US20030114085A1 - Superabrasive composition and superabrasive article comprising same for grinding CRT front panel - Google Patents
Superabrasive composition and superabrasive article comprising same for grinding CRT front panel Download PDFInfo
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- US20030114085A1 US20030114085A1 US09/966,665 US96666501A US2003114085A1 US 20030114085 A1 US20030114085 A1 US 20030114085A1 US 96666501 A US96666501 A US 96666501A US 2003114085 A1 US2003114085 A1 US 2003114085A1
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- Prior art keywords
- grinding
- superabrasive
- composition
- particles
- grinding layer
- Prior art date
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- Abandoned
Links
- 238000000227 grinding Methods 0.000 title claims abstract description 118
- 239000000203 mixture Substances 0.000 title claims abstract description 48
- 239000002245 particle Substances 0.000 claims abstract description 64
- 239000000758 substrate Substances 0.000 claims abstract description 27
- 239000011521 glass Substances 0.000 claims abstract description 23
- 229910003460 diamond Inorganic materials 0.000 claims abstract description 18
- 239000010432 diamond Substances 0.000 claims abstract description 18
- 229910052582 BN Inorganic materials 0.000 claims abstract description 7
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 claims abstract description 7
- 239000000463 material Substances 0.000 claims description 28
- 238000000034 method Methods 0.000 claims description 25
- 238000005245 sintering Methods 0.000 claims description 11
- 239000011347 resin Substances 0.000 claims description 9
- 229920005989 resin Polymers 0.000 claims description 9
- 239000002184 metal Substances 0.000 claims description 5
- 229910052751 metal Inorganic materials 0.000 claims description 5
- 229910044991 metal oxide Inorganic materials 0.000 claims description 4
- 150000004706 metal oxides Chemical class 0.000 claims description 4
- 238000007731 hot pressing Methods 0.000 claims 1
- 238000002360 preparation method Methods 0.000 claims 1
- 238000007789 sealing Methods 0.000 claims 1
- 238000000465 moulding Methods 0.000 description 7
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 6
- 229910000906 Bronze Inorganic materials 0.000 description 4
- 239000010974 bronze Substances 0.000 description 4
- KUNSUQLRTQLHQQ-UHFFFAOYSA-N copper tin Chemical compound [Cu].[Sn] KUNSUQLRTQLHQQ-UHFFFAOYSA-N 0.000 description 4
- 239000005011 phenolic resin Substances 0.000 description 4
- 239000000843 powder Substances 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 2
- 239000003082 abrasive agent Substances 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000010355 oscillation Effects 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 229910052718 tin Inorganic materials 0.000 description 2
- 239000011135 tin Substances 0.000 description 2
- 239000002351 wastewater Substances 0.000 description 2
- 241000283707 Capra Species 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000010962 carbon steel Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000002223 garnet Substances 0.000 description 1
- 230000009477 glass transition Effects 0.000 description 1
- 231100001261 hazardous Toxicity 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 239000011812 mixed powder Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000008262 pumice Substances 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000004575 stone Substances 0.000 description 1
- 230000003746 surface roughness Effects 0.000 description 1
Images
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
- B24D3/04—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 inorganic
- B24D3/06—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 inorganic metallic or mixture of metals with ceramic materials, e.g. hard metals, "cermets", cements
- B24D3/10—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 inorganic metallic or mixture of metals with ceramic materials, e.g. hard metals, "cermets", cements for porous or cellular structure, e.g. for use with diamonds as abrasives
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B13/00—Machines or devices designed for grinding or polishing optical surfaces on lenses or surfaces of similar shape on other work; Accessories therefor
- B24B13/015—Machines or devices designed for grinding or polishing optical surfaces on lenses or surfaces of similar shape on other work; Accessories therefor of television picture tube viewing panels, headlight reflectors or the like
-
- 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
- B24D3/04—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 inorganic
- B24D3/06—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 inorganic metallic or mixture of metals with ceramic materials, e.g. hard metals, "cermets", cements
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K3/00—Materials not provided for elsewhere
- C09K3/14—Anti-slip materials; Abrasives
- C09K3/1409—Abrasive particles per se
Definitions
- the present invention relates to a superabrasive composition for grinding the front panel of a cathode ray tube, which comprises a mixture of diamond and cubic boron nitride particles in a specified ratio dispersed in a bonding material, also to a superabrasive article formed in a specified shape using said composition.
- a cathode ray tube is comprised of a face glass panel and a funnel glass body which are separately prepared by hot-press molding a glass goat.
- the resulting hot-press molded glass is subjected to a sequential grinding process using abrasive materials such as garnet, pumice and rouge lap to provide a finished front glass panel having a smooth surface for screen display.
- Such a superabrasive material is combined with a bonding material and sintered to provide a superabrasive grinding article, whose performance characteristics are influenced by particle size, hardness, grade and structure of the superabrasive particles, as well as by the kind of bonding material used and the porosity of the sintered composite thereof.
- a grinding article for grinding CRT front panel may be formed in various shapes as disclosed in various documents.
- Korean Patent Laid-open Publication No. 95-25832 discloses a superabrasive article for grinding the front glass panel of CRT, in the form of a rubber pad having implanted buttons of diamond particles.
- this article does not generate wastewater, when diamond particles are employed alone as a grinding material, the ground surface is glazed.
- a superabrasive composition for grinding the front glass panel of a cathode ray tube which comprises superabrasive particles and a bonding material, the superabrasive particles being a mixture of diamond particles and cubic boron nitride (CBN) particles in a mix ratio of 8.5:1.5 to 9.5:0.5 in volume.
