JP2002507491A - Polishing tool - Google Patents

Abstract

(57) Abstract A polishing tool suitable for precision grinding of hard and brittle materials, such as ceramics and composites containing ceramics, at a grinding wheel peripheral speed of up to 160 m / s is provided. The polishing tool includes a grinding wheel core (2) attached to a dense, metal bonded superabrasive segment (8) with a thermally stable binder (6). Suitable tools for back grinding of ceramic wafers include a graphite filler and a relatively low concentration of abrasive grains (4).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] This application is related to US application Ser. No. 09/0
This is a 49,623 continuation-in-part application. The present invention provides precision grinding of hard and brittle materials, such as ceramics and composites containing ceramics, at peripheral speeds of up to 160 m / s.
suitable for dying and surface grinding of ceramic wafers
It relates to abrasive tools suitable for grinding. The polishing tool includes a wheel core or hub attached to a metal bonded to a superabrasive rim with a thermally safe binder during a grinding operation. These polishing tools grind ceramics at high removal rates (eg, 19-380 cm ³ / min / cm),
Less grinding wheel wear and less damage to workpieces than conventional grinding tools.

A polishing tool suitable for grinding sapphire and other ceramic materials is disclosed in US Pat. No. 5,607,489 to Li. The tool is described as containing metal-clad diamond bonded in a vitrified matrix having 2-20 vol% solid lubricant and at least 10 vol% porosity.

An abrasive tool comprising diamond bonded in a metal matrix having 15 to 50 vol% of a selected filler such as graphite is disclosed in US Pat. No. 3,925,035 to Keat. The tool is made of cemented carbide (cement)
Used to grind ed carbides. Cutting wheel made of metal combined with diamond abrasive
off wheel) is disclosed in US Pat. No. 2,238,3 to Van der Pyl.
No. 51. Binders include copper, iron, tin, and optionally nickel, and the fixed abrasive is sintered to a steel core, optionally with a soldering process to ensure proper adhesion. Is also good. The best binders are reported to have a Rockwell hardness of 70.

[0004] A polishing tool comprising fine diamond grains (borts) bound in a relatively low melting temperature metal binder, such as a bronze binder, has been disclosed in US Reissue Patent No. 21,165. Is disclosed. The low melting point binder helps to avoid oxidation of the fine diamond grains. The abrasive rim is assembled as a single, annular abrasive segment and then attached to a central disc of aluminum or other material.

[0005] None of these polishing tools has been shown to be satisfactory enough for precision grinding of ceramic components. These tools do not meet stringent specifications for part shape, size and surface quality when operated at commercially viable grinding speeds. The most mass-produced polishing tools recommended for use in these operations are:
A resin or vitrified bonded superabrasive wheel designed to operate with relatively low grinding efficiency to avoid surface and semi-surface damage to the ceramic components. Grinding efficiency is further reduced due to the tendency of the ceramic workpiece to plug the grindstone surface, often requiring dressing and truing of the grindstone to maintain a precise shape.

[0006] In products such as engines, refractory equipment and electronic devices (eg, wafers, magnetic heads and display windows), as the market demand for precise ceramic components increases, improvements for precision grinding of ceramics. There is an increasing demand for such abrasive tools. In the finishing of high performance ceramic materials for electronic components such as, for example, alumina-titanium carbide (AlTiC), surface grinding or "back grinding"("backgrinding").
The grinding operation requires a high quality, flat surface finish with a relatively slow grinding operation of low force. In the back grinding of these materials, the grinding efficiency is determined by the control of the quality of the workpiece surface and the resistance used, as well as the high removal rate and the wear resistance of the grinding wheel.

[0007] The present invention is directed to a method for producing a material having a minimum specific strength parameter of 2.4 MPa-cm ³ / g and a core density of 0.5 to 8
. A surface grinding and polishing tool comprising a core having 0 g / cm ³ , a circular perimeter, and an abrasive rim defined by a number of abrasive segments;
Super abrasive grains of 0.05 to 10 vol%, brittle filler of 10 to 35 vol%, and fracture toughness of 1.0 to 3.0 MPa M ^1/2 in a selected amount based on a total of 100 vol%. 55-89.95 vol% of metal binder matrix. The specific strength parameter is the yield strength or fracture strength (fra) of the material.
(cure strength) divided by the density of the material. The brittle filler is selected from the group consisting of graphite, hexagonal boron nitride, hollow ceramic spheres, feldspar, nepheline cyanite, pumice, calcined clay and glass spheres, and combinations thereof. In a preferred embodiment, the metal binder matrix has a porosity of up to 5 vol%.

The polishing tool of the present invention is a grinding wheel that includes a core having a center hole for attachment to the wheel, the core being designed to support a metal bonded superabrasive rim along the circumference of the wheel. Have been. These two parts of the wheel are supported by a binder which is thermally stable under grinding conditions, and the wheel and its components are subjected to stresses generated at a peripheral speed of the wheel of at least up to 80 m / s, preferably up to 160 m / s. Designed to withstand. Preferred tools are type 1A wheels and cup-shaped wheels, for example 2
Mold or 6-type grindstone, or 11V9-type bell-shaped cup grindstone.

[0009] The core is substantially circular in shape. The core has a minimum specific strength of 2.4 MPa-cm^Three/ G
, Preferably 40-185 MPa-cm^Three/ G of any material
. The core material has a density of 0.5 to 8.0 g / cm.^Three, Preferably 2.0 to 8.0 g / cm ^Three Having. Examples of suitable materials are steel, aluminum, titanium and bronze, as well as
In their composites and alloys and their combinations
is there. Reinforced plastic with the specified minimum specific strength also assembles the core
Can be used for Composites and reinforcing core materials are usually metal or plastic.
Having a continuous phase of the matrix, often in powder form, to which it is harder,
Discontinuous fibers and particles of a more resilient and / or lower density material
Added as a phase. Examples of reinforcing materials suitable for use in the tool core of the present invention
Are glass fiber, carbon fiber, aramid fiber, ceramic fiber and ceramic particles.
With hollow filling materials such as glass, mullite, alumina and zeolite spheres
is there.

