Specification
[Title of the Invention] GAS WIPING METHOD AND GAS WIPING APPARATUS
[Technical Field of the Invention]
[OOO 11
The present invention relates to a gas wiping method and a gas wiping
apparatus.
Priority is claimed on Japanese Patent Application No. 20 12-2 1 1 120, filed on
September 25,2012, the contents of which are incorporated herein by reference.
[Related Art]
[0002]
Typically, a process of forming a coating layer on a surface of a steel sheet by
a hot dip coating is as follows. First, the steel sheet is dipped into a coating bath, and
I
I then is pulled upward in a vertical direction from the coating bath. For example, as
1
illustrated in FIGS. 7A, 7B and 7C, a gas wiping apparatus 100 is provided above the
coating bath.
FIG. 7A is a view (a front view of the gas wiping apparatus 100) when the gas
wiping apparatus 100 is seen in a thickness direction (in an X direction in FIG. 7A) of a
coated steel sheet W that is pulled upward from the coating bath (not illustrated). FIG.
7B is a view (a plan view of the gas wiping apparatus 100) when the gas wiping
apparatus 100 is seen in a direction (in a vertically upward direction: in a Z direction in
FIG. 7B) in which the coated steel sheet W is pulled upward. FIG. 7C is a view (a
side view of the gas wiping apparatus 100) when the gas wiping apparatus 100 is seen
in a width direction (in a Y direction in FIG. 7C) of the coated steel sheet W.
[0004]
The gas wiping apparatus 100 of the related art includes a pair of wiping
nozzles 10 1 and 102 which are disposed so as to face each other and interpose the
coated steel sheet W therebetween in the thickness direction of the coated steel sheet W
(that is, a steel sheet onto which coating metal is deposited) that is pulled upward from
the coating bath, and each of which ejects a wiping gas Gw along the width direction
of the coated steel sheet W.
[0005]
The wiping nozzle 10 1 has a slit-shaped wiping gas ejection port 10 la
provided in the Y direction at a tip end thereof. The wiping nozzle 102 has a slitshaped
wiping gas ejection port 102a provided in the Y direction at a tip end thereof.
In FIGS. 7A and 7C, a dotted chain line NZ indicates center positions (that is, positions
at which the wiping gases Gw are ejected in the Z direction) in the Z direction of the
wiping gas ejection ports 1 0 1 a and 102a.
[0006]
The pair of wiping nozzles 101 and 102 blows the wiping gas Gw (for
example, an inert gas, air or the like) onto both surfaces of the coated steel sheet W
along the width direction thereof immediately after the coated steel sheet W is pulled
upward. As a result, unsolidified coating metal (hot dip coating metal) is removed
from the surfaces of the coated steel sheet W, and the amount of a coating deposit on
the surfaces of the coated steel sheet W is adjusted.
[0007]
As illustrated in FIGS. 7A and 7B, typically, each of the wiping nozzles 101
and 102 has a length in the Y direction longer than the width of the coated steel sheet
W. That is, both ends of each of the wiping nozzles 10 1 and 102 extend to the
outsides farther than both end portions of the coated steel sheet W.
Accordingly, as illustrated in FIGS. 8A and 8B, in a region on the outside of
each end portion of the coated steel sheet W, the wiping gases Gw ejected from the pair
of wiping nozzles 101 and 102 collide with each other.
[0008]
In a collision region GC (hereinafter, referred to as a gas collision region) of
the wiping gas Gw, as illustrated in FIG. 9, collision (occurrence of a negative
pressure) and repulsion (occurrence of a positive pressure) of the wiping gases are
repeated and thus, gas turbulence (a gas flow, of which a pressure pulsates between a
positive pressure and a negative pressure) occurs to accompany the occurrence of the
negative pressure.
During the ejection of the wiping gas Gw, the negative pressure resulting from
the gas turbulence occurring in the gas collision region GC causes the hot dip coating
metal deposited on each end portion of the coated steel sheet W to be pulled to the
outside of each end portion of the coated steel sheet W. As a result, as illustrated in
FIG. 8A, a liquid membrane LC of the hot dip coating metal is forrned on each end
portion of the coated steel sheet W to swell toward the outside.
