JPH11323519A - Galvanizing apparatus and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make construction simple and to efficiently remove dross in a plating vessel and to prevent the deposition of the dross. SOLUTION: A galvanizing apparatus having the plating vessel housing a galvanizing bath contg. >=0.5 wt.% aluminum and a snout in which a steel strip immersed into the plating vessel travels is provided with a partition wall for dividing the plating vessel to a pot where the steel strip is plated and a dissolving pot where an ingot 19 is dissolved. A flow passage which is >0.1 m in the hydraulic diameter defined by the following equation, is opened in the upper part and connects the respective pots so as to provide the same bath surface is disposed at the partition wall. Further, the apparatus is provided with a pump for pouring the plating bath of the plating pot from one end in the longitudinal direction of the snout into the snout and a pump for discharging the plating bath of the snout into the dissolving pot at the other end thereof in order to clean the plating bath in the snout. The hydraulic diameter = (the cross-section of the flow passage/the wetting length of the flow passage) ×4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hot-dip galvanizing apparatus and method, and more particularly to a hot-dip galvanizing apparatus and method suitable for producing a high-quality continuous hot-dip galvanized steel strip mainly containing zinc.

[0002]

2. Description of the Related Art Conventionally, a hot-dip galvanized steel strip is manufactured by a plating apparatus shown in FIG. That is, the steel strip S travels in the direction of the arrow and travels in the snout 1 to be immersed in the plating bath 4, turned by the sink roll 2, pulled up from the plating bath 3, and plated by the adhesion amount control device (not shown). After adjusting the amount of adhesion, it is cooled, given post-treatment,
It becomes the required plated steel strip. In order to make up for the reduced plating metal adhered to the steel strip S, a zinc-based solid metal ingot 19 was used.
Is dissolved in the plating tank 4.

[0003] While the steel strip S passes through the plating bath 4, iron eluted from the steel strip S reacts with zinc as a main component in the plating bath 3 or aluminum added in a small amount to form zinc iron aluminum or the like. To form an intermetallic compound, so-called dross. In addition, on the bath surface in the snout 1, zinc oxide evaporated from the bath surface and oxidized and agglomerated in the snout, and zinc oxide and dust dropped from the snout wall surface accumulate.

[0004] These cause surface defects of the hot-dip galvanized steel strip. Among them, the surface defect due to so-called dross is the most serious problem among the surface defects of the galvanized steel strip. Particularly serious of intermetallic compounds formed by the reaction of iron and zinc eluted from the steel strip (such as FeZn ₇₎
And the size is 5 to 300 microns in spherical equivalent diameter. If this bottom dross is in a stationary state with no plating bath flow,
It will be deposited on the bottom of the plating tank. However, the plating bath in the tank is agitated by running of the steel strip, rotation of a roll in the bath in the plating tank, or natural convection of the plating bath caused by dissolution of the zinc-based ingot. As a result, dross with a small specific gravity difference from the plating bath cannot be deposited on the bottom,
Alternatively, the deposited dross is rolled up and adheres to the plated steel strip, which becomes a surface defect of the hot-dip galvanized steel strip due to the dross.

Conventionally, there have been many proposals for removing the dross. Many of these suggestions are
This is a method in which the plating bath is once pumped out of the plating tank to settle and separate dross or a method in which dross is separated by filtration.

However, despite many proposals, none of the conventional proposals have been put to practical use. The reason for this is that, although these proposed technologies can be realized on a desk, there are many problems in the complexity, durability, and operability of the mechanism in actual equipment, and it is practically impossible.

With respect to the sedimentation and separation of dross proposed so far, it is important to design an apparatus so that the plating bath being transferred to the outside of the tank does not solidify, and even if the plating bath leaks from the transfer piping, Since the equipment must be designed on the assumption, the equipment is enormously expensive and not realistic.

