Arcelormittal

Jean-Marc Pipard

Artem Arlazarov

Marc Olivier Thenot

Hassan Ghassemi-Armaki

Anirban Chakraborty

Olga A Girina

Damon Panahi

Pavan Challa Venkata Surya

Sebastien Cremel

Astrid Perlade

Florence Pechenot

Aurelie Milani

Bastien Weber

Pierre Targy

Yacine Benlatreche

Aurélie Milani

A cold rolled and heat treated steel sheet having a composition with the following elements, expressed in percentage by weight:0.10%≤Carbon≤0.5%, 1%≤Manganese≤3.4%, 0.5%≤Silicon≤2.5%, 0.03%≤Aluminum≤1.5%, 0%≤Sulfur≤0.003% 0.002%≤Phosphorus≤0.02%, 0%≤Nitrogen≤0.01% and can contain one or more of the following optional elements 0.05%≤Chromium≤1%, 0.001%≤Molybdenum≤0.5%, 0.001%≤Niobium≤0.1%, 0.001%≤Titanium≤0.1%, 0.01%≤Copper≤2%, 0.01%≤Nickel≤3%, 0.0001%≤Calcium≤0.005%, 0%≤Vanadium≤0.1%, 0%≤Boron≤0.003%, 0%≤Cerium≤0.1%, 0%≤Magnesium≤0.010%, 0%≤Zirconium≤0.010% the remainder composition being composed of iron and unavoidable impurities caused by processing, the microstructure of the steel sheet having in area fraction, 10 to 30% Residual Austenite, 10 to 40% Bainite, 5% to 50% Annealed Martensite, 1% to 20% Quenched Martensite and less than 30% Tempered Martensite, wherein the cumulated amounts of Bainite and Residual Austenite is more than or equal to 25%.

Cold rolled heat treated steel sheet and a method of manufacturing thereof

A tempered and coated steel sheet having a composition containing the following elements, expressed in percentage by weight: 0.17%≤carbon≤0.25%, 1.8%≤manganese≤2.3%, 0.5%≤silicon≤2.0%, 0.03%≤aluminum≤1.2%, sulphur≤0.03%, phosphorus≤0.03%, the remainder composition being composed of iron and unavoidable impurities caused by processing, the microstructure of said steel sheet containing in area fraction, 3 to 20% residual austenite, at least 15% of ferrite, 40 to 85% tempered bainite and a minimum of 5% of tempered martensite, wherein cumulated amounts of tempered martensite and residual austenite is between 10 and 30%. The composition may also contain one or more of the following elements chromium≤0.4%, molybdenum≤0.3%, niobium≤0.04%, titanium≤0.1%. Methods of manufacturing and use of the tempered and coated steel sheets are also described.

Tempered and coated steel sheet having excellent formability and a method of manufacturing the same

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 μm 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×α), α 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 Tup to a temperature Tbetween 720° C. and 1000° C. in a furnace zone under an atmosphere (A2) of nitrogen containing from 2 to 15% hydrogen and more than 0.1% CO by volume, with an oxygen partial pressure higher than 10atm., wherein the duration to of heating of the sheet from temperature Tup to the end of soaking at temperature Tis between 100 and 500 s, soaking the sheet at T, then cooling the sheet at a rate between 10 and 400° C./s, then coating the sheet with zinc or zinc-alloy coating.

Zinc-coated steel sheet with high resistance spot weldability

A cold rolled heat treated steel sheet having a composition with the following elements, expressed in percentage by weight 0.1%≤Carbon≤0.5%, 1%≤Manganese≤3.4%, 0.5%≤Silicon≤2.5%, 0.03%≤Aluminum≤1.5%, 0%≤Sulfur≤0.003%, 0.002%≤Phosphorus≤0.02%, 0%≤Nitrogen≤0.01% and can contain one or more of the following optional elements 0.05%≤Chromium≤1%, 0.001%≤Molybdenum≤0.5%, 0.001%≤Niobium≤0.1%, 0.001%≤Titanium≤0.1%, 0.01%≤Copper≤2%, 0.01%≤Nickel≤3%, 0.0001%≤Calcium≤0.005%, 0%≤Vanadium≤0.1%, 0%≤Boron≤0.003%, 0%≤Cerium≤0.1%, 0%≤Magnesium≤0.010%, 0%≤Zirconium≤0.010%, the remainder composition being composed of iron and unavoidable impurities caused by processing, the microstructure of the steel sheet having in area fraction, 10 to 30% Residual Austenite, 50 to 85% Bainite, 1 to 20% Quenched Martensite, and less than 30% Tempered Martensite.

