JPH07252620A - Continuous hot-dip metal coating method - Google Patents

Abstract

PURPOSE:To improve coating quality by providing a snout with a cooling mechanism in the part thereof to be immersed into a coating bath and solidifying the coating bath in the snout exclusive of the moving passage of a metallic strip, thereby lessening the generation of the metal vapor of the coating bath and dross generated in the snout and preventing infiltration of the dross suspended in the coating bath by the solidified layer formed therein. CONSTITUTION:This coating method comprises continuously treating the metallic strip 6 from an annealing furnace 7 by passing the metallic strip through the snout 1 which is connected at one end to the annealing furnace 7 and is immersed at the other end into the coating bath 4 in a coating tank 3. The part 1a of the snout 1 to be immersed into the coating bath is provided with the cooling mechanism, for example, a conduit 2 for cooling over the entire part thereof and a liquid refrigerant is circulated therein, by which the solidified layer 5 is formed on the coating bath 4 on the inner side of this part. The thickness of the solidified layer 5 is cooled in accordance with a preset relation between a cooling capacity and the thickness of solidification, by which the molten metal exclusive of the part for passage of the steel strip 6 is solidified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention continuously introduces a metal strip into a metal plating bath in a plating tank through a snout in a hot-dip galvanizing line, and continuously performs a hot metal plating treatment on the metal strip. The present invention relates to a method for producing a high-quality hot-dip galvanized metal strip without causing defects due to dross in a snout when applied.

[0002]

2. Description of the Related Art In a hot-dip galvanizing line in which an annealing furnace is installed in a line, an annealed metal strip is placed in the metal plating bath in a plating tank from the annealing furnace and one end thereof is annealed. It is connected to a furnace and the other end thereof is continuously introduced through a snout which is immersed in a plating bath in the plating bath, and the plating bath in the plating bath continuously performs hot metal plating treatment on the metal strip. Is given.

In the above line, the snout is provided in order to prevent the surface oxidation of the metal strip that enters the plating bath, and the plating inside the snout immersed in the plating bath is performed. The bath has penetrated and the part of the snout that has not been immersed in the plating bath is full of reducing gas.

That is, the atmosphere gas mainly containing nitrogen and hydrogen is constantly supplied into the annealing furnace and the snout during operation. The atmospheric gas supplied in the snout is
The side of the plating bath containing the metal strip is kept in a strongly reducing atmosphere, and the surface of the metal strip is cleaned while flowing into the annealing furnace to keep the furnace pressure in the annealing furnace positive.

By the way, for example, for steel strips,
When performing the galvanizing process of zinc-containing metal, the bath is operated at a plating bath temperature of 420 ° C or higher, which is the solidification temperature of zinc. That is, as is clear from the graph showing the relationship between zinc temperature and vapor pressure in FIG. 13, the boiling point A of zinc is 910
Since it is ℃, at the point A, that is, at a temperature of 910 ℃ or higher, all zinc becomes vapor. Also, the melting point B of zinc is about 420 ° C.
And the temperature between points A and B, that is, about 420-910 ° C.
At temperatures in the range of, zinc is in the liquid-vapor mixture, and at point B, a temperature below about 420 ° C, zinc is in the solid-vapor mixture.

When the steel strip is subjected to a general hot dip galvanizing treatment, the galvanizing bath temperature is set to C in FIG.
Operate at about 450 ° C indicated by dots. Since the operating temperature C is between the points A and B, a large amount of zinc vapor is generated during operation, and the generated zinc vapor passes through the snout together with the atmospheric gas supplied into the snout. Flow into the annealing furnace. As a result, the following problems occur.

When the zinc vapor adheres to and is condensed on the deflector rolls and particularly on the transport rolls in the cooling zone, it causes surface flaws on the steel strip that contacts the rolls. If the condensed zinc powder adheres to the impeller of the cooling fan in the cooling zone, imbalance occurs in the fan and vibrations occur. As a result, the life of the bearing and impeller of the cooling fan is shortened. When zinc vapor adheres to and condenses on the heating element of the electric heater provided in the annealing furnace, the amount of heat generated changes due to the change in the resistance value of the heating element, which in turn damages the heating element. When zinc vapor adheres to the fins and tubes of the gas cooler in the cooling zone and condenses, it causes heat transfer resistance of the cooler, resulting in a decrease in heat exchange capacity.

