CA1179849A - Metal bonded diamond aggregate abrasive - Google Patents
Metal bonded diamond aggregate abrasiveInfo
- Publication number
- CA1179849A CA1179849A CA000408518A CA408518A CA1179849A CA 1179849 A CA1179849 A CA 1179849A CA 000408518 A CA000408518 A CA 000408518A CA 408518 A CA408518 A CA 408518A CA 1179849 A CA1179849 A CA 1179849A
- Authority
- CA
- Canada
- Prior art keywords
- diamond
- aggregate
- metal
- improved
- abrasive
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
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
-
- 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
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C26/00—Alloys containing diamond or cubic or wurtzitic boron nitride, fullerenes or carbon nanotubes
Abstract
IMPROVED METAL BONDED DIAMOND
AGGREGATE ABRASIVE
ABSTRACT OF THE DISCLOSURE
An improved diamond aggregate abrasive is disclosed comprising milled saw diamond having an average size less than 75 microns held in a silver/
copper alloy matrix which also contains a wetting agent fro (e.g. titanium). Tests of grinding wheels containing this new aggregate have shown a marked improvement in grinding ratio over commercially available diamond aggregates.
AGGREGATE ABRASIVE
ABSTRACT OF THE DISCLOSURE
An improved diamond aggregate abrasive is disclosed comprising milled saw diamond having an average size less than 75 microns held in a silver/
copper alloy matrix which also contains a wetting agent fro (e.g. titanium). Tests of grinding wheels containing this new aggregate have shown a marked improvement in grinding ratio over commercially available diamond aggregates.
Description
~11 7~84~
IMPROVED METAL BONDED DIAMOND
AGGRE-GAT~ ABRASIVE
Technical Field This invention relates to an improved metal bonded agglomerated diamond abrasive whereby the grinding ratio of wheels dry grinding cemented tungsten carbide is significantly improved over standard agglomerated abrasives. The term grinding ratio is the unit volume of workpiece material removed per unit volume of grinding wheel wear.
Background The use of diamond abrasives in metal bonds is well known. U.S. Patents Re 21,165; 2,737,454;
and 2,828,197 disclose abrasive bodies comprising diamond in metal bonds of various copper alloys and bronze bonds.
Metal bonded agglomerated or aggregated abrasives are also well known. U.S. Patent 2,216,728 discloses various forms of metal and glass bonded aggregates. U.S. 3,955,324, issued May 11, 1976 to Olle Lindstrom teaches the use of a metal/diamond aggregate in which diamond is completely surrounded by metal. U.S. 4,024,675, issued May 24, 1973 to Jury Naidich et al describes sintered diamond/metal aggregates containing an additive (titanium, zirconium, chromium, vanadium, or silicon) in an amount of 5 to 10 percent of the metal powder. The additive is said to impart the required degree of wettability of the ,v~
diamond grains with the metal and also cohesion of individual grits to each other.
U.S. Patent No. 4,246,006, issued January 20, 1981 to Cornelius Phaal discloses copper/silver alloy metal binders used in metal/diamond aggregates which aggregates include a wetting agent as in the aforementioned U.S. Patent 4,024,675. The metal alloy employed may be in powdered form for the starting mixture; however, it is preferred that the individual alloy components are used in the starting mixture in order to produce the alloy in situ. The amount of metal alloy powder used in the starting mixture for the aggregate is generally between 40 and 60 weight percent of the total, and the wetting agent is typically between 5 and 15 weight percent of the metal.
The diamond used in the aggregates of the aforementioned U.S. Patent 4,246,006 is selected from one or more of three specific types defined in the patent in terms of Friatest Index, metal content, color, shape, and surface roughness. The Friatest is one of a variety of measures of the strength or friability (i.e. susceptibility to fracture) of the diamond.
Typically in such friability tests, a sample of the diamond particles of a particular size is placed in a-capsule with a hard steel ball and shaken for a predetermined period of time. The abrasive particles are then removed from the capsule and screened through the next smaller screen size in relation to the smaller of the two screens used for determining the screen size of the original particles. That is, if 60/80 mesh (250/180 micron) diamond were being tested, the screen used would be the next standard size smaller than 80 mesh or 180 micron. The amount of diamona retained on the screen divided by the weight of the original sample yields a value (toughness index) which B~9 indicates the proportion of the diamond which was not broken down to smaller size.
The 4,246,006 patent states that it is preferable that the diamond particles used are all fine and have a size smaller than about 125 microns. A powdered mixture of diamond particles and metal is sintered under non-oxidizing conditions, above the liquidus temperature of the metal alloy (typically at a temperature in the range 700 to 1200C) for a time between 10 and 20 minutes. The sintered mass is then cooled to produce an ingot which is crushed and classified to produce the aggregate grits of desired size. The crushing is preferably by a means which reduces the size of the ingot primarily in the shear mode rather than by compression. This is also preferred for the invention described herein. Suitable crushers would be a jaw crusher or a laboratory mill such as the Alpine perplex mill by Alpine American Corp., Natick, Massachusetts.
There is a currently available commercial aggregate diamond grit, CDA-M from DeBeers Industrial Diamond Division of Johannesburg, South Africa. CDA-M
particles are relatively coarse, having a size which centers around 80 mesh (180 microns). The much smaller constituent diamond grits are said to cover a broader range of sizes, approximately 140 U.S. mesh-(106 microns) and finer. The metal bond alloy used in CDA-M grit is said to account for about 55 weight percent of the whole particle.
