WO2010092151A1 - Fixed abrasive sawing wire - Google Patents
Fixed abrasive sawing wire Download PDFInfo
- Publication number
- WO2010092151A1 WO2010092151A1 PCT/EP2010/051792 EP2010051792W WO2010092151A1 WO 2010092151 A1 WO2010092151 A1 WO 2010092151A1 EP 2010051792 W EP2010051792 W EP 2010051792W WO 2010092151 A1 WO2010092151 A1 WO 2010092151A1
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- WO
- WIPO (PCT)
- Prior art keywords
- wire
- skin
- particles
- sawing
- core
- Prior art date
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23D—PLANING; SLOTTING; SHEARING; BROACHING; SAWING; FILING; SCRAPING; LIKE OPERATIONS FOR WORKING METAL BY REMOVING MATERIAL, NOT OTHERWISE PROVIDED FOR
- B23D61/00—Tools for sawing machines or sawing devices; Clamping devices for these tools
- B23D61/18—Sawing tools of special type, e.g. wire saw strands, saw blades or saw wire equipped with diamonds or other abrasive particles in selected individual positions
- B23D61/185—Saw wires; Saw cables; Twisted saw strips
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23D—PLANING; SLOTTING; SHEARING; BROACHING; SAWING; FILING; SCRAPING; LIKE OPERATIONS FOR WORKING METAL BY REMOVING MATERIAL, NOT OTHERWISE PROVIDED FOR
- B23D61/00—Tools for sawing machines or sawing devices; Clamping devices for these tools
- B23D61/18—Sawing tools of special type, e.g. wire saw strands, saw blades or saw wire equipped with diamonds or other abrasive particles in selected individual positions
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C26/00—Coating not provided for in groups C23C2/00 - C23C24/00
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
Definitions
- the invention relates to a sawing wire, more specifically a sawing wire with fixed abrasive particles anchored in the outer skin of a carbon steel wire and fixed thereto with a binder layer.
- a low carbon content steel is used as the skin on a high carbon content steel wire core.
- Such wires can be used for cutting hard and brittle materials like quartz (for e.g. quartz oscillators or mask blancs), silicon (for e.g. integrated circuit wafers or solar cells), gallium arsenide (for high frequency circuitry), silicon carbide or sapphire (e.g. for blue led substrates), rare earth magnetic alloys (e.g. for recording heads) or even natural or artificial stone.
- Wires for sawing large and small objects made of hard and brittle materials are well known for centuries.
- workpieces made of hard and brittle materials
- 'wire saw' i.e. a saw that is a wire, although a saw apparatus using a wire could also be indicated by it
- 'sawing wire' a wire used for sawing
- a 'saw wire' a wire used as a saw
- 'Sawing ropes' or 'sawing cables' are ropes comprising a rope made of several filaments on which abrasive beads are fixed which are sometimes also referred to as 'sawing wires' but this falls outside the scope of this application.
- the sawing wire serves as a carrier for an abrasive member that abrades materials from the object to be cut.
- abrasive members - can be separate from the carrier and injected by one or another means between the wire and the object to be sawn.
- the process is sometimes referred to as 'third body abrasion' (the third body being the abrasive member) or 'loose abrasive cutting'.
- a notorious example is the cutting of silicon ingots by means of a plain carbon steel wire that entrains slurry into the cut.
- the slurry contains fine abrasive particles that roll stick between the wire and the workpiece, crush the material locally and thereby further deepen the cut, or
- the carrier wire can be attached to the carrier wire in the form of protruding teeth made from the same material as the wire (as in a wood saw) or
- the carrier wire in the form of abrasive particles of another material than the wire. In the latter case the particles must be hard and must be firmly attached to the carrier wire.
- a reciprocal motion implies repetitive accelerations and decelerations hence loss of energy and time.
- the thro and fro movement tends to wiggle the abrasive particles out of the wire leading to a premature wear of the wire due to loss of particles. So it is imperative that the abrasive particles are well fixed into or onto wire. With well fixed is not only meant that the abrasive particles must remain in place, but also that their elastic motion relative to the wire remains low.
- the kerf loss is the amount of workpiece material that is abraded away and lost. Less kerf loss implies better use of material. For materials that are costly (such as silicon, gallium arsenide or rare earth magnet alloys) a small reduction in kerf loss results in a large financial gain.
- the benchmark is set in loose abrasive cutting where wires of a gauge 120 ⁇ m are customary and tests are underway with 80 ⁇ m wire. This results in a kerf loss of 130 to 140 ⁇ m and 90 to 100 ⁇ m as the abrasive particles in the slurry carrier also take some space between wire and workpiece.
