KR100815684B1 - Adaptive coating weight controller in continuous steel strip galvanizing process - Google Patents

Abstract

The present invention relates to an apparatus for controlling the plating amount of the hot-dip galvanizing process in steel mills, the target plating amount is changed, difficulty in controlling the plating amount, the delay of the plating amount measurement time due to the distance between the plating amount sensor and the air knife, frequent line speed The present invention relates to an adaptive plating amount control device in a hot dip galvanizing process that predicts and compensates for changes in plating amount due to a change, and minimizes errors in plating amount and order plating amount during the steel plate plating process, thereby preventing under plating defects. The zinc loss caused by overplating can be prevented, thereby reducing the zinc consumption efficiently.

Steel plate, plating process, air knife, plating amount, plating amount control device

Description

ADAPTIVE COATING WEIGHT CONTROLLER IN CONTINUOUS STEEL STRIP GALVANIZING PROCESS}

1 is a schematic view showing a steel plate plating amount control apparatus in a conventional hot dip plating process

Figure 2 is an overall configuration diagram showing a plating amount control device in the steel plate hot dip plating process according to the present invention

Explanation of symbols on the main parts of the drawings

100: steel plate 110: zinc bath

112: sink roll 120: molten zinc hot water

130: Air Knife 140: plating amount sensor

141: plating amount measurement 150: pressure regulating valve

160: pressure controller 200: plating amount formula model

210: Preset Controller

220: feedforward controller

230: parameter estimator

300: adaptive plating amount control device

The present invention relates to a control device of an air knife for injecting air pressure to match the amount of zinc plating adhered to the surface of the steel sheet passed through the zinc bath in the steel plate hot dip plating process of the steel mill to meet the demand plating amount of the demand. Improves the performance of the plating amount prediction control when the target plating amount of steel sheet is changed or when the line speed (steel plate feed speed) is changed to minimize the difference between the plating amount attached to the steel sheet and the order plating amount of the demand The present invention relates to an adaptive plating amount control apparatus in a steel plate hot dip plating process for adjusting the pressure.

In general, the steel sheet (strip) produced in steel mills need a plating process. This is done to improve the corrosion resistance and the like of the steel sheet and to make the appearance beautiful. At present, such a plating process is a very important work process in the use environment of the steel sheet, that is, an electric steel sheet or an automobile sheet used for a special purpose.

Representative plating methods include a hot dip plating method for performing plating by passing a steel plate through a bath in which a hot dip plating solution is stored, an electroplating method using an electrolytic solution, and the like and a hot dip galvanizing process of a galvanized steel sheet.

Further, in the hot dip plating process, a plating operation is performed in such a manner that the steel sheet passes through a bath in which a plating liquid in a molten state such as molten zinc is stored, and adheres to the surface thereof, and thus separate equipment is required to control the plating amount of the steel sheet.

Usually, to control the plating amount of the steel sheet, the air of the proper injection pressure is sprayed on the surface of the steel sheet that has passed through the bath as an air knife to adjust the coating amount adhered to the surface of the steel sheet according to the demand plating amount of the demand. Plating amount control method using an air knife is called an air wiping method.

FIG. 1 schematically shows a plating amount control process of a steel sheet by an air wiping method.

As shown in FIG. 1, in the air wiping method, after the molten zinc 120 is fused to the surface of the steel sheet 100 while the steel sheet 100 passes through the zinc bath 110, the amount of plating attached is determined according to demand. In order to match the order of plating amount, the air knife 130 installed above the hot water surface of the zinc bath 110 is installed, and the air is sprayed to properly cut the adhesion plating amount of the molten zinc adhered to the surface of the steel sheet 100.

In the air wiping control of the coating amount as described above, when the welded portion, which is the boundary between two steel sheets having different target plating amounts, passes through the air knife, it is necessary to change the pressure setting value of the air knife according to the target plating amount of the next steel sheet.

To this end, conventionally, the operator has used the method of adjusting the pressure empirically or using the air knife pressure value table for each target plating amount in the past.

Further, in the conventional steel plate plating amount control method as described above, in order to compensate in advance the amount of plating amount change generated when the feed rate of the steel sheet is changed, the pressure set value of the air knife must be changed in accordance with the change of the feed rate of the steel sheet. There is a need.

To this end, conventionally, the operator empirically adjusts the pressure according to the feed rate change of the steel sheet, or uses the air knife pressure set value change amount table for each feed rate change of the steel sheet in the past.                         

However, the operator's empirical adjustment is inaccurate, and the method of using the table is difficult to tune all the values of the table according to the characteristics of the air knife changing at regular repairs.

As a result, when changing the target plating amount, which is essential to minimize the error between the target plating amount and the coating amount, the air knife pressure setting value is incorrectly changed when the line speed is changed. Unplated phenomena that are not under plating or overplating phenomenon that occur more than a proper amount frequently occur, which is caused by additional use of molten zinc more than necessary when overplating, as well as providing additional causes. There are problems.

The present invention has been proposed in order to improve the above-mentioned various problems. The object of the present invention is to accurately calculate the plating amount equation model and the parameters of the model so as to accurately perform the plating amount prediction control necessary at the time of changing the target plating amount or the line speed of the steel sheet. The present invention provides an adaptive plating amount control device in a steel plate hot dip plating process in which the difference between the plating amount and the target plating amount of the steel sheet is always minimized even if a periodic repair or physical change of the plating process occurs.

