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US5374322A
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Method of manufacturing high strength steel member with a low yield ratio
Assignee: Nippon Steel Corp
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Filing: 1993-07-08
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Granted: 1994-12-20
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Expires: 2013-07-08
Abstract
Abstract A high tensile strength, low yield ratio steel member has a steel composition consisting essentially of, by weight: C: 0.15-0.40%, Si: 0.10-0.70%, Mn: 1.0-2.7%, Cr: 1.0-3.5%, sol.Al: 0.01-0.05%, P: not larger than 0.025%, S: not larger than 0.015%, Mo: 0-1.0%, Ni: 0-2.5%, V: 0-0.10%, Ti: 0-0.10%, Nb: 0-0.10%, B: 0-0.0050%. Fe and incidental impurities: balance the below-described bainite index (%) of the steel composition being 0-50%, the steel being comprised of a single phase of martensite or a martensite and bainite duplex structure containing 50% or less of bainite. Bainite Index (%)=-209C+43Si-48Mn-58Cr-0.416R+317 wherein R is a cooling rate ( DEG C./min).
Inventors
- 👤 Yasutaka Okada
- 👤 Yasuhide Fujioka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 16:42
CPC Classifications
C; C21; C21D; C21D8/00; C21D8/10; C21D1/00; C21D1/26; C21D1/28; C21D8/02; C21D8/0247; C21D8/0263; C21D1/18; C21D2211/00; C21D2211/002; C21D2211/008; C21D8/0273; Y; Y10; Y10S; Y10S148/00; Y10S148/902; Y10S148/909
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
149 words
A method of producing a high strength, low yield ratio steel member having a steel composition which consists essentially of, by weight: C: 0.15-0.40%, Si: 0.10-0.70%, Mn: 1.0-2.7%, Cr: 1.0-3.5%, sol. Al: 0.01-0.05%, P: not larger than 0.025%, S: not larger than 0.015%, Mo: 0-1.0%, Ni: 0-2.5%, V: 0-0.10%, Ti: 0-0.10%, Nb: 0-0.10%, B: 0-0.0050%, Fe and incidental impurities: balance, the steel being comprised of a single phase of martensite or a martensite and bainite duplex structure containing 50% or less of martensite and having a bainite index of 0-50% defined by: Bainite Index (%)=-209C+43Si-48Mn-58Cr-0.416R+317 wherein R is a cooling rate (°C./min), the method comprising final hot working the steel member with a finishing temperature of 800°-1000° C., reheating the resulting steel member at a temperature of 850°-1050° C. for 0.5 minute-2 hours, and cooling the steel member at a cooling rate R defined by the following equation: 642-502C+103Si-115Mn-139Cr≦R≦762-502C+103Si-115Mn-139Cr.
Claim 2
Independent Claim
149 words
A method of producing a high strength, low yield ratio steel member having a steel composition which consists essentially of, by weight: C: 0.15-0.40%, Si: 0.10-0.70%, Mn: 1.0-2.7%, Cr: 1.0-3.5%, sol. Al: 0.01-0.05%, P: not larger than 0.025%, S: not larger than 0.015%, Mo: 0-1.0%, Ni: 0-2.5%, V: 0-0.10%, Ti: 0-0.10%, Nb: 0-0.10%, B: 0-0.0050%, Fe and incidental impurities: balance, the steel being comprised of a single phase of martensite or a martensite and bainite duplex structure containing 50% or less of martensite and having a bainite index of 0-50% defined by: Bainite Index (%)=-209C+43Si-48Mn-58Cr-0.416R+317 wherein R is a cooling rate (°C./min), the method comprising final hot working the steel member with a finishing temperature of 800°-1000° C., reheating the resulting steel member at a temperature of 850°-1050° C. for 0.5 minute-2 hours, and cooling the steel member at a cooling rate R defined by the following equation: 642-502C+103Si-115Mn-139Cr≦R≦762-502C+103Si-115Mn-139Cr.