In order to prevent the above-mentioned problems, it is necessary to remove the zinc powder adhering to each of the above equipments in the annealing furnace, but for that purpose, the operation of the line must be temporarily stopped, Therefore, the operation efficiency is lowered, and much work is required for the removal work.

On the other hand, a small amount of oxygen and water contained in the atmospheric gas supplied into the snout reacts with zinc in the plating bath in the snout, and zinc oxide (in the plating bath in the snout) Dross composed mainly of ZnO ₂ ) is generated.

Further, in the plating bath, iron stripped from the steel strip passing through the bath and the rolls and roll supporting members immersed in the plating bath reacts with zinc in the plating bath to produce iron-zinc (FeZn ₇ ) as the main component is generated, and this dross adheres to the galvanized layer surface of the steel strip, significantly deteriorating the surface quality of the steel strip,
The adhered hard dross becomes a starting point, causing problems such as press cracking during press molding.

As a means for preventing the adhesion of dross to the above-described hot dip galvanized steel strip, conventionally, aluminum is added to the plating bath, and the reaction between dross and aluminum causes an iron-aluminum alloy whose specific gravity is lower than that of zinc. (Fe ₂ Al ₅₎ to generate, and has been the practice to which was collected by floating on the surface of the plating bath removed.

However, the above-described method cannot remove the dross containing zinc oxide as the main component and the dross containing the iron-aluminum alloy as the main component, which are floated on the surface of the plating bath in the snout. Therefore, the dross adheres to the surface of the steel strip introduced into the plating bath, which causes a problem of deteriorating the plating adhesion.

As means for solving the above problems, the following proposals have been made. Japanese Patent Publication No. 53-35858: As shown in FIG. 14, an atmosphere gas is supplied into the snout 1 through a gas supply pipe 10.
Then, the atmospheric gas containing zinc vapor generated from the plating bath 4 in the plating tank 3 is taken out from the snout 1 through the conduit 11, the zinc in the gas is removed by the zinc removing device 12, and then returned to the annealing furnace 7. In this way, zinc vapor is prevented from flowing from the snout 1 into the annealing furnace 7 together with the atmospheric gas (hereinafter referred to as prior art 1).

Japanese Unexamined Patent Publication No. 51-56738: As shown in FIG. 15, the surface of the plating bath 4 in the snout 1 is provided with a roll 13 that rotates in the opposite direction to the traveling direction of the steel strip 6, and the roll 13 rotates. This prevents dross on the surface of the plating bath in the plating tank 3 from coming into contact with and adhering to the steel strip 6 (hereinafter referred to as prior art 2).

Japanese Utility Model Publication No. 57-38362: As shown in FIG. 16, a nozzle provided on the surface of the plating bath 4 in the snout 1.
Atmosphere gas is injected from 14 to prevent the dross on the surface of the plating bath 4 from contacting and adhering to the steel strip 6 (hereinafter referred to as prior art 3).

Japanese Patent Laid-Open No. 63-277746: As shown in FIG. 17, a cooling conduit 15 is provided directly above the surface of the plating bath 4 in the snout 1, and is locally cooled by a refrigerant flowing in the cooling conduit 15. The metal vapor generated from the plating bath 4 in the snout 1 is condensed and dropped into the plating bath 4 to prevent dross generation in the snout 1 (hereinafter referred to as prior art 4).

Japanese Patent Laid-Open No. 1-294851: As shown in FIG. 18, the surface of the plating bath 4 in the snout 1 is covered with an evaporation preventive material 16
By coating with, the evaporation of the molten metal from the surface of the plating bath 4 is prevented, and the generation of dross in the snout 1 is prevented (hereinafter referred to as prior art 5).

Japanese Utility Model Laid-Open No. 2-14355: As shown in FIG. 19, the dross generated on the surface of the plating bath 4 in the snout 1 is provided at the lower end of the snout 1 by a rake 17 that can move horizontally. By pushing it into the reservoir chamber 18,
It prevents the dross from contacting and adhering to the steel strip 6 (hereinafter referred to as prior art 6).

