US5784681A
Expired / Lapsed
US
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Method of making a sintered article
Assignee: Federal Mogul Coventry Ltd
•
Filing: 1995-03-16
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Granted: 1998-07-21
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Expires: 2015-03-16
Abstract
Abstract A method of making a sintered article is disclosed, the method comprising the steps of mixing a prealloyed ferrous powder having a composition in the following ranges in weight %: carbon 0.7-2.7/chromium 3-6/cobalt 5-10/vanadium 0.5-3/molybdenum 6-11/silicon 0.3-2/ others total 2 max/balance iron and optionally up to 3 wt % tungsten, with an addition of carbon powder of at least 0.1 wt %, compacting said powder mixture by uniaxial pressing to form a green compact of near net shape, sintering said green compact in a continuous gas atmosphere sintering furnace at a temperature in the range from 1130° C. to 1250° C. such that the final density of said sintered material is greater than 95% of the theoretical density as a result of the sintering operation alone.
Inventors
- 👤 Charles Grant Purnell
- 👤 Leslie John Farthing
- 👤 David Holme
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 08:55
CPC Classifications
C; C22; C22C; C22C33/00; C22C33/02; C22C33/0257; C22C33/0278; C22C33/0285; B; B22; B22F; B22F3/00; B22F3/10; B22F3/1003; B22F3/1007; B22F2201/00; B22F2201/01; B22F2201/013; B22F2201/02; B22F2998/00; B22F2999/00; Y; Y10; Y10S; Y10S75/00; Y10S75/95
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
134 words
A method of making a sintered article, the method comprising the steps of mixing a prealloyed ferrous powder having a composition in the following ranges in weight %: carbon 0.7-2.7 / chromium 3-6 / cobalt 5-10 / vanadium 0.5-3 / molybdenum 6-11 / silicon 0.3-2 / others total 2 max/balance iron and optionally up to 3 wt % of tungsten, with an addition of carbon powder of at least 0.10 wt %, compacting said powder mixture by uniaxial pressing to form a green compact, sintering said green compact in a continuous sintering furnace, having a gas atmosphere, at a temperature in the range from 1130° C. to 1250° C. such that the final density of said sintered material is greater than 95% of the theoretical density as a result of the sintering operation alone.
Claim 2
Independent Claim
134 words
A method of making a sintered article, the method comprising the steps of mixing a prealloyed ferrous powder having a composition in the following ranges in weight %: carbon 0.7-2.7 / chromium 3-6 / cobalt 5-10 / vanadium 0.5-3 / molybdenum 6-11 / silicon 0.3-2 / others total 2 max/balance iron and optionally up to 3 wt % of tungsten, with an addition of carbon powder of at least 0.10 wt %, compacting said powder mixture by uniaxial pressing to form a green compact, sintering said green compact in a continuous sintering furnace, having a gas atmosphere, at a temperature in the range from 1130° C. to 1250° C. such that the final density of said sintered material is greater than 95% of the theoretical density as a result of the sintering operation alone.
Claim 3
Dependent Claim
18 words
A method according to claim 1 wherein the prealloyed powder contains a minimum of 0.1 wt % tungsten.
Claim 4
Dependent Claim
39 words
A method according to claim 1 wherein the composition of the prealloyed powder lies in the ranges in wt %: carbon 0.7-1.6/ chromium 3-4.25/ cobalt 7.5-8.5/ vanadium 1-1.3/ tungsten 1-2/ molybdenum 9-10/silicon 0.3-1.5/ others total 2 max/ balance iron.
Claim 5
Dependent Claim
19 words
A method according to claim 1 wherein the total carbon content of the sintered article is 1-2.0 wt %.
Claim 6
Dependent Claim
20 words
A method according to claim 1 wherein the powder mixture contains a minimum of 0.3 wt % additional carbon powder.
Claim 7
Dependent Claim
17 words
A method according to claim 1 wherein the maximum addition of free carbon is 0.8 wt. %.
Claim 8
Dependent Claim
17 words
A method according to claim 1 further including a pre-sintering step at temperatures up to 1120° C.
Claim 9
Dependent Claim
25 words
A method according to claim 1 wherein the sintering step is carried out under a continuous gas atmosphere comprising a mixture of hydrogen and nitrogen.
Claim 10
Dependent Claim
17 words
A method according to claim 8 wherein said gas atmosphere comprises up to 30 volume % hydrogen.
Claim 11
Dependent Claim
19 words
A method according to claim 1 wherein the green density of the article is less than 85% of theoretical.
Claim 12
Dependent Claim
23 words
A method according to claim 1 wherein the density of the final sintered article is greater than about 97% of full theoretical density.
Claim 13
Dependent Claim
31 words
A method according to claim 1 further including the step of heat treating the article after sintering to produce a predominantly pearlitic structure having a uniform distribution of free carbides therein.
Claim 14
Dependent Claim
15 words
A method according to claim 12 wherein the heat treatment is an isothermal heat treatment.
Claim 15
Dependent Claim
66 words
A sintered iron-based alloy article when made by claim from 1, the article comprising a composition lying in the ranges in weight % of: carbon 0.8-3/ chromium 3-6/ cobalt 5-10/ vanadium 0.5-3/ molybdenum 6-11/ silicon 0.3-2/ others total 2 max/ balance iron and optionally up to 3 wt % tungsten, the article having a sintered density of greater than 95% of the alloy's full theoretical density.
Claim 16
Dependent Claim
16 words
A sintered article according to claim 14 further including a minimum of 0.1 wt % tungsten.
Claim 17
Dependent Claim
23 words
A sintered article according to claim 14 wherein the microstructure contains free carbides having a size range from 1 μm to 1 μm.
Claim 18
Dependent Claim
7 words
A sintered article according to claim 14.
Claim 19
Dependent Claim
18 words
A sintered article according to claim 17 and having a hardness of from 35 HRC to 45 HRC.
Claim 20
Dependent Claim
21 words
A sintered article according to claim 14 wherein the sintered article is a valve seat insert for an internal combustion engine.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2001-07-20 | 2002-01-19 | 2002-07-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-07-20 | 2006-01-19 | 2006-07-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-07-20 | 2010-01-19 | 2010-07-21 | $7700.00 | Window Closed / Lapsed |