WATER-BLOCKING API'ARATUS AND WATERBLOCKING
METHOD FOR COOLING WATER FOR HOT-ROLLED STEEL
SHEET
The present invention relates to a water-blocking apparatus and a waterblocking
method for blocking cooling water sprayed onto a hot-rolled steel sheet,
particularly, cooling water having a sprayed water density of higher than 4 m3/m2/min
and equal to or less than 10 m3/m2/min when the hot-rolled steel sheet is cooled after
finish rolling of a hot-rolling process.
Priority is claimed on Japanese Patent Application No. 2012-130630, filed on
June 8,2012 and Japanese Patent Application No. 2012-196536, filed on September 6,
2012, and the contents of which are incorporated herein by reference.
[Background Art]
[0002]
A hot-rolled stccl sheet after finish rolling of a hot-rolling process is cooled by
a cooling apparatus provided above and below a run-out table to a predetermined
temperature while being transported by the run-out table from a finishing mill to a
coiler, and is thereaftcr coiled by the coiler. In the hot rolling of the hot-rolled stecl
sheet, cooling manners after the linish rolling are important factors that dctermine
mechanical properties, workability, weldability, and the like of the hot-rolled steel
sheet, and thus it is important to uniformly cool the hot-rolled stccl sheet to a
predetermined temperature.
[00031
In the cooling process after the finish rolling, typically, the hot-rolled steel
sheet is cooled by using, for example, water (hereinafter, called cooling water) as a
coolant. Specifically, in a predetermined cooling area of the hot-rolled steel sheet, the
hot-rolled steel sheet is cooled by using the cooling water. In addition, as described
above, in order to uniformly cool the hot-rolled steel sheet to a predetermined
temperature, there is a need to prevent extra cooling water on the upstream sidc or the
downstream side of the cooling area from leaking.
[0004]
Therefore, blocking the cooling water on the hot-rolled steel sheet is
performed. As a water-blocking mcthod for the cooling water, various methods have
been proposed.
[OOOS]
In Patent Document 1, arranging onc or more rows of no/~lesth at spray
water-blocking water from slit-shaped or circular nozzle spray holes on the
downstream side of a cooling apparatus, that is, cooling nozzles that spray cooling
water so that spray angles thereof are inclined toward the upstream side of a hot-rolled
steel sheet in a sheet-thlcading dircction is proposed. In addition, blocking llre
cooling water is performed by the water-blocking water sprayed onto the hot-rolled
steel shect from the nozzles.
[OOO6]
In addition, in Patent Document 2, providing a water spray type waterblocking
Sacility in a cooling apparatus and arranging air nozzle groups on the
downstream side of the watcr spray type water-blocking facility is proposed. In
addition, water-bloclting watcr is sprayed onto a hot-rolled steel sheet from thc water
spray type water-blocking facility, and air is simultaneously ejected toward the hotrolled
stecl sheet from the air nozzle groups in an air wind direction substantially
perpendicular to a sheet-threading direction, thereby bloclting the cooling water is
pcrformed.
[0007]
Moreover, in Patent Document 3, a water-bloclting apparatus which includes a
header provided with nozzles that spray water-bloclting water onto a hot-rolled steel
sheet so that a momentum of the water-bloclting water per unit time and unit width (a
force of the water-blocking water) is maintained in a range of 1.5 to 5 times the
momentum of cooling water that stays on the surface of the hot-rolled steel sheet per
unit time and unit width (a force of the cooling water) to spray the water-bloclting
water onto the hot-rolled stecl sheet from the nozzles is proposed.
[Prior Art Document]
[Patent Document]
[0008]
[Patent Document 11 Japanese {Jnexanlined Patent Application, First
Publication No. 2007-152429
[Patent Docunlcnt 21 Japancse Unexamined Patcnt Application, F I I S ~
Publication No. 201 0-227966
[Patent Document 31 Japanese Unexa~nined Patent Application, First
Publication No. 2012-51013
[Summary of the Invention]
[Problems to be Solved by the invclltion]
[0009]
Here, when the hot-rolled steel sheet is cooled, there may be cases where
cooling water having a sprayed water density of, fol example, higher than 4 m3/m2/min
and equal to or less than 10 m3/m2/min is sprayed onto the hot-rolled steel sheet.
(00 101
However, in Patent Docu~ncnt 1, only the spray anglcs of the nozzles that
spray the water-blocking water are exemplified, and the other conditions, for example,
a watcr amount or flow velocity of thc water-bloclting water are not disclosed. In
addition, in Patent Document 2, conditions such as a water amount or flow velocity of
the water-blocliing water are not also disclosed. Moreover, in Patent Document 3, for
example, as described in Examples and Table 1 of the specification of Patent
Document 3, only the case where cooling water having a low sprayed water density of
4 m3im2/min or less is sprayed onto the hot-rolled steel sheet is considered. Therefore,
the water-bloclting methods described in Patent Documents 1 to 3 do not consider
bloclting thc cooling water having a high sprayed water density at all, and there may be
cases where cooling water having a high sprayed water density cannot be blocked.
[0011]
In addition, in a case where water on a sheet caused by cooling water having a
flow rate of 4 m3/m2/min or less is bloclted, as illustrated in FIG. 8, in a plan view,
arranging impact areas 101 of water-bloclting water which is sprayed from a plurality
of flat spray nozzles 100 and impacts on the surface ofa hot-rolled steel sheet 10, in
the shape of a mountain so as not to interfere with each other may be considered. In
this case, thc flow of the water on the sheet in a sheet-threading direction (a negative Y
direction in FIG. 8) is temporarily receivcd by the flat spray nozzles 100 such that a
flow in the width direction is generated, thereby discharging the watcr on the sheet by
the flow. Since the width-direction components of the flow of the water-blocking
water that do not interfere with each other are effectively operated, even when there is
a gap between the water-blocking water, in the case of the cooling water having a flow
rale of 4 m3/n12/min or less, the cooling water rarely leaks as indicated by the inclincd
arrows in FIG. 8.
[00 121
Furtherrnorc, the inventors had intensively researched and found that in the
case where cooling water having a high sprayed water density of higher than 4
rn3/m2/min and equal to or less than 10 m3/m2/min is sprayed onto a hot-rolled steel
sheet, when the momentum or water-blocliing water is maintained in a range of 1.5 to 5
times the momentum of the cooling water as desclibed in Patent Document 3, the
water-bloclting water submerges below the cooling water and the cooling ability of the
cooling water to cool the hot-rolled steel sheet is degraded.
[0013]
The present invention has been made taking the foregoing circumstances into
consideration, and an object thereof is to, when a hot-rolled steel sheet after finish
rolling of a hot-rolling process is cooled by a large amount of cooling water, to
appropriately block the cooling water while appropriately cooling the hot-rolled steel
sheet with the cooling water.
[Means for Solving the Problems]
[00 141
The plescnt invention employs the lbllowing means in ordcr to accomplish
the object to solve the problems. That is,
(1) According to an aspect of the prcsent invention, a water-blocking
apparatus for cooling water for a hot-rolled steel sheet, which bloclis cooling water
sprayed onto a hot-rolled steel sheet at a sprayed water density of highcr than 4
m3/m2/mm and equal to or less than 10 milm2/rni~w~h en the hot-lollcd steel sheet is
cooled after finish rolling of a hot-rolling process, includes: a plurality of waterbloclting
nozzles which spray water-blocking water onto the hot-rolled stcel sheet.
Impact areas of the watcr-blocking water respectively sprayed from the water-blocliing
nozzles are continuously lined up in a straight line in a width direction of the hot-rolled
steel shcct on a surface of the hot-rolled steel sheet and the adjacent impact areas
partially overlap.
[0015]
As described above, in many cooling facilities according to the related art, the
amount of cooling water is small, and thcre was no demand for bloclting the cooling
water in the vicinity of a cooling facility that uses a large amount of the cooling water
(refer to Patent Documents 1 to 3). Howcvcr, in recent years, sincc steel sheets
having various materials are required, the amount of watcr used in cooling facilities is
increased, and a water-blocking facility for preventing a largc amount of water on a
sheet from leaking is needed.
Therefore, as a result of intensive research by the inventors, it was provcd that
in a case where a hot-rolled steel sheet is cooled by cooling water having a high
sprayed watcr density of higher than 4 m3/m2/min and equal to or less than 10
m3/m2/min, by satisljiing the conditions in which impact areas of water-blocli~trgw atcr
sprayed from a plurality of water-blocking nozzles are continuously lined up in a
straight line in a width direction of the hot-rolled steel sheet on a surface of the hotrollcd
steel sheet and the adjacent impact areas partially overlap, the cooling water call
be appropriately blocltcd while appropriately cooling the hot-rolled steel sheet by the
cooling water.
