KR101008169B1 - Method for manufacturing galvanized dipping strip through monitoring - Google Patents

Abstract

One aspect of the present invention relates to a method for manufacturing a galvanized steel sheet through monitoring, and more particularly, to a method for manufacturing a steel sheet having excellent coating selectivity by real-time monitoring of a galvanized steel sheet online.

The galvanized steel sheet manufacturing method through the monitoring of the present invention, the galvanized steel sheet is plated in the plating bath to pass through the injector for spraying cooling water; A second step of irradiating light to the galvanized steel sheet passing between the injectors and photographing a region irradiated with light to generate an image; A third step of calculating a ratio of a defective area that is an area having a brightness distribution greater than or equal to a predetermined deviation in a width direction of the galvanized steel sheet in the area of the image; And a fourth step of controlling the position of the injector according to a ratio of the defective area in the generated image.

Hot-dip zinc, galvanized steel, paint sensibility, image, defect area

Description

Method for manufacturing galvanized dipping strip through monitoring

One aspect of the present invention relates to a method for manufacturing a galvanized steel sheet through monitoring, and more particularly, to a method for manufacturing a steel sheet having excellent coating selectivity by real-time monitoring of a galvanized steel sheet online.

When detecting the reflection of the light irradiated on the surface of the coated steel sheet, it is recognized that the paint selectivity is poor as the reflection of the light becomes uneven for each surface portion.

There are two methods of uniformly reflecting light: totally specular reflection of light on a mirror-like surface and totally diffuse reflection. Since hot-dip galvanized steel sheets tend to form various types of spangles with different crystal orientations, it is not practical to make a steel plate with perfect specular reflection like a mirror, and in particular, the surface of the steel sheet has a certain roughness in terms of formability. It is preferable.

In light of these considerations, a method of improving paint selectivity in hot-dip galvanized steel is to completely reflect light. In this aspect, it is desirable to refine the plating structure to reduce the fine irregularities of the surface.

In particular, it is impossible to visually check the plating structure of the galvanized steel sheet because the micronized plating structure of 88 μm or less is outside the recognition range that can be recognized by the human eye. This means that a person cannot detect the difference in the reflection of light locally on the surface, and in the plating structure of 88 μm or less, sufficient paint selectivity can be obtained.

In addition, when a large portion of the zinc plated texture, called a spangle, is mixed between the fine plated textures, a difference in reflection of light occurs for each portion, which may result in poor paint selectivity.

Therefore, it is very important to manufacture a galvanized steel sheet so that the plating structure is fine and uniform in order to improve the coating screenability.

Currently, galvanized steel sheet is manufactured by cooling the galvanized steel sheet, but it does not use the method of manufacturing galvanized steel sheet by controlling the position of the sprayer according to the distribution of the surface defect area of the galvanized steel sheet.

In addition, the method of calculating the deviation by measuring the size of the spangle several times to obtain the average value and comparing the average value with the predetermined value, but taking a galvanized steel sheet to take an area having a brightness distribution above the predetermined deviation It is not using the extraction method.

In such a situation, as galvanized steel sheet is used for the exterior of automobiles or home appliances that require strict paint selectivity, it is necessary to monitor the paint selectivity of the produced product at the time of production to produce a high quality product. Is increasing.

An aspect of the present invention is to provide a method for producing a galvanized steel sheet having excellent paint selectivity by detecting a change in the reflection of light on the surface of the steel sheet in real time online affecting the paint selectivity of the galvanized steel sheet. It is done.

One aspect of the present invention, the galvanized steel plate is plated in a plating bath to pass through an injector for spraying cooling water; Irradiating light onto the galvanized steel sheet passing through the injector, and photographing the light irradiated area to generate an image; A third step of calculating a ratio of a defective area that is an area having a brightness distribution greater than or equal to a predetermined deviation in a width direction of the galvanized steel sheet in the area of the image; And a fourth step of controlling the position of the injector according to a ratio occupied by the defective area in the generated image.

In one embodiment of the present invention, in the width direction of the galvanized steel sheet, when the ratio of the defective area occupies at the edge portion is higher than the central portion, the control to lower the position of the injector, the central portion than the edge portion When the ratio of the defect area is higher, it provides a method of manufacturing a galvanized steel sheet through monitoring, characterized in that to control to raise the position of the injector.

