Patent application number | Description | Published |
20110008647 | HIGH-STRENGTH COLD-ROLLED STEEL SHEET, HIGH-STRENGTH GALVANIZED STEEL SHEET, AND HIGH-STRENGTH ALLOYED HOT-DIP GALVANIZED STEEL SHEET HAVING EXCELLENT FORMABILITY AND WELDABILITY, AND METHODS FOR MANUFACTURING THE SAME - This cold-rolled steel sheet includes, in terms of mass %, C: not less than 0.05% and not more than 0.095%, Cr: not less than 0.15% and not more than 2.0%, B: not less than 0.0003% and not more than 0.01%, Si: not less than 0.3% and not more than 2.0%, Mn: not less than 1.7% and not more than 2.6%, Ti: not less than 0.005% and not more than 0.14%, P: not more than 0.03%, S: not more than 0.01%, Al: not more than 0.1%, N: less than 0.005%, O: not less than 0.0005% and not more than 0.005%, and contains as the remainder, iron and unavoidable impurities, wherein the microstructure of the steel sheet includes mainly polygonal ferrite having a crystal grain size of not more than 4 μm, and hard microstructures of bainite and martensite, the block size of the martensite is not more than 0.9 μm, the Cr content within the martensite is 1.1 to 1.5 times the Cr content within the polygonal ferrite, and the tensile strength is at least 880 MPa. | 01-13-2011 |
20110017360 | HOT-ROLLED STEEL SHEET EXCELLENT IN FATIGUE PROPERTIES AND STRETCH-FLANGE FORMABILITY AND METHOD FOR MANUFACTURING THE SAME - This hot-rolled steel sheet contains, in terms of mass%, C: 0.015% or more to less than 0.040%; Si: less than 0.05%; Mn: 0.9% or more to 1.8% or less; P: less than 0.02%; S: less than 0.01%; Al: less than 0.1%; N: less than 0.006%; and Ti: 0.05% or more to less than 0.11%, with the remainder being Fe and inevitable impurities, wherein Ti/C is in a range of 2.5 or more to less than 3.5, Nb, Zr, V, Cr, Mo, B and W are not included, a microstructure includes a mixed microstructure of polygonal ferrite and quasi-polygonal ferrite in a proportion of greater than 96%, a maximum tensile strength is 520 MPa or more and less than 720 MPa, an aging index AI is more than 15 MPa, a product of a hole expansion ratio (A) % and a total elongation (El) % is 2350 or more, and a fatigue limit is 200 MPa or more. | 01-27-2011 |
20110024004 | HIGH-STRENGTH STEEL SHEET AND GALVANIZED STEEL SHEET HAVING VERY GOOD BALANCE BETWEEN HOLE EXPANSIBILITY AND DUCTILITY, AND ALSO EXCELLENT IN FATIGUE RESISTANCE, AND METHODS OF PRODUCING THE STEEL SHEETS - The invention is directed to providing, for application in automobiles, construction materials, household appliances and the like, high-strength sheets excellent in formability properties such as hole expansibility and ductility, and also in fatigue resistance, characterized in comprising, in specified contents expressed in mass %, C, Si, Mn, P, S, Al, N and O and a balance of iron and unavoidable impurities, and having a steel sheet structure composed mainly of ferrite and hard structures, a crystal orientation difference between some ferrite adjacent to hard structures and the hard structures of less than 9°, and a maximum tensile strength of 540 MPa or greater. | 02-03-2011 |
20120141829 | SPOT WELDED JOINT AND SPOT WELDING METHOD - Provided is a spot welded joint ( | 06-07-2012 |
20120152411 | HIGH-STRENGTH GALVANIZED STEEL SHEET AND METHOD OF MANUFACTURING THE SAME - Provided is a galvanized steel sheet having a tensile strength of 770 MPa or more including a steel sheet portion, and a plated layer formed on the surface of the steel sheet portion, in which the plated layer is a galvanized plated layer or an galvannealed plated layer, the steel sheet portion has a soft layer that directly adjoins the interface with the plated layer and an inside layer that is other than the soft layer, the thickness D of soft layer is 0.001% to 5% of thickness t of the steel sheet portion, and, when the hardness of the soft layer measured by nano-indentation method is indicated by H1, and the representative hardness of the steel sheet portion measured by the nano-indentation method is indicated by Ha in cross section that goes along the thickness direction of the steel sheet portion, H1 is 5% to 75% of Ha. | 06-21-2012 |
20140170440 | HIGH STRENGTH STEEL SHEET AND HIGH STRENGTH GALVANIZED STEEL SHEET EXCELLENT IN SHAPEABILITY AND METHODS OF PRODUCTION OF SAME - High strength steel sheet which secures tensile maximum strength 900 MPa or more high strength while having excellent shapeability, which high strength steel sheet which is excellent in shapeability characterized by having a predetermined composition of ingredients, by the steel sheet structure including a ferrite phase and martensite phase, by the ratio of Cu particles incoherent with the bcc iron being 15% or more with respect to the Cu particles as a whole, by a density of Cu particles in the ferrite phase being 1.0×10 | 06-19-2014 |
