JPS6027737B2 - Plate temperature control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the temperature of a metal steel strip in a continuous heating furnace or continuous cooling furnace.

Rentsugi sintering anchor furnaces for metal steel strips generally consist of a heating zone, soaking zone, and cooling zone, and are required to maintain a specific heat cycle with high precision determined by the quality of the steel strip being treated. ing.

Cooling methods in the cooling zone can be broadly divided into direct cooling methods, in which cold soot such as gas or water is brought into direct contact with the steel strip to be treated;
There is an indirect cooling method that indirectly cools the treated steel strip by passing cold soot through a flow path such as a pipe and using the light radiation heat transfer, but the direct cooling method is generally superior in terms of performance. Therefore, it is often adopted. In addition, in continuous hammering furnaces, atmospheric cooling is generally performed in a reducing atmosphere due to quality constraints, so a circulation jet cooler is often used as a cooling device. This circulation type jet cooler (hereinafter simply referred to as a jet cooler) has a heat exchanger, a circulating gas blower, and a flow path for atmospheric gas inside the furnace or a completely sealed furnace connected to the furnace through a duct. This device is equipped with a duct, and the surface of the duct facing the steel strip has holes for blowing atmospheric gas onto the steel strip, and the atmospheric gas inside the furnace is pumped into the suction side duct by a circulation blower. Once it is sucked in, its temperature drops as it passes through a heat exchanger, and it is blown onto the steel strip through the blow-off hole of the blow-off side duct, after which it is sucked into the suction-side duct again, and this process is repeated thereafter. The steel strip is cooled mainly by convection heat transfer by cold atmospheric gas blown from a jet cooler. Control of the plate temperature in the cooling zone of a continuous dawn furnace using such a jet cooler has been carried out as follows.

A jet cooler type cooling zone is usually constructed by arranging a large number of jet coolers in series in the steel strip threading direction. Figure 1 shows an outline of a typical vertical Rentsugi-yaki Kushiro cooling zone as an example. In the figure, 1 is a furnace section in front of a cooling zone 2, which is generally referred to as a soaking zone. The steel strip 4 that has passed through the soaking zone 1 is guided to the cooling zone 2, passes through each strip passage made by a plurality of hearth rolls 3, and exits the furnace. A large number of jet coolers 5 are arranged in each strip passageway of the cooling zone 2 in series along the strip passing direction.
The steel strip 4 is cooled while passing through these 5 groups of jet coolers. Generally, as a method for controlling the plate temperature in the cooling zone 2, initial settings (hereinafter referred to as presets) are used to predict the furnace operation setting values required to cool the steel strip 4 to a target temperature and set them in the process.

), control that dynamically corrects the furnace operating set value to compensate for disturbances that can be detected in advance, such as fluctuations in plate threading speed and inlet plate temperature (hereinafter referred to as feedforward control), and There is control (hereinafter referred to as feedback control) that detects the value and dynamically corrects the furnace operating set value based on the deviation from the target value. Jakurai's preset sequentially allocates the required cooling capacity calculated from material information, target thermal cycle, and sheet threading speed to five groups of jet coolers from the furnace inlet or furnace outlet side. An example of the preset pattern obtained in this way is shown in A of FIG.

The figure shows a cooling zone 2 consisting of a total of 15 jet coolers 5, which are numbered 1 to 15 in order from the jet coolers 5 on the furnace outlet side. The preset pattern shown in this example is an example in which it is predicted that the required capacity will be obtained in 8 out of 15 units, and that capacity is allocated from the jet cooler 1 on the furnace outlet side. is running (on)
It is ra 5. In order to perform feed forward control and feedback control especially in the direction of increasing the cooling function with the jet cooler 5 groups preset in the pattern shown in A in Fig. 2, it is necessary to set the Now, we have no choice but to move No. 8) forward.

In other words, since jet coolers 5 1 to 8 are in a 100% operating state, the cooling capacity of this group of jet coolers 5 can be decreased but cannot be increased, so in order to increase the cooling capacity, 9 , 10, etc., it is necessary to sequentially turn on the jet cooler 5 on the furnace inlet side. B' in FIG. 2 shows an example of the operating pattern of the jet cooler 5 changed by feedforward control or feedback control to enhance the cooling capacity. When such a sheet temperature control method is used, although it is said that control is performed dynamically in addition to presets, the response characteristics of the sheet temperature due to disturbances and the response characteristics due to control operations are not taken into account. First, the operating end is a jet cooler 5 which is determined by the preset pattern.
Because it is fixed around the leading position of the group (No. 8 in this example), it may take a very long time for the plate temperature at the furnace outlet to settle to the target value, and in some cases it may become uncontrollable (plate temperature). Warm hunting) may also occur.

