Patent application number | Description | Published |
20120037282 | HIGH STRENGTH GALVANIZED STEEL SHEET WITH EXCELLENT WORKABILITY AND METHOD FOR MANUFACTURING THE SAME - A high strength galvanized steel sheet with excellent workability, having a component composition containing C: 0.04% or more, and 0.15% or less, Si: 0.7% or more, and 2.3% or less, Mn: 0.8% or more, and 2.2% or less, P: 0.1% or less, S: 0.01% or less, Al: 0.1% or less, N: 0.008% or less, and the remainder composed of iron and incidental impurities on a percent by mass basis, and a microstructure including 70% or more of ferrite phase, 2% or more, and 10% or less of bainite phase, and 0% or more, and 12% or less of pearlite phase on an area fraction basis and 1% or more, and 8% or less of retained austenite phase on a volume fraction basis, wherein an average crystal grain diameter of ferrite is 18 μm or less and an average crystal grain diameter of retained austenite is 2 μm or less. | 02-16-2012 |
20120118438 | HIGH-STRENGTH GALVANNEALED STEEL SHEET HAVING EXCELLENT FORMABILITY AND FATIGUE RESISTANCE AND METHOD FOR MANUFACTURING THE SAME - The present invention provides a high-strength galvanized steel sheet having excellent ductility, stretch flangeability, and fatigue resistance, and a method for manufacturing the same. A high-strength galvannealed steel sheet having excellent formability and fatigue resistance is characterized in that the steel sheet is composed of steel having a composition containing, by % by mass, C: 0.05% to 0.3%, Si: 0.5% to 2.5%, Mn: 1.0% to 3.5%, P: 0.003% to 0.100%, S: 0.02% or less, Al: 0.010% to 0.1%, and the balance including iron and unavoidable impurities, and the steel sheet has a microstructure containing 50% or more of ferrite, 5% to 35% of martensite, and 2% to 15% of pearlite in terms of an area ratio, the martensite having an average gain size of 3 μm or less and an average distance of 5 μm or less between adjacent martensite grains. | 05-17-2012 |
Patent application number | Description | Published |
20130206288 | HIGH-STRENGTH GALVANIZED STEEL SHEET HAVING EXCELLENT FORMABILITY AND CRASHWORTHINESS AND METHOD FOR MANUFACTURING THE SAME - A high-strength galvanized steel sheet having excellent formability and crashworthiness, including a component composition containing 0.03% to 0.13% C, 1.0% to 2.0% Si, 2.4% to 3.5% Mn, 0.001% to 0.05% P, 0.0001% to 0.01% S, 0.001% to 0.1% Al, 0.0005% to 0.01% N, and 0.0003% to 0.01% B on a mass basis, the remainder being Fe and unavoidable impurities, and a microstructure containing a tempered martensitic phase and a bainitic phase such that the sum of an area fraction of the tempered martensitic phase and an area fraction of the bainitic phase is 30% or more (the area fraction of the martensitic phase is 30% or more in the absence of the bainitic phase), wherein a distance of closest approach of the tempered martensitic phase is 10 μm or less and the contents of C, Mn, and B satisfy (1): | 08-15-2013 |
20130266821 | HIGH-STRENGTH GALVANIZED STEEL SHEET WITH HIGH YIELD RATIO HAVING EXCELLENT DUCTILITY AND STRETCH FLANGE FORMABILITY AND METHOD FOR MANUFACTURING THE SAME - A high-strength galvanized steel sheet with high yield ratio having excellent ductility and stretch flange formability, the steel sheet having a chemical composition containing, by mass %, C: 0.04% or more and 0.13% or less, Si: 0.9% or more and 2.3% or less, Mn: 0.8% or more and 2.4% or less, P: 0.1% or less, S: 0.01% or less, Al: 0.01% or more and 0.1% or less, N: 0.008% or less, and the balance being Fe and inevitable impurities and a microstructure including, in terms of area ratio, 94% or more of a ferrite phase and 2% or less of a martensite ferrite phase, wherein mean grain size of ferrite is 10 μm or less, Vickers hardness of ferrite is 140 or more, mean grain size of carbide particles existing at grain boundaries of ferrite is 0.5 μm or less, and aspect ratio of carbide particles existing at the grain boundaries of ferrite is 2.0 or less. | 10-10-2013 |
