JP2001288548A - Method for removing dross in hot dip metal coating bath and hot dip metal coating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of removing dross in a hot dip metal coating bath by which the dross in the hot dip metal coating bath is effectively removed with a simple device and the recovering work of the dross and the maintenance of this device are easily performed, and a hot dip metal coating apparatus. SOLUTION: In the method of removing the dross in the hot dip metal coating bath in the case of continuously applying a hot dip metal coating, as a dross removing vessel 10, the dross removing vessel 10 having coating metal liquid inflow port 11, plural baffles 13, 14 for separating the dross with the specific gravity and a coating metal liquid outflow port 15, is used. Then, the dross removing vessel 10 is dipped into the hot dip metal coating bath 1, and the coating metal liquid is introduced into the dross removing vessel 10 from the coating metal liquid inflow port 11 by using the flow F of the coating metal liquid developed with the rotation of a sink roll 3 in the bath as the driving force, and is made to pass through the lower part or the upper part of plural baffles 13, 14, and after separating the dross with the specific gravity, the coating metal liquid is recirculated from the coating metal liquid outflow port 15 into the hot dip metal coating bath 1 to remove the dross in the hot dip metal coating bath.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous apparatus for continuous hot-dip metal plating of steel strips, which effectively removes dross from a plating bath with a simple apparatus, facilitates the dross recovery operation, and facilitates maintenance of the apparatus. TECHNICAL FIELD The present invention relates to a method for removing dross from a hot-dip metal plating bath and a hot-dip metal plating apparatus having excellent heat resistance.

[0002]

2. Description of the Related Art FIG. 8 is a longitudinal sectional view of a conventional continuous strip metal plating apparatus for a steel strip. In FIG. 8,
1 is a plating bath which is a molten metal, 2 is a plating pot, 3
Is a sink roll disposed in the plating bath 1 (hereinafter referred to as a sink roll or sink roll in the bath), 4 is a steel strip,
5 snout, f ₁ is the transport direction of the steel strip (sheet passing direction), f ₂ represents the rotation direction of the sink roll.

That is, in a continuous strip metal plating apparatus for a steel strip, the steel strip is continuously penetrated into a plating bath 1 which is a molten metal, and after turning around a sink roll 3, the direction is changed.
The plating bath 1 is pulled up from the liquid level to perform plating continuously. Hereinafter, a conventional technique in hot-dip metal plating will be described by taking hot-dip galvanizing, which is a typical example of continuous hot-dip metal plating of a steel strip, as an example.

At present, in a hot-dip galvanizing line,
Generally, a normal hot-dip galvanized steel sheet as-plated and an alloyed hot-dip galvanized steel sheet which is subjected to an alloying process after hot-dip galvanizing are manufactured by appropriately switching the processing on the same line. Among them, alloyed hot-dip galvanized steel sheet is widely used mainly as a steel sheet for automobiles because it has excellent properties of corrosion resistance, weldability and workability, but especially when used as an exterior steel sheet. Demands for quality are becoming more and more severe, such as the requirement for high definition after painting.

[0005] Under these circumstances, in the hot-dip galvanizing pot, Fe and Zn eluted from a steel strip (hereinafter also referred to as a strip) react with each other to form bottom dross containing FeZn ₇ as a main component. Deposits on the bottom. Further, Al and Fe in the plating solution react with each other to generate floating dross mainly composed of Fe ₂ Al ₅ and float on the plating bath.

In this case, the bottom dross is wound up by the plating solution, which is an accompanying flow of the strip conveyed around the sink roll in the plating bath, and adheres to the strip. Further, the floating dross is partially involved in the plating solution again and adheres to the strip in the same manner as described above. As a result, when the manufactured plated steel sheet is pressed, a non-uniform surface portion called a press spot occurs, which not only impairs the sharpness but also causes a problem that the attached dross damages the mold.

In order to solve the above-mentioned problem, Japanese Patent Laid-Open No.
In Japanese Patent No. 248405, a dross removing device comprising a removable tank is installed in a hot-dip galvanizing bath, and the molten zinc in the bath is sucked up by a pump, and the molten zinc is introduced into the bath from an inlet provided in an upper side wall of the bath. After the dross is settled by a plurality of baffles arranged in the tank, the dross in the plating bath is removed by returning the molten zinc into the bath from a return pipe connected to the upper side wall of the tank. A removal method and apparatus are disclosed.

