KR20000039454A - Device for heating molten zinc and removing dross in plating tub by using alternating current electromagnetic field - Google Patents

Abstract

According to the present invention, molten zinc heating using an alternating electromagnetic field is made to heat molten zinc using an alternating magnetic field and an electromagnetic field applied by alternating current and efficiently remove and remove dross generated in the molten zinc in the molten zinc plating process. And a dross removal apparatus in the plating bath.

The present invention is provided with a passage 16, 19 which can pump circulation of the molten zinc in the plating tank 10 by an electromagnetic pump 15 on one side of the molten zinc plating tank 10, the passage 16 AC current applying device (3) and AC magnetic field applying device (6) is installed in place of, and the upper part of the passage (16) connects the dross separation pipe (17) and installs an AC electromagnetic field characterized by the configuration. It provides a molten zinc heating and dross removal apparatus in the plating bath.

Description

Dross removal device in molten zinc heating and plating bath using AC electromagnetic field

In the molten metal plating process of the steel sheet, the molten metal for plating, such as molten zinc, is heated by using an electromagnetic force generated by the application of an alternating magnetic field and an alternating current, and no chemical change is applied to the molten metal for plating. The present invention relates to a molten zinc heating and dross removal apparatus in a plating bath using an alternating electromagnetic field capable of separating and removing dross in molten metal for plating without causing it to occur.

During the hot dip galvanizing process, dross due to oxides or other impurities is generated in the plating bath. If the dross is not removed during the plating process, the dross quality is reduced.

Techniques that have been used to remove such dross in molten zinc include the following and each has a problem.

One Japanese patent introduces a technique for stacking a dam in a plating bath along a steel strip strip to pump fresh molten zinc around the strip inside the dam so that molten zinc with a relatively low dross is plated on the strip. There is a problem that the amount of dross can be increased during long-term operation due to the iron elution of the strip does not lower.

According to another method disclosed in Japanese patent, there is a method of disposing the sink roll in the plating bath close to the bottom of the plating bath so that the dross is spread out throughout the plating bath by vibrating when the steel sheet strip moves, thereby reducing the adhesion to the steel sheet. This means that there is no near countermeasure against the gradual increase in dross concentration during long working periods, and the dross dispersion effect due to vibration during simple strip movement is ultimately meaningless.

Another Japanese patent introduces a technology that prevents the dross from entering and frees the molten zinc by placing a mesh plate between the sink roll and the bottom of the plating bath, but according to the size of the net, It's only different and can't radically reduce the amount of dross.

Another Japanese patent proposes a method of extracting molten zinc from a plating bath with a pipe and depositing it in a tank to settle and remove dross.

According to another Japanese patent, the plating bath is pumped out to remove the dross, precipitated separation of dross, addition of aluminum and flotation by reaction with dross (formation of Fe-Al compound), molten zinc after re-removal of the added aluminum by chloride method. The method of returning the to the plating bath has been proposed, but it is uneconomical due to the complicated work and equipment.

Another Japanese patent proposes a method of installing a filter in a plating bath and circulating molten zinc to remove dross, which is cumbersome and inefficient in selecting a hole size and installing and replacing the filter.

According to another Japanese patent, a method of adding aluminum to the plating bath to aluminum alloy the bottom dross to form the top dross to separate the flotation, but the efficiency is low and the effective aluminum concentration is difficult to control. There is a problem not applicable to operation.

In addition, according to Japanese Patent Laid-Open No. 2-93052, a method of removing a bottom dross (Zn-Fe main component) by attaching a magnet or an electromagnet directly to the magnet outside or inside the plating bath is proposed, but the Zn-Fe compound system has been proposed. Except for alpha Fe, it is not feasible to be nonmagnetic.

In order to improve the above problems, a dross removal method using direct current electromagnetic force has been proposed in Korea. This method has high dross removal efficiency but requires an electrode for applying a direct current and generates heat generated by a direct current. Due to this small size, there is a disadvantage in that a separate heating device is installed around the removal pipe.

In addition, there is also a method of installing and using a high frequency induction heating device in the plating bath to maintain the temperature of the molten zinc, which has a problem in that convection occurs in the molten metal due to electromagnetic force during induction heating, rather promoting the formation of dross.

The present invention has been studied to solve the problems of the prior art as described above, the object of which is to apply the alternating current and alternating current of the dross produced during the molten metal plating of the steel sheet without causing any chemical change to the molten metal for plating It is an object of the present invention to provide an apparatus capable of heating molten metal while simultaneously separating and removing dross using an electromagnetic force generated by the same.

1 is a schematic view for explaining the configuration and operation principle of the main part of the present invention, (a) is a horizontal cross-sectional view, (b) is a vertical cross-sectional view,

2 is a schematic view of a molten zinc plating apparatus to which the present invention is applied;

Figure 3 is a photograph observing the sample structure of the result after applying the present invention to molten metal heating and intermetallic compound removal.

* Explanation of symbols for main parts of drawing *

1: transport pipe 2: molten metal

3: AC current applying device (transformer) 4: AC current direction

5: direction of alternating magnetic field 6: alternating magnetic field applying device (AC electromagnet)

7: intermetallic compound 8: steel strip

9: snout 10: plating bath

11: Sync roll 12: Stabilizing roll

13: molten zinc 14: dross particles

15 electromagnetic pump 16 passage

17: dross separation tube 18: dross collection tank

19: clean molten zinc passage

Hereinafter, with reference to the accompanying drawings, the present invention for achieving the above object will be described in more detail.