The abrasives art recognizes various classes of industrial diamond, the three major classes being resin bond diamond, metal bond diamond, and saw diamond. Resin bond diamond is suitable for resin bond or vitreous bond grinding wheels and comprises friable, irregular crystals usually coated with nickel alloy or copper. Metal bond diamond is used in metal matrix bonds or plated tools and comprises medium-toughness, regular crystals with a color range from yellow-green to light yellow. Crystal inclusions are generally low, but some heavily included crystals can be present. Saw diamond, used in sawing and drilling stone, concrete and refractories, comprises tough (low friability), blocky, cubo-octahedral crystals with predominately smooth faces. The saw diamond crys-tal is transparent or translucent having a color ranging from light yellow to medium yellow-green.
Due to the higher impact strength or toughness of saw diamond, its fracture during sawing operations is minimized and wear occurs largely by abrasion processes.
Saw diamond is generally more blocky in shape (i.e. has a lower aspect ratio) than metal bond or resin bond diamond. Diamond may be classified by shape separation on a shape sorting machine which separates the diamond crystals according to their aspect ratio.
Such machines comprise a vibrating inclined table which causes the particles to segregate according to shape, and it collects various fractions of the particles in separate cups or bins. Such machines are well known in the art, and a description may be found in Dyer, H.B., "E~B Natural Diamonds," Industrial Diamond Review, (August, 1964) page 192-196.
~ etal bonded agglomerated or aggregated diamond abrasives can exhibit higher grinding ratios under certain conditions than nickel or copper aggregates of U.S. 4,024,675 and 4,246,006 that this invention was achieved.
Disclosure of Invention This invention is summarized às:
an improved aggregated abrasive particle comprising diamond particles held in a silver/copper alloy metal bond matrix which contains a wetting agent for diamond, wherein the improvement comprises those aggregates containing diamond:
(a) having a largest dimension which, on the average, is less than 75 microns; and ~L~79~3~9 (b) characterized as milled saw diamond.
The improvement is realized principally through decreasing the average diamond particle size from that used in the standard commercially available agglomerated abrasive. In fact, it is preferred that the average diamond size than 270/325 U.S. mesh (53/45 microns) or less, and all the diamond is preferably under 70 microns.
This smaller size is achieved through milling saw diamond in an apparatus such as a jet mill whereby diamond crystals are accelerated to a high velocity in an air stream and then impact each other and the internal walls of the milling apparatus. The saw diamond raw material which was milled for use in developing this invention was over 20 mesh size (850 microns) predominantly crystal clusters. The milled saw diamond thus obtained does not exhibit the natural crystalline faces of normal saw diamond, and it is less tough (more friable) than metal bond diamond of the same size range. One test has shown the toughness index of milled saw diamond to be about 69 percent of equivalent sized metal bond diamond.
The volume ratio of the diamond to matrix metal powders may be in the range of 1:20 to 4:1; with the range of 2:1 to 4:1 being preferred.
Brief Description of the Figures Figure 1 is a photomicrograph (magnified 200X) showing one of the improved aggregated diamond abrasive particles of this invention, sample RGA-76E of Example II.
Figure 2 is a photomicrograph (magnified by 400X) showing the milled saw diamond raw material used in making these aggregates, which has a particle size less than 75 microns.
Figure 3 is a photomicrograph (magnified 400X) which shows metal bond diamond particles, to illustrate the shape and surface difference between metal bond and milled saw diamond.
Figure 4 is a photomicrograph (magnified 400X) 1~'79~
which shows resin bond diamond particles, in order to illustrate the difference in shape and surface between resin bond and milled saw diamond.
sest Mode for Carrying Out the Invention It is preferred that the level of metal matrix (copper/silver alloy and titanium) in the aggregate be about 50-80 weight percent, more prefereably 50-65 percent. However it is to be noted that the percent of matrix metal in the starting mix for making the aggregate is generally lower than the final percent. This is caused by the separation of some diamond from the aggregate during the milling and size separation steps.
As to the aspect ratio for the raw material saw diamond, 4:1 or lower is preferred, with 2:1 or less being more preferred.
It is also preferred to work with a pre-alloyed mixture of copper and silver rather than mixing powders of the two metals and forming the alloy in situ.
Test results during the development of this invention have indicated that the diamond wetting agent (titanium in the experiments) has a large effect on performance. While a minimum of about 5 weight percent titanium was needed to wet the diamond, additionally increasing the titanium amount decreased grinding ratio.
The titanium was incorporated into the system both by coating the diamond and by mixing it with the diamond and alloy powders. Techniques for coating diamond with titanium (e.g. sputtering) are known in the art (see e.g. U.S. Patents 3,654,110 issued April 4, 1972 to 30 Friedrich Kraus; 3,472,751 issued October 4, 1969 to William King; 3,325,393 issued June 13, 1967 to Darrow et al;
3,351,543 issued November 7, 1967 to Thomas Vanderslice;
and 3,650,714 issued March 21, 1972 to Peter Farkas).
While the aggregate metal matrix level was not found to significantly affect grinding ratio within experimental error (with the possible exception of a 1:~79t~349 small affect at high titanium concentrations) it was found to affect energy consumption. Increasing the amount of metal (titanium and/or the coppersilver alloy) increased specific energy.
This invention will be further clarified by a consideration of the following examples, which are intended to be purely exemplary. In these examples, grinding tests are describQd. All the grinding tests have utilized standard llV-9 flaring cup, resin-bonded grinding wheels, having a diameter of 3-3/4 inches (95.25 mm) and containing abrasive at a 75 concentration in the resin bond. Methods of making resin bond grinding wheels are well known to the art (see e.g. U.S. Patents 3,645,706 issued February 29, 1972 to Harold ~ovenkerk et al;
3,385,684 issued ~lay 28, 1968 to Roger Voter; 3,664,819 issued May 28, 1972 to Sioui et al; 3,779,727 issued December 18, 1973 to Sioui et al; and 3,957,461 issued May 18, 1976 to Lindstrom et al). In a typical preparation of a resin bond grinding wheel, a mixture of granulated resin (i.e. phenol-formaldehyde resin), abrasive particles (diamond) and filler is placed in a grinding wheel mold. A molding pressure appropriate to the particular resin - usually several thousand pounds per square inch - is applied, and the mold is heated to a temperature sufficient to make the resin plastically deform (and cure in cases where it is heat curable).
