Note: Descriptions are shown in the official language in which they were submitted.
1 srief _summary of the Invention
The subject matter of the following C~nadian patent
applications is of interest all of which were filed May 8,
1981 and may be referred to: Serial No. 377,201 en-titled
"Method and Apparatus for Strip Casting" by Battelle Develop-
ment Corporation"; Serial No. 377,216 entitled "Method of
Repetitiously Marking Continuously Cast Metallic Strip
Material" by Battelle Development Corporation; Serial No.377,13
entitled "Apparatus for Strip Casting" by Battelle Develop-
ment Corporation"; and Serial No. 377,152 entitled "StripCasting Nozzle" by Allegheny Ludlum Steel Corporation.
The present invention relates to the casting of
strip material at high quench rates and at hish producti~n
rates. More particularly, the present invention is directed
to an apparatus for rapidly casting thin metallic strip
materlal.
The apparent advantages and economic significance
of producing thin metallic strip material by a casting
process, as cornpared to the conventional rolling or reducing
operations, are numerous. The fact that strip casting may
be perormed at such high quench rates to produce amorphous
material i9 even more meaningful. However, it is equally
apparent that there are a multitude of strip casting para-
meters which must be controlled or monitored to assure that
the cast strip is Oe acceptable quality and of uniform
composition and structure. For these reasons, those skilled
in the art appreciate the intricacy involved in the develop-
men t O:e a commercially successful strip casting apparatus.
-- 2 --
'~``?
8 7 3
1 The general concep~ of casting thin metallic
materials such as sheet, foil, strip and ribbon was disclosed
in the early l900's. For example, U.S. Patents 905,758 and
993,90~ teach processes wherein molten material flows onto a
mov1ng cool surface and the material is drawn ~nd hardened
thereon into a continuous thin strip~ These references
~each that molten metal may be poured onto the smooth
peripheral surface of a rotating liquid-cooled copper drum
or disc to form strip materials. Despite early disclosure
of such concept, there is no evidence of co~mercial success
of strip casting during the early part of the 20th century.
Recently, in U.S. Patents 3,522,836 and 3,605,863
a method for manufacturing a continuous product, such as
metallic wire or strip, from moiten metal has been disclosed.
These references teach that a convex meniscus of molten
material should project from a nozzle~ A heat extracting
surPace, such as a water-cooled drum, is moved in a path
substanti~lly parallel to the outlet orifice and ~nto
contact with the meniscus of molten ~etal to continuously
draw material ~rom the meniscus to form a uniform continuous
product. The above-described method is commonly called the
~melt drag" process as the heat extracting surf~ce moving
pa~t the meniscus of molten metal at the nozzle orifice
Actually has ~n e~fect on the rate of molten metal flow, or
drag, through ~he nozzle.
More ~ec~nt strip casting developments focus on
relatively narrow refinements in the metallic strip casting
art. For ex~mple, U.S. Patent 49142,571 is particularly
--3^
~ 1 8~8~3
1 directed to a 810~ cons~ruction in a m~al ~tr~p ca~ting
nozzle having ~tringent dimensional requirements. Also,
U.S. Patent 4,077,462 pertains to the provision of a specific
con6truction for a st~tionary housing above the peripheral
S surface of a chill roll used for 6trip cas~ing.
There are a number of other rapid quenching
techniques known in the art. For example, melt spinning
proce6ses of producing metallic filament by cooling a fine
molten stream either in free flight or against 3 chill block
have been practiced. Also known are melt extraction
techni~ues, such as crucible` meit extraction disclosed in
U.S. Patent 3,838,185, pendant drop melt extraction technlques
taught in U.S. Patent 3,896,203 and splat cooling explained
in UOS. Patent 3,297,436. It has heen ~ound difficult to
produce uniform 6heet or 6trip by such alternar.ive techniques
of rapid quenching. There are many factors r such as casting
temperature and preæsure, auxiliary surface cooling rates,
~urface coatlngs for the casting surface, and the like which
appear to affect the product thickness, the quality and the
reproducibility of rapidly cast strip material.
