MXPA00008891A - Superabrasive wire saw and method for making the saw - Google Patents

Abstract

A wire saw has a small diameter metal wire and a layer of abrasive grains firmly affixed to the wire surface by a brazed or soldered active metal bond. Preferably, the grains are present in a single layer. The grains are disposed on the surface of the wire in a preselected surface distribution. The wire saw can be made by a completely continuous process involving coating the wire with a paste of metal bond powder components combined with a fugitive liquid binder component. Abrasive grains are deposited into a layer of the paste. Thereafter, the bond composition is fused at a elevated temperature to braze the grains to the wire. The abrasive grains can include superabrasive materials, such as diamond and cubic boron nitride. Accordingly, the novel wire saw is suitable for cutting ultra thin wafers ceramic wafers with minimum waste of the work piece.

Description

SUPERABRASIVE WIRE SAW AND METHOD TO MAKE THE SAW DESCRIPTIVE MEMORY This application is a continuation in part of the serial number of E.U. A. No. 09 / 038,300, filed March 8, 1998. The invention relates to a wire saw studded with superabrasive sand, more specifically, it refers to a wire saw having superabrasive particles fixed directly on a substrate of fine metal wire with hard or soft solder of active metal. The technology of wire saws is used in a variety of industrial applications. These wire saws have been used to cut rock in the mining industry. Conventional wire saws generally have abrasive globules strung along a wire, cable or rope threaded through a central bore of each bead. The abrasive grains are embedded to the outer surface of the beads and the beads are displaced longitudinally on the wire by spacers. See, for example, E.U.A.-A-5,377,659 to Tank et al. Also, U.S.-A-5,383,443 to Buyens provides an improvement to a wire saw with beads in which the beads are mounted eccentrically on the wire. China Grinding Wheel Co., Taipei, Republic of China, offers ^^^^ Wta a wire saw with globules that uses diamond grains welded in hard to the globule. These globules are obtainable under the tradename Kinik® DiaGrid® Pearls for use in cutting construction material such as marble, serpentine, granite and concrete. 5 Diamond-containing metal matrix segments have been welded into hard, high-wire cut slots (eg, 4.4 mm in diameter) to make stone cutting saws for the construction industry. See E.U.A.-A- 3,886,925. A wire saw made with sand abrasive grain relatively thick (45-150 microns), adhered to the tungsten or molybdenum wire, is disclosed in JP-A-3-104553. The patent directs the user to avoid a chemical reaction between the strong solder composition and the wire in the abrasive grain. Silver-copper solder is used for this purpose. A method and apparatus for making "armored" rod saws and disclosed in US-A-3,854,898 uses temperatures of about 1010-1180 ° C for hard welding of abrasive grains, such as tungsten carbide, to steel rods or wires from 0.5 to 6.35 mm in diameter. They are used in saws to cut refractory materials, steel pipe, cement or asbestos, brick and the like. Slicing of ceramics, especially single crystal silicon blocks which are occasionally referred to herein as a silicon microcrystal, to make thin plates is very important for * É * m m ***, the microelectronic, optical and photovoltaic industries. The presence of the cut is important to produce plates that are flattened to a high dimensional tolerance. Traditionally, the ceramic plates have been made by sawing the microcrystal with an unusual rubbing wheel having an abrasive adhering to the inner diameter of a central hole. Such "inner diameter sawing" allows extremely accurate cutting, but is limited to slicing only one plate at a time. The sawing with wire has been recently applied to the production of ceramic plates. Increased productivity can be obtained by using a long wire ribbon inserted in such a manner that many steps are made across the length of the microcrystal, thereby slicing many plates simultaneously. The piece of work is of very high quality and, therefore, even the slight wear of the starting material can be very expensive. The previous technology of wire saws involves using simple metal wire and loose abrasive grains applied to the interface between the wire and the microcrystal. Wire-saws or saws for conventional stoneworking are generally not suitable for the precision rubbing required for slicing plates. The globules increase the effective thickness of the tool that cuts too wide a sawing through a work piece. The mass of the workpiece removed by the saw with globules can be many times that of the plate alone. The use of spacers and sleeves further complicate the manufacture of saws with íííto | - "" - • * - - - * - -. -. . - -t¿ * -2 .. «~ - .. ^ A _., .. ^^., _,, .r,, .t,,«. globules. Another technique that could reduce the sawing of a wire saw for slicing plates involves the electrochemical deposition of abrasive directly on the wire substrate. Electrochemical deposition generally requires placing an electrically charged wire in a bed of abrasive particles in a liquid solution oppositely charged with an elemental compound. As the metal falls on the wire, it picks up the abrasive particles inside the thin metal layer and adheres the abrasive to the wire. For example, E.U.A.