JP2501654B2 - Continuous hot dip galvanizing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a continuous hot-dip galvanizing apparatus which eliminates the influence of dross or ash generated in a snout installed in a hot-dip galvanizing bath of a continuous hot-dip galvanizing apparatus. .

<Prior Art> Conventionally, in a plating apparatus widely used in a hot dip galvanizing line, in order to prevent the strip 1 coming out of the reduction annealing furnace from contacting the atmosphere as shown in FIG. 4, reduction annealing is performed. A tubular snout 3 is arranged between the furnace and the plating bath 11. This snout 3 is connected to a reduction annealing furnace at one end to shut off the inside from the atmosphere.
The other end is immersed in the plating bath 11, and the snout 3 is always filled with the reducing gas. The strip 1 introduced into the plating bath 11 is turned up via the sink roll 4 and then pulled up while being supported by the support roll 5.

However, this reducing gas contains a small amount of oxygen or water, and this oxygen or water reacts with the molten metal on the surface of the plating bath to form ash 2 '. On the other hand, dross made of an alloy of Fe and Al floats in the plating bath, and the dross floats and accumulates as dross 2 in the snout. Hereinafter, ash and dross are collectively referred to as dross. When the dross 2 accumulates in the snout 3, it adheres to or scratches the continuously moving strip 1, and the quality of the plating surface of the strip 1 is significantly impaired. It is regularly removed from the surface of the plating bath.

When the dross 2 is removed, after the plating operation is interrupted, the reducing atmosphere is first replaced with the reducing atmosphere, and then the snout 3 is lifted up to scrape out the dross 2.

As described above, in order to remove the dross 2 from the snout 3, the plating operation must be interrupted for a long time and frequently, and there is a problem that the productivity is greatly reduced.

Also, while the dross removal operation is a batch operation,
The generation of the dross 2 is continuous, and the generation amount of the dross 2 in the snout 3 increases in proportion to the plating operation time after the dross is removed. On the other hand, the adhesion of the dross 2 to the strip 1 or the occurrence of scratches is proportional to the amount of the dross 2 generated to some extent, and therefore the adhesion cannot be completely prevented.
There is a problem that product quality is not stable.

As a method for removing the dross 2 in the snout 3 or preventing the dross 2 from adhering to the strip 1, a method of blowing an inert gas to eliminate it (Japanese Patent Laid-Open No. 56-84453), a method of sucking with an electromagnetic pump or the like ( JP-A-60-230969, JP-A-62-141059, JP-A-62-148563), a method of scraping with a screw or the like (JP-A-61-149467,
JP-A-62-188766), a method of pumping with a bucket (JP-A-60-122359), a method of eliminating dross with a plating solution flow (JP-A-61-186463), and a clean molten metal There is a method of spraying (in Japanese Utility Model Publication No. 62-141058), or a method of stirring the inside of the snout with the molten zinc injection nozzle 6 as shown in FIG. However, in any of the methods, the contact between the strip and the dross 2 was unavoidable, and the occurrence of plating surface defects due to the dross adhesion was not completely eliminated.

Japanese Unexamined Patent Publication No. 2-11747 has been proposed as a hot dip galvanizing apparatus for eliminating the influence of dross in the snout. That is, in the apparatus proposed in the publication, as shown in FIG. 2, the strip 1 passes through the inside of the snout 3, and a guide plate 8 provided so as to surround the strip 1 at the upper and lower positions including the plating bath surface. It is guided through the inside to Syncroll 4. At this time, in the gap between the guide plate 8 and the strip 1, molten zinc pumped up by the pump 7 is discharged by the injection nozzle 6 and overflows from the upper part of the guide plate 8 to prevent the strip 1 from being contaminated with dross. This is something to prevent.

As another embodiment of the publication, as shown in FIG. 3, the molten zinc injection nozzle 6 is located above the plating bath surface, and the lower end of the snout 3 is hermetically connected to the guide plate 8. The lower end of the guide plate 8 is submerged below the plating bath surface. Therefore, the molten zinc drawn up by the pump 7 is discharged from the injection nozzle 6 into the gap between the guide plate 8 and the strip 1 and overflows from the lower end of the guide plate 8 into the plating bath.

<Problems to be Solved by the Invention> However, although the conventional technique proposed in the above-mentioned Japanese Patent Laid-Open No. 2-11747 is effective in preventing the dross from adhering to the strip 1, In the former case, when the molten zinc supplied from the injection nozzle 6 overflows from the upper part of the guide plate 8, the molten zinc scatters and adheres and grows on the inner wall surface of the snout 3, so that it contacts the strip 1 and causes a scratch. .

In addition, there is a problem that the strip that adheres to the inside of the snout 3 is also attached in a splash form, which causes nonuniform formation of the Al-rich layer on the plate surface and causes nonuniformity of the plating composition. In order to solve this problem, it is necessary to control the overflow velocity of the molten zinc that overflows from the upper end of the guide plate 8, but it is difficult to control because there is jetting from the jet nozzle 6.

On the other hand, the latter has a problem that a part of the molten zinc supplied from the jet nozzle 6 leaks at the upper portion and adheres and grows on the jet nozzle 6 to cause scratches on the strip 1.

An object of the present invention is to propose a hot dip galvanizing apparatus which eliminates the influence of dross on the plating bath surface in a snout.

Another object of the present invention is continuous molten zinc that does not require the work of removing dross on the plating bath surface inside the snout to the outside of the snout, and that can stably produce high quality products without dross adhesion. A plating apparatus is provided.