In another embodiment of the present invention, further comprising the step of supplying the wind to the galvanized steel plate plated in the plating bath by using a blower, in accordance with the ratio occupied by the defect area in the generated image, the control unit is It provides a galvanized steel sheet manufacturing method through monitoring, characterized in that to control the temperature and the amount of wind supplied by the blower.

In another embodiment of the present invention, in the case where the ratio of the defective area at the center of the galvanized steel sheet in the width direction of the galvanized steel sheet at the highest position of the injector is lower, the central portion of the galvanized steel sheet to cool the And controlling the blower to control the blower to heat the edge portion of the galvanized steel sheet at a lower position of the injector, when the proportion of the defective area at the edge portion is lower than the center portion in the width direction of the galvanized steel sheet. It provides a galvanized steel sheet manufacturing method through the monitoring.

In another embodiment of the present invention, the galvanized steel sheet manufacturing method through the monitoring, characterized in that to control the temperature and the amount of wind supplied by the blower to have a uniform temperature in the width direction to provide.

In another embodiment of the present invention, the third step may include: receiving a color image represented by the captured image and converting the color image into a black and white image; Extracting an area having a brightness distribution greater than or equal to a predetermined deviation from the black and white image; Detecting a boundary between the extracted area and the non-extracted area; Converting the extracted region and the non-extracted region into a binarized image based on the detected boundary; And calculating a region having a brightness distribution greater than or equal to a predetermined deviation in the binarization image as a ratio occupied by the defect region. 2.

According to an aspect of the present invention, by detecting in real time the change in the reflection of light on the surface of the steel sheet affecting the coating selectivity of the galvanized steel sheet in real time, cooling a portion of the galvanized steel sheet according to the proportion of the defect area Alternatively, it is possible to produce a galvanized steel sheet having excellent coating sensibility by heating.

According to another aspect of the present invention, it is possible to ensure the consumer's reliability by producing excellent galvanized steel sheet, thereby increasing the demand of the consumer.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention may be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. The shape and the size of the elements in the drawings may be exaggerated for clarity and the same elements are denoted by the same reference numerals in the drawings.

1 is a configuration of the galvanized steel sheet manufacturing apparatus through the monitoring of the present invention.

There are two methods for manufacturing a hot dip galvanized steel sheet as follows.

In the first method of manufacturing a hot-dip galvanized steel sheet, the galvanized steel sheet 10 is passed through a plating bath 20 containing a plating solution, and the galvanized steel sheet 10 passing through the plating bath 20 receives cooling water. The galvanized steel sheet 10 is cooled by the cooling water injection of the injector 30 by passing through the injector 30 provided on one side and the other side to inject.

In the second method of manufacturing the hot-dip galvanized steel sheet, in the first method, the blower 40 is further provided between the plating bath 20 and the injector 30 so that the blower 40 passes through the plating bath 20. It is to supply wind to the galvanized steel sheet (10).

As described above, after the galvanized steel sheet 10 is cooled by spraying the coolant injection of the injector 30 through the plating bath 20, an apparatus for monitoring the coating selectivity of the galvanized steel sheet 10 online is required. .

As shown in FIG. 1, the galvanized steel sheet manufacturing apparatus through monitoring includes a plating bath 20, an image generator 100, an image analyzer 200, and a controller 300.

The injector 30 is provided at one side and the other side to inject the coolant to the galvanized steel sheet plated in the plating bath 20.

The image generator 100 includes a light source 120 and a camera 110. The light source 120 is plated in the plating bath 20 and passed through the injector 30 between one side and the other side of the galvanized steel sheet 10. The light is irradiated to the camera 110, and the camera 110 generates an image by photographing the light irradiated area.

The image analyzer 200 analyzes the generated image and calculates a ratio of defective areas in the galvanized steel sheet. The defect area referred to in the present invention is defined as an area representing a brightness distribution above a predetermined deviation.

Detailed configuration of the image analyzer 200 will be described with reference to FIG. 2.

