Abstract: A method for producing a zinc or zinc-alloy coated steel sheet with a tensile strength higher than 900 MPa, for the fabrication of resistance spot welds containing in average not more than two Liquid Metal Embrittlement cracks per weld having a depth of 100 ?m or more, with steps of providing a cold-rolled steel sheet, heating cold-rolled steel sheet up to a temperature T1 between 550° C. and Ac1+50° C. in a furnace zone with an atmosphere (A1) containing from 2 to 15% hydrogen by volume, so that the iron is not oxidized, then adding in the furnace atmosphere, water steam or oxygen with an injection flow rate Q higher than (0.07%/h×?), ? being equal to 1 if said element is water steam or equal to 0.52 if said element is oxygen, at a temperature T?T1, so to obtain an atmosphere (A2) with a dew point DP2 between ?15° C. and the temperature Te of the iron/iron oxide equilibrium dew point, then heating the sheet from temperature T1 up to a temperature T2 between 720° C. and 1000° C.

Abstract: A cold rolled steel sheet having a composition including of 0.05 % ? Carbon ? 0.15 %, 1.8% ? Manganese ? 2.7%, 0.1% ? Silicon ? 1%,0.01% ? Aluminum ? 0.8%,0.1% ? Chromium ? 0.9%,0% ? Phosphorus ? 0.09%,0.0001% ? Titanium ? 0.1%,0.0005% ? Boron ? 0.003%, 0.01% ? Niobium ? 0.1%, 0 % ? Sulfur ? 0.09 %, 0 % ? Nitrogen ? 0.09%, 0% ? Vanadium ? 0.2%, 0%?Molybdenum?0.2%, 0%?Nickel?2%, 0% ? Copper ? 2%, 0% ? Calcium ? 0.005%, 0% ? Cerium ? 0.1%, 0% ? Magnesium ? 0.05%, 0% ? Zirconium ? 0.05%, the remainder being composed of iron and unavoidable impurities caused by processing, the microstructure of the steel sheet including in area fraction, 40% to 60% martensite, 15 to 40% of inter-critical ferrite, a cumulated amount of 10 to 35% of transformed ferrite and bainite and 0% to 5% of residual austenite.

Abstract: A method for producing a zinc or zinc-alloy coated steel sheet with a tensile strength higher than 900 MPa, for the fabrication of resistance spot welds containing in average not more than two Liquid Metal Embrittlement cracks per weld having a depth of 100 ?m or more, with steps of providing a cold-rolled steel sheet, heating cold-rolled steel sheet up to a temperature T1 between 550° C. and Ac1+50° C. in a furnace zone with an atmosphere (A1) containing from 2 to 15% hydrogen by volume, so that the iron is not oxidized, then adding in the furnace atmosphere, water steam or oxygen with an injection flow rate Q higher than (0.07%/h×?), ? being equal to 1 if said element is water steam or equal to 0.52 if said element is oxygen, at a temperature T?T1, so to obtain an atmosphere (A2) with a dew point DP2 between ?15° C. and the temperature Te of the iron/iron oxide equilibrium dew point, then heating the sheet from temperature T1 up to a temperature T2 between 720° C. and 1000° C.

Abstract: A method for producing a coated steel sheet having a tensile strength TS of at least 1450 MPa and a total elongation TE of at least 17% includes the successive steps of providing a cold rolled steel sheet made of a steel having a chemical composition comprising, in weight %: 0.34%?C?0.45%, 1.50%?Mn?2.30%, 1.50?Si?2.40%, 0%<Cr?0.7%, 0%?Mo?0.3%, 0.10%?Al?0.7%, and optionally 0%?Nb?0.05%, the remainder being Fe and unavoidable impurities, annealing the cold-rolled steel sheet at an annealing temperature AT higher than the Ac3 transformation point of the steel, quenching the annealed steel sheet by cooling it down to a quenching temperature QT lower than the Ms transformation point of the steel and comprised between 150° C. and 250° C., and reheating the quenched steel sheet to a partitioning temperature PT between 350° C. and 450° C.