- the wire must be tensioned during the sawing process in order to press the abrasive particles into the object, the wire must be able to sustain a certain tension.
- a higher tension that can be maintained results in more contact force on the abrasive particles and hence a higher sawing speed (although there is a limit to this).
- the tension is typically 20 N and higher.
- the tensile strength of the wire is defined as the breaking load - the force at which the wire breaks - divided by the cross-sectional area of the wire and is expressed in N/mm 2 .
- the minimum breaking load of the wire should at least be about twice the tension force. In the case of e.g. a 200 ⁇ m fixed abrasive sawing wire this leads to a minimal tensile strength of 1300 N/mm 2 and in the case of a 140 ⁇ m to 2600 N/mm 2 .
- the sawing wire should not pollute the workpiece with contaminants.
- EP 0 243 825 describing a method to produce a fixed abrasive sawing wire starting from a steel wire rod and a tube surrounding the rod with a gap in between.
- the gap is filled with a mixture of metal powder and abrasive particles.
- the ends are sealed and the rod is heat treated and cold drawn in repeated steps to obtain a fixed abrasive sawing wire after the outer tube has been removed by etching it away.
- Drawbacks are that the method does not allow to produce fixed abrasive sawing wires of an appreciable length (above 100 meters), the tensile strength of the resulting wire is relatively low (say below 1800 N/mm 2 ) and the resulting wires are too thick (1 mm).
- EP 0 982 094 describes a fixed abrasive sawing wire with a stainless steel core, an intermediate layer for preventing hydrogen embrittlement of the core wire and a binding layer with diamond particles incorporated in them.
- the binding layer with the diamonds in it is deposited through electroplating or electroless deposition out of deposition bath comprising the diamonds.
- Embodiments given describe nickel as both the intermediate layer as well as the binding layer.
- WO 99/46077 describes a fixed abrasive sawing wire comprising a metal wire, and superabrasive grains affixed to the wire through a brazed or soldered metal bond, wherein the grains are preferably disposed upon the surface with a preselected surface distribution.
- steel wires might lose strength due to the heat treatment needed for the brazing and soldering. This is not desirable to meet the tensile strength requirement.
- EP 0 081 697 describes a method and an apparatus to incrust a wire with diamond particles.
- JP 5016066 A2 describes the production of a sawing wire with a high carbon steel core and a low carbon steel skin through controlled decarburisation of a high carbon steel wire.
- the wire is intended for use with a loose abrasive slurry process.
- the abrasive particles out of the loose abrasive slurry are not fixed in the carbon skin but get stuck and come loose again in a continuous way.
- the decarburisation always results in a loss of carbon, hence a loss of strength of the wire. Disclosure of Invention
- the main object of the invention is to provide a fixed abrasive sawing wire with improved properties.
- a further object of the invention is to provide a wire wherein the abrasive particles are not only well fixed but also show less elastic movement during sawing.
- Another object is to provide a fixed abrasive sawing wire that has a sufficiently high tensile strength to enable low kerf loss in combination with a high sawing speed. A method is described to make such wires in lengths longer than say one kilometer, which is a further object of the invention.
- a product in the form of a fixed abrasive sawing wire comprises a central wire made of steel.
- steel is an alloy of iron and carbon and other elements it always comprises carbon in a certain amount.
- the outer periphery of the wire has a different composition than the inner core of the wire. In what follows this outer periphery will be called the skin. In the skin abrasive particles are fixed. A binder layer is applied on said skin to better hold the particles in the skin.
- the cross section of the wire can have any suitable shape.
- the shape is dictated by the method of sawing.
- the cross section is preferably round. Indeed in such a multi wire saw the wire tends to rotate due to the many bendings over pulleys and guiding rolls, hence rotational symmetric wire i.e. round wire is most suited.
- the overall diameter (i.e. including abrasive particles) of such a round fixed abrasive sawing wire can be from 80 micron up to 300 micron again determined by the machine it is used on.
- a wire of around 250 micron would be more appropriate as a lot of force is needed to drag the wire through over the long length of 1 meter.
- an 80 micron wire might do the job.
- a wire of 100 to 200 micron seems most appropriate, where the user will of course favour the thinnest wire.
- the cross section can be of oval or even of rectangular shape.
- the tear drop shape as disclosed in US 5 438 973 is most preferred when using a frame saw (in a frame saw the individual wires are tensioned parallel to one another in a frame that is reciprocally moved over the workpiece).
- the tear drop shape allows to further reduce the kerf loss without giving in on strength.