De~pite the relatively long history of the
art of ~trip casting, and the recent developments in this
~rea~ strip c~sting is no~ a widely acceptecl and commercially
~igniPicant oper~tion at ~he present time~ It appears that
vAri~u~ improvementsi modifications and innova~ion~ are
r~uire~ in the ar~ to efect~ate a si~nific~n~ commercial
lmp~ct in the ~rt of strip ca~ting. In particular, proper
rel~tionshlp~ among ~uch vari~ble~ ~8 molten metal tundlsh
con~truc~ion, no~zle or~fice ~ze and dimen~ions, ~pacing
-4-
)873
1 from a casting sur~ace, speed at which such ~urface is
moved, quench rates, metal temperature and feed rates, and
the like may require more accurate identification and
interrelation in order to accomplish the uniformity and
conslstency required for successful, commercial production
of cast strip. In particular, certain nozzle structures
and their dimensional relationship to the castlng surface
onto which strip material is cast, have been found to be
inadequate to yield uniform strip casting results when
utilized in various casting parameters.
Accordingly, a new and i~proved apparatus
for casting relatively wide, thin strip material is
desired which overcomes the disadvantages of the prior
art structures. Such desired apparatus should be
reliable, more e~ficient and more effective than the
structures disclosed in the prior art, and should lead to
reproducibility, uniformity and consistency in strip casting.
The present invention may be summarized as
providing a new and improved apparatus for continuously
casting metallic strip material. Such apparatus co~prises a
tundish and a nozzle comprising a curvilinear element, with
an oriice passage in the element having substantially
uniform cross-sectional dimensions throughout the longitudinal
extent thereof, Disposed outside the nozzle is a cooled
~sting sur~ace movable past the noz%le in a direction
subst~ntially perpendlcular to the longitudinal axis of the
oriice pa~æ~ga. ~irst and second inside surfaces of the
element d~fine the orifice passage through which molten
metal is fed to the castlng surface.
~5-
~ ~80~73
1 Among the advantages of the present lnvention
is the provision of a strip casting apparatus which is
capable of continuously casting metallic strip material of
substan~ially uniform dimension and substantially uniform
quality throughout its length.
Another advantage of the present invention is the
provision of a strip casting apparatus havlng a nozzle
construction which promotes the efficient rapid casting of
metal strip material with a minimum of ~etal turbulence
during casting.
An objective of the present invention is to
provide a strip casting apparatus capable of reproducing
successful strip casting operations.
Another objective of this invention is to provide
a strip casting apparatus which can effectuate sufficiently
rapid quenching of the produced strip to result in the
production of amorphous strip. ~owever, it should be
understood that the production of continuously cast crystalline
material is equally comprehended by the present invention~
A further objective of this invention is to
identify certain design and dimensional requirements,
particularly with regard to nozzle structure~ which per~it
continuous ~nd repetitious rapid casting of metallic strip
~aterial o~ uniorm dimension and unifor~ quality.
~5 These and other objectives and ~dvantages wiil
be more fully understood and appreciated with reference ~o
the followlng detailed description and the accompanying
draw~ngs.
~6--
~ ~8~)873
1 ~rief Descri~tion of the Draw~ngs
Figure 1 is an elevation view, partially in
cross-section, illustrating a typical apparatus used for
continuously casting strip material.
Figùre 2 is a cross-sectional view of a nozzle
of the present invention.
Figùre 3 is a perspective view of a curvilinear
element which forms a nozzle of the present invention.
Figure 4 is an enlarged frag~entary cross sectional
view through the orifice passage of the element shown in
Figures 2 ~nd 3.
Fisùre 5 is an elllaryed fragmentary cross-sectional
view through the orifice passage of an alternative element
of the present Invention.
~igure 6 is a cross-sectional view of the orifice
passage of an ~lternative element of the present invention.
Figure 7 is an enlarged~ fragmentary cross-sectional
view, illustrating an alternative orifice passase in an
element of the present invention.
Figure 8 is an enlarged fragmentary, cross-sectional
view, illustrating an alternative orifice passage in an
ele~ent o~ the present inYentien.
Detailed DQscription
Re~erring partlcularly to the drawingsr ~igure
1 generally illustrates an apparatus for casting metallic
--7~
7 ~
strip material lo ln accordan~e with the present invention.
This apparatus includes a castin~ drum, wheel, belt, or the
like upon which the strip 10 is cast. In a preferred
e~bodiment a continuous strip 10 is cast on~o ~ smooth,
S outer peripheral surface 14 of a circular drum or wheel as
shown in Figure 1. It should be understood that eonfigurations
other than circul~r may be employed. ~or example, a wheel
with a smooth, frustoconieal outer peripheral surface (not
shown) may be employed. Also, a belt capable of rotating
through a generally ovular path may be e~ployed as the
casting element, Regardless of the configuration employed,
the casting surface 14 should be cooled to a temperature
below the solidus te~perature of the metal being cast and
should be at least as wide as the strip to be cast.
