JPH0465887B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is aimed at controlling the material temperature so as to satisfy the heat treatment conditions of the treated material when heat treating a treated material such as a metal strip or steel billet in a continuous furnace. The present invention relates to a furnace operating method that allows a continuous furnace to exhibit its maximum capacity while controlling the furnace internal temperature to a predetermined value.

(Prior art) Conventionally, in the operation method of a continuous furnace, each combustion zone of the continuous furnace is set at a fixed furnace temperature determined in advance theoretically or empirically depending on the processing purpose, while The furnace is operated at a fixed conveyance speed.

For example, in a catenary-type continuous annealing furnace for metal strip, the method shown in FIG. 12 is common.

That is, in the figure, 1 is a continuous annealing furnace, 2 is a conveyance roll driven by a drive motor 3, and 4 is a speed setting device for controlling the rotational speed of the drive motor 3. The speed setting device 4 includes a processing material W.
Various setting speed commands 5 that are theoretically or empirically predicted in advance to satisfy the quality of the treated material after heat treatment depending on the type, size, etc. of the material W are input, and are selected as appropriate depending on the material W to be treated. There is.

Note that 6 is a speed controller that controls the drive motor 3 by comparing the speed of the transport roll 2 detected by the pulse generator 7, which is a transport speed detector, with the set speed.

On the other hand, the material extraction temperature is detected by a surface thermometer 8, which is a material temperature detector, and this detected temperature is input to a material temperature controller 9, where it is compared with a material set temperature (extraction target material temperature). Then, based on this comparison signal, the furnace temperature controller 10 in each zone operates the fuel flow controller 11 and the combustion air flow controller 12, and the extraction temperature of the processing material W is controlled to be the set temperature. In addition, 13 is a burner, 1
4 and 15 are flow control valves, 16 and 17 are flow meters,
Burners 13 are provided in each zone.

(Prior art and its problems) As described above, in the past, the conveyance speed of the processing material W, the material temperature control system, and the combustion control system are unrelated to each other, and moreover, these are not fixed by the processing material. Therefore, production efficiency remained constant.

Therefore, in order to improve productivity in continuous furnaces, improvements other than those mentioned above have been taken, and it is no longer possible to hope for any further improvement in productivity.

As a result of various studies on the above-mentioned points, the present inventors found that the operating conditions of a continuous furnace, such as the set combustion amount in each combustion zone, the set furnace temperature, the set conveyance speed, etc., are relative to the equipment capacity of the continuous furnace. In particular, when processing a variety of materials in the same equipment, continuous furnace equipment must necessarily have the ability to satisfy each maximum setting condition for the materials to be processed. In order to effectively utilize the maximum processing capacity of the equipment, the furnace temperature and conveyance speed are calculated based on the heat treatment conditions of each material to be treated, and each set value is controlled using these calculated values. This book focuses on the fact that accurate control cannot be achieved due to errors between It is an invention.

(Means to Solve the Problems) Therefore, in the present invention, in a continuous furnace having a plurality of combustion zones, each combustion zone is provided with a furnace temperature controller, a fuel flow rate controller, a combustion air flow rate controller, and a combustion air flow rate controller. A furnace temperature detector is installed to form a feedback control system, and an extracted material temperature detector and a conveyance speed detector are installed to monitor the furnace temperature in each zone, fuel flow rate in each zone, and material conveyance during furnace operation. The speed and material extraction temperature are detected, each detected value is compared with a judgment element consisting of heat treatment conditions of the processing material and equipment limitations, and the material conveyance speed is increased within a range that satisfies the judgment factors. Alternatively, it is designed to perform deceleration control.

(Example) Next, the present invention will be explained with reference to drawings which are examples.

FIG. 1 shows a continuous furnace for carrying out the furnace operation method of the present invention.

Roughly speaking, the preheating zone 20, the first combustion zone 21,
It consists of a catenary furnace T which is a continuous furnace consisting of a second combustion zone 22 and a third combustion zone 23, a furnace temperature/combustion control device 30, and a conveyance speed control device 50.

The furnace temperature/combustion control device 30 includes a material temperature controller 3
1, and a furnace temperature controller 33 that changes the combustion amount while keeping the air-fuel ratio to the burners 32 provided in the first to third combustion zones 21 to 23 constant. By the furnace temperature setting signal from 31,
The optimum set temperature for each combustion zone is set by the furnace temperature controller 33. In this case, the furnace temperature is compared with the furnace temperature from the furnace temperature detector 40 of the combustion zone, and signals are output from the fuel flow controller 34 and the combustion air flow controller 35, and the fuel flow controller 36 and the combustion air The flow control valve 38 opens and closes proportionally. In addition, 37 is a fuel flow meter, and 39 is a combustion air flow meter, which serves as a measurement input for each flow rate controller 34, 35, and each flow rate adjustment is performed by a control output signal calculated by comparison with the setting value of each flow rate adjustment valve. The valves 36 and 38 are controlled to a predetermined opening degree.

