KR101137621B1 - Plating bath for fabricating galvanized steel contained apparatus for removal of dross - Google Patents

Abstract

The present invention relates to a hot dip galvanizing bath having a dross reducing device, and includes a plating bath box containing a hot dip galvanizing solution, a snout, a sink roll, and a stabil provided in the plating bath box. In a hot dip galvanizing bath comprising a rising roll, a correction roll, and a zinc ingot, the upper end is higher than the surface of the hot dip galvanizing solution and the lower end is submerged in the hot dip galvanizing solution. The dross is efficiently prepared by collecting a dross floating on the surface of the hot dip galvanizing solution, and preparing a plating bath provided to heat the collected dross to redissolve in the hot dip galvanizing solution. The present invention relates to the present invention, which can be removed in an efficient manner, and which enables the hot dip galvanizing process to be performed efficiently.

Description

PLATING BATH FOR FABRICATING GALVANIZED STEEL CONTAINED APPARATUS FOR REMOVAL OF DROSS

The present invention relates to a molten zinc plating tank having a dross reduction device, by using a reduction device that guides a floating dross generated in the molten zinc plating tank to one side of the plating tank, collects it, and then re-dissolves it. The present invention relates to a technique for efficiently removing dross.

The occurrence of surface defects due to dross of the hot-dip galvanized steel sheet is the most serious problem in the hot-dip galvanized steel sheet. Dross is ZnO, Al ₂ O ₃ , formed by the reaction of iron and zinc eluted from the steel sheet in a plating bath containing zinc-based molten metal. FeZn ₇ , And Fe ₂ intermetallic compound such as Zn _x Al _5, the size is 5 ~ 300㎛ the spherical equivalent (球形換算) diameter. The dross is deposited at the bottom of the plating bath as long as the dross is in a stationary state in which there is no flow of molten metal in the plating bath.

However, due to the natural convection of the molten metal caused by the running of the steel plate, the rotation of the bath roll in the plating bath, or the dissolution of the zinc ingot which supplies the plated metal which is lost to the steel plate, The molten metal inside is stirred. As a result, dross having a small specific gravity difference with the molten metal cannot be deposited at the bottom, or the deposited dross is wound up and adhered to the plated steel sheet, resulting in surface defects of the hot-dip galvanized steel sheet.

1 is a schematic cross-sectional view showing a hot dip galvanizing bath according to the prior art.

FIG. 1 is a schematic diagram showing a distribution state of a dross obtained by using a water model and practical performance data of a hot dip galvanizing solution 20 filled in a plating bath 10. The cross section is shown.

Referring to FIG. 1, a zinc ingot 80 is charged on one side of the snout 30. At this time, the hot dip galvanized solution 20 around the zinc ingot 80 may exhibit a local low temperature state, the upper dross (Top Dross, 32, 34) can be formed while the Fe solid solution limit is lowered. In the region between the snout 30 and the sink roll 40, the Al Lean zone 36 generated by the reaction between the Fe-Al layer formed on the surface of the steel sheet 90 and the hot dip galvanizing solution 20 is formed. This increases the solubility limit of Fe, promotes the elution of Fe, and eventually causes the lower dross 22 and 24 to occur by lowering the solubility limit at the Al concentration equilibrium.

In addition, such as ZnO or Al ₂ O ₃ due to the influence of the air knife 70 provided on both sides of the steel sheet 90 discharged through the stabilizing roll (50) and the correction roll (Correction Roll, 60) Oxides 26 may be generated. Such oxides 26 may be suspended at the surface of the hot dip galvanizing solution 20 and then combined with the upper dross 32 and 34. These drosses promote surface defects in the steel sheet, and their actual state is shown as follows.

2a and 3b are SEM pictures showing the surface defects of the steel sheet according to the prior art.

Figure 2a is a plan view showing the surface defects by the upper dross in the GI process, Figure 2b is a cross-sectional picture thereof.

Next, Figure 3a is a plan view showing the surface defects by the lower dross in the GA process, Figure 3b is a cross-sectional picture thereof.

