MXPA01006959A - Superabrasive wheel with active bond - Google Patents

Abstract

A straight, thin, monolithic abrasive wheel formed of hard and rigid abrasive grains and a sintered bond including a metal component and an active metal component exhibits superior stiffness. The metal component can be selected from among many sinterable metal compositions. The active metal is a metal capable of reacting to form a bond with the abrasive gains at sintering conditions and is present in an amount effective to integrate the grains and sintered bond into a grain-reinforced composite. A diamond abrasive, copper/tin/titanium sintered bond abrasive wheel is preferred. Such a wheel is useful for abrading operations in the electronics industry, such as cutting silicon wafers and alumina-titanium carbide pucks. The stiffness of the novel abrasive wheels is higher than conventional straight monolithic wheels and therefore improved cutting precision and less chipping can be attained without increase of wheel thickness and concomitant increased kerf loss.

Description

SUPERBRASIVE WHEEL WITH ACTIVE LINK This invention relates to thin abrasive wheels for scraping very hard pads such as those used by the electronics industry. Abrasive wheels that are both very thin and extremely rigid are important from a commercial point of view. For example, thin abrasive wheels are used when cutting thin sections and performing other scraping operations in the processing of silicon wafers and so-called mixed alumina-titanium carbide discs in the manufacture of electronic products. Silicon pellets are generally used for integrated circuits and the alumina-titanium carbide discs are used to fabricate thin film heads to record and reproduce magnetically stored information. The use of thin abrasive wheels for scraping silicon wafers and alumina-titanium carbide discs is well explained in the U.S. patent. No. 5,313,742, the entire description of which is incorporated herein by reference. As mentioned in the '742 patent, the manufacture of silicon wafers and alumina-titanium carbide discs creates the need for dimensionally accurate cuts with little waste of the material of the workpiece. Ideally, the cutting blades to make such cuts should be as stiff as possible and as thin as convenient since the thinner the blade, the less waste will be produced and the stiffer the blade, the more straight it will cut. However, these characteristics are in conflict because the thinner the blade becomes, the less rigid it becomes. The industry has developed using monolithic abrasive wheels, usually coupled together on a shaft mounted on a tree. Individual wheels in the coupling are separated axially from one another by means of incompressible and durable separators. Traditionally, the individual wheels have a uniform axial dimension from the axle hole of the wheel to its periphery. Although quite thin, the axial dimension of these wheels is greater than desired to provide sufficient rigidity for good cutting accuracy. However, to keep waste generation within acceptable limits, thickness is reduced. This diminishes the rigidity of the wheel less than ideally. Therefore, it is seen that the conventional straight wheel generates more scrap from the workpiece than a thinner wheel and produces more shavings and inaccurate cuts than would a more rigid wheel. The patent 742 sought to improve on the performance of coupled straight wheels by increasing the thickness of an inner portion extending radially outwardly of the shaft hole. It was described that a monolithic wheel with a thick internal portion was stiffer than a straight wheel with spacers. However, the wheel of the patent 742 has the disadvantage that the inner portion is not used to cut, and consequently, the volume of abrasive in the inner portion is discarded. Because thin abrasive wheels, especially those for cutting alumina-titanium carbide, employ expensive abrasive substances such as diamond, the cost of a wheel of the 742 patent is high compared to a straight wheel due to the volume of abrasive discarded. It is advisable to have a thin, monolithic, straight abrasive wheel that has an improved stiffness compared to conventional wheels. In addition to the geometry of the wheel, the stiffness is determined by the intrinsic rigidity of the materials of the wheel construction. The monolithic wheels consist basically of abrasive grains and a bond that keeps the abrasive grains in the desired shape. Until now, a metal bond has typically been used for thin abrasive wheels which is intended to cut hard materials such as silicon wafers and alumina-titanium carbide discs. A variety of metal bonding compositions to hold diamond grains, such as copper, zinc, silver, nickel or iron alloys, for example, are known in the art. It has now been discovered that the addition of at least one active metal component to a metal bonding composition can cause the diamond grains to react chemically with the active metal component during bond formation thereby forming an integrated, reinforced mixed material. of grains. The very high intrinsic stiffness of the grains together with the chemical bond of the grains to the metal thus produces an abrasive structure of substantially increased stiffness.

