Note: Descriptions are shown in the official language in which they were submitted.
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D E S C P~ I p T I O N
._ _ _ _ _ _ _
METHOD FOR PRODUCING GLASS FIBER
TECHNICAL FIELD
The lnvention disclosed herein relates to the centri-
fugal production of glass fibers or filaments by post fabrica-tion
-treatment of the spinner to improve the ph~sical attributes of
the spinner and to improve the quality of the glass filaments pro-
duced thereby.
BACKGROUND ART
The production of glass filamen-ts for use as insulation
by the centrifugal or rotory process is well known. Cobalt,
nickel, or iron based superalloys can be employed as the material
of the rotor, or centrifuge, with cobalt based and nickel based
receiving more widespread use because of their superior proper-
t:ies. For example, see U.S. Patent Nos. 3,933,484, 3,318,694,
3,010,201, 3,980,473, 3,881,918, 3,806,338, 3,984,240 and
~,203,747-
The requirements for the rotor alloys include high tem-
perature strength and creep resistance as well as oxidation
resistance and corrosion resistance to molten glass. Unfortun-
ately, the strongest alloys generally exhibit poor corrosion
resistance, and the more corrosion resistant alloys are, as a
practical matter, limited to service in the fiberization of tradi-
tional insulation forming glasses which generally e~hibit a low
fiberization temperature, i.e., glasses having a liquidus tempera-
ture of less than about 971 C (1780 F) and a viscoslty of about
316 poise at 1199 C (2190 E') or less.
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1 Further, some of the present rotors exhibit a
20-40 hour (or more) break-in period. During the break-in
period, the fibers produced from such spinners are
generally brashy and of low quality. Also~ an
objectionable amount of dust is produced during the
break in period which, along with the lo~ quality fibers,
produce a glass wool mat or pack having a lower thermal
resistance than that of a dust free, high quality fiber
wool pack.
~ DISCL_ URE OF THE INVENTION
This invention pertains to a method of producing
glass fibers wherein the spinner employed in a rotary
process is subjected to post fabrication treatments of hot
isostatic pressing and/or electropolishing to improve the
properties and performance of the rotor and to improve the
quality of the glass fibers and glass fiber pack produced
therefrom.
BRIEF DESCRIPTION OF DRA~IINGS
FIG. 1 is a semi-schematic, front elevational
view oF a rotary fiber-~orming system for producing glass
wool.
FIG. 2 is an enlarged cross-sectional view of the
spinner shown in FIG. l.
FIG~ 3 is a photograph of the mic.rostruc~ure of a
cross-section of a standard or "untreated" spinner.
FIG. 4 is a photograph of the microstructure of a
spinner of the same alloy composition as that shown in FIG.
3 which has been treated by hot isostatic pressing (HIP)
according to the principles of this invention.
FIG. 5 is a histogram of the fiber diameter
distribution produced on a standard spinner after 20
minutes of operation.
FIG. 6 is a histogram of the fiber diameter
distributlon produced by spinner receiving a HIP treatment
according to the principles of this in~ention after 20
minutes of operation.
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1 FIG. 7 is a histogram of the fiber diameter
distribution produced on a standard spinner after 100 hours
of operation.
FIG. 8 is a histogram of the fiber diameter
distribution produced by spinner receiving a HIP treatment
after 100 hours of operation.
FIG. 9 is a photograph of a portion of a pack of
glass fibers produced on a standard or untreated spinner
after 15 minutes of operation~
FIG. 10 7s a photograph of a portion of a mat or
pack of glass fibers produced on an electropolished spinner
according to the principles of thi~ invention after 15
minutes of operation.
FIG. 11 is a histogram of the fiber diameter
distribution produced on a standard spinner after 15
minutes of operation~
FIG. 12 is a histogr~m of the fiber diameter
distribution produced ~y a spinner receiving an
electropolishing treatment according to the principles oF
this invention after 15 minutes of operation.
