Note: Descriptions are shown in the official language in which they were submitted.
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MICROFIBER REINFORCEMENT FOR ABRASIVE TOOLS
TECHNICAL FIELD
Chopped strand fibers are used to reinforce resin-based grinding wheels. The
chopped strand
fibers typically 3-4 mm in length, are a plurality of filaments. The number of
filaments can
vary depending on the manufacturing process but typically consists of 400 to
6000 filaments
per bundle. The filaments are held together by an adhesive known as a sizing,
binder, or
coating that should ultimately be compatible with the resin matrix. One
example of a chopped
strand fiber is referred to as 183 Cratec , available from Owens Coming.
Incorporation of chopped strand fibers into a dry grinding wheel mix is
generally
accomplished by blending the chopped strand fibers, resin, fillers, and
abrasive grain for a
specified time and then molding, curing, or otherwise processing the mix into
a finished
grinding wheel.
In any such cases, chopped strand fiber reinforced wheels typically suffer
from a number of
problems, including lower strength, poor grinding performance as well as
inadequate wheel
life, presumably due to incomplete dispersal of the filaments within the
chopped strand fiber
bundle.
There is a need, therefore, for improved reinforcement techniques for abrasive
processing
tools without compromising grinding performance.
SUMMARY OF INVENTION
One embodiment of the present invention provides a composition, comprising an
organic
bond material (e.g., thermosetting resin, thermoplastic resin, or rubber), an
abrasive material
dispersed in the organic bond material, and microfibers uniformly dispersed in
the organic
bond material. The microfibers are individual filaments and may include, for
example,
mineral wool fibers, slag wool fibers, rock wool fibers, stone wool fibers,
glass fibers, and in
particular milled glass fibers, ceramic fibers, milled basalt fibers, carbon
fibers, aramid fibers,
and polyamide fibers, and combinations thereof. The microfibers can have an
average length,
for example, of less than about 1000 nm. In one particular case, the
microfibers have an
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average length in the range of about 100 to 500 nm and a diameter less than
about 10
microns. In some embodiments, chopped strand fibers, e.g., fiberglass chopped
strand fibers,
are also present. In many instances the composition further includes one or
more fillers with
at least one being an active filler, capable of chemically reacting with the
microfibers at the
temperatures that occur during grinding. These chemical reactions of the
active filler and
microfibers provide various abrasive process benefits (e.g., improved wheel
life, higher G-
ratio, and/or anti-loading of abrasive tool face). Examples of suitable active
fillers include
manganese compounds, silver compounds, boron compounds, phosphorous compounds,
and
combinations thereof. In one specific such case, the one or more active
fillers include
manganese dichloride. Other fillers that do not chemically react with the
microfibers may
also be incorporated.
The composition may include, for example, from 10 % by volume to 50 % by
volume of the
organic bond material, from 30 % by volume to 65 % by volume of the abrasive
material, and
from 1 % by volume to 20 % by volume of the microfibers. In another particular
case, the
composition includes from 25 % by volume to 40 % by volume of the organic bond
material,
from 50 % by volume to 60 % by volume of the abrasive material, and from 2 %
by volume
to 10 % by volume of the microfibers. In another particular case, the
composition includes
from 30 % by volume to 40 % by volume of the organic bond material, from 50 %
by volume
to 60 % by volume of the abrasive material, and from 3 % by volume to 8 % by
volume of
the microfibers. In some instances, the composition also contains chopped
strand
fibers, e.g., in an amount within the range of from about 0.1 to about 10 % by
volume, for
example, from about 2 to about 8 % by volume.
In another embodiment, the composition is in the form of an abrasive article
used in abrasive
processing of a workpiece. In one such case, the abrasive article is a wheel
or other suitable
form for abrasive processing. Typically, the composition is a bonded abrasive
article e.g., a
wheel or another type of tool, in which abrasive grains are held in a three
dimensional
organic bond matrix.
In one aspect, an abrasive article includes an organic bond material; an
abrasive material,
dispersed in the organic bond material; chopped strand fibers dispersed in the
organic bond
material; mineral wool microfibers that are uniformly dispersed in the organic
bond material,
wherein said microfibers are individual filaments; and one or more fillers. In
specific
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implementations, the one or more fillers include a manganese compound. In some
cases, an
abrasive article contains chopped strand fibers, mineral wool microfibers, a
manganese
compound and, optionally, other fillers such as, for example, lime, pyrites
and others, yet it
does not include potassium salts (e.g., potassium sulfate and/or potassium
chloride).
Another embodiment of the present invention provides a method of abrasive
processing a
workpiece. The method includes mounting the workpiece onto a machine capable
of
facilitating abrasive processing, and operatively coupling an abrasive article
to the machine.
The abrasive article includes an organic bond material, an abrasive material
dispersed in the
organic bond material, and microfibers uniformly dispersed in the organic bond
material,
wherein the microfibers are individual filaments, e.g., having an average
length of, for
example, less than about 1000 nm. The abrasive article may further include
chopped strand
fibers, dispersed in the organic bond material. In specific implementations,
the abrasive
article contains one or more fillers, e.g., including a manganese compound. In
some cases, the
abrasive article excludes potassium salts. The method continues with
contacting the abrasive
article to a surface of the workpiece.
The abrasive article can be reinforced, e.g., internally reinforced,
containing, for example,
one or more fiberglass reinforcements. For instance, an abrasive article
comprises an organic
bond material; an abrasive material, dispersed in the organic bond material;
mineral wool
microfibers that are uniformly dispersed in the organic bond material, wherein
said
microfibers are individual filaments; one or more fillers, the one or more
fillers including a
manganese compound; and at least one glass web reinforcement.
Aspects of the invention provide compositions in the form of abrasive articles
such as, for
example, grinding wheels or other bonded abrasive tools that exhibit improved
strength (as
reflected, e.g., by the burst speed characterizing the tool) and impact
resistance, with tools
according to embodiments of the invention being robust and less prone to
breakage. Abrasive
articles according to embodiments of the invention also display improved wheel
wear rate, G-
ratio and a longer tool life. Examples of the bonded articles disclosed herein
can exhibit good
thermal shock resistance with little or no thermal cracking being observed.
