SK14402000A3 - Abrasive tools - Google Patents

Abstract

Abrasive tools suitable for precision grinding of hard brittle materials, such as ceramics and composites comprising ceramics, at peripheral wheel speeds up to 160 meters/second are provided. The abrasive tools comprise a wheel core (2) attached to an abrasive rim of dense, metal bonded superabrasive segments (8) by means of a thermally stable bond (6). A preferred tool for backgrinding ceramic wafers contains graphite filler and a relatively low concentration of abrasive grain (4).

Description

Technical field

This application is a partial continuation of U.S. application Ser. This invention relates to abrasive tools suitable for precision grinding of hard brittle materials, such as ceramic materials and composites containing ceramic materials, at a peripheral wheel speed of up to 160 meters / second and suitable for surface grinding of ceramic plates. These grinding tools include a blade head or core attached to a superabrasive rim joined by a metal binder that is thermally stable during grinding operations. These grinding tools grind ceramic materials with high material removal rates (e.g.

up to 380 cm ³ / min / cm), with less blade wear and less damage to the workpiece than conventional grinding tools.

BACKGROUND OF THE INVENTION

One grinding tool suitable for grinding sapphire and other ceramic materials is disclosed in US-A-5,607,489, Li.

This tool is described as comprising a metal coated diamond bonded in a ceramic matrix containing 2 to 20 volume% solid lubricant and at least 10 volume% porosity.

One abrasive tool containing a diamond bonded in a metal matrix is disclosed in US-A-3,925,035 to Keat. This tool is used for grinding cemented carbides.

In US-A-2,238,351 to Van der Pyl, a parting disc made of metal-bonded diamond abrasive grain is disclosed.

The binder consists of copper, tin iron, and possibly nickel, and the bonded abrasive grain is bonded to a steel core, or a bonded abrasive grain. · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Rockwell B hardness 70 is reported to have the best binder.

One abrasive tool comprising a fine diamond grain (crumb) bonded in a metal binder with a relatively low melting point, such as a bronze solder, is disclosed in US-Re-21,165. The low-melting binder serves to prevent oxidation of the fine diamond grain. The abrasive ring is constructed as a separate, annular abrasive segment, which is then attached to the center disk of aluminum or other material.

None of these grinding tools has proven to be entirely satisfactory for precision grinding of ceramic parts.

These tools fail to encounter accurate data in shape, size and surface quality when operated under commercially available grinding conditions. Most commercial grinding tools recommended for use in such operations are superabrasive wheels bonded with resin or ceramic binder and are designed to operate with relatively low grinding performance to avoid surface and subsurface damage to ceramic components. Abrasive efficiency is further reduced due to the tendency of ceramic workpieces to clog the face of the wheel, requiring frequent cleaning and alignment of the wheel to ensure accurate shapes.

As there has been a demand on the market for precision ceramic components for products such as engines, refractory equipment and electronic devices (such as pads, magnetic heads and display windows), there is an increasing need for improved grinding tools for precision grinding of ceramic materials.

When finishing high-performance ceramic materials such as aluminum-titanium carbide (AlTiC) for electronic components, surface grinding or additional grinding operations require high quality, fine surface finish with low strength and relatively low grinding speed operations. At ··

The grinding performance of these materials is the grinding performance determined by both the surface quality of the workpiece and the applied force control, as well as the high material removal rates and wear resistance of the grinding wheel. .

SUMMARY OF THE INVENTION

The invention is a surface grinding tool which comprises a core having a minimum specific strength parameter of 2.4 MPa-cm ³ / g, a core density of 0.5 to 8.0 g / cm ³ , an orbital circumference and an abrasive rim defined by the series abrasive segments, wherein the abrasive segments comprise in amounts selected to a total maximum of 100 volume% from 0.05 to 10% superabrasive grain volume, from 10 to 35% fine filler volume, and from 55 to 89.95% volume of metal bonded matrix having fracture toughness from 1.0 to 3.0 MPa M ^1/2 . The specific strength parameter is defined as the ratio of the smaller of the commercial yield strength or the material strength limit divided by the specific weight of the material. The crumb filler is selected from the group consisting of graphite, hexagonal boron nitride, hollow ceramic beads, feldspar, nepheline syenite, pumice, clay and glass beads, and combinations thereof. In one preferred embodiment, the metal bonded matrix comprises a maximum of 5% by volume of porosity.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a continuous garland of grinding wheels connected to the periphery of a metal core to form an abrasive grinding wheel of type 1A1.

Figure 2 shows a discontinuous rim of grinding wheels attached to the periphery of the metal core to form a pot wheel.

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Figure 3 shows the relationship between the amount of raw material removed and the normal force during grinding of the AlTiC workpiece with the abrasive wheels of Example 5.

DETAILED DESCRIPTION OF THE INVENTION

The abrasive tools of the present invention are abrasive wheels that include a core having a central bore for mounting the wheel to the grinder, the core being designed to support a superabrasive metal-bonded rim around the periphery of the wheel. The two parts of the roll are held together by a binder which is thermally stable under grinding conditions, and the roll and its components are designed to tolerate stresses generated at a peripheral speed of the roll of at least 80 m / sec., Preferably up to 160 m / sec. . Preferred tools are type 1A discs and cup type 11V9 discs shaped like a bell.

The core has a substantially circular shape. The core may consist of any material having a minimum specific strength of 2.4 MPa-cm ³ / g, preferably 40-185 MPa-cm ³ / g. The core material has a density of from 0.5 to 8.0 g / cm ³ , preferably 2.0 to 8.0 g / cm ³ . Examples of suitable materials are steel, aluminum, titanium and bronze, and mixtures and alloys thereof, and combinations thereof. Reinforced plastics having the required minimum specific strength can be used for the core construction. Composites and reinforced core materials typically have a continuous phase of metal or plastic matrix, often in powder form, to which fibers or grains or particles of a harder, more durable and / or less dense material are added as a discontinuous phase. Examples of reinforcing materials suitable for use in the core of the tool of the invention are glass fibers, carbon fibers, aromatic polyamide fibers, ceramic fibers, ceramic particles and grains and hollow glass materials such as glass, mullite, alumina and Zeolite® beads.

