Abstract: A steel sheet for the manufacture of a press hardened part is provided, having a composition of: 0.15%?C%?0.22%, 3.5%?Mn<4.2%, 0.001%?Si%?1.5%, 0.020%?Al?0.9%, 0.001%?Cr?1%, 0.001%?Mo?0.3%, 0.001%?Ti?0.040%, 0.0003%?B?0.004%, 0.001%?Nb?0.060%, 0.001%?N?0.009%, 0.0005%?S?0.003%, 0.001%?P?0.020%. A microstructure has less than 50% ferrite, 1% to 20% retained austenite, cementite, such that the surface density of cementite particles larger than 60 nm is lower than 10?7/mm2, and a complement of bainite and/or martensite, the retained austenite having an average Mn content of at least 1.1*Mn %. Press-hardened steel part obtained by hot forming the steel sheet, and manufacturing methods thereof.

Abstract: A method for resistance spot welding comprising the following successive steps: —providing at least two steel sheets with thickness (th) comprised between 0.5 and 3 mm, at least one of the sheets being a zinc or zinc-alloy coated steel sheet (A) with a tensile strength (TS) higher than 800 MPa and a total elongation (TEL) such as (TS)×(TEL)>14000 MPa %, wherein the composition of the steel substrate of (A) contains, in weight: 0.05%?C?0.4%, 0.3%?Mn?8%, 0.010%?Al?3%, 0.010%?Si?2.09%, with 0.5%?(Si+Al)?3.5%, 0.001%?Cr?1.0%, 0.001%?Mo?0.5% and optionally: 0.005%?Nb?0.1%, 0.005%?V?0.2%, 0.005%?Ti?0.1%, 0.0003%?B?0.005%, 0.001%?Ni?1.0%, the remainder being Fe and unavoidable impurities, —performing resistance spot welding of the at least two steel sheets for producing a weld with an indentation depth (IDepth) on the surface of said steel sheet (A) such as: 100 ?m?(IDepth)?18.68 (Znsol)?55.1, wherein (IDepth) is in micrometers and wherein Znsol is the solubility of Zn in the steel of sheet (A) at 750° C.

Abstract: A cold rolled and hot dip coated steel sheet presenting a tensile strength above 1000?50×Al MPa, a uniform elongation above 15% and a low density is provided. The steel includes, by weight percent: 0.1?C?0.5%, 3.5?Mn?10.0%, 0?Al?9.0%, Si?5.0%, Ti?0.2%, V?0.2%, Nb?0.2%, S?0.004%, P?0.025%, 0.5?Si+Al?9.0%, B?0.0035, Cr?1%, The balance being Fe and impurities and the microstructure containing 25% to 90% of ferrite, 10% to 50% of austenite, kappa precipitates lower than 5% and martensite lower than 25%. The steel is able to be coated using total oxidation.

Abstract: A spot welded joint of at least two steel sheets is provided. At least one of the steel sheets presents yield strength above or equal to 600 MPa, an ultimate tensile strength above or equal to 1000 MPa, uniform elongation above or equal to 15%. The base metal chemical composition includes 0.05?C?0.21%, 4.0?Mn?7.0%, 0.5?Al?3.5%, Si?2.0%, Ti?0.2%, V?0.2%, Nb?0.2%, P?0.025%, B?0.0035%, and the spot welded joint contains a molten zone microstructure containing more than 0.5% of Al and containing a surface fraction of segregated areas lower than 1%, said segregated areas being zones larger than 20 ?m2 and containing more than the steel nominal phosphorus content.

Abstract: The present invention provides a spot welded joint of at least two steel sheets. At least one of the steel sheets presents yield strength above or equal to 600 MPa, an ultimate tensile strength above or equal to 1000 MPa, uniform elongation above or equal to 15%. The base metal chemical composition includes 0.05?C?0.21%, 4.0?Mn?7.0%, 0.5?Al?3.5%, Si?2.0%, Ti?0.2%, V?0.2%, Nb?0.2%, P?0.025%, B?0.0035%, and the spot welded joint contains a molten zone microstructure containing more than 0.5% of Al and containing a surface fraction of segregated areas lower than 1%, said segregated areas being zones larger than 20 ?m2 and containing more than the steel nominal phosphorus content.