~EST MODE OF _ RRYING OUT THE INVENTION
As shown in FIG. 1, rotary or centrifugal fiber-
forming system 40 is comprised of a flow means or channel
42 having a body of molten inorganic Material 44, such as
glass7 therein. A stream of molten glass ~6 is supplied to
the rotor or spinner 50 from channel 42, as is kno~n in the
art~
Spinner 50, which is adapted to be rotated at
high speeds is comprised of a quill 52 and a
circumferential stream defining or working wall 54 having a
plurality of orifices 55 therethrough to supply plurality
of pre-filament or primary streams of molten and inorganic
mdterial to be fiberized. After forming the body of the
rotor by any suitable process, such dS casting, thousands
of holes are formed in the circumferential wall, for
example, by electron beam drilling.
~ 2~ 3 3~316d
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[n conjunc-tion with rotor 50, a shroud 56 and circum~er-
en-tial hlower or fluid attenuation means 57 are adapted to fluid-
ically assist in the attenua~ion of the streams of molten material
into fibers or filaments 60. A binder material or coating may be
applied to the fibers 60 by means of binder applicators 58 as is
known in the art. The fibers then may be collected as a pack or
mat to produce "wool" type glass fiber insulation.
According to the principles of this invention, spinner
50 receives a post-fabrica-tion treatment (i.e., a -treatment subse-
1~ quent to the formation of the thousands of oriices 55 in the cir-
cumferential wall 54) of hot isostatic pressing and/or electro-
polishing to improve the physical properties and performance of
the spinner and/or improve the quality of the fibers and wool pack
produced therefrom. However, it is to be understood tha-t the
alloy may be HIP'd prior to the formation of orifices 55, if de-
sired, to achieve the strengthening o:E the alloy.
Rotor 50 may be of any of the alloys conventionally
employed in a rotary fiber forming process such as a cobalt (Co~
based superalloy, or nickel (Ni) based superalloy or iron (Fe)
based superalloy which contain carbon and carbide formers.
Exemplary carhide formers are tungsten (W)~ chromium (Cr),
vanadium (Va)~ tantalum (Ta), hafnium (Hf), zirconium (Zr~ and
titanium (Ti). Desirably, the rotor is a nickel based superalloy
or a cobalt based superalloy with the latter being preferred. The
HIP treatment o~ such superalloys provides a mechanically stronger
spinner having greater high-temperature service capability than an
un-HIP'd spinner of the same alloy composition. With such im-
~21;)331~
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p:~oved h:Lyh~temperature service capabilities, HIP treated spinners
ar~ capable of fiberizing not only traditional insulation forming
g]asses but also glasses which are of a higher liquidus tempera-
-ture and of higher viscosity. The service life of un-HIP'd spin-
ners on such higher liquidus glasses is unacceptably brief.
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1 In addttion to the improved rupture strength and
improved creep rate3 thus providing a mechanically stronger
spinner, it has been surprisingly found that diameters of
the orifices 55 are rendered more uniform by the HIP
treatment~ Also, the HIP treatment appears to reduce the
rate of orifice wear to prolong rotor life, and to a lesser
extent9 smooths the orifice walls to provide "smoother or
less brashy" filaments immediately upon start-up.
It is believed that the improved high-temperature
strengtn is provided by redistribution of the metallic
car~ides in the alloys through precipitation hardening.
~lith the simultaneous application of a sufficient amount of
heat and pressure during HIP'ing for a sufficient period of
time, the metallic carbides precipitate along grain
boundaries to provide grain boundary locking to reduce the
amount of ~islocation rnovement. Merely heating the rotor
doPs not produce the tight, regular network of precipitated
carbi~es as can be seén in FIG. 4.
