Patent application number | Description | Published |
20100196189 | HIGH-STRENGTH STEEL SHEET - A high-strength steel sheet has high stretch flangeability after working and corrosion resistance after painting. The steel sheet contains, on the basis of mass percent, C: 0.02% to 0.20%, Si: 0.3% or less, Mn: 0.5% to 2.5%, P: 0.06% or less, S: 0.01% or less, Al: 0.1% or less, Ti: 0.05% to 0.25%, and V: 0.05% to 0.25%, the remainder being Fe and incidental impurities. The steel sheet has a substantially ferritic single phase, the ferritic single phase containing precipitates having a size of less than 20 nm, the precipitates containing 200 to 1750 mass ppm Ti and 150 to 1750 mass ppm V, V dissolved in solid solution being 200 or more but less than 1750 mass ppm. | 08-05-2010 |
20110139316 | HIGH STRENGTH GALVANNEALED STEEL SHEET WITH EXCELLENT APPEARANCE AND METHOD FOR MANUFACTURING THE SAME - A high strength galvanized steel sheet with excellent appearance that does not have non-uniformity of coating or coating defects or allow linear defects to occur after press forming includes a steel sheet having a ferrite single-phase structure and having a composition containing 0.0005% to 0.0040% by mass of C; 0.1% to 1.0% by mass of Si; 1.0% to 2.5% by mass of Mn; 0.01% to 0.20% by mass of P; 0.015% by mass of less of S; 0.01% to 0.10% by mass of Al; 0.0005% to 0.0070% by mass of N; 0.010% to 0.080% by mass of Ti; 0.0005% to 0.0020% by mass of B; 0.05% to 0.50% by mass of Cu; 0.03% to 0.50% by mass of Ni; and the balance of Fe and incidental impurities. | 06-16-2011 |
20110271733 | METHOD FOR MANUFACTURING HIGH STRENGTH HOT ROLLED STEEL SHEET - A method for manufacturing a high strength hot rolled steel sheet includes heating a slab to a temperature in the range of 1150 to 1300° C.; hot rolling the slab with a finishing rolling temperature being in the range of 800 to 1000° C.; cooling the steel sheet at a mean cooling rate of 30° C./s or higher to a cooling termination temperature in the range of 525 to 625° C.; suspending cooling for a time period in the range of 3 to 10 seconds; cooling the steel sheet in such a manner that cooling of the steel sheet is nucleate boiling; and coiling the steel sheet at a temperature in the range of 400 to 550° C. | 11-10-2011 |
20110290383 | HIGH STRENGTH COLD ROLLED STEEL SHEET EXCELLENT IN WELDABILITY AND METHOD FOR MANUFACTURING THE SAME - A high strength cold rolled steel sheet excellent in weldability and has a TS of 440 MPa or more includes a composition including C: 0.0005 to 0.005%, Si: 0.1 to 1.0%, Mn: 1 to 2.5%, P: 0.01 to 0.2%, S: 0.015% or less, sol. Al: 0.05% or less, N: 0.007% or less, Ti: 0.01 to 0.1%, B: 0.0005 to 0.0020%, Cu: 0.05 to 0.5%, and Ni: 0.03 to 0.5% by mass with the balance Fe and incidental impurities; and a microstructure constituted by a ferrite single phase. | 12-01-2011 |
20120107633 | HIGH STRENGTH STEEL SHEET AND METHOD FOR MANUFACTURING THE SAME - A high-strength steel sheet includes a composition containing, in mass percent, 0.08% to 0.20% of carbon, 0.2% to 1.0% of silicon, 0.5% to 2.5% of manganese, 0.04% or less of phosphorus, 0.005% or less of sulfur, 0.05% or less of aluminum, 0.07% to 0.20% of titanium, and 0.20% to 0.80% of vanadium, the balance being iron and incidental impurities. | 05-03-2012 |
20130032253 | HIGH-STRENGTH GALVANIZED STEEL SHEET HAVING EXCELLENT FORMABILITY AND METHOD FOR MANUFACTURING THE SAME - A galvanized steel sheet having excellent formability is provided including steel having a composition which contains, on a percent by mass basis, 0.03% to 0.15% of C, less than 0.5% of Si, 1.0% to 2.5% of Mn, 0.05% or less of P, 0.01% or less of S, 0.05% or less of Al, 0.0050% or less of N, 0.05% to 0.8% of Cr, 0.01% to 0.1% of V, and the balance being Fe and inevitable impurities; and a zinc plating film on a surface of a steel sheet, and wherein a microstructure of the steel contains ferrite having an average grain diameter of 15 μm or less and 5% to 40% of martensite in an area ratio, and the ratio of martensite having an aspect ratio of less than 3.0 to all the martensite is more than 95% in area ratio. | 02-07-2013 |