[0008] However, the above method is as follows:
Problem. Replacement of pump and blockage of piping: In order to suck up molten zinc in the bath and allow it to flow into the tank of the dross removing device,
A pump using a rotary wing or the like is required. As a result, it is inevitable that the pump and the piping are clogged or damaged by zinc or dross, and maintenance of the device such as replacement of the pump and removal of the clogging material in the piping is required.

Attachment of dross having a low specific gravity to a plated steel sheet: As described above, the dross adhered to a plated steel sheet includes Fe-Zn-based dross having a higher specific gravity than molten zinc and Fe-Al-based dross having a specific gravity lower than molten zinc. Both of the dross are generated.
On the other hand, in the case of the dross removing method and the removing device described above, the tank of the removing device has a hermetic structure due to its configuration, and it is impossible to separate Fe-Al dross having a low specific gravity. -Al-based dross is recirculated in the bath, making it impossible to solve the above-mentioned problem caused by the dross adhering to the plated steel sheet.

In Japanese Patent Application Laid-Open No. 4-52257, a dross reservoir is provided at a part of the bottom of a plating pot, and an opening which can be opened and closed to shut off a space in which the dross reservoir is provided and a space in which a sink roll is provided. A method has been proposed in which a blocking member is provided to prevent bottom dross accumulated in the dross pool from floating in the plating bath and adhering to the strip surface by the action of the blocking member.

In Japanese Patent Application Laid-Open No. 55-128569, the inside of a plating pot is divided into a plating tank and a reaction tank by a partition having an openable upper opening and a lower opening.
By making the bottom of the plating tank an inclined surface that descends toward the reaction tank, the bottom dross is introduced into the reaction tank, and the bottom dross is lifted up by operating the stirrer in the reaction tank. A method of recovering as a dross has been proposed.

However, in the case of the method proposed in Japanese Patent Application Laid-Open No. 4-52257, enclosing the space in which the sink rolls are provided with an openable and closable blocking member is not practical because the snout becomes an obstacle and the installation space is reduced. It is difficult to secure the top dross floating on the bath surface, and it is extremely difficult to remove and collect the top dross.

In the case of the method proposed in Japanese Patent Application Laid-Open No. 55-128569, the bottom dross can be guided into the reaction tank by the inclined bottom surface of the plating tank, but the bottom dross at the bottom of the partition wall which is open remains. Since the bottom dross stirred in the reaction tank enters the plating tank through the opening and the opening above the partition wall, there is a problem that the dross adhesion preventing effect is insufficient.

[0014]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and in a continuous hot-dip metal plating, dross in a plating bath is effectively removed by a simple apparatus, and dross is removed. It is an object of the present invention to provide a method for removing dross in a hot-dip metal plating bath and a hot-dip metal plating apparatus, which can easily recover the molten metal and have excellent maintainability of the apparatus.

[0015]

According to a first aspect of the present invention, a steel strip is continuously intruded into a plating bath 1 which is a molten metal, and after turning around a sink roll 3 in the bath, the direction is changed and a plating bath 1 solution is formed. A dross removing method in a molten metal plating bath using a dross removing tank 10 in a molten metal plating in which plating is continuously performed by being pulled up from a surface, wherein the dross removing tank 10 includes a plating solution flowing into the tank. A dross removal tank 10 having an inlet 11, a plurality of baffles 13 and 14 for dross specific gravity separation provided in the tank and having a plate surface arranged vertically, and a plating solution outlet 15 from the inside of the tank. The dross removing tank 10 is immersed in the plating bath 1 and the plating solution is applied to the sink roll 3 in the bath.
The flow F of the plating solution generated by the rotation of the plating solution is introduced into the dross removing tank 10 from the plating solution inlet 11 as a driving force, and passes below or above each of the plurality of baffle plates 13 and 14 to form a plating solution. A dross removal method for a molten metal plating bath, comprising dross in a solution is separated into specific gravity and then recirculated through the plating solution outlet 15 into the plating bath 1.

