Note: Descriptions are shown in the official language in which they were submitted.
Brief Summary of the Invention
Releva~t subject matter is dIsclosed in co-filed
Canadian Patent Applications entitled "Strip Casting
Apparatus" Serial Number 366,164; "Method and Apparatus
for Strip Casting" Serial Number 377,201; "Method of
Repetitiously Marking Continuously Cast Metallic Strip
Material" Serial Number 377,216; and "Apparatus :Eor Strip
Casting" Serial Number 377,134, all of which are assigned to
Battelle Development Corporation.
The present invention relates to the casting of
strip material at high quench rates and at high production
rates. More particularly, the present invention is directed
to an apparatus for rapidly cas-ting thin metallic strip
material characterized by an outwardly diverging nozzle design.
The apparent advantages and economic significance
of producing thin metallic strip material by a casting
process, as compared to the conventional rolling or reducing
operations, are numerous. The fact that strip casting may
be performed at such high quench rates to produce amorphous
material is even more meaningful. However, it is equally
apparent that there are 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 composikion and structure. For these reasons,
those skilled in the art appreciate the intricacy involved
in the development of a commercially successful strip
casting apparatus.
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.~..".~,",. ;.
, ~ ..
1 The general concept of casting thin metallic
materials suc~ a~ sheet, foil, strip ~nd ribbon was disclosed
~n the early l900's. For example, U.S. Patents 905~758 and
993,904 teach processes wherein molten material flows onto a
moving cool surface and the material is drawn and hardened
thereon into a continuous thin 6tripO These references
teach that molten metal may be poured onto ~he smooth
peripheral surface of a rotating liquid cooled copper dr~m
or disc to form strip materials. Despite early disclosure
of such ~oncept, there i~ no evidence of commercial 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 molten metal has been disclosed.
These references teach that a convex meniscus of molten
material should project from a nozæle. A heat extracting
surface, 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 met:al to continuously
draw material from the meniscus to form a uniform continuous
product. The above-described method is commonly called the
nmelt drag" process as the heat extracting surface moving
pas~ the meni~cus of molten metal at the nozzle orifice
actually has an effect on the rate of molten metal flow, or
drag, through the nozzle.
More recent strip casting developmen~s ocus on
relat~vely narrow refinements ln the metallic s~rip casting
art. ~or exa~ple, U.`S. Patent 4~142,571 is particularly
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, L~
1 directed to a ~lot construction in a metal strip casting
nozzle having ~tringent dimen~ional requirements. Also,
U.S. Patent 4,077,462 pertains to the provision of a specific
construction for a stationary housing above the peripheral
6urface of a chill roll used for strip cast.ing.
There are a number of other rapid ~uenching
techniques known in the art. For example, melt spinning
processes of producing metallic filament by cooling a fine
molten stream either in Pree flight or against a chill
block have been practiced. Also known are melt extraction
techniques, such as crucible melt extraction disclosed in
U.S. Patent 3,838,185 and pendant drop melt extraction
techniques taught in U.S. Patent 3,896,203. It has been
found difficult to produce uniform heet or strip by such
alternative techniques of raFid casting. There are many
factors, such as casting temperature and pressure, auxiliary
surface cooling rates, ~urface coatings for the casting
surface, and the like which appear to affect the product
thickness and the quality of rapidly cast strip material.
Despite the relatively long history o the
art of ~trip casting, and the recent developmen~s in this
area, strip casting is not a widely accepted and commercially
significant operation at the present time. I~ appears that
various improvements, modification~ and innovations are
required in the art to effectuate a significant commercial
~mpact in the art of ~trip casting. In particular, proper
relationships among such variables as molten metal tundish
construction, nozzle orifice ~ize and dimensions~ spacing
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1 from a ca~ting surface, ~peed at which uch surface is
moved, quench rates, metal temperature and feed rates, and
the like may requlre more accurate identification and
interrelation in order to accompli~h the uniformity and
consi~tency required for successful, commercial production
o~ cast strip In particular, certain nozzle and 610t
structures and their dimensional relationship to the casting
surface onto which strip material is cast, h~ve been found
to be inadequate to yield uniform strip castin~ results when
utilized in various casting parameters.
Accordingly, a new and improved 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
efficient and more effective than the structures disclosed
in the prior art, and should lead to reproducibility,
uniformity and consistency in strip casting.
