JPS60159127A - Method for controlling cooling of steel strip in continuous annealing installation - Google Patents

Abstract

PURPOSE:To control the temp. of a steel strip so as to follow up accurately a target temp. by detecting the inlet side temp., welding point, tension and conveying speed of the steel strip in a cooling device and the temp. of a refrigerant and controlling the winding angle of the steel strip to cooling rolls. CONSTITUTION:A steel strip 6 is cooled by passing the same through cooling rolls 1-5 in which a refrigerant flows, via an inlet side bridle roll 16, and is ejected from an outlet side bridle roll 17. The inlet side temp. of the strip 6 is detected by a thermometer 7, the line speed by a speedometer 13, the tension of the strip 6 by a tension detecting meter 14, the refrigerant temp. of the cooling roll 3 by a refrigerant thermometer 15 and the welding point by a detector 9, respectively, in each prescribed period and the detected values are outputted to a control device 12. The device 12 determines the temp. of the strip 6 on the inlet and outlet sides of the respective rolls from the input data and a working schedule chart, calculates the contact length between the strip 6 and the rolls 1-5 in the respective rolls 1-5, calculates the pressing rate of the rolls 2, 4 and moves hydraulic cylinders 10 by control devices 11 for hydraulic cylinders thereby adjusting the positions of the movable rolls 2, 4.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a cooling control system that cools a steel strip by wrapping a copper strip around a cooling roll installed in a continuous annealing facility and having a refrigerant flowing through the inside. It is about the method.

(Prior art) In continuous annealing equipment, a copper strip heated to around 700°C is
It is necessary to cool it to around ℃. For this purpose, the copper strip is brought into contact with a metal roll through which cooling water flows, and by moving the roll, the contact length between the roll and the copper strip is changed to obtain the desired temperature of the copper strip. The cooling method is described in Japanese Patent Publication No. 57-14414 and Japanese Patent Publication No. 58-4745.
There is a method described in Publication No. 7.

R11, the former is a thermometer that detects the temperature of the steel strip is installed on the exit side of the cooling device, and the actual temperature obtained from the thermometer,
This is a feedback control that measures the deviation from the target temperature and changes the contact length between the steel strip and the cooling roll based on the deviation. This is a control method that combines feedback control and feedforward control, in which temperature changes that cannot be absorbed by the above-mentioned feedback are compensated for by feedforward control by installing the controller -1 and obtaining the actual inlet temperature.

However, the conventional method has the following drawbacks and is not completely satisfactory. That is, in both of the above-mentioned conventional methods, the contact length is controlled only by the temperature of the copper strip. This means that when the steel strip thickness or line speed changes, the conventional method has poor followability. This is because in continuous annealing equipment, the copper strips that are threaded are welded copper strips with different thicknesses, strip widths, heat cycles, etc., and the line speed is determined by the heating furnace, soaking furnace, overaging furnace, etc. This is because the line speed is determined by equipment other than the cooling device, and it is difficult to change the line speed depending on the capacity of the cooling device.

For example, a case where the plate thickness changes from 0.8 mm to 1.0 mm will be explained. The temperature of the copper strip is from 800℃ to 400℃
The temperature shall be lowered by the cooling device to ℃. Here, there is an experimental result that in a cooling method in which a copper strip is brought into contact with a metal roll into which cooling water is allowed to flow, the cooling rate is about 100° C./sea. Suppose the cooling rate is 100
If it is ℃/@ea, it will take 4 seconds to lower the temperature by 400℃.

Therefore, it can be considered that it takes about 4 to 5 seconds for the welding point to pass through the cooling device and reach the outlet thermometer. Until the welding point reaches the exit thermometer, the temperature detected by the exit thermometer is that of the copper strip with a plate thickness of 0.8 wn, which is approximately equal to the target value, so the contact length is not changed. After the welding point passes the exit side thermometer, the temperature of the steel strip with a plate thickness of 1.0 mm is detected, but even though the required cooling amount is 1.25 times larger, the contact length with the roll is is plate thickness 0.8m+n
Since the contact length of the copper strip is equal to the contact length of the copper strip, the actual temperature deviates greatly from the target temperature. In feedback control, the control 1111 mechanism operates at this point to change the contact length. That is,
Control is often performed with a delay of around 5 seconds.

