KR20160079199A - Method and Apparatus for controlling the pressure of air knife in Continuous Galvanizing Line - Google Patents

Abstract

The present invention provides a method for controlling the plating amount in a melting and plating process to control the plating amount in response to a plating amount difference between the upper and lower surfaces of a steel plate. The method includes the steps of: (a) measuring an upper surface plating amount and calculating a first difference by subtracting the measured upper surface plating amount from the target upper surface plating amount; (b) measuring a lower surface plating amount and calculating a second difference by subtracting the measured lower surface plating amount from the target lower surface plating amount; (c) calculating an upper surface gap control amount based on the first difference and a lower surface gap control amount based on the second difference; (d) calculating a determination reference value based on the upper and lower surface gap control amounts; (e) determining whether the determination reference value is greater than a lower gap limit value; and (f) calculating the gap control amount when the determination reference value is greater than the lower gap limit and calculating a pressure control amount when the determination reference value is less than the lower gap limit.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for controlling a plating amount in a hot dip galvanizing process,

The present invention relates to a method of controlling a plating amount in a hot-dip coating process, and more particularly, to a method of controlling a coating amount in a hot-dip coating process for controlling an interval or pressure of an air knife, Control method, and control device.

Generally, a steel sheet produced in a steel mill is plated on the surface of a steel sheet in order to improve the corrosion resistance and to improve the appearance. In the process of producing automotive steel sheet for special purpose, such a plating process is very important As a typical working method, a hot-dip plating process is performed in which zinc is attached to a steel sheet while passing through a steel sheet through a port stored in a hot-dip galvanizing solution.

In this continuous plating process, the amount of plating adhered to the steel sheet can be controlled by adjusting the jet pressure of the gas such as air coming from the air knife installed in the vertical direction of the steel sheet passed through the plating port, or by controlling the distance between the air knife and the steel sheet .

As an example of a method of controlling the amount of plating, the upper and lower plating amount deviations of the steel sheet can be obtained from the measured values and the target values measured by the plating amount measuring unit, respectively, and the interval control amounts can be calculated using the plating amount prediction formula in the interval control.

However, since there is a risk of contact between the air knife and the steel sheet due to the vibration or bending of the steel sheet during the gap control, there is a danger in the control to narrow the gap. If the air knife touches the steel plate, the surface of the steel plate may be scratched or foreign matter may be formed, thereby causing defects in the product.

Therefore, at the interval control, the lower limit of the gap is set so that the air knife and the steel plate are not narrowed to a certain distance or less. As a result, when the value obtained by adding the current interval and the control amount becomes less than or equal to the set lower limit value in the interval control, the control is performed using the pressure of the air knife without performing the interval control.

However, at the time of pressure control, control is performed with the same pressure on the upper surface and the lower surface of the steel plate, respectively. Therefore, there is a problem that either the top surface or the bottom surface does not reach the target amount of plating due to the difference in plating amount between the top surface and the bottom surface.

For example, in the case where the upper surface of the steel sheet is subjected to pressure control using the difference in average plating amount between the upper surface and the lower surface when the actual plating amount is larger than the target plating amount and the actual plating amount is smaller than the target plating amount on the lower surface of the steel sheet, As a result, the amount of plating is close to the target amount of plating on the upper surface of the steel sheet, but the amount of plating on the lower surface of the steel sheet may not reach the target amount of plating.

Korean Patent No. 10-0815815 (Announcement of Mar. 14, 2008)

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a plating amount control method and a control device in a hot-dip plating process capable of controlling a plating amount in accordance with a variation in plating amount between an upper surface and a lower surface of a steel sheet .

The problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned here can be understood by those skilled in the art from the following description.

According to a first aspect of the present invention, there is provided a method for measuring a plating amount, the method comprising the steps of: a) measuring a top plating amount and calculating a first deviation obtained by subtracting the top plating amount measured from a target top plating amount; b) Calculating an upper gap control amount on the basis of the first deviation and calculating a lower gap control amount based on the second deviation; d) calculating a discrimination reference value based on the upper gap control amount and the lower gap control amount, e) determining whether the discrimination reference value is greater than a lower limit value, and f) if the discrimination reference value is greater than the lower limit value, And calculating the pressure control amount when the determination reference value is smaller than the lower limit value, can be provided by the method of controlling the plating amount in the hot-dip plating step.

Preferably, in the step c), the upper surface gap control amount can be calculated by the following equation (1).

&Quot; (1) "

? S1 = a *? Cw1

Here,? S1 is the upper surface gap control amount, a is the adjustment coefficient, and? Cw1 is the first deviation.

