Liquid or slurry application device and method for producing coated metal strip

Abstract

To provide a liquid / slurry coating applicator which can inhibit an edge overcoat phenomenon caused by wiping, with a simpler constitution than in prior art.SOLUTION: A coating applicator includes: spray nozzles for supplying liquid or the like to a metal strip; roll coaters with rolls for coating the metal strip with the liquid or the like; and gas spray nozzles which are provided on a downstream side in a strip passing direction of the roll coaters, in order to spray gas onto the metal strip. The gas spray nozzle includes: a nozzle body; and a straightening vane which divides the interior of the nozzle body and extends in a width direction. In the straightening vane, multiple holes are provided in several rows in the width direction, and when A0 denotes an area of a hole located in the center in the width direction among the multiple holes, Ak denotes an area of a hole located at a k-th place in a left and right direction from the center, and An denotes an area of a hole at an end in the left and right direction, Ak-1 / Ak is 0.3 to 1.0, and A0 / An is less than 1.0, and when SR denotes the whole area of the multiple holes and SG denotes an area of an aperture, SR / SG is 0.8 to 1.8.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a liquid or slurry application device that uses a roll coater to apply a liquid or slurry to a metal strip being passed through, and a method for producing a coated metal strip. [Background technology]

[0002] Conventionally, coating liquids having various physical properties are applied to the surface of a continuously passing metal strip, such as a steel sheet, to form coating films, thereby imparting properties such as corrosion resistance, workability, aesthetics, and insulation to the metal strip. A roll coater is generally used as a coating device for this treatment. In a method of applying a liquid or slurry to a metal strip using a roll coater, the excess liquid or slurry is previously supplied to the metal strip and squeezed out of the metal strip by the pressing load of the roll, thereby adjusting the amount of liquid or slurry adhered to the metal strip.

[0003] In such a roll coater method, a rubber roll having grooves engraved on its outer circumferential surface may be used as the roll of the roll coater to ensure that the necessary amount of liquid or slurry is applied to the metal strip. In addition, a spray nozzle or a slit nozzle is generally used to supply the liquid or slurry to the metal strip.

[0004] A typical coating defect in the coating process of liquid or slurry using a roll coater is an appearance defect called ribbing, in which streaky patterns that occur in the outer circumferential direction of the roll of the roll coater are transferred to the metal strip. Ribbing is known to occur when fluctuations in the fluid pressure of the liquid meniscus formed between the roll of the roll coater and the metal strip exceed the stabilizing effect of surface tension.

[0005] As a technique for preventing ribbing, Patent Document 1 discloses a technique in which the thickness of a slurry is adjusted using a roll coater, and then the thickness is readjusted by spraying gas onto the slurry using a gas wiping method. This gas wiping method is commonly applied to continuous hot-dip galvanizing in the steelmaking process. In this process, a metal strip is immersed in a molten metal bath and then raised above the bath. After this, excess coating material adhering to the surface of the metal strip is removed using a slit nozzle, thereby controlling the desired coating weight. However, even if the gas ejection rate from the slit nozzle is uniform across the width of the metal strip, the gas escapes laterally at the width edge of the metal strip, resulting in weaker gas impingement pressure at the edge compared to areas other than the width edge. This results in an edge overcoat phenomenon, in which the coating weight at the width edge of the metal strip is increased after gas wiping, impairing productivity.

[0006] Patent Document 2 discloses a technique for suppressing the edge overcoating phenomenon, in which an edge auxiliary nozzle and a main nozzle are used together, air is ejected from the edge auxiliary nozzle in advance to adjust the amount of coating on the edge, and then the entire surface is gas-wiped with the downstream main nozzle, thereby suppressing the edge overcoating phenomenon. Patent Document 3 also discloses a technique for suppressing the edge overcoating phenomenon by crossing wiping nozzles provided on the front and back sides of the metal strip to avoid opposing jets on the edge in the width direction. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 7-62445 [Patent Document 2] Japanese Patent Application Publication No. 4-221054 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the technology disclosed in Patent Document 2 has a problem in that an edge auxiliary nozzle is installed below the main nozzle near the edge of the steel sheet, and splashes generated during main wiping adhere to the lower edge wiping nozzle, causing nozzle clogging. Furthermore, using a main nozzle and an edge auxiliary nozzle increases the number of nozzles, resulting in higher equipment installation and maintenance costs. The present invention has been made in consideration of these problems, and its purpose is to provide a liquid or slurry application device that can suppress the edge overcoat phenomenon caused by wiping with a simpler configuration than conventional devices. [Means for solving the problem]

