Z765
- 1 -
4|t 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, is
discharged to the lateral bottom sides of the sink roll
- 2 -
™ 52, is reflected at the side walls of the coating tank 51
and flows downward, and stirs up the bottom dross 72.
[0004] If the bottom dross 72 is stirred up, the
stirred up bottom dross 72 deposits on the surface of the
5 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
stir-up of bottom dross 72 and preventing bottom dross
10 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
prevent stir-up of the bottom dross 72.
15 [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.
Citations List
20 Patent Literature
[0007] PLT 1: Japanese Patent Publication No. 2002-
69602A
PLT 2: Japanese Patent Publication No. 2000-54097A
PLT 3: WO2007/139206
25 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
53 which support the sink roll 52 or to the bearing parts
30 of the sink roll 52 (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
support members 53 or the sink roll 52, so the work of
35 replacement of the sink roll 52 becomes troublesome.
[0009] Further, when replacing the sink roll 52, the
line has to be made to stop and the tension between the
- 3 -
steel sheet and the sink roll 52 eased. The flow I
regulating members which are shown in PLT 1 and PLT 2
completely cover the bottom of the sink roll 52, so if
easing the tension between the steel sheet and the sink
5 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
comprised of ceramic. For this reason, to prevent
10 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
support members 53 rise in temperature becomes necessary.
15 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
entirely cover the bottom of the sink roll 52, so the
20 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
the surface of the steel sheet 75.
25 [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
not have side plates serving as flow regulating plates.
30 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
the above problems and provide a flow regulating member
35 of a hot dip coating tank which can suppress stir-up of
bottom dross and provide a continuous hot dip coating
system which uses the same.
- 4 -
^* Solution to Problem
[0014] The inventors worked to complete the above task
by studying in depth the structure of a system for
preventing stir-up inside of a continuous hot dip plating
5 bath tank. As a result, they discovered as follows. By
providing inside the plating bath tank a flow regulating
member which comprises horizontal plates and side members
which extend above the end parts of the bath tank wall
side of the horizontal plates vertical to the horizontal
10 plates and which are formed with large numbers of
dispersion holes, 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 effectively
prevented.
15 [0015] That is, by using horizontal plates to
attenuate the flow of the trailing flow while changing
the direction of flow and using side members in which
large numbers of dispersion holes are formed so as to
further attenuate and disperse the flow of the trailing
20 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 after the trailing flow strikes the wall
surfaces of the plating system can be rendered harmless.
25 [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
horizontal plates which are respectively arranged
30 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
side members which are arranged at positions
35 separated from the two ends of the sink roll, which
extend upward from the end parts of the respective
horizontal plates, and in which large numbers of
- 5 -
w* dispersion holes are formed,
the side members having an aperture ratio of 20 to
80%, and
the dispersion holes having a hole diameter of 5 to
5 50 mm.
[0018] (2) The flow regulating member of a hot dip
coating tank of (1), characterized in that the side
members have an aperture ratio in a range of 30 to 70%
and hole diameters in a range of 10 to 35%.
10 [0019] (3) A continuous hot dip coating system
characterized by being provided with a flow regulating
member of a hot dip coating tank of (1) or (2).
[0020] (4) The continuous hot dip coating system of
(3), characterized in that a horizontal direction
15 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.
20 [0021] (5) The continuous hot dip coating system of
(3) or (4), characterized in that a separation dimension
from a bottom end of the sink roll to the horizontal
plates is 100 to 160 mm.
[0022] (6) The continuous hot dip coating system of
25 any of (3) to (5), characterized in that the horizontal
plates are 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.
[0023] (7) The continuous hot dip coating system of
30 any of (3) to (6), characterized in that the flow
regulating member is attached by the support members and
horizontal members to edge faces of the hot dip coating
tank.
Advantageous Effects of Invention
35 [0024] In the present invention, the flow regulating
member of a hot dip coating tank is comprised of
horizontal plates which are respectively arranged
- 6 -
^P 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 side members which are arranged at positions
5 separated from the two ends of the sink roll, which
extend upward from the end parts of the respective
horizontal plates, and in which large numbers of
dispersion holes are formed. Therefore a trailing flow of
molten zinc strikes the horizontal plates, flows changed
10 in direction toward the outside directions, is dispersed
by the dispersion holes of the side members in various
directions at the outsides of the side members, and is
attenuated in flow rate, so stir-up of the bottom dross
is suppressed.