The response characteristics of the plate temperature due to control operations or the response characteristics of the plate temperature due to disturbances are determined by the structure of the furnace or the structure of the heating or cooling device. We investigated the plate temperature response characteristics and found that it is impossible to accurately control plate overflow using conventional plate temperature control methods. A part of the investigated response characteristics is schematically shown in Figure 3. A, B and D in Figure 3
shows the operation pattern of the continuous Akatsuki Furnace cooling zone 2, each of which has a total of 30 jet coolers 5. The shaded area indicates the jet cooler 5 operating at 100% capacity, and the non-shaded area shows the jet cooler 5 which is stopped (off). C and E in FIG. 3 show changes in furnace outlet plate temperature over time.

C in the same figure shows a sudden change in the pattern of the jet cooler 5 to A in the same figure at time tl from a state in which the inlet plate temperature and sheet threading speed are kept constant and the jet cooler 5 is operated in the pattern A in the figure. It shows the transient response characteristics of the outlet plate overflow when the outlet plate temperature pattern is changed, and it does not change until time t2 after the outlet plate temperature pattern is changed, and after time t2, it starts to gradually decrease and reaches about 15 to
It stabilizes at time 0 after 20 minutes. From time tl to t2
The time required for this process corresponds to the time taken to transport the steel strip from the jet cooler 25 to the furnace outlet. In Fig. 3, E shows that the furnace inlet plate temperature and plate passing speed are kept constant, and the jet cooler 5
is being operated in pattern B in the same figure, at time t
Figure 1 shows the transient response characteristics of the outlet overflow when only the pattern of the jet cooler 5 is suddenly changed to D in the same figure.
It becomes stable after the sand is deposited. In other words, the response time of the plate temperature to a change in the operating pattern of the jet cooler 5 varies depending on the position of the jet cooler 5 to be changed, and the response time is longer for a change in the operating state of the jet cooler 5 on the furnace inlet side. short for changes. Although FIG. 3 illustrates a method of increasing the cooling capacity of the jet cooler 5, similar characteristics are obtained in the direction of decreasing capacity.
G in Figure 3 shows the operating pattern of the jet cooler 5 and A in the same figure, and the response characteristics of the furnace outlet plate temperature when the furnace inlet plate temperature is kept constant and the sheet passing speed is abruptly changed in steps. It is shown over time, and F in FIG. 3 shows the sheet passing speed V at that time, with the time axis matching G in the same figure.

That is, at time tll, the plate passing speed V rapidly decreases from VI to V2, and the furnace outlet plate temperature gradually rises and becomes stable at time t2, approximately 15 to 20 minutes later. In this example, the case where the sheet passing speed is decreased is shown as an example, but similar sheet temperature response characteristics are obtained also when the sheet passing speed is increased in the opposite direction. In addition, the response time of the furnace outlet plate temperature to changes in the sheet passing speed varies depending on the tip position of the operating jet cooler group.When the jet cooler 5 on the furnace inlet side is on, it takes a long time, and when it is off, the plate temperature changes in a short time. becomes stable. The plate temperature response characteristics obtained through these experiments can be explained by considering the heat transfer between the steel strip 4 and the hearth roll 3.

A in Figure 4 is the plate temperature Ts just before contacting the hearth roll 3.
In i, B in the same figure is the heat quantity QR possessed by the hearth roll, and C in the same figure is the plate temperature Ts immediately after contact with the hearth roll. The figure shows changes over time with the time axes matching. Before time tl, the steel strip 4 and the hearth roll 3 are in a thermal equilibrium state, and the sheet temperature Tsi before and after contact with the hearth roll, and the heat possessed by T carp roll QR.
are Tsi・, Ts, respectively.