-A-5,438,973 to Schmid et al. exposes sheets having diamond abrasive particles fixed in a nickel layer to a cutting surface of a stainless steel wire core with a drop-shaped cross section. The wire saws made by electrochemical arrangement have the main drawback that there is no chemical bond between the abrasive coating and the deposit. During operation, the outer surface of the thin layer wears quickly and the abrasive particles are easily dislodged from the wire, when approximately half of the deposited metal wears out. Consequently, the saw becomes ineffective prematurely, that is, before the abrasive particles get blunted. The applied material can also be separated from the wire under cyclic loading. Another drawback of electrochemically deposited wire saws is that they are expensive to manufacture. The mass of abrasive in the - * • * "The bed should be much larger than the one that actually ends up on the wire." Of course, superabrasive particles are considerably expensive and the need to maintain an inventory of particles in the bed increases the cost. The distribution of abrasive particles on the wire is not practicable.It is desirable to have a superabrasive wire residue having a small cross-sectional dimension, especially for cutting thin sections such as ceramic plates.A superabrasive wire saw is also needed. have long service life that is simple and relatively inexpensive to do.It is also desired to have a procedure to make such a wire saw that provides sensitive precise control of the abrasive distribution on the wire, while minimizing thermal damage and maintaining the mechanical strength of the wire According to this, the present invention provides a saw wire comprising a core metal wire and an abrasive layer, characterized in that the abrasive layer has abrasive grains affixed directly to the wire by a welded metal adhesion substance and the abrasive grains comprise superabrasive grains. A wire saw is also provided comprising a metal core wire bonded by a metal adherent substance to an abrasive layer, characterized in that the abrasive layer has abrasive grains fixed directly to the wire by a hard-tack metal adherent substance; the wire saw has a maximum cross-sectional dimension of 150-250 μm; and the abrasive grains are superabrasive grains present in a layer of single particle thickness. A method for making a wire saw of metal wire, adherent metal composition and abrasive grain is also provided, characterized in that the method comprises the steps of: (a) providing a paste comprising a composition of adhesive substance of metal selected from the group consisting of a hard metal solder composition and a solder composition in soft metal; (b) coating the surface of a wire with a layer of the paste; (c) depositing a layer of abrasive grains on the paste layer; (d) heating the wire in an inert atmosphere at a temperature of at most 950 ° C and for an effective duration to melt the sticky substance composition; and (e) cooling the wire by adhering the grains to the wire. In one aspect, the wire saw according to the present invention includes a metal wire core and a single layer of abrasive grains affixed directly thereto by a hard or soft metal bonded substance, which is preferably a substance adherent of active metal. The saw can be used in conventional cutting operations. Accordingly, the wire must be capable of ^ ^ ^ ^ * ^^^^ * ^^^ resist the stress, heat and bending to which such saws are usually subjected. Therefore, the wire material must have sufficient strength, flexibility and high melting temperature so that it can serve satisfactorily in cutting. The wire metal must also be melted at a temperature sufficiently far greater than the liquid phase temperature of the metal adherent substance so that the wire is not weakened or otherwise adversely affected by hard and soft welding of the beads to the wire. . Representative wire metals include iron, nickel, cobalt, chromium, modililene, tungsten and alloys containing any of them (e.g., nickel alloy Inconel). Steel is applicable for soft welding procedure; however, it may lose tensile strength due to exposure to hard solder temperature. High carbon steel is usually less affected by hard welding at high temperatures. The strength of the high grade steel wire can be recovered by including a tempering step (i.e., rapid cooling) to the process. Tungsten is preferred because it is substantially unaffected by the heat treatment involved in making the wire saw; however, any metal having the specific conformation and physical properties would be suitable for its use of this invention. As used herein, "hard solder" or "hard solder" refers to a process by which a metal of adherent substance, which has a melting point lower than the materials being joined, is heated, at an elevated temperature of 400 ° C or above which the metal flows and then cooled to a temperature at which the metal solidifies to form an adherent substance. The term "soft-solder" or "soft-solder" refers to a brass-like metal adherent material 5 that flows at temperatures below 400 ° C (for example, 200-399 ° C). Preferably, the wire has a cylindrical geometric configuration characterized by a longitudinal axis and a perpendicular circular cross section thereof. You can get wire saws suitable, adapted for specialized benefits through the use of non-circular wires of cross section. For example, the cross section may be oval, flattened, non-squashed, rectangular, such as square, trapezoidal and low-order polygonal, ie polygons of 3-6 sides. By "squashed" it is implied that the wire is section A rectangular cross section, with a high aspect ratio, like a belt, that is to say, having a characteristic long dimension and a characteristic wide dimension, the wide dimension being less than about 10% of the long dimension. One can appreciate that tapes made in accordance with the invention can be useful as bandsaw blades, including those with abrasive sand placed on the entire surface or only part of the surface of the sheet. According to a main purpose of the wire saw to cut thin ceramic plates, namely "precision cutting", the diameter - • * "•• - * ---" - - • * The wire should be as small as practicable to minimize cutting loss. The tension on the wire during sawing effectively limits the diameter. The wire diameter in its largest dimension will usually be in the range of about 140-1000 μm 5, and preferably about 150-250 μm. In another aspect of this invention, the wire saw may also be useful for cutting construction material or rock, such as in mining applications, ie in "coarse cutting" benefits. To obtain an effectively strong wire with