[0016]
IIithel-to, in the case where a small amount of cooling water is blocked,
generally, a method of arranging impact areas of water-blocliing water sprayed from a
plurality of water-blocking nozzles onto a surface of a hot-rolled steel sheet in a wedge
shape with respect to a flowing direction ol the water on the sheet to push the water on
the sheet to the left and the right was employed (see FIG. 8). In this watcr-blocking
method according to the related art, even when there is a gap bctween the adjacent
impact areas of the water-blocking water, in the case where the hot-rolled steel sheet is
cooled by a small amount of the cooling water having a flow rate of 4 m3/m2/min or
less, the water on the sheet (the cooling water) does not leak from the gap as indicated
by the inclined arrows in FIG. 8.
I-Iowever, in a case where the hot-rolled steel sheet is cooled by the cooling
water having a large amount of higher than 4 m3/m2/min and equal to or less than 10
m3/m2/min, in the water-blocking method according to the related art as described
above, the water on the sheet leaks froin the gap between thc adjacent impact areas of
the water-blocking water as indicated by the inclined arrows in FIG. 8, and thus
cooling of the hot-rolled steel sheet and blocking thc cooling water could not be
appropriately performed.
'Therefore, first, the inventors had verified a water-blocking effect by adjusting
the arrangement or spraying direction of nozzles for the water-blocking watcl to allow
a plurality of impact areas of the water-blocking water to be continuously lined up in a
straight line in thc width direction of the hot-rolled steel shcel on the surface of the hotrolled
steel sheet. As a result, no gap was formed between thc adjacent impact areas
of the water-blocking water and thus an iinprovement in the leakage of the waler on the
sheet had succeeded comparcd to the method according to the related art. However,
the inventors perror~nedn ew examinations to cope with a larger amount of cooling
water.
100 171
In the water-blocking method according to the related art to cope with a small
amount of cooling water, as illustrated in FIG. 8, the arrangement ol: the water-blocking
nozzles, the spraying direction of the water-blocking water, and the like are set so that
the adjacent impact areas of the water-blocking water do not overlap (in other words,
the water-bloclting water does not interfere with each other). For example, even for
the cooling water or high-pressure water for descaling, generally, the arrangement of
nozzles, the spraying direction or watel; and the like are set so that water sprayed from
the nozzles does not interfere with each other. The reason is that it is difficult to
predict the influence of the interference between the water sprayed from the nozzles
pertaining to a cooling ability or a descaling ability and a largc loss occurs in the water
stream. Therefore, even in the water-blocliing method according to thc related art, thc
interference between the water-blocking water is avoided depending on a method of
spraying the cooling water or the high-pressure water for dcscaling.
However, m the case where the water-blocking water is sprayed onto the hotlolled
steel sheet, there is no need to consider thc influence of the inte~fercnccb ctwecn
the water-blocking water pertaining to the cooling ability, the loss of the water stream,
and the like, and lealtagi: prevention ofthe water on the sheet by the water slrc:~rn
formed on the surface of the steel sheet by spraying the water-bloclting water is the
first object.
LOO1 81
Therefore, regardless of the common technical lmowledge according to the
related art, the inventors had verified the water-blocking effect by adjusting the
arrangement or spraying direction of the nozzles for the water-blocking waicr to allow
the plurality or impact areas ofthe water-blocking watcr to be continun~~slliyn cd up in
a straight line in the width direction ofthc hot-rolled stccl sheet on the surfacc ofthc
hot-rolled steel sheet and to allow the ad,jacent impact areas to partially overlap (that is,
the adjacent water-bloclting water interferes with cach other), and had succeeded in
significantly improving the lealtage of the water on the sheet compared to the method
according to the related art even in the casc where the hot-rolled steel sheet is cooled
by the cooling water having a large amount of higher than 4 m3/m2/min and equal to or
less than 10 m3/m2/min.
The reason is that in addition to the absence of the gap between the adjacent
impact areas of the water-bloclting water, a strong water wall was formed by the
interference between the adjacent water-blocking water, and thus the leakage of a largc
amount of water on the sheet at a high water level could be obstructed. In addition, as
the verification result, it was confirmed that a problem of which the cause was thought
to be the interference between the water-bloclting watcr did not occur.
LO0191
As described above, according to the water-bloclti~lga pparatus described in
(I), the lealtage of a large amount of water on the sheet (the cooling water) could be
significantly improved compared to the method according to thc related art. The
configuration of the wals~.-blockinga pparatus can be realized because of the ~trventors
who have changed thc way of thinking apart from the general common technical
lmowlcdge according to the related art in order to cope with a large amount of cooling
water which is difficult to bc rcalized by those sltilled in the art.
[0020]
(2) In the water-bloclting apparatus described in ( I ) , a height at which sprays
of the water-blocking water which are adjacent to each other in the width direction of
the hot-rolled steel sheet join may be higher than 400 mm froin the surfacc of thc hotrollcd
steel sheet in a side view as viewed from a sheet-threading direction of the hotrollcd
steel sheet.
That is, the water-blocking water is present without gaps in the vertical
direction to a height higher than 400 mm from the surface of thc hot-rolled steel shcct.
According to the verification by the inventors, it was proved that even in the case
where the hot-rolled steel sheet is cooled by a large amount of cooling water, the height
of the cooling water is lower than 400 mm lrom the surrace of the hot-rolled steel sheet.
Therefore, by satisfying the condition in which the height at which the adjacent sprays
of the water-blocking water join is higher than 400 mm from the surface of the hotrolled
steel sheet, the cooli~lgw ater does not overflow the water-bloclting water and
leak. In addition, particularly in the case where the cooling water having a high
sprayed water density is sprayed onto the hoerolled steel sheet, the cooling water is
scattered vertically upward from the surfacc of thc hot-rolled steel sheet. Thercforc,
it is preferable that the height condition of the water-bloclsing water be satisfied.
[0021]
(3) In thc water-blocking apparatus described in ( I ) or (2), a momentum FA of
the water-blocking water that flows in the sheet-threading direction of the hot-rolled
steel sheet on the surljcc of the hot-rolled steel sheet may be 1.0 to 1.5 times the
momentum FB of thc cooling water that flows in the sheet-threading direction ofthe
hot-rolled steel sheet.
As such, since the momentum FA of the water-blocking water is cqual to or
greater than the momentum FB of the cooling watel; the water-blocking water can
block the cooling water, and thus the cooling water does not pass through the waterbloclting
water and leak. In contrast, according to the verification by the inventors, it
was proved that when the momentum FA of thc water-blocking water is greater than
1.5 times the momcntum Fu of the cooling watel; thc water-bloclting water submerges
below the cooling watel; and the cooling ability or the cooling water to cool the hotrolled
steel sheet is degraded. Therefore, as dcscribcd above, it is preferable that the
momcntum FA of the water-bloclting water be 1.0 to 1.5 times thc momentum FB of the
cooling water.
[0022]
In addition, as described above, in Patent Document 3, the momentum of [he
water-blocking watcr per unit time and unit width (a force of the water-blocking water)
is 1.5 to 5 times the momcntum of the cooling water per unit time and unit width (a
force of thc cooling water). This condition is a condition for blocking the cooling
water when the hot-rolled steel shcet is cooled by the cooling water having a low
sprayed watcr density of 4 m3/m2/min or less (hereinafter, the range of this sprayed
water density is called a low sprayed water density) as described in Examples and
Table 1 of Patent Document 3, and cannot be applied to a case where the hot-rolled
steel sheet is cooled by the cooling water having a high sprayed water density of higher
than 4 m3/m2/min and equal to or less than 10 m3/m2/min (hereinafter, the range of this
sprayed water density is called a high sprayed water density).
100231
According to the verification by the inventors, it was proved that the case
where the hot-rolled steel sheet is cooled by the cooling water having a low sprayed
water density as described in Patent Documcnt 3 and thc case where the hot-rolled
steel sheet is cooled by the cooling watcr having a high sprayed water density as in the
prcsent invention have different mechanisms of cooling the hot-rolled steel sheet.
roo241
For example, in the case where the hot-rollcd steel sheet is cooled by the
cooling watcr having a low sprayed water density, thc dominant factor for defining the
momentum of thc cooling water is, for example, the depth (potcntial energy) olthe
cooling water that stays on the surface of the hot-rolled steel sheet as defined in
paragraph 0019 or the specification of Patent Document 3 regarding the momentum of
the cooling water. That is, the cooling water that stays on the surface of the hot-rolled
steel sheet contributes the most to cooling of the hot-rolled steel sheet. In this case,
the momentum of the cooling water is reduced. Therefore, when the momentum of
the watcr-bloclting water is equal to or greater than the momentum of the cooling watcr,
the water-blocking water submerges below the cooling water, resulting in a different
cooling ability than a case of cooling without bloclting the cooling water.