[0009]
As described above, droplets S (hereinafter, referred to as splashes) spatter
from the liquid membrane LC of the hot dip coating metal, which is formed on each
end portion of the coated steel sheet W, and are deposited on the wiping nozzles 10 1
and 102, peripheral equipment or the coated surface of the coated steel sheet W. For
convenience of description, FIGS. 8A and 8B illustrate only the outside of one end
portion of the coated steel sheet W, but the same phenomenon occurs on the outsides of
both end portions of the coated steel sheet W.
[OO 101
When the splashes S are deposited on the wiping nozzles 101 and 102,
opening areas of the wiping gas ejection ports 10 1 a and 102a reduce. When the
splashes S are increasingly deposited on the wiping nozzles 10 1 and 102, the wiping
gas ejection ports 10 1 a and 102a are blocked. When the splashes S are deposited on
the peripheral equipment, there is a possibility that the deposition portions of the
splashes S corrode. When the splashes S are deposited and solidified on the coated
surface of the coated steel sheet W, the dimension or the exterior of the coated surface
is adversely affected.
[OO 1 11
In the related art, there is a case where as illustrated in FIGS. 10A and 1 OB, a
gas shield plate 103 for suppressing the spattering and the deposition of the splashes S
is disposed at a position which separates toward the outside from each end portion of
the coated steel sheet W. The gas shield plate 103 is disposed so that the gas shield
plate 103 is interposed between the wiping nozzle 10 1 and the wiping nozzle 102.
That is, the wiping gases Gw ejected from the pair of wiping nozzles 10 1 and 102
collide with both surfaces of the gas shield plate 103.
[OO 1 21
As a result, as illustrated in FIGS. 10A and 1 OB, the gas collision region GC
has reduced width in the Y direction, and the gas turbulence occurring in the gas
collision region GC also generates reduced negative pressure, thereby causing the
liquid membrane LC of the hot dip coating metal to swell less toward the outside from
each end portion of the coated steel sheet W, and decreasing the amount of the splashes
S that spatter from the liquid membrane LC.
As such, when the gas shield plate 103 is provided, the spattering and the
deposition of the splashes S can be suppressed to some extent. For convenience of
description, FIGS. 10A and 10B illustrate only the outside of one end portion of the
coated steel sheet W, but the same phenomenon occurs on the outsides of both end
portions of the coated steel sheet W.
[00 131
A distance between each end portion of the coated steel sheet W and the gas
shield plate 103 is preferably set to be as short as possible (the gas collision region GC
is set to be small) in order for the Iiquid membrane LC on each end portion of the
coated steel sheet W to be less affected by the negative pressure of the gas turbulence
occurring in the gas collision region GC.
However, in a real operation, each end portion of the coated steel sheet W
pulled upward from the coating bath is not always at a constant position in the Y
direction. Accordingly, it is necessary to set the distance between each end portion of
the coated steel sheet W and the gas shield plate 103 to a value with a safety margin so
that the coated steel sheet W and the gas shield plate 103 do not come into contact with
each other. That is, there is a limit to the splash suppression effect by the gas shield
plate 103.
[00 141
As described above, only with the gas shield plate 103 being provided at the
position which separates toward the outside from each end portion of the coated steel
sheet W, it is difficult to sufficiently suppress the spattering and the deposition of the
splashes S.
In particular, in the recent hot dip coating, the amount of coating liquid that is
picked up increases in conjunction with a high coating velocity, there is a tendency that
a pressure of ejecting the wiping gas is increased in order for the amount of a coating
deposit to be reduced and thus, a countermeasure against the splashes becomes an
- 5 -
important task. Accordingly, a wiping process of the hot dip coating requires a
measure that serves to effectively suppress or prevent the spattering and the deposition
of the splashes S.
[OO 151
For example, as illustrated in FIGS. 1 1 A and 1 1 B, Patent Document 1
discloses a technology in which a purge gas ejection nozzle 104 is provided in a gap
between each end portion of the coated steel sheet W and the gas shield plate 103, and
the purge gas ejection nozzle 104 ejects a purge gas Gp in a direction (in a vertically
downward direction) reverse to the direction in which the coated steel sheet W is
pulled upward.