As shown in FIGS. 2 and 3, the material temperature controller 31 compares the target material temperature setting value SV ₁ of the material W to be heat-treated with the extracted material temperature from the material temperature detector 24. and the furnace temperature controller 3 for each zone.
3, a furnace temperature setting signal is output.

In addition, this material temperature controller 31 is equipped with a
A corrector 41 is provided so that immediate action can be taken. Then, if there is a change in the processed data, a correction coefficient corresponding to this change is set in the corrector 41,
Change the furnace temperature set value. In addition, in order to prevent the above-mentioned correction from becoming excessive correction, as shown in FIG.
There are upper and lower limits.

The conveyance speed control device 50 includes an increase/deceleration determination section 5
1, a conveyance speed setting section 52, and a conveyance speed control section 60.

The increase/deceleration determination unit 51 determines whether to increase or decelerate the processing material conveyance speed based on the opening degree of the combustion flow rate control valve 36 in each fuel zone, the furnace temperature, the material extraction temperature, and the conveyance speed. . That is, as shown in FIG. 4, each furnace temperature measurement value of the first to third combustion zones 21 to 23 is compared to the lower deviation set value (DSL) with respect to the furnace temperature set value (TF) of each combustion zone and each combustion zone. between the furnace temperature upper limit setpoint (TSH) in the zone, and
If the opening degree of the fuel flow rate control valve 36 in each combustion zone is equal to or lower than the valve opening degree lower setting value (MCH) for the opening degree of the fuel flow rate control valve 36 in each combustion zone, the extracted material temperature measurement value is the target material temperature setting value. (SV ₁ ), or when the measured extracted material temperature is greater than or equal to the low deviation set value (DTLS) with respect to the target material temperature set value (SV ₁ ), this function is activated. It is determined that there is sufficient processing capacity in the equipment, and a speed increase command is issued to the current transport speed within a range below the speed controllable upper limit value of the transport device.

On the other hand, as shown in FIG.
The furnace temperature measurement value in step 3 is the furnace temperature setpoint (TF) for each combustion zone.
lower deviation set value (DSL) or less, and
If the opening degree of the fuel flow rate control valve 36 in each combustion zone is equal to or higher than the valve opening degree high setting value (MVH) for the fuel flow rate valve opening degree in each combustion zone (however, MVH>MCH), or if the extraction material temperature If the measured value is less than the lower deviation set value (DTLS) with respect to the target material temperature set value (SV ₁ ), it is determined that the processing capacity of this equipment is insufficient, and the speed of the transport device is determined to be lower than the current transport speed. Issue a deceleration command within the range above the controllable lower limit.

In this case, the conveyance speed must be increased or decelerated step by step by a predetermined amount (DS) using the rate of change limit, as described below, and must be such that the conveyance speed increase condition and decrease condition are not satisfied. If so, maintain that transport speed.

In addition, the above DSL, TSH, MCH, MVH,
The meanings of DTHS and DTLS are as follows.

*DSL... [One of the conditions for slowing down the conveyance speed] Determines whether the temperature control system is properly controlling the furnace temperature by following the required furnace temperature set value at the current conveyance speed. Lower deviation setpoint for furnace temperature setpoint.

*TSH... [One of the conditions for increasing the conveyance speed] The temperature control system determines that the upper limit dangerous temperature of the furnace body will not be reached in response to the expected furnace temperature increase request as a result of future speed increase commands. Upper limit setting value for.

*MCH... [One of the conditions for increasing the conveyance speed] A low setting value for the fuel flow control valve opening.
This is a set value to determine that the combustion flow rate control valve has enough margin to cope with the increase in combustion capacity due to future increases in conveyance speed.

*MVH...[One of the conditions for decelerating the conveyance speed] A high setting value for the fuel flow control valve opening.
Set value to determine that the target material temperature cannot be maintained due to insufficient combustion capacity unless the conveyance speed is reduced.

*DTHS...[Conveyance speed increase condition] The high deviation setting value for the measured value of material temperature indicates that it is necessary to increase the conveyance speed when it is determined that the material temperature will rise above or below at the current conveyance speed. Setting value for determining.