[002S]
In contrast, in the case where the hot-rolled steel sheet is cooled by the
cooling water having a high sprayed water density as in the present invention, thc
dominant factor for defining the momentum FR of the cooling water is a horizontal
component of the cooling water sprayed onto the hot-rolled stcel sheet from the
nozzles. That is, the cooling water sprayed from the nozzles contributes the most to
cooling of the hot-rolled steel sheet. In this case, the momentum of the cooling water
having a high sprayed water density is increased. Thereforc, when the momrntum FA
of the water-blocking water is greater than 1.5 times the momentum Fg of the cooling
water, as described above, the water-bloclting water submerges below the cooling
water, and thus the cooling ability of the cooling water to cool the hot-rolled stccl shect
is degraded.
[0026]
(4) In the water-bloclting apparatus described in any one of (1) to (3), the
plurality of watcr-bloclting nozzles may be lined up and arranged in thc width direction
of the hot-rolled steel sheet so that a distance between the water-blocking nozzle and
the surface of the hot-rolled stccl sheet in a spraying direction of the water-blocliing
water is 2000 mm or less.
According to the verification by the inventors, it was proved that in a case
where the distance between the water-blocking nozzle and thc surface of the hot-rolled
steel shcet in the spraying direction of the water-blocking water exceeds 2000 mm, the
water-blocking water spraycd from the watcr-blocking nozzle onto the hot-rolled steel
sheet is dampcd by air resistance, the momentum of the water-blocking water is
reduced, and there is a possibility that a large amount of the cooling water may not be
appropriately bloclted. 'I'hercfore, as describcd above, it is preferablc that thc
distance between the water-blocking noz/le and the surface of thc hot-rolled steel sheet
in the spraying direction of the watcr-blocking water be set to be 2000 mm or less.
[0027]
(5) In the water-blocking apparatus described in any one or (1) to (4), a spray
angle of the water-blocking water sprayed from the water-blocking nozzle with respect
to a vcrtical direction may bc 20 to 65 degrces
(00281
(6) In the watcl blocking apparatus described in any one of (1) to (S), thc
plurality of water-blocking nozzles may bc arrangcd on each of an upstream side and a
downstream side of cooling water nozzles which sprays the cooling water onto the hotrolled
steel sheet.
[00291
(4) In the water-blocking apparatus described in any one of (1) to (6), the
plurality of water-blocking nozzles may bc flat spray nozzles.
[003 01
(8) According to another aspcct of thc present invention, a water-bloclting
method for cooling water for a hot-rolled stcel shcet, in which cooling water sprayed
onto a hot-rolled steel sheet at a sprayed water density of higher than 4 m3/m2/min and
equal to or less than 10 m3/n~*/minw hen the hot-rolled steel sheet is cooled after finish
rolling of a hot-rolling process is bloclted, the water-bloclting method includes:
spraying water-blocking water from a plurality ol water-bloclting nozzles onto the hotrolled
steel sheet so that a plurality of impact areas of the water-bloclting water are
continuously lined up in a straight line in a width direction of the hot-rolled steel sheet
on a surface of the hot-rolled steel sheet and the adjacent impact areas partially overlap.
1003 11
(9) In the water-bloclting method described in (a), a hcight at which sprays of
the water-blocking water which are adjacent to each other in the width direction of the
hot-rolled steel sheet join may be higher than 400 mm from the surface of the hotrolled
stcel sheet in a side view as viewed from a sheet-threading direction or the hotrolled
steel shcct.
100321
(10) In the water-blocking method described in (8) or (9), a momentum FA of
the water-blocliing watcr that flows in the sheet-threading direction of thc hut-rolled
steel sheet on thc surface of the hot-rolled steel sheet may be 1.0 to 1.5 times the
momentum Fu of the cooling water that flows in the sheet-threading direction of the
hot-rolled steel sheet.
[0033]
(I 1) ln the water-bloclting method described in any one of (8) to (lo), the
plurality of watcr-blocking nozzles may be lined up and arranged in the width direction
ofthe hot-rolled steel sheet so that a distance betwcen the water-blocking nozzle and
the surface of the hot-rolled steel sheet in a spraying direction of the water-blocking
water is 2000 mm or less.
[0034]
(12) In the water-bloclting method dcscribcd in any one of (8) to (1 l), a spray
angle of the water-blocking water sprayed from the water-blocking nozzle with respect
to a vertical direction may be 20 to 65 degrees.
[0035]
(13) In the water-bloclzing method described in any one of (8) to (12), the
plurality of water-blocking njzzles may be arranged on each of an upstream side and a
downstream side of a cooling water nozzle which sprays the cooling water onto the
hot-rolled steel sheet, and the cooling water on the upstream side and the downstlearn
sidc of the cooling water nozzle may be blocked by the water-blocking water sprayed
fiom the water-bloclting nozzles disposed 011 the upstream side and the downstrcani
side of the cooling water nozzle.
[0036]
(14) In the water-bloclting method described in any onc of (8) to (1 3), the
plurality of water-blocking nozlles may be flat spray nozzles.
[Effects of the Inventionl
[0037]
According to the aspects, when the hot-rolled steel sheet after finish rolling of
the hot-rolling process is cooled by a large amount ofthe cooling water, thc cooling
water can be appropriately bloclzed.
[Brief Description of thc Drawings]
100381
FIG. 1 is an explanatory view illustrating a schematic configuration of a hot
rolling facility having a water-blocking apparatus according to an embodiment of thc
present invention.
FIG. 2 is a side view illustrating schematic configurations of a cooling
apparatus and the water-blocking apparatus.
FIG. 3 is a plan view illustrating the schematic configurations of the cooling
apparatus and the water-blocking apparatus.
FIG. 4 is an explanatoly view schematically illustrating the arrangement of
water-blocking nozzles in a side view from a sheet-threading direction of a hot-rolled
steel sheet.
FIG. 5 is an explanatory view schematically illustrating the arrangement of the
water-blocking nozzles with respect to cooling water nozzles in a side view from a
width direction of the hot-rolled steel sheet.
FIG. 6 is an explanatory view ola method of deriving Expression (1) that
expresses a momcntum FA of water-blocking water and Expression (2) that expresses a
momentum Fu of cooling water.
FIG. 7A is a diagram illustrating a modified example of the arrangement of the
water-blocking nozzles.
FIG. 7B is a diagram illustrating a modified example of the arrangcnrcnt of the
water-blocking nozzles.
FIG. 8 is an explanatory view illustrating impact surfaces of flat spray nozzles
and flows of water on a sheet in a plan view in a case whcre the water on the sheet
caused by cooling water having a flow rate of 4 m3/m2/min or less is blocked.
[Embodiments of thc Invention]
[0039]
Hereinafter, an embodiment of the present invention will be described. FIG.
1 is an explanatory view illustrating a schematic configuration of a hot rolling facility 1
having a water-blocking apparatus according to this embodimcnt.
[0040]
In the hot rolling facility 1, a hcated slab S is vertically interposed between
rolls, is continuously rolled to be thinned to, for example, a sheet thickness of 1 mm,
and is coiled as a hot-rolled steel sheet 10. The hot rolling facility 1 includes: a
heating furnace 11 for heating the slab S; a width-direction rolling mill 12 which rolls
the slab S heated by the heating lirrnace 11 in a width direction; a roughing mill 13
which vcrtically rolls thc slab S rolled in the width direction to make a rough bar; a
i
finishing mill 14 which continuously performs hot finish rolling on the rough bar
further to a predetermined thickness; a cooling apparatus 15 which cools the hot-rolled
steel sheet 10 subjected to the hot finish rolling by the finishing mill 14 with cooling
water; a water-blocking apparatus 16 which bloclts the cooling water sprayed from thc
cooling apparatus 15; and a coiler 17 which coils the hot-rolled steel sheet 10 cooled
by the cooling apparatus 15 in a coil shape.
[0041]
In the heating furnacc 11, a side burner, an axial flow burnel; and a roof
burner arc arranged to hcat the slab S by blowing flames toward the slab S cacried Srom
the outside via a charging port. The slab S carried into the heating furnace 11 is
sequentially heated by heating zones formed in corresponding zones, and the slab S is
further uniformly hcated by the roof burner in a soaking zone formed in a final zonc
for heat retaining trcatcnent so as to bc transported at an optimum temperature. When
all heat treatment in the heating furnace 11 are ended, the slab S is transported to the
outside of the heating furnace 11 to be transited to a rolling process by the roughing
mill 13.
100421
The roughing mill 13 allows the transported slab S to pass through a gap
between columnar rotating rolls arranged over a plurality of stands. For example, in
the roughing mill 13, hot rolling is performed on the slab S only by work rolls 13a
vertically arranged in the first stand to be made into a rough bar. Next, the rough bar
that passes through the work rolls 13a is further continuously rolled by a plurality of
four-high mills 13b constituted by work rolls and back-up rolls. As a result, at the
time of ending the rough-rolling process, the rough bar is rolled to a sheet thicltness of
about 30 to 60 mm and is transported to the finishing mill 14.
