U.S. patent number 3,863,700 [Application Number 05/360,887] was granted by the patent office on 1975-02-04 for elevation of melt in the melt extraction production of metal filaments.
This patent grant is currently assigned to Allied Chemical Corporation. Invention is credited to John R. Bedell, John A. Wellslager.
United States Patent |
3,863,700 |
Bedell , et al. |
February 4, 1975 |
ELEVATION OF MELT IN THE MELT EXTRACTION PRODUCTION OF METAL
FILAMENTS
Abstract
A method and apparatus for the production of metal filaments
which are extracted using melt extraction techniques and quenched
on a quench wheel, in which a discrete amount of the melt is
elevated to contact the quench wheel thereby substantially
increasing the quench rate.
Inventors: |
Bedell; John R. ((Lake Mohawk)
Sparta, NJ), Wellslager; John A. (Mount Arlington, NJ) |
Assignee: |
Allied Chemical Corporation
(New York, NY)
|
Family
ID: |
23419801 |
Appl.
No.: |
05/360,887 |
Filed: |
May 16, 1973 |
Current U.S.
Class: |
164/463; 164/423;
164/429; 164/479 |
Current CPC
Class: |
B22D
11/0614 (20130101) |
Current International
Class: |
B22D
11/06 (20060101); B22d 011/06 () |
Field of
Search: |
;164/87,276,283M
;264/8,165 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
77,782 |
|
Nov 1970 |
|
DL |
|
20,518 |
|
May 1910 |
|
GB |
|
Primary Examiner: Annear; R. Spencer
Attorney, Agent or Firm: Plantamura; Arthur J.
Claims
We claim:
1. In a melt extraction method for the production of metal
filaments from a molten reservoir wherein a quenching wheel is
positioned contiguous to the melt and extracts a filament directly
from the melt reservoir, the improvement comprising elevating a
discrete amount of the melt directly from the melt reservoir to
contact the quenching wheel by means of an auxiliary rotating hot
wheel which is partially immersed within the melt thereby utilizing
substantially the entire quenching capacity of said quenching wheel
to quench said discrete amount of the melt.
2. The method of claim l wherein the rotating hot wheel and the
quench wheel are complementarily contoured so as to produce a
correspondingly shaped metal filament.
3. In an apparatus for the production of metal filaments from a
molten source using a quenching wheel as a quenching element, the
improvement which comprises employing a rotating hot wheel which is
partially immersed within the melt to elevate a discrete amount of
the molten melt to contact with the quench wheel.
4. The apparatus of claim 3 wherein the hot wheel and quench wheel
are complementarily contoured.
5. In a melt extraction method for the production of metal
filaments from a molten reservoir wherein a quenching wheel is
positioned contiguous to the melt and extracts a filament directly
from the melt reservoir, the improvement comprising elevating a
discrete amount of the melt directly from the melt reservoir to
contact the quenching wheel by bubbling gas through the melt
contiguous to said quenching wheel, thereby utilizing substantially
the entire quenching capacity of said quenching wheel to quench
said discrete amount of the melt.
6. In a melt extraction method for the production of metal
filaments from a molten reservoir wherein a quenching wheel is
positioned contiguous to the melt and extracts a filament directly
from the melt reservoir, the improvement comprising elevating a
discrete amount of the melt directly from the melt reservoir to
contact the quenching wheel by contacting the melt surface with a
gas jet, thereby utilizing substantially the entire quenching
capacity of said quenching wheel to quench said discrete amount of
the melt.
7. In a melt extraction method for the production of metal
filaments from a molten reservoir wherein a quenching wheel is
positioned contiguous to the melt and extracts a filament directly
from the melt reservoir, the improvement comprising elevating a
discrete amount of the melt directly from the melt reservoir to
contact the quenching wheel by a pump located within the body of
the melt, thereby utilizing substantially the entire quenching
capacity of said quenching wheel to quench said discrete amount of
the melt.