Preferably, in the step c), the bottom clearance control amount may be calculated by the following equation (2).

&Quot; (2) "

? S2 = a *? Cw2

Here,? S2 is the lower gap control amount, a is the adjustment coefficient, and? Cw2 is the second deviation.

Preferably, the discrimination reference value can be calculated by the following equation (3).

&Quot; (3) "

S = (S1r + S2r) / 2

Here, S is a discrimination reference value, S1r is the sum of the upper surface interval average measurement value and the above-mentioned? S1, and S2r is the sum of the lower gap average measurement value and the above?

Preferably, in the step f), when the discrimination reference value is smaller than the interval lower limit value, only the pressure control amount is calculated when the first deviation and the second deviation are equal to either of the positive sign and the negative sign, If the two deviations have different signs between the positive and negative signs, the pressure control amount and the gap control amount can be calculated.

Preferably, in the step (f), the pressure control amount may be calculated by the following equation (4).

&Quot; (4) "

? P = b * (? Cw1 +? Cw2) / 2

Here, DELTA P is a pressure control amount, b is a proportional coefficient, DELTA Cw1 is a first deviation, and DELTA Cw2 is a second deviation.

According to another aspect of the present invention, there is provided a plating amount control apparatus for controlling a gap control amount between a steel plate and an air knife and a pressure control amount of an air knife, the plating amount control apparatus comprising: a plating amount measurement unit for measuring an upper surface plating amount and a lower surface plating amount; A deviation calculating section for calculating a first deviation obtained by subtracting the upper surface plating amount measured in the upper surface plating amount and a second deviation obtained by subtracting the lower surface plating amount measured in the plating amount on the basis of the amount of the upper surface plating; An interval control amount calculating section that calculates a control amount and calculates a bottom gap control amount based on the second deviation; a pressure control amount calculating section that calculates a pressure control amount based on the first deviation and the second deviation; A discrimination reference value calculation unit for calculating a discrimination reference value based on the control amount and the lower interval control amount; And a control unit for controlling the pressure control amount calculating unit to calculate the pressure control amount when the determination reference value is smaller than the lower limit of the interval, It is possible to provide a plating amount control apparatus in the plating step.

Preferably, the selection control unit controls to calculate only the pressure control amount when the first reference deviation and the second deviation are equal to either positive or negative sign when the determination reference value is smaller than the interval lower limit value, When the first deviation and the second deviation have different signs from each other in the sign and the negative sign, it is possible to control to calculate the pressure control amount and the gap control amount.

According to one embodiment of the present invention, a discrimination reference value is calculated based on a difference between an upper surface plating amount and a lower plating amount of a steel sheet. If the discrimination reference value is larger than the lower limit value, the interval control amount is calculated. If the discrimination reference value is smaller than the lower limit value, . It is possible to control the amount of plating in accordance with the variation in plating amount between the upper and lower surfaces of the steel sheet.

According to an embodiment of the present invention, when the discrimination reference value is smaller than the lower limit value, and when the first deviation and the second deviation, which are deviations of the upper surface plating amount and the lower surface plating amount, respectively, are equal to either positive or negative, And when the first deviation and the second deviation have different signs from each other in the sign and the negative sign, the pressure control amount and the gap control amount are calculated to control the plating amount in accordance with the deviation in the plating amount between the upper surface and the lower surface of the steel sheet Providing a beneficial effect.

1 is a flowchart showing a plating amount control method in a hot dip coating process according to a preferred embodiment of the present invention,
2 is a view showing a plating amount control apparatus in a hot dip coating process according to a preferred embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The objectives, specific advantages, and novel features of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG. The terms and words used in the present specification and claims should not be construed to be limited to ordinary or dictionary terms and the inventor should properly define the concept of the term in order to describe its own invention in the best way. The present invention should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

The terms including ordinal, such as second, first, etc., may be used to describe various elements, but the elements are not limited to these terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the second component may be referred to as a first component, and similarly, the first component may also be referred to as a second component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

FIG. 1 is a flowchart showing a plating amount control method in a hot dip coating process according to a preferred embodiment of the present invention, and FIG. 2 is a view illustrating a plating amount control device in a hot dip coating process according to a preferred embodiment of the present invention.

1 and 2, molten zinc is stored in the plating port 1, the steel sheet S is immersed in molten zinc by rotation of the sink roll 2, and then passes through the air knives 4 and 3 .

The plating amount control apparatus in the hot dip coating process according to the preferred embodiment of the present invention includes a plating amount measuring unit 100, a deviation calculating unit 200, an interval control amount calculating unit 300, a discrimination reference value calculating unit 400, And a selection control unit 500.

