JPH07243015A - Plating deposition control method of continuous type hot dip metal coating line - Google Patents

Abstract

PURPOSE:To prevent generation of splashing and scumming and to deal with a remarkable change of a set plating deposition even during operation. CONSTITUTION:A nozzle jet pressure is set according to the set plating deposition, the pass speed of a steel strip and the nozzle spacing between gas-jetting nozzles and the steel strip at the time of controlling the plating deposition on the steel strip by blowing gas from the gas-jetting nozzles onto the surface of the steel strip past a molten metal bath. Feed forward control to set the height of the gas-jetting nozzle from the surface of the molten metal surface according to the set nozzle jet pressure, the set wating deposition, the pass speed of the steel strip and the nozzle spacing is executed. The nozzle jet pressure is corrected and set to eliminate the deviation between the set coating deposition and the actual coating deposition. Further, the feed back control to correct and set the nozzle height according to the corrected and set nozzle jet pressure, the set coating deposition, the pass speed of the steel strip and the nozzle spacing is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a steel strip (strip).
In a continuous hot-dip galvanizing line for continuously applying hot-dip galvanizing such as galvanizing, a gas such as nitrogen gas is injected from the gas injection nozzle onto the surface of the steel strip plated through the hot-dip galvanizing bath. The present invention relates to a plating adhesion amount control method for controlling the plating adhesion amount of molten metal onto a steel strip by spraying.

[0002]

2. Description of the Related Art In a continuous hot-dip galvanizing line, such as a hot-dip galvanizing line for producing galvanized steel sheets, for continuously performing hot-dip galvanizing on a steel strip, a hot-dip galvanizing bath is installed above A gas injection nozzle (wiping nozzle) is installed, and a gas such as nitrogen gas is blown from the gas injection nozzle toward the surface of the steel strip that has passed through the molten metal plating bath to determine the amount of molten metal plated on the steel strip. The gas wiping method of controlling is adopted.

In this gas wiping method, the amount of plating adhered is determined by the steel strip running speed (line speed) of the steel strip, the nozzle injection pressure (wiping gas pressure) from the gas injection nozzle to the steel strip, the gas injection nozzle and the steel strip. It changes depending on the interval between the and, plating bath temperature, etc. In addition, the actual measurement of the amount of deposited plating needs to be performed while the steel strip is sufficiently cooled by the amount of deposited plating meter, for example, about 100 m behind the gas injection nozzle, which causes a detection delay. For this reason, feedforward control including preset control is indispensable, and set plating deposits during steady operation where there is no change in the process amount such as the strip running speed, the distance between the gas jet nozzle and the steel strip, and the nozzle jet pressure. Feedback control is performed to cancel the deviation amount between the actual amount and the actual amount of plating applied, and the error due to the set value such as the nozzle injection pressure set by the feedforward control to obtain the set amount of plating applied is corrected. Has been done.

As a method for controlling the amount of plating adhered in such a continuous molten metal plating line, for example, Japanese Patent Publication No. 46-14521 discloses a gas injection nozzle and a steel according to the steel strip running speed. Feed-forward control that adjusts the gap between the strip and the nozzle injection pressure from the gas injection nozzle to the steel strip according to the measured plating adhesion amount, or the gap between the gas injection nozzle and the steel strip is adjusted. A combination of the feedback control and the feedback control is disclosed. Further, in Japanese Patent Publication No. 51-28263, the nozzle injection pressure and the nozzle height from the molten metal plating bath surface of the gas injection nozzle are adjusted according to the set plating deposition amount and the steel strip passing speed. Things are disclosed.

[0005]

In the former conventional method of the above-mentioned conventional techniques, the gas is changed in accordance with the set plating deposition amount, the nozzle injection pressure, the steel strip passing speed, and the distance between the gas injection nozzle and the steel strip. The height of the nozzle from the plating bath surface of the injection nozzle is not set. Therefore, depending on the nozzle spray pressure, if the nozzle height is too close to the plating bath surface, the sprayed gas that collides with the steel strip collides with the plating bath surface due to reflection and splashes the molten plating bath, and the splashed molten plating A splash phenomenon occurs in which the bath adheres to the steel strip surface. Conversely, if the nozzle height of the gas injection nozzle is too far from the plating bath surface, the molten metal plating on the surface of the steel strip will solidify depending on the steel strip passing speed, and the nozzle injection pressure will be insufficient and the plating will adhere. This causes a scraping phenomenon that the amount of thickness is not uniform in the width direction of the steel strip and becomes thicker at both ends in the width direction. Therefore, there is a problem that the product quality may be deteriorated.

