JPH05263147A - Method for controlling strip temperature in continuous annealing furnace - Google Patents

Abstract

PURPOSE:To provide a control method of strip temp. in a continuous annealing furnace, by which the response characteristic is good and the strip temp. can be controlled at high accuracy and the aimed strip temp. at the outlet side can stably be achieved in the aimed strip passing speed. CONSTITUTION:The setting furnace temp. value TFO for which the strip temp. TS at the outlet side becomes the aimed strip temp. TSO at the outlet side at the time of passing the strip in the aimed strip passing velocity VSO, is decided according to a physical model procedures (S1-S5). By considering the response delay time of the furnace temp. produced attending with the switch of the setting value, the furnace temp. switching timing tFO is decided (S6-S8). Correcting strip passing velocity VS for controlling the strip temp. TS at the outlet side in the heating furnace in the permissible range of the aimed strip temp. TSO at the outlet side at the time of passing the strip at the actual furnace temp. TF detected as the result, is decided according to the physical model procedures (S9-S14). By considering the time necessary for the change of the strip temp. at the outlet side generated attending to the change of the setting, strip passing velocity setting switching timing tSO is decided (S15-S17). Then, in this control method, the physical parameters included in the model procedures are corrected by the learning control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to continuous annealing in which steel strips having different plate thicknesses, plate widths or target plate temperatures on the exit side of the heating furnace are continuously passed through the heating furnace for continuous annealing. The present invention relates to a method for controlling the plate temperature of a steel strip on the outlet side of a heating furnace in a furnace.

[0002]

2. Description of the Related Art In particular, a cold-rolled steel strip has large changes in metallurgical structure, mechanical strength, internal strain, etc., and it is necessary to anneal this to remove these changing elements. The need is particularly great in ultra-low carbon steel strips, which have recently been receiving attention. Steel strips with different plate thickness, plate width or target outlet side plate temperature on the outlet side of the heating furnace are made into a series of strips by the welding process, etc., and this is passed through the heating furnace of the continuous annealing furnace for continuous annealing. Is common.

On the other hand, the plate temperature on the outlet side of the heating furnace has a great influence on the mechanical properties of the steel sheet to be manufactured. Therefore, the target value of the plate temperature on the outlet side of the heating furnace and this target for each steel strip having different specifications It is necessary to set a permissible range including values and control so that the strip temperature of each steel strip falls within the set permissible range of the target delivery side strip temperature. As such a plate temperature control method in a continuous annealing furnace, it is common to set the temperature of the heating furnace (furnace temperature) and the plate passing speed according to the specifications including the plate thickness and plate width of the steel strip. is there. However, the responsiveness of the actual furnace temperature to changes in the furnace temperature setting of the heating furnace is extremely slow and relatively unstable, so that the actual plate temperature and the plate temperature are There is a problem that the deviation from the target value becomes large and the temperature tends to be in an unsteady region, the plate temperature of the steel strip deviates from the allowable range, and the yield decreases.

As one of the plate temperature control methods for solving such a problem, a method described in Japanese Patent Application Laid-Open No. 61-190026 has been proposed. This plate temperature control method is
Calculate the theoretical optimum transition trajectory of the plate temperature in the unsteady region,
The fuel supply amount to the heating furnace is controlled so that the plate temperature follows the calculated orbit. Further, as another method, there is a plate temperature control method described in JP-A-2-258933. This plate temperature control method estimates the change amount of the set furnace temperature value of the heating furnace, the response change amount of the furnace temperature of the heating furnace with respect to the changed amount, and the plate temperature change amount in the strip running direction of the steel strip. When the deviation between the estimated plate temperature change amount and the target outlet side plate temperature is within the allowable range, the furnace temperature of the heating furnace is controlled at a preset plate passing speed, and the estimated plate temperature change amount is set. If the deviation between the target delivery side plate temperature and the target output side plate temperature is outside the permissible range, correction control of the plate passing speed is also performed.

[0005]

Among these methods for controlling the plate temperature of the continuous annealing furnace, in the former case, it is possible to suppress the actual plate temperature from deviating from the permissible range to some extent in the temporary and unsteady regions of the steel strip. Is possible. However, since the poor response of the actual plate temperature due to the essential response delay of the furnace temperature has not been improved, the possibility that the actual plate temperature deviates from the allowable range has not been sufficiently solved.

On the other hand, in the latter case, the poor response of the actual plate temperature due to the delay in the response of the essential furnace temperature is improved by controlling the strip running speed having a response characteristic far better than those. Therefore, there is no problem as described above. However, since the furnace temperature change amount and the plate temperature change amount are estimated and the plate passing speed is corrected and controlled based on these estimated values, it is possible to change the furnace temperature, for example, when an unstable change occurs. If a condition with poor estimation accuracy occurs, there is a problem that the actual plate temperature accuracy decreases. Further, although the present invention discloses that the speed is corrected by the actual plate temperature change amount,
Since feedback of the actual plate temperature causes a delay in the plate temperature response to the correction control of the plate passing speed, highly accurate plate temperature control cannot be expected.

The present invention has been developed in view of these problems, and controls the furnace temperature according to a predetermined condition, and uses the controlled actual furnace temperature to satisfy the predetermined condition. An object of the present invention is to provide a plate temperature control method for a continuous annealing furnace, which has good response characteristics and can control the plate temperature with high accuracy by controlling the plate speed.

[0008]

As a result of intensive studies to solve the above problems, the present inventor has obtained the following findings.
That is, the response time of the furnace temperature is about 10 to 20 minutes, although it depends on the stripping speed and the size of the steel strip (plate thickness, strip width, etc.). On the other hand, the response time of the strip running speed depends on the acceleration / deceleration associated with the facility capacity, etc., but is generally about 10-40 mpm / sec., Which is a sufficiently high response value that can be almost ignored in the plate temperature control. is there. Also, the change of the outlet side plate temperature due to the change of the strip passing speed depends on the strip passing speed and the heating furnace length. That is, the exit side plate temperature will change until the steel strip that has entered the heating furnace exits the heating furnace after reaching the changed strip passing speed, but the required time is about 2 to 3 minutes. ..

As described above, the response of the outlet side plate temperature to the change of the strip passing speed is sufficiently quicker than the response of the furnace temperature. Therefore, the amount of change in the furnace temperature from the inlet side to the outlet side of the heating furnace is ignored and the current furnace temperature is ignored. Thus, it is possible to obtain the strip running speed for achieving the output side plate temperature to the target output side plate temperature. Then, the setting of the furnace temperature and the correction of the strip passing speed are determined using the same model formula, and the parameters of the model formula are corrected by the actual furnace temperature and the actual plate temperature, so that the correction is made while the control is continuously performed. We also paid attention to the fact that the gap between the strip running speed and the target strip running speed becomes smaller. The present invention was developed based on these findings.

