Technical Field
[OOOl] The present invention relates to a cooling apparatus,
and a manufacturing apparatus and a manufacturing method of a
hot-rolled steel sheet. More particularly, it relates to a
cooling apparatus that is excellent in discharging cooling water
and able to secure a high cooling capability, and amanufacturing
apparatus and manufacturing method of a hot-rolled steel sheet.
Background Art
[ 0 0 0 2 ] A steel material used for automobiles, structural
materials, and the like is required to be excellent in such
mechanical properties as strength, workability, and toughness.
In order to improve these properties comprehensively, it is
effective to make a steel material with a fine-grained structure;
to this end, a number of manufacturing methods to obtain a steel
material with a fine-grained structure have been sought.
Further, by making the fine-grained structure, it is possible
to manufacture a high-strength hot-rolled steel sheet having
excellent mechanical properties even if the amount of alloy
elements added is reduced.
[ 0 0 0 3 ] As a method for making a steel sheet with a
fine-grained structure, it is known to carry out a large rolling
reduction especially in the subsequent stage of hot finish
rolling (in any rolling mill to roll a steel sheet on downstream
side when a plurality of rolling mills are aligned in parallel),
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2
d e f o r m i n g a u s t e n i t e g r a i n s g r e a t l y and i n c r e a s i n g a d i s l o c a t i o n
d e n s i t y ; a n d t h e r e b y t o o b t a i n f i n e - g r a i n e d f e r r i t e a f t e r r o l l i n g .
F u r t h e r , i n view of f a c i l i t a t i n g t h e f e r r i t e t r a n s f o r m a t i o n by
i n h i b i t i n g r e c r y s t a l l i z a t i o n and r e c o v e r y of t h e a u s t e n i t e
g r a i n s , it is e f f e c t i v e t o c o o l a s t e e l s h e e t t o 600"~t o 7 5 0 " ~
a s q u i c k l y a s p o s s i b l e a f t e r r o l l i n g . I n o t h e r words, s u b s e q u e n t
t o h o t f i n i s h i n g r o l l i n g , it is e f f e c t i v e t o r a p i d l y c o o l a s t e e l
s h e e t a f t e r t h e r o l l i n g , b y a r r a n g i n g a c o o l i n g a p p a r a t u s c a p a b l e
of c o o l i n g more q u i c k l y t h a n e v e r b e f o r e . I n r a p i d l y c o o l i n g
a s t e e l s h e e t a f t e r r o l l i n g i n t h i s way, it i s e f f e c t i v e t o have
a l a r g e volume of c o o l i n g w a t e r s p r a y e d o v e r t h e s t e e l s h e e t p e r
u n i t a r e a , and t o make a volume d e n s i t y of c o o l i n g w a t e r
(sometimes r e f e r r e d t o a s " c o o l i n g w a t e r volume d e n s i t y " ) l a r g e
i n o r d e r t o enhance a c o o l i n g c a p a b i l i t y .
[0004] However, i f t h e c o o l i n g w a t e r volume d e n s i t y is
i n c r e a s e d i n t h i s way, t h e w a t e r a c c u m u l a t e d ( i . e . r e t a i n e d
w a t e r ) on an upper s u r f a c e of a s t e e l s h e e t i n c r e a s e s due t o a
r e l a t i o n between w a t e r s u p p l y and w a t e r d i s c h a r g e . By t h e
i n c r e a s e of t h e r e t a i n e d w a t e r , t h e r e t a i n e d w a t e r r e a c h e s an
upper surfaceguidedisposedbetweenthe s t e e l s h e e t a n d a c o o l i n g
n o z z l e and having a h o l e t h a t a l l o w s c o o l i n g w a t e r s p r a y e d from
t h e c o o l i n g n o z z l e t o p a s s t h r o u g h , whereby s o - c a l l e d o v e r f l o w
can o c c u r . The o v e r f l o w sometimes c a u s e s t r o u b l e s a s f o l l o w s .
[0005] (1) By making a t h i c k l a y e r of t h e r e t a i n e d w a t e r , j e t
p r e s s u r e of t h e c o o l i n g w a t e r s p r a y e d from t h e c o o l i n g n o z z l e
d e c a y s . I f t h e l a y e r of t h e r e t a i n e d w a t e r becomes even t h i c k e r
and r e a c h e s t h e c o o l i n g n o z z l e , t h e j e t p r e s s u r e d e c a y s more.
( 2 ) I n d i s c h a r g i n g t h e r e t a i n e d w a t e r , t h e r e t a i n e d
w a t e r h a s c o n t a c t w i t h t h e upper s u r f a c e g u i d e and c r e a t e s a flow
r e s i s t a n c e , whereby d i s c h a r g i n g c a p a b i l i t y d e g r a d e s .
@ ( 3 ) S i n c e it is d i f f i c u l t t o c o n t r o l o v e r f l o w e d w a t e r ,
t h e w a t e r c a n f l o w i n t o o t h e r a r e a s and s o on, which can c a u s e
u n e x p e c t e d p r o b l e m s .
[ 0 0 0 6 ] T h e r e f o r e , b e c a u s e of such t r o u b l e s a s above, t h e r e
is a problem t h a t h i g h c o o l i n g c a p a b i l i t y c a n n o t b e e x e r t e d , and
sometimes it i s d i f f i c u l t t o e f f e c t i v e l y have c o o l i n g w a t e r w i t h
a l a r g e volume d e n s i t y t o s p r a y t o a s t e e l s h e e t .
[0007] With r e g a r d t o d i s c h a r g i n g w a t e r on an upper s u r f a c e
s i d e of a s t e e l s h e e t , t e c h n i q u e s such a s P a t e n t Document 1 and
2 h a v e b e e n d i s c l o s e d . I n a c o o l i n g a p p a r a t u s of a h o t - r o l l e d
s t e e l s t r i p d e s c r i b e d i n P a t e n t Document 1, a h o l e is p r o v i d e d
t o an upper s u r f a c e g u i d e c o n f i g u r e d t o s u p p l y c o o l i n g w a t e r by
a l l o w i n g t h e c o o l i n g w a t e r t o p a s s t h r o u g h , and t o o v e r f l o w
r e t a i n e d w a t e r . A l s o , i n a c o o l i n g a p p a r a t u s of a s t e e l s h e e t
d e s c r i b e d i n P a t e n t Document 2 , a h o l e t o s u p p l y c o o l i n g w a t e r
t o an upper s u r f a c e g u i d e and a s l i t t o h a n d l e o v e r f l o w a r e
p r o v i d e d s e p a r a t e l y t o a l l o w r e t a i n e d w a t e r t o d i s c h a r g e smoothly
t h e r e t o i n h i b i t d e g r a d a t i o n of c o o l i n g c a p a b i l i t y .
C i t a t i o n L i s t
P a t e n t L i t e r a t u r e
[0008]
P a t e n t Document 1: J a p a n e s e P a t e n t No. 3770216
P a t e n t Document 2: J a p a n e s e P a t e n t No. 4029871
Summary of t h e I n v e n t i o n
Problems t o be Solved by t h e I n v e n t i o n
[0009] However, t h e c o o l i n g a p p a r a t u s h a v i n g a c o n f i g u r a t i o n
o f t h e u p p e r s u r f a c e g u i d e d e s c r i b e d a b o v e i s b a s e d o n t h e p r e m i s e
t h a t o v e r f l o w o c c u r s , i n o t h e r words, t h e r e t a i n e d w a t e r r e a c h e s
9
'r
0 the upper surface guide. Consideringincreasing of water volume
density and volume of cooling water to supply thereby improving
cooling capability, another technique to improve water
discharging capability needs to be provided.
[OOlO] If the upper surface guide is disposed at a high
position, possibility of the overflow can be reduced. However,
in order to avoidbreaking ofthe cooling nozzle by having contact
with a steel sheet, the upper surface guide needs to be disposed
at a lower position than a position of a water ejection outlet
of the cooling nozzle. Also, the cooling nozzle is desired to
be provided as close (as low) to the steel sheet as possible in
order to inhibit degradation of the cooling capability.
Therefore, it is preferable that the upper surface guide is also
disposed as low as possible.