In the first aspect, the dross removing tank 10 is connected to the plating solution inlet 11 of the dross removing tank 10.
It is preferable to attach a movable rectifying plate 12 for adjusting the amount of plating solution flowing into the inside, and adjust the amount of plating solution flowing into the dross removing tank 10 by the movable rectifying plate 12 (a preferred embodiment of the first invention). A second invention is to provide a plating pot 2 for continuously intruding a steel strip into a plating bath 1 which is a molten metal to apply a molten metal plating, and to change the direction of the steel strip and pull it upward from a liquid level of the plating bath 1. Bath roll 3 and a dross removing tank 10 for removing dross from the hot-dip metal plating bath.
A dipping removal tank 10, a plating solution inflow port 11 into the tank, and a movable for adjusting a plating solution inflow amount into a tank provided at the plating solution inflow port 11. Rectifying plate 12, and a plurality of baffle plates 13 and 14 for dross specific gravity separation provided in the tank and having plate surfaces arranged in the vertical direction.
And a dross removing tank having a plating solution outlet 15 from inside the tank
10, the dross removing tank 10 is immersed in the plating bath 1, and the plating solution inlet 11 is connected to the plating solution outlet 15 by the rotation of the sink roll 3 in the bath. This is a hot-dip metal plating apparatus that is arranged on the upstream side.

In the second aspect of the present invention, the plating solution outlet 15 is positioned such that the lowermost position of the opening of the plating solution outlet 15 is at least 100 mm above the bottom of the dross removing tank 10. It is preferable to arrange them so as to be located at positions. In the second invention, the plating solution outlet 15 is provided.
The position of the lowermost end of the opening of the plating solution outlet 15 is at a position of 100 mm or more from the bottom of the dross removing tank 10, and the height of the plating solution level in the dross removing tank 10. It is preferable that the height is lower than both of the plating bath 1 and the bath surface outside the dross removing tank 10.

In the second aspect of the present invention, it is preferable that at least one of the plurality of baffle plates 13 and 14 has a removable structure. Further, the second
In the present invention, it is preferable that the dross removing tank 10 is integrated with the plating bath 1 so as to be able to be pulled up from the plating bath 1. In the preferred embodiment of the first invention and the movable baffle 12 in the second invention, the dross removing tank is used.
10 is provided at the plating solution inflow port 11 and has a surface that gives resistance to the flow of the plating solution. The plating solution in the plating bath 1 is introduced into the dross removing tank 10, and the surface tilts and The shape and structure of the movable member are not particularly limited as long as it is movable.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In order to solve the above-mentioned problem, the present inventors used a dross removing tank 30 in which a plurality of baffle plates 32 and 33 were vertically mounted in a tank shown in FIG. The specific gravity separation experiment of dross was performed by changing the flow rate of 31.

FIG. 7 shows the obtained results. FIG.
Is determined from the moving speed of particles in the molten zinc, the area of the cross section inside the tank orthogonal to the flow of the molten zinc, and the density of the molten zinc.
Determined from (1). Dross removal efficiency: η = [(AB) / A] × 100% (1) In the above formula (1), A: particles having a particle diameter of ≧ 20 μm in the molten zinc at the entrance of the dross removal tank. B: The number of particles having a particle diameter of ≧ 20 μm in the molten zinc at the outlet of the dross removing tank. The above number is obtained by sampling the molten zinc at the inlet and the outlet of the dross removing tank and observing the cross section of the solidified zinc. Was measured by

As shown in FIG. 7, according to the above experiment, the molten zinc flow rate of not more than a certain value, that is, in the experimental apparatus described above, the molten zinc flow rate of 0.5 t / min or less was substantially obtained.
It was found that dross removal efficiency η close to 100% was obtained. The present inventors paid attention to the experimental results obtained above and the circulating flow of a plating solution in a plating bath for continuous molten metal plating of a steel strip using a sink roll in a rotating bath.

That is, in a plating bath for continuous hot-dip metal plating of a steel strip using a sink roll in a rotating bath,
The plating solution flows along the rotation direction of the sink roll in the bath,
A circulating flow is formed in the plating bath. The present inventors have arranged the dross removing tank in the plating bath while immersing the dross removing tank in the plating bath, and effectively utilizing the circulating flow described above, and introducing the molten metal into the dross removing tank so that the dross removing tank is not used in the plating bath without using a pump. We thought that dross could be separated by specific gravity.