[0010] Steel, and other metals having a density of 0.5 to 8.0 g / cm ³ , can be used to make the core for the tool of the present invention. High speed grinding (eg at least 80m /
S) used in the manufacture of aluminum, magnesium and titanium,
Preference is also given to powder forms of light metals, such as their alloys and their mixtures. Aluminum and aluminum alloys are particularly preferred. If a co-sintering assembly process is used to produce the tool, a metal having a sintering temperature of 400-900C, preferably 570-650C, is chosen. Low density filler material can be added to reduce the mass of the core. Porous and / or hollow ceramic or glass fillers, such as glass and mullite spheres, are suitable materials for this purpose. Also useful are inorganic and non-metallic fiber materials. When dictated by processing conditions, lubricants or other processing aids known in the art of metal abrasives and superabrasives may be added to the metal powder prior to molding and sintering. .

[0011] The tool has a potentially destructive resistance generated by high speed operation.
orcs) should be strong, durable, and dimensionally stable. The core must have a minimum specific strength to operate the wheel at the very high angular velocity required to achieve a tangential contact speed of 80-160 m / s. The minimum specific strength parameter required for the core material used in the present invention is 2.
4 MPa-cm ³ / g.

[0012] The specific strength parameter is the yield (or fracture) (fr) of the core material.
acture) is defined as the ratio of strength divided by core material density. In the case of a brittle material having a breaking strength lower than the yield strength, the specific strength parameter is determined using the smaller number, the breaking strength. The yield strength of a material is determined by the material strain (
strain) is the minimum resistance to increasing tension without further increase in resistance. For example, ANSI 4 cured above about 240 (Brinell hardness)
140 steel has a tensile strength of more than 700 MPa. The density of this steel is about 7.8
g / cm ³ . Thus, its specific strength parameter is about 90 MPa-cm ³ / g. Similarly, certain aluminum alloys, such as Al2024, Al7075 and Al7178, which can be heat treated to a Brinell hardness of greater than about 100, have a hardness of about 300.
Has a tensile strength higher than MPa. Such an aluminum alloy is about 2.7
It has a low density of g / cm ³ and therefore exhibits a specific strength parameter greater than 110 MPa-cm ³ / g. Titanium alloys and bronze composites and alloys made to have a density of 8.0 g / cm ³ or less are also suitable for use.

The core material is stiff and reaches the temperature reached in the grinding zone (eg, about 50-200 ° C.)
And should be thermally stable, resistant to chemical reactions with the coolants and lubricants used for grinding, and resistant to wear from corrosion due to the movement of cuttings in the grinding zone. Some of alumina and other ceramics, but has a breakdown value accepted (failure values) (i.e., greater than ^{60 MPa-cm 3 / g)} , they are usually too brittle, structurally fast grinding by disruption fall into disrepair. Therefore, ceramics are not suitable for use in tool cores. Metals, especially hardened tool quality steel, are preferred.

The abrasive grains of the grinding wheel used in the present invention are segmented or continuous rims attached to the core. The segmented abrasive rim is shown in FIG. The core 2 has a center hole 3 for attaching a grindstone to a power-driven (not shown) arbor. The abrasive rim of the whetstone includes superabrasives 4 embedded (preferably in a uniform concentration) in a metal matrix binder 6. The large number of abrasive segments 8 constitute the abrasive rim shown in FIG. Although the illustrated embodiment shows ten segments, the number of segments is not important. As shown in FIG. 1, each abrasive grain segment has a truncated, rectangular, annular shape (arch shape) characterized by a length l, a width w, and a depth d.

The embodiment of the grinding wheel shown in FIG. 1 is a representative example of a wheel that can be successfully operated in accordance with the present invention and should not be viewed as limiting. Numerous configurations of segmented grinding wheels that may be suitable include cup-shaped wheels as shown in FIG. 2, wheels with openings through the core and / or gaps between successive segments, and Includes whetstones having abrasive segments of different widths. The opening or gap is
It may be used to provide a passageway for introducing coolant into the grinding zone and for pumping out cuttings from that zone. Segments wider than the core width may be used to protect the core structure from corrosion through contact with the chips as the grinding wheel penetrates the workpiece in the radial direction.

The wheel can be manufactured by first shaping individual segments of pre-selected dimensions and then attaching the pre-shaped segments to the perimeter 9 of the core with a suitable adhesive. Another preferred manufacturing method is to form a segment precursor unit of a powder mixture of abrasive and binder, mold the composition around the periphery of the core, and make and attach the segments in-situ ( That is, it involves applying heat and pressure to co-sinter the core and the rim. Co-sintering method is Al
It is suitable for manufacturing a surface grinding cup wheel used for back grinding wafers and chips of hard ceramics such as TiC.

The abrasive rim component of the polishing tool of the present invention can be a continuous rim or a discontinuous rim, as shown in FIGS. A continuous abrasive rim comprises one abrasive grain, or at least two abrasive segments, which are separately sintered in a mold and then a thermally stable binder (ie, a segment directed from the grinding surface). At the temperature encountered during grinding, typically about 50-350 ° C., with a stable binder) attached individually to the core. As shown in FIG. 2, a discontinuous abrasive rim is manufactured from at least two such segments, and the segments are separated by grooves or gaps in the rim, and as in a segmented continuous abrasive rim wheel. Cannot be matched end-to-end along length 1. The figures illustrate preferred embodiments of the invention and are not intended to limit the type of tool design of the invention. For example, a discontinuous rim is 1
An A wheel can be used, and a continuous rim can be used for a cup wheel.