[0009] The means for solving the above problems are as follows. (1) A method for manufacturing a roll coater for a metal strip, the method comprising: a liquid or slurry injection nozzle for supplying a liquid or slurry to a metal strip being passed; a roll coater having a roll for applying the liquid or slurry supplied to the metal strip to the metal strip; and a gas injection nozzle provided downstream of the roll coater in the sheet passing direction and for injecting a gas onto the metal strip, wherein the gas injection nozzle has a nozzle body which is a housing having an opening at one end thereof extending in the width direction of the metal strip and an inclined surface inclined toward the opening, and a gas supply path at the other end thereof through which the gas to be injected from the opening is supplied; and a straightening plate extending in the width direction which divides the interior of the housing into an area where the opening is provided and an area where the gas supply path is provided, the straightening plate having a plurality of holes formed in a plurality of rows in the width direction, and wherein the area of ​​the hole at the center in the width direction among the plurality of holes is defined as A0, and the area of ​​the hole located at the kth hole (k is an integer from 1 to n) from the center in the left-right direction is defined as A1. k The area of ​​the hole at the left and right ends is A n In this case, A k-1 / A k is 0.3 or more and 1.0 or less, and A0 / A n is less than 1.0, The total area of ​​the plurality of holes is S R and the area of ​​the opening is S G In this case, S R / SG is 0.8 or more and 1.8 or less. (2) The liquid or slurry application device according to (1), wherein the plurality of holes are arranged in parallel in the straightening plate. (3) The liquid or slurry application device according to (1), wherein the plurality of holes are arranged in a staggered pattern in the straightening plate. (4) A liquid or slurry application device according to any one of (1) to (3), wherein the angle of the gas ejected from the gas ejection nozzle with respect to the direction of travel of the metal strip is 15° or more and 75° or less. (5) A method for producing a coated metal strip, comprising applying a liquid or slurry to the metal strip using the liquid or slurry application device according to any one of (1) to (4). [Effects of the Invention]

[0010] In the liquid or slurry application device according to the present invention, the edge overcoating phenomenon caused by wiping can be suppressed simply by adjusting the area of ​​the plurality of holes in the straightening plate of the gas ejection nozzle and the area of ​​the opening within a predetermined range. In this way, the liquid or slurry application device according to the present invention can suppress the edge overcoating phenomenon caused by wiping without using an edge auxiliary nozzle, and therefore is an apparatus that can suppress the edge overcoating phenomenon with a simpler configuration than conventional devices. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram showing a liquid application device 10 according to the present embodiment. [Figure 2] FIG. 2 is a perspective view of an upper gas ejection nozzle 18. [Figure 3] FIG. [Figure 4] FIG. 2 is an enlarged view of part A in FIG. [Figure 5] FIG. 2 is a cross-sectional view of an upper gas ejection nozzle 18. [Figure 6] FIG. 10 is a front view of another straightening plate 40. DETAILED DESCRIPTION OF THE INVENTION

[0012] The inventors of the present invention have conducted extensive research to find a way to suppress the edge overcoating phenomenon, and have discovered that the edge overcoating phenomenon can be suppressed by adjusting the area of ​​multiple holes in a straightening plate provided in a gas ejection nozzle and increasing the flow rate of gas ejected toward the edge portion of the metal strip compared to the center portion, thereby completing the present invention. The present invention will be described below through embodiments of the present invention. In the following description, liquid or slurry will be referred to as "liquid, etc."

