TWI552820B - A fixed abrasive sawing wire and producing method thereof - Google Patents

Description

Fixed abrasive sawing wire and manufacturing method thereof

The present invention relates to fixed abrasive sawing wires suitable for sawing hard and brittle materials, wherein the abrasive particles are attached to the top of the substrate line by an electrolytically applied adhesive layer.

The primary technology currently used to saw hard and brittle materials such as tantalum, quartz, gallium arsenide, tantalum carbide, sapphire, magnetic materials, or any other expensive material with a cut length less than the length of the arm utilizes a multi-turn single-wire saw. In such a saw, a slurry containing abrasive particles (mostly strontium carbide) suspended in a carrier liquid (usually polyethylene glycol) is towed to the workpiece by a round, thin, high tensile steel wire. Cutting. The wire is guided by a grooved winch in a circle arranged in parallel with one another, thus forming a wire web. The workpiece is cut by the action of a roll-stick of abrasive particles rolling between the workpiece and the workpiece. The process is susceptible to change due to changes in the composition of the slurry during use; this method is expensive because both the wire and the abrasive wear and must be replenished; the process is messy due to splashing near the winch, and due to the use The slurry (along with the scrap of the workpiece material and the steel components therein) and the wire must be disposed of in a controlled manner, which has a high environmental cost.

Therefore, the industry seeks to waive the solution for slurry preparation, slurry control and disposal. One of the proposed solutions is to eliminate the carrier liquid using the abrasive particles and to fix the abrasive particles directly on the wire. Then only the coolant is still needed to wash away the debris that may be concentrated on the line. This caused

- Since the full force of the abrasive particles is transferred for cutting into the workpiece (no more particle rolling), this results in a better sawing action,

- since the coolant mainly contains processed pieces of debris, this forms a purer residual product, and

- This is a preferred use of consumables due to the preferred use of abrasives and the much less wear of the wire (as the abrasive is fixed relative to the wire).

Wire saws inherently cause loss of workpiece material (sometimes valuable material). Therefore, efforts have been made to keep the "saw loss" (the amount of workpiece material lost as sawdust) as low as possible. This can be achieved by keeping the diameter of the wire as small as possible. In the case of a loose grinding saw, the standard is 120 μm, however it has been shown that a wire of 80 μm can be used to cut, for example, a bismuth ingot. Since the abrasive also causes some width in the cutting, the 120 μm-scale line forms a kerf loss of about 135 μm.

In addition, in a wire saw, there must be tension on the wire. Since the wire is pressed against the workpiece, the longitudinally applied tension is transferred to the transverse force in the cutting plane. The lateral force combines with the longitudinal movement of the wire such that the wire cuts the workpiece. Therefore, the line is bowed during sawing. The greater the tension, the smaller the bow and the faster the cutting. In practice, the tension in the net is about 25 Newtons. Therefore, the wire must be able to withstand 1.5 to 2 times the force, otherwise there is a risk of wire breakage. Therefore, there is a contradiction between further reducing the width of the kerf scaled with the diameter of the wire and the strength of the line scaled with the square of the diameter of the wire. This problem becomes more apparent when the abrasive particles are fixed to the wire in a fixed abrasive saw wire to be further shown.

Various techniques are explored to fix the abrasive particles (usually diamond dust particles) to the carrier wire:

- Fixation can be accomplished via mechanical bonding: by pressing the diamond particles into a soft sheath high tension line, such as described in Applicant's Application No. EP2010/055678.

- Metallurgical bonding, for example by brazing or soldering particles to the surface of the wire, has also been considered, for example as described in WO 99/46077. However, this situation is disadvantageous because of the thermal load of the wire causing the loss of strength of the improper wire. The use of a thin wire of less than 150 μm will make the thermal load a more difficult problem because the ratio of the surface of the wire to the volume of the wire becomes too high: the heat inflow is increased, and the block of heated wire is reduced to form a higher The heat load.

- Resin bonding has also been extensively studied, as described, for example, in US 6070570. However, it was found that it was difficult to hold the particles in the resin during sawing.

- Fixing the diamond particles by electrolysis or without electricity. This approach is derived from the replacement blade technology used to cut bismuth ingots and is often used in other diamond cutting tools.