the appropriate duration of the As a tool for such benefits, the diameter of the wire must be increased significantly to the range between about 1-5 mm. In coarse-cut applications, a single-wire metal wire may be used or multiple strands of the metal wire may be braided together to obtain the cable or rope of the desired total diameter. It can be welded in hard abrasive to substrates of single or multiple branches. Consistent with the stated primary purpose of the novel wire saw of slicing ceramic plates and, especially, silicon plates, the abrasive sand preferably comprises a superabrasive. The diamond, cubic boron nitride and mixtures thereof in any proportion are adequate. The diamond can be natural or synthetic. The abrasive component of the saw may also include non-superabrasive particles in combination with superabrasives, with the proviso that the superabrasive can withstand the hard welding procedure with ? "fame*"**. «,» ».«. . . _t i j. , -.to. - »- t * - - • -Hr '....- ..,. * -, -..-". ..... -, -. -. *. ^ í -. i * - metal for its substance adherent to the wire. Preferably, the main fraction, ie greater than 50% by volume of the abrasive component will be superabrasive. Representative non-superabrasives which are useful include silicon carbide, aluminum oxide, tungsten carbide and the like, which has a Knoop hardness value of about 1000-3000 measured under an applied load of 500 g. Particular preference is given to a wire saw in which the abrasive component is exclusively superabrasive. In a preferred embodiment, the abrasive particles are placed on the wire in substantially a single particle thickness layer. The term "single particle thickness layer" means that a single layer of abrasive particles is present on the substrate. Grains must also be selected to provide a limited distribution of particle sizes. This provides a more uniform cutting edge of the saw. You can "rectify" the saw to produce a more precisely uniform cutting edge; however, generally the more similar in size the particles are, the less rectification is needed. The distribution of particle sizes can be controlled by selective multiple sieving of the sand supply. For precision cutting, preference is given to particles of about 5-50 μm or the uniform distribution of particle sizes in which at least about 90% of the grains are approximately 0.85-1.15 of the average size of the particles. grain. Accordingly, the total cross-sectional dimension of the novel wire saw having abrasive for the precision friction of ceramic plates should preferably be about 180-300 μm. For coarse rubbing, abrasive sand of large particle size, i.e. approximately 600 μm, is preferred, and thus the total cross-sectional dimension of the saw will be approximately 2.2-6.2 mm. As mentioned, the grains are fixed directly to the metal wire preferably by a hard or soft-welded metal adherent substance, and more preferably an adherent active metal substance. Compositions for hard or soft metal weldings for securing the abrasive grains to a metal tool preform are well known. Illustrative compositions of metal adhesion substance include gold, silver, nickel, zinc, copper, tin, alloys of these metals and alloys of those metals with other metals, such as phosphorus, cadmium, vanadium and the like. Minor amounts of additional components in the composition can generally be included to modify the properties of the adherent substance, for example to modify the melting temperature, the melt viscosity, the wetting of the abrasive surface and the strength of the adherent substance. Bronze-based alloys or copper / tin nickel based alloys are preferred for abrasives of adherent substance, especially superabrasives to metal. By "adherent substance of active metal" is given to understand an adherent substance created from of a metal composition as described above to which certain so-called "active metals" or "reactive metals" are additionally incorporated. These active metals are characterized by an ability to react with carbon or nitrogen to form carbides or nitrides while the metal adherent substance composition is melted at an elevated temperature from the hard welding process. The carbides or nitrides thus formed are chemically compatible with the abrasives in order to improve the wetting of the superabrasive particles by the liquid or melted tackifier composition and promote the bond strength between particle and adherent substance. Representative active metals of particularly high value for diamond bonding include titanium, tantalum, chromium and zirconium. Generally, the active metals must be present as a minor fraction of the metal adherent substance composition and can be as low as about 0.5% by weight thereof. A particularly preferred active metal adhesion substance composition comprises a bronze-titanium alloy. The bronze alloy is preferably about 10-30 wt.% Tin and more preferably about 23-25 wt.% Tin, the complementary amount to be 100 wt.% Total being copper. Titanium is present in about 2-25% by weight and preferably about 5-10% by weight. Particular preference is given to the active metal adherent substance compositions comprising about 19-21% by weight of tin, about 69-73% by weight of copper and about 8-10% by weight of titanium. The titanium must be in the adherent substance composition in a form that can react during hard welding. It can be added either as an element or as a compound. Elemental titanium reacts with water at a low temperature to form titanium dioxide and could thus be rendered inapplicable to react with the diamond during hard welding. Therefore, adding elemental titanium is less preferred when water is present. Water can sometimes be a constituent of the liquid binder, described above. If titanium is added as a compound, the compound must be capable of dissociation during the hard welding step to allow titanium to react with the superabrasive. Preferably titanium hydride, TiH2, which is stable up to about 500 ° C, is added in titanium to the adhering substance material.

