JPH07207419A - Device for removing bottom dross in galvanizing bath tank in galvanizing line - Google Patents

Abstract

PURPOSE:To prevent adhesion of bottom dross to a plated steel sheet and to obtain the beautifully plated steel sheet by disposing a hermetically sealed settling tank in a galvanizing tank, sucking and removing the bottom dross deposited in this bath tank into this settling tank and allowing the bottom dross to deposit therein. CONSTITUTION:The steel sheet 1 emerging from a continuous annealing furnace is immersed via a snout 2 into a plating bath 4 in the plating bath tank 3 and is drawn outside via a bottom roll 5. The excess plating layers are wiped by gas wiping nozzles 6 and the surfaces of the steel sheet 1 are subjected to plating of a prescribed thickness. At this time, the settling tank 11 hermetically closed by a cap 8 is disposed in the bath tank 3 and a suction pump 8 is operated by a motor 14 to suck the bottom dross 10 deposited on an inclined plate 7 which is disposed in the lower part of the bottom roll 5 and has inclination of 15 to 30 deg. via a conduit 13 into the settling tank 11 up to its upper part. The dross 5 sucked therein is allowed to fall and to deposit in the lower part of the settling tank 11. The sucked plating bath 4 is returned from a drain hole 15 into the bath tank 3. As a result, the adhesion of the dross to the steel sheet 1 is prevented and the plated steel sheet having the beautiful plating appearance is thus obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bottom dross removing device in a hot dip galvanizing bath in a hot dip galvanizing line.

[0002]

2. Description of the Related Art Conventionally, as a hot dip metal plating method, a steel sheet to be plated is heated and annealed, an upper part thereof is connected to an annealing furnace, and a lower end thereof is passed through an inside of a snout immersed in the hot dip metal plating bath to form a hot dip metal bath. It is a method of obtaining a hot-dip metal-plated steel sheet by immersing it inside, changing the direction of travel by a pot roll in a bath and pulling it upward, and controlling the amount of hot-dip metal plating adhered by a gas drawing method. It is well known that, in such a hot dip galvanizing process, bottom dross, which is an impurity, adheres to the plated steel sheet in the zinc bath and impairs the appearance of the plated steel sheet.

In order to solve these problems, the bottom dross is conventionally dealt with by, for example, Japanese Patent Laid-Open No. 4-232235.
As shown in Japanese Patent Publication, a tube is erected on the side opposite to the pot roll in the zinc bath of the hot dip galvanizing line,
A porous refractory is provided in the lower part of the cylinder, a gas introducing pipe is communicated with the porous refractory from the outside, and a suction duct having an opening is provided at the bottom of the zinc bath below the pot roll, and the suction duct is connected to the suction duct. A device for removing impurities accumulated in the bath bottom in a molten zinc bath, in which the bottom of the cylinder is connected by a conduit and a partition plate is erected between the cylinder and the pot roll near the cylinder. That is, with respect to bottom dross that accumulates on the bottom of the molten zinc bath, a technique has been reported in which the bottom dross is sucked by a gas lift pump and the bottom dross is accumulated on a cylinder having an opening on the side surface surrounding the gas lift pump.

Further, as in Japanese Utility Model Laid-Open No. 4-53048, the accompanying flow of the plating bath accompanying the progress of the strip is rectified below the sink roll immersed in the plating bath in the plating bath in the molten metal plating apparatus. A bottom dross roll-up suppressing device having a flow straightening plate, wherein the material surface of the flow straightening plate is covered with a highly corrosion-resistant substance having a low leak property to the plating bath. That is, a straightening vane is provided below the sink roll to suppress the winding of bottom dross.

[0005]

However, in the above-mentioned Japanese Patent Laid-Open No. 4-232235, during recovery of bottom dross, zinc flows into the cylinder one after another, so that zinc comes into contact with air. The amount of top dross generated is higher than when the device is not used. Therefore, although the bottom dross is eliminated, the top dross adheres to the plated steel sheet due to the occurrence of the top dross, which impairs the appearance of the plated steel sheet. The bottom dross is sucked only in the vicinity of the suction port, and the bottom dross of the entire bath bottom is not sucked. Further, in Japanese Utility Model Application Laid-Open No. 4-53048, there is an effect of rectifying the accompanying flow of the plating bath accompanying the progress of the strip below the sink roll, but the bottom dross is not completely removed and the bottom dross is accumulated. There is a problem that it is useless to eliminate the prevention of.

