'. Z766
- 1 -
DESCRIPTION
Title of Invention: Flow Regulating Member of Hot Dip
Coating Tank and Continuous Hot Dip Coating System
5
Technical Field
[0001] The present invention relates to the art of
inhibiting stir-up of bottom dross due to a flow of a hot
dip coating metal occurring along with running of a steel
10 sheet or rotation of a sink roll.
Background Art
[0002] A hot dip galvanizing system which performs
hot dip galvanization on a steel sheet, as shown in FIG.
10, is comprised of a coating tank 51 in which molten
15 zinc 71 is filled and a sink roll 52 which is supported
by roll support members 53 to hang down inside the
coating tank 51 in a rotatable manner. A steel sheet 75
which enters the inside of the coating tank 51 from above
is wound around the sink roll 52 whereby it is changed in
20 direction to head upward and is pulled up from the
coating tank 51. During this time, the surface of the
steel sheet 75 has molten zinc deposited on it whereby a
galvanized layer is formed.
[0003] If performing such hot dip galvanization, the
25 iron which is eluted from the steel sheet and the molten
zinc react whereby bottom dross 72 which is mainly
comprised of an iron-zinc alloy is produced and deposits
at the bottom of the coating tank 51. In such a hot dip
galvanization process, as shown in FIG. 10(B), along with
30 movement of the steel sheet 75 which enters the coating
tank 51 from above, a flow in the direction of movement
of the steel sheet 75 (below, referred to as a "trailing
flow" ) is formed in the molten zinc 71 which contacts the
steel sheet 75. The trailing flow of molten zinc 71, as
35 shown in FIG. 10(A) runs into a dead end at the position
where the steel sheet 75 and the sink roll 52 contact and
is discharged to the lateral bottom sides of the sink
•• - 2 -
roll 52. The flow of the molten zinc 71 is reflected at
the side walls of the coating tank 51, flows downward,
and stirs up the bottom dross 72.
[0004] If the bottom dross 72 is stirred up, the
5 stirred up bottom dross 72 deposits on the surface of the
steel sheet 75. The bottom dross 72 is hard, so at the
time of rolling or working, the surface of the steel
sheet 75 is formed with dents as bottom dross defects.
[0005] PLT 1 and PLT 2 propose the arts of preventing
10 stir-up of bottom dross 72 and preventing bottom dross
defects by providing flow regulating members which cover
the bottom or sides of the sink roll 52 and blocking the
flow of molten zinc 71 toward the lateral bottom sides of
the sink roll 52 by the flow regulating members so as to
15 prevent stir-up of the bottom dross 72.
[0006] PLT 3 proposes the art of providing the bottom
of a sink roll 52 with a flow regulating member which is
provided with a plurality of holes so as to prevent stirup
of the bottom dross 72.
20 Citations List
Patent Literature
[0007] PLT 1: Japanese Patent Publication No. 2002-
69602A
PLT 2: Japanese Patent Publication No. 2000-54097A
25 PLT 3: W02007/139206
Summary of Invention
Technical Problem
[0008] The flow regulating members which are shown in
PLT 1 and PLT 2 are attached to the roll support members
30 53 which support the sink roll 52 or to the sink roll 52
itself (side members which are shown in PLT 2) .
Therefore, when pulling up the sink roll 52 from the
coating tank 51 to replace the sink roll 52, the flow
regulating members have to be detached from the roll
35 support members 53 or the sink roll 52, so the work of
replacement of the sink roll 52 becomes troublesome.
[0009] Further, when replacing the sink roll 52, the
•• - 3 -
line has to be made to stop and the tension between the
steel sheet and the sink roll 52 eased. The flow
regulating members which are shown in PLT 1 and PLT 2
completely cover the bottom of the sink roll 52, so if
5 easing the tension between the steel sheet and the sink
roll 52, the drooping steel sheet will contact the flow
regulating members and damage the steel sheet or the flow
regulating members will break.
[0010] Further, the bearings of the sink roll 52 are
10 comprised of ceramic. For this reason, to prevent
cracking of the ceramic bearings due to sudden heat
expansion, before immersing the sink roll 52 and the roll
support members 53 in the molten zinc 71, a preheating
step of gradually making the sink roll 52 and the roll
15 support members 53 rise in temperature becomes necessary.
If the flow regulating members are attached to the sink
roll 52 and roll support members 53 at this time, energy
is wasted for preheating the flow regulating members.
[0011] Furthermore, the flow regulating members
20 entirely cover the bottom of the sink roll 52, so the
bottom dross 72 which is produced builds up on the flow
regulating members. The built up bottom dross 72 is
stirred up by the flow of molten zinc 71 which
accompanies rotation of the sink roll 52 and deposits on
25 the surface of the steel sheet 75.
