JP2954485B2 - Method of controlling winding temperature of hot-rolled steel strip - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a winding temperature of a hot-rolled steel strip, in which cooling water is injected from a cooling facility to a hot-rolled steel strip (hot strip) to control a winding temperature.

[0002]

2. Description of the Related Art FIG. 7 is a schematic view showing an example of a hot-rolled steel strip winding temperature control equipment.

The finishing mill 1 comprises a pair of rollers arranged symmetrically in the vertical direction, and a finishing outlet thermometer 2 for measuring the temperature of the hot strip and a plate for measuring the thickness of the hot strip at its output side. Thickness gauge 3 is installed. In addition, at the top and bottom of the run-out table,
Cooling equipment 5, 6 for cooling hot strip 4
Is installed.

The cooling equipments 5 and 6 are internally divided into N cooling banks 7 in the longitudinal direction, and each cooling bank is provided with n valves. / Stop can be performed. A wind-up thermometer 8 for measuring the temperature of the hot strip 4 at the outlet side is provided downstream of the cooling equipments 5 and 6. Further, a winding machine 9 for winding the hot strip 4 having been subjected to the cooling process is provided downstream of the winding thermometer 8.

[0005] A speed detector 10 for detecting the rotation speed of the rolling roll is connected to the finishing mill 1, and a speed detector for measuring the rotation speed is similarly connected to the winding machine 9. A vessel 11 is connected and both are used to measure the speed of the hot strip 4.

Next, conventional winding temperature control for the above-structured winding temperature control equipment will be described.

[0007] The winding temperature control is performed for each fixed length of the hot strip 4 traveling from the finishing mill 1 to the winding machine 9 by interruption of a fixed length pitch from a preset counter. And the finishing outlet temperature and the sheet thickness are actually measured by the sheet thickness gauge 3 to predict a speed pattern such as an acceleration / deceleration rate.
No. 9-118655). Further, a temperature drop caused only by water cooling and a temperature drop caused only by radiation are calculated by a model formula, and the calculation is repeatedly performed until the target winding temperature is reached. Using this winding target temperature as a control target,
The opening and closing of each valve of the cooling equipments 5 and 6 are controlled. That is, this method is characterized in that the number of on-valves of each bank is determined for the purpose of making the temperature calculated by the temperature estimation model coincide with the target temperature.

[0008] As regards this type of technology,
For example, there is Japanese Patent Application No. 4-330781.

[0009]

However, in the above-mentioned prior art, the number of valves is determined only by making the temperature calculated by the temperature estimation model coincide with the target temperature as an evaluation index. In some cases, the operation of turning on / off the valve may be repeated, causing an unsteady state such as a response delay of the valve and a change in water injection pressure, resulting in an error in the temperature estimation model. In addition, the deterioration of the equipment of the valve itself is accelerated.

Therefore, an object of the present invention is to turn on / off a valve.
An object of the present invention is to provide a method for controlling a winding temperature of a hot-rolled steel strip, which eliminates a phenomenon that turning-off is repeated in a short cycle and can improve the accuracy of model estimation.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a finish-rolled hot-rolled steel strip which is cooled by cooling means to control a winding temperature. In the control equipment, the error between the predicted temperature and the target temperature when the cooling water injection valve is opened and closed by the temperature estimation model, and the stability of the valve assuming the time from the previous change time of the valve as a fuzzy evaluation index. The number of valve-ons is determined by inference.

[0012]

According to the above-mentioned means, fuzzy inference is performed so that the temperature calculated by the temperature estimation model is used to open and close the cooling water injection valve and to prevent the valve from being opened and closed in a short cycle in consideration of the stability of the equipment. Done. This makes it possible to suppress a change in the valve in a short period while keeping the error from the target temperature within an allowable range, and to avoid an unsteady state such as a response delay of the valve and a change in injection pressure.

[0013]

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

FIG. 1 is a block diagram showing an example of a winding temperature control device for achieving the method of controlling the winding temperature of a hot-rolled steel strip according to the present invention.

Output signals from the finishing outlet thermometer 2 and the speed detector 10 are taken into a finishing outlet coil piece temperature calculating unit 12. The finish outlet coil piece temperature calculating section 12 is connected to a run-out table coil piece temperature determining section 13.
The output signal of the thickness gauge 3 and the output signal of the valve ON-OFF (on / off) result input unit 15 are applied to the coil piece temperature determining unit 13 on the run-out table.

Further, the run-out table upper coil piece temperature determining unit 13 is connected to a valve-on number determining unit 14 based on fuzzy prediction, and the valve-on number determining unit 14 is connected to a valve ON-OFF setting output unit 16.

