Chilled casting wheel

The method and apparatus of the invention provide a rotatable casting wheel having an outer peripheral quench surface and an interior, annular coolant chamber. A wheel hub has a concentric axis of rotation, and two spaced-apart, annular, radially extending side members connected thereto and located concentric therewith delimit the side walls of the wheel and the coolant chamber. A cylindrical, axially extending wheel rim member is connected between the peripheral circumferential edges of the side members to provide the wheel quench surface and delimit the peripheral, circumferential wall of the coolant chamber. The rim has a frusta-conical inner surface that is sloped radially outward along the intended direction of coolant flow. A flow director located within the coolant chamber is comprised of at least one annular, radially extending support member and a cylindrical, axially extending flange member connected to the support member. The flange member is spaced radially inward from the inner surface of the wheel rim to delimit a sloped coolant flow gap therebetween which is substantially continuous, both circumferentially and axially. A coolant mechanism is connected to the wheel hub and communicates with the coolant chamber to pass a coolant through the flow gap while the wheel is rotating. Then, to cast a filament, an extrusion mechanism deposits molten metal onto the rotating quench surface.

DESCRIPTION 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a method and apparatus for rapid solidification 
of molten metal. More particularly, it relates to a casting wheel useful 
in the continuous casting of metallic filament. 
2. Description of the Prior Art 
In the production of glassy alloy continuous filaments, typically, an 
appropriate molten alloy is quenched at extreme quench rates, usually at 
least about 10.sup.4 .degree. C./sec. by extruding the molten alloy from a 
pressurized reservoir through an extrusion nozzle onto a high speed 
rotating quench surface as is representatively shown in U.S. Pat. No. 
4,142,571 for "Continuous Casting Method for Metallic Strips" issued Mar. 
6, 1978 to Narasimhan, hereby incorporated by reference. Such filaments 
are necessarily thin, typically about 25 to 100 microns, due to the 
extreme heat transfer rate required to prevent substantial 
crystallization, though considerable selectivity may be exercised 
respecting the transverse dimensions and cross-section of the filament. 
Casting wheels of the prior art generally have been cooled by spraying a 
fluid, usually water, onto the inner surface of the wheel. However, such 
spray-cooled wheels do not provide sufficiently uniform cooling along the 
wheel quench surface. Casting wheels of the prior art have also been 
cooled by forcing a coolant to flow through separate discrete passages 
which are drilled axially through a portion of the wheel and located about 
the periphery of the casting wheel near the wheel quench surface. Such a 
casting wheel is representatively shown in U.S. Pat. No. 4,307,771 for 
"Forced-Convection-Cooled Casting Wheel" issued Dec. 29, 1981, to Draizen, 
et al., the disclosure of which is hereby incorporated by reference 
thereto. The casting wheel has an internal stiffening section which is 
particularly effective in preventing crowning-type distortions of the 
quench surface, which can be significant when casting relatively wide 
filaments of material. The casting wheel of Draizen, et al., however, is 
rather expensive, and impractical for use in casting narrow ribbons less 
than about 0.20 cm in width where crowning is generally not a problem. In 
addition, prior art casting wheels have no satisfactory means for 
adjusting the size of the cooling passages to accommodate different alloy 
compositions, and have undesireable circumferential temperature variations 
along the wheel quench surface caused by the presence of separate coolant 
passageways. 
SUMMARY OF THE INVENTION 
The apparatus of the invention provides an economical, rotatable casting 
wheel having an annular interior coolant chamber and a more uniformly 
cooled outer peripheral quench surface. The casting wheel includes a wheel 
hub having a concentric axis of rotation. Two spaced-apart, annular, 
radially extending side members are connected to the hub and located 
concentric therewith to delimit the side walls of the wheel and the 
coolant chamber. A cylindrical, axially extending wheel rim member 
connected between the peripheral, circumferential edges of the side 
members provides the wheel quench surface and delimits the peripheral 
circumferential wall of the coolant chamber. The rim has a frusta-conical 
inner surface that is sloped radially outward along the intended direction 
of coolant flow. A flow director located within the coolant chamber is 
comprised of at least one annular, radially extending support portion, and 
a cylindrical, axially extending flange portion connected to the support 
member. The flange portion is spaced radially inward from and 
substantially parallel to the inner surface of the wheel rim to delimit a 
sloped flow gap therebetween which is substantially continuous, both 
circumferentially and axially. A coolant means connected to the wheel hub 
communicates with the coolant chamber to pass coolant through the flow gap 
while the wheel is rotating. 