[OOll] Accordingly, considering the above problems, an
object ofthe present invention is to provide: a coolingapparatus
of a steel sheet capable of discharging water adequately
corresponding to increase of volume density of cooling water,
to thereby secure a high cooling capability; and a manufacturing
apparatus and manufacturing method of a hot-rolling steel sheet
using the cooling apparatus.
Means for Solving the Problems
The present invention will be described below.
[0013] A first aspect of the present invention is a cooling
apparatus disposed on a downstream side from a row of hot finish
rolling mills, capable of supplying cooling water from above a
pass line towardthe pass line, comprising: apluralityofcooling
nozzles aligned in parallel in a direction of the pass line; and
an upper surface guide to be disposed between the pass line and
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0 the cooling nozzles, wherein each cooling nozzle ofthe plurality
of cooling nozzles can spray cooling water with a cooling water
volume densityof 0.16 (m3/(m2 sec)) ormore, andwhen the cooling
water volume density to be sprayed is defined as q m (m3/(m2
sec)), a pitch of the cooling nozzle in a pass line direction
is defined as L (m), a distance between a lower surface of the
upper surface guide and the pass line is defined as h, (m), a
uniform cooling width is defined as W, (m), and a cross-sectional
area of virtual flow path of discharging water flowing in a width
direction of a steel sheet per pitch of the cooling nozzle in
the pass line direction is defined as S (m2), the following
relation is satisfied.
[0014] Asecondaspectofthepresentinventionisthe cooling
apparatus according to the first aspect, wherein the upper
surface guide has a configuration in which a distance between
the pass line and the upper surface guide changes in the pass
line direction, and a corresponding height h,' of the upper
surface guide is applied instead of h,.
[0015] Athird aspect of the present invention is the cooling
apparatus according to the first or second aspect, wherein at
least either one of the upper surface guide or the cooling nozzle
can move in top and bottom direction.
[0016] A fourth aspect of the present invention is a
manufacturing apparatus of a hot-rolled steel sheet comprising:
a row of hot finish rolling mills; and the cooling apparatus
according to any one of the first to third aspects disposed on
downstream side from the row hot finish rolling mills,
0 wherein an end portion on upstream side of the cooling apparatus
is disposed inside a final stand in the row of hot finish rolling
mills.
[0017] A fifth aspect of the present invention is a
manufacturing method of a hot-rolled steel sheet comprising a
step to supply cooling water to at least an upper surface of a
steel sheet after final rolling to cool the steel sheet by a
cooling apparatus disposed to a downstream side from a row of
hot finish rollingmills, wherein following relation is satisfied
when a volume density of cooling water from a cooling nozzle
provided to the cooling apparatus is defined as q, (m3/ (m2 sec) )
that is 0.16 (m3/ (m2 sec) ) or more, a pitch of the cooling nozzle
in a sheet passing direction is defined as L (m), a distance
between a lower surface of an upper surface guide disposed to
the cooling apparatus and an upper surface of the steel sheet
to be passed is defined as ha (m), a width of the steel sheet
to be passed is defined as W, (m), and a cross-sectional area of
virtual flow path of discharging water flowing in a width
direction of the steel sheet per pitch of the cooling nozzle in
the sheet passing direction is defined as Sa (m2).
[0018] A sixth aspect of the present invention is the
manufacturing method of a hot-rolled steel sheet according to
the fifth aspect, wherein a corresponding height haf of the upper
surface guide is applied instead of ha when the upper surface
guide has a configuration in which a distance between the steel
sheet and the upper surface guide changes in the sheet passing
direction.
[0019] A seventh aspect of the present invention is the
manufacturing method of a hot-rolled steel sheet according to
the fifth or sixth aspect, wherein at least either one of the
upper surface guide or the cooling nozzle can move in top and
bottom direction.
[0020] An eighth aspect ofthe invention is themanufacturing
method of a hot-rolled steel sheet according to any one of the
fifth to seventh aspects, wherein an end portion on upstream side
of the cooling apparatus is disposed inside a final stand in the
row of hot finish rolling mills.
Effect of the Invention
[0021] By the present invention. it is possible to provide
a cooling apparatus capable of: providing a large amount of
cooling water with a high volume density thereto cool a steel
sheet; and discharging the water smoothly, thereby enabling
manufacturing a hot-rolled steel sheet with a fine-grained
structure. In other words, as a result of discharging water
smoothly, it is possible to prevent an upper side of retained
water from reaching the upper surface guide, thereby enabling
cooling the steel sheet effectively. Further, smooth
discharging water like this inhibits cooling non-uniformity in
the width direction of the steel sheet. thereby enabling cooling
more uniformly.
Brief Description of The Drawings
[0022]
Fig. 1 is a schematic view showing a part of a manufacturing
apparatus of a hot-rolled steel sheet that comprises a cooling
apparatus according to one embodiment.
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8
e Fig. 2Ais an enlargedview of an area in Fig. 1, where the cooling
apparatus is disposed, showing the cooling apparatus in its
entirety. Fig. 2B is a view further focusing on an upstream side
of the Fig. 2A.
Fig. 3 is a view seen from an arrow I11 in Fig. 2A
Fig. 4 is a view to describe a cooling nozzle.
Fig. 5 is another view to describe the cooling nozzle.
Fig. 6 is a view to describe the formula (1).
Fig. 7 is a view illustrating a portion in which an upper surface
guide is inclined.
Fig. 8 is a viewillustratinganexampleinwhichtheupper surface
guide is not flat.
Fig. 9 is a view illustrating another example in which the upper
surface is not flat.
Modes for Carrying out the Invention
[0023] The functions and benefits of the present invention
described above will be apparent from the following modes for
carrying out the invention. The present invention will be
described based on the embodiments shown in the accompanying
drawings. However, the invention in not limited to these
embodiments.
[0024] Fig. 1 is a schematic view showing a part of a
manufacturing apparatus 10 of a hot-rolled steel sheet including
a cooling apparatus 20 (hereinafter, sometimes referred to as
"cooling apparatus 20") according to one embodiment. In Fig.
1, a steel sheet 1 is transported from left on the sheet of paper
(upstream side, upper process side) to right (downstream side,
lower process side), a direction from top to bottom on the sheet
of paper being vertical direction. A direction fromthe upstream
@
s i d e ( t h e upper p r o c e s s s i d e ) t o t h e downstream s i d e ( t h e lower
p r o c e s s s i d e ) may be r e f e r r e d t o a s a s h e e t p a s s i n g d i r e c t i o n .
F u r t h e r , a d i r e c t i o n of a w i d t h of t h e s t e e l s h e e t t o be p a s s e d ,
which is o r t h o g o n a l t o t h e s h e e t p a s s i n g d i r e c t i o n m a y b e r e f e r r e d
t o a s a width d i r e c t i o n of s t e e l s h e e t . H e r e i n a f t e r , r e f e r e n c e
symbols may be o m i t t e d i n t h e below d e s c r i p t i o n s of t h e drawings
f o r t h e p u r p o s e of e a s y v i e w i n g . I n view of F i g . 1, a l i n e t h a t
a s t e a d y r o l l i n g p a r t ( a p a r t e x c e p t f o r a t o p p o r t i o n a n d a b o t t o m
p o r t i o n ) of t h e s t e e l s h e e t 1 p a s s e s t h r o u g h i s shown a s a p a s s
l i n e P . T h e r e f o r e , t h e s t e a d y r o l l i n g p a r t of t h e s t e e l s h e e t
p a s s e s t h e p a s s l i n e P .
[0025] A s shown i n F i g . 1, t h e m a n u f a c t u r i n g a p p a r a t u s 10 of
a h o t - r o l l e d s t e e l s h e e t c o m p r i s e s : a row of h o t f i n i s h r o l l i n g
m i l l s 11; t h e c o o l i n g a p p a r a t u s 20; t r a n s p o r t i n g r o l l s 12, 12,
... ; and a p i n c h r o l l 13. F u r t h e r , a h e a t i n g f u r n a c e , a row of
rough r o l l i n g m i l l s , and t h e l i k e , t h e f i g u r e s and d e s c r i p t i o n s
t h e r e o f a r e o m i t t e d , a r e d i s p o s e d on an u p s t r e a m s i d e from t h e
row of h o t f i n i s h r o l l i n g m i l l s 11. These s e t b e t t e r c o n d i t i o n s
f o r a s t e e l s h e e t t o go t h r o u g h t h e row of h o t f i n i s h r o l l i n g
m i l l s l l . O n t h e o t h e r hand, a n o t h e r c o o l i n g a p p a r a t u s o r v a r i o u s
k i n d s of equipment such a s a c o i l e r t o s h i p t h e s t e e l s h e e t a s
a s t e e l s h e e t c o i l , a r e d i s p o s e d on a downstream s i d e from t h e
p i n c h r o l l 13.
