JPH05179366A - Plate temperature control method for heating zone of continuous annealing furnace - Google Patents

Abstract

PURPOSE:To suppress the fluctuation of the plate temperature due to changes in the line speed by equivalently increasing the responsiveness of the furnace temperature while the line speed is increased/reduced. CONSTITUTION:At the time t1 when the line speed of a continuous annealing furnace is reduced, the decelerating mode is turned on, and the line speed is reduced stepwise. In this decelerating mode, the furnace temperature set value where the plate temperature is set lower than the target plate temperature by the specified value is operated according to the line speed value detected with the specified period, and the set value is changed. At the time t3 when the line speed is accelerated, the accelerating mode is turned on, and the line speed is increased stepwise. In this accelerating mode, the furnace temperature set value where the plate temperature is set higher than the target plate temperature by the specified value is operated according to the line speed value detected in the specified period, and the set value is changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous annealing furnace heating zone plate temperature control method suitable for controlling the heating zone plate temperature during line speed acceleration / deceleration of a continuous annealing furnace.

[0002]

2. Description of the Related Art A continuous annealing furnace is a facility for welding the rear end of a thin plate coil after cold rolling and the front end of a next coil and continuously heating and cooling the strip. That is, as shown in FIG. 3, the continuous annealing furnace includes a heating zone 2, a soaking zone 3,
It is composed of a first cooling zone (primary cooling zone) 4, a second cooling zone (secondary cooling zone) 5, and a third cooling zone (tertiary cooling zone) 6, and each zone has a heat cycle as shown in FIG. make it happen.

FIG. 5 is a schematic configuration diagram of the heating zone 2 among them. In the heating zone 2, a plurality of rows of radiant tubes 11 are provided in parallel in the furnace, and fuel gas is burned and heated in the radiant tubes 11. That is, the strips 13 passing vertically between the rows of the radiant tubes 11 are heated by radiant heat while changing the direction of the rolls 12.

The conventional plate temperature control in the heating zone 2 is indirectly carried out by adjusting the fuel flow rate so that the furnace atmosphere temperature (furnace temperature) becomes a predetermined value. That is, in FIG. 5, a furnace temperature detector 14, a furnace temperature controller 15, and a fuel flow rate controller 16 are provided, and by these, the furnace temperature control systems A, B ... For each of a plurality of zones along the longitudinal direction are provided. I am configuring. Although not shown, the fuel flow rate for each zone is controlled by operating the control valve by the fuel flow rate controller 16 for each zone so that the fuel flow rate detected by the fuel flow rate detector becomes a predetermined value. .. Further, the operator corrects the set value of the furnace temperature so that the detected value of the plate temperature by the plate temperature detector 22 becomes equal to the target value.

Recently, the number of facilities for calculating the furnace temperature set value by a computer is increasing. In this type of equipment, a computer calculates the set value of the furnace temperature control system in the zone according to the line speed, the plate thickness, the target plate temperature, etc. and sets it in the furnace temperature control system.

Usually, the line speed is changed by the operator in accordance with the plate thickness, the target plate temperature, etc., aiming at the maximum production amount (corresponding to the maximum value of the furnace temperature). Further, for example, when the plate thickness is thin and the heating capacity is maintained, the line speed is set to the maximum value on the equipment. Although not shown in FIG. 3, a welding machine that connects the tail end of the preceding material and the leading end of the following material, an entrance looper that secures welding time, and the like are installed on the entrance side of the line. Similarly, on the delivery side, there are a cutting machine, a delivery looper that secures the time, a temper rolling mill (skin pass mill), and the like. However, the line speed is also changed due to factors other than the above, due to malfunctions of the equipment on the input and output sides and the roll change of the skin pass mill. In this case, the change of the line speed is deceleration, but after the trouble is solved, the acceleration for recovery is always involved.

As a method for controlling the plate temperature by a computer when the line speed changes, for example, Japanese Patent Publication No. 59-52935.
The following proposals are made in the issue. That is, as shown in FIG. 2, the line speed detector 9 detects the line speed at a constant cycle, and the furnace temperature set value that statically satisfies the target plate temperature is calculated by the computer 10 according to the line speed. Temperature controller 15
Is set and output.

[0008]

In the continuous annealing furnace, the responsiveness of the furnace temperature is worse than the passage time of the heating zone (about 2 minutes), and in terms of step response, the furnace temperature rises to the set value. It takes about 10 minutes.

Therefore, in the conventional plate temperature control method in which the furnace temperature set value corresponding to the line speed is calculated and the setting is changed as described above, the furnace temperature is lower than the set value during deceleration, as shown in FIG. The present inventor has come to recognize that it becomes higher and becomes over-annealed, and becomes lower and becomes unannealed at the time of acceleration. These over-annealing and non-annealing are problems in terms of materials, and especially non-annealing is a problem.

