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
  • B24D3/02—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent
  • B24D3/20—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent and being essentially organic
  • B24D3/28—Resins or natural or synthetic macromolecular compounds
• • 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
  • B24D3/02—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent
  • B24D3/20—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent and being essentially organic
  • B24D3/28—Resins or natural or synthetic macromolecular compounds
  • B24D3/285—Reaction products obtained from aldehydes or ketones
• • 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
  • B24D3/02—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent
  • B24D3/20—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent and being essentially organic
  • B24D3/28—Resins or natural or synthetic macromolecular compounds
  • B24D3/32—Resins or natural or synthetic macromolecular compounds for porous or cellular structure
• • 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
  • B24D3/344—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 the bonding agent being organic

Definitions

• the invention relates to a high structure, organic I bonded abrasive body and particularly to high structure cold-pressed, resin-bonded, abrasive grinding, snagging and cut-off wheels of exceptionally high efficiency.
• the invention concerns itself with abrasive wheel compositions for making what are known in the art as relatively hard grade high structure non-reinforced and reinforced organic-bonded thin disc and peripheral type grinding wheels.
• the cold-pressed wheels are for grinding, snagging and/or cutting off metal from welds, gates and risers from castings and cutting bars or rods of carbon and stainless steels.
• Another method that is not as commonly used to vary grinding performance is to vary the ratio of bond (resin and filler) to abrasive in the wheel structure. It is commonly known, especially in medium to dense cold pressed grinding wheels, that if the abrasive content is reduced to provide a more open structure and is replaced by an equivalent volume of bond, the grinding wheel would act softer, i.e., the metal removal rate would increase and the wheel life (grinding G-ratio) would decrease in constant pressure grinding.
• the common explanation of this phenomenon is that as the structure becomes more open as abrasive content is reduced, interference in chip formation is likewise reduced and the wheel becomes freer cutting with a significant increase in metal removal rate. However, due to the higher forces exerted on the individual abrasive particles, the wheel life or G-ratio is significantly decreased.
• Applicant's concept is to vary the ratio of resin to filler for each change in structure by replacing each reduction in abrasive content with an equal volume of an active filler material.
• the filler portion of the bond is an active grinding aid, i.e., the filler portion consisting of one or more finely divided materials that enhance and improve the grinding quality and efficiency
• the filler portion of the bond is an active grinding aid, i.e., the filler portion consisting of one or more finely divided materials that enhance and improve the grinding quality and efficiency
• medium density cold-molded wheels of improved grinding quality and efficiency can be made with reduced abrasive content and correspondingly increased active filler content and differing from U.S. Patent 4,253,850 in that the resin content is higher.
• This increased resin content is necessary for cold molding and extends the range of usefulness to higher porosity and less dense grinding wheels.
• organic bonded cold formed or pressed and post- cured abrasive bodies of relatively high structures, grinding efficiency, performance and life such as disc and peripheral metal grinding and cut-off wheels have abrading portions comprising a greater and equal volume of active filler replacing the reduction in abrasive content whereby a high structure wheel has a greater ratio of filler to resin than a lower structure wheel.
• the abrading portion of the abrasive body or wheel may comprise 30 to 44% by volume of 12-100 grit size abrasive particles suitable for removing metal, 24 to 36% by volume of an organic thermosetting resin, 14 to 29% by volume of an active filler material and 5-18% by volume pores. additionally the abrading portion may contain 0 to 5% by volume of one or more suitable wetting agents which are 3eemed to be part of the resin content.
• the abrasive bodies may be reinforced with suitable and conventional discs of open mesh fiber glass cloth, glass or other fibers and/or with a strong non-abrading backing or center portion adjoining the abrading portion.
• the abrasive bodies may have, what are known in the art as "rough sides" to enhance grinding, quality of finish and prevent burning of the metal workpiece being ground or cut.
• the organic bonded abrasive bodies of the invention are preferably high structure cold formed or pressed and post cured grinding wheels of medium to low porosity normally utilized in grinding, removing or snagging metal from various types of workpieces, weldments, castings and cutting-off metal rods, bars or strip stock to shorter length.
• the abrasive bodies are relatively hard grade, high structure cold pressed grinding wheels in which the porosity is in the range of from 5-18% by volume of the abrading portion.
• the cold pressed wheels of the invention have varying greater ratio of filler to resin content and thus substantially much more active filler than that normally provided in conventional prior art cold pressed wheels of comparable size, volume, grade and structure.