[00 161
According to the technique, a gas curtain resulting from the purge gas Gp is
formed in the gap between each end portion of the coated steel sheet W and the gas
shield plate 103. As a result, the directions in which the splashes S spatter from each
end portion of the coated steel sheet W are limited to the vertically downward direction,
and the spattering and the deposition of the splashes S are suppressed.
[Prior Art Document]
[Patent Document]
[00 171
[Patent Document 11 Japanese Unexamined Patent Application, First
Publication No. H07-33 1404
[Disclosure of the Invention]
[Problems to be Solved by the Invention]
[0018]
As described above, according to Patent Document 1, the spattering and the
deposition of the splashes S can be further suppressed by the provision of the purge gas
ejection nozzle 104 compared to when only the gas shield plate 103 is provided.
However, according to research performed bythe inventor, it is determined that the
technique disclosed in Patent Document I does not sufficiently cope with a high
wiping gas pressure in conjunction with a high-speed hot dip coating process, and there
is still room for improvement in the viewpoint of the splash suppression effect.
[00 191
The present invention is made in consideration of the above-described
problems, and an object of the present invention is to provide a gas wiping method and
a gas wiping apparatus which have a splash suppression effect greater than that of the
related art.
[Measures for Solving the Problem]
[0020]
The present invention adopts the following measures to solve the abovedescribed
problems and to achieve the related object.
(1) A gas wiping method according to an aspect of the present invention is a
method in which a wiping gas is ejected along a width direction of a coated steel sheet
from a pair of wiping nozzles which are disposed so as to face each other and interpose
the coated steel sheet therebetween in a thickness direction of the coated steel sheet
that is pulled upward from a coating bath and thus, the amount of a coating deposit of
the coated steel sheet is adjusted. The method includes disposing a gas shield plate at
a position which separates toward an outside from each end portion in the width
direction of the coated steel sheet so that the gas shield plate is interposed between the
pair of wiping nozzles, ejecting a gas from a side nozzle disposed at a predetermined
position and thus, forming a gas flow along each surface of the gas shield plate in a
direction reverse to a direction in which the coated steel sheet is pulled upward.
[002 11
(2) In the gas wiping method according to (I), the side nozzle may be
disposed on each surface of the gas shield plate.
[0022]
(3) In the gas wiping method according to (1) or (2), the gas ejected from
the side nozzle may be air or an inert gas.
[0023]
(4) A gas wiping apparatus according to an aspect of the present invention
includes a pair of wiping nozzles which are disposed so as to face each other and
interpose a coated steel sheet therebetween in a thickness direction of the coated steel
sheet that is pulled upward from a coating bath, and each of which ejects a wiping gas
along a width direction of the coated steel sheet; a gas shield plate that is disposed at a
position which separates toward an outside from each end portion in the width
direction of the coated steel sheet so that the gas shield plate is interposed between the
pair of wiping nozzles; and a side nozzle that ejects a gas to form a gas flow along each
surface of the gas shield plate in a direction reverse to a direction in which the coated
steel sheet is pulled upward.
[0024]
(5) In the gas wiping apparatus according to (4), the side nozzle may be
disposed on each surface of the gas shield plate.
[0025]
(6) In the gas wiping apparatus according to (4) or (9, a gas ejected from
the side nozzle may be air or an inert gas.
[Effects of the Invention]
[0026]
According to the aspects, it is possible to significantly suppress the spattering
and the deposition of the splashes of unsolidified coating metal in a hot dip coating
process compared to the related art. That is, according to the aspects, it is possible to
provide the gas wiping method and the gas wiping apparatus which have a splash
suppression effect greater than that of the related art.
[Brief Description of the Drawings]
[0027]
FIG. 1A is a front view of a gas wiping apparatus 1 according to an
embodiment of the present invention.
FIG. 1B is a plan view of the gas wiping apparatus 1 according to the
embodiment of the present invention.
FIG. 1 C is a side view of the gas wiping apparatus 1 according to the
embodiment of the present invention.
