Claims
- 1. A cold-rolled steel sheet having excellent bake hardenability and non-aging properties at room temperature, consisting essentially of, in terms of % by weight, 0.0005 to 0.0070% of C, 0.001 to 0.8% of Si, 0.3 to 4.0% of Mn, 0.002 to 0.15% of P, 0.0005 to 0.015% of S, 0.005 to 0.1% of Al and 0.0003 to 0.0060% of N with the balance consisting of Fe and unavoidable impurities and composed of a structure of only low-temperature transformation products consisting of at least one member selected from the group consisting of massive ferrite, bainite, Widmanstatten ferrite, martensite, and acicular ferrite, said cold-rolled steel sheet having a bake hardenability property, BH, of not less than 5 kgf/mm.sup.2.
- 2. The cold-rolled steel sheet according to claim 1, which further consists essentially of at least one element selected from the group consisting of B in an amount satisfying a requirement of less than 0.0030% by weight with B/N.ltoreq.1.5 and 0.01 to 3.0% by weight of Cr.
- 3. A cold-rolled steel sheet having excellent bake hardenability and moldability, consisting essentially of, in terms of % by weight, 0.0005 to 0.0070% of C, 0.001 to 0.8% of Si, 0.01 to 4.0% of Mn, 0.002 to 0.15% of P, 0.0005 to 0.015% of S, 0.005 to 0.1% of Al and 0.0003 to 0.0060% of N and further consisting essentially of at least one additional element selected from the group consisting of 0.003 to 0.1% to Ti and 0.003 to 0.1% of Nb with the balance consisting of Fe and unavoidable impurities and composed of a structure of only low-temperature transformation products, said cold-rolled steel sheet having a bake hardenability property, BH, of not less than 5 kgf/mm.sup.2.
- 4. The cold-rolled steel sheet according to claim 3, which further consists essentially of at least one element selected from the group consisting of less than 0.0030% by weight of B and 0.01 to 3.0% by weight of Cr.
- 5. The cold-rolled steel sheet according to claim 3, wherein the structure of only low-temperature transformation products consists of at least one member selected from the group consisting of massive ferrite, bainite, Widmanstatten ferrite, martensite and acicular ferrite.
- 6. A hot-dip galvanized cold-rolled steel sheet having excellent bake hardenability and non-aging properties at room temperature, consisting essentially of, in terms of % by weight, 0.0005 to 0.0070% C, 0.001 to 0.8% of Si, 0.3 to 4.0% of Mn, 0.002 to 0.15% of P, 0.0005 to 0.015% of S, 0.005 to 0.1% of Al and 0.0003 to 0.0060% of N with the balance consisting of Fe and unavoidable impurities and composed of a structure of only low-temperature transformation products, said hot-dip galvanized cold-rolled steel sheet having a bake hardenability property, BH, of not less than 5 kgf/mm.sup.2.
- 7. The hot-dip galvanized cold-rolled steel sheet according to claim 6, which further consists essentially of at least one element selected from the group consisting of B in an amount satisfying a requirement of less than 0.0030% by weight with B/N.ltoreq.1.5 and 0.01 to 3.0% by weight of Cr.
- 8. The hot-dip galvanized cold-rolled steel sheet according to claim 6, wherein the structure of only low-temperature transformation products consists of at least one member selected from the group consisting of massive ferrite, bainite, Widmanstatten ferrite, martensite and acicular ferrite.
- 9. A hot-dip galvanized cold-rolled steel sheet having excellent bake hardenability and moldability, consisting essentially of, in terms of % by weight, 0.0005 to 0.0070% of C, 0.001 to 0.8% of Si, 0.01 to 4.0% of Mn, 0.002 to 0.15% of P, 0.0005 to 0.015% of S, 0.005 to 0.1% of Al and 0.0003 to 0.0060% of N and further consisting essentially of at least one additional element selected from the group consisting of 0.003 to 0.1% of Ti and 0.003 to 0.1% of Nb with the balance consisting of Fe and unavoidable impurities and composed of a structure of only low-temperature transformation products, said hot-dip galvanized cold-railed steel sheet having a bake hardenability property, BH, of not less than 5 kgf/mm.sup.2.
- 10. The hot-dip galvanized cold-rolled steel sheet according to claim 9, which further consists essentially of at least one element selected from the group consisting of less than 0.0030% by weight of B and 0.01 to 3.0% by weight of Cr.
- 11. The hot-dip galvanized cold-rolled steel sheet according to claim 9, wherein the structure of only low-temperature transformation products consists of at least one member selected from the group consisting of massive ferrite, bainite, Widmanstatten ferrite, martensite and acicular ferrite.
- 12. A process for producing a cold-rolled steel sheet having excellent bake hardenability and non-aging properties at room temperature, comprising the steps of: heating a slab consisting essentially of, in terms of % by weight, 0.0005 to 0.0070% of C, 0.001 to 0.8% of Si, 0.3 to 4.0% of Mn, 0.002 to 0.15% of P, 0.0005 to 0.015% of S, 0.005 to 0.1% of Al and 0.0003 to 0.0060% of N with the balance consisting of Fe and unavoidable impurities to provide a heated slab; hot-rolling the heated slab at a finish hot rolling temperature of not lower than (Ar.sub.3 --100).degree.C. to provide a hot-rolled steel strip; coiling the hot-rolled steel strip at a temperature of not higher than 750.degree. C. to provide a coil of hot-rolled steel strip; cold-rolling the hot-rolled steel strip uncoiled from the coil of hot-rolled steel strip with a reduction ratio of not less than 60% to provide a cold-rolled steel strip; subjecting the cold-rolled steel strip to continuous annealing at an annealing temperature of not lower than the Ac.sub.3 transformation point and in a .gamma. single-phase region, thereby providing a cold-rolled steel sheet having a structure of only low temperature transformation products.
