Arcelormittal

Michel Soler

Hassan Ghassemi-Armaki

Anirban Chakraborty

Olga A Girina

Damon Panahi

Jean-Christophe Hell

Ian Alberto Zuazo Rodriguez

Xavier Garat

Irène De Diego Calderon

Gunhild Föjer

Ronan Jacolot

Alexey Koltsov

Gunhild Fojer

Patrice Alexandre

Magali Bouzat

Aude Nadler

Irene De Diego Calderon

A cold rolled and annealed steel sheet includes by weight: 0.6&#x3c;C&#x3c;1.3%,15.0&#x3c;Mn&#x3c;35%, 6.0&#x3c;Al&#x3c;15%, Si&#x3c;2.40%, S&#x3c;0.015%, P&#x3c;0.1%, N&#x3c;0.1%, iron and inevitable impurities, optionally one or more of Ni, Cr and Cu in an individual amount of up to 3% and optionally one or more of B, Ta, Zr, Nb, V, Ti, Mo, and W in a cumulated amount of up to 2.0%, a microstructure of the sheet comprising at least 0.1% of intragranular kappa carbides, at least 80% of the kappa carbides have an average size below 30 nm, the remainder being made of austenite, an average grain size of the austenite being below 6 &#x3bc;m, an average aspect ratio of the austenite being between 1.5 and 6, an average grain size of the ferrite, when present being below 5 &#x3bc;m, and an average aspect ratio of the ferrite, when present, being below 3.0.

Cold rolled and annealed steel sheet, method of production thereof and use of such steel to produce vehicle parts

A method for manufacturing a high-strength sheet having improved formability and ductility accord which the chemical composition of the steel contains, in percent by weight: 0.25%&#x3c;C&#x2264;0.4% 2.3%&#x2264;Mn&#x2264;3.5% 2.3%&#x2264;Si&#x2264;3% Al&#x2264;0.040% the remainder being Fe and unavoidable impurities, the method comprising the steps of annealing a rolled sheet made of said steel by soaking it at an annealing temperature AT higher than the Actransformation point of the steel, quenching the sheet by cooling it down to a quenching temperature QT between Ms&#x2212;65&#xb0; C. and Ms&#x2212;115&#xb0; C., being in order to obtain a final structure containing at least 65% of martensite and at least 5% of residual austenite, the sum of the ferrite and bainite contents being less than 10%, Ms being the Ms transformation point of the steel according to the Andrews formula, heating the sheet up to an overaging temperature PT between 360&#xb0; C. and 500&#xb0; C. and maintaining it at said temperature for a time Pt between 10 s and 600 s, and cooling the sheet down to the ambient temperature.

Method for manufacturing a high strength steel sheet having improved formability and ductility and sheet obtained

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Maizieres-les-Metz, France

Michel Soler