[0013] 1 is a schematic diagram showing a liquid application device 10 according to this embodiment. The liquid application device 10 according to this embodiment will be described with reference to FIG.

[0014] The liquid application device 10 according to this embodiment includes an upper liquid spray nozzle 12, a lower liquid spray nozzle 14, a roll coater device 16, an upper gas ejection nozzle 18, and a lower gas ejection nozzle 20. The upper liquid spray nozzle 12 is a spray nozzle that sprays a liquid 22 from the upper surface of a metal strip 24 that is continuously passed horizontally, thereby supplying the liquid to the upper surface of the metal strip 24. The lower liquid spray nozzle 14 is a spray nozzle that sprays a liquid 22 from the lower surface of the metal strip 24, thereby supplying the liquid 22 to the lower surface of the metal strip 24. The upper liquid spray nozzle 12 and the lower liquid spray nozzle 14 are not limited to spray nozzles and may be slit nozzles. Any nozzle structure capable of supplying a liquid to the metal strip 24 may be used. Note that the liquid application device 10 according to this embodiment is not limited to metal strips that are continuously passed horizontally, but can also be applied to metal strips that are passed vertically.

[0015] The roll coater device 16 is installed downstream of the upper liquid spray nozzle 12 and the lower liquid spray nozzle 14 in the sheet passing direction of the metal strip 24. The roll coater device 16 has an upper roll 26 and a lower roll 28, which are installed so as to sandwich the metal strip 24 vertically. The upper roll 26 is a grooved roll with grooves on its surface, which adjusts the amount of liquid 22 adhered to the upper surface of the metal strip 24. The lower roll 28 is also a grooved roll with grooves on its surface, which adjusts the amount of liquid 22 adhered to the lower surface of the metal strip 24. The upper roll 26 and the lower roll 28 are preferably made of rubber, and particularly, urethane rubber, nitrile rubber, or the like, which have excellent abrasion resistance. The hardness of the rubber forming the rubber rolls is preferably within the Shore hardness range of A45 to A85 inclusive, in order to extend the roll life.

[0016] If the roll diameter is small, the pass line of the metal strip 24 is likely to fluctuate, so the roll diameter of the upper roll 26 and the lower roll 28 is preferably φ50 to 400 mm. The rotation direction of the upper roll 26 and the lower roll 28 is preferably the same as the running direction of the metal strip 24. By rotating the upper roll 26 and the lower roll 28 in the same direction as the running direction of the metal strip 24, wear of the upper roll 26 and the lower roll 28 can be suppressed.

[0017] The upper gas ejection nozzle 18 is provided above the roll coater device 16 on the downstream side in the sheet passing direction of the metal strip 24. The upper gas ejection nozzle 18 ejects gas onto the upper surface of the metal strip 24. This makes it possible to suppress the occurrence of an appearance defect called ribbing on the upper surface side of the metal strip 24.

[0018] The lower gas ejection nozzle 20 is provided below the roll coater device 16 on the downstream side in the sheet passing direction of the metal strip 24. The upper gas ejection nozzle 18 ejects gas onto the underside of the metal strip 24. This makes it possible to prevent appearance defects known as ribbing from occurring on the underside of the metal strip 24. In this manner, a coated metal strip coated with a liquid or the like is manufactured using the liquid or the like application device 10. In the following description, ejecting gas onto the metal strip 24 from the upper gas ejection nozzle 18 and the lower gas ejection nozzle 20 may be referred to as "wiping."

[0019] Fig. 2 is a perspective see-through view of the upper gas ejection nozzle 18. In Fig. 2, the housing 30 is shown see-through to explain the internal structure of the upper gas ejection nozzle 18. The configuration of the upper gas ejection nozzle 18 will be explained using Fig. 2. Note that the configuration of the lower gas ejection nozzle 20 is the same as the configuration of the upper gas ejection nozzle 18, so a redundant explanation of the configuration of the lower gas ejection nozzle 20 will be omitted.

