KR100332897B1 - Method for controlling widthwise coating thickness deviation in continuous hot dip galvanizing line - Google Patents

Abstract

PURPOSE: A method for controlling widthwise coating thickness deviation of strip using an air knife equipped with variable nozzles in a continuous hot dip galvanizing line is provided. CONSTITUTION: The method for controlling widthwise coating thickness deviation in continuous hot dip galvanizing line comprises the steps of obtaining coating thickness deviation (Coj¬t) from arbitrary 't' measured strip widthwise coating thickness values (Cj¬t); obtaining coating thickness error (Ce¬t) using the obtained coating thickness deviation (Coj¬t); obtaining nozzle gap variation (ΔE¬(t+1)) using the obtained coating thickness error (Ce¬t); changing a nozzle gap as much as the obtained nozzle gap variation (ΔE¬(t+1)) by driving a nozzle gap driver; obtaining coating thickness deviation (Coj¬(T+1)) from (t+1)th measured strip widthwise coating thickness values (Cj¬(t+1)) after coating in the state that the nozzle gap is changed; obtaining coating thickness error (Ce¬(t+1)) using the obtained coating thickness deviation (Coj¬(t+1)); obtaining nozzle gap variation (ΔE¬(t+2)) using the obtained coating thickness error (Ce¬(t+1)); changing the nozzle gap as much as the obtained nozzle gap variation (ΔE¬(t+2)) by driving the nozzle gap driver; and repeating the steps of changing the nozzle gap after obtaining the coating thickness error (Ce¬(t+2)) and nozzle gap variation (ΔE¬(t+3)) after obtaining the coating thickness deviation (Coj¬(t+2)) from (t+2)th measured strip widthwise coating thickness values (Cj¬(t+2)) after coating in the state that the nozzle gap is changed.

Description

Width Thickness Determination Control Method in Continuous Hot-Plating Line

The present invention relates to a method for controlling the variation in the thickness in the width direction of the strip by using an air knife (Knife) having a variable nozzle in a continuous hot-dip plating line.

Air knife systems have been widely used as a device for controlling the thickness of the plating layer in a continuous hot dip plating line.

As shown in FIG. 1, the air knife 1 is located on both sides of the strip 6 exiting the plating bath 5 through the sink roll 3 and the guide roll 4, and the nozzle portion of the air knife. By controlling the plating layer to be plated on the strip by using the gas coming out through, the strip of the plated layer is passed through the plating thickness meter (5).

The plating thickness depends on the impingement pressure of the gas injected onto the strip, which depends on the pressure of the gas (8), the distance (9) between the nozzle and the strip, and the traveling speed of the strip.

The plating thickness is controlled in the longitudinal direction and the width direction.

Background Art A method of controlling the plating thickness in the longitudinal direction is known by controlling the pressure of the gas and the distance between the nozzle and the strip.

On the other hand, as a method of controlling the plating thickness in the width direction, it is known to use a nozzle having a constant nozzle interval or a fixed nozzle changed according to the size of the strip, but there is a problem in that the control of the width plating deviation is impossible.

Accordingly, the present inventors conducted research and experiments to solve the above-mentioned problems of the prior art, and based on the results, the present invention proposes the present invention, and the present invention provides an air having a variable nozzle in a continuous hot dip plating line. It is an object of the present invention to provide a method for controlling the variation of the thickness in the width direction of a strip using a knife.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The present invention is a front and rear of the strip having a variable nozzle consisting of a variable lip that can be varied by a nozzle interval driver installed at regular intervals and a fixed lip fixed with this variable lip and a fixed interval (nozzle interval) In the method of controlling the thickness thickness variation of the hot-dip strip by using an air knife installed in the

Any t-th measured strip width plating thickness value ( Plating thickness deviation from the following equation (1) Providing a;

(Where t is the control time of the plating thickness controller)

Obtaining a plating thickness error Ce ^t by substituting the plating thickness deviation Co _j obtained as described above in Equation (2);

Ce ^t = C m ^t d-C m ^t -Co ^t ‥‥ · (2)

(Cm ^t : plating thickness deviation prediction value, Cm ^t d: time delay plating thickness deviation of Cm ^t )

Obtaining a nozzle gap change amount ΔE ^{t + 1} using the plating thickness error Ce ^t obtained as described above (3);

[Where r: constant, G ^T : transpose of G matrix]

Changing the nozzle interval by the nozzle interval change amount? E ^{t + 1} obtained by driving the nozzle interval driver;

Strip thickness direction thickness value of t + 1 after plating with the nozzle spacing changed as above ( (1a) and grinding thickness deviation from Obtaining;

Plating thickness deviation calculated as above ( ) To obtain the plating thickness error Ce ^{t + 1} by substituting the following formula (2a);

(here, : G x ΔE ^{t + 1} , : Time Delay Plating Thickness Deviation]