[0012] The flow regulating member which is shown in
PLT 3 has the effect of attenuating the wall surface flow
rate which occurs at the two side surface parts of the
sink roll and stirs up the bottom dross. However, it does
30 not have side plates serving as flow regulating plates.
The effect is insufficient in particular when the running
speed of the steel sheet is fast and when the running
steel sheet is wide.
[0013] The present invention has as its task to solve
35 the above problems and provide a flow regulating member
of a hot dip coating tank which can suppress stir-up of
bottom dross and provide a continuous hot dip coating
- 4 -
system which uses the same.
Solution to Problem
[0014] The inventors worked to complete the above task
by studying in depth the structure of a system for
5 preventing stir-up inside of a continuous hot dip plating
bath tank. As a result, they discovered as follows. By
providing inside the plating bath tank a flow regulating
member which is provided with horizontal plates and, as
side members, louvers which are provided above the end
10 parts of the bath tank wall side of the horizontal plates
in directions vertical to the horizontal plates and have
flow direction changing members, the strong flow of the
trailing flow can be weakened while passed by a two-stage
mechanism. Therefore stir-up of the bottom dross can be
15 effectively prevented.
[0015] That is, by using horizontal plates to
attenuate the flow of the trailing flow while changing
the direction of flow and using louvers which have flow
direction changing members at their tips so as to further
20 attenuate and disperse the flow of the trailing flow.
Therefore, even if the trailing flow strikes the side
walls of the coating tank, it no longer has enough
strength to stir up the bottom dross and therefore the
flow motion of the trailing flow can be rendered
25 harmless.
[0016] The present invention was made based on the
above discoveries and has as its gist the following.
[0017] (1) A flow regulating member of a hot dip
coating tank characterized by being provided with
30 horizontal plates which are respectively arranged
horizontally from below two side end parts of a sink
roll, which is arranged inside of a coating tank in a
rotatable manner, toward outside directions of the sink
roll and,
35 as side members, louvers which are arranged above
from the end parts of the respective horizontal plates at
positions separated from the two ends of the sink roll
.,
- 5 -
and which have flow direction changing members which are
slanted so that their heights become gradually higher
toward the wall surface sides of the coating tank.
[0018] (2) The flow regulating member of a hot dip
5 coating tank of (1), characterized in that the louvers
have entrance side members which slant so as to gradually
increase in height from base ends of the flow direction
changing members toward the sink roll direction.
[0019] (3) The flow regulating member of a hot dip
10 coating tank of (1) or (2), characterized in that the
louvers have plated-shaped ribs which hang down from base
ends of the flow direction changing members.
[0020] (4) The flow regulating member of a hot dip
coating tank of any of (1) to (3), characterized in that
15 a pitch between a bottom end of a flow direction changing
member of a louver and a bottom end of the louver which
is provided adjoining the louver above it is 100 to 300
mm.
[0021] (5) The flow regulating member of a hot dip
20 coating tank of any of (2) to (4), characterized in that
an angle 81 of entrance side members of the louvers with
respect to the horizontal plane and an angle 82 of the
flow direction changing members with respect to the
horizontal satisfy -82s81s70° and 20os82s40°.
25 [0022] (6) A continuous hot dip coating system
characterized by being provided with a flow regulating
member of a hot dip coating tank of any of (1) to (5).
[0023] (7) The continuous hot dip coating system of
(6), characterized in that a horizontal direction
30 dimension from bearing parts of the sink roll in a steel
sheet exit side direction is 300 mm or more and in that a
horizontal direction dimension from bearing parts of the
sink roll in a steel sheet entry side direction is 350 mm
or more.
35 [0024] (8) The continuous hot dip coating system of
(6) or (7), characterized in that a separation dimension
- 6 -
of the louvers and wall surfaces of the coating tank is
50 mm or more.
[0025] (9) The continuous hot dip coating system of
any of (6) to (8), characterized in that the flow
5 regulating member is laid from below the end parts of the
sink roll in inside directions of 0 to 15% of a barrel
length of the sink roll.
[0026] (10) The continuous hot dip coating system of
any of (6) to (9), characterized in that the flow
10 regulating member is attached by the support members and
horizontal members to edge faces of the hot dip coating
tank.
