JP3123033B2 - Control method of coating thickness in double-sided simultaneous coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a coating thickness in simultaneous double-side coating, and more particularly to a method for controlling simultaneous coating on both sides of a strip such as a steel strip at the entrance of a catenary type drying furnace. The present invention relates to a method for controlling the thickness of a coating in simultaneous double-side coating capable of controlling the film thickness with high accuracy.

[0002]

2. Description of the Related Art Steel strips are generally coated with chromium, resin, or the like, for example, on galvanized steel strips (steel plates) in order to improve the performance such as corrosion resistance.

Conventionally, the coating on the steel strip has been
The steel strip paid out from the pay-off reel in the entrance facility is continuously transported while being passed through each step of degreasing, coating with a roll coater, and drying with an oven. In a delivery facility, winding is performed by a winding device.

In general, a roll coater (coating apparatus) used for continuous coating of a steel strip includes a steel pickup roll for pulling up the paint in a paint pan, and receiving the paint from the pickup roll and applying the paint on the surface of the steel strip. It has a rubber-lined applicator roll for transfer and painting. In the case of coating with this roll coater, the coating film thickness is controlled by appropriately controlling the peripheral speed of the roll, the pressing force between the rolls, and the pressing force between the steel strip and the applicator roll with respect to the conveying speed of the steel strip. Have been done.

Conventionally, as a method of controlling the coating film thickness when coating with a roll coater, for example, Japanese Patent Laid-Open No.
-6268, JP-B-60-56553, JP-B-62-4
No. 1077, a method for constantly controlling the pressing force between the pick-up roll and the applicator roll and the pressing force between the steel strip and the applicator roll to a constant value. A method of controlling a pressing force between a pickup roll and an applicator roll based on data on a relationship between a pressing force applied in the past and a coating film thickness, as disclosed in US Pat.

Further, as a specific equipment for performing continuous double-side coating on a strip, for example, a steel strip, in a coating line having a catenary type drying furnace (catenary type path) 22 shown in FIG. After the first roll coater 10 was coated with the next second roll coater 20, the coating was dried by passing through a heating furnace 22 and cooled by passing through a cooling furnace 24.
What is sent to the next process is known. Note that 2 in the figure
Reference numeral 6 denotes a lift roll, and reference numeral 28 denotes a delivery-side fulcrum roll.

The first roll coater 10 picks up a paint P in a paint pan (paint reservoir) 12 and sends a part of the paint P pulled up by the pickup roll 14 in the direction of the steel strip S. An applicator roll 16 for transferring the paint to the steel strip S, and a backup roll 18 for pressing the steel strip S against the applicator roll 16 when the paint is transferred by the applicator roll 16. The second roll coater 20 has substantially the same configuration as the first roll coater 10 except that there is no backup roll.

When the steel strip S is coated on both sides by the above-mentioned coating equipment, the steel strip S is wound around the backup roll 18 of the first roll coater 10 while the steel strip S is wound between the applicator roll 16 and the backup roll 18. , And the steel strip S, which is continuously transported in a catenary form (suspended state), is pushed up from below by the applicator roll 16 of the second roll coater 20, and the second roll The back side is painted by passing over the coater 20.

At this time, since the film thickness applied to the steel strip S is greatly affected by the pressing force between the steel strip S and the applicator roll 16, it is necessary to control the pressing force to a target value. It becomes important.

[0010]

However, when the front side is coated with the first roll coater 10, the pressing force between the steel strip S and the applicator roll 16 is positively applied by the backup roll 18. On the other hand, when the back side is coated with the second roll coater 20, the pressing force between the steel strip S and the applicator roll 16 is determined by the tension acting on the steel strip S, The pressing force cannot be actively controlled.

Therefore, when the steel strip S is warped in the width direction, the steel strip S can be coated with a uniform film thickness by the first roll coater 10, but can be coated in the width direction by the second roll coater. There is a problem that the film thickness becomes uneven.

As a technique for solving this problem, for example, as shown in FIG. 1 which will be described later in detail, a two-sided roll comprising an upper roll coater 40 and a lower roll coater 50 installed on the entrance side of a catenary type drying furnace 22 is used. The steel strip S is moved between the upper applicator roll 42 and the lower applicator roll 52 while supporting the catenary portion formed between the lower applicator roll 52 and the outlet fulcrum roll 28 by the simultaneous coating device. It is conceivable that the paint is continuously applied while being sandwiched.

However, when the coating is performed by the double-sided simultaneous coating device installed on the entrance side of the catenary type drying furnace as shown in FIG. 1, the back surface (lower surface) of the steel strip S having warpage in the width direction is formed. Even though it can be painted with a uniform film thickness,
By simply applying a method of controlling the pressing force between the upper and lower applicator rolls and the steel strip to be constant as disclosed in the above-mentioned publication, it is not possible to paint the front and back surfaces with the same film thickness. A new problem was found.