Using the plating thickness error Ce ^{t + 1} obtained as described above, obtaining a nozzle interval change amount ΔE ^{t + 2} as shown in Equation (3a);

[Where r: constant, G ^T : transpose of G matrix]

Changing the nozzle interval by the nozzle interval change amount? E ^{t + 2} obtained by driving the nozzle interval driver; And t + 2th measured strip width direction thickness value after plating with the nozzle spacing changed as described above ( Plating thickness deviation as above from ) And then obtaining the plating thickness error (Ce ^{t + 2} ) and the nozzle gap change amount (ΔE ^{t + 3} ) as described above, and then repeating the steps of changing the nozzle gap as described above. The present invention relates to a method for controlling variation in width in the thickness direction in a continuous hot dip plating line.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

FIG. 2 shows one conceptual diagram of a variable nozzle structure in a continuous hot dip plating line to which the present invention is applied, and FIG. 3 shows a control block diagram of width plating thickness variation in accordance with the present invention. The present invention will be described in detail with reference to FIGS. 2 and 3.

According to the present invention, an air knife having a variable nozzle must be used as shown in FIG.

As shown in FIG. 2, the variable nozzle 11 is a variable lip 11a that can be varied by the nozzle interval driver 10 provided at regular intervals, and a constant spacing (nozzle) with the variable lip 11a. And a fixed granule 11b fixed at an interval thereof.

In Fig. 2, "E _i " (i = 1, ..., K) denotes the interval between the variable lip 11a and the fixed lip 11b, i.e., nozzle interval, and " LA " of the distance, "X _i" is the distance from the i-th nozzle spacing actuator from the reference point (X1) of the nozzle, "L" represents a width direction length of the air knife.

In order to control the widthwise thickness variation of the hot dip galvanizing strip according to the present invention, first, an arbitrary t-th strip width thickness value ( )

Next, the plating thickness deviation obtained as described above ( ) Is substituted into the following formula (2) to obtain the plating thickness error Ce ^t .

Ce ^t = C m ^t d-C m ^t -Co ^t ‥‥ · (2)

Where Cm ^t = G x ΔE ^t

In the formula (2), when t = 1, that is, the plating thickness error Ce ^t is obtained from the first measured width plating thickness values, ΔE is 0 (Zero), and thus the plating thickness deviation predicted value Cm ^t and Time delay plating thickness deviation of Cm ^t ( ) Becomes 0 (Zero).

Next, the plating thickness error obtained as described above ( Using the following formula, obtain the nozzle gap change amount ΔE ^{t +1} as shown in the following equation (3).

The nozzle interval change amount ΔE ^{t + 1} obtained in Equation (3) represents the nozzle interval change amount that minimizes the cost function, which will be described below.

The price function may be expressed as in Equation 4 below.

Where S is a constant

In the calculation of the change amount of the nozzle interval ΔE _i using the price function of Equation (4), when the total sum of the change amount of the nozzle interval ΔE _i is changed, the pressure of the gas is changed, so The sum of E _i ) must be zero. Therefore, the optimum nozzle gap variation with respect to the plating thickness error Ce is represented by the following equations (4a) and (4b).

The optimum nozzle interval that satisfies the conditions of the above formulas (4a) and (4b) is expressed as shown in the above formula (3).

In order to control the plating thickness, the thickness of the plating is modeled according to the change of the nozzle interval. If the model of the plating thickness variation according to the change amount of nozzle interval (ΔE) is G, the plating thickness deviation is changed when the nozzle interval changes by ΔE. The model D is represented in a matrix form as shown in Equation 5 below.

D = G x ΔE ‥‥‥ (5)

[Where, G: Plating thickness variation with nozzle spacing (△ E)

N x K Diagonal Matrix, (unit: g / ㎥)

ΔE: amount of change in nozzle spacing (E)

K x 1 Matrix, in mm

Next, the nozzle spacing driver is driven to change the nozzle spacing by the nozzle spacing change amount ΔE ^t obtained as described above.

Next, the t + 1th measured strip width direction thickness value after plating with the nozzle spacing changed as described above ( Plating thickness deviation from the following equation (1a) )

Next, the plating thickness deviation obtained as described above ( ) Is substituted into the following formula (2a) to find the plating thickness error (Ce ^{t + 1} ).

Ce ^{t + 1} = - Co ^{t + 1} ..... (2a)

Next, using the plating thickness error Ce ^{t + 1} obtained as described above, the nozzle gap change amount DELTA E ^{t + 2} is obtained as in the following formula (3a).

Next, the nozzle spacing driver is driven to change the nozzle spacing by the nozzle spacing change amount? E ^{t + 2} determined as described above.