A h o t - r o l l e d s t e e l s h e e t is g e n e r a l l y m a n u f a c t u r e d i n
t h e f o l l o w i n g way.
f u r n a c e and has
Aroughbarwhichhasbeentaken f r o m a h e a t i n g
been r o l l e d rough r o l l i n g t o have a
p r e d e t e r m i n e d t h i c k n e s s is r o l l e d c o n t i n u o u s l y by t h e row of h o t
f i n i s h r o l l i n g m i l l s 11 t o have a p r e d e t e r m i n e d t h i c k n e s s , w h i l e
a t e m p e r a t u r e t h e r e o f is c o n t r o l l e d . A f t e r t h a t , t h e s t e e l s h e e t
i s r a p i d l y c o o l e d i n t h e c o o l i n g a p p a r a t u s 2 0 . Here, t h e c o o l i n g
a(
16
apparatus 20is disposedinsideahousing llghthatsupports rolls
(work rolls) in a final stand llg of the row of hot finish rolling
mills 11, in a manner as closely to the rolls llgw, llgw (see
Fig. 2) ofthe final stand llg as possible. Then, the steel sheet
passesthroughthepinch roll13, and is cooledby another cooling
apparatus to a predetermined coiling temperature to be coiled
by a coiler.
[0027] Hereinafter, the manufacturing apparatus 10 of a
hot-rolled steel sheet (hereinafter sometimes referred to as
"manufacturing apparatus lo"), including the cooling apparatus
20, will be described. Fig. 2 is an enlarged view of an area
in Fig. 1, where the cooling apparatus 20 is provided. Fig. ZA
is an enlarged view showing the cooling apparatus in entirety,
whereas Fig. 28 is a view further focusing on the vicinity of
the final stand 119. Fig. 3 is a schematic view of the
manufacturing apparatus 10 seen from a downstream side of the
final stand 119, from a direction shown by an arrow I11 in Fig.
2A. Therefore, in Fig. 3, a direction from top to bottom on the
sheet of paper is vertical direction of the manufacturing
apparatus 10, a direction fromleft to right on the sheet of paper
is the width direction of steel sheet, and a direction from back
to front is the sheet passing direction.
[0028] In the row of hot finish rolling mills 11 in the
embodiment, seven stands (lla, llb, ..., 119) are aligned along
the sheet passing direction as can be seen from Fig. 1. Each
of the stands lla, llb, ..., 119 includes a rolling mill, and a
rolling reduction and the like are set in each rolling mill to
allow a steel sheet to meet conditions for thickness, mechanical
properties, surface quality, and the like which are required as
a final product. Here, the rolling reduction of each of the
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stands lla. llb, .... llg is set in a manner that the steel sheet
to be manufactured satisfies the required properties. However,
in view of carrying out a large rolling reduction to deform
austenite grains greatly and to increase a dislocation density,
thereby obtaining a steel sheet having a fine-grained ferrite
after rolling, the rolling reduction is preferably large at the
final stand llg. The rolling mill of each stand of lla, ..., llf,
llg has a pair of work rolls llaw, llaw, ..., Ilfw, llfw, llgw,
llgw to roll actually sandwiching the steel sheet, and a pair
of backup rolls Ilab, llab, ..., llfb, llfb, llgb, llgb disposed
in a manner that an outer periphery thereof has contact with an
outer periphery ofthe work rolls llaw, llaw, ..., llfw, Ilfw, llgw,
llgw. Also, the rollingmill includes the work rolls llaw, llaw,
..., llfw, llfw, llgw, Ilgw, the backup rolls Ilab, llab, ..., llfb,
llfb, llgb, llgb thereinside, and housings llah, ..., llfh, llgh
each forming an outer shell of each of the stands lla, ..., llf,
llg that support the work rolls llaw, llaw, ..., Ilfw, llfw, llgw,
llgw and the backup rolls llab, llab, ..., llfb, llfb, llgb, llgb.
Each of the housings llah, ..., llfh, llgh has a standing portion
vertically disposed facing to the housings llah, ..., llfh, llgh
(for example, in the final stand llg, the standing portion llgr,
llgr shown in Fig. 3) . That is, as can be seen from Fig. 3, the
standing portion of the housing is disposed in a manner to
sandwich the steel sheet 1 (pass line P) in the width direction
of steel sheet. Also, the standing portions llgr, llgr of the
final stand llg are vertically disposed in a manner to sandwich
a part of the cooling apparatus 20 and the steel sheet 1 (pass
line P) in the width direction of the steel sheet.
[ 0 0 2 9 ] Here, a distance between the shaft center of the work
roll llgw and an end surface on downstream side of the standing
@
portions llgr, llgr of the housing, which is shown by L1 in Fig.
2A is preferably larger than a radius rl of the work roll llgw.
This makes it possible to dispose a part of the cooling apparatus
20 in a portion corresponding to L1-rl as mentioned below. In
other words, it is possible to dispose a part of the cooling
apparatus 20 in a manner to insert it inside the housing llgh.
Also, as shown in Fig. 3, in the portion in which the cooling
apparatus 20is insertedbetweenthe standing portions llgr, llgr
of the housing, the standing portions llgr, llgr of the housing
exist as side walls in both sides of the cooling apparatus 20
in the width direction of steel sheet. And a predetermined space
is formed between the end portions of the cooling apparatus 20
in the width direction of steel sheet and the standing portions
llgr, llgr of the housing.
[0030] Next, the cooling apparatus 20 willbe described. The
cooling apparatus 20 comprises: upper surface water supplying
devices 21, 21, ...; lower surface water supplying devices 22, 22,
... ; upper surface guides 30, 30, ...; and lower surface guides 35,
35, ....
[0031] The upper surface water supplying devices 21, 21, ...
are devicesto supply coolingwater fromabovetoan upper surface
side of the steel sheet 1, which is the pass line P. The upper
surface water supplying devices 21, 21, ... comprise: cooling
headers 21a, 21a, ...; conduits 21b, 21b, ..., respectively provided
to the cooling headers 21a, 21a, ..., in a form of a plurality of
rows; and cooling nozzles 21c, 21c, ... respectively attached to
end portions of the conduits 21b, 21b, .... In the embodiment,
each cooling header 21ais a pipe extendingin the width direction
of the steel sheet as can be seen from the figs. 2 and 3, and
the cooling headers 21a. 21a. ... are aligned in the sheet passing
w
13
a direction. Each conduit 21b is a thin pipe diverging from each
cooling header 21a in a plural form, and an opening end of the
conduit is directed toward the upper surface side of the steel
sheet (the pass line P ) . A plurality of the conduits 21b, 21b,
... are arranged in a comb-like manner along a direction of a tube
length of the cooling header 21a, namely, in the width direction
of the steel sheet.
[0032] An end portion of each of the conduits 21b, 21b, ... is
provided with each of the cooling nozzles 21c, 21cf .... The
cooling nozzles 21cf 21c, ... according to the embodiment are flat
spray nozzles each can forma fan-like jet of cooling water (with
a thickness of approximately 5 mm to 30 mm for example). Figs.