[0020] The upper gas ejection nozzle 18 is a slit nozzle and includes a housing 30 and a straightening plate 32 extending in the width direction of the metal band 24, dividing the interior of the housing 30 into an area where an opening 34 is provided and an area where a gas supply path 38 is provided. The housing 30 is a hollow member and includes a slit (hereinafter referred to as opening 34) provided at one end side and extending in the width direction of the metal band 24, an inclined surface 36 that gently slopes toward the opening 34, and a gas supply path 38 provided at the other end side. The straightening plate 32 is a rectangular plate-like member with a plurality of holes provided in the longitudinal direction in two parallel rows vertically.

[0021] 3 is a front view of the straightening plate 32. In the upper gas ejection nozzle 18 of this embodiment, the area of ​​the holes in the widthwise center of the straightening plate 32 is made smaller than the area of ​​the holes at the widthwise end portions in order to increase the gas flow rate ejected toward the edge portions at both widthwise ends of the metal strip 24. Specifically, the area of ​​the hole in the widthwise center is defined as A0, and the area of ​​the hole located at the kth hole (k is an integer from 1 to n) from the center in the left-right direction is defined as A1. k The area of ​​the holes at both ends in the width direction is A n In this case, Ak-1 / A k is between 0.3 and 1.0, and A0 / A n is set to be less than 1.0. By specifying the area of ​​the holes in this way, the gas flow rate on the edge portion side of the metal strip 24 increases, and the wiping force on the edge portion is improved, thereby suppressing the edge overcoat phenomenon. In addition, in order to make the gas flow rate on the edge portion side even greater than that on the central portion side, A k-1 / A k is preferably 0.3 or more and less than 1.0, and more preferably 0.5 or more and 0.8 or less.

[0022] On the other hand, A k-1 / A k If A is greater than 1.0, the gas flow rate on the edge side of the metal strip 24 decreases, and the wiping force on the edge side decreases, making it impossible to suppress the edge overcoat phenomenon. k-1 / A k If the ratio is less than 0.3, the gas flow rate on the edge side increases significantly, which may result in excessive wiping power on the edge side, resulting in the occurrence of the edge undercoat phenomenon, which refers to the phenomenon in which the amount of liquid or the like adhering to both ends of the metal strip 24 in the width direction after wiping decreases.

[0023] Furthermore, it is preferable that the distance L1 between the holes provided at both ends of the rectifying plate 32 in the width direction and the plate end of the rectifying plate 32 is within a range of 2 mm to 15 mm. By providing the holes so that the distance L1 is within a range of 2 mm to 15 mm, it is possible to prevent the gases from colliding near the inner wall of the nozzle, the gas flow from branching into a component that flows along the wall surface and another component that does not, and the other component from turning into a turbulent vortex, causing separation of the gas flow, and preventing the gas from being ejected non-uniformly onto the edge portion of the metal strip 24.

[0024] The gas that has passed through the holes in the straightening plate 32 flows along the inclined surface 36 and is ejected from the openings 34 toward the metal strip 24. In the upper gas ejection nozzle 18 according to this embodiment, the area of ​​all the holes provided in the straightening plate 32 is S R The area of ​​the opening 34 is S G In this case, S R / SG is set to 0.8 or more and 1.8 or less. R / S G By setting S within the above range, it is possible to suppress turbulence of the airflow from passing through the hole to the opening 34, and also to reduce the pressure loss of the gas within the housing 30. R / S G If S is less than 0.8, the gas ejected from the nozzle tip will spread out in a broad manner, losing its ability to flow in a straight line, causing the gas ejection flow to become turbulent and reducing the wiping force. R / S G If S is larger than 1.8, the pressure loss due to the contraction at the nozzle tip increases. R / S G It is necessary that the ratio is 0.8 or more and 1.8 or less, and more preferably 1.0 or more and 1.6 or less.

[0025] It is also preferable that the spacing between the multiple holes provided in the width direction of the metal strip 24 is uniform. By making the spacing between the multiple holes uniform, turbulence in the gas flow in the width direction within the nozzle can be suppressed, thereby stabilizing the flow rate of the gas ejected from the upper gas ejection nozzle 18 in the width direction.

