JP2022171449A - Coating method of coated steel panel, coated steel panel, and coating evaluation method - Google Patents

Abstract

To provide a coating method of a coated steel panel which can accurately estimate and evaluate a state of coating formed on a coated steel panel during coating, and form a coating film having an excellent appearance property without a defect.SOLUTION: In order to achieve the above-mentioned purpose, a coating method of a coated steel panel for coating a steel plate 6 that continuously travels with coating liquid 2 by a roll coater having a pickup roll 4 and an applicator roll 5 comprises: imaging the coating state of the coating liquid 2 formed on the roll 3 in the coating and the state of excess coating liquid (state of a curtain 7) scraped off by a gap or a nip between the pickup roll 4 and the applicator roll 5; and performing coating of the coating liquid 2 on the basis of the evaluation result of the photographed image.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a coating method for a coated steel sheet, which can accurately estimate and evaluate the state of the coating film formed on the coated steel sheet during coating, and can form a coating film excellent in appearance.

Conventionally, as a means of coating the surface of a metal strip such as a galvanized steel strip that generally runs continuously with a coating solution such as a chemical conversion agent or paint, the metal strip is immersed in the coating solution, or the surface of the metal strip is There are various means such as spraying the coating liquid onto the substrate, applying the coating liquid using a roll coater, a brush, or the like.

Among these various means, the roll coater uses a roll coater in which two (2-roll coater) or three (3-roll coater) coating rolls are arranged on the continuously running steel plate surface. is commonly done.

FIG. 1 shows an example of a two-roll coater. Equipped with a pickup roll 4 and an applicator roll 5, the pickup roll 4 picks up the coating liquid 2 in the coater pan 1, transfers the drawn coating liquid 2 to the applicator roll 5, and the applicator roll 5 applies the transferred coating liquid 2 to the steel. By transferring to a band (steel plate) 6, the coating liquid is coated on the steel plate. Natural coating and reverse coating are methods of coating a steel plate with a coating liquid. The roll coater shown in FIG. 1 is a reverse coater, and the solid line arrow indicates the rotation direction of the roll.

In the method of coating a coated steel plate using a roll coater as described above, it is normal to check the state of coating film formation after coating, and to adjust the coating conditions afterward if there is a problem. .
Therefore, from the viewpoint of eliminating waste of materials such as steel strips and coating liquid, it is possible to estimate the state of the coating film formed on the steel plate when coating the coating liquid, and based on the estimated coating film state, the coating conditions of the coating liquid There has been a demand for the development of technology that can control

In view of such circumstances, the present invention provides a coating method for a coated steel plate that can accurately estimate and evaluate the state of the coating film formed on the coated steel plate during coating, and can form a coating film with excellent appearance without defects. It is an object of the present invention to provide a coated steel sheet on which a coating film having excellent appearance is formed, and a coating evaluation method capable of accurately estimating and evaluating the state of the coating film formed on the coated steel sheet during coating.

The inventors of the present invention have investigated a method for coating a coated steel plate, in which a continuously running steel plate is coated with a coating liquid by a roll coater equipped with a pickup roll and an applicator roll, in order to solve the above problems. , By evaluating the state of the excess coating liquid scraped off by the pickup roll, the applicator roll, and the gap or nip between the pickup roll and the applicator roll during coating, the state of the coating film formed on the steel sheet is evaluated. It was found that it is possible to accurately estimate and evaluate during coating, and that a coating film with excellent appearance without defects can be formed by adjusting the conditions of the pickup roll and applicator roll based on the obtained evaluation results.

The present invention was made based on the above findings, and the gist thereof is as follows.
1. A method of coating a coated steel plate, in which a continuously running steel plate is coated with a coating liquid by a roll coater equipped with a pickup roll and an applicator roll,
During the coating, the state of the coating liquid formed on the pickup roll, the state of the coating liquid formed on the applicator roll, and the gap or nip between the pickup roll and the applicator roll scraped off. Take a picture of the state of the excess coating liquid (state of the curtain),
A method of coating a coated steel plate, wherein coating is performed with the coating liquid while adjusting the roll peripheral speed and the gap or nip pressure of the pickup roll and the applicator roll based on the evaluation results of the captured image. .

2. The coating state of the coating liquid formed on the pickup roll and the coating state of the coating liquid formed on the applicator roll are the states of uniformity, width and pitch of the roping formed on each roll,
2. The method for coating a coated steel plate according to 1 above, wherein the state of the curtain is the uniformity of the scraped-off excess coating liquid and the presence or absence of irregular lifting failures of the excess coating liquid.