That is, in the plate temperature control method for a continuous annealing furnace according to claim 1 of the present invention, a steel strip having a different plate thickness, plate width, or target outlet plate temperature on the outlet side of the heating furnace is used as a heating furnace. In a continuous annealing furnace that performs continuous sheet passing and continuous annealing, the plate temperature control of the continuous annealing furnace that controls the exit side plate temperature of the heating furnace by controlling the set furnace temperature value of the heating furnace and the plate passing speed In the method
The target strip running speed is defined as the steady strip running speed at which the strips and steel strips in the furnace are stably annealed, and when the strip is run at this target strip running speed, the exit side strip temperature of the heating furnace is set to the target output. While determining the set furnace temperature value that becomes the side plate temperature according to a predetermined condition, the furnace temperature setting change timing is determined in consideration of the response delay time of the furnace temperature calculated from the set furnace temperature value, and the set furnace temperature value and To detect the actual furnace temperature as a result of control at the furnace temperature setting change timing and to control the heating furnace exit side plate temperature within a predetermined range with respect to the target exit side plate temperature when the plate is passed at the actual furnace temperature. The modified strip passing speed is determined according to a predetermined condition, and the strip running speed setting change timing is determined in consideration of the time required to change the delivery side plate temperature calculated from the corrected strip running speed. ..

A plate temperature control method for a continuous annealing furnace according to a second aspect of the present invention calculates the furnace temperature set value and the corrected plate passing speed according to the same predetermined model formula, and is included in this model formula. It is characterized in that the physical parameters to be corrected are modified by learning control.

[0012]

In the plate temperature control method for the continuous annealing furnace of the present invention, the plate passing speed in a steady state in which annealing of the plate and the steel strip in the furnace is stably performed is set as the target plate passing speed. In addition to determining the set furnace temperature value at which the outlet side plate temperature of the heating furnace becomes the target outlet side plate temperature when passing the plate according to a predetermined condition, considering the response delay time of the furnace temperature calculated from the set furnace temperature value. The furnace temperature setting change timing is determined according to the set temperature, and the actual furnace temperature as a result of control at the set furnace temperature value and the furnace temperature setting change timing is detected, and when the plate is passed at the actual furnace temperature, the heating furnace exit side plate temperature is detected. The corrected strip running speed for controlling the target strip temperature within the predetermined range with respect to the target strip temperature is determined in accordance with the predetermined conditions, and the time required for the change of the strip temperature calculated from the corrected strip speed is taken into consideration. In order to determine the plate speed setting change timing,
Even if the actual furnace temperature does not satisfy the set furnace temperature due to some unstable factors, the actual furnace temperature can be suppressed within the allowable range of the target outlet plate temperature by the actual furnace temperature, and the strip speed can be set. Since the response characteristic to the change is extremely good, the strip speed can be corrected and controlled almost in real time with respect to the detected actual furnace temperature, and the strip temperature can be controlled with high accuracy.

Further, in the plate temperature control method for the continuous annealing furnace of the present invention, the set furnace temperature value is determined so as to satisfy the target exit side plate temperature and the target plate passing speed as described above, and the set furnace temperature is set. The value and the corrected strip running speed were calculated according to the same predetermined model formula, and the physical parameters contained in this model formula were modified by learning control.Therefore, while continuing continuous annealing using this control method, In addition, the corrected strip running speed asymptotically approaches the target strip running speed, and it becomes possible to operate at the desired target strip running speed to satisfy the target delivery side strip temperature.

[0014]

FIG. 1 shows an example of an apparatus embodying the method for controlling the plate temperature of a continuous annealing furnace according to the present invention. The strip 1 shown in the figure is formed in series by welding a plurality of steel strips having different plate thicknesses, plate widths, or target outlet side plate temperatures on the outlet side of the heating furnace. This strip 1 is fed into the heating furnace 3 by the rotation of the roll 2, passes through the heating furnace 3 by the rotation of the roll 4, and passes through the outside of the heating furnace 3 in the direction of the arrow by the rotation of the rolls 5 and 6. To be done. These rolls 2-6
Are rotated individually by a motor 7 provided for each, or in series with the passage of the strip 1. A tachometer 8 is attached to the roll 6, and a detection signal of the tachometer 8 is sent to the plate passing speed control device 15.

Combustion gas is introduced into the heating furnace 3 through a flow valve 9, and the combustion gas is inside a radiant tube (not shown) arranged in the vicinity of the strip 1 passing through the heating furnace 3. It is sent to and burns. Therefore, the furnace temperature in the heating furnace 3 is the heat transfer between the roll 4 and the strip 1,
Although it includes specifications such as convective heat transfer in the furnace and radiant heat transfer in the furnace wall, it is controlled by the flow rate of the combustion gas.
A furnace thermometer 10 is attached to the heating furnace 3, and its detection signal is sent to the furnace temperature control device 11.

On the other hand, various furnace temperature condition signals set by the strip condition setting device 12 provided in the centralized control room of the continuous annealing equipment are sent to the furnace temperature setting device 13, and the furnace temperature setting device is operated. The furnace temperature setting signal of the set furnace temperature set in 13 is sent to the furnace temperature control device 11, and the opening / closing degree of the flow valve 9 is controlled based on the furnace temperature control signal from the furnace temperature control device 11. The inflow amount of the combustion gas is controlled, and the inflow amount of the combustion gas is feedback-controlled based on the detection signal from the furnace thermometer 10. Incidentally, in the furnace temperature condition signal sent from the strip condition setting device 12, each steel plate (steel plates with different specifications are usually wound around individual coils, so hereinafter, steel plates with different specifications are simply referred to as coils. ) Target outlet plate temperature T at outlet of heating furnace
_SO , upper limit outlet plate temperature T at outlet of heating furnace determined by quality
_SU and the lower limit outlet plate temperature T _SL at the outlet side of the heating furnace, the upper limit furnace temperature T _FU and the lower limit furnace temperature T _FL determined from the heating furnace capacity, etc., and the upper limit strip speed V _SU determined to prevent meandering , The lower limit plate passing speed V _SL determined to prevent buckling, and the mechanical specifications of each coil. It should be noted that these upper and lower values are prioritized when an operator's operation is present, and most prioritized when an alarm signal on mechanical equipment is transmitted. In many cases, the target outlet plate temperature T
_SO is set close to the lower limit outlet plate temperature T _SL so as to reduce the amount of heat more than necessary, but the fact that the actual outlet plate temperature T _S is lower than the lower limit outlet plate temperature T _SL is in terms of quality. Most must be avoided.

