JPH10298725A - Dross removing device for hot dip galvanizing equipment, and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dross removing device for hot dip galvanizing equipment that is simple in construction, durable, high in the efficiency of removing dross, and facilitates the discharge of the drops to the outside of a galvanizing equipment, and a method therefor. SOLUTION: This dross removing device is installed adjacently to a plating tank 1 and has a dross settling tank 3 for settling the dross and a transferring means for transferring and circulating molten zinc between this plating tank and the dross settling tank. The transferring means has transfer pipings 4, 5 having straight pipe parts and bent pipe parts. These pipings 4, 5 have inside pipes consisting of castable ceramics, reinforcing pipes disposed on the outer side thereof and the adhesives between these inside pipes and reinforcing pipes. The straight pipe parts have a taper grading downward from 1/200 to 1/25 and the bent pipe parts have curvature of >=2 times the diameter of the pipings and have a taper of the downward grade similar to that of the straight pipe parts. Further, the projections and differences in level of the inside surfaces of the pipings 4, 5 are within 10 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dross removing apparatus and method in a hot dip galvanizing facility.

[0002]

2. Description of the Related Art Surface defects of hot-dip galvanized steel sheets caused by dross are the most serious problems among hot-dip galvanized steel sheets. The dross is an intermetallic compound (FeZn ₇ or the like) generated by a reaction between iron and zinc eluted from the steel sheet to be plated, and has a diameter of 5 to 300 μm in terms of sphere diameter. This dross will accumulate at the bottom of the plating tank if it is stationary without the flow of molten zinc.

However, since the molten zinc is agitated by the running of the steel sheet, the rotation of the roll in the bath in the plating tank, or the natural convection of the molten zinc generated by the zinc ingot, the dross having a small difference in specific gravity from the molten zinc is formed at the bottom. It cannot be deposited on the steel sheet, or even if it is deposited, it is rolled up and adheres to the coated steel sheet, and this becomes a surface defect of the hot-dip galvanized steel sheet by dross.

Heretofore, numerous proposals have been made to remove dross. These proposals include a method of pumping molten zinc out of a plating tank to precipitate dross, a method of filtering, and a method of adding aluminum to floatation and separating.

However, despite many proposals, none of the conventional proposals have been put to practical use. The reason 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 impossible to actually adopt them. is there.

A typical precipitation method is described in JP-A-53-88.
No. 633, JP-A-56-170260, JP-A-3-2
67357 and JP-A-4-154948.

[0007] JP-A-53-88633 discloses that molten zinc is cooled in a sedimentation tank to form dross in the sedimentation tank.
It is disclosed to remove the precipitate. Further, the embodiment shows that the size of the sedimentation tank is reduced to about 1/4 of the size of the plating tank. However, dross cannot be sufficiently removed by this method.

Japanese Utility Model Application Laid-Open No. Sho 56-170260 discloses that molten zinc and dross are pumped from the bottom of a plating tank, introduced into a sedimentation tank, and after the dross settles, the molten zinc is returned to the plating tank. I have. However, this method does not describe a method for precipitating dross.

Japanese Patent Application Laid-Open No. 3-267357 discloses providing a baffle plate in a settling tank. But,
The effect of promoting dross sedimentation described in this publication is small. That is, this gazette does not propose any fundamental measures for sedimentation removal of dross.

Japanese Patent Application Laid-Open No. 4-154948 discloses that in order to prevent dross from settling in the plating tank, the plating tank is made to have a specific size and shape, and dross is deposited and deposited on the bottom of the settling tank. It is disclosed that the sedimentation tank has sufficient plane area and depth to facilitate.

By the way, regarding the sedimentation tank, unlike the field of water treatment, the dross treatment does not accumulate and systematize the technology at all. And, as shown below,
Because the growth mechanism is completely different from foreign substances in water, the techniques described in these prior art documents do not show a specific means for facilitating sedimentation of dross.

Dross is an intermetallic compound (FeZn ₁₃ , FN) formed by the chemical reaction of iron as a solute with zinc as a solvent.
eZn _7, an Fe etc. ₅ Zn _21). The iron solubility of the molten zinc is greatly affected by the temperature, for example, 460
0.04% at ℃ and 0.01% at 430 ° C. The change in the temperature of the solubility and the change in the concentration of the solute greatly affect dross generation and growth. In addition, dross is thought to undergo a phase transformation as it grows. Different phases have different physical properties such as density. That is, the sedimentation behavior changes.
The above does not occur in water treatment for exogenous foreign substances having no reactivity with water.