FIG. 2A is a schematic view illustrating a splash suppression effect of the gas
wiping apparatus 1 according to the embodiment of the present invention.
FIG. 2B is a schematic view illustrating the splash suppression effect of the
gas wiping apparatus 1 according to the embodiment of the present invention.
FIG. 3A is a schematic view illustrating the splash suppression effect of a
technique disclosed in Patent Document 1.
FIG. 3B is a schematic view illustrating the splash suppression effect of the
technique disclosed in Patent Document 1 .
FIG. 4 is a schematic view illustrating a modification example of the
embodiment.
I FIG. 5A is a schematic view illustrating a modification example of the
embodiment.
FIG 5B is a schematic view illustrating the modification example of the
embodiment.
FIG. 6A is a schematic view illustrating a modification example of the
embodiment.
,
FIG. 6B is a schematic view illustrating the modification example of the
embodiment.
FIG. 7A is a front view of a gas wiping apparatus 100 of the related art.
FIG. 7B is a plan view of the gas wiping apparatus 100 of the related art.
FIG. 7C is a side view of the gas wiping apparatus 100 of the related art.
FIG. 8A is a schematic view illustrating a mode in which splashes S spatter
from each end portion of a coated steel sheet W due to gas turbulence occurring in a
collision region GC of a wiping gas Gw.
FIG. 8B is a schematic view illustrating the mode in which the splashes S
spatter from each end portion of the coated steel sheet W due to the gas turbulence
occurring in the collision region GC of the wiping gas Gw.
FIG. 9 is a schematic view illustrating a mechanism in which gas turbulence (a
gas flow, of which a pressure pulsates between a positive pressure and a negative
pressure) occurs in the collision region GC of the wiping gas Gw to accompany
occurrence of a negative pressure.
FIG. 10A is a schematic view illustrating a mode in which the splashes S
spatter from each end portion of the coated steel sheet W when a gas shield plate 103 is
provided.
FIG. 10B is a schematic view illustrating the mode in which the splashes S
spatter from each end portion of the coated steel sheet W when the gas shield plate 103
is provided.
FIG 11A is a schematic view illustrating the technique disclosed in Patent
Document 1.
FIG 11B is a schematic view illustrating the technique disclosed in Patent
Document 1.
[Embodiments of the Invention]
[0028]
Hereinafter, an enlbodiment of the present invention will be described in
detail with reference to the accompanying drawings.
FIGS. 1 A, 1 B and 1 C are schematic views illustrating a configuration of a gas
wiping apparatus 1 according to the embodiment. FIG. 1A is a view (a front view of
the gas wiping apparatus 1) when the gas wiping apparatus 1 is seen in a thickness
direction (in an X direction in FIG. 1A) of a coated steel sheet W that is pulled upward
from a coating bath (not illustrated). FIG. 1B is a view (a plan view of the gas wiping
apparatus 1) when the gas wiping apparatus 1 is seen in a direction (in a vertically
upward direction: in a Z direction in FIG. 1B) in which the coated steel sheet W is
pulled upward. FIG. 1 C is a view (a side view of the gas wiping apparatus 1) when
the gas wiping apparatus 1 is seen in a width direction (in a Y direction in FIG. 1 C) of
the coated steel sheet W.
[0029]
As illustrated in FIGS. 1 A, 1B and 1 C, the gas wiping apparatus 1 according
to the embodiment includes a pair of wiping nozzles 11 and 12; two gas shield plates
13 and 14; two first side nozzles 15 and 16; and two second side nozzles 17 and 18.
In FIG. 1 A, the wiping nozzles 11 and 12 are not illustrated.
[003 01
The pair of wiping nozzles 11 and 12 are disposed so as to face each other and
interpose the coated steel sheet W therebetween in the thickness direction of the coated
steel sheet W (that is, a steel sheet on which coating metal is deposited) that is pulled
upward from the coating bath, and each of the pair of wiping nozzles 11 and 12 ejects a
wiping gas Gw along the width direction of the coated steel sheet W. The wiping
nozzle 1 1 has a slit-shaped wiping gas ejection port 1 1 a provided in the Y direction at a
tip end thereof. The wiping nozzle 12 has a slit-shaped wiping gas ejection port 12a
provided in the Y direction at a tip end thereof. In FIGS. 1A and lC, a dotted chain
line NZ indicates center positions (that is, positions at which the wiping gases Gw are
ejected in the Z direction) in the Z direction of the wiping gas ejection ports 11 a and
12a.