- CBN cubic boron nitride
- a grinding article for grinding the front glass panel of a cathode ray tube which comprises a superabrasive grinding layer formed by sintering the inventive superabrasive composition and a substrate element for securing the superabrasive grinding layer, said grinding layer has a cylindrical protrusion extending outward from a portion of bottom surface thereof, and the substrate element, which has on a portion of the top surface thereof a dimple which is shaped to closely receive said cylindrical protrusion, is tightly bonded to the grinding layer forming an interface which extends from the remaining portion of the bottom surface of the grinding layer to the surface of said protrusion.
- FIG. 1 a perspective view of an example of a superabrasive article according to the present invention
- FIG. 2 a cross-sectional view taken along the face A-A′ of the superabrasive article of FIG. 1;
- FIGS. 3 and 4 two examples of means for firmly securing the grinding layer on a substrate element in the inventive superabrasive grinding article
- FIG. 5 a conventional means for attaching the grinding layer to a substrate element
- FIG. 6 the variation in the grinding efficiency of superabrasive grinding articles prepared using a metallic bonding material, depending on the sintering conditions.
- the superabrasive composition of the present invention is characterized in that a specific mixture of diamond and cubic boron nitride (CBN) particles is employed as a superabrasive material, i.e., in accordance with the present invention, the mix ratio of diamond particles and CBN particles is in the range of 8.5:1.5 to 9.5:0.5 in volume.
- CBN particles cubic boron nitride
- the mix ratio of diamond particles and CBN particles is in the range of 8.5:1.5 to 9.5:0.5 in volume.
- the mixed superabrasive particles are combined with a bonding material in a mix ratio of 1.5:8.5 to 2.5:7.5 by volume, to provide the inventive composition.
- the bonding material may be metallic or a mixture of a metal oxide and a resin, and it functions to disperse and tightly hold the superabrasive particles during a high pressure sintering process to give a highly compacted composite having a high degree of physical integrity.
- a metallic bonding material which may be used in the present invention, include particles of Fe, Cu, Sn, an oxide thereof having an average particle size ranging from 30 to 50 ⁇ m.
- the resin may be preferably a phenol resin, and combined with the metal oxide component in a mix ratio of 9:1 to 7:3.
- lie inventive superabrasive composition is subjected to a hot press-molding process to provide the inventive grinding article having the specified structure.
- the hot press-molding process may be carried out by incorporating the inventive superabrasive composition into a mold to be hot-pressed under a high-temperature, high-pressure condition, the mold holding a pre-fabricated substrate element designed for securing the grinding layer generated by sintering the inventive composition.
- the hot press-molding process may be suitably conducted at a temperature ranging from 150 to 800° C. and a pressure ranging from 0.1 to 0.5 ton/cm 2 , depending on the component of the bonding material used, in a vacuum electrical furnace.
- the sintering-molding process may be conducted at a high temperature of 650 to 750° C., under a pressure of 0.1 to 0.25 ton/cm 2
- the sintering-molding may be conducted at a low temperature ranging from 150 to 200° C., under a pressure of 0.25 to 0.35 ton/cm 2 , although the condition may be varied depending on the Tg (glass transition temperature) and decomposition temperature of the resin used.
- the mold and the securing substrate element may be made of a stainless steel, carbon steel or other materials conventionally known in the art, and the mold is sealed during the hot press-molding process conducted in a vacuum.
- the substrate element is pre-shaped to have a dimple so that the grinding layer obtained by sintering the inventive composition can be firmly attached thereto. That is, in the inventive grinding article, the grinding layer has a cylindrical protrusion extending from the bottom surface thereof toward the inside of the dimple of the sintered element in a tightly locking manner.
- a specific structural feature such as a flange, circumferential groove or screw groove may be further provided to the interface between the grinding layer and the substrate element.
- the grinding article for grinding the front glass panel of a CRT according to the present invention may be shaped in a form, e.g., a round or a rectangular pad, suitable for the selected method of grinding.
- a round pad form is preferably used for a LAP machine which operates in a rotational mode
- a rectangular pad form for AGM which operates in an oscillational mode.
- the particle size and the toughness index of the superabrasive particles may be suitably controlled.
- the bonding material comprises a resin component
- a rotational grinding tool is used
- the superabrasive particles preferably have an average particle size of 75 to 90 ⁇ m and a toughness index of 50 to 60, while when an oscillation method is used, it is preferred that the average particle size is smaller, in the range of 30 to 38 ⁇ m.
- the superabrasive particles preferably have an average particle size of 75 to 90 ⁇ m and a toughness index of 50 to 60, like the above case, but when a vibrational grinding method is selected, the average particle size of the superabrasive particles preferably range from 30 to 38 ⁇ m, and the toughness indexes of the diamond and CBN particles, from 50 to 60, and from 40 to 50, respectively.
- the particle size is greater than the upper limit, the surface of the polished glass panel becomes too rough, while if it is smaller than the lower limit, the grinding efficiency decreases. Further, if the toughness index is greater than the upper limit, the abrasive particles do not sufficiently break out at a suitable rate to renew the grinding surface and the grinding surface tends to get glazed, while if it is lower than the lower limit, the use life becomes short.
- FIG. 1 represents a perspective view of one embodiment of the grinding article of the present invention
- FIG. 2 shows a cross-sectional view thereof taken along the face A-A′ in FIG. 1.
- the inventive superabrasive grinding article ( 100 ) consists of a superabrasive grinding layer ( 110 ) and a substrate element ( 120 ) for securing the grinding layer, wherein the bottom part of the grinding layer ( 110 ) has a cylindrical protrusion with a circular flange ( 141 ) positioned at the lower end thereof, which extends into, and closely fits the preformed substrate element ( 120 ).