In the method of filtering dross, there is a large difference in the size of dross that can be filtered between when filtration is first started and when the filtration device is clogged, and dross that causes quality defects is efficiently removed. It cannot be removed, and when replacing the filtration filter of the filtration device, it is necessary to remove in some way in the plating bath, which is expensive and impractical as in the case of transferring the plating bath. .

Recently, the point of view is changed from that of the conventional method, and the generated bottom dross is immediately removed from the plating tank, for example, Japanese Patent Laid-Open No. 5-222500 (prior document 1), and the method for reducing the dross generation, for example, Kaihei 5-186
No. 857 (prior document 2) has been proposed.

In the prior art document 1, as shown in FIG.
Ingot 1 separately from main pot 40 for plating on
A sub-pot 41 for dissolving 4 is provided, and the main pot 40 and the sub-pot 41 are connected at the side and bottom below the bath surface. That is, a molten metal introduction pipe 42 to the main pot 40 is provided at an upper position below the bath surface, and a molten metal outlet pipe 43 from the main pot and a stirring gas injection nozzle 46 provided in the sub pot 41 are provided below the pipe. The inlet pipe 42 and the molten metal outlet pipe 43 include heating devices 44 and 45, respectively.

In the above apparatus, the main pot 40 and the molten metal outlet pipe 4 are provided between the main pot 40 and the sub-pot 41.
A circulation flow is formed in the order of 3 → sub pot 41 → molten metal introduction pipe 42 → main pot 40. The dross generated in the main pot 40 is quickly transferred to the sub-pot 41 by a stirring gas injection nozzle 46 or the like, and the ingot 14 is dissolved and the dross is settled and separated in the sub-pot 41, and the purified molten zinc is returned to the main pot 40. Thereby, dross accumulation in the main pot 40 is prevented.

In Prior Document 2, as shown in FIG. 9, a weir 51 is provided in a plating tank 50 to form a double structure.
A portion 52 for dissolving the ingot 14 with the plating tank 50;
In addition to being separated into a portion 53 for plating on the steel strip S, a communication hole 54 for a portion 52 for dissolving the ingot 14 and a portion 53 for plating is provided in the weir 51.
The heating means 56 is disposed in the vicinity of the ingot charging portion.
When the ingot 14 is melted, the heating means 56 is used to prevent the temperature of the portion 52 where the ingot 14 is melted from being locally reduced, thereby reducing the generation of dross.

[0013]

However, in the prior art document 1, the main pot 40 and the sub pot 41 are connected by pipes 42 and 43 provided at the bottom and side portions, respectively, to circulate the plating bath. Further, when the plating bath leaks from the pipe, there is no measure to stop the leak. Further, in a situation where the plating bath is insufficiently heated, for example, when a power failure occurs, the plating bath in the pipe is easily solidified. That is, not only is the facility complicated and hinders the operation, but also there are many problems to be solved in engineering, so that it cannot be easily applied to actual machines.

In the prior art 2, the ingot 14 is connected to the weir 51
Although the non-uniformity of the temperature distribution of the plating bath is eliminated by melting while controlling the temperature using the heating device 56 in the portion 52 partitioned by the above, no consideration has been given to the generation or growth of dross itself. Therefore, it is impossible to sufficiently reduce dross in the plating tank 51.

The present invention has been made in view of the above circumstances, and has a simple structure, a dross in a plating tank can be efficiently removed, and a dross-based galvanizing apparatus and method can be prevented. The purpose is to provide.

[0016]

The above-mentioned prior art documents 1 and 2 are as follows.
In each case, the conventional processes such as sedimentation, stirring, and uniform temperature distribution are examined to prevent dross from being generated or dross is removed. Does not do.

The present invention is intended to maximize the effect while maximizing the actual process in consideration of the temperature-dependent changes in the iron solubility of the plating bath and the reaction between aluminum and iron, which have not been studied before. It proposes an innovative process that can be performed, and the gist of the present invention is as follows.