Abstract: A cold rolled and heat-treated steel sheet having a composition including, by weight percent: C 0.3-0.4%, Mn 2.0-2.6%, Si: 0.8-1.6%, Al 0.01-0.6%, Mo 0.15-0.5%, Cr 0.3-1.0%, Nb?0.06%, Ti?0.06%, Ni?0.8%, S?0.010%, P?0.020% and 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 15% and 30% of retained austenite, said retained austenite having a carbon content of at least 0.7%, between 70% and 85% of tempered martensite, at most 5% of fresh martensite and at most 5% of bainite. It also deals with a manufacturing method thereof.

Abstract: A method for producing a cold rolled steel sheet having a tensile strength?1470 MPa and a total elongation TE?19%, the method comprising the steps of annealing at an annealing temperature AT?Ac3 a non-treated steel sheet whose chemical composition contains in weight %: 0.34%?C?0.40%, 1.50%?Mn?2.30%, 1.50?Si?2.40%, 0%<Cr?0.5%, 0%<Mo?0.3%, 0.01%?Al?0.07%, the remainder being Fe and unavoidable impurities, quenching the annealed steel sheet by cooling it to a quenching temperature QT<Ms transformation point and between 150° C. and 250° C., and making a partitioning treatment by reheating the quenched steel sheet to a partitioning temperature PT between 350° C. and 420° C. and maintaining the steel sheet at this temperature during a partitioning time Pt between 15 seconds and 120 seconds.

Abstract: A method for producing a cold rolled steel sheet having a tensile strength ?1470 MPa and a total elongation TE?19%, the method comprising the steps of annealing at an annealing temperature AT?Ac3 a non-treated steel sheet whose chemical composition contains in weight %: 0.34%?C?0.40%, 1.50%?Mn?2.30%, 1.50?Si?2.40%, 0<Cr?0.5%, 0<Mo?0.3%, 0.01%?Al?0.07%, the remainder being Fe and unavoidable impurities, quenching the annealed steel sheet by cooling it to a quenching temperature QT<Ms transformation point and between 150° C. and 250° C., and making a partitioning treatment by reheating the quenched steel sheet to a partitioning temperature PT between 350° C. and 420° C. and maintaining the steel sheet at this temperature during a partitioning time Pt between 15 seconds and 120 seconds.

Abstract: A method IS for producing a cold rolled steel sheet having a tensile strength ?1470 MPa and a total elongation TE?19%. The method includes the steps of annealing at an annealing temperature AT?Ac3 a non-treated steel sheet whose chemical composition contains in weight %: 0.34%?C?0.40%, 1.50%?Mn?2.30%, 1.50?Si?2.40%, 0%<Cr?0.7%, 0%?Mo?0.3%, 0.01%?Al?0.07%, the remainder being Fe and unavoidable impurities, quenching the annealed steel sheet by cooling it to a quenching temperature QT<Ms transformation point and between 150° C. and 250° C., and making a partitioning treatment by reheating the quenched steel sheet to a partitioning temperature PT between 350° C. and 420° C. and maintaining the steel sheet at this temperature during a partitioning time Pt between 15 seconds and 250 seconds.

Abstract: A method for producing a coated steel sheet having a tensile strength of at least 1450 MPa and a total elongation of at least 17% is provided. The method includes providing a cold rolled steel sheet having a chemical composition in weight %: 0.34%?C?0.45%, 1.50%?Mn?2.30%, 1.50%?Si?2.40%, 0%<Cr?0.7%, 0%?Mo?0.3%, 0.10%?Al?0.7%, optionally 0%?Nb?0.05%, and a remainder of Fe and unavoidable impurities. The sheet is annealed at an annealing temperature higher than the Ac3 transformation point of the steel, quenched to a quenching temperature lower than the Ms transformation point of the steel and between 150° C. and 250° C., reheated to a partitioning temperature between 350° C. and 450° C., maintained at the partitioning temperature for at least 80 s, then coated by galvannealing, with an alloying temperature between 470° C. and 520° C. A steel sheet is also provided.