- the lower portion of the substrate element ( 120 ) is equipped with a circular groove ( 130 ) at the outside surface thereof, which is used for loading the grinding article to a carrier such as a rubber pad.
- the circular flange ( 141 ) prevents the grinding layer from detaching from the substrate element when the article is subjected to a vibrational motion in the axial direction.
- FIGS. 3 and 4 represent two other embodiments of the inventive grinding article.
- the means for attaching the superabrasive grinding layer to the substrate element have an additional structural feature, i.e., a circumferential groove ( 142 ) positioned at the bottom surface ( 160 ) of the grinding layer ( 110 ), or a screw groove ( 143 ) provided on the outer surface of the cylindrical protrusion ( 140 ).
- a bonding material composed of 75 wt % of a bronze-based powder (M325, a product of KENNAMETAL COMPANY, U.S.A) and 25 wt % of a tin powder were superabrasive particles of diamond and CBN in various ratios as shown in Table 1, the amount of superabrasive particles being 25% by volume based on the total weight of the resulting mixture, and the resulting mixture was homogenized using a tumbler mixer to obtain various superabrasive compositions.
- the mold was sealed with a carbon punch, placed in a vacuum electric furnace, and subjected to sintering under a pressure of 0.2 ton/cm 2 for 20 minutes at 700° C., to provide a sintered, superabrasive grinding article having the shape shown in FIGS. 1 and 2.
- Example 1 The procedure of Example 1 was repeated except that while fixing the diamond to CBN mix ratio at 9.5:0.5, the amount, the average particles size and the toughness index of the superabrasive particles used were varied as shown in Table 2, to provide superabrasive grinding articles.
- the superabrasive grinding device was loaded in an LAP machine and employed in grinding a 15′′ CRT glass panel for 30 seconds at 5.5-7 Hz and 0.15 kgf/cm 2 .
- the grinding efficiency and the roughness of the machined surface were measured.
- the apparatus used for measuring the surface roughness was Surftest301 TM (stylus type) of Japan, Mitsutoyo Company.
- Run 2-6 90 ⁇ 75 60 ⁇ 80 5 48 8.2 Com.
- Run 2-7 90 ⁇ 75 40 ⁇ 50 25 31 6.1 Com.
- Run 2-8 90 ⁇ 75 40 ⁇ 50 20 29 5.9 Com.
- Run 2-9 90 ⁇ 75 40 ⁇ 50 15 27 6.3 Com.
- Run 2-10 90 ⁇ 75 40 ⁇ 50 10 30 5.7 Com.
- Run 2-11 90 ⁇ 75 40 ⁇ 50 5 33 6.7 Com.
- Run 2-12 106 ⁇ 90 60 ⁇ 80 25 65 13.1 Com.
- Run 2-13 106 ⁇ 90 60 ⁇ 80 15 67 9.8 Com.
- Run 2-14 106 ⁇ 90 60 ⁇ 80 5 75 10.1 Com.
- Run 2-15 106 ⁇ 90 50 ⁇ 60 25 60 11.2 Com.
- Run 2-16 106 ⁇ 90 50 ⁇ 60 15 58 10.1 Com. Run 2-17 106 ⁇ 90 50 ⁇ 60 10 55 11.2 Com. Run 2-18 106 ⁇ 90 50 ⁇ 60 5 64 12.1 Com. Run 2-19 106 ⁇ 90 40 ⁇ 50 25 53 9.6 Com. Run 2-20 106 ⁇ 90 40 ⁇ 50 15 49 10.0 Com. Run 2-21 106 ⁇ 90 40 ⁇ 50 5 51 10.8 Com. Run 2-22 75 ⁇ 63 60 ⁇ 80 15 22 5.1 Com. Run 2-23 75 ⁇ 63 50 ⁇ 60 5 2 4.8 Com. Run 2-24 75 ⁇ 63 40 ⁇ 50 25 25 6.0 Com. Run 2-25 75 ⁇ 63 40 ⁇ 50 15 18 5.4 Com. Run 2-26 75 ⁇ 63 30 ⁇ 40 5 20 5.1
- Example 2 The procedure of Example 1 was repeated except that while fixing the diamond to CBN mix ratio at 9.5:0.5, the amount, particles size and toughness index of the superabrasive particles were varied as shown in Table 2, to provide a number of superabrasive grinding articles, which were each implanted in a rectangular rubber pad to prepare a grinding device.
- the grinding device thus obtained was loaded in an A.G.M. (orbital Aspherical Grinding Machine) (operated in an oscillation mode), and employed in grinding a 29′′ CRT glass panel for 35 seconds at 5.5-7 Hz and 0.15 kgf/cM 2 .
- the grinding efficiency and the roughness of the machined surface were measured as in Example 2. The result is shown in Table 3.
- Run 3-5 30 ⁇ 38 60 ⁇ 80 15 64 5.9 Com.
- Run 3-6 30 ⁇ 38 60 ⁇ 80 5 62 6.2 Com.
- Run 3-7 30 ⁇ 38 40 ⁇ 50 25 78 4.0 Com.
- Run 3-8 30 ⁇ 38 40 ⁇ 50 20 75 3.8 Com.
- Run 3-9 30 ⁇ 38 40 ⁇ 50 15 74 3.9 Com.
- Run 3-10 30 ⁇ 38 40 ⁇ 50 10 76 3.8 Com.
- Run 3-11 30 ⁇ 38 40 ⁇ 50 5 71 4.0 Com.
