JPH0459955A - Continuous hot dip galvanizing device - Google Patents

Abstract

PURPOSE:To stably produce a galvanized steel sheet having a beautiful surface free of foreign matter by providing a cleaned molten zinc supply discharge nozzle at the tip of a snout surrounding the vicinity of the admission point into the hot dip galvanizing bath surface of a strip to be dipped in the bath through the snout with one end connected to a reduction annealing furnace and the other end dipped in the bath. CONSTITUTION:A cleaned molten zinc discharge nozzle 10 is provided at the tip of the snout 3 surrounding the vicinity of the admission point into the hot dip galvanizing bath surface of a strip 1 to be dipped in the bath 11 through the snout 3 with one end connected to a reduction annealing furnace (not shown in the figure) and the other end dipped in the bath 11. A hooked overflow weir 13 for cleaned molten zinc surrounding the strip l with the lower surface connected to the tip of the snout 3 and closed, and the upper part opened is provided within the nozzle 10, and molten zinc is supplied into the weir 13 from a supply header 12 through the nozzle 10.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a continuous hot-dip galvanizing device that eliminates the influence of dross or ash generated in the snout installed in the hot-dip zinc bath of the continuous hot-dip galvanizing device. .

<Prior art> Conventionally, in the plating equipment widely used in continuous hot-dip galvanizing lines, reduction annealing is performed to prevent the strip 1 coming out of the reduction annealing furnace from coming into contact with the atmosphere, as shown in Fig. 4. A cylindrical snout 3 is arranged between the furnace and the plating bath 11.

This snout 3 isolates the inside from the atmosphere,
One end is connected to a reduction annealing furnace, the other end is immersed in a plating bath 11, and the snout 3 is always filled with reducing gas. The strip l introduced into the plating bath 11 is turned upward via the zinc roll 4 and then pulled up while being supported by the support roll 5.

However, this reducing gas contains a trace amount of oxygen or moisture, and this oxygen or moisture 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 M is floating in the plating bath, and 20 dross floats to the surface and accumulates in the snout as dross 2. Hereinafter, ash and dross will be collectively referred to as dross.

If this dross 2 accumulates inside the snout 3, it will adhere or scratch the continuously moving strip 1, significantly impairing the quality of the plating surface of the strip 1. It is regularly removed from the surface of the plating bath.

When removing the dross 2, after stopping the plating work, the reducing atmosphere in the snout 3 is first replaced with an atmospheric atmosphere, and then the snout 3 is raised upward to scrape out the dross 2.

As described above, in order to remove the dross 2 in the snout 3, the plating operation must be interrupted frequently for a long time, which poses a problem of significantly reducing productivity.

Further, while the dross removal work is a batch work, the generation of dross 2 is continuous, and the amount of dross 2 generated in the snout 3 increases in proportion to the plating work time after dross removal. On the other hand, since the adhesion of dross 2 to the strip 1 or the occurrence of scratches is to some extent proportional to the amount of dross 2 generated, the adhesion cannot be completely prevented, resulting in the problem of unstable product quality.

In addition, remove dross 2 or strip 1 in snout 3
As a method of preventing dross 2 from adhering to the surface, a method of blowing an inert gas to remove it (Japanese Patent Application Laid-Open No. 56-84453)
, a method of suction using an electromagnetic pump, etc.
No. 69, Japanese Utility Model Application No. 62-141059.

Utility Model Application Publication No. 62-1485 [; Method No. 3], method of collecting with a screw etc. (Japanese Patent Application Laid-open No. 61-119467, Japanese Patent Application Publication No. 62488766), method of pumping with a packet (Japanese Utility Model Application Publication No. 1987-119467, Japanese Patent Application Publication No. 62488766) ), a method of removing dross with a flow of plating solution (Japanese Unexamined Patent Publication No. 186463/1983), and a method of spraying clean molten metal (Japanese Unexamined Utility Model Publication No. 186463/1983).
1410511), or a method in which the inside of the snout is stirred once with a molten zinc injection nozzle 6, as shown in FIG. However, in either method, contact between the strip and the dross 2 was unavoidable, and the occurrence of defects on the plating surface due to dross adhesion could not be completely eliminated.

JP-A-2-11747 has proposed a hot-dip galvanizing apparatus for eliminating the influence of dross in the snout. In other words, in the device proposed in the same publication, as shown in FIG. 2, the strip l passes through the snout 3 and guide plate 8 is provided surrounding the strip 1 at a position above and below including the plating bath surface. Jin crawl through the inside 4
guided by.

At this time, the molten zinc pumped 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 is caused to overflow from the upper part of the guide plate 8, thereby preventing the strip 1 from being contaminated with dross. It is intended to prevent this.

The publication also describes another embodiment in which, 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 airtightly connected to the guide plate 8. The lower end of the guide plate 8 is sunk below the surface of the plating bath. Therefore, the molten zinc pumped 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 prior art proposed in the above-mentioned Japanese Patent Application Laid-Open No. 2-11747 is effective in preventing dross from adhering to the strip 1, the above-mentioned prior art disclosed in the same publication is In the former case, the molten zinc supplied from the injection nozzle 6 is passed through the guide plate 8.
When the molten zinc overflows from the upper part of the snout 3, the molten zinc flies off and grows and adheres to the inner wall surface of the snout 3, so that it comes into contact with the strip 1 and causes scratches.