[0043]
The finishing mill 14 performs finish rolling on the transported rough bar to a
sheet thickness of several millimeters. The ilnishing mill 14 allows the rough bar to
pass through a gap between finishing rolls 14a that are vertically lined up in a straight
line over six to seven stands so that the rough bar is gradually rolled. The hot-rolled
steel sheet 10 subjected to the linish rolling by the finishing mill 14 is transported by
transporting rolls 18, which will bc described later, to be sent to the cooling apparatus
15.
[0044]
The configurations of the cooling apparatus 15 and thc water-bloclting
apparatus 16 will be described later in dctail.
[0045]
The coiler 17 coils the hot-rolled steel sheet 10 cooled by thc cooling
apparatus 15 at a predetc~minedc oiling temperature. The hot-rolled steel sheet 10
coiled by the coiler 17 in a coil shapc is transported to the outsidc of the hot rolling
facility 1.
100461
Next, the configuration of the above-mentioned cooling apparatus 15 will be
described. As illustrated in FlG. 2, the cooling apparatus 15 includes a plurality of
cooling water nozzles 20 which spray the cooling water onto the surface of the hotrolled
steel sheet 10 from above the hot-rolled steel sheet 10 transported on the
transporting rolls 18 of a run-out table. As the cooling water nozzle 20, for example,
a full cone spray nozzle is used.
As illustrated in FIG. 3, a plurality of, for example, five cooling water nozzles
20 are arranged in the width direction (X direction in the figure) of the hot-rolled steel
sheet 10 and a plurality of, for example, four cooling water nozzles 20 are arranged in
the sheet-threading direction (Y direction in the figure) of the hot-rolled steel sheet 10.
In addition, the cooling water nozzles 20 in this embodiment spray the cooling water
on the hot-rolled steel sheet 10 at a high sprayed water density of higher than 4
m31m21min and equal to or less than 10 m3/m2/min to cool the hot-rolled steel sheet 10
to a predetermined temperature.
[0047]
In addition, as illustrated in FIG. 2, the cooling apparatus 15 includes a
plurality of the other cooling water nozzles 21 which spray the cooling watc~o nto, for
example, thc back surface of the hot-rolled steel sheet 10 from below the hot-rolled
steel sheet 10. As the other cooling water nozzle 21, for example, a full cone spray
n o ~ ~isl ues ed. Ln addition, the arrangement of the other cooling water noz~les2 1 is
the same as that of the cooling water nozzles 20 described above.
In addition, as the cooling water nozzles 20 and 21, nozzles other than the
spray nozzles of this embodiment, for example, various nozzles such as pipe laminar
nozzles may be used. For example, when the pipe laminar nozzles are used as the
cooling nozzlcs 20, the cooling water is sprayed from the cooling nozzles 20 in the
vertical direction, and thus a spray angle BB with respect to the vertical direction of the
cooling water sprayed from the cooling water nozzle 20, which will be described latel;
is 0".
100481
Next, the configuration of the above-mentioned water-blocking apparatus 16
will be described. The water-bloclting apparatus 16 includes water-hloclting nozzles
22 above the hot-rolled steel sheet 10, which spray water-blocking water onto the
surface of the hot-rolled steel sheet 10 on each of the upstream side and the
downstream side of the cooling water nozzles 20. As the water-blocking nozzle 22,
for example, a flat spray nozzlc is used. In addition, as illustrated in FIG. 3, thc
water-blocking n o ~ ~ l2e2s o n the upstream side block the cooling water that flows
toward the upstream side from the cooling watcr nozzles 20 using the water-blocking
water sprayed from the corresponding water-blocking nozzles 22. Similarly, the
water-blocking nozzles 22 on the downstream side block the cooling water that flows
toward the downstream side from the cooling water nozzles 20 using the waterblocking
water sprayed from thc conesponding water-bloclting nozzles 22.
100491
Next, the arrangement of the water-blocking nozzles 22 for the abovedescribed
cooling water nozzles 20 and the action of the water-bloclting water for the
cooling water will be described. In addition, the al~angcmcnot f the water-blocking
nozzles 22 and the action ol the water-blocking water for the cooling water are the
samc on the upstream side and the downstreanl side.
[0050]
As illustrated in FIG. 3, a plurality ol; for example, five water-blocking
nozzles 22 are lined up and ai~angedin the width direction or the hot-rolled ?tee1 sheet
10. The plurality of water-blocking nozzles 22 are arranged so that impact areas 30
of sprays of the water-bloclting water that are sprayed from the water-bloclcing nozzles
22 and impact on the surface of the hot-rolled steel sheet 10 are continuously lined up
in a straight line in the width direction of the hot-rolled steel sheet 10 in a plan view
and adjacent impact areas 30 partially overlap. For example, in the width direction of
the hot-rolled steel sheet 10, whcn a gap is present bctween the adjacent impact areas
of the water-blocking water, there is a possibility that the cooling water (water on the
sheet) leaks from the gap. For this, in this embodiment, in the width direction of the
hot-rolled steel sheet 10, the impact areas of the watcr-bloclcing water are present
without gaps, and thus the cooling water does not leak. In addition, the waterbloclting
nozzles 22 are arranged so that the spray angle olthe water-blocking water is
inclined toward thc cooling water nozzle 20.
[0051]
FIG. 4 schematically illustrates thc arrangement of the watcr-blocking nozzles
22 in a side vicw from the sheet-threading direction of the hot-rolled steel sheet 10.
As illustrated in FIG. 4, an interval P between the adjacent water-blocking nozzles 22
and 22 in the width diicction of the hot-rollcd stccl sheet 10 is set so that a lrc~glHt at
which sprays of the water-blocking water adjacent to each other in the width direction
of the hot-rolled steel sheet 10 join is higher than 400 mm from the surface of the hotrolled
steel sheet 10.
That is, the water-blocking water is present without gaps in the vertical
direction to the height H which is higher than 400 nun from the surfacc of the hotrolled
steel sheet 10. According to thc verification by the inventors, it was provcd
that even in a case where the hot-rolled steel sheet 10 is cooled by a large amount of
the cooling water, the height of thc cooling water is lowcr than 400 mm 5oin thc
surface of the hot-rolled steel sheet 10. Therefore, by satisfying the condition in
which the height at which the adjacent sprays of the watcr-blocking water join is
higher than 400 mm from the surface of the hot-rolled steel sheet 10, the cooling water
does not overflow the water-blocking water and leak. Particularly, as in this
embodiment, in the case where the cooling water having a high sprayed water density
is sprayed onto the hot-rolled steel sheet 10, the cooling water is scattered vertically
upward from the surface of the hot-rolled steel sheet 10. Therefore, it is preferable
that the height condition of tile water-blocking water be satisfied.
[0052]
In addition, the height H at which the sprays of the water-blocking water join
is geometrically calculated by the following Expression (3). In addition, so as to
allow the height M at which the sprays of the water-blocking water join to be higher
than 400 mm from the surface of the hot-rolled steel sheet 10, thc interval P between
the water-blocking nozzles 22 and 22, the angle BA of attack of the water-blocking
water, and the spray angle 0s of the water-blocking water are set in the following
Expression (3). In addition, the height I3 at which the sprays of the water-blocking
water join is naturally less than a height hA of the water-blocking nozzle 22 from the
surface of the hot-rolled steel sheet 10, and the upper limit ofthe height H is
substantially 900 mm.
FI={hl\/c0~8~xtan(8s/2)-P/x2c}o s8~/ta11(~~./. (23)).
Here, in the Expression (3), 11i~s the height (about 1000 mm) ofthe waterbloclcing
nozzle 22 from the surface of the hot-rolled steel sheet 10, 8~ is the spray
angle (hereinafter, may be called the angle of attack) of the water-blocking water
sprayed from the water-blocking nozzle 22 with respect to the vertical direction, Os is
the spray angle ofthe water-blocking water from thc water-blocking nozzle 22, and P
is the interval between the water-blocking nozzles 22 and 22 in the width direction of
the hot-rolled steel sheet 10.
[0053]
The spray angle 0s ol'the water-blocking water is, for example, 5" to 150'.
The spray angle 0s of the water-blocking water is preferably 10" to 130°, and more
preferably, 20 to 60°.
When the spray angle OS of the water-blocliing water is too small, the nozzle
pitch is reduced to ensure the height for bloclting the cooling water, and the number of
nozzles is increased, which results in poor economic efficiency. In contrast, when thc
spray angle 0s of the water-blocking water is too large, the nozzle pitch is increased,
and the number of nozzles is reduced, which results in good economic efficiency.
However, the amount of water-blocking water in a direction pushing back the cooling
water is reduced, and thus the function to block the cooling water is degraded.
Therefore, the spray angle 05 of the water-blocking water is, realistically, 5 to 150'.
