Arcelormittal

Arcelormittal France

Arcelormittal Investigacion Y Desarrollo, S.l.

Université De Nantes

Astrid Perlade

Kangying Zhu

Coralie Jung

Frederic Kegel

Artem Arlazarov

Jean-Michel Mataigne

Jean-Marc Pipard

Frédéric Kegel

Alice Dumont

Martin Beauvais

Florence Pechenot

Jean Marc Pipard

Xavier Garat

Alexandre Gibot

Samuel Vignier

Olivier Bouaziz

Coralie Magar

Jean-Louis Uriarte

Jonas Staudte

Ian Alberto Zuazo Rodriguez

Didier Huin

Céline Musik

Aurelie Milani

Bastien Weber

Christine Kaczynski

Remi Cavallotti

Josée Drillet

Josee Drillet

Yacine Benlatreche

Renaud Frappier

Farid E Hassani

Didier Hun

Erik Stenback

Aurelie Milami

Ian Alberto Zuazo-Rodriguez

Franco Del Frate

Celine Musik

Aurelie Amard

Aurélie Milani

Aurélie Amard

A cold rolled and heat-treated steel sheet having a composition including, 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, the partitioned martensite having a carbides density strictly less than 2×10/mm, between 10% and 30% of retained austenite, less than 8% of fresh martensite, a part of the fresh martensite being combined with retained austenite in the shape of martensite-austenite islands in total surface fraction less than 10%.

Cold rolled and heat-treated steel sheet and method of manufacturing the same

A hot rolled steel sheet having a composition including, by weight percent: C: 0.10-0.25%, Mn: 3.5-5.0%, Si: 0.80-1.60%, B: 0.0003-0.004%, 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 50% and 80% of lath bainite, lower than 30% of granular bainite, the rest being martensite, martensite-austenite islands and austenite films, and having less than 20% of martensite and M-A islands having the multiplication of the maximum length Lof the grain by the maximum width Wof the grain higher than 1 μm.

High toughness hot rolled steel sheet and method of manufacturing the same

A cold rolled and annealed steel sheet, made of a steel having a composition including, by weight percent: C: 0.03-0.18%, Mn: 6.0-11.0%, Al: 0.2-3%, Mo: 0.05-0.5%, B: 0.0005-0.005%, S≤0.010%, P≤0.020%, N≤0.008%, and including optionally one or more of the following elements, in weight percentage: Si≤1.20%, Ti≤0.050%, Nb≤0.050%, Cr≤0.5%, V≤0.2%, the remainder of the composition being iron and unavoidable impurities resulting from the smelting, the steel sheet having a microstructure including, in surface fraction, from 25% to 55% of retained austenite, from 45% to 75% of ferrite, less than 5% of fresh martensite, a carbon [C]and manganese [Mn]content in austenite, expressed in weight percent, such that the ratio ([C]×[Mn])/(C %×Mn %) is from 19.0 to 41.0 wt %, C % and Mn % being the nominal values in carbon and manganese in weight % and a carbides density below 3×10/mmand—an inhomogeneous repartition of manganese characterized by a manganese distribution with a slope above or equal to −30.

Cold rolled and annealed steel sheet and method of manufacturing the same

A cold-rolled and heat-treated steel sheet, having a composition comprising, by weight percent: 0.10%≤C≤0.40%, 3.5%≤Mn≤8.0%, 0.5%≤Si≤2.5%, 0.003%≤Al≤3.0%, with Si+Al≥0.8%, 0.001%≤Mo≤0.5%, S≤0.010%, P≤0.020%, N≤0.008%, and optionally one or more elements selected from amongst Cr, Ti, Nb, V and B, such that: 0.01%≤Cr≤2.0%, 0.010%≤Ti≤0.080%, 0.010%≤Nb≤0.080%, 0.010%≤V≤0.30%, 0.0005%≤B≤0.003%, A remainder of the composition being iron and unavoidable impurities resulting from the smelting. The microstructure consists of, in surface fraction, between 10% and 50% of retained austenite, at most 8% of fresh martensite, and tempered martensite. The retained austenite comprises Mn-enriched austenite, having a Mn content higher than 1.3*Mn %, Mn % designating the Mn content of the steel sheet, the surface fraction of said Mn-enriched austenite with respect to the whole microstructure being comprised between 2% and 12%; and Mn-poor austenite, having a Mn content comprised between 0.5*Mn % and 1.3*Mn %.

Resistance spot welded joint and a process for producing a resistance spot welded joint

A hot rolled and annealed steel sheet having a composition including, by weight percent: C: 0.1-0.25%, Mn: 3.00-5.00%, Si: 0.80-1.60%, B: 0.0003-0.004%, 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: more than 20% of recrystallized ferrite, the balance being non-recrystallized ferrite, more than 15% of the recrystallized ferrite having grain size larger than 5 μm and a density of carbides at grain boundary of recrystallized ferrite less than 5 carbides per 10 μm of grain boundary length.

High toughness hot rolled and annealed steel sheet and method of manufacturing the same

A pre-coated steel substrate coated with: a first pre-coating including titanium, the first coating having a thickness of 40 nm to 1200 nm, optionally, an intermediate pre-coating layer including at least 8% by weight nickel and at least 10% by weight chromium, the rest being iron or an intermediate pre-coating layer including Fe, Ni, Cr and Ti wherein the amount of Ti is above or equal to 5 wt. % and wherein the following equation is satisfied: 8 wt. %<Cr+Ti<40 wt. %, the balance being Fe and Ni, the intermediate pre-coating layer having a thickness between 2 and 30 nm a second pre-coating being a zinc-based coating and the steel substrate including above 0.05 wt. % of Si.