The invention further provides a method for continuously casting a metallic 
filament. A casting wheel, which has an interior coolant chamber and a 
wheel rim member that provides an outer peripheral quench surface, is 
rotated about a concentric axis of rotation. Coolant is directed toward an 
inner surface of said wheel rim and passed through a flow gap region to 
cool the quench surface. The flow gap region is substantially continuous, 
both circumferentially and axially, and is adjacent to the wheel rim inner 
surface. The flow gap region is also sloped radially outward along the 
intended direction of coolant flow to minimize the formation of gas 
bubbles against the rim. A stream of molten metal is then deposited onto 
the quench surface to cast the filament. 
The casting wheel of the invention is less expensive to construct and has 
an improved flow control. The flow director, in cooperation with the 
sloped flow gap, provides a circumferentially continuous coolant passage, 
reduces the variations in heat transfer rate along the circumference of 
the wheel quench surface, and is easily modified to adjust the size of the 
coolant flow gap, thereby adapting the casting wheel to cast different 
allow compositions. Thus, the invention provides a more versatile, less 
expensive casting wheel having a more uniformly cooled quench surface than 
spray cooled wheels or wheels employing separated, discrete cooling 
passages.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
For the purposes of the present invention and as used in the specification 
and claims, a wheel is a cylinder of substantially circular cross-section 
whose width (in the axial direction) is substantially smaller than its 
diameter. In contrast, a roller is generally understood to have a greater 
width than diameter. 
Also, for the purposes of this invention and as used in the specification 
and claims, the term "filament" is a slender body whose transverse 
dimensions are much smaller than its length. Thus, the term "filament" 
includes wire, ribbon, sheet and the like, having regular or irregular 
cross-section. 
Referring to FIG. 1 of the drawings, a representative apparatus for the 
continuous casting of a glassy alloy filament is illustrated to point out 
the general use of the present invention. The apparatus has an extrusion 
means comprising a crucible 1 and an extrusion nozzle 9. Molten alloy 
contained in crucible 1 is heated by a heating element 2, and 
pressurization of the crucible with an inert gas extrudes a molten stream 
through nozzle 9 located at the base of the crucible onto quench surface 6 
of casting wheel 3. 
The apparatus of this invention is suitable for forming polycrystalline 
strip of aluminum, tin, copper, iron, steel, stainless steel and the like. 
However, metal alloys that, upon rapid cooling from the melt, form solid 
amorphous, glassy structures are preferred. Such alloys are well known to 
those skilled in the art, and examples are disclosed in U.S. Pat. Nos. 
3,427,154; 3,981,722 and others. 
When forming amorphous alloys and certain crystalline metal alloys, quench 
rates of at least about 10.sup.4 .degree. C. are required to produce 
desired physical properties. The quench surface velocity, the composition 
and dimensions of the casting wheel, and the coolant flow rate through the 
wheel are sized and selected to provide this quench rate. For example, the 
casting wheel is rotated to provide a quench surface velocity ranging from 
about 100 to 4000 m/min, and preferably ranging from about 1000 to 2000 
m/min. 
FIGS. 2 and 3 illustrate a preferred embodiment of the rotatable casting 
wheel of the invention, shown generally at 3, which provides an outer 
peripheral quench surface 6 and an interior toroidal coolant chamber 7. A 
casting wheel hub 5 is adapted to mount on a suitable drive shaft and has 
a concentric axis of rotation. Two spaced-apart, annular, radially 
extending side members 10 and 11 connect to hub 5 and are concentric 
therewith to delimit the side walls of wheel 3 and coolant chamber 7. A 
cylindrical, axially extending wheel rim member 8 connects between the 
peripheral, circumferential edges of side members 10 and 11 to provide the 
wheel quench surface 6 and delimit the peripheral circumferential wall of 
coolant chamber 7. A flow director 12, located within coolant chamber 7, 
is comprised of at least one annular, radially extending support member 13 
and a cylindrical, axially extending flange member 14. Flange member 14 is 
spaced radially inward from the interior surface of wheel rim 8 to delimit 
a circumferentially and axially continuous coolant flow gap 18. A coolant 
means, comprised of coolant passages 15 and 16 and coolant leader 17, 
connects to wheel 3 and communicates with coolant chamber 7 to pass a 
fluid coolant through coolant flow gap 18 while wheel 3 is rotating. 