~he present invention may be summarized as
providing a new and improved apparatus for continuously
casting metallic strip material. Such appar~tus comprises a
tundish and a nozzle comprising a slotted element, with the
slot having substantially uniform cross~sectional dimensions
throughout the longitudinal extent thereof. Di~posed
outside the nozzle is a cooled casting surface movable past
the nozzle in a directon ~ubstantially perpendicular to the
longitudinal axis of the slot. ~he slot is defined between
first and second lips of the nozzle which have inside
~urfaces facing one ~nother at least at an inner portion
1 of the slot. The facing ~nside surfaces diverge from one
another at an outer port~on of the slot. The Pirst and
~econd lips are further provided with bottom sufaces facing
the casting surface at a standoff distance less than 0.120
inch.
Among the advantages of the present invention
is the provision of a strip casting apparatus which is
capable of continuously casting metallic strip material of
substantially uniform dimension and substantially uniform
Quality throughout its length.
Another advantage of the present invention is the
provision of a strip casting apparatus having an outwardly
diverging nozzle construction which promotes the efficient
rapid casting of metal strip material.
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 ca~ting apparatus which can effec~uate sufficiently
rapid quenching of the produced strip to result in the
production o amorphous strip. ~owever, it should be
understood that the production of continuously cas~ ceystalline
material is also comprehended by the present invention.
A further objective of this invention $s to
identify certain design and dimensional requirements,
particularly with regard to an outwardly diverging nozzle
1 structure, which permit continuous and repetitious rapid
casting of ~etallic strlp material of uniform dimension and
unlform quality.
These and other objectives and advantages will
be more fully understood and appreciated with reference to
the following detailed description and the accompanying
drawings .
Brief Description of the Drawings
Figure 1 is an elevation view, partially in
cross-section, illustrating a typical apparatus used for
continuously casting strip material,
Figure 2 is a cross-sectional view of an outwardly
diverging nozzle in a strip casting apparatus of the present
invention.
Figures 3r 4 and 5 are cross-sectional views
of alternative outwardly diverging nozzles in strip casting
apparatu~ of the present invention.
Detailed Description
Referring particularly to the drawings, Figure
1 generally illustrates an apparatus for casting metallic
strlp material 10 in ~ccordance with the present invention.
This apparatus includes an element 12 upon which the str ip
10 i~ cast. In a preferred embodiment a con~lnuous strip 10
1~ caEt onto a ~mooth, outer peripheral surface 14 of a
circular drum or wheel as ~hown ln Figure 1. It 6hould be
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?!$ ~
1 understood that confi~uration~ other than circular may be
employed. Por example, a wheel with a smooth, frustoconical
outer peripheral surface (not 6hown) may be employed. Also,
a 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 urface
~hould ~e at least as wide as the trip to be cast.
In a preferred embodiment, the casting element 12
comprises a water cooled, precipitation hardened copper
alloy wheel containing about 98% copper and about 2~
chromium~ Copper and copper alloys are chosen for their
high thermal conductivity and wear resistance, however,
berillium copper alloys, steel, brass~ aluminum, aluminu~
alloys or other materials may be utilized alone, or in
combination. For example, multipiece wheels having sleeves
of molybdenum or other material may be employed. Likewise,
cooling may be accomplished with the use of a medium other
than water. Water is typically chosen for its low cost and
its ready availability.
In the operation of the strip casting apparatus
of the present invention, the surface 14 of the casting
wheel 12 must be able to absor~ the heat generated by
contact with molten metal at the initial castiny location
16, and ~uch heat must be conducted substantially in~o the
copper wheel during each rotation of the wheel. The initial
ca6tlng point 16 refer to the approximate location on the
casting 6urface 14 where molten metal 20 from ~he tundish 22
fir~t contact~ the casting ~urface 14. Cooling, by heat
1 conduction, may be accomplished by delivering a 6uf~icient
qu~ntity of water through lnternal passageways located near
the periphery of the casting wheel 12. Alternatively, the
cooling medium may be delivered directly to the underside of the
ca~ting surface. Understandably, refrlger~tion techniques
and the like may be employed to accelerate or decelerate
cooling rates, and/or to effectuate wheel expan~ion or
contraction during strip casting.
Whether a drum, wheel or belt is employed for
casting, the casting surface should be generally smooth and
symmetrical to maximize uniformity in strip casting. For
example, in certain strip castiny operations the distance
between the outer peripheral casting surface 14 and the
surfaces defining the orifice of the nozzle which is feeding
the molten material onto the casting surface 14 must not
deviate from a desired or set distance during the casting
operation. This distance shall hereinafter be called
standoff distance or gap. It is understandable that the gap
6hould be substantially maintained throughout the casting
operation when it is the intention to cast uniform strip
material.