20150027594 | THIN STEEL SHEET AND PROCESS FOR PRODUCING THE SAME - A thin steel sheet having sheet thickness ≦1.6 mm, but tensile strength ≧780 MPa and Young's modulus ≧240 GPa in transverse direction is provided, where the steel sheet has composition including, in mass %, C: 0.06-0.12%, Si: 0.5-1.5%, Mn: 1.0-3.0%, P: 0.05% or less, S: 0.01% or less, Al: 0.5% or less, N: 0.01% or less, Ti: 0.02-0.20%, and the balance being Fe and incidental impurities, where the composition satisfies relations of Formula (1) and (2), and microstructure such that ferrite phase has area ratio ≧60% and martensite phase has area ratio of 15-35%, ferrite and martensite phases are 95% or more in total, average grain size of ferrite is ≦4.0 μm and that of martensite is ≦1.5 μm, | 01-29-2015 |
20160047011 | HIGH-STRENGTH GALVANIZED STEEL SHEET AND METHOD FOR MANUFACTURING THE SAME (AS AMENDED) - A high-strength galvanized steel sheet has a chemical composition containing, by mass %, C: 0.16% or more and 0.24% or less, Si: 0.8% or more and 1.8% or less, Mn: 1.0% or more and 3.0% or less, P: 0.020% or less, S: 0.0040% or less, Al: 0.01% or more and 0.1% or less, N: 0.01% or less, Ca: 0.0001% or more and 0.0020% or less, and the balance including Fe and incidental impurities, and a microstructure, in which the total area ratio of a ferrite phase and a bainite phase with respect to the whole microstructure is 30% or more and 70% or less, in which the area ratio of a tempered martensite phase with respect to the whole microstructure is 20% or more and 40% or less, in which the area ratio of a retained austenite phase with respect to the whole microstructure is 10% or more and 20% or less, and in which the area ratio of a martensite phase with respect to the whole microstructure is 2% or more and 20% or less. | 02-18-2016 |
20160047025 | HIGH-STRENGTH GALVANNEALED STEEL SHEET AND METHOD FOR MANUFACTURING THE SAME (AS AMENDED) - A high-strength galvannealed steel sheet has a chemical composition containing, by mass %, C: 0.14% or more and 0.24% or less, Si: 0.8% or more and 1.8% or less, Mn: 1.0% or more and 3.0% or less, P: 0.020% or less, S: 0.0040% or less, Al: 0.01% or more and 0.1% or less, N: 0.01% or less, Ca: 0.0001% or more and 0.0020% or less, and the balance including Fe and incidental impurities, and a microstructure, in which the total area ratio of a ferrite phase and a bainite phase with respect to the whole microstructure is 30% or more and 70% or less, in which the area ratio of a tempered martensite phase with respect to the whole microstructure is 20% or more and 40% or less, in which the area ratio of a retained austenite phase with respect to the whole microstructure is 1% or more and 5% or less, in which the area ratio of a martensite phase with respect to the whole microstructure is 2% or more and 20% or less, and in which the total area ratio of cementite and a pearlite phase with respect to the whole microstructure is 10% or less. | 02-18-2016 |
20160083819 | HIGH-STRENGTH STEEL SHEET AND METHOD FOR PRODUCING THE SAME - There is provided a high-strength steel sheet having a tensile strength (TS) of 900 MPa or more and excellent elongation, stretch flangeability, and bendability in a component system in which an expensive alloy element is not intentionally added. A high-strength steel sheet includes a composition including, on a mass % basis, C: 0.15 to 0.40%, Si: 1.0 to 2.0%, Mn: 1.5 to 2.5%, P: 0.020% or less, S: 0.0040% or less, Al: 0.01 to 0.1%, N: 0.01% or less, and Ca: 0.0020% or less, with the balance including Fe and incidental impurities. The high-strength steel sheet has a microstructure including 40% to 70% of a ferrite phase and a bainite phase in total, 20% to 50% of a martensite phase, and 10% to 30% of a retained austenite phase in terms of an area fraction relative to the entire microstructure. | 03-24-2016 |