Further, in the latter conventional method described above, the nozzle injection pressure and the nozzle height of the gas injection nozzle are also adjusted according to the change of the set plating deposition amount and the steel strip passing speed. Since the distance between the gas injection nozzle and the steel strip is constant, when the set plating deposition amount is changed significantly during operation, if the settings are changed only by the nozzle injection pressure and the nozzle height, the change of However, there is a problem that it is difficult to achieve the drastically changed set plating coating amount.

The present invention has been made to solve the above-mentioned problems, and a gas is sprayed from a gas injection nozzle onto a steel strip in a continuous molten metal plating line to combine feedforward control and feedback control. In addition to setting and adjusting the nozzle injection pressure in both feedforward control and feedback control when controlling the amount of plating applied to the steel strip so that it becomes the set amount of plating, gas injection By setting and adjusting the nozzle height from the plating bath surface of the nozzle as well, it is possible to prevent the occurrence of splashes and scraps and improve the product quality, and to significantly increase the set plating deposit amount during operation. To provide a method for controlling the amount of plating deposited on a continuous molten metal plating line that can accommodate various changes The target.

[0008]

In order to achieve the above-mentioned object, a method for controlling the amount of plating adhered to a continuous type molten metal plating line according to the present invention has a gas injection nozzle disposed above a molten metal plating bath, When spraying gas from the gas injection nozzle toward the surface of the steel strip that has passed through the molten metal plating bath, in controlling the amount of plating adhered to the steel strip of the molten metal so that it is the set amount of plating adhered,
Set the nozzle injection pressure to the steel strip from the gas injection nozzle according to the set plating adhesion amount, the steel strip passage speed and the interval between the gas injection nozzle and the steel strip, and the set nozzle injection pressure, setting Feed-forward control is performed to set the nozzle height from the molten metal plating bath surface of the gas injection nozzle according to the amount of plating adhered, the steel strip threading speed and the distance between the gas injection nozzle and the steel strip. In combination with control, the nozzle injection pressure from the gas injection nozzle to the steel strip is corrected and set so as to eliminate the deviation amount between the set plating adhesion amount and the actual plating adhesion amount, and the corrected and set nozzle injection is also performed. From the molten metal plating bath surface of the gas injection nozzle according to the pressure, the set coating amount, the steel strip passing speed, and the distance between the gas injection nozzle and the steel strip. It is characterized in that performing feedback control of setting correct the nozzle height.

[0009]

According to the method for controlling the amount of deposits in the continuous type molten metal plating line according to the present invention having the above-mentioned features, the nozzle injection pressure, the set amount of deposits, and the steel strip flow rate are controlled in both feedforward control and feedback control. By setting and adjusting the nozzle height from the molten metal plating bath surface of the gas injection nozzle according to the plate speed and the distance between the gas injection nozzle and the steel strip, it is possible to prevent the occurrence of splashing and scraping. . In addition, by comprehensively setting and adjusting the three factors, the nozzle injection pressure, the distance between the gas injection nozzle and the steel strip, and the nozzle height of the gas injection nozzle, it is possible to significantly change the set plating deposition amount during operation. Can also respond.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an apparatus for carrying out the method for controlling the amount of plating deposit according to the present invention.
In FIG. 1, 1 is a steel strip and 2 is a hot dip galvanizing bath in which a hot dip galvanizing bath is stored. 3a and 3b are steel strips 1
Is a gas injection nozzle for adjusting the adhesion amount of the molten zinc that has adhered to the gas. The gas injection nozzles 3a and 3b are gas (for example, nitrogen gas) toward the surface of the steel strip 1 that has passed through the hot dip galvanizing bath 2. The amount of plating adhered on the steel strip 1 (the amount of zinc adhered) is adjusted by spraying
It is arranged above the hot-dip galvanizing bath 2 near the steel strip outlet.

Reference numerals 4a and 4b are pressure adjusting valves for adjusting the nozzle injection pressures of the gas injection nozzles 3a and 3b. Reference numerals 5 are for adjusting the valve openings of the pressure adjusting valves 4a and 4b so that the nozzle injection pressure becomes the set value. The pressure regulator 6 is a pressure transmitter for measuring the nozzle injection pressure.

Further, 7a, 7b are gas injection nozzles 3a,
3b is moved horizontally to move the gas injection nozzle 3
Nozzle interval adjuster for adjusting the distance between the steel strips 1 and 3b and the steel strip 1 to the set value, 8 is the gas injection nozzles 3a and 3
It is a nozzle interval measuring device for measuring the interval between b and the steel strip 1. Nozzle height adjusters 9a and 9b adjust the height position which is the nozzle height from the hot-dip galvanizing bath surface of the gas injection nozzles 3a and 3b to the set value, and 10 measures the height position. This is a nozzle height measuring device.

