U.S. patent number 3,856,074 [Application Number 05/348,814] was granted by the patent office on 1974-12-24 for method of centrifugal production of continuous metal filaments.
This patent grant is currently assigned to Allied Chemical Corporation. Invention is credited to Sheldon Kavesh.
United States Patent |
3,856,074 |
Kavesh |
December 24, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
METHOD OF CENTRIFUGAL PRODUCTION OF CONTINUOUS METAL FILAMENTS
Abstract
A method for producing and concomitantly winding continuous
metal filament in which a quenching wheel is used as a quenching
element and in which sufficient pressure is exerted on the filament
just beyond the point of solidification to counteract the tensional
stress exhibited by the winder on the filament.
Inventors: |
Kavesh; Sheldon (Whippany,
NJ) |
Assignee: |
Allied Chemical Corporation
(New York, NY)
|
Family
ID: |
23369659 |
Appl.
No.: |
05/348,814 |
Filed: |
April 6, 1973 |
Current U.S.
Class: |
164/463; 164/423;
164/479; 264/164; 164/429; 164/484 |
Current CPC
Class: |
B22D
11/0694 (20130101) |
Current International
Class: |
B22D
11/06 (20060101); B22d 011/06 () |
Field of
Search: |
;164/87,276,278
;264/164,165 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Annear; R. Spencer
Attorney, Agent or Firm: Plantamura; Arthur J.
Claims
I claim:
1. In a method for the production of metal filaments from a molten
source using a rotating quenching wheel as a quenching element, the
improvement which comprises exerting sufficient nipping pressure on
the formed filament at a point on the quenching wheel beyond the
point of solificiation of the filament and prior to the point said
filament is separated from the quenching wheel by centrifugal
action to retain the filament against the quenching wheel and
subsequently collecting the filament.
2. The method of claim 1 wherein the formed filament is directed
onto a tension regulated winding device and the nipping pressure
exerted is sufficient to counteract the tensional stress exhibited
on the filament by the winder and to create a tension free zone in
which continuous lengths of filament can be produced and
concomitantly wound.
3. The method of claim 2 wherein the nipping pressure in lbs/inch
exerted is at least as great as that derived from the equation:
T/.mu..sub.QR + .mu..sub.NR
where T is the winding tension in lbs/inch of filament width and
.mu..sub.QR and .mu..sub.NR are coefficients of friction between
the filament and quenching wheel and the filament and nip roller
respectively.
4. The method of claim 1 wherein the nipping pressure is exerted by
a cold nipping wheel.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in the production
of continuous metal filaments of indefinite length which are
normally wound on spools. More specifically, for the purposes of
the invention, filament is herein used to represent a slender body
whose transverse dimensions are much less than its length. In the
present context, the filaments may be ribbons, sheets, wires or
irregular cross-sections.
During recent years, researchers developed various methods directed
to the formation of metal filaments which avoid the inherent
difficulties of previous casting and rolling techniques. These
methods include, for example, melt extraction and chill block
spinning.
Melt extraction connotes a process wherein a cold quenching wheel
rotates at high velocity in "kissing," i.e., skimming, contact with
a liquid metal surface. The molten metal wetting the wheel is
carried up out of the molten bath, where it solidifies and thereby
shrinks away from the wheel and is flung off by centrifugal action.
The melt extraction techniques discussed herein are to be
distinguished from other extraction methods such as those described
in U.S. Pat. No. 1,025,848 to Wagner and U.S. Pat. No. 2,074,812 to
Sendzimer, which primarily employ a casting technique in which the
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.
Chill block spinning is exemplified by U.S. Pat. No. 905,758 to
Strange and Pim, U.S. Pat. No. 2,825,108 to Pond, U.S. Pat. No.
2,886,866 to Wade, and U.S. Pat. No. 2,899,728 to Gibbons. In this
process, a free jet of molten material is impinged upon a moving
chilled quenching surface, preferably a rotating wheel. The molten
jet is solidified in the form of a ribbon or sheet and is flung
away from the rotating chill surface by centrifugal action.
