JPH0192349A - Device for controlling molten metal plating amount - Google Patents

Abstract

PURPOSE:To uniformly plate the whole surface of a long-sized band steel in desired amts. by providing a plated metal amt. meter directly above a wiping nozzle and a crosswise plated metal amt. meter on the downstream side, and feedback-controlling the nozzle pressure and the distance from the band steel based on the measured values at the time of plating the band steel with molten metal. CONSTITUTION:The band steel 1 is passed through the inside of a molten metal plating bath 2, and the molten metal plating amt. is adjusted by the injection of the gases from the wiping nozzles 3 and 3. The plated metal amt. meter 7 is provided above the nozzle 3, the measured value is inputted to a feedback controller 12 and a feedback characteristic compensator 15, the measured value from the crosswise plated metal amt. meter 18 is also inputted to the compensator 15, both measured values are compared, and the resulting compensated value is inputted to the controller 12. As a result, the distance between the wiping nozzle 3 and the band steel 1 and the pressure of the gas injected from the nozzle 3 are controlled by an adjusting valve 4, and the desired amt. of the plating layer is uniformly formed in the lengthwise and cross wise directions of the band steel 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for controlling the amount of plating to a target value when plating a steel strip surface with molten metal such as zinc plating.

[Prior Art] Conventionally, for example, as described below, a coating amount control device for continuous hot-dip galvanizing has been provided with a wiping nozzle near the bath surface of a galvanizing bathtub, and the wiping nozzle is activated according to the measured coating amount. This is done by adjusting the wiping pressure or the distance between the wiping nozzle and the steel strip. For example, (1) Japanese Patent Publication No. 48-14521 discloses feedforward control that adjusts the distance between the wiping nozzle and the steel strip according to the passing speed of the steel strip, and the wiping pressure or A device that combines feedback control to adjust the distance between the wiping nozzle and the steel strip. A device that combines feedback control that adjusts the wiping pressure according to the deviation of the measured adhesion amount and feedforward control that adjusts the wiping pressure according to the target adhesion■ and the steel strip threading speed, (3) JP-A-52 In the -60238 publication, the above (1)
, (2), a device for correcting the feedforward control output based on the measured values of the coating amount, the steel strip threading speed, the wiping pressure, and the distance between the wiping nozzle and the steel strip; (4) JP-A-5F3 No.-134EtS discloses a method of performing feedbank control in which the amount of plating deposited at the center and both ends of the steel strip in the width direction is actually measured and the wiping pressure is adjusted according to these values.

[Problems to be Solved by the Invention] Among the above-mentioned conventional techniques, the apparatuses (1) to (3) all measure plating adhesion at the center of the steel strip in the width direction using one plating adhesion meter. Feedback control and feedforward control are performed by actually measuring the amount. However, according to the JIS standard, the amount of coating on galvanized steel sheets is 3 at the center and at both ends.
Quality is supposed to be guaranteed based on the point average value, but these conventional techniques do not measure the amount of plating deposited in the width direction, so it is not possible to ensure product quality sufficiently.

In addition, in the conventional technique (4) above, it takes several tens of seconds to scan the plating thickness meter in the board width direction, which increases the wasted time in the feedback control loop and increases the control gain. The problem is that it becomes impossible to do so.

The present invention is intended to solve the above-mentioned problems, and aims to realize coating amount control with excellent responsiveness, stability, and reliability in terms of product quality assurance.

Means for Solving the Problems] In order to solve the above problems, the present invention provides an apparatus for controlling the amount of plating deposited by providing a wiping nozzle near the outlet of the steel strip above the molten metal plating bath. A coating amount meter directly above the nozzle that detects the amount of plating deposited directly above the nozzle, a width direction coating amount meter that is installed downstream from the nozzle and detecting the amount of plating deposited in the width direction of the steel strip, and a coating amount meter directly above the nozzle. A feedback control device that controls the distance between the wiping nozzle and the adjustment belt and/or the wiping pressure of the wiping nozzle based on the detection results, and the detection results of the coating amount meter directly above the nozzle and the coating amount meter in the width direction are compared and The molten metal plating adhesion amount control device is characterized in that it includes a feedback characteristic compensator that outputs a correction calculation output to the feedback control device according to a comparison result.

[Function] According to the present invention, by feedback-controlling the amount of plating deposited based on the detection result of the deposit amount meter directly above the nozzle, wasted time in the control loop is eliminated (and the amount of plating deposited directly above the nozzle is controlled in the width direction). By comparing and comparing the detection results of the coating amount meters and outputting correction calculations to the feedback control device according to the comparison results, molten metal can be controlled with excellent accuracy in controlling the coating amount in the longitudinal and width directions of the steel strip. A plated steel strip can be produced.