Claim 3
Dependent Claim
34 words
A method of producing a high strength, low yield ratio steel member as set forth in claim 1 wherein at least Mo or Ni is included, and the equation is modified as follows: 642-502C+103Si-115Mn-139Cr-31Ni-151Mo≦R≦762-502C+103Si-115Mn-139Cr-31Ni-151Mo.
Claim 4
Dependent Claim
37 words
A method of producing a high strength, low yield ratio steel member as set forth in claim 1 wherein tempering at a temperature of 300° C. or less is carried out after cooling at the rate R.
Claim 5
Independent Claim
152 words
A method of producing a high strength, low yield ratio steel member having a steel composition which consists essentially of, by weight: C: 0.15-0.40%, Si: 0.10-0.70%, Mn: 1.0-2.7%, Cr: 1.0-3.5%, sol. Al: 0.01-0.05%, P: not larger than 0.025%, S: not larger than 0.015%, Mo: 0-1.0%, Ni: 0-2.5%, V:0-0.10%, Ti: 0-0.10%, Nb: 0-0.10%, B: 0-0.0050%, Fe and incidental impurities: balance, the steel being comprised of a single phase of martensite or a marten site and bainite duplex structure containing 50% or less of martensite and having a bainite index of 0-50% defined by: Bainite Index (%)=-209C+43Si-48Mn-58Cr-0.416R+317 wherein R is a cooling rate (°C./min), the method comprising hot working the steel member with a finishing temperature of 800°-1000° C., carrying out additional working, reheating the resulting steel member at a temperature of 850°-1050° C. for 0.5 minute-2 hours, and cooling the steel member at a cooling rate R defined by the following equation: 642-502C+103Si-115Mn-139Cr≦R≦762-502C+103Si-115Mn-139Cr.
Claim 6
Independent Claim
152 words
A method of producing a high strength, low yield ratio steel member having a steel composition which consists essentially of, by weight: C: 0.15-0.40%, Si: 0.10-0.70%, Mn: 1.0-2.7%, Cr: 1.0-3.5%, sol. Al: 0.01-0.05%, P: not larger than 0.025%, S: not larger than 0.015%, Mo: 0-1.0%, Ni: 0-2.5%, V:0-0.10%, Ti: 0-0.10%, Nb: 0-0.10%, B: 0-0.0050%, Fe and incidental impurities: balance, the steel being comprised of a single phase of martensite or a marten site and bainite duplex structure containing 50% or less of martensite and having a bainite index of 0-50% defined by: Bainite Index (%)=-209C+43Si-48Mn-58Cr-0.416R+317 wherein R is a cooling rate (°C./min), the method comprising hot working the steel member with a finishing temperature of 800°-1000° C., carrying out additional working, reheating the resulting steel member at a temperature of 850°-1050° C. for 0.5 minute-2 hours, and cooling the steel member at a cooling rate R defined by the following equation: 642-502C+103Si-115Mn-139Cr≦R≦762-502C+103Si-115Mn-139Cr.
Claim 7
Dependent Claim
34 words
A method of producing a high strength, low yield ratio steel member as set forth in claim 4 wherein at least Mo or Ni is included, and the equation is modified as follows: 642-502C+103Si-115Mn-139Cr-31Ni-151Mo≦R≦762-502C+103Si-115Mn-139Cr-31Ni-151Mo.
Claim 8
Dependent Claim
37 words
A method of producing a high strength, low yield ratio steel member as set forth in claim 4 wherein tempering at a temperature of 300° C. or less is carried out after cooling at the rate R.
Claim 9
Dependent Claim
52 words
A method of producing a high strength, low yield ratio steel member as set forth in claim 4 wherein the above-mentioned additional working is cold rolling, and the following softening heat treatment is applied prior to the cold rolling: 175≦T{[ log(t)+20)]/100}≦200 wherein T: Softening Heat Treatment Temperature (K) t: Heating Time (hour).
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1997-12-19 | 1998-06-20 | 1998-12-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-12-19 | 2002-06-20 | 2002-12-20 | $3760.00 | Window Closed / Lapsed |
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