The present invention has been made in view of the above circumstances, and an object thereof is to equivalently increase the responsiveness of the furnace temperature at the time of acceleration / deceleration of the line speed, thereby suppressing the plate temperature fluctuation due to the change of the line speed and stabilizing it. It is an object of the present invention to provide a plate temperature control method for a heating zone of a continuous annealing furnace capable of performing an annealing operation to obtain the desired quality.

[0011]

According to the present invention, when accelerating the line speed of a continuous annealing furnace, the furnace temperature becomes higher than a target plate temperature by a predetermined value according to the changing line speed detected at a constant cycle. The "acceleration mode" that calculates the set value and sets it in the furnace temperature control system, and when decelerating the line speed, calculates the furnace temperature set value that is lower than the target plate temperature by a predetermined value according to the changing line speed. It is characterized in that the plate temperature of the continuous annealing furnace heating zone is controlled by two kinds of operation modes of "deceleration mode" set in the furnace temperature control system.

[0012]

In the above structure, at least when the line speed of the continuous annealing furnace is accelerated or decelerated, the line speed is detected at a constant cycle. The "acceleration mode" is applied when the line speed is accelerated, and the "deceleration mode" is applied when the line speed is decelerated.

The operator turns on the "acceleration mode" or "deceleration mode" before accelerating or decelerating, and turns it off when the acceleration or deceleration is completed and the line speed is fixed.

When the "acceleration mode" is turned on, the furnace temperature set value is calculated according to the line speed detected at a constant cycle. In the "acceleration mode", a furnace temperature set value that is higher than the target plate temperature by a predetermined value is obtained and the setting is changed.

Further, even when the "deceleration mode" is turned on, the furnace temperature set value is calculated according to the line speed detected at regular intervals. In the "deceleration mode", contrary to the "acceleration mode", a furnace temperature set value that is lower than the target plate temperature by a predetermined value is obtained and the setting is changed.

As described above, in the acceleration mode, the set value of the furnace temperature becomes higher than the value corresponding to the line speed, so that the rising rate of the furnace temperature becomes faster than the conventional one. Further, in the deceleration mode, on the contrary, the value becomes lower than the value corresponding to the line speed, so that the falling rate of the furnace temperature becomes faster than the conventional one. Therefore, equivalently, it corresponds to a temporary improvement in the responsiveness of the furnace temperature,
It is possible to suppress the plate temperature fluctuation due to the line speed change.

[0017]

FIG. 1 is a diagram showing an embodiment of a plate temperature control method for a continuous annealing furnace heating zone according to the present invention. The control method shown in FIG. 1 is applied to the plate temperature control system of the continuous annealing furnace heating zone shown in FIG.

First, in this embodiment, two kinds of operation modes, that is, "acceleration mode" and "deceleration mode" are introduced.
The “acceleration mode” is a line speed detection value (V) detected by the line speed detector 9 at a constant cycle using the static characteristic model formula f of the following formula (1) when accelerating the line speed of the continuous annealing furnace. In accordance with the above, the furnace temperature set value (Tzset) is calculated by the computer 10 and set and output to the furnace temperature controller 15. In the “deceleration mode”, when decelerating the line speed, the static temperature model value f (Equation 2) is used to calculate the furnace temperature set value Tzset according to the detected line speed value (V) by the computer 10. And outputs it to the furnace temperature controller 15. Tzset = f (V, Tss + ΔTs, T, etc) (1) Tzset = f (V, Tss-ΔTs, T, etc) (2) where Tzset: furnace temperature set value (° C) Tss: target Plate temperature (° C) V: Line speed detection value (mpm) T: Plate thickness (mm) ΔTs: Plate temperature added amount (° C) (about 10 ° C) Conventionally, the following formula (3) was used. .. Tzset = f (V, Tss, T, etc) (3)

As is clear from a comparison of the above equations (1), (2) and equation (3), in this embodiment, the plate temperature is replaced with the conventional target plate temperature Tss at the time of acceleration of the line speed. Addition amount Δ
Tss + ΔTs to which Ts (predetermined temperature value) is added is used, and at the time of deceleration of the line speed, the plate temperature addition amount ΔTs (predetermined temperature value) is subtracted in place of the conventional target plate temperature Tss.
ss-ΔTs is used.

The operator turns ON the "acceleration mode" or "deceleration mode" before accelerating or decelerating the line speed of the continuous annealing furnace, and turns it OFF when the acceleration or deceleration is completed and the line speed is fixed. .. If these can be set from the CRT screen for driving, the operator can quickly respond.