,,QR, remains constant. Here, at time tl, the plate temperature Tsi just before the hearth roll touches the jet cooler 5
Tsi. If there is a sudden change from Tsi2 to Tsi2, steel strip 4 and hearth roll 3
When the thermal equilibrium relationship between the steel strips breaks down and the plate temperature decreases as shown in this example, the amount of heat moves from the hearth roll 3 to the steel strip 4, and a new equilibrium state is attempted. Since the heat transfer rate inside the hearth roll or the heat transfer rate between the hearth roll 3 and the steel strip 4 is finite, it takes time to transition between equilibrium states, and the heat retained by the hearth roll QR and the plate after contact with the hearth roll are finite. The temperature T changes over time P,
At time t21, the equilibrium state is again reached and stabilized. Fig. 4 focuses on one hearth roll 3 to explain the response delay in plate temperature before and after contact with the hearth roll, but an actual Renzuki refining furnace is generally configured with multiple passes, and the steel strip 4 is processed through a large number of hearth rolls 3. Therefore, the phenomenon shown in this figure occurs in each hearth roll 3, and the change in plate temperature at the furnace outlet in response to a change in plate temperature at a certain point in the furnace due to changes in the pattern of the jet cooler 5, line speed changes, etc. The response appears as multiple delays, and the response delay time is determined by the number of hearth rolls 3 existing between the point where the plate temperature change occurs and the furnace exit. Strictly speaking, when changing the strip threading speed, all the hearth rolls 3 in the furnace are involved in the response delay, but since the cooling of the steel strip 4 by the off jet cooler is slight, in reality, the on jet cooler 5 It is safe to assume that the response delay time is determined by the number of hearth rolls from the beginning of the group to the furnace exit. Such an overflow response characteristic appears conspicuously in a furnace where the contact area and contact pressure between the hearth roll 3 and the steel strip 4 are larger and the number of hearth rolls is large, and generally in a horizontal furnace.
Considering the controllability of plate overflow when the conventional plate stripe control method is adopted based on the transient response characteristics of the plate temperature at the furnace outlet when various conditions change as described above, the preset pattern shown in Fig. 2 A is If the line speed or furnace inlet plate temperature is detected from , and feedforward control is performed in pattern B in the same figure, the desired control can be performed, but if the line speed or furnace inlet plate temperature is detected from When feedback control is performed from A to B, the response delay time of plate temperature due to pattern change is long (
According to actual furnace data, it can take as long as 15 to 20 minutes.

), during that time, the plate temperature will be off due to insufficient cooling. Furthermore, if the feedback control cycle is shorter than the plate temperature response delay time, there is a possibility that the control will become a divergence condition, so the control cycle must be selected to be extremely long from a safety standpoint, and accurate feedback control must be performed. That is impossible. In order to solve the above-mentioned drawbacks, the present invention has developed a continuous heating furnace or a continuous cooling furnace that is divided into a plurality of zones along the threading direction of the metal steel strip, and each zone is provided with a heating device or a cooling device. In plate temperature control, one or more zones on the furnace outlet side are used as feedback control zones, and the zone is set to have a heating or cooling capacity close to 50% of the full capacity at the time of presetting, and detects the furnace outlet plate temperature. Deviations from the target value are controlled by changing the capacity of the zone with quick control response.
On the other hand, one or more zones on the furnace inlet side other than the zones mentioned above are designated as feedforward control zones, and when presetting, priority is given to the capacity necessary to exert the specified heating or cooling capacity from the furnace outlet side within the zone. The preset pattern is corrected by changing the position of the frontmost part of the on-zone group in the zone in response to plate temperature disturbances that can be predicted in advance, such as the plate threading speed or the plate temperature at the furnace entrance. Perform control.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 5 shows the configuration of a device in which the present invention is applied to the cooling zone of a Renzuki hammer furnace, and the same parts as in FIG. 1 are given the same reference numerals. Figure 6 shows the number of jet coolers 5 in cooling zone 2.
30'', each cooling capacity is shown in air volume (%), and zone numbers (jet cooler numbers in this example) 1, 2, 3, etc. are assigned sequentially from the rear side of the furnace. In the preset pattern, that is, the initial air volume setting, as shown in A in Fig. 6, a predetermined number of jet coolers (10 in this example) on the furnace outlet side are set as a feedback control zone, and this zone is set so that all jet coolers are turned off in any case. It is preferable to set the air volume to 50% of that capacity. Each jet cooler (in this example 11~
13 of 20 machines). The air volume WFF (%) distributed to the feed forward control zone is expressed by the following equation, where n (units) is the number of jet coolers in the feedback control zone and Wo (%) is the overall air volume required to obtain a predetermined cooling capacity. WFF (%) = W.

