of the metal strip are performed with the assistance of the adapted computer-aided model. The annealing furnace 200 is then operated with the newly calculated target values for temperature distribution or speed distribution.

LIST OF REFERENCE SIGNS

(14) 100 Metal strip 200 Annealing furnace 220 Computer-aided model 230 Furnace control system as control element 240 Adaptation value calculation device E Information relating to the metal strip MP.sub.Actual Actual material property of the metal strip MP.sub.Target Target material property of the metal strip T.sub.Actual Actual temperature distribution of the metal strip in the annealing furnace T.sub.Target Target temperature distribution of the metal strip in the annealing furnace T.sub.Comp Comparative temperature distribution for the metal strip V.sub.Actual Actual speed of the metal strip in the annealing furnace V.sub.Target Target speed of the metal strip in the annealing furnace V.sub.Comp Comparative speed for the metal strip in the annealing furnace ΔT Temperature deviation ΔV Speed deviation