Abstract: A manufacturing method of a body frame includes a pre-strain step of press molding a wavy shape portion in the body frame to apply pre-strain after any press molding to mold the body frame.

Abstract: A manufacturing method of a body frame includes a pre-strain step of press molding a wavy shape portion in the body frame to apply pre-strain after any press molding to mold the body frame.

Abstract: A vehicle collision energy absorbing member is excellent in collision energy absorbing performance in the axial direction upon collision. The vehicle collision energy absorbing member is formed of a high strength thin steel sheet having TS of at least 980 MPa and having an n-value and a limit bending radius Rc satisfying the following Formula: Rc/t?1.31×ln(n)+5.21.

Abstract: A high-strength steel sheet comprises, by weight, not less than 0.25% and not more than 0.5% of C, not less than 4% and not more than 14% of Mn, not less than 6.5% and not more than 9.5% of Cr, and not less than 0.3% and not more than 3% of Si. The high-strength steel sheet satisfies formulas 1 and 2, formula (1) being 12?2.0Si+5.5Al+Cr+1.5Mo?25 and formula (2) being 13?30C+0.5Mn+0.3Cu+Ni+25N?17, and mainly consists of austenite, and the high-strength steel sheet has yield strength of not less than 1000 MPa and total elongation of not less than 20%. In formulas 1 and 2, each element in the above formulas indicates the content, in weight %, of the element.

Abstract: The present invention provides a vehicle collision energy absorbing member formed by shaping a thin steel sheet. At least one of the thin steel sheet and the vehicle collision energy absorbing member has tensile properties of a tensile strength TS of 980 MPa or more and a yield point elongation Y-El of 2% or more.

Abstract: A vehicle collision energy absorbing member is excellent in collision energy absorbing performance in the axial direction upon collision. The vehicle collision energy absorbing member is formed of a high strength thin steel sheet having TS of at least 980 MPa and having an n-value and a limit bending radius Rc satisfying the following Formula: Rc/t?1.31×ln(n)+5.21.

Abstract: A high-strength steel sheet includes a stress-strain diagram obtained by a tensile test of the steel, and a gradient of stress in the stress-strain diagram, wherein the gradient d?/d? in 3 to 7% of true strain is 5000 MPa or more.

Abstract: A high-strength steel sheet having high strength and ability to absorb impact energy to a high degree is formed into a strengthening member for an vehicle, having both superior energy absorption efficiency and bonding properties. The high-strength member has a high-strength steel sheet having not less than 5000 MPa of gradient du/de of a stress-strain diagram in a range of 3 to 7% of true strain obtained in a tension test, and a steel sheet having 0.3 to 0.85 of tension strength ratio against tension strength of the high-strength steel sheet, the steel sheets bonded at their ends with space extending in a prescribed direction between the steel sheets, and a load is to be applied on the member from the prescribed direction when the member is acted upon.

Abstract: A high-strength steel sheet comprises a metallic structure consisting of a ferrite phase and a hard second phase dispersed in the ferrite phase, the hard second phase in the metallic structure having an area ratio of 30 to 70%, and the ferrite of which grain sizes are not more than 1.2 ?m having an area ratio of 15 to 90% in the ferrite phase. The term ds is an average grain size of the ferrite of which grain sizes are not more than 1.2 ?m, the term dL is an average grain size of ferrite of which grain sizes are more than 1.2 ?m, and the ds and the dL satisfy the following equation (1): dL/ds?3??(1).

Abstract: A high-strength steel sheet comprises, by weight, not less than 0.25% and not more than 0.5% of C, not less than 4% and not more than 14% of Mn, not less than 6.5% and not more than 9.5% of Cr, and not less than 0.3% and not more than 3% of Si. The high-strength steel sheet satisfies the following formulas 1 and 2 and mainly consists of austenite, and the high-strength steel sheet has yield strength of not less than 1000 MPa and total elongation of not less than 20%. 12?2.0Si+5.5Al+Cr+1.5Mo?25 ??(1) 13 ?30C+0.5Mn+0.