(%)-nx50(%).・---[1} A in Figure 6
In this example, the number of jet coolers in the feedback control zone is 10 (units) and the required overall air volume Wo is 2030 (%). Therefore, the air volume in the feed forward control zone is WFF = 2030 - 10 x 50 = 1530 (%). ).

Each jet cooler in the feed forward control zone is set to have an air volume of 100% preferentially from the furnace outlet side. 1
The number m of jet coolers with 00% air volume setting can be determined using the following formula. WFF (%) / 100 (%) = m (units)
Remainder Q (%) ・・・・・・
・[21 In this example, the air volume WFF in the feedforward control zone is 1530 (%), so m = 15 (units),
Q = 30 (%), therefore, in the feedforward control zone, the 15 jet coolers (11 to 25) from the furnace outlet side have 100% airflow, and the remaining airflow is 30%.
% is placed further in front of the jet cooler 26.

The optimal number of feedback control zones is selected based on the amount of plate temperature variation due to unpredictable causes (for example, variations in actual plate thickness relative to the nominal original plate thickness) on the target line and the cooling capacity of each jet cooler. There is no need to limit the number to 10 as illustrated in FIG. Further, the initial air volume of the jet cooler in the feedback control zone does not necessarily have to be 50%, and can be changed depending on the characteristics of the object to be controlled. For example, if the deviation limit for the outlet plate temperature of cooling zone 2 is stricter on the higher side and more gentle on the lower side, it is preferable that the plate temperature deviation correction speed is increased in the direction of increasing the air volume. It is also possible to set the initial air volume setting of the feedback control zone to 40%. The initial air volume calculation device 14 in FIG. 5 calculates the outlet plate temperature T of the cooling zone 2 based on the initial air volume setting condition S.
The overall air volume W required to bring o to the target plate temperature Ts.

(2030% in this example) is calculated. Initial air volume setting condition S is the inlet plate temperature Ti of cooling zone 2, outlet target plate temperature Ts, strip threading speed V, and other factors necessary to determine the cooling air volume in the case of cooling zone 2 in a continuous phosphorescent furnace. This is a condition.
Overall air volume W. is determined, this W. is input to the air volume pattern setting device 15. This setting device 15 calculates the m formula and the ■ formula, determines the air volume of each jet cooler, and determines the jet cooler rotational speed reference value J,, J2, . . . for each jet cooler.
. . . jet cooler rotational speed control device 16,
, 162, and so on. The steel strip position tracking device 11 is used to determine the output timing. This tracking device I1 tracks the position of the steel strip 4 by counting pulses from a pulse oscillator 18 attached to a roll 17 for conveying the steel strip. When changing the air volume setting pattern to a new initial air volume setting pattern, changes such as the thickness of the steel strip 4 are tracked by the steel strip position tracking device 11, and the changed points pass through each jet cooler 5. Each jet cooler rotation speed standard J,, J2, etc. determined by a new air volume pattern is outputted each time, and when the changed point has passed through cooling zone 2, the initial air volume pattern is set. be completed. By using the above method, it is possible to suppress transient plate temperature fluctuations during presetting as much as possible. In the feedback control, the outlet plate temperature To detected by the outlet plate thermometer 7 of the cooling zone 2 is compared with the target plate temperature TS by the feedback plate temperature control device 10, and the deviation is converted into the air volume change amount WB to be canceled and the air volume is adjusted. This is done by inputting it to the pattern setting device 15.

The air volume pattern setting device 15 converts the air volume change amount WB into the jet cooler rotation speed, and calculates only the change as the jet cooler rotation speed reference value J,, J2, etc. in the feedback control zone at that time. Change and output. In feedback control, the shorter the delay time from changing the manipulated variable (in this case, the jet cooler rotational speed) until the result of the operation (in this case, the outlet plate temperature T) appears, the faster the control will respond. Because it is performed with high precision,
Changes in the manipulated variable through feedback control are performed as far as possible from the jet cooler 5 on the furnace outlet side. B in Figure 6 is 2
The overall air volume W is obtained by subtracting 120% of the air volume from the initial overall air volume setting of 0.030%.

This shows an example in which feedback control is performed so that the ratio becomes 1910%, and three jet coolers 5, that is, 1 to 3 jet coolers 5, are adjusted from the furnace outlet side. That is, the air volume of jet coolers 5 1 and 2 is reduced from 50% to 0%, and the air volume of jet cooler 3 is reduced from 50% to 30%, so that the overall air volume is reduced by 120% by this feedback control. There is. Even when the amount of change in air volume is in the increasing direction, the jet cooler 5 on the furnace outlet side is operated in the same manner. In the present invention, a feedback control zone is provided on the furnace outlet side,
Furthermore, since the initial air volume pattern is set so that the air volume setting of the zone is close to 50%, high-speed response in control operations can be obtained, and both directions of increase and decrease can be performed from the furnace outlet side. As a result, the delay in plate temperature control of the steel strip 4 can be kept to a minimum.