For high-speed grinding, particularly for grinding a workpiece having a cylindrical shape, a continuous rim, a mold 1
A grindstone is preferred. Segmented continuous abrasive rims are preferred and are very easy to achieve a truly round, planar shape while manufacturing tools from multiple abrasive segments, so over a single continuous abrasive rim It is molded as a single piece in a loop. For relatively low speed (e.g., 25-60 m / sec) operation, especially for flat workpiece surfaces and finish grinding, discontinuous abrasive rims (e.g., the cup wheel shown in FIG. 2) are preferred. Since surface quality is important in low speed surface finishing operations, grooves are formed in the segments, or some segments are omitted from the rim to help remove debris material that can scratch the workpiece surface. sell.

The abrasive rim component comprises superabrasives held in a metal matrix binder, and the metal rim component in a mold designed to produce the desired size and shape of the abrasive rim or abrasive rim segment. It is usually obtained by sintering a mixture of binder powder and abrasive grains. The superabrasive used in the abrasive rim may be selected from natural or synthetic diamond, CBN, and combinations of these abrasives. The choice of particle size and type will vary depending on the nature of the workpiece and the type of grinding process. For example, in grinding and polishing of sapphire or AlTiC, a superabrasive particle size in the range of 2 to 300 μm is preferable. For other alumina grinding, a superabrasive grain size (60-120 grit; Norton Company grit diameter) of about 125-300 μm is usually preferred. For grinding silicon nitride, about 45-80 μm (200
A particle size of ~ 400 grit) is usually preferred. Relatively small grit diameters are preferred for surface finishes, and relatively large grit diameters are suitable for cylinders, profiles or inner dirs where relatively large amounts of material are ground.
a) Suitable for grinding.

As a volume% of the abrasive rim, the tool has a superabrasive of 0.5 to 10 vol%, preferably 0.1 to 10 vol%.
5-5 vol%. A small amount of filler having a lower hardness than the metal binder matrix can be added as a binder filler to increase the wear rate of the binder. As volume% of the rim component, the filler can be used at 10-35 vol%, preferably 15-35 vol%. Suitable friable filler materials are characterized by suitable thermal and mechanical properties to withstand the sintering temperature and pressure conditions used to produce the abrasive segments and assemble the wheels. Graphite, hexagonal boron nitride, hollow ceramic spheres, feldspar, nepheline cyanite, pumice, calcined clay and glass spheres, and combinations thereof, are examples of useful brittle filler materials.

Suitable for bonding superabrasives, and fracture toughness 1.0 to 6.0 MPa · m^1/2,
Preferably 2.0 to 4.0 MPa · m^1/2Any metal binder having
Can be used. Fracture toughness means that cracks that occur in the material
It is a stress intensity factor that leads to material failure. The fracture toughness is K_1c= (Σ_f) (Π^{1 / Two} ) (C^1/2) Where K_1cIs the fracture toughness, σ_fIs destroyed
Stress, and c is 1/2 of the crack length. Used to measure fracture toughness
There are several methods that can be used, each of which will test for cracks of a known size.
The first stage occurs in the material, then the stress is applied until the material fails
. The stress at fracture and the length of the crack are substituted into the equation
(For example, the fracture toughness of steel is about 30-60 MPa · m^1/2, Al
Mina is about 2-3MPa ・ m^1/2, Silicon nitride is about 4-5MPa · m^1/2And Jill
Konia is about 7-9MPa ・ m^1/2It is. ).

In order to optimize wheel life and grinding performance, the binder wear rate must be equal to or slightly greater than the abrasive wear rate during the grinding operation.
Fillers such as those described above may be added to the metal binder to reduce the wear rate of the wheel. Metal powders that tend to form relatively dense binder structures (ie, less than 5 vol% porosity) are preferred because they allow relatively high grinding rates during grinding.

Materials useful in rim metal binders include bronze, copper and zinc alloys (brass),
Including cobalt, and iron, and their alloys, and mixtures thereof,
Not limited to them. These metals may be carbides or nitrides between the abrasive and the binder at the surface of the superabrasive under selected sintering conditions that enhance the titanium or titanium hydride or abrasive / binder status. Having the ability to form chemical bonds
It can be used with materials that are reactive with other superabrasives (ie, active binding components).

[0024] The relatively strong abrasive / binder interaction results in a rapid loss of abrasive and workpiece damage,
As well as limiting the shortened tool life caused by fast abrasive loss. In a preferred embodiment of the abrasive rim, the metal matrix comprises 55-89.9 of the rim.
5 vol%, preferably 60 to 84.5 vol%. The brittle filler comprises 10 to 35 vol%, preferably 15 to 35 vol% of the abrasive rim. The porosity of the metal matrix binder should be maintained up to 5 vol% during the production of the abrasive segments. Preferably, the metal binder has a Knoop hardness of 2-3 GPa.

In a preferred embodiment of the Type 1A grinding wheel, the core is made of aluminum and the rim contains a bronze binder made of copper and tin powder (80/20 wt%),
It may optionally contain phosphorus in the form of phosphorus / copper powder in an amount of 0.1 to 3.0 wt%, preferably 0.1 to 3.0 wt%.
１．０1.0 wt% may be added. During the production of the abrasive segment, the metal powder of this composition is mixed with 100-400 grit (160-45 μm) diamond abrasive, formed into abrasive rim segments, and 400-400 g at 20-33 MPa.
Sintered or densified in the range of 550 ° C., preferably having a density of at least 95% of theoretical density (ie having a porosity of less than 5 vol%)
To produce a dense abrasive rim.