Since the application improvement is for the latter type of fixed technology, it will be discussed in more detail. Basically, there are two distinct ways to attach the diamond to the wire by electrochemical methods: there is no electro-nickel (EN) method. In this method, the wire is immersed in abrasive particles having an aqueous solution containing diamond and an electrolyte comprising metal ions (nickel), a reducing agent (such as sodium hypophosphite), a complex (such as citric acid), and a bath stabilizer. In the bath. The bath is autocatalytic and a nickel coating is formed on the line by immersing the wire therein. A current source is not required to plate the wire (hence the name "no electricity"). When the diamond particles are now covered with a conductive layer (preferably nickel), the diamond particles are also conformally covered with nickel, so that the diamond particles are fixed to the wire. The disadvantage of this method is that it is slow, the bath has a limited lifespan and requires strict bath management. Again, this method produces hydrogen on the surface that is detrimental to the fatigue life of the steel. Typically, the EN coating is rich in phosphorus to make the coating harder. This hardening requires a heat treatment exceeding 400 ° C, which is again not good for thin wires.

US 2003/0140914 describes the application of nickel to steel wires of chrome-nickel steel with diamond particles using an electroless plating bath. In order to prevent hydrogen embrittlement of the wire, the stainless steel wire is first coated with an intermediate layer (copper, nickel or brass) having a thickness of 1 to 10 μm to prevent hydrogen from diffusing into the steel.

The use of stainless steel has problems in terms of strength: it is indeed more difficult to obtain high tension levels due to the high level of strain hardening that is not allowed in stainless steel or in the field. Again, the oxide skin on the stainless steel wire prevents autocatalytic reactions from starting on the surface, which requires pretreatment of the wire with, for example, nickel plating.

When coated in an electroless plating bath, a batch process is typically used, an example of which is described in 2004/0001922.

Second, there are electrolytically deposited nickel and nickel coated abrasive particles. In this case, a current is caused to flow between the wire substrate and the electrolyte bath, which causes the cation (nickel ion) to move toward the substrate in the electric field formed in the bath. By contacting the diamond particles with the wire substrate, the diamond particles are also covered with nickel and adhered to the wire.

JP 2010 082773 describes a method of first covering a normal carbon steel with a stainless steel coating to prevent hydrogen embrittlement. The diamond particles are then fixed in a nickel coating deposited by electrolysis. The publication also mentions that the current density must be limited below the threshold to limit the generation of hydrogen upon entering the bath. Limiting the current density means that the length of the plating bath is also increased and/or the coating speed is lowered, which is not preferable.

During the electrolytic deposition of nickel and nickel-coated diamond, current is passed through the substrate line, so contact between the line and the source must be established. Since this purpose is to make the length of the wire long (at least tens of kilometers), such electrical contact must be able to move between the driven wire and the current source to allow the reel-to-reel manufacturing process. Although it is easy to establish by the contact roller when the surface of the wire is smooth, as long as the abrasive particles adhere to the surface, this cannot be done again. The presence of particles does result in a significant reduction in the contact surface of the rolls with the wire, and as a result a local high current density (spark) occurs.

There are many possibilities for providing a movable electrical contact between a current source and a moving wire with an irregular coating (fixed abrasive saw wire). For example, an electrolyte is used as the possibility of contact with the anode of the wire. This is for example described in WO 2007/147818 of the present application. However, this contact has the disadvantage of partially re-dissolving the previously applied coating, which loosens the abrasive particles that are only partially attached to the wire.

Another solution is to use a wheel covered with conductive fibers, such as described in JP 2004 082253. The fibers (e.g., stainless steel fibers) are arranged in a brush-like arrangement on the contact wheel and ensure good electrical contact even under the presence of the diamond particles. However, the disadvantage is that the fibers may also be coated with nickel, which needs to be replaced periodically.

Therefore, when manufacturing a fixed abrasive saw wire according to an electrolytic route, it is necessary to overcome the problem of "electrical contact".

Accordingly, the inventors have conceived a solution to the problems associated with both electrical products and methods to overcome the problems associated with electrical contact problems. Furthermore, the inventors' proposals also overcome the problems that arise when attempting to manufacture small-scale saw wires by electrolytic coating methods. "Small scale" means that the substrate line is thinner than 150 μm. Furthermore, the inventors have provided solutions with other attendant advantages such as adequate breaking load, increased manufacturing speed, and improved shielding from hydrogen.