- Run 3-12 38 ⁇ 45 60 ⁇ 80 25 84 9.2 Com.
- Run 3-13 38 ⁇ 45 60 ⁇ 80 15 87 9.4 Com.
- Run 3-14 38 ⁇ 45 60 ⁇ 80 5 88 9.4 Com.
- Run 3-15 38 ⁇ 45 50 ⁇ 60 25 78 7.5 Com.
- Run 3-16 38 ⁇ 45 50 ⁇ 60 15 78 8.2 Com.
- Run 3-17 38 ⁇ 45 50 ⁇ 60 10 80 9.4 Com.
- Run 3-18 38 ⁇ 45 50 ⁇ 60 5 84 9.2 Com.
- Run 3-19 38 ⁇ 45 40 ⁇ 50 25 79 7.6 Com.
- Run 3-20 38 ⁇ 45 40 ⁇ 50 15 76 8.1 Com.
- Run 3-21 38 ⁇ 45 40 ⁇ 50 5 79 8.5 Com.
- Run 3-22 20 ⁇ 30 60 ⁇ 80 15 42 3.2 Com.
- Run 3-23 20 ⁇ 30 50 ⁇ 60 5 49 3.5 Com.
- Run 3-24 20 ⁇ 30 40 ⁇ 50 25 38 3.5 Com.
- Run 3-25 20 ⁇ 30 40 ⁇ 50 15 46 3.4 Com.
- Run 3-26 20 ⁇ 30 30 ⁇ 40 5 42 3.1
- Example 1 The procedure of Example 1 was repeated except that while fixing the diamond to CBN mix ratio at 9.5:0.5, the average particle size at 50 to 60 ⁇ m, and the toughness index at 90 to 75, the sintering temperature and pressure were varied as shown in FIG. 6, to provide grinding articles having various sintered characteristics.
- the grinding efficiency of each of the grinding articles thus prepared was measured and represented by a relative value based on 10 set for the value obtained for the grinding article prepared by sintering at 700° C. and 0.10 ton/cm 2 . The result is shown in FIG. 6.
- FIG. 6 shows that a grinding article prepared using a bronze-based metal as a bonding material is suitably sintered at a temperature of 650 to 750° C. and a pressure of 0.10 to 0.25 ton/cm 2 .
- Example 1 The procedure of Example 1 was repeated using a 9.5:0.5 mixed powder of diamond and CBN having a particle size of 50 to 60 ⁇ m and a toughness index of 90 to 75, except for conducting additional runs using a phenol resin composition containing 10 to 30% of iron oxide as a bonding material using a steel mold and sintering at a condition of 160 to 170° C. and 0.25 to 0.35 ton/cm 2 , to provide two types of grinding articles having the structure as shown in FIG. 2.
Abstract
Description
- The present invention relates to a superabrasive composition for grinding the front panel of a cathode ray tube, which comprises a mixture of diamond and cubic boron nitride particles in a specified ratio dispersed in a bonding material, also to a superabrasive article formed in a specified shape using said composition.
- A cathode ray tube (CRT) is comprised of a face glass panel and a funnel glass body which are separately prepared by hot-press molding a glass goat. In a conventional face panel manufacturing process, the resulting hot-press molded glass is subjected to a sequential grinding process using abrasive materials such as garnet, pumice and rouge lap to provide a finished front glass panel having a smooth surface for screen display.
- Superabrasives such as diamond and a cubic boron nitride (CBN) have been widely used for grinding molded glass or steel articles because they have higher hardness and toughness than such abrasive materials as alumina and silicon carbide (see U.S. Pat. Nos. 6,096,107 and 6,200,360), and a grinding process that employs a superabrasive material does not generate environmentally hazardous wastewater as the conventional slurry process does.
- Such a superabrasive material is combined with a bonding material and sintered to provide a superabrasive grinding article, whose performance characteristics are influenced by particle size, hardness, grade and structure of the superabrasive particles, as well as by the kind of bonding material used and the porosity of the sintered composite thereof.
- A grinding article for grinding CRT front panel may be formed in various shapes as disclosed in various documents. For example, Korean Patent Laid-open Publication No. 95-25832 discloses a superabrasive article for grinding the front glass panel of CRT, in the form of a rubber pad having implanted buttons of diamond particles. Although the use of this article does not generate wastewater, when diamond particles are employed alone as a grinding material, the ground surface is glazed.
- It is, therefore, a primary object of the invention to provide an improved grinding composition suitable for use in the manufacture of the front glass panel of a cathode ray tube, which has excellent grinding efficiency without the above-mentioned environmental or scratch problem.
- It is a further object of the invention to provide a grinding article prepared from such a composition having improved durability and use life.
- In accordance with one aspect of the present invention, there is provided a superabrasive composition for grinding the front glass panel of a cathode ray tube, which comprises superabrasive particles and a bonding material, the superabrasive particles being a mixture of diamond particles and cubic boron nitride (CBN) particles in a mix ratio of 8.5:1.5 to 9.5:0.5 in volume.
- In accordance with another aspect of the present invention, there is provided a grinding article for grinding the front glass panel of a cathode ray tube, which comprises a superabrasive grinding layer formed by sintering the inventive superabrasive composition and a substrate element for securing the superabrasive grinding layer, said grinding layer has a cylindrical protrusion extending outward from a portion of bottom surface thereof, and the substrate element, which has on a portion of the top surface thereof a dimple which is shaped to closely receive said cylindrical protrusion, is tightly bonded to the grinding layer forming an interface which extends from the remaining portion of the bottom surface of the grinding layer to the surface of said protrusion.