On the other hand, the above-mentioned prior art documents do not sufficiently describe the transfer of molten zinc, and it is considered from these prior art documents that the molten zinc can be easily transferred by installing a pump and piping.

However, according to the experiments conducted by the present inventors, the molten zinc in the plating bath is heated to a temperature required by the sensible heat of the running strip or the installation of a heater (usually 30 ° C. to 50 ° C. from the melting temperature). (Overheated to about ℃), but the heat loss is very large in the transfer pipe with a large specific surface area, and the specific heat of molten zinc is only about 25% of water. The energy up to the required temperature is surprisingly small, so that with a simple transfer method the molten zinc solidifies due to heat loss. Therefore, although it is necessary to select an appropriate means for transferring the molten zinc, there is no example examined so far.

The most basic means for preventing solidification is heating. However, when used for a long time, it promotes erosion which will be described later, generates a large amount of fume, and has a high running cost of heating equipment. Although implementation is possible for reasons such as the device itself becoming complicated, it does not exist as practical equipment.

Further, molten zinc is very liable to react with other metals, and many metals form a eutectic alloy, which lowers the melting point and melts the piping metal. Gold and uranium are metals that do not react with zinc, but are not practical. Therefore, in the past, it was often the case that the piping was designed as a consumable, but this would require labor and cost for replacing the piping.

[0017] Therefore, there is a demand for a means for transferring the molten zinc which minimizes manufacturing or running costs and minimizes damage to the piping due to melting and erosion of the molten zinc. In the field of aluminum smelting technology, the use of special steel has reached a level that satisfies this requirement and has been put to practical use. However, the material is very expensive and is not practical in a hot-dip galvanizing apparatus.

[0018]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a simple structure, is durable, has high dross removal efficiency, and discharges dross to the outside of a facility. It is another object of the present invention to provide a dross removing apparatus and method for a hot-dip galvanizing facility, which is also easy.

[0019]

In order to solve the above problems, the present invention has been completed as a result of repeated experiments on dross generation / growth behavior, dross sedimentation behavior, and structures and materials suitable for practical equipment. It was done.

That is, the present invention relates to a dross removing apparatus for removing a dross tank generated in a plating tank of a hot-dip galvanizing facility, wherein the dross removing tank is provided adjacent to the plating tank and precipitates dross. Transfer means for transferring and circulating the molten zinc between the plating tank and the dross settling tank; andthe transferring means includes a pipe for circulating the molten zinc having a straight pipe portion and a curved pipe portion. The pipe has an inner pipe made of castable ceramics, a reinforcing pipe provided outside the pipe, and an adhesive between the inner pipe and the reinforcing pipe.
A taper having a descending slope of 0 to 1/25, the curved pipe portion having a curvature of twice or more the diameter of the pipe, and having a taper having a descending slope similar to that of the straight pipe section; A dross removing device in a hot-dip galvanizing facility, wherein a protrusion and a step on an inner surface of the hot dip galvanizing apparatus are within 10 mm.

Further, the present invention provides a dross removing apparatus in a hot-dip galvanizing facility, wherein the dross removing apparatus has a heating means for heating the pipe in the transfer means.

Further, the present invention provides the dross removing apparatus according to any one of the above dross removing apparatuses, wherein the length of the pipe in the transfer means is 2 m or less per one pipe.

Still further, the present invention provides any one of the above-described dross removing apparatuses, further comprising a seal box having a lower part opened at an end of the transfer means on the plating tank side of the pipe. Provided is a dross removing device in a hot dip galvanizing facility.

Still further, according to the present invention, in the above dross removing apparatus, further, the molten zinc from the piping is provided at an end of the piping on the plating tank side of the transfer means, the molten zinc from the piping being in the plating tank. A dross removing device in a hot-dip galvanizing facility, characterized in that the dross removing device has a buffering means for impact when it collides with the steel sheet.

