Abstract: A steel material having a chemical composition contains 0.0010% to 0.0030% C, 0.05% or less Si, 0.1% to 0.5% Mn, 0.021% to 0.060% Ti, and 0.0005% to 0.0050% B on a mass basis such that B/C satisfies 0.5 or more, whereby a resulting cold-rolled steel sheet has a microstructure dominated by ferrite with an average grain size of 10 ?m to 30 ?m, a proportional limit of 100 MPa or less, and excellent shape fixability.

Abstract: The high strength steel sheet has a chemical composition including 0.08% to 0.20% of C, 0.3% or less of Si, 0.1% to 3.0% of Mn, 0.10% or less of P, 0.030% or less of S, 0.10% or less of Al, 0.010% or less of N, 0.20% to 0.80% of V, and the remainder composed of Fe and incidental impurities on a percent by mass basis, and a microstructure which includes 95% or more of ferrite phase on an area percentage basis, in which fine precipitates are dispersed having a distribution in such a way that the number density of precipitates having a particle size of less than 10 nm is 1.0×105/?m3 or more and the standard deviation of natural logarithm values of precipitate particle sizes with respect to precipitates having a particle size of less than 10 nm is 1.5 or less.

Abstract: A steel sheet and a method for producing the same are disclosed. The steel sheet has a composition containing 0.015% to 0.05% C, less than 0.10% Si, 0.1% to 2.0% Mn, 0.20% or less P, 0.1% or less S, 0.01% to 0.10% Al, 0.005% or less N, and 0.06% to 0.5% Ti in percent by mass, C and Ti satisfying the inequality Ti*/C?4, where Ti* (mass percent)=Ti-3.4N and Ti, C, and N represent the content (mass percent) of each element. The steel sheet has a microstructure which contains a ferrite phase as a base, in which the average grain diameter of the ferrite phase is 7 ?m or more, and in which the ratio of the rolling-direction average grain diameter to thickness-wise average grain diameter of the ferrite phase is 1.1 or more.

Abstract: A high-strength hot rolled steel sheets with excellent stretch flangeability has small variations in mechanical properties in individual coils. Variations in strength from place to place in a coil are decreased by minimally reducing the Si and Mn contents to suppress the occurrence of problems such as segregation. Further, the microstructure of the steel sheets is configured such that a ferrite phase represents an area ratio of not less than 95%, the ferrite crystal grains have an average grain size of not less than 1 ?m, and the ferrite crystal grains contain TiC with an average particle size of not more than 7 nm dispersed in the crystal grains.

Abstract: A cold-rolled steel sheet includes, on a percent by mass basis: C: 0.0010% to 0.0030%, Si: 0.05% or less, Mn: 0.1% to 0.3%, P: 0.05% or less, S: 0.02% or less, Al: 0.02% to 0.10%, N: 0.005% or less, and Nb: 0.010% to 0.030% and the remainder composed of Fe and incidental impurities, wherein values in a rolling direction and a direction perpendicular to the rolling direction are within a range of 1.0 to 1.6, and a mean value Elm of elongations in the rolling direction, a direction at 45° with respect to the rolling direction, and the direction perpendicular to the rolling direction is 40% or more, where Elm=(ElL+2×ElD+ElC)/4 and ElL: elongation in the rolling direction, ElD: elongation in the direction at 45° with respect to the rolling direction, and ElC: elongation in the direction perpendicular to the rolling direction.

Abstract: A cold-rolled steel sheet includes, on a percent by mass basis: C: 0.0010% to 0.0030%, Si: 0.05% or less, Mn: 0.1% to 0.3%, P: 0.05% or less, S: 0.02% or less, Al: 0.02% to 0.10%, N: 0.005% or less, and Nb: 0.010% to 0.030% and the remainder composed of Fe and incidental impurities, wherein r values in a rolling direction and a direction perpendicular to the rolling direction are within a range of 1.0 to 1.6, and a mean value Elm of elongations in the rolling direction, a direction at 45° with respect to the rolling direction, and the direction perpendicular to the rolling direction is 40% or more, where Elm=(ElL+2×ElD+ElC)/4 ElL: elongation in the rolling direction, ElD: elongation in the direction at 45° with respect to the rolling direction, and ElC: elongation in the direction perpendicular to the rolling direction.

Abstract: A high strength steel sheet and a method for manufacturing the same has superior phosphatability properties and hot-dip galvannealed properties besides a tensile strength of 950 MPa or more and a high ductility, and also having a small variation in mechanical properties with the change in annealing conditions.

Abstract: A high strength steel sheet and a method for manufacturing the same has superior phosphatability properties and hot-dip galvannealed properties besides a tensile strength of 950 MPa or more and a high ductility, and also having a small variation in mechanical properties with the change in annealing conditions.

Abstract: There is provided a high-stiffness high-strength thin steel sheet having a tensile strength of not less than 590 MPa and a Young's modulus of not less than 225 GPa, which comprises C: 0.02-0.15%, Si: not more than 1.5%, Mn: 1.5-4.0%, P: not more than 0.05%, S: not more than 0.01%, Al: not more than 1.5%, N: not more than 0.01% and Nb: 0.02-0.40% as mass %, provided that C, N and Nb contents satisfy 0.01?C+(12/14)×N?(12/92.9)×Nb?0.06 and N?(14/92.9)×(Nb?0.01) and the remainder being substantially iron and inevitable impurities, and has a texture comprising a ferrite phase as a main phase and having a martensite phase at an area ratio of not less than 1%.

Abstract: There is provided a high-stiffness high-strength thin steel sheet having a tensile strength of not less than 590 MPa and a Young's modulus of not less than 230 GPa, which comprises C: 0.02-0.15%, Si: not more than 1.5%, Mn: 1.0-3.5%, P: not more than 0.05%, S: not more than 0.01%, Al: not more than 1.5%, N: not more than 0.01% and Ti: 0.02-0.50% as mass %, provided that C, N, S and Ti contents satisfy Ti*=Ti?(47.9/14)×N?(47.9/32.1)×S?0.01 and 0.01?C?(12/47.9)×Ti*?0.05 and the remainder being substantially iron and inevitable impurities, and has a texture comprising a ferrite phase as a main phase and having a martensite phase at an area ratio of not less than 1%.