Accordingly, the present invention provides an abrasive wheel comprising a monolithic, grain reinforced, abrasive disc having a uniform width in the range of about 20-2,500 μm, consisting essentially of about 2.5-50% by volume of abrasive grains in concretion, the active metal being present in an effective amount to produce an elastic modulus of the grain reinforced abrasive disc at least 24% higher than the elastic modulus of a concreted disc of the same composition but free of active metal. Also provided is a method for cutting a workpiece comprising the step of contacting the workpiece with an abrasive wheel comprising an abrasive, grain-reinforced, straight, monolithic disc having a uniform width on the scale of about 20-2,500 μm, consisting essentially of about 2.5-50% by volume of abrasive grains and a complementary amount of a bond comprising a metal component and an active metal that forms a chemical bond with the abrasive grains in specification, the active metal being present in an effective amount to produce an elastic modulus of the grain reinforced abrasive disc at least 24% higher than the elastic modulus of a concreted disc of the same composition but free of active metal. Also, this invention provides a method for making an abrasive tool comprising the steps of (a) providing preselected proportions of ingredients formed of particles comprising; (1) abrasive grains; (2) a metal component consisting essentially of a main copper fraction and a minor tin fraction; and (3) an active metal that can form a chemical bond with the abrasive grains in concreting; (b) mixing the ingredients formed of particles to form a uniform composition; (c) placing the uniform composition in a mold in a preselected manner; (d) compressing the mold at a pressure in the range of about 345-690 MPa for an effective duration to form a molded article; (e) heating the molded article to a temperature on the scale of approximately 500-900 ° C for an effective duration to concrete the metal and active metal component to a specified bond, thereby integrating the abrasive grains and concretely bonding into a mixed material reinforced grain; and (f) cooling the mixed grain reinforced material to form the abrasive tool. The present invention can be applied to straight, circular, monolithic abrasive wheels. The term "straight" means that the axial thickness of the wheel is uniform to all spokes from the radius of the tree hole to the outer radius of the wheel. An important application that is intended for these wheels is to slice thin sections such as pellets and disks of inorganic substances with precision and reduced cutting loss. Higher results are often achieved by operating the wheel at high cutting speeds, ie speed of the abrasive surface in contact with the workpiece. Said performance criteria and operating conditions are generally achieved by using wheels of extremely small, uniform thickness and a large diameter. Therefore, the preferred wheels of this invention prominently exhibit a characteristically high aspect ratio. The aspect ratio is defined as the ratio of the external diameter of the wheel divided by the axial cross-sectional dimension, that is, the thickness of the wheel. The aspect ratio should be about 20-6000, preferably about 100-1200, and most preferably, about 250-1200 to 1. The uniformity of the wheel thickness is maintained at a tight tolerance to achieve the desired cutting performance. Preferably, the uniform thickness is in the range of about 20-2,500 μm, most preferably, about 100-500 μm, and most preferably, about 100-200 μm. Variability in thickness of less than about 5 μm is preferred. Typically, the diameter of the shaft hole is approximately 12-90 mm and the wheel diameter is approximately 50-120 mm.

The term "monolithic" means that the abrasive wheel material is a uniform composition completely from the radius of the tree hole to the radius of the wheel. That is, basically the entire body of the monolithic wheel is an abrasive disk comprising abrasive grains embedded in a particular bond. The abrasive disc does not have an integral, non-abrasive portion for structural support of the abrasive portion, such as a metal core in which the abrasive portion of a grinding wheel is fixed, for example. Basically, the abrasive disc of this invention comprises three ingredients, namely, abrasive grains, a metal component and an active metal component. The metal component and the active metal together form a specific bond to maintain the abrasive grains in the desired shape of the wheel. The specific link is achieved by subjecting the components to suitable concretion conditions. The term "active metal" means an element or compound that is capable of reacting with the surface of the abrasive grains in the concretion. Therefore, the active metal is chemically bound to the abrasive grains. In addition, the active metal is present in an effective amount to integrate the grains and the concreted bond into a mixed grain reinforced material. Consequently, by judiciously choosing a suitably high stiffness as well as high hardness abrasive grains, the total stiffness of the concreted bond-bonding matrix is enhanced by the active metal component which chemically bonds to the abrasive grains during concretion.

A primary consideration in selecting the abrasive grain is that the abrasive substance must be harder than the material to be cut. Usually the abrasive grains of thin abrasive wheels will be selected from very hard substances because these wheels are typically used to scrape extremely hard materials such as alumina-titanium carbide. As mentioned, it is important that the abrasive substance also have a sufficiently high stiffness to reinforce the structure of the bond. This additional criterion for selection of the abrasive substance usually corresponds to ensuring that the elastic modulus of the abrasive substance is higher, and preferably, significantly higher than that of the particular bond. Representative hard abrasive substances for use in this invention are so-called superabrasives such as diamond and cubic boron nitride, and other hard abrasives such as silicon carbide, molten aluminum oxide, microcrystalline alumina, silicon nitride, boron carbide and carbide. tungsten. Mixtures of at least two of these abrasives can also be used. Diamond is preferred. Abrasive grains are usually used in the form of a fine particle. The particle size of the grains for wheels up to about 120 mm in diameter in general should be in the range of about 0.5-100 μm, and preferably, about 10-30 μm. The size of the grains for larger diameter wheels can be proportionally larger.