In the first invention, 0.05 wt% of aluminum is used.
% In a hot dip galvanizing apparatus including a plating bath containing a hot dip galvanizing bath containing at least% and a snout in which a steel strip immersed in the plating bath runs. A partition wall for dividing the ingot into melting pots is provided in the plating tank, and a hydraulic diameter defined by the following equation is 0.1 m or more, and the pots are connected to the same bath surface. In order to further clean the plating bath in the snout, a pump for pouring the plating bath of the plating pot into the snout from one end in the long side direction of the snout and a snout at the other end are provided in order to clean the plating bath in the snout. A hot-dip galvanizing apparatus comprising a pump for discharging a plating bath into a melting pot. Hydraulic diameter = (cross-sectional area of channel / wetting length of channel) x 4

According to a second aspect, in the first aspect, the volume of the plating pot is 10 m ³ or less, and the volume of the melting pot is 10 m ^3.
The hot-dip galvanizing apparatus according to claim 1, wherein:

According to a third aspect of the present invention, when a steel strip traveling in a snout is immersed in a plating tank containing a hot-dip galvanizing bath containing 0.05 wt% or more of aluminum to perform hot-dip galvanizing plating, A partition wall is provided, the plating tank is divided into a plating pot for plating the steel strip and a melting pot for dissolving the ingot, and the plating bath of the plating pot is poured into the snout with a pump from one end in the long side direction of the snout, Discharging the plating bath of the plating pot into the melting pot while cleaning the plating bath in the snout by discharging the plating bath of the snout from the other end to the melting pot with a pump, provided on the partition wall,
The hydraulic diameter defined by the following formula is 0.1 m or more, and the plating bath of the melting pot is returned to the plating pot through a flow path with an open top connecting both pots so as to have the same bath surface. Hot-dip galvanizing method. Hydraulic diameter = (cross-sectional area of channel / wetting length of channel) x 4

In a fourth aspect based on the third aspect, the volume of the plating pot is 10 m ³ or less, and the volume of the melting pot is 10 m ^3.
Above, the circulation flow rate of plating bath between the plating pot and dissolved pot 0.5 m ³ / h or more and equal to or less than 5 m ³ / h, is galvanized method according to claim 3 .

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION In order to improve the workability of a plating film of a hot-dip galvanized steel strip, a plating bath containing zinc as a main component contains 0.05% (hereinafter, wt%) of aluminum. When the steel strip is immersed in the plating bath, iron is eluted from the steel strip.

When iron eluted from the steel strip generates zinc and an intermetallic compound, the specific gravity becomes larger than that of the plating bath, and the bottom dross settles. On the other hand, when iron forms an intermetallic compound with aluminum, the specific gravity is lower than that of the plating bath, and the iron becomes a top dross that floats. The dross that usually becomes a problem is that the sinking bottom dross emerges for some reason,
Adhering to steel strip. Even if the floating top dross adheres to the steel strip, there is little problem.

The solubility of iron in the plating bath (hot-dip zinc) is proportional to the temperature of the plating bath. The higher the temperature, the better the iron dissolves in the plating bath, and the lower the temperature, the more supersaturated iron forms an intermetallic compound with zinc. And the amount of dissolved iron becomes appropriate for the temperature of the plating bath.

The iron eluted from the steel strip and the iron that has reacted with zinc to become an intermetallic compound and that has been lost from the steel strip are not present near the steel strip but are agitated as the steel strip moves. It is sufficiently dissolved in the plating bath or suspended as a solid, and the iron solubility of the plating bath during operation is always in a saturated state. If there is a stagnant portion at the bottom of the plating pot, heat escapes to the outside of the plating pot at that portion, so that the plating bath is cooled and a low-temperature portion is generated. Since the iron solubility of the plating bath is in a saturated state, the iron solubility in the low-temperature portion decreases, so that iron in the plating bath reacts with zinc to form bottom dross, or iron further reacts with the existing dross. It changes to a bottom dross having a high iron content and settles and deposits on the bottom of the plating tank, or, in the case of dross missing from the steel strip, sinks as it is and deposits on the bottom of the plating tank.