In this case, since the line speed was forced to be lowered in order to secure the time for changing the roll of the skin pass mill, the operator turned on the "deceleration mode" at the time of t1 in FIG. 1 and stepped the line speed. It has been lowered.

In this "deceleration mode", the static velocity of the above equation (2) is determined according to the line velocity detection value (hereinafter simply referred to as "line velocity value") V detected by the line velocity detector 9 in FIG. Using the characteristic model formula f, the furnace temperature set value Tzset which is lower than the target plate temperature Tss by a predetermined value (plate temperature addition amount) ΔTs is calculated by the computer 10 and set and output to the furnace temperature controller 15. As a result, as shown in FIG. 1, the amount of change in the “lowering” of the furnace temperature becomes larger than in the conventional case, so that the temporary rise in plate temperature is small.

As described above, in this embodiment, since the computer 10 lowers the furnace temperature set value from the static set value (shown by the alternate long and short dash line in FIG. 1) by the equation (2) according to the decrease in the line speed, the furnace The rate of temperature drop is faster than before. That is, in the present embodiment, overannealing can be prevented by compensating for the increase in plate temperature due to the deceleration of the line speed. Now, when the deceleration of the line speed is completed and the line speed is fixed, for example, at time t2 in FIG. 1, the operator turns off the “deceleration mode”. Next, at the time of t3 in FIG. 1, when the roll changing work is completed and the line speed is restored, the operator is in the “acceleration mode”.
Turn ON to increase the line speed step by step.

In this "acceleration mode", the line speed value V detected by the line speed detector 9 of FIG.
According to the above, using the static characteristic model equation f of the above equation (1), the computer 10 calculates the furnace temperature set value Tzset which becomes higher than the target plate temperature Tss by a predetermined value (plate temperature addition amount) ΔTs, and the furnace temperature set value Tzset is calculated. The setting is output to the controller 15. As a result, as shown in FIG. 1, the amount of change in the furnace temperature "raising" is larger than in the conventional case, and therefore the temporary plate temperature drop is small.

As described above, in this embodiment, the computer 10 raises the furnace temperature set value from the static set value (shown by the chain double-dashed line in FIG. 1) according to the above equation (1) in accordance with the increase in the line speed. The furnace temperature rises faster than before. That is, in this embodiment, the unannealing can be prevented by compensating the plate temperature drop due to the acceleration of the line speed. Now, when the line speed is completed at t4 in FIG. 1, the operator is in the "deceleration mode".
Turn off.

[0026]

As described above in detail, according to the present invention, when accelerating the line speed of the continuous annealing furnace, the line temperature detected in a constant cycle is kept higher than the target plate temperature by a predetermined value. When setting the furnace temperature control value and setting it in the furnace temperature control system and decelerating the line speed, the furnace temperature set value that is lower than the target plate temperature by a predetermined value is calculated according to the line speed. By setting the temperature control system, the responsiveness of the furnace temperature during line speed acceleration / deceleration was increased equivalently, so the plate temperature fluctuation during line speed acceleration / deceleration should be made much smaller than before. Therefore, it is possible to perform the annealing operation that obtains stable quality without causing the yield deterioration as in the conventional case.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a plate temperature control method for a heating zone of a continuous annealing furnace of the present invention.

FIG. 2 is a configuration diagram showing an embodiment of a plate temperature control system for a heating zone of a continuous annealing furnace to which the present invention is applied.

FIG. 3 is a diagram showing an overall configuration of a conventional continuous annealing furnace.

FIG. 4 is a diagram showing an example of a heat cycle in the configuration of FIG.

FIG. 5 is a diagram showing a configuration of a plate temperature control system of a conventional continuous annealing furnace heating zone.

FIG. 6 is a diagram for explaining a plate temperature control method for a conventional continuous annealing furnace heating zone.

[Explanation of symbols]

2 ... Heating zone, 9 ... Line speed detector, 10 ... Calculator, 1
3 ... strip, 15 ... furnace temperature controller, 16 ... fuel flow controller, 22 ... plate temperature detector.

Claims (1)

[Claims] 1. A method of controlling a plate temperature by calculating and setting a furnace temperature control system set value of a continuous annealing furnace heating zone by a computer, wherein a line speed which is changing when the line speed of the continuous annealing furnace is accelerated. Is detected in a fixed cycle, and according to the detected line speed, a furnace temperature set value that is higher than the target plate temperature by a predetermined value is calculated and set in the furnace temperature control system, and when decelerating the line speed, , The changing line speed is detected at a constant cycle, and according to the detected line speed, a furnace temperature set value that is lower than the target plate temperature by a predetermined value is calculated and set in the furnace temperature control system. Method for controlling plate temperature of continuous annealing furnace heating zone.