Abrasive articles
that contain glass web reinforcements, and, optionally, chopped strand fibers,
typically
display improved impact properties.
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The features and advantages described herein are not all-inclusive and, in
particular, many
additional features and advantages will be apparent to one of ordinary skill
in the art in view
of the drawings, specification, and claims. Moreover, it should be noted that
the language
used in the specification has been principally selected for readability and
instructional
purposes, and not to limit the scope of the inventive subject matter.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 is a plot representing the strength analysis of compositions
configured in accordance
with various embodiments of the present invention.
Figure 2 is a plot representing the grinding performance of a tool according
to embodiments
described herein.
DESCRIPTION OF EMBODIMENTS
As previously mentioned, chopped strand fibers can be used in dense resin-
based grinding
wheels to increase strength and impact resistance, where the incorporation of
chopped strand
fibers into a dry grinding wheel mix is generally accomplished by blending the
chopped
strand fibers, resin, fillers, and abrasive grain for a specified time.
However, the blending or
mixing time plays a significant role in achieving a useable mix quality.
Inadequate mixing
results in non-uniform mixes making mold filling and spreading difficult and
leads to non-
homogeneous composites with lower properties and high variability. On the
other hand,
excessive mixing leads to formation of "fuzz balls" (clusters of multiple
chopped strand
fibers) that cannot be re-dispersed into the mix. Moreover, the chopped strand
itself is
effectively a bundle of filaments bonded together. In either case, such
clusters or bundles
effectively decrease the homogeneity of the grinding mix and make it more
difficult to
transfer and spread into a mold. Furthermore, the presence of such clusters or
bundles within
the composite decreases composite properties such as strength and modulus and
increases
property variability. Additionally, high concentrations of glass such as
chopped strand or
clusters thereof have a deleterious affect on grinding wheel life. Increasing
the level of
chopped strand fibers in the wheel can also lower the grinding performance
(e.g., as
measured by G-Ratio and/or WWR).
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In one particular embodiment of the present invention, producing microfiber-
reinforced
composites involves complete dispersal of individual filaments within a dry
blend of suitable
bond material (e.g., organic resins) and fillers. Complete dispersal can be
defined, for
example, by the maximum composite properties (such as strength) after molding
and curing
of an adequately blended/mixed combination of microfibers, bond material, and
fillers. For
instance, poor mixing results in low strengths but good mixing results in high
strengths.
Another way to assess the dispersion is by isolating and weighing the
undispersed (e.g.,
material that resembles the original microfiber before mixing) using sieving
techniques. In
practice, dispersion of the microfiber reinforcements can be assessed via
visual inspection
(e.g., with or without microscope) of the mix before molding and curing. As
will be apparent
in light of this disclosure, incomplete or otherwise inadequate microfiber
dispersion generally
results in lower composite properties and grinding performance.
In accordance with various embodiments of the present invention, microfibers
are small and
short individual filaments having high tensile modulus and can be either
inorganic or organic.
In one example, the microfibers are mineral wool microfibers, also known as
slag or rock
wool microfibers. Examples of other microfibers that can be utilized include
but are not
limited to milled glass fibers, milled basalt fibers, ceramic fibers, carbon
fibers, aramid or
pulped aramid fibers, polyamide or aromatic polyamide fibers.
One particular embodiment of the present invention uses a microfiber that is
an inorganic
individual filament with an average length that is less than or equal to about
4,000 microns
and filament diameter less than or equal to 40 microns and a reinforcing
aspect ratio (length
to diameter or L/d) of at least 10. For instance, an average length of about
100 microns and
filament diameter of about 10 microns result in a reinforcing aspect ratio of
10. A filament
length of about 50 microns with a filament diameter of about 5 microns has a
reinforcing
aspect ratio of 10. Similarly, a filament length of about 20 with a filament
diameter of about 2
microns has a reinforcing aspect ratio of 10.
In addition, this example microfiber has a high melting or decomposition
temperature (e.g.,
over 800 C), a tensile modulus greater than about 50 GPa, and has no or very
little adhesive
coating. Preferably, the microfibers are highly dispersible as discrete
filaments, and resistant
to fiber bundle formation. Typically, the microfibers will chemically bond to
the bond
material being used (e.g., organic resin).
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In contrast, a chopped strand fiber and its variations include a plurality of
filaments held
together by adhesive and have aspect ratios less than 10. However, some
chopped strand
fibers can be milled or otherwise broken-down into discrete filaments, and
such filaments can
be used as microfiber in accordance with an embodiment of the present
invention. In some
such cases, the resulting filaments may be significantly weakened by the
milling/break-down
process (e.g., due to heating processes required to remove the adhesive or
bond holding the
filaments together in the chopped strand or bundle). Thus, the type of
microfiber used in the
bond composition will depend on the application at hand and desired strength
qualities.
Mineral wool microfibers, in the form of individual filaments, can be present
in the
compositions and/or tools described herein in an amount within the range of
from about 0.4
to several volume percents, for example, within the range of from about 0.4 to
about 12 vol.
%. Some abrasive articles according to aspects of the invention contain
mineral wool
microfibers in an amount of from about 0.5 to about 10 vol %. In specific
implementations,
the abrasive article contains mineral wool microfibers in an amount within the
range of from
about 0.8 to about 8 volume percent, e.g., within the range of from about 0.8
to about 4
volume %.
In one such embodiment, microfibers suitable for use in the present invention
are mineral
wool fibers such as those available from Sloss Industries Corporation, AL, and
sold under the
name of PMF . Similar mineral wool fibers are available from Fibertech Inc,
MA, under the
product designation of Mineral wool FLM. Fibertech also sells glass fibers
(e.g., Microglass
9110 and Microglass 9132). These glass fibers, as well as other naturally
occurring or
synthetic mineral fibers or vitreous individual filament fibers, such as stone
wool, glass, and
ceramic fibers having similar attributes can be used as well. Mineral wool
generally includes
fibers made from minerals or metal oxides. An example composition and set of
properties for
a microfiber that can be used in the bond of a reinforced grinding tool, in
accordance with
one embodiment of the present invention, are summarized in Tables 1 and 2,
respectively.