In a preferred embodiment, the casting element 12
comprises a water cooled, precipitation hardened copper
alloy wheel containing about 98~ copper with about 2~
chromium. ~opper and copper alloys are preferable because
of their high thermal conduct~vity and wear resistance,
however, berillium copp~r ~lloys, steel~ brass, aluminu~,
~luminum alloys or other materials ~ay be utilized alone, or
in combination. ~or example, ~ultipiece wheels having outer
peripher~l ~leeves of molybdenum or other material may be
~p~oyed~ Likewise, coollng m~y be Accompliæhed with the
2S U~ of a ~edi~m other than water. Water is typic~lly chosen
~or its low ~os~ &nd lts ready ~vail~bllity.
In the operation of the strip castlng apparatuS
of the present ~nventlon, the surf~ce 14 of the c~sting
wheel ~2 ~ust be ~ble ~o ~bsor~ ~he ~eat g~nerated by
-8-
7 3
1 contact with m~lten metal at the initial castiny point 16,
rnd such heat must be conducted ~ubstantially into the
copper wheel during each rotation of the wheel. The initial
casting point 16 refers to the approximate location on the
casting 14 where molten metal 20 flowing from the tundish 22
cont3cts the casting 6urface 14~ Cooling, by heat conduction,
may be accompl~shed by delivering a suffi~ient quantlty of
water through internal passageways located near the periphery
of the casting wheel 12. Alternatively, the cooling medium
may be delivered directly to the underside of ~he casting
surface. Understandably, refrigeration techniques and the
like may be employed to accelerate or decelerate cooling
rates, and/or tv effectuate wheel expansion or contraction
dur~ng strip casting.
Whether a drum, wheel or belt is employed for
cas~ing, the casting surface should be generally smooth and
symmetrical to ~aximize uniformi~y in strip casting. For
exampl2, ln certaln ~trip casting operations the distance
between the outer peripheral casting ~urface 14 ~nd the
surf~ces de~ining the orifice p~ssage of the nozzle which is
feeding th~ molten material onto the castin~ surface 14 must
not devi~te fro~ ~ desired or set distance during the
castlng operation. This distance shall hereinafter be
called ~t~ndoff distance or gap. It is und~r~tand~ble that
the g~p should be ~ubstantially maint~ine2 ~hroughout the
c~ting oper~tion when it is the intention to ~st uniform
~trlp material.
It ~hould be und~r~tood that lf the ~asting
i~ p~r~on~ed on a rot~tlng body 12~ ~uch as ~ dru~ or a
08 '~3
1 wheel; the body 12 should be carefully constructed so as
not to be out of-round dur~ng operation to insure unifor~ity
in gtrlp ca~t~ng~ Alo~g these lines~ lt h~s been found that
a dru~ or wheel whlch is out-of-round by about ~.020 inch,
or ~ore, may h~ve ~ ~agnitude of dimensional lnstability
wh~ch unless corrected or comp@nsated during operation, may
be una~ceptable for c~rtain strip casting operations. It
has been found that acceptable dimensional symmetry, as well
as the elimination of problems assoclated with weld porosity
may be more readily a~co~plished by fabricating a wheel or
drum fro~ a single, integral slab of cold rolled or forged
copper alloy. However, as mentioned above alternative
materials including sleeves and coatings may be employed.
The molten material 20 to be cast in the apparatus
lS described herein ls preferably retained in a ~rucible 22,
or tundish, which is provided with a nozzle 24. The nozzle
is typically, though not neces~arily, located at a lower
portion of the tundish 22 as shown in lFigure 1~ As will be
apprecisted fro~ the foregoing dlscus~ion, the nozzle
comprises a curvilinear ~lement 24 in the tundish ~2~
The curvilinear element 24, located in or forming
a lower portion o~ the tundish 2~ is best shown in the
tundi~h 2~ ln ~igure ~, and in perspective vi~w in Figure 3.
A~ 8hown ln the dr~wing/ an orifice pa~sage 30 i~ preferably
2$ 8ub8tantiMlly centr~lly located in the nuzzle ~lement 24.