ONE IMPORTANT DISADVANTAGE IN THE MELT EXTRACTION AND CHILL BLOCK
SPINNING PROCESSES AS PRESENTLY EMPLOYED IS THAT THEY PRODUCE LONG,
BUT NOT GENUINELY CONTINUOUS FILAMENTS. The flinging action which
removes the filament from the wheel induces an oscillating or
whipping motion in the filament which inevitably causes breakage.
Presently filaments are produced with a maximum length of only
about 300 meters. Continuous metal filaments in the range of 1,000
to greater than 30,000 meters in length are required for such
applications as strapping, springs, filament-wound vessels,
aerospace skins and the like.
An additional problem encountered in the melt extraction and chill
block spinning processes is that of winding the lengths of filament
formed. The incorporation of a tension regulated winder or similar
collecting device into the system results in a great amount of
stress being transmitted back to the solidification zone, a factor
which contributes to the breakage of the filaments. Since the "down
time" caused by rethreading the filaments onto the winder after
breakage is considerable, the metal filaments must be wound in a
separate operation. There is obviously a need for a method to
produce continuous lengths of metal filaments which can be wound
concomitantly with production.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to produce continuous
metal filament, or ribbon or sheet.
It is another object to produce a continuous filament or sheet
which can be automatically collected in a neat coiled package
concomitantly with its production.
These and other objects and advantages will become apparent from
the description and examples provided herein.
Accordingly, this invention is directed to an improvement in the
production of metal filaments, ribbons or sheets. In the production
of these materials using a rotating wheel as the quenching source,
the improvement comprises establishing a tension-free zone by
positioning a pressure exerting means in nipping contact with the
quenching source beyond the point of solidification; ideally, just
at the point where shrinkage of the filament causes detachment from
the quenching source. In an additional aspect of the invention, the
filament can then be directed from the nipping means and wound on a
tension controlled winder or other collecting means such as a
spinning bucket. Thus, the nipping action isolates the fragile
filament or sheet in the solidification zone from the tension
exerted by the winder. The continuous tension exerted by the winder
and/or tension regulating mechanism used in conjunction with the
winder prevents whipping, thereby avoiding filament breakage and
enabling production of a truly continuous filament.
The nipping means employed may be any device having freedom of
movement and capable of exerting sufficient pressure on the
solidifying filament to counteract the stress transmitted by the
winder and also by inherent centrifugal and gravitational forces
thereby preventing breakage. The device may be in the form of a
bar, a blunt blade or preferably, a cold wheel freely rotating or
driven at the same surface velocity as the quench wheel. In this
regard, it is to be noted that the role of the nipping device is
not merely that of a "guide." It is intrinsic to this invention
that pressure be exerted by the device onto the solidifying
filament and not merely that the filament be guided around the
device. The mere positioning of a guide wheel at the point of
solidification does not prevent breakage of the filament since it
does not counteract the centrifugal or gravitational forces or the
tensional stress transmitted by the winder. The arrangement of the
invention requires, as an essential facet, freedom of movement so
that the nipping device can readily adapt to use in forming
filaments of various thickness and does not have to be individually
adjusted.
The amount of pressure which the device exerts upon the filament
depends upon the magnitude of the winding tension and the
coefficients of friction between the filament and the quench roller
and between the filament and nip roller. The relationship between
those quantities is expressed by the following inequality:
P .gtoreq. T/.mu..sub.QR + .mu..sub.NR Eq. ( 1)
wherein P is the applied nipping pressure represented in lbs/inch
of filament width. T is the winding tension in lbs/inch of filament
width. .mu..sub.QR and .mu..sub.NR are the coefficients of friction
between the filament and the quench roller and the filament and the
nip roller respectively.
This novel method for producing continuous wound filaments could be
easily adapted to any process for preparing filaments in which the
quenching step is carried out on a chill wheel, drum, etc. and the
filament is separated after solidification by centrifugal
force.
This method is particularly useful in very high speed forming
operations where formation and subsequent winding occurs very
rapidly and a great amount of stress is transmitted to the
solidifying filament.