FIGSo 3 and 4 are photos of enlarg.ed
cross-sections of spinners fabricatêd from a cobalt based
superalloy containing about 45% cobalt (Co), 31~ chromium
(Cr), 1~ nickel (Ni) and containing lesser amounts of
tungsten (W), tantalum (Ta), carbon (C), silicon (Si),
zirconium (Zr), and boron tB). FIG. 3 shows the
~icrostructure of an unused and un-HIP'd spinner of such an
alloy, and FIG, 4 shows the micros~ructure of an unused
spinner after HIP treatment a~ 1204~C (2200~F) and 103.42
MPa (15,000 psi) for two hours. Clearly, a metallurgical
change hds taken place as a result of the HIP treatment
sufficient to increase the mechanical strength and
high-temperature service capability of the rotor 50. In
general, the pressure applied during the HIP'ing treatment
should be greater than the yield strength of the material
at that ternperature to render thee orifices in the rotor
wall rnore uniform and to provide the strength improvement
in the material itself.
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1 Regarding the HIP treatment, temperatures within
the range from about 1093 to 1204~C (2000 to 2200F)
pressures within the range from about 68.95 MPa (10,000
psi) to about 206.84 MPa (30,000 psi), and times of about 1
to about 4 hours are exemplary to produce the metallurgical
changes and orifice uniformity improvement heretofore
discussed. A HIP temperature of 1177C (2150~F)~ pressure
of 103.42 MPa (15,000 psi) for a period of two hours was
employed on a number of spinners to produce the results
shown in FIGS. 4, 6 and ~ for the aforementioned cobalt
based alloy~ At the end of the HIP treatment cycle, the
HIP chamber is purged of its working fluid9 usually an
inert gas such as argon9 and the oxygen containing
atmosphere is permitted to enter the HIP chamber. Since
the spinners are still extremely hot, it is believed the
oxygen in the air reacts with the surface of the alloy to
form a thin metallic oxide coatirg thereon, including the
walls of the orlfices themselves. For example, for the
aforementioned cobalt base alloy9 which contains Cr, an
20 oxide of Cr is believed formed9 wilich is less suscept~ble
to the corrosive attack of the mollten glass,
Regarding the increase lin uniformity of the
orificed dlameters, FIGS. 5 and 6 show the percent
frequency distribution of filaments produced, from
traditional insulation Forming glasses, after 20 minutes of
operation from HIP'd and un-HIP'd spinners of the
aforementioned cobalt based superalloy.
FI60 5 shows the ~iber diameter distribution
produced from the untreated spinner. Analysis indicates
that the mean fiber diameter collected was 5.g microns, and
the standard deviation therefrom was 4.8 microns. The
fiber diameter distribution of the HIP treated spinner is
shown in FIG. 6, with a mean fiber diameter oF 4,1 microns,
~nd d standard deviation therefrom of 4.3 microns. With
each of these spinners being fabricated essentially
identical to one another, with the exception of the HIP
treatment, it can be seen that the diameter of the fibers
33~3;~
1 produced from the HIP'd spinners are more uniform than the
un-HlP'd spinners.
FIGS. 7 and 8 are simiiar percent frequency
histograms of the fiber diameters produced by HlP'd and
un-HlP'd spinners after 100 hours of operation employing
traditional insulation forming glasses. FIG~ 7, shows the
fiber distribution produced from standard or un-HlP'd
spinner of the aforementioned cobalt base super alloy. The
fibers produced therefrom had a mean fiber diameter of 7.64
~ microns with a standard deviation of 5tl3 microns~
F IG. 8 shows the fiber distribution of filaments
produced on a substantially identical spinner to that
represented in FIG. 7, with the exception of a
post-fabrication HIP treatment according to the principles
Of this invention. The fibers produced therefrom had a
mean diameter of 5.69 microns with a standard deviation of
3.75 microns, Once again, the diameter of the fibers
produced by the HIP'd spinner are more uniform than the
fibers produced on the untreated spinner~
Further, measurements of orifice diameters taken
at selected sections aiong a spinner wall before and after
~IIP treatment also show that the hole diameters are
rendered more uniform as 3 result of the HIP treatment.
Also, orifice diameters were rendered smaller after HIPIing
from about 0.0 cm (0.0") (iOe., no change) to about 0.00254
cm (0.001"), with an average orifice diameter decrease of
about 37~ being observed. Thus, it is believed that fibers
having a narrower diameter distribution are produced as
represented in th~ comparisons provided in F15S. 5 through
8. It is also interesting to note that the HIP treated
spinners produced fewer larger diameter filaments which
accounts in part, at least, for the reduction in the mean
fiber dia~eter for such spinners.