According to a first embodiment of the present invention, it is claimed that the fixed abrasive sawing wire comprises a common carbon steel core wire having a diameter of "d" and a metal sheath covering the steel core wire. The diameter "d" means the diameter of a circle having the same area as the steel area of the cross section of the line passing through the plane perpendicular to the axis of the line. The common steel core includes a sheath protective layer having a total diameter of "D". Therefore, the thickness of the sheath is (D-d)/2. The abrasive particles are fixed to the metal sheath by a metal binder layer. The difference from the prior art is that the metal of the metal sheath has higher conductivity than the ordinary carbon steel of the core wire, the former is at least three times the latter, and the diameter "d" of the core wire is smaller than the steel covered with the sheath. 96% of the diameter "D" of the core wire. The latter requirement may also be such that the sheath must be at least 2% of the overall diameter "D".

Although diameters as small as 100 μm have been explored, it is preferred that the normal carbon steel core wire has a diameter of less than 150 μm, preferably less than 140 or even 130 μm, for example 120 μm.

As the resistance per meter is significantly increased and becomes a limiting factor in electrolytic coating methods, efforts to reduce diameters increasingly present a serious problem with small scale lines having diameters less than 150 μm. This is illustrated in Table I, which calculates the resistance per meter of many steel types for two extreme line sizes (250 μm and 120 μm (no coating)).

The increase in electrical resistance per meter of the small-scale line causes a longitudinal voltage drop in the plating bath, resulting in an increase in the plating current density on the wire surface on the contact side of the bath, but a decrease in current density away from the side. "Contact side" means that the plating bath feeds current so current flows into one side of the bath. The local high current density results in increased hydrogen production at the bath inlet due to the depletion of metal ions, and as the voltage index decreases, the more distal the line along the line, the less the coating.

The table also clearly shows that the line resistance is not a problem for thicker wires.

Since the conductivity of the ordinary carbon steel core has been significantly higher, it is preferred to select a common carbon steel core. Ordinary carbon steel can also be cold drawn to a true elongation of 3 or higher, which forms a suitable tensile property.

The actual ordinary carbon steel composition contains not only iron and carbon, but many other alloys and trace elements, some of which have a profound influence on the strength, ductility, formability and corrosion resistance of the steel. With regard to the critical strength of this application, the following elemental composition is preferred for ordinary carbon steel cores:

- at least 0.70% by weight of carbon, the upper limit depending on the other alloying elements forming the line (see table below)

- The manganese content is between 0.30 and 0.70% by weight. Manganese (like carbon) is added during strain hardening on-line and also acts as a deoxidizer in the manufacture of steel.

- The cerium content is between 0.15 and 0.30% by weight. Tantalum is used to deoxidize steel during manufacture. Like carbon, niobium helps to increase the strain hardening of steel.

- The presence of elements such as aluminum, sulfur (less than 0.03 wt%), phosphorus (less than 0.30 wt%), copper (less than 0.60 wt%) is also kept to a minimum.

- The rest of the steel is iron and other elements.

With such ordinary carbon steel, it is easy to achieve a tensile strength of more than 3,500 N/mm ² under appropriate selection of materials and treatment, and an strength of more than 3,750 N/mm ² or even 3,900 N/mm ² can be obtained. These levels are obtained on the steel core wire (regardless of the strength of the sheath).

The presence of trace amounts of chromium (0.005 to 0.30% by weight), vanadium (0.005 to 0.30% by weight), nickel (0.05-0.30% by weight), molybdenum (0.05-0.25% by weight) and boron may reduce the carbon content above the eutectoid composition (0.80) The grain boundary celite of weight % C) is formed to improve the formability of the wire. Such alloying results in a carbon content of from 0.90 to 1.20% by weight and a tensile strength of up to 4000 MPa at the steel core level. These steels are also preferred and are presented in US 2005/0087270.

The tensile strength "TS" of a steel core wire usually expressed in N/mm ² must be higher than:

TS 4700-7.4×d

Where "d" is the diameter of the core wire expressed in microns.

However, even the use of a more conductive ordinary carbon steel core wire is not sufficient to eliminate the resistance problem experienced by the inventors.

