JP2002030408A - Method for uniformizing metal coated rate on hot-dip coated band steel edge part and hot-dipping metal coating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a hot-dip metal coated band steel uniformizing the metal coated rate without developing over-coating on the edge part by sucking disturbulent flow caused by collision of wiping gases WG with suction nozzles 4R, 4L. SOLUTION: When the excessive stuck hot-dip coated metal is removed by blowing the wiping gases WG on both surfaces at the front and the back sides of the metal coated original plate S just after pulling up from a hot dipping bath M, the edge parts in the width direction of the metal coated original plate S are interposed with interposing plates 3R, 3L and a part of the wiping gases WG is sucked outside a system through the suction nozzles 4R, 4L opened between the interposing plates 3R, 3L and the atmospheric pressure near the edge parts in the width direction of the metal coated original plate S is brought close to the atmospheric pressure at the center part in the width direction of the plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for equalizing the amount of plating applied to eliminate the edge overcoat that tends to occur at both ends of a steel strip pulled up from a hot-dip plating bath, and a method for applying a uniform coating amount in the width direction. The present invention relates to an apparatus for producing a hot-dip coated steel strip.

[0002]

2. Description of the Related Art In a hot-dip plating method, a reduction-annealed base plate is introduced into a plating pot through a snout from an annealing furnace, brought into contact with a hot-dip plating metal such as Zn or Al, and then pulled up from the plating pot. A large amount of hot-dip galvanized metal lifted from a plating pot is attached to the plating base plate immediately after being pulled up as the plating base plate travels.
Most of the hot-dip plated metal falls into the plating pot by gravity. However, if the plating base plate is transported to the next step in this state, excessive adhesion of the hot-dip plated metal and uneven plating adhesion cannot be avoided.

Therefore, a method has been adopted in which a pressurized gas is blown onto the surface of a plating plate immediately after being lifted from a plating pot to remove excessively deposited hot-dip plating metal and adjust the amount of plating applied. Specifically, wiping nozzles 1F and 1B are arranged on both sides of the passage of the original plate S pulled up from the hot-dip plating bath M, opposite to both surfaces of the original plate S, and compressed air is supplied from the wiping nozzles 1F and 1B. The wiping gas WG is blown (FIG. 1). Excess hot-dip plated metal is removed from the plating base sheet S by the wiping gas WG injection pressure, and the plating base sheet S whose plating adhesion amount has been adjusted is transported to the next step.

Most of the wiping gas WG ejected from the wiping nozzles 1F and 1B is sprayed on the front and back surfaces of the original plating plate S. However, the wiping gas WG ejected from each of the wiping nozzles 1F and 1B collides with the plating base plate S without colliding with the plating base plate S on both sides of the plating base plate S. Turbulence is generated on both sides of the original plating plate S due to the collision of the wiping gas WG. When the turbulence flows toward the center in the width direction of the original plating sheet S, the effect of adjusting the amount of applied plating at both ends in the width direction of the original plating sheet S is weakened. As a result, an edge overcoat in which an excessive amount of hot-dip metal remains at both ends in the width direction occurs, which causes poor appearance such as a beard and pock.
In addition, when the steel strip on which the edge overcoat has occurred is wound around a coil, the coil becomes drum-shaped. If the drum-shaped coil is unwound, a flatness defect called edge elongation or ear elongation occurs at the widthwise end of the steel strip, which adversely affects bending, forming, punching, and the like performed in a later step.

[0005]

Various methods have been conventionally proposed to prevent the occurrence of edge overcoat. For example, the high-pressure gas injection nozzles 2F, 2B are directed to the width direction end of the plating original sheet S at positions immediately above the wiping nozzles 1F, 1B, and the high-pressure gas HG having a pressure higher than the wiping gas WG is sharply formed on the plating original sheet S. Spraying at both ends in the width direction eliminates turbulence that tends to occur near both ends in the width direction. However, since it is necessary to supply pressurized gases having different pressures to the wiping nozzles 1F and 1B and the high-pressure gas injection nozzles 2F and 2B, the equipment configuration is likely to be complicated. Moreover, the high-pressure gas injection nozzles 2F, 2B
When the hot-dip metal is scattered by the high-pressure gas HG blown out of the hot-dip steel strip, the appearance of the end in the width direction of the hot-dip steel strip deteriorates. When the width and thickness of the plating base sheet S are different,
Accordingly, the running speed of the steel strip S, the ejection pressure of the wiping gas, and the like fluctuate, so that the wiping nozzles 1F, 1F
1B and the high pressure gas injection nozzles 2F and 2B are plated
It is necessary to adjust the position in accordance with the width of, and a complicated adjustment work is required, but a stable effect is hardly obtained.