Since the line speed is around 200 mpm, 5
A second delay means a significant temperature difference across the approximately 17m copper strip.

Furthermore, in the conventional method that performs feedback control, υ is based on the deviation between the target value and the actual value.
Since the feedback gain is forced to be small, the actual value is slow to follow the target value, and here too, a large copper band where the temperature deviates occurs. Therefore,
In the conventional method, if the plate thickness etc. change significantly, the temperature of the steel strip several tens of meters in length may deviate, making it impossible to maintain good quality.

In order to prevent the above-mentioned drawbacks that occur when attempting to control using only feedback control, it is possible to combine feedback control and feedforward control, but the conventional method described above Feedforward control is performed based on the deviation between the actual temperature and the same target temperature, so if the plate thickness changes as in the example above, but the target temperature at the entrance of the cooling system does not change significantly, It cannot produce any effect.

Furthermore, considering the effect on the shape of the copper strip, uniform cooling in the width direction is required, but when multiple cooling rolls are used, uniform cooling in the width direction can be achieved by distributing the amount of cooling between each roll. In the past, there was no concept of deciding what to do.

(Objective of the Invention) The present invention has been made in view of the above-mentioned drawbacks of the conventional method. ■Reducing the length of the steel strip where the temperature deviates; ■Preventing the occurrence of non-uniform cooling in the width direction. The purpose is to stably produce copper strips with good shape.

(Construction and Effect of the Invention) The present invention provides a mechanism in which a copper strip is wound around one or more cooling rolls installed in a continuous annealing facility and through which a refrigerant flows, and the winding angle is changed. When controlling a cooling device for steel strips with A control device is installed to control the copper strip cooling device that has a mechanism for changing the temperature of the copper strip, a copper strip thermometer and a copper strip weld line detector are installed on the inlet side of the cooling roll, and a copper strip tension meter is installed inside the cooling device. , a refrigerant thermometer and a steel strip conveyance speed meter are installed, and the dimensions and physical properties of the steel strip in transit, which are recognized from the number of weld lines passing and the work schedule, and the temperature of the steel strip on the entrance side of the cooling roll,
By substituting the copper strip tension, refrigerant temperature, and copper strip conveyance speed into the above relational expression, the wrapping angle of the copper strip with respect to the cooling roll is calculated periodically, and the wrapping angle is changed based on the value. , the wrap angle is controlled while the weld line of the copper strip passes through the cooling roll; a new equation for correcting the controlled steel strip target temperature on the exit side of the cooling roll is added to the relational equation in the control device. A steel strip thermometer is installed on the center side of the cooling roll, and the control target steel strip temperature on the exit side is periodically corrected based on the input from the thermometer, and the wrapping angle is recalculated. To further improve cooling accuracy by correcting the wrapping angle of the copper strip to the cooling roll; and when multiple cooling rolls are installed, controlling the wrapping angle of the copper strip to the cooling roll so that it becomes larger as the succeeding rolls become larger. The purpose is to stably produce copper strips with good shape.

(Example) A first example of the present invention will be described. The wrapping angle can be calculated as follows.

In other words, when the contact length between the roll and the steel strip in one cooling roll is l, considering the heat balance in a section of minute arc length d/, the amount of heat released by the steel strip 6 per unit time Δq, and the steel The amount of heat Δq2 flowing from the zone 6 to the refrigerant is equal. Here ΔQ1+
Δq is given by the following equations.

Δq1=cp・ρ1w ``di''``'ΔQ2''
'K(1', p) ・w-(T-TW), d
/However, C: Specific heat ρ of steel strip: Specific gravity W of copper strip: Width d of copper strip: Thickness V of steel strip Niline speed lI: Contact length T: Minute arc length dA! The temperature of the copper strip at 'D' is the diameter of the two rolls: Thermal transmission coefficient (function of contact length l and roll surface pressure p)'
2 TW: Temperature of the refrigerant Therefore, if the temperature of the copper strip on the inlet side of the cooling roll is T and the temperature on the outlet side is TD, then TD=TW+(T8-TW)/exp(K(l,p)・
l/C1s・d−V)・(1).