Still further, the present invention provides a dross sedimentation tank provided adjacent to a plating tank of a hot dip galvanizing facility for sedimenting dross, and transferring molten zinc between the plating tank and the dross sedimentation tank. Transfer means for circulating the molten zinc having a straight pipe portion and a curved pipe portion, the pipe having an inner pipe made of castable ceramics, And a glue between the inner pipe and the reinforcing pipe, wherein the straight pipe portion is 1/200 to 1/2.
5, the curved pipe portion has a curvature of twice or more the pipe diameter, and has the same downward slope taper as the straight pipe portion, and further has a projection on the inner surface of the pipe. A dross removing method using a dross removing device in a hot-dip galvanizing facility having a step difference of 10 mm or less,
Before starting the transfer of the molten zinc by the transfer means,
The high-temperature gas is allowed to pass through the pipe, the temperature of the atmosphere in the pipe is raised to a temperature within the range of 100 ° C. or more and the temperature of the molten zinc passing through the pipe, and thereafter, the molten zinc is transferred. To provide a dross removing method in a hot-dip galvanizing facility.

Still further, according to the present invention, in the above dross removing method, when the molten zinc is transferred by the transferring means, a pipe of the transferring means is filled with the molten zinc. A method for removing dross in equipment is provided.

The operation of the present invention configured as described above is as follows. Dross is generated in the plating tank according to the throughput of the steel sheet, and is sent to the settling tank before the dross grows and reaches a harmful size. The important thing is to circulate the molten zinc for a long time. At first glance, it seems difficult to actually circulate the molten zinc for a long time without clogging the piping.

In order to prevent clogging of the piping, it is generally considered that the piping itself is heated. However,
When the molten zinc is heated by heating the pipe itself, iron solubility is increased as described above, and dross may be lost during transfer. In addition, since the steam pressure of molten zinc rapidly rises with an increase in temperature, the generation of a large amount of fume becomes a problem. This is also considered to be one of the reasons for the lack of practical use described above. Furthermore, since the pipe is heated unevenly in a normal heating state, the pipe undergoes thermal deformation, and the flow of the molten zinc is not always kept good.

On the other hand, as described above, such a molten zinc transfer pipe is required to have high durability.

Therefore, the present inventors have carried out a number of experiments to prevent clogging of the molten zinc in the piping and to increase the durability of the piping. As a result, first, the structure and material of the pipe, the taper of the straight pipe portion and the bent portion of the pipe and the radius of curvature of the bent portion are appropriately adjusted, and the protrusions and steps on the inner surface of the pipe are not more than a predetermined value. I found it important.

Regarding the structure and material of the pipe, the pipe has an inner pipe made of castable ceramics and a reinforcing pipe provided outside thereof, and a thermal expansion is absorbed by a joint between the inner pipe and the reinforcing pipe. By using a pipe made of an adhesive having a buffering property for the pipe, thermal expansion can be minimized, erosion can be prevented, and sufficient strength can be obtained.

Further, regarding the taper of the straight pipe portion and the curved pipe portion of the pipe, if the taper is 1/200 or less, it is difficult to construct.
There is a danger that a horizontal portion will be formed, and when an emergency stop occurs, molten zinc may solidify in this portion. Also 1/25
With the above taper, the flow of the molten zinc becomes faster, so that when the molten zinc flows into the tank, the surrounding gas is entrapped in the vicinity of the pipe outlet and may generate new impurities. Therefore, the taper of the pipe needs to have a descending gradient of 1/200 or more and 1/25 or less. In consideration of the fact that clogging is likely to occur in the curved pipe portion, the curvature is set to be twice or more the pipe diameter.

Further, the projections and steps in the pipe are constructed so as to be within 10 mm. 1
Protrusions and steps exceeding 0 mm tend to be the starting point of solidification when molten zinc solidifies, and it is confirmed that clogging in the piping can be prevented by using protrusions and steps below this level. Therefore, the protrusion and the step were set to be within 10 mm.

On the other hand, in order to prevent the initial solidification of the molten zinc and zinc in the pipe, a method of heating the inside of the pipe with a gas is adopted, so that unnecessary heat loss is not given to the outside and the necessary pipe is provided. The inner surface temperature can be secured. Therefore, before the transfer of the molten zinc is started by the transfer means, a high-temperature gas is passed through the pipe, and the atmosphere temperature in the pipe is set to a temperature within a range of 100 ° C. or more and a temperature of the molten zinc passing through the pipe or less. The temperature is raised, and then the molten zinc is transferred.