The metal component of this invention may be a single metal element or a mixture of multiple elements. Representative elements suitable for use in this invention include copper, tin, cobalt, iron, nickel, silver, zinc, antimony and manganese. Examples of mixtures include copper-tin, copper-tin-iron-nickel, copper-zinc-silver, copper-nickel-zinc, copper-nickel-antimony. Metal compounds such as cobalt-tungsten carbide, and nickel-copper-antimony-tantalum carbide, and alloys containing non-metals can also be used. The non-metallic component typically improves the hardness of the metal or reduces the melting temperature of the metal, which helps reduce the concreting temperature and thus prevents diamond damage from exposure to high temperatures. Examples of such compounds and alloys containing non-metals include nickel-copper-manganese-silicon-iron, and nickel-boron-silicon. The metal component is generally provided as a powder of small particle size. The powder particles of a multi-element metal component may be individual elements, pre-alloys or a mixture of both. Due to the active metal component, the concreted bond is chemically bonded to the abrasive grains rather than simply surrounding them. Therefore, the grains of the novel, actively linked, and thin abrasive wheel can be presented to the workpiece with greater exposure than the non-active linked wheel grains could. In addition, milder, concretely bonded compositions can be used. These characteristics provide the advantage that the wheel will cut more freely with less tendency to load, and therefore, operate at a reduced energy consumption. Copper-tin is a preferred composition for a metal component that produces a relatively smooth bond. For a copper-tin metal component, generally a main fraction (ie, >; 50% by weight) is copper and a minor fraction (ie, < 50% by weight) is tin. Preferably, the copper-tin composition consists essentially of about 50-90% by weight of copper and about 10-40% by weight of tin; most preferably, about 70-90% by weight of copper and about 10-30% by weight of tin; and most preferably about 70-75% by weight of copper and 25-30% by weight of tin. As will be explained by the following description of the preparation of the novel active bonded thin abrasive wheels, the metal component is usually supplied to the fine particle-shaped wheel manufacturing process. The active metal component is chosen for compatibility with both the metal component of the particular bond and with the abrasive grains. These are, under conditions of concretion, the active metal must be densified with the metal component to form a resistant concrete bond, and must react with the surface of the abrasive grains to form a chemical bond with them. The selection of the active metal component can depend considerably on the composition of the metal component, the composition of the abrasive grains, and concretion conditions. Representative materials for the active metal component are titanium, zirconium, hafnium, chromium, tantalum and mixtures of at least two of them. In a mixture, the active component metals can be supplied as individual metal particles or as alloys. Titanium is preferred, especially in relation to the copper-tin metal component and diamond abrasive. The active component can be added either in elemental form or as a metal compound and non-active component elements. The elemental titanium reacts with water and oxygen at low temperature to form titanium dioxide and, therefore, becomes unavailable to react with the abrasive during concretion. Therefore, adding elemental titanium is less preferred when water or oxygen is present. If titanium is added as a compound, the compound must be capable of dissociation to elemental form before the concreting step to allow the titanium to react with the abrasive. A preferred form of titanium compound for use in this invention is titanium hydride, TÍH2, which is stable up to about 500 ° C. Above approximately 500 ° C, the titanium hydride dissociates to titanium and hydrogen. Both the constituents of the metal component and the active metal components are preferably incorporated into the particle-shaped binding composition. The particles should have a small particle size to help achieve a uniform concentration throughout the concreted bond and optimum contact with the abrasive grains during concretion, and develop good bond strength to the grains. Fine particles of maximum dimension of about 44 μm are preferred. The particle size of the metal powders can be determined by filtering the particles through a sieve of specified mesh size. For example, nominal maximum particles of 44 μm will pass through a standard mesh screen 325 E.U.A. In a preferred embodiment, the actively bonded thin abrasive wheel comprises concreted linkage of about 45-75% by weight of copper, about 20-35% by weight of tin and about 5-20% by weight of active metal, the total increasing to 100% by weight. In a particularly preferred embodiment, the active metal is titanium. As mentioned, preference is given to incorporating the titanium component in the form of titanium hydride. The slight difference between the molecular weight of elemental titanium and titanium hydride can usually be ignored. However, for clarity it is noted that the compositions mentioned herein refer to the titanium present, unless otherwise specifically indicated. The novel abrasive wheel is basically produced by a densification process of the types called "cold press" or "hot press". In a cold press process, occasionally called "non-pressured concreting," a mixture of the components is introduced into a mold of desired shape and a high pressure is applied at room temperature to obtain a compact but friable molded article. Usually the high pressure is above about 300 MPa. Subsequently, the pressure is released and the molded article is removed from the mold and then heated to concretion temperature. The heating for concreting is normally performed while the molded article is pressurized in an inert gas atmosphere at a pressure lower than the pressure of the preconcretion step, ie, less than about 100 MPa, and preferably less than about 50 MPa. The concretion can also take place under vacuum. During this low pressure machining, the molded article, such as a disc for a thin abrasive wheel, can advantageously be placed in a mold and / or as a sandwich between flat plates. In a hot pressing process, the mixture of the components of the bonding composition formed from particles is placed in the mold, typically graphite, and compressed at a high pressure as in the cold process. However, an inert gas is used and the high pressure is maintained while the temperature is high thus achieving densification while the preform is under pressure. An initial step of the abrasive wheel process involves packing the components in a configuration forming mold. The components can be added as a uniform mixture of separate abrasive grains, constituent particles of metal component and particles constituting the active metal component. This uniform mixture can be formed using any suitable mechanical mixing apparatus known in the art to combine a mixture of the grains and particles in the preselected proportion. Illustrative mixing equipment may include double cone mixers, double deck V-shaped mixers, ribbon mixers, horizontal drum mixers, and fixed deck / internal screw mixers. Copper and tin can be prealloyed and introduced as bronze particles. Another option includes combining and then mixing to uniformity a composition formed of supplying bronze particles, additional copper and / or tin particles, active metal particles and abrasive grains. In a basic embodiment of the invention, the abrasive grains are uncoated before concreting the bond. That is, the abrasive grains are free of metal on their surface. Another embodiment requires pre-coating the abrasive grains with a layer comprising all or a portion of the active metal component before mechanically mixing all the components. This technique can improve the chemical bond formation between the abrasive grains and the active metal during concretion. The layer can be of molecular thickness, for example as can be obtained by chemical vapor deposition or physical vapor deposition, or of macromolecular thickness. If a molecular thickness is used, it is recommended to supplement the amount of active metal in the pre-coating with additional active metal in the mixture of grains and components of binding composition. Usually a pre-coating molecular thickness does not only possess a sufficient amount of the active metal to achieve the beneficial results that can be achieved by this invention. A coating of macromolecular thickness can be achieved (A) by mixing in the uniform composition a fine powder of the active metal component and an effective amount of a fugitive liquid binder to form a sticky paste; (B) mixing the abrasive grains with the adhesive paste to wet at least a major fraction of the grain surface area with the adhesive paste; and (C) drying the liquid binder usually with heat, to leave a residue of the active metal powder particles mechanically bonded to the abrasive grains. The purpose of mechanical bonding is to keep the active metal particles near the grains at least until concretion when the chemical bond makes the permanent bond. Any conventional fugitive liquid binder can be used for the paste. The term "fugitive" means that the liquid binder has the ability to empty the binding composition at elevated temperature, preferably below the concretion temperature and without having an adverse impact on the concreting process. The binder must be sufficiently volatile to evaporate substantially completely and / or pyrolyzed during concretion without leaving any residue that could interfere with the function of the bond. Preferably, the binder will vaporize below about 400 ° C. The binder can be mixed with the particles by many methods well known in the art. The mixture of components to be charged to the forming former mold may include minor amounts of optional process auxiliaries such as paraffin wax, "Acrowax", and zinc stearate which are commonly employed in the abrasive industry. Once the uniform mixture is prepared, it is loaded into a suitable mold. In a preferred cold press forming method, the contents of the mold can be compressed with mechanical pressure applied externally at room temperature at about 345-690 MPa. For this operation, for example, a platen press can be used. The compression is usually maintained for approximately 5-15 seconds, after which the pressure is released. The content of the mold is then raised to the concretion temperature, which must be high enough to cause the bonding composition to become densified but not substantially completely melted. The concreting temperature must be at least approximately 500 ° C. The heating must take place in an inert atmosphere, such as under vacuum at low absolute pressure or under a blanket of inert gas. It is important to select metal and active metal bonding components that do not require concretion at such high temperatures that the abrasive grains are adversely affected. For example, the diamond begins to graphitize above about 1100 ° C. Therefore, the concreting of diamond abrasive wheels must be designed to occur safely below this temperature, preferably below about 950 ° C, and most preferably below about 900 ° C. The concretion temperature must be maintained for an effective duration to specify the binding components and to react simultaneously the active metal with the abrasive grains. The concreting temperature is typically maintained for about 30-120 minutes. In a preferred hot press process, the conditions are generally the same as for cold pressing except that the pressure is maintained until the concretion ends. In the concretion without pressure or hot pressing, after the concretion, the molds are reduced to room temperature and the concreted products are removed. The products are finished by conventional methods such as stoning to obtain the desired dimensional tolerances. The concretion and bonding mentioned above therefore integrate the abrasive grains into the concreted bond to form a mixed grain reinforced material. To facilitate the formation of the mixed grain reinforced material as well as to provide well exposed abrasive, it is preferred to use about 2.5-50% by volume of abrasive grains and a complementary amount of binding specified in the particular product.