15 Brief Description of Drawings
[0025] [FIG. 1] An explanatory view of a flow
regulating member of a hot dip coating tank which shows
an embodiment of the present invention.
[FIG. 2] An explanatory view of the action of a flow
20 regulating member of a hot dip coating tank of the
present invention.
[FIG. 3] An explanatory view which shows the advantageous
effect of the present invention.
[FIG. 4] An explanatory view of a flow of a trailing
25 flow.
[FIG. 5] A graph which shows a relationship between a
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
30 separation dimension of a flow regulating member from a
bottom end of a sink roll and a dross stir-up index.
[FIG. 7] An explanatory view of an optimum separation
distance of a flow regulating member from a bottom end of
a sink roll.
35 [FIG. 8] An explanatory view which shows an aperture
ratio and hole diameter of dispersion holes of side
members.
- 7 -
^P [FIG. 9] A graph which shows the advantageous effects of
the present invention.
[FIG. 10] An explanatory view of a conventional hot dip
galvanizing system.
5 Description of Embodiments
[0026] Below, while referring to the drawings,
preferable embodiments of the present invention will be
shown. As shown in FIG. 1, a flow regulating member 10 of
a hot dip coating tank of the present invention (below,
10 simply referred to as the "flow regulating member 10") is
comprised of horizontal plates 1 and members at their
sides, that is, side members 2. The horizontal plates 1
are arranged from below two side ends of a sink roll 52
toward outside directions of the sink roll 52 in the
15 horizontal direction. As shown in FIG. 1(A), the
horizontal plates 1 are not positioned below a steel
sheet 75.
[0027] As shown in FIG. 1(A), the side members 2
extend upward from the outside ends of the horizontal
20 plates 1 and are arranged at positions separated from the
two ends of the sink roll 52.
[0028] As shown in FIG. 1(B), the side members 2 are
formed with large numbers of dispersion holes 2a. In the
present embodiment, as one embodiment of the present
25 invention, the side members 2 are so-called "punched
metal sheets", and the dispersion holes 2a are round
holes. Note that, the dispersion holes 2a which are
formed in the side members 2 are not limited to round
holes and may also be triangular holes, square holes,
30 hexagonal holes, or other polygonal holes or elongated
holes etc.
[0029] Further, the diameters of the dispersion holes
2a do not have to be constant from the sink roll sides of
the side members 2 to the wall surface sides of the
35 plating bath tank. For example, the holes may be shapes
which gradually increase in diameters from the sink roll
sides of the side members 2 to the wall surface sides of
- 8 -
the plating bath tank or the opposite. I
[0030] Note that, when the diameters of the dispersion
holes 2a differ at the sink roll sides and the wall
surface sides of the plating bath tank, the "hole
5 diameter" which is defined in the present invention shall
mean the diameter at the sink roll sides. Further, when a
dispersion hole 2a is not a round hole, the "hole
diameter" shall mean the circle equivalent diameter of
the dispersion hole 2a which is calculated from the area
10 of the hole.
[0031] As shown in FIG. 1(A), the flow regulating
member 10 which is comprised of the horizontal plates 1
and the side members 2 is supported by support members 3
which are attached to the coating tank 51. In other
15 words, the flow regulating member 10 is not attached to
the sink roll 52 or roll support members 53 which support
the sink 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
20 of the sink roll 52 does not become troublesome.
[0032] In the present embodiment, as shown in FIG.