While this application is directed to the use of the nipping
pressure means in conjunction with the use of a tension regulating
winder, it is obvious that the invention also includes the
production of long or continuous filaments which are not wound
concomitantly with their production but are collected in another
manner.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 illustrates diagrammatically an apparatus which uses a wheel
melt extraction in conjunction with a nipping wheel in accordance
with the invention to produce continuous filaments. FIG. 1a
illustrates the relationship of the melt extraction wheel, nip
roller and filament during start-up.
FIG. 2 represents a modified apparatus in accordance with the
invention in which a molten jet is extruded onto a chill wheel
before being acted upon by the nipping roll.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 1 and 2 are representative of the novel aspects of the
present invention. In FIG. 1, a cold wheel 10 rotates in "kissing"
contact as shown at 12 with surface 17 of a liquid metal 18
confined in a suitable reservoir 11. The molten metal solidifies on
the surface 19 of the wheel 10 and is carried up out of the
reservoir 11, and at a point 13 at which it begins to shrink away
from the wheel 10 it comes into contact with a second cold wheel 14
which exerts a nipping pressure (between wheels 10 and 14) on the
filament 15. The filament 15 is then continuously drawn by a
conventional tension control device 16 and wound onto a roller 17.
The position of the nipping roller 14 and the pressure which it
exerts on the filament 15 are controlled by means of a pressure
exerting mechanism such as an air cylinder operating through a
conventional connecting link between the roller 14 and the cylinder
(not shown).
During start-up of the process, the nipping roller 14, as shown in
FIG. 1a is swivelled to a remote position. Rotation of the
quenching wheel 10 is initiated and the level of liquid metal 18 in
the reservoir 11 is raised by opening a valve from a supplemental
reservoir (not shown). When the liquid metal 18 contacts the quench
wheel 10, at the contact point 12, formation of the metal filament
commences. The filament is flung away by centrifugal action at the
point 13 and the nipping roller 14 is then converged toward
quenching wheel 10 so that the filament 15 is held between these
rotating elements and the filament is conveyed via a tension
control regulator 16 to a winder.
The pressure exerted by the nipping roller 14 on the filament 15
isolates the fragile solidification zone 12 to 13 from the tension
of the winding arrangement and prevents filament breakage from this
source and/or from "whipping" of the filament as it is drawn by the
winder. The metal filament 15 is then continuously wound up in
packages whose lengths are determined only by the capacity of the
winder. Molten metal is admitted to the reservoir 11 to maintain
the continuous filament forming process.
Moderate changes in the rotational speed of the quench roller 10 or
changes in the thickness of the filament do not substantially
affect the winding process or continuity of the filament. As noted
hereinabove, an air cylinder or other suitable positioning and/or
pressure applying device may be used to hold the nip roller against
the quench roller thereby permitting the filament thickness to vary
without reduction of nipping pressure.
In FIG. 2, an alternate apparatus is employed to provide a similar
result. In FIG. 2, the melt 28 is contained in an insulated
container 29 provided with heating element 31. During start-up of
the process, the nipping roller 24 is swiveled to a remote position
in a manner as described in connection with FIG. 1a. Rotation of
the quenching wheel 21 is initiated and inert gas 34 is admitted to
the melting container or vessel 29. A molten jet 32 is extruded
from a suitable opening 33 in the bottom of the container 29 and
impinges upon the rotating quench wheel 21 to form a filament 30.
The filament has a tendency to be flung away by centrifugal action
at that point 23. The nipping roller 24 is converged on wheel 21
and the solidified filament 25 is conveyed to a tension controlled
windbar 26 to a storage roller 27 as previously described in
connection with FIG. 1.
The nipping rollers 14 and 24 are preferably freely rotating,
lightweight devices supported by roller bearings. They may comprise
a solid cylinder, a hollow cylinder, or a composite cylinder. A
desirable configuration has been found to be a composite hollow
cylinder having an outer shell consisting of a material of a high
coefficient of friction bonded to an inner annular tube of high
strength. The high coefficient of friction of the outer material
permits the use of lower nipping pressures as expressed by equation
(1). The use of an annular core of high strength permits
construction of a nip roller or low movement of inertia. The outer
material must also be resistant to the temperature of the
solidified filament at the point of contact.
