JPH0434906Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a gas throttling nozzle that ejects gas to throttle molten metal or liquid in continuous galvanizing or the like.

(Prior art) For example, when plating is performed in continuous hot-dip galvanizing equipment, generally a strip is introduced into a molten zinc liquid and the molten zinc is deposited on the surface of the strip. The thickness of the zinc coating is made uniform. Incidentally, in recent years, there has been a trend toward higher speeds and thinner coatings in such equipment for the purpose of improving productivity and reducing costs. When the strip is run at high speed,
The weight becomes thicker because the amount of lifted molten zinc that adheres to the strip increases. To aim for high-speed thinning, the slit gap of the gas restriction nozzle should be increased, or high temperature or high pressure gas should be used.
Must be operated with close nozzle to strip spacing. However, in such operations,
Significant noise and splash are generated, resulting in deterioration of the working environment and contamination of the nozzle and strip by the splash, resulting in a decline in product quality. In addition, an edge overcoat occurs in which the edge portions of the strip are thicker than the center portion, which not only goes against the desire for high quality, but also causes the load to collapse during coil winding.

Conventionally, various preventive measures have been taken against such problems. First, as a first example, as shown in FIG.
In the slit 12 formed in 1, by forming a slope outward from a position slightly narrower than the width of the strip S, a wide slit part 13 with a wide slit gap is formed on both sides, and the edge part of the strip S is formed. There is an example in which the squeezing force is increased by increasing the amount of gas. In addition, as a second example, as shown in FIG. 4, the slit 12 formed at the front end of the nozzle 11 has the same cap over the entire width of the nozzle 11, but the slit 12 has a cap at a position opposite to the edge of the strip S. An auxiliary nozzle 14 is provided in the auxiliary nozzle 14, and a slit 15 is formed in the auxiliary nozzle 14.
This is an example in which the amount of gas to the edge portion of the strip S is increased by ejecting more gas.

(Problems to be Solved by the Invention) However, the above conventional examples each have various problems. First, in the first example, it is necessary to change the nozzle each time the width of the strip changes, which causes a decrease in productivity.Also, the slit gap at the edge is wide and the amount of gas is large, so it is difficult to splatter or Significant noise generation.
In particular, the contamination of the nozzle and strip by splash was increased compared to when a nozzle with a uniform slit gap was used, and the nozzle had to be cleaned periodically. Furthermore, even with this method, edge overcoat could not be completely prevented. On the other hand, in the second example, only the auxiliary nozzle needs to be moved each time the strip width changes, so it is possible to prevent productivity loss due to nozzle replacement as in the first example, but it also increases the risk of splash and noise. The situation was the same as in the first example, and periodic cleaning of the nozzle was unavoidable.

In addition, as a nozzle that facilitates maintenance and management of the nozzle and allows for thinner coatings,
Although methods such as those shown in the official gazette and Japanese Utility Model Publication No. 61-352 have been proposed, these do not take any fundamental measures to prevent splashes.

Here, we focus on the causes of edge overcoat and splash splash, including measuring the dynamic pressure distribution of the jet flow in the nozzle width direction, visualizing the wiping gas flow on the strip surface, and high-speed photography of the flow of molten zinc on the strip and the situation where splash occurs. This can be explained as follows. Below, the fifth
This will be explained based on the drawings, which are schematic diagrams of wiping using a conventional nozzle, in which A shows a front view, B shows a side view, C shows a cross-sectional view after plating, and D shows a cross-sectional view of the wiping part.

In other words, although the dynamic pressure distribution of the gas jet in the width direction at the nozzle slit is uniform,
The wiping gas that impinges on the strip S at position 16 of the nozzle 11 and flows on the surface of the strip S is parallel to the strip S at the center of the strip S, as shown by the arrow, while flowing outward near the edges. Due to this outward drift, the portion of the molten zinc 17 deposited on the strip S that is closer to the center than the edges flows in the direction of the edges (arrows), and is attached to the strip edge due to the surface tension of the molten zinc 17. As the thickness of the molten zinc 17 deposited on this strip edge increases, the velocity of the surface layer of the deposited zinc increases, and the outward drift of the wiping gas causes the molten zinc 17 to become thicker.
The film 7 protrudes outward from the strip edge in the form of a film, and this film 18 flutters due to the wiping gas flow and is scattered as a splash 19. As a result, the basis weight of the plating 20 is almost uniform at the center of the strip S, as shown in FIG.

The present invention was developed in view of the above-mentioned conventional problems, and is a gas squeezing device that suppresses the generation of edge overcoat and splash, and contributes to improved productivity, cost reduction, and high quality of continuous hot-dip galvanized steel sheets. It provides a nozzle.

(Means for Solving the Problems) In order to solve the above problems, the gas throttling nozzle of the present invention includes a nozzle body with a nozzle slit in the front part, and a nozzle slit inside the nozzle body near both ends. Each of the nozzles is equipped with an internal nozzle provided toward the center of the nozzle.