8. In a melt extraction method for the production of metal
filaments from a molten reservoir wherein a quenching wheel is
positioned contiguous to the melt and extracts a filament directly
from the melt reservoir, the improvement comprising elevating a
discrete amount of the melt directly from the melt reservoir to
contact the quenching wheel by a rotating hot wheel which is
submerged within the melt, thereby utilizing substantially the
entire quenching capacity of said quenching wheel to quench said
discrete amount of the melt.
9. In an apparatus for the production of metal filaments from a
molten source using a quenching wheel as a quenching element, the
improvement which comprises employing a gas bubbling means to
elevate a discrete amount of the molten melt into contact with the
quench wheel.
10. In a apparatus for the production of metal filaments from a
molten source using a quenching wheel as a quenching element, the
improvement which comprises employing a gas jet to elevate a
discrete amount of the molten melt into contact with the quench
wheel.
11. In a apparatus for the production of metal filaments from a
molten source using a quenching wheel as a quenching element, the
improvement which comprises employing a pump to elevate a discrete
amount of the molten melt into contact with the quench wheel.
12. In an apparatus for the production of metal filaments from a
molten source using a quenching wheel as a quenching element, the
improvement which comprises employing a rotating hot wheel which is
submerged within the melt to elevate a discrete amount of the
molten melt into contact with the quench wheel.
Description
BACKGROUND OF THE INVENTION
Metal filaments may be produced by extracting from a molten metal
bath and quenching on a chill or quench wheel. This invention is
directed to an apparatus and method for improving the quench rate
of the extracted molten metal by elevating the melt so that only a
discrete amount of molten metal comes into contact with the quench
wheel at any one time.
For purposes of the invention, the term "filament" is meant to
include any slender metallic body whose transverse dimensions are
much less than its length. These filaments may be ribbon, sheet or
wire or may have an irregular cross-section.
Such filaments are presently formed by melt extraction techniques
rather than by the previous casting or extrusion methods. Melt
extraction is a process wherein a cold wheel rotates at high
velocity in "kissing" contact with a liquid metal surface. The
molten metal wetting or contacting the wheel is carried up out of
the molten bath, solidifies, shrinks away from the wheel and is
flung off by centrifugal action. This technique is to be
distinguished from the essentially casting technique described in
U.S. Pat. Nos. 1,025,848 and 2,074,812 in which a cold wheel is
substantially immersed in the liquid metal and in which the
rotational velocity of the wheel is appreciably lower than in the
melt extraction system.
In this melt extraction system, contact between the quench wheel
and the large surface area of the high temperature molten metal
reservoir occurs over an appreciable distance as shown in FIG. 1.
This extended contact causes some turbulence, sizeable exposure to
melt and therefore considerable heat exchange between the wheel and
the melt without adequate temperature reduction. The amount of heat
absorbed from the melt by the wheel is well in excess of the
necessary amount which must be absorbed from the discrete portion
of the melt which is to be quenched to form the filament. This
excess heat absorbed by the wheel reduces the quenching capability
of the wheel thereby decreasing the effective rate of chill by the
wheel in the area of molten contact. The efficiency of this thermal
transfer can be expressed as ##SPC1##
Due to the low efficiency of the system and the excess thermal
exchange, the metal often is not quenched at the desired rate or to
the desired temperature before centrifugal and gravitational forces
cause it to depart from the wheel. This incomplete quenching leads
to products possessing some undesired properties including
relatively large grain size in polycrystalline metals and some
crystalline structure in otherwise amorphous metals. Thus, in the
case of polycrystalline metals, rapid and thorough solidification
is advantageous since it produces filaments of finer grain size
with better attendant physical properties and also avoids the
problems, such as embrittlement, associated with oxidation.
