Note: Descriptions are shown in the official language in which they were submitted.
7 5
Brlef Sunmary o the_Invention
The following related Canadian patent applications,
all of which were filed May 8, 1981, are of in~erest:
Serial No. 377,164 entitled "Strip Casting Apparatus" by
Battelle ~evelopment Corporation; Serial No, 377,201 entitled
"Method and Apparatus for Strip Casting" by Battelle Develop-
ment Corporation"; Serial Mo. 377,216 entitled "Method of
Repetitiously Marking Continuously Cast Me-tallic Strip
Material" by Battelle Development Corporation; and Serial
No. 377,152 entitled "Strip Casting Nozzle" by Allegheny
Ludlum Steel Corporation.
The present invention relates to the casti.ng of
strip material at high quench rates and at high production
rates. More particularly, the present invention is directed
to a new and improved method and apparatus for rapidly
casting thin metallic strip material.
~he apparent advantages and economic significance
of produc.ing thin metallic strip material by a casting
process, as compared to the conventional rolling or reduc.ing
opexati.ons, are numerous. rrhe fact that strip casting may
be performed at such high quency rates to produce amorphous
material is even rnore mean:ingful. However, it is equally
apparent that there a a multitude of strip casting parameters
which must be controlled or monitored to assure that the
cast strip is of acceptable quality and of uniform com-
position and structure. For these reasons, those skilled in
the art appreciate that the development of a commercially
successful stri.p casting apparatus is di.ff:icult.
-- 2 --
, ~{)8~5
1 ~he general concept of casting thin metallic
materials such as sheet, foil, strip and ribbon wa~ disclosed
in the early l900's. For example, U.S. Patents 905,758 and
993,904 teach processes wherein molten material flows onto a
moving cool surf~ce and the material is drawn and hardened
thereon into a continuous thin strip. These references
teach that molten metal may be poured onto the ~mooth
pèxipheral surface of a rotating liquid-cooled copper drum
or di~c to form strip materials. Despite early disclosur~
of such concept, there is no evidence of commercial success
of strip casting during the early part of the 20th cent~ry.
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 molten metal has been disclosed.
These references teach that a convex meniscus of molten
material ~hould project from a nozzle. A heat extracting
~urface, such as a water-cooled drum, is moved in a path
substantially parallel to the outlet orifice and into
contact with the meniscus of molten metal to continuously
draw material from the meniscus to form a uniform continuous
product. Th~ above-described method is commonly called the
~melt drag" proce~s as the heat extxacting surface moving
past the meniscus of molten metal at the no~zl~ orific~
actually h~s an e~fec~ on the rate of molten metal flow, or
2S drag, throu~h ~he no~zle.
Even ~ore recent strip casting developments
focu~ on relatively narrow refinements in the metallic strip
ca~tin~ art. For example~ U.S. Patent 4,142,571 is par~icularly
`J 8 7 ~
1 directed to a Rlot construction in a metal strip casting
nozzle having stringent dimensional requirements. Also,
U.S. Patent 4,077~462 pertains to the provision of a specific
construction for a tationary housing above the peripheral
surface of a chill roll used for strip casting1
There are a number of other rapid quenching
techniques known in the art. For example, melt zpinning
processes of producing metallic filament by cooling a fin~
molten stream either in free flight or against a chill block
have been practiced. Als~ known are melt extraction
techniqu~ uch as crucibl~ melt extraction disclosed in
U~S. Patent 3,838,185 and pendant drop melt extraction
techniques taught in U.S. Pa~ent 3,896,203. It has been
found difficult to produce uniform sheet or strip by such
alternative techniques of rapid casting. There are many
factors, such as ~uxiliary surface cooling, surface coatings
and the like which appear to affect product thickness and
~uality of rapidly cast strip material.
Despite the relatively long history of the
2l0 art of strip casting, and the recent developments in this
area, strip casting is not a widely accepted and commercially
significant operation at the present time. It appears that
various improvements, modifications and innovations are
required in the ~rt to e~fectuate a significant commercial
2$ impact in the art of strlp casting. In particul~r, proper
rel~tion~hips among ~uch variable~ as molten metal ~undish
construction, nozzle orifice size and dimensions, spacing
from a ~a~ting ~urface, ~peed ~t which such 6urface ~s
1 ~8~ 5
1 moved, quench rates, metal tempera~ure and feed rates, and
the like may require more accura~e identification in order
to accomplish the uniformity and consistency requir~d for
succe sful, commercial production of cast strip. In
particular, c~rtain no2zle and slot structures and their
dimensional relationship to the casting surface onto which
6trip material is cast, have been found to be inadequate to
yield uniform strip casting results.