[0019]

However, the above-mentioned respective prior arts have the following problems. That is, as in the prior art 1, supplying the atmosphere gas into the snout 1,
Then, the means for taking out the atmospheric gas containing zinc vapor generated from the plating bath 4 in the snout 1 through the conduit 11 requires complicated and large-scale equipment, resulting in a high equipment cost and repair cost. .

Reverse rotating roll 13 as in prior art 2
The means for preventing the dross on the plating bath surface in the snout 1 from contacting the steel strip 6 by means of the roll 13
Due to the fluctuation of the liquid surface caused by, the liquid surface of the plating bath in the snout 1 becomes wider than the stationary state, and the boundary layer between the liquid surface and the gas in the snout is destroyed by the rotation of the roll 13,
On the contrary, the generation of zinc vapor from the liquid surface is promoted.

As in the prior art 3, the means for injecting the atmospheric gas from the nozzle 14 provided on the surface of the plating bath 4 to prevent the dross on the surface of the plating bath from contacting and adhering to the steel strip 6 is as described above. Similarly, the destruction of the boundary layer between the liquid surface and the gas in the snout promotes the generation of zinc vapor from the liquid surface, and the large-density dross floating on the liquid surface is moved by the small-density gas body. In order to do so, it is necessary to inject the gas at a high pressure and at a high speed, which causes a problem that the running cost increases.

Locally cooling the surface of the plating bath 4 just like the prior art 4 with the refrigerant flowing in the cooling conduit 15,
The means for condensing the metal vapor cannot prevent the defects caused by the floating dross on the surface of the plating bath in the snout 1, especially the iron-aluminum alloy dross, and another equipment is required to prevent this. As a result, the equipment near the snout becomes complicated and the repair cost increases.

Further, in the arrangement of the local cooling device, if the space between the local cooling device and the metal strip is too wide, the local cooling effect is reduced, while if the space is too narrow, the metal strip contacts the local cooling device. As a result, the surface of the strip is easily scratched, and in extreme cases, the strip breaks, and the production must be stopped, which causes a problem that a lot of time is required for the recovery work.

As in the prior art 5, the means for coating the surface of the plating bath in the snout 1 with the evaporation preventing material 16 to prevent the molten metal from evaporating from the surface of the plating bath is the surface of the plating bath in the snout 1. The iron-aluminum alloy dross that floats on the surface is deposited between the evaporation preventing material and the liquid surface of the molten metal and adheres to the surface of the steel strip 6 immediately before being immersed in the plating bath, resulting in deterioration of the plating adhesion. The problem arises.

A device for pushing dross on the surface of the plating bath into a reservoir chamber 18 at the lower end of the snout 1 by a rake 17 which can be moved horizontally as in the prior art 6 prevents evaporation of metal vapor from the surface of the plating bath. Can not do it. Further, when the dross is pushed by the rake 17, unless the gap between the rake 17 and the steel strip 6 is made small, the dross in the vicinity of the steel strip 6 cannot be removed. When the steel strip 6 comes into contact with the steel strip 6, a flaw is generated on the surface of the steel strip 6.

Therefore, an object of the present invention is to solve the above-mentioned problems, and in a hot metal plating line, a metal strip is continuously introduced into a metal plating bath in a plating tank through a snout, and the metal in the plating tank is continuously introduced. When continuously performing hot metal plating treatment on the metal strip by the plating bath, the metal vapor generated from the plating bath surface inside the snout flows into the annealing furnace through the snout together with the atmospheric gas, and the equipment inside the annealing furnace To prevent the trouble from occurring, and the dross generated on the surface of the metal plating bath in the snout adheres to the surface of the metal strip,
It is an object of the present invention to provide a method of deteriorating the surface quality of a strip and preventing the occurrence of various defects, and thereby producing a hot-dip galvanized metal strip of excellent quality.

[0027]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems. As a result, if the liquid surface portion of the plating bath in the snout immersed in the plating bath is solidified, no metal vapor is generated from the plating bath surface in the snout, and the plating bath in the snout is It was found that impurities in the plating bath can be prevented from entering the molten metal in the snout by solidifying the tip portion of the snout.