- the high bending stiffness when bend in the plane of the longer side allows a higher sawing pressure in the cut.
- the fixed abrasive steel wire is different from the prior art that the core of the steel wire has a pearlitic metallographic structure while the skin has a ferritic metallographic structure.
- the determination of the metallographic structure of a steel is a standardised technique: the wire is embedded into an epoxy block which is cut through perpendicular to the axis of the wire and subsequently polished. The shiny surface of the cross section is then etched in a nital solution which is a mixture of about 3% by volume nitric acid (HNO3) and alcohol, for example ethanol (C2H5OH). Due to the etching the grain structure of the steel becomes visible under a metallographic microscope at about 100 to 500 magnification.
- HNO3 nitric acid
- C2H5OH ethanol
- the pearlitic structure (or 'pearlite' for short) shows a brownish-grey pearly aspect (from which the name is derived) under the microscope.
- the pure pearlitic structure is formed after proper heat treatment of the steel (austinisation at temperatures above 723°C followed by slow cooling).
- Pearlite is a mixture of 88 wt% of ferrite (iron containing almost no carbon) and 12 wt% of cementite (F ⁇ 3C) resulting in a eutectic concentration of 0.80 wt% carbon.
- the carbon content of the steel is below 0.80 wt%, e.g.
- steels are called hypo-eutectoid and formed pearlite is visible in regions that are surrounded by ferrite.
- steels are called hyper-eutectoid and have a microstructure that comprises pearlite and cementite ('grain boundary cementite').
- An experienced analyst can estimate the carbon content by weight through metallographic pictures in steps of about 0.2 wt% carbon.
- the skin of the fixed abrasive sawing wire shows a substantially ferritic metallographic structure or 'ferrite' for short.
- the ferrite is clearly discernable in a metallographic picture because it shows much lighter and is not coloured.
- ferrite is formed in steel with a carbon content of between 0.04 wt% and 0.20 wt%.
- Manganese adds - like carbon - to the strain hardening of the wire and also acts as a deoxidiser in the manufacturing of the steel.
- the steel composition of the skin of the wire is less critical as it is predominantly iron with some carbon (between 0.04 wt% and 0.20 wt%) and other trace elements in it.
- 'low carbon content' or 'low carbon steel' it is to be understood as the carbon content or the steel of the skin of the steel wire.
- All the above steel compositions are characteristic of a 'plain carbon steel' composition as the main alloying constituent is carbon. Steels that enable high strength are thus most preferred as the core of the wire must carry all force, the skin being of low strength, low carbon steel even further reduced in strength by the presence of the abrasive particles. Moreover - as in a circular cross section most of the area is at the periphery of the circle - a lot of area is low carbon steel hence does not contribute to the overall breaking load of the fixed abrasive sawing wire. This makes a fixed abrasive sawing wire of fine diameter with sufficient strength a non- obvious challenge.
- Fixed abrasive sawing wires according to the invention typically have a tensile strength of above 2000 N/mm 2 for diameters smaller than 250 ⁇ m, above 2250 N/mm 2 for diameters smaller than 150 ⁇ m, and above 2500 N/mm 2 for diameter smaller than 120 ⁇ m.
- the tensile strength is defined as the breaking load of the fixed abrasive sawing wire divided by its metallic surface (excluding the area taken up by the abrasive particles).
- the metallic surface is determined on a cross section of the wire as used for the metallographic structure determination. Any metallic layer is taken into account for the surface.
- the local carbon content as radially measured from the core to the skin will show a decreasing function.
- the easiest to determine is of course the average carbon content ' C ' e.g. by means of a LECO CS230 carbon and sulphur tester.
- the carbon content should be determined after removal of the particles and the fixing layer in order not to have interference of these.
- the average carbon content should at least be 0.40 percent by weight. More preferred is if it is above 0.55 wt% carbon or even above and 0.60 wt% carbon.
- the measurement of l ⁇ (r) is difficult but can be done in a number of ways:
- An indirect measurement of the relative carbon distribution can be obtained through Vickers micro-hardness measurements.
- a microindentor with a square-based diamond pyramid with a face angle of 136° is pushed with a specified force (0.9807 N, Hardness symbol HV 0.1) for a specified time (10 seconds) into the material. Thereafter, the geometry of the indentations is measured, out of which a local micro-hardness (expressed in N/mm 2 ) can be calculated.
- a wire is encased in epoxy resin, cut under an angle to the axis of the wire and polished.
- the hardness at regular spots along the major axis of the ellipse that forms, is measured and the correct radial position with respect to the axis of the wire is calculated.