In normal operation, a low temperature ingot is supplied to a plating bath maintained at a constant temperature. In this case, as shown in FIG. 1, the temperature around the ingot 19 is lower than the plating bath temperature. Since the iron solubility of the plating bath decreases due to the temperature decrease, the iron in the plating bath forms an intermetallic compound with zinc or aluminum.

For example, the solubility of iron in a plating bath at 420 ° C. decreases as it approaches zero, but at 460 ° C., 0.03% of iron can be dissolved in the plating bath. Therefore, when the plating bath at 460 ° C. flows over the surface of the ingot and becomes a low-temperature plating bath at about 420 ° C., 0.03% of the dissolved iron can be dissolved in the plating bath. Instead, it reacts with the aluminum in the ingot to become an iron-aluminum intermetallic compound or an iron-zinc intermetallic compound. Once formed, these intermetallic compounds have a high melting temperature and thus have an original temperature of 460.
It does not dissolve when returned to ° C.

Since a change in temperature during melting of the ingot and a change in iron solubility accompanying the melting of the ingot are inevitable, it is clearly an effective method not to perform this melting in the plating pot. However, this improvement alone does not significantly reduce the dross of the plating pot, but merely reduces the amount of dross generated when the ingot is melted, and is therefore insufficient as a dross countermeasure.

Therefore, in the present invention, a partitioning wall is provided in the plating tank, and the plating tank is separated into a melting pot for melting the ingot and a plating pot for plating the steel strip. The plating bath is circulated between the plating pot and the dissolving pot, the bottom dross in the plating pot is transferred to the dissolving pot, the bottom dross is settled and separated in the dissolving pot, and the cleaned plating bath is returned to the plating pot.

The transfer of the plating bath is generally performed by a pump or an overflow. The present inventors have thought of simultaneously cleaning the snout plating bath when transferring the plating solution in order to produce a higher quality plated steel strip, and set the plating bath of the plating pot along the long side direction of the snout. A snout plating bath cleaning device is installed from one end of which is poured into a snout by a pump, the snout plating bath is sucked by a pump from the other end in the long side direction of the snout, and discharged out of the snout, and the plating bath discharged from this device is installed. Was provided in the melting pot, and the plating bath of the plating pot was transferred to the melting pot.

Usually, zinc evaporated from the plating bath surface is oxidized and solidified on the snout bath surface, and zinc oxide and dust dropped from the snout wall surface are present. These may cause surface defects of the plated steel strip. is there. As described above, by feeding the plating bath of the plating pot to the snout and transferring the plating bath from the snout to the dissolving pot, not only can the plating bath be transferred from the plating pot to the dissolving pot,
At the same time, the snout bath surface can be cleaned to prevent the above defects.

In the present invention, the plating bath is renewed before dross grows to harmful dimensions in the plating pot. For this purpose, the capacity of the plating pot is preferably set to 10 m ³ or less. The plating solution containing fine dross discharged from the plating pot is received in the dissolving pot, and the dross is separated and removed over time. For this purpose, it is preferable that the dissolving pot has a capacity of 10 m ³ or more.

In order to improve the snout bath surface cleaning effect,
The circulation flow rate of the plating bath is preferably about 0.5 m ³ / h to 5 m ³ / h. If it is less than 0.5 m ³ / h, the effect of preventing quality defects is insufficient due to slow renewal of the bath surface.
If the flow rate is more than m ³ / h, the flow rate is too large, which may cause ripples and splashes on the bath surface and cause another quality defect. Further, by setting the circulation amount within the flow rate range, the plating bath of the plating pot can be transferred to the melting pot while the dross in the plating pot is small.

In the melting pot, the iron bath solubility decreases due to a decrease in the plating bath temperature due to the melting of the ingot and a decrease in the plating bath temperature in the stagnation region of the flow at the bottom of the melting pot due to the flow of the plating bath being calmed down. The iron inside becomes top dross and bottom dross. The dross is separated and removed from the plating bath containing the transferred fine dross over a long time in the melting pot.

