Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents
  • B24D3/34—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents characterised by additives enhancing special physical properties, e.g. wear resistance, electric conductivity, self-cleaning properties
  • B24D3/342—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents characterised by additives enhancing special physical properties, e.g. wear resistance, electric conductivity, self-cleaning properties incorporated in the bonding agent
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D11/00—Constructional features of flexible abrasive materials; Special features in the manufacture of such materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D7/00—Bonded abrasive wheels, or wheels with inserted abrasive blocks, designed for acting otherwise than only by their periphery, e.g. by the front face; Bushings or mountings therefor
  • B24D7/02—Wheels in one piece
  • B24D7/04—Wheels in one piece with reinforcing means

Definitions

• 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.
• 183 Cratec® available from Owens Corning.
• 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.
• 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 ⁇ .
• the microfibers have an average length in the range of about 100 to 500 ⁇ and a diameter less than about 10 microns.
• chopped strand fibers e.g., fiberglass chopped strand fibers
• 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.
• active fillers include manganese compounds, silver compounds, boron compounds, phosphorous compounds, and combinations thereof.
• 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.
• 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.
• 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
• the composition is in the form of an abrasive article used in abrasive processing of a workpiece.
• the abrasive article is a wheel or other suitable form for abrasive processing.
• 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.
• 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.
• the one or more fillers include a manganese compound.
• 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 ⁇ .
• the abrasive article may further include chopped strand fibers, dispersed in the organic bond material.
• 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.
• 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.
• 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.
• 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
• 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.
• 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.
• excessive mixing leads to formation of "fuzz balls" (clusters of multiple chopped strand fibers) that cannot be re-dispersed into the mix.
• the chopped strand itself is effectively a bundle of filaments bonded together.
• such clusters or bundles effectively decrease the homogeneity of the grinding mix and make it more difficult to transfer and spread into a mold.
• the presence of such clusters or bundles within the composite decreases composite properties such as strength and modulus and increases property variability.
• 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).
• producing microfiber-reinforced composites involves complete dispersal of individual filaments within a dry blend of suitable bond material (e.g., organic resins) and fillers.
• suitable bond material e.g., organic resins
• 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.
• 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.
• microfibers are small and short individual filaments having high tensile modulus and can be either inorganic or organic.
• 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, poly amide or aromatic poly amide 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.
• 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.
• a filament length of about 20 with a filament diameter of about 2 microns has a reinforcing aspect ratio of 10.
• 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.
• the microfibers are highly dispersible as discrete filaments, and resistant to fiber bundle formation.
• the microfibers will chemically bond to the bond material being used (e.g., organic resin).
• 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.
• 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).
• 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 %.
• 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 %.
• 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.
• 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 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.
• 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.
• the abrasive article contains the minimum level of chopped strand fibers determined to provide one or more such desired property.
• 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.
• organic resins such as epoxy, polyester, phenolic, and cyanate ester resins
• suitable thermosetting or thermoplastic resins include polyphenolic resins, such as Novolac resins.
• 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, 8686SP, and 843 ISP.
• 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.
• 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.
• the composition from which grinding tools are made comprises greater than or equal to about 50% by weight of abrasive material.
• 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.
• the microfiber-reactive active filler is selected from: manganese compounds, silver compounds, boron compounds, phosphorous compounds, and any combinations thereof.
• 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.
• 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.
• 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.
• a filler component also referred to herein as a filler “component”
• 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, pyrites, potassium sulfate (K2S04), 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.
• the filler package excludes potassium salts.
• 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 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.
• 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.
• 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.
• 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.
• composition or abrasive article can further include secondary abrasive grains capable of acting as fillers.
• secondary abrasive grains capable of acting as fillers. Examples include silicon carbide, brown fused alumina, and others, as known in the art.
• 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.
• internally reinforced abrasive wheels include discs cut from nylon, carbon, glass or cotton cloth.
• 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.
• 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
• 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. 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.
• microfibers e.g., mineral wool, milled glass or milled basalt fibers
• the high aspect ratio of microfibers 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.
• potassium salts such as potassium chloride or potassium sulfate interferes with this
• Example 1 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.
• Example 1 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.
• Example 1 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.
• 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 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 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.
• 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).
• primary abrasive may be, for example, extruded bauxite, 16 grit.
• SaranTM 506 is a
• compositions are equivalent except for the type of reinforcement used.
• vol of filler in this case, brown fused alumina
• 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.
• 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.
• E-Mod stress and elastic modulus
• 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).
• 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.
• Example 2 which includes Tables 6, 7, and 8, demonstrates composite properties as a function of mix quality.
• 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
• 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.
• such fillers assist with dispersal and may also operate as secondary abrasives.
• 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.
• 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 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.
• 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.
• the sample compositions A through H were blended with furfural-wetted abrasive grains aged for 2 hours before molding.
• Table 8 Means and Std Deviations Figure 1 is a one-way ANOVA analysis of composite strength for each of the samples A 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 which includes Tables 9 and 10, demonstrates grinding performance as a function of mix quality.
• 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.
• Formulation 1 Formulation 2 may be used as well, as previously described.
• 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.
• 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.
• 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 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.
• 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.
• the material removal rate (MRR), which is measured in cubic inches per minute, of Formulation 1 was relatively similar to that of Formulation 2.
• the wheel wear rate (WWR), which is measured in cubic inches per minute, of Formulation 1 is consistently lower than that of Formulation 2.
• the G-ratio, which is computed by dividing MRR by WWR, of Formulation 1 is consistently higher than that of Formulation 2.
• Formulation 2 was effectively too short when compared to the improved performance of Formulation 1 and its 45 minute mix time.
• Example 4 which includes Tables 11, 12, and 13, demonstrates grinding performance as a function of active fillers with and without mineral wool.
• Table 11 components of four sample composites are provided (in vol ).
• the composite samples A and B are identical, except that sample A includes chopped strand fiber, and no brown fused alumina (220 Grit) or Sloss PMF® mineral wool.
• Sample B includes Sloss PMF® mineral 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® mineral wool.
• Sample D includes Sloss PMF® mineral wool and no chopped strand fiber.
• the composite density is slightly higher for sample C relative to sample D.
• 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.
• 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 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.
• MKC-S active filler manganese dichloride
• 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.
• samples B and D were tested on slabs made from austenitic stainless steel and carbon steel.
• 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.
• 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).
• CSF chopped strand fibers
• MW microfibers of mineral wool
• 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.
• Table 15 components of eight sample composites are provided (in vol%). 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 % (Expl, Exp2, Exp5 and Exp 6) and a low level of 4 volume % (Exp 3, Exp. 4, Exp7 and Exp8).
• 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 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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• Polishing Bodies And Polishing Tools (AREA)

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