Reference numeral 11 denotes a plate thermometer which is arranged on the inlet side of the hot dip galvanizing bath 2 and measures the temperature of the steel plate 1 entering the pot.
Reference numeral 2 is a bath thermometer for measuring the temperature of the hot-dip galvanizing bath in the hot-dip galvanizing bath 2. Further, 13 is disposed about 100 m behind the position where the gas injection nozzles 3a and 3b are disposed,
A plating adhesion meter (thickness meter) for measuring the plating adhesion amount (plating thickness) of the steel strip 1, 14 is connected to a bridle roll rotating in contact with the steel strip 1 to measure the movement amount of the steel strip 1 in the longitudinal direction. A pulse generator for the operation, 15 is a pulse generator 1
4 is a speed converter that converts the output of No. 4 into a signal indicating the speed and measures the steel strip running speed of the steel strip 1.

Reference numeral 20 denotes a manufacturing condition setting device for setting manufacturing conditions such as a set plating deposit amount, and a set plating deposit amount (plating deposit amount set value) 31 as a control input from the manufacturing condition setting device 20. Feedback control device 2
1. Adhesion amount prediction feedforward control device 22, feedforward control device 23, and preset control device 24. These control devices 21 to 24 and the sequential learning calculation device 25 described later are C
It is configured by a programmed computer having a PU, a memory, an input / output interface and the like.

The preset controller 24 obtains initial set values corresponding to the change of the set plating deposit amount when the set plating deposit amount is changed by the type change, and outputs them. Set value 36
d, the set value 37d of the distance between the gas injection nozzles 3a and 3b and the steel strip 1 (hereinafter, simply referred to as the nozzle distance) is obtained, and these values and the set plating deposit amount 31 and the output from the speed converter 15 are obtained. The set value 38d of the nozzle height (the height position from the hot-dip galvanizing bath surface of the gas injection nozzles 3a, 3b) at which splashing or scraping does not occur is obtained and controlled according to the steel strip passing speed measured value 34. As an output, the nozzle injection pressure set value 36d is output to the pressure adjuster 5, and the nozzle interval set value 3 is output to the nozzle interval adjusters 7a and 7b.
7d, and the nozzle height set value 38d is output to the nozzle height adjusters 9a and 9b.

The feedback control device 21 obtains the nozzle injection pressure and the nozzle interval for eliminating the deviation amount between the set plating deposit amount 31 and the plating deposit amount actually measured value 32 which is the output from the plating deposit amount meter 13, and at the same time, obtains these values. The nozzle height at which splashing or scraping does not occur is obtained according to the value and the set plating adhesion amount 31 and the steel strip passing speed measured value 34, and the nozzle injection pressure set value 36a is set to the pressure regulator 5 as a control output. Output, nozzle interval adjusters 7a, 7
The nozzle interval set value 37a is output to b, and the nozzle height set value 38a is output to the nozzle height adjusters 9a and 9b. Such a feedback control device 21
Feedback control by means of the steel strip moving speed, the distance between the gas jet nozzle and the steel strip, and the amount of movement of the steel strip that is the output from the pulse generator 14 during steady operation without changing the process amount such as the nozzle injection pressure. It is designed to be performed for each steel strip length preset based on 33 (for example, for every 100 m).

The feed-forward control device 23 is arranged to eliminate the deviation of the plating adhesion amount caused by the change when the process amount (for example, steel strip passing speed) is changed, that is, the process amount (for example, steel). The nozzle spray pressure and the nozzle interval are calculated so that the current measured values of the amount of adhered plating before changing the strip passing speed) are maintained, and these values and the set amount of adhered plating 31 and the steel strip passing speed are actually measured. According to the value 34, the nozzle height at which splashing or scraping does not occur is obtained, and the nozzle injection pressure set value 36c is output to the pressure adjuster 5 as a control output, and the nozzle interval setters 7a and 7b are set. The value 37c is output, and the nozzle height set value 38c is output to the nozzle height adjusters 9a and 9b.