Further, various strip passing speed condition signals set by the strip strip condition setting unit 12 are sent to the strip passing speed setter 14.
And the furnace temperature detection signal of the furnace thermometer 10 is also sent to the plate passing speed setting device 14, and the plate passing speed setting signal set by the plate passing speed setting device 14 is The rotation speed of the motor 7 is controlled by controlling the rotation speed of the motor 7 on the basis of the threading speed control signal from the threading speed control device 15, and the rotation speed of the roll 6 is controlled. The rotation speed of the motor 7 is feedback-controlled based on the rotation speed detection signal from the rotation speed meter 8. By the way, in the strip speed condition signal sent from the strip condition setter 12, the target outlet side plate temperature T _{SO at} the heating furnace outlet side of each coil, the upper limit outlet side plate temperature T _SU at the heating furnace outlet side, and the heating There are a lower limit outlet side plate temperature T _SL at the furnace outlet side, an upper limit furnace temperature set value, a lower limit furnace temperature set value, an upper limit plate passing speed V _SU , a lower limit plate passing speed V _SL , and mechanical specifications of each coil. Further, these upper and lower values have the same priority as above, when the operator's operation is involved, and give the highest priority when the alarm signal on the mechanical equipment is transmitted.

Further, in this continuous annealing equipment, a plate thermometer 16 for detecting the actual delivery side plate temperature T _S is installed on the outlet side of the heating furnace. The actual output side plate temperature detection signal of the plate thermometer 16,
The detection signals of the tachometer 8 and the furnace thermometer 10 are sent to the learning controller 17. In the learning controller 17, when it becomes necessary to correct the physical parameters of the physical model formula described later from these detection signals, the parameters are corrected toward the furnace temperature setting device 13 and the strip speed setting device 14. Send a signal.

The furnace temperature setting device 13 and the plate passing speed setting device 1
4, a computer (not shown) is installed, and this computer calculates a set set value and a corrected stripping speed in accordance with predetermined conditions based on the various condition signals. The predetermined conditions generally include, for example, the furnace temperature and the plate temperature. The physical model equation shown in the following equation 1 representing the correlation with is used.

DT _S / dt = φ _cg σ (T _S ⁴ −T _F ⁴ ) ... (1) where T _S : outlet plate temperature, t: time, φ _cg , σ: physical parameter, T _F : Indicates furnace temperature. Therefore, the left side dT _S / d
t represents the temperature gradient of the outlet plate temperature per hour, φ _cg ,
If the time difference Δt is determined assuming that σ, T _S , and T _F are constants, the change amount ΔT _S of the outlet plate temperature is determined, and if the change amount ΔT _S of the outlet plate temperature is determined, the time difference Δt is determined. It

The computer in the furnace temperature setter 13 executes the basic program shown in the flowchart of FIG. 2a to determine the target strip running speed V _SO , the set furnace temperature T _FO , and the furnace temperature setting change timing t _1. It Further, the computer in the strip passing speed setting unit 14 executes the basic program shown in the flowchart of FIG. 2B to determine the corrected strip passing speed V _S , the strip passing speed setting change timing, and the change standing.

The program shown in the flow chart of FIG. 2A requires the response of the actual furnace temperature to the change of the setting of the furnace temperature as described above, whereas the passage time of each coil in the heating furnace is several minutes. Therefore, each coil is performed in advance before passing through the heating furnace. In this program, first, in step S1, the target outlet plate temperature T _SO of each coil is read from the condition signal.

Next, in step S2, the target strip running speed V _SO of each coil is determined. This target strip speed V
_SO needs to be set between the upper limit sheet passing speed V _SU and the lower limit sheet passing speed V _SL, and in view of productivity, it is as close as possible to the upper limit sheet passing speed V _SU side, that is, high. However, it is not desirable to set this to the upper limit value for the correction control of the strip running speed described later. In this embodiment, as shown in FIGS. 3 and 4, the target strip running speed V _SO was set constant for each coil and set slightly lower than the upper limit strip running speed V _SU .

Next, in step S3, it is determined whether or not a correction signal for the physical parameter φ _cg of the physical model equation 1 is transmitted from the learning controller 17, and the correction signal is transmitted. If so, the process proceeds to step S4, and if not, the process proceeds to step S5. In step S4, the one set of correction parameters is read and the process proceeds to step S5.

In step S5, the set furnace temperature T _FO for achieving the target outlet side plate temperature T _SO of each coil when each coil is passed at the target running speed V _SO determined in step S2 is set. , Is calculated according to the above formula 1. In this case, the target outlet-side plate temperature T _SO is substituted for the plate temperature T _S in the equation 1 and the set furnace temperature T _FO is substituted for the furnace temperature T _F to calculate the set furnace temperature T _FO . Note that the plate temperature gradient dT _SO / dt on the left side of the equation 1 is substituted based on the specifications (plate thickness, plate width) of each coil by quoting required data from a memory table obtained from empirical values and the like. To do. In this case, for example, the integrated value of the time change rate dt,
The time difference Δt is calculated from the furnace length and the target strip speed V _SO , the integrated value of the plate temperature change rate dT _SO , and the plate temperature change amount ΔT _SO is calculated from the current inlet plate temperature and the target outlet plate temperature T _SO. . Of course, in this case, the set oven temperature T _F in the upper furnace temperature T _FU when set furnace temperature T _F is the upper limit reactor temperature T _FU or, if the set furnace temperature T _F is lower furnace temperature T _FL or Set the furnace temperature T _F to the lower limit furnace temperature T
Must be set to _FL .

Next, in step S6, the response delay of the outlet side plate temperature caused by the response delay of the actual furnace temperature with respect to the set furnace temperature T _FO calculated in step S5 is calculated, and the response of the outlet side plate temperature is calculated. The furnace temperature setting change timing is calculated in consideration of the delay time. In this case, the response delay of the actual furnace temperature is the difference between the current actual furnace temperature and the set furnace temperature, and the response delay of the outlet plate temperature is the difference between the actual furnace temperature and the actual outlet plate temperature. The required data is quoted from the obtained storage table. These data are appropriately processed to calculate the response delay time of the outlet plate temperature, and the furnace temperature setting change timing is calculated based on this response delay time.