SUch approxim~e centr~l location of the ori~lce pas5age, or
~lot, ~0 helps to assure uniform~ty ~s the pressure of the
~olten ~et~l bearing ~here~gainRt i~ ~ubs~antially equalized
during ~be c~tin3 oper~tionc It should be under~tood,
--10--
1 ~(J8'73
1 however, that the slot may ~e located in off-center positions
as may be desired.
The longitudinal extent of the orifice passage 30
should approximate the width of the strip to be cast. There
does not appear to be a limitation on the longitudinal
extent of the orifice passage, and, passages as long as
thirty six inches, or longer, in a curvilinear element are
comprehended by the present invention. It is highly desired
that the molten metal flow uniformly ~hrough the orifice
passage 30 in the curvilinear element 24 of the present
invention in order to form uniform, high quality strip
material. In an alternative embodimen~, strip of various
widths may be produced by cutting multiple longitudinally
aligned orifice passages 30 of appropriate longitudinal
extent in the curvilinear element 24 forming the nozzle of a
tundish 22, as opposed to a single orifice passage 30.
Regardless of the size of the orifice passage 30, or passages,
the cross-sectional dimensions of each passage 30 should
be substantially uniform throughout the longitudinal
extent thereof to produce strip material having uniform
dimensions. In the operation of the strip casting apparatus
of the present inven~ion, the cooled casting surface 14
moves past the orifice passage 30 in a direction substantially
perpendicul~r to the longitudinal axis of the passage 30.
As best shown in Figure 4, the orifice passage 30
is deflned between a first side portion 32 and a second side
portion 34 of the curvilinear element 24. The fir~t side
portion 32t i~ located on the downstream side of the
orifi~e passage 30, with respect to the direction of movement
~ ~8~1~73
1 of the casting surface 14 ~ndlc~ted by the arrow ~n Figure
4. ~he first side portion 32 ha~ ~n ln~de surface 36
which, preferably, 1~ sub~tantially pl~nar, ~nd an outer lip
projecting ~urface 38 disposed toward and facing the
cast~ng surface 14. At a downstream locatlon from the
orifice pa86age 30, the outer lip projecting ~urf~ce 38 is
relieved, ~uch as at 40, to define a lip projection 42. The
second ~ide portion 34 i8 located on the upstream side of
the orifice passage 30, with respect ~o the direction of
movement of the casting surface 14 indica~ed by the arrow in
Yigure 4. The seeond ~ide portion 34 ha~ an inside ~urface
46, which preferably, i6 8ubst~ntially planar and, also
preferably, 1~ ~ubstantially parallel to afld facing the
inside 8urface 36 of the fir8t side portion 32 at least at
lS an outer portion of the orifice passage 30 with respect to
the direction of metal flow ~ro~ the tundish 22 thro~gh the
pa~age 30. A bottom surface 48 of the second ~ide portion
34 i~ di~posed toward and facing the ca~ting surface 14.
In a preferred embodiment, the outer lip projecting
~urface 38 of the first ~ide portion 32 ~nd a portion of the
bottom 8urface 48 of the 8econd side portion 34 are ln
substantially complete paralleli~m with the casting surface
14 movable therebelow. When utllizing a drum or wheel, and
a grindable curvilinear element 24, ~ueh aubstantially
~5 ~omplete par~llell~m may be accompl:Lshed by placirlg a ~heet
12-
D 18t)87~
1 of sandpaper9 or the like, against the casting surface 14
with the grit side of the sandpaper facing the curvilinear
element 24. By moving the curvilinear element 24 into tight
contact with the castlng ~urface 14, with the sandpaper
disposed therebetween, and by moving the casting surface 14
a~d sandpaper slmultaneously past the nozzle 24, the outer
lip projecting surface 38 of the first side portion 32 and
the botto~ surface 48 oE the second side portion 34 are
ground by the grit side of the sandpaper into substantially
comple~e parallelism with the casting surface 14. Such
parallelism may be achieved on most refractory nozzles, even
when round or other curvilinear casting surfaces are employed.
To achieve such parallelism by this procedure 400 or 600
grit sandpaper has been found to be adequate.