FIG. 2 shows a representative axial cross-section of rotatable casting 
wheel 3 adapted for cantilevered type mounting. Wheel hub 5 has a 
concentric axis of rotation 29 and delimits an inlet chamber 24 and outlet 
chamber 25. The back face of hub 5 has a tapered cavity disposed therein 
concentric with axis 29 that is adapted to mate with a correspondingly 
tapered shaft mounting plate 22 attached to drive shaft 19. The peripheral 
surface 30 of hub 5 delimits the inner peripheral wall of coolant chamber 
7. An annular, radially extending side member 11 is connected to the front 
side of hub 5 and is concentric therewith. So connected, side member 11 
delimits one side wall of chamber 7. An annular, radially extending side 
member 10 is connected to the back side of hub 5 and is concentric 
therewith; side member 10 delimits the second side wall of chamber 7. A 
cylindrical, axially extending wheel rim member 8 is connected between the 
peripheral circumferential edges of side members 10 and 11. Rim 8 provides 
the wheel quench surface 6 and delimits the outer peripheral wall of 
chamber 7. Thus, hub 5, side members 10 and 11, and rim 8 cooperate to 
form an annular coolant chamber 7. 
While wheel 3 is described in terms of separate hub, side member and rim 
elements, it is clear that some or all of these elements may be formed 
together in various combinations as integral units. For example, rim 8 can 
be formed as an integral part of side member 11 and side plate 10 can be 
formed as an integral part of hub 5. In such case, rim 8 and side plate 10 
are fastened together employing an annular clamp plate 33, screws 55 and 
suitable elastomeric seals 57 and 39 to prevent fluid leaks. 
Wheel rim 8 should be sized and constructed to withstand the thermal and 
mechanical stresses encountered during casting operations. Suitable 
construction materials include stainless steel alloys, but copper alloys, 
such as beryllium-copper, are preferred because of their high thermal 
conductivity and corrosion resistance. Depending on the rim material, the 
thickness of the wheel rim measured radially ranges from about 0.31 cm to 
about 0.96 cm. 
In addition, rim 8 is configured to have a tapered cross-section. The 
outer, quench surface extends parallel to the wheel rotational axis, but 
the inner surface 37 of the rim slopes radially outward along its axially 
extending, width dimension. As shown in the drawing, the slope progresses 
radially outward as one traverses the rim width in the direction of 
intended coolant flow, and preferably, there is a sloped incline 42 of 
about 1.5 degrees, measured relative to the wheel rotational axis. This 
incline provides the desired slope while minimizing the variation in rim 
thickness which could cause nonuniform quenching. Thusly configured, it is 
readily apparent that inner surface 37 of rim 8 delimits a frusta-conical 
surface. 
Flow director 12, located within coolant chamber 7, has at least one 
annular, radially extending support member 13 connected to hub 5 with 
suitable fastening means such as screws 28. A cylindrical, axially 
extending flange 14 is connected to support member 13. Thus, when viewing 
a cross-section of flow director 12, it has an "L" shaped appearance. 
Support member 13 is suitably sized and configured to position flange 14 
substantially parallel to and spaced radially inward at a substantially 
constant distance from the interior surface of wheel rim 8. Preferred 
spacing distances range from about 0.038 cm to about 0.11 cm. So 
positioned, flange 14 and wheel rim 8 delimit a sloped coolant flow gap 18 
therebetween which extends substantially continuous and uninterrupted in 
both the axial and circumferential directions. 
Since flow gap 18 slopes radially outward along the direction of the 
coolant flow, the centripetal acceleration imparted by rotating wheel 3 
produces an inertial reaction that assists the flow of coolant along the 
rim inner surface in the axial direction. Additionally, the sloped 
configuration advantageously minimizes the entrapment of gas bubbles 
against the inner surface of rim 8. Such bubbles would inhibit heat 
transfer from the rim into the fluid coolant and degrade the properties of 
the cast filament. 
Since flow gap 18 is continuous and uninterrupted, it provides a more 
uniform cooling of wheel quench surface 6 than conventional cooled rollers 
and casting wheels with discrete axial passages. The quench surfaces of 
such rollers and casting wheels are cooler where a coolant passage runs 
directly under a quench surface and warmer where a wall section separates 
the individual coolant passages. Consequently, there is a nonuniform 
cooling of the extruded molten metal which can cause variations in the 
properties of the cast filament. In contrast to such devices, the casting 
wheel of the present invention allows substantially uniform coolant 
contact along the entire inside surface of wheel rim 8, and provides more 
uniform cooling of exterior quench surface 6. 