Abstract: A cold-rolled and annealed ferritic steel sheet is provided. The steel has a composition comprising, expressed by weight: 0.001?C?0.15%; Mn?1%; Si?1.5%; 7.5%?AI?10%; 0.020%?Ti?0.5%; S?0.050%; and P?0.1%. A balance of the composition includes iron and inevitable impurities resulting from the smelting. The structure includes kappa (?) precipitates and equiaxed ferrite, an average grain size d? of the equiaxed ferrite is less than 50 microns, and a linear fraction f of intergranular ? precipitates is less than 30%. The linear fraction f is defined by f = ? ( A ) ? di ? ( A ) ? Li . ?(A)di denotes the total length of grain boundaries containing ? precipitates relative to an area (A) and ?(A)Li denotes the total length of the grain boundaries relative to the area (A). A content of carbon in solid solution is less than 0.005% by weight, and the cold-rolled and annealed ferritic steel sheet has a thickness between 0.6 mm and 1.5 mm.

Abstract: The present invention provides a hot rolled steel sheet. The hot rolled steel sheet has a yield stress greater than 680 MPa and less than or equal to 840 MPa, at least in a direction transverse to a rolling direction, strength between 780 MPa and 950 MPa, elongation at failure greater than 10% and hole-expansion ratio (Ac) greater than or equal to 45%. The chemical composition includes, with the contents expressed by weight: 0.04%?C?0.08% 1.2%?Mn?1.9% 0.1%?Si?0.3% 0.07%?Ti?0.125% 0.05%?Mo?0.35% 0.15%<Cr?0.6% when 0.05%?Mo?0.11%, or 0.10%?Cr?0.6% when 0.11%<Mo?0.35% Nb?0.045% 0.005%?Al?0.1% 0.002%?N?0.01% S?0.004% P?0.020% and optionally 0.001%?V?0.2%. The remainder includes iron and unavoidable impurities resulting from processing. The microstructure includes granular bainite, the area percentage of which is greater than 70%, and ferrite, the area percentage of which is less than 20%, with the remainder, if any, including lower bainite, martensite and residual austenite.

Abstract: A cold-rolled and annealed ferritic steel sheet is provided. The steel has a composition comprising, expressed by weight: 0.001?C?0.15%; Mn?1%; Si?1.5%; 7.5%?AI?10%; 0.020%?Ti?0.5%; S?0.050%; and P?0.1%. A balance of the composition includes iron and inevitable impurities resulting from the smelting. The structure includes kappa (?) precipitates and equiaxed ferrite, an average grain size d? of the equiaxed ferrite is less than 50 microns, and a linear fraction f of intergranular ? precipitates is less than 30%. The linear fraction f is defined by f = ? ( A ) ? di ? ( A ) ? Li . ?(A)di denotes the total length of grain boundaries containing ? precipitates relative to an area (A) and ?(A)Li denotes the total length of the grain boundaries relative to the area (A). A content of carbon in solid solution is less than 0.005% by weight, and the cold-rolled and annealed ferritic steel sheet has a thickness between 0.6 mm and 1.5 mm.

Abstract: The invention relates to a hot-rolled ferritic steel sheet, the composition of the steel of which comprises, the contents being expressed by weight: 0.001?C?0.15%, Mn?1%, Si?1.5%, 6%?Al?10%, 0.020%?Ti?0.5%, S?0.050%, P?0.1%, and, optionally, one or more elements chosen from: Cr?1%, Mo?1%, Ni?1%, Nb?0.1%, V?0.2%, B?0.010%, the balance of the composition consisting of iron and inevitable impurities resulting from the smelting, the average ferrite grain size dIV measured on a surface perpendicular to the transverse direction with respect to the rolling being less than 100 microns.