In consideration of thermal expansion, the length per pipe is preferably 2 m or less. Further, from the viewpoint of operational stability, thermal distortion, and prevention of splash, the molten zinc flow flowing through the pipe is preferably a filling flow. Furthermore, when returning the transferred molten zinc to the plating tank, in order to prevent oxidation of the zinc by returning the molten zinc in the plating tank without disturbing the liquid level and without involving gas, the piping of the transfer means is provided. It is preferable to provide a seal box with a lower part opened at the end on the plating tank side. In addition to this, it is possible to more effectively prevent disturbance of the liquid level by providing a buffer means such as a slide or a slider for reducing the impact when the molten zinc from the pipe collides with the molten zinc in the plating tank. it can.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific example of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view showing a hot-dip galvanizing facility provided with a dross removing apparatus according to an embodiment of the present invention, and FIG. 2 is a plan view thereof. The hot-dip galvanizing equipment has a plating tank 1 in which hot-dip zinc L is stored, and a dross removing device. This dross removing device is composed of a plating tank 1
, A first transfer pipe 4 for transferring molten zinc from the plating tank 1 to the precipitation tank 3,
It has a second transfer pipe 5 for transferring molten zinc from the precipitation tank 3 to the plating tank 1, and a pump 6 provided in each of the transfer pipes 4 and 5.

Further, as a device for preheating pipes,
A nitrogen gas preheating device 9 is installed above each pump 6. Further, on the opposite side of the precipitation tank 3 from the plating tank 1, an induction heating device 10 is provided near the second transfer pipe 5.

The pump 6 used for pumping the transfer device 4 is preferably a ceramic pump, and the inlet of the pump for sucking the molten zinc in the plating tank 1 is preferably closer to the bottom of the plating tank 1. This is because the dross concentration is higher at the bottom than at the top, so the dross collection efficiency and transfer efficiency are higher.

The first and second transfer pipes 4 and 5
Has the structure shown in FIG. That is, these transfer pipes 4 and 5 have an inner pipe 14 made of castable ceramics such as alumina and a reinforcing pipe 12 provided on the outermost side made of steel or the like. The bonding portion has an adhesive 13 having a buffering property for absorbing thermal expansion. The inside of the inner tube 14 is a molten zinc channel 15. By using a transfer pipe having such a structure, thermal expansion can be minimized, erosion can be prevented, and sufficient strength can be obtained.

The straight pipe portions of the transfer pipes 4 and 5 are 1 / 200-
The taper has a 1/25 descending slope. The curved pipe has a radius of curvature that is at least twice as large as the pipe diameter, and has the same taper as the straight pipe. Thereby, the dischargeability of the molten zinc is improved, and the clogging of the pipe can be effectively prevented. The upper limit of the taper is set to 1/25, because the flow of the molten zinc is increased, and the molten zinc flowing in at the pipe outlet may entrain the surrounding gas and generate new impurities. .

The transfer pipes 4 and 5 are constructed such that projections and steps inside the transfer pipes 4 and 5 are within 10 mm. 10mm
This is because the projections and steps exceeding the above tend to be the solidification starting points when the solidification of the molten zinc occurs, causing clogging of the pipe. These transfer pipes 4
If the length 5 is too long, the influence of thermal expansion increases, so that the length is preferably 2 m or less. Further, from the viewpoint of facilitating attachment and detachment, it is preferable to use a flange for the joint portion of the pipe and use a plurality of ceramic sheets for the flange packing.

In the hot-dip galvanizing equipment thus constructed, the steel sheet S to be plated out of the heating furnace is passed through the snout 11 to the plating tank 1, and
Immersed in the molten zinc L stored in the tank. Then, after the steel sheet S is turned by the sink roll 2 provided in the plating tank 1, the steel sheet S is passed in the direction shown by the arrow.

During this time, iron is eluted from the steel sheet S to be plated. It is considered that the form of iron elution at this time is the case where the powdery substance adhering to the steel sheet and the fine iron-zinc alloy layer formed on the steel sheet surface are separated and dissolved, or the case where it is directly eluted from the steel sheet. Can be

The iron dissolved in this way reprecipitates and grows into dross. The amount of dross generated is proportional to the throughput of the steel sheet (total surface area of the passing steel sheet). The amount generated when a 1 m steel plate is passed at a speed of 120 m per minute is approximately 50 kg per hour. The dross immediately after generation is extremely small with a diameter of 5 to 10 microns. At this size, the sedimentation velocity is slow. The molten zinc temperature during operation in the plating tank 1 is in the range of 455 to 465 ° C., and this temperature depends on the temperature and heat capacity of the steel sheet to be passed, and the amount of heat released from the plating tank and the amount of heat to the plating tank. I can decide.