The controller 300 controls the position of the injector 30 according to the ratio of the defective area in the generated image. That is, when the image analyzer 200 detects how fine the galvanized steel sheet 10 is, the controller 300 controls the position of the injector 30 according to the detected fineness. When the injector 30 injects the cooling water in order to refine the plating structure of the galvanized steel sheet 10, it is most efficient to spray the cooling water when the temperature of the plating layer of the galvanized steel sheet 10 is just before solidification. . Therefore, when the temperature of the galvanized steel sheet 10 is high and the plating structure of the center of the galvanized steel sheet 10 is not miniaturized, the sprayer 30 is controlled upward, and the temperature of the galvanized steel sheet 10 is low so that the zinc If the plating structure of the edge portion of the plated steel sheet 10 is not miniaturized, the injector 30 is controlled to be lowered. At this time, the edge portion of the galvanized steel sheet 10 is defined as an area from the edge to the 10m point in the width direction, and the center portion is defined as other regions, it is also possible to set the edge portion and the center portion by setting different standards Of course.

In general, since the temperature deviation occurs in the width direction of the galvanized steel sheet 10, the temperature of the galvanized steel sheet 10 is lower than the center portion. Therefore, when the spraying water is sprayed while the sprayer 30 is positioned at the lower portion, the plating structure starts to be refined from the edge portion of the galvanized steel sheet 10. When the plating structure of the galvanized steel sheet 10 is measured according to the position of the injector 30, when the injector 30 is in the lower position, only the edge portion of the galvanized steel sheet 10 is refined. When the injector 30 is upwardly adjusted in the lower position and moved to a predetermined position, the plating structure of the whole galvanized steel sheet 10 becomes fine, and when the injector 30 is in an upper position than the proper position, the galvanized steel sheet 10 The temperature of the edge portion of the sheet) becomes too low (that is, because cooling water is injected after the plating layer of the galvanized steel sheet 10 is solidified), and the plating structure of the center of the galvanized steel sheet 10 becomes fine.

Therefore, in the image of the galvanized steel sheet 10, when the ratio of the defective area to the edge portion in the width direction of the galvanized steel sheet 10 is higher than that of the central portion, the portion of the galvanized steel sheet 10 into which the coolant is injected is injected. It means that the temperature is low, and if the ratio of the defective area in the center portion is higher than the edge portion, it means that the temperature of the part of the galvanized steel sheet 10 to which the coolant is injected is high.

Accordingly, the controller 130 controls to lower the position of the injector 30 when the ratio of the defective area at the edge portion is higher than the center portion in the width direction of the galvanized steel sheet 10 in the photographed image. In the case where the ratio of the defective area to the center of the edge portion is higher than that of the edge portion, by controlling the position of the injector 30 to be raised, an appropriate temperature at which the injector 30 can be miniaturized with respect to the galvanized steel sheet 10 can be obtained. When it is possible to spray the cooling water can be galvanized steel sheet 10 can have a uniform plating structure in the width direction. Since the controller 300 may control the position of the injector 30 in real time, the state of the galvanized steel sheet 10 may be immediately reflected in the manufacture of the galvanized steel sheet 10.

Between the plating bath 20 and the injector 30 may further include a blower 40 for supplying air to the galvanized steel sheet plated in the plating bath 20, wherein the control unit 300 is defective in the generated image The temperature and the amount of wind supplied to the galvanized steel sheet 10 passed through the plating bath 20 by the blower 40 are controlled according to the proportion of the area. Specifically, the control unit 300 to control the temperature and the amount of wind supplied by the blower 40 so that the galvanized steel sheet 10 has a uniform temperature in the width direction.

Even if the galvanized steel sheet 10 passed through the plating bath 20 has a large temperature variation in the width direction of the galvanized steel sheet 20, it is difficult to obtain a uniform plating structure even when spraying the coolant from the sprayer 30. Can be. In this case, a blower 40 may be provided between the plating bath 20 and the injector 30 to control the temperature of the galvanized steel sheet 10 to be uniform in the width direction. For example, when the temperature of the center of the galvanized steel sheet 10 is high enough that the plating structure is not refined, the low temperature wind may be blown to the center of the galvanized steel sheet 10 to cool the galvanized steel sheet. When the temperature of the edge portion (10) is low enough that the plating structure is not refined, a high temperature wind can be blown into the edge portion of the galvanized steel sheet 10 to be heated.

