Note: Descriptions are shown in the official language in which they were submitted.
-- 1 --
POROUS NOZZ~ FOR ~
This invention relates to an improvement in a porous
nozzle which is arranged at the bottom of a molten metal
vessel, and the objects of which are to float up and separate
the non-metallic inclusions in molten metal in said ves~el
and to preven-t a slag involvement and a nozzle opening
closl~e. More particularly it relate~ to an improvement
of a porous nozzle mounted. at the bo-ttom of a ladle or
tunidish container of the molten metal vessel.
Generally the nozzle of a ladle or tundish container
is constructed with a dense refractory. However, non-
metal.lic inclusions in the molten steel often adhere in
the nozzle opening during the flowing-down of the melt to
cause a contraction and a closure thereby often bring about
troubles in the pouring operation of the meltO To prevent
these disadvantageous phenomena, therefore, it is generally
carried out to employ a refractory porous nozzle in which
inert gases are jetted into the inner peripheral surface
of the nozzle through the pores thereby to form a gas film
and remove the things adhered to the nozzle openingO
~urther, for another porpose, in order that the non-
metallic inclusions in the molten steel within the vessel
are removed to make a purified and good quality molten steel
there is also carried out a method in which separatel~ from
a porous nozz:Le, a refractory porous plug is arranged at the
~ ~ .
6~
-- 2 --
bottom of a container such as ladle or tundish, and inert
gases are jetted into the molten steel through the pores
of` the porous plug when the non-metallic inclusions are
floated up and separated and the purity of said molten
steel is improved. ~here is another method which does not
use a porous plug. ~o take a tundish for example, a re-
fractory weir is provided within said vessel to change the
flow of the molten steel, and the non-metallic inclusions
in the molten steel are floated up and separated. Accord-
ing to the method in which a weir is provided in a tundish
container, it exhibits e-ffects in its own way for floating
up and separating the non-metallic inclusions. In view
that the dimension of t~mdish is limited because of
structure and design of a continuous casting equipment,
however, it is difficult to make an effective weir shape
or arran~e an effective weir within a comparatively narrow
tundish, and it is known that not only the tundish design
becomes complicate but also it is difficult to fix a weir
within the tundish~
Further, the porous nozzle arran!~ed in conventional
tundishes has e~fects for preventing contraction and
closure of nozzle, but generally in a continuous casting
working said nozzle may involve the non-metallic inclusions,
slag, etc. which float up by a -turbulence generated at the
upper portion o~ the nozzle opening when the ladle is-
replaced, thereby causing a lowered quality of steelO
-
~41~61)
-- 3 --
Furthermore, a~cording to the method in which a porous plug
i.s provide~ at the bottom of a tundish cont~iner and inert
g~se5 c~re jetted into the molten steel1 i1; is ef~ective Por
floating up and separating the inclusions 9 but the plug
must be arranged at a position different from that of the
nozzle so that a complete effect cannot be exhibited for
preventing the slag invol~ement, due to the tubulence
generated at the upper portion of the nozz]e opening when
replacing the ladle as referred to above.
In view of sai.d various demerits of conventional
methods, the present ]nvention provides an integral, f].ange-
shaped, porous nozzle ~1hich has in combi.nation a function
of jetting inert gases up.wardly into the molten steel by
a porous plug and a function of jetting the inert gases
from the inner peripheral surface of a porous nozz]e to
prevent the nozzle from closing, and in which the in-
clusions in the molten steel are floated up and separated
whereb~ the nozzle is prevented from closure, and it can
avoid a slag involvement caused by the turbulence generated
at the upper portion of the nozzle opening when the ladle
is replaced, while alIowing a continuous casting of a
molten steel of bigh quality. That is, it is the charac-
teristic feature of the invention that the porous nozzle
of the invention has in combination both the functions
of jetting inert gases from the porous refraotory layer
of the flange portion into the upper portion in the
' ' - ' .
.' ' ~ '
'
-- 4 --
molten steel, and of' ~jet-ting -the inert gases into the
nozzle o~ening.
The invention ~i~l now be described ~ore in detail
with reference to the accompanying dra~ings which show some
embodiments of the invention, in which
Fig. 1 shows an embodiment of a porous nozzle of
the invention and a vertical section of a porous nozzle in
one body in which the bottom of the flange portion is
communicated with à gas pool of the cylindrical outer
circumference;
Fig. 2 shows another embodiment of the invention
and a vertical section of a porous nozzle in which the
flange portion and the cylindrical portion are made in
one body through a sealing member;
Fig. 3 shows still another embodiment of the
invention and a vertical section of a porous nozzle in
which the flange portion and the cylindrical portion are
made in one body throllgh a fine porous refractory layer;
and
Fig. 4 is a vertical sectional view showing a
state in which the porous nozæle of Fig. 2 is set at the
bottom of a molten metal vessel.