Numerous other microfiber compositions and properties sets will be apparent in
light of this
disclosure, and the present invention is not intended to be limited to any
particular one or
subset.
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Oxides Weight %
Si02 34-52
A1203 5-15
CaO 20-23
MgO 4-14
Na20 0-1
K20 0-2
TiO2 0-1
Fe203 0-2
Other 0-7
Table 1: Composition of Sloss PMF Fibers
Hardness 7.0 mohs
Fiber Diameters 4 - 6 microns average
Fiber Length 0.1 - 4.0 mm average
Fiber Tensile Strength 506,000 psi
Specific Gravity 2.6
Melting Point 1260 C
Devitrification Temp 815.5 C
Expansion Coefficient 54.7 E-7 C
Anneal Point 638 C
Strain Point 612
Table 2: Physical properties of Sloss PMF Fibers
The composition can further include chopped strand fibers, for instance
fiberglass chopped
strand fibers, such as those described above. Chopped strand fibers can have a
length of, for
example, 3-4 mm, each strand being formed from a plurality of filaments held
together by an
adhesive known as a sizing, binder, or coating. The number of filaments and
filament
diameters can vary depending on the manufacturing process but typically
consists of 400 to
6000 filaments per bundle with filament diameters being 10 microns or greater.
The average
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reinforcing aspect ratio is less than 3. One example of a chopped strand fiber
material that
can be utilized is referred to as 183 Cratec , available from Owens Corning.
Based on the total volume of the composition or abrasive article, chopped
strand fibers may
be added at levels that represent a few volume percents. Higher or lower
levels can be
selected based, for example, on desired properties, e.g., impact resistance,
in the finished
abrasive article. In some embodiments, the abrasive article contains the
minimum level of
chopped strand fibers determined to provide one or more such desired property.
In specific
implementations, chopped strand fibers are present in an amount of from about
0 to about 10
vol. %, e.g., from about 0.1 to about 10, for instance from about 2 to about 8
vol. %, such as
from about 3 to about 6 vol. %.
Bond materials that can be used in the bond of grinding tools configured in
accordance with
an embodiment of the present invention include organic resins such as epoxy,
polyester,
phenolic, and cyanate ester resins, and other suitable thermosetting or
thermoplastic resins. In
one particular embodiment, polyphenolic resins are used (e.g., such as Novolac
resins).
Specific examples of resins that can be used include the following: the resins
sold by Durez
Corporation, TX, under the following catalog/product numbers: 29722, 29344,
and 29717;
the resins sold by Dynea Oy, Finland, under the trade name Peracit and
available under the
catalog/product numbers 8522G, 8723G, and 8680G; and the resins sold by Hexion
Specialty
Chemicals, OH, under the trade name Rutaphen and available under the
catalog/product
numbers 9507P, 86865P, and 8431SP. Numerous other suitable bond materials will
be
apparent in light of this disclosure (e.g., rubber), and the present invention
is not intended to
be limited to any particular one or subset.
Abrasive materials that can be used to produce grinding tools configured in
accordance with
embodiments of the present invention include commercially available materials,
such as
alumina (e.g., extruded bauxite, sintered and sol gel sintered alumina, fused
alumina), silicon
carbide, and alumina-zirconia grains. Superabrasive grains such as diamond and
cubic boron
nitride (cBN) may also be used depending on the given application. In one
particular
embodiment, the abrasive particles have a Knoop hardness of between 1600 and
2500
kg/mm2 and have a size between about 10 millimeters and 3000 microns, or even
more
specifically, between about 5 millimeters to about 2000 microns. Combinations
of two or
more types of abrasive grains also can be utilized. In one case, the
composition from which
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grinding tools are made comprises greater than or equal to about 50% by weight
of abrasive
material.
In specific embodiments, the composition further includes one or more active
fillers with at
least one filler being capable of chemically reacting with the microfibers at
the temperatures
that occur during grinding. In one such case, the microfiber-reactive active
filler is selected
from: manganese compounds, silver compounds, boron compounds, phosphorous
compounds, and any combinations thereof. In specific implementations, the
active filler
utilized is a manganese compound, e.g., a manganese halogenide, such as, for
instance,
manganese dichloride, metallic compound complex salts containing manganese,
combinations containing one or more manganese compounds and so forth. Amounts
of
manganese compound active filler present in the composition and/or abrasive
article can be
within the range of from about 1 to about 10 vol. %, e.g., within the range of
from about 2 to
about 4 vol. %. Other amounts can be utilized.
Thus, an abrasive article composition that includes a mixture of microfibers,
e.g., mineral
wool microfibers, and active fillers is provided. Benefits of the composition
include, for
example, improvements in both strength and grinding performance.
Other fillers that do not chemically react with the microfibers may also be
incorporated.
These additional fillers may be added to facilitate dispersion of the
microfibers or enhance
grinding performance through conventional mechanisms known to those skilled in
the art
such as resin degradation, work-piece degradation, abrasive degradation,
antiloading
qualities, and lubrication. Suitable examples include pyrite, zinc sulfide,
cryolite, calcium
fluoride, potassium aluminum fluoride, potassium floroborate, potassium
sulfate, potassium
chloride, and combinations thereof.
During the manufacture of abrasive articles, fillers often are provided as a
filler "package",
also referred to herein as a filler "component", containing a combination of
compounds that
act as processing aids, to disperse the microfibers, provide lubricantion
during the pressing
cycle, absorb moisture or volatiles during curing and so forth. Such fillers
can, for example,
decrease the friction between a finished abrasive article and a workpiece,
protect the abrasive
grains used, and/or provide other benefits, as known in the art. Filler
components that can be
employed in the compositions and/or articles described herein include, for
example, lime,
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pyrites, potassium sulfate (K2SO4), potassium chloride (KC1), zinc sulfide,
cryolite, calcium
fluoride, potassium aluminum fluoride, potassium floroborate, combinations
thereof, as well
as active fillers such as the manganese compounds discussed above, and so
forth. In some
aspects described herein, the filler package excludes potassium salts.