On the other hand, feedforward control is a method of controlling the outlet plate temperature of the cooling zone 2, which occurs due to fluctuations in the Ti detected by the inlet plate temperature meter 6 of the cooling zone 2 and the plate passing speed V detected by the line speed detector 13. In order to suppress the fluctuation, the inlet plate temperature Ti and the plate threading speed V are input into the feed forward plate temperature control device 8, and the fluctuation occurs due to the deviation from the inlet plate temperature Ti and the plate threading speed V at the time of initial air volume calculation. Exit plate temperature T.

This is done by calculating the air volume change amount WB that should eliminate the fluctuation in air volume and inputting it to the air volume pattern setting device 15. Here, the air volume change amount WB is converted to the jet cooler rotation speed, and only the change is calculated as the jet cooler speed reference J, . ,,2...・
Change and output. By setting the output timing to be the point at which the air volume change point on the steel strip passes through the jet cooler 5 where the air volume needs to be changed, fluctuations in the outlet plate temperature To can be minimized. The amount of operation is changed by feedforward control by shifting the leading position of the group of operating jet coolers 5 in the zone back and forth. 203 of A in Figure 6
Increase the air volume to 320% from the initial overall air volume setting pattern of 0%.
Increase the total air volume W. A feed forward control pattern in the case of 2350% is illustrated in C of the same figure. In this example, the air volume of the jet cooler 26 is from 30% to 100%.
The air volume of jet coolers 27 and 28 is 0% each.
By increasing the air volume of the jet cooler 29 from 0 to 100% and from 0 to 50%, the overall air volume is increased by 320% due to this feedforward control. The broken line a in D in Fig. 6 indicates the case where the sheet passing speed V increases in a stepwise manner at time tl with the jet cooler 5 set in the pattern shown in Fig. 6 A, and no compensation is performed despite this. It shows the change over time in the overflow To at the furnace outlet, and the dash-dotted line b in the figure D represents the furnace outlet plate temperature T when the jet cooler pattern suddenly changes from A to C in the figure with a constant sheet passing speed.
It shows the change over time. If the feedforward control of the present invention is performed here, the outlet plate temperature T is indicated by the broken line a in D in FIG. Fluctuations in the furnace exit plate temperature T are compensated for by the operational influence shown by the solid line b in Figure D. is maintained at the target overflow Ts as shown by the solid line c in FIG.
Even when the air flow rate changes in the negative direction, it is preferable to similarly perform this by shifting the leading position of the 5 groups of jet coolers that are turned on toward the furnace exit. In the present invention, a feedforward control zone is provided on the furnace inlet side, and it is possible to compensate for the plate temperature with the same response time to the plate overflow change response characteristic due to disturbance, and its operation can be performed by increasing or decreasing the air volume. Since it is controllable in both directions, it is possible to minimize the temperature deviation of the outlet plate caused by external disturbances.

In the above embodiment, the blower motor of each jet cooler 5 is driven by a DC or AC variable remote motor, and the air volume can be continuously adjusted. When using a jet cooler 5 that cannot continuously adjust the air volume, that is, can only be controlled to be on (100%) or off (0%), the method shown in FIG. 7 is used. Figure 7 shows a cooling zone 2 having a total of 30 jet coolers 5, with 20 jet coolers on the furnace inlet side serving as a feedforward control zone and 10 jet coolers on the furnace outlet side.
This is an example of control when the stand is configured as a feedback control zone. A in the same figure has a total required cooling air volume of 200
This is an example of the initial air volume setting pattern in the case of 0%, but by setting every other jet cooler 5 in the feedback control zone on or off, it is possible to adjust the air volume in both directions during feedback control. is possible. Figure B shows an example of a feedback control pattern when the settings of jet coolers 5 2 and 4 are changed from off to on, and the air volume is increased by 200%. C in the same figure is an example of a feed forward control pattern when the setting of jet coolers 5 24 and 25 is changed from on to off to reduce the air volume by 200%. In addition, in the same manner, both the increasing and decreasing directions of the air volume are possible in both feedback control and feed forward control. However, when using a jet cooler 5 that can only perform on-off control, the maximum unit of control operation is 100% air volume, so the plate temperature control accuracy should also be higher than the plate temperature influence cost equivalent to 100% air volume. I can't. The embodiments so far have been explained by showing examples in which there is sufficient processing capacity, but FIG. Illustrated.