Advantageous Effects of Invention
[0027] In the present invention, the flow regulating
15 member of a hot dip coating tank is characterized by
being provided with horizontal plates which are
respectively arranged horizontally from below two side
end parts of a sink roll, which is arranged inside of a
coating tank in a rotatable manner, toward outside
20 directions of the sink roll and louvers which are
arranged above from the end parts of the respective
horizontal plates at positions separated from the two
ends of the sink roll and which have flow direction
changing members which are slanted so that their heights
25 become gradually higher toward the wall surface sides of
the coating tank. Therefore, a trailing flow of molten
zinc strikes the horizontal plates, flows changed in
direction toward the outside directions of the horizontal
plates, is changed in flow to the upward direction by the
30 flow direction changing members of the louvers, so stirup
of the bottom dross is suppressed.
Brief Description of Drawings
[0028] [FIG. IJ An explanatory view of a flow
regulating member of a hot dip coating tank which shows
35 an embodiment of the present invention.
[FIG. 2J A detailed diagram of louvers.
[FIG. 3J An explanatory view which shows the advantageous
As shown in FIG. 2, the louvers 2 are comprised
•• - 7 -
effect of the present invention.
[FIG. 4] An explanatory view of a flow of a trailing
flow.
[FIG. 5] A graph which shows a relationship between a
5 separation dimension of side plates from wall surfaces of
a coating tank and a dross stir-up index.
[FIG. 6] A graph which shows a relationship between a
pitch between louvers and a dross stir-up index.
[FIG. 7] An explanatory view of an optimum separation
10 distance of a pitch between louvers.
[FIG. 8] An explanatory view which shows preferable
angles of louvers.
[FIG. 9] A graph which shows the advantageous effects of
the present invention.
15 [FIG. 10] An explanatory view of a conventional hot dip
galvanizing system.
Description of Embodiments
[0029] Below, while referring to the drawings,
preferable embodiments of the present invention will be
20 shown. As shown in FIG. 1, a flow regulating member 10 of
a hot dip coating tank of the present invention (below,
simply referred to as the "flow regulating member lO") is
comprised of horizontal plates 1 and side members made of
louvers 2. The horizontal plates 1 are arranged from
25 below two side ends of a sink roll 52 toward outside
directions of the sink roll 52 in the horizontal
direction. As shown in FIG. 1 (A) , the horizontal plates 1
are not positioned below a steel sheet 75.
[0030] As shown in FIG. 1 (A) , the louvers 2 are
30 arranged upward from the ends of the horizontal plates 1
at positions separated from the two ends of the sink roll
52.
[0031]
of entrance side members 2a, flow direction changing
35 members 2b, and plate-shaped ribs 2c. The entrance side
members 2a slant so as to gradually increase in height
from joints 2d of base ends of flow direction changing
15 member 10 which
and the louvers
are attached to
flow regulating
roll 52 or roll
•• - 8 -
members 2b (sink roll 52 direction side ends) toward the
sink roll 52 direction. The flow direction changing
members 2b slant so as to gradually increase in height
toward the wall surface direction of the coating tank 51.
5 The plate-shaped ribs 2c hang down from the joints 2d of
the base ends of the flow direction changing members 2b.
These form cross-sectional shapes of figure Y-shapes.
[0032] Pluralities of such louvers 2 are arranged in
the vertical direction. In the present embodiment, as one
10 embodiment of the present invention, two louvers 2 are
provided in the vertical direction. The flow direction
changing members 2b are attached at the wall surface
direction ends of the horizontal plates 1.
[0033] As shown in FIG. l(A), the flow regulating
is comprised of the horizontal plates 1
2 is supported by support members 3 which
the coating tank 51. In other words, the
member 10 is not attached to the sink
support members 53 which support the sink
20 roll 52. For this reason, when replacing the sink roll
52, the flow regulating member 10 is not pulled up from
the coating tank 51, so the work of replacement of the
sink roll 52 does not become troublesome. In the present
embodiment, as shown in FIG. l(A), the support members 3
25 are comprised of horizontal members 3a which are attached
to edge faces 51a of the coating tank 51 and extend to
the inside of the coating tank 51 in the horizontal
direction and vertical members 3b which hang down from
the front ends of the horizontal members 3a and which
30 support the louvers 2 or horizontal plates 1.
[0034] Next, using FIG. 2, the action of the flow
regulating member 10 of the present invention will be
explained. As shown in FIG. 2, (1), a trailing flow of
the molten zinc 71 which is discharged to a lateral
35 bottom side of the sink roll 52 strikes a horizontal
plate 1 and flows changed in direction to the outside
direction of the horizontal plate 1 (louver 2 direction)
- 9 -
(FIG. I(A), (2)). At this time, the flow rate of the
trailing flow is attenuated. Further, if the trailing
flow reaches the louvers 2, the trailing flow strikes the
entrance side members 2a and the ribs 2c and is
5 attenuated in flow rate, then is changed in direction of
flow to an upward direction by the flow direction chamber
members 2b of the louvers 2 and flows to the wall surface
side of the coating tank 51 (FIG. I(A), (3)). In this
way, the trailing flow is attenuated in flow rate by the
10 louvers 2, then is changed in direction of flow to the
upward direction and flows to the wall surface side of
the coating tank 51, so even if the trailing flow strikes
the wall surface of the coating tank 51, stir-up of the
bottom dross 72 is suppressed.