In the grinding wheel art, 100 concentration is conventionally defined as 4.4 carats/cm3 with 1 carat equal to 0.2 g. The concentration of abrasive grit is linearly related to its carat per unit volume concen-tration. Thus, 75 concentration equals about 3.3 carats of abrasive per cubic centimeter of the grinding wheel abrasive section.
In all the grinding tests, the size of the experimental aggregate used was 250/150 microns. CONTROL
1 was a commercially available aggregate grit, CDA-M, nominally 180 microns. CONTROL 2 was a commercially 1:1'79~349 available nickel coated single crystal diamond grit obtained as RVG-W from the General Electric Company. CONTROL 3 was a commercially available copper coated single crystal diamond grit obtained as RVG-D from the General Electric Company.
Also, in the examples which follow: SD designates milled saw diamond; MD designates metal bond diamonds; and RD designates resin bond diamond.
ExAMæLE I
A series of grinding tests was performed at two standard conditions which are given below.
Condition Standard Condition #1 Standard Condition #2 Wheel Speed (Meters/sec.) 22 18 Infeed tmm) 0.064 0.076 Table Speed (M/min)1.5 1.5 15 Workpiece MaterialWC-Co* WC-Co*
Workpiece Size (mm )6.4 x 19.16.4 x 19.1 (16 pieces) *a 6% cobalt cemented tungsten carbide obtained as Carboloy 44A cemented carbide from General Electric Company.
All aggregate abrasives tested were made from a mixture of 45 weight percent silver:copper alloy and 10 weight percent titanium, the balance being diamond. The resulting weight percent of the matrix after crushing was in the range of 64 - 68. All the aggregates were fabricated by liquid phase sintering at 920 for one hour in argon, followed by crushing and screening.
There were two grinding wheels made of each abrasive. Each test was preceded by a pre-grind until power consumption stabilized.
A minimum of four sets of infeeds were run for each wheel, and the grinding ratio and specific energy were recorded for each infeed set.
With the exception of C0NTROL 2, no consistent significant (95 condidence level) wheel performance differences were detected between the two wheels of each abrasive. The grinding results of the two wheels of each abrasive type combined are summarized in Table 1.
~.~79~34g TABLEl Abr~ive DiEmond G~nding Ratio Con~onl Con~on2 Size Stand~d ~tand~d Type (mi~ro~) Mean De~ation Mesn De~at~on RGA~3C MD 106/90 20 1.5 22 2.2 RGA~OB MD 75/6326 2.2 31 1.7 10 RGA~lC MD 53/45130 4~ 4~ 7.6 R~A~2E SD 106~024 2.1 28 2.4 RGA~9D SD 75/6350 12 48 6.2 RGA~OE SD 53/45380 97 86 18 RGA~SD MD 75/381.3 0.1 1.2 0.1 15 RGA-38D SD 106/3~ 31 1.7 41 2.
CO~TROL2 RD 106~0 21 3.8 29 4.1 Analysis of the results shows that, at both Condition 1 and 2, there is a significant performance difference between metal bond and milled saw diamond. Generally the results show that decreasing mesh size increases grinding ratio, and milled saw exhibits greater grinding ratios than metal bond diamond.
EXAMPLE II
- Four experimental aggregate abrasives were fabricated by liquid phase sintering in flowing argon for one hour at 960C. All the aggregates contained feed diamond obtained by milling greater than 20 mesh (850 micron) saw diamond.
The resulting sintered 20 gram ingots were initially crushed in a jaw crusher and then milled to final size (250/150 microns) in an Alpine TM Perplex mill at 3900 rotations per minute using the 2.5 millimeter half-track screen inside the mill. The experimental aggregates are described in Table 2.
9~349 Aggregate RGA-76E RGA-81DRGA-82B RGA 82E
Mix for Fabrication (weight percent) AgCu eutectic 50 45 45 45 Ti powder 5 5 5 5 Diamond 45 50 50 50 Diamond PSD~* ~weight Dercent) (microns) 125/10~ - 7.8 - 2.9 106/90 - 18 . 4 - ~ . 0 90/75 - 49 . 2 - 18. 8 75/63 - 24. 6 7. 6 14. 1 63/53 - - 13~ 6 8.4 53/45 100 - 56.9 35.2 45/38 - - 19 . 5 12 . 1 ~38 - - 2 .4 1 . 5 Ag~regate Grit M~trix Le~ el ~weight percent) 78 70 67 70 Density ~g/cm3) 6 . 25 . 9 5 . 6 6 . O
GrindiDg tests were carried out at the fbllowing conditions:
Wheel Speed (m/sec.) 18 Ta~leSpeed (mm) 1.5 Infeed (mm) 0.050 Workpiece ~Iaterial WC-Co*
~Jorkpiece Size (mm x mmj 6. 4 x 19.1 x 16 pieces ~n 8.5% cobalt cemented tungsten carbide ~72~6 WC, 8.0~6 titanium carbide and 11.5% tantalum c~rbide) obtained ~s Carboloy Grade 370 ceme carbide from General Electric Company. ~Particle size distribution.
A milumwn of four infeed sets were rrtn~ for each wheel. Two whe~ls of each type were tested except four wheels containing CONTROLS 1 and 2 wers tested.