Here, in the case of GI, the Al content in the hot dip galvanizing solution 20 is 0.18 to 0.20% by weight, and the Al content of GA is 0.12 to 0.14% by weight. In both cases, the problem of surface defects caused by dross can be fatal in improving the properties of the steel sheet.

Therefore, in order to remove dross conventionally, there have been many proposals. These proposals include a method of pouring a hot dip galvanizing solution out of the plating bath to precipitate dross or filtering.

However, despite numerous proposals being made, none of the conventional proposals have been put into practical use. The reason for this is that these proposed techniques are theoretically established, and there are many problems in the complexity, durability, and operability of the apparatus in actual equipment, which is impossible in practice.

Recently, as a method of changing the focus of the conventional method, a method of directly removing the generated bottom dross in a plating bath has been proposed. For example, the first method is to remove dross from a precipitation bath installed separately from the plating bath, and in the plating bath, to close the distance from the steel plate to the bottom of the plating bath to prevent dross from settling, The transfer of the hot dip galvanized solution to the settling bath is carried out through a shallow flow path for the top dross of the plating bath to flow into the settling bath, and the hot dip galvanized solution is transferred from the settling bath to the plating bath through a pump. Is characteristic.

The second method is to form a flow path for circulating molten metal in a partition plate provided in close proximity to the inner wall of the plating bath, to install a circulation device for circulating molten metal in the flow path, and to heat the molten metal at the inlet of the flow path. This method is characterized by providing a heating apparatus for large curing of the dross to promote sedimentation and recovering the settled dross in the dross recovery apparatus provided adjacent to the outlet of the flow path.

The third method is to have a plating bath having a metal plate plated with an arc and a precipitation bath for sedimenting and depositing a bottom dross generated in the plating bath, and the plating bath near the side wall of the plating bath. The communication holes are excreted so that the molten metal for plating inside can freely enter or exit the precipitation bath, and the molten metal containing dross is deposited into the precipitation bath by the accompanying flow of the metal plate. It discharges, and separates and sediments a lower dross | flour by a slow settling bath, and returns the molten metal from which the dross was removed to a plating tank.

In the first method, the suction port of the hot dip galvanizing solution in the precipitation bath must be located substantially lower than the bath surface, so the hot dip galvanizing solution containing dross in the sediment is sucked and transferred to the plating bath. . In addition, since the transfer of the hot-dip galvanized solution from the precipitation bath to the plating bath is pumped, a large amount of upper dross is generated in the plating bath with the discharge hole. That is, not only the effect of sedimentation and removal of dross is insufficient, but there is also a problem that an upper dross occurs.

Since the capacity of the settling bath is increased and problems such as coagulation and leakage due to the transfer of the hot dip galvanized solution between the plating bath and the separated settling bath are not solved, there is a problem that the installation cost and the operating cost are increased.

As shown in the second method, the flow path capacity is considered to be small, so the effect of sedimentation and removal of a large amount of dross generated in the plating bath is insufficient. In addition, there is a problem that dross is settled and deposited in the flow path, flow path capacity is reduced, the flow of molten zinc becomes faster, and the required settling time cannot be secured, thereby reducing the dross removal efficiency. In addition, there is a problem that it is not easy to take out the dross deposited in the narrow flow path.

In the third method, the discharge flow rate cannot be controlled because the molten zinc is discharged from the plating bath to the settling bath due to the accompanying flow of the steel sheet. Therefore, since the dross in a plating tank cannot be reliably discharged by a precipitation bath, there exists a problem that dross accumulates and grows in a plating tank.

The present invention is equipped with a dross reduction device for causing the top dross (floating top dross) floating in one corner of the hot-dip galvanized bath box to be collected, and re-dissolve inside the molten zinc plating solution by heating the collected dross The upper dross generated in the plating bath by circulating the lower dross by the hot dip galvanizing solution which is re-dissolved and injected into the lower part of the dross reduction device. It is an object of the present invention to provide a hot dip galvanizing bath including a dross reducing device capable of efficiently removing the loss, improving the hot dip galvanizing property of the steel sheet, and maximizing the productivity.