In addition, in a case where the spray angle 0s of the water-blocking water is
10 to 130°, water-blocking characteristics are enhanced, which is preferable.
Furthermore, tl~csp ray angle OS of the water-blocking water is mow
preferably 20 to 60'. For this reason, by increasing the number of nozzlcs to sct the
spray angle Bs to be small, the amount of water-blocking water in a direction pushing
back the cooling water is easily ensured, and thus the size of a feedwater system (pipes
or the capacity of pumps, and the like) can be reduced, which results in high economic
cfficicncy.
[0054]
FIG. 5 schematically illustrates the arrangement of the water-blocking nozzles
22 with respect lo the cooling water nozzles 20 in a side view from the width direction
of thc hot-rolled steel sheet 10. As illustrated in FIG. 5, the water-bloclting nozzle 22
6
is disposed at such a position that a distance L between the water-blocking nozzle 22
and the surface of the hot-rolled steel sheet 10 in a spraying direction of the waterbloclting
water from the water-bloclting nozzle 22 is 2000 mm or less. According to
the verilication by the inventors, it was proved that in a case where the distance L
between the water-blocking nozzle 22 and the surface of the hot-rolled steel sheet 10 in
the spraying direction of the water-bloclting water exceeds 2000 rnm, the waterblocking
water sprayed from the water-bloclting noz~le22 onto the hot-rolled stcel
sheet 10 is damped by air resistance, the momentum of the water-bloclting water is
reduced, and there is a possibility that a large amount of the cool~ngw ater may not be
appropriately blocked. Therefore, as described above, it is preferable that the
distance L between the water-blocking nozzle 22 and the surface of the hot-rolled steel
sheet 10 in the spraying direction of the water-blocking water be set to be 2000 mm or
less.
[0055]
In addition, when the plurality of water-bloclting nozzles 22 are arrangcd at
positions close to the cooling water noziles 20, the occupancy area of the hot tolling
facility 1 can be reduced. However, the water-blocking nozzles 22 are arranged at
such positions that the water-bloclting water spraycd from the water-blocking nozzles
22 and the cooling watcr sprayed from the cooling water nozzles 20 do not impact on
each other before leaching the hot-rolled steel sheet 10. That is, the water-bloclting
nozzle 22 is disposcd at a position at wh~cha distance D between the water-bloclting
nozzle 22 and thc cooling water nozzle 20 satisfies the following Explession (4).
D>(hAxtaneA+h~xtdn8.~ . ()4 )
IHere, 111 thc Expression (4), h~ is the he~ghot f the water-bloclting nozzle 22
fro111 the surface ol'the hot-rolled steel sheet 10, 8~ is the angle of attack ofthe waterbloclting
water sprayed from the water-bloclting nozzle 22 with respect to the vertical
direction, hB is the height of the cooling water nozzle 20 from the surface of the hotrolled
steel sheet 10, and 8~ is the spray angle of the cooling water sprayed from the
cooling water nozzle 20 with respect to the vertical direction.
[0056]
The water-blocking water sprayed from the water-bloclting nozzle 22 is
sprayed so that a illomenturn FA of the water-bloclting water that flows toward the
cooling water nozzle 20 on the surface of the hot-rolled steel shcet 10 in the sheetthreading
direction of the hot-rolled steel sheet 10 is 1.0 to 1.5 times the momentum FB
of the cooling water that flows toward the water-bloclting nozzle 22 in the sheetthreading
direction of the hot-rolled steel sheet 10.
The momentum FA ol' the water-blocking water is defined by, for example, the
following Expression (1) from a density p of water, an amount QA of the waterblocking
water sprayed from the water-bloclting nozzle 22, a flow velocity v~ of the
water-bloclting water sprayed lrom the water-blocking nozzle 22, and the spray angle
BA of the water-bloclti~lgw atcr sprayed from the water-blocking nozzle 22 will1 respect
to the vertical direction.
In addition, the momentum FB of the cooling water is defined by, for example,
the following Expression (2) from the density p of water, an amount QB of the cooling
water sprayed from a row of the cooling water nozzles 20 arranged in the width
direction orthe hot-rolled steel shcet 10, a flow velocity v~ of thc cooling water
sprayed from the cooling water nozzles 20, and the spray angle 8~ of the cooling watcr
sprayed from the cooling water nozzles 20 with respect to the vertical direction.
FA=p.QA.vA.(1-i-sinO~)/2.(.I.)
F~=p.Q~.v~.(l+sinO~)/.(22.) .
LO0571
Hereinafter, a method of deriving the above Expression (1) is described. In
addition, a method of deriving the above Expression (2) is the same as the method of
deriving the above Expression (1).
As illustrated in FIG. 6, it is assumed that the amount of the water-blocking
water sprayed from the water-blocking nozzlc 22 is QA, the flow velocity of the waterbloclting
water sprayed from thc water-bloclting nozzle 22 is VA, the spray arigle of the
water-blocking water sprayed from the water-bloclting nozzle 22 with respcct to the
vertical direction is OA, and the density of water is p. I-Iere, the momentum FA of the
water-blocking water that flows toward the cooling water nozzle 20 along thc surface
of the hot-rolled steel sheet 10 after impacting on the surface of the hot-rolled steel
sheet 10 is defined by the following Expression (5).
In addition, a momentum FA' of the water-blocking water that flows in the
opposite direction to the cooling water nozzle 20 along the surface of thc hot-rolled
steel sheet 10 afier impacting on the surface of the hot-rolled steel sheet 10 is defined
by the following Expression (6).
FA=P.QI.vI.. (.5 )
FA'=P.Q~.v. .~(.6 )
Herc, in the above Expression (5), QI is the amount of the water-bloclting
water that flows toward the cooling water nozzle 20 along the surSace of the hot-rolled
steel sheet 10, and vl is the flow vclocity of the watel~blocltingw ater that flows toward
the cooling water nozzle 20 along the surface of the hot-rolled steel sheet 10.
In addition, in thc abovc Expression (6), Qz is the amount of the waterbloclting
water that flows in thc opposite direction to the cooling water nozzle 20 along
the surface of thc hot-rolled steel sheet 10, and VZ. is the flow vclocity of the waterblocking
water that flows in the opposite dircction to the cooling water nozzle 20 along
the surfacc of the hot-rolled steel sheet 10.
[OOSS]
When it is assumed that there is no loss such as friction before and after the
water-blocking water impacts on the hot-rolled steel sheet 10, the following Expression
(7) is established on the basis ofthe conservation of momentum in a fluid.
p.Q.b..~.b..sinQ.b.'p.Q~V I-P.Q~.V.(Z7.).
100591
Here, when it is thought that the following Exprcssion (8) is established from
the assumption that there is no loss before and alter the water-bloclting water impacts
on the hot-rolled steel sheet 10, the above Expression (7) can be expressed as the
following Expression (9).
v~=vl=v.~. (8. )
Q*.sinQ~=Q I-Q2... (9)
[0060]
Regarding the amounts QA,Q i, and Qzo. f the water-blocking water, the
following Expression (10) is established. Therefore, on the basis of the above
Expression (9) and the following Expression (lo), the amount QI of the watw-bloclung
water is expressed by the following Expression (1 l), and the amount Qz. of the waterblocking
water is expressed by the following Expression (12).
QA= Qi+Q2 ... (lo)
Q,=Q~.(l+sinO~)../.2( 11)
Q2=Q~.(l-siuO~)/2.(.1.2 )
[0061]
From thc above Expressions (5), (8), and (11), finally, the following
Expression (1) which expresses the momentum FA of the water-blocking water (that is,
the water-blocking water that flows toward the cooling water nozzle 20 along the
surface of the hot-rolled stcel shect 10) is derived.
FA=p.Q~.v~.(l+sinO~)/.2(I.).
In addition, as can be seen lrom the method of deriving the above-described
Exprcssion (1 ), the momentum FB of the cooling watcr expressed by Expression (2) is
the momentum or the cooling water that flows toward the water-bloclsing no~fle22
along the surface of the hot-rolled steel sheet 10 (see FIG. 5).
[0062]
In this cmbodimeut, on the basis of the above Expressions (I) and (2), various
device parameters (the variables in the above Expressions (1) and (2)) are set so that
thc momentum FA of the water-bloclsing water is 1.0 to 1.5 times the momentum FB or
the cooling water. The momentum FA of the water-bloclsing watcr and the
momentum FB of the cooling water are vector quantities directed in a dircctioii in
which the water-blocking water and the cooling water impact on each other on the
surface of the hot-rolled steel sheet 10.