20140174608 | METHOD FOR MANUFACTURING HIGH STRENGTH GALVANIZED STEEL SHEET HAVING EXCELLENT STABILITY OF MECHANICAL PROPERTIES, FORMABILITY, AND COATING APPEARANCE - A method of manufacturing a high strength galvanized steel sheet has a first heating step including heating to 400° C. to 750° C. in an atmosphere containing O | 06-26-2014 |
20140377584 | HIGH-STRENGTH HOT-DIPPED GALVANIZED STEEL SHEET HAVING EXCELLENT FORMABILITY AND IMPACT RESISTANCE, AND METHOD FOR PRODUCING SAME - A galvanized steel sheet has a composition containing, by mass %, C: 0.05% or more and 0.5% or less, Si: 0.01% or more and 2.5% or less, Mn: 0.5% or more and 3.5% or less, P: 0.003% or more and 0.100% or less, S: 0.02% or less, Al: 0.010% or more and 0.5% or less, B: 0.0002% or more and 0.005% or less, Ti: 0.05% or less, a relationship of Ti>4N being satisfied, and the balance comprising Fe and inevitable impurities, and a microstructure containing 60% or more and 95% or less of tempered martensite in terms of area ratio and 5% or more and 20% or less of retained austenite in terms of area ratio, or further containing 10% or less (including 0%) of ferrite in terms of area ratio and/or 10% or less (including 0%) of martensite in terms of area ratio, the tempered martensite having an average grain diameter of 5 μm or less. | 12-25-2014 |
Patent application number | Description | Published |
20100104891 | ZINC-PLATED HIGH-TENSION STEEL SHEET EXCELLENT IN PRESS FORMABILITY AND METHOD FOR PRODUCTION THEREOF - A high-strength galvanized steel sheet having excellent formability contains as a chemical component of steel on a mass percent basis: 0.05% to 0.3% of C; more than 0.60% to 2.0% of Si; 0.50% to 3.50% of Mn; 0.003% to 0.100% of P; 0.010% or less of S; 0.010% to 0.06% of Al; 0.007% or less of N; and the balance including Fe and inevitable impurities, and in the microstructure of the steel sheet, the standard deviation of nano-hardness is 1.50 GPa or less. | 04-29-2010 |
20100218857 | HIGH TENSILE STRENGTH GALVANIZED STEEL SHEET EXCELLENT IN FORMABILITY AND METHOD FOR MANUFACTURING THE SAME - A high tensile strength galvanized steel sheet with excellent formability and anti-crush properties contains, in terms of % by mass, 0.05 to 0.3% of C, 0.01 to 2.5% of Si, 0.5 to 3.5% of Mn, 0.003 to 0.100% of P, 0.02% or less of S, 0.010 to 1.5% of Al, 0.007% or less of N, in addition, 0.01 to 0.2% in total of at least one element selected from Ti, Nb, and V, the remainder being Fe and unavoidable impurities, the steel sheet having a microstructure composed of, in terms of area fraction, 20 to 87% of ferrite, 3 to 10% in total of martensite and residual austenite, and 10 to 60% of tempered martensite, and a second phase composed of the martensite, residual austenite, and tempered martensite having an average crystal grain diameter of 3 μm or less. | 09-02-2010 |