Next, in step S7, the coils that have been calculated up to step S6 are passed through or inside the heating furnace from the current time to the target delivery side plate temperature arrival time. Of the set furnace temperature T _FO set for each of the coils, the highest set furnace temperature T _FO is selected, and this set furnace temperature is set as the target set furnace temperature T _FO. Determined as _FO . In addition, the calculation of the coil that passes through or is fed into the heating furnace from the current time to the time when the target outlet plate temperature is reached is calculated by each coil length, furnace length,
It is calculated based on the target running speed V _SO .

Next, at step S8, the furnace temperature setting timing t _FO of the coil closest to the current time is combined with the target set furnace temperature T _FO determined at step S7. A signal is output to the furnace temperature control device 11, and the program ends. The program shown in the flowchart of FIG.
Processing time, the response time of the motor 7 and the roll 6, the processing time of the tachometer 8, and the processing time of the strip speed setting device 14, with respect to the detection signal from the furnace thermometer 10, for example, 5 seconds. Every time it is done in real time.

In this program, first, in step S9, the target outlet side plate temperature T _SO , the upper limit plate passing speed V _SU , and the lower limit plate passing speed V _SL are read. Next in step S10
Then, the actual furnace temperature T _F is read from the actual furnace temperature detection signal from the furnace thermometer 10. Next, in step S11, it is determined whether or not a correction signal for the physical parameter φ _cg ε of the equation 1 has been sent from the learning controller 17.
If the correction signal is transmitted, the process proceeds to step S12, and if not, the process proceeds to step S13.

In step S12, the one set of correction parameters is read, and the process proceeds to step S13.
In step S13, each coil is connected to the actual furnace temperature T _F.
In the target delivery side temperature gradient dT _SO / dt when the strip passing is calculated by substituting the actual furnace temperature T _F in furnace temperature T _F of the equation (1).

Next, the routine proceeds to step S14, where the corrected running speed V _S for achieving the target outlet side plate temperature gradient dT _SO / dt.
To calculate. In this case, for example, the integrated value of the time change rate dt and the time difference Δt are the target output side plate temperature change based on the distance from the target output side plate temperature change point (temporary stage) to the heating furnace output side and the corrected running speed V _S. The integrated value of the rate dT _SO and the plate temperature change amount ΔT _SO are calculated from the current actual delivery side plate temperature T _S and the target delivery side plate temperature T _SO .

Next, in step S15, if the corrected strip passing speed V _S is equal to or higher than the upper limit sheet passing speed V _SU , the corrected sheet passing speed V _S is set to the upper limit sheet passing speed V _SU , When the corrected passing speed V _S is equal to or higher than the lower limit passing speed V _SL , the corrected passing speed V _S is set to the lower limit passing speed V _SL , and
From the exit side plate temperature T _SN of the coil currently passing through the exit side of the heating furnace 3, the rate of change of the passing speed of the corrected running speed V _S , that is, the acceleration / deceleration, and the corrected passing speed V delay time, The passage speed setting change timing t _SO of _S is calculated.

Next, in step S16, the coil that passes through or is fed into the heating furnace is calculated from the current time to the time when the target delivery side plate temperature is reached when the running speed is corrected. Of these coils, the corrected threading speed of the coil having the lowest corrected threading speed V _S is selected, and this is determined as the corrected threading speed V _S. Next, the process proceeds to step S17, where the determined corrected strip passing speed V _S is combined with the strip passage speed setting change timing t _{SO of the} coil closest to the current time and the speed change rate. Is output and the program ends.

Next, the operation of the present invention by these program processes will be described with reference to FIGS. Of these, FIG. 3 shows the case where the target output side plate temperature of the trailing plate is higher than the current output side plate temperature of the preceding plate, and FIG. 4 shows that the target output side plate temperature of the following plate is higher than the current output side plate temperature of the preceding plate. The case is low.
For example, as shown in FIG. 3a, when the preceding plate has the current actual delivery side plate temperature T _SN and the trailing plate is changed to the target delivery side plate temperature T _SO , a condition signal from the strip condition setting device 12 is used. The mechanical specifications of the trailing plate and the target running speed V _SO
The target arrival side plate temperature arrival time t _O is obtained from. At this time, the target delivery side plate temperature reaching time t _O coincides with the delivery side passage time of the trailing plate leading edge stage. The furnace temperature setting device 13 which has obtained these pieces of information reads the target exit side plate temperature T _SO of the trailing plate in step S1 and determines the target passing speed V _SO of the trailing plate in step S2. In this case, the target strip running speed V _SO was determined so as to match the _{strip running} speed V _SN of the preceding plate.

Next, in steps S3 and S4, the physical model formula
Modify the physical parameters of and set the furnace temperature in step S5.
T_FOAnd the current furnace temperature T in step S6._FNFrom setting furnace
Temperature T _FOCalculates the plate temperature response delay time when the setting is changed to
Then, the target delivery side plate temperature reaching time t₀From the delay time
Move the furnace forward and change the furnace temperature setting timing t_FOTo decide. Shi
However, the furnace temperature setting change timing t_FOWhen it becomes, set furnace temperature T
_FOChange the setting to.

Here, originally, predetermined processing is performed in steps S7 and S8, but here, for simplification, the coil passing through the heating furnace between the current time and the target delivery side plate temperature arrival time is trailing. The description will proceed assuming that only the plate is used, and the operation of steps S7 and S8 will be described later with a preferred embodiment. On the other hand, in the step S9, the target delivery side plate temperature T _SO of the trailing plate, the upper limit plate speed V _SU and the lower limit plate speed V _SL are read in the step S9,
Next, in step S10, the current actual furnace temperature T _F is read.

Next, in steps S11 and S12, the physical parameters of the physical model formula are modified, and in steps S13 and S12.
In step S14, the corrected running speed V _S is determined, and in step S15, the delivery side plate temperature response delay time is calculated when the current running speed V _{SN is changed} to the corrected running speed V _S , and the target delivery side plate temperature is reached. From the time t _{0, the} plate passing speed setting change timing t _SO is determined by moving forward by the delay time, and when the plate passing speed setting change timing t _SO is reached, the corrected plate passing speed V _S is changed.

