JPH07145460A - Method for removing dross in hot-dipping bath - Google Patents

Abstract

PURPOSE:To remove top dross in a hot-dipping bath vessel by shifting along the bath surface while restraining entrapment of the top dross into the bath. CONSTITUTION:The molten metal 2 is incorporated in the hot-dipping bath vessel 1 and a steel sheet 4 can be carried from the end part of a snout. The steel sheet 4 is changed upward to the carrying direction with a sink roll 5. Two pieces of spouting headers 6 are arranged above the hot-dipping bath vessel 1 along the line center and plural nozzles 6a are arranged at the side surface of each spouting header 6. The spouting direction of the nozzle 6a is set toward a little lower part in the width direction of the carried steel sheet 4. In the spouting header 6, the nozzle is connected with a gas tank 8 sealing gaseous nitrogen through piping 7 to supply the gaseous nitrogen from this gas tank 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing hot-dip plating dross, which removes top dross floating on the bath surface in a hot-dip galvanizing tank in which a material to be plated such as a steel plate is moved to a predetermined location and eliminated. is there.

[0002]

2. Description of the Related Art Generally, when a molten metal containing Zn-based, Al-based or Pb-based metal ions is used as a plating solution and a steel sheet to be plated is continuously plated, For example, as shown in FIG. 4, the end portion of the snout 3 is arranged in the bath, the steel plate 4 continuously fed from the end portion is dipped in the molten metal 2, and then the sink roll 5 is continuously fed. The steel plate 4 is immersed in the plating solution while the steel plate 4 is fed to the outside of the hot dip plating tank 1 by changing the conveying direction upward by a plating treatment, so that the surface of the steel plate 4 is coated with metal. Precipitate.

At this time, when the steel plate 4 is dipped in the bath to cause a plating reaction, top dross 9 is generated and the top dross 9 floats on the bath surface near the position where the steel plate 4 is dipped. If you leave this top dross 9 as it is,
A part of the top dross 9 is taken into the bath by convection of the molten metal 2 generated when the sent steel plate 4 is immersed in the plating bath.
It adheres to a plating facility such as a roll or a roll, or rises again due to convection of the molten metal 2 and enters the snout 3, causing defects such as scratches on the steel plate 4.

Therefore, conventionally, as shown in FIG. 5, a worker scrapes the top dross 9 floating on the bath surface 2a by a scraping jig 20 at the end of the hot dipping bath 1, that is, the steel plate 4 to be dipped. It was scraped up to a position away from the or snout 3 and then removed by pumping up with a pump or the like. In FIG. 4, 21 is a bottom dross.

[0005]

However, in the method in which the worker scrapes the top dross 9 floating on the bath surface 2a by the jig 20, the jig 20 is immersed in the bath from above when scraping. Part of the top dross 9 floating on the bath surface 2a is entrained in the bath due to convection of the molten metal 2 due to.

Therefore, the molten metal 2 in the hot dip bath 1
Depending on the convection conditions of the top dross 9
However, there is a problem in that it may adhere to the surface of the steel plate 4 or the roll to cause a surface defect, or may get into the snout 3 to cause scratches. The present invention is
The above problems have been taken into consideration, and the object is to remove the top dross in the hot dip bath along the bath surface while preventing the top dross from being taken into the bath.

[0007]

In order to achieve the above object, the method of removing hot-dip galvanized dross of the present invention is directed toward a top dross floating on the bath surface in the hot-dip galvanizing tank or a bath surface near the top dross. It is characterized in that the top dross is moved to a predetermined position along the bath surface by blowing a gas, and then the top dross is removed from the hot dip bath.

At this time, a non-oxidizing gas may be used as the gas to be blown onto the top dross. Further, the temperature of the gas blown onto the top dross may be set to be equal to or higher than the melting point of the molten metal in the hot dip bath.

[0009]

The gas is blown onto the top dross floating on the bath surface in the hot dip bath or in the vicinity thereof to cause the molten metal located near the bath surface to flow along the bath surface. As a result, the top dross with a low specific gravity moves along with the flow. At this time, since only the flow along the bath surface is formed in the molten metal in the vicinity of the bath surface by spraying, the occurrence of convection that involves top dross in the molten metal is suppressed, so that the top gas taken into the molten metal is suppressed. The amount of dross is reduced.

In order to suppress the flow only in the vicinity of the bath surface as much as possible, it is advisable to blow the gas from diagonally above the bath surface at a slanting speed which is not so strong that the top dross can move. . The place where the top dross is collected is set to a place sufficiently away from the plating device such as a snout or roll or the immersion position of the object to be plated such as a steel plate as in the conventional case.

Then, at a place apart from the above steel plate,
As in the conventional method, the top dross is pumped up by a pump or the like and removed from the tank. At this time, since the top dross is separated from the steel plate or the like, even if the top dross is caught in the molten metal, it is possible to prevent the top dross from reaching the arrangement position of the snout or the like.

By using a non-oxidizing gas such as nitrogen or argon as the above-mentioned gas to be blown, it is possible to suppress the generation of unnecessary redox reaction between the gas and the molten metal. Also, by setting the temperature of the gas above the melting point of the molten metal, the molten metal on the bath surface blown with the gas melts to improve the fluidity and floats even if the gas blowing speed is low. It will be easier for the top dross to move.

