Abrasive sawing wire, production method thereof and use of same

Abstract

An abrasive wire including a steel core and an outer coating including a binder and abrasive particles, the binder being formed by at least one nickel-cobalt alloy layer having a cobalt content of between 20 wt.-% and 85 wt.-% in relation to the weight of the Ni/Co alloy.

Claims

1. An abrasive wire comprising a steel core and an external coating comprising a binder and abrasive particles, said binder being formed of at least one layer of nickel/cobalt alloy having a cobalt content in the range from 20% to 85% by mass with respect to the mass of the Ni/Co alloy.

2. The abrasive wire of claim 1, wherein the Ni/Co alloy comprises from 37 to 65% by mass of cobalt.

3. The abrasive wire of claim 1, wherein the external coating comprises two layers of binder made of a Ni/Co alloy, having, independently from each other, a cobalt content in the range from 20% to 85% by mass.

4. The abrasive wire of claim 1, wherein the Ni/Co alloy contains sulfur.

5. The abrasive wire of claim 1, wherein the abrasive particles are made of a material selected from the group consisting of silicon carbide; silica; tungsten carbide; silicon nitride; boron nitride; chromium dioxide; aluminum oxide; diamond; and diamonds pre-coated with nickel, iron, cobalt, copper, or titanium, or with alloys thereof.

6. The abrasive wire of claim 1, wherein the abrasive particles are formed of grains at least partly covered with a film made of a ferromagnetic material.

7. A method of manufacturing the abrasive wire of claim 1, comprising the steps of: electrodeposition on a steel wire of a coating comprising a binder and abrasive particles, said binder being made of a layer of nickel/cobalt alloy having a cobalt content in the range from 20% to 85% by mass relative to the mass of the Ni/Co alloy, by passing in an electrolyte bath (B.sub.1) comprising at least cobalt II and nickel II ions, and abrasive particles; optionally, electrodeposition of an additional binder layer by passing in an electrolyte batch (B.sub.2) comprising at least cobalt II and nickel II ions, said additional layer being made of a Ni/Co alloy having a cobalt content in the range from 20% to 85% by mass.

8. The abrasive wire manufacturing method of claim 7, wherein the baths (B.sub.1) and (B.sub.2) comprise, independently from each other, from 1 to 150 g/L of cobalt II ions and from 50 to 150 g/L of nickel II ions.

9. The abrasive wire manufacturing method of claim 7, wherein the bath (B.sub.1) comprises from 1 to 100 g/L of abrasive particles.

10. A use of the abrasive wire of claim 1, to saw a material selected from the group consisting of silicon, sapphire, and silicon carbide.

11. The abrasive wire of claim 4, wherein the Ni/Co alloy contains sulfur in an amount in the range from 100 to 1,000 wt.Math.ppm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates a device enabling to obtain the abrasive wire according to a specific embodiment of the invention.

(2) FIG. 2 illustrates a cross-section view of the abrasive wire according to a specific embodiment of the invention.

(3) FIG. 3 illustrates a cross-section view of an abrasive particle of the abrasive wire according to a specific embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) The device (2) illustrated in FIG. 1 enables to implement a specific embodiment of the electrodeposition method on a steel wire (4) to prepare the abrasive wire (3) according to the present invention.

(5) The method especially comprises the steps of: unwinding a steel core (4) (steel wire) stored in the form of a coil (24), along the direction of arrow F; optionally, degreasing steel core (4) in an alkaline medium; optionally, pickling steel core (4) in an acid medium; optionally, passing steel core (4) through a magnetization device (26) which applies a magnetic field, having an intensity advantageously greater than 800 Nm. Core (4) is thus permanently magnetized; electrodepositing on the steel core a coating comprising a binder and abrasive particles, said binder being a nickel/cobalt alloy having a cobalt content in the range from 20% to 85% by mass relative to the mass of the Ni/Co alloy, by passing in a bath (B.sub.1) (36) of electrolyte (38) comprising at least cobalt II and nickel II ions, and abrasive particles (6); optionally, electrodepositing a second bonding layer by passing in a bath (B.sub.2) of electrolyte (52) comprising at least cobalt II and nickel II ions. obtaining abrasive wire (3); optionally storing abrasive wire (6), advantageously in the form of a coil (68) by means of a motor (70).

(6) The device (2) used comprises a source (28) which generates an electrolysis current i.sub.e. The positive terminal of source (28) is connected to electrode (40) located in bath (B.sub.1) (36) of electrolyte (38) which is contained in vessel (34). The negative terminal of source (28) is connected to two conductive pulleys (30) and (48) arranged on either side of vessel (34) via electric conductors (32) and (46). The two conductive pulleys (30) and (48) enable to provide two points (A) and (B) of mechanical contact with steel core (4) which is thus connected to the negative terminal of source (28).

