Method for producing a steel sheet having improved strength, ductility and formability

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United States of America Patent

PATENT NO 12084738
APP PUB NO 20190003005A1
SERIAL NO

16064513

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Abstract

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A method produces a steel sheet having a microstructure including, in area fraction, 20% to 50% intercritical ferrite, 10% to 20% retained austenite, 25% to 45% tempered martensite, 10% to 20% fresh martensite, and bainite. The sum of tempered martensite and bainite is between 30% and 60%. A cold-rolled steel sheet provided includes 0.18% ≤C≤0.25%, 0.9% ≤Si≤1.8%, 0.02% ≤Al≤1.0%, with 1.00% ≤Si+Al≤2.35%, 1.5% ≤Mn≤2.5%, 0.010% ≤Nb ≤0.035%, 0.10% ≤Cr≤0.40%. The steel sheet is annealed to obtain 50% to 80% austenite and 20% to 50% of ferrite, quenched at a cooling rate between 20° C/s and 50° C/s to between Ms-50° C. and Ms-5° C., heated to a partitioning temperature between 375° C. and 450° C. and maintained at the partitioning temperature for at least 50s, then immediately cooled to room temperature.

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Patent Owner(s)

Patent OwnerAddress
ARCELORMITTAL24 - 26 BLVD D'AVRANCHES LUXEMBOURG L-1160

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Inventor(s)

Inventor Name Address # of filed Patents Total Citations
Jun, Hyun Jo East Chicago, US 26 49
Venkatasurya, Pavan East Chicago, US 4 11

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