JP3421794B2 - Continuous hot metal plating equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for continuously producing a hot-dip galvanized steel sheet, and more particularly to an apparatus for continuously producing a hot-dip metal sheet on a thin steel sheet surface. The present invention relates to a continuous hot-dip metal plating apparatus excellent in operability for stable plating. [0002] Molten metal (Zn, Al, Sn, Pb and alloys thereof) plated steel sheets are used for automobiles, building materials, home appliances, and the like.
Widely used for cans. The general manufacturing method of a hot-dip metal-plated steel sheet is as follows. After cleaning the surface of the cold-rolled thin steel sheet in a pretreatment step, the surface oxide film is removed by annealing in a non-oxidizing or reducing atmosphere, and then the steel sheet is cooled without being oxidized. Then, the sheet temperature is lowered to almost the temperature of the molten metal bath, and then immersed in the bath. Excess molten metal adhering to the surface of the steel sheet in the bath is removed with a gas wiper to adjust the amount of the adhering metal, and then cooled as it is. FIG. 5 shows a conventional hot-dip metal plating apparatus having a sink roll. The steel sheet 1 is drawn into the molten metal bath 2 from the snout 4 and pulled up vertically by the sink roll 3. The sink roll 3 in the metal bath vertically changes the passing direction of the steel sheet 1 to which the molten metal adheres, thereby vertically raising the steel sheet 1 without contacting the roll until the molten metal on the steel sheet surface solidifies. It is an important device for preventing the occurrence of surface defects such as scratches. [0004] When deposits are formed on the surface of the sink roll 3, there is a case where a press flaw is formed on the surface of the steel sheet, or the deposits migrate to the surface of the steel sheet and become surface defects. 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 long period of time, the surface of the sink roll becomes uneven, so it is necessary to take out and maintain the sink roll from the molten metal bath. As described above, the conventional hot-dip metal plating apparatus is
There was a drawback that operability deteriorated due to the presence of bath equipment such as sink rolls. Also, due to the presence of in-bath equipment such as sink rolls, the molten metal bath becomes extremely large,
When the bath composition is changed, particularly when the product type is changed drastically, it is necessary to pump out a part of the molten metal bath and add another molten metal. This is a huge expense,
Because of the time and labor required, there are limits to the types of products that can be manufactured on a single plating line. In order to solve such a problem, techniques that do not use a sink roll have been proposed. [0006] JP-B-51-20334 and JP-A-Hei 2
In JP-298247-A, electromagnetic force is used to hold the molten metal at the bottom of the bathtub, and in JP-A-4-356, the molten metal is held by a non-contact seal plate against a steel plate. However, when trying to adjust the amount of deposition using a gas wiping gas device conventionally used in these plating devices, a downward flow of the wiping gas occurs along the steel plate, and an excessive head pressure is applied to the molten metal near the steel plate. As a result, there is a problem that the molten metal easily leaks from the opening at the bottom of the bathtub. Furthermore, when using a molten metal bath with an extremely low bath surface height, the downward flow of the wiping gas along the steel plate causes the bath surface near the steel plate to drop, and the molten metal that adheres to the steel plate is depleted. is there. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide an apparatus for manufacturing a hot-dip coated steel sheet, which does not use a sink roll. In the present invention, the trouble caused by the conventionally used gas wiping is solved, and the amount of the plated metal adhered to the steel plate can be adjusted stably. [0008] The present invention uses a molten metal bath having a slit-shaped opening at the bottom of a bathtub, pulls up a steel sheet that has entered from the bottom of the molten metal bath, and performs plating. After applying, in a continuous hot-dip metal plating apparatus for controlling the amount of adhesion by a gas wiper, a shielding plate is provided between the wiping nozzle and the molten metal bath surface , and the shielding plate and the steel plate
The continuous hot-dip metal plating apparatus is characterized in that the distance between them is 10 mm or less . In this device, a gas suction device may be provided between the wiping nozzle and the molten metal bath surface instead of the shielding plate to suction the wiping gas descending along the steel plate. Moreover, you may use both together. The specific structure and operation of the present invention will be described. In the present invention, a bath 12 as shown in FIG. 1 is used as a bath of molten metal. After passing through the non-oxidizing or reducing atmosphere 15, the steel sheet 1 is turned in the vertical direction by the deflector roll 7, the warp is corrected by the support roll 5,
Molten metal bath 2 while vibration is suppressed by support roll 8
Infiltrate continuously. Bathtub 12 holding molten metal bath 2
An opening 11 through which the steel plate 2 enters is provided at the bottom of