15 [0035] Note that the horizontal plates 1 are flat
plate shapes and are arranged in the horizontal
direction, so dross will almost never accumulate on the
horizontal plates 1. However, when operation is stopped
etc., slight dross may accumulate, so the horizontal
20 plates 1 may also be provided with holes. Even if the
horizontal plates 1 are provided with holes, the trailing
flow will strike the horizontal plates 1 at a slant, so
the mechanism by which the flow rate is attenuated and
the direction of flow is changed to an upward direction
25 will work. However, when the running speed is fast, the
trailing flow which passes through the holes easily
causes dross to be stirred up, so the horizontal plates 1
are preferably flat plates with no holes.
[0036] Below, using FIG. 3 and Table 1, the
30 advantageous effects of the flow regulating member 10 of
the present invention will be explained. The inventors
ran tests on a flow regulating member of a hot dip
coating tank wherein they filled water into a water tank
representing a coating tank, caused the precipitation of
35 tracers 73 simulating bottom dross, and matched the
Froude number in a coating tank in actual operation and
the Froude number in the water tank representing the
- 10 -
coating tank (water model test) so as to study various
structures. In the water model tests, as the tracers,
they used acryl particles of a particle size of 10 to 300
~m and density of 1050 kg/m3
, while for the stir-up of the
5 precipitated tracers, they used a commercially available
solution particle counter which enables the range of
particle size and the number of particles to be counted
by a laser scattering method. For evaluating the stir-up
of the tracers 73 simulating the bottom dross, a dross
10 stir-up index Dr was used. Here, the "dross stir-up index
Dr" is the dimensionless index which is represented by
the following formula (1).
[0037] Dr = number of tracers of particle size of 50
~m or more stirred up/Total number of stirred up tracers
15 (1 )
[0038] Table 1
Structure Roll bottom members B: Side Bottom dross
A: members stir-up index
(1 ) No roll bottom members
No side
1.0 members
(2) Horizontal plates
Flat plates
0.8 (no holes)
(3) Punched metal sheets
Flat plates
0.6 (no holes)
(4) Punched metal sheets
No side
0.4 members
Punched metal sheets with
(5) flow direction changing Louvers 0.4
members
( 6) Horizontal plates with flow Louvers 0.2 direction changing members
[0039] FIG. 3, (2) shows a case when forming the roll
bottom member A by a horizontal plate and the side member
20 B which is arranged above the end parts by a flat plate
(no holes). In this case, the trailing flow of the molten
zinc 71 which is discharged to the lateral bottom side of
the sink roll 52 strikes and is reflected at the
horizontal plate A and the side member B (flat plate (no
25 holes)), is discharged along the flow of the steel sheet
75 from the deepmost part of the horizontal plate 1
• - 11 -
(paper depth side), and stirs up the tracers 73 which
simulated the bottom dross.
[0040] As shown In FIG. 3, (3), when forming the roll
bottom member A by a punched metal sheet and the side
5 member B by a flat plate (no holes), the trailing flow of
the molten zinc 71 which is discharged to the lateral
bottom side of the sink roll 52 becomes a downward flow
which is dispersed by the punched metal sheet comprising
the roll bottom member A and a downward flow which
10 strikes and is reflected at the side member B and flows
down from the part of the center bottom of the roll with
no roll bottom member A. In this case as well, the stirup
of the bottom dross 72 by the trailing flow is reduced
compared with the case of no roll bottom member A and
15 side member B (FIG. 3, (1)), but the trailing flow which
is dispersed and flows downward stirs up the tracers 73
simulating the bottom dross.
[0041] As shown in FIG. 3, (4), when making the roll
bottom member A a punched metal sheet and eliminating the
20 side member B, the trailing flow of the molten zinc 71
which is discharged to the lateral bottom side of the
sink roll 52 includes a flow which is dispersed by the
roll bottom member A and flows downward and a flow which
directly strikes the wall surface or is reflected at the
25 roll bottom member A and then strikes it. At this time,
the trailing flow which strikes the wall surface and
flows downward stirs up the tracers 73 simulating the
bottom dross.