The results of the grinding tests are summarized in TABLE 3.
9~349 Grindin~Ratio Standard - Abrasive Mean Deviation CONTROL 2 (106/90 micron) 15 0.9 CONTROL 3 (75/64 micron) 17 0.~7 CONTROL 1 (250/150 micron) 38 4.8 RGA-76E(250/15û micron) 138 28 RGA-81D (25û/150 micron)17 0.7 RGA-82~ (250/150 micron) 58 8.8 RGA-82F (250/150 micron) 39 4.3 The mean csilDn is the average of all infeed sets for all whe~s of an ab~asive type.
A comparison of the res~ts from TABL}~S 1 and 3 reveals that the lower fftanium concentration (5 percent in TABLE 3 compared to 10~6 in TABI.E 1) hasgiven a benefit in terms of improved grinoing raffo over CONTROL 1. In addiffon,the benefit of using diamond crystals in the aggregste having a largest dimension less than 75 microns on the average is clearly pointed out by a comparison of th.e 20 gcinding ratio ~ samples RGA-76E snd RGA-82B with RGA-81D. The superiority of fine, mined saw diamond raw material for the aggregates is clealiy demonstrated. In those preferred cases (RGA-76E and RGA-82B) where the raw .materi~ diamond was an below 75 microns in largest .dimension, the mean grindingratio was 1.53 to 3.~8 times that obt~ined with CONTROL 1.
Other embodiments of this invention will be spparent to those skilled in the art from a consideration of ~his specification or practice of the invention dis~lc6ed herein. Valious omissions, modi~lcations and changes to the principlesd~cribed herein may be made by one skilled in the art without departing from thetrue scope and spirit of the invention which is indicated by the followin~ claims.
.. .
IMPROVED METAL BONDED DIAMOND
AGGRE-GAT~ ABRASIVE
Technical Field This invention relates to an improved metal bonded agglomerated diamond abrasive whereby the grinding ratio of wheels dry grinding cemented tungsten carbide is significantly improved over standard agglomerated abrasives. The term grinding ratio is the unit volume of workpiece material removed per unit volume of grinding wheel wear.
Background The use of diamond abrasives in metal bonds is well known. U.S. Patents Re 21,165; 2,737,454;
and 2,828,197 disclose abrasive bodies comprising diamond in metal bonds of various copper alloys and bronze bonds.
Metal bonded agglomerated or aggregated abrasives are also well known. U.S. Patent 2,216,728 discloses various forms of metal and glass bonded aggregates. U.S. 3,955,324, issued May 11, 1976 to Olle Lindstrom teaches the use of a metal/diamond aggregate in which diamond is completely surrounded by metal. U.S. 4,024,675, issued May 24, 1973 to Jury Naidich et al describes sintered diamond/metal aggregates containing an additive (titanium, zirconium, chromium, vanadium, or silicon) in an amount of 5 to 10 percent of the metal powder. The additive is said to impart the required degree of wettability of the ,v~
diamond grains with the metal and also cohesion of individual grits to each other.
U.S. Patent No. 4,246,006, issued January 20, 1981 to Cornelius Phaal discloses copper/silver alloy metal binders used in metal/diamond aggregates which aggregates include a wetting agent as in the aforementioned U.S. Patent 4,024,675. The metal alloy employed may be in powdered form for the starting mixture; however, it is preferred that the individual alloy components are used in the starting mixture in order to produce the alloy in situ. The amount of metal alloy powder used in the starting mixture for the aggregate is generally between 40 and 60 weight percent of the total, and the wetting agent is typically between 5 and 15 weight percent of the metal.
The diamond used in the aggregates of the aforementioned U.S. Patent 4,246,006 is selected from one or more of three specific types defined in the patent in terms of Friatest Index, metal content, color, shape, and surface roughness. The Friatest is one of a variety of measures of the strength or friability (i.e. susceptibility to fracture) of the diamond.
Typically in such friability tests, a sample of the diamond particles of a particular size is placed in a-capsule with a hard steel ball and shaken for a predetermined period of time. The abrasive particles are then removed from the capsule and screened through the next smaller screen size in relation to the smaller of the two screens used for determining the screen size of the original particles. That is, if 60/80 mesh (250/180 micron) diamond were being tested, the screen used would be the next standard size smaller than 80 mesh or 180 micron. The amount of diamona retained on the screen divided by the weight of the original sample yields a value (toughness index) which B~9 indicates the proportion of the diamond which was not broken down to smaller size.
The 4,246,006 patent states that it is preferable that the diamond particles used are all fine and have a size smaller than about 125 microns. A powdered mixture of diamond particles and metal is sintered under non-oxidizing conditions, above the liquidus temperature of the metal alloy (typically at a temperature in the range 700 to 1200C) for a time between 10 and 20 minutes. The sintered mass is then cooled to produce an ingot which is crushed and classified to produce the aggregate grits of desired size. The crushing is preferably by a means which reduces the size of the ingot primarily in the shear mode rather than by compression. This is also preferred for the invention described herein. Suitable crushers would be a jaw crusher or a laboratory mill such as the Alpine perplex mill by Alpine American Corp., Natick, Massachusetts.
There is a currently available commercial aggregate diamond grit, CDA-M from DeBeers Industrial Diamond Division of Johannesburg, South Africa. CDA-M
particles are relatively coarse, having a size which centers around 80 mesh (180 microns). The much smaller constituent diamond grits are said to cover a broader range of sizes, approximately 140 U.S. mesh-(106 microns) and finer. The metal bond alloy used in CDA-M grit is said to account for about 55 weight percent of the whole particle.