4 and 5 schematically show the jets of cooling water formed on
a surface of the steel sheet. Fig. 4 is a perspective view. In
Figs. 4 and 5, the sheet passing direction andthe widthdirection
of steel sheet are shown together. Fig. 5 schematically shows
a manner of an impact by the jets of cooling water formed on the
surface of the steel sheet. In Fig. 5, open circles show
positions right below the cooling nozzles 21c, 21cf .... Further,
thick lines schematically show impact positions and shape of the
jets of cooling water. In Fig. 5, "... ..." means an omitted
description. As can be seen from Fig. 5, a low of nozzles (for
example, a row A of nozzles, a row B of nozzles, and a row C of
nozzles) is formed by the cooling nozzles 21c, 21c, ... arranged
to one cooling header 21a of the cooling headers. Also, as can
be seen from Figs. 4 and 5, in the embodiment, the rows of nozzles
next to each other (for example, the row A of nozzles and the
row B ofnozzles, and the rowB of nozzles and the rowC ofnozzles)
are arranged in a manner that the position of one of the rows
in the width direction of the steel sheet differs from the
a'=
'9
Y position of its adjacent row. Further, the rows of nozzles are
arranged in a so-called zigzag manner so that the position of
the rows is the same as the position of the row that is located
further next, in the sheet passing direction of steel sheet.
[ 0 0 3 3 ] In the embodiment, the cooling nozzles are arranged
so that an entire position on the surface of the steel sheet 1
in the width direction of steel sheet can pass through the jets
of cooling water at least twice. That is, a point ST located
on the passing steel sheet 1 moves along a linear arrow in Fig.
5. At this time, in such a manner as twice in the rowA of nozzles
(Al, A2); twice in the row B of nozzles (81, B2); and twice in
the row C of nozzles (Cl, C2), the jets of water from the cooling
nozzles belonging to any one of the rows strike twice. As such,
the cooling nozzles 21c, 21c, ... are arranged in a manner that
the following relation is satisfied among a interval P, between
the cooling nozzles 21c, 21c, ...; an impact width Lf of the jets
of cooling water; and a twisting angle 8 .
Herein, the number of times at which the steel sheet passes
through the jets of cooling water is set to be twice, to which
the number of time is not limited; it may be three or more times.
For a purpose of uniforming a cooling capability in the width
direction of the steel sheet, in the rows of nozzles adjacent
to each other in the sheet passing direction, the cooling nozzles
21c, 21c, ..in one ofthe rows aretwistedin an opposite direction
from the nozzles in its adjacent row.
[0034] Also, the "uniform cooling width" relating to cooling
is fixed by arrangement of the cooling nozzles. This means,
I) considering properties of the plurality of cooling nozzles to
be arranged, a size of the steel sheet 1 in the width direction
with which a steel sheet to be passed can be cooled uniformly.
Specifically, the uniform cooling width often corresponds to a
width of the largest steel sheet that can be manufactured by a
manufacturing apparatus of a steel sheet. In particular, the
size shown by W, in Fig. 5 for example.
[ 0 0 3 5 ] Here, in the embodiment, in the rows A, 8 , and C of
nozzles adjacent to one another as shown above, the cooling
nozzles in one of the rows are twisted in an opposite direction
from the nozzles in its adjacent row. However, a configuration
is not limited to this; and the cooling nozzles may be configured
to be twisted to a same direction. The twisting angle (angle
as shown above) is not particularly limited either; and the
twisting angle may be adequately determined in view of required
cooling capability and well fitting of disposed equipments.
Further, in the embodiment, in view of the above benefits, the
rows A, B and C of nozzles adjacent to one another in the passing
direction of the steel sheet are arranged in a zigzag manner.
However, a configuration is not limited to this; and the cooling
nozzles may be configured to be aligned in a linear manner in
the sheet passing direction.
[ 0 0 3 6 ] A position where the upper surface water supplying
device 21is providedinthe sheet passing direction (a direction
of the pass line P ) is not particularly limited; however, the
upper surface water supplying device 21 is preferably arranged
as follows. That is, a part of the cooling apparatus 20 is
disposed right after the final stand llg in the row of hot finish
rolling mills 11, from inside the housing llgh of the final stand
llg, in a manner as closely to the work roll llgw in the final
Is'
I6
I @ s t a n d l l g a s p o s s i b l e . T h i s a r r a n g e m e n t e n a b l e s r a p i d c o o l i n g
I of t h e s t e e l s h e e t 1 i m m e d i a t e l y a f t e r it has been r o l l e d by t h e
I row of h o t f i n i s h r o l l i n g m i l l s 11. I t is a l s o p o s s i b l e t o s t a b l y
I g u i d e t h e t o p p o r t i o n of t h e s t e e l s h e e t 1 i n t o t h e c o o l i n g
I I a p p a r a t u s 20. A p o s i t i o n a t h e i g h t of t h e upper s u r f a c e w a t e r
s u p p l y i n g d e v i c e 21 is a l o n g t h e p o s i t i o n of t h e upper s u r f a c e
g u i d e 30 d i s p o s e d i n a m a n n e r t o s a t i s f y t h e f o r m u l a (1) mentioned
below. However, a p o r t i o n i n t h e h o u s i n g l l g h o f t h e f i n a l s t a n d
l l g is a r r a n g e d i n a manner t o be c l o s e t o t h e p a s s l i n e P ( t h e
s t e e l s h e e t I ) , i n o t h e r words, a r r a n g e d i n a manner t o be low.
I
I [0037] A d i r e c t i o n i n which t h e c o o l i n g w a t e r i s s p r a y e d from
I
1 t h e c o o l i n g w a t e r e j e c t i o n o u t l e t of each of t h e c o o l i n g n o z z l e s ~
21c, 21c, ... i s b a s i c a l l y a v e r t i c a l d i r e c t i o n ; however, t h e
e j e c t i o n of t h e c o o l i n g w a t e r from t h e c o o l i n g n o z z l e t h a t i s
c l o s e s t t o t h e work r o l l l l g w o f t h e f i n a l s t a n d l l g i s p r e f e r a b l y
d i r e c t e d more toward t h e work r o l l l l g w t h a n v e r t i c a l l y . T h i s
c o n f i g u r a t i o n can f u r t h e r s h o r t e n t h e t i m e p e r i o d from r e d u c t i o n
o f t h e s t e e l s h e e t l i n t h e finalstandllgtoinitiationofcooling
t h e s t e e l s h e e t . And t h e r e c o v e r y t i m e of r o l l i n g s t r a i n s
accumulated by r o l l i n g can a l s o be r e d u c e d t o a l m o s t z e r o .
T h e r e f o r e , a f i n e - g r a i n e d s t e e l s h e e t c a n b e m a n u f a c t u r e d .
[0038] The lower s u r f a c e w a t e r s u p p l y i n g d e v i c e s 22, 22, ...
a r e d e v i c e s t o s u p p l y c o o l i n g w a t e r t o t h e lower s u r f a c e s i d e
of t h e s t e e l s h e e t 1, i n o t h e r words, s u p p l y c o o l i n g w a t e r from
u n d e r n e a t h o f t h e p a s s l i n e P . The lower s u r f a c e w a t e r s u p p l y i n g
d e v i c e s 22, 22, ... c o m p r i s e : c o o l i n g h e a d e r s 22a, 22a, ... ; c o n d u i t s
22b, 22b, ... r e s p e c t i v e l y p r o v i d e d t o t h e c o o l i n g h e a d e r s 22a,
22a, ... i n a form of a p l u r a l i t y o f r o w s ; and c o o l i n g n o z z l e s 22c,
22c, ... r e s p e c t i v e l y a t t a c h e d t o end p o r t i o n s of t h e c o n d u i t s 22b,
22b. .... The lower s u r f a c e w a t e r s u p p l y i n g d e v i c e s 22, 22, ... a r e
ib?
17
() arranged opposite to the above described upper surface water
supplying devices 21, 21, ...; thus, a direction of a jet of cooling
water by the lower surface water supplying device differs from
that by the upper surface water supplying device. However, the
lower surface water supplying device is generally the same in
structure as the upper surface water supplying device; so the
descriptions of the lower surface water supplying device will
be omitted.
[0039] Next, upper surface guides 30, 30, ... will be described.
The upper surface guides 30, 30, ... are sheet-shaped members, and
are disposed between the upper surface water supplying device
21 and the pass line P (the steel sheet 1) so that the top portion
of the steel sheet 1 does not get stuck with the conduits 21b,
21b, ... and the cooling nozzles 21cf 21c, ..., when the top portion
of the steel sheet 1 is passed. Each of the upper surface guides
30, 30, ... is provided with an inlet hole (s) which allow (s) ,a jet
of water fromthe upper surface water supplying device 21to pass.