3. 3. The method of coating a coated steel plate according to 1 or 2 above, wherein the coating liquid has a Ford cup viscosity (Ford cup No. 4) of 45 to 80 seconds.

4. 3. The method for coating a coated steel plate according to 1 or 2 above, wherein the roll coater is a two-roll coater.

5. A coated steel sheet having a coating film formed by the coating method according to any one of 1 to 4 above,
For the coating film, the surface unevenness height (H) and roughness (R) are measured using a 3D microscope, and the average unevenness height (H _ave ), the average roughness (R _ave ) and the film thickness ( A coated steel sheet, characterized in that T) (μm) satisfies the following (1) and (2).
0.30×T≦ _Have ≦0.50×T (1)
R _ave ≦0.09×T (2)

6. A coating evaluation method for evaluating the state of a coating of a coating liquid formed on a steel plate by a roll coater equipped with a pickup roll and an applicator roll,
During the coating, the state of the coating liquid formed on the pickup roll, the state of the coating liquid formed on the applicator roll, and the gap or nip between the pickup roll and the applicator roll scraped off. A coating evaluation method comprising photographing the state of excess coating liquid (curtain state) and evaluating the coating state of the coating liquid from the photographed image.

According to the present invention, the state of the coating film formed on the coated steel plate can be accurately estimated and evaluated during coating, and a method for coating a coated steel plate that can form a coating film with excellent appearance without defects, and with excellent appearance without defects. It is possible to provide a coated steel sheet on which a coating film is formed and a coating evaluation method capable of accurately estimating and evaluating the state of the coating film formed on the coated steel sheet during coating.

1 is a perspective view schematically showing a roll coater provided with a pick-up roll and an applicator roll; FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which showed typically one Embodiment of the roll coater used for the coating method of the coated steel plate of this invention. FIG. 4 is a cross-sectional view schematically showing roping formed on a roll; Examples of evaluation points used as criteria for evaluating each of the state of the coating liquid formed on the pickup roll, the state of the coating liquid formed on the applicator roll, and the state of the curtain are shown. is. The best evaluation score (5 points) and the worst evaluation score (1 point) were obtained for the coating film state of the coating liquid formed on the pickup roll, the coating film state of the coating liquid formed on the applicator roll, and the curtain state, respectively. ).

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Coating method for coated steel plate)
The method for coating a coated steel plate of the present invention (hereinafter sometimes simply referred to as the "coating method of the present invention") includes a pickup roll 4 and an applicator roll 5 (hereinafter collectively referred to as "roll 3”) is used to coat a continuously running steel plate 6 with the coating liquid 2.

Here, the pickup roll 4 is provided so that the lower part of the roll is immersed in the coating liquid 2 in the coater pan 1, as shown in FIG. The pickup roll 4 picks up the coating liquid 2 in the coater pan 1 as it rotates. FIG. 2 illustrates a case where the pickup roll 4 rotates counterclockwise.

The applicator roll 5 contacts the peripheral surface of the pickup roll 4 with a predetermined nip pressure or gap, and the coating liquid 2 on the pickup roll 4 moved to the position of the transfer portion is applied with a predetermined nip pressure or gap. is transferred to the peripheral surface of the applicator roll 5 while being squeezed to a film thickness of . The coating liquid 2 transferred to the applicator roll 5 moves toward the steel plate 6 as the applicator roll 5 rotates, and is continuously applied to the surface of the steel plate 6 . In the example shown in FIG. 2, the applicator roll 5 rotates clockwise, and the coating liquid 2 transferred from the pick-up roll 4 moves toward the steel plate 6 as the applicator roll 5 rotates. A liquid 2 is coated on a steel plate 6 .

The material and dimensions of the pickup roll 4 are not particularly limited, and can be appropriately selected according to the type of the coating liquid 2 and the required performance.
The material and dimensions of the applicator roll 5 are also not particularly limited, and can be appropriately selected according to the type of the coating liquid 2 and the required performance. For example, when the applicator roll 5 is a roll made of metal, since it does not come into contact with the pickup roll 4 , a gap is formed in the contact surface with the pickup roll 4 . On the other hand, when the applicator roll 5 is a rubber roll, it is in contact with the pickup roll 4 with a predetermined pressure.

In FIG. 1, the coating liquid 2 is transferred from the applicator roll 5 to the steel plate 6 while the steel plate (steel strip) 6 is wound around the backup roll 8. It is also possible to eliminate the backup roll by disposing a roll coater or by disposing a support roll on the opposite side of the coating surface.
Further, the pick-up roll 4 and the applicator roll 5 may each be provided with a scraping device (not shown) for removing the remaining coating liquid 2 without being transferred.