The hot dip galvanizing bath including the dross reducing apparatus according to the present invention includes a plating bath box containing a hot dip galvanizing solution, a snout, a sink roll, and a stabilizing roll provided in the plating bath box. (Stabilizing Roll), a correction roll (Correction Roll) and a zinc ingot comprising a zinc ingot, the upper end is higher than the surface of the hot dip galvanizing solution, the lower end is provided in a form immersed in the hot dip galvanizing solution And collecting the dross floating on the surface of the hot dip galvanizing solution, and heating the collected dross to redissolve it in the hot dip galvanizing solution.

Here, the dross reduction device is collected in the dross reduction body portion having an upper and lower ends in the open shape, a cover portion covering the upper end of the dross reduction body portion and the dross reduction body portion. It characterized in that it comprises a heating unit provided to be heated to re-dissolve the dross.

In this case, the cross section of the body portion for reducing dross may be provided in a rectangular, circular and polygonal shape, it is preferable that the cover portion is provided to be opened and closed.

In addition, the dross reduction body portion may include a dross collecting entrance to the portion in contact with the surface of the hot dip galvanized solution, the entrance may further include a cover that can be opened and closed.

In addition, the heating unit of the dross reduction device may be provided in the cover portion, the heating unit is characterized in that the resistance heating or induction heating method.

Next, the hot-dip galvanizing bath includes a plurality of dross reducing devices, and the hot-dip zinc plating bath detaches the dross-reducing device from the inner wall of the plating bath box or an area adjacent to the inner wall. It characterized in that it further comprises a frame device, the dross reduction device is heated to 460 ~ 600 ℃, it is characterized in that it is heated for 1 to 2 hours.

In the hot dip galvanizing bath including the dross reducing device according to the present invention, a dross reducing device in the form of a box-type heating device is installed at an upper edge portion of the hot dip galvanizing bath, and the upper dross is collected therein, and then the dross is heated. By using the method of re-dissolving in the hot-dip galvanizing solution, a separate equipment for purifying and re-injecting the hot-dip galvanizing solution is not required, so that the equipment cost can be reduced.

In addition, the present invention provides an effect of increasing the productivity by making it possible to easily provide a clean hot dip galvanizing solution, preventing the dross from adhering to the steel sheet and performing the plating process efficiently.

Based on the above object of the present invention will be described in detail with respect to the hot-dip galvanizing bath including a dross reduction device as follows.

First of all, Al and Fe, which are the main compositions of the above-described dross, are mainly used to improve plating adhesion, but Al is a major cause of dross by forming an lean region. In particular, Al or Zn is combined with Fe is a major cause of dross.

Accordingly, the present invention provides an apparatus for controlling the concentration of Al or Zn, the temperature of the plating bath and the state of the steel sheet to reduce dross and efficiently perform the hot dip galvanizing process.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, only the present embodiments to make the disclosure of the present invention complete, and common knowledge in the art to which the present invention pertains. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims.

4 is a schematic cross-sectional view showing a hot dip galvanizing bath including a dross reduction device according to the present invention.

Referring to FIG. 4, a plating bath box 100 containing a hot dip galvanizing solution based on a cross section of the steel plate 190 in a traveling direction, and a snout 30 provided in the plating bath box 100. , Sink Roll (140), Stabilizing Roll (150) and Correction Roll (Correction Roll, 160) follows the general basic plating tank structure. In addition, the behavior and generation of the lower dross 122, 124, the Al lean region 136, and the floating dross 132, 134 are equally applicable. At this time, although the zinc ingot is not shown in the form covered by the dross reduction device 110, the charging state of the zinc ingot also follows the existing structure as it is.