- the hardness measured is a function of the steel metallographic structure, the amount of strain hardening given to the wire (which is equal over the cross section of the wire) and the carbon content.
- the measurement of the Vickers micro-hardness is particularly important because it gives a measure how easy abrasive particles can be indented in the skin. [0031] In much the same way as with the carbon content, a weighed average
- Vickers micro-hardness ⁇ V aV g' can be calculated by replacing T(r)' by the local Vickers micro-hardness as a function of radial distance ' ⁇ (r)':
- the integral can conveniently be approximated by taking the average of the under and upper sum of the discrete measuring points weighed with the annular surface between the points.
- this average hardness is higher than 500, or more preferred between 550 and 650 N/mm 2 . Too low an average hardness will not allow enough strength, too high an average hardness will not allow proper indentation of the particles. See Figures 2a and 2b for a schematic drawing.
- the skin can be defined as that part of the wire which has a below average hardness and the core as that part of the wire that has an above average hardness.
- the skin and the core meet at a border. At the border, the local Vickers micro-hardness crosses the weighed average micro-hardness. This border lies at an approximate radius 'b'.
- the skin must prevent the core of the steel wire of micro-crack damage by indentation of the abrasive particles. Indeed, steel wires become more vulnerable to surface damage with increasing tensile strength. This is expressed in a loss of fatigue strength (as the damage is the start of a crack) and/or loss of strength. The skin must also hold the particles in position. Hence the indentation dept of the particles should never be larger than the skin thickness ' ⁇
- the transition from high carbon core to low carbon skin can be abrupt as shown in Figure 2a. Although there will be a carbon exchange between core and skin at nanoscopic level, no metallographic mixed phase is discernable on a microscopic level.
- the transition from high carbon core to low carbon skin is smooth and comprises a mixed metallographic phase showing increased ferrite presence and a decreasing pearlite presence when observing from core to skin.
- the transition becomes smooth due to the processing which will be explained later on.
- the carbon content distribution is then like the one depicted in Figure 2b.
- the width of the transition ' ⁇ ' can be defined as the distance between which ⁇ (r) varies from 350 to 650 N/mm 2 .
- the values correspond with what one can expect from a hard drawn, low carbon steel with less than 0.2 wt%C and a hard drawn, high carbon steel with more than 0.40 wt%C.
- the transition has as an advantage that the abrasive particle meets a constantly increasing indentation force, rather than an abrupt change when reaching the core of the wire when being pushed into the skin.
- the transition has also as an advantage that the skin is diffusion bonded to the core and loss of adhesion between skin and core is virtually impossible.
- the transition layer width ' ⁇ ' should therefore at least be wider than 5 micron, preferably wider than 10 micron in order to have an excellent bond.
- the abrasive particles can be superabrasive particles such as diamond (natural or artificial, the latter being somewhat more preferred because of their lower cost and their grain friability), cubic boron nitride or mixtures thereof.
- particles such as tungsten carbide (WC), silicon carbide (SiC), aluminium oxide (AI2O3) or silicon nitride (Si3N 4 ) can be used: although they are softer, they are considerably cheaper than diamond. Most preferred is diamond.
- the size of the abrasive particles somewhat scales with the diameter of the wire. Determining the size and shape of the particles themselves is a technical field in its own right. As the particles have not - and should not have - a spherical shape, for the purpose of this application reference will be made to the 'size' of the particles rather than their 'diameter' (as a diameter implies a spherical shape).
- the size of a particle is a linear measure (expressed in micrometer) determined by any measuring method known in the field and is always somewhere in between the length of the line connecting the two points on the particle surface farthest away and the length of the line connecting the two points on the particle surface closest to one another.
- the size of particles envisaged for the fixed abrasive sawing wire fall into the category of 'microgrits'.
- the size of microgrits can not longer be determined by standard sieving techniques which are customary for macrogrits. In stead they must be determined by other techniques such as laser diffraction, direct microscopy, electrical resistance or photosedimentation.
- the standard ANSI B74.20-2004 goes into more detail on these methods.
- the particle size as determined by the laser diffraction method or 'Low Angle Laser Light Scattering' as it is also called
- the output of such a procedure is a cumulative or differential particle size distribution with a median dso size (i.e. half of the particles are smaller than this size and half of the particles are larger than this size) or in general 'dp' wherein 'P' percent of the particles is smaller than this 'dp' the remaining part (100-P) percent being larger sized than
- Superabrasives are normally identified in size ranges by this standard rather than by sieve number. E.g. particle distributions in the 20-30 micron class have 90% of the particles between 20 micrometer (i.e. 'ds') and 30 micrometer (i.e. 'd ⁇ s') and less than in 1 in 1000 over 40 microns while the median size dso must be between 25.0 +/ 2.5 micron.
