KR20030017111A - Apparatus for controlling distance of an air knife in continuous galvanizing line - Google Patents

Abstract

PURPOSE: An apparatus for controlling gap of air knives in continuous galvanizing line is provided to enable more accurate controlling of plating amount and reduce product defects by constantly maintaining gap between strip and air knives in width direction of the strip and minimizing variation of the plating amount adhered onto the strip. CONSTITUTION: The apparatus for controlling gap of air knives in continuous galvanizing line comprises a plural gap measuring sensors(60,61,62) that are positioned at the center of the air knife(6) in the rear of the strip to measure a gap between the strip and the air knife; a plural gap adjusting motors (M1 to M4) which are positioned at the end of both sides of each of the air knives(3,6) to adjust a gap between the air knife and the strip; width sensing sensors(70,71) for sensing position of the air knives for the strip in a width direction of the strip; and a position adjusting motor (M5) for adjusting position of the air knives so that the gap measuring sensors are positioned at the center of width of the strip according to sensing results of the width sensing sensors, wherein the width sensing sensors(70,71) comprise light emitting parts that are installed at the air knife(3) in front of the strip and light receiving parts that are installed at the rear of the strip to transmit light from the light emitting parts and sense whether the light is penetrated or not in the light receiving parts.

Description

Air knife gap control device in the hot dip plating process {APPARATUS FOR CONTROLLING DISTANCE OF AN AIR KNIFE IN CONTINUOUS GALVANIZING LINE}

The present invention relates to an air knife gap control apparatus in a hot dip plating process, and more particularly, an air knife and a steel sheet so that a predetermined amount of plating liquid is plated on the steel sheet by passing the steel sheet through a bath in which a plating liquid in a molten state is stored. The present invention relates to an air knife gap control device that controls the gap between them at all times.

In general, the steel sheet manufactured in the steel mill needs a plating process, which is performed to improve the corrosion resistance of the steel sheet and at the same time to improve the appearance. Representative methods of such plating processes include a hot dip plating process for performing plating by passing a steel sheet through a bath in which a hot dip plating solution is stored, and an electroplating process using an electrolyte.

On the other hand, in the hot-dip plating process, a separate facility is provided to control the amount of plating attached to the steel sheet in such a manner that the plating liquid adheres to the surface of the steel sheet while passing through the steel sheet through the bath in which the plating liquid in a molten state, such as molten zinc, is stored. Is needed. Commonly used to perform the above operation is an air knife (Air Knife), by spraying the air of the appropriate injection pressure on the surface of the steel sheet passed through the bath to adjust the amount of plating adhered to the surface of the steel sheet. As described above, the plating amount control method using the air knife is called an air wiping method.

In this manner, it is important to properly maintain the plating amount of the steel sheet. Accordingly, the maintenance of the gap between the steel plate and the air knife is the most important factor, and in general, the operation of properly maintaining the gap between the steel plate and the air knife is being performed.

FIG. 1 is a general configuration diagram of a conventional plating amount control process of a steel sheet, and schematically illustrates a plating amount control process of a steel sheet by the air wiping method. As shown in FIG. 1, after the molten zinc adheres to the surface of the steel sheet 1 while the steel sheet 1 passes through the zinc bath 2 through the sink roll 5, the amount of plating adhered is ordered by the consumer. In order to match the plating amount and the like, the air is blown using an air knife 3 installed on the hot water surface of the zinc bath 2 so that the adhesion plating amount of the molten zinc adhered to the surface of the steel sheet 1 is properly cut. The amount of plating attached to the surface of (1) is controlled.

In the molten plating process of the steel sheet as described above, the distance between the surface of the steel sheet 1 and the nozzle of the air knife 3 should be maintained in parallel in the width direction d, and between the nozzle and the steel sheet of the front air knife. The distance and distance between the nozzle and the steel plate of the rear air knife should be equal to each other. This is because the amount of plating attached to the steel sheet is inversely proportional to the distance between the nozzle and the steel sheet, and the nozzles of the steel sheet 1 and the air knife 3 should be kept as parallel as possible in order for the plating amount attached to the steel sheet to be uniform in the width direction d. This is because the spacing must be equal to each other in order for the amount of plating applied on the front and back of the steel sheet to be the same.