Adhesion amount prediction feedforward controller 2
No. 2 is a nozzle injection pressure that eliminates a predicted deviation amount that is a deviation between the predicted plating adhesion amount calculation value and the set plating adhesion amount 31 when the process amount is changed and a predicted value of the plating adhesion amount is obtained. In addition to obtaining the nozzle interval, the nozzle height at which splashing or scraping does not occur is obtained according to these values and the set plating adhesion amount 31 and the steel strip passing speed measured value 34, and the pressure adjuster 5 is used as the control output. To the nozzle interval adjusters 7a and 7b, and to the nozzle height adjusters 9a and 9b.
b is output. It should be noted that this feed amount prediction feedforward control device 22 uses the measured plating deposit amount 32 and the set plating deposit amount 31 when the process amount is changed.
When the deviation is within a permissible range, the feedforward control device 23 operates.

The successive learning calculation device 25 measures the measured values of the predetermined process amount for each preset steel strip length (nozzle injection pressure measured value 39, nozzle interval measured value 40, steel strip running speed measured value 34, The plating bath temperature actually measured value 42 and the pot entry plate temperature actually measured value 43) are sampled and accumulated, and
A learning coefficient for measuring the plating adhesion amount on the steel strip 1 at the time of sampling and learning-calculating the plating adhesion amount on the steel strip 1 based on the actual measurement value of the plating adhesion amount and a predetermined process amount as described later. α (indicated by reference numeral 35 in FIG. 1)
Is given to each of the control devices 21 to 24. The learning coefficient α is used to enhance the control accuracy of the control devices 21 to 24, and is used in the later-described plating adhesion amount model formula used to determine the nozzle injection pressure and the like in these control devices 21 to 24. It is included.

The preset control device 24, the feedforward control device 23 and the feed amount prediction feed forward control device 22 adjust the nozzle injection pressure, the nozzle spacing and the nozzle injection pressure so that the amount of plating attached to the steel strip 1 will be the set amount of plating. Feedforward control for setting the nozzle height is performed, and by the feedback control device 21,
Feedback control is performed to correct and set the nozzle spray pressure, the nozzle interval, and the nozzle height so that the deviation amount between the set plating deposit amount and the actual plating deposit amount is eliminated.

Next, the method for controlling the amount of plating deposited according to the present invention, which is carried out by using the apparatus thus constructed, will be described. The steel strip 1 is guided to a hot dip galvanizing bath 2 through a continuous annealing furnace, Snout (not shown),
With the molten zinc adhered to be plated, the gas jet nozzles 3a and 3b wipe the zinc to a desired amount. Here, when the plating adhesion amount to the steel strip 1 is changed by the product type switching, the changed set plating adhesion amount 31 is used as a control input from the manufacturing condition setting device 20.
Are provided to the respective control devices 21 to 24. In response to this set plating adhesion amount 31, the preset control device 24 obtains the nozzle injection pressure, the nozzle interval, and the nozzle height so that the plating adhesion amount on the steel strip 1 becomes the changed set plating adhesion amount. , The set values will be output.

Here, the above-mentioned plating adhesion amount model formula will be described. Plating adhesion amount W (g / m ² ), steel strip passing speed V (m / min), nozzle injection pressure P (kgf / cm
² ), the distance between the gas injection nozzle and the steel strip (nozzle distance) d
(Mm), the plating bath temperature T ₁ (° C.), and the pot entry plate temperature T ₂ (° C.) are represented by the following formula, which is a model formula of the amount of adhered plating.

[0023]

[Equation 1]

Where α is a learning coefficient, a₀~ A_FiveIs a model
Is a constant. Model constant a₀~ A _FiveA number of past
It is the value obtained by multiple regression from the actual operation data.
It is decided appropriately in the manufacturing equipment.

In the preset control device 24, first,
In the equation, W is a set plating adhesion amount 31, V is a steel strip running speed measured value 34, d is a nozzle interval measured value 40,
The actual measured value 42 of the plating bath temperature is substituted for T ₁ , and the actual measured value 43 of the pot entrance plate temperature is substituted for T ₂ , respectively, to obtain the nozzle injection pressure set value 36d by calculation and output it.
In this case, the calculated nozzle injection pressure set value is the upper limit value of the adjustable pressure of the pressure adjuster 5 (for example, 1.8 kgf /
cm ² ), the upper limit value is output as the nozzle injection pressure set value 36d instead of the calculated nozzle injection pressure set value, and the lower limit value of the adjustable pressure of the pressure adjuster 5 (for example, 0. When it is less than 4 kgf / cm ² ), the lower limit value is output as the nozzle injection pressure set value 36d instead of the calculated nozzle injection pressure set value.

In this way, since the calculated nozzle injection pressure set value is out of the adjustable pressure range, the upper limit value or the lower limit value of the adjustable pressure of the pressure regulator 5 is set as the nozzle injection pressure set value 36d. When outputting, the calculation for obtaining the nozzle interval set value for achieving the set plating adhesion amount 31 is performed.