The present invention has been made in view of the above problems, and by changing the pump system from a gas lift pump to a motor-driven pump and completely submerging the stationary tank in a zinc bath, bottom dross is eliminated. The purpose is to prevent the recovery and the generation of top dross and obtain a beautiful plated steel sheet.

[0007]

DISCLOSURE OF THE INVENTION The present invention is to achieve the above-mentioned object, and the gist of the invention is as follows: (1) A suction pump is provided in the molten zinc bath. , A stationary tank having an opening on the side so as to surround the suction pump is submerged below the zinc bath surface, an inclined plate with an inclined upper surface is provided below the pot roll, and the suction pump sucks the inclined plate. A bottom dross removing device in a hot dip galvanizing bath in a hot dip galvanizing line, characterized in that a mouth is connected to a static bath.

(2) A suction pump is provided in the molten zinc bath, and a stationary tank having an opening on the side so as to surround the suction pump is provided below the zinc bath surface, and the upper surface is inclined below the pot roll. A molten zinc bath in a hot dip galvanizing line, in which a suction port of a suction pump is connected to a static tank at the bottom of the inclined plate, and the plate is provided directly above the suction port. It is in the inner bottom dross removing device.

[0009]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram of a bottom dross removing device in a hot dip galvanizing bath in a hot dip galvanizing line according to the present invention. In the continuous hot dip metal plating apparatus, as shown in FIG.
After the steel plate 1 exiting from the continuous annealing furnace passes through the snout 2 and is immersed in the plating bath in the plating bath 3, the pot roll 5
After that, the gas wiping nozzle 6 outside the bath removes the excess plating layer attached to the surface, and the surface of the steel sheet 1 is plated with a predetermined thickness.
When the alloying treatment is performed thereafter, an alloying heating device is provided.

By the way, in hot dip galvanizing, iron powder Fe and Zn carried from the furnace by a steel plate react with each other to form FeZn _7, which is deposited as so-called bottom dross on the bottom of the bath. Furthermore, all the foreign substances carried from the furnace by the steel plate are transported to the vicinity of the steel plate by the surface flow toward the steel plate side caused by the invasion of the steel plate in the bath and adhere to the steel plate in progress, and at the same time the bottom dross is wound up by the sink roll, Adheres to the steel plate in progress. As a result, plating defects such as indentation defects due to non-plating and dross adhesion occur.
Even if it doesn't cause a lot of these,
This causes a problem of impairing the appearance of the plated steel sheet.

Although FIG. 1 shows the steps described above,
In such a process, the inclined plate 7 having an inclination of 15 ° to 30 ° is installed below the pot roll 5 in the zinc bath, and the suction port 9 of the suction pump 8 is arranged at the lowermost part of the inclined plate 7. The reason why the inclination of the inclined plate is 15 ° to 30 ° is that the inclined plate is 15 °.
If it is less than this, the flow of the bottom dross is poor, and the suction transfer effect is low at the bottom of the inclined plate. Further, if the angle exceeds 30 °, the flow of the bottom dross is good, but the flow is so good that it easily moves to the suction port, and conversely, the bottom dross concentrates on the suction port, which causes the suction port to be clogged.

Thus, the stationary tank 11 is installed on the outer circumference of the suction pump 8 and completely submerged in the zinc bath. Moreover, the stationary tank 11 is provided with a lid 12 that can be opened and closed on the upper surface. Then, when the suction pump 8 is operated by the motor 14, the bottom dross 10 moves downward along the inclined plate 7, moves from the suction port 9 into the stationary tank 11 through the conduit 13, and is lifted up above the stationary tank. , And lower it to deposit on the bottom of the static tank. In addition, the zinc sucked together with the bottom dross 10 is returned to the zinc bath through the zinc extraction hole 15 provided on the side surface of the stationary tank 11. On the other hand, at this time, since the interior of the stationary tank 11 is sealed, it is possible to completely prevent the generation of top dross.

Further, by opening the lid 12 on the static control tank 11, adding Al into the static control tank 11 and bubbling the static control tank 11 with nitrogen gas, the static control tank 11 is deposited on the lower part of the static control tank 11. In the bottom dross 10, the Al reacts with Fe and Fe
₂ Al ₅ is formed and floated on the bath surface as so-called top dross to remove bottom dross from the inside of the zinc bath.