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Steel and other metals having densities of from 0.5 to 8.0 g / cm ³ can be used to produce cores for the tools of the invention. In the manufacture of cores used for high-speed grinding (for example at least 80 m / sec.), Lightened metals in powder form (i.e. metals having a specific gravity of about 1.8 to 4.5 g / cm ³ ), such as aluminum, magnesium and titanium and their alloys and mixtures thereof. Aluminum and aluminum alloys are preferred. Metals having a melting point of between 400 and 900 ° C, preferably 570 to 650 ° C, are selected when the co-sintering assembly process is used for tool production. Low density fill materials can be added to reduce the weight of the core. Materials suitable for this purpose are porous and / or hollow ceramic or glass fillers, such as glass beads and multiple beads. Inorganic and non-metallic fibrous materials are also useful. When specified by the processing conditions, an effective amount of a lubricant or other processing means known in metal bonding and superabrasive products may be added to the metal powder prior to compression and sintering.

Such a tool should be strong, durable and dimensionally stable to withstand the potential destructive forces caused by high speed operation. The core must have a minimum specific strength to operate the grinding wheels at the very high angular velocity necessary to achieve a tangential contact speed between 80 and 160 m / s. The minimum specific strength parameter necessary for the core materials used in the present invention is about 2.4 MPa-cm ³ / g.

This specific strength parameter is defined as the ratio of the conventional yield strength of the core material divided by the specific weight of the core material. For brittle materials having less fracture strength than conventional yield strength, the specific strength parameter is determined using a smaller number, fracture strength. The conventional yield strength of a material is the smallest tensile force for which the deformation of the material increases without further increasing the force. For example, ANSI 4140 steel hardened above about 240 (Brinell scale) has a tensile strength of more than 700 MPa. The specific weight of this steel is about 7.8 g / cm ³ . Thus, its specific strength is about 90 MPa-cm ³ / g. Similarly, some aluminum alloys, such as Al 2024, Al 7075 and Al 7178, which are heat-treatable to a Brinell hardness of about above 100, have tensile strengths higher than about 300 MPa. Such aluminum alloys have a low specific gravity of about 2.7 q / cm ³ and thus exhibit a specific strength parameter of more than 110 MPacm ³ Ig. Also suitable for use are titanium alloys and bronze composites and alloys made so that the specific gravity does not exceed 8 g / cm ³ .

The core material should be tough, thermally stable at temperatures achieved in the abrasive zone (e.g., about 50 to 200 ° C), resistant to chemical reaction with coolants and greases used in the abrasive, and resistant to erosion wear caused by movement of abrasive chips in the abrasive zone. Although some aluminum oxides and other ceramic materials have acceptable damage values (i.e., greater than 60 MPa-cm ³ / g, they are generally very brittle and fail structurally due to fracture grinding. Therefore, ceramic materials are not suitable for use with tool cores Preference is given to metal, especially hardened quality tool steel.

The abrasive segment of an abrasive wheel for use with the present invention is a segmented or continuous ring mounted on a core. One segmented abrasive ring is shown in FIG. 1. The core 2 has a central bore 3 for mounting the disc on the spindle of a mechanical drive (not shown). The wheel abrasive ring comprises superabrasive grains 4 embedded (preferably in a uniform concentration) in a metal matrix binder 6. The abrasive ring shown in FIG. 1, there are several abrasive segments 8. Although the representation of the embodiment shows ten segments, the number of segments is not critical. The sanding segment itself, such as • «• · · · ·

The figure shown in FIG. 1 is shown in FIG. 1, has the shape of a truncated rectangular ring (arcuate shape) characterized by length 1, width w and depth d.

The embodiment of the grinding wheel shown in FIG. 1 is considered to be representative of the rolls that can be successfully operated according to the present invention and cannot be viewed as limiting in any way. A number of geometric variations of the segmented grinding wheels that are considered suitable include pot-shaped wheels as shown in FIG. 2, rolls with dressings across the core and / or with gaps between successive segments and wheels with grinding segments with a width different from the core. Apertures or gaps are occasionally used to provide coolant conveying paths to the grinding zone and direct the abrasive pulp away from this area. A segment wider than the width of the core is occasionally used to protect the core structure from erosion caused by contact with the abrasive sludge material when the roll penetrates radially into the workpiece.

The roll may be formed by first forming the individual segments with a preselected size and then attaching the previously formed segments to the core circumference 9 with a suitable adhesive. Another preferred manufacturing method includes forming the precursor units of the segments from the abrasive grain / binder powder mixture, forming the composition around the periphery of the core, and applying heat and pressure to form and attach the segments in place (i.e., melt the core and rim together). The co-sintering process is advantageous for the production of surface grinding discs used for sanding pads and debris of hard ceramic materials such as AlTiC.

The abrasive ring component of the abrasive tools of the invention may be a continuous garland or a discontinuous garland, as shown in Figures 1 and 2. The continuous abrasive garland may include a continuous abrasive garland.

one sanding segment or at least two sanding segments molded separately in molds and then mounted individually on the core with a thermally stable binder (i.e., a binder stable at temperatures encountered during sanding in a portion of the segments facing away from the abrasive face) typically about 50 to 350 ^and C). Discontinuous abrasives. wreaths as shown in FIG. 2, they are made of at least two such segments and these segments are separated in the crown by cracks or slits and are not end-to-end along their lengths 1 as in the case of a segmented continuous abrasive ring. The figures show preferred embodiments of the invention and are not intended to limit the embodiments of the tool according to the invention, so that, for example, discontinuous rims can be used on rolls 1A and continuous rims can be used on pot rolls.

For high-speed grinding, in particular grinding workpieces having a cylindrical shape, a continuous rim type 1A wheel is preferred. Segment continuous abrasive rims are advantageous over a single continuous abrasive rim shaped as a single piece of annular shape, due to the greater ease of achieving a true circular, planar shape during the manufacture of the tool from many abrasive segments.

For lower speed grinding operations (e.g. 25 to 60 m / sec.), In particular surface grinding and finishing of flat workpieces, discontinuous grinding rims (e.g., the pot wheel shown in Fig. 2) are preferred. Since the surface quality is critical in low speed surface finishing operations, the grooves may be formed in segments, or some segments may be omitted from the rim to assist in the removal of waste material that could scratch the workpiece surface.

The abrasive rim component comprises a superabrasive grain held in a metal matrix binder formed typically by bonding a mixture of a metal binder powder and an abrasive grain in a form designed for And aaa providing the desired size and shape to the abrasive rim or segments of the abrasive rim.