Rupture tests conducted on test samples of the
aforementioned cobalt based super alloy also show
surprising improv~ments in critical properties for spinner
materials~ Specimens of un-HIP'd and HlP'd cobalt based
3~2
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1 super alloys were individually placed under a tensile load
of 20.68 MPa (3,000 psi) at a temperature of 1149C
(2~100F) and held there until the specimen rupturedO The
standard or un-HlP'd specimens had a life of about 32
hours, whereas the HIP treated specimens had a life of
about 7n hours. The untreated specimens had a rupture
ductility of about 4.2 percent whereas the HIP treated
specimens had a rupture ductility of about 6.7 percent.
Further, the untreated specimens had a creep rate of 6.6 x
10 4 cm per Cm per hour whereas the HIP treated specimens
had a creep rate of 4.2 x 10 4 cm per cm per hour.
Further comparisons between un-HlP'd and HlP'd
spinners indicate that after 180 hours of operation on
traditional insulation forming glasses, the HIP treated
spinners had approximately an 18 perc~nt reduction in hole
we3r as compared to the standard or un-HlP'd spinners oF
the aforementioned cobal~ base superalloy. Such a
reduction in hole wezr may be based in part on the
toughening of the metal itself and in part based upon the
formation of an oxide coating on the alloy surface as a
result of the HIP treatment process as discussed previously
herein,
Surprisingly, the k-value or thermal conductance
of the insulation pack produced by the HIP treated spinner
is lower than that produced by the un-HIP'd spinner. An
exptanation may be found in the fact that for the HIP'd
spinner the fiber distribution para~eter or ~ (which
actually is the standard deviation from the mean fiber
diameter) has a lower value. This reduces the equivalent
3~ radiation conductivity k rad for the pack~
1 A ~
~ B
k rad ~ 2 + ~2
l/h~ e
35 ~, B ~re constants
is tne pack density
is the mean fiber diameter
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1 ~ ;s the fiber distribution parameter
FIGS. 5 through 8 clearly indicate that for thP
HlP'd spinner, ~ has a lower value.
The use of electropolishing as a post-fabrication
treatment ~i.e., after the orifices 55 are formed in rotor
50) has been snown to (a~ virtually eliminate any break-in
period normally ~ssociated with such spinners and to (b)
provide a glass fiber pack of improved quality.
Electropolishing, which is the opposite of the
electroplating process, is particularly effective since
electropolishing preferentially attacks or dissolves the
sharp edges or discontinuities in the orifices or at the
edges of the orifices, which occur as a result of the
orifice formation process.
A spinner composed of the aforementioned cobalt
base superalloy having a preselected number of orifices
formed therein, was placed in a polyethylene electrolytic
cell having a stainless steel cathode ring and a stainless
steel anode disk ln contact with the spinner, thus making
the spinner the anode, in the el~ctrolytic circuit. The
electrolytic cell was suitably filled with an electrolyte
composition of 75.76 percent (by volume) methonol, 1S.15
percent phosphoric acid ~H3pO4), and 9,09 percent sulFuric
acid (H2S04), and energized to suitably polish the orifices
of the spinner. Current density is desirably held within
the range from about 0.11 amps/cm2 to about 0.14 amp/cm2
for about 30 minutes. Typically, times may vary~ but they
usually fdll within the range from about 10 minutes to
about 50 minutes for suitable polishing to take place.
As a preparatory step to the electropolishing
treatment itself, the spinner should be thoroughly cleaned
of any residue and/or foreign material by means of solvent
washing and/or vapor honing and the like to achieve the
maximu~ electropolishing rate~
At fiberi~ation start-up, the electropolished
spinners immediately began producing glass Fibers having a
surface smoothness or texture similar to that produced by
3~'~
- 10-
1 seasoned spinners, without the electropolishing tredtment.