For this reason, an experiment was conducted by disposing a dross removing tank utilizing a circulating flow of the plating bath in the plating bath. As a result, as shown in Examples described later, it was found that dross in the plating bath was efficiently separated by specific gravity, and it was possible to extremely effectively prevent dross from adhering to the hot-dip coated steel sheet. Reached.

FIG. 1 is a plan view showing one example of a hot-dip metal plating apparatus and a dross removing tank according to the present invention, FIG. 1B is a sectional view taken along arrow AA (vertical side view), and FIG. (Vertical cross section)
Indicated by (c). In FIG. 1, 1 is a molten metal plating bath, 2 is a plating pot, 3 is a sink roll in the bath (: sink roll), 4 is a steel strip, 5 is a snout,
10 is a dross removing tank, 11 is a plating solution inlet into the dross removing tank 10, 12 is a movable rectifying plate for adjusting the amount of plating solution flowing into the dross removing tank 10 provided at the plating solution inlet 11, 12S Is a rotating shaft of the movable rectifying plate 12, 13 and 14 are baffles for separating dross specific gravity in the plating solution whose plate surfaces are arranged vertically, 15 is a plating solution outlet from the dross removing tank 10, and F plating solution flow, f is the flow direction of the plating solution, f ₁ is the transport direction of the steel strip (sheet passing direction), f ₃ is the uppermost opening in the rotational direction, h is the plating solution outlet 15 of the movable current plate 12 The height of the lower end portion with respect to the bottom of the dross removing tank 10 and the angle θ indicate the horizontal angle of the movable rectifying plate 12 with respect to the plating solution inlet 11 (hereinafter also referred to as rectifying plate angle).

In the molten metal plating apparatus shown in FIG. 1, a dross removing tank 10 for removing dross in the molten metal plating bath is immersed in the plating bath 1. Further, as the dross removal tank 10, a plating solution inflow port 11 into the tank,
A movable rectifying plate 12 for adjusting the inflow amount of a plating solution into a tank provided at a plating solution inlet 11 and a dross specific gravity separation in a plating solution provided in a tank and having a plate surface arranged vertically. And a dross removing tank 10 having a plating solution outlet 15 from the inside of the tank.

In the dross removing tank 10 shown in FIG. 1, the tank wall of the dross removing tank 10 protrudes above the plating bath surface (plating bath liquid surface) without immersing the entire tank in the plating bath. A baffle plate 13 and a baffle plate 14 for dross specific gravity separation are arranged as shown below. That is, in the molten metal plating apparatus shown in FIG. 1, the baffle plate 13 for dross specific gravity separation has an upper end of the plate surface projecting above the liquid surface of the plating solution, and a lower end of the plate surface and the dross removing tank 10. It is arranged so as to form a flow path for plating solution distribution between the bottom of the tank and the bottom of the tank.

The baffle plate 14 for dross specific gravity separation has an upper end portion of the plate surface immersed in the plating solution to form a flow path for plating solution distribution above the upper end portion of the plate surface. The portion is arranged so as to reach the bottom of the dross removing tank 10. Also, both the baffle 13 and baffle 14 for dross specific gravity separation are:
The lower end of the baffle plate 13 is disposed at a position lower than the upper end of the baffle plate 14.

As a result, when the plating solution passes below or above each of the baffles 13 and 14 disposed in the dross removing tank 10, the plating solution flows downward and upward in the dross removing tank 10. The dross having a low specific gravity in the plating solution floats on the surface of the plating solution in the dross removing tank 10, and the dross having a high specific gravity in the plating solution deposits on the bottom of the dross removing tank 10. Then, dross in the plating solution is separated by specific gravity.

In the molten metal plating apparatus shown in FIG. 1, a movable rectifying plate 12 for adjusting the flow rate of a plating solution into a dross removing tank 10 is arranged so that the plate surface is vertically oriented. , current plate, and has a rotatable structure in a horizontal direction (direction f ₃₎ around the rotation axis 12S of the movable current plate 12. As a result, the flow of the plating solution is subjected to resistance by the movable rectifying plate 12, and the movable rectifying plate 12
The opening angle of the plating solution inlet 11 into the dross removing tank 10 is adjusted by adjusting the horizontal angle θ of the The inflow can be adjusted.

The movable rectifying plate 12 in the present invention has a surface which is provided at the plating solution inlet 11 of the dross removing tank 10 for the above-mentioned purpose and gives resistance to the flow of the plating solution. The plating solution in bath 1 is removed from dross removal tank 10
The shape and structure of the movable member are not particularly limited as long as the movable member is capable of being tilted and / or moved while being introduced into the inside.

