Arcelormittal

Elena Uta

Véronique Hebert

Veronique Hebert

A cold rolled and heat treated steel sheet is provided. The steel sheet includes a composition including 0.17%&#x2264;carbon&#x2264;0.24%, 1.9%&#x2264;manganese&#x2264;2.2%, 0.5%&#x2264;aluminum&#x2264;1.2%, 0.5%&#x2264;silicon&#x2264;1%, Si+Al&#x2265;1.3%, 0.05%&#x2264;chromium&#x2264;0.2%, 0.015%&#x2264;niobium&#x2264;0.03%, sulphur&#x2264;0.003%, phosphorus&#x2264;0.03% and optionally 0.005%&#x2264;titanium&#x2264;0.05%, 0.001%&#x2264;molybdenum&#x2264;0.05%, a remainder of the composition including iron and the unavoidable impurities. A microstructure of the coated steel sheet includes, in area fraction, 10 to 20% residual austenite, said austenite phase having a carbon content between 0.9 to 1.1%, 40 to 55% polygonal ferrite, 15 to 40% granular bainite and at least 5% tempered martensite, a sum of tempered martensite and residual austenite being between 20 to 30%. A method is also provided.

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Montigny les Metz, France

Elena Uta