The type of the coating liquid 2 is not particularly limited, and can be appropriately selected according to the type of coating film to be formed on the steel plate 6 (a chemical conversion film, an undercoat film, a topcoat film, etc.).
Furthermore, from the viewpoint of being able to more significantly exhibit the effect of the present invention that a coating film having excellent appearance can be formed without defects, the viscosity of the coating liquid 2 is preferably high. Cup No. 4) is preferably about 45 to 80 seconds, more preferably about 50 to 60 seconds. When the coating liquid 2 has a Ford cup viscosity (Ford cup No. 4) of 45 seconds or more, the appearance of the coating film tends to deteriorate due to defects such as roping, so the effects of the present invention can be exhibited more remarkably. .

1 and 2, the roll coater may be a two-roll coater provided with the pickup roll 4 and the applicator roll 5, or other rolls such as an intermediate roll and an auxiliary roll ( not shown).
Among them, the roll coater is preferably a two-roll coater. This is because the effect of forming a defect-free coating film excellent in appearance according to the present invention can be exhibited more remarkably.

The coating method of the present invention, as shown in FIG. 2, and the state of the surplus coating liquid 7 scraped off by the gap or nip between the pickup roll 4 and the applicator roll 5 (the state of the curtain 7),
It is characterized in that coating with the coating liquid 2 is performed while adjusting the roll peripheral speed and the gap or nip pressure of the pickup roll 4 and the applicator roll 5 based on the evaluation result of the photographed image.

The state of the coating such as roping of the coating liquid 2 formed on the pickup roll 4 and the applicator roll 5 and the state of the curtain 7 greatly affect the surface properties of the coating 6A formed on the steel plate 6. Therefore, by accurately grasping and evaluating these states, the state of the coating film 6A formed on the steel plate 6 can be accurately estimated and evaluated during coating without actually observing it. .
Then, based on the evaluation results, by adjusting the roll peripheral speed and gap or nip pressure of the pickup roll 4 and the applicator roll 5, the coating liquid 2 formed on the pickup roll 4 described above, the applicator The state of the coating liquid 2 formed on the roll 5 and the curtain 7 can be brought to a good state, and the coating film 6A having no defects and excellent appearance can be formed.

The state of the coating film formed on the pickup roll 4 and the applicator roll 5 means the state of existence, shape, etc. of the coating film formed by the coating liquid 2 transferred onto each roll 3 . The coating state of the coating liquid 2 formed on the roll 3 is not particularly limited as long as the state of the coating 6A formed on the steel plate 6 can be grasped. The presence or absence, uniformity, size, width or pitch of the ropings 2′ and 2″ formed thereon, or the unevenness or thickness of the coating film can be mentioned. From the viewpoint of estimating and evaluating the state, the state of the coating film formed on the pickup roll 4 and the applicator roll 5 depends on the uniformity, uniformity, Width and pitch conditions are preferred.

1 and 3, the ropings 2' and 2'' are protrusions formed on the coating film of the coating liquid 2 on the roll 3. These ropings 2' and 2'' is mainly due to the peripheral speed of the roll 3, the nip pressure or gap, and the physical properties of the coating liquid (viscosity, surface tension, etc.). The smaller the peripheral speed difference of 5, the more likely it is to occur. However, since this roping is gradually leveled and smoothed after the coating liquid 2 is coated on the steel plate 6, there is no problem if the roping occurs if the coating liquid 2 is of a certain size. It is important that the ropings 2', 2'' formed on the pick-up roll 4 and applicator roll 5 are uniformly formed so that they are evenly smoothed after being coated.
The widths of the ropings 2' and 2'' are the widths of the convex portions of the ropings 2' and 2'' as shown in FIG. As such, it is the spacing at which the ropings 2' and 2'' are formed.

The state of the curtain 7 is the state of existence, shape, etc. of the surplus coating liquid scraped off by the gap or nip between the pickup roll 4 and the applicator roll 5 . The state of the curtain 7 is not particularly limited as long as the state of the coating film 6A formed on the steel plate 6 can be grasped. Presence or absence of regular lifting failure, etc. can be mentioned. Among these, the uniformity of the surplus coating liquid and the presence or absence of irregular lifting failures of the surplus coating liquid are preferable from the viewpoint of more reliably estimating and evaluating the state of the coating film 6A.
The uniformity of the surplus coating liquid means the uniformity of the shape (uniformity of the shape of the curtain 7) when the scraped-off surplus coating liquid falls, and the surplus coating liquid falls in the same state. If the curtain 7 continues to fall in the same shape, it is uniform. If there is no uniformity), there is no homogeneity. Further, the failure to lift the excess coating liquid means a state in which there is unevenness in the manner in which the excess coating liquid falls.