In Fig. 1 the porous nozzle arranged at the pouring-
out portion a-t the bottom of a molten steel vessel is
mounted in the nozzle socket at the central portion of
a nozzle-receiving brick, the outer peripheral surface of
16t~
-- 5
which brick being .in contac-t W:i th -the :Li.n:i.n~ refrcactory
brick o:~ said vessel bottom. 'I'he ob,jec-t o-L'-the ~n-vention
is to provide an exce~lent pvrc)us nozY,:Ie in T~hich -the
vessel. ls surrouned with an lron she:L] (3~ ln such a
manner that a circular gas pool (2) ls provided at least
at a part or -the whole of t;he ou-ter periphera] sur~'ace of
a porous refractory layer constitu-ting the main body of
a porous no~æle (1) and at least at a pa:rt or the whole o-f
the flange portion at the lo~er end Or a f1.ange porous
~ayer (la), the gas pool (2) is communicated with a vent
cleara.nce (2a) in the outer periphera] surface of the
noz~,le cylindrical portion9 inert gases are jetted through
a piping ~rom the outside into a nozzl.e opening (lla)
~rom the upper surface of said porous refrac-tory layer (la)
constitutin~ the ~lange portion of the porous nozzle and
from the inner periphery surface of a porous refractory
layer (lb) constituti.ng the nozzle cylindrical portion,
and by doing so it is possible easily to float up and
separate the non-metallic inclusions in the molten steel
while preventing th.e nozzle openin~ from cl.osure and slag
involvement,
Fig. 2 shows an embodiment of a pOI'OUS nozzle where
the porous refractory layer of Fig. 1 is ma.de double.
~hat is, this porous nozæle is the one in w}hich the porous
refractory layer (la) is isolated by a sealin~ member'(5)
from the porous refractory layer (lb) constituting the
.
-- 6 -
cylindrical portion whereby -the f-llnctio:n o.t jet-ti.n~ the
inert gases upwardly in -the mol-ten s-teeL is separa-ted from
the funct.ion of jetting them i.nto an nozæle openlng (].la).
The present porous noz%]e has in one u.nlt a mechanism of
jetting ~ases to the upper su.r-face of the ~lange, per-
meating the pores of t;he f].ange porous refractory layer
through a gas bl.owing opening (4) rnounted at the end of
a gas pool (2) prov].aed i.n the c.ircumference at -th.e lower
end o. the f1ange of said porous nozz].e, and a mechanism
of jetting t;he gases in-to the nozzle opening (lla),
permea.ting the pores of the porous refractory layer (lb)
o.E the nozzle cylindrical portion through a gas pool (2a)
surrounded by an iron shell (3). A sealin~ member (5) of
separeting said two mechanism may be made of silica, alumina
or any other optional sintered refractory -to prevent gas
leakage completely, and the importan-t thing is that a gas
leakage to the outside is prevented and that a gas per-
meation is prevented between the refractory porous layer
of the flange portion and the porous refractory layer of
the nozzle cylindrical portion through said sealing
member (5).
The reason of separating the gas ejection mechanism
in the flange upper sur~ace from that in the noPzle opening
(lla) is that specifically in a porous nozæle for tundish
container, owing to the physical pressure difference between
the molten steel sta-tic pressure within the tundish, which
.
L60
7 -
is received by the upper sur.~ace o'' the ~]"ange, and the
molten steel kine-tic pressure (pressure is reduced ~ased
on the ~ernoulli's theorem) ~rh:i.ch is recei.ved by the inner
peripheral surf~ce O r the :nozz:l.e dur:i.ng the time when the
molten steel flows down within said nozzle opening, it is
necessary to separa.tely adjlls-t -the gas bl.owing pressure in
the fl.ange portion and that in1;o the noz%le opening (lla).
Concerning the pressure of the ga,s blown into the nozzle
opening (lla), it is possible to prevent the nozzle from
contrac-tion and closure by forming a gas curtai.n in the
inner peripheral surface o~ the nozzl,e opening, and with
a gas pressure unnecessarily raised the inert gases are
involved into the molten steel when the melt ~lows down
into the nozzle opening, and -there-fore there is an un-
favorable possibility that pin holes occur in the solidi,fy-
ing process of the molten steel. Further, the present
invention has a great number of merits in such that in
the case o~ a closing mechanism of a sl.iding nozzle (lo~er
nozzle) constituting the lo~er portion of said porous nozzle,
it wi~l suf~ice only -to eject gas from the upper surface
of the flange thanks to a plurality of blow openin~s as
arranged, and if necessary it is capable of adjusting the
gas ejection and gas pressure ~reely so as to save the use
amount of inert gases.