Moreover, in order to achieve completely amorphous or glassy metals
or ceramics, it is essential that the molten stream be quenched
below the characteristic glass transition temperature at a
sufficiently high quench rate to avoid nucleation and growth of
crystalline material in the amorphous structure.
It would be desirable to try to limit the thermal exchange between
the extracted material and the chill wheel to only that amount
required for adequately quenching the discrete portion of the
material to be formed into a filament and thereby achieve a maximum
quenching capability in the quench wheel. In order to do this, it
is necessary to regulate to a minimum the amount of heat picked up
from the melt by that quantity of molten metal being extracted for
quenching; to regulate to a minimum the heat picked up by the
quench wheel from the body of the melt; and to regulate the
residence time of the melt on the wheel to that time required for
adequate quenching of the extracted material. In an ideal
situation, the thermal exchange would be confined to the heat
exchanged between the quench wheel and the exact quantity of melt
being quenched and there would be no heat exchange with the
remaining body of the melt.
SUMMARY OF THE INVENTION
It is obvious that there is a need for a method to reduce the
maximum thermal exchange in the melt extraction system.
It is therefore an object of this invention to provide a method of
this kind for enhancing the thermal exchange.
It is a further object to provide a method which will increase the
quench rate of the system.
Additionally, it is an object of the invention to provide a method
which will substantially increase the quench rate so as to provide
that the amorphous metal product be quenched below its
characteristic glass transition temperature before departure from
the wheel.
It is also an object of the invention to minimize the turbulence
present during the melt extraction and subsequent freezing of the
metal, thereby minimizing transfer of additional heat from the
unfrozen melt to the wheel.
It is another object of the invention to provide an improved
apparatus for the melt extraction and chill wheel quenching of
metal filaments.
These and other objects will become apparent from the following
description and examples.
These objects are accomplished in a melt extraction system wherein
the quench wheel is positioned contiguous to the molten bath, by
elevating a portion of the molten metal to make contact with the
wheel in a more restricted zone, the melt contact length being
correspondingly reduced, from that shown in FIG. 1 to that of FIG.
2, so only a discrete amount of molten metal comes into contact
with the wheel at any one time, thus the capability of the wheel to
quench, as well as the effective quench rate of the filament on the
wheel is thereby substantially increased.
In accordance with the present invention, the melt may be elevated
in a variety of ways. Included among these are elevation by using a
hot wheel which draws the melt into contact with the chill wheel at
a position remote from the molten bath or by use of capillary
action, submerged wheels, gas jets, gas bubbled through the melt,
or pumps. Any of these devices for elevating a discrete portion of
the melt can be readily adapted for use in conventional melt
extraction apparatus to produce an improved apparatus for melt
spinning of metal filaments.
When the melt is elevated, the distance between the molten bath and
the quench wheel is increased, and the amount of melt coming into
contact with the wheel at any one moment is decreased. These
factors of distance and reduced contact combine to minimize the
thermal exchange, thus permitting the quench wheel to effectively
act on a small quantity of melt.
In the case of polycrystalline metal products, when the quench rate
is increased in this manner, cooling can be controlled to assure
sufficient quench temperature to achieve a product possessing the
desired properties. In particular, when polycrystalline metal
filaments are formed using the method of this invention, the
resulting filaments are of very fine grain size in the range of
about 0.01 micron to 1 micron. Such fine grain size gives a
material possessing superior physical properties. By way of
example, the ductility of the narrow filament is improved since one
grain does not bridge as much of the filament diameter as in larger
grained filaments. Thus the movement along the slipplanes of the
grain does not cause total yield to deformation or breakage through
a single grain. Most importantly, when the procedure of the present
invention is followed, amorphous metal filaments can be readily
produced since the cooling of the amorphous metal at the required
quench rate is assured.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 represents the effective melt contact length of the chill
wheel extraction technique as it is currently practiced.
FIG. 2 illustrates the use of capillary action to raise the melt.
This figure also illustrates the decreased melt contact length
achieved using the novel method of the present invention.