At this time, the control unit 300 may use the temperature of the edge portion and the center of the galvanized steel sheet 10 detected by a temperature sensor (not shown), etc., but the ratio occupied by the defect area calculated by the image analyzer 200 is used. By using the blower 40, the galvanized steel sheet 10 can be cooled or heated.

For example, when the injector 30 is in the highest position, if the ratio of the defective area to the center of the galvanized steel sheet 10 in the width direction of the galvanized steel sheet is higher than that of the edge portion, the plating structure is not refined. Since it means that the temperature is high, the control unit 300 controls the blower 40 to cool the center of the galvanized steel sheet (10). When the injector 30 is at the lowest position, when the ratio of the defective area at the center of the galvanized steel sheet 10 in the width direction of the galvanized steel sheet is lower than the edge portion, the temperature of the edge portion is so low that the plating structure is not refined. Therefore, the control unit 300 controls the blower 40 to heat the edge portion of the galvanized steel sheet 10.

In this case, the controller 300 may simultaneously control the amount and temperature of the wind supplied to the galvanized steel sheet 10 by the blower 40. Through such control, even when the galvanized steel sheet 10 passing through the plating bath 20 has a deviation in the width direction, it is possible to control the plating structure of the galvanized steel sheet 10 to be uniform.

FIG. 2 is a detailed configuration diagram of the image analyzer of FIG. 1. As illustrated in FIG. 2, the image analyzer 200 may include an image preprocessor 210, a boundary detector 220, a binarizer 230, a defect region calculator 240, and a calculator 250. .

The image preprocessor 210 receives a color image represented by the captured image, converts the color image into a black and white image, and extracts an area having a brightness distribution greater than or equal to a predetermined deviation from the black and white image.

The boundary detector 220 detects a boundary between the extracted region and the non-extracted region.

The binarization unit 230 converts the extracted region and the non-extracted region into a binarized image based on the detected boundary.

The defect area calculator 240 calculates a region having a brightness distribution greater than or equal to a predetermined deviation in the binarized image as a proportion of the defect area. The ratio occupied by the defect area in the binarization image may be calculated as a ratio of the number of pixels of the defect area to the number of pixels of the binarization image as shown in Equation 1.

The calculator 250 calculates an average value of brightness of the extracted region. The average value of the brightness is the sum of the brightnesses of the pixels of the defective area divided by the number of pixels of the defective area.

3 is a surface of a galvanized steel sheet showing a normal region and a defective region of the present invention and a screen analyzing the same. In FIG. 3, (a) is a surface of a galvanized steel sheet showing a normal region and a defective region, and (b) is a screen analyzing the line portion of (a).

As shown in (a) of FIG. 3, in the normal region where the plating structure is fine and uniform, light brightness is not large and there is a fluctuation in a narrow range, but in the defect area where the plating structure is coarse, the light is specularly and diffusely reflected. The areas to be mixed are mixed, and the variation in brightness of light is increased. That is, when comparing the normal region and the defective region, it can be seen that the deviation of the brightness of light in the defect region is very large compared to the normal region.

The deviation of the brightness defining the defect area is determined by the level of paint selectivity targeted, and the greater the paint selectivity, the smaller the deviation.

As shown in (b) of FIG. 3, the horizontal axis represents the number of pixels and the brightness of the light, respectively, and the line portion of (a) is composed of 861 pixels, and the linear ( The brightness of the light of the 861 pixels represented by the mapping mode of Linear) is 83.00 and 194.00, respectively, for the minimum value and the maximum value. The mean value thereof is 144.42 and the standard deviation is 14.33. With this analysis result, it can be seen that even with the naked eye, the deviation of the brightness of light is larger in the defective area (marked with a square) than in the normal area.

4 is a surface of the galvanized steel sheet of the present invention, Figure 5 is a screen showing the black and white image of the galvanized steel sheet of Figure 4, Figure 6 is a screen showing the binary image of FIG.