The finishing outlet coil piece temperature calculator 12 receives the timing of the constant progress of the hot strip 4 and the passing speed from the speed detector 10 and calculates the coil piece temperature detected by the finishing outlet thermometer. And outputs the sheet passing speed and the coil piece temperature at the finishing outlet position.

A coil piece temperature determining unit 13 on the run-out table based on the calculation result of the finishing outlet coil piece temperature calculating unit 12
Then, the amount of temperature drop of each coil piece on the run-out table while the hot strip 4 is traveling for a certain length is calculated. This calculation is based on the results of valve ON-OFF and valve ON-OF
F is taken from the results input unit 15 and the thickness value
For the coil pieces closest to the finishing mill 1, use the finishing exit position coil piece temperature of the previous loading,
Using the already calculated threading speed as an input, the temperature drop amount is obtained by the following equation.

(Temperature drop only by water cooling) T ₁ = T _W + (T ₁₀ −T _W ) exp (−αΔt / CpρH) (1) (Temperature drop only by radiation) T ₂ = [(6ε ₀ σΔt) / (CpρH) + 1 / (T ₂₀
³ )] ^1/3 where T ₁ , T ₂ : cooling temperature (K) T ₁₀ , T ₂₀ : pre-cooling temperature (K) T _W : cooling water temperature (K) α: heat transfer coefficient (Kcal / m ² hr) ° C) Cp: Specific heat of hot strip (Kcal / K
g · ° C.) ρ: density of rolled material (Kg / m ³ ) Δt: required cooling time (hr) ε ₀ : emissivity H: plate thickness σ: Stefan-Boltzmann constant (Kcal /
m ² hr ° C.) The temperature drop amount is obtained using the equations (1) and (2), and the current coil piece temperature on the run-out table is determined. For coil pieces that have already passed through the finish exit position, the previously calculated coiling temperature on the run-out table is used as input, and the already calculated threading speed is used as an input. Similarly, equations (1) and (2) are used. Is used to determine the temperature drop amount, and the current coil piece temperature on the runout table is determined. Further, if there is a coil piece whose water supply has been started for the first time, the coil piece temperature [T _i ] and the time [t _i ] at the start of the water injection are stored in a storage device (not shown).

Next, the valve-on number determining section 14 determines the error between the predicted temperature and the target temperature when the cooling water valve obtained by the temperature estimation model is turned on and off, and the error from the previous change time of the valve. Two contradictory evaluation indices of time and assumed valve stability are evaluated using a fuzzy technique, and finally ON / OFF of the valve is determined. This makes it possible to suppress a change in the valve in a short cycle while keeping the error from the target temperature within an allowable range, and to avoid the above-mentioned unsteady state.

FIGS. 2 and 3 are explanatory diagrams showing an example of the membership function used in the valve-on number determining section 14. FIG.

FIG. 2 shows a membership function (MSF) related to stability evaluation, which is provided for each steel type of the hot strip 4. FIG. 2A shows a membership function when the number of valves is not changed, and FIG. 2B shows a membership function when the number of valves is changed. In the figure, the vertical axis represents the certainty factor and the horizontal axis represents the elapsed time.

FIGS. 3A and 3B show membership functions relating to temperature accuracy evaluation. FIG. 3A shows a membership function when the number of valves is not changed, and FIG. 3B shows a membership function when the number of valves is changed. is there. The stability evaluation is expressed by the excess time since the last change in the number of valves, and the temperature accuracy evaluation is expressed by the temperature deviation (° C.) from the target cooling pattern. In the figure, the vertical axis represents the certainty factor and the horizontal axis represents the temperature deviation.

As shown in FIGS. 2 and 3, the function when the number of valves is not changed shows a flat function, and the function changes when the number of valves is changed. In this embodiment, the case of FIG. 2 is referred to as antecedent part membership function 1 (hereinafter referred to as “antecedent M
SF1) and the case of FIG. 3 as antecedent membership function 2 (hereinafter referred to as “antecedent MSF2”).

FIG. 4 is an explanatory view showing the principle of determining the number of valve-ons in the number-of-valves-on determination unit 14.

Here, the number of valve-on is set to ± 7. In this case, the number of valve-on is eight cases of “current state ± 0”, “current state + 1” to “current state + 7”, and “current state−1” to “current state−7”. The temperature prediction model is executed for each case, and the error between the predicted temperature of each case and the target temperature when the cooling water valve is turned on / off, and the stability of the valve assuming the time from the previous change time of the valve. About degree, antecedent MSF1 and antecedent MSF2
And perform fuzzy inference based on this. That is, the minimum (MIN) processing and the maximum (MAX)
The process is executed, and the number of valves having the highest certainty factor is adopted as the determined value.