In one implementation, the composition and/or abrasive article includes,
abrasive grains, an
organic bond, mineral wool microfibers that are uniformly dispersed in the
organic bond, the
mineral wool microfibers being individual filaments, chopped strand fibers, a
manganese
compound and, optionally, other fillers. The composition and/or abrasive
article, however,
excludes potassium salts such as, for example, potassium sulfate and/or
potassium chloride. It
has been discovered that omitting potassium salts from some of the
compositions and/or
abrasive articles described herein can result in enhanced grinding performance
of the tool,
relative to a comparative tool that contains potassium sulfate and/or other
potassium salts. As
used herein, the term "comparative" refers to articles or compositions that
are similar to the
experimental article or composition in all aspects except for the amount,
property, and/or
compound or component being investigated.
In specific implementations, the composition or abrasive article includes
(based on the total
volume of the composition or abrasive article) from about 10 to about 50 vol
%, e.g., from
about 38 to about 41 vol% organic bond; from about 30 to about 65 vol %, e.g.,
from about
49 to about 59 vol. % abrasive grain; from about 0.4 to about 12 vol %, e.g.,
from 0.8 to
about 8 vol % of mineral wool microfibers; from about 0 to about 10 vol %, for
example
from about 0.1 to about 10 volume %, e.g., from about 2 to about 8 or from
about 3 to about 6
volume % of chopped strand fibers; and from about 1 to about 10, e.g., from
about 2 to about
4 vol. % manganese compound active filler.
Optionally, one or more other fillers such as described above, e.g., lime,
iron pyrite,
potassium sulfate, potassium chloride and so forth, also are present. Suitable
amounts used
can be selected as known in the art. In some cases, the volume % of potassium
salts is 0.
Also optionally, the composition or abrasive article can further include
secondary abrasive
grains capable of acting as fillers. Examples include silicon carbide, brown
fused alumina,
and others, as known in the art.
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Some of the abrasive articles described herein can contain abrasive grains, a
bond,
microfibers that are individual filaments, e.g., mineral wool microfibers, an
active filler, for
example a manganese compound, one or more reinforcements and, optionally,
chopped
strand fibers. As used herein, terms such as "reinforced" or "reinforcement"
refer to discrete
layers or inserts or other such components of a reinforcing material that is
different from the
bond and abrasive materials employed to make the bonded abrasive tool. Terms
such as
"internal reinforcement" or "internally reinforced" indicate that these
components are within
or embedded in the body of the tool. Background details related to
reinforcement techniques
and materials are described, for example, in U.S. Patent No. 3,838,543, issued
on October 1,
1974 to Lakhani, which is incorporated herein by reference in its entirety.
Reinforced wheels
also are described in U.S. Patent Nos. 6,749,496 issued to Mota, et al. on
June 15, 2004 and
6,942,561 issued to Mota, et al. on September 13, 2005, both being
incorporated herein by
reference in their entirety.
In many cases, internally reinforced abrasive wheels include discs cut from
nylon, carbon,
glass or cotton cloth. In specific implementations, the abrasive article
includes a fiberglass
reinforcement that is in the form of a web, e.g., a material woven from very
fine fibers of
glass, also referred to herein as glass cloth. One, two or more than two such
fiberglass webs
can be used and they can be arranged in the bonded abrasive tool in any
suitable manner.
The fiberglass utilized can be E-glass (alumino-borosilicate glass with less
than 1 wt% alkali
oxides. Other types of fiberglass, e.g., A-glass (alkali-lime glass with
little or no boron
oxide), E-CR-glass (alumino-lime silicate with less than 1 wt% alkali oxides,
with high acid
resistance), C-glass (alkali-lime glass with high boron oxide content, used
for example for
glass staple fibers), D-glass (borosilicate glass with high dielectric
constant), R-glass
(alumino silicate glass without MgO and CaO with high mechanical
requirements), and 5-
glass (alumino silicate glass without CaO but with high MgO content with high
tensile
strength), glass fiber webs and so forth can be used.
Compositions in the form of abrasive articles can include porosity, e.g., at
levels suitable for
a given application. In specific examples, the porosity is less than 30 volume
%, for instance
within the range of from about 2 % to about 8 % by volume.
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Without wishing to be held to any particular interpretation, it is believed
that manganese
compounds chemically interact with mineral wool microfibers providing multiple
abrasive
process benefits, such as, for instance, increased tool strength and grinding
performance
and/or wheel life benefits. In contrast to chopped strand fibers, the high
aspect ratio of
microfibers (e.g., mineral wool, milled glass or milled basalt fibers) offers
an increased
surface area, resulting in synergistic reactions with the active filler or
fillers employed. The
presence of discrete filaments with very low coating levels, in conjunction
with one or more
manganese compounds, provides optimal composite and grinding benefits as
opposed to fiber
bundles with high coating levels. Furthermore, it has been observed that the
presence of
potassium salts such as potassium chloride or potassium sulfate interferes
with this
"synergistic" interaction of the maganaese salts and discrete filaments.
Abrasive articles that
contain glass web reinforcements, and/or chopped strand fibers, typically
display improved
impact properties. The combination of mineral wool microfibers that are
individual filaments
(as opposed to fiber bundles), preferably in the presence of an active filler,
e.g., a manganese
compound, with (bundled) chopped strand fibers and/or fiber web products
(reinforcements)
provides increased tool strength, increased grinding performance and/or
improved tool life, as
well as enhanced impact resistance, diminishing tendencies of the abrasive
article to break.