The superabrasive grain used in the abrasive garment can be selected from diamond, natural and artificial, CBN and a combination of these abrasives. The choice of grain size and type will vary depending on the nature of the workpiece and the type of grinding process. For example, in sanding and polishing sapphire or AlTiC, a superabrasive grain size ranging from 2 to 300 microns is preferred. For grinding other alumina, a superabrasive grain size of from about 125 to 300 microns (60 to 120 grit; Norton Company grit size) is generally preferred. For grinding silicon nitride, a grain size of about 45 and 80 microns (pulp 200 to 400) is generally preferred. The finer grit size is advantageous for grinding operations of cylindrical surfaces, profiles or internal diameters where larger amounts of material are removed.

As a percentage of the abrasive rim volume, these tools comprise 0.05-10% by volume of the superabrasive grain, preferably 0.5-5% by volume. To increase the wear rate, a smaller amount of friable filler material having a hardness less than that of the metal binder matrix may be added as the bonding filler. The filler may comprise from 10 to 35% by volume, preferably 15 to 35% by volume, of the wreath component. A suitable friable filler material must be characterized by suitable thermal and mechanical properties to withstand the conditions of annealing temperature and pressure used in the manufacture of grinding segments and wheel assembly. Examples of useful friable filler materials are graphite, hexavalent boron nitride, hollow ceramic spheres, feldspar, nepheline syenite, pumice, calcined kaolin and glass spheres, and combinations thereof.

Any metal binder suitable for brazing superabrasives having a fracture toughness from <RTIgt;% </RTI> can be used herein. · · ··· ·· ·· ···· ·· ·

1.0 to 6.0 MPa. m ^1/2 , preferably 2.0 to 4.0 MPa. m ^1/2 . Fracture toughness is a stress intensity factor at which a crack induced in a material will propagate into the material and lead to a rupture / fracture of the material. Fracture toughness is expressed as:

K _1C = (σ _Γ ) (tt ^1/2 ) (C ^1/2 ), where:

Kic is fracture toughness, o _f is the fracture stress and C is half the crack length. There are several methods that can be used to determine fracture toughness, and each has an initial step where a test material of a known size is developed in the test material, and then a stress load is applied until the material breaks. This fracture stress and crack length are substituted for this equation and fracture toughness is calculated (e.g., fracture toughness of steel is about 30-60 MPa. M ^1/2 , aluminum is about 2-3 MPa. M ^1/2 , for nitride the silicon is about 4-5 MPa ^/ m ² and the zirconium is about 7-9 MPa ^/ m ² ).

In order to optimize the wheel life and grinding performance, the binder wear rate must be equal to or slightly higher than the grinding grain wear rate during the grinding operation. Fillers such as those mentioned above may be added to the metal binder to reduce the wear rate of the roll. To permit higher material removal rates during grinding, metal powders that tend to form a relatively dense binder structure (i.e. less than 5% by volume porosity) are preferred.

Materials useful in the metal binder of the wreath include, but are not limited to, bronze, copper and zinc alloys (brass), cobalt and iron, and alloys and mixtures thereof. These metals may optionally be used with a titanium or titanium hybrid or other superabrasive reactive (ie active binder) material capable of enhancing the grain / binder support to form a carbide or nitride chemical bond between the grain and the binder on the superabrasive grain surface at selected dimmer. · · · · · · · · · · · · · · · · · · · · · · · · · · · · Stronger grain / binder interactions will limit premature grain loss and workpiece damage and shortened tool life due to premature grain loss.

In one preferred embodiment of the abrasive rim, the metal matrix comprises 55 to 89.95 volume% of the rim, more preferably 60 to 84.5 volume%. The crumb filler comprises 10 to 35 vol% of the abrasive ring, preferably 15 to 35 vol%. The porosity of the metal matrix binder should be maintained at a maximum of 5% by volume during the manufacture of the abrasive segment. The metal binder preferably has a Knoop hardness of 2 to 3 Gpa.

According to one preferred embodiment of the type 1A grinding wheel, the core is made of aluminum and the rim comprises a bronze binder made of copper and tin powder (80/20% by weight) and optionally also with an addition of 0.1 to 3.0% by weight, preferably 0, 1 to 1.0% by weight of phosphorus as phosphorus / copper powder. During the manufacture of the abrasive segments, the metal powders of this composition are admixed with grit of 100 to 400 (160 to 45 microns) diamond abrasive grain, formed into abrasive ring segments, and compacted or compacted in the range of 400 550 ° C at to form a dense abrasive ring, which preferably has a density of at least 95% of the theoretical density (i.e., does not comprise more than 5 volume percent porosity).

In one typical method of making a roll by co-melting, the core metal powder is poured into a steel mold and cold pressed at 80 to 200 kN (pressure of about 10 to 50 MPa) to form a raw portion having a size of about 1.2 to 1.6 times greater than the desired final core thickness. This portion of the raw core is placed in graphite form and a mixture of abrasive grain (particle size 2 to 300 microns) is added and a mixture is added to the cavity between the core and the outer rim of the graphite form. Aaaa aaaa aaaa aaaa binder powder. A settling ring may be used to compact the abrasive and metal binder powder to the same thickness as the core preform. The graphite form contents are then heat-sealed at 370-410 ° C at 20-48 MPa for 6-10 minutes. As is known in the art, the temperature may be increased (e.g., from 25 to 410 ° C for 6 minutes, held at 410 ° C for 15 minutes) or increased gradually before applying pressure to the mold content.

Following hot melt, the graphite mold is partially removed, this portion is cooled, and this portion is completed by conventional techniques to form an abrasive ring having the required dimensions and tolerances. For example, this part can be finished in size using ceramic grinding wheels on grinders or carbide cutting tools on a lathe.

With the simultaneous compounding of the core and the rim of the invention, little material removal is required to bring this part to its final shape. In other methods of shaping a thermally stable binder between the abrasive rim and the cores, it may be necessary to machine both the cores and the rim prior to the cementing, bonding or diffusion step to provide an adequate surface to mute and join these portions.

Any thermally stable adhesive having a strength that can withstand a peripheral wheel speed of up to 160 m / sec can be used to form a thermally stable bond between the rim and the core using segmental abrasive rims. The thermally stable adhesives are stable to the temperatures of the grinding process that they are likely to encounter in a portion of the grinding segments oriented away from the grinding surface. Such temperatures typically range from 50-350 ° C.