This configuration enablesthe jet of water fromthe upper surface
water supplying device 21 to pass the upper surface guides 30,
30, ... and reach the upper surface of the steel sheet 1, whereby
it is possible to cool the steel sheet 1 efficiently. Herein,
the shape of the upper surface guide 30 is not particularly
limited; and a known upper surface guide can be used.
The upper surface guides 30, 30, ... are arranged as
shown in Fig. 2. In the embodiment, three upper surface guides
30, 30, 30 are used, and they are aligned in a line direction
of the pass line P. All of the upper surface guides 30, 30, 30
are arranged so as to correspond to a position at height of the
cooling nozzles 21c, 21, .... The upper surface guides 30, 30,
... are arranged in a position at height in a manner to satisfy
P /u
a t h e formula (1) d e s c r i b e d below. A s can b e s e e n from F i g s . 2A
and 2B, t h e p o r t i o n of t h e f i n a l s t a n d l l g i n t h e h o u s i n g l l g h
is p o s i t i o n e d i n a t i l t e d manner t o g e t c l o s e t o t h e p a s s l i n e
P ( t h e s t e e l s h e e t 1) c o r r e s p o n d i n g t o t h e p o s i t i o n a t h e i g h t
of t h e n o z z l e s 21c, 21, ....
[ 0 0 4 1 ] The lower s u r f a c e g u i d e s 3 5 , 3 5 , ... a r e s h e e t - s h a p e d
members a r r a n g e d b e t w e e n t h e l o w e r s u r f a c e w a t e r s u p p l y i n g d e v i c e
22 and t h e p a s s l i n e P ( t h e s t e e l s h e e t 1 ) . T h i s a r r a n g e m e n t
e n a b l e s t o p r e v e n t a t o p end o f t h e s t e e l s h e e t f r o m g e t t i n g s t u c k
w i t h t h e lower s u r f a c e w a t e r s u p p l y i n g d e v i c e s 22, 22, ... and t h e
t r a n s p o r t i n g r o l l s 1 2 , 1 2 , ... e s p e c i a l l y when t h e s t e e l s h e e t 1
is p a s s e d i n t o t h e m a n u f a c t u r i n g a p p a r a t u s 10. F u r t h e r , t h e
lower s u r f a c e g u i d e s 35, 35, ... a r e p r o v i d e d w i t h an i n l e t h o l e ( s )
t h a t a l l o w ( s ) a j e t of w a t e r from t h e lower s u r f a c e w a t e r
s u p p l y i n g d e v i c e s 2 2 , 2 2 , ... t o p a s s . T h i s c o n f i g u r a t i o n e n a b l e s
t h e j e t of w a t e r from t h e lower s u r f a c e w a t e r s u p p l y i n g d e v i c e s
i 22, 22, ... t o p a s s t h e lower s u r f a c e g u i d e 35 and r e a c h t h e lower
1 s u r f a c e of t h e s t e e l s h e e t 1, whereby it is p o s s i b l e t o c o o l t h e
I s t e e l s h e e t 1 e f f i c i e n t l y . The s h a p e of t h e lower s u r f a c e g u i d e
I
i 35 t o be used i s n o t p a r t i c u l a r l y l i m i t e d ; and a known lower
I s u r f a c e g u i d e c a n b e u s e d .
I [0042] The lower s u r f a c e g u i d e s 3 5 , 3 5 , ... , which h a v e b e e n
d e s c r i b e d above a r e a r r a n g e d a s shown i n F i g . 2 . I n t h e
embodiment, f o u r lower s u r f a c e g u i d e s 35, 35, ... a r e used and t h e y
a r e r e s p e c t i v e l y d i s p o s e d between t h e t r a n s p o r t i n g r o l l s 12, 12,
12, a n d b e t w e e n t h e work r o l l l l g w and t h e p i n c h r o l l 13. A l l
of t h e lower s u r f a c e g u i d e s 35, 35, ... a r e d i s p o s e d a t a p o s i t i o n
t h a t i s n o t t o o low i n r e l a t i o n t o upper end p o r t i o n s of t h e
t r a n s p o r t i n g r o l l s 1 2 , 1 2 , ....
a [00431
In the embodiment, an example in which the lower
surface guide is provided has been described; however, the lower
surface guide does not have to be disposed.
[0044] The transporting rolls 12, 12, ... of the manufacturing
apparatus 10 are rolls to transport the steel sheet 1 to the
downstream side, and are aligned having predetermined intervals
in the line direction of the pass line P.
[0045] The pinch roll 13 also functions to remove water, and
is disposed on a downstream side from the cooling apparatus 20.
This pinch roll can prevent cooling water sprayed in the cooling
apparatus 20 from flowing out to the downstream side.
Furthermore, the pinch roll prevents the steel sheet 1 from
ruffling in the cooling apparatus 20, and improves a passing
ability of the steel sheet 1 especially at a time before the top
portion of the steel sheet enters in a coiler. Here, an
upper-side roll 13a of the pinch roll 13 is movable upside down,
as shown in Fig. 2A.
[0046] A steel sheet is manufactured by the above described
manufacturing apparatus of a hot-rolled steel sheet 10, for
example, in the following way. After the steel sheet 1 is coiled
by the coiler, the ejection of cooling water in the cooling
apparatus 20 is stopped during a non-rolling time until rolling
ofthe next steel sheet is started. Duringthe non-rollingtime,
the upper-side roll 13a of the pinch roll 13 on the downstream
side of the cooling apparatus 20 is moved up to a position higher
than the upper surface guide 30 ofthe cooling apparatus 20; then
r o l l i n g o f t h e n e x t s t e e l s h e e t 1is started. When the topportion
of the next steel sheet 1 reaches the pinch roll 13, cooling by
the ejection of cooling water is started. And immediately after
the top portion of the steel sheet passes through the pinch roll
w
?O.
13, the upper side roll13a is lowered to start pinching the steel
sheet 1. At this time, cooling water supplied to the upper
surface side of the steel sheet 1 is, after cooling the steel
sheet 1, discharged from both edges of the steel sheet 1 in the
width direction of steel sheet.
LO0471 By starting spraying cooling water before the top
portion of the steel sheet 1 is transported into the cooling
apparatus 20, it is possible to shorten a length of unsteady
cooling portion of the top portion of the steel sheet 1. In
addition to this, the sprayed cooling water is capable of
stabilizing a passing ability of the steel sheet 1. In other
words, in a case when the steel sheet 1 rises, trying to come
close to the upper surface guide 30, an impact force received
from the jets of cooling water sprayed by the cooling nozzles
21c, 21c, ... increases and a vertically downward force acts on
the steel sheet 1. As such, even in a case when the steel sheet
1 strikes against the upper surface guide 30, the impact of the
steel sheet on the upper surface guide is eased by the impact
force received from the jets of cooling water. Also, since
friction heat between the steel sheet 1 and the upper surface
guide 30 is reduced, it is possible to reduce abrasion defects
produced on the surface of the steel sheet. Therefore, if a
hot-rolled steel sheet is manufactured by the manufacturing
apparatus 10 of a hot-rolled steel sheet comprising the cooling
apparatus 20 operated as above on the downstream side of the row
of hot finish rolling mills 11, cooling with a large volume of
cooling water with a high volume density becomes possible. In
other words, by manufacturing a hot-rolled steel sheet with the
manufacturing method, the hot-rolled steel sheet with a
fine-grained structure is obtained.
T
21
a [ 0 0 4 8 ] F u r t h e r , a s h e e t p a s s i n g r a t e i n t h e row of h o t f i n i s h
r o l l i n g m i l l s can be kept c o n s t a n t e x c e p t f o r t h e a r e a i n which
t h e s t e e l s h e e t s t a r t s t o p a s s . T h i s e n a b l e s m a n u f a c t u r i n g of
a steelsheetwithanenhancedmechanicalstrengthoverthe e n t i r e
l e n g t h of t h e s t e e l s h e e t .
[ 0 0 4 9 ] The c o o l i n g a p p a r a t u s 20 i n t h e embodiment f u r t h e r h a s
t h e f o l l o w i n g c h a r a c t e r i s t i c s . The c h a r a c t e r i s t i c s w i l l be
d e s c r i b e d w i t h r e f e r e n c e of F i g . 6 . F i g . 6 i s an e n l a r g e d view
s c h e m a t i c a l l y showing an a r e a of t h e c o o l i n g a p p a r a t u s 20. F i g .
