Patent application number | Description | Published |
20100035079 | HIGH-STRENGTH COLD-ROLLED STEEL SHEET AND METHOD FOR MANUFACTURING THE SAME - A high-strength cold-rolled steel sheet having a tensile strength of 340 MPa or more, which can prevent galling, can be manufactured even if a large number of the steel sheets are continuously press-formed. This is because a surface texture thereof is con-trolled so that the surface texture includes flat areas in which a roughness profile has a deviation of ±2 μm or less from a filtered waviness curve and a dented portion having a maximum depth between 10 μm and 50 μm from the filtered waviness curve, wherein an average area of the dented portion is more than 0.01 mm | 02-11-2010 |
20100132849 | HIGH TENSILE-STRENGTH GALVANIZED STEEL SHEET AND PROCESS FOR MANUFACTURING HIGH TENSILE-STRENGTH GALVANIZED STEEL SHEET - A high tensile-strength galvanized steel sheet includes C: at least 0.05% but less than 0.12%, Si: at least 0.01% but less than 0.35%, Mn: 2.0% to 3.5%, P: 0.001% to 0.020%, S: 0.0001% to 0.0030%, Al: 0.005% to 0.1%, N: 0.0001% to 0.0060%, Cr: more than 0.5% but not more than 2.0%, Mo: 0.01% to 0.50%, Ti: 0.010% to 0.080%, Nb: 0.010% to 0.080%, and B: 0.0001% to 0.0030%, the remainder being Fe and unavoidable impurities, wherein the high tensile-strength galvanized steel sheet has a microstructure that contains 20% to 70% by volume ferrite having an average grain size of 5 μm or less. The high tensile-strength galvanized steel sheet has a tensile strength of at least 980 MPa, and excellent formability and weldability. | 06-03-2010 |
20120040203 | HIGH STRENGTH GALVANIZED STEEL SHEET HAVING EXCELLENT FORMABILITY, WELDABILITY, AND FATIGUE PROPERTIES AND METHOD FOR MANUFACTURING THE SAME - A high strength galvanized steel sheet including all in mass %, C: 0.05% to <0.12%, Si: 0.35% to <0.80%, Mn: 2.0 to 3.5%, P: 0.001 to 0.040%, S: 0.0001 to 0.0050%, Al: 0.005 to 0.1%, N: 0.0001 to 0.0060%, Cr: 0.01% to 0.5%, Ti: 0.010 to 0.080%, Nb: 0.010 to 0.080%, and B: 0.0001 to 0.0030%, optionally one or more of Mo: 0.01 to 0.15%, Ca: 0.0001 to 0.0050%, REM: 0.0001 to 0.1%, and Sb: 0.0001 to 0.1%, and Fe and unavoidable impurities as the balance, has a microstructure containing a ferrite phase with a volume fraction in a range of 20 to 70% and an average grain diameter equal to or smaller than 5 μm, and has a galvanized layer on a surface thereof at a coating weight (per side) of 20 to 150 g/m | 02-16-2012 |
20130071687 | HIGH STRENGTH GALVANIZED STEEL SHEET HAVING EXCELLENT BENDABILITY AND WELDABILITY, AND METHOD OF MANUFACTURING THE SAME - A high strength galvanized steel sheet having excellent bendability and weldability, comprising by mass %: C: equal to or more than 0.05% and less than 0.12%; P: 0.001 to 0.040%; and S: equal to or less than 0.0050%, wherein a steel sheet surface layer, constituting a portion of the steel sheet up to a depth of 10 μm measured from each surface of the steel sheet, has a structure containing more than 70% of ferrite phase by a volume fraction, a steel sheet inner layer portion, on an inner side than the depth of 10 μm measured from each surface, has a structure containing 20 to 70% by a volume fraction of ferrite phase with an average crystal grain size equal to or smaller than 5 μm, the steel sheet has a tensile strength equal to or larger than 980 MPa, and the steel sheet has a galvanized layer on a surface thereof. | 03-21-2013 |