In addition, the strip that enters the snout 3 will also be attached to the strip in a splash shape, and it will go to the board surface! There is a problem in that the enriched layer is non-uniformly formed and the plating composition is non-uniform. In order to solve this problem, it is necessary to control the overflow speed of the molten zinc overflowing from the upper end of the guide plate 8, but this is difficult because there is also jetting from the jetting nozzle 6.

On the other hand, the latter method has a problem in that a part of the molten zinc supplied from the injection nozzle 6 leaks from the upper part and adheres to and grows on the injection nozzle 6, causing scratches on the strip 1.

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

Another object of the present invention is to eliminate the need for removing dross on the surface of the plating bath inside the snout to the outside of the snout, and to enable the stable production of high-quality products free of dross adhesion. The present invention provides plating equipment.

<Means for Solving the Problems> The present invention provides a solution to the plating bath surface entry point of the strip, which is immersed in the hot-dip galvanizing bath through a snout, one end of which is connected to a reduction annealing furnace and the other end of which is immersed in the hot-dip galvanizing bath. A continuous hot-dip galvanizing apparatus is provided with a discharge nozzle for supplying cleaned molten zinc at the tip of a snout that surrounds the surrounding area, and more preferably, a discharge nozzle is connected to the tip of the snout inside the discharge nozzle so that the bottom surface is closed and the top is closed. A clean molten zinc overflow weir with a hook-shaped cross section surrounds the open strip.

<Example> Hereinafter, the structure and operation of the present invention will be explained 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 connected to a hot-dip zinc plating bath 1.
A discharge nozzle I for cleaned molten zinc is placed at the tip of the snout 3 that surrounds the vicinity of the plating bath surface entry point of the strip immersed in the plating bath via the snout 3 immersed in the plating bath 1.
Provide O.

Inside the discharge nozzle 10, there is provided an overflow [13] for cleaned molten zinc, which is connected to the tip of the snout 3 and has a cylindrical cross section and surrounds the strip 1 whose lower surface is closed and whose upper surface is open.

Molten zinc is supplied from the feeder 12 through the discharge nozzle 10 into the overflow weir 13 . Incidentally, the molten zinc in the plating bath 11 is sucked up by a pump 7 and is supplied to the supply ladder 12 via a pipe 14 after removing dross and the like from the molten zinc by a filter 9.

The clean molten zinc thus supplied into the overflow weir 13 overflows in the direction a over the upper end of the overflow weir 13, which has a relatively large gap with the snout 3, which is open at the top, so that the strip 1
It will be a soft touch.

In addition, in order to prevent the strip 1 from coming into contact with the overflow weir 13 when the vibration becomes large due to path fluctuations of the strip 1, it is effective to provide a support roll 8 above the overflow weir 13. .

In the present invention, since cleaned 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, dross adhesion to the strip 1 is prevented.

In addition, since the overflow weir 13 is used to bring the molten zinc into contact with the strip, the flow rate is reduced by 61 compared to the conventional injection nozzle method.
And it's easy. The molten zinc is soft-touched to the strip I, and splashes can be prevented. In addition, the overflow weir is always immersed in molten zinc, and the overflow weir 13
There is no concern about zinc adhesion or assimilation.

Next, continuous hot-dip galvanizing was performed using the apparatus shown in FIG. 1 under the following plating conditions.

Hot 1 anti-medium 1 11000a board thickness
0.7m Line speed 120m/s+in Fabric weightffl 90g/po (single side) in bath^1
Concentration: 0.15% Plating bath temperature: 450°C The results were compared with those obtained using the conventional technique disclosed in JP-A-2-11141 (the type shown in Figure 2 attached to the specification of this application). are shown in Table 1.

Table 1 As shown in Table 1, by adopting the device of the present invention, the quality defect rate due to scratches caused by molten zinc splash, uneven plating composition, etc. has been significantly reduced, and the number of surface foreign substances such as dross has also been reduced. Good results were obtained with O pieces/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, so it is possible to stably produce hot-dip galvanized steel sheets with a beautiful surface free of foreign matter. It can be manufactured by

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the apparatus of the present invention, and FIGS. 2 to 5 are sectional views of conventional examples using different methods. 1... Strip, 2... Dross, 2'...
・Ansh, 3... Snout, 4... Zinc 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. Patent applicant: Kawasaki Steel Corporation

Claims (2)

[Claims] 1. Cleaned molten zinc is applied to the tip of the snout that surrounds the vicinity of the entry point of the strip into the bath surface through the snout, which is connected to the reduction annealing furnace and the other end is immersed in the hot dip galvanizing bath. Continuous hot-dip galvanizing equipment equipped with a supply discharge nozzle. 2. The series according to claim 1, further comprising a cleaned molten zinc overflow weir with a hook-shaped cross section connected to the tip of the snout inside the molten metal discharge nozzle and surrounding a strip whose lower surface is closed and whose upper surface is open. Hot dip galvanizing equipment.