Next, the t + 2th measured strip width direction thickness value after plating with the nozzle spacing changed as described above ( Variation of the above and ground plating thickness from ), Then obtain the plating thickness error (Ce ^{t + 2} ) and the nozzle gap change amount (ΔE ^{t + 3} ) as described above, and then repeat the steps of changing the nozzle gap as described above, thereby performing widthwise plating. Thickness deviation is controlled.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example

If there are 14 nozzle spacing drivers and the spacing is 160, the position (x) of each nozzle spacing driver is as follows.

X = {0 160 320 480 640 800 960 1120 1280 1440 1600 1760 1920 2080}

When the strip width is 1780mm, the position (P) for measuring the plating thickness in the plating measuring instrument is as follows.

P = {160 240 320 400 480 560 640 720 800 880 960 1040 1120 1200 1280 1360 1440 1520 1600 1680 1760 1840}

Initially, the width thickness variation measured was as follows.

Co = {-4.5 -3.5 2.5 8.5 8.5 10.5 10.5 5.5 0.5 -6.5 -9.5 -10.5 -10.5 8.5 -4.5 -0.5 0.5 3.5 5.5 5.5 1.5 -4.5}

At this time, since ΔE = 0, the plating thickness error Ce is equal to the plating thickness deviation Co.

Obtain the nozzle gap change amount ΔE using the plating thickness error Ce, adjust the nozzle gap as shown in FIG. 4, perform plating, measure the width plating thickness, and calculate the width plating thickness deviation, The results are shown in FIG.

FIG. 4 shows the nozzle spacing before applying the present invention (the conventional method), and FIG. 5 shows the variation in the plating thickness in the width direction when applying the present invention.

As shown in FIG. 5, in the case of controlling the plating thickness variation in accordance with the present invention, it can be seen that the plating thickness variation is much smaller than in the conventional method.

As described above, the present invention can increase the productivity and quality by controlling the variation of the thickness of the strip in the width direction when the width of the strip is changed, the shape of the strip is changed or the deviation occurs at the edge portion of the strip. It is effective.

1 is a schematic diagram of a continuous hot dip plating line to which the present invention can be applied.

2 is a schematic view of a variable nozzle structure in a continuous hot dip plating line to which the present invention can be applied.

3 is a width control thickness plating control block diagram of the present invention

4 is a graph showing the nozzle spacing according to the length of the air knife width direction before and after applying the present invention

5 is a graph showing the variation in the plating thickness in the width direction according to the plating thickness measurement position in the strip width direction before and after applying the present invention.

Explanation of symbols on the main parts of the drawings

1 ..... Air Knife 2 ..... Plating Bath

5 ..... Plating Thickness Meter 6 ..... Strip

7 ..... Nozzle Spacing 9 ..... Distance between Nozzle and Strip

10 .... Nozzle spacing actuator 11 .... Variable nozzle

Claims (1)

It is provided with a variable lip which is variable by nozzle interval actuators which are installed at regular intervals and a variable nozzle which is fixed to the variable lip and a fixed lip which is fixed at a fixed interval (nozzle interval). In the method for controlling the variation in the plating thickness in the width direction of the hot dip coating strip using an air knife, Any measured t-th width measured in the width direction of the strip ( Plating thickness deviation from the following equation (1) Obtaining; Plating thickness deviation calculated as above ( ) To obtain the plating thickness error Ce ^t by substituting the following formula (2); (Cm ^t : plating thickness deviation prediction value, Cm ^t d: time delay plating thickness deviation of Cm ^t ) Obtaining a nozzle gap change amount ΔE ^{t + 1} using the plating thickness error Ce ^t obtained as described above (3); [Where r: constant, G ^T ; Transpose of G Matrix] Changing the nozzle interval by the nozzle interval change amount? E ^{t + 1} obtained by driving the nozzle interval driver; T + 1st measured strip width direction thickness value after plating with the nozzle spacing changed as above ( Plating thickness deviation from the following equation (1a) Obtaining; Plating thickness deviation calculated as above ( ) To obtain the plating thickness error Ce ^{t + 1} by substituting the following formula (2a); (here, ; G x ΔE ^{t + 1} , : Time delay plating thickness deviation) Using the plating thickness error Ce ^{t + 1} obtained as described above, obtaining a nozzle interval change amount ΔE ^{t + 2} as shown in Equation (3a); [Where r: constant, G ^T : transpose of G matrix] Changing the nozzle interval by the nozzle interval change amount? E ^{t + 2} obtained by driving the nozzle interval driver; And the t + 2th measured strip width direction thickness value after plating with the nozzle spacing changed as described above ( Plating thickness deviation as above from ) And then obtaining the plating thickness error (Ce ^{t + 2} ) and the nozzle gap change amount (ΔE ^{t + 3} ) as described above, and then repeating the steps of changing the nozzle gap as described above. Width Thickness Determination Control Method in Continuous Hot-Plating Line