By increasing the opening degree of the slits formed in the wiping nozzles 1F and 1B at both ends in the width direction as compared with the center part in the width direction, and increasing the flow rate of the wiping gas hitting both ends in the width direction of the original plate S. In addition, a method of suppressing edge overcoat is also partially adopted. However, since the position where the flow rate of the wiping gas is increased is fixed for each of the wiping nozzles 1F and 1B, when using the plating base plate S having different widths, the use of the wiping nozzles 1F and 1B having slits corresponding to the widths is required. Is required, and complicated replacement of the wiping nozzles 1F and 1B is inevitable. Also, when winding a plated steel strip with edge overcoat, the coil becomes drum-shaped by sandwiching a spacer such as a cardboard narrower than the steel strip at the center in the width direction and winding it together with the plated steel strip. There are also known ways to prevent this. However, the use of spacers not only complicates coil winding and rewinding operations, but also imposes a burden on the storage of spacers and the processing of used spacers.

[0007]

SUMMARY OF THE INVENTION The present invention has been devised to solve such a problem, and a part of the wiping gas is sucked from the vicinity of both ends in the width direction where turbulence is likely to occur. Hot-dip galvanized steel that eliminates turbulence and, consequently, suppresses the flow of wiping gas toward the center in the plate width direction, thereby preventing edge overcoating and uniforming the amount of plating applied in the plate width direction. The purpose is to manufacture the belt.

[0008] In order to achieve the object, the method of the present invention for equalizing the amount of deposited coating is to blow a wiping gas onto both the front and back surfaces of the original plating plate immediately after being lifted from the hot-dip plating bath to remove the excessively deposited molten metal. At the time of removal, a part of the wiping gas is sucked out of the system from the vicinity of the end of the plating base sheet in the plate width direction, and the atmospheric pressure in the vicinity of the end of the plating base sheet in the plate width direction approaches the atmospheric pressure in the center of the plate width direction. It is characterized by.

Further, the hot-dip plating apparatus according to the present invention comprises:
A wiping nozzle with slits longer than the plate width of the plating base plate, and a wiping nozzle that is disposed opposite to the front and back sides of the plating base plate pulled up from the hot-dip plating bath, An opening suction nozzle is provided, and a part of the wiping gas is sucked out of the system through the suction nozzle from near the end in the width direction of the plating original plate. The sandwiching plate and the suction nozzle are arranged near both ends of the original plate at positions above, below, or both above and below the wiping nozzle.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Wiping gas WG injected from wiping nozzles 1F and 1B toward both surfaces of plating base sheet S
Has the effect of removing an excessive amount of hot-dip metal deposited on the surface of the original plating sheet S by colliding with both sides of the original plating sheet S within the range of the original plating sheet S width. However, in a region exceeding the plate width range, collision of the wiping gas WG on the surface of the plating original sheet S cannot be expected, and turbulent flow occurs due to mutual collision of the wiping gas WG injected from the front and rear wiping nozzles 1F and 1B. Therefore, in the present invention, in order to prevent the turbulent flow generated by the collision between the wiping gases WG from flowing toward the center, the hot-dip plating bath M is used.
Left and right sandwiching plates 3R, 3L sandwiching both ends in the width direction of the plating base sheet S pulled up from the front and back sides, respectively.
The suction nozzles 4R and 4L provided with are opened (FIGS. 2 and 3). The sandwiching plates 3R and 3L have an effect of facilitating the suction of the wiping gas WG which is going to flow toward the center of the plating original plate.

In FIGS. 2 and 3, the sandwiching plates 3R, 3L and the suction nozzles 4R, 4L are arranged between the oil surface of the hot-dip bath M and the wiping nozzles 1F, 1B.
Of course, the R and 3L and the suction nozzles 4R and 4L may be arranged above or above and below the wiping nozzles 1F and 1B. Which installation method is adopted is selected in consideration of manufacturing conditions such as plating type, plating adhesion amount, and plate thickness in addition to the installation space. The sandwiching plates 3R, 3L are positioned in such a manner that the wiping nozzles 1F, 1L overlap with both ends in the plate width direction of the plating base plate S in which edge overcoat is likely to occur.
B and the plating original sheet S are arranged.

