Stone working – Sawing – Rotary
Reexamination Certificate
1999-11-22
2002-09-24
Rose, Robert A. (Department: 3723)
Stone working
Sawing
Rotary
C051S307000, C451S542000
Reexamination Certificate
active
06453899
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to powder metallurgy and more specifically to sintered powder parts and articles. Powder metallurgy includes, but is not limited to, compacting, casting, and sintering including sintering with and/or without a liquid phase, and/or infiltration, and/or under a load and/or pressure. Some examples of sintered powder parts and articles that can be made according to this invention include structural, porous, friction, anti-friction, cutting, corrosion-, wear- and heat-resistant parts, and inserts. In particular the present invention relates to sintered powder abrasive and super-abrasive parts and articles such as tools for cutting, drilling, de-burning, grinding, dressing, polishing, lapping, honning, and roughening and workpieces and wear resistant items.
Powders and powder pre-forms are widely used in the manufacturing of numerous sintered powder products including but not limited to wear-resistant, abrasive and super-abrasive parts and/or articles and/or tools. Powders for manufacturing abrasive products are conventionally manufactured by mixing hard and/or super-hard particles with sinterable and/or fusible retaining powders with or without a binder additive. Some powder preforms are conventionally manufactured by compacting the powders at room temperature (so called “green” compacts or segments) or casting and curing a mixture of the powder and a liquid and/or paste binder.
In the abrasive industry, sintered abrasive parts and articles comprise hard particles that in most cases are randomly distributed in a sintered powder retaining matrix. Specifically, cutting segments for segmented tools (blades, drill bits, etc.) are manufactured by mixing hard particles with powders of the retaining matrix, then compacting the powder at room temperature into a “green” segment, then sintering the “green” segment or a plurality of “green” segments into an individual sintered segment or a plurality of individual sintered segments respectively. Sintering may include infiltration of other components or compaction. Such infiltration and/or compacting also can take place before and/or after sintering and/or after a preliminary sintering.
Typically the sinterable segments or parts such as abrasive cutting segments are sintered as individual or separate bodies. In other words, each segment is separated from another one by compacting means (punches/plungers) and/or solid dividers and/or walls. These compacting means and dividers are strong bodies (i.e., graphite or metallic parts) that are not supposed to be crushed or substantially deformed in the process of compacting and/or sintering the “green” segments. In the case of radiant or induction and/or microwave sintering, pressure and heat and/or an appropriate atmosphere can be provided by appropriate means. In the case of electro-resistant and/or electro-discharge sintering, electrical current and/or pressure are provided by and or delivered through the compacting means.
This is illustrated in
FIG. 1
where sinterable powder segments
1
are placed in a sinter mold
5
containing punches
2
and a solid divider
3
and having opposing pressure plates
6
.
FIG. 2
illustrates a more efficient arrangement where the punches
2
also serve as dividers between the segments. In either case a plurality of individual sintered parts are produced.
These solid compacting means and/or dividers occupy a substantial part of the volume of the sinter mold, generally 50% to 70%, resulting in a lower efficiency and utilization of the sinter mold volume, e.g., only 50% to 30%.
Moreover, assembling numerous “green” segments and punches together into a sinter mold is a time consuming process. Mechanization and automation of this process is a challenging task. Also while disassembling this type of sinter mold after sintering, one has to deal with separating the sintered parts from the punches and collecting and cleaning numerous small and thin punches and dividers to prepare them for use in the next sintering step.
Producing the sintered parts by filling a powder instead of “green” compacts or segments into the cavities of the sinter mold that also includes compacting means and/or dividers is also known, but it results in an even lower efficiency of sintering because the powders have 1.5 to 5 times lower densities than the “green” segments and it also creates problems because of the difficulty in achieving a uniform distribution of the powder in the cavities.
As taught in WO 94/20252, published Sep. 15, 1994, it is also known to make sintered abrasive cutting segments by providing a sheet of sintered abrasive material and then cutting out the sheet into a plurality of cutting segments with a laser or the like.
SUMMARY OF THE INVENTION
In accordance with the present invention, a new and improved method is provided for making unique sintered products in the form of a sintered article or plate as well as to individual sintered segments or bodies that can be extracted from the sintered article by suitable extracting means, such as laser cutting, water jet cutting, electro-erosion cutting, abrasive cutting, edge tool cutting, and mechanical distraction (breakage).
More specifically, a method is provided for making a sintered article comprising providing a plurality of individual blocks of sinterable matrix material, arranging said blocks in abutting relationship to form an assembly of said blocks, wherein said assembly comprises a plurality of said blocks extending in at least one direction thereof, and sintering said assembly to form an integrated sintered article.
The method according to the invention thus is characterized by sintering together, for example, a plurality of powder preforms or green powder compacts made of a sinterable powder to form a sintered powder article.
In the process, the blocks or preforms are integrated with neighboring blocks during sintering to form the sintered article. Diffusion of the components of the blocks can promote their integration. The individual sintered segments or bodies, extracted from the sintered powder article, can or cannot correspond to the original green powder blocks or preforms.
Sintering in a sinter mold, preferably under pressure, can be used to obtain the sintered article. Sintering under pressure (so called “hot compacting”) is a particularly
The assemblies can be of a variety of shapes including square, rectangular or round shapes and can optionally be provided with one or more through openings, such as a central opening.
In an advantageous embodiment of the invention a plurality of individual sintered powder segments or bodies are extracted from the sintered powder article. These individual sintered powder bodies can be used as articles or as parts of a larger article. They also can be of various one, two, or three dimensional shapes including, but not limited to, polygon, rectangular, square, round, cube, elliptical, cylindrical, pyramid, core, frustum cone, arc, nail, needle, pen, spiral and can have at least one indent and/or through opening.
If necessary, these extracted bodies can be readily joined or fixed to a carrier and/or to each other by gluing, welding, braising or by mechanical means such as locking or riveting, or by any combination thereof.
The blocks of sinterable matrix material can be made out of the same or different compositions. Therefore, depending on shape, size of the blocks, layout of the assembled blocks or the assembly and conditions of sintering, the resulting integrated sintered powder article can comprise a variety of compositions distributed through the article in a pre-determined, including but not limited to non-random, and desired manner. This enables the integrated sintered articles to be provided with unique characteristics of man-made material.
Furthermore, the assembly can comprise multiple layers, each layer comprising a plurality of the blocks so that individual bodies extracted from the same sintered assembly but from different parts thereof can have the same and/or different compositions and characteristics, and
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Rose Robert A.
Ultimate Abrasive Systems, L.L.C.
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