Here, both the coating state of the coating liquid 2 formed on the pickup roll 4 and the applicator roll 5 and the state of the curtain 7 can be photographed by an imaging device 10 . For example, in FIG. 2, the coating state of the coating liquid 2 formed on the pickup roll 4, the coating state of the coating liquid 2 formed on the applicator roll 5, and the state of the curtain 7 can be observed, respectively. Photographing devices 11, 12, and 13 are provided, and each state can be photographed.
The type of the photographing device 10 is not particularly limited as long as it can accurately photograph the state of the coating film formed on the pickup roll 4 and the applicator roll 5 and the state of the curtain 7. For example, high speed A camera or the like can be used.
It is desirable to observe the state of the coating film formed on the pickup roll 4 and the applicator roll 5 and the photographed images of the state of the curtain 7 as still images and moving images.

The method for evaluating the photographed still images and moving images is not particularly limited as long as it is a method capable of accurately estimating and evaluating the state of the coating film 6A formed on the steel plate 6 .
As one of the evaluation methods, for example, the state of the coating films formed on the pickup roll 4 and the applicator roll 5 and the photographed image of the state of the curtain 7 are each evaluated in five grades.
Here, FIG. 4 shows the state of the coating of the coating liquid 2 formed on the pickup roll 4, the state of the coating of the coating liquid 2 formed on the applicator roll 5, and the state of the curtain 7, each evaluated in five stages. The image (evaluation point example) of the state that serves as a reference when performing is shown. For example, FIG. 4 shows an image of the coating state of the coating liquid 2 formed on the pickup roll 4, the coating state of the coating liquid 2 formed on the applicator roll 5, and the state of the curtain 7. Points can be assigned and evaluated by comparing with the example evaluation points.

Here, FIG. 5 shows photographed images of the state of the coating liquid 2 formed on the pickup roll 4, the state of the coating liquid 2 formed on the applicator roll 5, and the state of the curtain 7, respectively. , the best score (5 points) versus the worst score (1 point). As can be seen from FIG. 5, in the photographed image with an evaluation point of 1, the uniformity and clarity of the ropings 2' and 2'' of the coating film are poor, and the state of the curtain 7 is also uneven.

Then, when the roping state of the coating film formed on the pickup roll 4, the roping state of the coating film formed on the applicator roll 5, and the state of the curtain 7 are all good Although it is not necessary to adjust the roll peripheral speed of the roll 3, the gap/nip pressure, etc., which will be described later, the roll peripheral speed and the gap or the nip pressure of the roll 3 are adjusted if the results are not satisfactory.
The criteria for determining whether the roping state of the coating film formed on the pickup roll 4 and the roping state of the coating film formed on the applicator roll 5 are good depend on the required performance. Can be set as appropriate. For example, when performing the five-step evaluation described above, a threshold is set for the total evaluation value, and whether or not the threshold is exceeded determines whether the roll peripheral speed and the gap or nip pressure of the roll 3 are adjusted. It can be performed.

Moreover, the method of adjusting the roll peripheral speed and the gap or nip pressure of the pickup roll 4 and the applicator roll 5 is not particularly limited, and may be carried out according to usual procedures and conditions.
For example, when the roping of the coating film formed on the pickup roll 4 and the pickup roll 5 is uneven, the roping is made uniform by adjusting the roll peripheral speed difference between the pickup roll 4 and the pickup roll 5. can do. Further, when the curtain 7 is uneven, or when there is an irregular lifting failure of the excess coating liquid, the roll peripheral speed difference between the pickup roll 4 and the pickup roll 5 is adjusted so that the curtain 7 is formed. You can adjust the state.

The roll peripheral speeds of the pickup roll 4 and the applicator roll 5 are not particularly limited, and can be appropriately set according to the conditions of the coating apparatus. For example, the peripheral roll speeds of the pickup roll 4 and the applicator roll 5 are preferably set in the range of 10 to 200 mpm, respectively, and the roll peripheral speed difference between the pickup roll 4 and the pickup roll 5 is adjusted. Therefore, it is more preferable to set the roll peripheral speed of the pickup roll 4 to 20 to 30 mpm.