The presence of a highly conductive metal sheath around the steel core wire reduces the electrical resistance per metre of the wire. Since most of the cross-sectional area of the round wire is just less than its circumference, the best system makes the sheath a more conductive part. In addition, current is drawn on the sheath by metal ions in the bath rather than being consumed in the core. The "B core" portion of the core through which the overall current passes is obtained by:

Wherein α=d/D and A=γ _sheath /γ _core , wherein the γ _sheath and the γ _core are the conductivity of the sheath and the core (ie, Siemens/meter, S/m). The current portion passing through the sheath is a B- _sheath = 1 - B _core .

In either case, the current through the sheath must be higher than the portion passing through the core, i.e., the B _core must be less than 0.5 to have the most current (the line surface) most of the current. This can be achieved by applying two restrictions:

- The higher the conductivity of the sheath metal, the higher the current will pass through the sheath and the thinner the sheath. Preferably, the sheath metal must have at least three times the conductivity of the steel core, ie, A. 3. In this case, the core may be greater than 0.866 x D, i.e., the core still has sufficient strength. Suitable sheath metals are silver (conductivity 62.1 MS/m, million Siemens/meter), copper (58.8 MS/m), gold (41.7 MS/m), aluminum (37.0 MS/m), cobalt (17.2) MS/m), zinc (16.8 MS/m). Since the conductivity of the alloy is lower than that of the constituent metal, the alloy is less preferred.

- if the sheath metal is at least eight times more conductive than the steel core (ie A 8) It is better. The only metals that can still be used are copper and silver. Among them, copper is preferred because of its availability and lower cost. In the case of copper, the optimum diameter of the core is between 0.88 and 0.95 times the diameter "D" of the sheathed steel core, which corresponds to a sheath diameter between 2.5 and 6% of the overall sheathed steel core. .

- The diameter of the core is not more than 96% of the diameter "D" of the steel core wire covering the sheath (ie, "D" includes the outer sheath). Larger cores do not result in further reduction in resistance per meter.

Another advantage of this line is the closed metal sheath to prevent hydrogen embrittlement. Hydrogen embrittlement is a particularly serious problem for high tension lines of ordinary carbon steel.

A further advantage of reducing the resistance per metre of the wire is that there is less resistance heat generated per unit length. This heat can cause problems in this process because the small temperature rise on the long lines may have caused the length of the line to relax between different method steps.

The interface between the steel core and the first metal layer can exhibit a particular roughness and can even be interlocked. The advantage of such an interface is that the sheath layer is preferably adhered to the steel core wire. "Interlocking" means that a particular projection of the metal sheath is hooked into a corresponding recess of the steel core wire. For the purposes of this application, the roughness is expressed as the arithmetic mean deviation roughness "R _a " measured on the metallographic cross section. The average "R _a " must be greater than 0.50 microns, more preferably greater than 0.70 microns.

The average "R _a " is _a separate photograph of the different sectors around the shot line and the roughness "R _a " of each sector is measured and then the average value is calculated. At least half of the circumference of the cross section must be measured in different sectors to achieve good coverage for the overall surroundings. A magnification of 500 to 1000 times should be used.

The abrasive particles can be superabrasive particles, such as diamond (natural or artificial, due to the lower cost and friability of the latter, the latter being slightly better), cubic boron nitride or mixtures thereof. For lower applications, particles such as tungsten carbide (WC), tantalum carbide (SiC), alumina (Al ₂ O ₃ ) or tantalum nitride (Si ₃ N ₄ ) may be used: although it is softer, But it is much cheaper than diamonds. The best is artificial diamond.

The abrasive particles are at least partially coated with a conductive layer that would otherwise be unable to electrolytically coat the metal adhesive layer. Exemplary coatings are titanium, titanium carbide, tantalum, zirconium, palladium, tungsten, tungsten carbide, chromium, iron, copper or nickel coatings. Copper and nickel coatings are the best because they are easy to obtain. The metal coating weight ratio should be less than 50% of the total weight (diamond and coating), preferably less than 30%.

Since the binder layer attaches the abrasive particles to the layer of the sheathed steel core wire, it is quite important. The abrasive particles are attached to the metal sheath by electrolytic deposition. The method of pressing the abrasive particles into the sheath is not explicitly considered here. Thus, the sheath of the saw of the present invention is substantially free of abrasive particle indentation, i.e., only the metal binder layer is utilized without the use of the sheath to retain abrasive particles.