The preferred abrasive tool according to this invention is an abrasive wheel. Consequently, the typical mold shape is that of a thin disc. A solid disk mold can be used, in which case after concreting a central disk portion it can be removed to form the tree hole. Alternatively, an annular mold can be used to form the tree hole in situ. The second technique avoids wastes because the centrally charged abrasive portion of the concreted disk is discarded. By successfully forming a structure of mixed material reinforced with grains, the abrasive grains will contribute to the rigidity of the wheel. Therefore, as mentioned above, it is important that the abrasive be selected not only for traditional characteristics of hardness, impact resistance and the like, but also for stiffness properties as determined by elastic modulus, for example. While not wishing to be bound by any particular theory, it is believed that very rigid abrasive particles integrated in the bond concreted by virtue of chemical bonding with the active metal component contribute significantly to the rigidity of the mixed material. It is believed that this contribution occurs because stress loads in the mixed material during the operation are effectively transferred to the intrinsically very rigid abrasive grains. Accordingly, it is possible by the practice of this invention to obtain thin, actively bonded, straight abrasive wheels that are stiffer than conventional wheels of equal thickness. The innovative wheels are useful to provide more precise cuts and less formation of shavings without additional sacrifice of loss of cut in relation to the traditional straight wheels. The rigidity of the novel abrasive wheel must be considerably improved in relation to conventional wheels. In a preferred embodiment, the elastic modulus of the abrasive wheel in active form is higher than the elastic modulus of the concreted bonding components alone (ie, metal component plus active metal component free of abrasive grains) and is also at least about 100 GPa and preferably at least about 150 GPa. In another preferred embodiment, the elastic modulus of the wheel is at least about twice the elastic modulus of the concreted bond free of abrasive grains. This invention is illustrated by examples of certain representative embodiments thereof, wherein, unless otherwise indicated, all parts, proportions and percentages are by weight and the particle sizes are mentioned by means of the size designation. standard EU mesh screen: A. All the units of weight and measure not originally obtained in units Sl (international system of units) have been converted into units Sl.