The image analyzer converts a color image photographing the surface of the galvanized steel sheet as shown in FIG. 4 into a black and white image as shown in FIG. 5, and extracts an area having a brightness distribution greater than or equal to a predetermined deviation from the black and white image. Then, the boundary between the extracted region and the non-extracted region is detected and the extracted region and the non-extracted region are converted into black and white binarization images as shown in FIG. 6 based on the detected boundary.

FIG. 7 is a table showing the number of pixels of a defective area in the binarization image of FIG. 6, and FIG. 8 is a histogram showing a brightness distribution of light represented by pixels of the defective area of FIG. 7.

In FIG. 7, it can be seen that the binarized image includes pixels having a total of 193161 defect areas in the object of 17 areas. In FIG. 8, the brightness of light of these pixels is shown. In FIG. 8, the horizontal axis represents the brightness of light, and the vertical axis represents the number of pixels.

The total area of FIG. 6 is composed of 2589600 pixels. In FIG. 8, the brightness of the light of 2589600 pixels represented by the linear mapping mode on the horizontal axis is the minimum value and the maximum value. Maximum values are 29.00 and 244.00, respectively. And the mean value thereof (Mean value) is 135.45, and the standard deviation (Std Deviation) is 13.60. The naked eye can see that the maximum light brightness is between 125 and 150.

임을 알 수 있다.Since the number of pixels represented by the entire area of the binarization image and the number of pixels represented by the defective area are shown in FIGS. 7 and 8, using Equation 1, the ratio of the defective area in the binarized image is calculated.

It can be seen that.

9 is a flow chart of the galvanized steel sheet manufacturing method through the monitoring of the present invention. 9 will be described below with reference to FIGS. 1 and 2.

First, the galvanized steel sheet 10 is plated in the plating bath 20 passes between the injector 30 on one side and the other side to spray the cooling water (S100).

Thereafter, the light source 120 of the image generator 100 irradiates light to the galvanized steel sheet 10 passed between the injectors 30, and the camera 110 of the image generator 100 is irradiated with light. Photographing to generate an image (S200).

Subsequently, the ratio of the defective area, which is a region having a brightness distribution greater than or equal to a predetermined deviation in the width direction of the galvanized steel sheet in the width direction of the galvanized steel sheet, is calculated in the region of the image generated by the image analyzer 200 (S300).

Thereafter, the controller 300 controls the position of the injector 30 according to the ratio of the defective area in the generated image (S400). However, when the blower 40 is further provided between the plating bath 20 and the injector 30, the blower 40 may supply wind to the galvanized steel sheet 10 plated by the plating bath 20. In this case, the control unit 300 may further control the temperature and the amount of wind supplied to the galvanized steel sheet 10 passed through the plating bath (20).

Looking specifically at the step S300, it is composed of steps S310 ~ S350.

First, the image preprocessor 210 receives a color image indicated by the captured image and converts it to a black and white image (S310).

Thereafter, the image preprocessor 210 extracts an area having a brightness distribution greater than or equal to a predetermined deviation from the black and white image (S320).

Thereafter, the boundary detector 220 detects a boundary between the extracted region and the non-extracted region (S330).

Subsequently, the binarization unit 230 converts the extracted region and the non-extracted region into black and white binarization images based on the detected boundary (S340).

Thereafter, the defect area calculator 240 calculates a region having a brightness distribution greater than or equal to a predetermined deviation in the binarized image as a proportion of the defect area (S350).

In addition, regardless of the steps S330 to S350, after the step S320, the average value of the brightness of the extracted region may be obtained.

With respect to the method in which the control unit 300 controls the injector 30 in the step S400, when the ratio of the defective area in the edge portion in the width direction of the galvanized steel sheet 10 is higher, the control unit 300 ) Controls to raise the position of the injector 30. In addition, when the ratio of the defective area in the center portion of the galvanized steel sheet 10 in the width direction is higher than that of the edge portion, the controller 300 controls to lower the position of the injector 30.

In relation to the method in which the control unit 300 controls the blower 40 in step S400, the control unit 300 is provided between the plating bath 20 and the injector 30 according to the ratio of the defective area in the generated image. The blower 40 is controlled to control the temperature and amount of wind supplied to the galvanized steel sheet 10 passed through the plating bath (20). Specifically, the controller 300 controls the temperature and amount of wind supplied by the blower 40 so that the galvanized steel sheet 10 has a uniform temperature in the width direction.

