Patent application number | Description | Published |
20100132850 | HIGH STRENGTH GALVANIZED STEEL SHEET AND METHOD FOR PRODUCING THE SAME - A high-strength hot-dip galvanized steel sheet that even on the premise of ordinary CGL heat cycle, has a low yield stress and excels in resistance to natural aging and baking hardenability without reliance on the use of expensive Mo; and a process for producing the same. The constituent composition thereof comprises 0.01 to less than 0.08% C, 0.2% or less Si, more than 1.0 to 1.8% Mn, 0.10% or less P, 0.03% or less S, 0.1% or less Al, 0.008% or less N and more than 0.5% Cr so that the relationship 1.95≦Mn(mass %)+1.3Cr(mass %)≦2.8 is satisfied and comprising the balance iron and unavoidable impurities. The structure thereof has a ferrite phase and a martensite phase of 2 to 15% area ratio, and the cumulative area ratio of pearlite phase and/or bainite phase is 1.0% or less. In the production of this hot-dip galvanized steel sheet, the temperature and cooling rate are controlled during the annealing/plating operation subsequent to cold rolling. | 06-03-2010 |
20100314010 | HIGH-STRENGTH HOT-ROLLED STEEL SHEET AND METHOD FOR MANUFACTURING SAME - A high-strength hot-rolled steel sheet has a tensile strength (TS) of 540 to 780 MPa, only small variations in strength, and excellent uniformity in strength using a general-purpose Ti-containing steel sheet, which is inexpensive. The high-strength hot-rolled steel sheet includes, on a mass percent basis, 0.05%-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, 0.030%-0.080% Ti, and the balance being Fe and incidental impurities. The microstructure have a bainitic ferrite fraction of 70% or more, and the amount of Ti present in a precipitate having a size of less than 20 nm is 50% or more of the value of Ti* calculated using formula ( | 12-16-2010 |
20100319819 | HIGH-STRENGTH HOT-ROLLED STEEL SHEET AND METHOD FOR MANUFACTURING SAME - A high-strength hot-rolled steel sheet has a tensile strength (TS) of 540 to 780 MPa, only small variations in strength, and excellent uniformity in strength using a general-purpose Ti-containing steel sheet, which is inexpensive. The high-strength hot-rolled steel sheet includes, on a mass percent basis, 0.05%-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, 0.030%-0.080% Ti, and the balance being Fe and incidental impurities. The microstructure have a volume fraction of polygonal ferrite of 70% or more, and the amount of Ti present in a precipitate having a size of less than 20 nm is 50% or more of the value of Ti* calculated using formula (1): Ti*=[Ti]−48/14×[N] (1) where [Ti] and [N] represent a Ti content (percent by mass) and a N content (percent by mass), respectively, of the steel sheet. | 12-23-2010 |
20100326572 | METHOD FOR PRODUCING LOW YIELD STRENGTH COLD ROLLED STEEL SHEET EXCELLENT IN UNIFORMITY - A method produces a high-strength cold-rolled steel sheet includes hot-rolling and cold-rolling steel having a composition which contains, by % by mass, over 0.01% to less than 0.08% of C, 0.2% or less of Si, 0.8% to less than 1.7% of Mn, 0.03% or less of P, 0.02% or less of S, 0.3% or less of sol. Al, 0.01% or less of N, and over 0.4% to 2% of Cr, and which satisfies 1.9<[Mneq]<3 and 0.34≦[% Cr]/[% Mn], the balance being composed of iron and inevitable impurities; heating at an average heating rate of less than 3° C./sec in a temperature range of 680° C. to 740° C.; annealing at an annealing temperature of over 740° C. to less than 820° C.; cooling at an average cooling rate of 2 to 30° C./sec in a temperature range of the annealing temperature to 650° C.; cooling at an average cooling rate of 10° C./sec or more in the temperature range of 650° C. to Tc° C. | 12-30-2010 |
20100330392 | GALVANIZED STEEL SHEET EXCELLENT IN UNIFORMITY AND METHOD FOR PRODUCING THE SAME - A high-strength galvanized steel sheet has a steel composition which contains, by % by mass, 0.01 to 0.12% of C, 0.2% or less of Si, less than 2% of Mn, 0.04% or less of P, 0.02% or less of S, 0.3% or less of sol. Al, 0.01% or less of N, and over 0.3% to 2% of Cr, and which satisfies 2.1≦[Mneq]≦3 and 0.24≦[% Cr]/[% Mn], the balance being composed of iron and inevitable impurities, and has a steel microstructures containing ferrite and a second phase. | 12-30-2010 |
20140103684 | VEHICLE COLLISION ENERGY ABSORBING MEMBER EXCELLENT IN ENERGY ABSORBING PERFORMANCE AND MANUFACTURING METHOD THEREFOR - A vehicle collision energy absorbing member is excellent in collision energy absorbing performance in the axial direction upon collision. The vehicle collision energy absorbing member is formed of a high strength thin steel sheet having TS of at least 980 MPa and having an n-value and a limit bending radius Rc satisfying the following Formula: Rc/t≦1.31×ln(n)+5.21. | 04-17-2014 |
20140242416 | HIGH-STRENGTH STEEL SHEET AND METHOD FOR MANUFACTURING SAME - A high strength pressed member has excellent ductility and stretch flangeability and tensile strength of 780-1400 MPa, with a predetermined steel composition and steel microstructure relative to the entire microstructure of steel sheet, where area ratio of martensite 5-70%, area ratio of retained austenite 5-40%, area ratio of bainitic ferrite in upper bainite 5% or more, and total thereof is 40% or more, 25% or more of martensite is tempered martensite, polygonal ferrite area ratio is above 10% and below 50% to the entire microstructure of steel sheet, and average grain size is 8 μm or less, average diameter of a group of polygonal ferrite grains is 15 μm or less, the group of polygonal ferrite grains represented by a group of ferrite grains of adjacent polygonal ferrite grains, and average carbon content in retained austenite is 0.70 mass % or more and tensile strength is 780 MPa or more. | 08-28-2014 |
20140290810 | HIGH STRENGTH COLD ROLLED STEEL SHEET WITH EXCELLENT DEEP DRAWABILITY AND MATERIAL UNIFORMITY IN COIL AND METHOD FOR MANUFACTURING THE SAME - A high strength cold rolled steel sheet includes a chemical composition containing, by mass %, C: 0.010% or more and 0.060% or less, Si: more than 0.5% and 1.5% or less, Mn: 1.0% or more and 3.0% or less, P: 0.005% or more and 0.100% or less, S: 0.010% or less, sol.Al: 0.005% or more and 0.500% or less, N: 0.0100% or less, Nb: 0.010% or more and 0.100% or less, Ti: 0.015% or more and 0.150% or less and the balance comprising Fe and inevitable impurities. The microstructure includes, in area fraction, 70% or more of a ferrite phase and 3% or more of a martensite phase. The tensile strength is 440 MPa or more and an average r value is 1.20 or more. | 10-02-2014 |