Here, an important feature of the present invention is the dross reduction device 110 provided in the upper side wall portion of the plating bath box 100. As shown, the dross reducing device 110 collects dross 132 and 134 floating on the surface of the hot dip galvanizing solution 120 with a box-type heating device, and re-dissolves them. Then, the re-dissolved clean molten zinc plating solution assists the circulation of the lower dross 122 and 124 while being discharged to the lower portion of the dross reduction device 110, and thus the lower dross 122 and 124 circulated in this manner. With the floating dross it is possible to build a system that can be collected and cleaned again in the dross reduction device 110. Such a dross reduction device 110 can be installed in various embodiments, looking at the specific details are as follows.

5 is a plan view schematically showing a dross reduction device according to the present invention.

Referring to FIG. 5, the dross reduction device 210 fixed to the corner portion of the plating bath box 200 can be seen. In the dross reduction device 210, dross 234 floating on the surface of the hot dip galvanizing solution is collected. In addition, one side of the dross reduction device 210 is provided with a white paper portion 230 for coupling the cover part 220, and a heating part 250 is provided in the cover part 220, and a dross reduction device ( The dross 234 in 210 may be re-dissolved. In this case, the heating unit 250 may be a resistance heating or an induction heating method and the like, the shape shown is formed on the surface of the cover 220, but is not always limited thereto. In particular, in the case of the induction heating method is preferably a form embedded in the cover 220, looking at the specific form as follows.

6 is a cross-sectional view schematically showing a dross reduction device according to the present invention.

FIG. 6 is a cross-sectional view showing only the dross reduction device separately described above. First, the upper portion is provided in an open form to collect dross, and the molten zinc plating solution that is re-dissolved after being collected is discharged back to the lower portion. The body portion 310 of the dross reduction device is provided to provide a structure to enable.

Next, the cover portion 320 that can cover the upper portion of the body portion 310 is connected by the white paper portion 330, the heating portion 350 is provided inside the cover portion 320.

Here, a part of the upper end of the body portion 310 should always be exposed to the upper portion of the hot dip galvanizing solution, the lower end should be provided in a form that is locked in the hot dip galvanizing solution. At this time, the height of the upper end exposed to the upper portion of the hot dip galvanizing solution is preferably to be within 1.2H, based on the plating tank box height (H) of FIG. If it is provided at the same height as the hot dip galvanizing solution, it is impossible to collect the dross at all, so that it cannot function as a dross reducing device. If the height is increased to 1.2H, the worker may not be able to easily float the dross into the body part 310, and the distance between the surface of the hot dip galvanizing solution and the cover part 320 may increase. Since the heating energy is also increased, the efficiency of the dross reduction device cannot be increased. Therefore, the upper end of the body portion 310 of the dross reduction device is provided higher than the surface of the hot dip galvanizing solution, it is preferable to be within 1.2H based on the total height of the plating bath box (H).

In addition, in the above description, but the method of scooping the dross by the operator using a device such as a ladle, the method of scraping the dross immediately in the dross reduction device can be used, and the schematic configuration thereof will be described as follows. Can be.

7 is a cross-sectional view schematically showing a dross reduction device according to an embodiment of the present invention.

FIG. 7 illustrates a dross reduction device fixed to the sidewall of the hot-dip galvanizing bath box 100, and has a cover part 420 and a heating part 450 as described above, and has a body part 410. One side of the) is provided with an entrance 460 through which the dross 134 can enter and exit. The cover 470 may be provided to open and close the doorway 460 as necessary. In this case, the dross may be collected in a manner in which the dross is not scooped and collected, and the energy consumption of opening and closing the cover 420 including the heating unit 450 may be reduced.

In addition, in the above-described embodiment, all of the dross reduction apparatus is shown only in the form fixed to the side wall of the hot-dip galvanizing tank box, but is not always limited to this, and may be provided in a form spaced apart from the inner wall corners at predetermined intervals. The specific form is as follows.

8 is a plan view showing an arrangement state of the dross reduction device according to the present invention.