In a typical co-sintering whetstone manufacturing process, the core metal powder is injected into a steel mold and
Cold pressed at 0-200 kN (pressure about 10-50 MPa) to form a green part having a size of about 1.2 to 1.6 times the desired final thickness of the core. The green core part is placed in a graphite mold, and a mixture of abrasive grains (grit diameter 2 to 300 μm) and a metal binder powder blend is added to the cavity between the core and the outer end of the graphite mold. A setting ring may be used to compress the abrasive and metal binder powder to the same thickness as the core preform. The graphite-type content is then hot-pressed at 370-410 ° C. under a pressure of 20-48 MPa for 6-10 minutes. As is known in the art, the temperature is ramped before applying pressure to the contents of the mold (e.g.
Min; hold at 410 ° C. for 15 min) or increase to removal.

[0027] Following hot compaction, the graphite mold is removed from the part, the part is cooled,
The part is then finished in a conventional manner to obtain an abrasive rim having the desired dimensions and tolerances. For example, the part can be sized using a vitrified grinding wheel on a grinder or carbide on a lathe. When co-sintering the core and rim of the present invention, little grinding is required to bring the part to its final shape. In another method of creating a thermally stable bond between the abrasive rim and the core, cutting both the core and the rim ensures that the parts match and that a suitable surface to bond is obtained. It may be required before the joining, connecting or diffusing steps.

When using a segmented abrasive rim to create a thermally stable bond between the rim and the core, any thermally stable bond that is strong enough to withstand a peripheral wheel speed of up to 160 m / sec. Agents may also be used. A thermally stable adhesive is stable to the grinding process temperatures that are likely to be encountered at the portion of the abrasive grain segment directed from the grinding surface. Such temperatures typically range from about 50-350 ° C.

The adhesive bond must be mechanically very strong to withstand the destructive resistance that exists during rotation of the grinding wheel and during the grinding operation. Two-part epoxy resin binders are preferred. A suitable epoxy adhesive, Technodyne ™ H
T-18 epoxy resin (obtained from Taoka Chemical, Japan) and its modified amine curing agent can be mixed in a ratio of 19 parts curing agent to 100 parts resin. Fillers, such as fine silica powder, may be added in 3 parts per 100 parts of resin to increase the viscosity of the bonding agent.
. It can be added in a ratio of 5 parts. Segments around the entire circumference of the grinding wheel core,
Alternatively, it can be attached to a part of the core using a bonding agent. The perimeter of the metal core may be sandblasted to achieve a degree of roughness prior to segment attachment. The densified epoxy binder is used on the ends and bottoms of the segments which are positioned around the core substantially as shown in FIG. 1 and which are properly mechanically held during curing. The epoxy binder is allowed to cure (eg, at room temperature for 24 hours,
(At 68 ° C. for 48 hours). During cure and segment transfer, binder drainage is minimized during cure by adding sufficient filler to optimize the viscosity of the epoxy binder.

The strength of the adhesive bond is set to 45 r so that it is possible to measure the burst rate of the grinding wheel.
It can be tested by a spin test at an acceleration of ev / min. Wheels must exhibit a burst rating equal to at least 271 m / s tangential contact speed to qualify for operation at 160 m / s tangential contact speed, currently applicable in the United States It is.

The abrasive tool of the present invention is specifically designed for precision grinding and finishing of brittle materials, such as advanced ceramic materials, glass, and components including ceramic materials and ceramic composites. The tools of the present invention include silicon, mono- and polycrystalline oxides, carbides, borides and silicides; polycrystalline diamond; glass; and ceramic composites in non-ceramic matrices; and combinations thereof. Suitable (not limited) for grinding ceramic materials.

Examples of representative workpiece materials include AlTiC, silicon nitride, silicon oxynitride, stabilized zirconia, aluminum oxide (eg, sapphire), boron carbide, boron nitride, titanium diboride, and aluminum nitride, and These include, but are not limited to, composites of these ceramics, as well as certain metal matrix composites, such as hardmetals, and hard, brittle amorphous materials, such as mineral glass.
Both single crystal and polycrystalline ceramics can be ground with these improved polishing tools. For any type of ceramic, the quality of the ceramic part and the efficiency of the grinding operation increases as the peripheral speed of the wheel of the invention increases from 80 to 160 m / s.
To increase.

Among the ceramics, the parts that are improved using the abrasive tool of the present invention include ceramic engine valves and rods, pump seals, ball bearings and fittings,
Cutting tool inserts, wear parts, stretch dies for metal forming, refractory elements, visual display windows, windshields, flat glass for doors and windows, insulators and electronic components, and silicon wafers, AlTiC chips, read-write magnetic heads , And a ceramic electronic element, including, but not limited to, a substrate.

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

Example 1 A grinding wheel of the present invention was manufactured in the form of a 1A1 metal bonded diamond wheel utilizing the following materials and methods.

Copper powder (dendritic FS grade, particle size + 200 / −325 mesh, Sintertech
43.74 wt% (obtained from International Marketing Corp., Ghent, NY);
Phosphorus / copper powder (1501 grade, + 100 / -325 mesh particle size, New Jers
ey Zinc Company, Palmerton, PA) 6.24 wt%; and tin powder (M
D115 grade, +325 mesh, maximum 0.5%, particle size, Alcan Metal Powd
50.02 wt% (obtained from ers, Inc., Elizabeth, New Jersey). Diamond abrasive grains (320 grit synthetic diamond obtained from General Electric, Worthington, Ohio) were added to the metal powder blend and mixed until homogeneously compounded. The mixture is placed in a graphite mold until a matrix having a target density greater than 95% of theory is formed (eg, for the # 6 wheel used in Example 2: greater than 98.5% of theoretical density). , 40
Hot pressed at 3000 psi (2073 N / cm ² ) at 7 ° C. for 15 minutes. The Rockwell B hardness of the segments manufactured for the # 6 grinding wheel was 10 ⁸ . The segments contained 18.75 vol% abrasive. The segments are ground to the arcuate shape required to fit around a ground alumina core (7075 T6 aluminum, obtained from Yarde Metals, Tewksbury, MA) and have a grinding wheel having an outer diameter of about 393 mm and a thickness of 0.62 cm. I got

The abrasive segments and aluminum core are silica filled epoxy bonding system (Technodyne HT-18 adhesive, from Taoka Chemical, Japan) to create a grinding wheel with a continuous rim consisting of multiple abrasive segments. obtain)
Assembled using The contact surfaces of the core and the segments were degreased and sandblasted to ensure proper adhesion.