The present invention has been made in order to solve the above-mentioned problems. The present invention is directed to a double-sided simultaneous coating apparatus installed on the entrance side of a catenary type drying furnace. When the strip is sandwiched between the side applicator roll and the upper applicator roll and the simultaneous double-side coating is performed continuously, the same thickness can be applied to both surfaces of the strip with the same film thickness. An object of the present invention is to provide a method for controlling a coating thickness in coating.

[0015]

According to the present invention, a lower side applicator roll is provided by a double-sided simultaneous coating apparatus provided with an upper applicator roll and a lower applicator roll, which is installed on the entrance side of a catenary type drying furnace. While supporting the catenary portion of the band, sandwiching the band between the upper applicator roll and the lower applicator roll and simultaneously coating the front and back surfaces of the band, controlling the coating thickness of the front and back surfaces In addition to applying a film thickness control formula including the pressing force between the applicator roll and the band as a film thickness control factor, the pressing force between the applicator roll and the band is set to the tension of the catenary part. The above problem has been solved by making corrections between the strip and the upper and lower applicator rolls based on the above.

According to the present invention, in the method for controlling the coating film thickness in the simultaneous double-side coating, the film thickness control formula is used to elastically remove the actual gap existing between the rolls or between the roll and the band which is an apparently negative gap. It is determined by applying the theory of fluid lubrication, and is assumed to be a film thickness control formula derived from a formula that gives the mass balance of the paint on the roll using the gap.

[0017]

According to the present invention, the belt is sandwiched between the upper applicator roll and the lower applicator roll while the catenary portion is supported by the lower applicator roll, and simultaneous coating on both sides is performed. When setting the pressing force between the applicator roll and the band, which is the film thickness control factor included in the formula, the pressing force is corrected based on the tension of the catenary part, so that the warpage in the width direction Can be applied with a uniform film thickness in the width direction on both front and back sides, and between the upper applicator roll and the lower applicator roll and the belt due to the tension of the catenary part. Since different pressing forces can be set to appropriate values, it is possible to paint accurately on both sides with the target film thickness.

Further, in the present invention, the film thickness control formula determines the actual gap existing between the rolls and the roll and the band, which are apparently negative gaps, by applying the theory of elastic fluid lubrication. In the case of using a film thickness control formula derived from a formula that gives the mass balance of the paint on the rolls, it is possible to accurately control a thin coating film thickness.

Regarding the film thickness control formula to which the elastohydrodynamic lubrication theory is applied, the present applicant has already filed Japanese Patent Application No. Hei 4-2813.
23.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a side view showing a schematic configuration of a coating facility applied to a coating film thickness control method according to one embodiment of the present invention.

The above-mentioned coating equipment is provided with a double-sided simultaneous coating apparatus having an upper roll coater 40 and a lower roll coater 50 installed on the entrance side of the same catenary type drying furnace as shown in FIG.

In this double-sided simultaneous coating apparatus, the steel strip S moving rightward is sandwiched between the upper applicator 42 of the upper roll coater 40 and the lower applicator roll 52 of the lower roll coater 50. In this state, both sides of the steel strip S are simultaneously coated continuously.

In the upper roll coater 40, the paint pan 12
From the paint pan 12, the paint is pulled up by the pickup roll 44, and is supplied to the applicator roll 42 by the transfer roll 46. The lower roll coater 50 similarly picks up the paint from the paint pan 12 by the pickup roll 54 and the transfer roll 56. The coating material is supplied to the applicator roll 52.

The coating apparatus is capable of appropriately applying a desired pressing force between the applicator roll 42 of the upper roll coater 40 and the applicator roll 52 of the lower roll coater 50. The coating apparatus is provided with a measuring device (not shown) such as a load cell for measuring the pressing force. The measuring device uses the measuring device to measure the upper applicator roll 42 and the lower applicator roll 52, respectively. The pressing force between the steel strip S and the steel strip S can be measured.

In the present embodiment, the coating apparatus is provided with an upper roll coater and a lower roll coater, and positively presses between the upper and lower applicator rolls 42, 52. And steel strip S
Are forced to contact with each other, even when the steel strip S is warped in the width direction, the thickness distribution in the width direction can be made uniform, and even when the thickness of the steel sheet S is changed, Control can be easily performed.

Further, it is possible to measure the pressing force between the steel sheet S and the applicator roll at the time of coating, and to accurately control the film thickness based on the measured value.

The present embodiment is a method for controlling the film thickness of the steel strip S when performing simultaneous double-sided coating of the steel strip S by the double-sided simultaneous coating apparatus installed on the entrance side of the catenary type drying furnace 22.