In this case as well, the predetermined processing is normally performed in step S16, but here, the description will be continued as it is, and the operation of step S16 will be described later with a preferred embodiment. Further, since the target delivery-side plate temperature reaching time is earlier or later than the initial set time by the correction control of the strip passing speed, the actual controller, the furnace temperature setting device 13, and the strip-passing speed setting device 14 reach this target delivery-side plate temperature. Although the time variation is constantly corrected, for the sake of simplicity, the description will be made assuming that the target delivery-side plate temperature arrival time (= outgoing-side passage time of the trailing plate leading edge stage) t _O does not change.

In step S17, the corrected plate passing speed V _S
Since the strip running speed setting change timing t _SO at the present time and the speed change rate are combined to output the strip running speed setting signal, for example, with respect to the actual furnace temperature T _F shown by the solid line in the furnace temperature characteristic of FIG. Virtual output side plate temperature T indicated by a virtual line in the output side plate temperature characteristic of FIG.
_{Although the output} side plate temperature tries to follow like _Si, the virtual output side plate temperature with respect to the current output side plate temperature T _SN of the preceding plate, excluding the response delay amount of the target output side plate temperature with respect to the substantial correction control of the strip passing speed. Since the change to T _Si is useless, the useless temperature change given to the preceding plate can be removed by continuously correcting and controlling the passing speed from the current time. In the case of FIG. 3a, since the plate temperature rise amount of the preceding plate indicated by the hatched portion a is a wasteful heat amount, as shown by the actual (corrected) plate passing speed V _S in the figure, the plate passing speed setting change timing t _SO In order to reach the corrected strip running speed V _S , the strip running speed is accelerated between the furnace temperature setting change timing t _FO and the strip running speed setting change timing t _SO , and the target strip running temperature is reached at the target delivery side plate temperature reaching time t _O. timing t _sO exchange Tsuban speed setting so as to reach the plate velocity V _sO
It is possible to remove the extra heat of the hatched portion Lee by decelerating the Tsuban speed until the target delivery side temperature arrival time t _O from.

On the other hand, as shown in FIG.
Setting change timing t_FOTrailing plate due to delay
The exit side passage time of the provisional tip stage, that is, the target exit side plate temperature arrival time t
_OFor the set furnace temperature reaching time t_F1Is delayed
Removes the excess heat of the preceding plate (hatched area B) as above
And supplement the insufficient heat of the trailing plate (hatched area C).
Therefore, the strip speed must be corrected and controlled. others
Therefore, the actual (corrected) plate passing speed V in the figure_S, As shown in
Plate speed setting change timing t_SOCorrected plate passing speed V_SReached
To change the furnace temperature setting timing t_FOFrom passing speed setting
Replacement timing t_SOUp to the passing speed,
Degree setting change timing t_SOTo the target delivery side plate temperature at time t_O
Until the virtual outlet plate temperature T_SiAnd actual delivery side plate temperature T_SAnd
Crossing time t₁And target strip speed V_SOAnd zero cross
As shown in FIG._F1so
Target strip speed V_SOWhen the target outlet plate temperature is reached
Tick t _OFrom the set furnace temperature reaching time t_F1The strip speed
By accelerating, the heat quantity in the shaded area B is deleted,
Moreover, it becomes possible to supplement the heat quantity of the hatched portion c.

As shown in FIG. 3c, for example, a furnace temperature setting changer
Imming t_FOThe trailing edge of the trailing plate is
The passage-side passage time, that is, the target arrival-side plate temperature arrival time t_OThan
If the set furnace temperature is reached first,
As in the case, delete the surplus heat of the preceding plate (hatched area D)
The strip speed is corrected and controlled as follows. In this case
Replacement timing t_soFrom the set furnace temperature reaching time t_F1Preceded by
Therefore, the actual (corrected) plate passing speed V in the figure_SI'll show you
Sea urchin reaching the set furnace temperature t_F1Corrected plate passing speed V _SReached
To change the furnace temperature setting timing t_FOFrom reaching the set furnace temperature
Time t_F1When the set furnace temperature is reached,
Tick t_F1To passing speed setting change timing t _SOUp until
Straight plate speed V_SAt the target delivery side plate temperature t
_OAnd target strip speed V_SOChange the strip speed so that
Timing t_SOTo the target delivery side plate temperature at time t_OUntil
Reduces the heat of the shaded area by reducing the passing speed.
It is possible to delete the amount.

On the other hand, when the target delivery side plate temperature T _SO of the trailing plate is lowered with respect to the current delivery side plate temperature T _SN of the preceding plate as shown in FIG. It coincides with the passage speed setting change timing t _O. In this case as well,
For example, the output side plate temperature tends to follow the actual furnace temperature T _F shown by the solid line in the furnace temperature characteristic of FIG. 4a, like the virtual output side plate temperature T _Si shown by the virtual line in the output side plate temperature characteristic of FIG. The change in the virtual output side plate temperature T _Si with respect to the current output side plate temperature T _SN of the preceding plate, which excludes the delay in the response of the target output side plate temperature to the substantial correction control of the plate passing speed, is useless. Only by continuously correcting and controlling the strip passing speed from the current time, it is possible to remove the wasteful temperature change given to the preceding strip. In the case of FIG. 4A, since the amount of heat increase of the preceding plate indicated by the shaded portion E is a wasteful amount of heat, as shown by the actual (corrected) plate passing speed V _S in the same figure, the target delivery side plate temperature arrival time t _O In order to reach the corrected strip running speed V _S , the strip running speed is accelerated between the strip running speed setting change timing t _SO and the target exit side plate temperature reaching time t _O, and the target strip passing speed is reached at the set furnace temperature reaching time t _F1. Plate speed V _SO
By decelerating the plate passing speed between the target outlet plate temperature arrival time t _O and the set furnace temperature arrival time t _F1 so as to reach the above, it is possible to remove the excess heat amount of the shaded portion e.

On the other hand, as shown in FIG. 4B, for example, when the furnace temperature setting change timing t _FO lags behind the exit side passage time of the trailing plate leading edge stage, that is, the passing speed setting change timing t _SO , As in the case of FIG. 4a, the passage speed is corrected and controlled so as to delete the surplus heat amount (to the shaded portion) of the preceding plate. In this case, since the furnace temperature setting change timing t _FO is after the target delivery side plate temperature arrival time t _O , as shown in the actual (corrected) plate passing speed V _S in the figure, the target delivery side plate temperature arrival time accelerate Tsuban speed between the Tsuban speed setting replacement timing t _sO so as to reach the corrected through plate velocity V _S in t _O to the target delivery side temperature arrival time t _O, the target delivery side temperature arrival time t _O from the until the furnace temperature setting replacement timing t _FO maintains the modified passage plate velocity V _S, further setting oven temperature arrival time t _F1 in replacement furnace temperature set to reach the target through plate velocity V _sO timing t _FO It is possible to remove the heat quantity to the shaded portion by reducing the plate passing speed until the set furnace temperature reaching time t _F1 .