Here, in the cooling roll, heat transfers in the following order: contact heat transfer from the copper strip to the roll, heat conduction within the roll shell, and heat transfer between the roll shell and the refrigerant.
! , p) is given by the following equation.

However, k, (p): Contact heat transfer coefficient between the cooling roll and the copper strip (function of roll surface pressure p) D Roll diameter δ: Roll shell thickness λ Nigel heat transfer coefficient 2: Between the roll shell and the refrigerant Heat transfer coefficient (1), (
From equation 2), if the actual temperature of the copper strip on the inlet side of the cooling roll is T, and the target temperature on the outlet side of the cooling roll is TDo, the required contact length between the copper strip and the cooling roll can be calculated.

When cooling using multiple cooling rolls, the predetermined cooling amount of each roll (ΔTl, ΣΔTi =
Tzp -Ta2), the required contact length at each roll usually differs by determining the inlet and outlet temperatures of the copper strip in each cooling roll.

The procedure for applying the cooling control method described above will be explained using FIG.

FIG. 1 shows an example using five cooling rolls. The steel strip 6 conveyed from the previous process passes through the inlet priddle rolls, and then passes through the cooling rolls 1 to 1, which have refrigerant flowing through them.
5, and the output side priddle roll 17 to be conveyed to the next process. A copper strip thermometer 7 is installed on the inlet side of the cooling roll.
and a weld line detector 9 are provided and connected to a control device 12. The movable rolls are A2 cooling roll 2 and A4 cooling roll 4, and the control device 12 converts the pushing shaft from the wrapping angle to the hydraulic cylinder control device 11-1.11-2.
is input to the hydraulic cylinders 10-1, 10-
Move 2.

The copper strip conveyance speed is input to the control device from the copper strip conveyance speed meter 13, the copper strip tension from the copper strip tension side 14, and the refrigerant temperature from the refrigerant thermometer 15.

Note that the cooling device of the present invention refers to the parts from the inlet side prydle roll 16 to the outlet side prydle roll 17.

This embodiment is carried out in the following steps using the above equipment configuration. Note that the specifications of the cooling device are as shown in FIG.

The control device 121d measures the inlet side temperature T22 of the copper strip from the copper strip thermometer 7 on the inlet side of the cooling device at every predetermined period.
The line speed V is input from the steel strip conveyance speed meter 13, the tension applied to the copper strip is input from the tension detector 14, and the refrigerant temperature Tw is input from the refrigerant thermometer 15.
From the number of welding lines that have passed through and the work schedule, we know the work for the copper strip that is currently passing through the cooling device, and from the work schedule,
Copper strip specific heat CP, specific gravity ρ1 width W, thickness d, cooling device outlet target temperature T1. Take in o. Thereafter, the temperature of the copper strips on the inlet and outlet sides of each roll is determined by the distribution of the cooling m.

Using the method described above, the contact length t1 between the copper strip and the roll in each roll is calculated from the copper strip temperatures on the inlet and outlet sides of each roll. Using tl, the indentation tests H21 and H4 for the 20th and 40th rules are calculated using the following formulas.

Horse = D −4−(Lsln (θ, /2)−1))/
cos(θi/2) i=2.4 ・ (3) However, L
is the distance between the cooling rolls θ1 is the wrapping angle of the first coolant (θ1=2・L t/'D
) When the line speed τ or the entrance temperature TBP changes, the indentation meter 1 (2, H4 obtained by subtraction this time is transmitted to the hydraulic cylinder control device 11 as soon as the calculation is completed, and the hydraulic cylinder 10 is move and adjust the position of the movable roll 2°4.Also, when the weld line detector 9 detects a weld, move the movable rolls tH2 and H4 for the next copper strip using the same procedure as above. In addition, when the welded part, calculated in advance using the line speed υ, wraps around the movable roll 2, the pusher H2 is applied, and when the welded part wraps around the movable roll 4, the pusher 1H4 is applied hydraulically. The information is transmitted to the cylinder control device 11 so that the hydraulic cylinder 10 moves the movable roll 2.4 at each timing.