Referring to FIG. 8, two dross reduction apparatuses 500 fixed to corner portions may be seen based on a plan view of the plating bath box 100, and spaced apart from a corner of the plating bath box 100 by a predetermined interval. A dross reduction device 520 of the form can also be seen. As such, the positions of the dross reduction apparatuses 500 and 520 are not determined, and may be variously changed and used according to the situation of the plating bath and the circulation structure of the hot dip galvanizing solution. In this case, separate frame devices 550 and 555 are required for fixing the dross reduction apparatuses 500 and 520.

In addition, the planar shape of the dross reduction device (500, 520) is also not limited, and may be in the form of other polygons or circles, such as triangle, square, etc., the number of installation is also not limited, in consideration of the circulation structure of the hot-dip galvanized solution It is desirable to be installed within the range of about 2 to 10. At this time, the number is calculated based on the case where the plane area of the dross reduction device is about 1/16 the size of the plating tank box plane area, but the plane area of the dross reduction device is 1 / the size of the plating tank box plane area. If it is smaller than 16, the number can be increased, and vice versa, the installation number range can be further reduced.

As described above, the hot-dip galvanizing bath according to the present invention can reduce the dross by the dross reduction device, and continuously discharge the hot-dip galvanized solution in which the dross is reduced to the lower part of the dross reduction device, thereby The overall hot dip galvanizing solution in the tank can be kept clean.

This effect can be confirmed through the following table and graph data. The following experimental results are appropriate for the dross reduction in the hot dip galvanizing bath as a result of the output or ratio of Zn, Al and Fe, measured by varying the heating temperature after a certain amount of dross is added to the dross reduction apparatus according to the present invention. It is just one example of experimentation to determine the condition. That is, since the dross reduction state may be different according to the size and conditions of the hot dip galvanizing bath, the operating conditions of the hot dip galvanizing bath according to the present invention are not limited by the following temperature conditions and time ranges.

9 and 10 are graphs showing the results of the first dross redissolution test according to the present invention.

First, as shown in Table 1 below, as a result of performing a remelting process for 60 minutes while varying the dose and heating temperature of the dross as shown in Table 1 below, as the temperature increases, the amount of zinc (Zn) increases so that the dross is reduced. It can be seen that the loss (%) is reduced.

[Table 1]

In addition, FIG. 10 shows the results of Table 2 below. As the heating temperature is increased to 600 ° C., the Fe component amount is increased, and thus the dross amount is relatively decreased.

TABLE 2

Through the above results it can be seen that the heating temperature of the dross reduction device according to the present invention can produce a dross reduction effect in the range of 460 ~ 600 ℃.

In addition, the following shows the results of experiments taking a more specific temperature range.

11 and 12 are graphs showing the results of the second dross re-dissolution test according to the present invention, which was performed under the same conditions as the first dross re-dissolution test, in which the condition range of 550 ° C. was added. The result is.

This is summarized in Table 3 below, and specific graphs are shown in FIGS. 11 and 12.

[Table 3]

13 and 14 are graphs showing the results of the third dross re-dissolution test according to the present invention.

13 and 14 show the results of the test in order to derive the optimal time conditions in addition to the temperature conditions such as the first and second, as a result of performing for 1 to 2 hours was obtained as shown in Table 4 below The effect of reducing dross was obtained.

 [Table 4]

As described above, when the dross reduction apparatus according to the present invention is used, the dross reduction state can be easily maintained, and an optimal hot dip galvanizing process can be performed.

In addition, the present invention can easily provide a clean hot dip galvanizing solution, thereby preventing the dross from adhering to the steel sheet, it is possible to perform the plating process efficiently to increase the productivity.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above embodiments and can be modified in various forms, and having ordinary skill in the art to which the present invention pertains. It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without changing the technical spirit or essential features of the present invention. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

1 is a schematic cross-sectional view showing a hot dip galvanizing bath according to the prior art.

2a and 3b are SEM pictures showing the surface defects of the steel sheet according to the prior art.

4 is a schematic cross-sectional view showing a hot dip galvanizing bath including a dross reduction device according to the present invention.

5 is a plan view schematically showing a dross reduction device according to the present invention.

6 is a cross-sectional view schematically showing a dross reduction device according to the present invention.