The present invention has been made on the basis of the above-mentioned findings. In the invention according to claim 1, one end of the metal strip is annealed in a metal plating bath in a plating tank. In a continuous hot metal plating method, which is connected to a furnace and whose other end is continuously introduced through a snout which is immersed in a plating bath in the plating tank, and which performs a hot metal plating treatment on the metal strip, It is characterized in that the plating bath in the snout, which is immersed therein, is solidified by opening the moving passage of the metal strip by cooling.

According to a second aspect of the present invention, the liquid level portion of the plating bath in the snout immersed in the plating bath and the portion along the moving passage of the metal strip are
It is characterized in that the moving path of the metal strip is opened and solidified.

In addition to the above, only the liquid surface portion of the plating bath in the snout may be solidified by opening the movement passage of the metal strip, and only the snout tip portion of the plating bath in the snout may be moved. May be opened and solidified, or only the liquid surface portion of the plating bath and the tip portion of the snout in the snout may be solidified by opening the moving passage of the metal strip. Further, the liquid surface portion of the plating bath in the snout, the lengthwise intermediate portion of the snout tip portion and the plating bath immersion portion may be solidified by opening the moving passage of the metal strip, and the liquid of the plating bath in the snout may be solidified. The movement path of the metal strip may be continuously solidified so as to gradually reduce the horizontal cross-sectional area from the surface portion toward the tip of the snout.

The cooling for solidifying the plating bath in the snout described above is preferably performed only when the metal strip travels in the snout, and it is preferable to stop the cooling when the snout is moved up and down.

[0032]

According to the method of the present invention, the liquid level portion of the plating bath in the snout which is immersed in the plating bath is solidified by cooling except the portion where the metal strip passes, whereby the liquid level of the plating bath in the snout is solidified. The generation of metal vapor from the, and the generation of oxidized dross by the reaction with the gas in the snout can be reduced to the limit, by which, trouble occurrence of equipment in the annealing furnace due to the flow of the metal vapor, and, Dross defects can be prevented.

To solidify the liquid level portion of the plating bath in the snout except for the passing portion of the metal strip, for example, in the case of hot dip galvanizing, it is annealed in an annealing furnace and immersed in the plating bath. The temperature of the metal strip is about 450 ℃
Since the melting point of zinc is higher than 419.5 ° C, it can be easily performed by controlling the cooling of the plating bath liquid surface portion, which causes flaws on the metal strip surface when passing through the plating bath liquid surface. Is prevented.

The snout tip portion of the plating bath in the snout immersed in the plating bath is solidified by cooling except the portion through which the metal strip passes, so that the dross floating in the plating bath is generated by the solidified layer produced. The intrusion of the snout into the snout is prevented to the utmost
The amount of dross deposited in the snout is greatly reduced, and the occurrence of dross defects is prevented. The plating bath at the tip of the snout can be solidified except for the passing portion of the metal strip as described above.

In addition to the liquid surface portion of the plating bath in the snout and the tip portion of the snout, an intermediate portion in the lengthwise direction of the plating bath immersion portion is solidified by opening a moving path of the metal strip to obtain the length of the plating bath immersion portion. By forming the diaphragm plate-shaped solidified layer at the intermediate portion in the direction, it is possible to more reliably prevent the dross floating in the zinc plating bath from entering the snout.

Further, the liquid surface portion of the plating bath in the snout,
And, the part along the moving path of the metal strip is solidified by opening the moving path of the metal strip, or the horizontal cross-sectional area of the plating bath in the snout gradually decreases from the liquid surface part toward the snout tip. As described above, by continuously surrounding and solidifying the moving passage of the metal strip, the generation of zinc vapor in the snout is reduced and the solidified layer near the strip passage portion is surrounded by the upper solidified layer in the snout. Also, convection occurs in the hot dip galvanizing bath portion, and floating dross in the galvanizing bath gathers in this portion. Therefore, when pulling up the snout 1,
Floating dross can be easily collected.

Cooling for solidifying the plating bath in the snout immersed in the plating bath is performed only when the metal strip travels in the snout, so that wasteful cooling is not performed and energy is saved. Impurities in the plating bath are prevented from entering the molten metal in the snout, and vapor generation of the molten metal is prevented.