[003 11
The gas shield plate 13 is disposed at a position which separates toward the
outside from one end portion of the coated steel sheet W in the Y direction so that the
gas shield plate 13 is interposed by the wiping nozzles 1 1 and 12. The gas shield
plate 14 is disposed at a position which separates toward the outside from the other end
portion of the coated steel sheet W in the Y direction so that the gas shield plate 14 is
interposed by the wiping nozzles 11 and 12. The wiping gas Gw ejected from each of
the pair of wiping nozzles 11 and 12 collides with each surface of the gas shield plates
13 and 14.
The gas shield plates 13 and 14 are preferably disposed so that the thickness
directions of the gas shield plates 13 and 14 coincide with the thickness direction of the
coated steel sheet W.
[0032]
It is preferred that a distance between the gas shield plate 13 and one end
portion of the coated steel sheet W be short, but in a real operation, it is necessary to
set the distance between the gas shield plate 13 and one end portion of the coated steel
sheet W to a value with a safety margin so that the gas shield plate 13 and one end
portion of the coated steel sheet W do not come into contact with each other. A
distance between the gas shield plate 14 and the other end portion of the coated steel
sheet W is also set similarly to the distance between the gas shield plate 13 and one end
portion of the coated steel sheet W.
[003 31
The first side nozzle 15 is disposed in the vicinity of an upper end of a front
surface of the gas shield plate 1 3. The first side nozzle 16 is disposed in the vicinity
of an upper end of a rear surface of the gas shield plate 13. The first side nozzles 15
and 16 are disposed so as to face each other and interpose the gas shield plate 13
therebetween.
Each of the first side nozzles 15 and 16 ejects a side gas Gs in a direction (in a
vertically downward direction) reverse to the direction in which the coated steel sheet
W is pulled upward. Accordingly, a gas flow (hereinafter, referred to as a descending
side gas flow) is forrned along each surface (front and rear surfaces) of the gas shield
plate 13 in a direction reverse to the direction in which the coated steel sheet W is
pulled upward.
[0034]
A slit-shaped side gas ejection port (not illustrated) extending in the Y
direction is provided in a tip end of each of the first side nozzles 15 and 16.
Accordingly, the side gas Gs is ejected from each of the first side nozzles 15 and 16
and thus, the descending side gas flow having a constant width in the Y direction is
formed on each surface of the gas shield plate 13.
The shape of the side gas ejection port provided in the tip end of each of the
first side nozzles 1 5 and 16 is not limited to a slit shape. For example, it is preferred
that a plurality of circular side gas ejection ports be provided at constant intervals
along the Y direction in the tip end of each of the first side nozzles 15 and 16.
The second side nozzle 17 is disposed in the vicinity of an upper end of a
front surface of the gas shield plate 14. The second side nozzle 18 is disposed in the
vicinity of an upper end of a rear surface of the gas shield plate 14. The second side
nozzles 17 and 18 are disposed so as to face each other and interpose the gas shield
plate 14 therebetween.
Each of the second side nozzles 17 and 18 ejects a side gas Gs in a direction
reverse to the direction in which the coated steel sheet W is pulled upward.
Accordingly, a descending side gas flow is forrned along each surface of the gas shield
plate 14 in a direction reverse to the direction in which the coated steel sheet W is
pulled upward.
A slit-shaped side gas ejection port (not illustrated) extending in the Y
direction is provided in a tip end of each of the second side nozzles 17 and 18.
Accordingly, the side gas Gs is ejected from each of the second side nozzles 17 and 18
and thus, the descending side gas flow having a constant width in the Y direction is
formed on each surface of the gas shield plate 14.