EXAMPLE 1 Copper powder (mesh <400), tin powder (mesh <325) and titanium hydride (mesh <325) were combined in proportions of 59.63% Cu, 23.85% Sn and 16.50% TiH2. This binding composition was passed through a 165 mesh stainless steel screen to remove agglomerates and the sieved mixture was thoroughly mixed in a "Turbula" brand blender (Glen Mills, Inc., Clifton, New Jersey) for 30 minutes. Diamond abrasive grains (15-25 μm) from GE Superabrasives, Worthington, Ohio, were added to the metal mixture to form a mixture containing 18.75% by volume diamond. This mixture was combined in a Turbula mixer for 1 hour to obtain a uniform abrasive and bond composition. The abrasive and bonding composition was placed in a steel mold having a cavity of 121.67 mm external diameter, 6.35 mm internal diameter and uniform depth of 0.81 mm. A "n" wheel was formed by compacting the mold at room temperature under 414 MPa for 10 seconds. The n wheel was removed from the mold, then heated to 850 ° C under vacuum for 2 hours between flat horizontal plates with a weight of 660 g fixed on the top plate. The hot concreted product was allowed to cool gradually to 250 ° C and then cooled rapidly to room temperature. The wheel was milled to the final size by conventional methods, including "rectification" at a pre-selected discharge, and initial revival under the conditions shown in Table I. The finished wheel size was 114.3 mm external diameter, 69.88 mm of internal diameter (diameter of hole of tree) and 0.178 mm of thickness.

TABLE I EXAMPLES 1-2 of rectification conditions Rectified wheel Speed 5593 rev./min. Feed speed 100 mm / min. Exposure from the flange 3.68 mm Rectification wheel Model no. 37C220-H9B4 Composition Silicon carbide Diameter 112.65 mm Speed 3000 rev./min. Transverse speed 305 mm / min. No. of passes at 2.5 μm 40 to 1.25 μm 40 Initial revival Wheel speed 2500 rev./min. Revival rod Type 37C500-GV Width of the rod of 12.7 mm revival Penetration 2.54 mm Feed speed 100 mm / min. No. of passes 12.00 EXAMPLE 2 AND COMPARATIVE EXAMPLE 1 The novel wheel manufactured as deciphered in example 1 and a commercially available, conventional wheel of the same size (comparative example 1) were used to cut multiple slices through a block of 150 mm long x 150 mm wide x 1.98 mm thick alumina-titanium carbide type 3M-310 (Minnesota Mining and Manufacturing Co., Minneapolis, Minn.) glued to a graphite substrate. The wheel composition of Comparative Example 1 was 18.9% by volume of diamond grains of 15/25 μm in a bond of 53.1% by weight of cobalt, 23.0% by weight of nickel, 12.7% by weight of silver, 5.4% by weight iron weight, 3.4% by weight of copper and 2.4% by weight of zinc. Prior to each slice, the wheels were revived as described in Table 1 except that a single revival pass and a 19 mm wide (12.7 mm for revival rod for comparative example 1) were used. In each test the abrasive wheels were mounted between two metal support spacers of 106.93 mm outer diameter. The speed of the wheel was 7500 rev./min. (9000 rev / min for the example comp.1) and a feeding speed of 100 mm / min., And a cutting depth of 2.34 mm were used. The cut was cooled by a flow of 56.4 L / min. of demineralized water stabilized with 5% mold inhibitor discharged through a rectangular 1.58 mm x 85.7 mm nozzle at a pressure of 275 kPa.