It is known that new standard or untreated spinners
generally produce mats of glass fibers having a brashy
feel. Such an undesirable brashy Feel dissipates as the
spinner is seasoned during operation. In addition, the
electropolished spinners produced a pack of fibers that has
a significantly reduced dust cor,tent as compared to
unpolished, new spinnersO
FIG. 9 is a photo of a mat or pack of glass
fibers produced From a standard or untreated spinner after
15 mlnutes of operation. It is clear that there are a
number oF ultr2fine fibers in the pack, a number of which
are fused or bonded to tne surface of the larger diameter
fibers.
FIG. 10 is an enlarged photo of a pack oF glass
fibers produced on a spirnPr after receiving the post
Fabrication electropolish1ng treatment. Clearly, the
number of ultrafine filaments is substantially reduced.
Regarding the spinn~rs associated with FIGS.
9-12, such spinners were of the aforementionecl cobalt-based
superalloy, and the photos and histograms are based upon
samples taken approximately after 15 minu$es of operation.
FIG. 11 is a histogram of the percent frequency
distribution oF the filament diameters produced by standard
or untreated spinner, and FIG. 12 is a histogram of the
percent frequency distribution of the filament diameters
produced by an electropolished spinner according to the
principles of this invention. As can be seen therein, the
percentag~ of the fibers having a diameter of 1 micron or
less, (i.e. those in the submicron range) are substantially
reduced. Also, the number of filaments in the range from 0
to 3 microns are also substantially reduced.
Analysis nF the samples from the standard spinner
indic~tes ~he fibers ~xhibited a mean diameter of 7.4
microns and d standard deviation therefrom of 5.62 microns.
The fibers produced from the electropolished spinner
1 exhibited 3 mean filament diameter of 6.g4 microns with a
standard deviatisn therefrom of 5~04 micrors.
With regard to the number of filaments in the
submicron range, or those filaments having a diameter of l
micron or less, an analysis of product samples indicates
that the standard spinners produce a ~ool pack haviny
submicron filaments which comprise from about 2 to about
4.4 percent of the mat or pack. The electropolished
spinners, however, produced a pack of glass fibers having
frvm about ~4 to about 2.8 percent filaments in the
submicron range.
Additionally, the standard spinner prsduced a
pack of glass fibers having from about 18.8 to about 27.3
percent filaments having a diameter of 3 microns or less~
~he electropolished spinner produced a pack of glass fibers
having from about 15.3 to about 25~2 percent Filaments
having a diameter of 3 microns or less.
Wi~h the reduction of the percentaye of ultrafine
filaments, and, more importantly, those in the submicron
2() range, the pack does not e~hibit the same brashy feel to
the touch as exhibited by the untreated spinner at startup.
Further, the reduction of the ultrafine and submicron
diameter filaments contributes in large part to the
reduction in the "dust" produced by untreated spinners.
Thus, the quality of the glass filam2nts and pack
produced ~rom such spinners is surprisingly and
significantly improved by the application of an
electropolishing treatment to the fabricated spinner prior
to operation of the spinner for the production of fibers.
3~ As a result of the smooth, higl-quality fibers
and the reduced dust content, the k-value of the insulation
pack is also decreased since the fiber distribution
parameter is decreased as a result of the electropolishing
treatment. Thus, the thermal resistance of the pack
increased as compared to a pack produced employing
non-electropolished spinners.
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1 The hot isostatic pressing treatment ar,d the
electropolish~ng treatment may be used alone or desirably
in combination with one another to achieve the various
benefits noted herein. When combining the hot isostatic
pressing with the electropolishing treatment, it is
preferred th~t the electropolishing treatment precede the
HIP'ing treatment for maximum benefit. Otherwise, the
surface discontinuities and sharp edges may be more
difficult to remov by electropolishing if the HIP ' i ng
treatment precedes the electropolishing treatment.
lt is apparant that, within the scope of the
present invention, modifications of different arrangements
can be made other than as herein disclosed. The present
disclosure is merely illustrative with the inventi~n
comprehending all variations thereof.
INDUSTRIAL APPLICABILITY
The invention described herein is readily
applicable to th~ ~lass fiber industry.
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