JPS5811065A - Nozzle for gas wiping of coating liquid for steel strip - Google Patents

Abstract

PURPOSE:To reduce splashes during gas wiping and to prevent the clogging of a nozzle by setting the angle formed between the external lines of the section of the leading end of the nozzle, the angle formed between the bottom of the nozzle and the steel strip in the line, and the injection direction of a gas in specific angle ranges. CONSTITUTION:A slit type gas ejection nozzle 10 of which the angle theta' assumed by the external lines of both nozzle lip parts 9, 9' is 45-95 deg. in section and which has flat outside wall surfaces 11' extending to the leading end in one nozzle lip part is disposed by directing the wall surfaces 11' toward the upper stream side in the advance direction of a steel strip 1 to be wiped of coating liquid by a gas in the traveling line of the strip 1 in such a way that the angle gamma assumed by the surfaces 11' and the traveling line of the strip 1 is >=90 deg.. Further, the injection direction of the gas from the nozzle 10 is directed to the upper stream side in the advance direction of the steel strip, and the incident angle beta of the collision of the gas against the strip 1 is set within a 70-30 deg. range. As a result, the splashes during gas wiping are reduced and the contamination of the nozzle and the clogging of the nozzle slit are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is for adjusting the amount of adhesion, that is, the thickness of the coating film, by gas wiping the surplus of the coating type chemical conversion treatment liquid or coating liquid that has been continuously applied to the surface of the copper strip. This invention relates to improvements in nozzle devices.

Conventionally, when coating a hot-dip galvanized copper strip with a coating-type chromate treatment solution or painting with a colored iron plate coating solution continuously while the copper strip is running, there is a method to adjust the adhesion amount of the coating solution. Generally, a roll wiping method using a squeeze roll placed in the running line is adopted. However, such a roll wiping method is disadvantageous in increasing the line speed, and when continuously adjusting the coating amount of the coating liquid on the steel strip with a metal drawing roll on a high-speed line, it is difficult to maintain a uniform coating amount in the width direction of the copper strip. In addition, there is a decrease in the followability of coating amount control when changing the thickness of the copper strip or when the speed decreases.In addition, maintenance measures against roll wear and paint material that adheres to the roll and hardens when the line is stopped. Various problems that need to be solved, such as a decrease in wringability, become noticeable.

One way to solve these problems is to use so-called gas wiping, which does not contact the running copper strip and can easily control the amount of adhesion.
Application of law may be considered. This gas wiping method is widely used in hot dip metal plating lines for copper strips, a typical example of which is shown in FIG. In FIG. 1, a steel strip (1) is continuously drawn from a molten metal plating bath (2);
) Excess molten metal on the surface is wiped away by gas injected from multiple gas nozzles (31, (3')) that open in a slit shape across the width of both sides.
This controls the plating thickness. The gas wiping nozzle (3) (3') used in such a molten metal plating line is a nozzle formed by upper and lower nozzle shoulders (4) (4'), as shown enlarged in Fig. 2. The cutting angle of the cross-sectional outline of the tip [θ
1 is an obtuse angle, and the angle (α) between the gas injection direction shown by the arrow (5) and the copper strip (1) is also approximately a right angle of 90 to 85°.

However, if such a nozzle (31 (3')) is used as it is for gas wipe coating such as coating type chemical conversion treatment liquid or paint liquid for steel strips, the nozzle (3) (3') As shown by the arrow (7) in Figure 2, the entrainment of secondary air occurs on the upstream side of the
The disturbances caused by this, such as the generation of vortices, cause severe damage.
Occurrence of flash (6) and its nozzle shoulder (4) (4
), and the adhesion splash was drawn into the nozzle slit (8), clogging the slit, causing uneven noise in the width direction wiping effect, and the adhesion splash was attached to the steel strip again by the nozzle jet gas. product contamination caused by contact with the product.

This is thought to be due to the fact that the physical properties of coating-type chemical conversion treatment liquids and coating liquids are higher in viscosity and lower in density than molten metal, and are more likely to generate splashes. In other words, these coating type chemical conversion treatment liquids and coating liquids have a viscosity of 1 to several hundred C.
The pb density is about 1 t/-, and when compared with molten metal, the viscosity is about the same to about 100 times, and the density is several minutes lower. As a result, the amount of these coating liquids that adhere to and lift up the running steel strip is much larger than that of molten metal when the line speed is constant, and therefore the amount of the coating liquid that is lifted up by adhering to the steel strip is much larger than that of the molten metal. occurrence becomes more intense. It is known that the amount of coating liquid that adheres to and is lifted by a running copper strip is theoretically proportional to the square root of the product of viscosity and line speed, and inversely proportional to the square root of density. Considering this, the nozzle (4)
When applying gas wipe pink according to (4') to the gas wipe pin of these coating liquids #-i', the running speed of the copper strip must be much lower than in the case of molten metal plating. According to my experience, it is impossible to operate without splashing unless the distance is 30 m/- or less.