The cutting results are shown in table II. The innovative wheel had a good performance against all cutting performance criteria. The wheel of comparative example 1 needed to operate at 20% higher rotational speed and extracted a power approximately 45% higher than the novel wheel (approximately 520 W vs. 369 W).

TABLE II Slices Length Wear Piece that Straightness Extraction wheel slice works of power cut ac. of rotation ac .. radial ac. Factor1 Chip Average maximum chip No. No. m μm μjm μpi / rn μ μ μm W Ex. 1 9.0 9.00 1.35 5.08 5.08 3.70 8.00 < 5 < 5 0 9.0 18.00 2.70 0.00 5.08 0.00 900 5.00 < 5 0 9.0 27.00 4.05 0.00 5.08 o.oo 11.00 5 < 5 368-296 0 9.0 36.00 5.40 10.16 15.24 7.40 6.00 < 5 < 5 O 9.0 45.00 6.75 2.54 17.78 1.90 10.00 5.00 5 0 9.0 54.00 8.10 2.54 20.32 1.90 11.00 5.00 < 5 312-368 0 9.0 63.00 9.45 10.16 30.48 7.40 8.00 < 5 < 5 0 9.0 72.00 10.8 2.54 33.02 1.90 9.00 < 5 < 5 0 9.0 81.00 12.0 2.54 35.56 < 0.5 9.00 < 5 < 5 376-328 0 Comp. 9.0 9.00 1.35 5.08 5.08 3.70 11.00 < 5 5 520-536 1 0 9.0 18.00 2.70 10.16 15.24 7.40 0 9.0 27.00 4.05 5.06 20.32 3.70 0 9.0 36.00 5.40 2.54 22.86 1.90 10.00 < 5 < 5 0 9.0 45.00 6.75 5.08 27.94 3.70 0 9.0 54.00 8.10 2.54 X.48 1.90 0 9.0 63.00 9.45 5.08 35.56 3.70 14.00 < 5 < 5 560-576 0 1 desgaper factor; 5te = Radial wheel wear divided by the length of the piece that is worked slice EXAMPLES 3 AND 4. AND COMPARATIVE EXAMPLES 2-8 The rigidity of the reinforced grain abrasive wheel compositions was tested. A variety of fine metal powders with and without diamond grains were combined in the proportions shown in Table III and mixed until the uniformity of the composition as in Example 1. Tension test models were produced by compressing the compositions in molds. in form of dog bone at room temperature under a pressure of about 414-620 MPa for about 5-10 seconds and then concreted under vacuum as described in example 1. The test models were subjected to sonic modulus and standard voltage measurements on an Instron tension testing machine. The results are shown in table III. The elastic modulus of the reinforced samples of grains (Ex 3 and 4) exceeded 150 GPa. The increased concentration of diamond in Example 4 increased the modulus significantly which confirms that the diamond was integrated into the composition. By contrast, comparative example 2 revealed that the same bonding composition without grain reinforcement due to the absence of diamond dramatically reduced rigidity. Similarly, Comparative Example 3 demonstrates that diamond embedded in a brass bond composition without an active component provides relatively poor stiffness.

In comparative example 4, diamond grains previously commercially available from General Electric Co. were used which, as mentioned by the manufacturer, were coated on the surface with a thickness of about 1-2 μm titanium. The rigidity improved slightly compared to not having an active component present (comparative example 3), but did not reach the operating example compositions. Possible reasons for the reduced effectiveness are that too small an amount of an active component was present, that the titanium on the surface was in carbide form prior to concretion which made the titanium less compatible with the other metal components, and / or that the titanium that was not carbide in the grains was oxidized. Comparative examples 5 and 7 demonstrate that conventional thin diamond wheels with different copper / tin / nickel / iron link compositions have modules of only about 100 GPa. Comparative examples 6 and 8 correspond to the wheel compositions of Comparative Examples 5 and 7 without diamond grains. These examples show that the rigidity of the bonding compositions with or without diamond was about the same. This confirms the expectation that the free bond of active metal component does not integrate the diamond in the bond to reinforce the structure.