1(A), the support members 3 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
25 tank 51 in the horizontal direction and vertical members
3b which hang down from the front ends of the horizontal
members 3a and which support the side members 2.
j [0033] Next, using FIG. 2, the action of the flow
! regulating member 10 of the present invention will be
30 explained. As shown in FIG. 2, (1), a trailing flow of
the molten zinc 71 which is discharged to a lateral
bottom side of the sink roll 52 strikes a horizontal
plate 1 and, while having some upward directed
components, flows changed in direction to the outside
35 direction of the horizontal plate 1 (side member 2
direction) (FIG. 2, (2)). At this time, the flow rate of
the trailing flow is attenuated. Further, if the trailing
- 9 -
flow reaches the side member 2, the trailing flow is 1
dispersed by the dispersion holes 2a of the side member 2
to various directions at the outside of the side member 2
and flows to the wall surface direction of the coating
5 tank 51 (FIG. 2, (3)). Even if the trailing flow strikes
the wall surface of the coating tank 51, the trailing
flow is sufficiently dispersed and the flow rate is
attenuated, so stir-up of the bottom dross 72 is
suppressed.
10 [0034] 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 plates 1 may also be
15 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 will work. When the
20 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.
[0035] Below, using FIG. 3 and Table 1, the
25 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
30 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
coating tank (water model test) so as to study various
structures. In the water model tests, as the tracers,
35 they used acryl particles of a particle size of 10 to 300
\xm and density of 1050 kg/m3, while for the stir-up of the
precipitated tracers, they used a commercially available
- 10 -
solution particle counter which enables the range of I
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
5 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).
[0036] Dr = number of tracers of particle size of 50
um or more stirred up/Total number of stirred up tracers
10 (1)
[0037] Table 1
A: Roll bottom „. , , Bottom Structure , B: Side members ^. d.r oss
members stir-up index
(..1..) No rmoelmlb, ebrost tom No side members 1.0
/^> Horizontal „-, ^ -, ^ , , n r, 2 pln a^t es Flat p_l ates no holes 0.8
,_, Punched metal „,.,_-,.,_ , , , . n r (3) s,h eet^s Flat plates (no holes 0.6
Punched metal . . _ .
(4) s,h eets No side members 0.4
Punched metal , , ^ n n .
(5) s.h eets Punched metal sheets 0.4
(,•6->) Horpil,za ot^ne ts al Punched met^a nl sheets _0 .„2
[0038] As shown in FIG. 3, (2), when forming the roll
15 bottom member A and side member B by flat plates, 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 roll bottom member A and side
member B (flat plates (no holes)), is discharged along
20 the flow of the steel sheet 75 from the deepmost part of
the horizontal plate 1 (paper depth side), and stirs up
the tracers 73 which simulated the bottom dross.
[0039] FIG. 3, (3) shows a case when forming the roll
bottom member A by a punched metal sheet and the side
25 member B 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 becomes a
- 11 -
^p downward flow which is dispersed by the punched metal
sheet comprising the roll bottom member A and a downward
flow which strikes and is reflected at the side member B
and flows down from the part of the center bottom of the
5 roll with no roll bottom member A. In this case as well,
the stir-up of the bottom dross 72 by the trailing flow
is reduced compared with the case of no roll bottom
member A and side member B (FIG. 3, (1)), but the
trailing flow which is dispersed and flows downward stirs
10 up the tracers 73 simulating the bottom dross.
[0040] As shown in FIG. 3, (4), when making the roll
bottom member A a punched metal sheet and eliminating the
side member B, the trailing flow of the molten zinc 71
which is discharged to the lateral bottom side of the
15 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
roll bottom member A and then strikes it. At this time,
the trailing flow which strikes the wall surface and
20 flows downward stirs up the tracers 73 simulating the
bottom dross.
[0041] As shown in FIG. 3, (5), when making the roll
bottom member A and side member B punched metal sheets,
the main flow of the trailing flow of the molten zinc 71
25 which is discharged to the lateral bottom side of the
sink roll 52 is dispersed by the punched metal sheets
comprising the roll bottom member A and side member B.
However, when the running speed is fast, part of the
trailing flow which is dispersed at the roll bottom
30 member A and flows downward stirs up the tracers 73
simulating the bottom dross.
[0042] As shown in FIG. 3, (6), when making the roll
bottom member A a flat plate (no holes) and making the
side member B a punched metal sheet, the amount of stir-
35 up of the tracers 73 simulating the bottom dross becomes
the smallest.