It ~hould be understood that lf the casting
element is a drum or a wheel, the element should be
carefully constructed ~o as not to be out~of-round during
operation to insure uniformity in strip casting. Along
these l~nes, it has been found that a drum or wheel which is
out-of-round by about 0.020 inch, or more, may have a
magnitude of dimencional in~tability which unless corrected
g_
1 or compensated during operation~ ~ay be unacceptable for
certain strip casting operations. It has been found that
acceptable dimen6ional symmetry, as well as the elimination
of problems associated with weld porosity may be more
readily acco~plished by fabricating a wheel or drum from a
single, integral slab of cold rolled or forged copper
alloy. ~owever, as mentioned above alternative materials,
including ~leeves and co~tings may be employed.
The molten material 20 to be cast in the apparatus
described herein is pref2rably retained in a crucible 22,
or tundish, which is provided with a pOULin9 orifice 24 or
nozzle. The noz~le is typically, though not necessarily,
located at a lower portion of the tundish 22 as shown in
Figure 1. As will be appreciated from the foregoing
discussion, the nozzle 24 may be a separate element in
the tundish 22, or, the nozzle 24 and tundish 22 may be
monolithic, i.e. integrally formed, with all or any portion
of the tundish 22.
The nozzle 24, located in or forming a lower
portion of the tundish 22 may comprise a slotted element~ as
best ~hown in Figure 2. The slot 30 is preferably
substantially centrally located in the nozzle element 24.
Such approximate central location of the slot 30 helps ~o
asure uniformity as the pressure of the molten metal
bearing thereagainst i8 ~ubstantially equali~ed during
the casting operation. It should be understood, however,
that the slot 30 may be located in off-center posi~ions as
may be desired.
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1 The longitudinal extent o~ the ~lot 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 ~lot, ~nd, slots as long as thirty ix
inches, or longer, are comprehended by the present
lnvention. It is highly desired that the molten metal flow
uniformly through the slot 30 in the noz21e 24 ~f the
present invention in order to produce uniform, high quality
strip material. In an alternative embodiment, strip of
various widths may be simultaneously produced by cutting
multiple longitudinally aligned slots 30 of appropriate
longitudinal extent in the nozzle area of a tundish 22, as
opposed to a single slot 30. Regardless of the ~ize
of the slot 30, or slots, the cross-sectional dimensions of
each 610t 30 should be substantially uniform throughout the
longitudinal extent thereof to produce strip material
having uniform dimensions. In the operation of the str ip
casting apparatus of the present invention, the cooled
casting ~urface 14 moves past the slot 30 in a direction
6ubstantially perpendicular to the longitudinal axis of
the slot~
As shown in Figure 2, the slot 30 is defined
between a flrst lip 32 and a second lip 34 of the no~zle 24
The first lip 32 i located at the downstream edge of the
~lot 30, ~ith re~pect to the direction of movement of the
casting surface 14 indicated by the arrow in ~igure 2. The
~econd lip 34 i3 located at an upstream edge of the slot
with re~pect to the casting direction.
~ ~34 ~ ~
1 The fixst lip 32 and the second lip 34 have
inside surfaces 36 and 3~, respe~t~vely, which are
~ubstantially parallel to and acing one another at least at
an inner portion of the slot 30. The inner portion refers
to that portion which is near the molten metal holding
portion of the tundish, while ~n outer portion of the slot
30 refers to that portion near the casting surface 14. I~
should be understood that the innermost portion of the slot
may be relieved or tapered. For example, the innermost
portion of the fir6t lip 32 and/or the ~econd lip 34 may be
cut into a general V-shape, or a more rounded U-shape
creating an initial funnel type structure for the slot
as illustrated in Figures 3 and 5. Such relief of the
innermost portion of the slot 30 may assist in maintaining
uniform molten metal flow patterns and minimizing
irregularities or turbulence during strip casting. What
is required by the present invention is that the inside
surfaces 36 and 38 are facing and parallel at least at some
inner portion of the slot 30~
Beyond such inner, parallel, facing portion,
! in the direction of the casting surface 14, the inside
surfaces diverge outwardly from one another at an outer
portion of the slot 30. Preferred outwardly diverging
~urfaces are indicated by reference numerals 40 and 42 in
. Figure 2. Such outward divergence of the inside surfaces
may be accomplished by alternative structure~ ~u~h as those
~hown in Flgures 3, 4 and 5. It should be noted that only
one of the in~ide surfaces need to diverge to create the
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1 necessary relation~hip o outward divergence therebetween a~
~hown in Figures 3 and 4. Also, curved ~urface~9 radiused
either inwardly 40 or outwardly 4~ a~ ~hown in Figure 5,
may eQtablish 6uch outward divergence.