20140234657 | HOT-DIP GALVANIZED STEEL SHEET AND MANUFACTURING METHOD THEREOF - A hot-dip galvanized steel sheet includes: a steel sheet; and a plated layer on a surface of the steel sheet, a microstructure contains, by volume fraction, equal to or more than 20% and equal to or less than 99% in total of one or two of martensite and bainite, a residual structure contains one or two of ferrite, residual austenite of less than 8% by volume fraction, and pearlite of equal to or less than 10% by volume fraction, tensile strength is equal to or greater than 980 MPa, the plated layer is a hot-dip galvanized layer which contains oxides including one or two or more of Si, Mn, and Al, contains equal to or less than 15 mass % of Fe, and a remainder including Zn, Al, and unavoidable impurities, and when a cross section including the steel sheet and the hot-dip galvanized layer is seen in a sheet thickness direction, a projected area ratio is equal to or more than 10% and equal to or less than 90%. | 08-21-2014 |
20140234658 | GALVANIZED STEEL SHEET AND METHOD OF MANUFACTURING THE SAME - A galvanized steel sheet includes a steel sheet and a plating layer on the surface of the steel sheet, in which the steel sheet includes, as a steel chemical composition, by mass %, C: 0.05 to 0.40%, Si: 0.5 to 3.0% and Mn: 1.5 to 3.0%, a microstructure of the steel sheet includes ferrite, bainite, by volume fraction, 30% or more of a tempered martensite, and 8% or more of an austenite, and tensile strength of the steel sheet is 980 MPa or more, and the plating layer includes an oxide including at least one chemical element selected from Si, Mn and Al, and when seen at a cross section including the steel sheet and the plating layer in a plate thickness direction, a projection area fraction of the oxide is 10% or more. | 08-21-2014 |
20140242415 | HIGH-STRENGTH HOT-DIP GALVANIZED STEEL SHEET AND HIGH-STRENGTH ALLOYED HOT-DIP GALVANIZED STEEL SHEET HAVING EXCELLENT FORMABILITY AND SMALL MATERIAL ANISOTROPY WITH ULTIMATE TENSILE STRENGTH OF 980 MPa OR MORE AND MANUFACTURING METHOD THEREFOR - Provided is a high-strength hot-dip galvanized steel sheet having small material anisotropy and excellent formability with an ultimate tensile strength of 980 MPa or more. The hot-dip galvanized steel sheet includes a hot-dip galvanized layer formed on a surface of a base steel plate. The base steel plate contains, by mass %, C: 0.1 to less than 0.40%, Si: 0.5 to 3.0%, Mn: 1.5 to 3.0%, O: limited to 0.006% or less, P: limited to 0.04% or less, S: limited to 0.01% or less, Al: limited to 2.0% or less, N: limited to 0.01% or less, and a balance including Fe and inevitable impurities. A microstructure of the base steel sheet contains ferrite of 40% or more, residual austenite of 8 to less than 60%, by volume fraction, and a balance being bainite or martensite. In a sheet thickness range of ⅝ to ⅜ from the surface of the base steel sheet, a pole density of specific crystal orientation is within a predetermined range. The hot-dip galvanized layer contains Fe: less than 7 mass % and a balance including Zn, Al, and inevitable impurities. | 08-28-2014 |
20140342183 | HIGH-STRENGTH HOT-DIP GALVANIZED STEEL SHEET AND HIGH-STRENGTH ALLOYED HOT-DIP GALVANIZED STEEL SHEET HAVING EXCELLENT PLATING ADHESION, FORMABILITY, AND HOLE EXPANDABILITY WITH TENSILE STRENGTH OF 980 MPa OR MORE AND MANUFACTURING METHOD THEREFOR - Provided is a high-strength hot-dip galvanized steel sheet having excellent plating adhesion, formability, and hole expandability with an ultimate tensile strength of 980 MPa or more, the hot-dip galvanized steel sheet comprising a hot-dip galvanized layer formed on a surface of a base steel sheet. The base steel sheet contains, by mass %, C: 0.05% to 0.4%; Si: 0.01% to 3.0%; Mn: 0.1% to 3.0%; Al: 0.01 to 2.0%; in which Si+Al>0.5%, P: limited to 0.04% or less; S: limited to 0.05% or less; N: limited to 0.01% or less; and a balance including Fe and inevitable impurities, a microstructure of the base steel sheet contains 40% or more by total volume fraction of martensite and bainite, 8% or more by volume fraction of residual austenite, and a balance of the microstructure being ferrite or ferrite and 10% or less by volume fraction of pearlite. The martensite contains 10% or more by total volume fraction of two or more kinds of three kinds of martensites (1), (2), and (3), and the hot-dip galvanized layer contains less than 7 mass % of Fe. | 11-20-2014 |
20140377582 | HIGH-STRENGTH COLD-ROLLED STEEL SHEET AND METHOD FOR PRODUCING THE SAME - A high-strength cold-rolled steel sheet includes, as a component composition, by mass %: C: 0.075% to 0.300%; Si: 0.30% to 2.50%; Mn: 1.30% to 3.50%; P: 0.001% to 0.050%; S: 0.0001% to 0.0100%; Al: 0.001% to 1.500%; and N: 0.0001% to 0.0100%, in which a surface microstructure contains residual austenite of 3% to 10% and ferrite of 90% or less by volume fraction, an inner microstructure at a depth of t/4 from the surface assuming that a sheet thickness is t contains residual austenite of 3% to 20% by volume fraction, a ratio Hvs/Hvb between a surface hardness Hvs of the steel sheet surface and a hardness Hvb at a depth of ¼ of the thickness is more than 0.75 to 0.90, and a maximum tensile strength is 700 MPa or more. | 12-25-2014 |