Such an adhesive joint must be very mechanically strong in order to withstand the destructive forces that exist during the rotation of the grinding wheel and during the grinding operation. Two-component epoxy resin cements are preferred. One advantageous epoxide · II · II ··························· · Cement cement, Technodyne® HT-18 epoxy resin (obtained from Taoka Chemical, Japan) and its modified amine hardener can be mixed in a ratio of 100 parts resin to 19 parts hardener. A filler, such as a fine silica powder, can be added at a rate of 3.5 parts per 100 parts resin to increase the viscosity of the cement. The segments may be mounted around the entire periphery of the grinding wheel cores or the sub-periphery of the cement core. The circumference of the metal cores may be sandblasted to obtain a degree of roughness before the segments are attached. The reinforced epoxy cement is applied to the ends and the base of the segments which are arranged around the core, as essentially shown in FIG. 1 and are held in place mechanically during curing. The epoxy cement is designed for curing (eg at room temperature for 24 hours and then for 48 hours at 60 ° C). Drying of the cement during curing and movement of the segments is minimized during curing by adding sufficient filler to optimize the viscosity of the epoxy cement.

The adhesion strength can be tested by rotary testing at an acceleration of 45 rpm, as is done to measure the rupture rate of the roll. The blades need a proven nominal burst equivalent of at least 271 m / s of tangent contact speeds to be able to operate at the currently applicable 160 m / s of tangent contact speed safety standards in the United States.

The abrasive tools of the invention are particularly designed for precision grinding and finishing of brittle materials such as advanced ceramic materials, glass and ceramic materials containing components and ceramic composite materials. The tools of the invention are advantageous, but not limited, for grinding ceramic materials containing silicon, mono and polycrystalline oxides, carbides, borides and silicides, polycrystalline diamond, glass and ceramic composites in non-ceramics. · Matrix and combinations thereof. Examples of typical workpiece materials include, but are not limited to, AlTiC, silicon nitride, silicon oxynitride, carbide, boron nitride, titanium diboride, aluminum nitride and composites of these ceramic materials, as well as certain metal matrix composites such as cement carbides and hard, brittle amorphous materials such as mineral glass. With these improved abrasive tools, either monocrystalline ceramic materials or polycrystalline ceramic materials can be ground. For each type of ceramic material, the quality of the ceramic part and the efficiency of the grinding operation increase as the peripheral wheel speed of the wheels according to the invention is increased to 80 to 160 m / s.

Ceramic parts improved using the grinding tools of the present invention include ceramic valves and connecting rods, pump gaskets, ball bearings and fittings, cutting tool inserts, guide parts, metalworking diework, refractory components, visible display windows, flat glass for front guards glass, doors and windows, insulators and electrical parts, and ceramic electronic components which include, but are not limited to, silicone wafers, AlTiC chips, read / write heads, magnetic heads and substrates.

Unless otherwise indicated, all parts and percentages in the following examples are by weight. These examples are merely illustrative of the invention and are not intended to limit the invention.

Example 1

The abrasive wheels of the invention were prepared in the form of metal-bonded diamond wheels 1A1 using materials from the processes described below.

A mixture of 43.74 wt. Copper powder (DendRitic FS grade, particle size + 200 / -325 mesh, obtained from Sintertech International Marketing Corp., Ghent, NY); 6.24% wt.

Phosphorus / Copper Powder Phosphorus / Copper Powder (Grade 1501, particle size + 100 / -325, obtained from the New Jersey Zinc Company, Palmerton, PA); and 50.02 wt. Tin powder (grade MD115, particle size + 325 mesh, 0.5% maximum, obtained from Alcan Metal Powders, Inc., Elizabeth, New Jersey). A diamond abrasive grain (grit size of synthetic diamond 320 obtained from General Electric, Wortington, Ohio) was added to the metal powder mixture, and this combination was mixed until uniformly mixed. This mixture was placed in a graphite form and hot pressed at 407 ° C for 15 minutes at 3000 psi (2073 N / cm ² ) until a matrix with a target density of more than 95% of theoretical was formed (e.g. for roll 6) used in Example 2:> 98.5% of the theoretical density). The hardness of the segments produced for the disc no. 6, according to Rockwell B 108. The segments contained 18.75% v / v. Abrasive grains. The segments were ground to the required arc geometry to match the circumference of the machine machined aluminum core (7075 T6 aluminum obtained from Yarde Metals, Tewksbury, MA), to obtain a disc with an outside diameter of about 393 mm and segments with a thickness of 0.62 cm.

These grinding segments and the aluminum core were assembled with a silicon-filled epoxy cement system (Technodyne HT-18 adhesive obtained from Taoka Chemicals, Japan) to produce grinding wheels having a continuous rim consisting of many grinding segments. The contact surfaces of the core and segments were degreased and sandblasted to ensure adequate adhesion.

In order to characterize the highest working speed of this new type of blade, they were intentionally spun except for the destruction of the blade in actual size to determine the burst strength and nominal maximum working speed according to the Norton Company's highest working speed test. The table below includes burst test data for a typical test

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Examples of metal-bonded experimental discs, 393 mm in diameter.

Tear strength data of experimental metal bonded disc:

disc no. average disc cm (thumb) speed roztrhnu- tia 1 / min. speed roztrhnu- tia (M / s) speed roztrhnu- tia (Sfpm) Max. prevádz- Additive (M / s) 4 39.24 (15:45) 9950 204.4 40242 115.8 5 39.29 [15.47) 8990 185.0 36415 104.8 7 39.27 (15:46) 7820 160.8 31657 91.1 9 39.27 (15:46) 10790 221.8 43669 125.7

According to these data, the experimental grinding wheels of this design will be capable of operating speeds up to 90 m / s (17,717 surface feet / min). Higher working speeds up to 160 m / s can easily be achieved by some other modifications in the production processes and disc designs.

Example 2

Grinding performance rating:

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Three experimental metal-bonded discs, 393 mm in diameter, 15 mm thick and 127 mm in center drill (15.5 in x 0.59 in x 5 in) were tested for grinding performance and produced by the method of Example 1 above (No. 4). , which has segments with a density of 95.6% of theoretical density, No. 5 with 97.9% of theoretical density and No. 6 with 98.5% of theoretical density). Initial testing at 32 and 80 m / s determined disc no. 6 as the wheel having the best grinding performance of the three, although all experimental wheels were acceptable. Testing of roll No. 6 was made at three speeds: 32 m / s (6252 sfpm), 56 m / s (11,000 sfpm), and 80 m / s (15,750 sfpm). The two prior art commercial grinding wheels recommended for grinding modern ceramic materials served as control discs, and these were tested together with the discs of the invention. One was a diamond disc bonded with a ceramic binder (SD320-N6V10 disc purchased from Norton Company, Worcester, MA) and the other was a resin bonded diamond disc (SD320-R4BX619C disc purchased from Norton Company, Worcester, MA). This resin disc was tested at all three speeds. The ceramic bonded disc was only tested at 32 m / s (6.252 sfpm), due to velocity tolerance factors.