Furthermore, the fact that the surface tension of these coating liquids that adhere to and are lifted by the running steel strip is lower than that of molten metal is also one of the causes of splash generation. In other words, most of these coating liquids have a surface tension that is less than one-tenth of that of molten metal, and the droplet diameter of the generated splash is small and the density is also small, so secondary particles at the nozzle tip are It is easily affected by air entrainment and turbulence, leading to nozzle contamination, nozzle slit clogging, or deterioration of product quality. Such a phenomenon should be extremely important, especially in the case of quick-drying coating liquids.

Conventionally, in the field of molten metal plating, splash from the entire width of the copper strip was not considered for gas wiping nozzles, and countermeasures were taken to prevent the slight occurrence of splash on both edges of the copper strip from contaminating both ends of the nozzle. Terasure,
For example, there is a known technique for suppressing the occurrence of splash from both edges by abutting plate metal such as asbestos material or solid carbon on both edges of the steel strip. There are disadvantages such as a decrease in the amount of plating deposited, or if the plate cannot completely follow the swinging of the steel strip in the width direction, it becomes the same as if there were no patch plate at all. As a method to prevent nozzle contamination from the splash generated during 4i, auxiliary nozzles are installed near both edges of the copper strip above the gas throttling nozzle, and the gas is blown onto the steel strip in the upstream direction of the steel strip. There is a technique to blow away the splash generated from both sides of the belt, but
It is difficult to delicately control the air pressure of the gas throttle nozzle and the auxiliary nozzle, and there are problems such as poor uniformity in the amount of plating deposited in the width direction of the copper strip, so it has not been put into practical use, much less for molten metal. It is difficult to apply this method to gas wiping of the above-mentioned coating liquid, which tends to generate splashes.

As described above, even in the field of molten metal plating, the problem of nozzle contamination due to splash generated from both sides of the steel strip has not been completely resolved, and furthermore, gas wiping of coating liquids such as coated chemical conversion treatment liquids and paint liquids has not been completely solved. In the case of gas wiping of the type of structure used in the field of molten metal plating, considering that when the line speed increases, splash occurs in the entire widthwise direction of the steel strip. It is clear that it is impossible to directly apply the nozzle to wiping coating liquids such as coated chemical conversion treatment liquids and paint liquids in terms of operation, maintenance, or product quality.

This invention has physical properties of high viscosity, low density, and low interfacial tension, such as coating type chemical conversion treatment liquids such as coating type chromate treatment liquids, or coating liquids for colored steel plates, and moreover, the coating film itself is The purpose is to provide a nozzle device that performs gas wiping after applying a coating solution that forms a film on the surface of a copper strip.In particular, it aims to reduce the occurrence of splash during gas wiping and to reduce nozzle contamination due to splash. This prevents clogging of nozzle slits and nozzle slits, and prevents deterioration of product quality.
The aim is to achieve a line speed exceeding i.

That is, in the nozzle device for gas wiping of a copper band coating liquid of the present invention, in the cross-sectional shape, the angle formed by the contour lines of both nozzle shoulders is 45 to 90 degrees, and the outer wall surface is flat and extends to the tip of one nozzle lip. A slit-type gas jet nozzle is positioned so that the outer wall surface faces upstream in the traveling direction of the copper strip with respect to the traveling line of the steel strip where the coating solution is to be gas-wiped, so that the angle between the outer wall surface and the traveling line is 90 degrees or more, and the gas jet direction from the nozzle is directed upstream in the copper strip traveling direction, and the gas collision incidence angle on the copper strip is within the range of 70 to 30 degrees. It is a feature.

According to this invention, by optimizing the gas wiping nozzle and its arrangement, even at high wiping speeds of 200 m/- or more, the entire gas wiping splash of coating liquids with high viscosity, low density, and low interfacial tension can be reduced. This can be done without contaminating the nozzle or clogging the nozzle slit or degrading the product quality due to the occurrence of spraying, and the adhesion of the coating liquid can be adjusted as desired by adjusting the injection flow rate or injection angle, etc. It is.