The abrasives art recognizes various classes of industrial diamond, the three major classes being resin bond diamond, metal bond diamond, and saw diamond. Resin bond diamond is suitable for resin bond or vitreous bond grinding wheels and comprises friable, irregular crystals usually coated with nickel alloy or copper. Metal bond diamond is used in metal matrix bonds or plated tools and comprises medium-toughness, regular crystals with a color range from yellow-green to light yellow. Crystal inclusions are generally low, but some heavily included crystals can be present. Saw diamond, used in sawing and drilling stone, concrete and refractories, comprises tough (low friability), blocky, cubo-octahedral crystals with predominately smooth faces. The saw diamond crys-tal is transparent or translucent having a color ranging from light yellow to medium yellow-green.
Due to the higher impact strength or toughness of saw diamond, its fracture during sawing operations is minimized and wear occurs largely by abrasion processes.
Saw diamond is generally more blocky in shape (i.e. has a lower aspect ratio) than metal bond or resin bond diamond. Diamond may be classified by shape separation on a shape sorting machine which separates the diamond crystals according to their aspect ratio.
Such machines comprise a vibrating inclined table which causes the particles to segregate according to shape, and it collects various fractions of the particles in separate cups or bins. Such machines are well known in the art, and a description may be found in Dyer, H.B., "E~B Natural Diamonds," Industrial Diamond Review, (August, 1964) page 192-196.
~ etal bonded agglomerated or aggregated diamond abrasives can exhibit higher grinding ratios under certain conditions than nickel or copper aggregates of U.S. 4,024,675 and 4,246,006 that this invention was achieved.
Disclosure of Invention This invention is summarized às:
an improved aggregated abrasive particle comprising diamond particles held in a silver/copper alloy metal bond matrix which contains a wetting agent for diamond, wherein the improvement comprises those aggregates containing diamond:
(a) having a largest dimension which, on the average, is less than 75 microns; and ~L~79~3~9 (b) characterized as milled saw diamond.
The improvement is realized principally through decreasing the average diamond particle size from that used in the standard commercially available agglomerated abrasive. In fact, it is preferred that the average diamond size than 270/325 U.S. mesh (53/45 microns) or less, and all the diamond is preferably under 70 microns.
This smaller size is achieved through milling saw diamond in an apparatus such as a jet mill whereby diamond crystals are accelerated to a high velocity in an air stream and then impact each other and the internal walls of the milling apparatus. The saw diamond raw material which was milled for use in developing this invention was over 20 mesh size (850 microns) predominantly crystal clusters. The milled saw diamond thus obtained does not exhibit the natural crystalline faces of normal saw diamond, and it is less tough (more friable) than metal bond diamond of the same size range. One test has shown the toughness index of milled saw diamond to be about 69 percent of equivalent sized metal bond diamond.
The volume ratio of the diamond to matrix metal powders may be in the range of 1:20 to 4:1; with the range of 2:1 to 4:1 being preferred.
Brief Description of the Figures Figure 1 is a photomicrograph (magnified 200X) showing one of the improved aggregated diamond abrasive particles of this invention, sample RGA-76E of Example II.
Figure 2 is a photomicrograph (magnified by 400X) showing the milled saw diamond raw material used in making these aggregates, which has a particle size less than 75 microns.
Figure 3 is a photomicrograph (magnified 400X) which shows metal bond diamond particles, to illustrate the shape and surface difference between metal bond and milled saw diamond.
Figure 4 is a photomicrograph (magnified 400X) 1~'79~
which shows resin bond diamond particles, in order to illustrate the difference in shape and surface between resin bond and milled saw diamond.
sest Mode for Carrying Out the Invention It is preferred that the level of metal matrix (copper/silver alloy and titanium) in the aggregate be about 50-80 weight percent, more prefereably 50-65 percent. However it is to be noted that the percent of matrix metal in the starting mix for making the aggregate is generally lower than the final percent. This is caused by the separation of some diamond from the aggregate during the milling and size separation steps.
As to the aspect ratio for the raw material saw diamond, 4:1 or lower is preferred, with 2:1 or less being more preferred.
It is also preferred to work with a pre-alloyed mixture of copper and silver rather than mixing powders of the two metals and forming the alloy in situ.
Test results during the development of this invention have indicated that the diamond wetting agent (titanium in the experiments) has a large effect on performance. While a minimum of about 5 weight percent titanium was needed to wet the diamond, additionally increasing the titanium amount decreased grinding ratio.
The titanium was incorporated into the system both by coating the diamond and by mixing it with the diamond and alloy powders. Techniques for coating diamond with titanium (e.g. sputtering) are known in the art (see e.g. U.S. Patents 3,654,110 issued April 4, 1972 to 30 Friedrich Kraus; 3,472,751 issued October 4, 1969 to William King; 3,325,393 issued June 13, 1967 to Darrow et al;
3,351,543 issued November 7, 1967 to Thomas Vanderslice;
and 3,650,714 issued March 21, 1972 to Peter Farkas).
While the aggregate metal matrix level was not found to significantly affect grinding ratio within experimental error (with the possible exception of a 1:~79t~349 small affect at high titanium concentrations) it was found to affect energy consumption. Increasing the amount of metal (titanium and/or the coppersilver alloy) increased specific energy.