- the median size i.e. that size of particles where half of the diameters have a smaller size and the other half a larger size
- the particles can not be too small as then the material removal rate (i.e. the amount of material abraded away per time unit) becomes too low.
- the abrasive particles will be best held when they are indented into the skin over more than half their median size. So the indentation depth should at least be larger than half the median size of the particles. As the skin thickness should be thicker than the largest indentation depth, it follows that the skin thickness must at least be larger than half the median particle size in order to hold the particles well.
- the skin thickness is thicker than 'dgo' (90% of the particles have a size that is smaller than d ⁇ o). Hence the chances for micro-crack damages to the core become very small thereby avoiding breaks in service.
- the skin thickness will have to be about 10% of the diameter of the steel wire and should be at least 5% or at least be 7% of the diameter. So 8 ⁇ m to 15 ⁇ m for very thin wires of 80 to 150 ⁇ m and about 20 ⁇ m for a 210 ⁇ m wire. Note that with a 10% of the diameter skin thickness, already 36% of the cross sectional area of the wire is occupied by low tensile skin material.
- the target coverage ratio for the particles is depending on the material one intends to cut, the cutting speed one wants to reach or the surface finish one wants to obtain.
- the inventors have found that in order to have the best sawing performance for the materials envisaged the ratio of particle area over total area should be between 1 and 50%, or between 2 to 20% or even between 2 and 10%.
- the binder layer that is applied onto the outer surface of the wire and helps to keep the particles fixed in the skin or in other words to bind the particles in the skin.
- the binding layer is a metallic layer.
- Particularly favoured metals are nickel and iron.
- Alternative but still preferred metals are chromium, cobalt, molybdenum, tungstenand zinc and alloys thereof.
- the thickness of this layer is preferably between 1 to 5 ⁇ m.
- the inventive fixed abrasive sawing wire is substantially free of copper. No intentionally added copper is present in the wire or in the coating. Hence, contamination with copper of silicon workpieces is avoided during drawing. Copper atoms that diffuse into silicon form electronically active defects in the energy gap of silicon. Also the elimination of copper out of effluent streams (e.g. resulting from coolant, or rinsing of the finished wafers) can be avoided in this way.
- a method to produce the wire comprises three main steps:
- abrasive particles are fixed with a binding layer.
- the second and third step are implemented in a line concept where the wire is continuously fed from one process step to the following process step.
- separation of these steps is not excluded by that: e.g. a batch process as described in EP 1375043 for the third step is possible.
- the starting steel wire of the first step can be produced:
- a high carbon steel wire is coated with pure iron from an electrolytic bath (see for example US 5014760).
- Some alternative approaches become possible.
- a first alternative is that the final diameter steel wire is coated with iron. The transition between the iron skin layer and the high carbon core is abrupt and no mixed phase between core and skin will form. The embodiment as described in Figure 2a is then obtained.
- the advantage of this method is that relatively little iron must be laid down on the wire to reach a reasonable layer thickness (thickness more than 7% of steel wire diameter).
- the steel wire can be coated with iron at a suitable intermediate diameter prior to further wet wire drawing.
- an intermediate diameter is meant a diameter between the wire rod diameter and the final diameter of the wire (an intermediate diameter will typically lay between 2.70 and 0.90 mm).
- the heat generated during drawing will result in the formation of a minor transition region of about 5 micron or more due to the diffusion of the carbon into the iron.
- the wire can be coated with iron at an intermediate diameter level and - possibly repeatedly - patented and drawn.
- the transition region is higher due to the single thermal treatment of the skin which brings more diffusion of the carbon into the iron.
- the transition region is then between 5 and 30 micron.
- the high carbon steel core is wrapped with a low carbon steel strip or iron foil that is closed by welding and forms the skin.
- a low carbon steel strip or iron foil that is closed by welding and forms the skin.
- the high carbon steel core is wrap-coated with a low carbon or iron strip or foil at an intermediate diameter level and subsequently - possibly repeatedly - patented and drawn to final diameter.
- the transition region is somewhat broader due to the single or possibly two or three thermal treatment(s) of the wire inducing more diffusion of the carbon into the skin.
- the transition region is then between 5 and 30 micron. The transition region increases with the number of patenting steps.
- the first and second preferred embodiments of the first method step result in a hardness profile that tails up at the surface of the skin rather than showing a continuous decrease.