The cooling for solidifying the plating bath in the snout immersed in the plating bath is stopped when the snout is moved up and down, and the plating bath in the snout is not solidified, so that the snout can be easily moved up and down. It can be carried out.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings with respect to an example in which a hot-dip galvanizing process is applied to a steel strip. FIG. 1 is an explanatory diagram showing a first embodiment of the present invention. As shown in FIG. 1, between the annealing furnace 7 and the plating tank 3, one end is connected to the exit side of the annealing furnace 7, and the other end is immersed in the zinc plating bath 4 in the plating tank 3. A cylindrical snout 1 is provided. A reducing gas is blown into the snout 1 from the gas supply mechanism 8, and the reducing gas maintains the reducing gas atmosphere in the snout 1.

The steel strip 6 continuously annealed in the annealing furnace 7 is introduced into the plating bath 4 in the plating tank 3 through the inside of the snout 1, and is inverted upward by the sink roll 9 to be inverted in the plating bath 4. Move upward from. During this period, the steel strip 6 is subjected to hot dip galvanizing.

As a cooling mechanism, for example, a cooling conduit 2 is provided in the plating bath immersion portion 1a of the snout 1 as a plating bath immersion portion.
It is provided throughout 1a. In the cooling conduit 2, a fluid refrigerant, that is, water, steam, air, nitrogen, argon, CFCs, ammonia, molten salt, liquid metal (for example, mercury), etc. circulate. Therefore, the plating bath 4 penetrating into the plating bath immersion portion 1a of the snout 1 is cooled and solidified by the refrigerant circulating in the cooling conduit 2 to form the solidified layer 5. In this example, water was used as the refrigerant.

The temperature of the steel strip 6 immersed in the zinc plating bath 4 in the plating tank 3 is about the same as that of the zinc plating bath 4 in the plating tank 3 due to the annealing in the annealing furnace 7.
The temperature is 450 ° C, and the zinc plating bath 4 in the plating bath immersion part 1a
The heat of this steel strip 6 will be continuously supplied therein.

Therefore, the cooling capacity is adjusted by adjusting the condition of the refrigerant circulating in the cooling conduit 2, for example, the flow rate and temperature of the refrigerant, or changing the kind of the refrigerant such as water to steam. As a result, the thickness of the solidified layer 5 of the zinc plating bath 4 in the plating bath immersion portion 1a of the snout 1 is
Control is performed based on the graph of FIG. 3 showing the relationship between the cooling capacity and the thickness of the plating bath solidified layer. As a result, as shown in the horizontal sectional view in FIG. 2, the zinc plating bath 4 in the plating bath immersion portion 1a
Can be solidified except for the portion through which the steel strip 6 passes.

As described above, the plating bath liquid surface 4a in the plating bath immersion portion 1a of the snout 1 is solidified except for the portion through which the steel strip 6 passes, so that the area thereof is extremely small. Therefore, the solidified layer 5 significantly reduces the generation of zinc vapor in the snout 1. The tip of the snout of the galvanizing bath 4 in the galvanizing bath dipping portion 1a is solidified except for the portion through which the steel strip 6 passes, so that the solidified layer 5 causes the dross floating in the galvanizing bath 4 to float. Intrusion into the snout 1 is prevented to the utmost limit. As a result, the amount of dross deposited in the snout 1 is significantly reduced, and dross defects that occur in the steel strip 6 can be prevented.

In this example, the molten portion of the galvanizing bath 4 in the snout 1 was about 50 mm from both surfaces of the steel strip 6, and the portion exceeding about 50 mm was the solidified layer 5. This distance of about 50 mm is determined by taking into consideration the width that does not contact the solidified layer 5 even if the steel strip 6 passing through the snout 1 is deformed. As described above, the distance can be easily controlled by adjusting the cooling ability of the refrigerant circulating in the cooling conduit 2.
The cooling capacity may be sequentially changed according to the plate shape to control the thickness of the solidified layer.