Since it is apparent that dimensional relationships
between the casting nozzle and the casting surface are
critical, prior strip casting apparatus have been constructed
with the nozzle for~ing an inte~ral part of a molten metal
holding tundish or with the nozzle integrally mounted
therein. Thus, when it becomes necessary to move, align or
chan~e a nozzle, the tundish is also affected. Therefore,
th~ requirement of maintaining ri~id dimensional relationships
has prevent~d flexibility in design and operation of the
strip casting apparatus~
Accordingly, a new and improved apparatus for
casting r~latively wide, thin strip materlal is desired
which overcomes the disadvantages of the prior art struc~ur~s.
Such desir~d apparatus should be more efficient, more
effective and more flexible than the structures disclosed in
the prior ~rt~ and should lead to uniformity and consistency
in ~trlp castlng.
~he pre~3ent invention may be summarized as
providin~ a new and improved appar~tus for continuously
c~sting metallic ~trip material onto a ca~ting surface.
1 Such apparatus compris~s a tundish for receiving and holdinq
molten metal having a nozzle therein. The nozzle comprises
an orifice passage defined between a first inside surface
and ~ second inside surface, wherein at lea~t one in6ide
8urface compri8es an insert disposed again~t the tundish. A
nozzle gap of at least .010 inch is maintained, an outer
portion of the in~ert is able to be disposed to within 0.120
inch of the casting surface, and at least a portion of the
outside surface of the tundish at the orifice of the no7zle
is able to be disposed to within at least about .020 inch of
the casting surface,
Among the advantages of the pre~ent lnvention
is the provision of a strip casting apparatus which is
capable of contlnuously casting m~tallic ~trip material of
substantially uniform dimension and substantially uniform
quality throughout its length.
Another advantage of the present invention is the
provi~ion of a ~trip caæting apparatu~ having a nozzle
construction which promotes rapid casting of metals with a
minlmum of metal turbulence during casting~
An objective of the pre~ent invention is to
provide a ~trip casting apparatus capable of r~producing
~ucce~s~ul ~trip cafitlng operations~
~nother objective of this invention i~ to provide
A 8trip c~Bting ~pparatu~ which can effectuat~ ~ufficiently
r~pid quenching of the produced ~trip to result in the
production of ~norphou~ ~trlp. However, it ~hould be
)87~
1 understood that the production of continu~uslY cast crystalline
material is also comprehended by the present invention.
A further objective of this invention is to
identify certain design and dimensional requirements,
particularly with regard to nozzle ~tructure, which permit
ccntinuous and repetitious xapid casting of metallic strip
mat~rial of uniform dimension and uniform quality.
Another objective of the present invention
is to utilize at least one, separate insert to form a part
of the nozzle. Such insert may b~ moved, aligned or
changed without substantially effecting the remainder of the
apparatus. Such ins~rt may be generally unobstructed which
facilitates the physical adjustment thereof, permits direct
heating ther~of and allows virtually unr~strict~d visual
observation of the casting operation.
These and oth~r objectives and advantages will
be more ~ully understood and appreciated with reference to
the following detailed description and the accompanying
drawings.
Brief Description_of the Drawlnqs
Figure 1 i~ a side elevation view, partially in
cross-section, illustrating a typical apparatus used for
continuously casting strip material.
~ lgure 2 is a cro~ ectional view of a ~undish
and noz~le of the present invention~
1 Figure 3 is a front elevation view through
III - III of the tundi~h ~nd nozzle ~hown in Figure 20
Figure 4 is a cro6s-fiectional view of an alternative
tundish and nozzle of the present invention.
Figure 5 is a cross-sectional view of ~n alternative
tundish and nozzle of the present invention.
Figure 6 is a cross-sectional view of an alternative
tundish and nozzle of the present invention.
Fiyure 7 i8 a cross-sectional view of an alternative
tundish and nozzle of the pre~ent invention.
Figure 8 is a cross-sectional view of an alternative
tundish and nvzzle of the present invention.
Figures 9, 10 and 11 are enlarged cross-sectional
views of the nozzle area of a tundish of the present invention
illustrating ~quentlally the disposition of the nozzle with
respect to a castlng surface.
Figure 12 is a cross-sectional view of an alternative
tundish ~nd nozzle o~ the present invention.
Figure 13 is a top elevation view of an lnsert
~0 on a tundish of the present invent~on.
Figure 1~ is ~n enlarged cross-~ectional view
of the nozzle area of a tundish of the present invention.