Silicon nitride workpieces were made with more than one thousand embedded grinders having a width of 6.35 mm (0.25 inch) and a depth of 6.35 mm (0.25 inch). The grinding conditions were:

Grinding test conditions:

Machine: Studer model S40 CNC grinding machine

Exact blade description: SD320-R4BX619C, SD320-N6V10, size: diameter 393 mm, thickness 15 mm and hole 127 mm.

Wheel speed: 32, 56 and 80 m / s (6.252, 11.000 and 15.750 sfpm)

Refrigerant: Inversol 22 0 60% oil and 40% water

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Refrigerant Pressure: 270 psi (19 kg / cm ² )

Material removal rate: variable, starting at

3.2 mm ³ / s / mm (0.3 in ³ / min / in)

Working material: Si3N4 / rods made of silicon nitride NT551 obtained from Norton Advanced Ceramics, Northboro, Massachusetts) diameter 25.4 mm (1 inch) x length 88.9 mm (3.5 inch)

Working speed: 0.21 m / s (42 sfpm), constant Initial working diameter: 25.4 mm (1 inch)

Final Working Diameter: 6.35 mm (0.25 inch)

For alignment and cleaning operations, the conditions suitable for the metal-bonded discs of the invention were:

Alignment operations:

Disc: 5SG46IVS (purchased from Norton Company)

Wheel Size: Diameter 152 mm (6 inch)

Wheel speed: 3.000 rpm; at + 0.8

Relative to the grinding wheel

Feed: 0.015 in. (0.38 mm)

Compensation: 0.0002 in.

Cleaning operations:

Bar: 37C220H-KV (SiC)

Method: Hand stick cleaning

The tests were performed with a cylindrical outside diameter grooving method of grinding silicon nitride rods. To maintain the best rigidity of the working material during grinding, the 88.9 mm (3.5 in.) Samples were held in a chuck set for grinding of approximately 31 mm (1% in.). Each set of grooving grinding tests began from the distal end of each bar. First, the blade made a 6.35 mm (1/4 in.) Wide groove with a radial depth of 3.18 mm (1/8 in.) To complete one test. The working rpm was then reset to compensate for the loss of working speed.

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with reduced working diameter. In order to reduce the working diameter from 25.4 mm (1 in.) To 6.35 mm (1/4 in.), Two similar recesses were made at the same location. The disc was then offset laterally 6.35 mm (1/4 in.) Closer to the chuck to perform three additional grooves. Four lateral movements were made on the same side of one wax to complete twelve grooves at one end of the sample. The sample was then inverted to expose the other end for a further twelve grooves. A total of 12 depth grinders were made on each sample.

Initial comparative tests for the metal-bonded discs of the invention and the resin-bonded and ceramic-bonded discs were performed at a peripheral speed of 32 m / s and at three material removal rates (MRR ') of approximately 3.2 mm ³ / s / mm (0, 3 in ³ / min / in) to about 10.8 mm ³ / s / mm (1.0 in ³ / min / in). Table 1 shows the power differences, as described by the coefficients G, between the three different types of wheels after twelve depth grinders. The coefficient G is the dimensionless ratio of the volume of the material, broken by the volume of the disc wear. The data showed that the N-class ceramic bonding wheel had higher G coefficients at higher material removal rates than the R-bonded bonding wheel, suggesting that the softer wheel serves better when grinding ceramic workpieces. However, the harder, experimental roll no. The metal bond was much better than the resin bonded wheel and the ceramic bonded wheel at all material removal rates.

Table 1 shows the estimated coefficients G for the resin-bonded disc and the new metal-bonded disc (# 6) under the material removal rate conditions. Since there was no measurable disc wear after twelve grinding wheels at each material removal rate, a symbolic value of 0.01 mil (0.20 μιτι) of the radial disc wear was given for each grinding wheel. This gave a calculated coefficient of G of 6.051.

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Although the metal binder disc of the invention contained a diamond concentration of 75 (about 18.75 volume% of abrasive grain in the abrasive segment) and resin-ceramic bonded discs had a concentration of 100 and 150, respectively (25 volume% and 37.5 volume% respectively), disc according to the invention still improved grinding performance. At these relevant grain concentrations, better grinding performance could be expected from control discs containing a larger percentage of abrasive grain. These results were therefore unexpected.

Table 1 shows the surface quality (Ra) and waviness (Wt) data measured on samples grinded by these three rolls at low test speed. The waviness value Wt is the highest peak to the height of the waveguide profile depression. All surface quality data were measured on a surface produced by cylindrical grooving without sparking. These surfaces would normally be rougher than those produced by longitudinal grinding.

Table 1 shows the difference in abrasive energy consumption at different material removal rates for the three types of discs. The resin-bonded disc had less power consumption than the other two discs, but the experimental metal-bonded disc and the ceramic-bonded disc had comparable energy consumption. The experimental wheel took an acceptable amount of energy for ceramic grinding operations, particularly in view of the favorable coefficient G and the surface quality data observed for the wheels of the invention. In general, the discs of the invention demonstrated a power take-off proportional to the material removal rates.

Table 1

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sample MRR mm ³ with ' ¹ mm' ¹ Quickly. disc m / s Concerned. strength N / mm Unit. power W / mm Merná energ. Ws mm ³ Koefic. G quality surface. ra pm undulation Wt pm resin 973 3.2 32 00:48 40 12.8 585.9 00:52 0.86 1040 6.3 32 0.98 84 13.3 36.6 0.88 1.4 980 8.9 32 1.67 139 9.5 7.0 0.99 4:50 1016 3.2 56 00:49 41 13.1 586.3 00:39 1.22 1052 6.3 56 0.98 81 12.9 293.2 00:55 1:52 992 3.2 80 00:53 45 14.2 586.3 00:42 1.24 1064 6.3 80 0.89 74 11.8 293.2 0.62 1.80 1004 9.0 80 1:32 110 12.2 586.3 00:43 1.75 Ceramic gray 654 3.2 32 1.88 60 19.2 67.3 0.7 2.§0 666 9.0 32 4.77 153 17.1 86.5 1.6 5.8 678th 11.2 32 4.77 153 13.6 38.7 1.7 11.8 experimental metal SDOÍÍVO 407 3.2 32 2.9 67 2.1 6051 0.6 0.9 419 6.3 32 3.4 130 20.6 6051 0.6 0.9 431 9.0 32 5:52 177 19.7 6051 0.6 Q.8 443 3.2 56 1:41 80 25.4 6051 0.6 0.7 455 6.3 56 2.65 150 23.9 6051 0.5 0.7 467 9.0 56 3.70 209 23.3 6051 0.5 0.6 479 3.2 80 1.4 85 26.9 6051 0.5 1.2 491 6.3 80 1.89 153 24.3 6051 0.6 0.8 503 9.0 80 2:59 210 23.4 6051 0.6 Q.8