The shape of the side gas ejection port provided in the tip end of each of the
second side nozzles 17 and 18 is not limited to a slit shape. For example, it is
preferred that a plurality of circular side gas ejection ports be provided at constant
intervals along the Y direction in the tip end of each of the second side nozzles 17 and
18. The side gas Gs ejected from each of the first side nozzles 15 and 16 and each of
the second side nozzles 17 and 18 is preferably air or an inert gas.
[003 71
Hereinafter, operational effects of the gas wiping apparatus 1 with this
configuration will be described.
The wiping gases Gw ejected from the pair of wiping nozzles 11 and 12
collide with both surfaces of the gas shield plates 13 and 14. As a result, as illustrated
in FIGS. 10A and 1 OB, the gas collision region GC has reduced width in the Y
direction, and gas turbulence occurring in the gas collision region GC also generates
reduced negative pressure, thereby causing the liquid membrane LC of hot dip coating
metal to swell less toward the outside from each end portion of the coated steel sheet W,
and decreasing the amount of the splashes S that spatter from the liquid membrane LC.
[003 81
The fact that, as such, when the gas shield plates 13 and 14 are provided, the
spattering and the deposition of the splashes can be suppressed to some extent was
already discussed. However, in a real operation, since it is necessary to set the
distance between each end portion of the coated steel sheet W and each of the gas
shield plates 13 and 14 to a value with a safety margin so that the coated steel sheet W
and the gas shield plates 13 and 14 do not come into contact with each other, there is a
limit to a splash reduction effect by the gas shield plates 13 and 14.
[003 91
In the gas wiping apparatus 1 of the embodiment, the descending side gas
flow is formed on each surface of the gas shield plates 1 3 and 14 by the ejection of the
side gas Gs. When the gas shield plate 13 is taken as an example, as illustrated in
FIGS. 2A and 2B, a gas flow Ga (hereinafter, referred to as a descending associated
gas flow) is formed on the outside of each end portion of the gas shield plate 13 due to
the descending side gas flows formed on both surfaces of the gas shield plate 13, and
flows in the direction reverse to the direction in which the coated steel sheet W is
pulled upward.
[0040]
As such, part of the gas turbulence occurring in the gas collision region GC
stabilizes as a downward gas flow due to the descending associated gas flow Ga
formed between the gas shield plate 13 and one end portion of the coated steel sheet W
and thus, pressure pulsation is eliminated. This implies that the gas collision region
GC between the gas shield plate 13 and one end portion of the coated steel sheet W has
reduced width in the Y direction in practicality (the liquid membrane LC on each end
portion of the coated steel sheet W is less affected by a negative pressure). The gas
shield plate 14 is also subject to the same phenomenon.
[004 11
That is, according to the embodiment, the liquid membrane LC of the hot dip
coating metal can swell less toward the outside from each end portion of the coated
steel sheet W (refer to FIG. 2A) than in the related art in which only the gas shield plate
is provided. As a result, it is possible to further decrease the amount of the splashes S
that spatter from the liquid membrane LC of the hot dip coating metal.
[0042]
In contrast, as discussed above, the technique (in which the gas shield plate
103 and the purge gas ejection nozzle 104 are combined) disclosed in Patent Document
1 does not sufficiently cope with a high wiping gas pressure in conjunction with a
high-speed hot dip coating process, and cannot provide the same level of the splash
suppression effect as that of the embodiment. Hereinafter, a reason thereof will be
described.
[0043]
In the technique disclosed in Patent Document 1, the descending flow of the
purge gas Gp is formed in the gap between each end portion of the coated steel sheet
W and the gas shield plate 103 and thus, the directions in which the splashes S spatter
from the liquid membrane LC of the hot dip coating metal which swells toward the
outside from each end portion of the coated steel sheet W is limited to the vertically
downward direction (refer to FIG. 1 1A).
[0044]
Even in the technique disclosed in Patent Document 1, it is considered that
since the descending flow of the purge gas Gp is formed in the gap between each end
portion of the coated steel sheet W and the gas shield plate 103, part of the gas
turbulence occurring in the gas collision region GC stabilizes as a downward gas flow
and thus, pressure pulsation is eliminated. That is, even in the technique disclosed in
Patent Document 1, it is seemingly considered that similar to in the embodiment, the
gas collision region GC between the gas shield plate 103 and each end portion of the
coated steel sheet W has reduced width in the Y direction in practicality (the liquid
membrane LC on each end portion of the coated steel sheet W is less affected by a
negative pressure).