By maintaining at least a portion of the outer
lip projecting surface 38 in comple~e parallelism with the
casting surface 14, the standoff distance, or gap h, between
the outer lip projectlng surface 38 and the casting surface
14 may be maintalned throughout the length of the projection
42. ~t has been found that the gap h between the ou~er lip
projecting ~urface 38 and the castin~ surface 14 ~us~ be
maintained at less than about 0.120 inch in order to
successfully cast strip material. Preferably, this gap h is
~aintained at less than about 0.080 lnch and for casting
certain alloys into ~hin gage s~rip, a gap h o~ less than
0,010 is preferred. It has also been found that the gap h
between the bottom surace 48 of the ~econd side portion 34
does not Appear ~o be a~ criticalO What is preferred with
respect to the ~econd side portion 3~ $s that the inside
)873
1 surface 46 thereof extend toward the casting surface 14
while parallel to the inside surface 36 of the first side
portion ~32, at least ln an outer por~ion of the orifice
passage 30, so as not to interere with the ma~ntenance of a
stable flow of molten metal through ~he passage 30 in the
curvilinear element 24 and onto the moving casting surface
14. Accordingly, the bottom surface 48 of the second side
portion 34 may just clear the casting surface 14, i.e.
within about .002 inch as shown in Figure 7, or, alternatively,
the bottom surface 4~ may be tapered from the orifice in a
direction away from the casting surface 14, as shown in
Figure 8. In any event, the gap h between the bot~o~
surface 48 of the second side portion 3~ and the cas~ing
surface 14 must be sufficiently restricted at the nozzle
to prevent significant molten metal backflow therebetween
during casting.
In an ~lternative embodiment, shown in Figure
5, the inside surface 36 of the first side portion 32
extends through a curvilinear surface 50 to the outer lip
projecting surface 38, rather than through the abrupt 90
juncture shown in ~igure 4. Providing such radiused corner
surface 50 has been found beneficial in the production of
cer~ain grades of strip material~ More particularly, such
radiused corner surface 50 helps minlmize molten metal
turblllence durlng strlp casting and, t.herefore, results in
more uniform production parameters. I~ has also been found
th3t a ~harp corner between ~he inside surface 36 ~nd the
outer 11p pro,ec~ing surface 38 may be subjec~ed t~ various
pressur~s and flow p~tterns which could create ~tress
-14-
1 ~8~8~3
1 conditions for curvil~near elements 24 made of certaln
materials and, in some ins~ances, may break, crack or wear
during casting thereby upsetting balanced ~trip casting
conditions. Providing such rounded corner ~urface 50 may
minimize the adver~e affect~ of such turbulence and metal
flow through the ~urvilinear element 24 compri~ing the
nozzle of ~he tundish 22.
To further minimize turbulence during strip
casting through the apparatus of the present invention, an
inslde portion of the orifice passage 30 may be relieved, or
tapered. As shown in the drawlng, both the f~rst side
portion 32 and the second ~ide portion 34 may be cut into a
V-shape, or a more rounded U-shape at an ln~ide portion
theeeof, creating an inltial funnel type structure, which
fuxther maxim~zes uniformity in metal flow patterns and
minlmizes irregularities or turbulence during strip casting.
Another preferred arrangement, whtch minimi.zes
molten metal turbulence during strip casting, is to arrange
the curvilinear element 24 at an angle such that the metal
is ~ed in the ~ame direction as the casting ~urface 14.
Thls may be accompl~shed by disposing the inside surfaces 36
and 46, defining the orifice passage 30, tow~rd the casting
surace 14 at an angle of less than about 90, or preferably
~t an angle of ~bout 45. By such arrangement the flowing
2~5 moltan metal i~ nvt subjected to as ~e~ere a change in flow
rate as would be experl~nced by arranging the orifice
pas~age 30 to ~eed molten metal perpendicular ~o the casting
~urface 14.
-15
~ 18~73
1 The crucible 22 is preferably constructed of
a material having ~uperior insulatlng abillty. If the
insulating ~billty is not sufficient to retain the molten
material at a relatively constant temperat-lre, auxlliary
heaters such as induction coils may have to be prov~ded in
and/or around the crucible 22, or resistance elements s~ch
~S W1LeS may be provlded. A convenient material for the
crucible is an insulating board made from fiberized kaolin,
a naturally occurring, high purlty? alumlna-silica fire
clay. Such i~nsulating material is available under the trade
OL~
name ~Y~e~ HS board. ~owever, for susta~ned opera~ions,
and for casting hlgher melting tempera~ure alloys, vario~s
other materials may have to be employed for constructing the
crucible 22 or the curvilinear element 24 ~ncluding graphite,
alumina graphite, quartz, clay graphite, boron nitride,
silicon nitride, sillcon carbide, boron carbide, alumina,
zircon~a and various combinations or mixtures of such
materlals. It should also be understood that these materials
may be strengthened; for example fiberized kaolin may be
strengthened by impregnat~ng wlth a sll~ca gel or the
like.