- the skin is formed by decarburisation of a high carbon steel wire.
- Practical examples of decarburization are given in US 5014760.
- the outer layer of the steel wire then loses a substantial part of its carbon and forms a low carbon skin while the core retains most of the carbon.
- decarburisation requires passing the wire at elevated temperatures of 700°C to 1000°C in an oxidizing atmosphere furnace, it is not possible to decarburize the final diameter wire as this would lead to unacceptable strength loss.
- decarburization is by preference performed on intermediate wire diameters of higher than about 0.90 mm.
- the decarburization step can be performed on rod diameter level and followed by one or two regular (i.e. under reducing atmosphere) patenting steps with wire drawing operations in between and after.
- the decarburization step can be the last thermal treatment prior to final wire drawing. The latter is somewhat more preferred, as a subsequent regular patenting (under reducing atmosphere) results in a redistribution of carbon in the wire. Such redistribution results in a broadening of the transition region.
- the particles are fixed by means of fixing layer that is by preference metallic in nature.
- Application of the fixing layer should be done under low temperature conditions (below about 200°C) in order to avoid tensile strength degradation of the wire.
- the most preferred method is therefore to use an electrolytic deposition technique to deposit metal ions out of a metal salt electrolyte onto the wire that is held at a negative potential relative to the electrolyte. Even then care has to be taken not to have excessive resistive heating of the steel wire as steel is a less good electrical conductor and the wire is fine. Also the presence of the particles makes making the electrical contact to the wire difficult as the particles are insulators by nature and a simple rolling contact will result in sparking. Hence a non-contact method as e.g. described in WO 2007/147818 is preferred wherein contact with the wire is made through a second electrolyte in a bath separated from the metal deposition electrolyte bath.
- Fig. 1 'a' and 'b' are different metallographic cross sections of the same wire where the indented particles have been removed out of their indentation.
- Fig. 2 'a' schematically depicts the radial concentration by weight of the carbon content l ⁇ (r) or the local microscopic Vickers hardness ⁇ (r) in the case of steel wire with an abrupt transition from high carbon core to low carbon skin.
- Fig. 2 'b' schematically depicts the radial concentration by weight of the carbon content l ⁇ (r) or the local microscopic Vickers hardness ⁇ (r) in the case of steel wire in the case of steel wire with a smooth transition from high carbon core to low carbon skin.
- Fig. 3 'a' shows an actual measurement of the local microscopic Vickers hardness of a first example.
- Fig. 3 'b' shows an actual measurement of the local microscopic Vickers hardness of a second example.
- Fig. 4 shows how the coverage percentage of the abrasive particles can be determined.
- Fig. 5 shows how the indentation width and depth of a particle can be measured.
- a high carbon wire rod (nominal diameter 5.5 mm) with a carbon content of 0.8247 wt%, a manganese content of 0.53 wt%, a silicon content of 0.20 wt% and with Al, P and S contents below 0.01 wt% was chemically descaled to the methods known in the art.
- the wire was subsequently wrapped with a low carbon strip with 0.03 wt% carbon and a thickness of 0.60 mm. The seam was welded. The total diameter of the wrapped wire was thus about 6.7 mm. The strip thickness is 8.96% of the total wire thickness.
- This composite wire was dry drawn in the manner known in the art to a total diameter (i.e. core wire plus strip wrap) of 2.40 mm. The material was split in two separate batches.
- a first batch of material (referred to as example 1) was further dry drawn to a total diameter of 1.20 mm.
- the thickness of the low carbon strip was thereby reduced to 105 ⁇ m (i.e. 8.75 % of the total wire thickness).
- This material was then patented in the usual manner (lead patenting). After patenting there is already clear indication of carburisation of the low carbon strip and the strip is fully fused to the core. Thereafter, another dry drawing step to 0.90 mm total diameter is performed.
- This wire was subsequently wet wire drawn to a total diameter of 210 ⁇ m. Due to the patenting the low carbon strip was carburised and the transition from core to skin was not longer clearly discernable. The sample has undergone only one patenting operation.
- a second batch of material (referred to as example 2) was first patented in lead and subsequently dry drawn to 0.90 mm diameter and again patented in lead. Thereafter it was wet wire drawn to again 210 ⁇ m. This sample has undergone two patenting operations.
- 'Skin ⁇ HV refers to the measured Vickers micro-hardness as measured on the drawn wire.
- the initial Vickers micro-hardness of the low carbon steel strip was 143 N/mm 2 . This appears to have considerably increased due to:
- the hardness profile of the wire of example 1 was measured and is represented in Figure 3a.