Further, as shown in FIG. 4C, for example, when the furnace temperature setting change timing t _FO is earlier than the exit side passage time of the trailing plate leading edge stage, that is, the passing speed setting change timing t _SO , the same as above. In addition, it is necessary to correct the passage speed so as to delete the surplus heat amount of the leading plate (hatched portion) and supplement the insufficient heat amount of the trailing plate (hatched portion). Therefore, as shown in the actual (corrected) strip passing speed V _S in the figure, the furnace temperature setting change timing t _FO is reached from the furnace temperature setting change timing t _FO so as to reach the deceleration-side corrected strip passing speed V _S1 at the strip passing speed setting change timing t _SO. accelerate Tsuban speed until time t _SO exchange sheet passing speed setting, between the sheet passing speed setting replacement timing t _SO to the target delivery side temperature arrival time t _O, out virtual delivery side temperature T _Si and results At the time t ₂ at which the side plate temperature T _S intersects, the target plate running speed V _SO is zero-crossed, and at the target exit side plate temperature reaching time t _O , the acceleration side corrected plate running speed V _S2.
Accelerating Tsuban speed to reach the further from the target delivery side temperature arrival time t _O to reach the target through plate velocity V _SO settings furnace temperature arrival time t _F1 to set furnace temperature arrival time t _F1 By accelerating the plate passing speed in the meantime, it becomes possible to eliminate the heat quantity of the shaded area and supplement the heat quantity of the shaded area.

Of course, in these controls, the set furnace temperature T
_FO upper limit reactor temperature T _FU When it becomes more than the upper limit reactor temperature T _FU which is not shown, it is determined to set furnace temperature T _FO, set furnace temperature T _FO
Is below the lower limit furnace temperature T _{FL (} not shown), the lower limit furnace temperature T _FL is determined as the set furnace temperature T _FO . Similarly, the upper limit passing plate speed _SU is determined corrected through plate velocity V _S when the corrected through plate velocity V _S is equal to or higher than the upper limit passing plate speed _SU, modified through plate velocity V _S is lower passage plate velocity V _SL When it becomes the following, the lower limit plate passing speed V _SL is determined as the corrected plate passing speed V _S. Further, actual delivery side temperature T _S If is greater than or equal to the upper delivery side temperature T _SU, for example, a modified passage plate velocity V _S out performance, such as by controlling the speed reduction side plate temperature T _S is an upper limit delivery side temperature T _SU controlled not exceed, performance when the delivery side temperature T _S is less than or equal to the lower delivery side temperature T _SL, for example, actual delivery side temperature T _S, such as by controlling the modified passage plate velocity V _S in the acceleration side Control so as not to exceed the lower limit outlet plate temperature T _SL .

A preferred embodiment of the plate temperature control method for the continuous annealing furnace of the present invention will be described in detail with reference to FIG. In this embodiment as well, the target strip running speed V _SO of each coil was controlled to be a constant speed as in the case of the above description of the operation. Further, since the target delivery-side plate temperature reaching time is earlier or later than the initial set time by the correction control of the strip passing speed, the actual controller, the furnace temperature setting device 13, and the strip-passing speed setting device 14 reach this target delivery-side plate temperature. Although the fluctuation of the time is constantly corrected, here, for the sake of simplicity, the description will be made on the assumption that the target outlet plate temperature arrival time t _O does not change. On the other hand, in this embodiment, unlike the explanation of the above-mentioned action, subscripts are given to the time with time in the order of control.

First, the state of passing the plate in the heating furnace will be described. Coil A passed through the heating furnace by time t ₅ ,
Coil B passes through the heating furnace until the time t ₃ ~t _8, the coil C is passed through the heating furnace until the time t ₄ ~t _10, until time t ₈ ~t ₁₁ The coil D passes through the heating furnace, and the coil E passes through the heating furnace after time t ₉ . Therefore, it is necessary to reach the set furnace temperature that achieves the target outlet plate temperature of the trailing coil until the passage end time of each coil.

The target output side plate temperature T _SOA of the coil A is the actual output side output plate temperature T _SN . Below, the target _output side plate temperature of the coil B is T _SOB , the target _output side plate temperature of the coil C is T _SOC , and the coil D.
The target outlet plate temperature of the coil E is T _SOD , and the target outlet plate temperature of the coil E is T _SOD .
_SOE , the target outlet plate temperature T _SOB of the coil B is higher than the current actual outlet plate temperature T _SN , and the target outlet plate temperature T _{SO C of the} coil C is _SOE.
Is higher than the target outlet plate temperature T _SOB , the target outlet plate temperature T _SOD of the coil D is higher than the target outlet plate temperature T _SOC , and the target outlet plate temperature T _SOE of the coil E is higher than the target outlet plate temperature T _SOD. It is set low. The upper limit outlet plate temperature of coil A is T _SUA , the lower limit outlet plate temperature is T _SLA , the upper limit outlet plate temperature of coil B is T _SUB , the lower limit outlet plate temperature is T _SLB , and the upper limit outlet plate temperature of coil C is T _SUC. , Lower limit outlet plate temperature is T _SLC , coil D
The upper limit outlet plate temperature is T _SUD , the lower limit outlet plate temperature is T _SLD , the upper limit outlet plate temperature of coil E is T _SUE , and the lower limit outlet plate temperature is T _SLE .

These target outlet plate temperatures T_SOTo achieve
Setting furnace temperature T_FOA, Upper limit outlet plate temperature T _SUUpper limit setting furnace
Temperature T_FU, Lower limit outlet plate temperature T_SLLower limit setting furnace temperature T_FLCalculate
Out of these, the lower limit setting furnace temperature T_FLEasy about
The description is deleted in order. Carp calculated in this way
Target outlet plate temperature T of Le A_SOA(T_SN) To achieve
Constant furnace temperature is T_FOA(T_SN), Upper limit outlet plate temperature T_SUAOn
Limit furnace temperature is T_FUA, Target output plate temperature T of coil B_SOBTo
The set furnace temperature to achieve is T_FOB, Upper limit outlet plate temperature T_SUB
The upper limit setting furnace temperature is_FUB, Target output plate temperature of coil C
T_SOCTo set the temperature is T_FOC, Upper exit plate
Temperature T_SUCThe upper limit setting furnace temperature is_FUC, Coil D target
Delivery side plate temperature T_SODTo set the temperature is T_FOD,Up
Limited side plate temperature T_SUDThe upper limit setting furnace temperature is_FUD, Koi
Target outgoing plate temperature T of Le E_SOEThe set furnace temperature to achieve
T_FOE, Upper limit outlet plate temperature T_SUEThe upper limit setting furnace temperature is
_FUEIs.