6 shows a p o s i t i o n a l r e l a t i o n s h i p of t h e u p p e r s u r f a c e w a t e r
s u p p l y i n g d e v i c e s 2 1 , 2 1 , ..., t h e upper s u r f a c e g u i d e 30, and t h e
p a s s l i n e P . I n F i g . 6, l e f t on t h e s h e e t of p a p e r i s t h e u p s t r e a m
s i d e , r i g h t on t h e s h e e t of p a p e r i s t h e downstream s i d e , and
a d i r e c t i o n from t o p t o bottom on t h e s h e e t of p a p e r i s a v e r t i c a l
d i r e c t i o n of t h e m a n u f a c t u r i n g a p p a r a t u s 10. T h e r e f o r e . a
d i r e c t i o n from b a c k t o f r o n t on t h e s h e e t of p a p e r i s t h e width
d i r e c t i o n of s t e e l s h e e t .
[0050] When a p i t c h between t h e a d j a c e n t upper s u r f a c e w a t e r
s u p p l y i n g d e v i c e s 21, 21 i n t h e l i n e d i r e c t i o n of t h e p a s s l i n e
P i s d e f i n e d a s L ( m ) , a w a t e r volume d e n s i t y of c o o l i n g w a t e r
s p r a y e d f r o m t h e n o z z l e 2 1 c i s d e f i n e d a s q,(m3/m2* s e c ) , a u n i f o r m
c o o l i n g w i d t h of t h e c o o l i n g a p p a r a t u s is d e f i n e d a s W, ( m ) ( s e e
F i g . 5 ) , a c r o s s - s e c t i o n a l a r e a of v i r t u a l flow p a t h of
d i s c h a r g i n g w a t e r s p r a y e d from one upper s u r f a c e w a t e r s u p p l y i n g
d e v i c e 21 shown a s shaded a r e a s i n F i g . 6 i s d e f i n e d a s S ( m 2 ) ,
and a d i s t a n c e between t h e p a s s l i n e P and t h e lower s u r f a c e of
t h e upper s u r f a c e g u i d e 30 i s d e f i n e d a s h, (m), t h e f o l l o w i n g
formula (1) i s s a t i s f i e d .
[0051]
[0052] Herein, the cross-sectional area of virtual flow path
S (m2) is obtained as follows. A cross-sectional area Sall that
cooling water sprayed on the upper surface of the steel sheet
1 possibly has when discharged in the width direction ofthe steel
sheet is represented by the following formula (2) per upper
surface water supplying device 21.
[0053]
S,,, = hpmL (2)
[0054] However, Sail includes an area where cooling water
sprayed passes. Therefore, it is necessary to exclude the area
where cooling water sprayed passes from a cross-sectional area
of flow path for discharging water. If the area to be excluded
is defined as Sj (m2), the cross-sectional area of flow path for
discharging water can be represented by the following formula
(3).
[0056] Here, Ljl is, as shown in Fig. 6, in a cross section
of the jet in a jet direction, a length in the sheet passing
direction (m) ofthe cross section ofthe jet in the jet direction,
the length of a portion that passes the upper surface guide 30.
On the other hand, Lj2 is a length on the pass line P same as (m).
Therefore, the cross-sectional area S of virtual flow path can
be obtained by the following formula (4).
P a
[0058] The formula (4) and the formula (1) in which the
formula (4) is substituted can be appliedto nozzles in any forms.
As an example, when a flat nozzle is used, and a spread angle
I of the flat nozzle in the sheet passing direction is defined as
en, the above Ljl and Lj2 are represented by the formula (5) and
the formula (6).
[0061] Here, h, (m) represents a distance between the top
I
I portion of the nozzle and the pass line P.
I
[0062] Also, in the formula (I), in view of manufacturing a
hot-rolled steel sheet with a fine-grained structure and good
mechanical properties, the water volume density of cooling water
q, is 0.16 m3/ (m2 sec) (10m3/ (m2 min) ) or more.
[0063] By various exams and the like such as Examples
mentioned below based on the above idea, it was found out that,
according to the cooling apparatus in which the above formula
(1) is satisfied, and the manufacturing apparatus comprising the
cooling apparatus, it is possible to cool a steel sheet using
a large volume of cooling water with a high water volume density,
and it is also possible to discharge the water efficiently. In
r
9
a other words, by manufacturing a hot-rolled steel sheet using the
manufacturing apparatus of a hot-rolled steel sheet, it is
possible to manufacture a hot-rolled steel sheet with a
fine-grained structure. More particularly, as a result of
smooth discharging water, it is possible to prevent an upper
surface of retained water from reaching the upper surface guide
30, whereby it is possible to efficiently cool the steel sheet
1. Further, smooth discharging water like this inhibits cooling
non-uniformity in the width direction of the steel sheet 1,
thereby enabling cooling more uniformly.
[0064] The left part of the formula (1) shows that, when a
ratio of a secured cross-sectional area of the water discharging
path to volume of provided cooling water, in other words, a ratio
of a flowing speed of discharging water and a value obtained by
I the relationship of h,, a distance between the upper surface of
the steel sheet land the lower surface ofthe upper surface guide
30, is increased, discharging water becomes difficult.
[0065] In the above formulas (1) to (6), a portion in which
the upper surface guide 30 is disposed substantially parallel
to the pass line P has been described. As shown in Fig. 2 B , a
portion inwhich the upper surface guide 30is disposedinatilted
1 manner can be considered in the same way. Fig. 7 is a view
!
corresponding to Fig. 6, showing the portion in which the upper
I surface guide 30 is disposed in a tilted manner.
[0066] When the upper surface guide 30 is disposedin atilted
manner as described above, in the formulas (1) to (6), the
corresponding height h,' of the upper surface guide 30 is applied
instead of h,, the distance between the pass line P and the lower
surface of the upper surface guide 30. In the embodiment, the
corresponding height hp' is obtained by the following formula
( 7 )
[0067]
h,' = hpl + hp2
2
[0068] Here, as can be seen from Fig. 7, hpl is a distance
between the pass line P and the lower surface ofthe upper surface
guide 30 that are on an upper process side in the areas that
configure S,. On the other hand, hpn is a distance between the
pass line P and the lower surface of the upper surface guide 30
that are on a lower process side in the areas that configure S,11.
[0069] As shown the above, the formula (1) is a formula to
determine the distance between the pass line P (the steel sheet
1) and the upper surface guide 30, using flowing amount of cooling
water flowing between the pass line P (the steel sheet 1) and
the upper surface guide 30, and the cross-sectional area of
virtual flow path of the cooling water into the formula (1).
Therefore, this way can be also applied to a case in which the
upper surface guide 30 is not disposed parallel to the pass line
P (the steel sheet 1). Especially, it is important to cool
rapidly the area shown in Fig. 28 in order to obtain fine-grained
ferrite, bynotmerelyenlargingthevolume densityofthe cooling
water, but holding an upper limit of the volume density of the
cooling water within the range of the formula (1). it is possible
to inhibit overflow of the retained water, which works well for
effective cooling.
[0070] An example in which the upper surface guide 30 has a
plain-sheet shape has been described above. However, in view
of improving discharging capability, an upper surface guide that
w
2@
has an uneven shape may be applied. Fig. 8 shows an example in
which an upper surface guide 30' is applied. Fig. 8 corresponds
to Figs. 6 and 7.
[0071] In the example shown in Fig. 8, at a portion of the
upper surface guide 30'. where the coolingnozzle 21cis disposed,
I
I
a distance between the pass line P and the lower surface of the
upper surface guide 30' is h,. On the other hand, between the
adjacent cooling nozzles 21c, 21c. the distance between the pass
line P and the lower surface of the upper surface guide 30' is
defined as hp+hf . Even when the upper surface guide 30' as above
is applied, basically the same idea as the formulas (1) to (7)
can be applied. However, considering that the cross-sectional
I area of virtual flowpath fordischargingwaterhas been increased
1 by applying the upper surface guide 30f, a cross-sectional area I
of virtual flow passage Sf that has been changed and a
corresponding height hPf that has also been changed are applied
instead of S and h, in the formula (1). In the embodiment, S f
can be obtained from the formula (8), and h,' can be obtained
from the formula (9).