According to the porous nozzle of Fig. ~, the porous
refractory layer of the main body of said porous nozzle is
:
.
0
constructed in such a way tha-t bet-~een the porous refractory
layer o-~ the fl~.nge portlon a:nd that of the cylindrical.
p~rtion there i.s formecl a fine porous :reEractory layer (6)
which is fine porosity an~ has a great gas resistancy
compared with th.e porous refractory layer of the rnain porous
body, inert ga.ses are guided L:rom the ga~ blow opening (4)
and the gases are ~etted, -through the gas pool (2), -from
the upper surface of the flange, permeating the pores of
the porous refractory layer (la) o-f the,flange portion,
while a part of -the inert gases permeates through the
porous refractory layer (lb) of the vertical side through
the fine porous refractory layer (6) thereby to be jetted
into the nozzle opening. When a part of the inert gases
permeates through said :fine porous refractory layer (6)
. 15 the gas pressure is considerably reduced so that the amount
; of the gas entering into the nozzle opening (lla) is de-
;: creased and there-fore9 the molten steel will never be
involved with inert gas.
: In the drawings the fine porous refractory layer is
: 20 not flat in its sectional configuration.but i-t may be o-f
optional shape, and naturally the thickness o-f said layer
is optionally selected and said layer is formed in shape
and thickness answering the conditlons, considering the
permeation and resistance of the gas.
~: 25 Fig. 4 is a schematical sectional view of the porous
nozzle of Flg, 2, in which the porous nozzle wherein the
a~
.
, ' ' ' . ~ :
' ~ ":
.,:
o
_ 9 _
e~ection mech~nism ~rom the f]ange surface is separated
from that into the nozzle opening, ix arranged at the
bottom O:e a mo~ten me-tal vessel. Further, Fig. 4 is also
a sectional view o~ the porous nozzle (1) as arranged,
in T~rhlch a through hole is provided at the bottom of a
vessel where a iron casing (7) is lined wi-th re-fractory
bricks (8), said porous nozzle being mounted in the central
zone of the inner peripheral sur~ace of a nozzle-receiving
brick (9) flxed in said through hole. Fig, 4 is exampli~ied
with a porous nozzle being connected at its lower end to a
sliding nozzle (10), but said nozzle can naturally be
applicable to melt discharging nozzles which adopt a stopper
system as a nozzle opening and closing mechanism.
lhe invention will now be described by way o~ example.
By mounting the porous nozzle (shown in Fig. 2) of
the invention to a tundish container there was carried out
a 4-continuous casting operation for steel plates for motor-
cars, but as e~pected initially there was neither contraction
nor closure of the nozzle at all, and not observed any slag
involvement when the ladle was replaced. Moreover, even
the index of the non-metallic inclusions could be reduced
by 30~40~o compared with conventional porous nozzles to
obtain a very satisfactory result. ~he conditions of
carrying out the operation are as follows:
' ' ,
.~,a3L~ 60
Kind of ~teel: S-teel plate for motorcar
Ca~aclty of tundjsh: 45 t
Number of continuous 4-continuous casting (cc)
Capacity of ladle: 280 t
Casting tonnage: 280 x 4 = 1,120 t
Blow amount of lnert
gas (Ar):
A) Gas pool blow opening (4) of the -flange
portion
Gas pressure: 0.9 kg/cm2
Gas flow: 8 N~/min
B) Blow opening (4a) of the cylindrical portion
Gas pressure: 0 7 kg/cm2
as flow: 6 N~/min
The more the porous nozzle of the invention widens
its width in an operable range in the length in the width
direction of the flange, the more it produces its effect.
However, putting the shape and capacity of the melt vessel
and the problems of said vessel when operating into con-
sideratlon the optimum width and thickness of the flange
should be selected. In the draw~ngs the upper surface of
the ilange is shown in a flat con-figuration, but the shape
is not limited to said configuration and there is no
trouble in use even if the surface is curved or uneven
a little. The important thing is that the porous nozzle
has a function for ejecting an inert gas toward the upper
portion of the molten metal. The porous nozzle of the
.
invention has been described in detail particularly with
respect to a tundish nozzle for molten steel, but the
present inven-tion is very useful industrially in that
it is applicable to vessels for other molten metals such
as copper.
::
,