- The above and other objects and features of the present invention will become apparent from the following description thereof, when taken in conjunction with the accompanying drawings which respectively show:
- FIG. 1: a perspective view of an example of a superabrasive article according to the present invention;
- FIG. 2: a cross-sectional view taken along the face A-A′ of the superabrasive article of FIG. 1;
- FIGS. 3 and 4: two examples of means for firmly securing the grinding layer on a substrate element in the inventive superabrasive grinding article;
- FIG. 5: a conventional means for attaching the grinding layer to a substrate element; and
- FIG. 6: the variation in the grinding efficiency of superabrasive grinding articles prepared using a metallic bonding material, depending on the sintering conditions.
- The superabrasive composition of the present invention is characterized in that a specific mixture of diamond and cubic boron nitride (CBN) particles is employed as a superabrasive material, i.e., in accordance with the present invention, the mix ratio of diamond particles and CBN particles is in the range of 8.5:1.5 to 9.5:0.5 in volume. When diamond. particles are employed in an excess amount, the surface of a grinding article prepared therefrom can be suffered by glazing phenomena as the grinding process progresses, thereby lowering the grinding efficiency. Further, when CBN particles are employed in an amount exceeding the specified range, the superabrasive particles easily fall off from the grinding surface during use, and therefore, the grinding efficiency is reduced as well.
- The mixed superabrasive particles are combined with a bonding material in a mix ratio of 1.5:8.5 to 2.5:7.5 by volume, to provide the inventive composition.
- The bonding material may be metallic or a mixture of a metal oxide and a resin, and it functions to disperse and tightly hold the superabrasive particles during a high pressure sintering process to give a highly compacted composite having a high degree of physical integrity.
- Representative examples of a metallic bonding material, which may be used in the present invention, include particles of Fe, Cu, Sn, an oxide thereof having an average particle size ranging from 30 to 50 μm. when a mixture of a metal oxide and a resin is used a bonding material, the resin may be preferably a phenol resin, and combined with the metal oxide component in a mix ratio of 9:1 to 7:3.
- In accordance with the present invention, lie inventive superabrasive composition is subjected to a hot press-molding process to provide the inventive grinding article having the specified structure.
- The hot press-molding process may be carried out by incorporating the inventive superabrasive composition into a mold to be hot-pressed under a high-temperature, high-pressure condition, the mold holding a pre-fabricated substrate element designed for securing the grinding layer generated by sintering the inventive composition.
- The hot press-molding process may be suitably conducted at a temperature ranging from 150 to 800° C. and a pressure ranging from 0.1 to 0.5 ton/cm2, depending on the component of the bonding material used, in a vacuum electrical furnace. For example, when a metal such as copper or tin is employed as a bonding material, the sintering-molding process may be conducted at a high temperature of 650 to 750° C., under a pressure of 0.1 to 0.25 ton/cm2, whereas when a resin is incorporated in the bonding material, the sintering-molding may be conducted at a low temperature ranging from 150 to 200° C., under a pressure of 0.25 to 0.35 ton/cm2, although the condition may be varied depending on the Tg (glass transition temperature) and decomposition temperature of the resin used.
- The mold and the securing substrate element may be made of a stainless steel, carbon steel or other materials conventionally known in the art, and the mold is sealed during the hot press-molding process conducted in a vacuum.
- In the present invention, the substrate element is pre-shaped to have a dimple so that the grinding layer obtained by sintering the inventive composition can be firmly attached thereto. That is, in the inventive grinding article, the grinding layer has a cylindrical protrusion extending from the bottom surface thereof toward the inside of the dimple of the sintered element in a tightly locking manner.
- In order to still more firmly attach the grinding layer to the substrate element, a specific structural feature such as a flange, circumferential groove or screw groove may be further provided to the interface between the grinding layer and the substrate element.
- The grinding article for grinding the front glass panel of a CRT according to the present invention may be shaped in a form, e.g., a round or a rectangular pad, suitable for the selected method of grinding. For instance, a round pad form is preferably used for a LAP machine which operates in a rotational mode, and a rectangular pad form, for AGM which operates in an oscillational mode.
- Depending on the method of grinding and the composition of the bonding material, the particle size and the toughness index of the superabrasive particles may be suitably controlled. For example, in case the bonding material comprises a resin component, and a rotational grinding tool is used, the superabrasive particles preferably have an average particle size of 75 to 90 μm and a toughness index of 50 to 60, while when an oscillation method is used, it is preferred that the average particle size is smaller, in the range of 30 to 38 μm.
- In case a metallic bonding material is used and a rotational grinding method is adopted, the superabrasive particles preferably have an average particle size of 75 to 90 μm and a toughness index of 50 to 60, like the above case, but when a vibrational grinding method is selected, the average particle size of the superabrasive particles preferably range from 30 to 38 μm, and the toughness indexes of the diamond and CBN particles, from 50 to 60, and from 40 to 50, respectively.
- If the particle size is greater than the upper limit, the surface of the polished glass panel becomes too rough, while if it is smaller than the lower limit, the grinding efficiency decreases. Further, if the toughness index is greater than the upper limit, the abrasive particles do not sufficiently break out at a suitable rate to renew the grinding surface and the grinding surface tends to get glazed, while if it is lower than the lower limit, the use life becomes short.
- Several embodiments of the grinding article according to the present invention are shown in the accompanying drawings. FIG. 1 represents a perspective view of one embodiment of the grinding article of the present invention, and FIG. 2 shows a cross-sectional view thereof taken along the face A-A′ in FIG. 1.