Abstract: A method for producing a cold rolled steel sheet having a tensile strength?1470 MPa and a total elongation TE?19%, the method comprising the steps of annealing at an annealing temperature AT?Ac3 a non-treated steel sheet whose chemical composition contains in weight %: 0.34%?C?0.40%, 1.50%?Mn?2.30%, 1.50?Si?2.40%, 0%<Cr?0.7%, 0%?Mo?0.3%, 0.01%?Al?0.07%, the remainder being Fe and unavoidable impurities, quenching the annealed steel sheet by cooling it to a quenching temperature QT<Ms transformation point and between 150° C. and 250° C., and making a partitioning treatment by re-heating the quenched steel sheet to a partitioning temperature PT between 350° C. and 420° C. and maintaining the steel sheet at this temperature during a partitioning time Pt between 15 seconds and 250 seconds.

Abstract: A method for producing a coated steel sheet having a tensile strength TS of at least 1450 MPa and a total elongation TE of at least 17% includes the successive steps of providing a cold rolled steel sheet made of a steel having a chemical composition comprising, in weight %: 0.34%?C?0.45%, 1.50%?Mn?2.30%, 1.50?Si?2.40%, 0%<Cr?0.7%, 0%?Mo?0.3%, 0.10%?Al?0.7%, and optionally 0%?Nb?0.05%, the remainder being Fe and unavoidable impurities, annealing the cold-rolled steel sheet at an annealing temperature AT higher than the Ac3 transformation point of the steel, quenching the annealed steel sheet by cooling it down to a quenching temperature QT lower than the Ms transformation point of the steel and comprised between 150° C. and 250° C., and reheating the quenched steel sheet to a partitioning temperature PT between 350° C. and 450° C.

Abstract: A method for producing a zinc or zinc-alloy coated steel sheet with a tensile strength higher than 900 MPa, for the fabrication of resistance spot welds containing in average not more than two Liquid Metal Embrittlement cracks per weld having a depth of 100 ?m or more, with steps of providing a cold-rolled steel sheet, heating cold-rolled steel sheet up to a temperature T1 between 550° C. and Ac1+50° C. in a furnace zone with an atmosphere (A1) containing from 2 to 15% hydrogen by volume, so that the iron is not oxidized, then adding in the furnace atmosphere, water steam or oxygen with an injection flow rate Q higher than (0.07%/h×?), ? being equal to 1 if said element is water steam or equal to 0.52 if said element is oxygen, at a temperature T?T1, so to obtain an atmosphere (A2) with a dew point DP2 between ?15° C. and the temperature Te of the iron/iron oxide equilibrium dew point, then heating the sheet from temperature T1 up to a temperature T2 between 720° C. and 1000° C.

Abstract: A method for producing a cold rolled steel sheet having a tensile strength?1470 MPa and a total elongation TE?19%, the method comprising the steps of annealing at an annealing temperature AT?Ac3 a non-treated steel sheet whose chemical composition contains in weight %: 0.34%?C?0.40%, 1.50%?Mn?2.30%, 1.50?Si?2.40%, 0<Cr?0.5%, 0%<Mo?0.3%, 0.01%?Al?0.07%, the remainder being Fe and unavoidable impurities, quenching the annealed steel sheet by cooling it to a quenching temperature QT<Ms transformation point and between 150° C. and 250° C., and making a partitioning treatment by reheating the quenched steel sheet to a partitioning temperature PT between 350° C. and 420° C. and maintaining the steel sheet at this temperature during a partitioning time Pt between 15 seconds and 120 seconds.