[0027]

[Equation 2]

Here, the equation is obtained by partially differentiating the equation with respect to the nozzle spacing d. If the deviation amount between the calculated nozzle injection pressure set value and the upper limit value or the lower limit value of the adjustable pressure is ΔP, then ∂P / ∂
By multiplying the reciprocal of d by ΔP, the nozzle spacing correction value Δ indicating how much the nozzle spacing should be changed from its current value in order to achieve the set plating deposition amount 31.
d is calculated. The calculated nozzle interval correction value Δ
The nozzle interval set value 37d is obtained by adding d to the previous nozzle interval set value that is the current value, and this is output. When the calculated nozzle injection pressure setting value is within the adjustable pressure range of the pressure adjuster 5, the nozzle interval setting value 37d is set to the same value as the previous setting value. Has become.

Then, the preset control device 24 determines the gas according to the set plating adhesion amount 31, the steel strip passage speed measured value 34, the nozzle injection pressure set value 36d and the nozzle interval set value 37d set as described above. Injection nozzle 3a,
The set value of the nozzle height of 3b is obtained and this nozzle height set value 38d is output. A nozzle height setting data table is stored in the memories of the preset control device 24 and the other control devices 21 to 23. This nozzle height setting data table is obtained by analyzing the past operation data to determine the proper wiping condition,
(A) A data table showing the relationship between the nozzle height and the nozzle spray pressure satisfying the proper wiping range, (b) a data table showing the relationship between the nozzle height and the plating adhesion amount satisfying the proper wiping range, and (c) the proper wiping range. It is composed of a data table showing the relationship between the nozzle height satisfying the above conditions and the steel strip passing speed, and (d) a data table showing the relationship between the nozzle height satisfying the appropriate wiping range and the nozzle spacing. The data table in (a) above is for a case where the plating adhesion amount, the steel strip passing speed, and the nozzle interval are within a certain range as parameters, and the data table in (b) above is for the nozzle injection pressure and steel. The data table in (c) above is obtained when the banding plate speed and the nozzle interval are set to constant ranges as parameters.
The data is shown when the nozzle spray pressure, the plating deposition amount, and the nozzle interval are set as constant parameters, and the data table in (d) above has the nozzle spray pressure, the plating deposition amount, and the strip running speed as constant parameters. It is the one when it was turned on. FIG. 3 is a diagram showing an example of the relationship between the nozzle height and the nozzle injection pressure that satisfy the appropriate wiping range.

The preset control device 24 searches the nozzle height setting data table by using the nozzle injection pressure setting value 36d, the nozzle interval setting value 37d, the set plating deposition amount 31 and the steel strip passing speed measured value 34 as keys. Then, the nozzle height is determined within the proper wiping range in which no splash or dust is generated.
8d is output to the nozzle height adjusters 9a and 9b.

When the preset control device 24 sets the set values 36d, 37d, 38d in this way, the feedback control device 21 operates next. Here, prior to the explanation, the sequential learning calculation device will be described. 25 will be described.

In the sequential learning calculation device 25, when the learning coefficient α is set to α = 1, the above formula is applied to the following equation: plating adhesion amount W, steel strip passing speed V, nozzle interval d, plating bath temperature T ₁ , and pot entry. The nozzle injection pressure calculated value P _cal is obtained by substituting the actual measured values of the plate temperature T ₂ . The learning coefficient instantaneous value β shown by the following formula is obtained by taking the ratio of the calculated nozzle injection pressure value P _cal and the actual measured value P _{act of the} nozzle injection pressure (actually measured value of nozzle injection pressure 39). The value β,
Using the exponential smoothing gain γ, the learning coefficient α shown by the following equation is obtained. This learning coefficient α is set in each of the control devices 21 to 24.
And is used as a learning coefficient of the plating adhesion amount model equation. It should be noted that α'in the following equation is the previous learning coefficient.

Β = P _act / P _cal ... α = α '+ γ × (β-α')

The feedback control device 21 controls the deviation amount ΔW between the set plating adhesion amount 31 and the plating adhesion amount actually measured value 32.
To eliminate the nozzle injection pressure and nozzle spacing,
The nozzle injection pressure set value 36a and the nozzle interval set value 37a are output, and the nozzle height is determined according to these values and the set plating adhesion amount 31 and the steel strip passing speed measured value 34, and the nozzle height setting is performed. The value 38a is output. At this time, when the set plating adhesion amount 31 is W _set and the plating adhesion amount actual value 32 is W _act , the deviation amount ΔW is
Is calculated by the following formula.