Above approximately 500 ° C, the titanium hydride dissociates into titanium and hydrogen. In yet another highly preferred embodiment, the active metal adherent substance composition may contain bronze, titanium and minor fractions of other active ingredients, such as zirconium and elemental carbon. Zirconium is added mainly to increase the Viscosity of the adherent material in the molten state during hard welding. Preferably, the zirconium is added in elemental form. Zirconium in the form of a compound, such as zirconium hydride, is usually unstable because the compound does not dissociate to elemental zirconium at hard or minor welding temperatures. The carbon reacts with excess free titanium present in the adherent substance material during the adherent substance to form titanium carbide particles. The benefit of titanium carbide is discussed below. The carbon can also react with zirconium to form hard zirconium carbide. Such a composition comprises 100 parts by weight (w / w) of bronze alloy consisting essentially of about 10-30 wt% of tin and the remainder copper, about 10-20 wt / w of titanium about 5-10 w / w. of zirconium and approximately 0.1-0.5 w / w of elemental carbon. In another preferred embodiment any path, fine particles of a hard material, especially titanium carbide, can be added to the adherent substance composition, as set forth in U.S.-A-5,846,269. Other hard materials are also useful, such as titanium diboride, tool steel and carbonyl iron, as well as hard filler mixtures. The titanium carbide can be produced in situ as mentioned previously. It has been found that carbide and titanium particles can raise the impact strength of the hard-welded metal adhesion substance and thus provide an adherent substance of improved wear resistance. Preferably, the hard particles should be of a particle size of between about 1 μm and about 10 μm. When using soft solder, a metal-coated diamond (for example copper, titanium, nickel or chromium coating of 1 to 10 μm) is needed to ensure adequate wetting of the diamond and "R,., Ji, í ,. alJH ^. l ^ ^. . i i .. •. _ -. _. - - - - > ^. -to. ... J. . . - - - or - - - - - - - • - '»--'- effectively adhere the diamond to the wire. Suitable coated diamonds are obtainable from Tomei Dia (for example an IRM-CPS diamond coated with 50% by weight copper (approximately 2μm)). The reactive elements used in the hard solder compositions for this purpose do not react at soft solder temperatures and are thus not useful in soft solder compositions to improve the retention of the abrasive grains. A suitable composition of soft welding to make the wire saws is an almost eutectic material of tin and silver flowing at 221 ° C. A preferred soft solder composition comprises this tin and silver alloy (4 wt.% Silver in the alloy), together with 1-2 wt.% Copper and 10 wt.% TIB2 as a hard filler. Suitable soft solder compositions may include silver, tin, copper, zinc, cadmium and lead, and preferred compositions include soft solders of hard tin-based alloys such as a tin and lead eutectic material. The technique of coating abrasive grains before hard welding with an active metal can be applied to the present invention. In the case of hard solders of nickel-based alloys, a layer preferably of carbide, active metal, such as titanium, tungsten and zirconium can be used. The metal can be placed on the abrasive by well known methods, for example physical vapor deposition and chemical vapor position. As it is exposed in E.U.A. 5,855,314, which is incorporated by ~ - * - - ***** * to reference herein, it has been recently identified that if these advantages result from pre-coating the abrasive grains with a mechanically adhered layer of a first active component together with the use of a composition of hard solder copper / tin alloy containing a second active component. More specifically, the total amount of active component present in the resulting hard-welded composition is much less than necessary by adhesions made by incorporating only one active component in the hard-solder composition. This creates a strong injury to the abrasive, but minimizes the amount of active component available to form intermetallic compositions. Generally, the components of the adhering substance material are supplied in powder form. The particle size of the powder is not critical; however, powder less than about 325 mesh (44 μm particle size) is preferred. The adherent substance material is prepared by mixing the ingredients until the components are dispersed to a uniform concentration. The sticky substance in dry powder can be mixed with a liquid binder of low viscosity and unstable. The binder is added to the powder components in an effective portion to form a viscous sticky paste. In paste form, the adherent substance material can be delivered accurately and is adhesive to both the wire surface and abrasive grains. The viscosity of the pulp can vary within the wide range dependent on the procedure used to apply the pulp to the wire. Preferably, the paste of the adherent substance material must have the consistency of the toothpaste. The term "unstable" means that the binder must be sufficiently volatile to evaporate and / or pyrolize substantially completely during hard welding without leaving a residue that could interfere with the function of the adherent substance. Preferably, the binder will be evaporated at less than about 400 ° C. However, the volatility of the binder must be sufficiently low that the paste remains fluid and tacky at room temperature for a reasonable time ("drying time") to apply the adherent material and the abrasive to the wire. Preferably, the drying time should be about 1-2 hours at room temperature. Suitable liquid binders to meet the requirements of the novel tackifier material are commercially obtainable. Representative paste-forming binders suitable for use in the present invention include Braz ™ -Binder Gel from Vitta Company; "S" binder of Wall Colmonoy Corporation, Madison Heights, Michigan; and Cusil-ABA, Cusin-ABA, and Incusil-ABA from Wesgo, Belmont, California. Active metal hard solder composition pastes including premixed binder with hard metal solder composition components can be obtained from Lucas-Millane Company, Cudahy, Wisconsin under the tradename Lucanex ™, such as Lucanex 721. The binder can be mixed with powders by many The methods well known in the art, such as high shear mixing. The order of mixing the powders and the liquid binder is not critical. The paste is applied to the wire by any of the methods well known in the art, such as brushing, spraying, composition or emergence of the wire tool in the paste. The novel wire saw can be produced considerably efficiently by a continuous process. The wire can be conveniently supplied on a reel. The reel is unwound by pulling the wire through an area where the abrasive and adherent substance precursor is deposited. Optionally, you can notice the wire, for example by mechanically or chemically cleaning the surface to remove the oxides or to roughen the surface for the best adherent substance of the grains and of the adhering substance materials to be added. In one embodiment, the adherent substance precursor and the abrasive grains are applied sequentially. That is, while continuously pulling the wire through the deposition zone, a hard solder paste composition is first applied on the wire surface. The pasta layer forms a bed to receive the grains. After that, the abrasive grains are deposited in the pulp bed. The thickness of the hard solder paste layer should generally be approximately 100-200% of the average grain size.

