Claims
- 1. A process for producing a high tension steel sheet having excellent low-temperature toughness with a yield point not lower than 40 kg/mm.sup.2 which comprises heating a steel ingot or slab to a temperature not higher than 1150.degree. C., and rolling the steel ingot or slab thus heated with a total reduction amount not less than 50% in a temperature range not higher than 930.degree. C. and a finishing temperature not higher than 830.degree. C.,
- said steel ingot or slab containing 0.01 to 0.13% C, 0.1 to 1.0% Si, 0.7 to 2.0% Mn, not more than 0.1% total Al, 0.004 to 0.03% Ti, 0.001 to 0.009% total N, 0.01 to 0.10% Nb, 0.01 to 0.15% V, 0.05 to 0.40% Mo, with the balance being unavoidable impurities and Fe, in which (Nb%).times.(C%).ltoreq.5.times.10.sup.-3 and TiN not larger than 0.02.mu. is not less than 0.004%..]. .[.2. A process for producing a high tension steel sheet having excellent low-temperature toughness with a yield point not lower than 40 kg/mm.sup.2 which comprises heating a steel ingot or slab to a temperature not higher than 1150.degree. C., and rolling the steel ingot or slab thus heated with a total reduction amount not less than 50% in a temperature range not higher than 930.degree. C. and a finishing temperature not higher than 830.degree. C.,
- said steel ingot or slab containing 0.01 to 0.13% C, 0.1 to 1.0% Si, 0.7 to 2.0% Mn, not higher than 0.1% total Al, 0.004 to 0.03% Ti, 0.001 to 0.009% total N, 0.01 to 0.10% Nb, 0.05 to 0.40% Mo, 0.01 to 0.15% V, and one or both of 0.001 to 0.03% REM, 0.0005 to 0.03% Ca, with the balance being unavoidable impurities and Fe in which (Nb%).times.(C%).ltoreq.5.times.10.sup.-3, REM/S=1.0 to 6.0 in case of REM addition, and TiN not larger than 0.02.mu. is not less than 0.004%..]. .[.3. A process for production a high tension steel sheet having excellent low-temperature toughness with a yield point not lower than 40 kg/mm.sup.2 which comprises heating a steel ingot or slab to a temperature not higher than 1150.degree. C. and rolling the steel ingot or slab thus heated with a total reduction amount not less than 50% in a temperature range not higher than 930.degree. C. and a finishing temperature not higher than 830.degree. C.,
- said steel ingot or slab containing 0.01 to 0.13% C, 0.1 to 1.0% Si, 0.7 to 2.0% Mn, not more than 0.1% total Al, 0.004 to 0.03% Ti, 0.001 to 0.009% total N, 0.01 to 0.10% Nb, 0.01 to 0.15% V and 0.05 to 0.40% Mo, one or more of not more than 0.6% Cr, not more than 1.0% Cu, and not more than 4.0% Ni with the balance being unavoidable impurities and Fe in which
- (Nb%).times.(C%).ltoreq.5.times.10.sup.-3
- (Cu+Ni)/5+Cr+Mo.ltoreq.0.90%
- and TiN not larger than 0.02.mu. is not less than 0.004%..]. .[.4. A process for producing a high tension steel sheet having excellent low-temperature toughness with a yield point not lower than 40 kg/mm.sup.2 which comprises heating a steel ingot or slab to a temperature not higher than 1150.degree. C. and rolling the steel ingot or slab thus heated with a total reduction amount not less than 50% in a temperature range not higher than 930.degree. C. and a finishing temperature not higher than 830.degree. C.,
- said steel ingot or slab containing 0.01 to 0.13% C, 0.1 to 1.0% Si, 0.7 to 2.0% Mn, not more than 0.1% total Al, 0.004 to 0.03% Ti, 0.001 to 0.009% total N, 0.01 to 0.10% Nb, 0.01 to 0.15% V, 0.05 to 0.40% Mo, one or both of 0.001 to 0.03% REM and 0.0005 to 0.03% Ca, and one or more of not more than 0.6% Cr, not more than 1.0% Cu and not more than 4.0% Ni with the balance being unavoidable impurities and Fe, in which
- (Nb%).times.(C%).ltoreq.5.times.10.sup.-3
- REM/S=1.0 to 6.0 in case of REM addition
- (Cu.times.Ni)/5+Cr+Mo.ltoreq.0.90%
- and TiN not larger than 0.02.mu. is not less than 0.004%..]. .Iadd. 5. A process for producing steel sheet suitable for pipe lines, having excellent low temperature toughness with a yield point of 40 kg/mm.sup.2 or higher and a vTrs value of about -110.degree. C. lower for a 50% reduction of the steel comprising continuously casting a molten steel into the form of a slab, said molten steel containing 0.01 to 0.13% C, 0.1 to 1.0% Si, 0.7 to 2.0% Mn, not more than 0.1% total Al, 0.004 to 0.03% Ti, 0.001 to 0.009% total N, 0.01 to 0.10% Nb, 0.05 to 127 0.40% Mo, with the balance being Fe and unavoidable impurities and satisfying the condition of (Nb%).times.(C%).ltoreq.5.times.10.sup.-3, cooling the slab thus-obtained by continuous casting with an average cooling rate of 8.degree. C./min. or more as measured in the central portion of the slab through the temperature range from the temperature at the time of pouring to 1100.degree. C. to obtain a slab containing 0.004% or more TiN of a grain size not larger than 0.02.mu., heating the slab at 1150.degree. C. or lower and rolling the slab with a total reduction not less than 50% at temperatures not higher than 930.degree. C. and with a finishing temperature not higher than 830.degree. C. .Iaddend. .Iadd. 6. A process according to claim 5 in which the molten steel further contains one or more of a material selected from the group consisting of 0.01 to 0.15% V, up to 0.6% Cr, up to 1.0% Cu and up to 4.0% Ni within a range of (Cu+Ni)/5+Cr+Mo.ltoreq.0.90%. .Iaddend. .Iadd. 7. A process according to claim 5 in which the molten steel further contains one or more of a material selected from the group consisting of 0.001 to 0.03% REM, and 0.0005 to 0.03% Ca, and wherein REM/S is from 1.0 to 6.0. .Iaddend.
Priority Claims (1)
Number |
Date |
Country |
Kind |
51-40258 |
Apr 1976 |
JPX |
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Parent Case Info
This is a continuation of Ser. No. 029,868, filed Apr. 13, 1979, abandoned, reissue application of U.S. Pat. No. 4,105,474, which matured from Ser. No. 786,946, filed Apr. 12, 1977. .Iaddend.
US Referenced Citations (7)
Continuations (1)
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Number |
Date |
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Parent |
29868 |
Apr 1979 |
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Reissues (1)
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Number |
Date |
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786946 |
Apr 1977 |
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