- As shown in FIGS. 1 and 2, the inventive superabrasive grinding article (100) consists of a superabrasive grinding layer (110) and a substrate element (120) for securing the grinding layer, wherein the bottom part of the grinding layer (110) has a cylindrical protrusion with a circular flange (141) positioned at the lower end thereof, which extends into, and closely fits the preformed substrate element (120).
- The lower portion of the substrate element (120) is equipped with a circular groove (130) at the outside surface thereof, which is used for loading the grinding article to a carrier such as a rubber pad. The circular flange (141) prevents the grinding layer from detaching from the substrate element when the article is subjected to a vibrational motion in the axial direction.
- FIGS. 3 and 4 represent two other embodiments of the inventive grinding article. As can be seen from FIGS. 3 and 4, the means for attaching the superabrasive grinding layer to the substrate element have an additional structural feature, i.e., a circumferential groove (142) positioned at the bottom surface (160) of the grinding layer (110), or a screw groove (143) provided on the outer surface of the cylindrical protrusion (140).
- The following Examples are given for the purpose of illustration only and are not intended to limit the scope of the invention.
- Added to a bonding material composed of 75 wt % of a bronze-based powder (M325, a product of KENNAMETAL COMPANY, U.S.A) and 25 wt % of a tin powder were superabrasive particles of diamond and CBN in various ratios as shown in Table 1, the amount of superabrasive particles being 25% by volume based on the total weight of the resulting mixture, and the resulting mixture was homogenized using a tumbler mixer to obtain various superabrasive compositions.
- A securing substrate element (120) having the shape corresponding to FIG. 3 and made of SS41, which was previously fabricated using an NC(Numerical Control) machine, was positioned in a mold, and the above grinding layer composition was introduced over the substrate element. The mold was sealed with a carbon punch, placed in a vacuum electric furnace, and subjected to sintering under a pressure of 0.2 ton/cm2 for 20 minutes at 700° C., to provide a sintered, superabrasive grinding article having the shape shown in FIGS. 1 and 2.
- Superabrasive grinding articles thus prepared were implanted in a round rubber pad by a conventional implanting method, and the resulting grinding device was loaded in an LAP grinding machine and employed in grinding 200 CRT front glass panels in a rotational mode under 0.15 kgf/cm2 for 30 seconds to evaluate the grinding efficiency thereof which is represented by the amount of glass removed. The result is shown in Table 1.
TABLE 1 Superabrasive Materialsa Average Amount Removed (g) Diamond Cubic Boron Nitride 1˜10 glass 40˜50 glass 100˜200 glass Powderb (%) Powderc (%) plates plates plates Run 1-1 85 15 98 94 92 Run 1-2 90 10 95 97 95 Run 1-3 95 5 98 95 93 Com. Run 1-1 65 35 104 82 55 Com. Run 1-2 75 25 101 86 72 Com. Run 1-3 100 0 100 60 34 - As can be seen from Table 1, when the relative amount of CBN is not in the range of 5-15%, the grinding efficiency rapidly falls off as the grinding process proceeds.
- The procedure of Example 1 was repeated except that while fixing the diamond to CBN mix ratio at 9.5:0.5, the amount, the average particles size and the toughness index of the superabrasive particles used were varied as shown in Table 2, to provide superabrasive grinding articles.
- The superabrasive grinding device was loaded in an LAP machine and employed in grinding a 15″ CRT glass panel for 30 seconds at 5.5-7 Hz and 0.15 kgf/cm2. The grinding efficiency and the roughness of the machined surface were measured. The apparatus used for measuring the surface roughness was Surftest301 ™ (stylus type) of Japan, Mitsutoyo Company.
TABLE 2 Superabrasive Particles Tough- Amount Surface Particle ness Amount Removed Roughness Size (μm) Index (vol %)d (g) (Rt) Run 2-1 90˜75 50˜60 25 42 6.0 Run 2-2 90˜75 50˜60 22 45 6.4 Run 2-3 90˜75 50˜60 18 42 6.1 Run 2-4 90˜75 50˜60 15 44 5.9 Com. Run 2-1 90˜75 50˜60 10 37 6.4 Com. Run 2-2 90˜75 50˜60 30 36 5.4 Com. Run 2-3 90˜75 50˜60 35 32 5.6 Com. Run 2-4 90˜75 60˜80 25 42 7.6 Com. Run 2-5 90˜75 60˜80 15 46 7.4 Com. Run 2-6 90˜75 60˜80 5 48 8.2 Com. Run 2-7 90˜75 40˜50 25 31 6.1 Com. Run 2-8 90˜75 40˜50 20 29 5.9 Com. Run 2-9 90˜75 40˜50 15 27 6.3 Com. Run 2-10 90˜75 40˜50 10 30 5.7 Com. Run 2-11 90˜75 40˜50 5 33 6.7 Com. Run 2-12 106˜90 60˜80 25 65 13.1 Com. Run 2-13 106˜90 60˜80 15 67 9.8 Com. Run 2-14 106˜90 60˜80 5 75 10.1 Com. Run 2-15 106˜90 50˜60 25 60 11.2 Com. Run 2-16 106˜90 50˜60 15 58 10.1 Com. Run 2-17 106˜90 50˜60 10 55 11.2 Com. Run 2-18 106˜90 50˜60 5 64 12.1 Com. Run 2-19 106˜90 40˜50 25 53 9.6 Com. Run 2-20 106˜90 40˜50 15 49 10.0 Com. Run 2-21 106˜90 40˜50 5 51 10.8 Com. Run 2-22 75˜63 60˜80 15 22 5.1 Com. Run 2-23 75˜63 50˜60 5 2 4.8 Com. Run 2-24 75˜63 40˜50 25 25 6.0 Com. Run 2-25 75˜63 40˜50 15 18 5.4 Com. Run 2-26 75˜63 30˜40 5 20 5.1 - As can be seen from Table 2, if the amount of the abrasive particles employed is not in the range of 15-25% of the present invention or the toughness index is lower than 50, the grinding efficiency becomes unsatisfactory (see Com. Run Nos. 2-1 to 2-3 and 2-7 to 2-11), while if the toughness index is higher than 60 or the particle size is higher than 90 μm, the ground surface becomes too rough (see Com. Run Nos. 2-4 to 2-6 and 2-15 to 2-18). On the other hand, if the particle size is smaller than 75 μm, the grinding efficiency becomes unsatisfactorily low (see Com. Run No. 23). Further, other articles prepared in Com. Run Nos. 2-12 to 2-14, 2-19 to 2-22, and 2-24 to 2-26 using superabrasive particles having particle size and toughness value not in the range of the present invention show poor grinding efficiencies.