(7) Advantageously, two current sources (28A and 28B) may be used. Their respective negative terminals are connected together to conductive pulleys (30) and (48).

(8) The positive terminal of generator (28A) is connected to an anode (40A) made of nickel.

(9) The positive terminal of generator (28B) is connected to an anode (40B) made of cobalt.

(10) Assuming that the cobalt content in the nickel and cobalt alloy deposit should be 20%, it is preferably to have 20% of the current flow through the generator (28B) connected to the cobalt anode (40B), and 80% of the current flow through the generator (28A) connected to the nickel anode (28A). For more clarity, FIG. 1 shows a device comprising a single electric current generator, and a single anode in bath (B.sub.1) (36).

(11) Optionally, device (2) further comprises a device (44) for magnetizing abrasive particles (6) and steel core (4) once it is immersed in bath (B.sub.1) (36). It is positioned above bath (B.sub.1) (36).

(12) Optionally the abrasive particles used are magnetic to allow the electrodeposition of the external coating on the steel core. They can thus be attracted by the steel core, which is magnetized during this process.

(13) As already mentioned, the magnetic properties of the abrasive particles may in particular originate form a magnetic film covering them.

(14) The steel core is thus covered with a coating made of binder and of abrasive particles by electrodeposition on passing in the bath (B.sub.1).

(15) According to a specific embodiment, a second binder layer may then be deposited on the steel core, by passing through second bath (B.sub.2) (52).

(16) Second bath (B.sub.2) (52) which is contain in vessel (50), comprises an electrolyte. It advantageously comprises no abrasive particles.

(17) The step of electrodeposition of the second binder layer comprises, in particular, immersing the steel core covered with a first binder layer and with abrasive particles, in a bath having an electrode (54) connected to the positive terminal of a second current source (56) arranged therein.

(18) The negative terminal of second current source (56) is connected to two conductive pulleys (62) and (64) arranged on either side of vessel (50) containing second bath (B.sub.2) (52) via electric conductors (58) and (60).

(19) Advantageously, two current sources (56A and 56B) may be used. Their respective negative terminals are connected together to conductive pulleys (62) and (64).

(20) The positive terminal of generator (56A) is connected to an anode (54A) made of nickel.

(21) The positive terminal of generator (56B) is connected to an anode (54B) made of cobalt.

(22) Assuming that the cobalt content in the nickel and cobalt alloy deposit should be 85%, it would be advantageous to have 85% of the current flow through generator (56B) connected to the cobalt anode (54B), and 15% of the current flow through generator (56A) connected to the nickel anode (54A). For more clarity, FIG. 1 shows a device comprising a single electric current generator, and a single anode in bath (B.sub.2) (52).

(23) Conductive pulleys (62) and (64) provide the connection between steel core (4) and the negative terminal of second current source (56) at contact points (C) and (D).

(24) After the passing through the second electrolyte bath, abrasive wire (3) is obtained. It may be stored in the form of a coil (68).

(25) As already indicated, device (2) is described in further detail in the patent application filed under number FR 12.53017.

(26) As shown in FIG. 2, abrasive wire (3) according to the invention has a core (4) coated with a first binder layer (10) partially covering abrasive particles (6).

(27) According to this specific embodiment, the abrasive wire further comprises a second binder layer (12) covering abrasive particles (6). This second binder layer advantageously has a better abrasion resistance than the first layer. On the other hand, the second binder layer (12) is advantageously less hard and more ductile than the first layer (10) covering the steel core (4).

(28) The two layers (10) and (12) and abrasive particles (6) form external coating (8) of abrasive wire (3).

(29) According to a specific embodiment, abrasive particle (6) comprises an abrasive grain (16) covered with a film (18) (FIG. 3). The film is advantageously made of a magnetic material to ease the electrodeposition of the particles on steel core (4). Indeed, the electrodeposition of the external coating is advantageously implemented in the presence of magnetic particles.

Embodiments of the Invention

(30) A plurality of abrasive wires (examples 1-9) have been prepared from a steel core in the hardened state. The steel core comprises 0.8% of carbon, it has a 0.12-millimeter diameter.

(31) Operating procedure:

(32) The wires have been prepared according to the steps of: (1) degreasing the steel core in an alkaline medium; (2) pickling the steel core in an acid medium; (3) electrodeposition by passing the steel core in a first electrolyte bath (B.sub.1) comprising abrasive particles, to form a first external layer; (4) optionally, second electrodeposition by passing the steel core in a second electrolyte bath (B.sub.2), to form a second external layer.

(33) The respective compositions of electrolyte baths (B.sub.1) and (B.sub.2) have been adjusted according to the examples. The baths are water-based.