Abstract: A method for producing a cold rolled steel sheet having a tensile strength ?1470 MPa and a total elongation TE?19%, the method comprising the steps of annealing at an annealing temperature AT?Ac3 a non-treated steel sheet whose chemical composition contains in weight %: 0.34%?C?0.40%, 1.50%?Mn?2.30%, 1.50?Si?2.40%, 0<Cr?0.5%, 0<Mo?0.3%, 0.01%?Al?0.07%, the remainder being Fe and unavoidable impurities, quenching the annealed steel sheet by cooling it to a quenching temperature QT<Ms transformation point and between 150° C. and 250° C., and making a partitioning treatment by reheating the quenched steel sheet to a partitioning temperature PT between 350° C. and 420° C. and maintaining the steel sheet at this temperature during a partitioning time Pt between 15 seconds and 120 seconds.

Abstract: A method for producing a cold rolled steel sheet having a tensile strength ?1470 MPa and a total elongation TE?19%, the method comprising the steps of annealing at an annealing temperature AT?Ac3 a non-treated steel sheet whose chemical composition contains in weight %: 0.34%?C?0.40%, 1.50%?Mn?2.30%, 1.50?Si?2.40%, 0%<Cr?0.5%, 0%<Mo?0.3%, 0.01%?A1?0.07%, the remainder being Fe and unavoidable impurities, quenching the annealed steel sheet by cooling it to a quenching temperature QT<Ms transformation point and between 150° C. and 250° C., and making a partitioning treatment by reheating the quenched steel sheet to a partitioning temperature PT between 350° C. and 420° C. and maintaining the steel sheet at this temperature during a partitioning time Pt between 15 seconds and 120 seconds.

Abstract: A method for producing a coated steel sheet having a tensile strength of at least 1450 MPa and a total elongation of at least 17% is provided. The method includes providing a cold rolled steel sheet having a chemical composition in weight %: 0.34%?C?0.45%, 1.50%?Mn?2.30%, 1.50%?Si?2.40%, 0%<Cr?0.7%, 0%?Mo?0.3%, 0.10%?Al?0.7%, optionally 0%?Nb?0.05%, and a remainder of Fe and unavoidable impurities. The sheet is annealed at an annealing temperature higher than the Ac3 transformation point of the steel, quenched to a quenching temperature lower than the Ms transformation point of the steel and between 150° C. and 250° C., reheated to a partitioning temperature between 350° C. and 450° C., maintained at the partitioning temperature for at least 80 s, then coated by galvannealing, with an alloying temperature between 470° C. and 520° C. A steel sheet is also provided.

Abstract: A method for producing a cold rolled steel sheet having a tensile strength ?1470 MPa and a total elongation TE?19%, the method comprising the steps of annealing at an annealing temperature AT?Ac3 a non-treated steel sheet whose chemical composition contains in weight %: 0.34%?C?0.40%, 1.50%<Mn?2.30%, 1.50?Si?2.40%, 0%<Cr?0.5%, 0%<Mo?0.3%, 0.01%?A1?0.07%, the remainder being Fe and unavoidable impurities, quenching the annealed steel sheet by cooling it to a quenching temperature QT<Ms transformation point and between 150° C. and 250° C., and making a partitioning treatment by reheating the quenched steel sheet to a partitioning temperature PT between 350° C. and 420° C. and maintaining the steel sheet at this temperature during a partitioning time Pt between 15 seconds and 120 seconds.

Abstract: A method for producing a cold rolled steel sheet having a tensile strength?1470 MPa and a total elongation TE?19%, the method comprising the steps of annealing at an annealing temperature AT?Ac3 a non-treated steel sheet whose chemical composition contains in weight %: 0.34%?C?0.40%, 1.50%?Mn?2.30%, 1.50?Si?2.40%, 0%?Cr?0.7%, 0%?Mo?0.3%, 0.01%?Al?0.07%, the remainder being Fe and unavoidable impurities, quenching the annealed steel sheet by cooling it to a quenching temperature QT<Ms transformation point and between 150° C. and 250° C., and making a partitioning treatment by re-heating the quenched steel sheet to a partitioning temperature PT between 350° C. and 420° C. and maintaining the steel sheet at this temperature during a partitioning time Pt between 15 seconds and 250 seconds.