Included among the materials suitable for use in the outer shell of
the nipping wheel used in the practice of the present invention are
any materials which are wear resistant under the temperatures of
use. Illustrative examples include organic impregnated woven
asbestos-brass wire compositions manufactured by
Raybestos-Manhattan Corporation and designated as US98 and US2010.
The inner core may be steel or similar high strength material.
The wind-up mechanism may be used alone or in conjunction with a
separate tension regulating device as 16 and 26. If the wind-up
mechanism is used alone, it should contain a means of regulating
tension as for example by means of a slip clutch on the winding
drum. Alternatively, separate tension regulating devices may be
employed; illustrative devices could be counter-balanced,
spring-loaded or balanced by means of an air cylinder.
The invention will be further described in the following
illustrative examples:
EXAMPLE 1
A grey iron alloy containing 3.4 weight percent carbon, 2.2 weight
percent silicon, 0.6 weight percent manganese, 0.2 weight percent
phosphorus and 0.01 percent sulfur was melted at 1,200.degree. C.
in a conventional apparatus for melt extraction similar to that
depicted schematically in FIG. 1. However, a nip roller similar to
roller 14 was not utilized.
The quenching wheel was constructed of oxygen free high
conductivity copper of 8 inch outside diameter and provided with
internal channels for the circulation of cooling water. Cooling
water was admitted through a rotary union on one side of the hollow
quenching wheel shaft and was withdrawn through a rotary union on
the opposite side. The face width of the quenching wheel was one
inch.
Rotation of the quenching wheel was commenced at 1,800 revolutions
per minute. The level of the grey iron melt in the crucible was
raised by opening a valve to the connecting reservoir. The liquid
metal surface was brought into "kissing" contact with the rotating
quench wheel. A solidified filament of 1 inch width and
0.0001-0.008 inch thickness was formed on the face of the quench
wheel and was flung away by centrifugal action. The arcuate path of
the solidified filament commenced at a tangent to the surface of
the quenching roll, traveled upward at an angle of
30.degree.-60.degree. to the horizontal, reached a point of maximum
elevation and finally turned downward and fell into a catch basin
on the floor. The path of the filament was severely affected by
"whipping" oscillations induced by random changes in the point and
angle of departure of the filament from the quench roll. The
filament remained continuous for periods of several seconds until
at irregular intervals the oscillations caused the filament to
break off near the quench roll.
The filament was seized near the point of departure from the quench
roll and guided to engage the winder. At filament tensions of 1-100
grams filament oscillations persisted causing eventual breakage.
During the periods between breaks, only a relatively
unsatisfactorily loosely wound filament was produced. With higher
winding tensions the filament ruptured in the solidification zone
immediately as it was connected to the winder.
EXAMPLE 2
The apparatus of Example 1 was modified by utilizing a nipping
roller 14 as depicted in FIG. 1. The nipping roller was of 4 inch
overall diameter and consisted of a 4 inch diameter hollow steel
cylinder of one-quarter inch wall thickness. In addition, the nip
roller was of 2 inch face width and was supported by a one-half
inch steel shaft mounted on roller bearings. It was freely
rotatable.
The melt extraction process was started with grey iron alloy as
described in Example 1. The nip roller 14 was swiveled to the
remote position depicted in FIG. 1a, the path of the centrifugally
flung filament passed above and between the quench roll and the nip
roll. The nip roller was then actuated to the "closed" or converged
position by means of an air cylinder which pressed the filament
against the quenching wheel with a force of 30 pounds. This
pressure was chosen by reference to equation (1) as will be
explained below. The filament was seized as it passed through the
nip zone and guided to engage the winder. The filament was then
continuously wound without interruption at 10 pounds tension.
Tight, uniform packages of grey iron ribbon 1 inch wide by 0.008
inch thickness were produced for eight hours without experiencing a
break.
The coefficients of dynamic friction for several metal systems are
given by The Handbook of Chemistry and Physics, 51st Edition, pp.
F15-F17. The coefficient of friction between grey iron and steel is
0.4. The coefficient of friction between steel and a copper film (8
kg. load) is given as 0.2. Taking the latter to be the same as the
friction coefficient between grey iron and copper, the necessary
minimum nip roll pressure was obtained from equation (1) by making
the following substitutions.
