JPH0379727A - Method for controlling steel temperature in continuous annealing - Google Patents

Abstract

PURPOSE:To reduce errors in the estimated steel temp., to accurately regulate the cooling amt. or the like and to obtain a steel of stabilized material with good productivity by controlling the manipulated variable according to the steel temp. estimated by considering the state of progress in the transformation of the steel to be subjected to cooling or the like. CONSTITUTION:In continuous annealing, the amt. of cooling or heating is controlled according to the conditions in cooling or heating of a steel. Then, the steel temp. in a prescribed position on the line or a prescribed time is controlled to a prescribed objective one. At this time, the temp. of the above steel is estimated by a temp. estimated model in consideration of the state of progress in the transformation of the above steel. According to the accumulated steel temp., the above cooling amt. and heating amt. are determined.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method of controlling the temperature of a steel material (plate temperature) with high precision in a cooling zone or a heating zone of a continuous annealing furnace.

[Conventional technology]

Regarding the control of the plate temperature of steel materials during continuous annealing, the following technique is disclosed, for example, in Japanese Patent Publication No. 14051/1983. It is a copper strip cooling device that is installed in a continuous annealing facility, and has a mechanism in which a copper strip is wound around one or more cooling rolls through which a refrigerant flows, and the length of the wrapping is changed. When controlling #4-IF transport order,
A control device is installed on the entry side of the cooling roll, which stores a work schedule that describes dimensions and physical property values, calculates the wrapping angle from a relational expression obtained in advance, and controls a mechanism that changes the wrapping angle. A copper strip thermometer and #I4 zone weld line detector are installed, and a steel strip tension meter, refrigerant thermometer, and copper strip conveyance speed meter are installed in the cooling device, and recognition is made from the number of weld lines passing and the work schedule. By substituting the dimensions and physical property values of the copper strip during passing, the temperature of the 011s zone in the cooling roll, the tension of the copper strip, the refrigerant temperature, and the conveyance speed of the copper strip into the above relational expression, the wrapping angle of the steel strip with respect to the cooling roll can be calculated. The winding angle is calculated periodically and the winding angle is changed based on the calculated value, and the winding angle is controlled while the weld line of the copper strip passes through the cooling roll. This publication also discloses the following technology. It adds a new formula to the relational formula in the control device to correct the target temperature of the control steel strip for the opening of the cooling roll, installs a copper strip thermometer on the exit side of the final cooling roll, and Based on the input from the steel strip thermometer on the exit side, the target temperature of #j4 zone of opening control is periodically corrected, the wrapping angle is recalculated, and the wrapping angle of the copper strip with respect to the cooling roll is corrected. . On the other hand, Japanese Patent Publication No. 63-34210 discloses the following technology. It is a strip temperature control method in a continuous annealing furnace in which strips with different thicknesses, widths, or heating furnace exit temperatures are continuously passed through the heating furnace for continuous annealing. Due to the change (set change) of the output loss strip temperature standard (plate temperature base'? $), the fuel flow rate of the heating furnace as a manipulated variable or the rate of strip passing through the furnace is changed to increase the heating furnace output as a controlled variable. In controlling the loss strip temperature (strip temperature), first variable unknown parameters dynamically express the relationship between the furnace exit strip temperature, fuel flow rate, furnace temperature, strip thickness, strip width, and strip passing speed in the furnace. Set a plate temperature control model including a plate temperature transition trajectory that provides the minimum value of a predetermined number of evaluation intervals for upcoming changes in plate thickness, plate width, or furnace exit plate temperature standards (set change); If the speed at which the strip passes through the furnace is changed, the amount of speed change and the start time of the change are determined in advance using the above plate temperature control model, and the speed determined above is determined while constantly tracking the strip setting position. The sheet passing speed is changed at the change start time, and the fuel flow rate is calculated and controlled from time to time at a predetermined sampling period so that the sheet temperature moves toward a transition trajectory. When determining the set value of the fuel flow rate, the set value is preferably calculated using a plate temperature control model as the value that gives the minimum value of a predetermined evaluation function, and the variable unknown parameter is calculated using this value. It is mentioned that it may be estimated. The technique disclosed in the above-mentioned Japanese Patent Publication No. 14051/1983 sets the manipulated variable using a temperature model formula and eliminates the error using feedback control. On the other hand, the technique disclosed in the above-mentioned Japanese Patent Publication No. 63-34210 sets the manipulated variable using a temperature model formula, absorbs errors that occur through parameter estimation or learning, and improves model accuracy.