This thickness is governed by factors such as the abrasive concentration and the binder reaction used to make the paste of desired properties. Abrasive grains can be deposited by any methods, for example, by individual placement, sprinkling or sprinkling. Such processes make it possible to place the abrasive grains on the substrate at a preselected distribution of the surfaces. The distribution of the surface of the grains can be continuous or intermittent. The intermittent distribution of the surfaces is characterized by abrasive-free regions along the wire between the regions occupied by the abrasives. An intermittent distribution of the surfaces tends to reduce the forces exerted on the wire and promotes the effective elimination of minutes. The continuous distribution of the surfaces can be uniform and optionally non-uniform over the length of the wire saw. A non-uniform continuous distribution of the grains can approximate the realization of an intermittent distribution of surfaces. Optionally, any well-known filler components for use in abrasive tools can also be applied to dilute the other components. Generally, such filler components are inert to the hard welding process. That is, it does not react appreciably with the components of the hard solder composition, the abrasive grains by metal wire. A particular manufacturing method involves stretching the wire horizontally through the deposition zone while the * ~ í,. ÍÍ .lA * nin, * a. ,. «. . . ., »» »- - - ..» -.- ». - < * -. - ... »- *. ».- ........ .. - > J ». beads vertically down on the coated wire. This method characterizes the ability to control the distribution of the surfaces of the grains on the wire. That is, the distribution of the surfaces can be easily adjusted, indicated by the number, volume or weight of the abrasive grains per unit of wire surface, also by the rate of spraying of the grains on the coated wire in movement. to achieve any desired distribution of surfaces. Additionally, the amplitude of the spray may be pressed or otherwise varied periodically to achieve a periodic longitudinal variation in surface deposition. Alternatively, the wire can be passed through a fluidized bed of grains in a carrier gas. The sequential nature of the coating deposition steps is further characterized by the ability to deposit the abrasive grains substantially in a layer of single particle thickness. Since the grains are temporarily held in place prior to hard welding by the tackiness of the paste that is in the layer in contact with the wire, it is not possible for multiple layers of grains to form. As an optional step, the wire can be shaken gently to dislodge excess or loosely held grains. In addition, the wire can be stretched again through the deposition zone to increase the total distribution of surfaces and improve distribution in sparsely populated areas. Grains deposited vertically on a horizontal wire are not expected to contact the bottom of the wire. To coat the wire surface evenly, it is recommended to rotate the wire around its longitudinal axis through a preselected angle of rotation. Subsequently, the wire rotated through the deposition zone can be stretched again to allow the grains to fall on the recently turned up portion of the wire surface. Another method is contemplated for depositing the grains on the wire surface of a single step. This involves coating the circumference of the wire with hard solder paste. The coated wire can then be pulled up through a hole in the base of a colic deposit containing loose abrasive grains. The check and dimensions of the hole are selected to be slightly larger than those of the wire. Preferably, the gap between the hole and the wire is less than the average grain size to prevent the grains from falling through the hole. As the wire is drawn through the hole, the grains adhere to the sticky surface and pull together with the wire. The new grains are motivated by the conical conformation of the deposit to make coalition on wire that emerges from below. The conical reservoir may be vibrated or otherwise agitated to provide even distribution of the grains around the orifice. In another embodiment, the paste and the grains are applied concurrently. That is, the grains are premixed with the hard solder paste.