Method for manufacturing an assembly

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/mm, 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.

Steel sheet for manufacturing press hardened parts, press hardened part having a combination of high strength and crash ductility, and manufacturing methods thereof

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{circumflex over ( )}7/mm, 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.

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 μmand containing more than the steel nominal phosphorus content.

Production method for a spot welded joint using high strength and high forming steel

A cold-rolled and heat treated steel sheet, has a composition comprising 0.1%≤C≤0.4%, 3.5%≤Mn≤8.0%, 0.1%≤Si≤1.5%, Al≤3%, Mo≤0.5%, Cr≤1%, Nb≤0.1%, Ti≤0.1%, V≤0.2%, B≤0.004%, 0.002%≤N≤0.013%, S≤0.003%, P≤0.015%. The structure consists of, in surface fraction: between 8 and 50% of retained austenite, at most 80% of intercritical ferrite, the ferrite grains, if any, having an average size of at most 1.5 μm, and at most 1% of cementite, the cementite particles having an average size lower than 50 nm, martensite and/or bainite.

Steel sheet having excellent toughness, ductility and strength, and manufacturing method thereof

A cold-rolled and heat-treated steel sheet, has a composition comprising, by weight percent: n0.10%≤C≤0.25%, 3.5%≤Mn—≤6.0%, 0.5%≤Si≤2.0%, 0.3%≤Al≤1.2%, with Si+Al≥0.8%, 0.10%≤Mo≤0.50%, S≤0.010%, P≤0.020%, N≤0.008%. The cold-rolled steel sheet has a microstructure consisting of, in surface fraction: between 10% and 45% of ferrite, having an average grain size of at most 1.3 μm, the product of the surface fraction of ferrite by the average grain size of the ferrite being of at most 35 μm %, between 8% and 30% of retained austenite, the retained austenite having an Mn content higher than 1.1*Mn %, Mn % designating the Mn content of the steel, at most 8% of fresh martensite, at most 2.5% of cementite and partitioned martensite.

High strength and high formability steel sheet and manufacturing method

A steel sheet for the manufacture of a press hardened part is provided, having a composition of: 0.15%&#x2264;C&#x2264;0.22%, 3.5%&#x2264;Mn&#x3c;4.2%, 0.001%&#x2264;Si&#x2264;1.5%, 0.020%&#x2264;Al&#x2264;0.9%, 0.001%&#x2264;Cr&#x2264;1%, 0.001%&#x2264;Mo&#x2264;0.3%, 0.001%&#x2264;Ti&#x2264;0.040%, 0.0003%&#x2264;B&#x2264;0.004%, 0.001%&#x2264;Nb&#x2264;0.060%, 0.001%&#x2264;N&#x2264;0.009%, 0.0005%&#x2264;S&#x2264;0.003%, 0.001%&#x2264;P&#x2264;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{circumflex over (&#x2003;)}7/mm, 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.

A method for resistance spot welding comprising the following successive steps: &#x2014;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)&#xd7;(TEL)&#x3e;14000 MPa %, wherein the composition of the steel substrate of (A) contains, in weight: 0.05%&#x2264;C&#x2264;0.4%, 0.3%&#x2264;Mn&#x2264;8%, 0.010%&#x2264;Al&#x2264;3%, 0.010%&#x2264;Si&#x2264;2.09%, with 0.5%&#x2264;(Si+Al)&#x2264;3.5%, 0.001%&#x2264;Cr&#x2264;1.0%, 0.001%&#x2264;Mo&#x2264;0.5% and optionally: 0.005%&#x2264;Nb&#x2264;0.1%, 0.005%&#x2264;V&#x2264;0.2%, 0.005%&#x2264;Ti&#x2264;0.1%, 0.0003%&#x2264;B&#x2264;0.005%, 0.001%&#x2264;Ni&#x2264;1.0%, the remainder being Fe and unavoidable impurities, &#x2014;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 &#x3bc;m&#x2264;(IDepth)&#x2264;18.68 (Zn)&#x2212;55.1, wherein (IDepth) is in micrometers and wherein Znis the solubility of Zn in the steel of sheet (A) at 750&#xb0; C., in weight %.

Resistance spot welding method for joining zinc coated steel sheets

A cold-rolled and heat treated steel sheet, has a composition comprising 0.1%&#x2264;C&#x2264;0.4%, 3.5%&#x2264;Mn&#x2264;8.0%, 0.1%&#x2264;Si&#x2264;1.5%, Al&#x2264;3%, Mo&#x2264;0.5%, Cr&#x2264;1%, Nb&#x2264;0.1%, Ti&#x2264;0.1%, V&#x2264;0.2%, B&#x2264;0.004%, 0.002%&#x2264;N&#x2264;0.013%, S&#x2264;0.003%, P&#x2264;0.015%. The structure consists of, in surface fraction: between 8 and 50% of retained austenite, at most 80% of intercritical ferrite, the ferrite grains, if any, having an average size of at most 1.5 &#x3bc;m, and at most 1% of cementite, the cementite particles having an average size lower than 50 nm, martensite and/or bainite.

A cold-rolled and heat-treated steel sheet having a microstructure of, in surface fraction:

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Le Ban-Saint-Martin, France

Astrid Perlade