Next, a specific example will be described in detail. FIG. 5 shows the case where the elapsed time from the previous change in the number of valves is 2 seconds, and FIG. 6 shows the case where the elapsed time since the previous change in the number of valves is 4 seconds. Note that, for simplicity of explanation,
The number of valve-on cases will be illustrated only for three cases of “current state + 3”, “current state ± 0”, and “current state−3”.

In the case of FIG. 5, the antecedent MSF of “currently ± 0”
Only 1 has no change in confidence, in other cases the antecedent MSF
1 increases the confidence factor from 0.0 to 1.0 during the elapsed time of 1 to 3 seconds. The antecedent MSF2 changes in any case, but the change is gradual in the “current state ± 0 lines”. When the MIN is obtained for each case, the certainty of “the current state ± 0” is “1.0, 0.8, 0.
8 ", and the average of the certainty factors is the highest compared to the other cases (MAX). Therefore, the “current state ± 0” indicating the certainty factor indicating MAX is determined as the number of valve-on.

On the other hand, in FIG.
Looking at F1 after the elapse of 4 seconds, there is no change in the certainty factor. Further, in the antecedent MSF2, a change tendency similar to that in the case of FIG. 5 is observed. The MIN processing for this is
The certainty of “current state + 3” is “1.0, 1.0, 1.
0 ”,“ Present ± 0 ”confidence level is“ 1.0, 0.8,
0.8 ”and“ Present situation−3 ”are“ 1.0, 0.
4, 0.4 ". Therefore, the “current state + 3 pieces” in which the degree of certainty indicates MAX is determined as the number of valve-on pieces. Next, the number of valves ON determined by the number-of-valves-on determination unit 14 is set and output to the valve ON-OFF setting output unit 16, and the ON / OFF of each valve is controlled by the valve ON-OFF setting output unit 16.

As described above, the on / off of the valve is finally determined by evaluating the two evaluation indices by the foresight fuzzy, and the short-period valve is controlled while keeping the error from the target temperature within an allowable range. The change can be suppressed, the unsteady state as described above can be avoided, and a good control result can be obtained.

[0031]

As is apparent from the above, according to the present invention, a cooling apparatus for controlling a winding temperature by cooling a finish-rolled hot-rolled steel strip by cooling means is provided. The error between the predicted temperature and the target temperature when the water injection valve is opened and closed by the temperature estimation model, and the stability of the valve assuming the time from the previous change time of the valve and the valve stability as an evaluation index, the number of valves on by fuzzy inference. Since the determination is made, it is possible to suppress a short-cycle valve change while suppressing an error from the target temperature within an allowable range, and it is possible to improve the accuracy of model estimation. As a result, it is possible to avoid an unsteady state such as a valve response delay water injection pressure fluctuation. It is also possible to delay equipment deterioration.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a winding temperature control device that achieves a method of controlling a winding temperature of a hot-rolled steel strip according to the present invention.

FIG. 2 is an explanatory diagram showing membership function characteristics relating to stability evaluation.

FIG. 3 is an explanatory diagram showing membership function characteristics relating to temperature accuracy evaluation.

FIG. 4 is an explanatory diagram showing the principle of determining the valve-on number in the valve-on number determining unit of FIG. 1;

FIG. 5 is an explanatory diagram showing a valve-on number determination process in a case where the elapsed time from the previous change in the number of valves is 2 seconds.

FIG. 6 is an explanatory diagram showing a valve-on number determination process when the elapsed time from the previous change in the number of valves is 4 seconds.

FIG. 7 is a schematic diagram showing an example of a hot-rolled steel strip winding temperature control facility.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Finishing rolling mill 2 Finishing exit thermometer 3 Thickness gauge 4 Hot strip 5, 6 Cooling equipment 7 Cooling bank 8 Winding thermometer 9 Winding machine 10 Speed detector 11 Speed detector 12 Finishing exit coil piece temperature calculator 13 Coil piece temperature determination unit on run-out table 14 Number of valve ON determination unit 15 Valve ON-OFF actual result input unit 16 Valve ON-OFF setting output unit

Claims (1)

(57) [Claims] In a winding temperature control equipment for controlling a winding temperature by cooling a hot-rolled steel strip subjected to finish rolling by a cooling means, a cooling water injection valve is opened and closed by a temperature estimation model. Error between the predicted temperature and the target temperature,
And a method of controlling the winding temperature of the hot-rolled steel strip by fuzzy inference using as an evaluation index the time from the last change time of the valve and the assumed stability of the valve.