JPH0860318A - Manufacture of hot dip metal coated steel sheet and device therefor - Google Patents

Abstract

PURPOSE: To prevent the intrusion of outdoor air, etc., into an annealing chamber during the interruption of operation in a method for manufacturing a hot dip metal coated steel sheet by admitting the steel sheet into a molten metal bath from the aperture in its bottom and pulling up the steel sheet, thereby continuously coating the steel sheet. CONSTITUTION: Gaseous nitrogen is injected at 1.0Nm<3> /min under 2O00mAq to a position where the steel sheet passes right under the aperture 11 in the bottom of a bath chamber 12 from gas injectors 16 disposed on both sides of the aperture at the time of stopping the steel sheet 1 and changing the hot dip coating bath compsn. from zinc to aluminum. The next W operation is immediately started after the change of the coating bath.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a hot dip galvanized steel sheet.

[0002]

2. Description of the Related Art Molten metals (eg Zn, Al, Mg, M)
(n, Pb and alloys thereof, etc.) A general method for producing a plated steel sheet is as follows. That is, after the cold-rolled steel sheet surface is cleaned and annealed, the steel sheet temperature is adjusted to a temperature suitable for plating and the steel sheet is immersed in the plating bath without being oxidized. Excess molten metal adhering to the steel plate surface in the bath is removed by an adhering amount adjusting device such as gas wiping to adjust the adhering amount, and then cooled as it is.

FIG. 3 shows an apparatus for producing a hot-dip galvanized steel sheet by a conventional method. The steel sheet 1 is drawn into the molten metal bath 2 through a tubular portion called a snout 4, wound around a sink roll 3, and then pulled up vertically through a support roll 5, and the amount of plating is adjusted by an adhesion amount adjusting device 6. It is adjusted and plated. However, in the conventional method as described above, when deposits such as dross are formed on the surface of the sink roll 3, push marks are formed on the surface of the steel plate 1 or the deposits are transferred to the surface of the steel plate 1 to cause surface defects. May be. In many cases, since the sink roll 3 does not have a drive system, when the steel plate 1 slips and the rotation of the sink roll 3 becomes discontinuous, a scratch is formed on the surface of the steel plate. If the plating operation is continued for a longer period of time, the sink roll surface will have irregularities, so it will be necessary to take it out of the molten metal bath for maintenance, and the operability will deteriorate due to the presence of equipment in the bath such as the sink roll. was there.

The presence of in-bath equipment such as sink rolls also makes the molten metal bath very large. Therefore, when several types of hot-dip galvanized steel sheets are produced on the same plating line, the hot-dip bath may be completely replaced or the part of the bath may be pumped out and another hot-melt metal may be added depending on the operation switching. There is a need. The former requires a long time for replacement due to the structural problem of the device, while the latter requires a long time for the device for replacement, for example, the pumping speed of the pump is relatively slow, and the composition adjustment of the molten metal bath. It requires a great deal of expense, time and labor. Therefore, there are limits to the types of products that can be manufactured on the same plating line. Further, since the bath capacity is large, there is a problem that a large amount of dross is generated and a steel sheet surface defect is easily generated.
In order to solve such a problem, a technique for performing double-sided plating in a small-capacity plating bath that does not use a sink roll has been proposed so far. That is, it is an apparatus for producing a molten metal-plated steel sheet, in which the molten metal is held in a relatively small bath and the steel sheet is allowed to enter through the opening at the bottom of the bath to adhere the molten metal to the surface of the steel sheet.

According to Japanese Patent Laid-Open No. 4-356, a molten metal is held by installing a seal plate at a clearance of 0.05 to 1 mm from the steel plate. In addition, Japanese Patent Publication Sho 51-20
In Japanese Patent No. 334, an electromagnetic force is used to hold molten metal at the bottom of the bath, and in Japanese Patent Laid-Open Nos. 63-109148 and 63-303045, electromagnetic force and a gas injection device are used to hold the molten metal at the bottom of the bath. Prevents molten metal from flowing out.