[0042] As shown in FIG. 3, (5), when making the roll
30 bottom member A a punched metal sheet with a flow
direction changing member and making the side member B
louvers 2, the main flow of the trailing flow of the
molten zinc 71 which is discharged to the lateral bottom
side of the sink roll 52 is attenuated in flow rate by
35 the louvers 2 comprising the side member B, the upward
flow is changed, and the zinc flows along the wall
surface side of the coating tank 51. However, when the
• - 12 -
running speed is fast, part of the trailing flow which is
dispersed at the roll bottom member A and flows downward
stirs up the tracers 73 simulating the bottom dross.
[0043] As shown in FIG. 3, (6), when making the roll
5 changing bottom A member a flat plate with a flow
direction changing member and making the side member B
louvers 2, the amount of stir-up of the tracers 73
simulating the bottom dross becomes the smallest.
[0044] Next, the preferable sizes and installation
10 locations of the horizontal plates serving and louvers
will be explained.
[0045] In general, a sink roll 52 has an outside
diameter of 600 to 1000 rnrn (mostly 800 rnrn or so) and a
width dimension of 1800 to 2800 rnrn (mostly 2300 rnrn or
15 so). In this case, the louvers 2 are arranged separated
from the ends of the sink roll 52 by 200 to 800 rnrn or so.
[0046] Below, the optimum dimensions when the sink
roll 52 has the above dimensions will be explained. Note
that, the entry angle e of the steel sheet from the
20 vertical direction is usually 25 to 40° or so. The steel
sheet 75 which is wound around the sink roll 52 has a
width of 600 to 2000 rnrn.
[0047] Note that, FIGS. 4(A) and (B) are top views of
the coating tank 51, while FIG. 4(C) is a side view of a
25 sink roll 52.
[0048] When the steel sheet 75 is large in width, as
shown in FIG. 4(A), the trailing flow of the molten zinc
71 is discharged from the position where the steel sheet
75 and the sink roll 52 contact to the back and lateral
30 bottom sides of the sink roll 52. If viewing this from
the side of the sink roll 52, as shown in FIG. 4 (C) , (2 )
the trailing flow of the molten zinc 71 flows downward at
the steel sheet entry side from the position where the
steel sheet 75 and the sink roll 52 contact. Further, as
35 shown in FIG. 4 (C) , (1) , part of the trailing flow of the
molten zinc 71 flows downward toward the sink roll 52
from the position where the steel sheet 75 and the sink
• - 13 -
roll 52 contact. In this way, when the steel sheet 75 is
large in width, the trailing flow of the molten zinc 71
flows toward the back side and the bottom side of the
coating tank 51, strikes the side surfaces of the coating
5 tank 51, then changes in direction toward the bottom side
of the coating tank 51 and flows downward, and stirs up
the bottom dross 72 which deposited at the bottom of the
coating tank 51.
[0049] When the steel sheet 75 is small in width, as
10 shown in FIG. 4(8), the trailing flow of the molten zinc
71 is discharged to the front and to the lateral bottom
side of the sink roll 52 at the position where the steel
sheet 75 and the sink roll 52 contact. If viewing this
from the side of the sink roll 52, as shown in FIG. 4(C),
15 (3), the trailing flow of the molten zinc 71 flows
downward at the steel sheet exit side from the position
where the steel sheet 75 and the sink roll 52 contact.
Further, as shown in FIG. 4(C), (1), the trailing flow of
the molten zinc 71, in the same way as when the steel
20 sheet 75 is large in width, flows toward the bottom of
the sink roll 52 from the position where the steel sheet
75 and the sink roll 52 contact. In this way, when the
steel sheet 75 is small in width, the trailing flow of
the molten zinc 71 flows toward the front and toward the
25 bottom of the coating tank 51, strikes the side surface
of the coating tank 51, then changes direction to the
bottom side of the coating tank 51 and stirs up the
bottom dross 72 which is deposited at the bottom of the
coating tank 51.
30 [0050] In this way, depending on the width of the
steel sheet 75 which is wound around the sink roll 52,
the direction of flow of the trailing flow of the molten
zinc 71 changes. For this reason, the louvers 2 have to
be able to handle the flows which are created from all
35 widths of steel sheets 75 which are wound around the sink
roll 52. As shown in FIG. 1(8) and FIG. 4(C), the
preferable width direction dimensions of the louvers 2
- 14 -
will be explained for the case of designating the
horizontal direction dimension from the bearing parts of
the sink roll 52 to the steel sheet exit side direction
as "Bf" and designating the horizontal direction
5 dimension from the bearing parts of the sink roll 52 to
the steel sheet entry side direction as "Bb".