7 is a cross-sectional view schematically showing a dross reduction device according to an embodiment of the present invention.

8 is a plan view showing an arrangement state of the dross reduction device according to the present invention;

9 and 10 are graphs showing the results of the first dross re-dissolution test according to the present invention.

11 and 12 are graphs showing the results of the second dross re-dissolution test according to the present invention.

13 and 14 are graphs showing the results of the third dross re-dissolution test according to the present invention.

Claims (12)

delete A plating bath box containing a hot dip galvanizing solution, a snout, a sink roll, a stabilizing roll, a correction roll, and a zinc ingot are provided in the plating bath box. In the hot-dip galvanizing bath containing, The upper end is higher than the surface of the hot dip galvanizing solution, the lower end is provided in a form immersed in the hot dip galvanizing solution to collect the dross floating on the surface of the hot dip galvanizing solution, and the collected dross is heated. And a dross reduction device provided to re-dissolve in the hot dip galvanizing solution. The dross reduction device Dross reduction body portion is provided in the top and bottom open shape; A cover part covering an upper end of the body portion for reducing dross and provided to be opened and closed; And Hot-dip galvanizing bath comprising a heating unit provided to heat and re-dissolve the dross collected in the dross reducing body portion. The method of claim 2, Cross section of the body portion for reducing dross is hot-dip galvanized bath characterized in that the rectangular, circular or polygonal shape. delete The method of claim 2, The dross reducing body portion is a hot dip galvanizing tank characterized in that it comprises a dross collecting entrance to the portion in contact with the surface of the hot dip galvanizing solution. A plating bath box containing a hot dip galvanizing solution, a snout, a sink roll, a stabilizing roll, a correction roll, and a zinc ingot are provided in the plating bath box. In the hot-dip galvanizing bath containing, The upper end is higher than the surface of the hot dip galvanizing solution, the lower end is provided in a form immersed in the hot dip galvanizing solution to collect the dross floating on the surface of the hot dip galvanizing solution, and the collected dross is heated. And a dross reduction device provided to re-dissolve in the hot dip galvanizing solution. The dross reduction device A dross reduction body part having an upper end and a lower end in an open shape and including a dross collecting entrance in a portion in contact with the surface of the hot dip galvanizing solution; A cover part covering an upper end of the body portion for reducing dross; And And a heating part provided to heat and re-dissolve the dross collected in the body portion for reducing dross, Hot-dip galvanized bath characterized in that the dross collecting entrance further comprises a cover that can be opened and closed. A plating bath box containing a hot dip galvanizing solution, a snout, a sink roll, a stabilizing roll, a correction roll, and a zinc ingot are provided in the plating bath box. In the hot-dip galvanizing bath containing, The upper end is higher than the surface of the hot dip galvanizing solution, the lower end is provided in a form immersed in the hot dip galvanizing solution to collect the dross floating on the surface of the hot dip galvanizing solution, and the collected dross is heated. And a dross reduction device provided to re-dissolve in the hot dip galvanizing solution. The dross reduction device Dross reduction body portion is provided in the top and bottom open shape; A cover part covering an upper end of the body portion for reducing dross; And And a heating part provided in the cover part to heat and re-dissolve the dross collected in the dross reducing body part. The method according to any one of claims 2, 3, 5, 6 and 7, The heating part is a hot dip galvanizing bath, characterized in that the resistance heating or induction heating method. The method according to any one of claims 2, 3, 5, 6 and 7, The hot dip galvanizing bath comprises a plurality of the dross reduction device. The method according to any one of claims 2, 3, 5, 6 and 7, The hot dip galvanizing bath further comprises a frame device capable of detaching the dross reducing device. The method according to any one of claims 2, 3, 5, 6 and 7, The dross reduction device is hot-dip galvanizing bath, characterized in that heated to 460 ~ 600 ℃. The method according to any one of claims 2, 3, 5, 6 and 7, The dross reduction device is hot-dip galvanizing bath, characterized in that heated for 1 to 2 hours.

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