In addition, in the above Expressions (1) and (2), it is assumed that the
amount QA of the water-blocking water and the amount QB of the cooling water
sprayed from the water-blocking nozzle 22 and the cooling water nozzle 20 are
constant until the water-blocking watcr and the cooling watcr reach the surface of the
hot-rolled steel sheet 10 immediately after being sprayed from the watcr-blocking
nozzle 22 and the cooling water nozzle 20, respectively. In addition, it is assumed
that the spray angle Ou of the cooling water sprayed fiom the cooling water nozzle 20
is an angle with respect to the vertical direction, and it is assumed that the amount QH
of the cooling water sprayed from the cooling water nozzle 20 cntirely flows toward
any one of the upstream side and the downstream side on the surface of the hot-rolled
steel shcet 10.
[0063]
Therefore, in the case where the amount Qu of the cooling water is considered,
the amount of water on the most dangerous side (the safest side from the viewpoint of
blocking the cooling water) is considered, and thus the momentum FR of the cooling
water is maximized. In add~tioni,n the case where the amount Qu of the cooling
water is considered, the cooling water only from the cooling water noz~les2 0 on the
most upstream side or the most downstream side, that is, only a row of the cooling
water nozzles 20 closcst to the water-blocking noz~le2 2 is considered, and the cooling
water from the other cooling watcr nozzlcs 20 is not considered. In addition, thc
flows of the cooling water from the other cooling water nozzles 20 in the sheetthreading
direction of the hot-rolled steel sheet 10 cancel each other, and thus the
corresponding cooling water flows in the width direction of the hot-rolled steel sheet
10.
[0064]
In this embodiment, on the surface orthe hot-rolled stcel sheet 10, since the
momentum FA of the water-blocking water that flows in the sheet-threading direction
of the hot-rolled steel shect 10 is equal to or grcatcr than the momentum FB of the
cooling watcr, the water-blocking watcr can block the cooling water, and thus the
cooling water docs not pass through the water-bloclting water and leak. In contrast,
according to the veriiication by the inventors, it was proved that when the n~omentum
FA of the water-blocliing water is greater than 1.5 times the momentum FB of the
cooling water, the water-bloclting water submerges below the cooling water, and the
cooling ability of the cooling water to cool the hot-rolled steel sheet 10 is degraded.
Therefore, as in this embodiment, it is preferable that the momentum FA of the waterbloclting
water be set to 1.0 to 1.5 times the momentum FB of the cooling water.
100651
In addition, the angle 0A of attaclt of the water-blocking water sprayed fiom
the water-bloclting nozzle 22 with respect to the vertical direction is 20 to 65 degrees,
and more preferably, 30 to 50 degrees. For example, when the angle 0~ of attaclt is
smaller than 20 degrees, there is concern that the water-blocking water spraycd from
the water-bloclcing nozzle 22 may flow in the opposite direction to the cooling water.
In this case, there is a possibility that the cooling water may not be appropriately
blocked by the water-bloclcing water. In addition, for example, when the angle 0~ of
attack is greater than 65 degrees, the distance between the water-blocking nozzle 22
and the impact area 30 is increased, and thus the occupancy area of the hot rolling
facility 1 is increased. Therefore, it is preferable that the angle 0~ of attaclc be 20 to
65 degrees.
[0066]
As described above, in this embodiment, the arrangement of the warcrbloclting
nozzles 22 and the spray angle of the water-blocking water are set so that the
impact areas 30 of the water-bloclting water respectively sprayed from the waterbloclting
nozzles 22 are continuously lined up in a straight line on thc surface of the
hot-rolled steel sheet 10 in the width direction of the hot-rolled steel sheet 10 and the
adjacent impact areas 30 partially overlap.
In addition, in this embodiment, the plurality of water-bloclting nozzles 22 are
lined up and arranged in thc width direction of the hot-rolled steel sheet 10 so that the
distance L between each of the watcr-bloclting nozzles 22 and the surface of the hotrolled
steel shcet 10 in the spraying direction of the water-blocking water is 2000 mm
or less.
In addition, in this embodiment, the height H at which the sprays ofthe waterblocking
water which are adjacent to each other in the width direction of the hot-rolled
steel sheet 10 join is set to be higher than 400 mm from the surface of the hot-rolled
steel sheet 10 in the side view as viewed from the sheet-threading direction of the hotrolled
steel sheet 10.
Moreover, in this embodiment, the momentum FA of the water-bloclting water
that flows in the sheet-threading direction olthe hot-rolled steel sheet 10 (toward the
cooling water nozzle) on the surface of the hot-rolled steel sheet 10 is set to be 1.0 to
1.5 times the momentum Fu of the cooling water that flows in the sheet-threading
direction of the hot-rolled steel sheet 10 (toward thc water-blocking nozzle).
Therefore, according to this embodiment, even in the case where the hotrolled
stcel sheet 10 is cooled by the cooling water having a high spraycd watcr density
of higher than 4 m3/m2/min and equal to or less than 10 m3/m2/min, the cooling water
can be appropriately blocked while appropriately cooling the hot-rolled steel sheet 10
with thc cooling water In addition, the effect of each condition is as dcsc~~hcabdo ve.
[0067]
In addition, since the cooling water is appropriately blocked by the waterbloclcing
water from the water-blocking nozzle 22 as described above, the cooling
water does not overflow the cooling area of the cooling apparatus 15 and leak.
Therefore, the hot-rolled stccl sheet 10 can be uniformly cooled to a predetermined
temperature by using the cooling apparatus 15. In addition, since the hot-rolled steel
sheet 10 is cooled by the cooling water having a high sprayed water density of higher
than 4 m31m2/min and equal to or less than 10 m3/m2/min, the hot-rolled steel sheet 10
can be appropriately cooled with a high cooling ability.
[0068]
In addition, the present invention is not limited to the above-described
embodiment, and can employ the following modified examples.
(1) In the above-described embodiment, the water-blocking nozzles 22 are
provided on both sides including the upstream side and the downstream side of the
cooling water nozzles 20. However, for example, instead of the water-blocking
nozzles 22 on any one'of the sides, restraining rolls, side sprays, or the like may be
used.
[0069]
(2) In the above-described embodiment, the case where the plurality of waterbloclcing
nozzles 22 are lincd up and arranged in the width direction of the hot-rolled
steel sheet 10 is exemplified. However, for example, as illustrated in FIGS. 7A and
7B, in a plan view, the plurality of water-blocking nozzles 22 may be lined up and
arranged in a direction inclined with respect to the width direction of the hot-rolled
steel sheet 10.
FIG. 7A illustrates a case where the plurality of water-bloclting nozzles 22 are
lined up and arranged in a direction inclined countercloclcwise at an angle of a1 with
respect to the width direction ofthe hot-rolled steel sheet 10. FIG. 7B illustrates a
case where the plurality of water-blocking nozzles 22 are lined up and arranged in a
direction inclined clockwise at an angle of a2 with respect to thc width direction of the
hot-rolled stcel sheet 10.
It is preferable that both the anglcs a1 and a2 bc 0" or higher and 30" or less.
When the angles a1 and a2 exceed 30°, the pipc lcngth and the number of nozzles is
increased and thus the facility size is increased, which rcsults in poor economic
efficiency. In addition, when the angles a1 and a2 exceed 30°, there is a possibility of
a problem of a tcmperature difference between a worlc side and a drive side in the steel
sheet.
[0070]
(3) Although not particularly mentioned in the above-described embodiment,
the water-bloclting nozzles 22 may be arranged so that the water-bloclting water
directly abuts on the table rolls. In a case where the water-blocking water is sprayed
onto an intermediate position between the adjacent table rolls, there is a need to
consider that sheet-threading characteristics of the tip end portion of the steel sheet
should not be harmed. For example, there is a need to reduce the amount of the
water-bloclting water, the pressure thereor, and the like only during the passage of the
tip end portion of the steel sheet or to spray the water-blocking water after the passage
of the tip end portion of the stecl sheet. Therefore, it is preferable that the waterblocking
blocking ~lozzles2 2 be arranged to cause the water-blocking water to directly abut on
the table rolls.
[0071]
(4) In addition. in the above-described embodiment, the flat spray nozzles 22
are used as the water-blocking nozzle 22. However, other nozzles may also be used
as long as all the conditions in the above-described embodiment are satisfied. That is,
as long as the impact areas 30 of the sprays of the water-blocking water on the surface
of the hot-rolled steel sheet 10 are continuously lined up in a straight line in the width
direction orthe hot-rolled steel sheet 10 in a plan view, the height 1-1 at which the
sprays of the water-bloclcing water which are adjacent to each other in the width
direction of the hot-rolled steel sheet 10 join is higher thau 400 mm from the surface of
the hot-rolled steel sheet 10, and the cooling water is sprayed so that the momentum FA
of the water-blocking water that flows in the sheet-threading direction of the hot-rolled
steel sheet 10 on the surface of the hot-rolled steel sheet 10 is equal to or greatcr than
thc momentum FR of the cooling water, other nozzles, for example, full cone spray
nozzles or the like may be used as the water-bloclting nozzles 22.