~~
3()87~
1 Detailed Descri~tion
Referring particularly to the drawings, Fig~re
1 generally lllustrates an apparatus for ca~ting metallic
strip material lO in accordance with the present inven~ion.
This ~pparatus includes an element 12 upon wh~ch the strip
10 is cast. In a preferred embodiment a continuous strip 10
is cast onto a smooth, outer peripheral surface 14 of a
circular drum or wheel as shown in Figure 1. It should b~
understood that configurations other than circular may b~
employed. For example, a wheel with a smooth, frustoconical
outer periph~ral surface (not shown) may be employed. Also,
~ belt capable of rotating through a generally ovular path
may also be employed as the casting element. Regardless of
the configuration employed, the cooled casting surface
lS ~hould be at least as wide as the strip to be cast.
In ~ preferred embodiment, the casting elem~nt 1
compri5es a water cooled, precipitation hardened copper
alloy wheel containing about 90% copper. Copper and copper
alloys are chosen for their high thermal conductivity and
wear re~i~tance, however, 6teel, brass, aluminum, aluminum
alloys or other materials may be utilized alone, or
~nultipiece wheels having sleeves of molybdenum or other
material may also be employed. Likewise~ cooling may b~
aecompll~hed with the u~e of a medium other than water.
W~ter ls chosen or its low cost and it~ ready availability.
~n the operation of the ~trip ~a~ting ~pparatus
of the present ~nvention, the surface 14 of the casting
wheel 12 mu~t be ~ble to ~b~orb the heat gener~ted by
1 contact with molten metal at the init~al casting poin~ 16
and ~uch heat must diffuse ~ub~tantially into the copper
wheel during each rotation of the wheel. ~eat diffusion,
cooling, ~ay be accomplished by delivering a sufficlent
quantity of water through internal passageways located near
the periphery of the casting wheel 12. Alternatively, th~
cooling medium may be delivered to ~h~ underside of the
casting ~urface. Vnderstandably, refrigeration techniques
and the like may be employed to accelerate or decelerate
cooling rates, and/or to effectuate wheel expansion or
contraction during strip casting.
Whether a drum, wheel or belt i8 employed for
casting, the casting surface should be generally ~mooth and
symm~trical to maximize uniEormity in strip casting. For
lS example, in certain strip ca~ting op~rations wherein it is
desired to cast uniform gage strip, the distance between
the outer peripheral casting surface 14 and the suraces
deflning the orifice of the nozzle which is feeding the
molten material onto the casting ~urface ~hould not
~ubstantially deviate ~rom a desired or set distance. This
dlstance ~hall hereinafter be called standoff distance
or gap. It is understandable that the gap mu~t be
sub~tantially maintained throughout the casting operation
when it i~ the intentlon of the operator to cast uniform
~trlp material.
It ~hould al~o be understood that if the casting
elemen~ i~ a drum or a wheelv the element should be
caYefUlly congtructed ~0 &S not to be out-of-round during
8~
1 operation to in~ure uniformity in strip casting. Along
the~e lines, it has been found ~hat a drum or wheel whi~h is
out-of-round by about 0.020 inch, or more, may have a
magnitude of dimensional instability which, unless correc~ed
or compens~ted during operation, may be unacceptable for
certain strip casting operations. It has been found that
accept~ble dimensional symmetry, as well as the elimination
of problems a~sociated with weld porosity may be more
readily accomplished by fabricating a wheel or dru~ from a
single, inte~ral slab of cold rolled or forged copper.
However, as mentioned above alternative materi~ls may be
employed.
The molten material 20 to be cast in the apparatus
described herein is preferably retained in a crucible 22,
IS or tundish, which is provided with a pouring orifice 2~ or
nozzle. The nozzle i8 typically, though not nece~sarily,
located at a lower portion of the tundish 22 as shown in
Figure 1.
The tundish 22 is constructed for receiving
and holding molten metal therein. It will be appreciated
that appropriate materials mu~t be utilized for the tundish
22 to with6tand the molten metal conditions, and wher~ the
tundish 22 is not a monolithic struc~ure, the joints and
~e~ms between ~eparate pleces of ~he tundish mus~ be assembled
to prevent molten metal leakage during su~tained operation.