Since the temperature of the galvanizing bath in the surface layer of the steel strip 6 is about 450 ° C., segregation of the components of the bath hardly occurs, and a hot dip galvanizing layer is stably formed on the surface of the steel strip 6. You can

The cooling of the plating bath in the snout 1 by the cooling mechanism, that is, the cooling conduit 2, is performed only when the steel strip 6 runs in the snout 1. When the steel strip 6 is not running, convective heat transfer from the plating bath 4 is the only heat source to be supplied, so that the plating bath 4 in the snout 1 is all solidified.

In this embodiment, unless the traveling speed of the steel strip 6 is 30 mpm or more, the cooling mechanism by the cooling conduit 2 does not operate. The plating bath 4 in the snout 1 may be operated with a cooling capacity such that all of the plating bath 4 does not solidify. However, in this embodiment, water is used as the refrigerant, so in such an operation, the inside of the cooling conduit 2 is Water boils at. Therefore, when the traveling speed of the steel strip 6 is less than 30 mpm, the operation of the cooling mechanism is stopped. At the time of restarting, a slight boiling occurs at the beginning of water flow, but since the cooling water discharge port is opened to the atmosphere so that steam does not stay in the cooling conduit 2, internal pressurization due to evaporation occurs. Without it, the equipment will not be destroyed.

When the snout 1 immersed in the plating bath 4 is pulled up for the purpose of terminating the operation or repairing, the supply of the refrigerant into the cooling conduit 2 is stopped and the snout 1 is stopped.
The solidified layer 5 of the plating bath formed inside is melted. Therefore, the load on the lifting device for lifting the snout 1 is reduced, so that the lifting equipment can be simplified and the facility cost can be reduced. When the snout 1 is immersed in the plating bath 4, the lower part of the snout 1 is immersed in the plating bath 4 and then the supply of the refrigerant into the cooling conduit 2 is started.

FIG. 4 is an explanatory view showing the second embodiment of the present invention. In this embodiment, a cooling conduit 2 as a cooling mechanism is provided only in the plating bath liquid surface 4a of the plating bath immersion portion 1a of the snout 1.
Therefore, due to the refrigerant circulating in the cooling conduit 2, only the liquid surface 4a of the plating bath 4 that has penetrated into the plating bath immersion portion 1a is the upper solidified layer excluding the portion through which the steel strip 6 passes.
5a is formed, and the snout 1 is formed by the upper solidified layer 5a.
Generation of zinc vapor in the interior is reduced.

FIG. 5 is an explanatory view showing the third embodiment of the present invention. In this embodiment, a cooling conduit 2 as a cooling mechanism is provided only at the tip 1b of the plating bath immersion portion 1a of the snout 1. Therefore, by the refrigerant circulating in the cooling conduit 2, the lower solidification layer 5b is formed only in the zinc plating bath in the snout tip portion 1b except the portion through which the steel strip 6 passes, and the lower solidification layer 5b is formed. This prevents dross floating in the galvanizing bath from entering the snout 1.

FIG. 6 is an explanatory view showing a fourth embodiment of the present invention. In this embodiment, a cooling conduit 2 as a cooling mechanism is provided at the plating bath liquid surface 4a portion of the plating bath immersion portion 1a of the snout 1 and the snout tip portion 1b. Therefore, an upper solidified layer 5a is formed on the liquid surface 4a of the plating bath 4 penetrating into the plating bath immersion portion 1a by the refrigerant circulating in the cooling conduit 2, and
Add a steel strip 6 to the zinc plating bath inside the snout tip 1b.
As a result of forming the lower solidified layer 5b excluding the portion through which the metal passes, the upper solidified layer 5a and the lower solidified layer 5b generate zinc vapor in the snout 1 and the snout of dross floating in the zinc plating bath. 1 is prevented from entering.

FIG. 7 is an explanatory view showing the fifth embodiment of the present invention. In this embodiment, in addition to the plating bath liquid surface 4a portion of the plating bath dipping portion 1a and the snout tip end portion 1b in the snout 1, a portion along the moving path of the steel strip 6 in the snout 1 serves as a cooling mechanism. A cooling conduit 2 is provided, which is different from the method of the fourth embodiment in that the solidified layer 5c near the strip passage portion is formed in the galvanizing bath near the steel strip passage portion.