Preferred metals as the metal in the metal binder layer are iron, nickel, chromium, cobalt, molybdenum, tungsten, copper, zinc, tin and alloys thereof. Nickel is by far the best because other metals imply environmental or health constraints or their use is different from processed material (such as semiconductor materials, especially germanium). The layer of the present invention is applied only by electrolytic coating (non-electroless coating). Therefore, the adhesive layer exhibits a crystal structure having particles. Electroless nickel shows an amorphous structure.

The thickness of the metal bond layer is between 2 and 10 microns, preferably between 3 and 6 microns, and preferably between about 4 microns.

The size of the abrasive particles must be chosen according to the thickness of the metal binder layer (or vice versa). Measuring the size and shape of the particles themselves is a technical field of the technology itself. Since the particles are not (and should not be) spherical, for the purposes of this application, reference will be made to the particle "size" rather than its "diameter" (diameter means spherical). The size of the particles is determined by linear measurement (in microns) of any measurement method known in the art, and the length of the two points (through the particle body) that are always farthest from each other on the surface of the connected particles is spaced from the surface of the particles. The length between the two recent points (through the particle body).

It is conceivable that the size of the particles of the fixed abrasive sawing wire falls within the category of "fine particles". The size of the particles can no longer be determined by standard screening techniques commonly used for giant particles. Rather, it must be determined by other techniques, such as laser diffraction, direct microscopy, electrical resistance or photosedimentation. These methods are described in more detail in the standard ANSI B74.20-2004. For the purposes of this application, when referring to particle size, it is meant the particle size as determined by laser diffraction (or "low angle laser light scattering"). The output of such a process is a cumulative or differential distribution of the median size d ₅₀ (ie, half of the particles are smaller than the size and half of the particles are larger than the size).

Superabrasives are usually identified by the size range of the standard rather than the mesh number. For example, 90% of the 20-30 micron particle distribution is between 20 microns (ie "d ₅ ") and 30 microns (ie "d ₉₅ ") and less than 1/1000 over 40 microns, while The median size d ₅₀ must be between 25.0 +/- 2.5 microns.

The median size d _{50 of the} abrasive particles is preferably between 1 and 5 times the thickness of the metal binder layer. Smaller particles disappear into the coating and larger particles cannot be properly held by the adhesive layer. It is more preferable if the median particle size is between 1 and 3 times the thickness of the metal binder layer, if the particle is 1 to 2 times the thickness of the metal binder layer.

The amount of abrasive particles present depends on the material of the workpiece to be cut. The density should not be too high on the one hand to prevent the load on the wire, and on the other hand should not be too low, otherwise the wire cannot be cut. Typically, a coverage area between 1 and 50%, or between 2 and 20%, or even between 2 and 10% is preferred. In this way, sufficient cutting performance can be obtained while the load of the wire does not occur during use. This coverage area can be assessed by visual inspection.

According to a second embodiment of the present invention, a method of making a fixed abrasive sawing wire of the present invention is provided. The method includes the following steps:

a. Select a normal carbon steel core wire with a diameter of “d”. Preferably, the wire has a diameter of less than 150 μm and has a composition according to the sixth row from the bottom of page 11 to the eleventh row on the 12th page or the twelfth row to the 18th row on the 12th page. The tensile strength of the steel core wire in N/mm ² must be higher than 4700-7.4xd ("d" in μm).

b. The steel core is coated with a coating metal having a conductivity of at least three times higher than that of ordinary carbon steel having a steel core wire. The coating is thickened until the steel core wire comprising the coating has an overall diameter of at least d/0.96.

c. The sheathed steel core wire is electrolytically coated with a metal binder layer by directing the wire through an electrolyte bath comprising a binder metal ion species and abrasive particles. This step is carried out in a continuous process in which the sheathed steel core wire is unwound from the unwinder, coated with the adhesive layer and abrasive particles, and wound on a winding shaft. The point of contact is on the line with the sheath and not on the line where the abrasive is applied, and all current is supplied at the point of contact, through the line and through the bath. Therefore the contact point is only on the line entrance side of the bath.

In the step "a", a possible ordinary carbon steel core wire such as a saw wire is used for a loose saw.

In step "b", the coating can be electrolytically coated to a desired thickness from an electrolytic bath containing a preferred metal species as mentioned in line 10 on page 13 to line 6 on page 14.