[0051] If the Bf dimension is smaller than 300 mm or
the Bb dimension is smaller than 350 mm, depending on the
width of the steel sheet 75, much of the trailing flow of
10 the molten zinc 71 will not strike the louvers 2, but
will leak out from the louvers 2. Therefore, the
preferable width direction dimensions of the louvers 2
are a Bf dimension of 300 mm or more and a Bb dimension
of 350 mm or more. Note that, if the Bf dimension is
15 larger than 500 mm or if the Bb dimension is larger than
850 mm, no further improvement in the effect of
dispersion of the trailing flow by the louvers 2 can be
obtained. Further, depending on the variation in flow of
the trailing flow of the molten zinc 71, even if setting
20 the louvers 2 to the preferable width dimensions, the
trailing flow of the molten zinc 71 is liable to leak out
from the louvers 2. Therefore, it is more preferable to
add 100 mm to the preferable width dimensions of the
louvers 2. Therefore, the preferable width dimensions of
25 the louvers 2 are a Bf dimension of 400 to 500 mm and a
Bb dimension of 450 to 850 mm.
[0052] Note that, the height of the top ends of the
louvers 2 from the bottom of the coating tank 51 is
preferably made approximately the same height as the
30 bearing parts of the sink roll 52. If the top end
positions of the louvers 2 are lower than the bearing
parts of the sink roll 52, the trailing flow of the
molten zinc 71 is liable to leak out from the louvers 2.
On the other hand, even if making the top end positions
35 of the louvers 2 higher than the bearing parts of the
sink roll 52 (for example, 50 mm or more from the axial
center of the sink roll), no further effect of
- 15 -
suppression of stir-up of bottom dross can be obtained.
[0053] Below, using FIG. 5, the optimum separation
distance of the louvers 2 from the wall surfaces of the
coating tank 51 will be explained. The graph of FIG. 5 is
5 a graph which shows the relationship between the
separation dimension La of the louvers 2 from the wall
surfaces of the coating tank 51 (shown in FIG. l(A)) and
the dross stir-up index Dr while expressing the dross
stir-up index Dr at La=O mm as "1.0". When obtaining the
10 data of FIG. 5, the above-mentioned water model test was
performed.
[0054] As shown in the graph of FIG. 5, if the louvers
2 approach the wall surfaces of the coating tank 51 too
much, the dispersion effect of the trailing flow of the
15 molten zinc 71 by the louvers 2 can no longer be
obtained. As shown in the graph of FIG. 5, if the
separation dimension La of the louvers 2 and the wall
surfaces of the coating tank 51 becomes smaller than 50
mm, the dross stir-up index suddenly rises. Therefore,
20 the separation dimension La of the louvers 2 and the wall
surfaces of the coating tank 51 is preferably 50 mm or
more.
[0055] Below, using FIG. 6 and FIG. 7, the optimum
value of the pitch ~p between the bottom end of the flow
25 direction changing member 2b of a louver 2 and the bottom
end of the louver 20 which is provided adjoining that
louver 2 above it (shown in FIG. 2 or FIG. 7) will be
explained. The "bottom end of a louver 2" means the
bottom end of a rib in the case where a louver 2 has a
30 rib and a bottom end of a flow direction changing member
in the case where it does not have a rib. As shown in
FIG. 7A, when ~p is small, the trailing flow of the
molten zinc 71 has an extremely hard time flowing to the
wall surface direction of the coating tank 51 and behaves
35 in a manner very similar to Table 1 (2) and FIG. 3, (2),
so this is not preferable. On the other hand, when ~p is
..
- 16 -
large, most of the trailing flow which is attenuated in
flow by the horizontal plates while changing in the
direction of flow is not attenuated by the entrance side
members 2a or the ribs 2c. Further, the effect of
5 changing the flow to the upward direction by the flow
direction changing members 2b of the louvers 2 also
becomes smaller.
[0056] FIG. 6 is a graph which shows the relationship
between dP in the case when making the lengths of the
10 entrance side members 2a and flow direction changing
members 2b 100 ffiffi, making the height Ph of ribs 2c 40 ffiffi,
making the angle 81 of the entrance side members 2a with
respect to the horizontal plane 30°, and making the angle
82 of the flow direction changing member 2b with respect
15 to the horizontal plane 60° and the dross stir-up index Dr
while expressing the dross stir-up index Dr at dP=O as
"1.0". As shown in FIG. 6, dP is preferably 100 to 300
ffiffi, more preferably 150 to 250 ffiffi.
[0057] Further, the separation distance Hb of the
20 horizontal plates 1 from the bottom end of the sink roll
52 is not particularly limited, but is preferably 100 to
160 ffiffi from the viewpoint of the dross stir-up. The
distance between the horizontal plates 1 and the bottom
of the coating tank is also not particularly limited. It
25 is sufficient that a suitable space be maintained.
