US4033789A
Expired / Lapsed
US
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Method of producing a high strength steel having uniform elongation
Assignee: Jones and Laughlin Steel Inc
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Filing: 1976-03-19
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Granted: 1977-07-05
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Expires: 1996-03-19
Abstract
Abstract A steel product having a combination of high strength and formability (as measured by percent tensile uniform elongation) is produced by austenitizing a steel consisting essentially of from 0.04 to 0.17% carbon, 0.8 to 2.0% manganese, up to 1.0% silicon, up to 0.12% vanadium, up to 0.1% columbium, up to an effective amount of titanium to form titanium carbonitrides, 0.001 to 0.025% nitrogen, balance essentially iron and then cooling at a rate of no more than about 70° F/sec. to about 850° F and at a rate of more than about 10° F/sec. to transform the freshly formed austenite to a microstructure of from 10 to 35% by volume of martensite and/or lower bainite (MLB), balance essentially proeutectoid ferrite. Slower cooling rates may be employed to obtain the desired microstructure if a restricted chemical composition is used. The heat-treated steel product is characterized by an ultimate tensile strength of 80,000 p.s.i. minimum and a uniform elongation of 16% minimum.
Inventors
- 👤 Emil G. Hamburg
- 👤 Robert L. Cryderman
- 👤 John F. Butler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 16:50
CPC Classifications
C; C21; C21D; C21D8/00; C21D8/02; C21D8/0221; C21D8/0226; C21D2211/00; C21D2211/002; C21D2211/005; C21D2211/008; C21D8/0247; C21D8/0263
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
161 words
A method of heat treating steel to produce a high strength product having high tensile uniform elongation, comprising: a. heating a steel product having a composition consisting essentially of from 0.04% to 0.17% carbon, 0.8% to 2.0% manganese, up to 1.0% silicon, up to 0.12% vanadium, up to 0.1% columbium, up to an effective amount of titanium to form titanium carbo-nitrides, 0.001% to 0.025% nitrogen, balance iron to a temperature above the Ac 3 temperature of the steel for a time sufficient to austenitize said steel product; b. cooling said austenitized steel product at a rate of no more than about 70° F./sec. to about 850° F.; and c. cooling said steel product at a rate of more than about 10° F./sec. from 850° F. to obtain a high-treated steel product having a minimum ultimate tensile strength of 80,000 p.s.i., a minimum tensile uniform elongation of 16%, and a microstructure of from about 10% to 35% MLB, balance essentially proeutectoid ferrite.
Claim 2
Independent Claim
161 words
A method of heat treating steel to produce a high strength product having high tensile uniform elongation, comprising: a. heating a steel product having a composition consisting essentially of from 0.04% to 0.17% carbon, 0.8% to 2.0% manganese, up to 1.0% silicon, up to 0.12% vanadium, up to 0.1% columbium, up to an effective amount of titanium to form titanium carbo-nitrides, 0.001% to 0.025% nitrogen, balance iron to a temperature above the Ac 3 temperature of the steel for a time sufficient to austenitize said steel product; b. cooling said austenitized steel product at a rate of no more than about 70° F./sec. to about 850° F.; and c. cooling said steel product at a rate of more than about 10° F./sec. from 850° F. to obtain a high-treated steel product having a minimum ultimate tensile strength of 80,000 p.s.i., a minimum tensile uniform elongation of 16%, and a microstructure of from about 10% to 35% MLB, balance essentially proeutectoid ferrite.
Claim 3
Dependent Claim
22 words
The method of claim 1, wherein: said steel product is heated to from between its Ac 3 temperature to about 1750° F.
Claim 4
Dependent Claim
29 words
The method of claim 1, wherein: said fully austenized steel product is cooled at a rate from about 10° F. to 70° F. so as to obtain said microstructure.
Claim 5
Dependent Claim
17 words
The method of claim 1, wherein: said steel product is in the hot-rolled condition prior to heat-treatment.
Claim 6
Dependent Claim
39 words
The method of claim 1, wherein: said fully austenized steel product is cooled in accordance with the following relationship: 80≧32.186+8.891 log CR+.026 Mn× Cr+ 160.561 C+14.173 Mn; wherein, Cr== cooling Rate, °F./sec.; Mn== Manganese, %; and C== carbon, %.