- The procedure of Example 1 was repeated except that while fixing the diamond to CBN mix ratio at 9.5:0.5, the amount, particles size and toughness index of the superabrasive particles were varied as shown in Table 2, to provide a number of superabrasive grinding articles, which were each implanted in a rectangular rubber pad to prepare a grinding device.
- The grinding device thus obtained was loaded in an A.G.M. (orbital Aspherical Grinding Machine) (operated in an oscillation mode), and employed in grinding a 29″ CRT glass panel for 35 seconds at 5.5-7 Hz and 0.15 kgf/cM2. The grinding efficiency and the roughness of the machined surface were measured as in Example 2. The result is shown in Table 3.
TABLE 3 Superabrasive Particles Tough- Removal Surface Particle ness Amount Amount Roughness Size (μm) Index (vol %)d (g) (Rt) Run 3-1 30˜38 50˜60 25 86 4.9 Run 3-2 30˜38 50˜60 22 85 4.7 Run 3-3 30˜38 50˜60 18 83 4.8 Run 3-4 30˜38 50˜60 15 84 4.2 Com. Run 3-1 30˜38 50˜60 10 76 4.1 Com. Run 3-2 30˜38 50˜60 30 77 4.9 Com. Run 3-3 30˜38 50˜60 35 62 4.5 Com. Run 3-4 30˜38 60˜80 25 65 5.8 Com. Run 3-5 30˜38 60˜80 15 64 5.9 Com. Run 3-6 30˜38 60˜80 5 62 6.2 Com. Run 3-7 30˜38 40˜50 25 78 4.0 Com. Run 3-8 30˜38 40˜50 20 75 3.8 Com. Run 3-9 30˜38 40˜50 15 74 3.9 Com. Run 3-10 30˜38 40˜50 10 76 3.8 Com. Run 3-11 30˜38 40˜50 5 71 4.0 Com. Run 3-12 38˜45 60˜80 25 84 9.2 Com. Run 3-13 38˜45 60˜80 15 87 9.4 Com. Run 3-14 38˜45 60˜80 5 88 9.4 Com. Run 3-15 38˜45 50˜60 25 78 7.5 Com. Run 3-16 38˜45 50˜60 15 78 8.2 Com. Run 3-17 38˜45 50˜60 10 80 9.4 Com. Run 3-18 38˜45 50˜60 5 84 9.2 Com. Run 3-19 38˜45 40˜50 25 79 7.6 Com. Run 3-20 38˜45 40˜50 15 76 8.1 Com. Run 3-21 38˜45 40˜50 5 79 8.5 Com. Run 3-22 20˜30 60˜80 15 42 3.2 Com. Run 3-23 20˜30 50˜60 5 49 3.5 Com. Run 3-24 20˜30 40˜50 25 38 3.5 Com. Run 3-25 20˜30 40˜50 15 46 3.4 Com. Run 3-26 20˜30 30˜40 5 42 3.1 - As in Table 2, the result in Table 3 shows that satisfactory grinding efficiency and surface smoothness can be obtained only when the particle size, toughness index and amount of abrasive particles are controlled in the specified ranges of the present invention.
- The procedure of Example 1 was repeated except that while fixing the diamond to CBN mix ratio at 9.5:0.5, the average particle size at 50 to 60 μm, and the toughness index at 90 to 75, the sintering temperature and pressure were varied as shown in FIG. 6, to provide grinding articles having various sintered characteristics. The grinding efficiency of each of the grinding articles thus prepared was measured and represented by a relative value based on 10 set for the value obtained for the grinding article prepared by sintering at 700° C. and 0.10 ton/cm2. The result is shown in FIG. 6.
- FIG. 6 shows that a grinding article prepared using a bronze-based metal as a bonding material is suitably sintered at a temperature of 650 to 750° C. and a pressure of 0.10 to 0.25 ton/cm2.
- The procedure of Example 1 was repeated using a 9.5:0.5 mixed powder of diamond and CBN having a particle size of 50 to 60 μm and a toughness index of 90 to 75, except for conducting additional runs using a phenol resin composition containing 10 to 30% of iron oxide as a bonding material using a steel mold and sintering at a condition of 160 to 170° C. and 0.25 to 0.35 ton/cm2, to provide two types of grinding articles having the structure as shown in FIG. 2.
- For control, the above procedure was repeated to obtain two comparative grinding articles having the conventional structure of FIG. 5.
- The grinding articles thus fabricated were subjected to a test to examine whether the grinding layer is detachable from the substrate element during the grinding process. The result is shown in Table 4.