[0013]

Embodiments of the present invention will be described with reference to the drawings. First, the configuration will be described. As shown in FIGS. 1 to 3, a molten metal 2 such as a Zn-based metal is stored in a hot dip bath 1 as a plating solution, and the bath is placed from one end of the center line in the hot dip bath 1 to the bath. The end of the snout 3 is dipped inside,
The steel plate 4, which is the object to be plated, can be carried in along the line from the end of the snout 3.

A sink roll 5 around which the steel plate 4 is wound is arranged in the center of the hot-dip galvanizing tank 1 so that the conveying direction of the immersed steel plate 4 can be changed upward. Further, two blowing headers 6 are installed above the hot dip bath 1 along the line center, and a plurality of nozzles 6a are provided on the side surface of each blowing header 6. The blowing direction of the nozzle 6a is set to be slightly downward in the width direction of the conveyed steel plate 4 (direction orthogonal to the center line).

The blow-out header 6 is connected via a pipe 7 to a gas tank 8 in which nitrogen gas is sealed, and the nitrogen gas is supplied from the gas tank 8. In the plating processing equipment equipped with the above-mentioned top dross removing function, by constantly or intermittently blowing out the nitrogen gas from each nozzle 6a of the blowing header 6,
On the bath surface 2a, a flow of the molten metal 2 is formed along the bath surface 2a toward both ends 1a and 1b of the hot dip bath 1 orthogonal to the center line.

On the other hand, the steel sheet 4 continuously fed from the snout 3 is dipped in the molten metal 2 to be subjected to a plating treatment, and is carried out of the molten plating tank 1 via the sink roll 5. Then, during the plating reaction, dross 9 is generated and floats on the bath surface 2a. The top dross 9 floating on the bath surface 2a is blown to both ends of the hot dip bath 1 along the flow on the bath surface 2a formed by the blowing of the nitrogen gas.

Further, the top dross 9 blown up at the end of the hot dip bath 1 is appropriately removed from the hot dip bath 1 by a suction pump device or the like. Since the respective end portions 1a and 1b of the hot-dip galvanizing tank 1 in which the top dross 9 is collected are sufficiently separated from the steel plate 4 to be plated, the sink roll 5, the snout 3, etc., from the hot-dip galvanizing tank 1 Even if a part of the top dross 9 is taken into the molten metal 2 when the top dross 9 is removed, the top dross 9 does not adhere to the steel plate 4, the roll 5, or the like.

By using nitrogen gas as the gas to be blown out, it is possible to prevent the gas from causing an unnecessary redox reaction with the molten metal 2. Further, as the temperature of the nitrogen gas is raised, the temperature of the sprayed bath surface 2a rises and melts, and the viscosity decreases, so that only the molten metal 2 near the bath surface 2a has high fluidity, The top dross 9 floating on the surface 2a becomes easy to move. For this reason, the frictional resistance between the dopp dross 9 and the molten metal 2 is reduced, and the wind velocity of the gas blown out can be reduced, so that the top dross 9 can be further prevented from being taken into the molten metal 2.

Although nitrogen gas is used as the non-oxidizing gas in the above embodiment, other non-oxidizing gas such as argon gas may be used. However, nitrogen gas is advantageous in terms of cost. Further, in the above embodiment, the blowing header 6 that blows out the nitrogen gas is fixed, but it may be movable along the bath surface 2a.

[0020]

As described above, according to the hot dip dross removing method of the present invention, it is possible to collect the top dross in a specific place while suppressing the incorporation of the top dross into the molten metal. As a result, the adhesion of dross to an object to be plated such as a steel plate or plating equipment such as a roll is reduced, and the yield is improved.

At this time, by using a non-oxidizing gas as the gas to be sprayed, an unnecessary redox reaction between the gas and the molten metal does not occur. Further, by increasing the temperature of the gas, the fluidity of only the molten metal in the vicinity of the bath surface sprayed with the gas is improved, the top dross is easily moved, and the wind velocity of the sprayed gas can be suppressed to a low level.
It is possible to further suppress the incorporation of top dross into the molten metal.

[Brief description of drawings]

FIG. 1 is a side view showing a hot-dip galvanizing facility according to an embodiment of the present invention.

FIG. 2 is a plan view showing a hot-dip galvanizing facility according to an embodiment of the present invention.

FIG. 3 is a front view showing a hot-dip galvanizing facility according to an embodiment of the present invention.

FIG. 4 is a side view showing a general hot dip plating facility.

FIG. 5 is a side view showing scraping of a conventional top dross.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hot dip bath 2 Hot metal 2a Bath surface 4 Steel plate 6 Blowout header 6a Nozzle 9 Top dross

Claims (3)

[Claims] 1. The top dross is moved to a predetermined location along the bath surface by blowing gas toward the top dross floating on the bath surface in the hot dip bath or the bath surface in the vicinity thereof. After that, such a top dross is removed from the inside of the hot dip bath, a hot dip dross removing method. 2. The method for removing hot-dip galvanized dross according to claim 1, wherein a non-oxidizing gas is used as the gas blown onto the top dross. 3. The method for removing hot dip dross according to claim 1 or 2, wherein the temperature of the gas blown onto the top dross is set to be equal to or higher than the melting point of the molten metal in the hot dip bath.