In step "c", the abrasive particles are preferably at least partially coated with a conductive layer to provide good binder metal growth on the abrasive particles. Preferably, the abrasive particles are brought into intimate contact with the wire by passing the wire through a mixture of abrasive particles and an electrolyte metal containing the electrolyte.

In another preferred embodiment, step "c" is followed by further thickening the metal bond by electrolytic coating in an electrolytic bath containing a metal binder by attracting current from the same electrical contact point as step "c". Agent layer. Preferably, the electrolyte bath is the same as step "c" except that no abrasive particles are present in the electrolyte bath.

In another preferred embodiment of the method, a plain carbon steel wire having a diameter "d ₀ " is selected and then coated with a metal sheath until an overall wire diameter of "D ₀ " is obtained. "D ₀ " is at least d ₀ /0.96. The metal sheath is the preferred metal species mentioned on the 13th page from the 10th line to the 14th page, line 6. The diameter of the wire is now reduced by pulling the wire through a subsequent smaller die until the final diameter D is obtained. The preferred reason for this method is:

- It is more economical to allow the use of sheath metal strips to cover large diameter steel core wires (which cannot be applied to wires with a diameter of less than 150 μm).

Or, it allows a higher current density to electrolyze the sheath metal coating on the thicker line. Indeed, for this thicker line, the resistance per meter of the line is low enough to cause problems.

In addition, the interface between the steel core wire of the drawn wire and the metal sheath exhibits a rough interface on the metallographic cross section. Such a rough interface is beneficial for improving the adhesion between the steel core wire and the metal sheath.

Figure 1 shows schematically a cross section of a fixed abrasive sawing wire 100 of the present invention. There are a common carbon steel core wire 110 having a diameter "d" and a metal sheath 120 covering the steel core wire. The steel core wire covered with the sheath has a diameter "D". The abrasive particles 130, 130', 130" are attached to the metal sheath with a layer of metal adhesive 140. When the interface between the steel core and the sheath is rough (as shown here), we must use the average of the steel core wire The diameter is "d".

In the first series of tests, ordinary carbon steel rods (nominal diameter 5.5) used high carbon steel with a nominal carbon content of 0.925% by weight and a composition according to lines 12 to 18 of page 12. The wire was descaled, dry drawn to 3.05 mm, toughened and further dry drawn to a diameter of 0.89 mm and then toughened again. The material is divided into two parts. The first part is then plated with copper and zinc and then allowed to diffuse. The coating amount was about 5 to 6 g/kg and the copper content of the coating was 67% Cu. The wire was further drawn on a wet wire drawing machine to a wire diameter totaling 120 μm. The brass coating then has a thickness of about 0.15 μm. The conductivity of brass is about 13 MS/m. The drawn line has a breaking load of 45.3 N.

This thread is used as a metal sheathed core wire for electrolytically coating abrasive particles on the reel-to-reel device 200 shown in FIG. The apparatus has a unwinding station for unwinding the feed spool 210 of the core of the sheath, a series of rides I, II, III, IV (separate electrolyte solution is continuously circulated therein) and having a winding shaft 260 Winding unit. Each of the pass-throughs has anodes 242, 242', 242", 242"' that are connected to individual controlled current sources 240, 240', 240", 240"'. All sources are connected to a common conductor 250 that is connected to a single electrical contact roller 230. There are no other contact rolls. It is clear from the electrical diagram that all currents "tot" from the currents i ₁ , i ₂ , i ₃ and i ₄ of the coating bath must pass through the line 220, i _tot = i ₁ + i ₂ + i ₃ + i ₄ .

The first pan I contained a mixture of nickel-coated diamond and an electrolyte having a dipping length of 70 cm. The diamond has a median size of 9 μm, a range of 6 to 12 μm (5% and 95% limit), and is coated with nickel (30% by weight of nickel). The electrolyte flowing through the disk I has the following composition, acidity and temperature:

Baths II, III, IV are identical and have an impregnation length of 25 cm. It is used to "thicken" the nickel binder layer to a total thickness of nickel of 4 μm and is free of abrasive particles.

The first bath maintained a current density of 15 A/dm ² at 10.7 volts. The current density in the other bath was maintained at 20 A/dm ² at the voltage of the last disk from 10V to 19V. The total current i _tot delivered through the line is 0.96 amps, forming 14.7 watts of heat dissipation per meter. Hydrogen production at the inlet of the bath is significant and the coating poorly holds the abrasive particles. The line is also very brittle during processing, which is an indication of hydrogen embrittlement. It is not possible to perform a sawing test with it. The breaking load fell to 41.4 N (down 8.6%).