The tundish 22 ha~ a front wall ~6 ~nd a rear
28, with refipect to the caRting direction, which casting
~irection i~ ~ndic~t~d by the arrow ad~acent the casting
~1 1--
~ ~8~)8~
1 ~urface lq in Figure 2. The front wall 26 has an inside
~urface 30 and an outside surface 32 with respect to the
molten metal holding portion of the tundish 22. Lik~wise,
the rear wall 28 has an inside surface 34 and an outside
~urface 36 with respect to the molten metal holding portion
of the tundish 22. The inside surfaces 30 and 34 extend
toward the nszzle area of th~ tundish 22~ It should be
understood that the molten metal holding portion of the
tundish 22, which is formed between the inside surfaces 30
and 34, may take a variety of forms or shapes. However, it
is preferable that the upper portion of the tundish 22 hav~
a significantly larger cross-sectional volume than that of
the nozzle area of the tundish 22 in order that the molten
metal head height, above the nozzle, is substantially
unaffected by minor variations in molten metal volume in th~
tundish 22. Such ~tructurè contribut~s to the maintenanc~
of a substantially constant metallostatic h~acl pressure at
the no~zle, even with minor variations in metal volume in
the tundish 22.
It is also preferable that the inside surfaces
30 and 34 converge toward one another in the direction of
the nozzle, and that such surfaces 30 and 34 be radiu~ed,
rounded or generally curvilinear at locations of turns or
r bends ~n the tundish 22 to minimize metal turbulence th~r~in
2$ durin~ the casting operation.
~ he molten metal holding area, formed between
the in6ide ~urfaces 30 and 34, ~hould be enclosed with
sidewall 38 and 40, as indicated in Figur~ 3. It i~ noted
~ ~ ~087~
1 that no fi~ed width dimension is fihown in Figure 3. It
has been found that ~ tundish and nozzle of the present
invention may be constructed by first cutting or carving
refractory boards, such as insulating boards made from
S fiberized kaolin, into the desired tundish shape, such as
that shown in Figure 2. Any number of thes~ boards 42 may
be stacked upon one another to obtain the desired tundish
and nozzle width. There is not expected to be a restriction
on th~ maximum width of th~ tundish and nozzle of the
present invention, and widths in excess of thirty six inches
are comprehended by the present inv~ntion. After the
requisite number of boards are stacked the inside surfaces
30 and 34 are formed by th~ stack may be sanded or otherwise
finished to provide generally smooth inside su~faces 30 and
34 across the width of the stacked elem~nts forming the
tundish 22. It should also be understood that single piece
mate~ials may be used to construct the tundish in which cas~
stacking would not be necessary. Aft~r the carved boards 42
are Rtacked, th~ stack may be disposed between uncarved
boards 44, which may serve as the sidewalls 38 and 40 for
the tundish 22.
To hold the stacked boards, including the sidewalls
38 and 40 in position, it has been found convenient to
dispose a metal plate 46 against the outside surface of each
~ldewall and to bolt the plates together at a ~uitable
number oP location~ about the tundish~ thereby tightly
compacting the tundish assembly. With ~uch assembly, a
minor ~mount of molten metal may tend to flow into the seams
-~3-
~ ~8087~
between the boards ~ but the compaction of the assembly and
the high in~ulative value of ~he boards causes the metal to
freeze, and thereby arrest the flow before it adversely
affects the tundish or the strip casting operation. It
~hould be under~tood that the tundish 22 of the present
invention may be assembled with refractory cements, or khe
like, or may be constructed of a monolothic structure which
does not require assembly.
As discussed above, a nozzle 24 is located i~
the tundish 22, preferably in a lower portion thereof. The
nozzle 24 comprises an orifice pas~age 80 defined between
the first inside ~urface 34 of the rear wall 28 of the
tundish 22 and the second inside surface 48 of an insert
50. A portion of the inside surface 48 of an insert 50,
which is Figure ~, is disposed against a portion of a ridge
52 ~ormed by the outside surface 32 of the front wall 26
of the tundish ~2. As shown in Flgure 3, the insert 50
completely encloses the ori~ice passage, or slot 80 such
that the end portions of the inside surface 4B of the insert
S0 are dispo~ed against ridges on the sidewalls 38 and 40 of
the tundish 22. Such disposition may be necessary to
maintain the ~tability of the insert 50. In a preferred
embodiment, a portion of the inside surface 4B of the
in~ert 50 extends beyond the ~ront wall 26 of the tun~ish 22
;25 ln the di~ection of the casting surface 14. It ~hould
be appreci~ted that the extent of the insert 50 may be
~lu~h with the extent of the ront wall 32 of the ~undi~h
a~ mea~ured in a direction toward the casting 3urface~
-1~
D 1 80875
1 Preer~bly, the e~tent of the insert~ as indicated by
numeral 70 in Figure ~, is maintained at a distanee of at
least 0.010 inch from the insid~ ~urface 34 of the rear wall
28, at the orifice pas~age 80.