Next, FIG. 2 is a perspective view showing the hot-dip metal plating apparatus shown in FIG. In FIG. 2, reference numeral 16 denotes a suspension member attached to the dross removing tank 10 so that the dross removing tank 10 can be lifted out of the plating bath as a whole (at the time of maintenance) during maintenance of the dross removing tank 10. It shows the same contents as FIG.

According to the molten metal plating apparatus of the present invention shown in FIGS. 1 and 2 described above, the plating solution is supplied to the dross removing tank 10 by using the plating solution flow F generated by the rotation of the sink roll 3 in the bath as a driving force. The dross in the plating solution is introduced into the dross removing tank 10 from the plating solution inflow port 11 and passed under or above each of the plurality of baffle plates 13 and 14, and the dross in the plating solution is separated by specific gravity. From the plating bath 1.

As shown in FIG. 3, in the present invention, in order to more effectively use the flow F of the plating solution, a resistance plate 20 for the plating solution flow is provided in the plating pot 2. Is also good. This is because the resistance plate 20 described above increases the flow resistance of the plating solution at the location where the resistance plate 20 is provided, and increases the inflow amount (flow speed) of the plating solution into the dross removing tank 10.

The above-described resistance plate 20 is not limited to the resistance plate 20 attached to the side wall of the plating pot shown in FIG. It is sufficient that the resistance plate 20 is mounted at a position where the inflow amount (inflow speed) of the plating solution can be increased. According to the molten metal plating apparatus of the present invention, dross having a high specific gravity
Not only does the sediment settle down at the bottom of the dross tank, but also the dross with a low specific gravity can be removed from the dross removal tank 10 because the dross with a low specific gravity can be opened to the atmosphere or a space can be formed above it. Floats and stays on the plating solution level in the tank of tank 10,
The floating dross is prevented from being caught in the plating solution again.

As a result, according to the present invention, dross in a plating bath can be effectively removed in continuous hot-dip metal plating. Further, according to the present invention, a pump and a piping are unnecessary, and maintenance for clogging or breakage of the pump and the piping by zinc or dross is not required, and a continuous hot-dip metal plating apparatus excellent in maintainability can be achieved.

In the present invention, the dross removing tank 10
It is preferable that the plating solution outlet 15 is arranged such that the position of the lowermost end of the opening of the plating solution outlet 15 is at a height of 100 mm or more from the bottom of the dross removing tank 10. this is,
By arranging the plating solution outlet 15 so as to satisfy the above conditions, it is possible to prevent dross settled at the bottom of the dross removing tank 10 from flowing out to the plating bath outside the tank.

In the present invention, the dross removing tank 10
So that the outflow of the plating solution from the plating solution outlet 15 into the plating bath 1 outside the tank is not hindered, the plating solution outlet 15 is positioned at the lowermost position of the opening of the plating solution outlet 15 in the dross removing tank.
10 at a height of 100 mm or more from the bottom of the tank, and the height of the plating solution level in the dross removal tank 10 and the dross removal tank
It is preferable to arrange so as to be at a position lower than both of the heights of the plating bath 1 and the bath surface outside the 10 tanks.

Further, in the present invention, it is preferable that at least one of the plurality of baffle plates 13 and 14 is configured to be removable. FIG. 4 shows an example of the above-described hot-dip metal plating apparatus in a longitudinal sectional view taken along the line BB in FIG. In FIG. 4, reference numerals 17a and 18a denote support members for holding the baffle plate 13 and the baffle plate 14 from both sides, respectively.
Reference numeral 18b denotes a support member for supporting each of the baffle plates 13 and 14 at the lower end of the baffle plate, and the other reference numerals indicate the same contents as in FIGS.

That is, in the hot-dip metal plating apparatus shown in FIG. 4, the baffle plate 13 and the baffle plate
14 can be pulled up and removed. In the present invention, as illustrated in FIG. 4, a plurality of baffle plates 13 and 14 are provided.
By making at least one of them removable, even during operation of the hot-dip metal plating apparatus, the baffle plate is removed, and the tank bottom dross deposited on the tank bottom in the dross removing tank 10 is easily scraped and collected. It becomes possible.