- the hardness was measured on an elliptical cross section such that the respective indentations were sufficiently far apart (indicated with ' ⁇ ').
- the outer point (' ⁇ ') is the point measured on the outer skin (cfr. table I).
- the dash-dot line marked with ⁇ V aV g' indicates the average micro-hardness weighed with the surface area and in this case was equal to 597 N/mm 2 (lower sum 586, upper sum 606).
- the thickness TY of the skin is that distance from the outer circumference to where the hardness is equal to the average Vickers micro-hardness.
- the border between skin and core is between 80 and 84 ⁇ m radius, hence the skin thickness TY is about 21 to 25 ⁇ m.
- the skin is thus about 8.5 to 12% of the steel wire diameter.
- the transition region ' ⁇ ' is about 17 ⁇ m thick.
- the different symbols represent a repeated measurement.
- the average weighed micro-hardness was respectively 577 N/mm 2 ('*', indicated with the dash-dot line; lower sum 559, upper sum 595) and 589 N/mm 2 (' ⁇ ', indicated with the dash-dot-dot line, lower sum 571 , upper sum 607).
- the skin thickness ' ⁇ ' is about 22 ⁇ m while the transition region ' ⁇ ' is broader namely 23 ⁇ m.
- Example 2 was selected for further processing.
- the wire was coated with a nickel binding layer after washing the adhesive away in hot water. This was done in an installation as described in WO 2007/147818.
- the thickness of the layer was about 3 micron.
- the coverage degree of the wire was about 5 to 8 % and was determined in a SEM in backscattered electron detection mode.
- Figure 4 shows the resulting picture with diamond particles on the surface of the fixed abrasive sawing wire 40 as black areas 42 on an otherwise grey background 44. By means of photoanalysis software the ratio black area over black and grey area or coverage degree can be readily assessed.
- Metallographic cross sections are shown in Figure 1a and 1 b which are cross sections of the same wire 10, but on different places.
- the core 14 of the wire 10 shows a different structure than the skin 12.
- the core 14 shows a high carbon, drawn pearlitic metallographic structure while the skin 12 shows a substantially ferritic structure i.e. with a low carbon content.
- the originally circular cross section of the wire has been indented with particles which are subsequently drawn out during polishing of the sample. They leave an indentation 16. It is clear that the indentation occurred prior to the coating with the nickel binding layer 18 as no nickel layer is visible inside the crevice left by the diamond. The crevice is about 20 micron deep (measured from the outer nickel surface) and does not enter the core.
- the quality of the indentation can be estimated by comparing the width of the crevice to its depth. How this can be done is illustrated in Figure 5 wherein a cross section 50 as in Fig. Va' or 'b' is reproduced. When connecting the outer points 'A' and 'B' of the crevice 52, the width 'Wm' can be determined. Likewise the depth 'D 1n ' is determined by measuring the maximum depth perpendicular to the line AB. The measure (2xD ⁇ n /W ⁇ n ) is independent of where exactly the cross section has been taken.
- Replacing copper with low carbon in a fixed abrasive sawing wire can lead to an increase of 17 % in breaking load, keeping all other things equal. It is thus possible to reduce further the diameter of the fixed abrasive wire - and thus kerf loss - while keeping the same breaking load.
- the low carbon clad wire was further indented with diamond particles and these particles were fixed by means of a nickel layer.
- Two different degrees of coverage degree were made: one with about 0.60% coverage and one with about 2% coverage degree.
- the samples were tested on a piece of mono crystalline silicon according to the same protocol as described before (paragraph [0088]) but with a variation in tension.
- For the 2% coverage ratio at 18 N tension, a sawing speed of 133 mm 2 /min was obtained which increased to 164 mnrVmin under a tension of 27 N.
- the 0.60% coverage ratio sample showed inferior cutting results.
- the modulus of elasticity of iron is 220 000 MPa compared to 124 000 MPa for copper and 196 000 MPa for nickel. Hence when the abrasive particle is wiggled thro and fro in the sawing process, the iron will give a stronger support to the particle than e.g. copper.
- the skin material adheres very well to the core material. When low carbon steel is put on high carbon steel the materials are compatible, hence adhere better to one another.