*DTLS...[Conveyance speed deceleration condition] This is the low deviation set value for the measured material temperature set value, and is used when it is determined that the target material temperature cannot be maintained at the current conveyance speed and that the conveyance speed needs to be decelerated. Setting value for judgment.

As shown in FIG. 6, the conveyance speed setting section 52 outputs a setting signal to the conveyance speed control section 60 described below when receiving an increase (deceleration) speed command from the increase/deceleration determining section 51. It is.

This conveyance speed setting section 52 includes a control output section 53,
It consists of a control amount setter 54, a control period setter 55, a rate of change limit setter 56, an initial value setter 57, and an adder/subtractor 58.

When either an increase/decrease signal is input from the increase/decrease determination section 51 to the control output section 53, a control amount signal +DS (-DS) is output from the control amount setting device 54 and added to the initial value LS _0. Alternatively, it is subtracted and output to the conveyance speed control section 60 described below.

By the way, since a sudden change in the conveyance speed may cause an accident such as breakage of the processed material, in this embodiment, when the increase (decrease) speed command is input, the timer time TMS of the control cycle setting device 55 (timer) is used to limit the speed. a predetermined time,
Rate of change signal from rate of change limit setter 56
According to the DLS, the amount is increased or decreased by a predetermined amount in stages (Figures 7 and 8).

If the increase/deceleration command continues to be input after that, the increase/deceleration is again increased/decelerated by +DS (-DS) in the same manner as above, and the control period TMS continues until the increase/deceleration command from the increase/deceleration determination section 51 is no longer received. Repeat the correction each time.

As shown in FIG. 9, the conveyance speed control section 60 performs manual speed control using a manual speed setting device 61, a setting signal from the manual speed setting device 61, and an increasing (decreasing) speed signal from the conveying speed setting section 52. A changeover switch 62 for selecting automatic speed control, a motor drive control device 63, and a pulse generator 26 that is a rotation speed detector for the conveyance roller 25 control the motor so that the difference between the command speed signal and the signal from the pulse generator 26, which is a rotation speed detector of the conveyance roller 25, is zero. It consists of a differential controller 64 that operates a drive control device 63.

Next, a method for operating a continuous furnace having the above configuration will be explained.

First, based on the processing data (plate thickness, plate width, line speed), the material temperature controller 31 sends a material temperature target set value SV ₁ to the furnace temperature controller 33 of each combustion zone 21 to 23 as shown in FIG. Indicated temperature setting temperature TF ₁ ~ TF ₃
The required amount of heat is calculated so that the amount of heat is calculated, and the calculated value is output to the furnace temperature controller 33. Here, it is compared with the signal from the furnace temperature detector 40, and the fuel flow rate control valve 3
6. While proportionally controlling the opening degrees of the combustion air control valves 38, the conveyance rollers 25 are driven by the initial value LS ₀ from the conveyance speed setting section 52, and the processing material W is heat-treated.

As time passes, each combustion zone 21~
The temperature of the furnace 23 and the extraction temperature of the treated material W rise to reach a steady state. As mentioned above, at this point, the conveyance speed is the standard conveyance speed (LS ₀ ) determined for each material to be processed based on experience, and the opening degree of the fuel flow control valve is the standard conveyance speed (LS 0 ) determined based on experience. ₀ ) and corresponds to the combustion amount necessary to ensure the target material temperature set value (SV ₁ ) (No. 11).
Figure A).

Then, when the conveyance speed control changeover switch 62 is turned on and conveyance speed control is started, the fuel flow rate control valve opening of each combustion zone 21 to 23, the furnace temperature, the extraction material temperature, and the conveyance speed are determined by the increase/deceleration determination section. 51
will be entered into.

If the correlation between the detected values satisfies the speed increase condition (see FIG. 4), the increase/deceleration determination section 51 issues a speed increase command to the conveyance speed setting section 52, and a signal from the conveyance speed control section 60 is output. Drive motor 27
is controlled to increase the conveying speed (11th B,
_B1 ).

On the other hand, if the correlation is in the speed reduction condition (see Figure 5), a deceleration command is issued in the same way (see Figure 5).
Figure 1C, _C1 ).

In addition, in the conveyance speed setting unit 52, an increase/decrease command of a predetermined setting value ±DSL, which increases (decreases) the speed at a constant rate of change, is added to the initial value LS ₀ to the timer time from the control cycle setting device 55. The value LSn is output to the conveyance speed control unit 52, and the conveyance roller 25 increases or decelerates based on this signal.