[0026] When gas is ejected from the upper gas ejection nozzle 18 and the lower gas ejection nozzle 20 onto a metal strip 24 coated with a liquid or the like, the ejected gas generates splashes of the liquid or the like. When gas is ejected from the upper gas ejection nozzle 18 in a direction perpendicular to the running direction of the metal strip 24, splashes are generated toward the upstream and downstream sides of the running direction of the metal strip 24. Of these, splashes that fly upstream are blocked again by the gas ejected from the upper gas ejection nozzle 18 and do not remain on the metal strip 24, but splashes that fly downstream remain attached to the metal strip 24 and may cause surface defects. Furthermore, when gas is ejected in a direction perpendicular to the metal strip 24, the position of the upper gas ejection nozzle 18 and the position where splashes are generated are the same, so the splashes may adhere to the lower gas ejection nozzle 20 and cause nozzle clogging.

[0027] Therefore, in the liquid application device 10 according to this embodiment, the angle (θ1 in FIG. 4) of the gas ejected from the upper gas ejection nozzle 18 relative to the running direction of the metal strip 24 and the nozzle angle (θ2 in FIG. 4) of the gas ejected from the lower gas ejection nozzle 20 relative to the running direction of the metal strip 24 are set within the range of 15° to 75°. In the following description, the angle of the gas ejected from the upper gas ejection nozzle 18 relative to the running direction of the metal strip 24 will be referred to as the "nozzle angle."

[0028] As described above, the gas ejection angle affects the direction of splashing. That is, when the nozzle angles θ1 and θ2 are smaller than 90°, the amount of splashing toward the upstream side in the sheet passing direction of the metal strip 24 increases, while the amount of splashing toward the downstream side in the sheet passing direction decreases. Therefore, by setting the nozzle angles θ1 and θ2 to an angle smaller than 90°, the amount of splashing toward the downstream side in the sheet passing direction can be suppressed. This suppresses the occurrence of surface defects due to the adhesion of splashing.

[0029] Furthermore, when the nozzle angles θ1 and θ2 are set to be less than 90°, the positions of the upper gas ejection nozzle 18 and the lower gas ejection nozzle 20 are spaced downstream in the passing direction of the metal strip 24 from the splash generation position, thereby reducing the possibility of splashes adhering to the lower gas ejection nozzle 20 and clogging the nozzle. Furthermore, when the nozzle angles θ1 and θ2 are set to be 15° or more, the upper gas ejection nozzle 18 and the lower gas ejection nozzle 20 are spaced apart from the metal strip 24, thereby reducing the risk of interference between the upper gas ejection nozzle 18 and the lower gas ejection nozzle 20 and the metal strip 24. Therefore, the nozzle angles θ1 and θ2 are preferably set to be greater than or equal to 15° and less than or equal to 75°, and more preferably greater than or equal to 30° and less than or equal to 60°.

[0030] The pressure of the gas ejected from the upper gas ejection nozzle 18 and the lower gas ejection nozzle 20 is preferably in the range of 1 kPa or more and 30 kPa or less. By setting the pressure of the gas ejected from the upper gas ejection nozzle 18 and the lower gas ejection nozzle 20 to be in the range of 1 kPa or more and 30 kPa or less, an increase in the amount of splashing from the metal strip 24 can be suppressed.

[0031] The distance from the metal strip 24 to the upper gas ejection nozzle 18 and the lower gas ejection nozzle 20 is preferably within a range of 10 mm to 50 mm. By making the distance from the metal strip 24 to the upper gas ejection nozzle 18 and the lower gas ejection nozzle 20 10 mm or more, contact between the upper gas ejection nozzle 18 and the lower gas ejection nozzle 20 and the metal strip 24 is suppressed even if the pass line fluctuates. Furthermore, by making the distance from the metal strip 24 to the upper gas ejection nozzle 18 and the lower gas ejection nozzle 20 50 mm or less, an increase in the gas flow rate required to suppress ribbing and edge overcoat phenomena due to excessive distance from the metal strip 24 can be suppressed.