The paste that has the grains is then applied to the bare wire. Preferably, the grains should be dispersed in the paste at a uniform concentration. The paste can then be applied to the wire by conventional wire coating methods. It is preferred that the excess thickness of the pulp having grains be removed to ensure that only one layer of the thickness of a single particle of abrasive remains on the wire. It can be appreciated well that a layer of abrasive of the thickness of multiple particles can provide extended abrasive durability which is sometimes very important. Extended durability is especially desirable in coarse-cut benefits in which the widest sawing of the multi-particle-thickness wire saw can be tolerated. Accordingly, the embodiment of the premixed grain / solder paste can also be used to provide an abrasive layer of multiple particle thickness. This is accomplished by placing an appropriately coarse layer of pre-blended grain / solder paste in a single step or forming a thick layer by repeatedly depositing and welding in thin layers in multiple passes. The single pass method is preferred because it reduces the exposure of the wire to high temperatures that can weaken the wire. It is not intended that the aforementioned methods and apply the solder paste in hard and abrasive particles are limiting. It is contemplated that other variations for preparing the mixed wire body, the hard-welded metal adherent substance composition and the hard-soldered abrasive that are apparent to one skilled in the art, fall within the scope of this invention. After the composition of the hard-welded metal adherent substance and the abrasive grains are in place on the wire, the adherent substance composition is subjected to heat treatment to finally hard weld the grains firmly to the wire. The mixed wire body / adherent / abrasive substance composition should be maintained at an intermediate temperature, usually much lower than the hard welding temperature for a duration sufficient to volatilize the unstable component of the liquid binder. After that, the temperature can be raised to melt the adherent substance components. This procedure can be carried out continuously by passing the moving wire through the process areas maintained in appropriately preselected conditions. At the conclusion of the procedure, the wire can be wound on a reel for storage. Hard solder is performed at selected elevated temperatures in consideration of numerous system parameters such as a solid-liquid temperature range of the hard solder metal tackifier composition, the geometrical configuration and the construction material of the solder. wire and the physical properties of the abrasive. For example, diamond can be graphitized at temperatures Superiores above about 1000 ° C in the air and above about 1200 ° C under vacuum or an inert atmosphere. Of course, the temperature at which the diamond is graphitized depends on the duration of the exposure. Also as mentioned, exposure to elevated temperatures can adversely affect the resistance of the wire. Therefore, it is often desirable to hard weld at the lowest possible temperatures. The hard metal solder composition for hard solder preferably should be selected at about 800-1150 ° C and, more preferably, at about 850-950 ° C. The heat treatment must be carried out in an inert atmosphere to protect against the undesirable oxidation of the hard solder components. The inert atmosphere can be affected well with an inert gas, such as nitrogen or argon, well with a complete vacuum, that is to say below approximately 0.001 mm Hg absolute. The heating can take place in an oven. Other suitable methods of heating include heating by electrical resistance and methods of heating localized areas, such as induction heating, laser heating, infrared radiation heating and electronic gas heating, and combinations of any of these. Localized heating methods reduce the potential to weaken the wire due to overexposure at high temperatures. Heating methods by localized areas are also given the opportunity to create intermittent abrasive coating including precise patterns of adherent substance of hard welded metal and grains on the wire. In such a case, the non-welded material can be removed hard, for example by brushing, stirring or blowing air into the wire. The stolen materials can be recovered for possible recirculation. When a soft weld is used to make the wire, soft metal welding with an aqueous binder system can not be applied because the hydrocarbon flow needed for effective soft welding is incompatible with the aqueous binder system. Instead, it is applied in metal of the soft solder composition as a paste in a hydrocarbon base. A suitable hydrocarbon is petroleum ointment. Paraffin oils and waxes are also useful. In a particularly preferred method for making the novel wire saw, a metal wire of circular cross-section from a supply spool is drawn and directed downwards along the central axis of a vertical cylindrical pulp chamber. The wire enters through a sealed hole in the chamber layer. The chamber is packed with a uniform mixture of superabrasive grains, a paste of a hard or soft solder metal adhesion substance composition and an unstable liquid binder or a hydrocarbon base, respectively. The wire is removed from the bottom of the chamber through a circular hole having an inner diameter greater than the diameter of the wire. Optionally, pressure is exerted on the mixture, for example by pumping new mixture of abrasive / solder paste into the chamber or compressing the mixture with a piston. The wire that comes out of the hole is coated with the abrasive grains embedded in the metal paste. The diameter of the hole is selected to ensure that the grain layer on the wire is either of a single particle thickness or of a multiple particle thickness. The coated wire immediately descends to a vertical furnace with multiple temperature zones. The region above the furnace to which the wire is exposed is controlled at intermediate high temperatures in the range of about 250-500 ° C. As the temperature of the wire increases in this region, the unstable liquid component of the binder volatilizes. If any reactive metal component, such as titanium hydride, is present, it also reacts to deposit active metal in the hard solder composition. The lower regions of the furnace are controlled independently at higher temperatures up to the hard soldering temperature in one or more zones. The height of the furnace zones, the temperatures of the zones and the linear speed of the wire passing through the furnace determines the duration of exposure to the various temperatures. The furnace can be sealed for its isolation from the ambient temperature. An entry in the base and an outlet in the upper part of the furnace are provided to sweep the interior with an inert gas. The hot wire welded in hard leaves the furnace through a central hole in the base. It is pulled by a rotating pulley that redirects the wire to a winding reel that oscillates horizontally. The rotating pulley can be located in a low temperature bath, it will reflect before the liquid to temper the wire before winding it. The pulley also puts the wire in tension, so that it passes through the center of the hole and the furnace. As mentioned, the wire saw of this invention is suitable for cutting thin ceramic plates from a workpiece. The conformation of the piece of work or ceramic is not critical. It is typically single cylindrical crystal up to about 20 cm in diameter. The wire saw may include a single wire sheet configured similar to a band saw to cut a single plate of a workpiece in each step or to cut multiple plates in one step, for example as set forth in US Pat. No. 5,616,065 of 15 Egglhuber, which is incorporated herein by reference. A series of conical blades may also be configured in front of one another to simultaneously cut multiple plates of a workpiece as shown in Figure 4 of the U.S. patent. No. 5,438,973 mentioned above. Due to the fixation of a single layer of small abrasive particles of uniform size, directly on a wire of small dimension discarding that of salt, the novel saw can cut thin plates (ie, thin as approximately 300 μm) with very little wear of work piece material. Minimal wear and high efficiency was observed Mjj ¿áMMMaMJ ^ - ^ - atM- ^ M ^ MM ^^^^^ _ ^^ il ^ M ^ _ ^ _, t t A m htmt. i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i - cut when the wires described in the following examples were used in ceramic cutting tests. This invention is illustrated by the following examples, in which all the parts the proportions and the percentages are by weight, unless indicated otherwise. All units of weight and measure not originally obtained in international scientific units have been converted to international scientific units.