[0045]
However, according to research performed by the inventor, it is determined
that even though the purge gas ejection nozzle 104 ejects the purge gas Gp in the
vertically downward direction along the gap between each end portion of the coated
steel sheet W and the gas shield plate 103, the width in the Y direction of the gas
collision region GC does not become small.
[0046]
As illustrated in FIGS. 3A and 3B, in the technique disclosed in Patent
Document 1, since the wiping gases Gw ejected from each of the wiping nozzles 10 1
and 102 collide with each other on both surfaces of the gas shield plate 103, an
ascending flow Gu and a descending flow Gd of the wiping gas Gw are formed in a
collision region (a position indicated by a reference symbol NZ in FIGS. 3A and 3B) as
a starting point along each surface of the gas shield plate 103. Furthermore, an
ascending associated flow Gua and a descending associated flow Gda occur in the
vicinity of each end of the gas shield plate 103 in conjunction with the ascending flow
Gu and the descending flow Gd of the wiping gas Gw.
[0047]
The descending flow of the purge gas Gp is greatly dampened due to the
ascending associated flow Gua occurring in the vicinity of each end of the gas shield
plate 103. As a result, part of the gas turbulence occurring in the gas collision region
GC does not stabilize as a downward gas flow, and the width in the Y direction of the
gas collision region GC does not become small.
[0048]
Since the ascending flow Gu of the wiping gas Gw, which is formed on each
surface of the gas shield plate 103, is pressurized as highly as the wiping gas Gw is
pressurized in conjunction with a high-speed hot dip coating process, the descending
flow of the purge gas Gp is also greatly dampened. That is, the splash suppression
effect caused by the purge gas Gp ejected from the purge gas ejection nozzle 104 is
reduced in conjunction with the high-speed hot dip coating process.
Accordingly, when the embodiment is compared to the technique disclosed in
Patent Document 1, the embodiment can provide the splash suppression effect greater
than that of the technique disclosed in Patent Document 1.
[0049]
The embodiment illustrates the configuration in which two first side nozzles
15 and 16 are directly disposed on both surfaces of the gas shield plate 13, and two
second side nozzles 17 and 18 are directly disposed on both surfaces of the gas shield
plate 14.
However, the present invention is not limited to the embodiment. As long as
the descending side gas flows can be formed on both surfaces of the gas shield plates
13 and 14, there is no limit to the number or disposition of side nozzles.
[0050]
For example, as illustrated in FIG. 4, the present invention may adopt a
configuration in which the first side nozzles 15 and 16 are disposed at positions which
separate upward from the gas shield plate 13, and eject the side gases toward both
surfaces of the gas shield plate 13 from the positions. FIG. 4 does not illustrate
positional relationships of the second side nozzles 17 and 18 with respect to the gas
shield plate 14, but the positional relationships are also the same.
[005 11
For example, as illustrated in FIGS. 5A and 5B, the present invention may
adopt a configuration in which in replacement of the first side nozzles 15 and 16, one
first side nozzle 2 1 is provided directly above the gas shield plate 1 3, and in
replacement of the second side nozzles 17 and 18, one second side nozzle 22 is
provided directly above the gas shield plate 14.
As illustrated in FIG. 5B, a side gas Gs ejected vertically downward from the
second side nozzle 21 is split into two descending flows centering around the gas
shield plate 13. As a result, descending side gas flows are formed on both surfaces of
the gas shield plate 13. A relationship between the second side nozzle 22 and the gas
shield plate 14 will be also the same.
