Claims
- 1. A method of producing cold reduced low carbon steel strip and sheet stock having a 0.2% offset yield strength of at least 90 ksi and an elongation in two inches of greater than 10% in the annealed condition, comprising the steps of providing a vacuum degassed, fully killed low carbon steel casting consisting essentially of, by weight percent, from 0.02% to about 0.10% carbon, about 0.1% to 0.9% manganese, 0.02% to about 0.18% columbium, residual phosphorus, sulfur, silicon, oxygen and nitrogen, about 0.01% to about 0.08% aluminum, and balance essentially iron except for incidental impurities, the columbium being substantially completely combined with carbon, hot rolling to intermediate gauge, coiling at a temperature .[.not higher than.]. .Iadd.of about 1000.degree. to .Iaddend.about 1300.degree. F., removing hot mill scale, cold reducing to final gauge with a reduction in thickness of 40% to 70%, and annealing at a temperature and for a time sufficient to recover ductility but not recrystallize whereby to obtain an elongation of greater than 10% with a yield strength of at least 90 ksi.
- 2. The method claimed in claim 1, .[.wherein coiling is effected within the range of about 1000.degree. to 1300.degree. F., and.]. wherein said annealing is conducted within the range of about 1100.degree. to about 1300.degree. F. with a time of about 7 minutes to 24 hours, said time being inversely proportional to said temperature.
- 3. The method claimed in claim 2, wherein said steel consists essentially of from about 0.03% to about 0.05% carbon, about 0.3% to about 0.6% manganese, about 0.04% to about 0.12% columbium, about 0.006% to about 0.01% phosphorus, about 0.01% to about 0.017% sulfur, about 0.004% maximum nitrogen, about 0.03% to about 0.05% aluminum, about 0.01% maximum oxygen, about 0.1% maximum silicon, and balance essentially iron.
- 4. The method claimed in claim 2, wherein said coiling is effected at about 1100.degree. F., wherein said cold reducing involves a reduction in thickness of 45% to 55%, and wherein said annealing is an open coil anneal conducted at about 1100.degree. F. with a time at temperature of about 1/2 hour.
- 5. The method claimed in claim 1, .[.wherein coiling is effected within the range of about 1000.degree. to 1300.degree. F., and.]. wherein said annealing is a continuous anneal at a peak strip temperature not exceeding 1300.degree. F. for about 7 to 10 minutes.
- 6. A method of producing hot dipped metallic coated low carbon steel strip and sheet stock having a 0.2% offset yield strength of at least 90 ksi and an elongation in two inches of greater than 10% in the annealed condition, comprising the steps of providing a vacuum degassed, fully killed, low carbon steel casting consisting essentially of, by weight percent, from 0.02% to about 0.10% carbon, about 0.1% to 0.9% manganese, 0.02% to about 0.18% columbium, residual phosphorus, sulfur, silicon, oxygen and nitrogen, about 0.01% to about 0.08% aluminum, and balance essentially iron except for incidental impurities, the columbium being substantially completely combined with carbon, hot rolling to intermediate gauge, coiling at a temperature .[.not higher than.]. .Iadd.of about 1000.degree. to .Iaddend.1300.degree. F., removing hot mill scale, cold reducing the final gauge with a reduction in thickness of 40% to 70%, subjecting the cold reduced steel to wet chemical cleaning, heating in a hydrogen-inert gas atmosphere to a temperature .Iadd.and for a time sufficient to recover ductility but not recrystallize whereby to obtain an elongation of greater than 10% with a yield strength of at least 90 ksi, cooling said strip to a temperature .Iaddend.about equal to that of the molten coating metal bath, said coating metal being chosen from the group consisting of aluminum, zinc, alloys of aluminum, alloys of zinc, and terne, passing said steel through said bath of molten coating metal, and solidifying said coating metal.
- 7. A method of producing hot dip metallic coated low carbon steel strip and sheet stock having a 0.2% offset yield strength of at least 90 ksi and an elongation in two inches of greater than 10% in the annealed condition, comprising the steps of providing a vacuum degassed, fully killed low carbon steel casting consisting essentially of, by weight percent, from 0.02% to about 0.10% carbon, about 0.1% to 0.9% manganese, 0.02% to about 0.18% columbium, residual phosphorus, sulfur, silicon, oxygen and nitrogen, about 0.01% to about 0.08% aluminum, and balance essentially iron except for incidental impurities, the columbium being substantially completely combined with carbon, hot rolling to intermediate gauge, coiling at a temperature .[.not higher than.]. .Iadd.of about 1000.degree. to .Iaddend.1300.degree. F., removing hot mill scale, cold reducing to final gauge with a reduction in thickness of 40% to 70%, heating the cold reduced steel in strip form in a continuous furnace to a temperature sufficient to remove oil and related surface contaminants, heating in a hydrogen-inert gas atmosphere capable of reducing residual surface oxide wherein said strip is brought to a temperature and for a time sufficient to recover ductility but not recrystallize whereby to obtain an elongation of greater than 10% with a yield strength of at least 90 ksi, cooling said strip approximately to the temperature of the molten coating metal bath, said coating metal being chosen from the group consisting of aluminum, zinc, alloys of aluminum, alloys of zinc, and terne, passing said strip through said molten coating metal bath, and solidifying said coating metal.
Parent Case Info
This is a division of application Ser. No. 554,158 filed Feb. 28, 1975, now U.S. Pat. No. 3,963,531.
US Referenced Citations (7)
Foreign Referenced Citations (2)
Number |
Date |
Country |
48-79722 |
Oct 1973 |
JPX |
48-81721 |
Nov 1973 |
JPX |
Divisions (1)
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Number |
Date |
Country |
Parent |
554158 |
Feb 1975 |
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Reissues (1)
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Number |
Date |
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Parent |
674862 |
Apr 1976 |
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