Abstract:
A method for producing a high strength coated steel sheet having a yield strength YS of at least 800 MPa, a tensile strength TS of > 1180 MPa, a total elongation > 14% and a hole expansion ratio HER > 30%. The steel contains in weight %: 0.13% ≤ C ≤ 0.22%, 1.2% ≤ Si ≤ 1.8%, 1.8% ≤ Mn ≤ 2.2%, 0.10% ≤ Mo ≤ 0.20%, Nb ≤ 0.05%, Al ≤ 0.5%, the remainder being Fe and unavoidable impurities. The sheet is annealed at a temperature TA higher than Ac 3 but less than 1000°C for more than 30 s, then quenched by cooling temperature QT between 325°C and 375°C, at a cooling speed sufficient to obtain a structure consisting of austenite and at least 60% of martensite, the austenite content being such that the final structure can contain between 3% and 15% of residual austenite and between 85 and 97% of the sum of martensite and bainite, without ferrite, then heated to a partitioning temperature PT between 430°C and 480°C and maintained at this temperature for a partitioning time Pt between 10 s and 90 s, then hot dip coated cooled to the room temperature. Coated sheet obtained.
Abstract:
The invention relates to a hot-rolled and batch-annealed enamelling steel sheet free of fish scale defects, wherein the steel has a composition comprising, in weight % unless indicated in weight ppm: up to 0.006% C, 0.20-0.390% Mn, 0.01-0.08% Al, 0.0005-0.030% S, 0.0005-0.030% P, 70-120 ppm N, 50-100 ppm B, up to 0.1% Si, up to 0.25% Cu, the balance being made by Fe and impurities, wherein the steel sheet suitable for enamelling has a thickness in a range of 0.30 mm to 4.50 mm, and is in a hot-rolled, batch-annealed and optionally temper-rolled condition but has not undergone any subsequent cold-rolling operation. The invention further relates to a method of manufacturing a hot-rolled and batch-annealed enamelling steel sheet.
Abstract:
The invention deals with a cold rolled and heat-treated steel sheet having a composition comprising, by weight percent C: 0.12 - 0.25 % Mn: 3.0 - 8.0 %, Si: 0.70 - 1.50 %, Al: 0.3 - 1.2 %, B: 0.0002 - 0.004 %, S ≤ 0.010 %, P ≤ 0.020 % N ≤ 0.008 %, the remainder of the composition being iron and unavoidable impurities resulting from the smelting, and having a microstructure consisting of, in surface fraction: between 5% and 45% of ferrite, between 25% and 85% of partitioned martensite, said partitioned martensite having a carbides density strictly less than 2x106 /mm2, between 10% and 30% of retained austenite, less than 8% of fresh martensite, a part of said fresh martensite being combined with retained austenite in the shape of martensite-austenite islands in total surface fraction less than 10%.
Abstract:
A hot-rolled strip steel product having a chemical composition consisting of, in terms of weight percentages (wt. %): 0.030%-0.10% C, 0%-1.10% Si, 0.50%-2.0% Mn,
Abstract:
Die Erfindung betrifft ein Stahlband aus einem hochfesten Mehrphasenstahl, welches eine Zugfestigkeit von mindestens 780 MPa in Längsrichtung aufweist, der Mehrphasenstahl bestehend aus den Elementen in Gewichts-%: C ≥ 0,08 bis ≤ 0,23, Mn ≥ 1,5 bis ≤ 3,5, Si + Al ≥ 0,25 bis ≤ 2, N ≥ 0,0020 bis ≤ 0,0160, P