The molten zinc L is sent from the plating tank 1 to the precipitation tank 3 by a first transfer pipe 4 as a transfer means. At this time, the transfer amount of the molten zinc L must be an amount capable of sufficiently removing dross from the plating tank 1. Assuming that the dross sedimentation speed is the terminal speed, it is about 4 hours, though it depends on the depth of the plating tank used. From this viewpoint, it is preferable that the transfer amount is specified to be equal to or more than the flow rate obtained by dividing the capacity of the plating tank 1 by 4 hours.

On the other hand, from the viewpoint of dross removal only, the greater the amount of molten zinc L transferred, the better.
However, as will be described later, when the transfer amount increases, the size of the precipitation tank 3 corresponding to the transfer amount is required, and the hot-dip galvanizing equipment itself becomes large, which is uneconomical. Therefore, since the sedimentation speed of the large dross that causes a quality defect is approximately one hour, it is preferable to set the upper limit of the transfer amount of the molten zinc to the flow rate obtained by dividing the capacity of the sedimentation tank 3 by one hour.

When dross is actually removed by the dross removing device 3, first, for example, nitrogen gas or other inert gas, combustion exhaust gas, oxygen-free gas or the like is preheated by the preheating device 9 prior to the flow of molten zinc. The high-temperature gas obtained by raising the temperature is passed through the transfer pipes 4 and 5. The temperature at this time is a temperature in the range of 100 ° C. or more and the temperature of the molten zinc passing through the pipe or less. Thereby, the transfer pipes 4, 5
No initial solidification of the molten zinc occurs.

Thereafter, the molten zinc is circulated and transferred into the transfer pipes 4 and 5 by the pump 6, and at this time, as described above, the structure and material of the transfer pipes 4 and 5 and the transfer pipes 4 and 5 are used. Since the taper of the straight pipe section and the curved pipe section and the radius of curvature of the curved pipe section were appropriately adjusted to reduce the protrusions and steps on the inner surfaces of the transfer pipes 4 and 5, clogging of the molten zinc in the transfer pipes 4 and 5 was prevented. Can be prevented, and the durability of the transfer pipes 4 and 5 can be increased.

When transferring the molten zinc, the transfer pipe 4
5 is preferably filled with molten zinc. Although the flow resistance itself increases when the flow is filled, the transfer pipes 4 and 5 can be heated by the sensible heat of the molten zinc, so that the operation can be stabilized and the thermal strain can be increased. Since the lower surface is the same, there is no structural problem, and splash which occurs in the pipe, which is the biggest problem in the case of non-filling, can be prevented.

The dross 8 in the molten zinc transferred to the settling tank 3 is grown and settled here. The basic idea to increase the sedimentation efficiency is to reduce the sedimentation time and iron solubility so that the dross itself can be as large as possible. For that purpose, the temperature of the molten zinc in the settling tank 3
By making the temperature lower than the temperature of the molten zinc in the plating tank 1, the iron solubility of the molten zinc is reduced and dross is easily grown.

Next, an operation example in which the above hot-dip galvanizing equipment is actually operated will be described. Here, castable ceramic made of alumina having an inner diameter of 50 mm was used as the inner pipe 14 as the transfer pipes 4 and 5, and a steel pipe material of 80 A was arranged as the reinforcing material 12 via the adhesive 13 outside the inner pipe 14. The length of one wire was about 1 m to 1.5 m, and a ceramic fibrous filter having poor wettability of molten zinc was used for a connection portion. This prevented solidification of the molten zinc in the flange portion when the pipe was removed.

The flow rate of the molten zinc was such that it could fill a pipe having an inner diameter of 50 mm. This is not a constant value because it is affected by the pipe length, surface roughness inside the pipe, etc.
By circulating 0 m ³ / h, it was possible to confirm that the flow was a filling flow.