S From that outwardly diverging ~urface,~ 40 ~nd 42
the first and second lips 32 and 34 extend to bottom
~urfaces 44 and 46 respectively. Such bottom surfaces 44
and 46 of the lips 32 and 34 face the casting surface 14~
and are located at a standoff distance, or gap, of less than
about 0.120 inch from the casting surface. In a preferred
embodiment, the standoff distance e be~ween the bottom
surface 44 of the first lip 32 and the castins surface 14 is
as small as possible consistent with permitting ~he casting
surface 14 to move thereunder in an unobstructed path. In
any event, the gap e between the bottom surface 44 of the
first lip 32 and the casting surface 14 must be small enough
at the nozzle orifice to prevent significant molten metal
backflow therebetween during casting. The gap d between the
casting surface 14 and the bottom surface 46 of the second
lip 34 is preferably less than 0.080 inch, and for casting
certain alloys into thin gage strip may be less than 0.010
inch.
Preferably, at least a portion of the bo~tom
surfaces 4~ and 46 are in sub~tantially complete parallelism
with the c~sting ~urface 14 movable therebelow, at least at
the nozzle orificeO When utilizing a drum or wheelt and a
refractory nozzle 24, such parallism may be accompll~hed by
placing a sheet of ~andpaper, or the like, against the
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1 ca~ting ~urface 14 with the grit ~ide of the sandpapex
facing the nozzle 2~. By moving the nozzle 2A into tight
contact wlth the casting 6urface 14, with the ~andpaper
disposed therebetween, and by movin9 the casting surface 14
and ~andpaper 6imultaneously past the nozzle 24, the
bottom surfaces 44 and 46 are ground by the grit into
substantially complete parallelism with the casting surface
14. Such parallelism may be achieved even when round or
other curvilinear casting surfaces are employed. To
achieve such parallelism on most refractory nozzles by this
procedure, 400 or 600 grit sandpaper has been Eound to be
adequate.
It has also been found that the corners between
the surfaces defining the slot 30 may be radiused to minimize
molten metal turbulence during casting. In certain instances
sharp corners may be subjected to various pre~s~re and flow
patterns which could create stress conditions for nozzles 24
made of certain materials, and in some instances, may break,
crack or wear during casting in a manner which may upset
balanced strip casting conditions. Providing ~uch rounded
corners may minimize the adver~e affects of such turbulence
and flow through the nozzle 24.
The crucible 22 is preferably constructed of
a ma~erial having superior insulating ability. If the
insulating ability is not sufficient to retain the mol~en
~aterial at a relatively constant temperature, auxiliary
heaters ~uch as indu~tion coils may have to be provided in
~nd/or around the crucible 22, or resistance elemen~s 6uch
1 as wires may be provided. A convenient material for the
crucible is an insulating board made from fiberized kaolin,
a naturally occurring, high purity, alumina-silica fire
clay. Such insulating material is available as KAOWOOL
(a trade mark for fiberized kaolin block) HS board. However,
for sustained operations~ and for casting certain high
melting temperature alloys, various other materials may
have to be employed for construc-ting the crucible or the
nozzle including graphite, alumina graphlte, quartz, clay
graphite, boron nitride, silicon nitride, silicon carbide,
boron carbide, alumina zirconia and various combinations or
mixtures of such materials. It should be understood that
these materials may be strengthened; for example, fiberized
kaolin may be strengthened by impregnating with a silica gel
or the like.
It is imperative that the orifice of the nozzle 24
remain open and its configuration remain substantiall~ stable
throughout at least one, and preferably many strip casting
operations. It is understandable that the orifice should
not erode or clog, significantly, during strip casting.
Along these lines, it appears that certain i~sulating
matierals may not be able to maintain their dimensional
stability over long casting periods. To obviate this
problem, lips 32 and 3~ forming th~ orifice oE the nozzle 2
may be constructed of a material which is better able to
maintain dimensional stability and integrity during e~posure
to high molten metal temperatures for prolonged time periods.