LO0721
h,' = h, fi (9)
[0074] Here, S1' in the formula (8) is a cross-sectional area
of virtual flow path in a portion having the height h,, as shown
by hutching in Fig. 8, and same as S in the formula (1) . On the
other hand, S2' in the formula (8) is a cross-sectional area of
virtual flow path in a portion having the height h' as shown by
r
applied, the cross-sectional area S f of virtual flow path that
is obtained by the formula (8) is substituted in the formula (1)
instead of the cross-sectional area of virtual flow path S.
[0075] The formula (9) is a formula to obtain the
I corresponding height h,' at the upper surface guide 30'. Here,
r represents expanding rate of the cross-sectional area of
virtual flow path, and r is obtained by S' /S1' in the embodiment.
I Therefore, it is also possible to apply the formula (1) to the
upper surface guide 30' by using the corresponding height h,'.
[0076] By applying the upper surface guide 30' as mentioned
above, a cross-sectional area for discharging cooling water is
enlarged and discharging capability can be further improved.
[0077] Fig. 9 also shows another example in which an upper
guide has an uneven shape. Fig. 9 shows an example in which an
upper surface guide 30" is applied, and corresponds to Figs. 6
and 7.
[0078] In the example shown in Fig. 9, in the area between
the adjacent cooling nozzles 21c, 21c of the upper surface guide
I 30", the distance between the pass line P and the lower surface I
!
I of the upper surface guide 30" is h,. On the other hand, in the
area where the cooling nozzle 21c is disposed, the distance
between the pass line P and the upper surface guide 30" is defined
as hP+hm. Even when the upper surface guide 30" as mentioned
above is applied, basically the same idea as the formulas (1)
to ( 7 ) can be applied. However, considering that the
cross-sectional area of virtual flow path for discharging water
has been increased by applying the upper surface guide 30", a
cross-section area of virtual flow path S' that has been changed
and the corresponding height h,' that has also been changed are
w
2u
appliedinsteadof S and hpinthe formula (1). In the embodiment,
S f can be obtained from the formula (lo), and h,' can be obtained
from the formula (11).
[0079]
[0081] Here, S1" in the formula (10) is a cross-sectionalarea
of virtual flow path in a portion having the height hp as shown
by hatching in Fig. 9, and same as S in the formula (1). On the
other hand, SzJ1 in the formula (10) is a cross-sectional area
of virtual flow path in a portion having the height h" as shown
by gray in Fig. 9. Therefore, when the upper surface guide 30"
is applied, the cross-sectional area of virtual flow path Sf
obtained by the formula (10) is substituted in the formula (1)
instead of the cross-sectional area of virtual flow path S.
[0082] The formula (11) is a formula to obtain the
corresponding height hpf at the upper surface guide 30". Here,
r represents an expanding rate of the cross-sectional area of
virtual flow path, and r is obtained by Sf /S1" in the embodiment.
Therefore it is possible to apply the formula (1) to the upper
surface guide 30" by using the corresponding height hPf.
[0083] By applying the upper surface guide 30" as above, the
cross-sectional area for discharging cooling water is enlarged,
and it is possible to improve discharging capability.
[0084] As shown in Figs. 7 to 9, when the distance between
the pass line P and the upper surface guide is changed in the
sheet passing direction (pass line direction), the relationship
w
height h,' as mentioned above.
i [0085] Also, when a hot-rolled steel sheet is manufactured
by using the cooling apparatus 20, the hot-rolled steel sheet
can be manufactured so as to satisfy the formula (12). Namely,
when a pitch between the upper surface water supplying devices
21, 21 that are adjacent to each other in the sheet passing
direction is defined as L (m), the water volume density of cooling
water sprayed from the nozzle 21c is defined as q, (m3/m2 sec),
a sheet width of the steel sheet to be passed is defined as W,
(m), the cross-sectional area of virtual flow path of discharging
water sprayed fromone oftheupper surfacewater supplyingdevice
21 shown as a shaded area in Fig. 6 is defined as S, (m2), and
the distance between the upper surface of the steel sheet 1 to
be passed and the lower surface of the upper guide 30 is defined
as ha (m), the steel sheet is cooled so as to satisfy the following
formula (12) .
[0087] Here, S, (m2) can be obtained by changing to calculate
the formulas (2) to (7) based on the distance ha between the upper
surface guide 30 and the steel sheet 1 instead of the distance
h, between the upper surface guide 30 and the pass line P. As
shown in Figs. 7 to 9, also when the distance between the pass
line P and the upper surface guide changes in the sheet passing
direction (pass line direction), S a t corresponding to the
cross-sectional area of the virtual flow path S f that has been
a changed, and the corresponding height haf corresponding to the
corresponding height h,' described above can be used.
[ 0 0 8 8 ] Also, in the formula (12), in view of manufacturing
a hot-rolled steel sheet with a fine-grained structure and good
mechanical properties, the water volume density of cooling water
g, is 0. 16m3/ (m2 sec) (lorn3/ (m2 min) ) or more.
[ 0 0 8 9 ] According to the manufacturing method of a hot-rolled
steel sheet as described above, it is possible to give
manufacturing conditions and/or conditions of spraying cooling
water and the like to satisfy the above formula (12) to the
manufacturing apparatus, corresponding torelationship with
other portions of the manufacturing apparatus and restriction
by surrounding environment.
[ 0 0 9 0 ] According to the cooling apparatus 20, the
manufacturing apparatus 10 comprising the cooling apparatus 20,
and the manufacturing method of a hot-rolled steel sheet that
are described above. when a cooling water volume densityto obtain
required cooling ability, a width of steel sheet, and a pitch
of the cooling nozzle are determined for example. a position of
the upper surface guide can be set so as to satisfy the formula
(1) and formula (12). Also, as in the cooling apparatus 20, in
some cases, the upper surface guide 30 needs to get close to the
pass line Pon the upstream side, in other words, h,inthe formula
(1) and ha in the formula (12) are determined. In such cases.
it is possible to change the cooling water volume density and
the pitch of the nozzle so as to satisfy the formula (1) and the
formula (12). and it is possible to know how much they need to
be changed in advance.
[0091] Also, the upper limit of the position at height of the
upper surface guide 30 is preferably I m in view of sheet passing
ability.
[0092] As described above, by the cooling apparatus of a
hot-rolled steel sheet, and the manufacturing apparatus and
manufacturing method of a hot-rolled steel sheet of the
embodiment, in manufacturing a hot-rolled steel sheet, it is
possible to discharge water smoothly even when the hot-rolled
steel sheet needs to be cooled by water with a high cooling water
volume density, and high cooling capability can be utilized
efficiently.
[0093] Further, as a variation of the cooling apparatus of
a steel sheet, and the manufacturing apparatus and manufacturing
method of a hot-rolled steel sheet of the above described
embodiment, the following configuration can be raised. Namely,
a position at height of at least either one of the upper surface
guide or the cooling nozzle of the cooling apparatus can be
configured to be movable. With this configuration, it is
possible to change h, and ha in the above formulas (1) and (12),
and securing further efficient water discharging capability, it
is possible to utilize high cooling capability. It should be
noted that, however, in this case, the lower surface of the upper
surface guide is not positioned higher than a lower end of the
cooling nozzle of the upper surface water supplying device.
Otherwise, the lower end of the cooling nozzle interrupts sheet
passing.
[0094] Meanstomovethe upper surface guide in top andbottom
direction is not particularly limited; for example, the upper
surface guide can be moved in top and bottom direction, by
providing a cylinder to a place where a arm and a rail, which
e are to displace the upper surface guide when work rolls are
exchanged, and the upper surface guide are connected, or moving
the arm and the rail themselves up and down or the like.
Examples
[0095] The present invention will be described below more in
detail on a basis of examples, to which the present invention
is not limited. In the examples, each element of the formula
( 1 2 ) described above was changed, and the relationship with the
water discharging performance was examined. The conditions and
results were shown in tables 1 to 5. Tables 1 to 3 show examples
in which each upper surface guide has a flat-sheet shape, and
each distance between the pass line P and the upper surface guide
is fixed in the sheet passing direction (pass line direction).