T = 10 lbs/in
.mu..sub.QR = 0.2
.mu..sub.nr = 0.4
from equation (1)
P .gtoreq. 10/0.2 + 0.4
P .gtoreq. 16.67 lbs/in
To provide a margin of safety, the nip roll pressure was set at 30
pounds.
EXAMPLE 3
An alloy formulated to be amorphous upon quenching was charged in
an apparatus for chill block spinning similar to that depicted
schematically in FIG. 2. However, no nip roller was provided. The
quenching wheel was an annular cylinder 16 inches O.D. .times. 15
inches I.D. .times. 2 inches face width construction of oxygen free
high conductivity copper. Steel end plates and a center supporting
shaft were attached to the copper cylinder. The supporting shaft
was of 11/2 inches O.D. and 1/2 inch I.D. Its interior communicates
with the interior of the quenching wheel. Cooling water was
circulated through the steel shaft and the interior of the
quenching wheel.
The alloy to be spun consisted of 38 atomic percent iron, 39 atomic
percent nickel, 14 atomic percent phosphorus, 6 atomic percent
boron and 3 atomic percent aluminum. It was melted in an argon
atmosphere at 1,000.degree. C. The quench wheel was set into motion
at 1,800 rpm and the molten alloy extruded through an orifice of
0.010 inch diameter at 300 cm/sec. The molten jet traversed a 1
inch air gap and impinged upon the surface of the rotating quench
wheel. A solidified filament 0.025 inch wide by 0.002 inch thick
was formed and was flung away by centrifugal action. The path of
the solidified filament commenced at a tangent to the surface of
the quench wheel, traveled downward at an angle of
30.degree.-60.degree. to the horizontal and terminated on the
laboratory floor.
The filament was seized near the point of departure from the quench
roll and guided to engage the winder. Attempts were made without
substantial success to wind the filament continuously under
controlled tension. At filament tensions of 1-10 grams filament
oscillations persisted causing eventual breakage. During the
periods between breaks, only an unsatisfactorily loose filament
winding was produced. With higher winding tensions the filament was
torn apart in the solidification zone immediately as it was
connected to the winder.
EXAMPLE 4
The apparatus of Example 3 was modified by provision of a nipping
roller depicted as 24 in FIG. 2. The nipping roller 24 was of 4
inch overall diameter and consisted of a 4 inch diameter hollow
steel cylinder of one-quarter inch wall thickness. Roller 24
comprised a 2 inch face width and was supported by a one-half inch
steel shaft mounted on roller bearings. The nip roller was freely
rotatable.
The chill block spinning process was started using the alloy
described in Example 3. The nip roller 24 was swiveled to a
position removed from chill roll 21 until the path of the
centrifugally flung filament passed above and between the quench
roll 21 and the nip roll 24. The nip roller was then actuated to
the "closed" or converged position as shown in FIG. 2. by means of
an air cylinder (not shown) which pressed the filament against the
quenching wheel with a force of 5 pounds. This pressure was chosen
by reference to equation (1) as explained below. The filament was
seized as it passed through the nip zone and guided to engage the
winder. The filament was then continuously wound without
interruption at 1 pound tension. Tight uniform packages of metal
ribbon 0.025 inch wide by 0.002 inch thickness were produced for 8
hours without experiencing a break.
The coefficients of dynamic friction for several metal systems are
given by The Handbook of Chemistry and Physics, 51st Edition, pp
F15-F17. The coefficient of friction between cast iron and steel is
0.4. The coefficient of friction between steel and a copper film (8
kg load) is given as 0.2. Taking these to be the same as the
friction coefficient between the alloy spun here and the necessary
steel and copper, minimum nip roll pressure was obtained from
equation (1) by making the following substitutions.
T = 1.0 lbs/in.
.mu..sub.QR = 0.2
.mu..sub.nr = 0.4
from equation (1)
P .gtoreq. 1.0/0.2 + 0.4
p .gtoreq. 1.67 lbs/in.
To provide a margin of safety, the nip roll pressure was set at 5
pounds.
* * * * *