[0052]
Furthermore, for example, as illustrated in FIGS. 6A and 6B, in replacement
of the first side nozzles 15 and 16, a pair of first auxiliary nozzles 25 and 26 may be
disposed downstream of the steel sheet W farther than the wiping nozzles 1 1 and 12 so
that the pair of first auxiliary nozzles 25 and 26 face each other to interpose the gas
shield plate 13 therebetween. In replacement of the second side nozzles 17 and 18, a
pair of second auxiliary nozzles 27 and 28 may be disposed downstream of the steel
sheet W farther than the wiping nozzles 1 1 and 12 so that the pair of second auxiliary
nozzles 27 and 28 face each other to interpose the gas shield plate 14 therebetween.
In FIGS. 6A and 6B, the second auxiliary nozzle 28 is not illustrated.
[0053]
Each of the first auxiliary nozzles 25 and 26 ejects the side gas Gs toward the
steel sheet W in the X direction. Accordingly, as illustrated in FIG. 6B, a descending
flow (a descending side gas flow) of the side gas Gs is formed on each surface of the
gas shield plate 13. Similarly, each of the second auxiliary nozzles 27 and 28 ejects
the side gas Gs toward the steel sheet W in the X direction. Accordingly, a
descending flow (a descending side gas flow) of the side gas Gs is formed on each
surface of the gas shield plate 14 (not illustrated in FIG. 6B).
[Industrial Applicability]
[0054]
As described above, according to the present invention, it is possible to
significantly suppress the spattering of the splashes in the hot dip coating process.
Accordingly, the present invention is highly applicable to a coating industry.
[Brief Description of the Reference Symbols]
[OOS 51
1,100: GAS WIPING APPARATUS
11,12,101,102: WIPINGNOZZLE
13, 14,103: GAS SHIELD PLATE
15,16,21: FIRSTSIDENOZZLE
17,18,22: SECOND SIDE NOZZLE
25,26: FIRST AUXILIARY NOZZLE
27,28: SECOND AUXILIARY NOZZLE
1 04: PURGE GAS EJECTION NOZZLE
W: COATED STEEL SHEET
Gw: WIPINGGAS
Gs: SIDEGAS
Gp: PURGEGAS
GC: GAS COLLISION REGION
LC: LIQUID MEMBRANE OF HOT DIP COATING METAL
S: DROPLET OF HOT DIP COATING METAL (SPLASH)
[Document Type] CLAIMS
[Claim 11
A gas wiping method in which a wiping gas is ejected along a width direction
of a coated steel sheet from a pair of wiping nozzles which are disposed so as to face
each other and interpose the coated steel sheet therebetween in a thickness direction of
the coated steel sheet that is pulled upward from a coating bath and thus, the amount of
a coating deposit of the coated steel sheet is adjusted, the method comprising:
disposing a gas shield plate at a position which separates toward an outside
from each end portion in the width direction of the coated steel sheet so that the gas
shield plate is interposed between the pair of wiping nozzles; and
ejecting a gas from a side nozzle disposed at a predetermined position and
thus, forming a gas flow along each surface of the gas shield plate in a direction
reverse to a direction in which the coated steel sheet is pulled upward.
[Claim 21
The gas wiping method according to claim 1,
wherein the side nozzle is disposed on each surface of the gas shield plate.
[Claim 31
The gas wiping method according to claim 1 or 2,
wherein the gas ejected from the side nozzle is air or an inert gas.
[Claim 41
A gas wiping apparatus comprising:
a pair of wiping nozzles which are disposed so as to face each other and
interpose a coated steel sheet therebetween in a thickness direction of the coated steel
sheet that is pulled upward from a coating bath, and each of which ejects a wiping gas
along a width direction of the coated steel sheet;
1
I a gas shield plate that is disposed at a position which separates toward an
outside from each end portion of the coated steel sheet in the width direction of the
coated steel sheet so that the gas shield plate is interposed between the pair of wiping
I nozzles; and
a side nozzle that ejects a gas to form a gas flow along each surface of the gas
shield plate in a direction reverse to a direction in which the coated steel sheet is pulled
upward.
[Claim 51
The gas wiping apparatus according to claim 4,
wherein the side nozzle is disposed on each surface of the gas shield plate.
[Claim 61
The gas wiping apparatus according to claim 4 or 5,
wherein a gas ejected from the side nozzle is air or an inert gas.
Dated 24.07.2014
TA-DUTT]
& SAGAR