Patent application number | Description | Published |
20100108200 | HIGH YIELD RATIO AND HIGH-STRENGTH HOT-DIP GALVANIZED STEEL SHEET EXCELLENT IN WORKABILITY AND PRODUCTION METHOD THEREOF - A high-strength hot-dip galvanized steel sheet excellent in workability according to the present invention: contains C, Si, Mn and other elements; has a dual phase structure containing ferrite and martensite as the metallographic structure; and, in the ferrite structure, satisfies the expression 0.2≦(L | 05-06-2010 |
20100247957 | HIGH-STRENGTH COLD-ROLLED STEEL SHEET EXCELLENT IN BENDING WORKABILITY - Disclosed is a cold-rolled steel sheet having a specific steel composition and having a composite steel structure including a ferrite structure and a martensite-containing second phase. In a surface region of the steel sheet from the surface to a depth one-tenth the gage, the number density of n-ary groups of inclusions determined by specific n-th determinations is 120 or less per 100 cm | 09-30-2010 |
20100247958 | HIGH-STRENGTH COLD-ROLLED STEEL SHEET EXCELLENT IN WORKABILITY AND SHAPE FREEZING PROPERTY - A high-strength cold-rolled steel sheet according to the present invention: satisfies the requirement of a prescribed chemical composition; has a structure comprising a mother phase structure of ferrite and a second phase structure of retained austenite and martensite (the martensite may not be included); and satisfies the following expressions (1) and (2) when the volume fraction of the ferrite in the whole structure is represented by Vf (%), the volume fraction of the retained austenite in the whole structure is represented by Vγ (%), the carbon content in the retained austenite is represented by Cγ (mass %), the shortest distance between the second phase structures is represented by dis (μm), and the average grain size of the second phase structures is represented by dia (μm), | 09-30-2010 |
20110186189 | HIGH-STRENGTH COLD-ROLLED STEEL SHEET EXCELLENT IN WORKABILITY AND METHOD FOR MANUFACTURING THE SAME - In a cold-rolled steel sheet in relation with the present invention, metallurgical structure of the steel sheet is made a mixture structure including bainite, residual austenite and tempered martensite, particularly, when the metallurgical structure is observed with a scanning electron microscope, bainite is constituted of composite structure of high temperature range forming bainite with 1 μm or above average distance between neighboring residual austenite and/or carbide and low temperature range forming bainite with below 1 μm average distance between neighboring residual austenite and/or carbide, and when the area ratio of the high temperature range forming bainite with respect to total metallurgical structure is made a and the total area ratio of the low temperature range forming bainite and the tempered martensite with respect to the total metallurgical structure is made b, a: 20-80%, b: 20-80%, and a+b: 70% or above are satisfied. The cold-rolled steel sheet in relation with the present invention is improved in all of the elongation (EL), stretch flange formability (A), and bending properties (R) with a good balance, is excellent in the overall workability, and has 980 MPa or above tensile strength. | 08-04-2011 |
20110287280 | HIGH-STRENGTH COLD-ROLLED STEEL SHEET EXCELLENT IN BENDING WORKABILITY - A cold-rolled steel sheet has a chemical composition of C: 0.12% to 0.3%, Si: 0.5% or less, Mn: less than 1.5%, Al: 0.15% or less, N: 0.01% or less, P: 0.02% or less, and S: 0.01% or less, with the remainder including iron and inevitable impurities and has a martensite single-phase structure as its steel microstructure. In a surface region of the steel sheet from the surface to a depth one-tenth the gauge, the number density of n-ary groups of inclusions determined by specific n-th determinations is 120 or less per 100 cm | 11-24-2011 |
20110318605 | HIGH STRENGTH STEEL SHEET HAVING EXCELLENT FORMABILITY - A high strength steel sheet contains, in percent by mass, 0.03 to 0.2% of C, 0.5 to 2.5% of Si, 1 to 3.0% of Mn, 0.01 to 0.5% of Cr, 0.01 to 0.5% of Mo, 0.02 to 0.15% of Al, 0.15% or less of Ti, 0.15% or less of No, and 0.15% or less of V; wherein the remainder includes Fe and inevitable impurities, and the content of Si satisfies the following formula (1), | 12-29-2011 |
20120312433 | HIGH-STRENGTH STEEL SHEET EXCELLENT IN WORKABILITY AND COLD BRITTLENESS RESISTANCE, AND MANUFACTURING METHOD THEREOF - The invention relates to a steel sheet having a tensile strength of 1180 MPa or more, which excels in workability and cold brittleness resistance. The high-strength steel sheet contains 0.10% to 0.30% of C, 1.40% to 3.0% of Si, 0.5% to 3.0% of Mn, 0.1% or less of P, 0.05% or less of S, 0.005% to 0.20% of Al, 0.01% or less of N, 0.01% or less of O, as well as Fe and inevitable impurities. The steel sheet has: (i) a ferrite volume fraction of 5% to 35% and a bainitic ferrite and/or tempered martensite volume fraction of 60% or more; (ii) a MA constituent volume fraction of 6% or less (excluding 0%); and (iii) a retained austenite volume fraction of 5% or more. | 12-13-2012 |
20140044988 | HIGH-STRENGTH STEEL SHEET EXCELLENT IN WORKABILITY AND MANUFACTURING METHOD THEREOF - Provided are: a high-strength steel sheet which is improved in both elongation and local formability and thus exhibits excellent workability; and a manufacturing method thereof. The high-strength steel sheet contains C, Si, Mn, Al, P and S with the remainder including iron and unavoidable impurities, and has a metal structure which includes polygonal ferrite, bainite, tempered martensite, and retained austenite. In the metal structure, (1) the bainite has a composite microstructure including both a high-temperature-formed bainite having an average distance between adjacent regions of retained austenite and/or carbide of 1 μm or more and a low-temperature-formed bainite having an average distance between adjacent regions of retained austenite and/or carbide of less than 1 μm each identified upon observation with a scanning electron microscope; and (2) the retained austenite is present in a volume percentage of 5% or more of the entire metal structure as determined by a saturation magnetization measurement. | 02-13-2014 |
20150086808 | HIGH-STRENGTH COLD-ROLLED STEEL SHEET, HIGH-STRENGTH HOT-DIP GALVANIZED STEEL SHEET, AND HIGH-STRENGTH HOT-DIP GALVANNEALED STEEL SHEET EXCELLENT IN FORMABILITY AND SHAPE FIXABILITY, AND METHODS FOR MANUFACTURING THEM - A high-strength cold-rolled steel sheet has a specific chemical composition and has a steel microstructure meeting conditions: a total content of bainitic ferrite (BF) and tempered martensite (TM) is 65% (in area percent, hereinafter the same for steel microstructure) or more; a fresh martensite (M) content is 3% to 18%; a retained austenite content is 5% or more; and a polygonal ferrite (F) content is 5% or less. The steel sheet has a specific average KAM | 03-26-2015 |