Claims
- 1. A process of producing low carbon steel hot rolled strip and sheet stock having no yield point elongation, freedom from critical grain growth and enhanced yield strength after straining 20% and heating to high temperature for a short period of time, excellent surface characteristics and substantial freedom from inclusions, which comprises the steps of melting a steel containing a maximum carbon content of about 0.05% by weight; vacuum degassing the melt to obtain a steel consisting essentially of, by weight percent, from about 0.002% to about 0.015% carbon, about 0.05% to about 0.60% manganese, sulfur up to about 0.035%, oxygen up to about 0.010%, nitrogen up to about 0.012%, aluminum up to about 0.080%, phosphorus and silicon in residual amounts, and remainder essentially iron; adding from above about 0.025% to about 0.30% columbium, said columbium being added in an amount sufficient to result in at least 0.025% by weight uncombined columbium at the subsequent hot rolling stage as determined by analysis at room temperature and calculated from the formula ##EQU2## when the amount of aluminum is insufficient to combine with all the nitrogen present in the steel; casting and solidifying the degassed steel; hot rolling the steel to strip and sheet thicknesses and coiling at a temperature up to about 1500.degree. F (1090.degree. K).
- 2. A process of producing low carbon steel cold rooled strip and sheet stock having substantially no yield point elongation, freedom from critical grain growth in the annealed condition and enhanced yield strength after straining 20% and heating to high temperature for a short period of time, excellent surface characteristics and substantial freedom from inclusions, which comprises melting a steel having a maximum carbon content of about 0.05% by weight; vacuum degassing the melt to obtain a steel consisting essentially of, by weight percent, from about 0.002% to about 0.015% carbon, about 0.05% to about 0.60% manganese, sulfur up to about 0.035%, oxygen up to about 0.010%, nitrogen up to about 0.012%, aluminum up to about 0.080%, phosphorus and silicon in residual amounts, and remainder essentially iron; adding from above about 0.025% to about 0.30% columbium, said columbium being added in an amount sufficient to result in at least 0.025% by weight uncombined columbium at the subsequent hot rolling stage as determined by analysis at room temperature and calculated from the formula ##EQU3## when the amount of aluminum is insufficient to combine with all the nitrogen present in the steel; casting and solidifying the degassed steel; hot rolling the steel to strip and sheet thicknesses; coiling at a temperature up to about 1500.degree. F (1090.degree. K); removing hot mill scale from the surface of the hot rolled material; and cold rolling the material substantially to final thickness.
- 3. A process of producing low carbon steel hot rolled strip and sheet stock having no yield point elongation, freedom from critical grain growth and enhanced yield strength after straining 20% and heating to high temperature for a short period of time, excellent surface characteristics and substantial freedom from inclusions, which comprises the steps of melting a steel containing a maximum carbon content of about 0.05% by weight, vacuum degassing the melt to obtain a steel consisting essentially of, by weight percent, from about 0.002% to about 0.015% carbon, about 0.05% to about 0.60% manganese, sulfur up to about 0.035%, oxygen up to about 0.010%, nitrogen up to about 0.012%, phosphorus and silicon in residual amounts, and remainder essentially iron; adding up to about 0.080% aluminum, said aluminum being in an amount sufficient to combine with all the nitrogen present in the steel; adding from above about 0.025% to about 0.30% columbium, said columbium being added in an amount sufficient to result in at least 0.025% by weight uncombined columbium at the subsequent hot rolling stage as determined by analysis at room temperature and calculated from the formula
- %Cb.sub.uncomb. = %Cb.sub.total - 7.75%C.sub. total ;
- casting and solidifying the degassed steel; hot rolling the steel to strip and sheet thicknesses and coiling at a temperature up to about 1500.degree. F (1090.degree. K).
- 4. A process of producing low carbon steel cold rolled strip and sheet stock having substantially no yield point elongation, freedom from critical grain growth in the annealed condition and enhanced yield strength after straining 20% and heating to high temperature for a short period of time, excellent surface characteristics and substantial freedom from inclusions, which comprises melting a steel having a maximum carbon content of about 0.05% by weight; vacuum degassing the melt to obtain a steel consisting essentially of, by weight percent from about 0.002% to about 0.015% carbon, about 0.05% to about 0.60% manganese, sulfur up to about 0.035%, oxygen up to about 0.010%, nitrogen up to about 0.012%, phosphorus and silicon in residual amounts, and remainder essentially iron; adding up to about 0.080% aluminum, said aluminum being in an amount sufficient to combine with all the nitrogen present in the steel; adding from above about 0.025% to about 0.30% columbium, said columbium being added in an amount sufficient to result in at least 0.025% by weight uncombined columbium at the subsequent hot rolling stage as determined by analysis at room temperature and calculated from the formula
- %Cb.sub. uncomb. = %CB.sub.total - 7.75%C.sub. total ;
- casting and solidifying the degassed steel; hot rolling the steel to strip and sheet thicknesses; coiling at a temperature up to about 1500.degree. F (1090.degree. K); removing hot mill scale from the surface of the hot rolled material; and cold rolling the material substantially to final thickness.
- 5. The process of claim 4, wherein the hot rolled material is quenched and coiled at a temperature of from about 940.degree. to about 1300.degree. F (780.degree. to 975.degree. K), and wherein the cold rolled strip is annealed at a temperature of from about 1200.degree. to about 1400.degree. F (920.degree. to 1035.degree. K), whereby to obtain a product having a yield strength ranging from about 20,000 to about 90,000 psi (138 to 620 MN/m.sup.2).
CROSS-REFERENCE TO RELATED APPLICATION
This is a division of application Ser. No. 107,077, filed Jan. 18, 1971 now U.S. Pat. No. 3,761,324, which is a continuation-in-part of copending application Ser. No. 15,415, filed Mar. 2, 1970 now abandoned.
US Referenced Citations (6)
Foreign Referenced Citations (1)
Number |
Date |
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1,192,794 |
May 1970 |
GBX |
Divisions (1)
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Number |
Date |
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Parent |
107077 |
Jan 1971 |
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Continuation in Parts (1)
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Number |
Date |
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15415 |
Mar 1970 |
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