[0032] Fig. 5 is a cross-sectional view of the upper gas ejection nozzle 18. If the inclination angle between the inclined surfaces 36 that slope toward the opening 34 of the housing 30 is taken as the nozzle tip angle θ3, then the nozzle tip angle θ3 is preferably 90° or less. Setting the nozzle tip angle θ3 to 90° or less can improve the linearity of the gas ejected from the opening 34. Note that, although the example shown in Fig. 5 shows an example in which the nozzle tip angle θ3 is symmetrical about the center, it is not limited to this and may be asymmetrical about the center.

[0033] Furthermore, assuming that the dimension L2 in Figure 5 is the nozzle gap, the nozzle gap is preferably in the range of 0.5 mm to 4.0 mm. By setting the nozzle gap in the range of 0.5 mm to 4.0 mm, splashing and nozzle clogging can be prevented. Furthermore, by setting the nozzle gap in the range of 0.5 mm to 4.0 mm, the increase in gas flow rate required to suppress ribbing and edge overcoat phenomena can be suppressed. Therefore, the nozzle gap is preferably in the range of 0.5 mm to 4.0 mm, and more preferably in the range of 1.0 mm to 3.0 mm.

[0034] Furthermore, the amount of splash increases as the amount of liquid etc. scraped off by wiping increases. For this reason, it is preferable to adjust the nip pressure of the roll coater device 16 so that the amount of liquid etc. applied is slightly thicker than the target value.

[0035] As described above, in the liquid application device 10 according to this embodiment, for the plurality of holes in the straightening plate 32 of the upper gas ejection nozzle 18 and the lower gas ejection nozzle 20, the area of ​​the hole at the center in the width direction is defined as A0, and the area of ​​the hole at the kth hole (k is an integer from 1 to n) from the center in the left-right direction is defined as A1. k The area of ​​the holes at both ends in the width direction is A n In this case, A k-1 / A k is between 0.3 and 1.0, and A0 / A n is set to be less than 1.0, and further, the total area of ​​the holes of the straightening plate 32 is set to S R and the area of ​​the opening 34 in the upper gas ejection nozzle 18 and the lower gas ejection nozzle 20 is S G In this case, S R / S GBy setting the ratio between 0.8 and 1.8, the edge overcoating phenomenon caused by wiping can be suppressed. As such, the liquid application device 10 according to this embodiment can suppress the edge overcoating phenomenon caused by wiping without using an edge auxiliary nozzle, and can therefore be said to be an device that can suppress the edge overcoating phenomenon with a simpler configuration than conventional devices. Note that, although the example shown in FIG. 1 illustrates an example of the liquid application device 10 having an upper gas ejection nozzle 18 and a lower gas ejection nozzle 20, this is not limiting. The liquid application device only needs to have at least one of the upper gas ejection nozzle 18 and the lower gas ejection nozzle 20, and this makes it possible to suppress the edge overcoating phenomenon with a simpler configuration than conventional devices.

[0036] 3 shows an example in which the plurality of holes are arranged in two parallel rows in the vertical direction in the rectifying plate 32, but this is not limiting. FIG. 6 is a front view of another rectifying plate 40. As shown in FIG. 6, the plurality of holes in the rectifying plate 40 are arranged in two staggered rows in the vertical direction. In this way, the plurality of holes may be arranged in a staggered row. The number of rows is also not limited to two, and may be two or more rows.

[0037] Furthermore, the upper liquid spray nozzle 12 and the lower liquid spray nozzle 14 are not limited to being configured with a series of spray nozzles or slit nozzles, but may be configured with multiple liquid spray nozzles arranged in the width direction of the metal strip 30. The upper roll 26 and the lower roll 28 downstream of the upper liquid spray nozzle 12 and the lower liquid spray nozzle 14 are not limited to rubber rolls and may be made of materials other than rubber, such as metal or resin. That is, the material of the rolls in the roll coater device 16 is not particularly limited. The number, number of stages, and arrangement of rolls in the roll coater device 16 may be as desired. Although the present embodiment has been described using grooved rolls, non-grooved rolls without grooves on the outer circumferential surface may also be used. The metal strip to which a liquid or slurry is applied by the liquid application device 10 according to this embodiment is not limited to a steel strip, but may also be a metal strip made of an iron alloy other than steel, or a metal strip made of a metal other than an iron alloy, such as copper or aluminum. [Example]