[0043] Next, the preferable sizes and installation
- 12 -
locations of the horizontal plates serving as the roll I
bottom members and the side members comprised of the
punched metal sheets will be explained.
[0044] In general, a sink roll 52 has an outside
5 diameter of 600 to 1000 mm (mostly 800 mm or so) and a
width dimension of 1800 to 2800 mm (mostly 2300 mm or
so). In this case, the side members 2 are arranged
separated from the ends of the sink roll 52 by 200 to 800
mm or so.
10 [0045] Below, the optimum dimensions when the sink
roll 52 has the above dimensions will be explained. Note
that, the entry angle 9 of the steel sheet from the
vertical direction is usually 25 to 40° or so. The steel
sheet 75 which is wound around the sink roll 52 has a
15 width of 600 to 2000 mm.
[0046] 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
sink roll 52.
[0047] When the steel sheet 75 is large in width, as
20 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
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)
25 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
shown in FIG. 4(C), (1), part of the trailing flow of the
molten zinc 71 flows downward toward the sink roll 52
30 from the position where the steel sheet 75 and the sink
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
35 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
- 13 -
^f coating tank 51.
[0048] When the steel sheet 75 is small in width, as
shown in FIG. 4(B), the trailing flow of the molten zinc
71 is discharged to the front and to the lateral bottom
5 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),
(3), the trailing flow of the molten zinc 71 flows
downward at the steel sheet exit side from the position
10 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
sheet 75 is large in width, flows toward the bottom of
the sink roll 52 from the position where the steel sheet
15 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
bottom of the coating tank 51, strikes the side surface
of the coating tank 51, then changes direction to the
20 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.
[0049] In this way, depending on the width of the
steel sheet 75 which is wound around the sink roll 52,
25 the direction of flow of the trailing flow of the molten
zinc 71 changes. For this reason, the side members 2 have
to be able to handle the flows which are created from all
widths of steel sheets 75 which are wound around the sink
roll 52. As shown in FIG. 1(B) and FIG. 4(C), the I
30 preferable width direction dimensions of the side members
2 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
35 dimension from the bearing parts of the sink roll 52 to
the steel sheet entry side direction as "Bb".
[0050] If the Bf dimension is smaller than 300 mm or
- 14 -
the Bb dimension is smaller than 350 mm, depending on the I
width of the steel sheet 75, much of the trailing flow of
the molten zinc 71 will not strike the side members 2,
but will leak out from the side members 2. Therefore, the
5 preferable width direction dimensions of the side members
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
larger than 500 mm or if the Bb dimension is larger than
850 mm, no further improvement in the effect of
10 dispersion of the trailing flow by the side members 2 can
be obtained. Further, depending on the variation in flow
of the trailing flow of the molten zinc 71, even if
setting the side members 2 to the preferable width
dimensions, the trailing flow of the molten zinc 71 is
15 liable to leak out from the side members 2. Therefore, it
is more preferable to add 100 mm to the preferable width
dimensions of the side members 2. Therefore, the
preferable width dimensions of the side members 2 are a
Bf dimension of 400 to 500 mm and a Bb dimension of 450
20 to 850 mm.
[0051] Note that, the height of the top ends of the
side members 2 from the bottom of the coating tank 51 is
preferably made approximately the same height as the
bearing parts of the sink roll 52. If the top end
25 positions of the side members 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 side
members 2. On the other hand, even if making the top end
positions of the side members 2 higher than the bearing I
30 parts of the sink roll 52 (for example, 50 mm or more
from the axial center of the sink roll), no further
effect of suppression of stir-up of bottom dross can be
obtained.
[0052] Below, using FIG. 5, the optimum separation
35 distance of the side members 2 from the wall surfaces of
the coating tank 51 will be explained. The graph of FIG.
5 is a graph which shows the relationship between the
- 15 -
separation dimension La of the side members 2 from the I
wall surfaces of the coating tank 51 (shown in FIG. 1(A))
and the dross stir-up index Dr while expressing the dross
stir-up index Dr at La=0 mm as "1.0". When obtaining the
5 data of FIG. 5, the above-mentioned water model test was
performed.