(34) For example, electrolyte bath (B.sub.1) according to example 9 contains: 100 g/L of Ni.sup.2+ in the form of nickel sulfamate and of nickel chloride; 4 g/L of Co.sup.2+ in the form of cobalt sulfamate; 15 g/L of Cl.sup. in the form of nickel chloride; 35 g/L of H.sub.3BO.sub.3 (boric acid); 2 mL/L of wetting agent UNW 89 (Mc Dermid), formed, among others, of sodium lauryl sulfate; 20 g/L of pre-nickel plated diamonds having a diameter from 12 to 22 micrometers and containing approximately 50% by mass of nickel.

(35) The pH of this bath (B.sub.1) is adjusted to 3.8 by addition of sulfamic acid.

(36) Electrolyte bath (B.sub.2) according to example 9 contains: 100 g/L of Ni.sup.2+ in the form of nickel sulfamate and of nickel chloride; 30 g/L of Co.sup.2+ in the form of cobalt sulfamate; 15 g/L of Cl.sup. in the form of nickel chloride; 35 g/L of H.sub.3BO.sub.3 (boric acid).

(37) The pH of this bath (B.sub.2) is adjusted to 3.8 by addition of sulfamic acid.

(38) The conditions of the treatment of the steel core in baths (B.sub.1) and (B.sub.2) are identical and are the following: temperature: 55 C.; wire speed: 5 m/min; current density: 2 A/dm.sup.2.

(39) The wires according to examples 1 to 8 of table 1 have been prepared according to steps (1) to (3) of this operating procedure by adjusting the quantity of cobalt and nickel. Only the passing in bath (B.sub.1) has been carried out.

(40) However the wire according to example 9 has been prepared according to steps (1) to (4) of the operating procedure. The binder of this wire is thus formed of two layers.

(41) Results:

(42) The hardness of the binder layers of the wires according to examples 1-9 have been measured according to known techniques (Vickers micro-hardness).

(43) The abrasion resistance of the binder layers is estimated from plates on which they have been previously deposited (in the same electrochemical conditions as for abrasive wires). The wafers have been placed in a hard stainless steel ball tribometer, in dry conditions, with no lubrication. The volume of eroded deposit has been observed. A small eroded volume corresponds to a good abrasion resistance.

(44) The experimental conditions implemented to prepare the wires according to examples 1-9 are specified in the following table. They especially comprise: the respective Ni.sup.2+ and Co.sup.2+ ion concentrations in the electrolyte, in grams per liter; the cobalt concentration in the deposit (binder)the rest being made of nickel and of traces of oxygen, hydrogen, and sulfur; the hardness of the deposit, expressed in Vickers (Hv); the resistance to abrasion of the deposit against a hard steel part.

(45) The wires according to examples 1-8 have a single binder layer having a thickness equal to 8 micrometers.

(46) The wire according to example 9 has a first binder layer with a thickness equal to 8 micrometers, and a second binder layer with a thickness also equal to 8 micrometers.

(47) TABLE-US-00001 TABLE 1 Hardness and abrasion resistance of abrasive wires according to the invention (INV) and counterexamples (CE). Cobalt in deposit Hardness Abrasion Ni.sup.2+ Co.sup.2+ (% by of deposit resistance Examples (g/l) (g/l) mass) (Hv) of deposit 1 (CE) 100 0 0 250 poor 2 (CE) 100 2 10 280 poor 3 (INV) 100 4 20 300 average 4 (INV) 100 10 37 350 average 5 (INV) 100 15 65 350 average 6 (INV) 100 30 85 300 good 7 (CE) 0 100 100 250 good 8.sup.(i) (INV) 100 4 20 500 Good, but low ductility 9.sup.(i) (INV) B.sub.1 100 4 20 300 good B.sub.2 100 30 85 300 not measured .sup.(i)addition of 5 g/L of sodium saccharin, C.sub.7H.sub.4NO.sub.3, Na, 2H.sub.2O in bath B.sub.1.

(48) By SIMS (Secondary Ion Mass Spectrometry), 3.10.sup.19 atoms/cm.sup.3 of sulfur have been measured, that is, approximately 300 ppm (parts per million, by mass). Presence of cracks during the traction test on the wire according to example 8.

(49) .sup.(ii) bilayer wire, deposition of two layers according to steps 1 to 4: The abrasion resistance of the external layer deposited in B.sub.2 is good, the other has not been measured since it is the internal layer deposited by B.sub.1.

(50) It should be noted that the hardness is high when the cobalt content in the binder is in the range from 37% to 65%. At this concentration, the abrasion is significantly decreased with respect to a pure nickel deposit. The layers are ductile.

(51) On the other hand, the abrasion is minimum for wires having a cobalt percentage in the binder at least equal to 85. The layers are ductile.

(52) A good hardness/abrasion tradeoff is obtained when the cobalt percentage is in the range from 20 to 85, advantageously from 37 to 65.