Preferably~ the insert 50 is reciprocal on the
ridge 52 of the tundish 22 in a direction toward and away
from the c~ting ~urface 14. Such reciprocal disposition of
the insert 50 may be o~tained by manual adj~stment~ b~t
preLerably the insert 50 should be automatically adju6table
and continuously m~asurable to insure that desir~d spacings,
gaps and the like are malntained during casting. In a
preferred embodiment, as shown ln Figure 2, the insert 50 is
reciprocal in a generally horizontal plane. However, it
~hould be understood that the insert 50 may be reciprocal
~long an angular path, aq shown in Figures 4 and 6, along an
arcuate path as shown in Figure 5, or in a generally
vertical plane as shown in Figure 7. In another embodim~nt,
as illustrated in Figure 1~., the insert 50 may be disposed
on an element 55 which element 55 may be adjus~ed ~o any
number of positions by rotati~g thereof about a pivot point
58 to obtain the desired disposition of the lnsert 50.
Although the lnfiert 50 may be reciprocal toward
an~ away from th~ casting surface 14, the in~ert 50 mu~t not
be permitted to llft from $ts fixed position against
2~ th~ rldge 52 ~f the tundish 22. This fixed pol;ltion is
nece~sary to counteract the pre~sure which the ~olten metal
may ~xhlbit against the ins~de surface 48 of the ln~ert 50.
In on~ embodiment, a weight may be placed on a top 6urface
-15-
~ ~ ~0~ 75
1 56 of the in~ert 50. In another embodiment, a pres~ure
exerting device such as a spring biased device, a hydraulic
cylinder arrangement, a clamp or the like, may be used to
urge the in ert against the ridge 52 of the tundish 22. In a
~urther embodiment, as illustrated in Figure B, the insert
50 may be held in a slot which provides such required
fixed ~upport for the insert 50. Wote that even with the
arrangement illustrated in Figure ~, the insert 50 is still
reciprocal toward and from the casting surface.
In addition to being reciprocal toward and
from the casting surface 14~ the insert 50 may be able to be
canted ~uch that one end portion 60 of the insert S0 may be
moved toward the respective end portion of the casting
~urface 14 while the other end portion 62 is moved away from
the other r~spective end portion of the casting ~urface 14,
as shown in Figure 13~ An lnsert structure which may be
utilized to facilitate such canting, as shown in Figure 13,
includes an arcuat~ rear surface 64 for the inqert 50, a
portion of which abuts a rearward wall 66 of the tundish 22
at a plvot point fi8. By rolling th~ rear surface 64 of the
insert 50, minor canting alignments can be effectuated.
Regardless of the means employed to cant the insert 50 with
respect to the casting surface 14, such canting variations
may be helpful to as~ure that uniform gage ~trip material is
~5 produced~ e~pecially during prolonged casting oper~tions.
~uch canting varl~tions may also assist in removing
~ntrapped material from the nozzle during casting~ or for
intentionally cas~ing strip materlal having a varying gage
~cro6s ~he wldth of th~ ~rip material.
~16-
~ ~û8'75
1 It should be appreciated that the insert 50
of the present invention may be easily replaced, although it
i~ preferred that the inserts 50 and the tundish 22 be
reused, either together or ~eparately a It should also be
noted that damage to an in~ert 50 will not render the entire
tundish 22 unserviceable. In the event of such insert
damage, the insert S0 is merely replaced and the process
continues.
In a preferred embodiment, as shown in enlarged
cross-~ection in Figure 14, the insert 50 is provided with a
front edge surface 70. In such embodiment, as the insert 50
has been reciprocated to its operating position, the front
edge surface 70 faces the casting surface 14 and is disposed
to within less than 0~120 inch of the casting surface 14.