In order to characterize the maximum working speed of this new type of grinding wheel,
Roton Company's maximum working test method was intentionally rotated to failure to determine burst strength and maximum working speed evaluated. The table below shows
The burst test for a representative example of a 393 mm diameter experimental metal bonded wheel is summarized. Burst strength data of experimental metal binder grindstone ────────────────────────────────── Grindstone # Grindstone diameter Burst Burst speed Burst speed Maximum working speed cm (inch) RPM (m / s) (sfpm) (m / s) ───────────────────────── ４ 4 39.24 9950 204.4 40242 115.8 (15.45) ──────────────────────────────── ５ 5 39.29 8990 185.0 36415 104.8 (15.47) ７ 7 39.27 7820 160.8 31657 91.1 (15.46) ９ 9 39.27 10790 221.8 43669 125.7 (15.46) ─── ─────────────────────────────── According to these data, Grinding wheels 90m / s (17,7
Qualified for working speeds up to 17 surface feet / min). 160m / s
Higher working speeds up to can be easily achieved by making some further changes in the manufacturing method and wheel design.

Example 2 Evaluation of Grinding Performance: An experimental metal-bonded segment grinding wheel (15.5 × 0.59 × 5) having a diameter of 393 mm, a thickness of 15 mm, and a center hole of 127 mm made by the method of Example 1 above. Inches) (# 4 has 95.6% of theoretical density segments, # 5 is 97.9% of theoretical density, and # 6 is 98.5% of theoretical density) tests grinding performance Was done. Initial tests at 32 and 80 m / s confirmed the # 6 wheel as the wheel with the best grinding performance of the three, but all experimental wheels were acceptable. The # 6 wheel was tested at three speeds: 32 m / s (6
252 sfpm), 56 m / s (11,000 sfpm), and 80 m / s (15.7
50sfpm). Two commercial prior art wheels recommended for grinding advanced ceramic materials were used as control wheels, and they were tested with the wheels of the present invention. One is a vitrified bonded diamond wheel (Norton Com
pany, Worcester, MA SD320-N6V10 grinding wheel) and others are resin bonded diamond wheels (Norton Company, Worcester, MA).
It was a 320-R4BX619C grindstone. The resin wheels were tested at all three speeds. The vitrified grinding wheel is 32 m / s (625 m) in consideration of the speed tolerance.
2sfpm).

More than 1000 plunge grindings of 6.35 mm (0.25 inch) wide and 6.35 mm (0.25 inch) deep were performed on silicon nitride workpieces. Grinding test conditions: Grinding test conditions: Machine: Studer Grinder Model S40 CNC grinding wheel specification: SD320-R4BX619C, SD320-N6V10, size: diameter 393mm, thickness 15mm and hole 127mm Wheel speed: 32, 56, and 80m / s (6252, 11000, and 1
5750 sfpm) Coolant: Inversol 22 (60% oil and 40% water) Coolant pressure: 270 psi (19 kg / cm ² ) Grinding speed: variation. Starting 3.2 mm ³ / s / mm (0.3 in ³ / min / in) Workpiece: Si ₃ N ₄ (rod made from NT551 silicon nitride, Norton A
obtained from advanced Ceramics, Northboro, MA), 25.4 mm (1 inch) in diameter
× Length 88.9 mm (3.5 inches) Workpiece speed: 0.21 m / s (42 sfpm), constant Workpiece start diameter: 25.4 mm (1 inch) Workpiece finish diameter: 6.35 mm (0.25 mm) Inches) For operations that require reshaping and reshaping, the conditions suitable for the metal bonded wheel of the present invention are: Reshaping operation: Wheel: 5SG46IVS (obtained from Norton Company) Wheel size: 152 mm (6) Inch) Wheel speed: 3000 rpm; at +0.8 ratio compared to grinding wheel.

Lead: 0.015 inch (0.38 mm) Correction: 0.0002 inch Reworking work: Stick: 37C220H-KV (SiC) Mote: Handstick reworking The test was performed in grinding silicon nitride rods. , Performed in a plunge mode with a cylindrical outer diameter. To maintain the best stiffness of the work piece during grinding, the 88.9 mm (3.5 inch) specimen was ground to about 31 mm (1 1/4)
Inch) chuck. A series of plunge grinding tests started from the far end of each rod. First, the whetstone is used to complete one test
A plunge of 6.35 mm (1/4 inch) wide and 3.18 mm (1/8 inch) radial depth was made. The workpiece rpm was then readjusted, reducing the workpiece diameter to compensate for the slowdown in workpiece speed. In addition, two similar plunges reduce the workpiece diameter from 1/4 inch to 6.35 mm (1/4) at the same location.
4 inches). The grinding wheel was then moved 6.35 mm (1/4 inch) laterally relatively close to the chuck to perform the next three plunges. Four lateral movements were made on the same side of the sample to complete 12 plunges at one end of the sample. The sample was then inverted and exposed on the other side for another 12 grindings. A total of 24 plunge grindings were performed on each sample.