FIG. 2a is a side view of the system of FIG. 2.
FIG. 3 represents an embodiment of the invention employing a hot
wheel to elevate the melt.
FIG. 3a illustrates a method of contouring the wheels to produce a
shaped metal filament.
FIG. 4 illustrates an alternate positioning of the chill wheel,
particularly useful in the production of metallic ribbons or
sheets.
FIG. 5 is a diagram of the action of gas jets to raise the molten
metal.
FIG. 6 illustrates a rotating wheel submerged within the melt.
FIG. 7 represents a pump situated within the melt.
FIG. 8 is a representation of a drum which is rotated by an
inclined drive shaft.
PREFERRED EMBODIMENT
The following embodiments are suggested means for elevating the
melt and the invention in its broadest scope is not intended to be
limited to these particular methods.
The melt may be elevated by capillary action. One of the methods
for producing this action is shown in FIGS. 2 and 2a. In this
embodiment, the melt 21 is elevated between two solid members 22
and 23 which are wetted by the melt to form an elevated concave
meniscus; the quench wheel 24, positioned contiguous to the bath,
then runs between the two solid members thereby contacting only
that discrete portion 25 of the melt which is raised and quenching
this portion to form a filament 26.
In addition to the advantages inherent in this invention, the use
of capillary action is advantageous in that it maintains a fairly
constant height of liquid to be contacted by the wheel, thus
stabilizing the filament size against effects caused by changes in
the melt level such as those due to turbulence or to fluctuations
in melt volume. The use of capillary action also permits the molten
material to be raised from the melt thereby reducing the
complications of thermal geometry introduced by the wheel. For
example, when high melting ceramic liquids, such as
yttrium-alumina-garnet are spun, the high temperatures required for
melting suggests a lid on the crucible to conserve against
radiation heat losses. A wire or ribbon arrangement, which serves
to produce a capillary column, thereby raising the melt to the
wheel, also can be used to generate heat by electrical resistance
in order to keep the melt in a molten state.
Another way to raise the molten metal from the melt before contact
with the quench wheel is shown in FIG. 3. Here, a hot wheel 32 is
employed to extract and raise the molten metal from the melt 31,
thereby retaining a layer of molten metal at its periphery. This
molten layer is then conveyed to a quenching wheel 34 where a
discrete portion 35 is rapidly quenched and then spun off as a
solid wire or ribbon 36. The hot wheel of this embodiment is
preferably made of a material which is wetted by the melt.
Otherwise, some means may be needed to retain the molten metal at
the surface of the hot wheel; such methods would include a split
through the wheel conveying a vacuum to the zone of contact with
the metal or else shaping of the hot wheel to permit it to carry
molten metal as by capillarity.
There are additional advantages inherent in the particular
embodiment of the invention. If the hot wheel surface is of low
thermal conductivity, low heat transfer between the metal to be
frozen and the hot wheel will occur and there will be even more
rapid quenching when the metal reaches the quench wheel. Moreover,
as shown in FIG. 3a, it is possible to achieve shaping of both
sides of the wire product by contouring both the hot wheel 38 and
the quench wheel 39 faces in a complementary manner so that the
entire metal filament can be "molded" into the desired shape. In
particular, this contouring could be adapted to produce round wire
products. In addition, it is possible to "meter" the proper
quantity of molten metal which is to be quenched by adjustment of
parameters at the hot wheel, i.e. surface contour, wheel
temperature, wheel velocity and wheel diameter. Proper metering is
useful in controlling uniformity and shape of the chilled product.
Optionally, the hot wheel 38 may be heated using a torch, induction
coil, or the like to facilitate the wetting of the wheel during the
initial stages of the operation. Once filament formation has begun,
the heat from the molten reservoir will be sufficient to insure
adequate wetting and no additional heat is needed.
