JPS63224766A - Method for coating band steel - Google Patents

Abstract

PURPOSE:To control the unevenness on the coated surface during high-speed coating, by arranging a blade connected to an ultrasonic vibrator between a roll and a roll or between the roll and a band steel, where paint is brought in, in a roll coating method. CONSTITUTION:The surface of a band steel 3 is coated by using plural rolls 1, 2, and 4 in the roll coating method. The blade 7 connected to an ultrasonic vibrator 8 is arranged between the roll and the roll or between the roll and the band steel 3, where paint is brought in. The tip of the blade 7 is inserted into the film 9 of paint to vibrate the film 9, and a paint is coated on the band steel surface. As a result, the velocity of the coating line can be increased to >=200m/min without changing the physical properties (viscosity and surface tension), and the unevenness (especially rolling knots) generated on the coated surface during high-speed coating can be controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial application field The present invention uses a plurality of rolls to coat plated materials (for example,
This relates to a method of applying paint to steel strips.

(b) Prior Art For example, paint is applied to the surface of a steel strip for rust prevention and decoration. A roll coating method is a conventionally widely used coating method. A typical example of this method is shown in FIG.

In the example shown in the figure (A), an applicator roll 4 is interposed between a pick-up roll 1 and a backup roll 2, and the surface of the steel strip is coated by using the applicator roll 4. In the example shown in FIG. 1B, a part of the pickup roll 1 is dipped in paint, and a backup roll 2 presses the steel strip 3 against the pickup roll 1 to paint the surface of the steel strip.

In the example shown in FIG. 3(C), excess paint is scraped off from the applicator roll 4'' by the blade 5. (D)
In the illustrated example, excess paint is scraped off using a metering roll 6 instead of the blade 5.

This roll coating method has the characteristic that it can withstand coating in a relatively wide range of viscosity (1 to 104 cp). However, when the roll rotation speed is increased, the distance between the rolls (Fig. 7 (8)) and between the roller and the steel strip (Fig. 7 (8))
When the paint passes through the minute gap created between the roll and the blade (Fig. 7 (C)), a pressure distribution of the paint occurs in the width direction of the roll, and the roll eyes (Fig. 8)
A rippled meniscus is formed, resulting in uneven coating thickness on the steel strip.

On the other hand, there is a gas squeezing method (Fig. 7 (A)) in which a gas is sprayed onto the excess paint adhering to the surface of a roll or steel strip to squeeze it out. This gas squeezing method cannot be expected to be sufficiently effective when the paint surface being squeezed out by the gas moves at high speed, and splashes occur with paints with low viscosity (several tens of cps or less). 1oOcp or higher) has disadvantages such as the painted surface becoming rough due to wiping.

Speeding up the coating line is directly linked to a significant reduction in coating costs, so various methods have been used in the past. Solutions have been taken from the viewpoint of improving the paint and optimizing the coating operating conditions, but in any case, the coating line speed has been limited to 60 to 130 m/min.

” - If the limit is exceeded, uneven film thickness (roll marks) will occur.
This leads to a decrease in corrosion resistance. Furthermore, in recent years, there has been a demand for high-definition coated steel sheets among decorative steel sheets, and roll marks are regarded as a fatal defect.

(c) Problems to be solved by the present invention The problems to be solved by the present invention are the non-uniformity of the coated surface that occurs during high-speed coating in the roll coating method.
In particular, the object of the present invention is to obtain a coating method that suppresses roll marks.

(d) Means for Solving the Problems The steel strip coating method of the present invention is a roll coating method in which a plurality of rolls are used to apply paint to the surface of the steel strip. A blade connected to an ultrasonic vibrator is placed on the side where the paint is drawn between the steel strip and the tip of the blade is inserted into the paint film,
The second problem is solved by applying the paint to the surface of the steel strip while applying vibration to the paint film.

(E) Example The method for coating a steel strip of the present invention includes a roll coating method as shown in FIG.
and applicator roll 4 ((A), (C)
), or between the pick-up roll 1 and the steel strip 3 ((B), (D)), on the side where the paint is drawn in (hereinafter referred to as the paint entry side), as shown in Figure 1. Place the blade 7.

A conventional ultrasonic transducer 8 is connected to the blade 7. The tip of the blade 7 is inserted into the paint film 9 on the paint entry side, as shown in FIG. During the painting process, the blade 7 is used to propagate ultrasonic vibrations within the paint film 9. This results in
The pressure within the paint film 9 is made non-uniform to control the meniscus shape on the paint outlet side.