Abstract: A hot rolled steel sheet with a yield stress greater than 690 MPa and less than or equal to 840 MPa, with strength between 780 MPa and 950 MPa, elongation at failure greater than 10% and a hole expansion ratio (Ac) greater than or equal to 50% is described. Methods for the fabrication of the sheet are also described.

Abstract: A cold rolled and hot dip coated steel sheet presenting a tensile strength above 1000?50×Al MPa, a uniform elongation above 15% and a low density is provided. The steel includes, by weight percent: 0.1?C?0.5%, 3.5?Mn?10.0%, 0?Al?9.0%, Si?5.0%, Ti?0.2%, V?0.2%, Nb?0.2%, S?0.004%, P?0.025%, 0.5?Si+Al?9.0%, B?0.0035, Cr?1%, The balance being Fe and impurities and the microstructure containing 25% to 90% of ferrite, 10% to 50% of austenite, kappa precipitates lower than 5% and martensite lower than 25%. The steel is able to be coated using total oxidation.

Abstract: The present invention provides a spot welded joint of at least two steel sheets. At least one of the steel sheets presents yield strength above or equal to 600 MPa, an ultimate tensile strength above or equal to 1000 MPa, uniform elongation above or equal to 15%. The base metal chemical composition includes 0.05?C?0.21%, 4.0?Mn?7.0%, 0.5?Al?3.5%, Si?2.0%, Ti?0.2%, V?0.2%, Nb?0.2%, P?0.025%, B?0.0035%, and the spot welded joint contains a molten zone microstructure containing more than 0.5% of Al and containing a surface fraction of segregated areas lower than 1%, said segregated areas being zones larger than 20 ?m2 and containing more than the steel nominal phosphorus content.

Abstract: A rolled steel sheet is provided. The rolled steel sheet has a mechanical strength greater than or equal to 600 MPa and an elongation at fracture that is greater than or equal to 20%. A a method for its fabrication is also provided. The chemical composition of the steel sheet includes 0.10?C?0.30%, 6.0?Mn?15.0%, 6.0?Al?15.0%, and optionally one or more elements selected from among: Si?2.0%, Ti?0.2%, V?0.6% and Nb?0.3%. The remainder of the composition includes iron and the unavoidable impurities resulting from processing. The ratio of the weight of manganese to the weight of aluminum is such that Mn Al > 1.0 . The microstructure of the sheet includes ferrite, austenite and up to 5% Kappa precipitates in area fraction.

Abstract: The invention relates principally to a hot rolled steel sheet with a yield stress greater than 690 MPa and less than or equal to 840 MPa, with strength between 780 MPa and 950 MPa, elongation at failure greater than 10% and a hole expansion ratio (Ac) greater than or equal to 50%. The chemical composition of the sheet claimed by the invention contains, whereby the contents are expressed in percent by weight: 0.40%?C?0.065%, 1.4%?Mn?1.9%, 0.1%?Si?0.55%, 0.095%?Ti?0.145%, 0.025%?Nb?0.045%, 0.005%?Al?0.1%, 0.002%?N?0.007%, S?0.004%, P<0.020. The microstructure of the sheet claimed by the invention also consists of granular bainite, ferrite, cementite in an area percentage of less than 1.5% and titanium and niobium carbonitrides, which results in a hole expansion ratio (Ac) greater than or equal to 50%, and the ratio between the grain size DL measured parallel to the rolling direction and the grain size DN measured perpendicular to the rolling direction is less than or equal to 1.4.

Abstract: The invention relates to a hot-rolled ferritic steel sheet, the composition of the steel of which comprises, the contents being expressed by weight: 0.001?C?0.15%, Mn?1%, Si?1.5%, 6%?Al?10%, 0.020%?Ti?0.5%, S?0.050%, P?0.1%, and, optionally, one or more elements chosen from: Cr?1%, Mo?1%, Ni?1%, Nb?0.1%, V?0.2%, B?0.010%, the balance of the composition consisting of iron and inevitable impurities resulting from the smelting, the average ferrite grain size dIV measured on a surface perpendicular to the transverse direction with respect to the rolling being less than 100 microns.