Preferably, the front edge surface 70 is disposed to
within 0.0~0 inch and in a more preferred embodiment, to
within 0.020 inch of the casting surface 14. It is also
preferred that in ~uch embodiment the front edge surface 70
be in substantially complete parallelism with the casting
surface 14 movable therebelow. When utilizing a drum or
wheel, and a refractory insert 50, such complete parallelism
may be accomplished by placing a sheet of sandpaper, or the
like, against the casting surface 14 with the grit side of
the ~andpap~r ~cing the insert 50~ By moving the insert 50
into tight contact with the casting surface 14~ with the
sandpaper di~posed therebetween, and by moving the casting
surfaca and ~andpaper ~imu.ltaneously past ~he inBert 50, the
~ront edge ~urfac~ 70 is ground by the grit side o~ the
~7-
~ 7 ~08'7~
1 sandpaper into substantially complete parallelism with the
casting surface 14. Such substantially complete parallelism
may be achieved even when round or other curvilinear casting
surfaces are employed. To achieve such parallelism by this
procedure 400 or 600 grit ~andpaper has been found to be
adequate. The outside surface 36 of the rear wall 28
dispose~ ~djacent the casting surface 14 may be bro~ght into
substantially complete parallelism therewith by this same
procedure ~
By maintaining the front edge surface 70 in
substantially complete parallelism with the casting surface
14, the ~tandoff distance, or gap h, between the front edge
~urface 70 and the casting surface 14 is maintained
throughout the length thereof. It has been found that the
gap h between the front edge surface 70 and the casting
surface 14 must be maintained at less than about 0.120 inch
in order to successfully cast strip material. Preferably,
this gap is maintained at less than about 0.080 inch and for
casting certain alloys into thin gage strip, gaps less ~han
0.020 inch are preferred. Alternativeiy, the front edge
~urface 70 of the insert S0 may comprise a line e~tending
acro6s the tundish, at a gO junction, or corner, o
~he front edge of the insert 50, as opposed to a
deflned ~urface length b as ~i~cusse~ above. To this
~5 extent the length b of the front edge surface 70 could
be ~ero~ Even i surface 70 approaches a line across
the tundi~h, such surface must be dispo6ed w~thin 0.120
inch of the castlng ~urface 14 to 5ucc2s.sfully cast
~trlp material.
-18-
) 8 7 5
1 It has also been found that the gap h between the
outside surface 36 of the rear wall 28 and the casting
surface 14, a~ best shown in Figure 14, does not appear
to be as critical~ What is preferred with respect to
the outside surface 36 of the rear wall 28 i5 that the
surface 36 be disposed as close as possible to the
casting ~urface 14, without causiny any interference
for the moveable casting surface therebelow. Accordingly,
the outside surface 36 of the rear wall 28 at the
orifice passage 80 of the nozzle may just clear the
casting surface 14, i.eO, perhaps within about .092
inch, as shown in the drawing. Such spacing must not
be large enough to allow significant molten metal
backflow therebetween during casting. Alternatively,
the outside surface 36 may be tapered from the orifice
of the noz~le in a direction away from the casting
surface 14.
The crucible 22 is preferably constructed of
a material having superior insulatin~ ability. If the
insulating ability is not sufficient to retain the molten
material at a relatively constant temperature, auxiliary
heaters such as induction coils may have to be provided in
and/or around the crucible 22, or resistance elements such
as wires may be provided. ~s mentioned above~ a convenient
2S material for the crucible is an insulating board made grom
~iberized koalin, ~ naturally occurring, high puri~y,
alumina~ilica fire clay. Such insulating material is
~lg--
1 ~ availa~le under the trade name ~ HS board.
~owever, for su~tained operations, and for casting
higher melting temperature alloys, various other
material~ may have to be employed for constructing the
cruc1ble ~r the insert including graphite, quartz, clay
graphite, boron nitride, 5ilicon nitride, boron carbid~,
silicon carbide, alumina, zirconia and various combinations
or mixtures of such materials~
Although other materials are comprehe~ded by the
present invention, the insert 50 is preferably constructed
of boron nitride, silicon nitride, silicon carbide, boron
carbide, zirconia or quartz.
It is imperative that the orifice passage 80 of
the nozzle 24 remain open and its configuration remain
1~ ~ub~tantially stable throughout a strip castin~ operation.
It is understandable that the orifice passaye 80 should
not erode or clog, significantly, during a strip
casting sequence or certain objectives such as maintaining
uniformity in the casting operation and of minimizing
metal flow turbulence in the tundish 22 may be defeatedO
Along these lines, it appears ~hat certain insulating
material~ may not be able to maintain their dimensional
~tability over long casting periods. To obviate this
problem the nozzle 24, especially that portion defined
2$ by the in~ert 50, may be constructed of a material
which i8 better able to maintain d.imensional ~tability
and lntegrity during exposure to high molten metal
temperatures ior prolonged time periods.
-20-
~6 r~ ~ rv)~k
8 7 ~
1 The drive system and housing for ~he dFum, wheel
or other casting surface 14 of the present ~nvention should
be rigidly constructed to permi~ drum rotat~on without
structural instability which could ca~se the drum to slip or
vibrate. In particular, care should be take~ to avoid
resonant frequences at ~he operating speeds or the drum.
The casting surface should be capable of mov~ng at a surface
speed of from about 200 linear surface ~eet ~er minute to
moxe that about 10,000 linear surface feet per minute.
