Patent application number | Description | Published |
20090173415 | Steel Sheet Excellent In Fine Blanking Performance and Manufacturing Method of the Same - A steel sheet excellent in FB performance-and also excellent in fabrication performance after FB working and a manufacturing method of the same are provided. The steel sheet is a steel sheet having a composition containing from 0.1 to 0.5% of C, not more than 0.5% of Si and from 0.2 to 1.5% of Mn in terms of % by mass, with P and S being adjusted at proper ranges, and having a structure in which a ferrite has an average grain size of from 1 to 10 μm, cementite has a spheroidization ratio of 80% or more, and of the cementite, an amount S | 07-09-2009 |
20090205756 | HOT-ROLLED THIN STEEL SHEET WITH EXCELLENT FORMABILITY AND EXCELLENT STRENGTH AND TOUGHNESS AFTER HEAT TREATMENT, AND METHOD FOR MANUFACTURING THE SAME - Provided is a hot-rolled thin steel sheet having a thickness of less than 6 mm and having high strength showing a tensile strength of 440 MPa or more, excellent formability, and excellent strength and toughness after heat treatment and a method of manufacturing the same. A steel base material containing 0.10 to 0.20% of C, and Si, Mn, Al, P, S, and N adjusted to suitable amount ranges, and 0.01 to 0. 15% of Ti and 0.0005 to 0.0050% of B is hot rolled so as to have a finishing temperature of finish rolling of 820 to 880° C.; after the completion of the rolling, the hot-rolled thin steel sheet is cooled to a surface temperature range of 550 to 650° C. at a surface cooling rate of 15 to 50° C./s; and the hot-rolled thin steel sheet is coiled at the temperature range. | 08-20-2009 |
20090260729 | HIGH-CARBON HOT-ROLLED STEEL SHEET AND METHOD FOR PRODUCING THE SAME - A high-carbon hot-rolled steel sheet with excellent width-direction homogeneity is provided. The steel sheet contains 0.2% to 0.7% carbon, 0.01% to 1.0% silicon, 0.1% to 1.0% manganese, 0.03% or less phosphorus, 0.035% or less sulfur, 0.08% or less aluminum, and 0.01% or less nitrogen, and the balance is iron and incidental impurities. The structure is such that the average ferrite grain size of edge parts of the steel sheet is less than 35 μm, the average ferrite grain size of a part closer to the center of the steel sheet than the edge parts is less than 20 μm, and the average carbide grain size is 0.10 μm or more and less than 2.0 μm. The steel sheet is produced by roughly rolling the steel, finish-rolling the steel at a finishing temperature of more than (Ar3+40° C.), cooling the steel at a cooling rate of more than 120° C./s within two seconds after the finish rolling to a cooling termination temperature of more than 550° C. and less than 650° C., coiling the steel at a temperature of 550° C. or less, pickling the steel, and subjecting the steel to spheroidizing annealing at a temperature of 670° C. to the Ac1 transformation point by a batch annealing method. | 10-22-2009 |
20090308504 | STEEL SHEET EXCELLENT IN FINE BLANKING PERFORMANCE AND MANUFACTURING METHOD OF THE SAME - A steel sheet excellent in FB performance and also excellent in fabrication performance after FB working and a manufacturing method of the same are provided. The steel sheet is a steel sheet having a composition containing from 0.1 to 0.5% of C, not more than 0.5% of Si and from 0.2 to 1.5% of Mn in terms of % by mass, with P and S being adjusted at proper ranges and having a structure having a ferrite having an average grain size of more than 10 μm and less than 20 μm and a cementite present in the ferrite grain having an average particle size of from 0.3 to 1.5 μm. In this way, the steel sheet becomes a steel sheet excellent in FB performance, mold life and performance (side bend elongation) after FB working. | 12-17-2009 |
20120138197 | HIGH-STRENGTH HOT-ROLLED STEEL SHEET AND METHOD FOR MANUFACTURING THE SAME - A steel sheet contains, on a mass percent basis, 0.03%-0.12% C, 0.5% or less Si, 0.8%-1.8% Mn, 0.030% or less P, 0.01% or less S, 0.005%-0.1% Al, 0.01% or less N, 0.035%-0.100% Ti, and the balance being Fe and incidental impurities and has microstructures with a fraction of polygonal ferrite of 80% or more, the polygonal ferrite having an average grain size of 5 to 10 μm. The amount of Ti present in a precipitate having a size of less than 20 nm is 70% or more of the value of Ti* calculated using expression (1): | 06-07-2012 |
20120216925 | HOT-PRESSED STEEL SHEET MEMBER, STEEL SHEET FOR HOT-PRESS, AND METHOD FOR MANUFACTURING HOT-PRESSED STEEL SHEET MEMBER - A hot-pressed steel sheet member has a composition containing, by mass, C: 0.09% to 0.38%, Si: 0.05% to 2.0%, Mn: 0.5% to 3.0%, P: 0.05% or less, S: 0.05% or less, Al: 0.005% to 0.1%, N: 0.01% or less, Sb: 0.002% to 0.03%, and the balance being Fe and inevitable impurities, and having a tensile strength TS of 980 to 2,130 MPa. | 08-30-2012 |
20130199678 | HIGH STRENGTH HOT-ROLLED STEEL SHEET AND METHOD FOR MANUFACTURING THE SAME - A high strength hot-rolled steel sheet with a tensile strength of not less than 590 MPa which exhibits excellent bake hardenability and stretch-flangeability has a chemical composition including, in terms of mass %, C at 0.040 to 0.10%, Si at not more than 0.3%, Mn at 1.7 to 2.5%, P at not more than 0.030%, S at not more than 0.005%, Al at not more than 0.1% and N at 0.006 to 0.025%, and microstructure wherein a bainite phase represents not less than 60%, the total of a ferrite phase and a pearlite phase represents not more than 10%, and the bainite phase includes grains among which cementite grains have been precipitated at not less than 1.4×10 | 08-08-2013 |
20140332123 | HIGH-STRENGTH STEEL SHEET AND METHOD FOR PRODUCING THE SAME - Provided are a high-strength steel sheet and a method for producing the same. A high-strength steel sheet has a composition containing 0.10% to 0.18% C, more than 0.5% to 1.5% Si, 0.5% to 1.5% Mn, 0.05% or less P, 0.005% or less S, and 0.05% or less Al on a mass basis, the remainder being Fe and inevitable impurities and also has a microstructure containing ferrite and pearlite. The volume fraction of the ferrite is 70% to 97%. The volume fraction of the pearlite is 3% or more. The volume fraction of cementite present at grain boundaries of the ferrite is 2% or less. The sum of the volume fractions of phases other than the ferrite, the pearlite, and the cementite is less than 3%. The average grain size of the ferrite is 7 μm or less. | 11-13-2014 |