The present invention as a technical configuration for achieving the above object is an air knife for controlling the plating amount by injecting air to the steel sheet passed through the plating amount sensor and the plating bath and the pressure to control the pressure of the air injected into the air knife In the adaptive plating amount control device in the hot dip plating process comprising a regulator,

A plating amount model unit which calculates a change amount of the plating amount by using the parameters α, β, and γ with respect to the feed rate of the steel plate, the distance between the air knife and the steel plate, and the pressure change amount of the air knife;

A parameter estimator for estimating parameters α, β, and γ of the plating amount model to minimize a difference between the plating amount measurement value measured by the plating amount measurement sensor and the plating amount calculation value calculated by the plating amount model unit;

A preset controller which presets the pressure of the air knife to adjust the plating amount to the target plating amount when the target plating amount of the steel sheet is changed; And,

When the feed rate of the steel sheet is changed, it is characterized by consisting of a feed forward controller for pre-adjusting the pressure of the air knife in order to compensate for the amount of change in plating amount according to the change of the feed rate.

Hereinafter, the structure of the plating amount control apparatus in the hot-plate steel plating process of the present invention based on the accompanying drawings in detail as follows.

Figure 2 shows the overall configuration of the adaptive plating amount control apparatus 300 in the steel plate hot dip plating process according to the present invention, such apparatus of the present invention is largely the plating amount equation model 200 including the parameter estimator 230 And a preset controller 210 and a feedforward controller 220, which will be described in more detail as follows.

First, the plating amount equation model 200, the plating amount (을) as shown in the following equation (1), the three parameters α, β, γ, the thickness (d) between the steel plate and the air knife, which is the plating amount change factor, the air pressure of the air knife ( P) and the line speed which is the feed rate of the steel sheet.

라 하고, 그 때 도금량을 Ｗ_k라 하고, 다음 시점 k+1 에서의 각 변수를

라 하면, 다음 시점 k+1 에서의 도금량(Ｗ_k+1)은 아래의 수학식 1과 같이 구할 수 있다.That is, each variable at the current time k

Then, the plating amount 때 _k , and each variable at the next time k + 1

Assuming that, following coating weight (W _{k + 1)} at the time k + 1 can be calculated as shown in Equation 1 below.

라 하고,

,

라 하고,

,

라 하고,

,

라 할때,

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The variables (V, D, P) of the plating amount equation model are all measured at each time point.

Next, referring to the preset controller 210 applied when the target plating amount of the steel sheet is changed, when the target plating amount of the steel sheet is changed from T _k to T _{k + 1} , the pressure set value P of the air knife at the next time point (P _{k + 1} ) is derived as in Equation 2 below.

Next, looking at the feed forward controller 220 applied at the time when the feed rate of the steel sheet is changed, when the feed rate of the steel sheet is changed from V _k to V _{k + 1} , the pressure set value of the air knife at the next time point ( P _{k + 1} ) is derived as in Equation 3 below.

In addition, the parameter estimator 230 performs a function of always adapting three parameters α, β, and γ to an optimal state in the plating amount equation model of Equation 1 above. If the parameters α, β, and γ are wrong, an error occurs between the plating amount W _{k + 1} calculated by Equation 1 and the actual plating amount measurement value measured by the plating amount measuring sensor 140. The parameter estimator 230 for minimizing such errors is implemented based on an optimization technique called a recursive least square method in academic terms in linear algebra.

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As described above, according to the adaptive plating amount control apparatus of the present invention, it is possible to minimize the difference between the target plating amount and the actual deposition amount by precisely adjusting the incorrect air knife pressure control when the conventional target plating amount or the line speed is changed. It is possible to prevent the loss of zinc due to poor products and over-plating as much as possible to provide an excellent effect that can reduce the production cost. In addition, the parameter estimator of the present invention provides an effect of reducing the burden on maintenance because it adapts the plating amount equation model in consideration of the changes occurring during the regular repair of the air knife facility and other plating amount related equipment.

Claims (5)

Adaptive plating amount control device in the hot-dip plating process including an air knife to control the plating amount by injecting air to the plate passing through the plating amount measurement sensor and the plating bath and a pressure regulator to control the pressure of the air injected into the air knife In Feed rate V _k , V _{k + 1} of steel sheet at time k, k + 1 and the distance D _k , D _{k + 1} , and time k, k + 1 between air knife and steel plate at time k, k + 1 The amount of change in the feed rate of the steel sheet with respect to the plating amounts W _k and W _{k + 1} at the air pressures P _k, P _{k + 1} , k and k + 1 of the air knife at

And the amount of change in gap between the air knife and the steel

And air knife pressure change

Depending on the plating amount change

of

A plating amount model portion calculated by; A parameter estimator for estimating parameters α, β, and γ of the plating amount model to minimize a difference between the plating amount measurement value measured by the plating amount measurement sensor and the plating amount calculation value calculated by the plating amount model unit; When the target plating amount of the steel plate changes from T _k to T _{k + 1} , adjust the pressure setting value (P _{k + 1} ) of the air knife at the next time point to match the plating amount with the target plating amount.

A preset controller derived by the preset controller; And When the feed rate of the steel plate changes from V _k to V _{k + 1} , to compensate for the amount of plating change due to the change of the feed rate, set the air knife pressure set value (P _{k + 1} ) at the next time.

Adaptive plating amount control device in a steel plate hot-dip galvanizing process characterized in that the feed forward controller for controlling the air knife pressure in advance by calculating by. delete delete delete delete

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