When utilizing a drum having a eircu~ference ~f about 8
feet, this rate calculate~ ~o a drum speed fr~m about
25 rmp to about 1250 rpm. A three horsepower variable
speed reversible~ dynamically braked motor provides an
adequate drive system for an integral copper casting
lS drum 2 to 10 inches thick and about 8 feet in circumference~
Power requirements may have to be modi~ied depending
upon the type and size o~ casting surface 14 employed.
It should be appreciated that the casting surface 14
can be moved in a direction opposite to that illustrated in
the drawing, and that the tundish 22 may be disposed at
any location about the cas~ing wheel illustrated in the
drawing.
In one embodiment, the casting sur~Ace 14 on
the wheel or drum o~ the apparatus of ~he present invention
.25 1~ smooth~ It has been ~ound that in certain applications
~or producing amorphous materials, finishing the peripheral
~u~Pac~ 14 o~ a ca~ting drum 12 with 400-grit paper and
-21-
8 7 ~
1 preferably with 600-grit paper may yield improved product
uniformity. It is anticipated that an etched surface may
yield the best, smooth s~rface, product uniformity.
A preferred structure for the nozzle 24 of ~he
apparatus of the present invention is shown in enlarged
cross-3ection in Fig~re 14. In one embodiment of this
apparatus~ the dimensions indicat~d in Figure 14 have the
following preferred limitations.
more
preferred preferred
dimension desi~nation limitation limitation
.
a nozzle gap .010 - .080 in. oO25 in. - .035 in
b length of .00 - .16 in. .02 - .06 in.
front edge
~urface
h insert gap le~s than .080 in~ .010 - .020 in.
e rear wall gap less than .020 in. less than .010 in.
~ imension c, representing the width of the rear
wall at the orifice of the nozzle 24 and d represen~ing the
20 width of the inser~ 50, appear ~o be arbitrary and do not
appear to be ~ignificantly critical to the strip casting
operation. In fact, it should be appreciated that dimension
c could apprach zero if the inside sur face 34 of the rear
wall could be tapered completely through the orifice passage
~S ~0.
Molten metal turbulence during ~trip casting
~hould be minimi~ed, and perhaps ~voided by relieving sharp
corner~ of the nozzle in the direction of casting. It will
be under~tood that Guch rounding may be accompllshed by
~22-
1 constructing the tundish walls of an eroding material, such
as Raowool HS board, which may provide natural erosion as a
result of the ~trip casting operation. Turbulence may also
be minimlzed by rounding other corners such as corner 72 on
the l~sert 50 and corner 74 on the rear wall 28 at the
no2zle as shown in Figure 14.
In an exemplary operation of ~he apparatus of
the present invention, molten metal is delivered to a heated
crucible 22. It i5 understood that a heater, such as
induction coils of resistance wire, may be provided in and
above the crucible 22 to maintain relatively constant molten
metal temperatures as may be desired. Also heating devices
may be employed on or near the insert 50 because of the
general accessibility of the insert 50 in the apparatus of
the pres~nt invention. For example, resistance wires, or
heating coils may be provided in a bottom portion of a
pressure exerting device located on or near the insert 50.
Al~o, a torch may have its fl~me directed against the insert
50 during casting. In the operation of the apparatus of
this invention metal may be poured directly into a preheated
crucible. Such metal preheat temperature and the heating of
the tundlsh ~2 and insert 50 should prevent freezing or
clogging o~ the orifice pa~sage or slot 80 during the
initial ca~ting operation~ and ~he ~emperature of the
2S flowing metal should thereafter keep the crucible 22 and the
insert 50 at ~u~ficlent temperature to in~ure uninterrupted
molten matal ~low ~hrough the oriflce passage ~0. In
certain applications, the nozzle ~hould be externally heated
-23
7 5
1 throug~out the casting operation. Also, the metal which is
fed to the crucible 22 may be superheated to allow a certain
degree of temperature loss without adversely affecting metal
flow~
S Also; a metallostatic head hei~ht in the tundish
22 should be maintained at a relatively constant level
throughout the casting operation to assure that a relatively
constant static head pressure may be maintained at the
orifice of the nozzle 24. This may be accomplished by
initially pouring the molten metal into the crucible to the
desired height and thereafter controlling the rate at which
additional molten metal is poured into the crucible to
maintain the metallostatic head. It is under~tandable that
the rate at which additional molten metal is fed to the
crucible 22 should be in substantial conformity with the
rate at which metal flows from the no~zle orifice onto the
casting surface 14 in forming trip material. Maintenance
of a relatively constant height of metal in the crucible
assures that the molten met~l flow pre sure through the
ori~ice is maintained re:latively constant to as not to
adversely afPect the casting operation or the quali~y of the
~trip material. Alternatively, externally applied pressure
may be employed to control ~he pressure at the nozzle.