(Function) With the above-described configuration, the present invention jets wiping gas from the nozzle body and jets high-pressure or high-temperature gas from the internal nozzle, thereby controlling the jetting of wiping gas near both ends of the nozzle. Can be directed towards the center,
Therefore, outward drift of the wiping gas at the edge portion is prevented.

Here, high pressure refers to 2 kg/cm ² or higher, and high temperature refers to 400°C or higher.

(Embodiment) A gas throttle nozzle according to an embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a nozzle body, and a nozzle slit 2 is formed over the entire width on the front surface of the nozzle body, and wiping gas is ejected from the inside of the nozzle body 1 through the slit 2. Reference numeral 3 designates an internal nozzle, and a plurality of internal nozzles are provided on each side of the nozzle main body 1 near both ends thereof, and are inclined from both ends toward the center of the nozzle.
I have made it to you. The internal nozzles 3 are each connected to a pipe 5 via a control valve 4, and this pipe 5
A high-pressure or high-temperature gas separate from the wiping gas supplied to the nozzle body 1 is supplied to the nozzle body 1. Here, the high pressure or high temperature gas supplied to the internal nozzle 3 refers to the wiping gas ejected from the slit 2 into the nozzle body 1, and together with the inclination of the internal nozzle 3,
At least as described below, it can contribute to changing the flow of the wiping gas.

With the above configuration, the wiping gas is ejected from the slit 2 and at the same time the internal nozzle 3
When higher pressure or high temperature gas is ejected, the wiping gas near both ends of the nozzle flows from the nozzle ends toward the center of the nozzle. As a result, the wiping pattern shown in FIG. 2 is obtained. That is, the wiping gas ejected from the nozzle 1 and collided with the strip S flows from the nozzle position 6 on the surface of the strip S as shown by the arrow, and flows parallel to the strip S or inward at the strip edge. . The molten zinc 7 adhering to the strip S also flows along with the flow of the wiping gas in the direction of the arrow, and the generation of splash is drastically reduced, and as shown in FIG. The adhesion of 7 is almost uniform over the entire width of the strip S. Therefore, the resulting galvanizing 8 is also substantially uniform over the entire width of the strip S, as shown in FIG.

Regarding the use of the internal nozzle 3, the one near the strip edge of the strip S is used among the plurality of internal nozzles 3. Therefore, as the strip width of the strip S changes, the one near the strip edge among the internal nozzles 3 is used. Select and use.
In such a case, the selection is made using the control valve 4, and the number of tubes to be used can be selected as appropriate.

According to experiments conducted by the present inventor, the inclination angle of the internal nozzle 3 toward the center is 10 to 60 degrees with respect to the axis of the wiping gas flow from the slit 2, and the nozzle tip is 2 degrees from the tip of the nozzle body 1. It is effective to install it ~20mm inside. Also, internal nozzle 3
In addition to the circular shape shown in FIG. 1, the shape of the tip may be rectangular or elliptical. Furthermore, although the internal nozzle 3 is shown as having a fixed angle and position in FIG. 1, it may be made adjustable in angle and position.

When high-temperature gas is used for the internal nozzle 3, a drop in temperature at the edge of the strip can be prevented, the viscosity and surface tension of the molten metal will be lower than in the center of the strip S, and edge overcoat can be more effectively prevented. Furthermore, the occurrence of splash and edge overcoat can be adequately dealt with by adjusting the pressure or flow rate of the gas ejected from the internal nozzle 3 using the control valve 4.

(Effects of the Invention) As described above, the present invention includes internal nozzles provided inside the nozzle body near both ends toward the center of the nozzle, and jets out wiping gas from the nozzle slit of the nozzle body. High-pressure or high-temperature gas is ejected from the internal nozzle, and the wiping gas ejected near both ends of the nozzle is directed toward the center of the nozzle. This prevents molten metal from drifting outward toward the strip edge, thereby reducing splatter. Also, the occurrence of edge overcoat can be suppressed. Therefore, it can contribute to improving productivity, reducing costs, and improving the quality of products, and is an extremely effective device for use in continuous hot-dip galvanized steel sheet production lines, etc.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of a gas throttling nozzle according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of the same wiping, in which A is a front view, B is a side view,
C is a cross-sectional view after plating, D is a cross-sectional view of the wiping portion, FIGS. 3 and 4 are perspective views of a conventional nozzle, and FIG. 5 is a schematic diagram of wiping when the conventional nozzle is used. S is the strip, 1 is the nozzle body, 2 is the nozzle slit, and 3 is the internal nozzle.

Claims (1)

[Scope of utility model registration request] A nozzle body with a nozzle slit in the front,
Inside the nozzle body, there are internal nozzles provided near both ends toward the center of the nozzle, so that wiping gas is ejected from the nozzle body, and high-pressure or high-temperature gas is ejected from the internal nozzle. 1. A gas throttling nozzle characterized in that the wiping gas is ejected near both ends of the nozzle and directed toward the center of the nozzle.