• ·· · · · · ·· · ·· · • · · · • · · · • ··· • 1 • • · • · · • · · • · ··· ·· · · ·· ·· · · · ·

When the grinding performance was measured at 80 m / s (15.750sfpm) in an additional grinding test under the same conditions, both the resin-bonded disc and the metal-bonded experimental disc had comparable energy consumption at a material removal rate (MRR) of 9.0 mm ³ / s / mm (0.8 in ³ / min / in). As shown in Table 2, experimental discs were observed at elevated MRR without loss of power or unacceptable force loads. The power consumption of the metal-bonded wheel was approximately proportional to the MRR. The highest MRR achieved in this study was 47.3 mm ³ / s / mm (28.4 cm ³ / min / cm).

The data in Table 2 are the averages of the twelve grinding passages. The individual performance data for each of the twelve passes remained remarkably identical to the experimental roll within the material removal rate. Normally, an increase in performance would be observed when successive abrasive passes are performed and the abrasive grains in the wheel begin to dull or the face of the wheel becomes clogged with the workpiece material. This is often observed when MRR increases. However, the steady-state power consumption levels maintained in each MRR over twelve pieces unexpectedly demonstrate that the experimental wheel maintained its sharp grinding fields throughout the test duration for all MRRs.

Throughout this test with material removal rates ranging from 9.0 mm ³ / s / mm (0.8 in ³ / min / in) to 47.3 mm ³ / s / mm (4 , 4 in ³ / min / in) furthermore, it was not necessary to shape or align the experimental disk.

Overall, the increasing amount of silicon nitride material ground without any evidence of disc wear was equivalent to 271 cm ³ per cm (42 in ³ per inch) of disc width. In contrast, the G coefficient for the 100 resin-bonded reel at a material removal rate of 8.6 mm ³ / s / mm (0.8 in ³ / min / in) was approximately 583 after twelve grooves. Experi23

• ·· ·· · • ··· · · • · • · · · • · • · · • · • · • 9 • · · • · • • 9 ··· ·· · · ···· · · 99

the mental disc showed no measurable disc wear after 168 grooves at 14 different material removal rates.

Table 2 shows that the specimens sanded with the metal bonded experimental roll maintained a surface quality between 0.4 µm (16 pin) and 0.5 µm (20 pin) at all 14 material removal rates and had waviness values between 1.0 µm (38 pin.) And 1.7 µm (67 pin.). The resin bonded disc was not tested at these high material removal rates. However, at a material removal rate of about 8.6 mm ³ / s / mm (0.8 in ³ / min / in), ceramic bars grinded with resin bonded discs had slightly better but comparable surface qualities (0.43 vs. 0.5 µm) and reverse waviness (1.73 vs. 1.18 pm).

Surprisingly, there was no noticeable deterioration in surface quality with increasing material removal rates when the ceramic bars were ground with a new metal-bonded disc. This is in contrast to the generally observed deterioration of surface quality with the growth of abrasion rates for standard disks as control disks were used herein.

Overall results show that the metal-bonded experimental wheel was able to grind efficiently at MRR that was more than 5 times greater than the MRR achievable with a standard, commercially used resin-bonded wheel. This experimental disc had, at lower MRRs, more than 10 times greater G coefficient compared to the resin-bonded disc.

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Table 2

MRR tested at a blade speed of 80 m / s

sample MRR mm ³ with ' ¹ mm' ¹ Concerned. strength N / mm Unit. power W / mm Merná energ. Ws mm ³ Koefic. G quality surface. ra pm undulation Wt pm resin 1040 9.0 1:32 110 12.2 586.3 00:43 1.75 metal invention 805 9.0 1.21 98 11.0 6051 00:51 1.19 817 18.Q 2:00 162 9.0 6051 00:41 Q.97 829 22.5 2.62 213 9.5 6051 00:44 1.14 841 24.7 2.81 228 9.2 6051 00:47 1.4 853 27.0 3.6 248 9.2 6051 00:48 1.9 865 29.2 3.24 262 9.Q 6051 00:47 1:37 877 31.4 3.64 295 9.4 6051 00:47 1:42 889 33.7 1.4 325 9.6 6051 00:44 1:45 901 35.9 4.17 338 9.4 6051 00:47 1.70 913 38.2 4:59 372 9.7 6Q51 00:47 1:55 925 40.4 4.98 404 10.0 6051 00:46 1:55 937 42.7 5.5 409 9.6 6051 00:44 1:57 949 44.9 5.27 427 9.5 6051 00:47 1.65 961 47.2 5.70 461 9.8 6051 00:46 1:42

When running at 32 m / s (6.252 sfpm) and 56 m / s (11,000 sfpm) (Table 1), the metal bonded power consumption was higher than the blade power consumption. • ·· ·· ·· ·· · · Resin bonded at the material removal rates tested. Aného spáj spáj spáj spáj spáj aného aného aného aného aného pri pri aného pri aného aného aného aného aného aného aného aného aného aného aného aného However, the energy consumption at a high blade speed of 80 m / s (15,750 sfpm) has become comparable to or slightly less than that of the resin bonded blade for the metal bonded disc (Tables 1 and 2). Overall, this trend showed that energy consumption decreased with increasing wheel speed when grinding at the same material removal rate for both resin bonded and experimental metal bonded rolls. Energy consumption during grinding, much of which goes to the workpiece in the form of heat, is less important in grinding ceramic materials than in grinding metal materials due to the greater thermal stability of these ceramic materials. As demonstrated by the surface quality of the ceramic samples ground by the discs of the invention, the energy consumption did not lose anything on the finished pieces and was at an acceptable level.

For the metal-bonded experimental roll, the G coefficient was essentially constant at 6051 for all material removal rates and roll speeds. For the resin-bonded roll, the G coefficient decreased with increasing material removal rates at any constant roll speed.