A number of examples of microfiber reinforced abrasive composites are now
provided to
further demonstrate features and benefits of an abrasive tool composite
configured in
accordance with embodiments of the present invention. In particular, Example 1
demonstrates composite properties bond bars and mix bars with and without
mineral wool;
Example 2 demonstrates composite properties as a function of mix quality;
Example 3
demonstrates grinding performance data as a function of mix quality; and
Example 4
demonstrates grinding performance as a function of active fillers with and
without mineral
wool. Example 5 compares the synergistic effects on grinding performance
obtained by
adding a manganese compound active filler to mineral wool microfibers relative
to adding the
manganese compound active filler to chopped strand fibers. Example 6
demonstrates grinding
performance as a function of active fillers with mineral wool microfibers used
in combination
with glass chopped strand fibers.
Example]
Example 1, which includes Tables 3, 4, and 5, demonstrates properties of bond
bars and
composite bars with and without mineral wool fibers. Note that the bond bars
contain no
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grinding agent, whereas the composite bars include a grinding agent and
reflect a grinding
wheel composition. As can be seen in Table 3, components of eight sample bond
compositions are provided (in volume percent, or vol%). Some of the bond
samples include
no reinforcement (sample #s 1 and 5), some include milled glass fibers or
chopped strand
fibers (sample #s 3, 4, 7, and 8), and some include Sloss PMF mineral wool
(sample #s 2
and 6) in accordance with one embodiment of the present invention. Other types
of individual
filament fibers (e.g., ceramic or glass fiber) may be used as well, as will be
apparent in light
of this disclosure. Note that the brown fused alumina (220 grit) in the bond
is used as a filler
in these bond samples, but may also operate as a secondary abrasive (primary
abrasive may
be, for example, extruded bauxite, 16 grit). Further note that SaranTM 506 is
a
polyvinylidene chloride bonding agent produced by Dow Chemical Company, the
brown
fused alumina was obtained from Washington Mills.
Samples ->
#1 #2 #3 #4 #5 #6 #7 #8
Components J.
Durez 29722 48.11
48.11 48.11 48.11 42.09 42.09 42.09 42.09
Saran 506 2.53 2.53 2.53 2.53 2.22 2.22
2.22 2.22
Brown Fused
12.66 6.33 6.33 6.33 18.99 9.50 9.50 9.50
Alumina - 220 Grit
Sloss PMF 6.33 9.50
Milled Glass Fiber 6.33 9.50
Chopped Strand 6.33 9.50
Iron Pyrite 20.4 20.4
20.4 20.4 20.4 20.4 20.4 20.4
Potassium
Chloride/Sulfate 9.8 9.8 9.8 9.8 9.8 9.8 9.8 9.8
(60:40 blend)
Lime 6.5 6.5 6.5 6.5 6.5 6.5 6.5 6.5
Table 3: Example Bonds with and without Mineral Wool
For the set of sample bonds 1 through 4 of Table 3, the compositions are
equivalent except
for the type of reinforcement used. In samples 1 and 5 where there is no
reinforcement, the
vol% of filler (in this case, brown fused alumina) was increased accordingly.
Likewise, for
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the set of samples 5 through 8 of Table 3, the compositions are equivalent
except for the type
of reinforcement used.
Table 4 demonstrates properties of the bond bar (no abrasive agent), including
stress and
elastic modulus (E-Mod) for each of the eight samples of Table 3.
Samples -> #1 #2 #3 #4 #5 #6 #7 #8
Stress (MPa) 90.1 115.3 89.4 74.8 103.8 118.4
97 80.7
Std Dev (MPa) 8.4 8.3 8.6 17 8 6.5 8.6 10.8
E-Mod (MPa) 17831 17784 17197 16686 21549 19574 19191 19131
Std Dev (MPa) 1032 594 1104 1360 2113 1301 851 1242
Table 4: Bond Bar Properties (3-point bend)
Table 5 demonstrates properties of the composite bar (which includes the bonds
of Table 3
plus an abrasive, such as extruded bauxite), including stress and elastic
modulus (E-Mod) for
each of the eight samples of Table 3. As can be seen in each of Tables 4 and
5, the
bond/composite reinforced with mineral wool (samples 2 and 6) has greater
strength relative
to the other samples shown.
Samples -> #1 #2 #3 #4 #5 #6 #7 #8
Stress (MPa) 59.7 66.4 61.1 63.7
50.1 58.2 34 34
Std Dev (MPa) 8.1 10.2 8.5 7.2 9.8 4.6 4.4 4.1
E-Mod (MPa) 6100 6236 6145 6199 5474 5544 4718 4427
Std Dev (MPa) 480 424 429 349 560 183 325 348
Table 5: Composite Bar Properties (3-point bend)
In each of the abrasive composite samples 1 through 8, about 44 vol% is bond
(including the
bond components noted, less the abrasive), and about 56 vol% is abrasive
(e.g., extruded
bauxite, or other suitable abrasive grain). In addition, a small but
sufficient amount of furfural
(about 1 vol% or less of total abrasive) was used to wet the abrasive
particles. The sample
compositions 1 through 8 were blended with furfural-wetted abrasive grains
aged for 2 hours
before molding. Each mixture was pre-weighed then transferred into a 3-cavity
mold (26 mm
x 102.5 mm) (1.5 mm x 114.5 mm) and hot-pressed at 160 C for 45 minutes under
140
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kg/cm2, then followed by 18 hours of curing in a convection oven at 200 C.
The resulting
composite bars were tested in three point flexural (5:1 span to depth ratio)
using ASTM
procedure D790-03.
Example 2
Example 2, which includes Tables 6, 7, and 8, demonstrates composite
properties as a
function of mix quality. As can be seen in Table 6, components of eight sample
compositions
are provided (in vol%). Sample A includes no reinforcement, and samples B
through H
include Sloss PMF mineral wool in accordance with one embodiment of the
present
invention. Other types of single filament microfiber (e.g., ceramic or glass
fiber) may be used
as well, as previously described. The bond material of sample A includes
silicon carbide (220
grit) as a filler, and the bonds of samples B through H use brown fused
alumina (220 grit) as
a filler. As previously noted, such fillers assist with dispersal and may also
operate as
secondary abrasives. In each of samples A through H, the primary abrasive used
is a
combination of brown fused alumina 60 grit and 80 grit. Note that a single
primary abrasive
grit can be mixed with the bond as well, and may vary in grit size (e.g., 6
grit to 220 grit),
depending on factors such as the desired removal rates and surface finish.