However, when plating is performed by the above method, when the molten metal does not exist in the opening, that is, when the steel plate stops at the opening and the molten metal flows out from the opening, or when the steel plate is broken in the opening, the steel plate is formed in the opening. When the molten metal does not exist and the molten metal flows out, there is a problem that the ambient atmosphere mixes into the annealing furnace below the bathtub through the opening. Further, when the supply of the plating solution to the bath is stopped due to the change of the plating type, there is a problem in that the ambient atmosphere also mixes into the annealing furnace under the bath through the opening.

Generally, the inside of the annealing furnace is maintained in a non-oxidizing or reducing atmosphere with respect to the steel sheet to be plated, and if ambient atmosphere (for example, air) is mixed, it takes time to adjust the atmosphere in the annealing furnace during operation. Operability deteriorates. Further, if the atmosphere in the annealing furnace contains a certain amount or more of hydrogen, there is a risk of causing an explosion due to the mixing of oxygen, and it is necessary to prevent the surrounding atmosphere from being mixed into the annealing furnace as much as possible. Furthermore, there is a problem that frequent maintenance of rolls is required because foreign matter is formed on rolls and the like in the annealing furnace due to mixing of the ambient atmosphere.

[0008]

DISCLOSURE OF THE INVENTION According to the present invention, when a steel sheet is pulled up from an opening at the bottom of a bath and plated, the ambient atmosphere is prevented from being mixed into the annealing furnace from the opening at the bottom of the bath to improve workability. And to improve safety.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a method for producing a hot-dip galvanized steel sheet in which a steel sheet is penetrated from a bottom opening of a hot-dipped metal bath, pulled upward, and continuously plated.
A method of manufacturing a hot-dip galvanized steel sheet, characterized in that a gas curtain is formed at a position where the steel sheet passes immediately below the opening when the operation is interrupted, and the opening is gas-sealed.

The apparatus of the present invention capable of suitably carrying out the above method is a molten metal plating for holding a molten metal, injecting a steel sheet from a bottom opening of a molten metal bath, pulling it upward and continuously plating. A hot-dip galvanized steel sheet manufacturing apparatus comprising a gas injection device for atmosphere sealing immediately below an opening at the bottom of a bath.

[0011]

The specific configuration and operation of the present invention will be described. FIG. 1 shows an embodiment of an apparatus in which the present invention can be suitably implemented, and is an example in which a bath is held by a static pressure in a sealing material 10 and a pressurized gas filling chamber 13 immediately below an opening. . In the present invention, as the molten metal bath, for example, a bath 12 as shown in FIG. 1 is used. The steel sheet 1 annealed in the annealing furnace 17 in a non-oxidizing or reducing atmosphere is passed through the pressurized gas filled chamber 13 without being oxidized. The steel plate 1 which has been deflected vertically by the deflector roll 7, whose warp has been corrected by the support roll 5, and whose vibration has been suppressed by the guide roll 8 continues from the opening 11 at the bottom of the bath for holding the molten metal bath 2. Then, the molten metal bath 2 can be penetrated to perform plating.

In FIG. 1, 6 is a unit weight adjusting device, and 9 is a guide roll. In addition, the pressurized gas filling chamber 13
A gas inlet 14 and an exhaust port 15 for feeding the pressurized gas are provided. A gas injection device 16 is provided below the periphery of the bottom opening 11 of the bathtub 12. In the present invention, the ambient atmosphere such as air is prevented from being mixed into the annealing furnace 17 from the opening 11 when the steel sheet is stopped or the molten metal flows out from the opening 11 for breaking the steel sheet, or when the composition of the plating bath is changed. As shown in the horizontal sectional view of FIG. 2, the gas injection device 1
6 is installed, gas is injected to the steel plate passage position just below the opening 11 at the bottom of the bath 12 to form a gas curtain, and the opening 11 is gas-sealed so that the ambient atmosphere is not mixed into the annealing furnace. Can be prevented. Further, it is preferable to use an inert gas such as nitrogen or argon as the gas injected from the gas injection device 16, and the gas injection pressure is 2000 mmAq and the gas can be sealed. Since the vibration of the steel sheet is induced during the plating and the pressure fluctuation in the pressurized gas filling chamber becomes large, the gas injection device shall be stopped.