The present invention will be described below based on embodiments and with drawings.

Fig. 3 is a cross-sectional view of one side of the basic structural unit of the gas wiping nozzle device of the present invention, where the front and back directions of the drawing correspond to the width direction of the copper strip (1), and the nozzle GO Nozzle slit (8) 1 (nozzle slit) (8) U upper and lower nozzle lips! (91 (9')) are formed by opposing gaps between the thin blade-like edges.

The nozzle structure shown in Fig. 3 was developed based on a simulation experiment using a water model that focused on the entrainment and turbulence of the secondary air mentioned above. This was obtained by optimizing the angle (θ') formed between the nozzle bottom surface and the copper strip in the line), and the gas injection direction (angle β).

In other words, this slit-type gas injection nozzle 00) consists of a pair of nozzle shoulders (9) (9') whose outer surfaces are tangential to the outer peripheral surface on the header side, and one nozzle shoulder (9').
9') is formed into a flat outer wall surface (11')' that reaches the tip by its outer surface, and the angle formed between the tapered end surface 0υ of the other nozzle shoulder (9) and the outer wall surface (11'). That is, the outline of both nozzle shoulders and the angle θ' at the nozzle tip are at an acute angle of 45 to 90 degrees, and the upstream side in the direction of movement of the copper strip (1) with respect to the line The outer wall surface (11') is directed to the line, and the outer wall surface (11') is arranged in a line so that the angle (γ) between the line and the outer wall surface is an obtuse angle of 90 degrees or more. The gas injection direction is directed toward the upstream side in the steel strip traveling direction, and the gas collision incidence angle φ) onto the steel strip (1) is set within a range of 70 to 60 degrees.

If the angle #(γ) is less than 90 degrees, the entrainment of the secondary air (1 to 1) will increase, causing airflow turbulence near the nozzle tip.
) exceeds 90 degrees, the tapered end surface 0υ of the nozzle bottom (9) will approach the surface of the copper strip running on the line in relation to the angle (γ), and interference will cause scratches on the surface of the copper strip. Since the attached metal nozzle may be damaged, keep it under 90 degrees.
Also, if the angle is smaller than 45 degrees, it will be difficult to maintain the shape of the slit nozzle and form it due to the nozzle bottom surface (9) (9'), so the angle should be 45 degrees or more.

Gas collision incidence angle φ) 4-t, the wiping gas is ejected diagonally onto the steel strip surface against the advancing direction of the steel strip (1), and thus the injection flow rate and flow velocity are appropriately set within the range of 30 to 70 degrees. By doing so, an appropriate gas wiping effect can be obtained depending on the physical properties and adhesion amount of the coating liquid to be wiped.

In Fig. 3, the inner surface of the tip of the lower nozzle bottom (9')
14') is rounded, but this is because the gas pressure applied to I is used effectively for injection, and the flat inner surface of the upper nozzle bottom (9) in the header part (near the tip). It is also possible to form a part parallel to the side, but if the length of this parallel part becomes long, the laminar flow and straightness of the injected gas will be improved, but the pressure drop will increase, so if a parallel part is provided, it is necessary to The length must be selected depending on the distance between the nozzle and the steel strip. In the example shown in FIG. 3, the header part Qa and the nozzle bottom surface (9
7 (9') are made from separate parts and assembled together.The nozzle bottom (9) (9') may be made of a hard material such as stainless steel as it is, or by nitriding or chrome plating after finishing the base material surface. It can be constructed from a surface-hardened material.

FIG. 4(a) shows the nozzle device (15) (15) of the present invention.
' ) shows a vertical line configuration in the case of wiping with the injection gas a8, and FIG. In FIG. 4(a), Q6) is a nozzle for spraying the aforementioned coating liquid, and in FIG. 4(b), α7) is a nozzle for spraying the coating liquid αω.

Examples and comparative examples of the present invention using these vertical or horizontal lines are shown below.

[Example 1] A hot-dip galvanized steel strip (1) with a plate thickness of 0.27 mm and a plate width of 1219 m was coated in an organic coating type chemical conversion treatment liquid αe in a vertical line as shown in Figure 4 (a). After passing through the immersion, gas wiping was performed above using a nozzle device α5) (15') based on the present invention in a double-sided facing manner. In this case, the viscosity of the coating type chemical conversion treatment liquid aO is 4 cp, @degree is 1.06 t/Ca
The surface tension is 56 dyn/α, the angle (θ') at the nozzle tip is 75 degrees, the distance between the nozzle and the steel strip is 15 degrees, the inside of the nozzle slit is 1.5 m, and the outer wall surface (11' )
The angle (γ) between the copper strip and the copper strip is 90 degrees, the air injection direction is 45 degrees downward from the horizontal, and the header air pressure is 0.8 kg/
*, but the line speed f 600 ml-h
However, there was no nozzle contamination due to splash generation, and the final film adhesion amount was approximately 59/n? It was possible to obtain a uniform coated steel strip on both sides.