• Abrasive bodies of the instant invention have an abrading portion comprising from 30 to 44% by volume of any suitable well known conventional abrasive material selected from the group consisting of fused aluminum oxide, fused alumina-zirconia, sintered alumina-zirconia, sintered alumina, sintered bauxite, silicon carbide and mixtures thereof.
• the abrasive material employed in the abrading portion has a particle size in a range of from 12 to 100 grit size or an average particle size of 2550 to.173 microns
• a conventional resinoid binder mixed with at least one active filler material is utilized to bind the -abrading composition together.
• the organic binder is preferably a thermosettable mixture of both liquid phenolic and powdered phenolic novalac resin including 9% of the cross linking aid hexamethylenetetramine.
• a suitable powered resin is Varcum 29344 standard thermosetting epoxy modified phenolic novalac resin available from Reichold Chemical Inc. Varcum Div., Niagara Falls, N.Y. However, other formulations of thermosetting phenolic-novalac resin with 6% to 16% hexamethylenetetramine may be employed.
• thermosetting resins include phenoxy, phenol-furfural, aniline formaldehyde, urea formaldehyde, epoxy, cresol aldehyde, resorcinal aldehyde, urea aldehyde, melamine formaldehyde and mixtures thereof.
• thermosetting resins Small amounts of various resinous material may be utilized to modify the thermosetting resins. They include epoxy, vinyl resins, vinyl chloride, vinyl butyral, vinyl formal, vinyl acetate, cross linking aids, such as, para formaldehyde or hexamethylenetetramine and suitable plasticizers or solvents such as furfuryl alcohol and mixtures thereof.
• the resin content in the abrading portions of the wheels of varying abrasive content and comparable size will range from 24 to 36% by volume.
• Fillers are usually considered to be part of the bond and are in a finely divided state. They may include organic and inorganic materials of various particle sizes well below and much smaller than the primary grinding abrasive particles.
• Suitable conventional and well known chemically active fillers are cryolite, fluorospar, magnesia, lead oxide, sodium chloride, iron pyrites (di-sulfide), iron sulfide, potassium sulfate, potassium fluoborate, potassium aluminum fluoride, potassium magnesium sulfate, alkali metal chloro ferrate, alkali metal chloro-fluoro ferrate, copolymer of vinylidene chloride and vinyl chloride (Saran B), polyvinylidene chloride, polyvinyl chloride, other sulfides, sulfates, halides, chlorides, fluorides, and mixtures thereof.
• a preferred active filler material is a mixture of 50% by volume of -200 mesh size potassium sulfate, and 50% by volume of -325 mesh size iron disulfide also known as iron pyrites.
• abrasive bodies of the invention may be . ; safety reinforced with various conventional chopped glass fiber up to 1/4" (6mm) long, inorganic fibers of short or long continuous length and/or open mesh fiber glass cloth discs.
• the fiber glass cloth may be of known twisted or of substantially untwisted strands or rovings of continuous glass filaments.
• the reinforced center usually comprises reinforcing a central non-abrading portion about the axis or an inner annular non-abrading portion extending around a spindle mounting aperture and normally engaged by the clamping flanges of the drive spindle.
• Adjoining and extending around the reinforced center portion is an outer annular abrading portion comprised of an abrading composition of the invention.
• an abrading composition of the invention is the composition of the abrading portion of the wheel to which the invention is directed.
• All of the cut-off wheels were made with the same 50% 24 and 50% 30 grit size (1035 - 930 microns) aluminum oxide abrasive particles in the volumes specified for each particular structure number. As the abrasive content is reduced, in increments of 4% by volume as conventional when going to a higher structure, it was replaced by an equal volume of the active filler. Also, when going from a T7 to the higher V7 grade wheel of the same structure number-, the pore volume decreases 4% by volume and is replaced -by an increase in bond which includes about 3% by volume of resin and about 1% by volume of the filler material. Note, with the exception of the wheel compositions 7-10 that regardless of structure number, wheels of the same grade have the same volume of resin and pore volume.
• a first group of wheels 1 and 2 are conventional T and V grade 7 structure wheels which are considered to be up to this discovery, the standard, most efficient, and most widely commercially used cold pressed cut-off wheel.
• the prior state of the art standard cold pressed wheels 1 and 2 have a relatively higher 50% by volume of abrasive, a lower 9% and 10% by volume of filler than the other wheels, 27% and 30% by volume of resin and 10% and 14% by volume of pores.
• abrasive was for the most part responsible for increasing the grinding efficiency of cold pressed grinding wheels.