Such materials may take the form of a single, generally
-15-
.,
~.
1 semi-circular element with a slot 30 cut therethrough or a
pair of insert6 held in the crucible to form a slot 30
therebetween. In a prferred embodimen~ the slot or slots in
single elements may be cut ultrasonically to in~ure that the
desired ~lot dimen~ions are accurately provided. Such
nozzles 24 may be constructed of materials ~uch as quartz,
graphite, clay graphite, boron nitride, alumina graphite,
silicon carbide, stabili~ed zirconia ~ilicate, zirconia,
magnesia, alumina or other similar molten metal resistan~
material. Such nozzle6 24 may be held in the orifice of the
crucible mechanically, with pressure, and/or with the aid of
adhesives such as various refractory cements, ~prinq biased
mechanisms, or the like.
The drive system and housing for the drum, wheel
or other casting surface 14 of the pre~ent invention should
be rigidly c~nstructed to permit drum rotation without
structural instability which could cause the drum to slip or
vibrate. In particular, care should be taken to avoid
resonant freguences at the operating speeds for the
casting &urfce 14. The casting surface 14 should be capable
of moving at a ~urface 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 feet~ this rate calculates to a
drum speed from about 25 rpm to about 1250 rpm. A three
horsepower variable speed rever~ible~ dynamically braked
motor provide~ ~n adequate drive ~ystem for an lntegral
copper alloy casting drum ~pproximately 2 inches thick and
about 8 eet in circumference.
1~
1 In one embodimellt, the casting surEace 14 on
the wheel or drum of the apparatus of the present invention
is smooth. It has been Eound tha-t in cer-tain applications,
such as for producing amorphous materials, finishing the
peripheral surface 14 of a casting drum 12 with 400-grit
paper and preferably with 600-grit paper may yield improved
product uniformity.
In a preferred embodiment as illustrated in
Figure 2, the nozzle 24 is defined by an insert made of clay
graphite, a molten metal resistant material, held in the
- walls of the crucible 22. The slot 30 is cut ultrasonically
in the clay graphite nozzle 24. The first lip 32 and
the second lip 34 of the nozzle 24 define the slot 30
therebetween. As alternative preferred examples of nozzle
24 materials, a plate made of quartz or VYCOR (a trade
mark for thermally resistant laboratory glass) material,or
an insert of boron nitride may be employed. The desired slot
forming the orifice 46, may be accurately cut therein with
an ultrasonic drill. A preEerred one piece element
forming a nozzle, as best illustrated in Figure 2, may
~e constructed of a semi-circular ring of molten metal
resistant material. In this example, a slot having a width
of about 0.010 to about 0.080 inch between the facing,
parallel inside surfaces 36 and 38 may be ultrasonically
drilled into a clay graphite insert material, and the insert
is held in the crucible 22. It should be understood that the
design of the insert~may be modified to assist in holding
the insert forming the nozzle 24 in the crucible 22.
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1 A preferred nozzle 24 of the ~pparatus of the
pre~ent invention i~ shown ln enlarged cross~section in
Figure 2. In one embodiment of this apparatus, the
dimensions indicated in Fi~ure 2 h~ve the following
preferred li~itations.
Ji
more
preferred preferred
dimension designation limitation limitation
a bottom surface at least .001 .25 - .50 inch
of first lip inch
b width of slot .020 - .200 inch 0.125 inch
at maximum
divergence
c bottom surface .01 - .16 inch .02 - .06 inch
of second lip
d standoff .01 - .080 inch less than .010
distance be- inch
tween first
lip and ca~ting
~urface
e standoff .01 - .080 inch less than .010
dlstance be- inch
tween ~econd
lip and casting
surface
f width of slot .010 - .080 inch .025 - .035 inch
between parallel,
facing ~urfaces
g depth of diverg- ~050 - .200 inch .125 inch
ing area of slot
h depth of para- .050 - .200 inch .125 inch
llel area of slot
.,
In the production of amorphous strip ma~erials
the width of the slot f is typically in the range of from
about 0.010 to 0.040 inch~ In the production OL cry6talline
strip material~ cuch a~ stainless ~t~el, the width of the
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1 ~lot f may be greater, perhaps a5 high as about 0.080 inch if
thick strip is being unifor~ly produced in accordance with
the present invention. Al~o, the primary purpose of a
relief at an ~nner portion of the slot 30, such as i6 shown
in Figures 3 and 5 is to eliminate clogging of molten metal
in the orifice during strip casting.
