Abrading – Machine – Reciprocating tool
Reexamination Certificate
2002-11-08
2004-08-31
Hail, III, Joseph J. (Department: 3723)
Abrading
Machine
Reciprocating tool
C125S012000, C125S021000, C125S022000, C051S295000
Reexamination Certificate
active
06783442
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a nickel-diamond coated saw wire with improved anchoring of the diamond particles in the metallic binder phase.
2. The Prior Art
In DE A 19839091 (corresponds to the U.S. application bearing Ser. No. 09/332722), a nickel-diamond coated saw wire, a process for its production and its use are described. A wire of this type can be used to saw hard, brittle material, such as silicon. The saw wire is produced by introducing a wire, after a chemical pretreatment, into a chemical nickel bath which contains diamond particles, preferably of a mean diameter of from 5 to 30 &mgr;m. The diamond particles which are deposited on the surface of the wire are initially fixed by weak chemical and/or physical bonding forces. During the coating process, the adhering diamond particles are firmly enclosed by the growing nickel layer and are thus securely anchored. The thickness of the metallic binder phase is preferably 5-20 &mgr;m. The properties of the metallic binder phase are considerably improved by subsequent thermal hardening. For example, a reduction in the residual tensile stresses in the metallic binder phase is observed, the adhesive strength is increased and the hardness of the layer rises considerably. When sawing silicon, a wire of this type provides very good sawing results, as can be seen from the abovementioned application.
On account of the properties described, the nickel-diamond coated saw wire also appears to be suitable for sawing hard ceramic materials, such as silicon carbide. Although tests have shown that in principle a saw wire of this type can be used to cut hard ceramic materials, the high hardness of the hard ceramic materials means that the sawing rates which can be achieved and also the service life of the coated saw wire are insufficient for industrial use.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a diamond-coated saw wire which has a high resistance to wear when sawing hard materials, such as for example hard ceramic materials.
The object is achieved by a saw wire, comprising a steel wire, an intermediate layer and a metallic binder phase in which diamond grains, with a mean diameter of 10 to 50 &mgr;m are embedded, the intermediate layer being undamaged and free of diamond grains and serving both to prevent hydrogen embrittlement of the wire and to ensure sufficient adhesive strength of the metallic binder phase, characterized in that the metallic binder phase has a hardness of between 600 and 1100 HV 0.1 and comprises an inner layer and an outer layer, which are arranged concentrically around the steel wire which has been provided with the intermediate layer, the inner layer having a thickness of approximately 10 to 25% of the mean diamond grain diameter and the outer layer having a thickness which is such that the total thickness of the metallic binder phase is 45-55% of the mean diamond grain diameter, and the diamond grains having a mean spacing between them of no more than five times their mean diameter and further fine particles with a mean diameter of from 1 to 6 &mgr;m being situated between the diamond grains with a mean diameter of from 10 to 50 &mgr;m.
The diamond grains which are fixed to the saw wire are therefore anchored in the metallic binder phase approximately as far as their equator.
The diamond grains which are fixed to the wire preferably have a mean diameter of from 25 to 45 &mgr;m. Said diamond grains are preferably positioned on the wire in a quantity which is such that their mean spacing amounts to no more than 0.5 to 3 times their mean diameter.
Further fine particles are situated between the diamond grains of mean diameter of from 10 to 50 &mgr;m. These fine particles are preferably hard-material particles. They have a mean diameter of from 1 to 6 &mgr;m, preferably 2 to 4 &mgr;m. These fine particles are preferably only present in the upper of the two layers of the metallic binder phase.
These relatively small hard-material particles are preferably likewise diamond grains. The mean diameter of these fine diamond grains is not taken into account when establishing the layer thickness of the binder phase (which according to the invention is 45-55% of the mean diamond grain diameter). Only the mean diameter of the coarser diamond grains is used to determine the layer thickness of the binder phase.
Including the coating of abrasive grains, the saw wire according to the invention preferably has a diameter of up to at most 0.35 mm.
The steel wire used is preferably stainless spring steel wire made from chromium-nickel steel. By way of example, material types 1.4310, 1.4401, 1.4539, 1.4568 and 1.4571 (as designated by DIN 17224) are suitable.
The steel wire preferably has a diameter of from 0.15 to 0.30 mm.
The intermediate layer preferably consists of a metal, a metal alloy or a combination of two metals or one metal and one metal alloy.
It is preferably a metal, a metal alloy or a combination of two metals or of one metal and one metal alloy which can be coated by electrodeposition with good adhesive strength and, at the same time, acts as a hydrogen barrier.
Examples of suitable metals are copper and nickel and an example of a suitable metal alloy is brass.
The intermediate layer preferably has a thickness of from 1 to 10 &mgr;m.
The metallic binder phase preferably consists of nickel or nickel alloys. It particularly preferably consists of nickel which has been deposited without external current (chemical nickel).
The metallic binder phase preferably has a hardness HV 0.1 of from 800 to 1100, particularly preferably from 1000 to 1100.
The thickness of the intermediate layer around the wire preferably varies by no more than 5%.
The thickness of the metallic binder phase around the wire preferably varies by no more than 5%, particularly preferably by no more than 2.5%.
In a particularly preferred embodiment, the layer thickness of the metallic binder phase is from 12 to 15 &mgr;m and the thickness of the metallic binder phase around the wire varies by at most 0.4 &mgr;m.
The saw wire according to the invention can be produced as follows:
As is already known from DE A 19839091, a wire which has been provided with an intermediate layer undergoes a chemical pretreatment which is adapted to the base material. This pretreatment is known in the prior art and usually comprises known degreasing, pickling and activation treatments. There then follows the coating in a so-called chemical nickel-diamond bath (bath for nickel-diamond deposition without external current). Baths of this type are likewise known in the prior art. As is also known from the prior art, it may be useful to initiate the commencement of the metallization by means of a short surge of current. Uniform diamond embedding over the entire circumference of the wire is achieved by means of a suitable movement of wire and electrolyte. In the process according to the invention, it is essential that the coating takes place in two stages, diamond particles with a mean diameter of 10-50 &mgr;m being deposited on the wire in the first stage and fine particles with a mean diameter of 1 to 6 &mgr;m being deposited on the wire in the second stage.
By means of the process according to the invention, it is possible within one hour to produce more coated wire by a factor of 10
3
than by means of electrodeposition in continuous throughput installations with a comparable installation size.
The coating is preferably followed by a heat treatment for at least one hour.
In the process according to the invention, the two-stage coating of the wire following the chemical pretreatment preferably takes place as follows: In the first coating stage, the wire is introduced into a chemical nickel bath which contains diamond particles with a mean diameter of from 10-50 &mgr;m, preferably 25-45 &mgr;m. The coating process is controlled in such a way that, in the ideal situation, a single layer of diamond grains is deposited on the surface of the wire and these grains are fixed by the growing layer of nickel duri
Lukschandel Jörg
Meyer Jürgen
Collard & Roe P.C.
Hail III Joseph J.
Ojini Anthnoy
Wacker-Chemie GmbH
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