[Example code] Hereinafter, the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a schematic configuration diagram showing a typical embodiment of the present invention. In the figure, 1 is a steel strip to be plated, 2 is a hot-dip plating bath, 3 is a wiping nozzle for adjusting the amount of molten metal attached to the steel strip, 4 is a pressure regulating valve for adjusting the wiping pressure, and 5 is a pressure regulating valve. A nozzle spacing adjuster moves the position of the wiping nozzle to adjust the distance between the wiping nozzle 3 and the steel strip 1, and 6 is a pressure regulator that adjusts the valve opening of the pressure regulating valve 4 so that the wiping pressure reaches a set value. A regulator, 7, is installed directly above the wiping nozzle and measures the amount of unsolidified plating deposited directly above the nozzle, and 8 is installed on the downstream side to measure the amount of solidified plating deposited in the width direction. 9 is a pulse transmitter that measures the longitudinal movement of the steel strip 1; 10 is a speed converter that converts the output of the pulse transmitter 9 into speed; 11 is a manipulated variable selector; 12 is a feedback The control device includes a preset control device 13, a feedforward control device 14, a feedback characteristic compensation device 15, and a manufacturing condition setting device 16 such as a host process computer.

The processing procedure of the apparatus of the present invention with such a configuration will be explained below.

The steel strip 1 passes through a continuous annealing furnace and a snout (not shown), is led to a plating bath 2, and is wiped to a desired amount by a wiping nozzle 3 with molten metal to be plated attached thereto. The amount of plating deposited on the wiped steel strip 1 is measured in an unsolidified state by a deposit meter 7 directly above the nozzle, and is inputted to the feedback control device 12 and the feedback characteristic compensator 15 as Wh. Here, the adhesion amount detection results are sampled at predetermined time intervals (for example, every second), averaged for each predetermined length of the steel strip (for example, every 10 m), and stored in a memory buffer. It is tracked according to the longitudinal movement of the steel strip 1 until it reaches the position of the meter, and is used as a value Wh2 that is matched with the installation position of the width direction adhesion meter 8 in the control calculation described later.

In addition, the width direction coating weight meter 8 on the downstream side moves in the width direction of the steel strip 1 and measures the coating weight at the center and both ends (for example, a position 50 mm from the edge of the plate), and measures the coating weight at these three points. A value Wc obtained by calculating the average value of the measured values is manually inputted to the feedback characteristic compensator 15. Although the width direction adhesion meter 8 is described here as measuring at three points in the width direction, it may be configured to measure at any plurality of points as necessary.

Further, the moving length and moving speed of the steel strip 1 are measured by a pulse transmitter 9 and a speed converter 10 provided on a measuring roll that rotates in contact with the steel strip 1, respectively, and are measured by a feed bank control device 12. , a feedback characteristic compensator 15, and a feedforward control device 14.

The feedback control device 12 includes a coating amount meter 7 directly above the nozzle.
Feedback calculation is performed based on the current detection signal Wh of , the distance D between the steel strip 1 and the wiping nozzle 3 (hereinafter referred to as the nozzle distance), the injection pressure P of the wiping nozzle 3 (
(hereinafter referred to as wiping pressure) is calculated and output to the manipulated variable selector 11.

Here, the method of outputting the adhesion amount target value Wr or D
It does not matter which method of outputting the output correction value, such as CN PC, is adopted. Both procedures will be explained below.

First, a method of outputting an output correction value such as DClPC will be explained. In the feedback characteristic compensator 15, a value W h obtained by tracking the detection signal of the adhesion meter 7 directly above the nozzle to the position where the width direction adhesion meter 8 on the downstream side is provided according to the length of movement in the longitudinal direction of the steel strip 1. 2. The output correction value Dc1Pc is calculated by the feedback control device 12 by calculating the detection signal Wc1 of the width direction material M plate meter 8 and the adhesion amount target value Ws set from the manufacturing condition setting device 18 according to the procedure described below. Output to.

First, MffiW with plating (g/+/), moving speed V (m/min) of steel strip 1, wiping pressure P (kg/c♂
), the relationship between nozzle spacing D (mm) is generally as shown below (1)
It is shown by the formula.

W=aXVbXD0XPd+e −−−−−−−(1
) However, a: constant (a≧O), b=constant (b≧0), C: constant (C≧0), d: constant (C50), e: constant (e≧0, or e≦0) .

The constant a − e in the above formula (1) is a value obtained by multiple regression from a large number of past actual operation data, and is determined as appropriate for each manufacturing facility.

Furthermore, from the relationship of equation (1) above, the following equations (2) and (3)
Equations (4) and (5) are derived.

Here, ζ The Dcv Pc derived in this way is output to the feedback control device 12, and is expressed by the following equations (6) and (7).
) performs the operation shown in the formula.

Tatashi, KO, K4: Control gain (0≦to≦1).

The next nozzle interval setting value DI obtained in this way
, and the next wiping pressure set value P.

is output to the manipulated variable selector 11, where the nozzle spacing regulator 5 and the pressure regulator 6 for regulating the wiping pressure are output.
Set the manipulated variable at an appropriate ratio for either or both.