[Problem to be solved by the invention]

However, when the steel material is cooled or heated, for example, when it is cooled, the steel material transforms from γ iron to α iron (for example, from austenite to ferrite), and at this time, an exothermic phenomenon occurs. Temperature changes due to this transformation cause errors in the temperature model, but in the conventional technology described above, this was dealt with by feedback control of the generated errors or by absorbing the generated errors through parameter estimation or learning. However, in such a method, the temperature cannot be controlled in sufficient consideration of the temperature change due to transformation, and the plate temperature control accuracy is also low. At,
Although a technology has been proposed in which heat treatment is controlled by magnetically monitoring the α/γ phase fraction during continuous annealing, temperature control that takes into account the amount of absorption/development accompanying phase transformation has not yet been achieved. The present invention has been made in view of such conventional problems, and it provides a steel material for continuous annealing that allows even the transformation state of the steel material to be accurately reflected in the temperature estimation model, thereby enabling more accurate temperature control. The purpose of this invention is to provide a temperature control method.

[Means to solve the problem] The present invention is capable of controlling the temperature of the steel material at a predetermined position on the line or at a predetermined time to a predetermined target temperature by controlling the amount of cooling or heating according to the cooling conditions or heating conditions of the steel material during continuous annealing. In the temperature control method of steel material during continuous annealing, the temperature of the steel material to be cooled or heated is estimated by a temperature estimation model, taking into account the progress of transformation of the steel material to be cooled or heated, and based on the estimated steel material temperature, The above object is achieved by determining the amount of cooling or heating. Further, in order to consider the progress of transformation of the steel material, the present invention easily and accurately determines the progress of transformation by considering changes in the heat value of transformation according to time changes in the transformation rate of the steel material. This is something that can be taken into consideration. Further, the present invention provides a sensor for detecting at least one of the transformation rate and the amount of austenite of the steel material in the continuous annealing line, and learns and corrects the parameters of the temperature estimation model, thereby enabling accurate temperature control. This is how it was done. [Effect]

In the present invention, when controlling the plate temperature of the steel material during continuous annealing, the temperature of the steel material is estimated taking into account the progress of transformation of the steel material that is undergoing temperature control (cooling or heating), and operations are performed based on the estimated temperature. Control quantity. Therefore, the temperature of the steel material can be estimated by taking into account the progress of transformation of the steel material during the process of temperature control, which greatly reduces the error in the estimated steel material temperature from the actual steel material temperature during cooling and heating. It is possible to perform temperature control in which a desired amount of temperature change is obtained by accurately controlling the amount of cooling and heating. Therefore, more stable steel materials can be manufactured with high productivity. In addition, if the progress of transformation of the steel material is considered by considering the change in the transformation calorific value according to the time change of the transformation rate of the steel material, the progress of the transformation can be objectively referred to as the transformation calorific value. It is easy to estimate the temperature of the steel material because it can be determined with a quantitative quantity. Furthermore, if a sensor is installed in the line to detect the amount of transformation or austenite in the steel material, and the actual measured value is compared with the estimated value to learn the variable parameters in the transformation progress model, the progress of transformation can be improved. It becomes possible to significantly improve the accuracy of estimating the situation.