- the skin and the core are as if welded to one another.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Polishing Bodies And Polishing Tools (AREA)
- Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
- Mechanical Treatment Of Semiconductor (AREA)
Abstract
Description
Claims
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SG2011056793A SG173579A1 (en) | 2009-02-13 | 2010-02-12 | Fixed abrasive sawing wire |
CN2010800052684A CN102292185A (en) | 2009-02-13 | 2010-02-12 | Fixed abrasive sawing wire |
JP2011549578A JP2012517906A (en) | 2009-02-13 | 2010-02-12 | Fixed abrasive sewing wire |
EP10704355A EP2396134A1 (en) | 2009-02-13 | 2010-02-12 | Fixed abrasive sawing wire |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP09152849.7 | 2009-02-13 | ||
EP09152849 | 2009-02-13 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2010092151A1 true WO2010092151A1 (en) | 2010-08-19 |
Family
ID=40929593
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/EP2010/051792 WO2010092151A1 (en) | 2009-02-13 | 2010-02-12 | Fixed abrasive sawing wire |
Country Status (7)
Country | Link |
---|---|
EP (1) | EP2396134A1 (en) |
JP (1) | JP2012517906A (en) |
KR (1) | KR20110119705A (en) |
CN (1) | CN102292185A (en) |
SG (1) | SG173579A1 (en) |
TW (1) | TW201043367A (en) |
WO (1) | WO2010092151A1 (en) |
Cited By (9)
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WO2011138192A2 (en) | 2010-05-04 | 2011-11-10 | Nv Bekaert Sa | Fixed abrasive sawing wire with removable protective coating |
WO2012055711A1 (en) * | 2010-10-28 | 2012-05-03 | Nv Bekaert Sa | A fixed abrasive sawing wire and a method to produce such wire |
EP2564965A1 (en) | 2011-08-31 | 2013-03-06 | NV Bekaert SA | Hand-held power wire saw and wire holder |
WO2014006119A1 (en) | 2012-07-05 | 2014-01-09 | Nv Bekaert Sa | Fixed abrasive sawing wire with cubo-octahedral diamond particles |
WO2014184457A1 (en) * | 2013-05-14 | 2014-11-20 | Commissariat A L'energie Atomique Et Aux Energies Alternatives | Abrasive sawing wire, production method thereof and use of same |
US20150045264A1 (en) * | 2010-08-24 | 2015-02-12 | Idemitsu Kosan Co., Ltd. | Silicon wafer processing solution and silicon wafer processing method |
JP2015187578A (en) * | 2014-03-27 | 2015-10-29 | 福井県 | Surface shape evaluation method and device of saw wire |
US20160082533A1 (en) * | 2013-05-14 | 2016-03-24 | Thermocompact | Abrasive Sawing Wire, Production Method Thereof And Use Of Same |
TWI552820B (en) * | 2010-10-29 | 2016-10-11 | Nv貝卡特股份有限公司 | A fixed abrasive sawing wire and producing method thereof |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
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WO2016146343A1 (en) * | 2015-03-13 | 2016-09-22 | Nv Bekaert Sa | Method to produce a fixed abrasive saw wire with a metal alloy fixation layer and the wire resulting therefrom |
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2010
- 2010-02-05 TW TW099103535A patent/TW201043367A/en unknown
- 2010-02-12 JP JP2011549578A patent/JP2012517906A/en not_active Withdrawn
- 2010-02-12 EP EP10704355A patent/EP2396134A1/en not_active Withdrawn
- 2010-02-12 CN CN2010800052684A patent/CN102292185A/en active Pending
- 2010-02-12 WO PCT/EP2010/051792 patent/WO2010092151A1/en active Application Filing
- 2010-02-12 KR KR1020117018854A patent/KR20110119705A/en not_active Application Discontinuation
- 2010-02-12 SG SG2011056793A patent/SG173579A1/en unknown
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WO2011138192A2 (en) | 2010-05-04 | 2011-11-10 | Nv Bekaert Sa | Fixed abrasive sawing wire with removable protective coating |
US9441179B2 (en) * | 2010-08-24 | 2016-09-13 | Idemitsu Kosan Co., Ltd. | Silicon wafer processing solution and silicon wafer processing method |
KR101809778B1 (en) | 2010-08-24 | 2017-12-15 | 이데미쓰 고산 가부시키가이샤 | Silicon wafer processing solution and silicon wafer processing method |
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JP2015187578A (en) * | 2014-03-27 | 2015-10-29 | 福井県 | Surface shape evaluation method and device of saw wire |
Also Published As
Publication number | Publication date |
---|---|
EP2396134A1 (en) | 2011-12-21 |
TW201043367A (en) | 2010-12-16 |
CN102292185A (en) | 2011-12-21 |
SG173579A1 (en) | 2011-09-29 |
JP2012517906A (en) | 2012-08-09 |
KR20110119705A (en) | 2011-11-02 |
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