[0035]

[Equation 3]

Here, the formula is obtained by partially differentiating the formula with respect to the plating adhesion amount W, and this influence coefficient ∂P / ∂
The correction value ΔP of the nozzle injection pressure is obtained by multiplying W by the deviation amount ΔW obtained by the equation. Then, the nozzle injection pressure correction value ΔP is added to the previous nozzle injection pressure setting value to obtain the nozzle injection pressure setting value 36a, which is output.

In this case, when the calculated nozzle injection pressure set value exceeds the upper limit value of the adjustable pressure of the pressure adjuster 5, the upper limit value is set instead of the calculated nozzle injection pressure set value. The nozzle injection pressure set value 36a is output, and when the value is below the lower limit value of the adjustable pressure of the pressure adjuster 5, the lower limit value is output as the nozzle injection pressure set value 36a instead of the calculated nozzle injection pressure set value. . In this way, when the calculated nozzle injection pressure set value deviates from the adjustable pressure range, the upper limit value or the lower limit value of the adjustable pressure of the pressure adjuster 5 is output as the nozzle injection pressure set value 36a. Is a calculation for obtaining a nozzle interval set value for eliminating the deviation of the amount of plating adhered due to this.

The procedure for obtaining the nozzle interval set value will be described. The equation is partially differentiated with respect to the nozzle interval d to obtain the influence coefficient ∂P / ∂d, and the calculated nozzle injection pressure set value and the adjustable pressure are calculated. When the deviation amount from the upper limit value or the lower limit value is ΔP, the reciprocal number of the influence coefficient ∂P / ∂d is multiplied by ΔP to obtain the correction value Δd of the nozzle interval. Then, this nozzle interval correction value Δd is added to the previous nozzle interval setting value to obtain the nozzle interval setting value 3
7a is obtained and this is output. When the calculated nozzle injection pressure set value is within the adjustable pressure range of the pressure adjuster 5, the nozzle interval set value 37a is set to the same value as the previous set value. Has become.

Then, the feedback control device 21 causes the nozzle injection pressure set value 36 thus corrected and set.
a and the nozzle interval set value 37a, and the set plating adhesion amount 31 and the steel strip passing speed measured value 34 are used as keys to search the nozzle height setting data table, and proper wiping that does not cause splashing or scraping The nozzle height is determined within the range, and this nozzle height set value 38a is set.
Is output to the nozzle height adjusters 9a and 9b.

When the process amount is changed during the steady operation by the feedback control device 21 as described above,
The feedforward control device 23 operates. The feed-forward control device 23 determines the nozzle injection pressure and the nozzle interval so as to maintain the current plating adhesion amount measured value before the change by eliminating the deviation of the plating adhesion amount due to the change of the process amount, and set the nozzle injection pressure set value. 36c and the nozzle interval set value 37c are output, the nozzle height is determined according to these values, the set plating deposition amount 31 and the steel strip strip speed actual measurement value 34, and the nozzle height set value 38c is output.

For example, when the strip running speed is changed, the feedforward control device 23 partially differentiates the formula with respect to the strip running speed V to obtain the influence coefficient ∂P / ∂V, and the influence coefficient ∂P. The correction value ΔP of the nozzle injection pressure is obtained by multiplying / ∂V by the change amount (change amount) ΔV of the steel strip passing speed. Then, the nozzle injection pressure correction value ΔP is added to the previous nozzle injection pressure setting value to obtain the nozzle injection pressure setting value 36c, which is output. As another process amount, for example, when the nozzle spacing is changed, the equation is partially differentiated with respect to the nozzle spacing d to obtain the influence coefficient ∂P / ∂d, and the influence coefficient ∂P / ∂d is
The correction value ΔP of the nozzle injection pressure can be obtained by multiplying the change amount (change amount) Δd of the nozzle interval.

When the calculated nozzle injection pressure set value exceeds the upper limit value of the adjustable pressure of the pressure regulator 5, the nozzle upper limit value is used instead of the calculated nozzle injection pressure set value. When it is output as the injection pressure set value 36c and is below the lower limit value of the adjustable pressure of the pressure regulator 5, the lower limit value is output as the nozzle injection pressure set value 36c instead of the calculated nozzle injection pressure set value. In this way, when the calculated nozzle injection pressure set value is out of the adjustable pressure range, the upper limit value or the lower limit value of the adjustable pressure of the pressure adjuster 5 is output as the nozzle injection pressure set value 36c. Is a calculation for obtaining a nozzle interval set value for eliminating the deviation of the amount of plating adhered due to this.