EXAMPLE 1 A dry mixture was prepared by combining 14,823 prealloyed powder of 23% Sn / 73% Cu (< 44 μm particle size), 1467 g of hydride &titanium powder (< 44 μm in size) of particle) and 3,480 g of diamond grains from 10 to 20 μm. This mixture resulted in a composition diamond to 33% by volume. An unstable liquid binder was prepared separately by combining 20 parts by weight of Vitta Braze-Gel (Vitra Corporation) with 50 parts by weight of distilled water. The liquid binder was added to the dry mixture and stirred morally with a spatula of a glass beaker until a uniform paste formed. 20 Approximately 2 m of steel with high carbon content was pulled, patented wire used in 0.178 mm diameter lead bath through the pulp at approximately 0.25 m / s to apply the paste on the wire. It was dried with air and the coated wire, then released in MmhiiÉhßrilih vacuum hard (<1 μm Hg) in an oven at 880 ° C for 20 minutes. Thus a diamond abrasive wire bonded with hard welded metal was produced.

EXAMPLE 2 A dry mixture was prepared by combining 90.9 g of prealloyed Sn powder at 23% / Cu at 73% (<44 μm), 9.1 g of titanium powder (<44 μm in particle size) was then added natural diamond the average particle size of 20 microns at a ratio of 75% by volume to 25% by volume of diamond. An unstable liquid binder was prepared separately by combining 85 pairs by weight of Vitta Braze-Gel (Vitta Corporation) with 15 parts by weight of propylene glycol. The dry mixture was added in liquid binder and stirred manually with a spatula in a glass beaker until a uniform paste of 40% by weight of binder mixture was formed. A 250 micron Inconel 718 wire was then drawn through this paste to a tube furnace (flowing argon with <1 ppm oxygen) in which the high heat section was adjusted to 915 ° C at a rate of 1 meter. per minute. A wire coated with hard-welded diamond was obtained which had sufficient mechanical strength and sufficient coating of abrasive grain to cut ceramic plates.

EXAMPLE 3 A dry mixture was prepared by combining 99 g of 96% Sn prealloyed powder / 4% Ag (<44 μm particle size) and 1 gram of copper powder (<44 μm particle size). The natural diamond set with a thin copper coating of average particle size of 20 microns was added at ratios of 75% by volume of metal to 25% by volume of coated diamond. The dry mixture was added to a mixture of petroleum ointment containing 2% by weight of chloride-containing ointment zinc and stirred manually with a spatula in a glass beaker until a uniform paste containing 75% by weight solid mixture was formed. A wire was then stretched through the part to a tube furnace in which the high heat section was adjusted at 350 ° C at a rate of 1 meter per minute. A wire coated with diamond soldered in soft was obtained that had sufficient mechanical strength and sufficient coating of abrasive grain to cut ceramic plates.

EXAMPLE 4 The wires of Examples 2 and 3 were tested in a laboratory wire saw machine by Laser Technology West, Inc., and used for slicing through 25 mm cubes of polycrystalline silicon. The tension of the wire used was 10 Newton, the average speed of the wire was 2-3 m / s and the cutting load that was used was 440 grams. Both wire had initial cutting speeds between 1.5 and 2.1 mm / min using glycol as a submerged coolant in the cut. After cutting, the wire of Example 2 had an unrelieved cutting speed, while the cutting speed of the wire of Example 3 had decreased to less than 1 mm / min. Although specific forms of the invention are selected for illustration in the example and a foregoing description is formed in specific terms for the purpose of describing these forms of The invention is not intended to limit the scope of the invention as defined in the claims.

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Claims (44)

NOVELTY OF THE INVENTION CLAIMS

1. A wire saw comprising a core metal wire and an abrasive layer, characterized in that the abrasive layer has abrasive grains fixed directly to the wire by an adherent substance of soft-welded metal and the abrasive grains consist of superabrasive grains. .

2. The wire saw according to claim 1, further characterized in that the abrasive layer is present in a layer of single particle thickness.

3. The wire saw according to claim 2, further characterized in that the abrasive grains are present on the wire in a preselected distribution of surfaces.

4. The wire saw according to claim 3, further characterized in that the distribution of surfaces is continuous.

5. The wire saw according to claim 4, further characterized in that the continuous distribution of surfaces is uniform.

6. The wire saw according to claim 3, further characterized in that the distribution of surfaces is intermittent.

7. The wire saw according to claim 1, ^ m ^ *** m ** ^ - 4? ~ * - further characterized because most of the abrasive grains are superabrasive grains, selected from the group consisting of diamond, cubic boron nitride or a mixture of them.

8. The wire saw according to claim 1, further characterized in that the wire is a metal selected from the group consisting of iron, nickel, cobalt, chromium, tungsten, molybdenum and alloys containing any of them.

9. The wire saw according to claim 8, further characterized in that the wire metal is tungsten.

10. The wire saw according to claim 8, further characterized in that the wire metal is steel.

11. The wire saw according to claim 1, further characterized in that the cross section of the wire is circular, oval, rectangular, square, trapezoidal or polygon having 3-6 sides.

12. The wire saw according to claim 1, further characterized in that the cross section of the wire is flattened.

13. The wire saw according to claim 1, further characterized in that the abrasive layer also comprises a filler component.

14. The wire saw according to claim 1, comprising a plurality of metal wires to which abrasive grains are directly fixed by a hard-tack metal adherent substance. * * *my

15. - The wire saw according to claim 1, further characterized in that the metal adherent substance comprises a soft welded metal selected from the group consisting of silver, tin, copper, zinc, cadmium and lead, and alloys of these metals, and 5 combination of these metals and alloys with at least one filler component.