TABLE III Ex Ej Ex Ej Ej Ej Ej Ej Ej Ej 3 Ej 4 Comp 2 Comp 3 Comp 4 Comp 4 Comp 5 Comp 6 Comp 7 Comp 8 Copper,% 5950 5950 5950 8000 8000 7000 7000 6200 6200 in weight Tin, 2400 2400 2400 2000 2000 9 10 9 10 920 920 % by weight Titanium, 1650 1650 1650% by weight Nickel,% 750 750 1530 1530 by weight Iron,% 1340 1340 1350 1350 by weight Diamond 1880 3000 1880 188 1880 1880,% by volume Module 17600 22000 6700 8000 9500 9900 sonic, GPa Module 27600 11000 6000 8400 10600 10300 9500 tension, GPa 'diamond coated with approximately 1-2 μm titanium Although specific forms of the invention have been selected for illustration in the examples, and the foregoing description is made in specific terms for the purpose of describing these forms of the invention, this description is not intended to limit the scope of the invention as defined in claims.

Claims (2)

NOVELTY OF THE INVENTION CLAIMS

1- An abrasive wheel comprising a grain reinforced abrasive disc, straight having a uniform width in the range of about 20-2,500 μm, consisting essentially of about 2.5-50% by volume of abrasive grains and a complementary amount of a bond comprising a metal component and an active metal that forms a chemical bond with the abrasive grains in the concretion, the active metal and the abrasive grains being present in an effective amount to produce a reinforced grain abrasive disc having a value of elastic modulus at least 24% higher than the elastic modulus value of an abrasive disc of the same composition but free of active metal.