It is imperative that the orifice passage 30 of
the curv~linear element 24 remain open and its configurat~on
remain uubstantlally stable throughout a strip casting
operation. It ~s understandable that the orifice passaye
30 ~hould not erode or clog, slgnificantly, durlng a ~trip
ca~ting ~e~uence or the primary ob~ectives of maintalning
uniformity in the castlng operation and of minimizing metal
flow turbulence in the ~undish 22 may be defeated, Along
16
fr~J ~ ~ an~ ~ _
~ ~0~3
l these lines, it appears ~hat cer~ain lnsulating materlals
may not be able to maintain their dimensional stability over
long casting perlods, To obviate this problem, side portions
32 and 34 foxmlng the orif~ce passage 30 of ~he curvil~near
element ~4 may be constructed of a material which is better
able to maintain dimensional stabllity and ~ntegr~ty dur~ng
exposure to hlgh molten metal temperatures for prolonged
tlme perlods. Such materials may take the form of a sinsle,
gene~ally seml-circular elemen~ 24 with a slot 30 cut
therethrough as shown in Figure 3, Alternatively, the
curvilinear element 24 may comprise a pair of facing inser~s
held in the crucible 22 to form a slot 30 therebetween as
shown in Fiyure 6. In a preferred embodiment the orifice
passages 30 in single curvilinear elements ~4 may be cut
lS ultrasonically to lnsure that the desired slot dlmensions
are accur~tely provided~ Such curvilinear elements ~4 may be
cons~ructed of materials such as quartz, graphite, clay
gr~phite, boron nitride, alumina graphite, silicon carbide,
stabllized z~rconla silicate, 2irconia, magnesla, alumina,
or other ~milar molten ~etal reslstant material. These
curvilinear elements 24 may be held in the crucible 22
mechanically, and/or with the aid of adhesives such as
various refractory cementsO
The dr~ve system and hou~ing for ~he drum, wheel
or other casting ~urface 14 of the present lnvention should
be rig~dly constructed to p~rmit drum rotation wlthout
~tructural instabili~y which could cause the drum to sllp or
vibrate. In particular, c~re should be taken to ~void
re~onan~ frequences at ~he opera~ing ~peeds for the casting
87~
1 surface 14~ The casting surface 14 should be capable
of moving at a surface speed of from about 200 linear
surface feet per minute to more that about 10,000 linear
~urface feet per minute. When utilizing a drum having a
circumference of about 8 f~et, this rate calculates to a
drum ~peed from about 25 r~p to about lZ50 rpm~ A three
horsepower variable speed reversible, dynamically braked
motor provides an adequate drive sys~em for an integral
copper alloy casting drum about 2 inches thick and about 8
feet in circumference.
In one embodiment, the casting surfa~e 14 on
the wheel or drum of the apparatus of the present invention
is smooth. It has been found that in c~rtain applications,
such as for produclng amorphous materials, finishing the
peripheral surface 14 of a casting drum 12 with 400-grit
paper and ~referably with 600-grit paper may yield lmproved
product uniformity.
In a preferred embodiment as illustrated in
Figure 2, the crucible 22 is cons~ructed of an insulating
board, such a Kaowool HS Board~ and the curvilinear element
24, as shown in Figure 3, is made of clay graphite, a
molten metal resisten~ ~aterial, held in the walls of ~he
crucible 22~ The orifice passage 30 is cut ultrasonically
ln the clay graphite element 24. The firs~ side portion 32
~nd the second ~lde portion 34 of the curvi]inear ele~ent 24
defin~ the orifice pas~age~ or slot, 30 therebetweenO As an
alternative, preferYed examples of curvilin~ear els~ent 24
materialæ, a plate made of qu~rt% or *~ material~
whi~h ~re highly molten metal r~s~tent materials~ having a
~r~ k
-18-
1 w~dth such a~ about one and one-half inch may be bent ~round
an appropriate ~mall radius, as shown in the dxaw~ng.