The transfer pipes 4 and 5 themselves are 1/5 in the straight pipe part.
A zero down slope was provided. In addition, the curved pipe part has a pipe diameter of 2
In this example, the pump and the transfer pipe, in order to bend at a curvature of twice or more, and to provide the same downward gradient in the bent pipe part as in the straight pipe part, and to make the projections and steps in all the pipes fall within 10 mm, The transfer pipes, the transfer pipes, and all the connecting portions of the outlets from the transfer pipes were constructed such that the steps were within 5 mm.

Before transferring the molten zinc to the transfer pipe, the inside of the transfer pipe is heated to prevent solidification of the molten zinc.
A gas preheated to nitrogen gas at 600 ° C. was flowed, and the pipe was preheated with high-temperature nitrogen gas such that the temperature at the outlet of the pipe was 420 ° C. This completely solved the initial molten zinc solidification problem in the piping.

By circulating the molten zinc in the transfer pipes 4 and 5 as described above, the dross 8 in the molten zinc transferred to the precipitation tank 3 grew here and was removed by precipitation.

Thus, after one month of continuous use, the dross in the plating tank was 10% or less of the conventional one, and it was confirmed that there was no dross that would cause a problem in quality. During the operation, the hot-dip galvanized steel sheet had no significant surface defects.

Next, a more preferred embodiment capable of solving the problem of oxidation of molten zinc will be described. When pumping the molten zinc, a mechanical pump is used, so that there is almost no problem of oxidation of the molten zinc. On the other hand, when returning the molten zinc to the plating tank, if the molten zinc is naturally dropped into the plating tank, the surface area of the interface increases,
Large amounts of zinc oxide are generated due to the increase in the new molten zinc interface.

Therefore, in this embodiment, a seal box is used. That is, as shown in FIGS. 4 and 5, a seal box 16 having an open lower portion is immersed in the molten zinc L of the plating tank 1, and the end of the second transfer pipe 5 is inserted into the seal box 16. It is connected. An inert gas such as nitrogen gas is introduced into the seal box 16 from a gas inlet 17, and the inside thereof is maintained in an inert gas atmosphere. Thereby, the fluctuation of the interface is reduced, and the generation of zinc oxide is reduced. Note that the gas inlet 17 also has a function as a gas diffusion tube.

However, in this state, molten zinc was transferred to transfer pipe 5.
If it is dropped naturally from the end of the
When the molten zinc from the transfer pipe 5 falls into the inside 6, the surrounding gas is entrained and the air bubbles float out of the seal box 16. Then, the air bubbles floating outside the seal box 16 are released to the atmosphere and simultaneously generate zinc oxide. At this time, the pressure inside the seal box 16 becomes negative due to the gas that has come out to the outside, so that air enters from a pipe flange or the like, and zinc oxide is generated.

For this reason, the impact when the molten zinc from the pipe collides with the molten zinc L in the seal box 16 on the portion from the end of the transfer pipe 5 to the surface of the molten zinc L in the seal box 16 is reduced. A slider 18 is provided as a buffer means. This prevents the surrounding gas from being entrained when the molten zinc from the pipe 5 falls into the plating tank, thereby further effectively preventing the oxidation of zinc. Then, even if involving gas, by the immersion length L ₂ of the sealing box 16 fall length L ₁ or more, and floating the gas into the sealing box 16,
No zinc oxidation occurs.

It is preferable that the inside of the seal box 16 is maintained at a positive pressure in order to prevent the inside of the seal box 16 from becoming negative pressure and air from entering through the flange of the pipe to generate zinc oxide. .

An operation example in which such a seal box and a slider are actually operated will be described.
Reduce the taper of the pipe to 1/100 and set the step on the inner surface of the pipe to 1m
m, except that the operating conditions were basically the same as those in the previous operation example.
0 mm height 800 mm, immersion length 40
The setting was set to 0 mm, and the molten zinc was smoothly returned to the plating tank using a slider. Nitrogen gas was supplied to the inside of the seal box, and the inside of the seal box was constantly controlled to have a positive pressure of 10 mmAq.

After continuous use for one month in this way, the dross in the plating tank was 10% or less of that of the conventional plating tank, and it was confirmed that there was no dross which would cause a problem in quality. On the other hand, it was confirmed that 90% of the amount of dross settled in the plating tank was conventionally deposited in the settling tank. Further, the oxidation of zinc was extremely low, and the hot-dip galvanized steel sheet had no significant surface defects during the operation.