The plating bath from which the dross has been removed is transferred from the melting pot to the plating pot via a flow path having a predetermined hydraulic diameter and having an open upper portion provided on the partition wall, with both pots having the same bath surface. By doing so, it is possible to circulate while minimizing the generation of zinc oxide during the transfer of the plating bath, and it is possible to prevent operational problems due to the generation of zinc oxide in the plating pot.

An embodiment of the present invention will be described with reference to FIGS. 2 to 4, 1 is a snout, 2 is a sink roll, 3 is a plating bath, 12 is a plating tank, 13 is a plating pot, 14 is a melting pot, 15 is a partition wall, 16
Is a flow channel provided in the partition wall 15, 17 is a pump for flowing the plating bath of the plating pot 13 into the snout 1, 18 is a pump for discharging the plating bath of the snout 1 to the melting pot 14,
19 is an ingot, 20 and 21 are heating devices (induction heating devices).

The steel strip S travels from the snout 1 in the direction of the arrow, is immersed in the plating pot 13, is plated, is turned by the sink roll 2, and is pulled up from the plating bath 3.
After adjusting the adhesion amount by an adhesion amount adjustment device (not shown), cooling and performing a predetermined post-treatment, a required plated steel strip is obtained.

A pump 1 for flowing a plating bath of a plating pot 13 into the snout 1 at one end of the snout 1 in the long side direction.
7. At the other end, a pump 18 for discharging the plating bath of the snout 1 to the melting pot 14 is provided. The suction part of the pump 17 is, as shown in FIG.
It is located both near the bath surface. The plating bath 3 is preferably sucked from the bottom of the plating pot 13, but may be sucked from near the bath surface if the plating pot 13 is small.

The discharge flow rate of the pump 18 becomes the circulation flow rate of the plating bath. As described above, the circulation flow rate is 0.5 m ³ / h
To about 5 m ³ / h. If the suction flow rate of the pump 17 is large, zinc oxide or the like on the snout liquid level may flow out of the snout lower part into the plating pot and generate surface defects. That is, the flow rate is preferably not more than the circulation flow rate.

From the melting pot 14 to the plating pot 13 through a flow path 16 provided in a partition wall 15 for partitioning the two pots.
Although the plating bath 3 flows through, the flow path 16 has a structure in which the upper part is opened in consideration of a maintenance problem so that the plating pot 13 and the melting pot 14 can be on the same bath surface. The flow path 16 only needs to be able to return the supernatant bath of the melting pot 14 without dross to the plating pot 13. That is, it goes without saying that the channel 16 need not be opened unless there is a problem of clogging of the plating bath 3.

The plating bath adhered to and taken out of the steel strip S replenishes the ingot 19 by dissolving it in the melting pot 14 to maintain the plating bath surface constant. In that case, the aluminum concentration of the ingot 19 is higher than the aluminum concentration in the plating bath 3 in consideration of the fact that aluminum reacts with iron to be consumed as an iron-aluminum intermetallic compound. In this embodiment, since the aluminum in the bath of the plating pot 13 was set to 0.12%, two types of aluminum in the ingot 19 were used, 0.35% and 0%. It does not mean that an ingot with a constant aluminum concentration is used, but 0.2
% And 0.1%, or 0.15% (one type), and the ingot 14 may be sequentially charged into the melting pot 14. It suffices that the aluminum concentration in the plating pot 13 eventually reaches a predetermined value, and thus there is no specification on the method of adding aluminum.

As shown in FIG. 5, when an ingot containing a high concentration of aluminum is dissolved, the iron solubility in the plating bath can be more removed since the iron solubility is lower than that of a low aluminum concentration. However, when an ingot having a high aluminum concentration is dissolved, it is necessary to pay attention to the fact that the amount of aluminum consumed in the ingot increases because the intermetallic compound formed contains more iron aluminum than iron zinc.