When the current flowing through the core and through the sheath is now calculated, we obtain only 1.4% of the total current through the sheath. The conductivity ratio "A" is only 2.9. The wire has a resistance of 15.9 Ω/m per metre, which is similar to an uncoated plain carbon steel wire. The inventors noticed that current did not flow through where it should flow.

In a subsequent test, a 0.89-retained toughened annealing line was partially coated with an electrolytic copper coating of approximately 370 g/kg of pure copper. The conductivity of pure copper is 59 MS/m. The wire was then drawn wet to a total diameter of 137.6 μm. The steel core has a diameter of 123 μm and a coating thickness of 7.3 μm. The breaking load was 48.2 N, which resulted in a tensile strength of the sheathed core of 3313 N/mm ² . The steel core wire tensile strength was evaluated to be about 4200 N/mm ² . This interface clearly shows roughness and even interlocking. The resistance per metre is 4.1 Ω/m.

A coating method identical to that of the first sample is performed on the sheathed core wire. Again, the first bath was maintained at a current density of 15 A/dm ² , but it only required a voltage of 4.7 volts. The current density in the other baths was maintained at 20 A/dm ² at a voltage of up to 7V. The total current i _tot delivered through the line is 1.10 amps, forming 4.8 watts of heat dissipation per meter. No hydrogen is produced at the inlet of the bath, and the coating holds the abrasive particles well. The final strength of the line in the tensile test was 48.1 N (no negligible loss of 0.2%).

The conductivity of copper is 10.6 times that of the ordinary carbon steel core. The diameter ratio of the diameter of the steel core wire to the diameter of the sheathed steel core wire is 89%. The current through the sheath is 73%, i.e., greater than 50%. Only 27% passed the steel core wire. The inventors have concluded that most current flows at the point where the current is required (on the surface).

Verify the sawing test on the DWT RTS-480 single-wire reel to the reel saw. A 25 x 125 mm ² single crystal block was sawed from the shorter side, that is, the contact length between the line and the block was 25 mm. The line reciprocates at an average line speed of 450 m/min at a length of 180 m, which is maintained at a constant tension of 12 N and a sawing speed of 4.5 mm/min. The bow formed during the cutting is measured as a function of time. Large bows mean low cutting capacity and small bows mean high cutting capacity. The wear of the wire can be evaluated by repeating the sawing on the same line. The line of the invention shows that the bow at the end of the first cut is 8 mm, 11 mm at the end of the second cut, and 16 mm at the end of the third cut.

Samples having different copper coating thicknesses were prepared in the same manner (under the same raw materials).

- The sample with a 1 μm thick coating has a total diameter of 122 μm. The line had a breaking load of 44 N prior to plating. The diameter ratio is 0.984 and the current through the core is 74%, ie only 26% of the current is passed through the coating. The resistance per metre is 11.7 Ω/m. Hydrogen production was observed during coating. The rupture load after coating was reduced to 42.6 N (loss of 3.2%).

- The sample with a 4 μm thick coating has a total diameter of 127 μm. The line had a breaking load of 46.1 N prior to plating. The diameter ratio is 0.937 and the current through the core is 40%, ie only 60% of the current is passed through the coating. The resistance per metre is 6.5 Ω/m. No hydrogen production was observed during the coating. After coating, the line showed a breaking load of 47.6 N (an increase of 3%).

These structures illustrate the minimum sheath thickness of the sheath metal that requires minimal conductivity to enable electrolytic coating on the fine lines using abrasive particles in a good manner.

100. . . Fixed abrasive sawing wire

110. . . Ordinary carbon steel core wire

120. . . Metal sheath

130/130'/130"...abrasive particles

140. . . Metal adhesive layer

d. . . Steel core wire diameter

D. . . Steel core wire diameter covered with the sheath

200. . . Reel to reel device

210. . . Feed reel

220. . . line

230. . . Electrical contact roller

240/240'/240"/240'''...current source

242/242'/242"/242'''... anode

260. . . Winding shaft

i ₁ /i ₂ /i ₃ /i ₄ . . . Current

i _tot . . . All current

Figure 1 illustrates a specific example of the product of the present invention.