[0064]

As described above, according to the present invention,
A dross removing device for hot-dip galvanizing equipment with a simple structure, high durability, high dross removal efficiency, and easy discharge of dross out of the facility. A dross removing method in a galvanizing facility can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a dross removing device according to an embodiment of the present invention.

FIG. 2 is a plan view showing a dross removing device according to one embodiment of the present invention.

FIG. 3 is a sectional view showing a molten zinc transfer pipe used in the dross removing apparatus according to the embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a portion for returning molten zinc to a plating tank in a dross removing apparatus according to another embodiment of the present invention.

FIG. 5 is a plan view showing a part for returning molten zinc to a plating tank in a dross removing apparatus according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Plating tank 2 ... Sink roll 3 ... Settling tank 4 ... First transfer pipe 5 ... Second transfer pipe 6 ... Pump 8 ... Dross 9 ... Nitrogen gas preheating apparatus 10 ... Induction Heating device 11 Snout 12 Reinforcement tube 13 Adhesive 14 Inner tube 15 Zinc channel 16 Seal box 18 Slider

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Keishi Yamashita 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Inside the Kokan Co., Ltd. (72) Inventor Hiroaki Nishio 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun Honko Co., Ltd.

Claims (7)

[Claims] 1. A dross removing device for removing a dross tank generated in a plating tank of a hot-dip galvanizing equipment, comprising: a dross settling tank provided adjacent to the plating tank to precipitate dross; Transfer means for transferring and circulating the molten zinc between the dross sedimentation tank, the transfer means has a pipe for circulating the molten zinc having a straight pipe portion and a curved pipe portion, The pipe has an inner pipe made of castable ceramics, a reinforcing pipe provided outside thereof, and an adhesive between the inner pipe and the reinforcing pipe, and the straight pipe portion is 1/200 to 1/25. The curved pipe portion has a curvature of twice or more the diameter of the pipe, and has a taper of the same gradient as the straight pipe portion, and further includes a projection on the inner surface of the pipe and Step is within 10mm A dross removing device for a hot dip galvanizing facility. 2. The apparatus according to claim 1, further comprising heating means for heating said pipe in said transfer means.
A dross removing apparatus in a hot-dip galvanizing facility according to item 1. 3. The dross removing apparatus according to claim 1, wherein the length of the pipe in the transfer means is 2 m or less per one pipe. 4. The apparatus according to claim 1, further comprising a seal box having a lower part opened at an end of said pipe in said transfer means on said plating tank side.
A dross removing apparatus in a hot-dip galvanizing facility according to item 1. 5. A buffering means provided at an end of the pipe on the side of the plating tank in the transfer means, the buffering means mitigating an impact when molten zinc from the pipe collides with molten zinc in the plating tank. 5. The method according to claim 4, wherein
A dross removing apparatus in a hot-dip galvanizing facility according to item 1. 6. A dross sedimentation tank provided adjacent to a plating tank of a hot-dip galvanizing facility and for dross sedimentation, and a transfer means for transferring and circulating molten zinc between the plating tank and the dross sedimentation tank. Wherein the transfer means has a pipe for circulating molten zinc having a straight pipe section and a curved pipe section, and this pipe is formed of an inner pipe made of castable ceramics, and a reinforcement provided outside the pipe. A pipe and an adhesive between the inner pipe and the reinforcing pipe, wherein the straight pipe section has a taper with a descending slope of 1/200 to 1/25, and the bent pipe section has a pipe diameter of 2/2. Has a curvature of twice or more, and has a taper of the same descending gradient as the straight pipe portion, and furthermore, a protrusion and a step on the inner surface of the pipe are 10 mm.
A dross removing method using a dross removing device in a hot-dip galvanizing facility, wherein before the transfer of the molten zinc is started by the transfer means,
The high-temperature gas is allowed to pass through the pipe, the temperature of the atmosphere in the pipe is raised to a temperature within the range of 100 ° C. or more and the temperature of the molten zinc passing through the pipe, and thereafter, the molten zinc is transferred. Dross removal method in hot-dip galvanizing equipment. 7. The method for removing dross in a hot dip galvanizing facility according to claim 6, wherein when the molten zinc is transported by the transporting means, a pipe of the transporting means is filled with molten zinc. .