Patent application number | Description | Published |
20120141829 | SPOT WELDED JOINT AND SPOT WELDING METHOD - Provided is a spot welded joint ( | 06-07-2012 |
20130037180 | HIGH-STRENGTH COLD-ROLLED STEEL SHEET AND METHOD OF MANUFACTURING THEREOF - A high-strength cold-rolled steel sheet includes, by mass %, C: 0.10% to 0.40%, Mn: 0.5% to 4.0%, Si: 0.005% to 2.5%, Al: 0.005% to 2.5%, Cr: 0% to 1.0%, and a balance of iron and inevitable impurities, in which an amount of P is limited to 0.05% or less, an amount of S is limited to 0.02% or less, an amount of N is limited to 0.006% or less, the microstructure includes 2% to 30% of retained austenite by area percentage, martensite is limited to 20% or less by area percentage in the microstructure, an average particle size of cementite is 0.01 μm to 1 μm, and 30% to 100% of the cementite has an aspect ratio of 1 to 3. | 02-14-2013 |
20130167980 | HIGH-STRENGTH STEEL SHEET AND HIGH-STRENGTH ZINC-COATED STEEL SHEET WHICH HAVE EXCELLENT DUCTILITY AND STRETCH-FLANGEABILITY AND MANUFACTURING METHOD THEREOF - This high-strength steel sheet includes by mass percentage: 0.05 to 0.4% of C; 0.1 to 2.5% of Si; 1.0 to 3.5% of Mn; 0.001 to 0.03% of P; 0.0001 to 0.01% of S; 0.001 to 2.5% of Al; 0.0001 to 0.01% of N; 0.0001 to 0.008% of O; and a remainder composed of iron and inevitable impurities, wherein a steel sheet structure contains by volume fraction 10 to 50% of a ferrite phase, 10 to 50% of a tempered martensite phase, and a remaining hard phase, wherein a 98% hardness is 1.5 or more times as high as a 2% hardness in a range from ⅛ to ⅜ of a thickness of the steel sheet, wherein a kurtosis K* of the hardness distribution between the 2% hardness and the 98% hardness is −1.2 to −0.4, and wherein an average crystal grain size in the steel sheet structure is 10 μm or less. | 07-04-2013 |
20140162088 | HIGH STRENGTH STEEL SHEET AND HIGH STRENGTH GALVANIZED STEEL SHEET EXCELLENT IN SHAPEABILITY AND METHODS OF PRODUCTION OF SAME - High strength steel sheet and high strength galvanized steel sheet which are excellent in shapeability which secure a tensile maximum strength 900 MPa or more high strength while obtaining excellent ductility and stretch flangeability, which sheets have predetermined compositions of ingredients, have steel sheet structures which contain volume fraction 1 to 20% of residual austenite phases, and which have martensite transformation points of the residual austenite phases of −60° C. or less. | 06-12-2014 |
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 |
20140205855 | HIGH-STRENGTH STEEL SHEET EXCELLENT IN IMPACT RESISTANCE AND MANUFACTURING METHOD THEREOF, AND HIGH-STRENGTH GALVANIZED STEEL SHEET AND MANUFACTURING METHOD THEREOF - [Summary] The present invention provides a high-strength steel sheet excellent in impact resistance. The high-strength steel sheet contains predetermined contents of C, Si, Mn, P, S, Al, Ti, N, and O, with the balance being iron and inevitable impurities, and has a steel sheet structure in which, in a ⅛ thickness to ⅜ thickness region across ¼ of a sheet thickness, 1 to 8% retained austenite is contained in volume fraction, an average aspect ratio of the retained austenite is 2.0 or less, an amount of solid-solution Mn in the retained austenite is 1.1 times an average amount of Mn or more, and TiN grains having a 0.5 μm average grain diameter or less are contained, and a density of AlN grains with a 1 μm grain diameter or more is 1.0 pieces/mm | 07-24-2014 |
20140212684 | HIGH-STRENGTH GALVANIZED STEEL SHEET EXCELLENT IN BENDABILITY AND MANUFACTURING METHOD THEREOF - The present invention provides a high-strength galvanized steel sheet with maximum tensile strength of 900 MPa or more. The high-strength galvanized steel sheet has an alloyed galvanized layer formed on a surface of a base steel sheet containing predetermined amounts of C, Si, Mn, P, S, Al, N, O with a balance being constituted of iron and inevitable impurities, in which in a structure of the base steel sheet, retained austenite is limited to 8% or less in volume fraction, kurtosis K* of the hardness distribution between 2% hardness and 98% hardness is −0.30 or less, a ratio between Vickers hardness of surface layer of the base steel sheet and Vickers hardness of ¼ thickness of the base steel sheet is 0.35 to 0.70, and a content of iron in the alloyed galvanized layer is 8 to 12% in mass %. | 07-31-2014 |
