Note: Descriptions are shown in the official language in which they were submitted.
WO 90/t3379 fCT/US9010233t
1 2063994
Field of the Invention
The present invention relates to c~onents for foundry and steel
mill applications, and more particularly to fed nozzles typically
fatu~d in ladles and tundishes used for teeming molten metals.
HacJarramd of the Invents ~
Idles and tundishes used for t~mir~g molten steel require an
outlet or outlets at the bottojn thereof to dir~act the flora of the molten
metal into a subsequent stage, e.g. a tiuxlish, inner mold, or continuous
casting molds. These outlets are typically formed by special nozzles made
of refractory material having good corrosion resistance. Oontrol of the
casting rates of the molten metal is generally carried out by means for
either a stopper rad assembly or a slide gate system, both of which
include similar refractory materials. Cbnventional nozzles are typically
alumina-silica, dzr~e-alumi.na, alumina
-graphite or ziroonia-graphite
refractories. A problem with such materials is that they have an affinity
for impurities in steel, especially in ahaninvm killed steels. In this
respect. deposits are apt to cynically and/or. n~ly attach to the
inner bore surface of the nozzles and form deposits thereon. These
deposits build-up to a point where they restrict flow, and sometimes block
the orifice to such a degree that flora stops.
In an attempt to solve the blocJtage problems created by deposit
build-ups, it has been known to use porous, gas permeable nozzles to
introduce an inert gas into the bore. Permeable nozzles knoGm heretofore
generally include a refractory and a metal jacket or housing spaced
WO 90/13379 PGT/US90/02331
2 20fi3994
therefrom, wherein an air space or manifold is defined therebetween. Gas
is introduced into the space or manifold thi~ough a fitting in the metal
jacket. Pressure builds up between the refractory and the jacket, until
it reaches a pressure sufficient to weroc$ne the resistance inherent in
the permeable refractory, at which point the inert gas flows thxu~h the
refractory into the nozzle bore. Ideally, the introduction of the inert
gas creates a gas film along the inner surface of the bore to retard
deposit build-up. (An additional advantage of using inert gas is that it
creates a positive pressure which prevents introduction of air into the
molten metal. Zhis prevents oxidation of the metal.) However, these
devices are not capable of directing greater gas flow to specific
locations in the bare where the build-up of deposits is most prevelant.
Moreover, while maintaining an inert gas film on the bore of the nozzle
increases nozzle life by ~g the build-up of deposits thereon, it
does not oc~letely eliminate the d~nicaa. and/or mechanical attraction
between conventional nozzle refractory material and the impurities in the
molten steel. In this respect, most vonventional nozzles are alumi.na-
silica based and hare a strong affinity for imp<irities found in steel.
Other materials, such as nsagnesium oxide (Mg0), which is known to have no
affinity for alumi,na, has frond little aoo~tance or use in
manufacture of nozzles. With respect to magnesium oxide (Mgp), i~
disfavor may be due to a perceived tendency to cracking.
In any event, the chemical attraction between impurities in molten
steel and material found in conventional nozzles, together with the
physical shape of the nozzle orifice (which may include areas or shapes
WO 90/13379 PCf/US90/02331
2os3~s~
which facilitate deposit build-up) tend to limit nozzle life.
The present invention overccanes these and other problems and
pravidns a nozzle for teeming molten steel having a substantially reduced
affinity for alunnirsa and other impurities within the molten metal, which
nozzle is porous and has a high degree of gas permeability and which
provides greater gas flow to specific areas within the nozzle.