Table 2 shows the improvement of surface quality and waviness on abrasive specimens at higher wheel speed. In addition, samples ground with a new metal-bonded disc had the lowest waviness measured at all disc speeds and material removal rates tested.

In these tests, the metal-bonded disc demonstrated a higher disc lifetime compared to control discs. Unlike commercial control discs, there was no need to align and shape the experimental discs during quite long grinding tests. The experimental blade was successfully operated at blade speeds up to 90 m / s.

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Example 3

In a subsequent experimental roll (No. 6) abrasive test at 80 m / sec under the same operating conditions as in the previous example, an MRR of 380 cm ³ / min / cm was achieved, producing a surface quality measure (Ra) of only 0.5 µm (12 pin) and an acceptable energy level was consumed. The observed high rate of material removal without damaging the surface on the ceramic workpiece, achieved by using the tool of the invention, was not recorded for any abrasive operation of the ceramic material by any commercial abrasive wheel of any type of bond.

Example 4

For grinding sapphire on a Blanchard-type machine with a vertical spindle, a pot-shaped grinding tool was prepared and tested.

The pot-shaped wheel (diameter = 250 mm) was made of grinding segments identical in composition to those used in Example 1, wheel no. 6, except that (1) the diamond had a grain size of 45 microns (US Mesh 270/325) and was present in the abrasive segments at 12.5 volume% (concentration 50) and (2) the segment sizes were 46.7 mm in length strings (133.1 mm radius), 4.76 mm width and 5.84 mm depth. These segments were attached along the perimeter of a pot-shaped steel core side surface having a central spindle bore. The core surface had grooves positioned along the perimeter, forming separate, shallow pockets having the same width and length dimensions as those of the segments. Epoxy cement (Technodyne HT-18 cement obtained from Taoka, Japan) was added to these caps and segments were placed in the caps and the adhesive was

• ·· • · • ··· · · • · • · • e • · • • · · • · ·· ·· · · ···· ·· ·

given to cure. The finished disc was similar to that shown in FIG. Second

This pot wheel has been successfully used to grind the surface of a working material consisting of a rigid sapphire cylinder of 100 mm diameter providing acceptable surface uniformity under favorable grinding conditions of the G, MRR and energy consumption coefficients.

Example 5

Pot type 2A2 grinding tools (280 mm diameter) suitable for grinding the rear surfaces of AlTiC or silicon wafers with grinding segments described in Table 3 below were prepared. In addition, segment sizes were 139.3 mm for radius length , 3.13 mm for width and 5.84 mm for depth, as noted below. By sieving the weighed components through a US Mesh 140/170 screen and mixing the components for uniform mixing, mixtures were prepared with a binder batch containing diamond abrasive sufficient to produce 16 segments per roll in proportions given in Table 3. The powder required for each segment was weighed and compacted. . The graphite segment forms were hot pressed at 405 ° C for 15 minutes at 3,000 psi (2,073 N / cm ² ). After cooling, the segments were removed from the mold.

The assembly of the roll by adhering the segments to the machined 7075 T6 aluminum core was performed as in Example 1. The segments were degreased, sandblasted, adhesive coated, and placed in the machined recesses of the adapted roll circumferences. After the adhesive had cured, the roll was machined, balanced to size, and tested for speed.

• ··························

Table 3 ··· ·· ·· ···· ·· ···

Binder composition

Weight% vol%

sample Cu sn P graphite Cu sn P graphite Control (Ex. D 49.47 50.01 00:52 00:00 43.71 54.03 2.26 00:00 (1) 7.5 / 204 0 46.50 47.01 00:49 6:00 35.70 44.14 1.86 18:30 (2) 7.5 / 204 0 46.50 47.01 00:49 6:00 35.70 44.14 1.86 18:30 (3) 7.5 / 205 1 (4) 5/2040 45.76 46.26 00:48 7:50 34.02 42.07 1.75 22:16 46.50 47.01 00:49 6:00 35.70 44.14 1.86 18:30 (5) 43.53 44.01 00:46 12:00 29.55 36.54 1:53 32.37

Explanation to Table 4 below:

a. All diamond grain used in the segments was a crumb size of 325 mesh (49 microns), except for the sample (1), which had a 270 mesh grain (57 microns). Diamond concentration levels are given by the lower volume% diamond.

b. Porosity was estimated from observing the microstructure of the segments. Due to the formation of intermetallic alloys, the density of the test samples often exceeded the theoretical density of the materials used in the segments.

Table 4

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composition grinding segment in vol % sample binder graphite Diamond ^and Porosity _b Control > 80 00:00 18.75 <5 (Ex.1) (75 conc) (D > 80 17.93 1.88 <5 7.5 / 2040 (7.5 conc) (2) > 80 17.93 1.88 <5 7.5 / 2040 (7.5 conc) (3) > 75 21.72 1.88 <5 7.5 / 2051 (7.5 conc) (4) > 80 7.18 1.25 <5 5/2040 (5 conc) (5) > 63 30.35 6.25 <5 25/2052 (24 conc)

Example 6

Evaluation of grinding performance:

For grinding performance, samples of experimental segmental discs produced according to Example 5, with a diameter of 280 mm, a thickness of 29.3 mm, with a center bore of 228.6 mm (11 in x 1.155 in x 9 in), with a low diamond concentration, were filled with graphite . The performance of these samples was compared to the performance of the control sanding disc of Example 5, which was made according to the composition of the high diamond abrasive segment (concentration 75) of Example 1 (Disc 6).

• Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaa without graphite filler. AlTiC workpieces (210 AlTiC Grade obtained from 3M Corporation, Minneapolis, MN) with square dimensions of either 4.5 in (114.3 mm) or 6.0 in (152.4 mm) were made over 70 grinders, each 114 in width. 3 mm (4.5 inch) and 1.42 mm (0.056 inch) deep, and microns of removed raw material and normal abrasive force were recorded. The grinding test conditions were:

Grinding test conditions:

Machine: Strasbaugh model 7AF grinding machine

Grinding mode: Grooving with vertical spindle Wheel specification i 280 mm diameter, 29.3 mm thickness, 229 mm hole

Wheel speed: 1.200 rpm

Working speed: 19 rpm

Refrigerant: deionized water

Material removal rate: variable, 1.0 micron / sec to

5.0 micron / sec.

The disks were aligned and shaped with a 6 inch (152.4 mm) alignment washer 38A240-HVS obtained from Norton Company, Worcester, MA. After the initial operation, the alignment and shaping were carried out periodically when necessary and when the lower feed rates were changed.