【Example】

Hereinafter, embodiments of the present invention will be described in detail using FIG. 2. In this embodiment, the cooling equipment includes a gas jet cooling zone 10 and a roll cooling zone 12, and the position of the steel strip 1 is tracked by the steel strip tracking unit 22 of the plate temperature control device 20 using a welding point detector 14 or the like. , the cooling condition Co given to the steel strip 1 is inputted to the cooling amount determination unit 24 according to the copper strip position. In the cooling amount determination unit 24, input cooling conditions CO (plate thickness, plate width, target plate temperature, etc.) and plate temperature sensors 71 to
From the current temperature information detected by 73, each cooling zone 1
Calculate the amount of cooling to be performed using 0.12. From the obtained cooling amount, according to the relationship between the cooling amount and the manipulated variable given in advance,
The operation amount of the gas jet cooling zone 10 in the gas jet control device 30, the operation amount of the opposing gas jets 41 and 42 in the opposing gas jet control device 40, and the operation amount of the roll cooling zone 12 in the roll cooling control device 50 are determined. In this embodiment, the amount of heat generated by transformation is taken into consideration when determining the amount of cooling. Further, when determining the cooling amount, variable parameters in the control model are obtained from the learning control section 26. The learning control unit 26 performs online estimation of the variable parameters in the metamorphosis progress model by comparing the actual measured values of the metamorphosis rate sensors 61, 62, and the estimated values of the metamorphosis progress model.
Further, this learning control unit 26 uses the predicted temperature value and the plate temperature sensor 7.
1.72... The variable parameters in the temperature model are estimated online by comparing the measured temperatures. According to this configuration, strange! Since variable parameters in the temperature model can be learned excluding disturbances caused by B heat generation, highly accurate temperature model learning can be performed. The gas jet control device 30, the opposing gas jet control device 40, and the roll cooling device 50 each control the gas jet pressure, the damper opening degree, and the roll pushing amount according to the operation amount determined by the cooling amount determination unit 24. The effects of the embodiment will be explained below. In this embodiment, when determining the cooling amount of the cooling equipment, the temperature change of the steel strip 1 after a predetermined period of time is estimated from the cooling time of the steel strip 1 and the cooling capacity of the cooling equipment, and at the same time,
For example, the transformation calorific value of the R band 1 is calculated from the progress of transformation due to cooling of the steel strip 1, and the error in the estimated temperature change of the steel strip 1 is corrected by the calculated transformation calorific value. Cooling is controlled to obtain the desired temperature change amount. First, a method of determining the progress of transformation of the steel strip 1 will be explained. The transformation rate W of the steel strip 1 during cooling can be calculated from the following equation (1) as a function of the cooling time t. W=,1-eXi)[A・(t/B)]-(1
) Here, A, B, and C are parameters determined by the composition, temperature, plate thickness, cooling rate, etc. of the steel strip 1. From this equation (1), it is possible to know the progress of transformation in the steel strip 1 with respect to time. Here, in the cooling equipment having the predetermined number of cooling zones, if the cooling time from the entrance side to the first cooling zone is ti, then the cooling time in the first cooling zone ΔT i ('' j i,
From the relationship between i i−+) and equation (1), the transformation rate change amount ΔWi (=Wi−Wi−
1) can be calculated. When this transformation rate change amount ΔWi is given, the transformation calorific value Qyi of the copper strip in the i-th zone can be calculated by the following equation (2). Qyi=HneΔWi (2) where H is the latent heat of transformation of the steel strip 1 (a physical quantity that can be determined for each component, steel type, and temperature of the steel strip 1). Therefore, first, the transformation calorific value QT in each cooling zone when cooling the steel strip 1 from the entrance temperature to the target temperature is calculated using equation (2), and then the transformation calorific value Qvi is calculated. If the temperature change of the steel strip 1 estimated from the cooling time of the steel strip 1 and the capacity of the cooling equipment is corrected,
Accurate temperature changes in each cooling zone of the steel strip 1 can be estimated. Therefore, in order to realize the temperature change estimated in this way in each cooling zone, the amount of temperature change ΔT during gas jet cooling in the first cooling zone shown in the following equation (3) is
io, the required cooling amount in each cooling zone is determined using the temperature model equation of the temperature change amount ΔT i R during roll cooling, which is also shown in equation (4). Thereby, cooling can be controlled so as to give a desired temperature change to the steel strip 1 in consideration of the transformation calorific value Qyi and the progress of the transformation. Cooling zone outlet temperature θD
becomes as follows. θ0=θtr++(θE−θtrt)xexp[(
-2XαoXJ2o) /<Cp*ρ*i *v) ] (2G=3.×Δpa! a()+θ
0) θE: Cooling zone entrance temperature αG = Gas jet cooling capacity J2 () Ni-gas jet cooling length CP: Specific heat ρ: Specific gravity h: Plate thickness ■ Ni-line speed θ0 Ni-gas jet refrigerant temperature al, al: Coefficient ΔP Ni-gas jet pressure and furnace pressure Differential pressure θO=θtr2+(θE−θtr2)xexp[(K
R-J2*) /(Cp ・ρ ・h-v)] θtr2=QviXρXh/KR+θR...(4) J2R: Roll contact length KR: Roll refrigerant to strip heat transfer rate θtr2: Transformation heat effect temperature θR: Roll Refrigerant temperature In the case of heating, equation (1) may be changed to equation (5), equation (2) may be changed to equation (6), and equation (3) may be changed to equation (7). w=exp[A'-(t/B)]=
(5) A', B', and C' are the composition, temperature, and thickness of the copper strip;
This is a parameter given as a number between heating rates. Q Ding H=-)(*ΔWi...(6
) θ0=θtr3 + (θE−θtr3)XeXp[−
(2 αi*J!i) / (Cp *ρ*hmV)1...(7) θt"3
: Variable B exothermic influence temperature (=Qvt Replaced by relationship.