The metal binding wheels of this invention, as well as the first comparison test against the resin and vitrified abrasive, about ^{3.2mm 3 /s/mm(0.3in 3 / min / in} ) to about 10
. ^Three workpiece removal rates (material) of 8 mm ³ / s / mm (1.0 in ³ / min / in)
ial removal rates (MRR ') at a peripheral speed of 32 m / s. Table 1 shows that between 12 different types of wheels after 12 plunge grindings,
This shows that there is a performance difference, as indicated by the G-ratio. The G-ratio is a unitless ratio of the grinding amount to the grinding wheel wear amount. The data showed that, at relatively high workpiece removal rates, N-grade vitrified wheels had better G ratios than R-grade resin wheels, which indicated that relatively soft wheels were more effective at grinding ceramic workpieces. , Indicating better. However, the relatively hard, experimental metal bonded wheel (# 6) is far superior to resin and vitrified wheels at all workpiece removal rates.

Table 1 shows the resin wheel and the new metal bonded wheel (
8 shows the evaluated G-ratio for # 6). Since there was no measurable wheel wear after 12 grindings at each workpiece removal rate for the metal bonded wheels, a symbolic value of 0.01 mil (0.25 μm) of radial wheel wear was given for each grinding. Was. This resulted in a calculated G-ratio 6051. The metal bonded whetstone of the present invention has a diamond concentration of 75 (about 18.75 vol% abrasive in the abrasive grain segment),
The resin and vitrified whetstone have a concentration of 100 and a concentration of 1 respectively.
Although it was 50, the grinding wheel of the present invention still showed excellent grinding performance. At these relative grain concentrations, superior grinding performance would have been predicted from a control wheel containing a relatively high grain vol%. Thus, these results were unpredictable.

Table 1 shows the surface finish (Ra) and swell (wa) measured on samples ground by three wheels at low test speeds.
(Wt). The undulation value Wt is the undulation cross section (wavi
It is the maximum peak for the height of the valley of the nest profile. All finish surface roughness data was measured on surfaces created by cylindrical plunge grinding without spark-out. Usually these surfaces are
It will be relatively rougher than the surface created by traverse grinding.

Table 1 shows the difference in grinding power consumption at various workpiece removal rates for the three types of grinding wheels. Resin whetstone is another 2
The experimental metal bonded wheels and vitrified wheels had lower power consumption than the two wheels; however, the equivalent power consumption. The experimental wheels consumed a satisfactory amount of power for the ceramic grinding operation, especially in view of the favorable G-ratio and finished surface roughness data observed for the wheels of the present invention. In general, the wheels of the present invention exhibited power draw proportional to the workpiece removal rate.

[0046]

[Table 1]

In an additional grinding test under the same grinding performance, 80 m / s (15,750 sfpm
), The resin wheel and the experimental metal wheel are 9.0 mm ³ / s /
It had equivalent power consumption at a workpiece removal rate (MRR) of 0.8 mm ³ / min / in. As shown in Table 2, the experimental wheels are operated with increased MRR without performance degradation or unacceptable power loading. The power consumption of the metal bonded wheel was approximately proportional to the MRR. The maximum MRR achieved in this study was 47.3.
mm ³ / s / mm (28.4 cm ³ / min / cm).

The data in Table 2 is an average of 12 grinding results. The individual power readings for the 12 grindings remained significantly compatible with the experimental wheels within each workpiece removal rate. Typically, an increase in power will be seen as continuous grinding is performed and the abrasive grains of the wheel begin to blind or the surface of the wheel becomes loaded with work material. This is often seen as the MRR increases. However, during 12 grindings, the level of stable power consumption seen within each MRR was surprisingly that the experimental wheel maintained a sharp cutting point during all testing at all MRRs. Is shown.

[0049] Further, the workpiece removal rate from ^{9.0mm 3 /s/mm(0.8in 3 / min / in} ) 4
During all of these tests, spanning 7.3 mm ³ / s / mm (4.4 in ³ / min / in), there was no need to reshape or redress the experimental wheels. The total cumulative amount of silicon nitride material ground without any indication of wheel wear was equal to 271 cm ³ (42 in ³ / in) per cm of wheel width. In contrast, the workpiece removal rate is 8.6.
In mm ³ / s / mm (08 in ³ / min / in), G of resin grindstone with concentration of 100
The ratio was about 583 after 12 plunges; The experimental wheels showed no measurable wheel wear after 168 plunges at 14 different workpiece removal rates.

Table 2 shows that for all 14 workpiece removal rates, the samples ground with an experimental metal bonded wheel had a constant finish of 0.4 μm (16 μin.) To 0.5 μm (20 μin.). Roughness is maintained and 1.0 μm (38 μin.) To 1.7 μm (67 μin.
.)). Resin wheels were not tested at these high workpiece removal rates. However, about 8.6 mm ³ / s / mm (0.8 in ³ / mi
At a workpiece removal rate of n / in), the ceramic bar ground by the resin wheel has a slight improvement, comparable surface roughness (0.43 vs 0.5 μm), and relatively poor undulation ( (1.73 to 1.18 μm).

Surprisingly, as the workpiece removal rate increased, there was no apparent deterioration in the finished surface roughness when the ceramic rod was ground with a new metal bonded wheel. This is in contrast to the standard wheels, such as the control wheels used herein, which generally show a decrease in finished surface roughness with increasing cutting speed. The overall results show that the experimental metal wheels were able to grind effectively with MRRs more than five times that achievable with standard, commercially used resin bonded wheels. The experimental whetstone has a low MRR and a G-
Had a ratio.

[0052]

[Table 2]

When working at wheel speeds of 32 m / s (6252 sfpm) and 56 m / s (11,000 sfpm) (Table 1), the power consumption for a metal bonded wheel is the percentage of all workpiece removal tested. And it was higher than resin whetstone. However, power consumption for metal bonded wheels is high at wheel speeds of 80 m / s (15,750 sfpm).
In Tables 1 and 2), it was equal to or slightly lower than the resin grindstone. Overall, when grinding at the same workpiece removal rate for both the resin wheel and the experimental metal bond wheel, the power consumption decreased with increasing wheel speed.
The trend was shown. Power consumption during grinding is mostly directed to the workpiece as heat, but due to the relatively large thermal stability of the ceramic material, grinding the ceramic material rather than grinding the metal material requires: Not relatively important. Power consumption, as indicated by the surface quality of the ceramic sample ground with the grinding wheel of the present invention, did not impair the finished workpiece and was at an acceptable level.