As described above, the conventional gap control between the steel plate and the air knife used a feedback method of measuring the plating amount in the width direction attached to the steel plate and adjusting the motors M1 to M4 of the air knife little by little when they are different from each other. This conventional method takes a lot of time until the gap between the surface of the steel sheet and the nozzle of the air knife is completely parallel, so that the plating amount is not uniform in the width direction (d) or the front plating amount and the back plating amount do not coincide with each other. Serious problems have occurred.

Therefore, the present invention is to solve the above problems as the interval between the width direction of the steel plate and the nozzle of the air knife to maintain the parallel and the average spacing of the front and rear surfaces of the steel sheet is the same so that the steel sheet is always before and after It is an object of the present invention to provide an air knife gap control device that automatically controls the gap motor of the air knife so as to be parallel to the nozzle in the middle between the plane air knife nozzles.

1 is a general configuration diagram of a plating amount control process of a conventional steel sheet.

2 is a block diagram of an air knife gap control apparatus according to the present invention.

Figure 3 is a block diagram showing the signal flow of the air knife gap control apparatus according to the present invention.

Explanation of symbols on the main parts of the drawings

1: steel sheet 2: plating bath

3: front air knife 6 rear air knife

31: distance sensor center adjustment unit 33: air knife gap adjustment unit

32,34,35,36,37: Motor position controller 60,61,62: Spacing sensor

70,71: width sensor 75,76: photodiode

M1, M2, M3, M4: Spacing motor M5: Positioning motor

In the present invention as a constituent means for achieving the above object, one side in the width direction of the steel sheet to be conveyed is called the work side (hereinafter referred to as WS) and the other side is referred to as driveside (hereinafter referred to as DS) in the steel plate plating process Air of the hot-dip galvanizing process equipment is provided on the front and rear of the steel sheet passing through the plating solution at predetermined intervals, respectively, and spraying air to the surface of the steel sheet to control the amount of plating attached to the surface of the steel sheet. In the knife spacing device,

A plurality of gap measuring sensors positioned at the center of the rear air knife and measuring a gap between a steel plate and the air knife;

A plurality of gap adjustment motors disposed at both ends of each air knife to adjust a gap between the air knife and the steel plate;

Width detecting sensor for detecting the position of the air knife relative to the steel plate in the width direction of the steel plate, And

And a positioning motor for adjusting the position of the air knife so that the gap measuring sensor is positioned at the center of the width of the steel sheet according to the detection result of the width detecting sensor.

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

2 is a plan view of the air knife gap control apparatus according to the present invention as viewed from the top of the process of FIG. As shown in FIG. 2, air knives 3 and 6 are shown on both the steel plate 1 plated and transported in the center of the drawing and on both front and rear surfaces of the steel plate 1. Air knife gap control apparatus according to the present invention, by adjusting the position of both end points of each air knife (3,6) to adjust the distance between the steel plate (1) and the air knife (3,6) to the X axis Three interval measuring motors (M1, M2, M3, M4) and three distance measurement for measuring the distance to the central portion of the steel plate (1) in the rear air knife (6) located at the rear of the steel plate (1) Sensors 60, 61 and 62 and two widths positioned at both ends of each of the air knifes 3 and 6 to detect the position of the air knifes 3 and 6 in the width direction with respect to the steel plate 1. According to the detection sensor (70, 71) and the width detection result, the position of the rear air knife (6) so that the distance measuring sensor (60, 61, 62) is always located in the center in the width direction of the steel sheet (1) It is composed of a positioning motor M5 that adjusts to the Y axis.

As shown in FIG. 2, the width detecting sensors 70 and 71 have a light emitting part 70 in the front air knife 3 and a light receiving part 71 in the rear air knife 6. In addition, in the state of the present drawing, in the light receiving portion 71, the region 75 through which light passes is represented by a white circle, and the region 76 where light does not pass through the steel sheet 1 is a black circle. Is indicated. Further, in FIG. 2, the upper side is a drive side (hereinafter referred to as DS) and the lower side is a work side (hereinafter referred to as WS). The left side is the front side and the right side is the rear side.

In addition, although not shown in the drawing, a control unit for controlling the overall operation including the operation of the components is provided. The controller (not shown) may be preferably configured as a microprocessor. Unexplained symbols will be described in the following actions and effects.