The length L of the sandwiching plates 3R and 3L overlapping the widthwise end of the original plating plate S is determined in advance by wiping conditions according to the plate thickness, steel type, plating adhesion amount, and the like.
Usually, it is selected in the range of 20 to 200 mm. However, if the overlap length L is too large, the action of the wiping gas WG on the widthwise end of the plating base sheet S is weakened, so it is preferable to set the overlap length L to at most 200 mm or less. Further, if the suction nozzles 4R, 4L are too far from the wiping nozzles 1F, 1B, the suction effect is reduced. Therefore, the distance from the wiping nozzles 1F, 1B to the suction nozzles 4R, 4L is set within 300 mm (more preferably, within 200 mm). Is preferred.

The suction nozzles 4R and 4L are opened between the sandwiching plates 3R and 3L, respectively, and a part of the wiping gas WG is sucked from the vicinity of the end in the width direction to reduce the pressure in the vicinity of the end in the width direction. Approach the pressure of the part. This eliminates or reduces the gas flow from the widthwise end to the widthwise center, and reliably prevents edge overcoating. The suction of the wiping gas WG through the suction nozzles 4R and 4L is realized by slightly setting the inside of the suction nozzles 4R and 4L to a negative pressure. Further, since the space between the wiping nozzles 1F and 1B is at a high pressure due to the injection pressure of the wiping gas WG, the suction nozzles 4R and 4
By simply opening the other end of L to the atmosphere, a part of the wiping gas WG can be sucked out of the system from the vicinity of the widthwise end of the original plating plate S. The suction amount of the wiping gas WG is controlled by the opening / closing degree of a flow control valve (not shown) provided in the middle of the suction nozzles 4R and 4L.

When manufacturing hot-dip galvanized steel strips having different sheet widths, the atmospheric pressure around the original plating sheet S can be properly controlled by adjusting the distance between the suction nozzles 4R and 4L. That is, wiping nozzles 1F and 1B having slits longer than the plate width of plating base sheet S are used so that they can be used for manufacturing various hot-dip coated steel strips. By changing the distance between the suction nozzles 4R and 4L according to the conditions, the sandwiching plates 3R and 3L can be wiped with the optimum overlapping length L by the wiping nozzle 1R.
It can be interposed between F, 1B and the end in the width direction of the original plating plate S.

The distance between the suction nozzles 4R and 4L can be adjusted and set by automatic control. For example, a plate width sensor is arranged in the middle of the passage of the original plating sheet S or the hot-dip steel strip, and the detected value from the sensor is sent to the suction nozzle 4.
A method is adopted in which the suction nozzles 4R and 4L are input to the drive systems of R and 4L, and are moved forward and backward along the plate width direction by a movement amount corresponding to the measured plate width. Alternatively, it is also possible to move the suction nozzles 4R, 4L back and forth along the plate width direction based on data input in advance according to the production plan.

[0016]

EXAMPLE After reducing and annealing a cold-rolled ordinary steel sheet having a width of 1000 mm and a thickness of 0.8 mm, the steel sheet was introduced into a hot-dip galvanizing bath M at a line speed of 90 m / min. Raised vertically upward and spray pressure 0.03 from the wiping nozzles 1F and 1B onto the plating original sheet S immediately after the lifting.
The wiping gas WG was blown at MPa. In addition, as the wiping nozzles 1F and 1B, a slit having a width of 1500 mm is formed in the width direction of the plate, and is disposed 400 mm above the bath surface of the hot-dip plating bath M in a positional relationship to face the front and back surfaces of the plating base plate S immediately after being pulled up. did.

A test piece was cut out from the manufactured hot-dip galvanized steel sheet, and the distribution of the amount of coating along the sheet width direction was examined. The average coating weight per side was 90 g / m ² on both the front and back surfaces.
mm, an edge overcoat of up to 150 g / m ² was obtained. Therefore, a suction nozzle which is disposed at a position 100 mm below the wiping nozzles 1F and 1B, sandwiches both ends in the plate width direction of the plating base plate S with sandwiching plates 3R and 3L having a length L = 100 mm and the other end opened to the atmosphere. 4R, 4L
Was opened between the sandwiching plates 3R and 3L. Under these conditions, the wiping gas WG is made in the same manner as the wiping conditions described above.
Was sprayed onto the plating base sheet S to produce a hot-dip galvanized steel strip.