20130087257 | ULTRA HIGH STRENGTH COLD ROLLED STEEL SHEET HAVING EXCELLENT DUCTILITY AND DELAYED FRACTURE RESISTANCE AND METHOD FOR MANUFACTURING THE SAME - An ultra.-high-strength cold-rolled steel sheet with excellent ductility and delayed fracture resistance includes 0.15% to 0.75 C. 1.0% to 3.0% Si, 1.5% to 2.5% Mn, 0.05% or less P, 0.02% or less 5, 0.01% to 0.05% Al, and less than 0.005% N on a mass ratio, the remainder being Fe and =avoidable impurities, the ultra-high-strength cold-rolled steel sheet having a metal microstructure including 40% to 85% of a tempered martensite phase and 15% to 60% of a ferrite phase on a volume fraction basis and a tensile strength of 1320 Mtn or more. | 04-11-2013 |
20130199679 | METHOD FOR MANUFACTURING ULTRA HIGH STRENGTH MEMBER AND METHOD FOR USING THE SAME - A method for manufacturing an ultra high strength member includes heating a steel sheet at a first heating temperature within a temperature range of 700 to 1000° C.; forming the steel sheet into a shape of a member at the first heating temperature and simultaneously cooling the steel sheet; after completion of the cooling, shear punching the steel sheet into a desired shape to obtain an ultra high strength member; and after the shear punching, subjecting the ultra high strength member to a first heat treatment including heating the ultra high strength member at second heating temperature within a temperature range of 100° C. or higher, but lower than 300° C. and retaining the member at the second heating temperature for 1 second to 60 minutes, wherein the resulting ultra high strength member has a tensile strength of 1180 MPa or more. | 08-08-2013 |
20140234655 | HOT-DIP GALVANIZED STEEL SHEET AND METHOD FOR PRODUCING SAME - A high-strength hot-dip galvanized steel sheet has excellent workability, namely, excellent ductility and hole expansion formability, and high yield ratio. The steel sheet has a chemical composition containing by mass %: C: 0.05-0.15%; Si: 0.10-0.90%; Mn: 1.0-1.9%; P: 0.005-0.10%; S: 0.0050% or less; Al: 0.01-0.10%; N: 0.0050% or less; Nb: 0.010-0.100%; and the balance being Fe and incidental impurities, in which: the steel sheet has a complex phase that includes: ferrite having an average crystal grain size of 15 μm or less to at least 90% in volume fraction; martensite having an average crystal grain size of 3.0 μm or less to 0.5% or more and less than 5.0% in volume fraction; pearlite to 5.0% or less in volume fraction; and the balance being a phase generated at low temperature. | 08-21-2014 |
20140246128 | HOT-ROLLED STEEL SHEET AND METHOD FOR PRODUCING SAME - Provided is a hot-rolled steel sheet that has a chemical composition including, by mass %: C: 0.060% to 0.150%; Si: 0.15% to 0.70%; Mn: 1.00% to 1.90%; P: 0.10% or less; S: 0.010% or less; Al: 0.01% to 0.10%; N: 0.010% or less; Nb: 0.010% to 0.100%; and the balance including Fe and incidental impurities. The hot-rolled steel sheet has a microstructure containing ferrite of 18 μm or less in average grain size by a volume fraction of at least 75% and pearlite of at least 2 μm in average grain size by a volume fraction of at least 5%, the balance being low-temperature-induced phases, the pearlite having a mean free path of at least 5.0 μm. | 09-04-2014 |
20140332119 | HIGH STRENGTH COLD ROLLED STEEL SHEET WITH HIGH YIELD RATIO AND METHOD FOR PRODUCING THE SAME - A high strength cold rolled steel sheet has a chemical composition including, by mass %, C: 0.06 to 0.13%, Si: 1.2 to 2.3%, Mn: 0.6 to 1.6%, P: not more than 0.10%, S: not more than 0.010%, Al: 0.01 to 0.10% and N: not more than 0.010%, the balance comprising Fe and inevitable impurities. The steel sheet includes a microstructure containing not less than 90% in terms of volume fraction of ferrite with an average grain diameter of less than 20 μm and 1.0 to 10% in terms of volume fraction of pearlite with an average grain diameter of less than 5 μm. The ferrite has an average Vickers hardness of not less than 130. The steel sheet has a yield ratio of not less than 65% and a tensile strength of not less than 590 MPa. | 11-13-2014 |