Here, in order to reach the set furnace temperature T _FOB which achieves the target outlet plate temperature T _SOB of the coil B at the time t ₅ , the time t ₂ must be the furnace temperature setting change timing.
Further, in order to reach the set furnace temperature T _FOC that achieves the target outlet plate temperature T _SOC of the coil C at the time t ₈ , the time t ₃ must be the furnace temperature setting change timing. Further, at time t ₁₃ , the set furnace temperature T for achieving the target outlet plate temperature T _SOE of the coil E is obtained.
_In order to reach the _FOE , the time t ₁₁ must be the furnace temperature setting change timing.

Here, in the step S7, the coil passing state in the heating furnace during the change of the furnace temperature for each trailing coil, that is, from the present time to the time when the target outlet side plate temperature is reached will be considered. Furnace YutakaNoboru Yutakachu for the coil B, ie time coil A between times t ₂ ~t _5, coil B, coil C is fed to a passage or heating furnace to the heating furnace.
Therefore, as the set furnace temperature within this time, the highest set furnace temperature T _{FOC of the} coil _C is selected. The selected set furnace temperature T _FOC is the upper limit set furnace temperature T of each passing coil.
_FUA, T _FUB, is lower than either of the T _FUC, target setting oven temperature is determined to be the set furnace temperature T _FOC. Then, in step S8, the setting of the furnace temperature is changed to the set furnace temperature T _FOC from the furnace temperature setting change timing t _{2 of the} coil B closest to the current time, and the set furnace temperature T _FOC is reached at the time t ₅ . ..

Similarly, during the temperature rise of the furnace for the coil C, that is, during the time between times t _{3 and} t ₈ , the coils B and C pass through the heating furnace or are fed into the heating furnace. However, since the furnace temperature reaches the set furnace temperature T _FOC at time t ₅ as described above, here, the set furnace temperature T _FOC is set until time t _8.
Maintained at _FOC . On the other hand, it fed the furnace YutakaNoboru Yutakachu, i.e. the time the coil C between times t ₆ ~t _10, coils D, and the coil E is passed or heating furnace to a heating furnace for coils D. Therefore, as the set furnace temperature within this time, the highest set furnace temperature _{TFOD of the} coil D is selected. The selected set furnace temperature T _FOD is lower than the upper limit set furnace temperatures T _FUC and T _FUE of the coil C and the coil E, but higher than the upper set furnace temperature T _{FUB of the} coil B. Therefore, although not described in the basic program described above, in such a case, the setting of the furnace temperature was changed from the furnace temperature setting change timing t _{6 of the} coil C closest to the current time to the set furnace temperature T _FOD. Assuming that the temperature gradient of the plate temperature, which is almost proportional to the temperature gradient of the furnace temperature, is calculated according to the above equation 1, this temperature gradient is the upper limit set furnace temperature at the exit side passage time t ₈ of the rear end temporary stage of the coil B. It is determined whether T _FUB is exceeded. In this case, the calculated assumed temperature gradient T _Fi is the upper limit set furnace temperature T at the exit side passage time t _{8.
Since the FUB} is not _exceeded , the furnace temperature setting is changed to the set furnace temperature T _FOD from the furnace temperature setting change timing t ₆ .

Further, during the temperature decrease of the furnace for the coil E, that is, during the time between the times t _{11 and} t _13, no other coil passes through the heating furnace or is fed into the heating furnace. Therefore, the set furnace temperature T _FOE of the coil E is determined as the set furnace temperature within this time, and the furnace temperature setting is changed to the set furnace temperature T _FOE with the time t ₁₁ as the furnace temperature setting change timing. Thus, the furnace temperature, between times t ₁ ~t ₂ is maintained to the current actual furnace temperature T _FN, between times t ₂ ~t ₅ rises as actual furnace temperature T _F, time t ₅ until ~t ₆ is maintained at the set furnace temperature T _FOC, time t ₆ until ~t ₁₀ is raised like a virtual furnace temperature T _Fi, between times t ₁₀ ~t ₁₁ set furnace temperature T is maintained _FOD, between times t ₁₁ ~t ₁₃ descends like a virtual furnace temperature T _Fi, it should be maintained at the set furnace temperature T _FOE from the time t _13. However, the actual actual reactor temperature T _F is the time t _{6 to} t
_The temperature rises above the virtual furnace temperature T _Fi until ₁₀ and reaches the set furnace temperature T _FOD at time t ₈ , and also rises above the virtual furnace temperature T _Fi between times t _{11 and} t _13. Oops. In accordance with this, it was expected that the output side plate temperature characteristic would change like a virtual output side plate temperature T _Si shown by a virtual line.

However, the strip passage speed setting device 14 constantly monitors the actual furnace temperature T _F, and the strip passage speed is controlled in real time in accordance with it. In other words, until the time t ₁ ~t ₂ is maintained to the current actual communication plate velocity V _SN (target passing plate velocity V _SO), modified through plate velocity between the said time t ₄ to time t ₂ ~t ₄ Accelerated to reach V _SA ,
The time t ₄ is time t ₅ as the passage speed setting change timing.
Until is decelerated so as to reach the corrected through plate velocity V _SBO at the time t _5, until time t ₅ ~t ₆ is maintained in the modified passage plate velocity V _SBO, the time t ₆ ~t ₇ Until then, the vehicle is accelerated so as to reach the corrected passing speed V _SB at the time t ₇ ,
The time t ₇ is time t ₈ as the passage speed setting change timing.
Until is decelerated so as to reach the corrected through plate velocity V _SC at the time t _8, between times t ₈ ~t ₉ is maintained in the modified passage plate velocity V _SC, passing the time t ₉ between times t ₁₀ as a plate speed setting replacement timing is decelerated to reach the target through plate velocity V _sO in the time t _10, until time t ₁₀ ~t ₁₁ to the target through plate velocity V _sO is maintained until a time t ₁₂ the time t ₁₁ as strip running speed setting replacement timing is accelerated so as to reach the corrected through plate speed V _SE at the time t _12,
Time t ₁₂ ~t until ₁₃ the time t ₁₃ target Masamichi plate velocity V
_{Slows down} to reach _SO .