Also, with a sloped flow gap 18, flow director 12 can be readily modified 
or adjusted to change the flow gap as needed to accomodate the casting of 
a particular alloy composition. In the shown embodiment, flow director 12 
can be removed by disengaging screws 28. A different flow director having 
an appropriately modified support member 13 or flange member 14 can then 
be substituted. For example, the radial dimension of support 13 can be 
changed to adjust the separation distance between flange 14 and the 
interior surface of rim 8. Alternatively, the assembly of support member 
13 and flange member 14 can be configured to move axially. As 
representatively shown in FIGS. A-C adjustment means, such as internal 
spacer shims 43 or externally adjustable displacement screws 44 and 45, 
can be employed to move flow director 12 in a direction parallel to the 
rotational axis of wheel 3. In cooperation with the sloped and tapered 
configuration of rim 8, this movement selectively increases or decreases 
the spaced distance between rim 8 and flange 14, thereby adjusting the 
size of flow gap 18. FIG. 5B shows a multiple screw adjustment means 
wherein displacement screws 44 passes through wheel side member 11 and is 
retained therein by retainer 47. Screws 44 engages threaded block 49, 
which is attached to flow director 12. As screws 44 are turned, flow 
director 12 can selectively move axially along a bearing surface of hub 5 
to adjust the size of gap 18. Seals 51 minimize leakage of coolant. FIG. 
5C shows a single point external adjustment means where a single 
displacement screw 45 engages threaded block 49 to selectively move flow 
director 12. Casting wheels with discrete axial passages, however, are 
much more difficult to modify because such modification would involve 
changing a substantial part of the wheel structure. 
A suitable fluid coolant, such as water, is provided by a coolant means 
connected to hub 5 and comprised of a coolant leader 17, plenum chambers 
24 and 25 and passages 15 and 16. Coolant leader 17 is constructed of 
conventional co-axial fluid piping having an inner pipe casing 31 and an 
outer pipe casing 32. Inner casing 31 provides an inlet conduit 26, which 
conducts coolant from a suitable source, through hub 5 and into inlet 
plenum chamber 24. Inlet passages 15 formed through hub 5 communicate 
between inlet chamber 24 and coolant chamber 7. Outer casing 32 is 
radially spaced outward from inner casing 31 to delimit an annular outlet 
conduit 27 therebetween. Outlet conduit 27 communicates with outlet plenum 
chamber 25, and outlet passages 16 formed through hub 5 communicate 
between coolant chamber 7 and outlet chamber 25. Coolant leader 17 is 
connected to an appropriate source of coolant by a conventional rotating 
union. Suitable, fastening means, such as assembly bolts 23, secure wheel 
3 to mounting plate 22; and sealing means, such as elastomeric "O" rings 
20 and 21, are located as required to prevent fluid leaks. 
During operation, wheel 3 is spun up to a desired rotational speed by a 
suitable drive means, such as a motor, connected to drive shaft 19. 
Coolant water is continuously pumped through conduit 26 into chamber 24, 
where it flows through passages 15 into coolant chamber 7. Flow direction 
12 directs the water into flow gap 18 where it flows in a substantially 
axial direction contacting wheel rim 8 and cooling quench surface 6. Water 
flows out of coolant chamber 7 through passages 16 into outlet chamber 25 
and then flows away from wheel 3 through conduit 27. When a suitable wheel 
temperature is established, nozzle 9 extrudes molten metal onto quench 
surface 6 to cast filament 4. 
FIG. 4 shows a second embodiment of the casting wheel of the invention 
employing "straight through" type coolant flow and incorporating a flow 
director with two support members. Hub 50, which has an axial bore adapted 
to engage and fit over drive shaft 190, delimits annular inlet chamber 240 
and annular outlet chamber 250. Drive shaft 190 has axial cavities 35 and 
34 that convey fluid to and from chambers 240 and 250. Cavity 34 
communicates with chamber 240 through openings 36, and cavity 35 
communicates with chamber 250 through openings 59. 
Flow director 120 is comprised of two annular, radially extending support 
members 130; and a cylindrical, axially extending flange member 140 
connected between the outer peripheral edges of support members 130. 
Flange member 140 is spaced radially inward from wheel rim 8 at a 
preselected distance to delimit a cooling flow gap 18 therebetween. 
In operation, coolant enters cavity 34 and then passes through openings 36, 
chamber 240 and passages 15 to enter coolant chamber 7. Flow director 120 
directs coolant into and through gap 18 where it contacts wheel rim 8 and 
cools quench surface 6. Coolant then flows out of coolant chamber 7 
through passages 16, outlet chamber 250 and openings 37 and into cavity 
35. 
Having thus described the invention in rather full detail, it will be 
understood that these details need not be strictly adhered to but that 
various changes and modifications may suggest themselves to one skilled in 
the art, all falling within the scope of the invention as defined by the 
subjoined claims.