Hereinafter, the operation and effects of the present invention will be described. As shown in FIG. 2, the gap measuring sensors 60, 61, and 62 are composed of three sensors to measure the distances (Dws, Dcs, Dds) of three points in the width direction of the steel sheet 1. have. Then, it is attached to the rear air knife 6 and moves together with the rear air knife 6. Here, a laser type sensor or an eddy current type sensor can be used as the type of the sensor for measuring the distance between the steel sheets 1, but the present invention is not limited to any specific sensor. The three sensors 60, 61, and 62 have a fixed distance Gss, and ultimately, the measurement result of the gap measurement sensor 60 and the measurement result of the gap measurement sensor 62 should be the same. It can be said that the nozzles of the air knife are parallel.

As described above, the gap Dds measured by the gap measurement sensor 60 on the DS side and the gap Dws measured by the gap measurement sensor 62 on the WS side should be the same, so that the steel plate 1 and the rear air knife 6 are equal to each other. It can be seen that the nozzles are parallel to each other. That is, it is a condition that the center distance measuring sensor 61 should be located in the middle of the width direction of the steel plate 1. In order to satisfy this, the distance measuring sensors 60, 61 and 62 should have a driving mechanism that can move in the width direction. In order to ensure that the bodies of the gap measuring sensors 60, 61 and 62 are always located in the middle in the width direction of the steel sheet 1, the width detecting sensors 70 and 71 of the steel sheet detect the edges of the steel sheet and make the WS The feed motor M5 is adjusted to have the same size of the light transmitting region 75 of the width detecting sensor 70 and the light transmitting region 75 of the width detecting sensor 70 of the DS. As a result, when the light transmission regions 75 and 76 of the two width sensors 70 and 71 become equal to each other, the bodies of the gap measuring sensors 60, 61 and 62 are always positioned in the middle of the width direction of the steel sheet. The above condition can be solved.

Width sensors 70 and 71 of the steel sheet 1 are attached to both sides of the body of the gap measuring sensors 60, 61 and 62, respectively, as shown in FIG. The photodiode 100 is arranged side by side in the width direction of the steel sheet in the width sensor 70 at the rear end of the steel sheet. The photodiode is a device in which current flows when light is input, and is used for detecting whether light emitted from the light emitting part 71 opposite to the steel sheet is transmitted. Since the transmission of light varies with the edge of the width of the steel sheet, the width of the steel sheet is detected at a specific point among the internal photodiodes 100 of the width sensors 70 and 71. The width sensing method of this type is a method widely used for grasping the width of steel sheets in steel mills. It is used.

Figure 3 is a block diagram showing the signal flow of the air knife gap control apparatus according to the present invention, Figure 3 (a) is a gap measuring sensor (60, 61) using the width information detected from the width direction width sensor of the steel sheet (62) is a diagram illustrating a process of controlling the transfer motor (M5) of the gap measuring sensor so that the body of the (62) in the middle of the width direction of the steel sheet, and (b) of FIG. 3 is from the gap measuring sensors (60, 61, 62) Using the measured results, the process of controlling the spacing motors (M1, M2, M3, M4) that adjusts the positions of the four points at both ends of the two air knives is illustrated. In FIG. 3, the signal flow of the controller (not shown) for controlling the operation of each component is not shown, but the entire system is operated by the controller (not shown) for instructing each operation and controlling each signal flow. will be.

In each case, it consists of arithmetic units (31, 33) for calculating the ultimate position adjustment amount of the corresponding motor and motor position controllers (32, 34, 35, 36, 37) in charge of position control of the motor. There are many types of the motor position controller according to the type of the motor to be controlled, and the calculation process also has many types, and thus, the specification of the present invention is not limited to a specific type of motor or position controller.

In the center adjusting unit 31 of the gap measuring sensors 60, 61 and 62, the movement amount ΔGc of the gap sensor is calculated by the following equation (1).

[Equation 1]

ΔGc = (Nws-Nds) × Pss

here,

ΔGc is the movement amount of the gap measuring sensor in the width direction of the steel sheet,

The Nws is the number of photodiodes through which the light of the width sensor 70 of the WS is transmitted,

The Nds is the number of photodiodes through which the light of the width sensor 70 of the DS is transmitted,

Pss is an interval between photodiodes.