Summ~rv of the Invention
In accordance with a preferred embodiment of the present invention
there is provided an inm~ersion nozzle for continuous metal casting which
includes an elongated nozzle body formed from a porws, gas pe~e~le
refractory material,. ~e nozzle body has a conduit
longitudinally therethrcugh and an inner surface which defines the
conduit. The nozzle body also includes an alter surface defining a
predetermined body ,pirofile, ail dyarn~el means fozrned al
ong the nozzle
body. A metallic housing encases the nozzle
body. The housing has an
inner surface dimensioned to substantially canfortn to the profile of the
nozzle body. Means for securing the housing to the nozzle body are
provided, which means for securing farms a rigid, relatively air-tight
layer between the housing and the nozzle body. wherein the charmel means
form internal passages within the nozzle. Port means are provided on the
housing in registxy with the charnel means in the nozzle body. The port
means are connectable to a source of inert gas, which is operable to force
the gas into the passages and into said porous refractory material.
More specifically, the elongated nozzle body is preferably fornied
of a mixture of magnesiwn oxide (Mg0) particles of several different grain
WO 90/13379 ~ PCT/US90/02331
2063994
sizes, wherein the nozzle body has a ~~fine open poroslt~,~~. Fine open
porosity meanirig that the passages or interstices between the magnesium
oxide (Mg0) particles are relatively small such that inert gas p~~g
thtrough the nozzle body provides a uni.fozm layer of microscopic gas bubbles
~ot~g' 'the inner surface of the nozzle bore. Zhe fine porosity also
requires a greater back pressure to force the inert gas through the small
passages and interstices between the magnesium oxide (Mg0) Particles. It
is believed that this relatively-high back pressu~ also assists in
maintaining a uniform, relatively thick layer of inert gas along the ~
surface of the nozzle bore thereby deterring contact between the ~lten
metal and the conduit surface. Zhis uniform layer of inert gas. together.
with the use of magnesium oxide (Mg0) which has no affinity for alumina
bu3,ld-up arr3 is generally mere inert to other itg~urities and allaying
agents foutxl in molten steel., p~du~ an innrersion nozzle which is less
susceptible to deposit build-up along the inner surface thereof.
'~~Y. ~e present invention provides means for directing
the flow of the inert gas into the nozzle bore or ~nduit to a~
which impurity build-up wow.d be most severe. In tt~ .
s ocmprised of annular charn~el,s or gxnotres are formed in the
surface of the nozzle body. Each d~arn~el is preferably located adjacent a
site within the nozzle bore where impurity build-up is most seve~~
~er~Y Providing a Pressurized source of inert gas immediately adjacent a
bore site susceptible to deposit build-ups. It has been fotmd that with
such an arrangement, increase flora of the inert gas o~ ~e
nozzle wall adjacent the channel. Zhus, with the preset ~~i~~
WO 90/13379 PCTIUS90/02331
increased flora of the inert gas may ~ a;,.e~~ ~tO9 9 4
-~- specific locations
within the nozzle bore by selective positioning of the channels along the
outer surface of the nozzle body.
Also important to the above-mentioned aspects of the present
5 invention is that unlike pernieable nozzles )mown heretofore which
typically included a space (i.e. manifold) between the refractory nozzle
body and the metal housing or jacket, the metal housing of the present
invention is secured directly to the nozzle body, this direct attachment
provides several advantages. First, the housing acts as a barrier or seal
to prevent the inert gas from escaping outside the surface of the nozzle
body. thereby confining and directing the gas flora through the wall of the
refractory nozzle toward the conduit therein. end, the housing serves
as a reinforcing sleeve to hold the refractory nozzle body together,
pz~vet~ing the opening of any thermal-shock cracks which wr~d allow steel
to penetrate into the nozzle. The present invention therefore allows the
use of materials such magnesium oxide (Mg0) which have a tendency, or
perceived tendency, for cracking. Third, the direct housing-to-refractory
nozzle arrange~t, facilitates the increased back-pressure
created by the fine open nozzle porosity preferred in the present
invention. Conventionally known permeable nozzles having manifold
(spacing) designs would be subjected to intrinsically higher hoop stresses
which can cause the manifold jacket to n.,
It is an aspect of the present invention to provide a nozzle for
ladles or tundishes used for teeming molten steel which has improved
operational life over nozzles known heretofore.