2 - The abrasive wheel according to claim 1, wherein the abrasive grains have an approximate size of 0.5-100 μm and the reinforced grain abrasive disk has an elastic modulus value of at least about 100 GPa. 3. The abrasive wheel according to claim 2, wherein the elastic modulus value is at least about twice as high as the elastic modulus value of the same concreted bond composition free of abrasive grains. 4. - The abrasive wheel according to claim 3, wherein the abrasive disk consists essentially of about 15-30% by volume of abrasive grains. 5. The abrasive wheel according to claim 1, wherein the metal component is selected from the group consisting of copper, tin, cobalt, iron, nickel, silver, zinc, antimony, manganese, metal carbide and alloys. of at least two of them. 6. The abrasive wheel according to claim 1, wherein the metal component comprises a metal alloy or metal compound containing a material selected from the group consisting of boron, silicon, and compounds and combinations thereof. . 7. The abrasive wheel according to claim 4, wherein the active metal is selected from the group consisting of titanium, zirconium, hafnium, chromium, tantalum and a mixture of at least two of them. 8. The abrasive wheel according to claim 7, wherein the abrasive grains are free of active metal coating. 9. The abrasive wheel according to claim 7, wherein the abrasive grains are coated with a layer of macromolecular thickness of metal. 10. The abrasive wheel according to claim 1, which is monolithic. 11. The abrasive wheel according to claim 5, wherein the concreted bond comprises (a) about 45-75% by weight of copper; (b) about 20-35 wt% of tin; (c) about 5-20% by weight of active metal in which the total of (a), (b) and (c) is 100% by weight. 12. The abrasive wheel according to claim 11 in which the active metal is selected from the group consisting of titanium, zirconium, hafnium, chromium, tantalum, and a mixture of at least two of them. 13. The abrasive wheel according to claim 12 in which the active metal is titanium. 14. The abrasive wheel according to claim 1, wherein the abrasive grains are of an abrasive selected from the group consisting of diamond, cubic boron nitride, silicon carbide, molten aluminum oxide, microcrystalline alumina, silicon nitride. , boron carbide, tungsten carbide and mixtures of at least two of them. 15. The abrasive wheel according to claim 14, in which the abrasive grains are diamond. 16. The abrasive wheel according to claim 1, consisting essentially of the abrasive disk having a circumferential projection of about 40-120 mm diameter, which defines an axial shaft hole of approximately 12-90 mm, having a width uniform in the scale of about 100-500 μm and consisting essentially of diamond grains and a concreted bond comprising approximately 59.5% by weight of copper, 24% by weight of tin and 16.5% by weight of titanium. 17. - The abrasive wheel according to claim 16 in which the uniform width is in the range of approximately 100-200 μm. 18. An abrasive wheel comprising a grain reinforced, straight abrasive disc having a uniform width and an aspect ratio of about 20-6000 to 1, consisting essentially of about 2.5-50% by volume of abrasive grains and an complementary amount of a bond comprising a metal component and an active metal that forms a chemical bond with the abrasive grains in the concretion, the active metal and the abrasive grains being present in an effective amount to produce a reinforced grain abrasive disc that it has an elastic modulus value at least 24% higher than the elastic modulus value of an abrasive disk of the same composition but free of active metal. 19. A method for cutting a workpiece comprising the step of contacting the workpiece with an abrasive wheel comprising a grain reinforcing abrasive disc, straight having a uniform width in the scale of approximately 20-2,500 μm, consisting essentially of about 2.5-50% by volume of abrasive grains and a complementary amount of a bond comprising a metal component and an active metal that forms a chemical bond with the abrasive grains in the concretion, the active metal and the abrasive grains being present in an effective amount to produce a grain reinforced abrasive disk having an elastic modulus value of at least 24% higher than the elastic modulus value of an abrasive disk of the same composition but free of active metal. 20. The method according to claim 19 wherein the abrasive disk further comprises a circumferential projection of about 40-120 mm diameter, and an axial shaft hole of about 12-90 mm, and in which the component Metal is selected from the group consisting of copper, cobalt tin, nickel, silver, zinc, antimony, manganese, metal carbide and alloys of at least two of them, and the active metal is selected from the group consisting of titanium, zirconium , hafnium, chromium, tantalum, and a mixture of at least two of them, and the abrasive grains are of an approximate size of 0.5-100 μm, and the reinforced grain abrasive disk has an elastic modulus of at least about 100 GPa and said module is at least about twice as high as the elastic modulus of the concreted bond free of abrasive grains. 21. The method according to claim 20 wherein the metal component comprises a metal alloy or metal compound containing a material selected from the group consisting of boron, silicon, and compounds and combinations thereof. 22. The method according to claim 20 in which the circumferential projection diameter is approximately 50-120 mm, the uniform width is in the range of approximately 100-500 μm, and the abrasive disk consists essentially of diamond grains. and a concreted link consisting essentially of (a) about 45-75% by weight of copper; (b) about 20-35 wt% of tin; (c) about 5-20% by weight of active metal, in which the total of (a), (b) and (c) is 100% by weight. 23. The method according to claim 19, in which the workpiece is alumina-titanium carbide. 24. A method for making an abrasive tool comprising the steps of (a) providing preselected proportions of ingredients formed of particles comprising; (1) abrasive grains; (2) a metal component consisting essentially of a main copper fraction and a minor tin fraction; and (3) an active metal that chemically reacts with the abrasive grains under concreting conditions; (b) mixing the ingredients formed of particles to form a uniform composition; (c) placing the uniform composition in a mold in a preselected manner; (d) compressing the mold at a pressure in the range of about 345-690 MPa for an effective duration to form a molded article; (e) heating the molded article to a temperature on the scale of approximately 500-900 ° C for an effective duration to concrete the metal and active metal component to a specified bond, thereby integrating the abrasive grains and concretely bonding into a mixed material reinforced grain; and (f) cooling the mixed grain reinforced material to form the abrasive tool. 25. The method according to claim 24 further comprising the step of reducing the pressure in the molded article to a pressure of less than about 100 MPa after the compression step and maintaining the pressure to less than about 100 MPa during the heating step . 26. The method according to claim 25 wherein the molded article is reduced to and maintained during the heating step at a pressure of about 10-40 MPa. 27. The method according to claim 25 in which the abrasive tool is a disk having a uniform width in the scale of approximately 100-500 μm, a circumferential projection of diameter of approximately 50-120 mm and which defines an axial shaft hole of approximately 12-90 mm. 28. The method according to claim 27 further comprising the steps of removing the disk from the mold after the compression step and sandwiching the disk between flat plates deflected against the disk during the heating step. 29. The method according to claim 27 in which the disk has a uniform width in the scale of approximately 100-200 μm. 30. The method according to claim 20, wherein the heating step occurs while the molded article is maintained at the pressure of the compression step. 31. - The method according to claim 24, in which the abrasive grains are provided free of active metal coating. 32. The method according to claim 24, in which the abrasive grains are coated with a layer of macromolecular thickness of metal before the mixing step. 33. The method according to claim 24 wherein the ingredients formed from particles comprise (a) about 45-75% by weight of copper; (b) about 20-35 wt% of tin; (c) about 5-20% by weight of active metal selected from the group consisting of titanium, zirconium, hafnium, chromium, tantalum and mixtures of at least two of them, the total of (a), (b) and (c) ) is 100% by weight. The method according to claim 33 wherein the step of providing further comprises (i) mixing to the uniform composition a fine powder of the active metal component and an effective amount of a liquid binder to form a sticky paste; (ii) mixing the abrasive grains with the adhesive paste to moisten at least a major fraction of the grain surface area with the adhesive paste; and (iii) drying the liquid binder effectively to leave a residue of the active metal powder particles mechanically bonded to the abrasive grains. The method according to claim 24, wherein the abrasive grains comprise approximately 20-50% by volume of abrasive grains of ingredients formed from particles, and consist essentially of an abrasive selected from the group consisting of diamond, nitride cubic boron, silicon carbide, molten aluminum oxide, microcrystalline alumina, silicon nitride, boron carbide, tungsten carbide and mixtures of at least two of them. 36. The method according to claim 35, in which the abrasive grains are diamond.