[0072]
However, it is not preferable to use a full width slit nozzle (a nozzle in which
its fluid spray hole extends over the entire width direction of the hot-rolled steel sheet)
as the water-bloclting nozzle 22. Generally, a full width slit nozzlc for hot rolling is
used for a low pressurc and a large flow rate. A full width slit nozzle for a high
pressure and a high flow rate results in a very high water amount and is thus used only
for a special process. The reason is that the fluid spray hole (slit) of the full width slit
nozzle cxtcnds over the entire width direction of the hot-rolled steel sheet and thus the
thicltness of thc slit needs to be small in order to achieve the same degree of spray
width as that of a spray nozzle.
For exanlple, in a case whcrc eight flat nozzlcs having fluid spray holes with a
diameter of 14 mm are lined up, the thicltness of the slit is 0.6 mm when the slit has a
width of 2 mm, and thus the slit becomes clogged very easily. When thc th~clinessis
set to, for exanlple, about 3 mm, the flow velocity is reduced to 115 and thus a
reduction in the flow velocity becomes significant. Therefore, it is difficult to arrange
thc conditions only by thc ratios of the momentums of thc water-blocking water and
the cooling water. For cxarnplc, a problem in drainage characteristics occurs due to a
very high amount ofthe water-bloclting water. For the above reasons, it is not
preferable to usc the width slit nozzle as ihe water-bloclting nozzle 22.
[0073]
While the appropriate embodime~ltsa nd modified examples of the present
invention havc been described with reference to the acconlpanying drawings, the
present invention is not limited to the embodiments and the modified examples. It is
apparent that various changes and nlodifications can be conceived by those skilled in
the art without departing from the scope of the gist described in the appended claims,
and it is understood that the changes and modificaiions naturally belong to the
technical scope of the present invention.
[Examples]
[0074]
I-Iereinafter, verification results of an effect of bloclting the cooling water in
the case where the water-bloclting apparatus and the water-blocking method ofthe
present invention are used are described. For the verification of the effect of blocking
the cooling water, the water-bloclting apparatus 16 illustrated in FIGS. 1 to 5 was used
as the water-bloclcing apparatus of the present invention.
[0075]
As shown in Table I, the effect of bloclting the cooling water was verified by
changing the amount (sprayed water dcnsity) QR of the cooling water, the amount
(sprayed water density) QA of thc water-blocking water, the spray angle 87 ol the
water-blocking water, the angle Oh of attack of the water-bloclting watcr, and the
interval (pitch) P between the water-blocking nozzles 22 and 22. In addition,
regarding the amount Qu of the cooling water, the cooling water only from the cooling
water nozzles 20 on the most upstream sidc or thc most downstream side, that is, only
the half oCa row of the cooling water nozzles 20 closest to the water-blocking nozzlc
22 is considered, and thc cooling water from the other cooling watcr nozzlcs 20 is not
considered. Moreovel; in any of Examples 1 to 15 and Comparative Examplcs 1 to
29 shown in Table 1, the impact areas 30 of the sprays of the water-blocking watcr on
the surface of the hot-rolled steel sheet 10 are continuously lined up in a straight line in
the width direction of the hot-rolled steel sheet 10 in a plan view, and the adjacent
impact areas 30 partially overlap.
[0076]
In the "Cooling ability degradation" field in Table 1, the degree of cooling
ability degradation is indicated by three levels of A, 8, and C. A means that the ratio
FAIFB of the momentutn FA or the water-blocking water and the momenturr~F B of the
cooling water is less than 1.3 and it is determined that there is little cooling ability
degradation (a degree of cooling power degradation of 0% or higher and less than
10%). B means that the ratio FA/FRo f the momentum FAo fthe water-bloclting water
and the momentun1 Fu of the cooling water is 1.3 or higher and less than 1.5 and it is
determined that there is a little cooling ability degradation (a degree of cooling ability
degradation of 10% or higher and less than 30%). C means that the ratio Fh/Fri of the
momentum FA of the water-bloclting water and the momentum Fn of the cooling water
is 1.5 or highcr and it is determined that there is cooling ability degradation (a degree
of cooling ability degradation of 30% or higher). Here, B and C are cases where
bloclting the cooling walcr is possible although the cooling ability of the coolli~g
facility is not as designed, and in a case where bloclting the cooling water has priority
over examining the cooling ability of the main body of the cooling facility, the ratio
FA/FB of the momentums may be equal lo or higher than 1.5. In addition, the ratio
FA/FB of the momentums is a reference, and the amount of cooling ability degraded is
also affected by the watel amouut of the cooling facility and the noz/le distance
In addition, in the "Watcr-blocking characteristics" ficld in Table 1, as a result
of actual observation of watcr-blocliing circumstances, "A" is written in a case where
water-blocliing is easily and appropriately performed, "B" is written in a case where
water-bloclting is appropriately perfonncd, and "C" is written in a case where the
cooling water overflows the water-bloclting water and lealts.
Furthermore, in a case where "Cooling ability degradation" is "A" or "R" and
"Water-blocking characteristics" is "A" or "B", "A" is written in the "Evaluation" field
in 'Table 1. On the other hand, in a case where "Cooling ability degradation" is "C" or
"Water-bloclting characteristics" is "C", "13" is written in the "Evaluation" field in
Table 1. Therefore, when "A" is written in the "Evaluation" field, the effect of the
present invention is proved.
[0077]
In addition, regarding the verification of the effect of "Water-blocking
characteristics", whether or not three conditions which are the conditions of the present
invcntion are satisfied was verified:
(1) The momentum FA of the water-blocking water that flows in the sheetthreading
direction of the hot-rolled steel sheet 10 is 1.0 to 1.5 times the momentum FR
or the cooling water.
(2) The height H at which the sprays of the water-blocking water which arc
adjacent to each other i r ~th e width direction of the hot-rolled steel shect 10 loin is
higher than 400 mm Crom the surface orthe hot-rolled steel sheet 10.
(3) The distance L between the water-blocking nozzle 22 and the surface of
the hot-rolled steel sheet 10 in the spraying dircction of the water-bloclting water from
the water-blocking nozzle 22 is 2000 mm or less.
[0078]
In Coinparative Exaniples 1 to 11 in Table 1, the amount (spraycd watel
density) QR of the cooling water is a low sprayed water density of 4 m3/m2/min or less.
111 contrast, in Examples 1 to 5, Cornparative Examples 12 to 17, Examples 6 to 10,
Comparative Examples 18 lo 23, Examples 11 to 15, and Comparative Examples 24 to
29 in Table 1, the amount (sprayed water density) Qu of the cooling watcr is a high
sprayed water density of higher than 4 m3/m2/min and equal to or less than 10
m3/m2/min.
100791
First, Comparative Examples 1 to 11 in which the amount (sprayed water
density) Qu of the cooling water is a low sprayed water density of 3.5 m3/n?/min arc
examined.
In Comparative Examples 1 to 6, all thc above conditions (I) to (3) were
satisfied, and bloclting the cooling water was appropriately performed. However, the
momentum FA or the water-bloclting water was equal to or higher than the momentum
Fu of the cooling water. In this case, sincc the hot-rolled steel sheet 10 was cooled by
the cooling water having a low sprayed water density and the momentum FB of the
cooling water was reduced, the water-blocking water had submerged below thc cooling
water and the cooling ability of the cooling water to cool the hot-rolled steel sheet 10
was degraded.
In addition, in ('omparative Example 7, the conditions (2) and (3) \vcsre
satisficd, the momentum FA of the water-blocking water was greater than 1.5 times the
momcntum Fe of the cooling water, and thus water-blocking characteristics were good.
Howevel; since the rnomentum FA of the water-blocking water was too great, the
water-blocliing water had submerged below the cooling water and the cooling ability
oE the cooling water to cool the hot-rolled steel sheet 10 was degraded. Therefore,
"Evaluation" of Comparativc Examples 1 to 7 was "B".
In Comparativc Examples 8 and 9, the rnomentum FA of the water-blocking
watcr was equal to or highcr than the lilomenturn Fu or the cooling water, and thus the
cooling ability of thc cooling water to cool the hot-tolled stcel sheet 10 was degraded.
Moreover, since any of the conditions (1) to (3) was not satisfied, blocking the cooling
water was not appropriately performed. The~efore", Evaluation" of Comparative
Examples 8 and 9 was "B".
In Comparative Examples 10 and 11, the momentum FA of the water-bloclting
water was smaller than the momentum FB ol'the cooling water, and thus the cooling
ability of the cooling water to cool the hot-rolled steel sheet 10 was not degraded.
However, the condition (1) was not satisfied, and blocking the cooling water was not
appropriately performed. Therefore, "Evaluation" of Comparative Examples 10 and
I1 was "B".
