JPH09217162A - Gas wiping nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas wiping nozzle adequate for hot dip metal coating. SOLUTION: This gas wiping nozzle consists of an inner tube 2 and a nozzle body 4. The inside of the nozzle body 4 is segmented by the inner tube 2 to a first equalizing pressure chamber 5 and a second equalizing pressure chamber 6 following an injection port 3. An orifice 7 facing the first equalizing pressure chamber 5 is opened at the inner tube 2. The narrowest spacings between the outside surface of the inner tube 2 and the inside surface of the nozzle body 4 are formed as throttling parts 8, 8. Guide surfaces 9, 9 for passing the flow of the gas flowing along a wall from the first equalizing pressure chamber 5 to the second pressure equalizing chamber 6 via these throttling parts 8, 8 are formed in the second equalizing pressure chamber 6. The gas wiping nozzle is so formed that the gas flowing from the first equalizing pressure chamber to the second equalizing pressure chamber via the throttling parts is passed along a guide face and, therefore, the gas wiping jet which does not generate vibration in the flow of the gas and has a uniform and stable pressure is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas wiping nozzle suitable for hot metal plating.

[0002]

2. Description of the Related Art Zinc on the surface of a metal strip (thin plate),
Continuous molten metal plating equipment is a technology for forming a metal film such as aluminum, and there is a technology for spraying gas to make the amount of metal adhered to the metal strip through the molten metal bath uniform. It is called a wiping nozzle (gas wiping nozzle), and is simply referred to as a wiping nozzle hereinafter.

In continuous molten metal plating, generally, a metal strip whose surface has been activated by a flux method or a hydrogen reduction method is immersed in molten metal, then continuously pulled up, and excess adhered molten metal is wiped with a wiping nozzle. To make the thickness of the molten metal on the strip surface uniform. The wiping nozzle is extremely important not only for controlling the metal deposition amount but also for determining the surface performance.

The invention relating to the improvement of the wiping nozzle is as follows.
For example, Japanese Patent Laid-Open No. 62-133058, "Gas Wiping Nozzle" and Japanese Utility Model Laid-Open No. 62-11168, "Gas Nozzle for Controlling Deposition of Molten Metal Plating" are known. As described above, as shown in FIG. 2 of the publication, a nozzle spacer 11 having a large number of diamond-shaped or parallelogram-shaped openings 12 is provided on the nozzle primary side, and the nozzle spacer 1
The straightening rods 9a and 9b are arranged on the secondary side of No. 1. As described above with reference to FIG. 2 of the publication, the above description shows that a damper 4 provided with a large number of openings 3 ... (... indicates a plurality, the same applies hereinafter) is provided on the primary side of the nozzle. Characterize.

[0005]

However, in the wiping nozzles described above and above, the gas is basically dispersed by a plate having a round or rhombic opening on the primary side of the slit, or further dispersed by a straightening rod. When a metal strip is processed by a wiping nozzle based on this principle, a striped pattern called "ripple mark" may occur at a substantially constant pitch at right angles to the running direction of the strip. This ripple mark spoils the appearance of the product. Then, the ripple marks appear irregularly in the width direction, further deteriorating the appearance.

The inventors of the present invention, who were skeptical that the ripple mark was generated even though the flow rate distribution and the pressure distribution from the slits were improved, thought that there might be another cause, and measured the pressure. In addition, we tried to confirm the "pressure fluctuation" with a high response pressure gauge, and as a result, we obtained the following findings. The generation frequency of the "ripple mark" in the plated product was 0.5 to 2.0 kHz, and the fluctuation frequency of the wiping jet pressure was found to have the same fluctuation frequency. The pressure fluctuation frequency of the wiping jet changes depending on the internal pressure of the wiping nozzle. Although the pressure of the wiping jet is uniform in the nozzle width direction, it is non-uniform in the pressure fluctuation width direction. The pressure fluctuation frequency of 0.5 to 2.0 kHz was not found in the original pressure of the gas supplied to the wiping nozzle. From the above results, it was found that the ripple mark is generated by the pressure fluctuation of the wiping jet, and this pressure fluctuation is generated in the wiping nozzle and is non-uniform in the width direction.

Further, in order to clarify the pressure fluctuation occurrence position in the wiping nozzle, the pressure inside the nozzle and the pressure fluctuation were measured in detail. FIG. 3 is a cross-sectional view of a conventional gas nozzle (equivalent to the “gas nozzle for controlling molten metal plating deposition amount” disclosed in Japanese Utility Model Laid-Open No. 62-11168), in which the gas nozzle 100 includes a nozzle body 101, a gas supply hole 102,
The first pressure equalizing chamber 103, the openings 104, 104, the second pressure equalizing chamber 105, and the injection port 106 are formed.
The width of the gas blown from 2 in the first pressure equalizing chamber 103 (the front and back of the figure)
Is a gas nozzle that disperses in the direction and is sent to the second pressure-equalizing chamber 105 through the openings 104, 104, and that the gas is dispersed in the width direction in the second pressure-equalizing chamber 105 to inject the gas from the injection port 106.