FIG. 2 is a schematic view of a bottom dross removing device in a hot dip galvanizing bath which is another embodiment of the hot dip galvanizing line according to the present invention. An inclined plate 7 having an inclination of 15 ° to 30 ° is installed below the pot roll 5 in the zinc bath, and a suction port 9 of a suction pump 8 is arranged at the bottom of the inclined plate 7. Furthermore, the plate 15 is placed on the suction port from the inclined plate to 100 to 40.
It is arranged at a distance of mm. If the distance from the inclined plate is less than 100 mm, the bottom dross 1 from the suction port 9
It is narrow to suck 0, and bottom dross may get stuck in the suction port. Also, if it exceeds 400 mm, the suction force from the suction port is reduced and the suction effect of the bottom dross is reduced. At this time, as in FIG. 1, the bottom dross 10 is sucked by the suction pump 8 and is transferred to the stationary tank 11 installed on the outer circumference of the suction pump.

[0015]

EXAMPLES In the apparatus shown in FIGS. 1 and 2, a pot roll having a tilted plate disposed below it, and in addition to the tilted plate, just above the suction port, (plating bath width or less) × (length 1.0 ~ 2.
(0 m) plate and a suction port having an opening at the bottom of the bath of the pot roll below the pot roll. This suction port is connected to the bottom of the statically stabilizing bath by a conduit to form an upward flow by a suction pump. The bottom dross accumulated in the lower part was sucked in, and the bottom dross was lifted and lowered to above the stationary tank. Then, the bottom dross accumulated on the bottom of this stationary tank is opened by opening the lid of the stationary tank, Al is introduced, and the bottom dross reacts with Al to float on the bath surface as top dross. From the upper part of the stationary tank, It was removed as this top dross. In this way, it became possible to suck and remove a wide range of bottom dross in the plating bath.

As a result, the bottom dross recovery amount shown in FIG. 3 could be obtained. That is, FIG. 3 is a diagram showing the relationship between the pump suction elapsed time and the bottom dross recovery amount when the device according to the present invention is used. As can be seen from this figure, it is shown that the bottom dross recovery amount in the statically-determining tank increases in proportion to the passage of the pump suction time in each case performed by the apparatus shown in FIGS. 1 and 2. There is. This means that the bottom dross at the bottom of the zinc bath is completely collected for a long period of time without being accumulated.

[0017]

As described above, according to the apparatus for removing impurities deposited at the bottom of a plating bath according to the present invention, it is possible to completely suppress the top dross generated in the static bath during the recovery of the bottom dross. It is possible to reduce the rolling up of impurities in the zinc bath and thus
It has an excellent effect that a beautiful plating appearance can be obtained without dross adhering to the plated steel sheet.

[Brief description of drawings]

FIG. 1 is a schematic view of a bottom dross removing device in a hot dip galvanizing bath in a hot dip galvanizing line according to the present invention,

FIG. 2 is a schematic diagram of a bottom dross removing device in a hot dip galvanizing bath which is another embodiment of the hot dip galvanizing line according to the present invention,

FIG. 3 is a diagram showing a relationship between a pump suction elapsed time and a bottom dross recovery amount when the device according to the present invention is used.

[Explanation of symbols]

 1 Steel Plate 2 Snout 3 Plating Bath 4 Plating Bath 5 Pot Roll 6 Gas Wiping Nozzle 7 Inclined Plate 8 Suction Pump 9 Suction Port 10 Bottom Dross 11 Static Control Tank 12 Lid 13 Conduit 14 Motor 15 Zinc Removal Hole

Claims (2)

[Claims] 1. A suction pump is provided in a molten zinc bath, and a stationary tank having an opening on its side so as to surround the suction pump is provided below the zinc bath surface, and the upper surface is inclined below the pot roll. A bottom dross removing device in a hot dip galvanizing bath in a hot dip galvanizing line, wherein a slanting plate is provided, and a suction port of a suction pump is connected to the static stabilizing tank. 2. A suction pump is provided in the molten zinc bath, and a stationary tank having an opening on the side so as to surround the suction pump is provided below the zinc bath surface, and the upper surface is inclined below the pot roll. Inside a molten zinc bath in a hot dip galvanizing line, which is characterized in that an inclined plate is provided, a suction port of a suction pump is connected to a stationary tank at the bottom of the inclined plate, and the plate is provided directly above the suction port. Bottom dross removing device.