JP2010209439A - Method for removing dross in hot-dip galvanizing bath - Google Patents

Abstract

The present invention provides a method capable of removing dross from a hot dip galvanizing bath without causing clogging as a problem and without requiring an increase in size of equipment.
SOLUTION: Extracting molten zinc from a hot dip galvanizing bath in which a steel plate is immersed and galvanizing is performed, and a porous material having a temperature lower than that of the extracted molten zinc is added to the extracted molten zinc. The dross removal method of the hot dip galvanizing bath characterized by the above-mentioned.
[Selection] Figure 1

Description

  The present invention relates to a method for removing an intermetallic compound called dross that floats in a hot dip galvanizing bath and adheres to a steel plate when the hot dip galvanized steel plate is produced, thereby deteriorating the surface properties.

  The hot dip galvanized steel sheet is manufactured by immersing the steel sheet in a hot dip galvanizing bath. In this hot dip galvanizing bath, aluminum is added to improve the adhesion between the steel plate and zinc, and iron is eluted from the steel plate, so an intermetallic compound called top dross in which zinc and aluminum are combined, or zinc and iron. An intermetallic compound called bottom dross is attached to the surface. Since these dross adhere to the surface of the steel sheet and deteriorate the surface properties thereof, it is necessary to remove them as much as possible from the hot dip galvanizing bath.

  In order to remove dross from the hot dip galvanizing bath, various apparatuses and methods for regenerating them have been proposed. For example, Patent Document 1 discloses a dross removing packed layer in which a large number of particles are packed so that gaps are formed between the particles, and Patent Document 2 precipitates a precipitate lump on the bottom surface of the plating bath. A dross removal device has been proposed in which floating masses are suspended. Patent Document 3 discloses a method for regenerating a filtration material in which pickling and electrolysis are performed on a filtration material in which plates of porous carbon fiber reinforced carbon material for removing dross are laminated.

Japanese Patent Laid-Open No. 5-255828 JP-A-8-311628 Japanese Patent Laid-Open No. 7-15324

  However, since the dross removing apparatuses described in Patent Documents 1 to 3 require the lamination of a fixed particle packed layer and a plate material, clogging is likely to occur, and the equipment is increased in size.

  An object of the present invention is to provide a method capable of removing dross from a hot dip galvanizing bath without causing clogging as a problem and without requiring an increase in size of equipment.

  The purpose of this is to extract molten zinc from a hot dip galvanizing bath in which a steel sheet is immersed and galvanized, and to introduce into the extracted molten zinc a porous material that is at a lower temperature than the extracted molten zinc. This is achieved by the dross removal method of the hot dip galvanizing bath.

  In the dross removal method of the hot dip galvanizing bath of the present invention, it is preferable to introduce a porous material having a specific gravity smaller than that of the hot zinc as the porous material. Moreover, porous ceramics can be used for the porous material.

  The recovered porous material can be recovered and heated to regenerate the porous material.

  The dross removal method of the hot dip galvanizing bath of the present invention makes it possible to remove dross without causing clogging and without requiring an increase in the size of equipment.

It is a figure which shows typically an example of the hot dip galvanization equipment for enforcing the dross removal method of the hot dip galvanizing bath of this invention.

  FIG. 1 schematically shows an example of a hot dip galvanizing facility for carrying out the dross removing method of the hot dip galvanizing bath of the present invention. In a normal hot dip galvanizing facility, the steel plate 3 is immersed in a hot dip galvanizing bath 2 in a hot dip galvanizing pot 1 to perform galvanizing treatment. At this time, the steel plate 3 is supported by the sink roll 4 provided in the hot dip galvanizing bath 2, and its moving direction is changed so that the galvanizing process can be continuously performed.

  In the present invention, a hot-dip zinc separation pot 8 is provided in the vicinity of the hot-dip galvanizing pot 1, the hot pot zinc extraction pipe 5 connects the pot 1 and the pot 8, and the pump 6 provided in the hot zinc extraction pipe 5 is used to reduce dross. Extract the molten zinc from the floated hot dip galvanizing bath 2, transfer it to the pot 8, put the porous material 10 into the molten zinc 9 accommodated in the pot 8 from the porous material charging device 7, and make the dross porous. The dross is removed by adsorbing to the material 10. At this time, the temperature of the porous material 10 to be charged needs to be lower than that of the contained molten zinc 9. This is because dross having a freezing point lower than that of molten zinc 9 can be preferentially deposited and adsorbed on the surface of the porous material 10 by introducing the porous material 10 at a lower temperature than the molten zinc 9. is there. The reason why the porous material 10 is used is not to remove dross by the function of sieving as in the prior art, but to increase the site where dross is preferentially precipitated by increasing the surface area. In addition, in the conventional fixed packed bed and laminated filter materials, the temperature is always close to the temperature of molten zinc, so that it is presumed that dross precipitation and adsorption phenomena as in the present invention hardly occur.

  Thus, in the dross removal method of the present invention, it is only necessary to introduce a porous substance, and since no fixed packed bed or laminated filtration material is used, the facility is large without causing clogging problems. It does not become.

  The molten zinc 9 from which dross has been removed moves through the molten zinc returning pipe 11 connected to the pot 8 by the pump 12 and is returned to the pot 8 for reuse.

  If a porous material having a specific gravity different from that of molten zinc is used as the porous material, the molten zinc 9 from which dross has been removed and the porous material 10 to which dross has been adsorbed can be easily separated. Reusable. In particular, if a porous material having a specific gravity lower than that of molten zinc is introduced, the porous material 10 floats on the surface of the molten zinc 9 as shown in FIG.

  As the porous material, it is preferable to use a spherical porous ceramic having a size of about 20 mm, but a coke lump or a refractory brick having a similar size can also be used.

  If the porous material adsorbed by the dross after charging is recovered and heated to a temperature equal to or higher than the temperature of the molten zinc, the adsorbed dross is removed, so that the porous material can be regenerated and reused. From the viewpoint of regeneration, the porous material is preferably a material that is hardly soluble in molten zinc, for example, a coke lump or a refractory brick as described above. When heated, the zinc adhering to the dross is also removed together, but only the zinc can be separated and purified using the difference in melting point between the dross and zinc and reused.

1 Hot-dip galvanized pot
2 Hot-dip galvanizing bath
3 Steel plate
4 Sync roll
5 Pipe for hot zinc extraction
6 Pump
7 Porous material input device
8 Molten zinc separation pot
9 Molten zinc
10 Porous material
11 Pipe for returning molten zinc
12 Pump

Claims (4)

Molten zinc is extracted from a hot dip galvanizing bath in which a steel sheet is immersed and galvanized, and a molten porous material is introduced into the extracted molten zinc at a temperature lower than that of the extracted molten zinc. How to remove dross from galvanized baths. 2. The dross removal method for a hot dip galvanizing bath according to claim 1, wherein a porous material having a specific gravity smaller than that of molten zinc is introduced as the porous material. 3. The dross removal method for a hot dip galvanizing bath according to claim 1, wherein the porous material is porous ceramics. 4. The dross removal method for a hot dip galvanizing bath according to claim 1, wherein the porous material after charging is recovered and heated to a temperature equal to or higher than that of the hot dip galvanizing.

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