This invention will be further clarified by a consideration of the following examples, which are intended to be purely exemplary. In these examples, grinding tests are describQd. All the grinding tests have utilized standard llV-9 flaring cup, resin-bonded grinding wheels, having a diameter of 3-3/4 inches (95.25 mm) and containing abrasive at a 75 concentration in the resin bond. Methods of making resin bond grinding wheels are well known to the art (see e.g. U.S. Patents 3,645,706 issued February 29, 1972 to Harold ~ovenkerk et al;
3,385,684 issued ~lay 28, 1968 to Roger Voter; 3,664,819 issued May 28, 1972 to Sioui et al; 3,779,727 issued December 18, 1973 to Sioui et al; and 3,957,461 issued May 18, 1976 to Lindstrom et al). In a typical preparation of a resin bond grinding wheel, a mixture of granulated resin (i.e. phenol-formaldehyde resin), abrasive particles (diamond) and filler is placed in a grinding wheel mold. A molding pressure appropriate to the particular resin - usually several thousand pounds per square inch - is applied, and the mold is heated to a temperature sufficient to make the resin plastically deform (and cure in cases where it is heat curable).
In the grinding wheel art, 100 concentration is conventionally defined as 4.4 carats/cm3 with 1 carat equal to 0.2 g. The concentration of abrasive grit is linearly related to its carat per unit volume concen-tration. Thus, 75 concentration equals about 3.3 carats of abrasive per cubic centimeter of the grinding wheel abrasive section.
In all the grinding tests, the size of the experimental aggregate used was 250/150 microns. CONTROL
1 was a commercially available aggregate grit, CDA-M, nominally 180 microns. CONTROL 2 was a commercially 1:1'79~349 available nickel coated single crystal diamond grit obtained as RVG-W from the General Electric Company. CONTROL 3 was a commercially available copper coated single crystal diamond grit obtained as RVG-D from the General Electric Company.
Also, in the examples which follow: SD designates milled saw diamond; MD designates metal bond diamonds; and RD designates resin bond diamond.
ExAMæLE I
A series of grinding tests was performed at two standard conditions which are given below.
Condition Standard Condition #1 Standard Condition #2 Wheel Speed (Meters/sec.) 22 18 Infeed tmm) 0.064 0.076 Table Speed (M/min)1.5 1.5 15 Workpiece MaterialWC-Co* WC-Co*
Workpiece Size (mm )6.4 x 19.16.4 x 19.1 (16 pieces) *a 6% cobalt cemented tungsten carbide obtained as Carboloy 44A cemented carbide from General Electric Company.
All aggregate abrasives tested were made from a mixture of 45 weight percent silver:copper alloy and 10 weight percent titanium, the balance being diamond. The resulting weight percent of the matrix after crushing was in the range of 64 - 68. All the aggregates were fabricated by liquid phase sintering at 920 for one hour in argon, followed by crushing and screening.
There were two grinding wheels made of each abrasive. Each test was preceded by a pre-grind until power consumption stabilized.
A minimum of four sets of infeeds were run for each wheel, and the grinding ratio and specific energy were recorded for each infeed set.
With the exception of C0NTROL 2, no consistent significant (95 condidence level) wheel performance differences were detected between the two wheels of each abrasive. The grinding results of the two wheels of each abrasive type combined are summarized in Table 1.
~.~79~34g TABLEl Abr~ive DiEmond G~nding Ratio Con~onl Con~on2 Size Stand~d ~tand~d Type (mi~ro~) Mean De~ation Mesn De~at~on RGA~3C MD 106/90 20 1.5 22 2.2 RGA~OB MD 75/6326 2.2 31 1.7 10 RGA~lC MD 53/45130 4~ 4~ 7.6 R~A~2E SD 106~024 2.1 28 2.4 RGA~9D SD 75/6350 12 48 6.2 RGA~OE SD 53/45380 97 86 18 RGA~SD MD 75/381.3 0.1 1.2 0.1 15 RGA-38D SD 106/3~ 31 1.7 41 2.
CO~TROL2 RD 106~0 21 3.8 29 4.1 Analysis of the results shows that, at both Condition 1 and 2, there is a significant performance difference between metal bond and milled saw diamond. Generally the results show that decreasing mesh size increases grinding ratio, and milled saw exhibits greater grinding ratios than metal bond diamond.
EXAMPLE II
- Four experimental aggregate abrasives were fabricated by liquid phase sintering in flowing argon for one hour at 960C. All the aggregates contained feed diamond obtained by milling greater than 20 mesh (850 micron) saw diamond.
The resulting sintered 20 gram ingots were initially crushed in a jaw crusher and then milled to final size (250/150 microns) in an Alpine TM Perplex mill at 3900 rotations per minute using the 2.5 millimeter half-track screen inside the mill. The experimental aggregates are described in Table 2.
9~349 Aggregate RGA-76E RGA-81DRGA-82B RGA 82E
Mix for Fabrication (weight percent) AgCu eutectic 50 45 45 45 Ti powder 5 5 5 5 Diamond 45 50 50 50 Diamond PSD~* ~weight Dercent) (microns) 125/10~ - 7.8 - 2.9 106/90 - 18 . 4 - ~ . 0 90/75 - 49 . 2 - 18. 8 75/63 - 24. 6 7. 6 14. 1 63/53 - - 13~ 6 8.4 53/45 100 - 56.9 35.2 45/38 - - 19 . 5 12 . 1 ~38 - - 2 .4 1 . 5 Ag~regate Grit M~trix Le~ el ~weight percent) 78 70 67 70 Density ~g/cm3) 6 . 25 . 9 5 . 6 6 . O
GrindiDg tests were carried out at the fbllowing conditions:
Wheel Speed (m/sec.) 18 Ta~leSpeed (mm) 1.5 Infeed (mm) 0.050 Workpiece ~Iaterial WC-Co*
~Jorkpiece Size (mm x mmj 6. 4 x 19.1 x 16 pieces ~n 8.5% cobalt cemented tungsten carbide ~72~6 WC, 8.0~6 titanium carbide and 11.5% tantalum c~rbide) obtained ~s Carboloy Grade 370 ceme carbide from General Electric Company. ~Particle size distribution.