In an exemplary operation of the apparatus of
the present invention, molten metal is delivered to a heated
crucible 22. It i8 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. Alternatively, the
molten metal may be poured direc~ly into a preheated
crùcible. The preheat temperature should prevent free~ing
or clogging of the slot 30 during the initial casting
operation, and the temperature of the flowing metal
should thereafter keep the crucible 22 and nozzle 24 at
sufficient temperature to insure uninterrupted mo~ten metal
flow through the orifice. In certain applications, the
nozzle itself may be externally heated throughout 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
through the no~le 24.
Also, a metallostatic head helght ~n the tundish
22 is preferably maintained at a relatively constant level,
typically ~t a level of less ~han ten inches abo~e the
nozzle 24, throughout the casting oper~tion to a~sure that a
--19-
2~
1 relatiYely constant stat~c head pressure may be maintained
at the nozzle 24. This may be accomplished ~y initially
pouring the molten metal into the crucible to the ~esired
height ~nd thereafter controlling the rate at which
additional molten metal i8 poured into the crucible to
maintain the metallostatic head. It is understandable that
the rate at which additional molten metal is fed to the
crucible 22 ~hould be in substantial conformity with the
rate at which metal flows from the no~zle orifice onto the
casting surface 14 in forming strip material. Maintenance
of a relatively constant height of metal in the crucible
assures that the molten metal flow pressure through the
orifice is maintained relatively constant so as not to
adversely affect the casting operation or the quality of the
strip material. Alternatively, externally applied pressure
may be employed to control the pressure at the noz21e.
The nozzle 24 of the present invention is
characterized by ~n outwardly diverginy lip surfaces 40 and
42 at the outer portion of the slot 30. Such structure
~acilitates increa6ed molten metal flow to a moving casting
surface 14, resulting in improved lateral flow of molten
metal onto a casting surface 14, and in the formation of
high quality 6trip material 10. In a preferred embodiment
the width b of the orifice of the slot 30 at the outermost
divergent portion may be as wide as about .200 inch~ which
may be in ~ceEs of about four times the width f of
the slot 30 as measured between the inner, parallel facing
surface6 of the 810t 30. Such ~tructure provides a
relatively l~rge castlng cavity ~t the outer portion of the
-20-
~~ - ~
1 noz~le 24, fed by a relatively narr~w internal orifice.
Lateral movement of the molten metal inside such cavity
during ~trip casting ha~ been found to improYe the
uniformity with which metal is ~upplied to the ca~ting
~urface 14, and thus improve the quality of the 6~rip 10
ca6t thereon. As discussed above, the presence of such
cavity further reduces the tendency ~or nozzle blockage
caused by freezing because the narrow metering orifice is
located further from the cool casting surface 14.
Various alloys may be successfully cast usin~
the apparatus of the present invention, including certain
brazing alloys, including nickel based brazing alloys,
stainless steel and certain silicon steel grades. In
certain applications, the cast alloy ha~ been shown to
be amorphous, and in other applisations, the cast strip
material has been shown to be crystalline.
During casting of strip material, the tendency
of the strlp 10 to adhere to the casting surface 14 for a
significant di~tance, such as several Eeet or more, beyond
the nozzle ha~ been observed. It is understandable that if
the strip material remains on a rotating casting drum or
wheel 12 for a full revolution damaye to the crucible 22,
particularly to the no~zle orifice could resul~. It has
been found that the u~e of a doctor blade ~ ~uch as a knife
ype element rlding at or near the drum surface 14, or an
air wlper, approximately 2.5 to 6 feet from the orifice,
or more, ea~ily counters ~uch adherence. With ~uch an
arrangement, the cast strip may be removed from the drum
-21-
!
26~
1 by such doctor blade. Such doctor blade has been found
particularly useful in the produc~ion of thinner amorphous
strip mater~als which appear to have a greater tendency to
adhere to the casting surface 14 than do the cry talline
strip materials~ It i6 believed that the force wb~ch
retains the strip on the casting surface may reflect the
quality of the thermal contact between the strip and the
casting surface~
The casting of relatively high quality strip
material including amorphous material, which for the purpose
of this invention includes materials which are at least 25%
amorphous, 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 material~ Quench rates may be accelerated such
as by increasin~ the speed of the casting surface, or the
like.
Whereas the preferred embodiment has been
described above for the purposes of illustration, it will be
apparent to those skilled in the art that numerous variations
of the details may be made without departing from the
invention.
I claim:
22-