【Effect of the invention】

As explained above, according to the present invention, when cooling or heating a steel material in a continuous annealing furnace, the temperature of the steel material is accurately estimated in consideration of the progress of transformation of the steel material, and the steel material is cooled based on this estimated temperature. Since the amount or heating amount is determined, it is possible to significantly reduce the estimated temperature error with respect to the actual steel material temperature, and it is possible to realize highly accurate steel material temperature control. Therefore, excellent effects such as being able to manufacture stable steel materials with high productivity can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the state of temperature change due to the transformation phenomenon to explain the basic principle of the present invention, and FIG. 2 is a diagram showing the plate temperature control system (cooling control FIG. 2 is a schematic block diagram showing the system. DESCRIPTION OF SYMBOLS 1... Steel strip, 10... Gas jet cooling zone, 12... Roll cooling zone, 0... Plate temperature control device, 2... Copper strip tracking part, 4... Cooling amount determination part , 6...Learning control unit, O...Gas jet control device, 0...Opposed gas jet control device, O...Roll cooling control device, 1.62...Transformation rate sensor, 1.72 ...Plate temperature sensor.

Claims (3)

[Claims] (1) By controlling the cooling amount or heating amount according to the cooling or heating conditions of the steel material during continuous annealing, the temperature of the steel material at a predetermined position on the line or for a predetermined time is controlled to a predetermined target temperature. In the temperature control method for steel materials during continuous annealing, the temperature of the steel material to be cooled or heated is estimated by a temperature estimation model, taking into account the progress of transformation of the steel material to be cooled or heated, and the temperature of the steel material is estimated based on the estimated steel material temperature. , a method for controlling the temperature of a steel material during continuous annealing, the method comprising determining the amount of cooling or the amount of heating. (2) The temperature of the steel material during continuous annealing according to claim 1, wherein in order to consider the progress of transformation of the steel material, a change in the transformation calorific value according to a time change in the transformation rate of the steel material is taken into consideration. Control method. (3) A sensor for detecting at least one of the transformation rate and the amount of austenite of the steel material is provided in the continuous annealing line, and the parameters of the temperature estimation model are learned and corrected. Temperature control method for steel materials during continuous annealing.