16. The wire saw according to claim 15, further characterized in that the soft welded metal comprises an alloy of tin and silver.

17. A wire saw comprising a metal core wire adhered by a metal alloy to an abrasive layer, further characterized in that the abrasive layer has abrasive grains fixed directly to the wire by a hard-welded metal alloy; the wire saw has a maximum cross-sectional dimension of 150-250 15 μm; and the abrasive grains are superabrasive grains present in a layer of single particle thickness.

18.- The wire saw in accordance with the claim 17, further characterized in that the metal adherent substance comprises a hard soldered metal selected from the group consisting of gold, silver, 20 nickel, zinc, mud, copper, tin, alloys of those metals, and alloys of those metals with phosphorus, cadmium or vanadium.

19.- The wire saw in accordance with the claim 18, further characterized in that the metal adherent substance comprises * ^ * * m * m a bronze alloy consisting essentially of 10-30% by weight of tin and a complementary amount of copper.

20. The wire saw according to claim 18, further characterized in that the metal adherent substance also comprises a minor fraction of an active metal selected from the group consisting of titanium, tantalum, chromium and zirconium.

21. The wire saw according to claim 18, further characterized in that the wire is a metal selected from the group consisting of iron, nickel, cobalt, chromium, tungsten, molybdenum and alloys containing any of them.

22. A method for making a metal wire wire saw, metal adherent substance composition and abrasive grain, further characterized in that the method comprises the steps of: (a) providing a paste comprising a composition of adherent substance of metal selected from the group consisting of a hard metal solder composition and a metal soft solder composition; (b) coating the surface of a wire with a layer of the paste; (c) depositing a layer of abrasive grains on the layer of the paste; (d) heating the wire in an inert atmosphere at a temperature of at most 950 ° C and for an effective duration to melt the adherent substance composition; (e) cool the wire by adhering the grains to the wire.

23. The method according to claim 22, further characterized in that the abrasive grains are deposited in a layer _ ^ _ of substantially unique particle thickness.

24. The method according to claim 23, further characterized in that the temperature of step (d) is 850-950 ° C.

25. The method according to claim 23, further characterized in that steps (b) - (e) are continuously carried out by stretching the wire through the areas of coating, depositing, heating and cooling.

26. The method according to claim 25, further characterized in that the drawing includes arranging the wire horizontally in the deposition zone and when depositing it includes sprinkling the beads downwardly on the horizontally arranged wire.

27. The method according to claim 26, further includes the steps of: (d) rotating the wire around the longitudinal axis of the wire after initially depositing the beads and before heating; (c2) repeating steps (c) and (d) until a preselected portion of the wire surface is deposited with the grains.

28. The method according to claim 23, further characterized in that the step of depositing includes passing the wire through a fluidized bed of abrasive grains in a carrier gas.

29. The process according to claim 22, further characterized in that the abrasive grains are mixed with the paste at a uniform concentration before coating the wire with paste and also because the paste containing grains is applied to the wire, thus effecting the steps to coat and deposit concurrently.

30. The method according to claim 29, further characterized in that the grains are deposited in a layer of single particle thickness.

31. The method according to claim 29, further characterized in that the grains are deposited in a layer of multiple particle thickness.

32. The method according to claim 29, further comprising the step of adding a filler component to the hard metal welding composition.

33. The method according to claim 29, further characterized in that the abrasive grains are deposited on the wire in a preselected distribution of surfaces.

34. The method according to claim 33, further characterized in that the preselected distribution of surfaces is continuous.

35.- The method according to claim 34, further characterized in that the continuous distribution of surfaces is uniform.

36.- The method according to claim 31, further characterized in that the preselected surface distribution is intermittent.

37. The method according to claim 22, further characterized in that the heating step includes heating methods in localized areas, selected from a group consisting of induction heating, laser heating, infrared radiation heating and electronic beam heating.

38.- The method according to claim 22, further characterized in that the grains are diamond, cubic boron nitride or a mixture thereof.

39.- The method according to claim 36, further characterized in that the wire is a metal selected from the group of iron, tungsten, molybdenum and alloys containing any of them.

40.- The method according to claim 37, further characterized in that the metal adherent substance comprises a hard soldered metal selected from the group consisting of gold, silver, nickel, zinc, lead, copper, tin, alloys of those metals , and alloys of those metals with phosphorus, cadmium or vanadium.

41.- The process according to claim 40, further characterized in that the metal adherent substance comprises a bronze alloy consisting essentially of 10-30% by weight of tin and a complementary amount of copper, and also comprises a fraction minor of an active metal selected from the group consisting of titanium, tantalum, chromium and zirconium.

42. - The process according to claim 40, further characterized in that the metal adherent substance comprises approximately 69-73% by weight of copper, approximately 19-21% by weight of tin and approximately 8-10% by weight of titanium.

43.- The method according to claim 40, further characterized in that the superabrasive grains are coated with an active metal layer formed of carbide before hard welding.

44. The method according to claim 22, further characterized in that the metal adherent substance composition is a metal soft solder composition. 45.- The method according to claim 44, further characterized in that step (d) is carried out at a temperature of less than 400 ° C.