As can be seen from the above explanation, in the method according to this example,
It has the following advantages:

■ Since the time when the welding line enters the cooling device is known, the movable roll can be moved while the welding line is wrapped around the cooling roll, eliminating wasted time unlike conventional methods.

■ In the conventional method, which performs control based on the deviation between the target value and the actual value of the copper strip temperature at the exit side of the cooling roll, for example, when the plate thickness changes from 0.8 to 1.0 m+n,
1.0 It is not possible to know in advance the required contact length with the steel strip,
Since the movable roll push-down is gradually changed, it takes time to finally obtain the required contact length for a 1.0 mm copper strip, but in the method of this example, the required contact length is determined in advance by using a silver strip. This reduces the time required to move the movable roll.

As described above, if the method according to this embodiment is used, the number of steel strips that are out of edge depth is significantly reduced compared to the conventional method.

Next, a second embodiment of the present invention will be described using FIG. 3.

In FIG. 3, a copper strip thermometer 8 is provided on the exit side of the cooling roll, and the other features are the same as in FIG. 1.

The above examples use the specific heat of the copper strip, the contact heat transfer coefficient between the copper strip and the roll, the thermal conductivity of the shell, etc., but these values may vary depending on the operating conditions and the copper strip. , which varies slightly. Therefore, the temperature of the copper strip after passing through the gold-plated j apparatus also differs slightly from the target temperature. If the control accuracy target is strict, consideration must be given to eliminating the influence of disturbances as described above. This embodiment has been made to solve the above-mentioned drawbacks, and is intended to further improve the cooling control accuracy of the above-mentioned embodiments.

In other words, from equations (11 and (2)), it can be seen that the temperature of the copper strip on the exit side of the cooling roll is determined by the contact length between the copper strip and the roll. Also, from equation (3), it can be seen that the contact length is variable. It is determined once the roll pushing amounts H2 and H4 are determined. Therefore, the temperature TD of the copper strip on the exit side of the cooling roll is determined as a function of the pushing amount of the 2nd and 40th rolls as follows: TD=F (H2, H4)...・(4)
It is expressed as

Substitute the steel strip exit side target temperature “Do” for the steel strip exit side temperature TD,
According to the first example of intermittent roll pushing, the outlet temperature TD of the copper strip should be the target temperature TDO, but the actual outlet temperature TDP measured by the outlet thermometer 8 is not as described above. For some reason, the target temperature is TD.

It's quite different from that. Therefore, the actual temperature TDP is adjustable and is expressed as TDP=GF(H2, H4) (5) using 41 rammeter G.

(However, F(H2, H4) is the same function as equation (4)) Actual temperature TDP at control time k is TD p (k) +
Assuming that the pushing amount of the movable rolls 2 and 4 is H2 (k), H4 [Yes]), the adjustable parameter G (k) at control time k is G) = TD, (k)/F' (I (2(k), H4(
k)) ... (6).

The adjustable parameter G (k) calculated using the above equation is smoothed using the following equation.

d)=(1-α)a(k-1)+αG)...
(7) After that, the target temperature “Do” is changed to the target temperature “T”.
Replace it with DP/d(k), and use the method of the first embodiment of the present invention to calculate the pushing amount correction value 怀2 [Yes]), 9(k), and correct the movable roll pushing amount.

The cooling control method according to the second embodiment of the present invention is based on the above method and is carried out in the following steps.

12 control devices, inlet thermometer 7 every predetermined period
The input side temperature of the copper strip TgP'c is determined from the output side thermometer 8, the line speed τ is determined from the steel strip conveying speed meter 13, and the tension applied to the copper strip is determined from the copper strip tension meter 14. , the temperature Tw of the refrigerant is input from the refrigerant thermometer 15.