[Example 2] A hot-dip galvanized steel strip (1) with a plate thickness of 0.27 wn and a plate width of 1219 mm was sprayed in a spray paint liquid αe by a nozzle αD in a horizontal line such as (1) in Figure 4 (1)). After passing, the nozzle device a (15') according to the present invention is inserted from both upper and lower surfaces.
In the case of FJIJ gas-wiped with
is 45 degrees, the distance between the nozzle and the copper strip is 15 m, the inside of the nozzle slit is 1.2 tm, the angle (γ) between the outer wall surface (11') and the steel strip is 90 degrees, and the air injection direction is the direction of steel strip advancement. Direction upstream.

The collision incidence angle of the injected air onto the steel strip 't is 22.5 degrees, and the header air pressure is #'i1. It was OKf/i, but
Even at a line speed of 200 m/-h, there was no nozzle contamination due to splash generation, and a uniform colored iron plate with a coating thickness of 28 μm could be obtained.

[Comparative Example] After applying the same coated chemical conversion treatment liquid to the surface of a hot-dip galvanized steel strip with a thickness of 0.27 m and a width of 1219 strips in the same manner as in Example 1, the nozzle tip angle (θ') was Using a 120 degree gas wiping nozzle for molten metal plating line, the distance between the nozzle and the steel strip is 115 mm, f in the nozzle slit is 1.51111, the angle between the bottom of the nozzle and the copper strip is 30 degrees, and the air jet direction is horizontal. When gas wiping was performed at header air pressure of 0.8 to 9/-,
Nozzle contamination occurred due to splash generation at a line speed of 90 m/-, and the nozzle slit became clogged after about 10 minutes of continuous operation, so subsequent operations had to be stopped.

As described above, according to the present invention, even on high-speed lines of 200 m/- or more, coating liquids such as off-the-shelf chemical conversion treatment liquids or coating liquids having physical properties of high viscosity, low density, and low surface tension can be used. The thickness of the coating film and the amount of coating liquid deposited can be uniformly adjusted to a desired value without contaminating the nozzle or clogging the nozzle slit due to the occurrence of splashes, and without causing any deterioration in product quality. In addition, in this invention, by configuring the nozzle tip with a hardened material or a hard material, the nozzle tip will not be deformed or damaged even by interference during vibration of the steel strip, and therefore, it will be stable for a long time. You can achieve the gasy pink color.

It should be noted that the nozzle device according to the present invention can of course be applied to a gas wiping device for controlling the amount of deposited molten metal plating, but in that case, the main part of the nozzle (9) (9'
) is preferably made of titanium or the like to prevent deformation due to heat.

[Brief explanation of the drawing]

The first panel is a schematic diagram showing a gas wiping device in a conventionally known molten metal plating line, FIG. 2 is an enlarged view of its nozzle part, and FIG. 3 is a sectional view showing all the basic structural units according to an embodiment of the present invention. FIG. 4(a) is a schematic diagram of vertical and horizontal swiving lines produced by the nozzle device of the present invention. 1... Steel strip, 9, 9'... Nozzle main part, 10...
・Nozzle device, 11... Tapered end surface, 11'...
Outer wall surface, 12...header part. Agent Patent Attorney Masatoshi Sato

Claims (1)

[Claims] In the cross-sectional shape, the angle formed by the outline of both nozzle lips is 4
A slit-type gas jetting nozzle having a flat outer wall surface at an angle of 5 to 90 degrees and reaching the tip of one nozzle lip is used to move the outer wall surface of the copper strip along the running line of the copper strip where the coating liquid is to be gas-wiped. The steel strip is disposed so that the angle between the outer wall surface and the traveling line is 90 degrees or more toward the upstream side of the copper strip, and the gas jet direction from the nozzle is directed toward the upstream side of the copper strip traveling direction. The upward gas collision incidence angle is 70
Did you mean it was within the range of ~30 degrees? Features: Nozzle device for gas wiping of steel strip coating liquid.