A milumwn of four infeed sets were rrtn~ for each wheel. Two whe~ls of each type were tested except four wheels containing CONTROLS 1 and 2 wers tested.
The results of the grinding tests are summarized in TABLE 3.
9~349 Grindin~Ratio Standard - Abrasive Mean Deviation CONTROL 2 (106/90 micron) 15 0.9 CONTROL 3 (75/64 micron) 17 0.~7 CONTROL 1 (250/150 micron) 38 4.8 RGA-76E(250/15û micron) 138 28 RGA-81D (25û/150 micron)17 0.7 RGA-82~ (250/150 micron) 58 8.8 RGA-82F (250/150 micron) 39 4.3 The mean csilDn is the average of all infeed sets for all whe~s of an ab~asive type.
A comparison of the res~ts from TABL}~S 1 and 3 reveals that the lower fftanium concentration (5 percent in TABLE 3 compared to 10~6 in TABI.E 1) hasgiven a benefit in terms of improved grinoing raffo over CONTROL 1. In addiffon,the benefit of using diamond crystals in the aggregste having a largest dimension less than 75 microns on the average is clearly pointed out by a comparison of th.e 20 gcinding ratio ~ samples RGA-76E snd RGA-82B with RGA-81D. The superiority of fine, mined saw diamond raw material for the aggregates is clealiy demonstrated. In those preferred cases (RGA-76E and RGA-82B) where the raw .materi~ diamond was an below 75 microns in largest .dimension, the mean grindingratio was 1.53 to 3.~8 times that obt~ined with CONTROL 1.
Other embodiments of this invention will be spparent to those skilled in the art from a consideration of ~his specification or practice of the invention dis~lc6ed herein. Valious omissions, modi~lcations and changes to the principlesd~cribed herein may be made by one skilled in the art without departing from thetrue scope and spirit of the invention which is indicated by the followin~ claims.
.. .
Claims (5)
1. An improved aggregated abrasive particle comprising diamond particles held in a silver/copper alloy metal bond matrix which contains titanium as a wetting agent for diamond, wherein the improvement comprises those aggregates in which:
(a) the particle size of the diamonds, on the average, is less than or equal to 53 microns;
(b) the diamonds are characterized as milled saw diamond; and (c) the meta bond matrix comprises 64 to 78 weight percent of the aggregate.
(a) the particle size of the diamonds, on the average, is less than or equal to 53 microns;
(b) the diamonds are characterized as milled saw diamond; and (c) the meta bond matrix comprises 64 to 78 weight percent of the aggregate.
2. The improved aggregated abrasive particle as recited in claim 1 wherein the milled saw diamond has an aspect ratio of less than or equal to 2:1.
3. A resin bond grinding wheel containing the improved aggregated abrasive particles of claim 1.
4. The improved aggregate abrasive particle of claim 1 wherein the volume ratio of diamond to metal matrix is in the range of 2:1 to 4:1.
5. The improved aggregated abrasive particle as recited in claim 1 wherein the wetting agent is titanium present in an amount of about 5 weight percent of the aggregate.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/290,131 US4373934A (en) | 1981-08-05 | 1981-08-05 | Metal bonded diamond aggregate abrasive |
| US290,131 | 1981-08-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1179849A true CA1179849A (en) | 1984-12-27 |
Family
ID=23114665
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000408518A Expired CA1179849A (en) | 1981-08-05 | 1982-07-30 | Metal bonded diamond aggregate abrasive |
Country Status (13)
| Country | Link |
|---|---|
| US (1) | US4373934A (en) |
| EP (1) | EP0071771B1 (en) |
| JP (1) | JPS5851076A (en) |
| AT (1) | ATE12604T1 (en) |
| AU (1) | AU553923B2 (en) |
| BR (1) | BR8204423A (en) |
| CA (1) | CA1179849A (en) |
| DE (1) | DE3262981D1 (en) |
| IE (1) | IE53307B1 (en) |
| IL (1) | IL65967A (en) |
| IN (1) | IN159232B (en) |
| NO (1) | NO822673L (en) |
| ZA (1) | ZA823829B (en) |
Families Citing this family (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6076964A (en) * | 1983-08-29 | 1985-05-01 | ジ−テイ−イ−・ベイルロン・コ−ポレ−シヨン | Polycrystal grinding grid |
| AU602778B2 (en) * | 1987-07-14 | 1990-10-25 | De Beers Industrial Diamond Division (Proprietary) Limited | Tool component |
| IE63857B1 (en) * | 1987-07-14 | 1995-06-14 | De Beers Ind Diamond | Method of brazing |
| FR2620362B1 (en) * | 1987-09-11 | 1993-05-21 | Combustible Nucleaire | NON-POROUS THERMOSTABLE ABRASIVE GRAINS FOR SAWING WORKS AND CUTTING ELEMENTS COMPRISING SUCH GRAINS |
| JPH072307B2 (en) * | 1988-09-13 | 1995-01-18 | 旭ダイヤモンド工業株式会社 | Metal bond diamond whetstone |
| JP2601333B2 (en) * | 1988-10-05 | 1997-04-16 | 三井金属鉱業株式会社 | Composite whetstone and method of manufacturing the same |
| US5120495A (en) * | 1990-08-27 | 1992-06-09 | The Standard Oil Company | High thermal conductivity metal matrix composite |