In the vicinity of the ingot 19 of the melting pot 14, iron reacts with aluminum to form a top dross 31, and zinc reacts with iron to form a bottom dross 32. Here, when a low aluminum ingot 19 is used, iron and zinc may react to generate bottom dross 32 in the melting pot. These are, when the high aluminum ingot 19 is thrown in, reacting with the aluminum again to become the top dross 31 and the bottom dross 32 as it is,
Although the situation changes with the introduction of the ingot 19, dross can be concentrated and removed in the melting pot 14 in the end, and the generation of dross in the plating pot 13 can be greatly suppressed.

When the flow path 16 becomes large, the structure becomes the same as that of the ordinary plating tank 4 as shown in FIG.
There is some optimum value for the dimension of. Since various shapes such as a circular shape and a rectangular shape can be considered for the cross-sectional shape of the flow path 16, the present inventors have studied using the hydraulic diameter used in hydraulics. The hydraulic diameter refers to the cross-sectional area of the flow path 16
6, divided by the perimeter of the channel cross-section,
Multiplied by four. For a circular cross section, the hydraulic diameter corresponds to the diameter of the circular cross section. In the case of a square cross section, the length is equal to the length of one side of the square.

Investigations were conducted using the hydraulic diameter. In a flow path having a hydraulic diameter of less than about 50 mm, solidified zinc was generated in the flow path and the plating solution could not be transferred stably. The dimensions were not applicable to the actual machine. A hydraulic diameter of at least about 100 mm was required. On the other hand, the flow path 16
Becomes larger, the functions of the plating pot 13 and the melting pot 14 are mixed, and the plating pot 1
3, dross generation increases, and the problem of leakage generation increases structurally. In order to remove the dross by the dissolving pot 14 and solve the problem of the occurrence of the leak from an engineering point of view, it has been found that the hydraulic diameter is preferably 0.3 m or less. In this embodiment, the capacity of the plating pot 13 is 10 m ³ , and the capacity of the melting pot 14 is 10 m ³ .
m ³ , and the partition wall 15 is made of a refractory material having a thickness of 0.5 m.
The cross section of the flow channel was 200 mm wide and 150 mm long, that is, the hydraulic diameter was 175 mm, the circulation flow rate was 3 m ³ / h, and the amount of the plating bath poured into the snout was the same flow rate.

Conventionally, there is no dross defect of the plated steel strip which occurs about 2% of the production amount in this embodiment, and the problem with the dross is completely eliminated.

Another embodiment of the present invention will be described with reference to FIG. In FIG. 6, a partition wall 15a for partitioning the plating pot 13a and the melting pot 14a is disposed so as to surround the sink roll 2, and the upper part of the side wall of the partition wall 15a on the side where the steel strip S is pulled up from the plating pot 13a. The flow path 16a is formed below the surface. The plating bath 3 to be transferred from the plating pot 13a to the melting pot 14a is a pump (not shown) installed at one end in the long side direction of the snout.
Then, the plating bath 3 is discharged from the snout 1 to the melting pot 14a by using the pump 18a provided at the other end of the snout 1 in the long side direction. In the melting pot 14a, the plating bath 3 flows in the ingot 19 charging portion, and flows down the plating pot 13a to settle and separate dross.
The ingot 19 returns to the plating pot 13a via a flow path 16a provided on the opposite side of the plating pot 13a with respect to the melting portion. In this embodiment, the plating pot is 7.5 m
^{3. The} circulation flow rate was 2.5 m ³ (the same flow rate of the plating bath to the snout was used), and the melting pot was 14.
It has become 5m ^3.

In this embodiment, there was no dross defect occurring at a line speed of 120 m / min, and no problem with dross occurred even if the line speed was increased to 160 m / min.