20110030854 | HIGH-STRENGTH STEEL SHEET AND METHOD FOR MANUFACTURING THE SAME - A high strength steel sheet has a tensile strength of 900 MPa or higher that can achieve both high strength and good formability and a composition including, on a mass basis, C: 0.1% or more and 0.3% or less; Si: 2.0% or less; Mn: 0.5% or more and 3.0% or less; P: 0.1% or less; S: 0.07% or less; Al: 1.0% or less; and N: 0.008% or less, with the balance Fe and incidental impurities. The steel sheet microstructure includes, on an area ratio basis, 5% or more and 80% or less of ferrite, 15% or more of autotempered martensite, 10% or less of bainite, 5% or less of retained austenite, and 40% or less of as-quenched martensite; the mean hardness of the autotempered martensite is HV≦700; and the mean number of precipitated iron-based carbide grains each having a size of 5 nm or more and 0.5 μm or less and included in the autotempered martensite is 5×10 | 02-10-2011 |
20110139315 | HIGH STRENGTH GALVANIZED STEEL SHEET WITH EXCELLENT FORMABILITY AND METHOD FOR MANUFACTURING THE SAME - A high-strength galvanized steel sheet has a TS of at least 590 MPa and excellent ductility and stretch flangeability and a method for manufacturing the high-strength galvanized steel sheet. The galvanized steel sheet contains, on the basis of mass percent, C: 0.05% to 0.3%, Si: 0.01% to 2.5%, Mn: 0.5% to 3.5%, P: 0.003% to 0.100% or less, S: 0.02% or less, and Al: 0.010% to 1.5%. The total of Si and Al is 0.5% to 2.5%. The remainder are iron and incidental impurities, contain 20% or more of ferrite phase, 10% or less of martensite phase, and 10% to 60% of tempered martensite, on the basis of area percent, and 3% to 10% of retained austenite phase on the basis of volume fraction. The retained austenite has an average grain size of 2.0 μm or less. | 06-16-2011 |
20110240176 | HIGH-STRENGTH COLD-ROLLED STEEL SHEET HAVING EXCELLENT FORMABILITY, HIGH-STRENGTH GALVANIZED STEEL SHEET, AND METHODS FOR MANUFACTURING THE SAME - A high-strength cold-rolled steel sheet and high-strength galvanized steel sheet has a TS of 1180 MPa or more and excellent formability including stretch flangeability and bendability. The high-strength cold-rolled steel sheet contains 0.05% to 0.3% C, 0.5% to 2.5% Si, 1.5% to 3.5% Mn, 0.001% to 0.05% P, 0.0001% to 0.01% S, 0.001% to 0.1% Al, 0.0005% to 0.01% N, and 1.5% or less Cr (including 0%) on a mass basis, the remainder being Fe and unavoidable impurities. | 10-06-2011 |
20120279617 | HIGH STRENGTH GALVANIZED STEEL SHEET HAVING EXCELLENT FATIGUE RESISTANCE AND STRETCH FLANGEABILITY AND METHOD FOR MANUFACTURING THE SAME - A steel sheet has the chemical composition containing, by mass %, C: 0.04 to 0.13%, Si: 0.9 to 2.3%, Mn: 0.8 to 1.8%, P: 0.1% or less, S: 0.01% or less, Al: 0.1% or less, N: 0.008% or less, the remainder being Fe and the inevitable impurities and a microstructure including, in terms of area ratio, a ferrite phase of 80% or more, a bainitic ferrite phase of 1.0% or more, a pearlite phase of 1.0 to 10.0%, and a martensite phase of 1.0% or more and less than 5.0%, wherein the mean grain size of ferrite is 14 μm or less, the mean grain size of martensite is 4 μm or less, the mean free path of martensite is 3 μm or more, the Vickers hardness of ferrite is 140 or more, and the relationship area ratio of martensite/(area ratio of bainitic ferrite+area ratio of pearlite) 0.6 is satisfied. | 11-08-2012 |