Abstract: A high-strength steel sheet includes a stress-strain diagram obtained by a tensile test of the steel, and a gradient of stress in the stress-strain diagram, wherein the gradient d?/d? in 3 to 7% of true strain is 5000 MPa or more.

Abstract: A high-strength steel sheet having high strength and ability to absorb impact energy to a high degree is formed into a strengthening member for an vehicle, having both superior energy absorption efficiency and bonding properties. The high-strength member has a high-strength steel sheet having not less than 5000 MPa of gradient du/de of a stress-strain diagram in a range of 3 to 7% of true strain obtained in a tension test, and a steel sheet having 0.3 to 0.85 of tension strength ratio against tension strength of the high-strength steel sheet, the steel sheets bonded at their ends with space extending in a prescribed direction between the steel sheets, and a load is to be applied on the member from the prescribed direction when the member is acted upon.

Abstract: A high-strength steel sheet has a metal structure consisting of a ferrite phase in which a hard second phase is dispersed and has 3 to 30% of an area ratio of the hard second phase. In the ferrite phase, the area ratio of nanograins of which grain sizes are not more than 1.2 ?m is 15 to 90%, and dS as an average grain size of nanograins of which grain sizes are not more than 1.2 ?m and dL as an average grain size of micrograins of which grain sizes are more than 1.2 ?m satisfy an equation (dL/dS?3).

Abstract: The present invention: provides a good-workability and high-strength cold-rolled steel sheet excellent in post-painting corrosion resistance to the extent of securing excellent resistance to salt warm water immersion which is a good-workability and high-strength cold-rolled steel sheet excellent in post-painting corrosion resistance characterized in that: said steel sheet contains, in mass, 0.16 to 0.19% C, 1.10 to 1.30% Si, 1.50 to 1.60% Mn, not more than 0.1% P and 0.015 to 0.050% Al, with the balance consisting of Fe and unavoidable impurities; the average of the amount of Si incrassating on the surface of said steel sheet is not more than 20 times the Si concentration in said steel sheet; and the area percentage of the portions where the ratio of the Si concentration on the surface of said steel sheet to the Si concentration in said steel sheet is not less than 10 is not more than 95%.

Abstract: A high-strength steel sheet comprises a metallic structure consisting of a ferrite phase and a hard second phase dispersed in the ferrite phase, the hard second phase in the metallic structure having an area ratio of 30 to 70%, and the ferrite of which grain sizes are not more than 1.2 ?m having an area ratio of 15 to 90% in the ferrite phase. The term ds is an average grain size of the ferrite of which grain sizes are not more than 1.2 ?m, the term dL is an average grain size of ferrite of which grain sizes are more than 1.2 ?m, and the ds and the dL satisfy the following equation (1): dL/ds?3??(1).

Abstract: A high-strength steel sheet has a metal structure consisting of a ferrite phase in which a hard second phase is dispersed and has 3 to 30% of an area ratio of the hard second phase. In the ferrite phase, the area ratio of nanograins of which grain sizes are not more than 1.2 ?m is 15 to 90%, and dS as an average grain size of nanograins of which grain sizes are not more than 1.2 ?m and dL as an average grain size of micrograins of which grain sizes are more than 1.2 ?m satisfy an equation (dL/dS?3).

Abstract: The present invention: provides a good-workability and high-strength cold-rolled steel sheet excellent in post-painting corrosion resistance to the extent of securing excellent resistance to salt warm water immersion which is a good-workability and high-strength cold-rolled steel sheet excellent in post-painting corrosion resistance characterized in that: said steel sheet contains, in mass, 0.16 to 0.19% C, 1.10 to 1.30% Si, 1.50 to 1.60% Mn, not more than 0.1% P and 0.015 to 0.050% Al, with the balance consisting of Fe and unavoidable impurities; the average of the amount of Si incrassating on the surface of said steel sheet is not more than 20 times the Si concentration in said steel sheet; and the area percentage of the portions where the ratio of the Si concentration on the surface of said steel sheet to the Si concentration in said steel sheet is not less than 10 is not more than 95%.