Furthermore, from the number of weld lines that have passed through the weld line detector 9 and the production schedule, it is possible to determine the production time of the steel strip that is currently passing through the cooling device.
Knowing c, from the work schedule mentioned above, the specific heat CPl specific gravity ρ1 of the copper strip
Input the width W, thickness d, and actual exit temperature TDo. Thereafter, the movable roll pushing amount correction values W, , R4 are calculated based on the above-mentioned method, and the values are transmitted to the full hydraulic cylinder control device #11 to move the hydraulic cylinder 10.
- Correct the ``le'' place @.

By using the control method according to this embodiment, it is possible to eliminate errors caused by disturbances and improve control accuracy without impairing the advantages of the cooling control method according to the first embodiment.

Furthermore, it is difficult to accurately determine in advance parameters such as the contact heat transfer coefficient between the copper strip and the roll, the heat conductivity of the shell, and the heat transfer between the shell and the refrigerant. Its value may fluctuate due to changes over time. In such a case, the input side actual paper temperature T2 of the steel strip, the output side actual temperature TDI', adjustable/4' parameter aQc), and the indentation temperature T2. ``Using 4th grade, (1).

(2+) The above parameters are calculated using equation (5), and then the true values are estimated using a Kalman filter, least squares estimation, or other statistical processing, and control accuracy can be further improved.

The control effects of this embodiment and the conventional method are shown in FIGS. 4 and 5. In each figure, the vertical axis indicates the flange thickness, steel strip temperature, and roll press from the top, and the horizontal axis indicates the longitudinal position of the copper strip.

In the case of this embodiment, as shown in FIG. 4, while the copper strip weld wire is detected and wound around a cooling roll, the temperature difference is Although this rarely occurs, in the conventional method, as shown in FIG. 5, a large temperature deviation occurs because the wrapping angle is changed depending on the deviation between the target temperature of the copper strip on the exit side and the actual value.

Finally, a third embodiment of the present invention will be described.

A characteristic of cooling a copper strip using a plurality of cooling rolls is that non-uniformity in the copper strip temperature in the width direction that occurs in the front roll is amplified in the rear roll. For example, in Figure 1, if the temperature of the copper strip on the exit side of No. 10 is low at the center and high at the ends, this is because the tension in the copper strip on the exit side of No. 10 is at the center. This causes an increase in the tension in the section, which further widens the temperature difference between the center and the ends of the 20th loop. Figure 6 shows the nth axis indicated on the horizontal axis.
This is an experimental result of how many times the temperature difference in the width direction generated at the second cooling roll is amplified on the exit side of the final cooling roll. As can be seen from the figure, the nonuniform cooling in the width direction that occurs in each roll is greatly amplified on the exit side of the final roll, such as #1 that occurs in the previous roll.

The main cause of non-uniform cooling that occurs on each roll is the thermal crown that occurs on the cooling roll, and the non-uniform cooling in the width direction that occurs in the preceding rolls has a large impact on the temperature of the steel strip in the width direction at the exit side of the final roll. Considering the impact on the thermal crown, it is necessary to keep this thermal crown small, such as on the front roll t. Thermal crown is for cooling and load Q. is proportional to. The cooling 9 load Qc is given by the following equation.

Qc=-HKD7? W (T-Tw) However, ° K: Heat transmission coefficient D: Roll diameter θ: Wrapping angle W: Plate width T Two Copper band temperature Tw: Refrigerant temperature Roll diameter D1 Plate width w1 Refrigerant temperature Tw Each roll There is a positive correlation between the thermal transmission coefficient and the wrap angle θ, and considering that the temperature T of the copper strip in the front roll is high,
In order to reduce the front roll cooling load QC, the front roll winding angle θ must be made smaller. That is, it is necessary to increase the winding angle of the second roll and apply a uniform cooling load or a high load to the second stage in order to achieve uniform cooling in the width direction.

In this example, ΔT, <ΔT2<ΔT, <ΔT4<ΔT
5 (where ΔT1 is the temperature drop at the 10th roll, therefore θ1 < θ2 < θ5 < θ4 < θ5).

By using the cooling control method according to this embodiment, it is possible to prevent non-uniform cooling in the width direction, and it is possible to avoid deterioration in the shape of the copper strip caused by temperature non-uniformity in the width direction. It is possible to stably produce excellent copper strips.