WO 90/13379 ~ PGT/US90/02331
20fi3994
Another aspect of the present invention to provide a nozzle as
described above which is less susceptible to deposit build-up on the inner
surfare thereof .
Another aspect of the present invention is to provide a nozzle as
described above wherein the nozzle has a substantially reduced affinity
for altm~ina, impurities or alloying agents in molten steel.
A still further aspect of the present invention is to provide a
nozzle as defined above wherein the nozzle is gas pern~eable and has a
uniform and high degree of porosity.
A still further aspect of the pxesent invention is to provide a
nozzle as described above wherein inert gas flow ther~et
~Y
directed to areas of the nozzle bore which are nbre susceptible to the
formation of deposits thereon,
A still Purthe~ aspect of the present invention is to provide a
nozzle as described above wherein the nozzle is made primarily of
magnesium oxide (Mgo).
A still further aspect of the present invention is to provide a
nozzle as described above which is less susceptible to crar.~ir~g.
A still further aspect of the present invention is the provision
of a method of forming a gas permeable component of magnesium oxide (Mgo)
for use in fourdZy and steel mill applications for teeming molten steel.
These and other aspects and advantages will beocane apparent from
the following description of a preferred embodiment of the invention taken
together with the a~anying drawings.
Brief Descrit~tion of the Drawirxts
WO 90/13379 PCTlUS90/02331
2053994
Zhe invention may take physical form in oextain parts and
arrangement of parts, an embodiment of whicfi is described in detail in the
specification and illustrated in the aceampariying drawings wherein:
FIG. 1 is a partially-sectioned, perspective view of a permeable
ttuxiish nozzle illustrating an embodi~ner~t of the present ~~,ion:
FIG. 2 is a sectional view taken along line 2-2 of FIG. It and
FIG. 3 is a sectional view taken along line 3-3 of FIG. 2.
e»tailed Descriution of a P~~farr~
ed ~ ~ ~~'11t
Referring now to the drawings wherein the shaaings are for the
purpose of . illustrating a preferred embodiment of the invention, and not
for the purpose of limiting same, FIG. 1 shows a ~zzle l0 for use in a
far teeming molten metal. Nozzle 10 is generally c~rised of a
core 12 of porous refractory material su:z~ounded by a housing 14. In the
embodiment shc~m, core 12 is generally cylindrical in shape and has an
outer surface 16 and an elongated bore or
opt is e~cter~;s,g
longitudinally ther~ethr~gh along the axis thereof. Fore or opening is
defines an inner surface 20. As best seen in FIGS. 2 and 3, opening 18 is
generally cylindrical in shape and includes a conical or flared portion 22
at the upper end of core 12. Conical portion 22 is provided to facilitate
passage of the molten metal thrwgh opening 18.
Zhe outer surface 16 of core 12 is provided with a plurality of
axially-spaced, annular d~annels or grooves 24, 26 and 28 which extend
about the periphery of core 12. A slightly larger vertical d~arn~el 30
connects channels 24, 26 and 28 to each other. Zhe position of channels
24, 26 and 28 may vary depending upon the size, configuration and function
WO 90/13379
PCT/US90/02331
203994
of the nozzle itself, as will be better understood from the description of
the operation of the irnrention set forth below.
~~ing to the present invention, core 12 is comprised of
magnesium oxide (Mg0) particles. However, it will be appreciated from a
further reading of the specification that the present invention finds
advantageous application with other porous ceramic ~~.i~s~ ~ is not
limited to magnesium oxide (Mg0). A c~~nical analysis of a nozzle
a~~ir~g to the present invention manufactured fr~n sea-water produced
magnesium oxide (Mgo) would be:
97.9%
0.8%
Si02 1.2%
~2~3 0. 9%
0.5%
Fe203
- the latter materials being impurities ~~,y found in naturally
ooct~rring magnesium oxide (Mg0)~ The magnesium oxide (Mg0) particles
farming core 12 may be from naturally occurring material, or may be either
fused or brine pzbdu~oed.