When the position adjustment motor M5 is controlled according to the movement amount of the gap measuring sensor in the width direction calculated by Equation 1, Nws and Nds are equal to each other and there is no more movement of the feed motor M5. Becomes In this state, the gap measuring sensor is located in the middle of the width direction of the steel sheet.

The air knife gap adjusting unit 33 performs calculation according to the procedure described in detail below, and ultimately calculates the movement amount of the four points which are the end points of the air knife.

First, in order to calculate an average amount of movement for equalizing the average distance between the front air knife 3 and the rear air knife 6 and the steel plate 1, the curve of the steel plate is expressed by a quadratic equation as shown in Equation (2). . The definition of the coordinate system to be applied is as shown in FIG.

[Equation 2]

S (x): y = ax ² + bx + c

here,

The coefficients a, b, and c of the equation are equations for each point because all three points (x0, y0), (x1, y1), and (x2, y2) of the gap measurement points on the steel sheet must satisfy Equation 2 above. If you solve all three together, you can get the value.

Referring to the application coordinates, as shown in FIG. 2, two-dimensional X-Y plane coordinates are applied using a direction perpendicular to the air knife as the Y axis and a direction perpendicular to the Y axis as the X axis. At this time, a random point is set as the reference point (0,0), and the bending curve of the steel sheet with respect to the reference point is represented by the second spinning equation S (x). In addition, as shown in FIG. 2, the distances to the steel sheets measured by the three gap sensors 60, 61, and 62, respectively, are represented by coordinates (x0, y0), (x1, y1), ( x2, y2).

When the average movement amount of the front air knife 3 and the rear air knife 6 is calculated using the quadratic equation of the steel plate 1 obtained by the above equation (2) is as shown in the following equation (3).

[Equation 3]

here,

ΔY is the average amount of movement of the front and rear air knives 3 and 6,

W is the width of the steel sheet detected by the width sensor of the steel sheet,

LT (x) represents the linear equation of the front air knife 3 nozzle,

LB (x) represents the linear equation of the rear air knife 6 nozzle.

In this case, the linear equations of the air knife nozzles 3 and 6 on the front and rear surfaces are linear lines that are linear equations when the front and rear air knifes 3 and 6 represent positions in a plane on a plane in the coordinate system applied in Equation 2. It can be represented by an equation. That is, as shown in Figure 2, the position of the air knife in the X-Y coordinate on the plane can be represented by a linear equation. Preferably, y = a'x + b '.

Next, the amount of movement of both end points is calculated so that the straight lines of the nozzles of the front and rear air knives are parallel to the steel plate.

First, the amount of movement of the front and rear air knives on the DS and WS sides is calculated by the following equations (4) and (5). The DS side is obtained by the following equation (4), and the WS is obtained by the following equation (5).

[Equation 4]

[Equation 5]

here,

[Delta] Yds is a DS side movement amount of the front and rear air knives,

[Delta] Yws is an amount of movement of the WS side of the front and rear air knives,

M is the linear distance in the X-axis direction between the center width sensor 61 and M4,

L is a distance between the WS-side spacing motor M3 and the DS-side spacing motor.

Therefore, the movement amount △ Yws of the WS / DS point for paralleling the average moving distance ΔY and the straight lines of the nozzles of the steel plate and the air knife to equally match the average distances of the front and rear air knife and the steel plate, respectively. , ΔYds is integrated to calculate the final value of each moving distance of the distance moving motors (M !, M2, M3, M4) using Equation 6 below.

[Equation 6]

△ Y1ws =-△ Y-△ Yws

△ Y2ds =-△ Y-△ Yds

△ Y3ws = △ Y + △ Yws

△ Y4ds = △ Y + △ Yds

here,

ΔY1ws is the final amount of movement of the space-side motor M1 on the WS side of the front air knife 3,

[Delta] Y2ds is the final movement amount of the space-side moving motor M2 of the front side air knife 3,

ΔY3ws is the final amount of movement of the gap-side motor M3 of the WS side of the rear air knife 6,

DELTA Y4ds is the final movement amount of the DS-side spacing motor M4 of the rear air knife 6.