Cold rolled steel sheet and a method of manufacturing thereof

A cold rolled and heat treated steel sheet, the steel having a composition with, in weight percentage,

Cold rolled and heat treated steel sheet and a method of manufacturing thereof

A tempered and coated steel sheet having a composition containing the following elements, expressed in percentage by weight:

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 &#x3bc;m or more, with steps of providing a cold-rolled steel sheet, heating cold-rolled steel sheet up to a temperature T1 between 550&#xb0; C. and Ac1+50&#xb0; 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&#xd7;&#x3b1;), &#x3b1; being equal to 1 if said element is water steam or equal to 0.52 if said element is oxygen, at a temperature T&#x2265;T1, so to obtain an atmosphere (A2) with a dew point DP2 between &#x2212;15&#xb0; C. and the temperature Te of the iron/iron oxide equilibrium dew point, then heating the sheet from temperature Tup to a temperature Tbetween 720&#xb0; C. and 1000&#xb0; C. in a furnace zone under an atmosphere (A2) of nitrogen containing from 2 to 15% hydrogen and more than 0.1% CO by volume, with an oxygen partial pressure higher than 10atm., wherein the duration tof heating of the sheet from temperature Tup to the end of soaking at temperature Tis between 100 and 500 s., soaking the sheet at T, then cooling the sheet at a rate between 10 and 400&#xb0; C./s, then coating the sheet with zinc or zinc-alloy coating.

A cold rolled and heat treated steel sheet having a composition with the following elements, expressed in percentage by weight: 0.10%&#x2264;Carbon&#x2264;0.5%,1%&#x2264;Manganese&#x2264;3.4%, 0.5%&#x2264;Silicon&#x2264;2.5%, 0.03%&#x2264;Aluminum&#x2264;1.5%, 0%&#x2264;Sulfur&#x2264;0.003% 0.002%&#x2264;Phosphorus&#x2264;0.02%, 0%&#x2264;Nitrogen&#x2264;0.01% and can contain one or more of the following optional elements 0.05%&#x2264;Chromium&#x2264;1%, 0.001%&#x2264;Molybdenum&#x2264;0.5%, 0.001%&#x2264;Niobium&#x2264;0.1%, 0.001%&#x2264;Titanium&#x2264;0.1%, 0.01%&#x2264;Copper&#x2264;2%, 0.01%&#x2264;Nickel&#x2264;3%, 0.0001%&#x2264;Calcium&#x2264;0.005%, 0%&#x2264;Vanadium&#x2264;0.1%, 0%&#x2264;Boron&#x2264;0.003%, 0%&#x2264;Cerium&#x2264;0.1%, 0%&#x2264;Magnesium&#x2264;0.010%, 0%&#x2264;Zirconium&#x2264;0.010% the remainder composition being composed of iron and unavoidable impurities caused by processing, the microstructure of the steel sheet having in area fraction, 10 to 30% Residual Austenite, 10 to 40% Bainite, 5% to 50% Annealed Martensite, 1% to 20% Quenched Martensite and less than 30% Tempered Martensite, wherein the cumulated amounts of Bainite and Residual Austenite is more than or equal to 25%.

A cold rolled and heat treated steel sheet having a composition with the following elements, expressed in percentage by weight 0.10%&#x2264;Carbon&#x2264;0.5%, 1%&#x2264;Manganese&#x2264;3.4%, 0.5%&#x2264;Silicon&#x2264;2.5%, 0.03%&#x2264;Aluminum&#x2264;1.5%, Sulfur&#x2264;0.003%, 0.002%&#x2264;Phosphorus&#x2264;0.02%, Nitrogen&#x2264;0.01% and can contain one or more of the following optional elements 0.05%&#x2264;Chromium&#x2264;1%, 0.001%&#x2264;Molybdenum&#x2264;0.5%, 0.001%&#x2264;Niobium&#x2264;0.1%, 0.001%&#x2264;Titanium&#x2264;0.1%, 0.01%&#x2264;Copper&#x2264;2%, 0.01%&#x2264;Nickel&#x2264;3%, 0.0001%&#x2264;Calcium&#x2264;0.005%, Vanadium&#x2264;0.1%, Boron&#x2264;0.003%, Ceriums&#x2264;0.1%, Magnesiums&#x2264;0.010%, Zirconiums&#x2264;0.010% the remainder composition being composed of iron and the unavoidable impurities caused by processing, and a microstructure of the said rolled steel sheet having by area fraction, 10 to 30% Residual Austenite, 5 to 50% Annealed Bainite, 10 to 40% of Bainite, 1% to 20% Quenched Martensite, and less than 30% Tempered Martensite where the combined presence of Bainite and Residual Austenite shall be 30% or more.

A cold rolled steel sheet, the steel containing, in weight percentage,

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Vaux, France

Jean-Marc Pipard