JPH08269658A - Hot dip metal coating device - Google Patents

Abstract

PURPOSE: To provide a hot dip metal coating device, in which even if the leakage and the flow-down of hot-dipping metal bath are developed, the surface of a steel strip supporting roll can always be kept to good condition without interrupting the plating work, in the production of a hot dip metal coated steel sheet by an air pot method. CONSTITUTION: In the hot dip metal coating device provided with a molten metal holding vessel 1 providing an opening part for invading the steel strip at the bottom part and the roll 4 for supporting the steel strip 2 to be invaded, invaded into the hot dipping metal bath at the lower part of this opening part, a nozzle 5 for spraying gas to the molten metal 2 leaked on the surface of the roll is arranged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-dip galvanized steel sheet manufacturing apparatus, and more particularly, to a molten metal holding container having a steel strip entry opening at the bottom thereof, which is used to continuously feed the steel strip from the opening. The present invention relates to a technique for preventing molten metal from leaking from the opening in a so-called aerial pot that is introduced and plated.

[0002]

2. Description of the Related Art A method for producing a hot dip galvanized steel sheet, particularly an alloyed hot dip galvanized steel sheet, is generally as follows. That is, after cold rolling, the surface is cleaned in a pretreatment step, and a steel strip that has been passed through a continuous annealing furnace in a non-oxidizing or reducing atmosphere is immersed from above the molten zinc bath through an antioxidant snout. The direction was changed by a so-called sink roll arranged in the bath, molten zinc was adhered to both surfaces of the steel strip while being pulled upward, and the excess amount of the zinc was removed outside the bath with an air knife or the like.

However, according to this method, since there are equipments in the bath such as sink rolls, the holding container for the molten zinc bath becomes extremely large, and the degree of freedom is small when changing the type of plating bath, and the maintenance of sink rolls is complicated. Alternatively, there is a problem that the dross is caught between the sink roll and the steel strip to be plated, resulting in quality defects such as surface scratches.

Therefore, various methods using no sink roll have been proposed, but the so-called aerial pot method has been proposed as a method capable of stably plating both sides of a steel strip. As shown in FIG. 6, it has an opening 12 for entering a steel strip at the bottom.
Holding a molten metal 2 to be plated in a holding container 1 having
The steel strip 3 is plated by passing the steel strip 3 from below to above the opening 4.

By the way, the important point of this method is that
This is to prevent the molten metal 2 from leaking out from the slit-shaped opening 12, and, for example, in Japanese Patent Laid-Open No. 4-356,
Therefore, the seal plate 16 is provided on the side wall of the opening, and the distance between the seal plate 16 and the steel strip 3 is set to about 0.05 to 1 (mm). Further, Japanese Patent Laid-Open No. 63-109148 discloses that a static pressure generating gas nozzle is provided below a steel strip introducing portion of an aerial pot, that is, below an opening, and a static pressure is applied by the gas to melt molten metal from the opening. Discloses technology to prevent leakage. Further, JP-A-63-109149 proposes an aerial pot using an electromagnetic pump.
Japanese Patent Publication No. -303045 describes that a static pressure is also applied by a gas to a steel strip entry opening of an aerial pot using electromagnetic force.

[0006]

However, in the conventional aerial pot described above, the molten metal 2 is formed by some method.
However, the holding mechanism of the molten metal bath is impaired due to the stop of power or the occurrence of disturbance due to an accident during use, and the molten metal 2 leaks from the holding container 1 and flows down. There were cases. In such a case, if there are rolls 4 and 11 that support the steel strip vertically below the opening 12 of the holding container 1, the rolls 4 and 11 may be accumulated on the rolls 4 and 11 to form an oxide film on the surface of the rolls 4 and 11 to form an end portion of the roll. Without flowing down from
It sometimes stayed on the roll for a long time.
If this state is left as it is, the molten metal 2 is picked up irregularly before the steel strip 3 to be plated is introduced into the molten metal plating bath, and a spotted pattern remains after plating, resulting in a defective product. was there. Also, during the long-term residence, the molten metal component reacts with the surface of the roll and the molten metal component forms a solid solution in the structure of the roll.
Even after this is removed, this molten metal component may be transferred to the steel strip 3 to be plated, resulting in a pattern after plating. Therefore, surface maintenance of the roll is required for smooth plating work. It was Further, if the solid-solved component is left to stand and the operation is continued, it sometimes penetrates from the surface layer of the roll to a deep part and cannot be completely removed by subsequent roll surface polishing.

In view of such circumstances, the present invention does not interrupt the plating operation even when the molten metal plating solution leaks or flows down in the production of the molten metal plated steel sheet by the aerial pot method, and the steel strip support It is an object of the present invention to provide a molten metal plating apparatus capable of always maintaining a good roll surface.

[0008]

In order to achieve the above-mentioned object, the inventor diligently studied a means for removing molten metal flowing down or adhering to a roll, and found that blowing a gas has the least influence on the plating quality. I found it. That is, the present invention comprises a molten metal holding container having a steel strip entry opening at the bottom, and a roll for supporting a steel strip to be plated which enters the molten metal plating bath below the opening. In the molten metal plating apparatus, a nozzle for injecting a gas onto the molten metal leaked onto the surface of the roll is provided, which is a molten metal plating apparatus. Further, the present invention is a molten metal plating apparatus characterized in that a static pressure holding chamber surrounding the roll is provided below the container, and further, the molten metal is provided above the steel strip entry opening. The molten metal plating apparatus is provided with an electromagnet for pulling up to.