For the experimental metal bonded wheels, the G-ratio was essentially constant at 6051 for all workpiece removal rates and wheel speeds. For resin wheels, the G-ratio decreased with increasing workpiece removal at a constant wheel speed. Table 2 shows that the finished surface roughness and waviness of the sample ground at a relatively high wheel speed were improved. In addition, the samples ground with the new metal bonded wheels had the lowest measured swell at all wheel speeds and compound removal rates tested.

In these tests, the metal bonded wheels exhibited superior wheel life as compared to the control wheels. Unlike commercial control wheels, there was no need to reshape or reshape the experimental wheels during the extended grinding test. The experimental wheels worked well at wheel speeds of up to 90 m / s.

EXAMPLE 3 Under the same working conditions as used in the previous example, an experimental whetstone (#
6) The following grinding test resulted in a finished surface roughness measurement (Ra) of only 0.5 μm (12 μin) and an MRR of 380 cm ³ / min / cm, although utilizing an acceptable level of power. Was achieved. The observed high workpiece removal rates without degrading the ceramic workpiece are achieved by utilizing the tool of the present invention, but the grinding of any ceramic material using any of the bonded grinding wheels No work was reported.

EXAMPLE 4 A cup-shaped polishing tool was prepared and a vertical spindle "blanchard type" (
"Blanchard type" machine was tested for grinding sapphire.

A cup-shaped grindstone (250 mm diameter) was made from abrasive segments of the same composition as used in grindstone # 6 of Example 1, except for the following: That is, (1) diamond has a grit diameter of 45 μm (US mesh 270/325),
It was present in the abrasive at 12.5 vol% (concentration 50). (2) The size of the segment was a chord length of 46.7 mm (radius 133.1 mm), a width of 4.76 mm and a depth of 5.84 mm. These segments were joined along the perimeter of the side of the cup-shaped steel core with a center spindle hole. The surface of the core had grooves placed along its perimeter forming separate, shallow pockets having the same width and length dimensions as the segments. An epoxy bonding agent (Technodyne HT-8 bonding agent from Taoka, Japan) was added to the pocket and the segments and bonding agent placed in the pocket were cured. The finished whetstone was similar to the whetstone shown in FIG.

Cup wheels have been successfully used to grind the surface of a workpiece material consisting of a 100 mm diameter solid sapphire cylinder and to accept under suitable grinding conditions of G-ratio, MRR and power consumption. The resulting surface flatness was high.

Example 5 A 2A2 cup diameter polishing tool (diameter 280 mm) suitable for back grinding AlTiC or silicon wafers was prepared using the abrasive segments described in Table 3 below. . Except as noted below, the size of the segment is radius 13
It was 9.3 mm, 3.13 mm wide and 5.84 mm deep. Diamond abrasive grains containing the binder batch mixture, sufficient to produce 16 segments per wheel, at the rate shown in Table 3, were obtained from U.S.A. S. By sifting the weighed ingredients through a mesh 140/170 sieve and mixing the ingredients and blending uniformly,
Was prepared. The powder required for each segment was weighed, introduced into a graphite mold, conditioned and compressed. The graphite segment type is 15
Min. At 3000 psi (2073 N / cm ² ). As it cooled, the segments were removed from the mold.

The assembly of the grindstone by attaching the segments to the machined 7075 T6 aluminum core was performed as in Example 1. The segments were degreased, sandblasted, coated with an adhesive, and placed in a machined cavity to fit around the grinding wheel. After curing of the adhesive, the grinding wheel is cut, sized, and balanced.
d) and speed tested.

[0062]

[Table 3]

[0063]

[Table 4]

A. All diamond grains used for the segments had a 325 mesh (49 μm) grit diameter, except that sample (1) was 270 mesh (57 μm) grains. Diamond concentration levels are shown below diamond vol%. b. Porosity was assessed from observation of the microstructure of the segment. Due to the formation of intermetallic alloys, the density of the test samples often exceeded the theoretical density used for the segments.

Example 6 Evaluation of grinding performance: 280 mm in diameter, 29.3 mm in thickness, 228.
Samples of 6 mm, low diamond concentration, graphite-filled experimental segment wheels (11 in x 1.155 in x 9 in) were tested for grinding performance. The performance of these samples was compared to that of the control back grinding wheel of Example 5 made with the high (concentration 75) diamond abrasive grain segment composition of Example 1 (Wheel # 6) without graphite filler.

More than 70 grindings, each of 114.3 mm (4.5 inches) wide and 1.42 mm (0.056 inches) deep, can be used with 114.3 mm (4.5 in) or 152.4 mm
(6.0 in) square AlTiC workpiece (3M Corporation, Minneapolis)
, 210 grade AlTiC obtained from MN, Inc., and the grinding amount (s
tock removed (μm) and normal grinding resistance (normal gr)
iding force) was recorded. Grinding test conditions: Grinding test conditions: Machine: Strasbaugh Grinder Model 7AF Grinding mode: Vertical spindle plunge grinding Wheel specifications: diameter 280 mm, thickness 29.3 mm and hole 229 mm Wheel speed: 1,200 rpm Workpiece speed: 19 rpm Coolant: Deionized water Workpiece removal rate: Varies. 1.0 μm / sec to 5.0 μm / sec Wheels are reshaped and 3 obtained from Norton Company, Worcester, MA
8 A 240-HVS specification 6 inch (152.4 mm) wrought with a wrench pad. After the initial operation, reshaping and reshaping were performed as needed and periodically when the down feed rate was changed.

The results of the grinding test (normal resistance versus the amount of grinding) for Example 5, Samples 2, 4 and 1 are shown in Table 5 below and FIG.