Samples-* A B C
D E F G H
Components J.
Durez 29722 17.77 16.88 16.88 16.88 16.88 16.88 16.88 16.88
Saran 506 1.69 1.57 1.57 1.57 1.57 1.57
1.57 1.57
Silicon Carbide -220 Grit 5.92 0.00 0.00 0.00 0.00 0.00
0.00 0.00
Brown Fused Alumina - 220 Grit 0.00 3.98 3.98 3.98 3.98 3.98 3.98 3.98
Sloss PMF 0.00 3.81 3.81 3.81 3.81 3.81
3.81 3.81
Iron Pyrite 10.15 9.64 9.64 9.64 9.64 9.64
9.64 9.64
Potassium Sulfate 4.23 4.02 4.02 4.02 4.02 4.02
4.02 4.02
Lime 2.54
2.41 2.41 2.41 2.41 2.41 2.41 2.41
Brown Fused Alumina - 60 Grit 28.5 28.5 28.5 28.5 28.5 28.5 28.5 28.5
Brown Fused Alumina - 80 Grit 28.5 28.5 28.5 28.5 28.5 28.5 28.5 28.5
Furfural - 1 wt% or less of total abrasive
Table 6: Example Composites with and without Mineral Wool
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As can be seen, samples B through H are equivalent in composition. In sample A
where there
is no reinforcement, the vol% of other bond components is increased
accordingly as shown.
Samples¨* A
Hobart w/
Hobart Interlator Interlator Eirich &
Mixing Hobart with Paddle &
with
Eirich @3500 @6500 Interlator@
Method Paddle Interlator
Wisk rpm rpm 3500rpm
@650Orpm
Mix Time 30 minutes N/A 15
minutes
minutes
Un-
dispersed
N/A 0.9 g 0.6 g 0 0.5 0
mineral
wool
Table 7: Composite Properties as a Function of Mixing Procedures
5
Table 7 indicates mixing procedures used for each of the samples. Samples A
and B were
each mixed for 30 minutes with a Hobart-type mixer using paddles. Sample C was
mixed for
30 minutes with a Hobart-type mixer using a wisk. Sample D was mixed for 30
minutes with
a Hobart-type mixer using a paddle, and then processed through an Interlator
(or other
10 suitable hammermill apparatus) at 6500 rpm. Sample E was mixed for 15
minutes with an
Eirich-type mixer. Sample F was processed through an Interlator at 3500 rpm.
Sample G was
processed through an Interlator at 6500 rpm. Sample H was mixed for 15 minutes
with an
Eirich-type mixer, and then processed through an Interlator at 3500 rpm. A
dispersion test
was used to gauge the amount of undispersed mineral wool for each of samples B
through H.
15 The dispersion test was as follows: amount of residue resulting after
100 grams of mix was
shaken for one minute using the Rototap method followed by screening through a
#20 sieve.
As can be seen, sample B was observed to have a 0.9 gram residue of mineral
wool left on
the screen of the sieve, sample C a 0.6 gram residue, and sample E a 0.5 gram
residue. Each
of samples D, F, G, and H had no significant residual fiber left on the sieve
screen. Thus,
depending on the desired dispersion of mineral wool, various mixing techniques
can be
utilized.
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The sample compositions A through H were blended with furfural-wetted abrasive
grains
aged for 2 hours before molding. Each mixture was pre-weighed then transferred
into a 3-
cavity mold (26 mm x 102.5 mm) (1.5 mm x 114.5 mm) and hot pressed at 160 C
for 45
minutes under 140 kg/cm2, then followed by 18 hours of curing in a convection
oven at 200
Sample # of Tests Mean Std. Dev. Std. Err. Mean Lower 95% Upper 95%
A 18 77.439 9.1975 2.1679 73.16
81.72
B 18 86.483 9.2859 2.1887 82.16
90.81
C 18 104.133 10.2794 2.4229 99.35 108.92
E 18 126.700 5.5138 1.2996
124.13 129.27
F 18 127.678 4.2142 0.9933 125.72
129.64
G 18 122.983 4.8834 1.1510
120.71 125.26
H 33 123.100 6.4206 1.1177 120.89 125.31
Table 8: Means and Std Deviations
through H. Table 8 demonstrates the means and standard deviations. The
standard error uses
a pooled estimate of error variance. As can be seen, the composite strength
for each of
samples B through H (each reinforced with mineral wool, in accordance with an
embodiment
of the present invention) is significantly better than that of the non-
reinforced sample A.
Example 3
Example 3, which includes Tables 9 and 10, demonstrates grinding performance
as a function
of mix quality. As can be seen in Table 9, components of two sample
formulations are
provided (in vol%). The formulations are identical, except that Formulation 1
was mixed for
45 minutes and Formulation 2 was mixed for 15 minutes (the mixing method used
was
identical as well, except for the mixing time as noted). Each formulation
includes Sloss
PMF mineral wool, in accordance with one embodiment of the present invention.
Other
types of single filament microfiber (e.g., glass or ceramic fiber) may be used
as well, as
previously described.