The sizing of the particles or drains used to foam core 12 is
fairly critical, it being desirable to provide a nozzle porous enough to
allow for excellent gas flora therethrvugh. yet dense enough to provide
excellent wear resistance. In other wants, it is desirable to prod~,ice a
nozzle having a fine, open porosity, Tb this end, nozzle care 12 is
prised of a combination of magnesium oxide (Mg0) particles of several
different sizes. An example of a nozzle core having sufficiently fine-
WO 90/13379
20fi3994
PCT/US90/02331
sized pores and good wear resistance, yet being porous erg to pride
good gas flow is as follows:
Particle Size Oc~osition
%
Coarsest Fraction- 0.125
"
+
U.S.
40
Mesh
10%
Coarser Fraction - U.S.40 Mesh + U.S. 50 Mesh20%
Coarse Fraction - U.S.50 Mesh + U.S. 65 Mesh30%
Fine Fraction - U.S.65 Mesh + U.S. 100 20%
Mesh
Piper Fraction - U.S.100 Mesh + U.S. 150 5%
Mesh
Finest Fraction- U.S.150 Mesh 15%
T otal: 100%
It will of cause be understood that the present inventi~ is not
limited to the particle sizes or pes~r~tEages discl~ Vie, ~ ~t
acceptable nozzles may be produced with vazy~ pg~ of the above
particle sizes. Zhough not specifically tested, it is believed that the
following ranges of particle sizes wrml,d be acceptable to produce a
satisfactory magnesium oxide (Mg0) core according to the p
inventions
particle Size Sition % Rome
Coarsest Fraction - 0.125" + U.S. 40 Mesh 0-15%
Coarser Fraction - U.S. 40 Mesh + U.S. 50 0-25%
Mesh
Coarse Fraction - U.S. 50 Mesh + U.S. 65 0-40%
Mesh
Fine Fraction - U.S. 65 Mesh + U.S. 100 0-25%
Mesh
WO 90/13379 PGT/US90/02331
l0 2063994
Finer Fraction - U.S. 100 Mesh + U.S. 150 Mesh 0-10%
Finest Fraction - U.S. 150 Mesh 2-20%
The magnesium oxide (Mgo) particles are thoroughly .blended, then
mixed with sufficient organic birder and/or water to retain. a fixed shape
after forming. The forming operation may be air-rannning, vibration-
casting, mechanical or isostatic pressing or other means well knoGm to
those skilled in the art of refractory fabrication. The formed article is
then dried or cured aryl subsequently fired to a temperature sufficiently
high to sinter the magnesium oxide particles together to produce a strong
shape. The drying and firing is also aoocm~lished by conventionally kncx~m
mPthads. After firing, oor~e 12 may be machined or shaped to a desired
dimension or shape. Charnels 24, 26, 28 and 30 may be melded into core 12
during the Forming process, but avocrding to the prefetz~ed embodiment of
the present invention, are machir~ed into core 12 after firing.
In the embodiment shown, core 12 is 14&1/2 irxfies in length and
has an outer diameter which varies frcen 7&3/16 i.rxW es in diaar~eter at one
end to 7& 7/16 inches in diameter at the other end. Bore or openir~g 18 is
approximately 3 inches in diameter. It will of oourse be appreciated that
the size or shape of core 12 are not critical to the present invention
which can find advantageous application in numerous and varied sizes aril
shapes~ It being understood that the overall shape of nozzle 10 and/or
core 12 is det~~mi.ned by the particular casting machine or system with
which it is to be used. As indicated by the dimensions set forth above,
WO 90/13379 PCT/US90/02331
11 2063994
oore 12 is slightly conical in shape, i.e. flaring outwardly slightly from
top to bottom. this shape is provided to facilitate assembly or nozzle 10
as will be described below, but is not critical to the present invention.