The sealing plate 10 is provided in the opening 11. The sealing plate 10 prevents the molten metal from leaking from the opening 11 at the bottom of the bathtub. The steel sheet 1 pulled up from the bathtub 12 and adhering to the molten metal is removed by a wiping gas blown from a gas wiper 6 to remove excess molten metal adhering to the steel sheet surface and adjust the amount of adhesion. This wiping gas becomes a downward flow along the steel plate 1 and applies a head pressure to the upper surface of the molten metal bath, thereby promoting the outflow of the molten metal bath from the opening 11 at the bottom of the bathtub 12. In the present invention, the downward flow of the wiping gas along the steel plate is suppressed by the shielding plate 13 provided between the wiping nozzle 6 and the molten metal bath surface, so that the excessive head pressure on the molten metal bath surface is reduced. Can be prevented from acting, and the outflow of the molten metal from the opening 11 at the bottom of the bathtub can be suppressed. The shielding plate 13 may have a slit-shaped opening 16 at the steel plate intrusion position and cover the entire surface of the molten metal bath. The distance between the shielding plate 13 and the steel plate 1 at the slit-shaped opening 16 may be 10 mm. It shall be the following. Further, as shown in FIG.
Thus, a structure capable of following the fluctuation of the pass line in the width direction of the steel plate is obtained. Further, by providing a gas suction device 14 for sucking the downward flow of the wiping gas along the steel plate instead of the shielding plate 13, the same effect as that of the shielding plate 13 can be obtained. As shown in FIG. 4, the gas suction device 14 for sucking the downward flow of the wiping gas is provided with a slit or a hole 18 having at least the width of the wiping nozzle and suctions the downward flow by an exhaust pump 19. . The distance between the slit or the porous member 18 and the steel plate 1 is preferably 10 mm or less. It is also effective to use the shielding plate 13 in combination with the wiping gas descending gas suction device 14. Next, the present invention will be described based on embodiments. FIG. 1 is a longitudinal sectional view of an embodiment of the present invention. Zinc was used as the molten metal, and the gap between the seal plate 10 and the steel plate 1 was 0.5
mm, the head height of the molten zinc bath 2 at the tip of the sealing plate was 30 mm, the molten zinc bath temperature was 470 ° C., and the plate thickness was 0.7.
mm and a sheet width of 500 mm were passed at a line speed of 100 m / min. When the distance between the shield plate 13 and the steel plate 1 was set to 2 mm using the shield plate 13 and the amount of molten zinc adhered was controlled to 50 g / m ² by a gas wiper, there was no leakage of the molten zinc from the opening at the bottom of the bathtub, and stable. The plating operation can be continued. COMPARATIVE EXAMPLE Zinc was used as the molten metal, the gap between the sealing plate and the steel plate was 0.5 mm, the height of the zinc bath head at the end of the sealing plate was 30 mm, the molten zinc bath temperature was 470 ° C., and the plate thickness was 0.1 mm.
A steel plate having a width of 7 mm and a width of 500 mm was passed at a line speed of 100 m / min. When the distance between the shield plate and the steel plate was set to 20 mm using a shield plate and the amount of molten zinc deposited was controlled to 50 g / m ² by a gas wiper, the bath surface vibrated violently due to the downward flow of the wiping gas, and molten zinc was generated near the steel plate. It was depleted intermittently, and stable plating operation could not be continued. As described above, according to the continuous hot-dip metal plating method of the present invention, the hot-dip metal-plated steel sheet can be continuously formed without using an in-bath equipment such as a sink roll which easily causes surface defects. Since it can be manufactured stably, the industrial significance is extremely large.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of hot-dip metal plating of the present invention. FIG. 2 is a plan view of the shielding plate of the embodiment. FIG. 3 is a front view of the shielding plate of the embodiment. FIG. 4 is a cross-sectional view of the gas suction facility of the embodiment. FIG. 5 is a longitudinal sectional view of a conventional apparatus for manufacturing a hot-dip metal-plated steel sheet. [Description of Signs] 1 Steel plate 2 Molten metal bath 3 Sink roll 4 Snout 5, 8, 9 Support roll 10 Seal plate 11 Opening 12 Bathtub 13 Shielding plate 14 Gas suction device 15 Non-oxidizing and reducing atmosphere 16 Slit-shaped opening Part 17 guide roll 18 slit or perforated

Continued on the front page (72) Inventor Shigeru Unno 1 Kawasaki-cho, Chuo-ku, Chiba-shi Kawasaki Steel Corp. Steel Research & Development Division Steel Research Laboratory (72) Inventor Kazuo Mochizuki 1- Kawasaki-cho, Chuo-ku, Chiba-shi Kawasaki Steel Corp. (56) References JP-A-4-356 (JP, A) JP-A 62-205258 (JP, A) JP-A 62-37363 (JP, A) JP JP-A-61-207559 (JP, A) JP-A-2-277757 (JP, A) JP-A-55-110766 (JP, A) JP-A-62-193671 (JP, A) JP-A-3-120348 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 2/00-2/40

Claims (1)

(57) [Claims 1] A molten metal bath having a slit-shaped opening at the bottom of a bathtub was used, and a steel sheet that had entered from the bottom of the molten metal bath was pulled up and plated. Thereafter, in a continuous hot-dip metal plating apparatus for controlling the amount of adhesion with a gas wiper, a shielding plate is provided between the wiping nozzle and the molten metal bath surface, and the distance between the shielding plate and the steel plate is set to 10 mm or less.
Continuous molten metal plating apparatus characterized by the.