This effect will be explained with reference to FIG. When no vibration is applied ((B)), the meniscus shape of the paint film 9 on the exit side has a large wavelength. On the other hand, when vibration is applied ((B)), the meniscus shape on the exit side is drawn toward the input side and the wavelength becomes shorter. As a result, roll marks are suppressed.

As for the blade 7, as shown in FIG.
- - 4 There are two types: one with a uniform thickness ((B)), and one with a tapered tip only ((C)).

In the method of the present invention, for convenience of explanation, Figure 2, Figure 4 (C
) The explanation is based on an example using a blade 7 having a shape as shown in FIG. FIG. 5 shows an example of typical dimensions of the blade 7. The dimensions of the blade 7 are selected so that the strongest vibration amplitude can be obtained at the tip of the blade 7 depending on the ultrasonic usage conditions.

FIG. 6 shows how the ultrasonic transducer 8 and the blade 7 are connected. The vibrator 8 may be connected to the rear end surface of the blade 7 ((A)), or the vibrator 8 may be connected to the top or bottom surface of the blade 7 ((B)).

The connection of the vibrator 8 is such that the ultrasonic vibration is transmitted in the width direction of the blade 7 (
The following method is used to ensure uniform distribution in the direction (parallel to the roll axis).

(1) Modulating the frequency of the ultrasonic transducer within a certain range.

(2) Arranging multiple vibrators with different frequencies.

−〇　− (3) Use a combination of (1) and (2).

Next, specific examples of the coating method of the present invention will be described.

<Specific Example 1> After diluting an acrylic paint with thinner to a Ford cup viscosity of 70 seconds, a coating experiment was conducted on a color line using the roll configuration shown in FIG. 1. The roll used was 300mm in diameter.
Hard chrome plated pickup roll 1 with x roll length 2000mm and diameter 300mm x length 200
A reverse coating method was applied using an applicator roll 4 lined with 0 mm urethane rubber.

The base material for painting is hot-dip galvanized steel sheet (0.5 m thick).
m

The blade 7 was made of carbon steel plated with hard chrome. The typical dimensions of the blade 7 (Fig. 5) are shown below.

ρ1 = 1800mm fl 2 = 300mm ρ3 = 50mm t = 5mm R = 150mm Four ultrasonic transducers 8 with the following specifications, 300mm
arranged at equal intervals.

Vibration frequency 18kHz±0.5kHz (No, 1
．． 3) 16.5kHz±0.5kHz (No,
2.4) Vibration output 400W 200W (
No, 1. 3) 400W 200W (N
o, 2.4) (Example 1) (Example 2) The roll peripheral speed is line speed/applicator roll/pickup roll = 1.0/1 :15/
0.25 and all were kept constant. The pressing force between the applicator φ roll 4 and the pi-sofa-urn roll 1 was constant in this experiment.

The experimental results are shown in Table 1. Conventional method: 90m/min
According to the method of the present invention, there was a line speed limit of 2.
Good painting was possible even at 00 m/min.

Table 1 (Specific Example 2) Applied to water-based chromate liquid coating. It is a 10% chromic acid solution, and the liquid viscosity is 2 cp. The equipment used is the same as in the first embodiment described above. A cold-rolled steel plate with a thickness of 0.4 mm and a width of 1450 mm was used as the coating base material. The results of this experiment are shown in Table 2.

= 9-Table 2 Effect According to the present invention, the coating line speed can be increased to 200 m/min or more without changing the physical properties (viscosity, surface tension) of the paint.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of the coating method of the present invention. Figure 2 is the first
Partially enlarged view of the figure. FIG. 3 is an explanatory diagram of the operation of the method of the present invention. FIG. 4 is an explanatory diagram of the shape of the blade. FIG. 5 is a dimensional explanatory diagram of an example of the blade. FIG. 6 is an explanatory diagram showing the connection relationship between the blade and the ultrasonic transducer. FIG. 7 is an explanatory diagram showing a typical example of the conventional roll coating method. FIG. 8 is a partial vertical cross-sectional view exaggerating the state of the coating film on the roll surface. 1... Roll during pickup 2... Backup roll 3... Steel strip 4... Applicator battle roll 5... Blade 6... Metering roll 7... Blade 8... Super Sound wave vibrator 9...Paint film section

Claims (1)

[Claims] In a roll coating method in which paint is applied to the surface of a steel strip using multiple rolls, a blade connected to an ultrasonic vibrator on the side where the paint is drawn between the rolls or between the rolls and the steel strip. The tip of the blade is inserted into the paint film, and the paint is applied to the surface of the steel strip while applying vibration to the paint film.