Basically, if the coating tank is sufficiently deep, the
problem of stir-up does not arise, but if making the
coating tank deeper, a large amount of molten metal
becomes necessary and the cost becomes high, so the depth
30 of the coating tank is limited to a certain extent. The
distance between the horizontal plates 1 and the bottom
of the coating tank is usually 500 to 1500 ffiffi or so.
[0058] FIG. 8 shows the optimum angles of the entrance
side members 2a and flow direction changing members 2b of
35 the louvers 2. In the graph, (A) to (C) correspond to the
figures (A) to (C) at the bottom. As shown in FIG. 8(A),
- 17 -
when the angle 81 of the entrance side members 2a from the
horizontal direction is large, almost all of the trailing
flow of the molten zinc 71 is stopped by the entrance
side members 2a and does not flow to the flow direction
5 changing members 2b. On the other hand, as shown in FIG.
8B, when the angle 82 of the flow direction changing
members 2b from the horizontal direction is small, almost
no effect is obtained of the trailing flow of the molten
zinc 71 being changed ln flow to the upward direction by
10 the flow direction changing members 2b. Further, as shown
in FIG. 8(C), when the angle 82 of the flow direction
changing members 2b from the horizontal direction is
large, the trailing flow of the molten zinc 71 is greatly
changed in flow to the upward direction by the flow
15 direction changing members 2b, a strong upward flow is
created near the wall surfaces of the coating tank 51,
and top dross which flows up at the surface layer of the
molten zinc 71 (not shown) deposits on the steel sheet,
so quality defects are caused. The above-mentioned top
20 dross is an alloy of the iron which is eluted from the
steel sheet and the aluminum which is dissolved in the
zinc bath for the purpose of adjusting the ingredients in
the zinc bath.
[0059] The angles 81 and 82 of the entrance side
25 members 2a and flow direction changing members 2b of the
louvers 2 with respect to the horizontal plane are
preferably an 81 and 82 which satisfy -82~81~70° and
200~82~40°, more preferably 200~81~40° and 300~82~70°, still
more preferably 50o~82~60°.
30 [0060] Further, the angle 83 of the end parts of the
horizontal plates 1 is not particularly limited, but is
preferably 0 to 70°, more preferably 50 to 60°.
[0061] Next, using FIG. 1, the optimum width dimension
of the horizontal plates 1 will be explained. As shown in
35 FIG. l(A), the horizontal plates 1 are laid from below
the end parts of the sink roll 52 in the inside
• - 18 -
directions by exactly a predetermined dimension Lw. The
predetermined dimension Lw is preferably 0 to 15% of the
barrel length of the sink roll 52. If the predetermined
dimension Lw is larger than 15% of the barrel length of
5 the sink roll 52, when making the line stop and the steel
sheet 75 droops down, the steel sheet 75 may contact the
horizontal plates 1. On the other hand, when the end
parts of the horizontal plates 1 are not below the end
parts of the sink roll 52, the trailing flow of the
10 molten zinc 71 which is discharged to the lateral bottom
sides of the sink roll 52 at the position where the steel
sheet 75 and the sink roll 52 contact is liable to not
strike the horizontal plates 1 and to stir up the bottom
dross 72.
15 [0062] The flow regulating member 10 of the present
invention, to secure work efficiency, may also be
attached to the edge faces of the coating tank 51 by
support members which connect to the flow regulating
member 10 and horizontal members which connect to the
20 support members.
Examples
[0063] The flow regulating member 10 of the present
invention was placed in an actually operating coating
tank 51 and the horizontal plates 1 and louvers 2 were
25 set at preferable places so as to confirm the
advantageous effects. The lengths of the entrance side
members 2a and the flow direction changing members 2b of
the louvers 2 were made 100 mm, the height Ph of the ribs
2c was made 40 mm, 81=30°, 82=60°, and ~P=160 mm. For the
30 method of confirming the advantageous effects, the dross
stir-up index was used in the same way as the water model
test. However, the particle size and the number of
particles of the bottom dross were visually viewed using
an electron microscope rather than a solution particle
35 counter.
[0064] The results are shown in FIG. 9. FIG. 9 is a
graph which compares the dross stir-up indexes when using
• - 19 -
the dross stir-up index Dr at a line speed of 110 mpm
with no countermeasures taken as "1.0". As shown in FIG.
9, it could be confirmed that compared with the case of
no countermeasures, by installing the flow regulating
5 member of the present invention, it is possible to great
lower the dross stir-up index.