[0068]

[Table 5]

A. 2a is Sample 2 of Table 3 having an abrasive grain segment rim width of 3.13 mm.
b. 2b is Sample 2 in Table 3 having an abrasive grain segment rim width of 2.03 mm. These results indicate that a significant increase in normal resistance was observed when surface grinding with a control wheel sample without graphite filler and with a diamond abrasive concentration of 75.
This shows that a relatively high MRR (1-3 to 5 μm / sec) was required to obtain a large amount of grinding. In contrast, with the low diamond concentration of Example 5 of the present invention, the graphite-filled wheels (samples 2a, 2b and 4) require only a significantly lower normal resistance during grinding. With an MRR of 2 μm / sec for the wheel of the present invention, the resistance required to obtain an equivalent amount of grinding is 1 μm / sec MR for the comparative wheel sample.
It was equivalent to that required for R.

In addition, the 2a sample required approximately equal normal resistance to grind with an MRR of 1 μm / sec or 2 μm / sec. Furthermore, the grindstones 2a, 2
b and 4 showed the requirement for a relatively stable normal resistance even though the grinding amount advanced from 200 to 600 μm. This type of grinding performance is highly desirable in back grinding AlTiC wafers. This is because this low resistance, steady state condition minimizes thermal and mechanical damage to the workpiece.

The control wheel (Example 1) has a high grinding level (eg, greater than about 300 μm)
Not tested on Because the resistance required to grind with these wheels exceeds the normal resistance capability of the grinding machine, it automatically shuts down the machine and accumulates data at relatively high grinding levels. Because they hinder you. While not wishing to be bound by any particular theory, the excellent grinding performance of the graphite-filled wheels of the present invention with low diamond concentration is such that the grinding wheel contacts the workpiece surface at any point during grinding. It is believed that this is related to the relatively small number of individual particles per unit area of the grain segment. Although those skilled in the art will expect relatively low MRR at low diamond concentration, the improved grinding resistance of the present invention is surprisingly achieved without lowering MRR. Grinding wheel 2b having an abrasive grain segment width of 2.03 mm required less resistance to grinding at the same grinding rate and speed as did abrasive wheel 2a having an abrasive grain segment width of 3.13 mm. The grindstone 2b sample has a relatively small surface area and relatively few grinding points that contact the workpiece surface at any point during the grinding operation than the grindstone 2a sample.

[Brief description of the drawings]

FIG. 1 illustrates a continuous rim of abrasive segments bonded around a metal core to form a type 1A1 grinding wheel.

FIG. 2 illustrates a discontinuous rim of abrasive segments bonded around a metal core to form a cup-shaped wheel.

FIG. 3 shows the relationship between the amount of grinding and the normal resistance during grinding of an AlTiC workpiece with the grinding wheel of Example 5.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), AU, BR, CA, CN, CZ, HU, ID, IL, IN, JP, KR, MX, NZ, PL, SG, SK (72) Inventors Williston, William H. United States, Massachusetts 01520, Holden, Donald Avenue 37 (72) Inventor Bourjan, Sergey-Tomislav United States, Massachusetts 01720, Acton, Washington Drive 23 F-term (reference) 3C063 AA02 AB03 BA03 BA10 BB02 BB07 BC02 BD01 BG01 BG10 FF23

Claims (11)

[Claims] 1. Minimum specific strength parameter 2.4 MPa-cm ³ / g, core density 0.
A surface grinding and polishing tool comprising a core having 5-8.0 g / cm ³ , a circular perimeter, and an abrasive rim defined by a number of abrasive segments, the abrasive segments comprising:
Super abrasive grains of 0.05 to 10 vol%, brittle filler of 10 to 35 vol%, and fracture toughness of 1.0 to 3.0 MPa M ^1/2 in a selected amount based on a total of 100 vol%. A surface grinding and polishing tool comprising 55 to 89.95 vol% of a metal binder matrix. 2. The polishing tool according to claim 1, wherein the core comprises a metal material selected from the group consisting of aluminum, steel, titanium and bronze, composites and alloys thereof, and combinations thereof. 3. The method of claim 2, wherein the abrasive segments comprise a metal binder matrix of 60 to 84.5.
2. The composition of claim 1, wherein the metal binder matrix comprises at least 5 vol%, at least 0.5-5 vol% abrasive, and at least 15-35 vol% brittle filler, and the metal binder matrix has a porosity of at most 5 vol%.
Polishing tool as described. 4. The fragile filler is selected from the group consisting of graphite, hexagonal boron nitride, hollow ceramic spheres, feldspar, nepheline cyanite, pumice, calcined clay and glass spheres, and combinations thereof. Polishing tool as described. 5. The polishing tool according to claim 1, wherein the abrasive grains are selected from the group consisting of diamond, cubic boron nitride, and combinations thereof. 6. The polishing tool according to claim 5, wherein the abrasive is diamond having a grit diameter of 2 to 300 μm. 7. The metal binder comprises 35 to 84% by weight of copper and 16 to 65% by weight of tin.
The polishing tool according to claim 1, comprising: 8. The polishing tool according to claim 7, wherein the metal binder further contains 0.2 to 1.0 wt% of phosphorus. 9. The polishing tool includes at least two abrasive segments having an elongated, arcuate shape, and an interior curve selected to match the circumference of the core. And each abrasive segment has two ends designed to match the adjacent abrasive segments, so that the abrasive rim is continuous and when the abrasive segments are bonded to the core The polishing tool according to claim 1, wherein there is substantially no gap between the abrasive segments. 10. The polishing tool according to claim 1, wherein the tool is selected from the group consisting of a 1A1-type grindstone and a cup grindstone. 11. The thermally safe binder is selected from the group consisting essentially of epoxy adhesive binders, metallurgical binders, mechanical and diffusion binders and combinations thereof. Polishing tool.