FIG. 8 is an explanatory view showing a sixth embodiment of the present invention. In this embodiment, in addition to the plating bath liquid surface 4a of the plating bath immersion portion 1a of the snout 1 and the snout tip portion 1b, a cooling conduit 2 as a cooling mechanism is provided in the inner peripheral portion of the snout 1. This is different from the method of the fourth embodiment in that the inner peripheral solidification layer 5d is formed in the zinc plating bath in the inner peripheral portion of the snout 1.

FIG. 9 is an explanatory view showing the seventh embodiment of the present invention. In this embodiment, in addition to the plating bath liquid surface 4a portion of the plating bath immersion portion 1a and the snout tip portion 1b in the snout 1, the lengthwise intermediate portion of the plating bath immersion portion 1a and the plating bath immersion portion 1a are included. A cooling conduit 2 as a cooling mechanism is provided around the circumference, whereby a diaphragm plate-shaped intermediate portion solidification layer 5e is formed in the lengthwise intermediate portion of the plating bath immersion portion 1a, and the snout 1 The difference from the method of the fourth embodiment is that an inner peripheral solidification layer 5d is formed on the inner periphery. According to this embodiment,
The diaphragm plate-shaped intermediate solidification layer 5e formed at the intermediate portion in the lengthwise direction of the plating bath immersion portion 1a further reliably prevents the dross floating in the zinc plating bath from entering the snout 1. .

FIG. 10 is an explanatory view showing the eighth embodiment of the present invention. In this embodiment, a cooling conduit as a cooling mechanism is provided in the plating bath liquid level 4a portion of the plating bath immersion portion 1a in the snout 1 and in the portion along the moving path of the steel strip 1 in the plating bath immersion portion 1a. Two are provided. Therefore, the upper solidified layer 5a except the portion through which the steel strip 6 passes is formed on the liquid surface 4a of the plating bath 4 penetrating into the plating bath immersed portion 1a, and the steel in the plating bath immersed portion 1a is formed. A solidified layer 5c near the strip passage portion is formed near the strip passage portion.

As a result, the upper solidified layer 5a reduces the generation of zinc vapor in the snout 1, and the molten zinc surrounded by the upper solidified layer 5a and the strip passing portion vicinity solidified layer 5c in the snout 1 is reduced. Convection occurs in the plating bath portion, and floating dross in the plating bath gathers in this portion. Therefore, the floating dross can be easily collected when the snout 1 is pulled up.

FIG. 11 is an explanatory view showing the ninth embodiment of the present invention. In this embodiment, in the plating bath dipping portion 1a of the snout 1, from the plating bath liquid surface 4a portion toward the snout tip portion 1b, along the movement passage of the steel strip 1 and surrounding the movement passage, the snout tip portion 1b is formed. A cooling conduit 2 is provided as a cooling mechanism, the horizontal cross-sectional area of which gradually decreases, and by this, the liquid level 4a of the plating bath 4 entering the plating bath immersion portion 1a.
A continuous solidified layer 5f having a horizontal cross-sectional area that gradually decreases is formed from the direction toward the snout tip portion 1b.

As a result, similarly to the eighth embodiment, the upper solidified layer 5a reduces the generation of zinc vapor in the snout 1, and at the same time, the hot dip galvanized layer in the snout 1 surrounded by the solidified layer 5f. Convection occurs in the bath part, and floating dross in the plating bath starts to collect in this part.
Floating dross can be easily collected.

FIG. 12 is an explanatory view showing the tenth embodiment of the present invention. In this embodiment, the plating bath liquid surface 4a in the plating bath immersion portion 1a of the snout 1, the inner peripheral portion of the snout 1, and the tip 1b of the plating bath immersion portion 1a are provided with a cooling conduit as a cooling mechanism. 2 is provided, and the tip portion 1b is formed in an inclined shape that gradually becomes thinner toward the tip direction. Therefore, the upper solidified layer 5a except the portion through which the steel strip 6 passes is formed on the liquid surface 4a of the plating bath 4 penetrating into the plating bath immersion portion 1a, and the zinc plating bath in the inner peripheral portion of the snout 1 is formed. Then, the inner peripheral solidification layer 5d is formed, and the continuous solidification layer 5f with a gradually decreasing horizontal cross-sectional area toward the snout tip 1b is formed.