[0053] As shown in the graph of FIG. 5, if the side
members 2 approach the wall surfaces of the coating tank
51 too much, the dispersion effect of the trailing flow
10 of the molten zinc 71 by the side members 2 can no longer
be obtained. As shown in the graph of FIG. 5, if the
separation dimension La of the side members 2 and the
wall surfaces of the coating tank 51 becomes smaller than
50 mm, the dross stir-up index suddenly rises. Therefore,
15 the separation dimension La of the side members 2 and the
wall surfaces of the coating tank 51 is preferably 50 mm
or more.
[0054] Below, using FIG. 6 and FIG. 7, the optimum
separation distance from the bottom end of the sink roll
20 52 to the horizontal plates 1 will be explained. The
graph of FIG. 6 is a graph which shows the relationship
between the separation dimension Hb of the horizontal
plates 1 from the bottom end of the sink roll 52 (shown
in FIG. 1(B) or FIG. 9) and the dross stir-up index Dr
25 while expressing the dross stir-up index Dr at Hb=15 mm
as "1". When obtaining the data of FIG. 6, the abovementioned
water model test was performed.
[0055] As shown in FIG. 6, when the separation
dimension Hb of the horizontal plates 1 from the bottom
30 end of the sink roll 52 is 100 to 160 mm, the dross stirup
index Dr becomes the smallest. The reason will be
explained using FIG. 7.
[0056] As shown in FIG. 7, (1), when the separation
dimension Hb of the flow regulating member from the
35 bottom end of the sink roll 52 is small, the trailing
flow of the molten zinc 71 which is discharged to the
lateral bottom sides of the sink roll 52 at the position
- 16 -
^P where the steel sheet 75 and the sink roll 52 contact
immediately strikes the horizontal plates 1. As a result,
the attenuation of the trailing flow at the horizontal
plates 1 becomes insufficient and a trailing flow with a
5 fast flow rate strikes the side members 2, so with
dispersion by the side members 2, the trailing flow
cannot be sufficiently attenuated.
[0057] On the other hand, as shown in FIG. 7, (2), I
when the separation dimension Hb of the horizontal plates
10 1 from the bottom end of the sink roll 52 is large, the
trailing flow of the 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 does not strike the horizontal plates 1, but
15 directly strikes the side members 2. As a result, a
trailing flow with a fast flow rate strikes the side
members 2, so with just dispersion by the side members 2,
the trailing flow cannot be sufficiently attenuated.
[0058] As shown in FIG. 7, (3), when the separation
20 dimension Hb of the flow regulating member from the
bottom end of the sink roll 52 is the optimum value, the
trailing flow of the 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
25 contact strikes the horizontal plates 1 to be attenuated.
Furthermore, the trailing flow which has become slower in
flow rate strikes the side members 2. As a result, by
dispersion at the side members 2, the trailing flow can
be sufficiently attenuated.
30 [0059] Next, using FIG. 1, the optimum width dimension
of the horizontal plates 1 will be explained. As shown in
FIG. 1(A), the horizontal plates 1 are laid from below
the end parts of the sink roll 52 in the inside
directions by exactly a predetermined dimension Lw. Lw is
35 preferably 0 to 15% of the barrel length of the sink roll
52. If Lw is larger than 15% of the barrel length of the
sink roll 52, when making the line stop and the steel
- 17 -
^ f 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
5 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.
10 [0060] Further, the distance between the horizontal
plates 1 and the bottom of the coating tank is also not
particularly limited. It is sufficient that a space be
suitably maintained. Basically, if the coating tank is
sufficiently deep, the problem of stir-up does not arise,
15 but if making the coating tank deeper, a large amount of
molten metal becomes necessary and the cost becomes high,
so the depth 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 mm
20 or so.