The air knives 3 and 4 may include a pressure control unit 10 and a gap control unit 20. The pressure control unit 10 may include a pressure control module including a pressure control valve for adjusting the jetting pressure of the air knives 3,4. The gap control unit 20 may include a position controller and a PLC for controlling motors of a driving unit such as a motor for controlling the distance between the steel plate S and the air knives 3,4.

When the material of the steel sheet S is changed and the position of the welding point has passed the predetermined position, the server confirms whether the material changes and the first feedback control point is reached. When the feed point is controlled, The plating amount control method is performed in the hot-dip plating process according to the example.

The plating amount measuring unit 100 may include a first measuring unit 110 for measuring a plating amount of the upper surface of the steel sheet S and a second measuring unit 120 for measuring a lower surface plating amount of the steel sheet S. The plating amount measuring unit 100 measures the upper surface plating amount and the lower surface plating amount of the steel sheet S, respectively.

Thereafter, the deviation calculating section 200 calculates a first deviation obtained by subtracting the upper surface plating amount measured from the target upper surface plating amount, measures a lower plating amount, and calculates a second deviation obtained by subtracting the lower plating amount measured in the plating amount, if desired (S100)

The first deviation [Delta] Cw1 is calculated as follows.

First deviation (DELTA Cw1) = amount of upper surface plating - amount of upper surface target amount of plating

The second deviation [Delta] Cw2 is calculated as follows.

Second deviation (DELTA Cw2) = amount of plated - amount of target plating

Next, the gap control amount calculating section 300 calculates the upper surface gap control amount based on the first deviation? Cw1 and calculates the lower surface gap control amount based on the second deviation? Cw2 (S200)

The upper surface gap control amount? S1 can be calculated by the following equation (1).

&Quot; (1) "

? S2 = a *? Cw2

Here,? S1 is the upper surface gap control amount, a is the adjustment coefficient, and? Cw1 is the first deviation. The lower gap control amount? S2 can be calculated by the following equation (2).

&Quot; (2) "

? S2 = a *? Cw2

Here,? S2 is the lower gap control amount, a is the adjustment coefficient, and? Cw2 is the second deviation.

Next, the discrimination reference value calculating section 500 calculates the discrimination reference value S based on the upper surface gap control amount? S1 and the lower surface distance control amount? S2 (S300)

The discrimination reference value S can be calculated by the following equation (3).

&Quot; (3) "

S = (S1r + S2r) / 2

Here, S is a discrimination reference value, S1r is the sum of the upper surface interval average measurement value and the above-mentioned? S1, and S2r is the sum of the lower gap average measurement value and the above?

Next, it is determined whether the discrimination reference value S is larger than the interval lower limit value (S400)

In the discrimination reference value S, the lower limit value of the interval can be discriminated by using the subtracted subtracted value as a threshold value.

Next, the gap control amount calculating unit 300 is controlled to calculate the gap control amount if the determination reference value S is larger than the gap lower limit value through the selection control unit 600 (S510). If the determination reference value S is smaller than the interval lower limit value, the pressure control amount is calculated (S520, S530, S540)

First, the selection control unit 600 determines whether the signs of the first deviation Cw1 and the second deviation Cw2 are the same when the determination reference value S is smaller than the interval lower limit (S520)

The selection control unit 600 can control the pressure control amount calculation unit 400 to calculate only the pressure control amount when the first deviation Cw1 and the second deviation Cw2 are equal to either positive or negative sign S530). For example, in the case where the first deviation and the second deviation have all negative notes, the interval should be larger than the present.

On the other hand, when the first deviation [Delta] Cw1 and the second deviation [Delta] Cw2 have different signs from each other in the sign and the negative sign, the selection control section 600 controls the interval The control amount calculating unit 300 and the pressure control amount calculating unit 400 can be controlled (S540)

For example, if the first deviation [Delta] Cw1 is a positive number and the second deviation [Delta] Cw2 is a negative number, the lower limit is a direction in which the interval becomes larger, so that the interval control is performed by an amount corresponding to the deviation, In the case of the upper surface, since the deviation is positive, it is controlled so as to increase the pressure to reduce the deviation. At this time, the pressure control amount calculating section 400 can calculate the pressure control amount by the following equation (4).

&Quot; (4) "

? P = b * (? Cw1 +? Cw2) / 2

Here, DELTA P is a pressure control amount, b is a proportional coefficient, DELTA Cw1 is a first deviation, and DELTA Cw2 is a second deviation.