The procedure for obtaining the nozzle interval set value will be described. The equation is partially differentiated with respect to the nozzle interval d to obtain the influence coefficient ∂P / ∂d, and the calculated nozzle injection pressure set value and the adjustable pressure are calculated. When the deviation amount from the upper limit value or the lower limit value is ΔP, the reciprocal of the influence coefficient ∂P / ∂d is multiplied by the ΔP to obtain the correction value Δd of the nozzle interval. Then, this nozzle interval correction value Δd is added to the previous nozzle interval setting value to obtain the nozzle interval setting value 3
7c is obtained and this is output. When the calculated nozzle injection pressure set value is within the adjustable pressure range of the pressure adjuster 5, the nozzle interval set value 37c is set to the same value as the previous set value. Has become.

Then, the feedforward controller 23
Is the nozzle height setting data using the nozzle spray pressure setting value 36c and the nozzle interval setting value 37c corrected in this way, the set plating adhesion amount 31 and the steel strip passing speed measured value 34 as keys. The table is searched to determine the nozzle height within the proper wiping range in which splashing or scraping does not occur, and this nozzle height set value 38c is output to the nozzle height adjusters 9a and 9b.

On the other hand, if the process amount is changed during the steady operation by the feedback control device 21 and the deviation between the measured actual plating deposition amount and the set plating deposition amount is large, the deposition amount predicting feedforward control device 22
Works. The feedforward control device 23 obtains the predicted value W _cal of the plating deposit amount at that time by using the following formula obtained by modifying the formula, and obtains the set plating deposit amount W _set (set plating deposit amount 31). A predicted deviation amount ΔW, which is a deviation from the calculated plating adhesion amount predicted calculation value W _cal, is calculated.

[0046]

[Equation 4]

Then, the predicted deviation amount Δ is given to the influence coefficient ∂P / ∂W obtained by partially differentiating the formula with respect to the plating adhesion amount W.
By multiplying by W, the correction value ΔP of the nozzle injection pressure is obtained. Then, the nozzle injection pressure correction value ΔP is added to the previous nozzle injection pressure setting value to obtain the nozzle injection pressure setting value 36b, which is output.

In this case, when the calculated nozzle injection pressure set value exceeds the upper limit value of the adjustable pressure of the pressure adjuster 5, the upper limit value is used instead of the calculated nozzle injection pressure set value. The nozzle injection pressure set value 36b is output, and when it is below the lower limit value of the adjustable pressure of the pressure regulator 5, the lower limit value is output as the nozzle injection pressure set value 36b instead of the calculated nozzle injection pressure set value. . In this way, when the calculated nozzle injection pressure set value deviates from the adjustable pressure range, the upper limit value or the lower limit value of the adjustable pressure of the pressure regulator 5 is output as the nozzle injection pressure set value 36b. Is a calculation for obtaining a nozzle interval set value for eliminating the deviation of the amount of plating adhered due to this.

The procedure for obtaining the nozzle interval set value will be described. The equation is partially differentiated with respect to the nozzle interval d to obtain the influence coefficient ∂P / ∂d, and the calculated nozzle injection pressure set value and the adjustable pressure are calculated. When the deviation amount from the upper limit value or the lower limit value is ΔP, the reciprocal of the influence coefficient ∂P / ∂d is multiplied by the ΔP to obtain the correction value Δd of the nozzle interval. Then, this nozzle interval correction value Δd is added to the previous nozzle interval setting value to obtain the nozzle interval setting value 3
7b is obtained and this is output. When the calculated nozzle injection pressure setting value is within the adjustable pressure range of the pressure adjuster 5, the nozzle interval setting value 37b is set to the same value as the previous setting value. Has become.

Then, the deposit amount feedforward controller 22 corrects the nozzle injection pressure set value 36b and the nozzle interval set value 37b thus corrected, the set deposit amount 31 and the actually measured strip running speed 34. Using the and keys as keys, the nozzle height setting data table is searched to determine the nozzle height within an appropriate wiping range in which splashing or scraping does not occur, and this nozzle height setting value 38b is used as the nozzle height adjuster. It outputs to 9a and 9b.

As a result, according to the method for controlling the amount of deposits in the continuous molten metal plating line according to the present invention, the nozzle injection pressure and the distance between the gas injection nozzle and the steel strip are controlled in both feedforward control and feedback control. In addition to setting and adjusting, the nozzle height from the plating bath surface of the gas injection nozzle is also set and adjusted, so that the occurrence of splash and scrap is prevented and product quality is improved. In addition to being able to improve, it is possible to set the plating pressure during operation by comprehensively setting and adjusting the three factors of the nozzle spray pressure, the distance between the gas spray nozzle and the steel strip, and the nozzle height of the gas spray nozzle. It is possible to cope with a large change in quantity.