Housing 14 is generally cylindrical in shape and has an inner
surface 32 dimensioned to closely match and conform to the outer profile
of care 12. A threaded fitting 34 is provided on housing 14. An aperture
36 extends through fitting 34 and housing 14. Housing 14 and core 12 are
preferably dimensioned such that a uniformed space or gap 38 of
appro~timately .06 to .20 inches is defined therebetw~een. A thin, uniform
layer of a eementitious refractory mortar 40 is provided in space or gap
38 to secure housing 14 to refractozy core 12. A conventionally lawwn
air-drying mortar or a phosphorio-acid containing mortar may be used.
Fitting 34 is positioned on housing 14 such that when housing 14 is
sec~.trec~ to core 12, aperture 36 is aligned with one of d~arn~e.~,s 24, 26,
28
or 30. Housing 14 basically encases core 12 and together with mortar 40
structurally reinforces core 12 as will be discussed in more detail below.
Housing 14 and n~tar 40 also produce a seal aramd core 12 and wen the
open portion of channels 24, 26, 28 ant 30. In other words, hcus3,ng 14
and mortar 40 form a generally air-tight barrier wen each channel as best
seen in FIG. 3. In the enbodirent shown, housing 14 is formed frrxn a low
carbon steel and has a uniform wall thic~~ess of .05 inches. Housing 14 is
14&1/2 inches in length and has an outer diameter which varies from 7&1/2
inches on one end to 7&3/4 inches on the other.
An important aspect of the present invention is the asseimbly of
nozzle l0. In this respect, as will be appreciated from a further reading
WO 90/13379 ~~ PCT/US90/02331
2063994
12
of the specification, it is ing~ortant to the ~~~ of nozzle 10 that
d~am~el.s 24, 26, 28 and 30 .z~nain ~~open~~ and do not ~ by
mortar 40 during assembly. the simplest method of assembling nozzle 12
mould be to coat nozzle 12 with mortar and slide housing 14 thereovex.. A
problean with such process, haaever, is that due to the relatively small
gap pausing 14 and core 12, n~ov~eme~t of housing 14 over core 12
creates a large hydraulic pressure in mortar 40 which tends to force the
~~r into the d~armels 24, 26, 28 and 30 forn~ed in nozzle 12. It has
been found that this pznblezn can be v~reraane by covering the dues with
1o a positionally stable barrier, and more iyortar~tly, ~i~
width of the d~arn~els such that the barrier can withstand the hydraulic
pressure e~certed then and not be famed into the dsaru~el. In this
it has been found that if an adhesive tape 42,
oos~ve~rtianally-l~an duet tape, is used to cover the d~armels tend the
width of the d~arn~l.s is maintained less than 1/2 inch, that irrespective
of the size of nozzle 10, horsing 14 trey be slid over core 12 without
mortar 40 being forced into and obst~s 24, 26, 28 and 30
therein. In the e~odin~t shown, d~armel.s 24, 26, and 28 are
appr~timatel.y 1/4 inch wide and 1/2 inch deep, and 30 is 1/2 irx~
wide and 1/2 inch deep. An elongated, ~hap~ . ~~ ~ ~y ~
yin gel 3o as a bridging member to preve~ tape 42 fran being
forced into d~artnes 30. Tb further facilitate such assanbly, core 12 and
inner surface 32 of hausirx3 14 are slightly conical,, as set forth above
arsd as best seen in FIG. 3. After the assembly is oc~leted, and
refractory mortar 40 has set, aperture 36 is cleared by madvni~~
WO 90/13370 PCT/US90/02331
13 2063994
mortar 40 or tape 42 which would obstruct its nication with channels
24, 26, 28, arid 30.
Referring now to the operation of the present,invention, nozzle 10
is adapted for use in a tiu~dish to direct the flora of molten metal to a
subsequent stage of operation in a steel making process. Nozzle l0 may
include flanges or other locating surfaces to facilitate assembly in the
tundish in a conventionally la~own fashion. It being understood that
present invention is not limited to a specifically shaped or sized nozzle.