<Means for Solving the Problems> In the present invention, one end is connected to a reduction annealing furnace and the other end is dipped in a hot dip galvanizing bath (11) and then immersed in the hot dip galvanizing bath (11). Both the downward facing clean molten zinc discharge nozzle (10) and the clean molten zinc overflow weir (13) are provided on the strip side of the tip of the snout that surrounds the vicinity of the entry point of the plating bath surface of the strip (1) Overflow weir (1
3) is the snout member (1) below the discharge nozzle (10).
5), a member (16) for closing the lower end of the overflow weir connected to the tip of the member (15) of the snout, and a member (1) for closing the overflow weir.
6) A plate-like member (1) parallel to the strip that is connected to the strip and is arranged so that its upper end projects above the plating bath surface.
7) is a weir having a U-shaped cross section, and a plate-like member (17) parallel to the strip is arranged between the nozzle discharge port (18) and the strip (1) for continuous melting. It is a galvanizing device.

<Example> Hereinafter, the configuration and operation of the present invention will be described based on preferred examples.

In the present invention, as shown in FIG. 1, one end is connected to a reduction annealing furnace (not shown) and the other end is a plating bath of molten zinc.
A downward clean molten zinc discharge nozzle 10 is provided at the tip of the snout 3 that surrounds the vicinity of the entry point of the plating bath surface of the strip 1 that is dipped in the plating bath 11 through the snout 3 that is dipped in 11.

A clean molten zinc overflow weir 13 having a U-shaped cross section is provided inside the discharge nozzle 10 so as to be connected to the tip of the snout 3 and surround the strip 1 whose lower surface is closed and whose upper portion is open.

Molten zinc is supplied from the supply header 12 into the overflow weir 13 via the discharge nozzle 10. The supply header 12 has a plating bath.
The molten zinc in 11 is sucked up by the pump 7, the dross in the molten zinc is removed by the filter 9, and then the molten zinc is supplied through the pipe 14.

The clean molten zinc thus supplied into the overflow weir 13 overflows in the a direction at the upper end of the overflow weir 13 where the gap between the clean molten zinc and the snout 3 having an open upper portion is relatively large.
And soft touch, that is, the strip 1 comes into contact with a liquid interface formed of clean molten zinc in an overflow state. Incidentally, in order to prevent the strip 1 from coming into contact with the overflow weir 13 when the vibration becomes large due to the path variation of the strip 1, it is effective to provide the support roll 8 above the overflow weir 13. .

In the present invention, clean molten zinc is supplied from the discharge nozzle 10 provided at the tip of the snout 3 and brought into contact with the strip 1, so that dross adhesion to the strip 1 is prevented. Further, since the molten zinc is brought into contact with the strip 1 by using the downward discharge nozzle 10 and the overflow weir 13 having a U-shaped cross section, a splash is generated due to the blowing of the molten zinc from the nozzle as compared with the conventional injection nozzle system. Etc. can be prevented, and since the generation of splash can be prevented by making the discharge nozzle 10 face down, flow rate control for making the weir an overflow state becomes easy. Further, the overflow weir is always immersed in the molten zinc, and there is no concern that zinc may solidify and adhere to the overflow weir 13.

Next, under the following plating conditions, continuous hot dip galvanizing was performed using the apparatus shown in FIG.

Plate width 1000mm Plate thickness 0.7mm Line speed 120m / min Unit weight 90g / m ² (one side) Al concentration in bath 0.15% Plating bath temperature 450 ℃ The result is disclosed in Japanese Patent Laid-Open No. 2-11747. The results are shown in Table 1 in comparison with the case of using (FIG. 2 type attached to the specification of the present application).

As shown in Table 1, by adopting the device of the present invention, the rate of defective quality due to scratches caused by splash of molten zinc, uneven plating composition, etc. is significantly reduced, and the number of surface foreign matters such as dross is 0 / Good results were obtained with m.

<Effects of the Invention> As described above, in the apparatus of the present invention, the strip does not come into contact with the dross or ash floating on the plating bath surface, and the scratches due to the splash of molten zinc, the nonuniform plating composition, etc. As a result, the defective rate of quality is significantly reduced, and a hot-dip galvanized steel sheet having a beautiful surface free from foreign matter can be stably manufactured.

[Brief description of drawings]

FIG. 1 is a sectional view of the device of the present invention, and FIGS. 2 to 5 are sectional views of a conventional example according to different systems. 1 ... strip, 2 ... dross, 2 '... ash,
3 ... Snout, 4 ... Sink roll, 5 ... Support roll, 6 ... Injection nozzle, 7 ... Pump, 8 ... Guide plate, 9 ... Filter, 10 ... Discharge nozzle, 11 ... Plating bath , 12 …… Supply header, 13 …… Overflow weir, 14 …… Piping,
15 …… Snout member below the discharge nozzle, 16 …… Member for closing the lower end of overflow weir, 17 …… Plate-shaped member parallel to the strip, 18 …… Nozzle discharge port.

Claims (1)

(57) [Claims] 1. Strip plating (1) immersed in a hot dip galvanizing bath (11) through a snout (3) having one end connected to a reduction annealing furnace and the other end being dipped in the hot dip galvanizing bath (11). Both the downward facing clean molten zinc discharge nozzle (10) and the clean molten zinc overflow weir (13) are provided on the strip side of the snout tip that surrounds the vicinity of the bath surface entry point, and the overflow weir (1
3) is a member (15) of the snout below the discharge nozzle (10), a member (16) for closing the lower end of the overflow weir connected to the tip of the member (15) of the snout, and the closing Is a weir having a U-shaped cross section, which is composed of a plate-like member (17) which is connected to the member (16) for use and which is arranged so that its upper end projects above the plating bath bath surface and is parallel to the strip. A continuous hot-dip galvanizing apparatus characterized in that parallel plate-like members (17) are arranged between a nozzle discharge port (18) and a strip (1).