In order to confirm the effect of the method for controlling the amount of plating applied according to the present invention, in a continuous hot dip galvanizing line, the thickness of the steel strip is 0.5 mm and the width of the steel strip is 900 m.
m, steel strip passing speed 90 m / min, set plating adhesion amount 120
→ This method was applied under the operating condition of 45 g / m ² . As a result, as shown in FIG. 2, the preset control device 24 performs preset control for changing the set plating deposition amount, setting the nozzle injection pressure, setting the gap between the gas injection nozzle and the steel strip, and the gas injection nozzle. When the nozzle height is set and then the nozzle injection pressure is corrected and set by the feedback control by the feedback control device 21, the set plating deposition amount can be achieved. Further, since the preset height is set to increase the nozzle height, it is possible to prevent the occurrence of splash even if the distance between the gas injection nozzle and the steel strip is narrowed and the nozzle injection pressure is increased.

[0053]

As described above, according to the method for controlling the amount of plating adhered in the continuous molten metal plating line according to the present invention, gas is sprayed from the gas injection nozzle onto the surface of the steel strip that has passed through the molten metal plating bath to feed the strip. When controlling the amount of plating adhered to the steel strip so that it becomes the set amount of plating adherence by combining the forward control and the feedback control, the nozzle injection pressure etc. are set in both the feedforward control and the feedback control. In addition to the adjustment, the nozzle height from the plating bath surface of the gas injection nozzle is also set and adjusted, so it is possible to prevent the generation of splashes and scraps and improve product quality. The nozzle injection pressure, the distance between the gas injection nozzle and the steel strip, and the nozzle height of the gas injection nozzle. By adjusting set comprehensively the tripartite, it is possible to cope with the significant changes of the setting coating weight in the operation.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an apparatus for carrying out a plating adhesion amount control method according to the present invention.

FIG. 2 is a diagram for explaining a control state according to a plating adhesion amount control method of the present invention.

FIG. 3 is a diagram showing an example of a relationship between a nozzle height and a nozzle injection pressure that satisfy an appropriate wiping range.

FIG. 4 is a diagram for explaining a conventional technique and is a diagram showing an example of a controllable range of a plating deposition amount (zinc deposition amount) when a nozzle injection pressure and a nozzle height are manipulated.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Steel strip 2 ... Hot dip galvanizing bath 3a, 3b ... Gas injection nozzle 4a, 4b ... Pressure regulating valve 5 ... Pressure regulator 6 ... Pressure transmitter 7a, 7b ... Nozzle interval regulator 8
... Nozzle interval measuring device 9a, 9b ... Nozzle height adjuster
10 ... Nozzle height measuring instrument 11 ... Plate thermometer 12 ... Bath thermometer 13 ... Plating adhesion amount meter 14 ... Pulse transmitter 15 ...
Speed converter 20 ... Manufacturing condition setting device 21 ... Feedback control device 22 ... Adhesion amount prediction feedforward control device 23 ... Feedforward control device 24 ...
Preset control device 25 ... Sequential learning calculation device

Claims (1)

[Claims] 1. A molten metal steel strip, wherein a gas jet nozzle is disposed above the molten metal plating bath, and gas is blown from the gas jet nozzle toward the surface of the steel strip that has passed through the molten metal plating bath. When controlling the amount of plating adhered to the set amount of plating to be set, the amount of applied plating, the speed of passing the steel strip, and the distance from the gas jet nozzle to the steel strip depending on the distance between the gas jet nozzle and the steel strip. The nozzle injection pressure to the steel strip is set, and the set nozzle injection pressure, set plating deposition amount, steel strip passage speed, and molten metal of the gas injection nozzle according to the distance between the gas injection nozzle and the steel strip. Feed-forward control that sets the nozzle height from the plating bath surface is performed, and in combination with this feed-forward control, the amount of deviation between the set plating deposition amount and the actual plating deposition amount In order to eliminate the above, the nozzle injection pressure from the gas injection nozzle to the steel strip is corrected and set, and the corrected and set nozzle injection pressure, set plating adhesion amount, steel strip passing speed, and the gas injection nozzle and the steel strip are set. And a feedback control for correcting and setting the height of the gas injection nozzle from the surface of the molten metal plating bath of the gas injection nozzle.