First, referring to Figure 1 will be described the principle of the present invention. Fig. 1A is a horizontal sectional view of the main part of the apparatus, and (B) is a vertical sectional view. As shown in (a), the molten metal 2 is filled inside the tube 1 capable of transporting molten metal, and a transformer (AC current applying device) for applying an alternating current to both sides of the tube 1 (3). ) Is used to induce an alternating current (4) in the molten metal. In the center of the tube 1, an AC electromagnet (AC field applying device) 6 for applying the AC magnetic field 5 is provided. The principle of operation is explained with reference to (b) which is a vertical cross section. An alternating magnetic field is applied through the magnetic poles of the alternating electromagnets 6 provided on the left and right sides inside the tube 1 filled with the molten metal 2 in which the intermetallic compound and the inclusions 7 are mixed. In addition, the transformer 3 is used to induce alternating current. At this time, the magnetic field and the phase of the current coincide so that the electromagnetic force acts in the opposite direction of gravity. In this case, since the molten metal is a good conductor, the electromagnetic volume force acts upward, but the intermetallic compound and the inclusions have less electromagnetic volume force than the molten metal. In other words, the intermetallic compound or inclusions have a downward force to increase the settling speed. Therefore, the present invention is effective even in sedimentation separation of fine inclusions. In addition, the molten metal 2 is heated by the induced current.

The main field of application of the present invention is the cleaning of molten metal and the removal of dross in the hot dip galvanizing bath. FIG. 2 illustrates the case where the present invention is particularly applied to dross removal in the hot dip galvanizing bath. As shown in FIG. 2, the hot dip galvanizing apparatus has a plating bath 10 in the case of a general continuous hot dip galvanizing of a steel sheet. (8) is introduced into the plating bath in the plating bath 10 through the snout 9 in the pretreatment furnace and exits the plating bath 10 via the sink 11 and the stabilizing roll 12. In the hot dip galvanizing using such equipment, the dross particles 14 generated in the plating bath are formed of iron metal dissolved by diffusion from the steel sheet strip 8 drawn into the plating bath and solid metal formed by the molten zinc 13. As a hepatic compound, its electrical conductivity is smaller than that of molten zinc and is mostly nonmagnetic. Such dross is mixed with molten zinc by FeZn13, FeZn7, Fe3Zn10, Fe5Zn21, etc. by moving the strip 8, rotating the sink roll 11, and convection of the plating bath, and then sticking to the surface of the strip 8 to sink roll. It is compressed by 11 and the stabilizing roll 12, and remains as a plating surface defect. Of these, Fe3Zn10 and FeZn21 dross have high hardness, which is a decisive cause of roll damage and surface defects.

According to the present invention for removing such dross, the molten zinc contaminated with dross is removed from the lower part of the plating bath 10 using the electromagnetic pump 15 as shown in the drawing, and is sent to the upper part through the passage 16 while alternating current. The application device 3 induces a current in the flow direction of the molten zinc, and uses an alternating electromagnet 6 to apply a magnetic field in a direction perpendicular to the current. When the molten zinc mixed with dross passes through the portion of electromagnetic volume generated by the action of electric current and magnetic field, the dross flows while moving in the opposite direction to the direction of the electromagnetic force. It is separated by the Ross separation pipe 17 and collected by the dross collection tank 18, and the clean molten zinc from which the dross is separated and removed is returned to the plating tank 10 through the clean molten zinc passage 19. do.

In the apparatus of the present invention, the plating bath 10 maintains the molten zinc at a predetermined working temperature (450 ~ 480 ℃) and the flow rate control can be precisely controlled by the power of the electromagnetic pump (15). The molten zinc passage 16 is made of a non-conductive material to prevent the flow of current through the material of the passage. The electric current may be applied with a large capacity as long as the installation permits from o A to use large electromagnetic force and induction heating. The magnetic field is related to the strength of the current and supplies a magnetic field from 0 to 3 tesla. At this time, to install a device for adjusting the phase of the current and the magnetic field in the power supply. The position of the dross separation pipe 17 is determined by adjusting the relationship between the electromagnetic force and the flow rate.

EXAMPLE

In order to apply the present invention to heating molten metal and removing intermetallic compounds, aluminum alloys (Al-12mass%, Si-2mass%, Fe-2mass%, Mn) are dissolved and maintained at 580 ° C to produce intermetallic compounds. After the application of the alternating magnetic field (0.12 T) and alternating current (5000 A) in the opposite direction of gravity using the apparatus as shown in Figure 1, the sample was quenched to observe the structure. 3A is a case where no electromagnetic force is applied, and it is observed that the metallization material is slightly settled. In the case of applying the electromagnetic force of (B), it can be seen that the intermetallic compound is settled in the lower part of the tube opposite to the electromagnetic force. In addition, as a result of examining the temperature rise of the molten aluminum with a thermocouple, it was confirmed that the temperature was raised at a rate of 0.3 ° C / s.

As described above, the present invention removes inclusions or dross from the molten metal by using electromagnetic volume force without using any chemical composition change, physical vibration, filtration and masking methods used in the prior art, and at the same time, As a device capable of heating, the separation and removal of inclusions or dross in the molten metal provides an effect that is much simpler and more efficient than conventional methods.

Claims (1)

One side of the hot dip galvanizing tank 10 is provided with passages 16 and 19 for pumping circulation of the hot dip zinc in the plating bath 10 by an electromagnetic pump 15, and in place of the passage 16. An alternating current applying device 3 and an alternating magnetic field applying device 6 are installed, and molten zinc using alternating electromagnetic fields is characterized in that a dross separation pipe 17 is connected to and installed in an upper portion of the passage 16. Dross removal device in heating and plating bath.