Therefore, when the movement amount of the space movement motors M1, M2, M3, M4 is calculated as described above, each motor position controller 34, 35, 36, 37 controls the position of the air knife. As a result, the average spacing of the front and rear surfaces of the air knife is always controlled to be the same, and the nozzles of the air knife are parallelly controlled in the width direction of the steel plate.

As described above, according to the automatic control apparatus of the present invention, since the average spacing of the front and rear surfaces of the air knife is always the same, and the nozzles of the air knife are always controlled in parallel in the width direction of the steel plate, the width direction plating amount unevenness and the front and It is possible to solve the serious problem that the back plating amount is different from each other, and furthermore, it is possible to prevent product defects such as under plating and over plating and zinc loss, thereby reducing the production cost.

Claims (8)

One side of the conveyed steel sheet in the width direction is called a work side (hereinafter referred to as WS) and the other side is referred to as a driveside (hereinafter referred to as DS). In the air knife gap control apparatus of the hot-dip galvanizing process equipment provided with air knives respectively installed at regular intervals to inject air to the surface of the steel sheet to control the amount of plating attached to the surface of the steel sheet, A plurality of gap measuring sensors positioned at the center of the rear air knife and measuring a gap between a steel plate and the air knife; A plurality of gap adjusting motors disposed at both ends of each air knife to adjust a gap between the air knife and the steel plate; A width detecting sensor for detecting a position of the air knife with respect to the steel sheet in a width direction of the steel sheet; And And a positioning motor for adjusting the position of the air knife such that the gap measuring sensor is positioned at the center of the width of the steel sheet according to the detection result of the width detecting sensor. The method of claim 1, wherein the width sensor, And a light emitting unit in the front air knife and a light receiving unit in the rear air knife to send light from the light emitting unit and detect whether the light is transmitted through the light receiving unit. The method of claim 2, And the positioning motor is controlled such that the amount of light detected by both light receiving parts of the air knife is equal to each other. The method of claim 2, wherein the light receiving unit, And a plurality of photodiodes arranged therein in the width direction of the steel plate. The method of claim 4, wherein the positioning motor, An air knife gap control apparatus, characterized in that for moving the air knife by the movement amount of the gap measurement sensor calculated by the following equation (1). [Equation 1] ΔGc = (Nws-Nds) × Pss here, ΔGc is the movement amount of the gap measurement sensor, The Nws is the number of photodiodes through which the light of the width sensor of the WS is transmitted, The Nds is the number of photodiodes through which the light of the width detection sensor of the DS is transmitted, Pss is the spacing between the photodiodes. The method of claim 1, wherein the interval measuring sensor, Air knife gap control device, characterized in that for positioning the same interval of each sensor. The method of claim 6, The gap measuring sensor is an air knife gap control device, characterized in that consisting of three sensors. The method of claim 7, wherein The movement distance of the air knife controlled by the spacing motor is calculated by the following equations 2, 3, 4, 5 and 6. [Equation 2] S (x): y = ax ² + bx + c [Equation 3] [Equation 4] [Equation 5] [Equation 6] △ Y1ws =-△ Y-△ Yws △ Y2ds =-△ Y-△ Yds △ Y3ws = △ Y + △ Yws △ Y4ds = △ Y + △ Yds here, S (x) is an equation for the curve of the steel sheet, A, b, and c are coefficients of S (x), ΔY is the average amount of movement of the front and rear air knives 3 and 6, W is the width of the steel sheet detected by the width sensor of the steel sheet, L _T (x) represents a linear equation of the front air knife 3 nozzle, L _B (x) represents the linear equation of the rear air knife (6) nozzle, [Delta] Yds is a DS side movement amount of the front and rear air knives, [Delta] Yws is an amount of movement of the WS side of the front and rear air knives, M is the linear distance between the center width sensor 61 and the DS-side motor (M4), L is the distance between the WS side spacing motor M3 and the DS side spacing motor M4. ΔY1ws is the final amount of movement of the space-side motor M1 on the WS side of the front air knife 3, [Delta] Y2ds is the final movement amount of the space-side moving motor M2 of the front side air knife 3, ΔY3ws is the final amount of movement of the gap-side motor M3 of the WS side of the rear air knife 6, ΔY4ds is the final movement amount of the space-side moving motor M4 of the rear side air knife 6.