In a pre~erred embodiment of the presen~ .invention,
the tundi6h 22 ~nd the insert 50 are indepenclently or
dependently moveable ~oward ~nd from ~he ca~ting ~urface 14.
A~ ~hown Bequentially ln Figures 9, 10 and 11. The tundish
22 and the insert 50 therean, are in a position away from
-~4-
1 the casting surface 14. ~he cast ng surface 14 is being
moved past the nozzle 24 at a rate of from about 200 to
10,000 linear feet per minute. Prior to or simultaneously
with the pouring o~ molten metal into the tundi~h, the
tundish 22 i9 moved toward the casting surface 14, such that
the outside surface 36 of the rear wall 28 at the nozzle 24
ls located to within 00020 inch, and preferably within ~010
inch, of the casting surface 14 as shown in Figure 10. In a
preferred embodiment the outside surface 36 is moved
as close as po~sible to the casting surface 14 without
interfering with the motion of the casting surface 14
~herebelow.
Usually, the insert 50 is not moved Erom its
position relative to the tundish 22, as the tundish 22 is
lS moved toward the casting surface 14. However, either after
the outside surface 36 of the rear wall 28 is in position,
or while the outside surface 36 is being positioned, the
position of the insert 50 should be adjusted such that
the front edge surface 70 is within ~.120 inch and more
preferably to about .01~ to .020 inch of the casting surface
14, a~ shown in Figure 11~ The tundish 22 and insert 50
should be position soon after casting begins. It will be
appreciated that the extent of the gaps h and/or e may be
adjusted during chsting by the apparatus of the present
lnvention, which provides significan~ flexibility in the
aasting operatlon~
It should be understood that the po~ition of the
insert S0 on the tundish 22 may be establlshed, set and
ma~ntain~d before the enti~e assembly, i~e., tun~ish 2
~25-
)8~
lncluding the insert 50t is moved toward i~ ca~ting
position. With such arrangemen~c the disposition of the
insert 50 is properly attained as the dispositio~ of the
outside ~urface 36 of the rear wall 28 is attained. In such
embodiment the insert 50 may be fixedly mounted in proper
relative position on the tundish 22.
During casting of str$p material, the tendency
of the strip 10 to adhere to the c~stiny 6urface 14 for a
significant distance, such as several feet or more, beyond
the nozzle has been observed~ It is understandable that if
the strip material remains on a rotating casting drum or
wheel 12 for a full revolution damage to the crucible could
result. It has been found that the use of a doctor blade,
such as a knife type element riding at or near ~he drum
surface 14, approximately 2.5 to 5 feet from the orifice
easily counters such adherenceu With ~uch an arrangement,
the cast strip may be removed from the drum by such doctor
blade, Such doctor blade has been found particularly useful
in the production of thinner amorphous strip materials which
appear to have a greater tendency to adhere to the casting
~urface 14 than do the crystalline strip materials. It is
believed that the force which retains the fitrip on the
casting ~urface reflects the quality o the thermal contact
between the strip and the casting surf~ce. Alternative
~5 arrangemen~s, ~uch as an air kni~e, may also be employed to
~eparate the ~trip rom the wheel.
The casting o~ relatively high quallty ~trip
material including amorphous materlal, which ~or ~he purpose
of thi~ lnventi~n lncludes ma~erial~ whi~h are at least 25%
~ ~8(~8 ~5
amorphou~, is feasible and practical using the apparatus and
procedures described above. Understandably, the quench
rates must be higher for amorphous material as compared to
crystalline materlalO Quench rates may be accelerated such
as by increasing the speed of the casting surface, or the
like. It is important to recognize that the proce3s
operates in two effective modes. Wi~ll the orifice quite
close to the drum ~urface, strip perhaps 0.001 to 0.003
inch thick can be cast of either amorphous or crystalline
materials. If the front edge surface 70 of the insert 50 is
moved away from the casting surface 14, and as casting surface
speeds are reduced, strip perhaps 0.005 to 0.050 inch thick
can be cast. In this later mode, the quench rate is much
lower due primarily to increased product thickness.
lS ~he problems associated with flexibility
reproducability and in-process control of strip casting
operations, a~ well as certain problems related to metal
turbulence have been overcome by the apparatus of the
present invention.
Whereas the pre~erred embodiment has been
de~cribed above for ~he purposes of illus~ration, it will be
apparent to those skilled in the art that numerous variations
o~ the details may be made without departing from the
invention.
I claim:
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