• the second group of wheels 3 to 6 includes a first series of V9-V15 grade and structure wheels made to evaluate the effect of replacing abrasive with an equal volume of active filler in accordance with the invention while maintaining a constant volume of resin for a particular grade of wheel.
• a third 7 to 9 group and second series of V9 to V13 grade and structure wheels were made to evaluate the grinding effect of replacing abrasive with high resin and lower filler content and compare their performance with the second group 3 to 6 and first group of T7 and V7 wheels.
• the last wheel 10 is a third V13 grade and structure wheel made to evaluate the effect of further varying the volume of filler and resin to a point intermediate that of the other V13 wheels 5 and 9.
• each composition for molding into wheels the ingredients of the bond comprising the active fillers and VARCUM V29344 powdered phenolic resin were blended together dry and then wetted with CARBOSOTA (20cc/lb dry resin).
• the abrasive was wetted by and mixed with-a compatible liquid phenolic resin comprising about 18% of the total volume of resin in the composition.
• the bond was then mixed with the wetted abrasive and further dampened with from 3 to 6 cc mixture of furfural and CL40 (chlorinated parafin) brand per lb. (6.6 to 13.2 cc/kg) of the mixed composition.
• CARBOSOTA is a registered trademark for a refined coal tar cresote oil wetting or dampening agent sold by Allied Chemical and Dye Corporation.
• the wetting or dampening agents furfural CL40 and CARBOSOTA comprise less than 3% by volume of the abrading portion of the wheel and may be considered part of the cured resin content thereof.
• the abrading portion of the wheels may contain 0 to 5% by volume of suitable wetting agents selected from furfural, furfuryl alcohol, liquid resin, CARBOSOTA, CL40 (Chlorinated Parafin) and mixtures thereof.
• Each of the various prepared mixtures of abrasive and bond was placed in a suitable mold and cold pressed at from 600 to 900 tons (544.3 - 826.4 metric T) total pressure.
• Wheels 2 through 6 required essentially the same molding pressure of 800 - 900 tons (725.7 - 826.4 metric T) total pressure and wheels 1 and 7 through 10 were molded at about 600 tons (544.3 metric T) total pressure.
• each wheel made 20 cuts at each of the constant feed rates of 2.5, 4, and 6 seconds per cut, 30 cuts each at 55 and 70 lb. (121.25 - 154.3 kg) of constant pressure and 30 cuts each at 2.5 seconds per cut through the C1018 carbon steel.
• each wheel was measured before and after each test and its diameter measured before and after each series of 10 cuts and compared with the amount of metal removed. Additionally the average peak KW of power consumption and of time/per cut was measured and recorded for each series of 10 cuts. Lastly, the range in % of work piece burn was observed and recorded for each series of the 10 cuts.
• the #4, V11 composition wheel produced 11% greater G-ratio and wheel life with 9% less power and at constant pressure, cut 6% faster with 20% better life and G-Ratio than the conventional standard #2, V7 wheel composition-of the same porosity and resin content but containing 8% more abrasive and less filler.
• the data also shows that the performance of the second series of wheels V9, Vll and V13 of the wheel compositions 7, 8 and 10 with higher resin and lower active filler content was, with the exception of #7, V9, below that of the first series 3 to 5 of V9, Vll and V13 wheel compositions, but better than the performance of both the standard #2, V7 and #1, T7 wheel compositions with greater volumes of abrasive taught to be necessary for increasing the grinding efficiency.
• V grade wheels tested cutting 304 stainless steel appears to be the #4, Vll composition followed in order of performance by #5, V13, #7, V9, #3, V9, #8, Vll, #2, V7, #6, V15 and #10, V13 wheels all of which performed better than the standard 01, T7 grade/structure wheel with less resin and filler.
• the various wheel compositions were prepared as before and depending on grade were cold pressed at about 450 tons (408.2 metric T) for R grade, 600 tons (544.3 metric T) for T grade and 700 - 850 tons (630.9 - 771.1 metric T) for V grade in rubber lined molds adapted to produce the rough sides.
• Table VI reveals the various grade and structure compositions and formulations 11 to 23 to which the second batch of wheels were made and tested.
• theorical density of a green uncured cold pressed cut-off wheel may be less than the actual measured density of the wheel after it is baked and cured.
• the increase in density can vary and depends upon how the green cold pressed wheel is supported, and arranged during the bake and cure.
• Table VII gives the actual measured cured volume, grade and structure for each of the theoretical R,T and V grade, 7-13 structure green cold pressed wheels, stacked together and separated by polytetrafluoroethylene (PTFE) coated glass cloth and clamped under 460 lbs. (208.kg) of pressure.