[0009]

According to the present invention, there is provided a molten metal holding container having a steel strip entry opening at the bottom thereof, and a roll for supporting the steel strip to be plated which is located below the opening and enters the molten metal plating bath. In the hot-dip galvanizing apparatus, since the nozzle for injecting the gas to the molten metal leaked on the roll surface is arranged, the leaked molten metal is immediately blown off the roll and removed. As a result, the adhesion of the molten metal to the surface of the steel strip before plating was eliminated, and the speckled pattern did not appear in the plated layer. Further, since the reaction between the roll and the molten metal staying on the surface of the roll does not occur, the roll surface can always be maintained in a good state, and maintenance of the roll becomes unnecessary.

Further, in the present invention, a static pressure holding chamber surrounding the roll is provided below the container, and an electromagnet for pulling up the molten metal upward is provided at the opening for entering the steel strip. Therefore, the amount of molten metal leaked from the opening of the container is reduced, and the gas blowing effect can be promoted.

[0011]

EXAMPLE An example of a molten metal plating apparatus according to the present invention is shown in FIG.
And shown in FIG. FIG. 1 is a longitudinal sectional view of the device,
By providing the nozzle 5 for gas injection and injecting gas,
Even if the molten metal 2 flows down from the container 1 and stays on the so-called deflow 4, the staying molten metal 7 is immediately removed. As a result, defective plating of the steel sheet when the molten metal 2 flows down is prevented, and maintenance of the roll surface is minimized. The accumulated molten metal 7 that has been driven to the end of the roll by blowing gas is dropped from the roll and held in a molten metal recovery container provided below. In addition,
FIG. 2 is an enlarged view of the gas blowing portion.

As the jet gas 15, a non-oxidizing gas mainly containing nitrogen is usually used, but it goes without saying that the furnace 8 is used.
It is preferable to be compatible with the atmosphere of. Further, when the temperature of the jet gas is too low, the retained molten metal 7 may solidify. Therefore, in order to prevent solidification, the atmosphere gas in the furnace 8 is circulated by the circulation device 9 as shown in FIG. It is desirable to reheat to the melting point of the molten metal with the heater 10 before use. Further, if the velocity of the jet gas 15 is too small, the accumulated molten metal 7 cannot be driven to the end of the roll. On the contrary, if the velocity is too large, the accumulated molten metal 7 is blown off more than necessary. It becomes difficult to receive it in the recovery container 6. Therefore, the flow rate of the jet gas 15 is adjusted to be appropriate according to the size of the plating apparatus.

Next, an example in which a plurality of gas injection nozzles 5 are provided in the width direction of the steel strip is shown in FIG. Therefore, the accumulated molten metal 7 can be easily driven to the end portion of the roll as compared with the case of the single nozzle shown in FIG. At this time, the nozzle 5 for injecting gas may be provided so that the retained molten metal 7 goes from the center of the roll toward both ends.
In this case, the recovery containers 6 may be prepared at both ends.

An embodiment in which the roll is a pinch type is shown in FIG. If the roll is a pinch type, the molten metal may not flow downward due to the action of shearing force or the like in the gap between the rolls even in the portion where the steel strip does not exist. Therefore, in order to drive the accumulated molten metal 7 to the end of the roll, the nozzle 5
It is necessary to consider the mounting angle and gas flow rate. Further, in FIG. 4, in order to suppress the amount of molten metal 2 leaking from the opening 12 of the container 1, the chamber surrounding the roll and the nozzle (indicated by symbol 8 in FIG. 1) is provided with a seal mechanism 14 for the gas 15 separately. The static pressure holding chamber 13 is provided. Further, as shown in FIG. 5, the present invention can also be applied to a molten metal holding container in which an electromagnet is arranged in a steel strip entry opening and an upward electromagnetic force is applied to the molten metal.

In the present embodiment, the molten metal 7 that has stagnated
Although the recovery container 6 is installed under the roll, it may have any shape as long as it can receive the molten metal after injection, and the injection gas does not have to be a circulation system.

[0016]

As described above, according to the present invention, it is possible to minimize the occurrence of defects in the plated steel sheet and the roll maintenance when the molten metal flows down and leaks from the opening at the bottom of the container. As a result, it becomes possible to enjoy the advantages of the molten metal plating method in which an opening is provided at the bottom of the molten metal container and the steel sheet is continuously immersed to perform plating, that is, the aerial pot method, and the molten metal is economical. It became possible to perform plating.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a molten metal plating apparatus according to the present invention.

FIG. 2 is an enlarged explanatory view of a gas injection portion of the molten metal plating apparatus according to the present invention.

FIG. 3 is a diagram showing a case where a plurality of gas injection nozzles are arranged in the molten metal plating apparatus according to the present invention.

FIG. 4 is a diagram showing a plating apparatus when the roll is a pinch type, in which a static pressure holding chamber surrounding the roll is provided.

FIG. 5 is a diagram showing an aerial pot in which an electromagnet is arranged in an opening.

FIG. 6 is a diagram showing a conventional aerial pot.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Holding container 2 Molten metal 3 Steel strip (steel strip to be plated) 4 Deflor 5 Nozzle 6 Recovery container 7 Molten metal that has stagnated 8 Furnace 9 Gas circulation device 10 Gas heater 11 Support roll 12 Opening 13 Static pressure holding chamber 14 Seal Mechanism 15 Gas 16 Seal plate 17 Electromagnet

Claims (3)

[Claims] 1. A molten metal holding container having an opening for entering a steel strip at the bottom, and a roll below the opening for supporting a steel strip to be plated which enters the molten metal plating bath. In the metal plating apparatus, a nozzle for injecting a gas onto the molten metal leaked onto the surface of the roll is provided, which is a molten metal plating apparatus. 2. The hot-dip galvanizing apparatus according to claim 1, wherein a static pressure holding chamber surrounding the roll is provided below the container. 3. The molten metal plating apparatus according to claim 1, wherein an electromagnet for pulling up the molten metal is provided in the opening for entering the steel strip.