A in the figure is the cooling zone 2 which has a total of 30 jet coolers 5, and the feedback control zone is 10 on the furnace outlet side.
Overall air volume W when used as a stand. This is the initial air volume setting pattern when 2660% is requested. Under such conditions, if a normal initial air volume setting pattern is used, the overall air volume W will be reduced even if all jet coolers 5 in the feed forward control zone are set to 100%. is 160% short. In such a case, in order to ensure cooling capacity, the insufficient air volume must be allocated to the jet cooler 5 in the feedback control zone. Then 10,9...)
It is preferable to allocate them in order. B in the same figure shows a control pattern when the air volume is reduced by 100% as a feedback control for the initial air volume setting pattern of A, and C in the same figure shows a control pattern when the air volume is reduced by 200% as a feed forward control for the initial air volume setting pattern in A. shows the control pattern. As mentioned above, in plate temperature control in a continuous heating furnace or continuous cooling furnace for metal steel strip, the furnace is divided into two zones, and the heating capacity or cooling capacity in the zone on the furnace exit side is initially set to around 50%. On the other hand, in the zone on the furnace inlet side, the heating capacity or cooling capacity is initially set in a pattern that is distributed from the furnace outlet side, and feedforward control is performed. The deviation from the target value is very large.
This makes it possible to control the plate temperature with high precision.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing a part of a continuous dawn furnace, A and B in Fig. 2 are explanatory diagrams showing an example of a cooling capacity setting pattern according to a conventional plate temperature control method, and A in Fig. 3. ~G is an explanatory diagram showing the transient response characteristics of the plate temperature at the furnace exit when changing the jet cooler pattern or changing the threading speed in the cooling zone of the Rentsugi sintered anchor furnace, and A to C in Figure 4 show the response delay of the plate temperature. FIG. 5 is a revised diagram showing a part of a continuous phosphor annealing furnace to which the present invention is applied, and A to D in FIG. 6 are examples of cooling patterns according to the plate temperature control method of the present invention. , A to C in FIG. 7 are explanatory diagrams showing other different examples using the plate temperature control method of the present invention, and A to C in FIG. 8 are explanatory diagrams showing the plate temperature control method of the present invention. FIG. 2 is an explanatory diagram showing an example of a pattern setting method in a special case. 2: Cooling zone, 3: Hearth roll, 4: Steel strip, 5: Circulating jet cooler, 6: Furnace inlet plate thermometer, 7: Furnace outlet plate thermometer, 8: Feedforward plate temperature control device, 10: Feedback plate temperature control device, 11: Steel strip position tracking device, 13
: Threading speed detector, 14: Initial air volume calculation device, 15: Air volume pattern setting device, 16, to 16■: Jet cooler rotation speed control device, 18: Pulse oscillator. Figure 1 Figure 2 Figure 3 Figure 3 Younger brother Figure 5 Figure 6 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1 A continuous heating furnace or continuous cooling furnace for metal steel strips is divided into multiple zones along the threading direction of the metal steel strip, and each zone is equipped with a heating device or cooling device that can be turned on and off independently or continuously adjusted. In the continuous furnace plate temperature control method,
The furnace is divided into zones on the furnace outlet side and furnace inlet side from the viewpoint of control functions, and the zone on the furnace outlet side is initially set to an intermediate capacity of the total capacity at the time of presetting the heating and cooling capacities of the individual heating and cooling devices. The zone on the furnace inlet side together with the zone on the furnace outlet side provides a predetermined heating and cooling capacity for the entire furnace, and the heating or cooling capacity is initially set at the back, and the detected value of the plate temperature at the furnace outlet is set. Based on this information, the heating or cooling capacity of the furnace outlet side zone is controlled, and disturbances to the furnace outlet plate temperature, such as plate passing speed fluctuations and furnace inlet plate temperature fluctuations, are detected, and based on this detected fluctuation information, the heating or cooling capacity of the furnace outlet side zone is controlled. A plate temperature control method characterized by keeping the furnace outlet plate temperature constant by controlling the heating or cooling capacity of the furnace.