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Formulation 1 Formulation 2
Sequence Component
(vol %) (vol %)
Durez 29722 22.38 22.38
Brown Fused Alumina-220
3.22 3.22
grit
Sloss PMFC) 3.22 3.22
Step 1: Bond
Iron Pyrite 5.06 5.06
Preparation
Zinc Sulfide 1.19 1.19
Cryolite 3.28 3.28
Lime 1.19 1.19
Tridecyl alcohol 1.11 1.11
Step 2:Mixing 45 minutes 15 minutes
Wt % of un-dispersed
Bond Quality
mineral wool from Rototap 1.52 2.36
Assessment
method
Abrasive 48 48
Step 3: Composite
Varcum 94-906 4.37 4.37
Preparation
Furfural 1 wt% of total abrasive
Step 4: Mold Filing
Porosity target 8% 8%
& Cold Pressing
30hr ramp to 175 C followed by
Step 5: Curing
17Hr soak at 175 C
Table 9: Grinding Performance as a Function of Mix Quality
As can also be seen from Table 9, the manufacturing sequence of a microfiber
reinforced
abrasive composite configured in accordance with one embodiment of the
presents invention
includes five steps: bond preparation; mixing, composite preparation; mold
filling and cold
pressing; and curing. A bond quality assessment was made after the bond
preparation and
mixing steps. As previously discussed, one way to assess the bond quality is
to perform a
dispersion test to determine the weight percent of un-dispersed mineral wool
from the
Rototap method. In this particular case, the Rototap method included adding
50g-100g of
bond sample to a 40 mesh screen and then measuring the amount of residue on
the 40 mesh
screen after 5 minutes of Rototap agitation. The abrasive used in both
formulations at Step 3
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was extruded bauxite (16 grit). The brown fused alumina (220 grit) is used as
a filler in the
bond preparation of Step 1, but may operate as a secondary abrasive as
previously explained.
Note that the Varcum 94-906 is a Furfurol-based resole available from Durez
Corporation.
Table 10 demonstrates the grinding performance of reinforced grinding wheels
made from
both Formulation 1 and Formulation 2, at various cutting-rates, including
0.75, 1.0, and 1.2
sec/cut.
MRR WWR
Formulation Cut Rate (sec/cut) G-Ratio
(in3/min) (in3/min)
Formulation 1 0.75 31.53 4.35 6.37
Formulation 1 1.0 23.54 3.29 7.15
Formulation 1 1.2 19.97 2.62 7.63
Formulation 2 0.75 31.67 7.42 4.27
Formulation 2 1.0 23.75 4.96 4.79
Formulation 2 1.2 19.88 3.64 5.47
Table 10: Demonstrates the Grinding Performance
As can be seen, the material removal rate (MRR), which is measured in cubic
inches per
minute, of Formulation 1 was relatively similar to that of Formulation 2.
However, the wheel
wear rate (WWR), which is measured in cubic inches per minute, of Formulation
1 is
consistently lower than that of Formulation 2. Further note that the G-ratio,
which is
Example 4
Example 4, which includes Tables 11, 12, and 13, demonstrates grinding
performance as a
function of active fillers with and without mineral wool. As can be seen in
Table 11,
25 components of four sample composites are provided (in vol%). The
composite samples A and
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B are identical, except that sample A includes chopped strand fiber, and no
brown fused
alumina (220 Grit) or Sloss PMF(Dmineral wool. Sample B, on the other hand,
includes Sloss
PMF(Dmineral wool and brown fused alumina (220 Grit), and no chopped strand
fiber. The
composite density (which is measured in grams per cubic centimeter) is
slightly higher for
sample B relative to sample A. The composite samples C and D are identical,
except that
sample C includes chopped strand fiber and no Sloss PMF(Dmineral wool. Sample
D, on the
other hand, includes Sloss PMF(Dmineral wool and no chopped strand fiber. The
composite
density is slightly higher for sample C relative to sample D. In addition, a
small but sufficient
amount of furfural (about 1 vol% or less of total abrasive) was used to wet
the abrasive
particles, which in this case were alumina grains for samples C and D and
alumina-zirconia
grains for samples A and B.
Composite Content (vol%)
Component
A B C D
Alumina Grain 0.00 0.00 52.00 52.00
Alumina-Zirconia Grain 54.00 54.00 0.00 0.00
Durez 29722 20.52 20.52 19.68 19.68
Iron Pyrite 7.20 7.20 8.36 8.36
Potassium Sulfate (K2504) 0.00 0.00 3.42 3.42
K2504/KC1 (60:40 blend) 3.60 3.60 0.00 0.00
MKC-S 3.24 3.24 3.42 3.42
Lime 1.44 1.44 1.52 1.52
Brown Fused Alumina - 220 Grit 0.00 3.52 0.00 0.00
Porosity 2.00 2.00 2.00 2.00
Sloss PMF 0.00 8.00 0.00 8.00
Chop Strand Fiber 8.00 0.00 8.00 0.00
Furfural 1 wt% of total abrasive
Density (g/cc) 3.07 3.29 3.09 3.06
Wheel Dimensions (mm) 760x76x203 760x76x203 610x63x203 610x63x203
Table 11: Grinding performance as a Function of Active Fillers
Table 12 demonstrates tests conducted to compare the grinding performance
between the
samples B and D, both of which were made with a mixture of mineral wool and
the example
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active filler manganese dichloride (MKC-S, available from Washington Mills),
and samples
A and C, which were made with chopped strand instead of mineral wool.
Test MRR WWR G-ratio Percentage
Sample Slab Material
Number (kg/hr) (dm3/hr) (kg/dm3) Improvement
A Austenitic 193.8 0.99 196
1 27.77%
B Stainless Steel 222.6 0.89 250
A Ferritic 210 1.74 121
2 27.03%
B Stainless Steel 208.5 1.36 153
C Austenitic 833.1 4.08 204
3 35.78%
D Stainless Steel 808.8 2.92 277
C 812.4 2.75 296
4 Carbon Steel 30.07%
D 784.1 2.03 385
Table 12: Demonstrates the Grinding Performance
As can be seen, grinding wheels made from each sample were used to grind
various
workpieces, referred to as slabs. In more detail, samples A and B were tested
on slabs made
from austenitic stainless steel and ferritic stainless steel, and samples C
and D were tested on
slabs made from austenitic stainless steel and carbon steel. As can further be
seen in Table
12, using a mixture of mineral wool and manganese dichloride samples B and D
provided
about a 27% to 36% improvement relative to samples A and C (made with chopped
strand
instead of mineral wool). This clearly shows improvements in grinding
performance due to a
positive reaction between mineral wool and the filler (in this case, manganese
dichloride). No
such positive reaction occurred with the chopped strand and manganese
dichloride
combination. Table 13 lists the conditions under which the composites A
through D were
tested.