Table 1 shows a case in which the width of the steel sheet is
1.0 m, Table 2 shows a case in which the width of the steel sheet
is 1.6 m, and Table 3 shows a case in which the width of the steel
sheet is 2.0 m. Tables 4 and 5 show examples in which each upper
surface guide has an uneven shape as shown in Fig. 8 and each
distance between the pass line P and the upper surface guide
changes in the sheet passing direction (pass line direction).
Table 4 shows a case in which h' in Fig. 8 is 0.1 m, and Table
5 shows a case in which h' in Fig. 8 is 0.2 m. The width of each
steel sheet was 2.0 m.
[0096] In each table, water discharging performance was
evaluated as follows. Namely, " x u was given if the top portion
of the cooling nozzle sank in discharging water that flowed back
from the hole where the jet of cooling water passes, and "0" was
given if the cooling nozzle did not sink in the dischargingwater.
This judgment is basedon the following reason: if the top portion
e of the cooling nozzle sinks in water, jet form of the cooling
water changes from in-air liquid jet (jet that passes in air)
to in-liquid liquid jet (jet that passes in water) and the jet
decays significantly, whereby the impact force of the jet to the
hot-rolled steel sheet greatly decreases.
[0097]
Pitch of Header
Performance
~ i ~ ~ h ~ ~ ~ i Performance
Evaluation
x
0
0
value of ~ ~ f t
Part of
Formula (1 2)
1.23
0.67
0.43
2-1
2-2
2-3
Total Flowing
Amount
Q [m3/sec]
0.04
0.04
0.04
Cross-sectional area of
Virtual Flow Path
S, [m21
8.80E-03
1.32E-02
1.76E-02
Cooling Water
Volume Density
e [m3/(m2-sec)]
0.16
0.16
0.16
Height of Upper
Surface Guide
ha [mI
0.10
0.1 5
0.20
Width of Steel
Sheet
Wa [mI
1.60
1.60
1.60
Pitch of
Header
I- CmI
0.1 6
0.1 6
0.1 6

[OlOO] In the examples in Tables 4 and 5, each upper surface
guide has an uneven shape as described above. Therefore, the
cross-sectional area of virtual flow path Saf (Sf) that has been
changed from S, and the corresponding height haf h 1 that has
also been changed from ha (h,) were obtained from the formulas
(8) and (9). The left part of the formula (12) was calculated
based on the obtained Saf (Sf) and haf (hpf).
[OlOl]
a [Table 4 1
0 aX z0 r -w9
S 9
M
;
0
N N V J
- I0
N N O
L
0 ' - - = $
22 I
- 0)
0)
ro,wm-rs-rwmwzo,wmwzzwmw
0 0 0 ~ 0 ~ 0 0 0 0 0 0 ~ 0 0 0 ' 0 0 0 ~ 0 0 ~ 0 ~ 0
& ~ ~ ( O ~ ~ ~ ~ w w w w w w w w w w w w w
~ 0 d 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 - - - - - - - - - - - - -
N N O N N O
5- 1
Cooling Water
Volume Density
q ,[m3/(m2.sec)]
0.16
Height Described in Fig. 8
Width of Steel
Sheet
Wa [ml
2.00
h,(h,) [m]
0.10
hq[mI
0.20
Pitch of
Header
L [ml
0.16
TOW Fbhg
haunt
Q [m3/sec]
0.05
Cross-sectional area of Virtual
flow Path S'a(S' )
Corresponding
Height
ha' [ml
0.1 7
SI' [m2]
8.80E-03
S2' [m2]
1.52E-02
value of Lefi
Part of
Formula (1 2)
0.44
Performance
Evaluation
O
a
[0103] As can be seen from Tables 1 to 5, when the value of
the left part of the formula (12) is over 1, problems occur to
water discharging performance. Also, it can be seen that water
discharging performance can be calculated in advance by using
the corresponding height ha' h ) when the upper surface guide
in which the distance between the pass line and the upper surface
guide changes in the sheet passing direction (pass line
direction) is used. By comparing the results in Tables 4 and
5 with the results in Table 3, it can be also seen that the water
discharging performance improves as the cross-sectional area of
virtual flow path is enlarged.
Description of the Reference Numerals
[0104]
1 steel sheet
10 manufacturing apparatus
11 row of rolling mills
llg final stand
llgh housing
llgr standing portion (of housing) (side wall)
12 transporting roll
13 pinch roll
20 cooling apparatus
21 upper surface water supplying device
21a cooling header
21b conduit
21c cooling nozzle
22 lower surface water supplying device
22a cooling header
a 22b c o n d u i t
-
2 2 c c o o l i n g n o z z l e
30 upper s u r f a c e g u i d e
3 5 lower s u r f a c e g u i d e
P p a s s l i n e

We claim: a
1. A cooling apparatus disposed on a downstream side from a
row of hot finish rolling mills, capable of supplying cooling
water from above a pass line toward the pass line, the cooling
apparatus comprising:
a plurality of cooling nozzles arranged parallel to a
direction of the pass line; and
an upper surface guide disposed between the pass line and
the cooling nozzles,
wherein each cooling nozzle of the plurality of cooling
nozzles can spray cooling water with a cooling water volume
density of 0.16 (m3/ (m2 sec) ) or more, and when the cooling water
volume density of water to be sprayed is defined as q, (m3/ (m2
sec)), a pitch of the cooling nozzle in a pass line direction
is defined as L (m), a distance between a lower surface of the
upper surface guide and the pass line is defined as hp (m), a
uniform cooling width is defined as W, (m), and a cross-sectional
area of virtual flow path of discharging water flowing in a width
direction of steel sheet per pitch of the cooling nozzle in the
pass line direction is defined as S (m2), following relation is
satisfied.
2. The cooling apparatus according to claim 1, wherein the
upper surface guide has a configuration in which a distance
between the pass line and the upper surface guide changes in the
pass line direction; and a corresponding height h,' of the upper
surface guide is applied instead of the distance hp.
3.
The cooling apparatus according to claim 1 or 2, wherein
at least either one of the upper surface guide or the cooling
nozzle can move in top and bottom direction.
4. A manufacturing apparatus of a hot-rolled steel sheet
comprising: a row of hot finish rolling mills; and the cooling
apparatus according to any one of claims 1 to 3 disposed on a
downstream side fromthe row of hot finish rolling mills, wherein
an end portion on upstream side of the cooling apparatus is
disposed inside a final stand in the row of hot finish rolling
mills.
5. A manufacturing method of a hot-rolled steel sheet
comprising a step to supply cooling water to at least an upper
surface of a steel sheet after final rolling to thereby cool the
steel sheet using a cooling apparatus disposed on a downstream
side from a row of hot finish rolling mills,
wherein following relationship is satisfied when a volume
density of cooling water from a cooling nozzle provided to the
cooling apparatus is defined as q, (m3/(m2 sec)) that is
0.16(m3/(m2* sec)) or more, a pitch of the cooling nozzle in a
sheet passing direction is defined as L (m), a distance between
a lower surface of an upper surface guide provided to the cooling
apparatus and an upper surface of the steel sheet to be passed
is defined as ha (m), a width of the steel sheet to be passed is
defined as W, (m), and a cross-sectional area of virtual flow path
of discharging water flowing in a width direction of steel sheet
per pitch of the cooling nozzle in the sheet passing direction
is defined as S, (m2).
C.r. ) I ~ ~ ~ A L
"
6. The manufacturing method of a hot-rolled steel sheet
according to claim 5, wherein a corresponding height ha' of the
upper surface guide is applied instead of the distance ha when
the upper surface guide has a configuration in which a distance
between the steel sheet and the upper surface guide changes in
the sheet passing direction.
7. The manufacturing method of a hot-rolled steel sheet
according to claim 5 or 6, wherein at least either one of the
upper surface guide or the cooling nozzle can move in top and
bottom direction.
8 . The manufacturing method of a hot-rolled steel sheet
according to any one of claims 5 to 7, wherein an end portion
on upstream side of the cooling apparatus is disposed inside a
final stand in the row of hot finish rolling mills.
Dated this 6th day of January, 2014.
Sumitomo Metal Corporation; and
Metals Machinery, Inc.
Attorneys for the Applicants