With respect to the position of the injector 30, in the case where the ratio of the defective area at the center of the galvanized steel plate 10 in the width direction at the highest position of the injector 30 is lower than the edge portion, the controller 300 is The blower 40 is controlled to cool the center of the galvanized steel sheet 10. Then, when the ratio of the defective area to the edge portion in the width direction of the galvanized steel sheet 10 in the width direction of the injector 30 is lower, the controller 300 is the edge portion of the galvanized steel sheet 10 The blower 40 is controlled to heat.

The present invention is not limited by the above-described embodiment and the accompanying drawings. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims, .

1 is a configuration of the galvanized steel sheet manufacturing apparatus through the monitoring of the present invention.

FIG. 2 is a detailed configuration diagram of the image analyzer of FIG. 1.

3 is a surface of a galvanized steel sheet showing a normal region and a defective region of the present invention and a screen analyzing the same.

4 is a surface of a galvanized steel sheet of the present invention.

5 is a screen showing the black and white image of the galvanized steel sheet of FIG.

6 is a screen illustrating the binarization image of FIG. 5.

FIG. 7 is a table illustrating the number of pixels of a defective area in the binarization image of FIG. 6.

FIG. 8 is a histogram illustrating a brightness distribution of light represented by pixels of a defective area of FIG. 7.

9 is a flow chart of the galvanized steel sheet manufacturing method through the monitoring of the present invention.

                 <Explanation of symbols for the main parts of the drawings>

10: plated steel sheet 20: plating bath

30: injector 40: blower

100: Image Generator 110: Camera

120: light source 200: image analyzer

210: image preprocessing unit 220: boundary detection unit

230: binarization unit 240: defect area calculation unit

250: brightness calculator 300: controller

Claims (6)

A first step in which a galvanized steel sheet is plated in a plating bath and passed through an injector for spraying cooling water; Irradiating light onto the galvanized steel sheet passing through the injector, and photographing the light irradiated area to generate an image; A third step of measuring a microstructure of the plating of the galvanized steel sheet by calculating a ratio of a defective region, which is a region having a brightness distribution greater than or equal to a predetermined deviation in a width direction of the galvanized steel sheet, in the region of the image; And A fourth step of controlling the degree of microstructure of the plating of the galvanized steel sheet by controlling the position of the injector according to a ratio of the defect area in the generated image; Includes, the third step, Receiving a color image represented by the captured image and converting the color image into a black and white image; Extracting an area having a brightness distribution greater than or equal to a predetermined deviation from the black and white image; Detecting a boundary between the extracted area and the non-extracted area; Converting the extracted region and the non-extracted region into a binarized image based on the detected boundary; And Calculating an area having a brightness distribution greater than or equal to a predetermined deviation in the binarized image as a ratio of a defective area; Galvanized steel sheet manufacturing method through the monitoring comprising a. The method of claim 1, wherein the fourth step When the ratio of the defect area to the edge portion in the width direction of the galvanized steel sheet is higher than the central portion, the control to lower the position of the injector, If the ratio of the defect area in the center portion than the edge portion is higher, the manufacturing method of the galvanized steel sheet through monitoring, characterized in that to control to raise the position of the injector. The method of claim 1, The method of manufacturing a galvanized steel sheet through monitoring further comprising supplying air by controlling a temperature and an amount according to a ratio of the defective area in the generated image by using a blower to the galvanized steel sheet plated in the plating bath. . The method of claim 3, wherein supplying the wind Controlling the blower to cool the center portion of the galvanized steel sheet when the ratio of the defective area at the center portion is lower than the edge portion in the width direction of the galvanized steel sheet at the highest position of the injector; And monitoring the blower to heat the edge portion of the galvanized steel sheet when the ratio of the defective area to the edge portion is lower than the center portion in the width direction of the galvanized steel sheet at the lowest position of the injector. Galvanized steel sheet manufacturing method through. The method of claim 3 or 4, wherein supplying the wind Method for producing a galvanized steel sheet through the monitoring, characterized in that for controlling the temperature and the amount of wind supplied by the blower so that the galvanized steel sheet has a uniform temperature in the width direction. delete

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