That is, the gas locally blown from the supply hole 102 can be uniformly injected from the injection port 106 by the dispersing action of the first pressure equalizing chamber 103 and the second pressure equalizing chamber 105. However, pressure fluctuations are observed. This generation mechanism is estimated as follows. FIG. 4 is a diagram for explaining pressure fluctuation generation in a conventional gas nozzle. When gas is injected at high speed from the opening 104 to the wide second pressure equalizing chamber 105, the jet flow 106A is generated.
Vibrates from the state of the solid line to the jet flow 106B of the broken line as shown by the arrow, and this becomes the source of pressure fluctuation. That is, it was found that the pressure fluctuation occurred in the abruptly enlarged portion of the flow path inside the wiping nozzle. Moreover, although the cross-sectional shape of the gas flow path was the same in the width direction, the pressure fluctuation was different in the width direction. This is due to the instability of the jet that is wide in the width direction and is jetted to the sudden expansion portion, and this jet partially oscillates with a slight disturbance to generate pressure fluctuation.

[0009]

Therefore, the present inventors have decided to modify the structure of the abruptly enlarged portion inside the wiping nozzle, and the vibration of the jet flow causes the gas to be jetted from the opening 104 into a wide space to cause the jet flow. It was found that there is a problem in the structure in which 106A and 106B are extremely unstable. FIG.
Is a principle diagram of a technique for stabilizing the jet flow. By providing the guide surface 111 at the outlet of the opening 104, the jet flow 106C jetted from the opening 104 into the pressure equalizing chamber 105 is
No unfavorable vibration is generated because it flows along 1. Therefore, the present invention applies this principle to the wiping nozzle.

Specifically, the first aspect of the present invention is that the gas wiping nozzle comprises an inner tube connected to a gas supply pipe and a nozzle body having an injection port and surrounding the inner tube, and the inside of the nozzle body is formed by the inner tube. 1 pressure equalizing chamber and 2nd pressure equalizing chamber following the injection port
An orifice is opened facing the pressure equalizing chamber, and a narrow gap between the inner tube and the nozzle body is used as a throttle portion, and a gas flow flowing from the first pressure equalizing chamber to the second pressure equalizing chamber through these throttle portions. The second pressure equalizing chamber is formed with a guide surface for flowing along the wall.

Since the gas flowing from the first pressure-equalizing chamber to the second pressure-equalizing chamber through the restrictor is made to flow along the guide surface, vibration does not occur in the gas flow and the pressure is uniform and the pressure is stable. A gas wiping jet is obtained.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view of a gas wiping nozzle according to the present invention.
Is the inner tube 2 connected to the gas supply pipe and the injection port 3
And a nozzle body 4 surrounding the inner tube 2, and the inside of the nozzle body 4 is divided into a first pressure equalizing chamber 5 and a second pressure equalizing chamber 6 following the injection port 3 by the inner tube 2. The orifice 7 facing the first pressure-equalizing chamber 5 is opened, and the narrowest gap between the outer surface of the inner tube 2 and the inner surface of the nozzle body 4 is defined as a narrowed portion 8,8. It is characterized in that the second pressure equalizing chamber 6 is formed with guide surfaces 9 and 9 for allowing a gas flow flowing from the first pressure equalizing chamber 5 to the second pressure equalizing chamber 6 through the wall along the wall.

For example, the nozzle body 4 includes a half-cylinder portion 4
a and a pointed portion 4b are separably combined via the flanges 4c and 4d, 11 is a sealing material, 12
Is a bolt. The seal material 11 is preferably a string-like packing having the same cross section as the O-ring, and the bolt 12 is preferably a hexagon socket head cap screw.

To give a detailed description, the gap of the injection port 3 is B, the gap of the throttle portions 8 and 8 between the inner tube 2 and the nozzle body 4 is C, and the opening area of the throttle portion 8 is S8. When the opening area of the orifice 7 is S7 and the inner cross-sectional area of the in-tube 2 is S2, the mutual relationships are as follows. The gap C of the narrowed portion 8 makes the gap of the injection port 3 larger than B. The opening area S7 of the orifice 7 is smaller than the inner cross-sectional area S2 of the inner tube 2. The opening area S7 of the orifice 7 is made larger than the opening areas S8 and S8 of the throttle portions 8 and 8. The orifice 7 may be a slit-shaped opening that is continuous in the nozzle width direction or a series of a plurality of small holes.