By this control, the time t₂~ T_FiveUntil
Is the corrected running speed T_SOBTarget delivery side plate temperature due to change of setting
Actual delivery side plate temperature T excluding delay time_STarget outlet plate temperature T
_SOCThe surplus amount of heat is deleted at time t_Five~ T₆Until
Is the actual delivery side plate temperature T_STarget outlet plate temperature T_SOCSurplus heat
Is deleted at time t₆~ T₈Until the passing time T
_SOCExcluding the delay time for reaching the target outlet plate temperature due to the setting change of
Actual output side plate temperature T_STarget outlet plate temperature T_SODExcess heat
Deleted at time t₈~ T_TenUntil the actual delivery side plate temperature T_S
Target outlet plate temperature T_SODThe surplus amount of heat is deleted at time t
₁₁~ T₁₃Until the passing time T_SOEAccompanying the setting change of
Actual delivery side plate temperature T excluding target delivery side plate temperature arrival delay time_Sof
Target outlet plate temperature T_SODThe surplus amount of heat is deleted.

By controlling in this way, the actual result output side
Plate temperature T_SIs the target outlet plate temperature T_SOReal Thai within the tolerance of
It becomes possible to control the temperature at the output side plate temperature T_SAttached to
Remove excess energy provided, or lack energy
It is also possible to replenish. In this example,
In this way, the actual delivery side plate temperature T_SSurplus energy given to
Since I also tried to control the deletion of Gi at the same time,
Through plate speed V_SFluctuates relatively, but of course
In the case of Ming, the set furnace temperature T_FOActual furnace temperature T against_FVariation of
The sheet passing speed may be corrected and controlled to compensate for the above. This place
If the virtual furnace temperature T as shown in FIG._FiAgainst actual furnace
Temperature T_FDeviation is the physical model equation
It is gradually reduced by modifying the dynamic parameters.
The target strip speed V _SOTarget output plate temperature T_SOTo achieve
It is possible to carry out the work stably.

[0057]

As described above, according to the plate temperature control method of the continuous annealing furnace of the present invention, the outlet side plate temperature of the heating furnace is set to the target outlet side plate temperature when the plate is passed at the target stripping speed. The furnace temperature value is determined according to the model formula, the furnace temperature setting change timing is determined in consideration of the response delay time of the furnace temperature calculated from the set furnace temperature value, and the set furnace temperature value and the furnace temperature setting change timing are determined. The corrected strip running speed for detecting the actual furnace temperature as a result of control by the above, and controlling the heating furnace exit side plate temperature within a predetermined range with respect to the target exit side plate temperature when the plate is passed at the actual furnace temperature. Is determined according to the model formula, and the passage speed setting change timing is determined in consideration of the time required for the change of the outlet side plate temperature calculated from the corrected strip speed, so that the actual furnace temperature is affected by some unstable factors. Even if the set furnace temperature is not satisfied, With the actual furnace temperature, the actual outlet plate temperature can be controlled within the allowable range of the target outlet plate temperature, and the response characteristics to the setting change of the strip passing speed are extremely good. The strip speed can be corrected and controlled almost in real time, and the strip temperature can be controlled with high accuracy. Moreover, by correcting the physical parameters included in the model formula by learning control, the corrected strip running speed asymptotically approaches the target strip running speed, and the target delivery side plate temperature is obtained at the desired target strip running speed. It is possible to carry out the operations to be achieved in a stable manner.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a continuous annealing equipment in which a plate temperature control method for a continuous annealing furnace of the present invention is implemented.

2A and 2B show a basic processing program executed in the continuous annealing equipment of FIG. 1, in which FIG. 2A is a flowchart showing furnace temperature setting, and FIG. 2B is a flowchart showing plate passing speed setting.

FIG. 3 is a correlation diagram of furnace temperature characteristics-outlet plate temperature characteristics-passing speed characteristics showing an operation when the target outlet plate temperature of the trailing plate is controlled to be high by the basic processing program of FIG.

FIG. 4 is a correlation diagram of furnace temperature characteristics-outlet plate temperature characteristics-passing speed characteristics showing an operation when the target outlet plate temperature of the trailing plate is controlled to be low by the basic processing program of FIG.

FIG. 5 is a correlation diagram of furnace temperature characteristics-outlet plate temperature characteristics-passing speed characteristics showing an embodiment of the outlet plate temperature control performed by the continuous annealing equipment of FIG. 1.

[Explanation of symbols]

 1 is a strip 2 to 6 is a roll 7 is a motor 8 is a rotation speed meter 9 is a flow valve 10 is a furnace thermometer 11 is a furnace temperature control device 12 is a strip condition setting device 13 is a furnace temperature setting device 14 is a plate passing speed setting device 15 is a plate speed control device 16 is a plate thermometer 17 is a learning controller

Claims (2)

[Claims] 1. A continuous annealing furnace in which steel strips having different plate thicknesses, plate widths, or target outlet plate temperatures on the outlet side of the heating furnace are continuously passed through the heating furnace to perform continuous annealing, In the plate temperature control method of the continuous annealing furnace, which controls the outlet plate temperature of the heating furnace by controlling the set furnace temperature value and the plate passing speed of the furnace, the plate passing and the steel strip in the furnace are stably annealed. A steady-state plate passing speed is set as a target plate-passing speed, and the set furnace temperature value at which the outlet plate temperature of the heating furnace becomes the target outlet plate temperature when the plate is passed at the target plate-passing speed according to a predetermined condition, The furnace temperature setting change timing is determined in consideration of the response delay time of the furnace temperature calculated from this set furnace temperature value, and the actual furnace temperature as a result of control at this set furnace temperature value and the furnace temperature setting change timing is detected. However, when passing the plate at the actual furnace temperature, the heating furnace outlet side plate temperature is set to the target outlet side plate temperature. The corrected strip passing speed for controlling within a fixed range is determined according to a predetermined condition, and the strip running speed setting change timing is determined in consideration of the time required for the change of the outlet side plate temperature calculated from the corrected strip running speed. A plate temperature control method for a continuous annealing furnace, which is characterized in that 2. The furnace temperature set value and the corrected strip running speed are calculated according to the same predetermined model formula, and the physical parameters included in this model formula are modified by learning control. The plate temperature control method for a continuous annealing furnace according to claim 1.