Then, when the conveyance roller 25 increases or decelerates, the time in the furnace of the treated material W changes, and similarly,
The temperature of the extracted material changes, but the material temperature controller 31 detects this change and commands a correction signal to the furnace temperature controller 33 to adjust the opening degree of the fuel flow rate control valve 36 and keep the furnace temperature within the temperature increase margin range. The fuel flow control valve 36 is controlled to maintain the extraction material temperature at the target material temperature.

The above explanation indicates that the continuous furnace is a catenary furnace,
We have shown the case where a certain treated material (metal strip) is heat treated in this furnace, but if you want to heat treat different types of metal strips continuously during the process,
When the joint passes a predetermined position in the furnace, the material temperature target value SV ₁ of the material temperature controller 31 and the conveyance speed setting section 52
The initial value of LS ₀ may be used as the value of the subsequent metal strip. Moreover, it goes without saying that the continuous furnace may be of other types.

(Effects of the Invention) As is clear from the above explanation, according to the furnace operation method of the present invention, the furnace temperature and fuel flow rate, material conveyance speed, and material extraction temperature in each zone of the furnace are controlled during furnace operation. The method detects each detected value and compares each detected value with judgment factors consisting of heat treatment conditions of the processed material and equipment limitations, and controls the material conveyance speed to be increased or decreased within a range that satisfies the judgment factors. As a result, the processing capacity of the equipment can be utilized to the maximum, and productivity can be greatly improved.

Furthermore, since the furnace temperature, extraction temperature, etc. are adjusted by feedback control as the conveyance speed increases or decreases, the mechanism is simple and there are few control errors.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram for carrying out the furnace operation method of the present invention, Fig. 2 is an explanatory diagram of the material temperature controller, Fig. 3 is an explanatory diagram of the corrector in Fig. 2, and Fig. 4 is an explanatory diagram of the Figure 5 is a condition diagram when issuing a speed command, Figure 5 is a condition diagram when issuing a deceleration command, Figure 6 is an explanatory diagram of the increase/deceleration determination section, Figure 7 is a diagram showing the conditions when issuing a speed command.
8 is a graph showing the relationship between the control amount setter, the control cycle setter and the rate of change limit setter,
Figure 9 is an explanatory diagram of the conveyance speed control section, Figure 10 is a graph showing the relationship between the furnace temperature setting temperature and material temperature in each zone, and Figure 11 is the conveyance speed, fuel control valve opening, furnace temperature and material. FIG. 12 is a graph showing the control relationship between temperatures, and is an explanatory diagram showing a control method in a conventional continuous furnace. T... Continuous furnace, W... Treated material, 21... First combustion zone, 22... Second combustion zone, 23... Third combustion zone,
24... Material temperature detector, 25... Conveyance roll,
26... Conveyance speed detector, 27... Drive motor,
30...Furnace temperature/combustion control device, 31...Material temperature controller, 32...Burner, 33...Furnace temperature controller, 34
... Fuel flow rate controller, 35... Combustion air flow rate regulator, 36... Fuel flow rate control valve, 38... Combustion air flow rate control valve, 40... Furnace temperature detector, 51
...Increase/deceleration determination section, 52...Conveyance speed setting section, 5
3... Control output unit, 54... Controlled amount setting device, 55
...Control cycle setter, 56... Rate of change limit setter, 60... Conveyance speed control unit.

Claims (1)

[Claims] 1. In a continuous furnace having a plurality of combustion zones, each combustion zone is provided with a furnace temperature controller, a fuel flow rate controller, a combustion air flow rate controller, and an in-furnace temperature detector to perform feedback control. Along with forming a system,
Provided with an extraction material temperature detector and a conveyance speed detector,
Detects the furnace temperature and fuel flow rate in each zone during furnace operation, as well as material conveyance speed and material extraction temperature,
Each of these detected values is compared with a determination element consisting of heat treatment conditions of the material to be treated and equipment limitations, and the material conveyance speed is controlled to be increased or decelerated within a range that satisfies the determination element. How to operate a continuous furnace. 2. The method for operating a continuous furnace according to claim 1, wherein the speed increase or deceleration control is performed in stages using a rate of change limit. 3. The heat treatment condition is the extraction temperature of the treated material, and the equipment limitations are the allowable maximum furnace temperature for each zone, the allowable maximum fuel flow rate for each zone, and the allowable conveyance speed variable range. A method for operating a continuous furnace according to claim 1 or 2, characterized in that: 4. The method for operating a continuous furnace according to claim 3, wherein the maximum allowable fuel flow rate is the maximum allowable valve opening of a fuel flow control valve.