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US3755004A
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Method for producing ultra fine-grained microstructure in ferrous alloys
Assignee: United States Steel Corp
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Filing: 1971-09-21
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Granted: 1973-08-28
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Expires: 1991-09-21
Abstract
Abstract Ferrous alloys containing up to about 25 percent Ni, 15 percent Mn, 1.2 percent C, 0.5 percent N are cooled to form a martensitic or bainitic structure. The material is then worked to an extent sufficient to remove the principal nucleating effect of the prior austenite boundaries and other microstructural interfaces, so that when subsequently heated into the multiphase region, recrystallization occurs by random nucleation of extremely fine austenite crystals thoughout the material. Exceptionally fine equiaxed grains in the micron and submicron range are achieved, thereby providing unique combinations of both increased strength along with increased ductility and increased notch toughness.
Inventors
- 👤 R Miller
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 21:08
CPC Classifications
C; C21; C21D; C21D8/00
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
10 words
The method of claim 1 wherein said structure is martensite.
Claim 2
Independent Claim
121 words
A method for producing an essentially uniform, ultrafine grain size in ferrous alloys capable of conversion to martensite or bainite, which comprises; a. heating said alloy to a temperature within the austenitizing range for a time sufficient to effect a substantially complete transformation to austenite; b. cooling the so-formed austenite to form a microstructure consisting substantially of martensite or bainiTe; c. deforming the structure of (b) to an extent sufficient to substantially diminish the nucleating effect of the prior boundary regions; d. tempering the so-worked alloy to a temperature above the ''''As'''' and below the ''''Af'''' for a time sufficient to effect the growth of equiaxed ultrafine grained austenite crystals; and e. cooling the so-worked alloy to below the ''''As'''' temperatures.
Claim 3
Dependent Claim
30 words
The method of claim 3 in which the extent of said deformation is such that the recrystallization effected during said tempering results in a substantially uniform equiaxed ultrafine grain microstructure.
Claim 4
Dependent Claim
55 words
The method of claim 4 wherein said alloy is selected from the range, consisting essentially of the austenitizing elements of up to about 25 percent nickel, up to about 15 percent manganese, up to about 1.2 percent carbon, up to about 0.5 percent nitrogen and mixtures thereof with the balance iron and incidental steelmaking impurities.
Claim 5
Dependent Claim
40 words
The method of claim 5 in which said alloy contains a sufficient amount of said austenitizing elements to provide sufficient austenite stability so that the austenite so formed during said tempering is retained during said cooling below the ''''As'''' temperature.
Claim 6
Dependent Claim
42 words
The method of claim 5 wherein the amount of said austenitizing elements is insufficient to provide sufficient stability to the austenite formed during said tempering, whereby the austenite transforms to decomposition products selected from the group consisting of pearlite, martensite and bainite.
Claim 7
Dependent Claim
17 words
The method of claim 7 wherein said cooling is at a rate sufficiently fast to produce martensite.
Claim 8
Dependent Claim
16 words
The method of claim 8 wherein said martensite is retempered at a temperature below the ''''As.''''
Claim 9
Dependent Claim
22 words
The method of claim 7 wherein said cooling is interrupted to convert said equiaxed, ultrafine grained austenite crystals to a martempered structure.
Claim 10
Dependent Claim
20 words
The method of claim 4 wherein said deformation is performed at a temperature above the ''''As'''' and below the ''''Af.''''
Claim 11
Dependent Claim
16 words
The method of claim 4 wherein said deformation is performed at a temperature below the ''''As.''''
Claim 12
Dependent Claim
22 words
The method of claim 3 wherein said tempering is conducted at a temperature within the range ''''As'''' to ''''As plus 150* C''''.
Claim 13
Dependent Claim
42 words
The method of claim 4 wherein said deformation is at least that required to increase the internal energy of the alloy to that represented by the increase achieved by a reduction in thickness of 35 percent, for a 1/2 inch thick plate.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-08-27 | 1977-02-26 | 1977-08-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-08-27 | 1981-02-26 | 1981-08-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-08-27 | 1985-02-26 | 1985-08-28 | $7700.00 | Window Closed / Lapsed |