| US5247765A (en) * | 1991-07-23 | 1993-09-28 | Abrasive Technology Europe, S.A. | Abrasive product comprising a plurality of discrete composite abrasive pellets in a resilient resin matrix |
| US6264882B1 (en) * | 1994-05-20 | 2001-07-24 | The Regents Of The University Of California | Process for fabricating composite material having high thermal conductivity |
| KR100407227B1 (en) | 1998-09-25 | 2003-11-28 | 미쓰비시 마테리알 가부시키가이샤 | Composite bond wheel and wheel having resin bonding phase |
| JP3641794B2 (en) * | 1999-07-14 | 2005-04-27 | きみ子 末田 | Diamond blade |
| US20030217869A1 (en) * | 2002-05-21 | 2003-11-27 | Snyder Shelly Rosemarie | Polycrystalline diamond cutters with enhanced impact resistance |
| KR100489547B1 (en) * | 2003-06-20 | 2005-05-16 | 일진디스플레이(주) | Diamond grits with good sintering properties in copper-based matrix alloy and production method thereof and the sintering tool using the same |
| SE532992C2 (en) * | 2007-11-08 | 2010-06-08 | Alfa Laval Corp Ab | Process for making a diamond composite, green body, diamond composite and use of the diamond composite |
| US20120100366A1 (en) * | 2008-09-16 | 2012-04-26 | Diamond Innovations, Inc. | Wear resistant coatings containing particles having a unique morphology |
| BR112013026817A2 (en) * | 2011-04-18 | 2017-01-10 | 3M Innovative Properties Co | resin bonded grinding wheel |
| US20170232571A1 (en) * | 2016-02-11 | 2017-08-17 | Corning Incorporated | Edge finishing apparatus and methods for laminate production |
| DE102019207822A1 (en) * | 2019-05-28 | 2020-12-03 | Robert Bosch Gmbh | Process for making an abrasive article and abrasive articles |
Family Cites Families (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| USRE21165E (en) | 1939-07-25 | Abrasive wheel | ||
| US2216728A (en) * | 1935-12-31 | 1940-10-08 | Carborundum Co | Abrasive article and method of making the same |
| US2828197A (en) * | 1954-09-15 | 1958-03-25 | Norton Co | Metal bonded diamond wheels |
| US3249410A (en) * | 1962-09-28 | 1966-05-03 | A P De Sanno & Son Inc | Process of making metal bonded diamond abrasive articles |
| US3293012A (en) * | 1962-11-27 | 1966-12-20 | Exxon Production Research Co | Process of infiltrating diamond particles with metallic binders |
| US3955324A (en) * | 1965-10-10 | 1976-05-11 | Lindstroem Ab Olle | Agglomerates of metal-coated diamonds in a continuous synthetic resinous phase |
| US3650714A (en) * | 1969-03-04 | 1972-03-21 | Permattach Diamond Tool Corp | A method of coating diamond particles with metal |
| US3795497A (en) * | 1969-06-10 | 1974-03-05 | S Weiss | Metal bonded grinding wheels |
| US3879901A (en) * | 1970-06-24 | 1975-04-29 | De Beers Ind Diamond | Metal-coated diamonds in a metal alloy matrix |
| US3850590A (en) * | 1970-09-28 | 1974-11-26 | Impregnated Diamond Prod Ltd | An abrasive tool comprising a continuous porous matrix of sintered metal infiltrated by a continuous synthetic resin |
| US4024675A (en) * | 1974-05-14 | 1977-05-24 | Jury Vladimirovich Naidich | Method of producing aggregated abrasive grains |
| ZA77465B (en) * | 1977-01-26 | 1978-09-27 | Edenvale Eng Works | Metal bonded abrasive tools |
| IE47393B1 (en) * | 1977-09-12 | 1984-03-07 | De Beers Ind Diamond | Abrasive materials |
| ZA777153B (en) | 1977-12-01 | 1979-02-28 | De Beers Ind Diamond | Abrasive materials |
| ZA787071B (en) * | 1978-12-18 | 1980-02-27 | De Beers Ind Diamond | Coated abrasive particles |
-
1981
- 1981-08-05 US US06/290,131 patent/US4373934A/en not_active Expired - Lifetime
-
1982
- 1982-05-27 IN IN612/CAL/82A patent/IN159232B/en unknown
- 1982-06-01 ZA ZA823829A patent/ZA823829B/en unknown
- 1982-06-03 IL IL8265967A patent/IL65967A/en unknown
- 1982-06-11 AU AU84837/82A patent/AU553923B2/en not_active Ceased
- 1982-07-08 AT AT82106119T patent/ATE12604T1/en not_active IP Right Cessation
- 1982-07-08 DE DE8282106119T patent/DE3262981D1/en not_active Expired
- 1982-07-08 EP EP82106119A patent/EP0071771B1/en not_active Expired
- 1982-07-23 BR BR8204423A patent/BR8204423A/en unknown
- 1982-07-30 CA CA000408518A patent/CA1179849A/en not_active Expired
- 1982-08-04 IE IE1876/82A patent/IE53307B1/en not_active IP Right Cessation
- 1982-08-04 JP JP57135277A patent/JPS5851076A/en active Pending
- 1982-08-04 NO NO822673A patent/NO822673L/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| EP0071771A1 (en) | 1983-02-16 |
| US4373934A (en) | 1983-02-15 |
| AU8483782A (en) | 1983-02-10 |
| ZA823829B (en) | 1984-02-29 |
| BR8204423A (en) | 1983-07-19 |
| EP0071771B1 (en) | 1985-04-10 |
| IE821876L (en) | 1983-02-05 |
| NO822673L (en) | 1983-02-07 |
| AU553923B2 (en) | 1986-07-31 |
| DE3262981D1 (en) | 1985-05-15 |
| IE53307B1 (en) | 1988-10-12 |
| IL65967A (en) | 1984-11-30 |
| IN159232B (en) | 1987-04-18 |
| IL65967A0 (en) | 1982-09-30 |
| ATE12604T1 (en) | 1985-04-15 |
| JPS5851076A (en) | 1983-03-25 |
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