In this embodiment, as shown in the enlarged view of FIG. 2, the double-sided simultaneous coating apparatus includes an upper roll coater 40 and a lower roll coater 50, each of which is provided with a pickup roll 4.
4 and 54 are peripheral speeds V _P , transfer rolls 46 and 56 are peripheral speeds V _T , and applicator rolls 42 and 52 are peripheral speeds V.
_{In A} , the pressing force (nip pressure) between the pick-up roll and the transfer roll is N _P , the pressing force between the transfer roll and the applicator roll is _NT , and the pressing force between the applicator roll and the steel strip S is N. with pressing force is set at N _a, the steel strip S moving in the right direction at a line speed LS
Is to be painted on both sides.

In this embodiment, the film thickness control formula expressed by the following formula (1) is applied, and the applicator roll and the steel strip included in the film thickness control formula are used by the method described later. Correction of the pressing force N _A between S and S is performed. The formula (1) is based on the premise that a part of the paint pulled up by the pickup roll is sent to a transfer roll, a part of the paint is sent to an applicator roll, and a part of the paint is further transferred to a steel strip S. The gap between each roll and the gap between the applicator roll and the steel strip were obtained by applying the theory of elastohydrodynamic lubrication.
-281323.

[0031]

(Equation 1)

Here, M is the amount of paint applied, C is the paint concentration, γ
Is the specific gravity of the paint, μ is the viscosity of the paint, α, β, λ ₁ , λ ₂
Are constants.

In the above equation (1), E _PT , E _TA and E _AS are equivalent elastic coefficients given by the following equations (2) to (4), respectively. The subscripts P, T, A, and S indicate a pickup roll, a transfer roll, an applicator roll, and a steel strip, respectively.

2 / E _PT = (1−ν _P ² ) / E _P + (1−ν _T ² ) / E _T (2) 2 / _{ET A} = (1−ν _T ² ) / E _T + ( ^{_{1-ν A 2) / E}} A ... (3) 2 / E AS = (1-ν A 2) / E A + (1-ν S 2) / E S ... (4)

Here, ν is Poisson's ratio, and E is Young's modulus.

In the above equation (1), R _PT , R _TA and R _AS
Is an equivalent roll radius, and is the following (5) to (7), respectively.
Given by the formula.

R _PT = _RP · _RT / ( _RP + _RT ) (5) _RTA = _RT · _RA / ( _RT + _RA ) (6) R _AS = _RS · _RA / (R _S ± R _A ) (7)

Here, R _P , R _T , and R _A are the roll radii of each roll (where R _S is the radius of curvature of the steel strip).
In the denominator of the equation (7), + corresponds to the case where the steel strip is circumscribed to the applicator roll, and-corresponds to the case where it is inscribed.

In this embodiment, when the film thickness is controlled by applying the above equation (1), the pressing force N _A between the applicator roll and the steel strip is corrected as follows.

In the case of performing simultaneous double-side coating with the coating equipment shown in FIG. 1, the pressing force N _A differs between the upper and lower applicator rolls 42 and 52 because the tension of the catenary portion acts on the lower applicator roll. I have.

When the upper applicator roll 42 is fixed and the pressing force is measured and controlled by the lower applicator roll 52, the measured value of the pressing force measured by the lower applicator roll 52 is denoted by N _A '. Then, the actual pressing force N _A between the upper and lower applicator rolls 42 and 52 and the steel strip S can be expressed by the following equations (8) and (9), respectively.

N _A = N _A ′ −2T sin (θ / 2) (upper side) (8) N _A = N _A ′ (lower side) (9)

Here, T is the tension of the catenary portion, and θ is the winding angle of the steel strip S around the lower applicator roll 52. The winding angle can be adjusted by the lift roll 26.

By substituting the above equations (8) and (9) into the above equation (1) as the pressing force N _A between the upper and lower applicator rolls 42 and 52 and the steel strip S, the front and back (up and down) both sides are obtained. The amount of each adhesion can be estimated, and it becomes possible to determine conditions for obtaining the target amount of adhesion.

[0045] Conversely, if the upper applicator roll 42 for measuring the N _A 'pushing force, the pressing force N _A between the upper and lower applicator roll 42, 52 and the steel strip S, respectively (10) , (11), the coating conditions can be similarly determined by substituting these two equations into the above-mentioned equation (1).

N _A = N _A ′ (upper side) (10) N _A = N _A ′ + 2T sin (θ / 2) (lower side) (11)

By adjusting the height of the lift roll 26, if the steel strip S is sandwiched between the upper and lower applicator rolls 42 and 52 on the tangent line of the catenary and painted,
Although it is not necessary to consider the influence of catenary tension on the pressing force between the applicator roll and the steel strip, in this case, the contact state between the applicator roll and the steel strip tends to change due to the vibration of the catenary part, As a result, uneven coating is likely to occur.
It is common to paint with wrapped around.