When the dross at the bottom of the tank is scraped out and collected during the operation of the molten metal plating apparatus, the movable rectifying plate with respect to the plating solution inlet 11 of the dross removing tank 10 is used.
The plating solution inlet 11 is closed by setting the horizontal angle θ of the 12 (: rectifying plate angle) to 0 degree, and the flow of the plating solution in the dross removing tank 10 is stopped. The dross and floating dross in the dross removing tank 10 can be prevented from flowing into the plating bath outside the tank.

Further, in the present invention, as shown in FIGS. 2 and 4, a suspension member 16 and the like are attached to the dross removing tank 10, and the dross removing tank 10 can be lifted up from the plating bath 1 as a whole (entirely). It is preferable to have a structure. This is because the dross removing tank 10 has the above-described structure,
This is because the dross removing tank 10 can be easily maintained and repaired by pulling up the plating bath 1 from the plating bath 1 as a whole (as a whole), and the maintenance and repairing time can be shortened.

Further, by making the dross removing tank 10 having the above-described structure, in the case of minor maintenance and repair, the dross removing tank 10 is integrated (total) even during operation of the molten metal plating apparatus. , And can perform maintenance and repair. Furthermore, according to the present invention, since the dross removing tank 10 is immersed in the plating bath 1, the amount of heat dissipated when the dross removing tank is provided outside the plating bath can be greatly reduced, and there is an effect that energy saving can be achieved. .

Further, according to the present invention, since the dross removing tank 10 is immersed in the plating bath 1, there is no problem of leakage of the plating solution from the dross removing tank and no safety problem. Although the present invention has been described above, the molten metal of the hot-dip metal plating in the present invention is not limited to molten zinc, and the molten metal containing zinc as a main component (zinc-aluminum: Zn-Al
), Aluminum-based melting (aluminium-zinc: Al-Zn)
) Can be used.

That is, the present invention also provides a method for removing dross from a molten metal plating bath and a molten metal plating apparatus in molten metal plating using a molten metal other than molten zinc, based on the functions and effects of the present invention. It can be suitably used.

[0045]

EXAMPLES Hereinafter, the present invention and the effects obtained by the present invention will be described more specifically based on examples. Continuous hot-dip galvanizing was performed on a steel strip using the hot-dip metal plating apparatus of the present invention shown in FIGS. 1 and 2, and the state of dross adhesion to the steel sheet was examined.

Further, continuous hot-dip galvanizing is performed on a steel strip using the conventional hot-dip metal plating apparatus shown in FIG. 8, and the state of dross adhesion of the steel sheet obtained by the hot-dip metal plating apparatus of the present invention and the conventional hot-dip Comparison with the dross adhesion state of the steel sheet obtained by the plating apparatus was performed. In the molten metal plating apparatus shown in FIGS. 1 and 2, the position of the lowermost end of the opening of the plating solution outlet 15 was set at a height of 500 mm from the bottom of the dross removing tank 10.

That is, in FIG. 1B and FIG.
00 mm. (Embodiment 1) Using the molten metal plating apparatus of the present invention shown in FIGS.
The relationship between the horizontal angle θ of the movable straightening plate 12 (: straightening plate angle) and the flow rate of the circulating molten zinc in the dross removing tank 10 was investigated in the same manner as in FIG.

FIG. 5 shows the obtained results. FIG.
The circulating molten zinc flow rate shown in (1) is shown as a relative value, with the circulating molten zinc flow rate in the dross removing tank 10 before the movable rectifying plate 12 is attached as 1. As shown in FIG. 5, the current plate angle: θ
= 90 degrees, the maximum circulating molten zinc flow rate was obtained. In the following experiments, the rectifying plate angle: θ was set to 90 degrees.

Next, the steel strip was subjected to continuous hot-dip galvanizing under the following conditions, and the quality of the obtained hot-dip galvanized steel sheet was evaluated by the following test method. (Conditions of hot-dip galvanizing :) Steel strip: cold-rolled steel sheet, sheet thickness 0.4 to 1.6 mm × sheet width 750 to 1850 mm Hot-dip galvanizing bath temperature: 470 to 480 ° C Hot-dip galvanizing bath Al concentration: 0.13 to 0.15% Passing speed: 30 to 150 m / min (Test method for hot-dip galvanized steel sheet :) The following test was performed on the obtained 50 coils of the steel strip to evaluate the quality.