[0065] Note that, in the embodiments which were
explained above, the louvers 2 were comprised of the
entrance side members 2a, flow changing members 2b, and
10 ribs 2c, but even if the louvers 2 are comprised of only
the flow changing members 2b, the trailing flow of the
molten zinc 71 is changed to an upward direction by the
flow direction changing members 2b and there is an effect
of suppression of stir-up of the bottom dross 72.
15 Further, either of the entrance side members 2a and ribs
2c may be omitted in other embodiments.
[0066] Note that, in the embodiments which were
explained above, the molten metal which is filled in the
coating tank 51 was molten zinc, but the molten metal is
20 not limited to that. Even if tin, copper, or another
molten metal, the technical idea of the present invention
can be applied needless to say.
[0067] Further, in the embodiments which were
explained above, the metal sheet material which was wound
25 around the sink roll 52 and subjected to the plating
treatment in the coating tank 51 was a steel sheet, but
the metal sheet material is not limited to this. Even
when subjecting an aluminum sheet, copper sheet, or other
metal sheet material to plating treatment, the technical
30 idea of the present invention can be applied needless to
say.
[0068] Above, the present invention was explained in
relation to embodiments which are believed to be the most
practical and preferable at the present point of time. Of
35 course, the present invention is not limited to the
embodiments which are disclosed in the description of the
present application. The present invention may be
- 20 -
suitably changed in a range not contravening the gist or
idea of the invention which can be read from the claims
or the description as a whole. A flow regulating member
of a hot dip coating tank which is accompanied with such
5 changes must be understood as being encompassed by the
technical scope.
Reference Signs List
[0069] 1 horizontal plate
2 louver
10 2a entrance side member
2b flow direction changing member
2c rib
2d joint
3 support member
15 3a horizontal member
3b vertical member
10 flow regulating member of hot dip coating tank
51 coating tank
51a edge face
20 52 sink roll
53 roll support member
71 molten zinc
72 bottom dross
73 tracer simulating bottom dross
25 75 steel sheet

- 21 -
CLAIMS
Claim 1. A flow regulating member of a hot dip coating
tank characterized by being provided with
horizontal plates which are respectively
5 arranged horizontally from below two side end parts of a
sink roll, which is arranged inside of a coating tank in
a rotatable manner, toward outside directions of the sink
roll and,
as side members, louvers which are
10 arranged above from the end parts of the respective
horizontal plates at positions separated from the two
ends of the sink roll and which have flow direction
changing members which are slanted so that their heights
become gradually higher toward the wall surface sides of
15 the coating tank.
Claim 2. The flow regulating member of a hot dip coating
tank as set forth in claim 1, characterized in that said
louvers have entrance side members which slant so as to
gradually increase in height from base ends of said flow
20 direction changing members toward said sink roll
direction.
Claim 3. The flow regulating member of a hot dip coating
tank as set forth in claim 1 or 2, characterized in that
said louvers have plated-shaped ribs which hang down from
25 base ends of said flow direction changing members.
Claim 4. The flow regulating member of a hot dip coating
tank as set forth in claim 1 or 2, characterized in that
a pitch between a bottom end of a flow direction changing
member of a louver and the bottom end of the louvers
30 which are provided adjoining said louver above it is 100
to 300 mID.
Claim 5. The flow regulating member of a hot dip coating
tank as set forth in claim 1 or 2, characterized in that
an angle 81 of entrance side members of said louvers with
35 respect to the horizontal plane and an angle 82 of the
flow direction changing members with respect to the
'. - 22 -
horizontal satisfy -82~81~70° and 20o~82~40°.
Claim 6. A continuous hot dip coating system
characterized by being provided with a flow regulating
member of a hot dip coating tank as set forth in claim 1
5 or 2.
Claim 7. The continuous hot dip coating syste~ as set
forth in claim 6, characterized in that a horizontal
direction dimension from bearing parts of the sink roll
in a steel sheet exit side direction is 300 mm or more
10 and in that a horizontal direction dimension from bearing
parts of the sink roll in a steel sheet entry side
direction is 350 mm or more.
Claim 8. The continuous hot dip coating, system as set
forth in claim 6, characterized in that a separation
15 dimension of said louvers and wall surfaces of the
coating tank is 50 mm or more.
Claim 9. The continuous hot dip coating system as set
forth in claim 6, characterized in that said flow
regulating member is laid from below the end parts of the
20 sink roll in inside directions of 0 to 15% of a barrel
length of the sink roll.
Claim 10. The continuous hot dip coating system as set
forth in claim 6, characterized in that the flo~
regulating member is attached by the support members and
25 horizontal members to edge faces of the hot dip coating
tank.
Dated this 14/06/2013 ~~\J~
NEHA SRIVASTAVA
OFREMFRY & SAGAR
ATTORNEY FORTHEAPPLICANT[S]