[0038] Next, we will explain an example in which a coated steel strip was produced by applying MgO slurry to a 0.3 mm thick, 1000 mm wide steel strip at a line speed of 160 to 200 mpm. The rolls in the roll coater device were HS58 grooved rubber rolls with a diameter of 165 mm and a surface with uniformly pitched irregularities. The rubber roll specifications were a groove depth of 0.3 mm and a groove pitch of 0.5 mm. The roll rotation direction was a forward direction, which was the same as the direction of the steel strip threading at the contact point of the rubber roll. To increase the amount of MgO slurry adhered to the steel strip, the nip pressure between each roll and the steel strip was reduced. To decrease the amount of MgO slurry adhered to the steel strip, the nip pressure between each roll and the metal strip S was increased.

[0039] The MgO slurry was prepared by suspending magnesium oxide (MgO) in water. The solids concentration of the MgO slurry was 10% by mass. The MgO slurry was supplied to the upper and lower spray nozzles using a supply pump, and then supplied to the steel strip from the spray nozzles. The MgO slurry was then applied to the steel strip by pressing the supplied MgO slurry with the rolls of a roll coater.

[0040] Next, wiping was carried out using an upper gas jet nozzle and a lower gas jet nozzle with a nozzle tip angle θ3 of 50°, installed downstream of the roll coater. The distance between the nozzle and the steel strip was 10 mm. The straightening plate had round holes with a diameter of 10 mm arranged at 5 mm intervals. The arrangement method was a parallel arrangement or a staggered arrangement, and the distance from the edge of the straightening plate to the round holes at both ends was 7.5 mm.

[0041] Arrangement of round holes in the straightening plate, A k-1 / A k Value of area ratio S R / S GWiping was performed using an upper gas ejection nozzle and a lower gas ejection nozzle with nozzle angles θ1 and θ2 changed to produce coated steel strips coated with MgO slurry. The coated steel strips produced were evaluated for the distribution of the MgO slurry adhesion amount in the width direction and the number of splash-related spot defects. The distribution of the MgO slurry adhesion amount in the width direction was determined by measuring the amount of MgO slurry adhesion at positions 50 mm, 250 mm, and 500 mm from one end of the strip in the width direction, and the distribution of the MgO slurry adhesion amount in the width direction was confirmed from these measurements. The evaluation criteria for the distribution of the MgO slurry adhesion amount were as follows:

[0042] [Evaluation criteria for adhesion distribution] ◎: Adhesion amount distribution in the width direction, deviation σ: 5.0 g / m 2 below ○: Adhesion amount distribution in the width direction, deviation σ: 5.0 g / m 2 Larger than 7.5g / m 2 Less than ×: Adhesion amount distribution in the width direction, deviation σ: 7.5 g / m 2 End

[0043] The evaluation criteria for the number of spot defects on the splash property of the coated steel strip are as follows: [Evaluation criteria for spot defects] ◎: Splash-like spot defects less than 3 points / 1000m ○: Splash-like spot defects 3 or more but less than 6 / 1000m △: Splash-like spot defects 6 or more but less than 10 / 1000m ×: Splash-like spot defects 10 or more / 1000m Table 1 below shows the manufacturing conditions of the coated steel strip, the results of the coating weight distribution evaluation, and the results of the spot defect evaluation.

[0044] [Table 1]

[0045] In Comparative Examples 1 and 2, the deviation σ of the adhesion amount was 8.2 g / m 2 , 7.9g / m 2Therefore, the adhesion amount distribution was marked as "x" and "x". In addition, splashes adhered to the steel sheet, and there were 13 and 9 spot defects, respectively, so the spot defects were marked as "x" and "△".