The gas injection device is installed in the front and back width direction of the steel plate immediately below the opening and injects gas to the steel plate passage position. In addition, the gas injection portion has a width equal to or larger than the opening width, and the shape and the gas injection direction are not particularly limited as long as they form a gas curtain that seals the opening with a gas. Further, after the plating, the adhesion amount can be controlled by installing an adhesion amount adjusting device such as wiping. After plating, the plated steel sheet may be introduced into a heating furnace for alloying treatment if necessary.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to FIG. After annealing the steel plate 1 (plate width: 500 mm, plate thickness: 0.7 mm), the opening 1 was opened at 470 ° C. through the deflector roll 7.
Introduced from 1. Zinc is used as the molten metal held in the bathtub 12, and the gap between the sealing material 10 and the steel plate is 1.5
mm, the height of the zinc bath in the seal portion was 30 mm, the temperature of the molten zinc bath was 470 ° C., and the plating operation was performed at a plate passing speed of 60 m / min. After that, when the steel plate 1 is stopped and the plating bath composition is changed from zinc to aluminum, the bath 12
When nitrogen gas 1.0 Nm ³ / min, 2000 mmAq was injected from the gas injection device 16 provided on both sides of the opening 11 at the bottom of the plate to the steel plate passing position immediately below the opening,
The ambient atmosphere was prevented from entering the annealing furnace, and the next plating operation could be started immediately after changing the composition of the plating bath.

[0015]

As described above, by using the continuous hot-dip galvanized steel sheet manufacturing apparatus according to the present invention, the operation can be started in a short time after the steel sheet is stopped when the bath composition is changed, etc. The safety has improved dramatically.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an embodiment of an apparatus for manufacturing a hot-dip galvanized steel sheet according to the present invention.

FIG. 2 is a cross-sectional view of an embodiment of an apparatus for manufacturing a hot-dip galvanized steel sheet according to the present invention.

FIG. 3 is a vertical cross-sectional view of a conventional hot-dip galvanized steel sheet manufacturing apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Steel plate 2 Molten metal bath 3 Sink roll 4 Snout 5 Support roll 6 Adhesion amount adjusting device 7 Deflector roll 8, 9 Guide roll 10 Seal material 11 Opening 12 Bath tub 13 Pressurized gas filling chamber 14 Gas inlet 15 Exhaust port 16 Gas injection device 17 Annealing furnace

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Chiaki Kato 1 Kawasaki-cho, Chuo-ku, Chiba City Kawasaki Steel Co., Ltd. Steel Research and Development Division Steel Research Laboratory (72) Inventor Teruo Hiramatsu Kawasaki-cho, Chuo-ku, Chiba City Kawasaki Steel Manufacturing Co., Ltd. Chiba Steel Works, Steel Development and Production Headquarters (72) Inventor Kazuya Miyakawa 1 Kawasaki-cho, Chuo-ku, Chiba City Kawasaki Steel Co., Ltd. Steel Development & Production Headquarters Chiba Steel Works

Claims (2)

[Claims] 1. A method for producing a molten metal-plated steel sheet in which a steel sheet is introduced from a bottom opening of a molten metal bath and pulled upward to continuously plate a gas curtain at a steel sheet passage position immediately below the opening when operation is interrupted. A method for producing a hot-dip galvanized steel sheet, which comprises forming and sealing the opening with a gas. 2. A molten metal-plated steel sheet manufacturing apparatus for holding molten metal, intruding a steel sheet from an opening at the bottom of a molten metal bath, and pulling it upward to continuously plate an atmosphere immediately below the opening at the bottom of the bath. A hot-dip galvanized steel sheet manufacturing apparatus comprising a gas injection device for sealing.