(Effect of the invention) By using the cooling control method according to the present invention when cooling a copper strip using a cooling roll in continuous annealing equipment,
The followability and control accuracy of the temperature of the copper strip after passing through the cooling device relative to the same target temperature are significantly improved compared to conventional methods, and this greatly contributes to improving the quality and yield of the copper strip after continuous annealing. Furthermore, uneven cooling in the width direction can be prevented, which greatly contributes to stable production of well-shaped copper strips.

[Brief explanation of drawings]

Fig. 1 is a side view of a cooling device showing a first embodiment of the present invention, Fig. 2 is a diagram showing dimensions of main parts of the cooling device, and Fig. 3 is a side view of a cooling device showing a second embodiment of the invention. Fig. 4 is a diagram showing the effect of the second embodiment of the present invention, Fig. 5 is a diagram showing the cooling control effect of the conventional method, and Fig. 6 is a diagram showing the effect of the cooling control in the width direction caused by the first roll. It is a figure which shows the amplification factor of the temperature difference on the exit side of the final cooling roll. 1.2.3.4.5: Refrigerant f inside: Cooling rolls (of which 2 and 4 are movable), 6: Steel strip, 7: Inlet side thermometer that measures the temperature of the steel strip, 8 : Exit thermometer that measures the temperature of the steel strip, 9: Welding point detector, 10: Hydraulic cylinder, 11
: Hydraulic cylinder control device, 12: Control device, 13: Copper strip conveyance speed meter, 14: Steel strip tension B1.15: Refrigerant thermometer,
16: Entry side priddle roll, 17: Output side priddle roll Figure 6 Leave pm low / use procedure amendment (method) % formula % ■, Indication of the case 1988 Patent Application No. 013907 2 Title of the invention: Method 3 of controlling cooling of steel strip in continuous annealing equipment; Relationship with the amended case; Patent applicant: 2-6-3 Otemachi, Chiyoda-ku, Tokyo (665); Takeshi, representative of Nippon Steel Corporation; 1) Figure 4, Figure S, subject to Yutaka 6 Supplement 1

Claims (3)

[Claims] (1) A copper strip is wrapped around one or more cooling rolls that are installed in a continuous annealing facility and have a refrigerant flowing through them.
When controlling a cooling device for copper strips that has a mechanism for changing the length, this service memorizes a work schedule that describes the conveyance order, dimensions, and physical properties of the copper strips17, and calculates them from relational equations obtained in advance. A control device is provided to calculate the wrapping angle and control a mechanism for changing the wrapping angle, and a copper strip thermometer and a copper strip weld line detector are provided on the inlet side of the cooling roll. belt tension meter,
A refrigerant thermometer and a copper strip conveyance speed meter are installed, and the dimensions and physical properties of the steel strip in transit, recognized from the number of weld lines passing and the work schedule, the temperature of the steel strip at the entrance of the cooling roll, the tension of the copper strip, the refrigerant temperature, The winding angle of the steel strip around the cooling roll is calculated periodically by substituting the copper strip conveyance speed into the above relational expression, and the winding angle is changed based on that value, and the weld line of the copper strip is cooled. A method for controlling cooling of a copper strip in continuous annealing equipment, the method comprising controlling the wrapping angle while passing through a roll. (2) Add a new equation to the relational expression in the control device to correct the control steel strip target temperature on the exit side of the cooling roll, install a steel strip thermometer on the exit side of the final cooling roll, and Based on the input from the steel strip thermometer on the exit side of the roll, the control steel strip target temperature on the exit side is periodically corrected, the wrapping angle is recalculated, and the wrapping angle of the copper strip with respect to the cooling roll is corrected. A method for controlling cooling of a copper strip in a continuous annealing facility according to claim 1. (3) In a plurality of cooling rolls through which a refrigerant flows, the winding angle of the steel strip with respect to the cooling rolls is controlled so as to increase as the succeeding rolls become larger. A method for controlling cooling of a copper strip in continuous annealing equipment according to item 1 or 2.