# US 7,465,432 B2 · Fine tungsten carbide powder and process for producing the same

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- Number: US 7,465,432 B2
- Document ID: US7465432B2
- Status: Granted
- Kind: B2
- Application number: 10/909,334
- Filed: 2004-08-03
- Published: 2005-01-13
- Granted: 2008-12-16
- Earliest claimed: 2001-07-30
- Assignees: Mitsubishi Materials Corporation; Japan New Metals Co., Ltd.
- Inventors: Hiroshi Yaginuma; Susumu Morita
- Web page: https://patentgrep.com/patent/US7465432B2

## CPC

- C01B 32/949: Tungsten or molybdenum carbides
- C01P 2002/77: by unit-cell parameters, atom positions or structure diagrams
- C01P 2004/62: Submicrometer sized, i.e. from 0.1-1 micrometer
- C01P 2006/12: Surface area
- C01P 2006/80: Compositional purity
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS

## Abstract

A process is provided for producing a fine tungsten carbide powder, which comprises the steps of drying a slurry, which is obtained by mixing an aqueous ammonium tungstate solution with a carbon powder, at low temperature, to form a precursor, mixing a reduction and carburization product, which is obtained by reducing and oxidizing the precursor in an inert gas, with a carbon powder in a proportion required to substantially carburize the entire tungsten component into tungsten carbide (WC), and carburizing the mixture; and a high-performance fine tungsten carbide powder produced by the process, which has an average particle size of 0.8 μm or less and is free of a coarse power having a particle size of more than 1 μm, and which also contains less metal impurities and contains oxygen and nitrogen in a predetermined amount.

## Claims

### Claim 1

A tungsten carbide powder comprising (a) an average particle size as measured by the Fischer Subsieve Sizer process of 0.8 μm or less, (b) a maximum particle size in a particle size distribution as measured in accordance with ASTM B430-79 of 1 μm or less, (c) the content of tungsten based on the component excluding a non-metal component being at least 99.9% by weight, (d) the content of nitrogen and that of oxygen in crystal lattices being respectively within a range of 0.08-0.30% by weight and 0.10-0.60% by weight and (e) a lattice constant of an a-axis and that of a b-axis being respectively within a range of 0.29020-0.29060 nm and 0.28380-0.28420 nm.

### Claim 2 (depends on 1)

The tungsten carbide powder according to claim 1, wherein the content of nitrogen and that of oxygen in crystal lattices being respectively within a range of 0.08-0.20% by weight and 0.10-0.60% by weight.

### Claim 3 (depends on 1)

The tungsten carbide powder according to claim 1, wherein the content of free carbon in the tungsten carbide powder is less than or equal to 0.08% by weight.

### Claim 4 (depends on 1)

The tungsten carbide powder according to claim 1, wherein a specific surface area of an average-sized particle of the tungsten carbide powder is within a range of approximately 1.42 m2/g and 4.24 m2/g.

### Claim 5 (depends on 1)

The tungsten carbide powder according to claim 1, wherein the content of free carbon in the tungsten carbide powder is less than or equal to 0.08% by weight and a specific surface area of an average-sized particle of the tungsten carbide powder is within a range of approximately 1.42 m2/g and 4.24 m2/g.