When the deviation of the plating amount is controlled by such a method, particularly when the distance between the air knife and the steel sheet is narrow and the gap can not be narrowed, that is, the gap can not be controlled, the deviation of the plating amount can be reduced. Particularly, when the signs of the deviation of the upper and lower plating amounts of the steel sheet are different, when the control is performed only by the conventional pressure, the deviation of the plating amount of one side may be further increased. In the hot-dip coating process according to the preferred embodiment of the present invention, This can be avoided through the device, and the cost can be reduced by reducing the excessive amount of overcharge.

As described above, the plating amount control method and the control apparatus in the hot dip coating process according to one preferred embodiment of the present invention have been specifically described with reference to the accompanying drawings.

It is to be understood that one embodiment of the invention described above is to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description. It is intended that all changes and modifications that come within the meaning and range of equivalency of the claims are to be embraced within their scope.

1: Plated port
2: sink roll
3,4: Air knife
100: Plating amount measuring unit
200: deviation calculating section
300: interval control amount calculating section
400: discrimination reference value calculating section
500:

Claims (8)

a) measuring a top plating amount and calculating a first deviation obtained by subtracting the top plating amount measured from the target top plating amount
b) measuring the amount of the lower plating and, if desired, calculating the second lower limit of the lower plating amount measured in the plating amount
c) calculating an upper surface gap control amount based on the first deviation and calculating a lower surface gap control amount based on the second deviation;
d) calculating a discrimination reference value based on the upper gap control amount and the lower gap control amount;
e) determining whether the discrimination reference value is greater than a lower limit value;
f) calculating the interval control amount if the determination reference value is greater than the lower limit value, and calculating the pressure control amount if the determination reference value is smaller than the interval lower limit value
In a hot dip galvanizing process. The method according to claim 1,
In the step c)
Wherein the upper surface gap control amount is calculated by the following equation (1).
&Quot; (1) "
? S1 = a *? Cw1
Here,? S1 is the upper surface gap control amount, a is the adjustment coefficient, and? Cw1 is the first deviation. 3. The method of claim 2,
In the step c)
Wherein the gap control amount is calculated by the following equation (2): " (2) "
&Quot; (2) "
? S2 = a *? Cw2
Here,? S2 is the lower gap control amount, a is the adjustment coefficient, and? Cw2 is the second deviation. The method of claim 3,
Wherein the determination reference value is calculated by the following equation (3).
&Quot; (3) "
S = (S1r + S2r) / 2
Here, S is a discrimination reference value, S1r is the sum of the upper surface interval average measurement value and the above-mentioned? S1, and S2r is the sum of the lower gap average measurement value and the above? 5. The method of claim 4,
In the step f)
When the discrimination reference value is smaller than the interval lower limit value, only the pressure control amount is calculated when the first deviation and the second deviation are equal to either of the positive sign and the negative sign. If the first deviation and the second deviation are positive Wherein the control amount and the gap control amount are calculated in the case of having different codes. The method according to claim 1,
In the step f)
Wherein the pressure control amount is calculated by the following equation (4).
&Quot; (4) "
? P = b * (? Cw1 +? Cw2) / 2
Here, DELTA P is a pressure control amount, b is a proportional coefficient, DELTA Cw1 is a first deviation, and DELTA Cw2 is a second deviation. A plating amount control device in a hot-dip plating process for controlling a gap control amount between a steel strip and an air knife and a pressure control amount of an air knife,
A plating amount measuring unit for measuring an upper surface plating amount and a lower surface plating amount;
A deviation calculating unit for calculating a first deviation obtained by subtracting the upper surface plating amount measured in the target upper surface plating amount and a second deviation obtained by subtracting the lower surface plating amount measured in the plating amount on a target basis;
An interval control amount calculating unit for calculating an upper surface gap control amount based on the first deviation and calculating a lower surface gap control amount based on the second deviation;
A pressure control amount calculating unit that calculates a pressure control amount based on the first deviation and the second deviation;
A determination reference value calculation unit that calculates a determination reference value based on the upper gap control amount and the lower gap control amount;
The control unit controls the interval control amount calculating unit to calculate the interval control amount when the determination reference value is greater than the lower limit value and to calculate the pressure control amount so as to calculate the pressure control amount when the determination reference value is smaller than the interval lower limit value A selection control unit
Wherein the plating amount control unit controls the amount of plating in the plating unit. 8. The method of claim 7,
The selection control unit,
And controls only the pressure control amount to be calculated when the first reference deviation and the second deviation are equal to either positive or negative sign when the determination reference value is smaller than the interval lower limit value, And controlling the pressure control amount and the gap control amount to be calculated when the sign and the negative sign are different from each other.

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