FIG. 4 shows another embodiment of the hot wheel elevating
technique, this embodiment being particularly adaptable to the
production of metallic sheets though it is obvious that all the
techniques herein described can be used to produce any filamentary
form. In this situation, a discrete sheet or fountain of metal 43
is elevated by means of one or more rotating hot wheels 42 which
are slightly more immersed in the melt than the wheel of FIG. 3. As
the molten metal 43 fans out to the side of the wheel, a second
wheel 44, positioned approximately perpendicular to the sheet and
serving as the quench wheel, then contacts the elevated metal along
a very narrow length 45 thus producing the desired product 46.
Other methods of elevating the melt in a discrete region include
bubbling gas up through the melt or directing at least one gas jet
52, as shown in FIG. 5, against the melt surface causing a
depression 53 as well as a rise 55 in the surface sufficient to
force the melt into contact with the quench wheel 54 to produce
filament 56.
FIG. 6 illustrates another alternative. Here, a hot wheel or drum
62 is submerged at such a position in the melt 61 that when it
rotates, it drags a layer 63 of melt over the upper surface and
above the level of the molten reservoir. The quench wheel 64 then
contacts the melt in a narrow contact length 65 to produce the
desired product 66.
In FIG. 7 an insulated pump 72 located within the melt 71 is used
to elevate a surge or discrete amount 73 of molten metal into
contact with the quench wheel 74 to form the fialment 76. A large
variety of pumps may be employed, in particular those of the
induction or electromagnetic thrust variety.
FIG. 8 illustrates a manner in which the rotating submerged wheel
62 of FIG. 6 or the submerged pump 72 of FIG. 7 can be driven from
above the melt without gears, belts or other linkages but rather by
using an inclined drive shaft 83. In the embodiment illustrated, a
drum 82 is shown which has a conical shape so that the uppermost
surface is horizontal. However, it is apparent that a similar
mechanism could be employed to drive a mechanical pump.
The following are illustrative examples and the invention in its
broadest scope is not intended to be limited thereto. Parts are in
atomic percent unless otherwise specified.
EXAMPLE 1
Using the apparatus of FIG. 4, a Type 304 stainless steel wheel,
5.08cm in diameter by 1.7cm thick was mounted on a 0.96cm
horizontal stainless steel shaft, and, while rotating at 40 to 50
revolutions per minute, was lowered approximately 0.32cm into a
bath of molten solder alloy, consisting of 65 weight percent lead,
30 weight percent tin and 5 weight percent antimony, at
320.degree.F. .+-. 20.degree.F., the bath being overlaid with a
fluxing skin of boric anhydride powder. Initially, some of the bath
was chilled by the wheel, and a frozen layer of solder became
attached to the wheel. With continued rotation and absorption of
heat from the bath the temperature of the wheel increased until the
frozen layer has melted back into the bath.
The wheel was then lowered to an immersion depth of abput 1.7cm and
the rotation speed of the wheel was increased until molten solder
was carried up from the melt and flung outward in a thin sheet from
the mid line of the periphery of the wheel, on the
upward-travelling side of the wheel. The sheet of molten metal thus
generated was 0.17 to 0.254cm thick, and was elevated 2.54 to 4.2cm
above the melt surface.
The elevation of the melt was thus maintained while a second wheel
was introduced to the system. This second wheel was of copper,
1.7cm thick by 10.16cm in diameter, rotating on its circular axis
at the end of a shaft on a flexible driving cable. The copper
wheel, which was initially at room temperature, was rotated at
about 1,500 revolutions per minute and, by holding its shaft
manually, its peripheral face was brought into contact with the
sheet of molten metal near to a point of maximum elevation of the
metal. The copper wheel, when in this position, has its axis in a
perpendicular direction to the direction of the axis of the
stainless steel wheel which was partially immersed in and elevated
the molten solder alloy. The axis of the copper wheel also was
approximately in the plane of the sheet of molten elevated alloy.