[0061] FIG. 8 shows the optimum hole diameter and
aperture ratio of the dispersion holes 2a of the side
members 2. In the graph, (1) to (4) correspond to the
figures of (1) to (4) at the bottom. When, as shown in
25 FIG. 8, (1), the side members 2 are too small in aperture
ratio or when, as shown in FIG. 8, (2), the dispersion
holes 2a are too small in hole diameter, the members
become close to flat plates and a sufficient dispersion
effect cannot be obtained. On the other hand, when, as
30 shown in FIG. 8, (3), the side members 2 are too large in
aperture ratio or when, as shown in FIG. 8, (4), the
dispersion holes 2a are too large in hole diameter, the
state becomes close to one where there are no side
members 2 and a sufficient dispersion effect cannot be
35 obtained.
[0062] In consideration of the above reasons, the
inventors ran water model tests. As a result, as shown in
- 18 -
^f FIG. 8, the side members 2 have to have an aperture ratio
of 20 to 80%, preferably 30 to 70%, more preferably 40 to
60%. Further, the dispersion holes 2a have to have a hole
diameter of 5 to 50 mm, preferably 10 to 35 mm, more
5 preferably 15 to 30 mm.
[0063] 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
10 member 10 and horizontal members which connect to the
support members.
Examples
[0064] The flow regulating member 10 of the present
invention was placed in an actually operating coating
15 tank 51 and the horizontal plates 1 and side members 2
were made preferred sizes and were set at preferable
places so as to confirm the advantageous effects. For the
method of confirming the advantageous effects, the dross
stir-up index was used in the same way as the water model
20 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
counter.
[0065] The results are shown in FIG. 9. FIG. 9 is a
25 graph which compares the dross stir-up indexes when using
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
30 member of the present invention, it is possible to great
lower the dross stir-up index.
[0066] Note that, in the embodiments which were
explained above, the molten metal which was filled in the
coating tank 51 was molten zinc, but the molten metal is
35 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.
- 19 -
ytr [0067] Further, in the embodiments which were
explained above, the metal sheet material which was wound
around the sink roll 52 and was coated in the coating
tank 51 was a steel sheet, but the metal sheet material
5 is not limited to this. Even when coating an aluminum
sheet, copper sheet, or other metal sheet material, the
technical idea of the present invention can be applied
needless to say.
[0068] Above, the present invention was explained in
10 relation to embodiments which are believed to be the most
practical and preferable at the present point of time. Of
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
15 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
changes must be understood as being encompassed by the
20 technical scope.
Reference Signs List
[0069] 1 horizontal plate
2 side member
2a dispersion hole
25 3 support member
3a horizontal member
3b vertical member
10 flow regulating member of hot dip coating tank
51 coating tank
30 51a edge face
52 sink roll
53 roll support member
71 molten zinc
72 bottom dross
35 73 tracers simulating bottom dross
75 steel sheet

- 20 -
%> 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 said
sink roll and
side members which are arranged at
10 positions separated from the two ends of said sink roll,
which extend upward from the end parts of the respective
horizontal plates, and in which large numbers of
dispersion holes are formed,
said side members having an aperture ratio
15 of 20 to 80%, and
said dispersion holes having a hole
diameter of 5 to 50 mm.
Claim 2. The flow regulating member of a hot dip coating
tank as set forth in claim 1, characterized in that said
20 side members have an aperture ratio in a range of 30 to
70% and a hole diameter in a range of 10 to 35%.
Claim 3. 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
25 or 2.
Claim 4. The continuous hot dip coating system as set
forth in claim 3, characterized in that a horizontal
direction dimension from bearing parts of said sink roll
in a steel sheet exit side direction is 300 mm or more
30 and in that a horizontal direction dimension from bearing
parts of said sink roll in a steel sheet entry side
direction is 350 mm or more.
Claim 5. The continuous hot dip coating system as set
forth in claim 3, characterized in that a separation
35 dimension from a bottom end of said sink roll to said
horizontal plates is 100 to 160 mm.
Claim 6. The continuous hot dip coating system as set
i
- 21 -
w forth in claxm 3, characterized in that said horizontal
plates are laid from below the end parts of said sink
roll in inside directions of 0 to 15% of a barrel length
of the sink roll.
5 Claim 7. The continuous hot dip coating system as set
forth in claim 3, characterized in that said flow
regulating member is attached by the support members and
horizontal members to edge faces of the hot dip coating
tank.