Figure 2 shows an apparatus in which the product of the invention can be made.

100. . . Fixed abrasive sawing wire

110. . . Ordinary carbon steel core wire

120. . . Metal sheath

130/130'/130"...abrasive particles

140. . . Metal adhesive layer

d. . . Steel core wire diameter

D. . . Steel core wire diameter covered with the sheath

Claims (13)

A fixed abrasive sawing wire comprising a common carbon steel core wire having a diameter d; a metal sheath covering the steel core wire, a steel core wire covered with the sheath having a diameter D, and an abrasive fixed to the metal sheath by a metal adhesive layer a particle, wherein the metal of the metal sheath has higher conductivity than the ordinary carbon steel of the core wire, the former being at least three times the latter, and wherein the metal sheath is composed of copper, silver, aluminum, gold, zinc, cobalt In one of the groups, the diameter d of the core wire is less than 96% of the diameter D of the steel core wire covered with the sheath, characterized by gold between the metal sheath and the core wire in a plane perpendicular to the wire A rough interface can be discerned in the cross-section of the phase; and wherein the arithmetic mean deviation roughness R _{a of} the rough interface is higher than 0.50 μm on average and the rough interface is interlocked. The fixed abrasive sawing wire of claim 1, wherein the metal sheath metal has a conductivity higher than that of the ordinary carbon steel of the core wire, the former being at least eight times greater than the latter. The fixed abrasive sawing wire according to claim 1, wherein the ordinary carbon steel comprises at least 0.70% by weight of carbon, the manganese content is between 0.30 and 0.70% by weight, the cerium content is between 0.15 and 0.30% by weight, and the aluminum content is less than 0.03% by weight, sulfur content less than 0.03% by weight, phosphorus content less than 0.30 weight The amount of copper is less than 0.60% by weight and the balance is iron. The fixed abrasive sawing wire according to claim 3, wherein the ordinary carbon steel additionally comprises a chromium content of 0.005 wt% to 0.30 wt%, a vanadium content of 0.005 wt% to 0.30 wt%, and a nickel content of 0.05 wt. From % to 0.30% by weight, the molybdenum content is between 0.05% and 0.25% by weight. A fixed abrasive sawing wire according to claim 1, wherein the ordinary carbon steel core wire has a diameter d of less than 150 micrometers. The fixed abrasive sawing wire of claim 1, wherein the ordinary carbon steel core wire has a tensile strength of at least 3500 N/mm ² . The fixed abrasive sawing wire according to any one of claims 1 to 6, wherein the abrasive particles are selected from the group consisting of diamond, cubic boron nitride, tantalum carbide, aluminum oxide, tantalum nitride, tungsten carbide or Group of mixtures. The fixed abrasive sawing wire of claim 7, wherein the abrasive particles are selected from the group consisting of titanium, titanium carbide, tantalum, zirconium, palladium, tungsten, tungsten carbide, chromium, iron, copper or nickel. Coating. The fixed abrasive sawing wire according to any one of claims 1 to 6, wherein the metal in the metal adhesive layer comprises iron, nickel, chromium, cobalt, molybdenum, tungsten, copper, zinc, tin and alloys thereof. One of the groups. The fixed abrasive sawing wire of claim 9, wherein the metal adhesive layer has a thickness of between 2 and 10 microns. A fixed abrasive sawing wire according to claim 10, wherein the median size of the abrasive particles is between 1 and 5 times the thickness of the metal adhesive layer. A method of manufacturing a fixed abrasive sawing wire according to any one of claims 1 to 11, comprising the steps of: - selecting a plain carbon steel core wire having a diameter d ₀ ; - coating the steel core wire with a metal sheath until Obtaining the diameter D ₀ , the diameter D _{0 is} greater than d ₀ /0.96, the conductivity of the metal of the metal sheath is higher than that of the ordinary carbon steel, the former is at least three times of the latter; - pulling the line of the obtained semi-finished product a step of reducing the diameter of the sheathed steel core wire to a smaller diameter D; - contacting the line containing the electrolyte bath of the binder metal and the abrasive particles on the sheathed wire by a continuous reel-to-reel method An electric current is supplied to the contact point on the inlet side to fix the abrasive particles in the metal binder layer to the metal sheath. As in the method of claim 12, the metal binder layer is further electrolyzed by applying a current through the same contact point in an electrolyte bath containing the binder metal.