[0046] On the other hand, in Examples 1 to 8, the deviation σ of the deposition amount was 7.5 g / m 2 From this result, it was confirmed that the edge overcoat phenomenon can be suppressed by using the liquid application device according to this embodiment.

[0047] In addition, since the gas impingement position was the same on the upper and lower surfaces in Examples 1 to 8, there was almost no pass line fluctuation. Furthermore, in Examples 1 to 8, no ribbing defects occurred, and no effect on the width direction deposition amount distribution due to the parallel and staggered arrangement of the straightening vanes was observed.

[0048] On the other hand, the number of spot defects in invention examples 1 to 4 was 6 or more. In contrast, the number of spot defects in invention examples 5 to 8, in which the nozzle angles of the upper gas ejection nozzle and the lower gas ejection nozzle were directed upstream, was less than 5. Specifically, the number of spot defects in invention example 5 was 4, the number of spot defects in invention examples 6 and 7 was less than 2, and the number of spot defects in invention example 8 was 5. From these results, it was confirmed that the nozzle angles θ1 and θ2 are preferably 15° or more and 75° or less, and more preferably 30° or more and 60° or less, and that this can suppress the edge overcoat phenomenon and reduce spot defects.

[0049] From these results, it was confirmed that by using the liquid application device according to this embodiment, it is possible to suppress the edge overcoat phenomenon caused by wiping without using an edge auxiliary nozzle, and that it is possible to suppress the edge overcoat phenomenon with a simpler configuration than conventional methods. [Explanation of symbols]

[0050] 10 Liquid application device 12 Upper liquid injection nozzle 14 Lower liquid injection nozzle 16 Roll coater device 18 Upper gas ejection nozzle 20 Lower gas ejection nozzle 22 Liquid etc. 24 Metal Strip 26 Upper Roll 28 Lower Roll 30 Case 32 Rectifier plate 34 Aperture 36 Slope 38 Gas supply line 40 Rectifier plate

Claims

1. a liquid or slurry injection nozzle for supplying a liquid or slurry to the metal strip being threaded; a roll coater having a roll for applying the liquid or slurry supplied to the metal strip onto the metal strip; a gas ejection nozzle provided downstream of the roll coater in the sheet passing direction and configured to eject gas onto the metal strip; the gas ejection nozzle has a housing having an opening at one end thereof extending in the width direction of the metal strip and an inclined surface inclined toward the opening, and having a gas supply path at the other end thereof through which the gas to be ejected from the opening is supplied; and a rectifying plate extending in the width direction that divides the interior of the housing into an area where the opening is provided and an area where the gas supply path is provided, The straightening plate has a plurality of rows of holes in the width direction, and the area of ​​a hole in the center of the width direction of the straightening plate among the plurality of holes is defined as A ０ The area of ​​the hole located at the kth position (k is an integer from 1 to n) from the center in the left-right direction is defined as A ｋ The area of ​​the hole at the left and right ends is A ｎ In this case, A ｋ－１ / A ｋ is 0.3 or more and 1.0 or less, and A ０ / A ｎ is less than 1.0, The total area of ​​the plurality of holes is S Ｒ and the area of ​​the opening is S Ｇ In this case, S Ｒ / S Ｇ A liquid or slurry application device, wherein the viscosity is 0.8 or more and 1.8 or less.

2. A liquid or slurry application device as described in claim 1, wherein the number of the plurality of holes in the width direction is an odd number.

3. 3. The liquid or slurry applying device according to claim 1, wherein the plurality of holes are arranged in parallel in the straightening plate.

4. 3. The liquid or slurry applying device according to claim 1, wherein the plurality of holes are provided in the current plate in a staggered arrangement.

5. 5. The liquid or slurry coating device according to claim 1, wherein the angle of the gas ejected from the gas ejection nozzle with respect to the direction of travel of the metal strip is 15 degrees or more and 75 degrees or less.

6. A method for producing a coated metal strip, comprising applying a liquid or slurry to the metal strip using the liquid or slurry application device according to any one of claims 1 to 5.

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