Alternatively, the curvilinear element 24 may com~ise cast
boron nitride. Tbe desired slot formlng the oriflce pa~sage
30 in the curvil~near element 24, may be accurately cut
therein with an ultrasonic drill. ~ preferred on~ piece,
curvilinear element 24, as best illustrated in Fig~res 2,
3 and 4 may be constructed of a semi-circular rin~ of molten
metal resistent material. In ~his example, a slot b having
a width of abou~ 0.010 to about 0.080 inch between parallel
inside surfaces 36 and 46 may be ultrasonlcally dr~lled into
a clay graphite insert material, and the insert may be
mo~nte~ into the crucible 22 as shown in Figure 2. It
should be understood that the design of the outer, peripher~l
edges of such curvilinear element nozzle may be modified to
asslst in holding the curvillnear element 24 ln the walls of
the crucible 22.
A preferred orifice passage 30 ln a curvilinear
element ~4 of the apparatus of ~he present invention is
shown in enlarged cross-section in Figure 4. In one embodiment
o~ this apparatus, the dimensions indicated in Fiyure 4
may have the following preferred limita~lons,
more
preferred preferred
d~men~ion ~ tion limitation lim1tat1on
a bottom sur~ace at least .001 inch .25 - .50 inch
o~ second side
portion
b wldth of orifice .010 - .080 lnch ~025 ~L035 inch
pas~age
c outer llp pro ,01 - .16 inch oO2 ~ ~06 lnch
~ectlng ~urface
length
-19
~()g7~
more
preferred preferred
dlmension ~ ml~a~ion llmitat~on
d rellefat least .01 inch at least .04 inch
distance
In the product~on of amorphous str~p materlals,
the w~dth b of the orlfice passage 30 is typically in the
range of Prom about 0.010 to about 0 040 inch. In the
production of crystalline str~p material, ~uch as stainless
steel, the width b of the orifice passage 30 may be greater,
perhaps as high as about 0.080 inch if thick strip is being
uniformly produced in accordance with the present invention.
Dimension e, represent~ng the cross-sectional
thickness of the curvilinear element 24, f, representing ~he
wldth to wh~ch a top portion of the oriflce passage 30 may
be rel ieved, and g, representing the depth to which a top
port~on of the orifice passage 30 may be rel~eved, appear to be
~omewhat arbitr~ry. Primarily, the purpose of the relief at
a top port~on of the orif:loe passage 30, ~dent~fied by
d~mensions f and g ln Figure 4, is to eliminate clogging
of molten metal in the orifice.
Molten metal turbulence during strip castlng
may be m~nim~zed, and perhaps avoided by relievins sharp
corners of the nozzle in the direction of ~asting~ It will
be understood that such corner relief, such as the r~diused
corner ~urPace 50 shown in ~igure 5, may be accompll~hed by
construc~ing the curvlllne~r element ~4 of an eroding
O~OA
~`~ material, such as ~4w4~ ~S board, wh~ch may provide
natural ero~ion as a result of the ~trlp casting operat~on.
3~ Tu~bulence may al~o be avoided by comple~ely round~ng ~he
;~ ~ra~ f/~
-20-
1 corner 50 of the projection 42 on the first side portion 3~
of the curvilinear ele~ent 24 as is shown in Figure 5 during
or after manufacture thereof.
In an exemplary operation of the apparatus of
the present invention, ~olten metal is delivered ~o a heated
crucible 22~ It is uslderstood that a heater, such as
indùction coils of resistance wire, may be provided in and
above the crucible 22 to ~aintain relatively constant molten
metal temperatures as may be desired. Alternatively, the
molten ~etal may be poured directly into a preheated
crucible. The preheat temperature should prevent freezing
or clogging of the orifice passage 30 during the initial
casting operation, and the temperature of the flowin~
metal should thereafter keep the crucible 22 and curvilinear
el~ment 24 formin~ the nozzle at sufficient temperature to
in~ure uninterrupted molten m~tal flow through the orifice
passage 30. In certain applications, the curvilinear
element 24 may be externally heated throughout the casting
operation~ Also, the metal which is fed to the crucible 22
~ay be superh~ated to allow a certain degree of te~perature
loss without adversely affecting ~etal flow through the
orifice passage 30~
Also, a metallostatic head height in the tundish
22 ~hould be maintained at a relatively constant level,
typically ~t less than ten inches above the orlfice passage
30, ~hroughout the casting operation to assure that a
rel~tively constant ~tatic head pressure ~ay be ~alrltained
~t the oriPlce passage 30. Thls may be ~ccomplished by
initially pouring the ~olten metal 20 lnto the crucible 22
--21-
1 to the desired height and thereafter controlling the rate at
which ~dditlonal molten metal 20 is poured into the
crucible ~2 to maintaln the deslres metallostatic head. It
~ understandable that the rate at wh~ch add~tional molten
melal 20 is fed to the crucible 22 should be ln Rubstan~al
conformity with the rate at which metal flows from the
orif ice passage 30 onto the casting surface 14 in forming
strip material 10. Maintenance of a relatively constant
helght o metal in the crucible 22 assures that the molten
metal flow pressure through the orifice passage 30 is
maintained relatively constant so as not to adversely affect
the castlng operat~on or the quality of the strip material
10. Alternatively, externally applied pressure may be
employed to control the pressure at the orifice pa~sage
30.