TABLE 4 Number of the stone Structure Bonding Material detached Comp. Bronze-based metal 2 Run 4-1 Comp. Iron oxide - containing phenol resin 4 Run 4-2 Run 4-1 Bronze-based metal 0 Run 4-2 Iron oxide - containing phenol resin 0 - The result in Table 4 shows that the grinding layer of the respective grinding article is much more firmly attached to the substrate element than that of a conventional grinding article.
- While the invention has been described in connection with the above specific embodiments, it should be recognized that various modifications and changes may be made to the invention by those skilled in the art without departing from the scope of the invention as defined by the appended claims.
Claims (12)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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KR1020000056720A KR20020024892A (en) | 2000-09-27 | 2000-09-27 | Superbrasive tool and manufacturing method of it using Superbrasive stone for grinding of Brown tube pannel face |
KR2000-56720 | 2001-09-27 |
Publications (1)
Publication Number | Publication Date |
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US20030114085A1 true US20030114085A1 (en) | 2003-06-19 |
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ID=19690677
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Application Number | Title | Priority Date | Filing Date |
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US09/966,665 Abandoned US20030114085A1 (en) | 2000-09-27 | 2001-09-27 | Superabrasive composition and superabrasive article comprising same for grinding CRT front panel |
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Country | Link |
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US (1) | US20030114085A1 (en) |
JP (1) | JP2002178265A (en) |
KR (1) | KR20020024892A (en) |
CN (1) | CN1346863A (en) |
DE (1) | DE10147707A1 (en) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20080148648A1 (en) * | 2005-04-14 | 2008-06-26 | Ehwa Diamond Industrial Co., Ltd. | Cutting Segment, Method For Manufacturing Cutting Segment, and Cutting Tool Comprising the Same |
US20080202488A1 (en) * | 2005-04-21 | 2008-08-28 | Ehwa Diamond Industrial Co., Ltd. | Cutting Segment for Cutting Tool and Cutting Tools |
US9168637B2 (en) | 2012-01-18 | 2015-10-27 | Noritake Co., Limited | Vitrified super-abrasive-grain grindstone |
US9266220B2 (en) | 2011-12-30 | 2016-02-23 | Saint-Gobain Abrasives, Inc. | Abrasive articles and method of forming same |
US10875152B2 (en) | 2016-03-24 | 2020-12-29 | A.L.M.T. Corp. | Super-abrasive grinding wheel |
US11123841B2 (en) | 2016-05-27 | 2021-09-21 | A.L.M.T. Corp. | Super-abrasive grinding wheel |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20030104763A1 (en) * | 2001-11-19 | 2003-06-05 | Einset Erik O. | Tough and weak crystal mixing for low power grinding |
JP5603591B2 (en) * | 2009-11-27 | 2014-10-08 | 株式会社アドマテックス | Abrasive grain for processing, processing tool, processing liquid, and processing method using them |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5694267U (en) * | 1979-12-19 | 1981-07-27 | ||
KR890006717Y1 (en) * | 1986-05-23 | 1989-09-30 | 이상규 | Garnet pad for grinding glass plate |
JPH06262527A (en) * | 1993-03-11 | 1994-09-20 | Mitsubishi Materials Corp | Grinding wheel |
JPH0775971A (en) * | 1993-09-07 | 1995-03-20 | Nachi Fujikoshi Corp | Extra-abrasive grain wheel for grinding wired sheet glass |
DE19513098C2 (en) * | 1995-04-07 | 1997-05-22 | Freudenberg Carl Fa | Sealing arrangement |
-
2000
- 2000-09-27 KR KR1020000056720A patent/KR20020024892A/en not_active Application Discontinuation
-
2001
- 2001-09-27 JP JP2001296270A patent/JP2002178265A/en active Pending
- 2001-09-27 US US09/966,665 patent/US20030114085A1/en not_active Abandoned
- 2001-09-27 CN CN01141491A patent/CN1346863A/en active Pending
- 2001-09-27 DE DE10147707A patent/DE10147707A1/en not_active Withdrawn
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20080148648A1 (en) * | 2005-04-14 | 2008-06-26 | Ehwa Diamond Industrial Co., Ltd. | Cutting Segment, Method For Manufacturing Cutting Segment, and Cutting Tool Comprising the Same |
US8002858B2 (en) | 2005-04-14 | 2011-08-23 | Ehwa Diamond Industrial Co., Ltd. | Cutting segment, method for manufacturing cutting segment, and cutting tool comprising the same |
US20080202488A1 (en) * | 2005-04-21 | 2008-08-28 | Ehwa Diamond Industrial Co., Ltd. | Cutting Segment for Cutting Tool and Cutting Tools |
US7954483B2 (en) * | 2005-04-21 | 2011-06-07 | Ehwa Diamond Industrial Co., Ltd. | Cutting segment for cutting tool and cutting tools |
US9266220B2 (en) | 2011-12-30 | 2016-02-23 | Saint-Gobain Abrasives, Inc. | Abrasive articles and method of forming same |
US9168637B2 (en) | 2012-01-18 | 2015-10-27 | Noritake Co., Limited | Vitrified super-abrasive-grain grindstone |
US10875152B2 (en) | 2016-03-24 | 2020-12-29 | A.L.M.T. Corp. | Super-abrasive grinding wheel |
US11123841B2 (en) | 2016-05-27 | 2021-09-21 | A.L.M.T. Corp. | Super-abrasive grinding wheel |
Also Published As
Publication number | Publication date |
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KR20020024892A (en) | 2002-04-03 |
DE10147707A1 (en) | 2002-09-05 |
JP2002178265A (en) | 2002-06-25 |
CN1346863A (en) | 2002-05-01 |
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