• PTFE polytetrafluoroethylene
• High structure wheels exhibited significantly higher densification during the bake especially the higher porosity R-grade wheels 11 to 14.
• the R10 wheel 14 achieved the greatest densification of 9.8% relative to the theoretical density to a V8 grade/structure. Rough side retention was observed to be excellent for all R-grade wheels.
• the higher structure V11 - V13 wheels 20 to 23 were more structurally stable during the bake achieving more moderate density increases of approximately 4% but still significantly greater than the 1.4% increase of the standard V7 wheel 19.
• wheel 20 a theoretical V11 achieved a cured grade/structure of X10 (6% porosity).
• the higher structure wheels 19 to 23 exhibited varying degrees of rough side loss depending on the ratio of resin to abrasive.
• the 12 and 13 structure V-grade wheels 22 and 23 exhibited a 65% loss in side roughness, in fact the V13 wheel 23 conformed almost entirely to the pattern of the interlayer material use to separate the wheels during the bake and cure.
• each rough sided wheel cutting 304 stainless steel is readily comparable to the standard rough sided R7, T7, V7 wheels 11, 15 and 19 respectively rated at 100%.
• the higher structure wheels of each grade group generally consumed less power, outperformed and have 24 to 52% better G-ratio and wheel life than the standard R7, T7, and V7.
• the best performing high structure #14, R10 and #20, V11 wheel achieved 52% and 35% better life and G-ratio than the standard #11, R7 and #19, V7 wheels.
• the overall results cutting burn sensitive C1018 carbon steel indicate that grinding quality and versatility are greatly improved by going to high structure/high active filler with rough sided wheels.
• wheel #14, an R10 (cured to V8) with high active filler achieved 37% overall greater wheel life relative to the standard #11, R7 wheel but with equal versatility.
• Wheel #17, a T11 (cured to W-X9) achieved 63% better life with equal freeness-of-cut and versatility relative to the standard #15 - T7 wheel.
• Wheel #20, a V11 (cured to X10) achieved 24% better life relative to the standard #19 - V7 wheel, but was also significantly freer cutting and delivering burn free cuts at the 4 sec/cut feed rate. It was expected that the #22, V13 might have demonstrated better performance than the results indicate, however, significant loss in rough side definition may have adversely affected the results.
• the grinding quality is increased significantly especially for V grade high structure wheels which have the highest concentrations of active fillers. This is the first time a high structure V grade has been able to achieve burn-free cuts at a feed rate of 4 sec/cut on 1-1/2" - C1018 Carbon Steel and at the same time producing a phenomenally high average G-ratio of 4.76 (wheel #20, V11).
• Table X indicates higher centrifugal burst strength for high structure wheels relative to standard 7 structure wheels. The higher strength in the high'structure wheels is attributable to higher densification during the bake and curing, relative to 7 structure wheels 11, 15 and 20.
• the ratios for all wheel compositions above the standard 7 structures are in the range of 1 volume of filler to 1.15 to 3 volumes of resin and to 1.3 to 4.1 volumes of abrasive.
• the ratios are preferably in the range of 1 volume filler to .8 to 2.6 volumes resin and to 1.0 to 3.2 volumes of abrasive in the abrading portion of the wheel composition.
• the standard 7 structure wheels contain 5 to 6.25 volumes of abrasive and no less than 3 volumes resin to 1 volume of filler.
• test data reveals conclusively that the performance and life of relatively hard grades, high structure grinding wheels is greatly improved by replacing reductions in abrasive content with active filler and thereby increasing the volume ratio of filler relative to both the abrasive and the resin in the wheel.
• the invention can be utilized in other various forms of cold formed organic bonded abrasive bodies. Especially in medium to coarse grit size abrading portions of abrasive bodies such as unitary cylindrical peripheral and radial face or disk wheels and abrasive segments for both cylindrical and radial segmental wheels usually mounted in rotary chucks adapted for attachment to the drive spindle of a machine.
• medium to coarse grit size abrading portions of abrasive bodies such as unitary cylindrical peripheral and radial face or disk wheels and abrasive segments for both cylindrical and radial segmental wheels usually mounted in rotary chucks adapted for attachment to the drive spindle of a machine.

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Cited By (47)

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• 1982
  • 1982-09-03 EP EP19820108161 patent/EP0078896A2/fr not_active Withdrawn
  • 1982-11-05 JP JP19359482A patent/JPS5882678A/ja active Pending

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