Defect rate due to dross adhesion of hot-dip galvanized steel sheet: A hot-dip galvanized steel sheet is pressed, and a product in which the number of dross adhering to the steel sheet after press working is 2 pieces / m ² or more is defective, and is defective in all products. The product incidence was defined as the defect rate. Maximum particle size of attached dross: The attached dross on the surface of the hot-dip galvanized steel sheet was observed with a microscope, the maximum particle size of the attached dross of each coil was determined, and the average maximum particle size of the attached dross for all the coils was determined.

Table 1 shows the test results obtained. (Comparative Example) Continuous hot-dip galvanizing of a steel strip was performed under the same conditions as in Example 1 except that the conventional hot-dip galvanizing apparatus shown in FIG. 8 was used. Evaluation was performed in the same manner as in Example 1 described above.

Table 1 shows the test results obtained. As shown in Table 1 by comparison between Example 1 and Comparative Example,
According to the present invention, the dross in the plating bath is efficiently separated by specific gravity by the action and effect of the circulating flow of the plating solution by the dross removing tank and the sink roll in the bath according to the present invention,
It has been found that dross adhesion to the hot-dip metal-plated steel sheet can be extremely effectively prevented.

(Embodiment 2) In the hot-dip metal plating apparatus shown in FIGS. 1 and 2 used in Embodiment 1 described above, a support member for holding the baffle plates 13 and 14 shown in FIG. 4 from both sides. Support members 17b and 18b for supporting the baffles 13a and 14 and the baffle plates 13 and 14 at the lower ends of the baffle plates were attached.

In this embodiment, the continuous hot-dip galvanizing of the steel strip is carried out in the same manner and under the same conditions as in the first embodiment, and the hot-dip galvanizing of the present invention is carried out by the following methods (1) and (2). The difficulty of maintenance of the equipment was evaluated. (1) Collection of accumulated dross in the dross removal tank: dross removal tank
When the bottom dross and floating dross accumulate in 10,
The dross was scraped up and collected while the device was operating.

That is, when the dross accumulated in the dross removing tank 10, the rectifying plate angle: θ of the movable rectifying plate 12 was set to 0 degree, and the plating solution inlet 11 was closed. Next, the baffle plate 13 and the baffle plate 14 were lifted up and removed, and the tank bottom dross and the floating dross were scraped up and collected. As a result, both the dross at the bottom of the tank and the floating dross in the dross removing tank 10 can be easily collected, and the amount of dross adhered to the steel plate manufactured at the time of collection is as small as the amount of dross before and after the collection. I understood.

(2) Maintenance and repair of the dross removing tank: Dross deposits in the recesses of the support members 17b and 18b of the baffle plates 13 and 14 in the dross removing tank 10, which hinders removal and attachment of the baffle plates 13 and 14. When this occurred, a chain was hung on the suspension member 16 of the dross removing tank 10, and the dross removing tank 10 was pulled up from the plating bath 1 as a whole (entire) using a hoisting machine.

Next, dross deposited in the recesses of the support members 17b and 18b was removed. After the dross removal, the dross removal tank 10 was immersed in the plating bath 1. As a result, it was found that the dross removing tank 10 can be maintained and repaired in a short time and easily even during the operation of the molten metal plating apparatus.

[0058]

[Table 1]

[0059]

According to the present invention, in continuous hot metal plating, dross in a plating bath can be effectively removed with an extremely simple apparatus, dross recovery operation is easy, and the maintainability of the apparatus is excellent. It has become possible to provide a method for removing dross from a molten metal plating bath and a molten metal plating apparatus.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view showing one example of a hot-dip metal plating apparatus and a dross removing tank according to the present invention, FIG. 1B is a sectional view taken along arrow AA (vertical side view), FIG. (C).

FIG. 2 is a perspective view showing one example of a hot-dip metal plating apparatus of the present invention.

FIG. 3 is a plan view showing one example of a hot-dip metal plating apparatus and a dross removing tank according to the present invention.

FIG. 4 is a view showing one example of a hot-dip metal plating apparatus of the present invention.
It is a BB section longitudinal cross-sectional view.

FIG. 5 is a graph showing a relationship between a flow straightening plate angle θ and a flow rate of circulating molten zinc in a dross removing tank.