In this respect, it is well la~wnn that the physical dimezasions and
configuration of a nozzle are determined by the particular casting machine
or system with which it is used. Fitting 34 is adapted to be se~~ ~ a
sof inert gas in a crnwentionally la~own fashion. the inert gas
flows through fitting 34 into channel 24, and into ~ar~els 26, 28 via
rharmel 30. When the pressure of the inert gas is sufficient to overcome
the resistance inherent in the impermeable magnesium oxide (Mgo) core 12,
gas flows thzthe core 12 into the nozzle opening or bore 18. Zhe
usual flaw rate of the inert gas in a nozzle as described above is
apprrncimately 15 Standard Cubic Feet per Hour (SCFH) with back pressures
of between 5 to 10 psi. Importantly, with the present inventi~, the flow
of the inert gas may be directed to a specific desired site within nozzle
opening 18 by locating the channels 24, 26 and 28 in the outer surface of
core 12 at location adjacent the desired sites. In this respect, it has
been found that flow of the inert gas through the nozzle wall is greater
adjacent the location of a channel. Accordingly, the nozzle may be
designed (i.e. the channels may be positioned on core 12) to direct the
WO 90!13379 ~~ PCT/US90/02331
14 2063994
flora of the inert gas to areas in which i~urity build-ups within bore or
opening 18 would be most severe. In other worc7s, the ~ifia location of
channels 24, 26, 28 and 30 in core 12 allows for a high degree of control
of the regions in openi~ 18 where it is desirable to have the greatest
gas Pressure. It has been found that while the greatest gas pressure in
bore 18 is adjacent the location of the d~annels in care ~ ~ ~ ply
uniformed distribution of the inert gas is also provided throughout
18 of nozzle 10 due to the fine, open porosity of the refractory
core 12 heretofore described.
A nozzle acoordir~g to the present invention has been shown to
provide increased operational life and substantially improve the erosion
~i~ance. Moreover, such a nozzle shows a significant in~roveme~
against the build-up of alumina, titani.a and/or other deposits.
remarkable characteristics of the present invention are the result of
several factors. Zhe application of magnesium oxide in forming the ~
provides a core having no affinity for alumina or other im~xu-ities found
~llent , porosity characteristics of the oox~e, i. e. the
fine-bpen porosity, is believed to generate small, fine bubbles which
maintain a minuscule gas gap bet~en the molten metal and surface 20 of
bore 18. The relatively high back pressure helps maintain a uniform layer
of gas bubbles between the molten metal and surface of the refractory.
ln~ortantly, the ability of the disclosed nozzle to direct the greatest
flow of gas to specific locations within the nozzle bore provides maximan
gas flea at sites having a susceptibility to deposit build-up. l~ditional
advantages of a nozzle according to the present invention is that the
WO 90/13379 PCT/US90/02331
15 2U6399~
attac~ent of housing 14 to core 12, in addition to sealing core 12, makes
the present nozzle less susveptible to catast~hic failure due to
cracking. In this respect, housing 14 holds the magnesium oxide (Mg0)
refractory material together much like a reinforcing band, thus preventing
the of any cracks which may be produced in the refractory material
as a result of thermal. shocJc.
The present invention has been described with
respect to a
preferred embodiment. It will be appr~eciatsd that modifications and
alterations will oowr to those skilled in the art upon a reading of the
specification aryl the claims herein. For example, while the present
invention has been described with respect to the use of magnesium oxide in
forming core 12, other materials may be utilized to provide a permeable
core, and would find advantageous application with other
aspens of the
pent invenition. Moreover, the present irnrention is mat limited to the
Z5 shape and size of the charn~,ls described herein. It will be appx~ciated
that other methods of assembly of nozzle l0, which would mat limit the
width of the channels, could be provided without deviating from the
present lion. For e~le, use of a metallic tape of strip over
charnels 24, 26, 28, and 30 world enable wider d~arnye~.s to be used. It is
intended that all such modifications a~i alterations be included insofar
as they ootne within the scope of the patent as claimed or the equivalents
thereof.
Having described the invention the following is claimed.