Next, a method for outputting the adhesion amount target value Wr will be described. Similar to the method described above, the feedback characteristic compensator 15 converts the detection signal from the coating weight meter 7 directly above the nozzle to the position where the width direction coating weight meter 8 is provided on the downstream side according to the longitudinal movement length of the steel strip 1. Tracked value Wh2, detection signal WCN of width direction adhesion meter 8 and manufacturing condition setting device 16
By calculating the adhesion amount set value Ws set from the following equation (8), the adhesion amount target value Wr is determined.

Wr=Ws+ (Wh2-Wc) ---(8) The adhesion amount target value Wr obtained in this way is output to the feedback control device 12, where the following (9),
The calculation shown in equation (10) is performed.

Tatami, P′. =Current wiping pressure setting value [kg/c+/]
, PI: Next wiping pressure setting value [kg/crI
! Ko, Do: Current nozzle interval setting value [ff1m]
, D, secondary nozzle spacing setting value [■], dP/dW:
Influence coefficient of wiping pressure and adhesion amount, dD/d
W: Influence coefficient of nozzle spacing and adhesion amount, wh,: Current detection signal of the adhesion meter directly above the nozzle, [g/n? K, K1, K2: Control gain (0≦to≦1).

The next gas pressure setting value P7 and nozzle interval setting value obtained in this way are as described above. , Pc is outputted to the manipulated variable selector 11, and then sent to either or both of the nozzle interval regulator 5 and the pressure regulator 6 that adjusts the wiping pressure. Set the manipulated variable at an appropriate ratio.

In the nozzle interval adjuster 5, the wiping nozzle 3 and the steel strip 1
The position of the wiping nozzle 3 is adjusted so that the interval of adjust.

On the other hand, when manufacturing conditions such as plate thickness, plate width, amount of plating deposited, etc. are changed for some reason, the preset control device 13 performs preset control of the nozzle spacing according to the change in the manufacturing conditions.

Furthermore, when the moving speed V1 of the steel strip 1 and the nozzle interval are changed for reasons other than control of the amount of adhesion, the feedforward control device 14 performs a feedforward control output so that the adhesion ff1W remains constant.

By controlling the adhesion amount using such a procedure, it is possible to realize the M fjt control with small wasted time in the control loop and excellent control accuracy in the longitudinal direction and the width direction of the steel strip 1.

Next, a case where the device of the present invention that outputs the target value Wr of the amount of n is applied to actual operation using the device configured as shown in FIG.
The results of comparing the adhesion amount control accuracy when the adhesion amount control is performed only by the detection signal of the conventional width direction adhesion n meter will be explained.

The width direction adhesion meter used in the apparatus of the present invention has a width direction movement speed of 60 mm/sec.

FIG. 2 is a graph showing the accuracy of controlling the adhesion 5 when the adhesion amount was controlled using the conventional device under the conditions shown in Table 1. In the figure, fluctuations within the coil occur due to large dead time in the control loop, and fluctuations between coils occur due to changes in manufacturing conditions at coil connection points.

On the other hand, FIG. 3 shows the adhesion amount control accuracy when adhesion amount control is performed under the same conditions using the apparatus of the present invention. As is clear from the figure, according to the apparatus of the present invention, it was possible to reduce the dead time in the control loop, and thus it was possible to significantly improve both the intra-fill variation and the coil-to-coil variation in the adhesion amount.

(Hereinafter, blank space) Table 1 [Effects of the Invention] As described above, according to the device of the present invention, by detecting the amount of adhesion directly above the nozzle and performing feedback control, wasted time in the control loop can be reduced, and By comparing the detection result of the coating amount directly above the nozzle with the detection result of the coating amount in the width direction on the downstream side and correcting the above feedback control loop, the coating amount in the longitudinal direction and width direction of the steel strip can be controlled. It is possible to manufacture hot-dip metal plated steel sheets with excellent precision.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a graph showing the adhesion amount control accuracy by the conventional device, and FIG. 3 is a graph showing the adhesion amount control accuracy by the device of the present invention. 1: Steel strip, 2: Plating bathtub, 3: Wiping nozzle, 4: Pressure control valve, 5: Nozzle interval regulator, 6: Pressure regulator, 7: Coating weight meter directly above the nozzle, 8: Width direction coating weight meter, 9: Pulse transmitter, 10: Speed converter, 11: Operation amount selector, 12: Feel pack Sm device, 13 Nib reset control device, 14: Feedforward control device, 15: Feedback characteristic compensation device, 16: Manufacturing conditions Setting device.

Claims (1)

[Claims] A wiping nozzle is provided near the outlet of the steel strip above the molten metal plating bath, and the device controls the amount of plating deposited, which includes a wiping nozzle directly above the nozzle for detecting the amount of plating deposited directly above the wiping nozzle, and a coating amount meter located downstream from the nozzle. a width direction coating amount meter that is provided to detect the coating amount in the width direction of the steel strip;
a feedback control device that controls the distance between the wiping nozzle and the steel strip and/or the wiping pressure of the wiping nozzle based on the detection results of the coating weight meter directly above the nozzle; A molten metal plating adhesion amount control device comprising a feedback characteristic compensator that performs a comparison and outputs a correction calculation to the feedback control device according to the comparison result.