The plane of rotation of the copper wheel was approximately
perpendicular to the average path of travel of molten metal in the
vicinity in which the copper wheel contacted the molten alloy. The
copper wheel intersected the outer edge of the molten sheet by
approximately 0.32cm. As the path of the molten metal in the molten
sheet was intersected, that portion of the molten metal whose path
was intersected by the body of the copper wheel became frozen at
the copper wheel's peripheral surface and was carried
perpendicularly from its prior free-falling path, temporarily
attached to the copper wheel. This frozen material, in the form of
a solid metal ribbon, then departed from the copper wheel after
travelling 1.7 to 7.6cm from the place of contact between the
molten sheet and the copper wheel. Continuous metal ribbons of
approximately ten to twenty foot lengths were thus generated, which
were 0.025 to 0.046cm thick; they were shown, using x-ray
diffraction techniques to possess very fine grain size.
EXAMPLE 2
Using a tungsten capillary and an apparatus similar to that of FIG.
2, copper was charged and melted to 1,180.degree.C. in an
atmosphere containing 5 percent hydrogen and 95 percent argon. The
molten metal wetted the capillary and formed a concave meniscus
within the capillary. A rotating copper wheel was allowed to
contact and quench the elevated portion to form a fine grained
polycrystalline copper filament.
EXAMPLE 3
Another alloy, formulated to be amorphous on quenching, and
comprising 48 % Ni, 30% Fe, 14% P, 6% B and 2% Al, was melted at
1,020.degree.C. in a melt extraction system similar to that
depicted in FIG. 6. Gaseous jets of argon were impinged upon the
area of contact between the wheel and the molten reservoir at a
flow rate of 3 m.sup.3 /min. through a .63cm orifice, causing only
a discrete amount of melt to contact the rotating copper quench
wheel. Upon analysis, the resulting filament was found to be
completely amorphous.
EXAMPLE 4
A gray cast iron alloy containing about 3.4% C, 2.2% Si, 10.6% Mn,
0.2% P and 0.1% S was melted at 1,200.degree.C. in an apparatus
similar to that depicted in FIGS. 6 and 8. A conical shaped alumina
drum was submerged within the molten reservoir, rotated using an
inclined drive shaft, thereby producing an elevated dragged metal
film which contacted a rotating copper quench wheel which was
driven in a direction opposite to that of the submerged drum. The
resulting filament was analyzed and found to be of very fine grain
size.
EXAMPLE 5
An alloy formulated to be amorphous on quenching and containing 76%
Fe, 15% P, 5% C, 3% Al and 1% Si was charged in an insulated
reservoir and melted in vacuum at 1,100.degree.C. A ceramic tube
was placed in the melt through which 15 gm/cm.sup.2 of gaseous
argon was bubbled, thereby raising a discrete portion of the molten
metal into contact with the quenching wheel. Discrete segments of
amorphous metal were thus produced.
EXAMPLE 6
In a device similar to that of FIG. 7, an alloy formulated to be
amorphous and containing 47% Ni, 30% Fe, 14% P, 6% B, 1% Si and 2%
Al was melted at 1,000.degree.C. An insulated induction coil
submerged in the melt and pumping with a force of 5gm/cm.sup.2
elevated a portion of the molten metal a height of about 0.60cm to
contact the quench wheel. X-ray diffraction analysis showed the
resulting filament to be totally amorphous.
EXAMPLE 7
A solder alloy was charged and heated as in Example 1. A heated
contoured steel wheel, similar to that shown in FIGS. 3 and 3a was
rotated so as to extract a small stream of the molten alloy from
the reservoir. The molten alloy remained in the groove on the
surface of the hot wheel and was raised so as to contact a
correspondingly contoured copper quench wheel. The metal filament
ejected from the quench wheel was circular in shape with a diameter
of 0.03cm and x-ray diffraction analysis indicated fine grain
size.
* * * * *