(Painted steel plate)
The coated steel sheet of the present invention is a coated steel sheet having a coating film formed by the coating method of the present invention described above.
Then, the coating film was measured for surface unevenness height (H) and roughness (R) using a 3D microscope, and the average unevenness height (H _ave ), the average roughness (R _ave ) and the film The thickness (T) (μm) is characterized by satisfying the following (1) and (2).
0.30×T≦ _Have ≦0.50×T (1)
R _ave ≦0.09×T (2)

When the coating film satisfies the above relationships (1) and (2), it is possible to obtain a coating film having no defects and excellent appearance.
From the same point of view, the above formula (1) is preferably the following formula (1)', and the above formula (2) is preferably the following formula (2)'.
0.35×T≦ _Have ≦0.45×T (1)'
R _ave ≦0.07×T (2)'

The unevenness height (H) and the roughness (R) are the height and roughness of the unevenness formed on the coating film surface, and can be measured with a 3D microscope. In addition, the average height of unevenness (H _ave ) and the average roughness (R _ave ) are average values thereof, and the unevenness height (H) and roughness (R) of three arbitrarily selected points are the average values thereof. is the average value of

In addition, the above-mentioned coating film means the coating film formed on the steel plate in general, and not only the undercoat coating film (primer) and the top coating film, but also the chemical conversion coating and other protective coatings are included in the coating film. be

(Painting evaluation method)
The coating evaluation method of the present invention, as shown in FIGS. a method,
During the coating, the coating state of the coating liquid 2 formed on the pickup roll 4, the coating state of the coating liquid 2 formed on the applicator roll 5, and the gap or gap between the pickup roll 4 and the applicator roll 5 The state of the surplus coating liquid scraped off by the nip (the state of the curtain 7) is photographed, and the coating state of the coating liquid 2 is evaluated from the photographed image.
The state of the coating such as roping of the coating liquid 2 formed on the pickup roll 4 and the applicator roll 5 and the state of the curtain 7 greatly affect the surface properties of the coating 6A formed on the steel plate 6. Therefore, by accurately grasping and evaluating these states, the state of the coating film 6A formed on the steel plate 6 can be accurately estimated and evaluated during coating without actually observing it. .

The structure of the coating evaluation method of the present invention is the same as the contents explained in the coating method of the present invention.

According to the present invention, the state of the coating film formed on the coated steel plate can be accurately estimated and evaluated during coating, and a method for coating a coated steel plate that can form a coating film with excellent appearance without defects, and with excellent appearance without defects. It is possible to provide a coated steel sheet on which a coating film is formed and a coating evaluation method capable of accurately estimating and evaluating the state of the coating film formed on the coated steel sheet during coating.

Claims (6)

A method of coating a coated steel plate, in which a continuously running steel plate is coated with a coating liquid by a roll coater equipped with a pickup roll and an applicator roll,
During the coating, the state of the coating liquid formed on the pickup roll, the state of the coating liquid formed on the applicator roll, and the gap or nip between the pickup roll and the applicator roll scraped off. Take a picture of the state of the excess coating liquid (state of the curtain),
A method of coating a coated steel plate, wherein coating is performed with the coating liquid while adjusting the roll peripheral speed and the gap or nip pressure of the pickup roll and the applicator roll based on the evaluation results of the captured image. . The coating state of the coating liquid formed on the pickup roll and the coating state of the coating liquid formed on the applicator roll are the states of uniformity, width and pitch of the roping formed on each roll,
2. The coating method for a coated steel plate according to claim 1, wherein the state of the curtain is the uniformity of the scraped-off excess coating liquid and the presence or absence of irregular lifting failures of the excess coating liquid. . The method of coating a coated steel plate according to claim 1 or 2, wherein the coating liquid has a Ford cup viscosity (Ford cup No. 4) of 45 to 80 seconds. The method for coating a coated steel plate according to claim 1 or 2, wherein the roll coater is a two-roll coater. A coated steel sheet having a coating film formed by the coating method according to any one of claims 1 to 4,
For the coating film, the surface unevenness height (H) and roughness (R) are measured using a 3D microscope, and the average unevenness height (H _ave ), the average roughness (R _ave ) and the film thickness ( A coated steel sheet, characterized in that T) (μm) satisfies the following (1) and (2).
0.30×T≦ _Have ≦0.50×T (1)
R _ave ≦0.09×T (2) A coating evaluation method for evaluating the state of a coating of a coating liquid formed on a steel plate by a roll coater equipped with a pickup roll and an applicator roll,
During the coating, the state of the coating liquid formed on the pickup roll, the state of the coating liquid formed on the applicator roll, and the gap or nip between the pickup roll and the applicator roll scraped off. A coating evaluation method comprising photographing the state of excess coating liquid (curtain state) and evaluating the coating state of the coating liquid from the photographed image.

Images