FIG. 6 is a vertical sectional view showing a dross removing tank.

FIG. 7 is a graph showing a relationship between a flow rate of molten zinc in a dross removing tank and a dross removing efficiency η.

FIG. 8 is a longitudinal sectional view showing a conventional hot-dip metal plating apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Plating bath (molten metal) 2 Pot for plating 3 Sink roll in bath (: sink roll) 4 Steel strip 5 Snout 10 Dross removal tank 11 Plating solution inlet into dross removal tank 12 Plating solution into dross removal tank Movable baffle plate for adjusting inflow amount 12S Rotating shaft of movable baffle plate 13, 14 Baffle plate for separating dross specific gravity in plating solution 15 Plating solution outlet from inside dross removal tank 16 Dross removal tank suspension members 17a, 17b , 18a, 18b Support member for baffle plate 20 Resistance plate F Flow of plating solution f Flow direction of plating solution f ₁ Transport direction of steel strip (passing direction) f ₂ Rotation direction of sink roll in bath f ₃ Moving rectifying plate Rotation direction h Height of the lowermost end of the opening of the plating solution outlet relative to the bottom of the dross removal tank θ Rectifier plate angle

Continued on the front page (72) Inventor Kazunari Adachi 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref.

Claims (6)

[Claims] 1. A steel strip is continuously intruded into a plating bath (1) which is a molten metal, and after turning around a sink roll (3) in the bath, the direction is changed and the plating bath (1) rises above the liquid level. Dross removal tank in hot-dip metal plating for continuous plating by lifting
A method for removing dross in a molten metal plating bath using (10), wherein as the dross removing tank (10), a plating solution inlet (11) into the tank, and a plate surface provided in the tank and having a plate surface is provided. Multiple baffles (13, 14) for vertical dross separation for specific gravity separation
And a dross removing tank (10) having a plating solution outlet (15) from inside the tank, and using the dross removing tank (10) as a plating bath.
(1), and the plating solution is introduced into the dross removing tank (10) from the plating solution inlet (11) with the flow F of the plating solution generated by the rotation of the sink roll (3) in the bath as a driving force. After passing through the lower or upper part of each of the plurality of baffle plates (13, 14) and separating dross in the plating solution by specific gravity, the dross in the plating solution is introduced into the plating bath (1) from the plating solution outlet (15). A method for removing dross from a molten metal plating bath, wherein the dross is recycled. 2. A movable rectifying plate (12) for adjusting the amount of plating solution flowing into the dross removing tank (10) is attached to the plating solution inlet (11) of the dross removing tank (10). 2. The method for removing dross in a molten metal plating bath according to claim 1, wherein the flow rate of the plating solution into the dross removing tank (10) is adjusted by the current plate (12). 3. A plating pot for continuously intruding a steel strip into a plating bath (1), which is a molten metal, to apply a molten metal plating.
(2), a plating bath (1) a sink roll in the bath for turning the steel strip up above the liquid level (3), and a dross removal tank (10) for removing dross in the molten metal plating bath. )
Wherein the dross removing tank (10) includes a plating solution inlet (11) into the tank, and a plating solution into a tank provided at the plating solution inlet (11). A movable rectifying plate (12) for adjusting the inflow amount, and a plurality of baffle plates for dross specific gravity separation provided in the tank and having the plate surface arranged vertically
(13, 14) and a dross removing tank (10) having a plating solution outlet (15) from the tank, the dross removing tank (10) is immersed in a plating bath (1), and the plating is performed. Liquid inlet (11)
The sink roll in the bath with respect to the plating solution outlet (15)
(3) A hot-dip metal plating apparatus, which is disposed upstream of a flow of a plating solution generated by the rotation of (3). 4. A dross removing tank (10), wherein the plating solution outlet (15) is positioned at the lowermost position of the opening of the plating solution outlet (15).
4. The hot-dip metal plating apparatus according to claim 3, wherein the apparatus is arranged so as to be at a height of 100 mm or more from the bottom of the tank. 5. The hot-dip metal plating apparatus according to claim 3, wherein at least one of the plurality of baffle plates (13, 14) has a removable structure. 6. The molten metal plating apparatus according to claim 3, wherein said dross removing tank (10) is integrated with said dross removing tank (10) so as to be able to be lifted from said plating bath (1).