20140234659 | HIGH-STRENGTH HOT-DIP GALVANIZED STEEL SHEET HAVING EXCELLENT DELAYED FRACTURE RESISTANCE AND MANUFACTURING METHOD THEREOF - A hot-dip galvanizing layer or an alloyed hot dip galvanizing layer is formed on the surface of a base steel sheet in which in volume fraction, 40 to 90% of a ferrite phase and 5% or less of a retained austenite phase are contained, and a ratio of non-recrystallized ferrite to the entire ferrite phase is 50% or less in volume fraction, and further a grain diameter ratio being a value of, of crystal grains in the ferrite phase, an average grain diameter in the rolling direction divided by an average grain diameter in the sheet width direction is 0.75 to 1.33, a length ratio being a value of, of hard structures dispersed in island shapes, an average length in the rolling direction divided by an average length in the sheet width direction is 0.75 to 1.33, and an average aspect ratio of inclusions is 5.0 or less. | 08-21-2014 |
20140234660 | HIGH-STRENGTH HOT-DIP GALVANIZED STEEL SHEET, HIGH-STRENGTH ALLOYED HOT-DIP GALVANIZED STEEL SHEET EXCELLENT IN BAKE HARDENABILITY, AND MANUFACTURING METHOD THEREOF - Steel contains each of C, Si, Mn, P, S, Al, N, O, at a range from ⅛ thickness centered around a ¼ sheet thickness from a surface to ⅜ thickness centered around the ¼ sheet thickness from the surface at a base steel sheet, a structure of the base steel sheet contains, in volume fraction, 3% or more of a retained austenite phase, 50% or less of a ferrite phase, and 40% or more of a hard phase, average dislocation density is 5×10 | 08-21-2014 |
20140242414 | HIGH-STRENGTH STEEL SHEET AND HIGH-STRENGTH GALVANIZED STEEL SHEET EXCELLENT IN SHAPE FIXABILITY, AND MANUFACTURING METHOD THEREOF - The present invention provides a high-strength steel sheet excellent in shape fixability. The high-strength steel sheet contains C, Si, Mn, P, S, Al, N, and O with predetermined contents, in which a retained austenite phase of 5 to 20% in volume fraction is contained, an amount of solid-solution C contained in the retained austenite phase is 0.80 to 1.00% in mass %, W | 08-28-2014 |
20140287263 | HIGH-STRENGTH HOT-DIP GALVANIZED STEEL SHEET AND HIGH-STRENGTH ALLOYED HOT-DIP GALVANIZED STEEL SHEET EXCELLENT IN MECHANICAL CUTTING PROPERTY, AND MANUFACTURING METHOD THEREOF - There is provided a high-strength hot-dip galvanized steel sheet and the like excellent in mechanical cutting property, which are capable of obtaining high ductility while ensuring high strength with maximum tensile strength of 900 MPa or more. The high-strength hot-dip galvanized steel sheet has a sheet thickness of 0.6 to 5.0 mm and has a plating layer on a surface of a steel sheet with component compositions being set in appropriate ranges, in which the steel sheet structure contains a 40 to 90% ferrite phase and a 3% or more retained austenite phase by volume fraction. In the retained austenite phase, a solid solution carbon amount is 0.70 to 1.00%, an average grain diameter is 2.0 μm or less, an average distance between grains is 0.1 to 5.0 μm, a thickness of a decarburized layer in a steel sheet surface layer portion is 0.01 to 10.0 μm, an average grain diameter of oxides contained in the steel, sheet surface layer portion is 30 to 120 nm and an average density thereof is 1.0×10 | 09-25-2014 |
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 |
20150083278 | High-Strength Hot-Dip Galvanized Steel Sheet Excellent in Impact Resistance Property and Manufacturing Method Thereof, and High-Strength Alloyed Hot-Dip Galvanized Steel Sheet and Manufacturing Method Thereof - A base steel sheet has a hot-dip galvanized layer formed on a surface thereof, in which, in a steel sheet structure in a range of ⅛ thickness to ⅜ thickness centered around ¼ thickness of a sheet thickness from a surface, a volume fraction of a retained austenite phase is 5% or less, and a total volume fraction of phases of bainite, bainitic ferrite, fresh martensite, and tempered martensite is 40% or more, an average effective crystal grain diameter is 5.0 μm or less, a maximum effective crystal grain diameter is 20 μm or less, and a decarburized layer with a thickness of 0.01 μm to 10.0 μm is formed on a surface layer portion, in which a density of oxides dispersed in the decarburized layer is 1.0×10 | 03-26-2015 |