Next, the result of actually applying this embodiment will be described.

Here, the plate thickness is 0.55 mm and the plate width is 1450.
A steel strip having a thickness of 70 mm / min was used for painting. However, the used steel strip had an upwardly convex warpage of about 80 mm at the center in the width direction.

According to the method of this embodiment, the operating conditions of the coating apparatus (roll peripheral speed, pressing force between rolls) and the like are determined by substituting the equations (8) and (9) into the equation (1). FIG. 3 shows the result of controlling the coating film thickness. This figure 3
3 shows the width direction distribution of the coating film thickness on the front surface (shown as the upper surface in the drawing) and the back surface (shown as the lower surface in the drawing) of the steel sheet.

For comparison, in the coating equipment shown in FIG.
23 when operating conditions are determined using the method proposed in No. 23 (a method of determining coating conditions using a film thickness control formula created by obtaining the roll gap by elastohydrodynamic lubrication theory as in the present embodiment). Is shown in FIG.

As shown in FIG. 4, according to the comparative example, although a uniform film thickness distribution is obtained in the width direction on the front surface, the film thickness is increased on the back surface as the steel strip warps and approaches both ends. And the distribution is non-uniform. On the other hand, according to the present embodiment, as is apparent from FIG. 3, both the front and back surfaces have a uniform film thickness in the width direction, and both surfaces can be almost exactly controlled to the target coating film thickness (the amount of paint applied). You can see that

Further, in the coating equipment shown in FIG.
When the plate thickness is changed from 0.5 mm to 1.6 mm with a steel strip of mm, the pressing force between the steel strip and the steel strip measured by the lower applicator roll is kept constant, and (8), (9) The result obtained by correcting the expression (1) with the expression and performing the film thickness control (the method of the present invention), and controlling the film thickness by applying the expression (1) as it is without performing the correction by the tension of the catenary portion. FIG. 6 shows the results of the adhesion amount on the upper surface side. At this time, the winding angle θ was set to 5 °.

As is apparent from FIG. 6, according to this embodiment, it is possible to accurately control the target film thickness even when the plate thickness changes. It should be noted that even when the correction by the tension was performed by the above equations (8) and (9), the film thickness on the back side was constant for both.

Although the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and can be variously modified without departing from the gist thereof.

For example, the film thickness control equation applicable to the present invention is not limited to the equation (1).

Further, in the embodiment, the double-side coating apparatus is shown in which each of the upper roll coater and the lower roll coater is composed of three rolls, but may be two rolls.

[0058]

As described above, according to the present invention, while supporting the catenary portion with the lower applicator roll installed on the entrance side of the catenary type drying furnace, the upper applicator roll and the lower applicator roll are connected to each other. When the simultaneous coating is performed on both sides by sandwiching the belt-like body between the two, it is possible to control both the front and back surfaces to the target film thickness.

[Brief description of the drawings]

FIG. 1 is a side view showing a coating facility applied to one embodiment according to the present invention.

FIG. 2 is an enlarged side view showing a simultaneous double-side coating device.

FIG. 3 is a diagram showing an example of a film thickness control result by the method of the present invention.

FIG. 4 is a diagram showing an example of a film thickness control result according to a comparative example;

FIG. 5 is another diagram showing an example of a film thickness control result by the method of the present invention.

FIG. 6 is a side view showing a conventional coating facility.

[Explanation of symbols]

 S ... steel strip 12 ... paint pan 26 ... lift roll 40 ... upper roll coater 42, 52 ... applicator roll 44, 54 ... pickup roll 46, 56 ... transfer roll 50 ... lower roll coater

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B05D 1/00-7/26

Claims (2)

(57) [Claims] 1. A catenary portion of a strip is supported by a lower applicator roll by a double-sided simultaneous coating apparatus provided with an upper applicator roll and a lower applicator roll installed on the entrance side of a catenary type drying furnace. While sandwiching the band between the upper applicator roll and the lower applicator roll and simultaneously coating the front and back surfaces of the band, the applicator roll and the band are used to control the coating film thickness on both the front and back surfaces. And a pressing force between the applicator roll and the band to be set is determined based on the tension of the catenary part. A coating film thickness control method for simultaneous double-sided coating, wherein correction is performed between applicator rolls. 2. The method according to claim 1, wherein the film thickness control formula obtains an actual gap existing between the rolls or between the roll and the strip, which is an apparently negative gap, by applying an elastic fluid lubrication theory. A coating thickness control method for simultaneous double-sided coating, which is a film thickness control formula derived from a formula for giving a mass balance of a paint on a roll by using a method.