As described above, in the case where the hot-rollcd steel sheet 10 was cooled
by the cooling water having a low sprayed water density, the cooling water could not
be appropriately bloclted while appropriately cooling the hot-rolled steel sheet 10 by
the cooling water.
[0080]
Next, Examples 1 to 5 and Comparative Examples 12 to 17 in which thc
amount (sprayed watet density) QR of the cooling water is a high sprayed walcr density
of 4.2 m3/m2/min are examined.
In Comparative Example 12, the conditions (2) and (3) were satisfied, the
momentum FA of the water-bloclting water was greater than 1.5 times the momentum
FR of the cooling water, and thus water-hloclting characteristics wcre good. However,
since the momentum FA of thc water-bloclting water was too great, the water-bloclting
water had submerged below the cooling water and the cooling ability of the cooling
water to cool the hot-rolled steel sheet 10 was degraded.
In Comparative Examples 13 and 15, the momentum FA of the water-bloclting
water was smaller than the momentum FB ol the cooling watel; and thus the cooling
ability of the cooling watcr to cool the hot-rolled steel sheet 10 was not degraded.
However, thc condition (1) was not satisfied, and bloclting the cooling water was not
appropriately performed.
In Comparative Example 16, the condition (1) was satisfied, and the cooling
ability of the cooling water to cool the hot-rolled steel sheet 10 was not degraded.
However, the height H at which the adjacent sprays of the water-bloclting water had
joined was 400 mm or less and thus the condition (2) was not satisfied, and bloclting
the cooling water was not appropriately performed.
in Comparative Examplc 17, the distance L between the water-blocking
nozzle 22 and the surface of the hot-rolled steel sheet 10 was greater than 2000 mm
and thus the condition (3) was not satislied, and blocking the cooling water was not
appropriately performcd. In addition, in this case, the water-blocking water had
submcrgcd below the cooling water and the cooling ability of the cooling water to cool
the hot-rollcd steel sheet 10 was degraded.
Contrary to this, in Examples 1 to 5, all the conditions ( I ) to (3) were satisfied,
and thus the cooling wakr could be appropriately bloclted while appropriately cooling
the hot-rolled steel sheet 10 by the cooling water.
[0081]
In the same manner, Examples 6 to 10 and Comparative Exarnplcs 18 to 23 in
which the amount (sprayed water density) QB of the cooling water is a high sprayed
watcr density of 6.0 m'/m2/min arc cxamined.
In Comparativc Examplc 18, the conditions (2) and (3) were satisfied, the
~nomentumF A of the watcr-blocking water was greater than 1.5 times the momentum
FB of thc cooling water, and thus water-bloclting characteristics were good. However,
since thc momentum F/\ of thc watcr-blocking watcr was too great, the water-blocking
water had submerged below the cooling water and the cooling ability or the cooling
water to cool the hot-rolled steel sheet 10 was degraded.
In Comparative Examples 19 to 21, the molnentum FA of the water-blocking
water was smaller than the momentum FB of the cooling water, and thus the cooling
ability of the cooling water to cool the hot-rolled steel sheet 10 was not degraded.
However, the condition (1) was not satisfied, and bloclcing the cooling water was not
appropriately performed.
In Comparative Example 22, the condition (I) was satisfied and thc cooling
ability of the cooling water to cool the hot-rolled steel sheet 10 was not degraded.
Howcver, the height H at which the adjacent sprays of the water-blocking water had
joined was 400 mm or lcss and thus the condition (2) was not satisfied, and bloclcing
the cooling watcr was not appropriately performed.
In Comparative Example 23, the distance L between the water-blocking
nozzle 22 and the surface orthe hot-rolled stcel sheet 10 was greater than 2000 mm
and thus the condition (3) was not satisfied, and blocking the cooling water was not
appropriately pcrforniecl. In addition, in this case, the water-bloclcing watc~h ad
submerged below the cooling water and the cooling ability of the cooling water to cool
the hot-rolled steel sheet 10 was degradcd.
Contrary to this, in Examples 6 to 10, all the conditions (1) to (3) were
satisfied, and thus the cooling watcr could be appropriately bloclced while
appropriately cooling the hot-rolled steel sheet 10 by the cooling watcr.

In the same manner, Examples 11 to 15 and Comparative Examplcs 24 to 29
in which the amount (sprayed water density) QB of the cooling water is a high sprayed
water dcnsity of 8.0 m3/m2/min are examined.
In Comparative Example 24, the conditions (2) and (3) were satisfied, the
momentum FA of the water-blocking water was greater than 1.5 times the momentum
FB of the cooling water, and thus water-bloclung characteristics were good. However,
since the momentum FA of thc water-bloclting water was too great, the water-blocking
water had submerged below the cooling water and the cooling ability of the cooling
water to cool the hot-rolled steel sheet 10 was degraded.
In Comparative Examples 25 to 27, the momentum FA of the water-hloclting
water was smaller than the momentum Fu of the cooling water, and thus the cooling
ability of the cooling water to cool the hot-rolled stcel sheet 10 was not degraded.
However, the condition (I) was not satisfied, and bloclting the cooling water was not
appropriately performed.
In Comparative Example 28, the condition (1) was satisfied, and the cooling
ability of the cooling water to cool the hot-rolled steel sheet 10 was not degraded.
I-Iowever, the height fI at which the adjacent sprays of the water-blocking water had
joined was 400 mm or less and thus the condition (2) was not satisfied, and bloclting
the cooling water was ~ioatp propriately perfoimed.
In Comparative Example 29, the distance L between the water-blocking
nozzle 22 and the surface of the hot-rolled steel sheet 10 was greater than 2000 mm
and thus the condition (3) was not satisfied, and blocliing the cooling water was not
appropriately performed. In addition, in this case, the water-bloclting water had
s~~bmergebdel ow the cooling watcr and the cooling ability of the cooling water to cool
thc hot-rolled steel shcct 10 was dcgraded.
Contrary to this, in Exaniples 11 to 15, all the conditions (1) lo (3) were
satisficd, and thus the cooling water could be appropriately bloclied while
appropriately cooling the hot-rolled steel sheet 10 by the cooling water.

According to the above verification results, it was confirmed that in the case
where the sprayed water density of the cooling water was a high sprayed water density
of higher than 4 m3/m2/min and equal to or less than 10 m3/m2/min and the waterblocliing
apparatus and the water-blocking method of the present invention were used,
that is, all the conditions (1) to (3) were satisfied, the cooling water could be
appropriately blocked while appropriately cooling the hot-rolled steel sheet 10 by the
cooling water. In contrast, in a case where the sprayed water density of the cooling
water was a low sprayed water density of equal to or less than 4 m3/m2/min or any one
of the conditions (1) to (3) was not satisfied, the cooling water could not be
appropriately bloclied while appropriately cooling the hot-rolled steel sheet 10 by the
cooling watcr.

In addition, in Examples 1 to 15 described above, Examples 2, 7, and 12 in
which "Water-blocking characteristics" was A are optimum examples. That is,
conditions in which thc >pray angle Os of the water-blocliing water is 50 deg~cest,h e
angle OA of attack of the water-blocliing water is 30 degrccs, and the interval P between
the water-blocking nozzles 22 and 22 is 225 mm are optimum conditions.

Compared to the conditions, when the spray angle Os of the watcr-blocking
water becomes greater than 50 degrees, the momentum Fg of the cooling water is
reduced. In contrast, when the spray angle Hs of the watcr-bloclting water becomes
smaller than 50 degrees, the height H at which the adjacent sprays of the waterblocliing
watcr join is reduced.

In addition, when the angle of attack of the water-bloclting water becomes
greater than 30 degrees, the distance L between thc water-bloclting nozzle 22 and the
surface orthe hot-rolled steel sheet 10 is increased. In contrast, when the angle HA of
attack of the water-blocking water becomes smaller than 30 degrees, the momentum Fu
of the cooling water is reduced.

In addition, when the interval P between thc water-blocking nozzles 22 and 22
becomes greater than 225 mm, the momentum Fu of the cooling water is reduced. In
contrast, when the interval P between the water-bloclting nozzles 22 and 22 becomes
smaller than 225 mm, a large number of water-bloclting nozzles 22 need to be provided,
resulting in an increase in the cost of the apparatus.

[Industrial Applicability]

The present invention is useful for bloclting cooliilg water sprayed onto a hotrolled
steel sheet when the hot-rolled steel sheet is cooled after finish rolling 01 a hotrolling
process.
[Brief Description of the Reference Symbols]

1 : HOT ROLLING FACILITY
10: HOT-ROLLED STEEL SIIEET
1 1 : I IEATING FURNACE
12: WIDTH-DIIaCTION ROLLING MILL
13: ROUGIIING MILL
13a: WORT< ROLL
13b: FOUR-HIGH MILL
14: FINISHING MILL
14a: FINISHING ROLL
15: COOLJNG APPARATUS
1 6: WATER-BI,OCI