A test piece was cut out from the obtained hot-dip galvanized steel strip and the distribution of coating weight in the sheet width direction was examined.
At 0 g / m ² , the maximum adhesion amount remained at 110 g / m ² even from the end in the plate width direction to 50 mm, and edge overcoat was suppressed. Holding plates 3R, 3L and suction nozzle 4
In order to investigate the influence of R and 4L, sandwiching plates 3R and 3L are arranged on the side of the end of the plating base sheet S in the width direction (overlapping length L <
The wiping gas WG was sprayed on the original plating plate S under the same conditions except that 0) was performed to adjust the amount of plating applied. The hot-dip galvanized steel sheet obtained in this case had an average coating weight of 90 g / m ² per side on both the front and back surfaces, but had a maximum coating weight of 130 mm from the edge in the width direction of the steel sheet to 130 g / m ^2.
g / m ² , an edge overcoat occurred. As is clear from this comparison test, when the suction nozzles 4R, 4L connected to the negative pressure source are opened between the sandwiching plates 3R, 3L, the ends in the width direction of the plating base plate S, which tend to be relatively high in pressure. Since a part of the wiping gas WG is sucked out of the system from the vicinity, it is confirmed that an edge overcoat is suppressed and a hot-dip coated steel strip having a uniform coating weight in the sheet width direction is manufactured.

[0019]

As described above, in the present invention, a part of the wiping gas is sucked out of the system through the suction nozzle opened near the end in the width direction of the plate, so that the wiping nozzles on both the front and back sides can be obtained. The turbulent flow generated by the wiping gas ejected from the colliding with each other without colliding with the original plating plate is suppressed from flowing to the central portion in the plate width direction. Therefore, the excess amount of hot-dip coated metal is removed under uniform wiping conditions in the sheet width direction,
A hot-dip steel strip having a uniform coating weight without edge overcoat is produced. In addition, since the wiping gas is partially removed by utilizing the relatively high pressure in the space between the front and back wiping nozzles, a simple mechanism for opening the suction nozzle at a predetermined location is sufficient.

[Brief description of the drawings]

FIG. 1 is a diagram (b) of a plating adhesion amount adjusting device provided with a high-pressure gas injection nozzle for eliminating edge overcoat in a direction perpendicular to the plate surface (a) and in a plate surface direction (b).

FIG. 2 is a diagram (b) of a plating adhesion amount adjusting device provided with a sandwiching plate and a suction nozzle according to the present invention when viewed in a direction perpendicular to the plate surface (a) and in a plate surface direction.

FIG. 3 is a horizontal cross-sectional view of a plating adhesion amount adjusting device also having a sandwiching plate and a suction nozzle.

[Explanation of symbols]

M: Hot-dip plating bath S: Plating plate WG: Wiping gas L: Overlapping length 1F, 1B: Wiping nozzle 3R, 3L: Clamp plate 4R, 4L: Suction nozzle

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Kazuaki Hosomi 5th Ishizu Nishimachi, Sakai City, Osaka Prefecture F-term in Nisshin Steel Co., Ltd. Technical Research Laboratory 4K027 AA02 AA22 AB42 AC52 AD21 AD22 AE24 AE35 AE37

Claims (2)

[Claims] When a wiping gas is sprayed on both front and back surfaces of a plating sheet immediately after being lifted from a hot-dip plating bath to remove excessively adhered hot-dip plating metal, a wiping gas is applied from the vicinity of an end of the plating sheet in the width direction of the sheet. A part of the steel sheet is sucked out of the system, and the atmospheric pressure near the end in the sheet width direction of the original plate is made closer to the atmospheric pressure in the center part in the sheet width direction. Method. 2. A wiping nozzle, which is disposed on both sides of a plating base plate pulled up from a hot-dip plating bath and has slits longer than the plate width of the plating base plate, and a sandwiching plate for sandwiching an end of the plating base plate in the plate width direction. And a suction nozzle opened between the sandwiching plates, wherein a part of the wiping gas is sucked out of the system via the suction nozzle from near the end in the width direction of the original plating plate.