Using a tundish or crucible 22 similar to ~hat
shown in Figure 1, macle of a commercially available tundish
material ava~lable un~er the trade name S~H~, a casting
run was made on Type 304 stainle~ steel. The orifice
p~ssage 30 at the base of the crucible was about 1.3 inches
long by 0.08 inch wide, and the distance, or gap, between
the outer, lip projecting surface 38 and casting surface 14
was between 0~02 to 0.04 ~nch. With the speed of a rotating
water cooled copper alloy drum held at about 930 feet per
minute, molten ~etal was poured ~nto ~he crucible 22 at a
tempera~ur~ of ~bou~ 2,900F es~ima~ed wi~h the use of an
optical pyrometer. A metallostatic head he~ght of
~pprox~mately æix inches was mainta~ned throughvut the
casting op~rat.~on. The str~p produced thereby was about
~ r~ c~
-22-
~ ~08~3
1 0.006 to 00008 inch thick and exhibited fairly good ~uality
in that it was tough and ductile as cast.
During casting of strip material, the tendency
of the strip 10 to adhere to the casting surface 14 for a
significant distance, such as several eet or more, beyond
the initial casting point 16 has been observed~ It is
understandable that if the strip ~aterial 10 remains on a
rota~ing casting dru~ or wheel 12 for a full revolution,
damage to the crucible 22, particularly to the orifice
passage 30 in the curvilinear element 24, could result. It
has been found that the use of a doctor blade, such as a
knife type element riding at or near the drum surface 14,
approxlmately 2.5 to 6 feet from the orifice easily counters
such adherence. With such an arrangement, ~he cast strip
lS may be removed from the drum 12 by such doctor blade. Such
doctor blade has been found particularly useful in the
production of thinner amorphous strlp materials which
appear to have a greater tendency to adhere to the casting
surface 14 than do the crys~alline strip ~aterials. It is
believed that the force which retains the strip on the
casting surface may reflect the quality of ~he thermal
contact b~tween the strip 10 and the casting surface 14.
Alternative arran~ements, such as an air knife, may also be
employed to s~parate the strip 10 from th2 wheel 12.
~5 The casting of relatively high quality strip
material including ~morphous material, which for the purpose
o this invention incl~des materials which are ~ least 25%
~morphous, is feasible and practical using the apparatus and
proc~dures described above. Understandably~ ~he quench
~ 1~0873
rates must be h~gher for amorphous material as compared 'co
6imilar gage crystalline strip material. Quench rates may
be accelerated such as by lncre~s~ng the speed of the
casting surface 14~ or the l~ke. It is ~mportant to recognize
that the process may be conducted ~n two effective modes.
With the orifice passage 30 quite close to the casting
surface 14 as measured between the outer lip projecting
surface 38 and the casting surface 14, ~trip perhaps 0. 001
to 0.003 ~nch thick can be cast of either amorphous or
crystalline materials. If the outer ].ip projecting surface
38 of the firs~ side portion 32 of the curvilinear element
24 is disposed further away from the casting surfa~e 14, and
as casting surface speeds are reduced, strlp perhaps 0.005
to 0.050 inch th~ck can be ca.st. In this later mode, the
quench rate may be significantly lower due at least in
part to the ~ncrease ~n the product thickness.
Whereas the preferred embodiment ~as been
described above for the purposes of illustration, it will be
apparent to those sk~lled in the art tha~ numerous variations
of the details may be made wlthout departing from the
lnvention ~
I ela~m:
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