[0049]

According to the present invention, dross generated in a plating pot can be moved to a dissolving pot different from the plating pot and removed as a top dross or a bottom dross. Bottom dross can be prevented from being deposited, and at the same time, the bath surface of the snout can be cleaned. According to the invention, in the hot-dip galvanizing equipment, surface defects of the steel strip due to dross and surface defects caused by zinc oxide in the snout and the like can be prevented, so that high-quality hot-dip galvanized steel strip can be manufactured. .

Further, with a facility having a simple structure, it is possible to solve serious problems such as leakage and solidification of a plating bath in a flow path, and it is excellent in operability.

[Brief description of the drawings]

FIG. 1 is a view showing a plating bath temperature distribution around an ingot when the ingot is put into the plating bath.

FIG. 2 is a view showing a plating apparatus according to an embodiment of the present invention.

FIG. 3 is a view showing an AA cross section of the plating apparatus of FIG. 2;

FIG. 4 is a diagram showing a BB cross section of the plating apparatus of FIG. 2;

FIG. 5 is a graph showing iron solubility when a plating bath temperature and an aluminum concentration are specified.

FIG. 6 is a view showing a plating apparatus according to another embodiment of the present invention.

FIG. 7 is a view showing a normal molten zinc pot.

FIG. 8 is a diagram showing a hot-dip galvanizing apparatus of Prior Document 1.

FIG. 9 is a view showing a hot-dip galvanizing apparatus of Prior Art 2.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Snout 2 Sink roll 2 3 Plating bath 3 4 Plating tank 12, 12a Plating tank 13, 13a Plating pot 14, 14a Melting pot 15, 15a Partition wall 16, 16a Channel 17, 18, 18a Pump 19 Ingot 20, 20a, 21, 21a Heating device (induction heating device) 31 Top dross 32 Bottom dross S Steel strip

Claims (4)

[Claims] 1. A hot-dip galvanizing apparatus comprising: a plating tank containing a hot-dip galvanizing bath containing 0.05% by weight or more of aluminum; and a snout in which a steel strip immersed in the bath runs inside. A plating pot for plating a steel strip and a dividing wall for dissolving an ingot are provided in a plating tank, and the hydraulic diameter defined by the following equation is 0.1 m or more on the partition wall, To provide the same bath surface, arrange a flow path with an open top, and in order to further clean the plating bath in the snout, remove the plating bath of the plating pot from one end in the long side direction of the snout. A hot-dip galvanizing apparatus comprising a pump for pouring into a snout and a pump for discharging a snout plating bath to a melting pot at the other end. Hydraulic diameter = (cross-sectional area of channel / wetting length of channel) x 4 2. The hot-dip galvanizing apparatus according to claim 1, wherein the volume of the plating pot is 10 m ³ or less, and the volume of the melting pot is 10 m ³ or more. 3. A hot-dip galvanizing method in which a steel strip traveling in a snout is immersed in a galvanizing bath containing a hot-dip galvanizing bath containing 0.05 wt% or more of aluminum. And a plating tank,
It is divided into a plating pot for plating the steel strip and a melting pot for dissolving the ingot.Furthermore, the plating bath of the plating pot is poured into the snout from one end in the long side direction of the snout with a pump, and the plating bath for the snout is pumped from the other end. While purifying the plating bath in the snout by discharging to the melting pot and discharging the plating bath of the plating pot to the melting pot, the hydraulic diameter defined by the following equation provided on the partition wall is 0.1 m or more. A hot-dip galvanizing method, wherein the plating bath of the melting pot is returned to the plating pot through a flow path having an open top connecting the two pots so as to have the same bath surface. Hydraulic diameter = (cross-sectional area of channel / wetting length of channel) x 4 4. A plating pot having a volume of 10 m ³ or less, a dissolution pot having a volume of 10 m ³ or more, a circulation flow rate of a plating bath between the plating pot and the dissolution pot of 0.5 m ³ / h or more,
The hot-dip galvanizing method according to claim 3, wherein the plating rate is 5 m ³ / h or less.