The results of this abrasive test (normal force against raw material removed) for Example 5, Samples 2, 4 and 1 are shown below in Table 5 and Figure 3.

Table 5

Normal abrasive force against removed raw material ·····························

disc Control Control Control 2 2 2b 4 sample (Ex1) (Ex.1) (Ex.1) MRR 1 3 5 1 2 2 2

Total raw material Normal grinding force lib. (Kg)

3rous (u)

25 6 (2.7) 8 (3.6) 11 (5.0) 11 (5.0) 50 16 (7.3) 20 (9.1) 23 (10.4) 6 (2.7) 7 (3.2) 19 (8.6) 20 (9.1) 75 12 (5.4) 7 (3.2) 22 (10.00) 100 24 (10.9) 34 (15.4) 40 (18.2) 17 (7.7) 7 (3.2) 27 (12.3) 28 (12.7) 150 27 (12.3) 45 (20.4) 50 (22.7) 22 (10.0) 7 (3.2) 31 (14.1) 32 (14.5) 200 33 (15.0) 50 (22.7) 59 (26.8) 28 (12.7) 21 (9.5) 34 (15.4) 36 (16.3) 250 37 (16.8) 53 (24.1) 60 (27.2) 31 (14.10) 38 (17.3) 38 (17.3) 300 40 (18.7) 57 (25.9) 63 (28.6) 33 (15.0) 35 (15.9) 40 (18.2) 36 (16.3) 350 36 (16.3) 39 (17.7) 42 (19.1) 400 39 (17.7) 41 (18.6) 40 (18.0) 33 (15.0) 450 42 (19.1) 42 (19.1) 40 (18.2) 500 42 (19.1) 45 (20.4) 41 (18.6) 550 43 (19.5) 46 (20.9) 43 (19.5) 600 46 (20.9) 46 (20.9) 39 (17.7)

T

a. 2a is a sample 2 of Table 3 with a grinding segment width of 3.13 mm.

b. 2b is a sample 2 of Table 3 with a grinding segment width of 2.03 mm.

These results demonstrate that after removing more raw material at higher MRRs, a large increase in normal force (if from 1 to 3 to 5 microns / second MRR) was needed when the surface was ground with a control disc sample that had no graphite filler and diamond concentration. In contrast, low diamond diamond wheels filled with graphite of Example 5 of the invention (samples 2a, 2b and 4) required substantially less normal force during grinding. The force required to remove an equivalent amount of feedstock at an MRR of 2 microns / second was equivalent to the force required for the roll according to the invention! at MRR of 1 micron / second for the sample of the reference disc.

In addition, the specimens of wheel 2a needed approximately the same normal grinding forces at either an MRR of 1 micron / second or an MRR of 2 micron / second. The wheels 2a, 2b and 4 of Example 5 according to the invention exhibited such relatively constant requirements for normal force when the amount of the raw material to be grew from 200 to 600 microns. This type of grinding performance is highly desirable for counter-directional grinding of AlTiC inserts, as these low-force and balanced conditions minimize thermal and mechanical damage to the workpiece.

The control disc (Example 1) could not be tested at higher levels of raw material removal (eg above about 300 microns) because the force required to grind with these discs exceeded the normal grinding force capacity, causing the machine to stop automatically and prevent data collection. at higher levels of raw material removal.

Although there is no desire to be associated with any particular theory, it is believed that the improved grinding performance of low diamond and graphite-filled discs of the invention is correlated with fewer individual grains per unit area of the abrasive segment, that comes into contact with the workpiece surface at any point during the grinding. Although one skilled in the art would expect less MRR at a lower diamond concentration, the improvement in the grinding power of the invention is unexpectedly achieved without a discount on MRR. The blade 2b, which has a grinding segment width of 2.03 mm, required grinding for the grinding wheel for the grinding segment 2.03 mm. with the same measures and material removal rates, less force than a wheel 2a having a grinding wheel width of 3.13 mm would need. The sample wheel 2b has a smaller surface area and fewer grinding points in contact with the workpiece surface at any point in time during the grinding operations than the sample wheel 2a.

Claims (11)

PATENT CLAIMS · »··· ·· An abrasive surface grinding tool comprising a core having a minimum specific strength parameter of 2.4 MPa-cm ³ / g, a core density of 0.5 to 8.0 g / cm ³ , a circumference and an abrasive ring defined by a series of abrasive segments, wherein the abrasive segments comprise, in amounts selected up to a maximum of 100 vol% totally from 0.05 to 10 vol% superabrasive grain, from 10 to 35 vol% friable filler and from 55 to 89.95 vol% straw binder matrix 1.0 to 3.0 MPa M ^1/2 . The abrasive tool of claim 1, wherein the core comprises a metal material selected from the group consisting of aluminum, titanium and bronze, their compositions and alloys, and combinations thereof. The abrasive tool of claim 1, wherein the abrasive segments comprise 60 to 84.5% by volume of the metal binder matrix, 0.5 to 5% by volume of the abrasive grain and 15 to 35% by volume of the friable filler and the metal binder matrix comprises 5 % by volume porosity. The abrasive tool of claim 1, wherein the friable filler is selected from the group consisting of graphite, hexagonal boron nitride, hollow ceramic spheres, feldspar, nepheline syenite, pumice, clay and glass spheres, and combinations thereof. The abrasive tool of claim 1, wherein the abrasive grain is selected from the group consisting of diamond and cubic boron nitride, and combinations thereof. • · • · 35 · ...: ·· ·· The abrasive tool of claim 6, wherein the abrasive grain is a diamond having a particle size of 2 to 300 microns. The abrasive tool of claim 1, wherein the metal binder comprises 35 to 84 wt% copper and 16 to 65 wt% tin. The abrasive tool of claim 7, wherein the metal binder further comprises 0.2 to 1.0 wt% phosphorus. An abrasive tool according to claim 1, wherein the abrasive tool comprises at least two abrasive segments and the abrasive segments have an elongated, arcuate shape and an internal curvature selected to fit flush with the circular periphery of the core, each abrasive segment having two ends. designed so that they abut against adjacent abrasive segments so that the abrasive ring is continuous and substantially free of any gaps between the abrasive segments when the abrasive segments are attached to the core. • The abrasive tool of claim 1, wherein the tool is selected from the group consisting of wheels. J type 1A1 and pot discs. The abrasive tool of claim 1, wherein the thermally stable binder is selected from the group consisting essentially of an epoxy adhesive binder, a metallurgical binder, a mechanical binder and a diffusion binder, and combinations thereof.