As a result, the upper solidified layer 5a and the lower solidified layer 5a
The 5f prevents generation of zinc vapor in the snout 1 and prevents dross floating in the galvanizing bath from entering the snout 1, and prevents floating dross from accumulating at the snout tip 1b. It

[0062]

As described above, according to the present invention,
The following industrially useful effects are exhibited. In a molten metal plating line, a metal strip is continuously introduced into a metal plating bath in a plating tank through a snout, and by the metal plating bath in the plating tank,
When continuously performing hot metal plating treatment on metal strip, the metal vapor generated from the plating bath surface inside the snout flows into the annealing furnace through the snout together with the atmospheric gas, causing troubles in the equipment inside the annealing furnace. Is prevented.

The dross generated on the surface of the metal plating bath in the plating tank is prevented from adhering to the surface of the metal strip passing through the snout and deteriorating the surface quality of the strip, thereby eliminating surface defects. It is possible to produce a hot-dip galvanized metal strip with excellent quality.

Since the central portion of the plating bath coagulation layer in the snout is in a molten state, the metal strip passing through the snout does not come into contact with the coagulation layer and a flaw does not occur on the surface thereof.

When the snout is pulled up from the metal plating bath in the plating tank for the purpose of ending the operation or repairing, the supply of the refrigerant into the cooling conduit is stopped and the plating formed in the snout is stopped. By melting the coagulated layer of the bath, the above-mentioned pulling up can be easily performed, and therefore, the load on the lifting device of the snout can be reduced and the lifting equipment can be simplified.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a first embodiment of the present invention.

FIG. 2 is a schematic horizontal sectional view showing a solidified state of a plating bath in a snout according to the first embodiment of the present invention.

FIG. 3 is a graph showing the relationship between cooling capacity and plating bath coagulated layer thickness.

FIG. 4 is an explanatory diagram showing a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a third embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a fourth embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a fifth embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a sixth embodiment of the present invention.

FIG. 9 is an explanatory diagram showing a seventh embodiment of the present invention.

FIG. 10 is an explanatory diagram showing an eighth embodiment of the present invention.

FIG. 11 is an explanatory diagram showing a ninth embodiment of the invention.

FIG. 12 is an explanatory diagram showing a tenth embodiment of the present invention.

FIG. 13 is a graph showing the relationship between zinc temperature and vapor pressure.

FIG. 14 is a schematic explanatory diagram showing Prior Art 1.

FIG. 15 is a schematic explanatory diagram showing Prior Art 2.

FIG. 16 is a schematic explanatory diagram showing Prior Art 3.

FIG. 17 is a schematic explanatory diagram showing Prior Art 4.

FIG. 18 is a schematic explanatory diagram showing Prior Art 5.

FIG. 19 is a schematic explanatory diagram showing Prior Art 6.

[Explanation of symbols]

 1 snout, 1a snout plating bath immersion part, 1b snout tip, 2 cooling conduit, 3 plating tank, 4 plating bath, 4a plating bath liquid level, 5 solidification layer, 5a upper solidification layer, 5b lower solidification layer, 5c strip passage Part solidification layer, 5d inner peripheral solidification layer, 5e intermediate solidification layer, 5f solidification layer, 6 steel strip, 7 annealing furnace, 8 gas supply mechanism, 9 sink rolls, 10 gas supply pipe, 11 conduit, 12 zinc removal Equipment, 13 rolls, 14 nozzles, 15 cooling conduits, 16 evaporation inhibitors, 17 rakes, 18 sump chambers.

Claims (2)

[Claims] 1. A snout in which a metal strip is immersed in a metal plating bath in a plating tank from an annealing furnace, one end of which is connected to the annealing furnace and the other end of which is immersed in the plating bath in the plating tank. In the continuous molten metal plating method, in which the metal strip is subjected to a molten metal plating treatment, the plating bath in the snout that is immersed in the plating bath is cooled to form a moving path of the metal strip. A continuous hot-dip metal plating method characterized by opening and solidifying. 2. The liquid level portion of the plating bath in the snout immersed in the plating bath and the portion along the moving path of the metal strip are solidified by opening the moving path of the metal strip. The method of claim 1.