Due to the above-mentioned damming action of the throttle portions 8 and 8, the primary side (right side in the drawing) of the throttle portions 8 and 8 becomes the first pressure equalizing chamber 5 and the secondary side becomes the second pressure equalizing chamber 6. .

The operation of the gas wiping nozzle described above will be described below. FIG. 2 is an explanatory view of the operation of the gas wiping nozzle of the present invention, which shows the orifice 7 of the inner tube 2.
The gas ejected from the nozzle collides with the inner surface of the cylindrical portion 4a of the nozzle body 4 as shown by the arrow a, and is diverted into an arc type, and is then rectified by the throttle portions 8 and 8.

Immediately after the gas exiting the narrowed portions 8 and 8 flows along the guide surfaces 9 and 9 (arrows b and b), the gas flows toward the injection port 3, merges, and flows out through the injection port 3 to the outside. To do.

The arrow b is the same as that shown in FIG. That is, the gas flow from the narrowed portion 8 is not injected into the free space but flows along the guide surface 9, and as a result, vibration does not occur in the gas flow. Therefore, it is possible to obtain a wiping jet that is uniform in the nozzle width direction and has no pressure fluctuation.

The flow of the above-mentioned arrow a is sufficiently wide in the first
The gas is injected into the pressure equalizing chamber 5, and the distance to the cylindrical portion 4a is sufficiently large when viewed in the radial direction of the nozzle 7 (vertical direction in the drawing). On the other hand, in FIG. 4, the wall of the second pressure equalizing chamber 105 is located relatively close to the wall of the second pressure equalizing chamber 105, which causes a vortex to generate vibration. Therefore, FIG. 4 and FIG.
Is different from. Or, for example, in FIG.
Even if a vibration similar to is generated, this vibration is slight and is eliminated by the diaphragm portions 8 and 8.

The gas wiping nozzle 1 shown in FIG. 1 of the present embodiment is merely an example, and the flanges 4c, 4
The presence or absence of d, and its position, if any, are arbitrary. Furthermore, it is sufficient for the pointed portion 4b to have the guide surfaces 9 and 9, and it is possible to form the pointed portion as a whole or the pointed portion locally. Further, the inner tube 2 may also serve as a gas supply pipe.

[0021]

The present invention has the following effects due to the above configuration. According to a first aspect of the present invention, the gas wiping nozzle includes an inner tube connected to the gas supply pipe and a nozzle body that includes an injection port and surrounds the inner tube. The inside of the nozzle body is formed by the inner tube into the first pressure equalizing chamber and the injection port. It is divided into the following second pressure equalizing chamber, an orifice is opened in the inner tube facing the first pressure equalizing chamber, and a narrow gap between the inner tube and the nozzle body is used as a throttle portion. First
The second pressure equalizing chamber is characterized in that a guide surface is formed in the second pressure equalizing chamber for allowing a gas flow flowing from the pressure equalizing chamber to flow into the second pressure equalizing chamber along the wall. Since the gas flowing from the first pressure-equalizing chamber to the second pressure-equalizing chamber through the throttle is made to flow along the guide surface,
No vibration occurs in the gas flow, and a uniform and stable pressure gas wiping jet can be obtained. Therefore, the thickness of the metal plating becomes constant, and the stable continuous molten metal plating operation can be continued.

[Brief description of drawings]

FIG. 1 is a sectional view of a gas wiping nozzle according to the present invention.

FIG. 2 is an operation explanatory view of the gas wiping nozzle of the present invention.

FIG. 3 is a sectional view of a conventional gas nozzle.

FIG. 4 is an explanatory diagram of pressure fluctuation occurrence in a conventional gas nozzle.

[Fig. 5] Principle diagram of technology for stabilizing jet flow

[Explanation of symbols]

1 ... Gas wiping nozzle, 2 ... Inner tube, 3 ...
Injection port, 4 ... Nozzle body, 4a ... Cylindrical part, 4b ... Tip part, 5 ... 1st pressure equalizing chamber, 6 ... 2nd pressure equalizing chamber, 7 ... Orifice, 8 ... Throttling part, 9 ... Guide surface.

Claims (1)

[Claims] 1. A gas wiping nozzle for controlling the thickness of adhered metal by spraying gas onto the surface of a steel strip continuously pulled from a molten metal plating bath, wherein the gas wiping nozzle is an inner tube connected to a gas supply pipe. And a nozzle body that has an injection port and surrounds the inner tube. The interior of the nozzle body is divided into a first pressure equalizing chamber and a second pressure equalizing chamber that follows the injection port, and the first inner tube
A gas flow flowing from the first pressure equalizing chamber to the second pressure equalizing chamber through the narrow gap between the inner tube and the nozzle body is used as the throttle portion. A gas wiping nozzle characterized in that a guide surface for flowing the gas along a wall is formed in the second pressure equalizing chamber.