- 13. A process for producing a cold-rolled steel sheet according to claim 12, wherein the slab further consists essentially of at least one element selected from the group consisting of B in an amount satisfying a requirement of less than 0.0030% by weight with B/N.ltoreq.1.5 and 0.01 to 3.0% by weight of Cr.
- 14. A process for producing a cold-rolled steel sheet having excellent bake hardenability and non-aging properties at room temperature, comprising the steps of: heating a slab consisting essentially of, in terms of % by weight, 0.0005 to 0.0070% of C, 0.001 to 0.8% of Si, 0.01 to 4.0% of Mn, 0.002 to 0.15% of P, 0.0005 to 0.015% of S, 0.005 to 0.1% of Al and 0.0003 to 0.0060% of N and at least one element selected from the group consisting of 0.003 to 0.1% of Ti and 0.003 to 0.1% of Nb with the balance consisting of Fe and unavoidable impurities to provide a heated slab; hot-rolling the heated slab at a finish hot rolling temperature of not lower than (Ar.sub.3 --100).degree.C. to provide a hot-rolled steel strip; coiling the hot-rolled steel strip at a temperature of not higher than 750.degree. C. to provide a coil of hot-rolled steel strip; cold-rolling the hot-rolled steel strip uncoiled from the coil of hot-rolled steel strip with a reduction ratio of not less than 60% to provide a cold-rolled steel strip; subjecting the cold-rolled steel strip to continuous annealing at an annealing temperature of not lower than the Ac.sub.3 transformation point and in a .gamma. single-phase region, thereby providing a cold-rolled steel sheet having a structure of only low temperature transformation products.
- 15. A process for producing a cold-rolled steel sheet according to claim 14, wherein the slab further consists essentially of at least one element selected from the group consisting of B in an amount satisfying a requirement of less than 0.0030% by weight with B/N.ltoreq.1.5 and 0.01 to 3.0% by weight of Cr.
- 16. A process for producing a hot-dip galvanized cold-rolled steel sheet having excellent bake hardenability and non-aging properties at room temperature, comprising the steps of: heating a slab consisting essentially of, in terms of % by weight, 0.0005 to 0.0070% of C, 0.001 to 0.8% of Si, 0.3 to 4.0% of Mn, 0.002 to 0.15% of P, 0.0005 to 0.015% of S, 0.005 to 0.1% of Al and 0.0003 to 0.0060% of N with the balance consisting of Fe and unavoidable impurities to provide a heated slab; hot-rolling the heated slab at a finish hot rolling temperature of not lower than (Ar.sub.3 --100).degree.C. to provide a hot-rolled steel strip; coiling the hot-rolled steel strip at a temperature of not higher than 750.degree. C. to provide a coil of hot-rolled steel strip; cold-rolling the hot-rolled steel strip uncoiled from the coil of hot-rolled steel strip with a reduction ratio of not less than 60% to provide a cold-rolled steel strip; subjecting the cold-rolled steel strip to in-line annealing hot-dip galvanizing at an annealing temperature of not lower than the Ac.sub.3 transformation point and in a .gamma. single-phase region, thereby providing a hot-dip galvanized cold-rolled steel sheet having a structure of only low temperature transformation produces.
- 17. The process for producing a hot-dip galvanized cold-rolled steel sheet according to claim 16, wherein the slab further consists essentially of at least one element selected from the group consisting of B in an amount satisfying a requirement of less than 0.0030% by weight with B/N.ltoreq.1.5 and 0.01 to 3.0% by weight of Cr.
- 18. A process for producing a hot-dip galvanized cold-rolled steel sheet having excellent bake hardenability and non-aging properties at room temperature, comprising the steps of: heating a slab consisting essentially of, in terms of % by weight, 0.0005 to 0.0070% of C, 0.001 to 0.8% of Si, 0.01 to 4.0% of Mn, 0.002 to 0.15% of P, 0.0005 to 0.015% of S, 0.005 to 0.1% of Al and 0.0003 to 0.0060% of N and at lease one element selected from the group consisting of 0.003 to 0.1% of Ti and 0.003 to 0.1% of Nb with the balance consisting of Fe and unavoidable impurities to provide a heated slab; hot-rolling the heated slab at a finish hot rolling temperature of not lower than (Ar.sub.3 --100).degree.C. to provide a hot-rolled steel strip; coiling the hot-rolled steel strip at a temperature of not higher than 750.degree. C. to provide a coil of hot-rolled steel strip; cold-rolling the hot-rolled steel strip uncoiled from the coil of hot-rolled steel strip with a reduction ratio of not less than 60% to provide a cold-rolled steel strip; subjecting the cold-rolled steel strip to in-line annealing hot-dip galvanizing at an annealing temperature of not lower than the Ac.sub.3 transformation point and in a .gamma. single-phase region, thereby providing a hot-dip galvanized cold-rolled steel sheet having a structure of only low-temperature transformation products.
- 19. The process for producing a cold-rolled steel sheet according to claim 18, wherein the slab further consists essentially of at least one element selected from the group consisting of B in an amount satisfying a requirement of less than 0.0030% by weight with B/N.ltoreq.1.5 and 0.01 to 3.0% by weight of Cr.
Priority Claims (3)
Number |
Date |
Country |
Kind |
4-232301 |
Aug 1992 |
JPX |
|
4-232319 |
Aug 1992 |
JPX |
|
5-044108 |
Mar 1993 |
JPX |
|
Parent Case Info
This application is a continuation of application Ser. No. 08/232,066 filed as PCT/JP93/01231 Aug. 31, 1993, now abandoned.
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Continuations (1)
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Number |
Date |
Country |
Parent |
232066 |
Jun 1994 |
|