Test Grinding Power
Slab Material Slab Condition
Number (kw)
First path at 120 Austenitic
1 Cold
and followed by 85 Stainless Steel
First path at 120 Ferritic Stainless
2 Cold
and followed by 85 Steel
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Austenitic
3 105 Hot
Stainless Steel
4 105 Carbon Steel Hot
Table 13: Demonstrates Grinding Conditions
Example 5
Experiments were undertaken to explore the effects of fiber type and levels of
MKCS on
wheel grinding performance. Wheels were prepared as in Example 4 and only
differed with
respect to the type of fibers and level of MKCS present. Specifically, wheels
included either
8 vol % of (glass) chopped strand fibers (CSF) or 8 vol % of microfibers of
mineral wool
(MW). For each category, the level of MKCS was either 0 or 3.42 vol %.
As seen in Table 14, the G-ratio for the wheels containing 8 vol% CSF was
decreased by
about 10% when MKCS was added (from 330 kg/dm3 without any MKCS to 296 kg/dm3
with MKCS). An opposite trend was observed with the wheels prepared with
mineral wool,
where adding MKCS resulted in an increase of about 20 % in the G-ratio (from
311 kg/dm3
at 0 levels of MKCS to 385 kg/dm3 when 3.42 vol % MKCS was added). This
clearly
demonstrates that MKCS interacts differently with the two fiber types and that
a synergistic
effect is obtained by combining MW microfibers with MKCS. No such effect was
observed
with the MKCS-CSF combination. On the contrary, adding MKCS to compositions
that
contain CSF had a negative effect on G-ratio.
G-Ratio (kg/dm3)
Fiber Type Level of MKCS (vol%)
0.00 3.42
CSF (8 vol%) 330.00 296.00 (Std.)
MW (8 vol%) 311.00 385.00
Table 14: Effects of MKCS levels and fiber types on G-ratios
Example 6
Example 6, which includes Table 15 and Figure 2, demonstrates grinding
performance as a
function of active fillers in combination with mineral wool and chopped strand
fibers. As can
be seen in Table 15, components of eight sample composites are provided (in
vol%).
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All samples (Expl through Exp8) included the same type and amount of abrasive
grain. Two
levels of fiberglass chopped strand fibers (CSF) were employed: a high level
of 6 volume %
(Exp 1, Exp2, Exp5 and Exp 6) and a low level of 4 volume % (Exp 3, Exp. 4,
Exp7 and
Exp8).
In all cases, the bond included (organic) resin, Sloss PMF mineral wool (MW)
microfibers,
iron compound (pyrite), lime, and the active filler manganese dichloride
(MKCS). Exp5
through Exp8 samples also included potassium sulfate filler, while the
remaining samples
(Expl through Exp4) did not.
The synergy between mineral wool microfibers and the manganese compound active
filler
was particularly significant in samples that had low levels of (fiberglass)
CSF. As glass fiber
level was increased, the MKCS/MW advantage was less pronounced. These results
demonstrated that the manganese compound active filler does not provide the
same benefits
with respect to glass CSF as it does with MW microfibers.
The data also showed that adding potassium sulfate (Exp5 through Exp8) had a
deleterious
effect on the cumulative G-ratio. Generally, highest cumulative Q-ratio
(defined as metal
removed (lbs)/wheel wear (lbs)) values were observed for samples that did not
contain
potassium sulfate, and this was particularly significant at low levels of
(fiberglass) CSF. (See,
e.g., Exp3 and Exp4). In comparison to the effects of MKCS, potassium sulfate
provided no
increase in grinding performance or provided a diminished grinding
performance.
The results demonstrated that grinding performance increased as MKCS and MW
were
increased and that the synergistic effects observed with these two ingredients
did not extend
to fiberglass chopped strand fibers or other fillers (e.g., potassium
sulfate). The experiments
showed that there is an unexpected performance advantage when the combination
of MW and
MKCS are used in a grinding wheel.
The data also indicate that potassium salts have an increased effect on
performance in
compositions which include the higher levels of glass chopped strand fibers,
mineral wool
microfibers and a manganese compound, and less of an effect in compositions
that include
mineral wool microfibers, a manganese compound and lower levels of chopped
strand fibers.
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Composite Content (vol%)
Component
1 2 3 4 5 6 7 8
Grain 55.5 55.5 55.5 55.5 55.5 55.5 55.5 55.5
Chopped Strand Fiber 6.0 6.0 4 4 6.0 6.0 4 4
Bond 38.5 38.5 40.5 40.5 38.5 38.5 40.5 40.5
Resin 19.25 19.48 20.23 20.49 19.25 19.48 20.23 20.49
Sloss PMF 1.44 0.97 1.52 1.02 1.25 0.84 1.31
0.88
MKC-S 3.65 3.69 3.83 3.88 2.50 2.53 2.63 2.66
Iron Pyrite 12.66 12.82 13.31 13.48 11.85 11.99 12.46 12.61
Lime 1.52 1.54 1.60 1.62 1.15 1.16 1.21 1.22
Potassium Sulfate 0.00 0.00 0.00 0.00 2.50 2.53 2.63 2.66
Cumulative Q-Ratio 70.1 68.4 84.0 71.4 69.4 65.4 68.0
55.3
Table 15: Performance of tool with combined MW, CSF and fillers
The foregoing description of the embodiments of the invention has been
presented for the
purposes of illustration and description. It is not intended to be exhaustive
or to limit the
invention to the precise form disclosed. Many modifications and variations are
possible in
light of this disclosure. It is intended that the scope of the invention be
limited not by this
detailed description, but rather by the claims appended hereto.
24