Claim 7
Independent Claim
166 words
A method of heat treating steel to produce a high strength product having high tensile uniform elongation, comprising: a. continuously heating a steel product having a composition consisting essentially of from 0.10% to 0.12% carbon, 1.2% to 1.4% manganese, 0.3% to 0.5% Si, up to 0.12% vanadium, up to 0.1% columbium, up to an effective amount of titanium to form titanium carbo-nitrides, 0.001% to 0.025% nitrogen, balance iron to a temperature above the Ac 3 temperature of the steel for a time sufficient to austenize said steel product; b. continuously force cooling said austenitized steel product at a rate of no more than about 70° F./sec. to about 850° F.; and c. continuously force cooling said steel product at a rate of more than about 10° F./sec. from 850° F. to obtain a heat-treated steel product having a minimum ultimate tensile strength of 80,000 p.s.i., a minimum tensile uniform elongation of 16%, and a microstructure of from about 10% to 35% MLB, balance essentially proeutectoid ferrite.
Claim 8
Independent Claim
166 words
A method of heat treating steel to produce a high strength product having high tensile uniform elongation, comprising: a. continuously heating a steel product having a composition consisting essentially of from 0.10% to 0.12% carbon, 1.2% to 1.4% manganese, 0.3% to 0.5% Si, up to 0.12% vanadium, up to 0.1% columbium, up to an effective amount of titanium to form titanium carbo-nitrides, 0.001% to 0.025% nitrogen, balance iron to a temperature above the Ac 3 temperature of the steel for a time sufficient to austenize said steel product; b. continuously force cooling said austenitized steel product at a rate of no more than about 70° F./sec. to about 850° F.; and c. continuously force cooling said steel product at a rate of more than about 10° F./sec. from 850° F. to obtain a heat-treated steel product having a minimum ultimate tensile strength of 80,000 p.s.i., a minimum tensile uniform elongation of 16%, and a microstructure of from about 10% to 35% MLB, balance essentially proeutectoid ferrite.
Claim 9
Independent Claim
139 words
A method of heat treating steel to produce a high strength product having high tensile uniform elongation, comprising: a. heating a steel product having a composition consisting essentially of from 0.10% to 0.17% carbon, 1.5% to 2.0% manganese, 0.3% to 1.0% silicon, up to 0.12% vanadium, up to 0.1% columbium, up to an effective amount of titanium to form titanium carbo-nitrides, 0.001% to 0.025% nitrogen, balance iron to a temperature above the Ac 3 temperature of the steel for a time sufficient to austenize said steel; and b. cooling said austenitized steel product at a rate of from 3° F./sec. to 10° F./sec. to obtain a heat-treated steel product having a minimum ultimate tensile strength of 80,000 p.s.i., a minimum tensile uniform elongation of 16%, and a microstructure of from about 10% to 35% MLB, balance essentially proeutectoid ferrite.
Claim 10
Independent Claim
139 words
A method of heat treating steel to produce a high strength product having high tensile uniform elongation, comprising: a. heating a steel product having a composition consisting essentially of from 0.10% to 0.17% carbon, 1.5% to 2.0% manganese, 0.3% to 1.0% silicon, up to 0.12% vanadium, up to 0.1% columbium, up to an effective amount of titanium to form titanium carbo-nitrides, 0.001% to 0.025% nitrogen, balance iron to a temperature above the Ac 3 temperature of the steel for a time sufficient to austenize said steel; and b. cooling said austenitized steel product at a rate of from 3° F./sec. to 10° F./sec. to obtain a heat-treated steel product having a minimum ultimate tensile strength of 80,000 p.s.i., a minimum tensile uniform elongation of 16%, and a microstructure of from about 10% to 35% MLB, balance essentially proeutectoid ferrite.
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) | 1980-07-04 | 1981-01-03 | 1981-07-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-07-04 | 1985-01-03 | 1985-07-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-07-04 | 1989-01-03 | 1989-07-05 | $7700.00 | Window Closed / Lapsed |