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 |
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 |
20130008570 | ULTRAHIGH-STRENGTH STEEL SHEET WITH EXCELLENT WORKABILITY, AND MANUFACTURING METHOD THEREOF - Disclosed is an ultra high strength steel plate with at least 1100 MPa of tensile strength that has both an excellent strength-stretch balance and excellent bending workability, and a method for producing the same. The metal structure of the steel plate has martensite, and the soft phases of bainitic ferrite and polygonal ferrite. The area of the aforementioned martensite constitutes 50% or more, the area of the aforementioned bainitic ferrite constitutes 15% or more, and the area of the aforementioned polygonal ferrite constitutes 5% or less (including 0%). When the circle-equivalent diameter of the aforementioned soft phases is measured, the coefficient of variation (standard deviation/mean value) is less or equal to 1.0. The ultra high strength steel plate has at least 1100 MPa of tensile strength. | 01-10-2013 |
20140305553 | HIGH-STRENGTH COLD-ROLLED STEEL SHEET HAVING SMALL VARIATIONS IN STRENGTH AND DUCTILITY AND MANUFACTURING METHOD FOR THE SAME - A high-strength cold-rolled steel sheet has a chemical composition including C of 0.05% to 0.30%, Si of greater than 0% to 3.0%, Mn of 0.1% to 5.0%, P of greater than 0% to 0.1%, S of greater than 0% to 0.02%, Al of 0.01% to 1.0%, and N of greater than 0% to 0.01%, in mass percent, with the remainder including iron and inevitable impurities. The steel sheet has a microstructure containing ferrite as a soft primary phase in an area percentage of 20% to 50% with the remainder including tempered martensite and/or tempered bainite as a hard secondary phase. The ferrite grains are adapted to contain cementite particles having an appropriate size in an appropriate number density. | 10-16-2014 |
20150111064 | HIGH-STRENGTH HOT-DIP GALVANIZED STEEL SHEET AND HIGH-STRENGTH ALLOYED HOT-DIP GALVANIZED STEEL SHEET HAVING EXCELLENT BENDING WORKABILITY AND MINIMAL STRENGTH DIFFERENCE BETWEEN CENTER PART AND END PARTS IN SHEET WIDTH DIRECTION, AND METHOD FOR MANUFACTURING SAME - Provided are: a high-strength hot-dip galvanized steel sheet in which bending workability of the high-strength hot-dip galvanized steel sheet is improved, and in which strength difference between a center part and end parts in the sheet width direction is reduced; and a method for manufacturing a high-strength hot-dip galvanized steel sheet. The steel sheet is a hot-dip galvanized steel sheet having a hot-dip galvanizing layer on a surface of a base steel sheet containing: C, Mn, P, S, and Al; Ti and B in amounts satisfying equation (1); and N; and Si as needed; the remainder comprising iron and unavoidable impurities; the metallographic structure of the base steel sheet having martensite, bainite, and ferrite, the ratios of each with respect to the overall metallographic structure being 50 area % or more of the martensite, 15-50 area % of the bainite, and 5 area % or less of the ferrite, | 04-23-2015 |
20150114524 | HIGH STRENGTH COLD-ROLLED STEEL SHEET EXHIBITING LITTLE VARIATION IN STRENGTH AND DUCTILITY, AND MANUFACTURING METHOD FOR SAME - In a high strength cold-rolled steel plate having a specific chemical composition, a soft first phase (ferrite) has an area ratio of 20-50%, the remainder being a hard second phase (tempered martensite and/or tempered bainite), among all the ferrite grains, ferrite grains that have an average grain diameter of 10-25 μm account for a total area ratio of 80% or more, the number of the cementite grains that have an equivalent circle diameter of 0.3 μm or more is more than 0.15 piece and 1.0 piece or less per 1 μm | 04-30-2015 |