20130133792 | HIGH-STRENGTH COLD ROLLED SHEET HAVING EXCELLENT FORMABILITY AND CRASHWORTHINESS AND METHOD FOR MANUFACTURING THE SAME - A high-strength cold rolled steel sheet has excellent formability and crashworthiness and includes, on a mass % basis, C: 0.05 to 0.3%, Si: 0.3 to 2.5%. Mn: 0.5 to 3.5%, P: 0.003 to 0.100%, 5: 0.02% or less, Al: 0.010 to 0.5%, the balance being iron and unavoidable impurities, the high-strength cold rolled steel sheet having a microstructure including 20% or more of ferrite on an area fraction basis, 10 to 60% of tempered martensite on an area fraction basis, 0 to 10% of martensite on an area fraction basis, and 3 to 15% of retained austenite on a volume fraction basis. | 05-30-2013 |
20140182748 | METHOD FOR MANUFACTURING HIGH STRENGTH GALVANIZED STEEL SHEET WITH EXCELLENT FORMABILITY - A method of manufacturing a high-strength galvanized steel sheet includes hot-rolling a slab to form a steel sheet; during continuous annealing, heating the steel sheet to a temperature of 750° C. to 900° C. at an average heating rate of at least 10° C./s at a temperature of 500° C. to an A | 07-03-2014 |
20140209217 | HIGH-STRENGTH GALVANNEALED STEEL SHEET HAVING EXCELLENT FORMABILITY AND FATIGUE RESISTANCE AND METHOD FOR MANUFACTURING THE SAME - The present invention provides a high-strength galvanized steel sheet having excellent ductility, stretch flangeability, and fatigue resistance, and a method for manufacturing the same. A high-strength galvannealed steel sheet having excellent formability and fatigue resistance is characterized in that the steel sheet is composed of steel having a composition containing, by % by mass, C: 0.05% to 0.3%, Si: 0.5% to 2.5%, Mn: 1.0% to 3.5%, P: 0.003% to 0.100%, S: 0.02% or less, Al: 0.010% to 0.1%, and the balance including iron and unavoidable impurities, and the steel sheet has a microstructure containing 50% or more of ferrite, 5% to 35% of martensite, and 2% to 15% of pearlite in terms of an area ratio, the martensite having an average gain size of 3 μm or less and an average distance of 5 μm or less between adjacent martensite grains. | 07-31-2014 |
20140335374 | HIGH TENSILE STRENGTH GALVANIZED STEEL SHEETS EXCELLENT IN FORMABILITY AND METHODS OF MANUFACTURING THE SAME - A formable galvanized steel sheet includes, in terms of % by mass, 0.05 to 0.3% of C, 0.01 to 2.5% of Si, 0.5 to 3.5% of Mn, 0.003 to 0.100% of P, 0.02% or less of S, 0.010 to 1.5% of Al, and 0.01 to 0.2% in total of at least one element selected from Ti, Nb and V, the remainder being Fe and unavoidable impurities, having a microstructure composed of, in terms of area fraction, 20 to 87% of ferrite, 3 to 10% in total of martensite and residual austenite, and 10 to 60% of tempered martensite, and a second phase composed of the martensite, residual austenite, and tempered martensite having an average crystal grain diameter of 3 μm or less, and having a ratio of absorption energy AE to tensile strength TS (AE/TS) not less than 0.063. | 11-13-2014 |
20140360632 | METHOD FOR MANUFACTURING HIGH STRENGTH STEEL SHEET HAVING EXCELLENT FORMABILITY - A method of manufacturing a high strength steel sheet having excellent formability suitable for the material of an automotive part has a tensile strength (TS) of 980 MPa or more and total elongation (EL) is 25% or more. A steel slab has a chemical composition containing C: 0.03% to 0.35%, Si: 0.5% to 3.0%, Mn: 3.5% to 10.0%, P: 0.100% or less, S: 0.02% or less, and the remainder includes Fe and incidental impurities on a percent by mass basis is hot-rolled, a heat treatment is performed, in which an achieved temperature of Ac1 to Ac1+100° C. is held for 3 minutes or more, subsequently, cold rolling is performed at a rolling reduction of 20% or more and, annealing is performed, in which an achieved temperature of Ac1−30° C. to Ac1+100° C. is held for 1 minute or more. | 12-11-2014 |