HIGH-STRENGTH STEEL AND PRODUCTION METHOD

WIPO Patent Application WO/2016/198940

A3

The invention relates to a cold-rolled, annealed steel sheet having a thickness of between 0,7 mm and 2mm, a mechanical strength of between 1180 MPa and 1320 MPa, a hole expansion ratio (Ac%) greater than 20%, a bending angle greater than or equal to 40°, and a chemical composition comprising (concentrations expressed by weight): 0.09 < C < 0.11 %, 2.6 ≤ Mn < 2.8%, 0.20 ≤ Si ≤ 0.55%, 0.25 ≤ Cr < 0.5 %, 0.025 < Ti ≤ 0.040 %, 0.0015 ≤ B < 0.0025 %, 0.005 ≤ Al < 0.18 %, 0.08 ≤ Mo < 0.15 %, 0.020 < Nb ≤ 0.040%, 0.002 ≤ N < 0.007 %, 0.0005% ≤ S ≤ 0.005%, 0.001 % ≤ P ≤ 0.020%, Ca ≤ 0.003%, the remainder comprising iron and inevitable impurities resulting from production. The sheet has a microstructure comprising martensite and/or lower bainite, said martensite comprising fresh martensite and/or self-tempered martensite, the sum of the surface area percentages of martensite and lower bainite being between 40 and 70 %, with between 15 and 45 surface area-% low-carbide-content bainite, between 5 and less than 20 surface area-% ferrite, the fraction of non-recrystallised ferrite in relation to the total ferrite fraction being less than 15%, and less than 5 surface area-% residual austenite in the form of islets, the fraction of former austenite grains with a size of less than one micrometre representing between 40 and 60% of the total population of said former austenite grains.

JPH0987819	METHOD FOR PREVENTING UNCOATING AT CONTINUOUS HOT DIP METAL COATING
JP2964910	METHOD AND APPARATUS FOR PRODUCING HOT DIP GALVANIZED STEEL SHEET
WO/2022/130124	ANNEALING METHOD

DRILLET JOSEE (FR)
HEBERT VERONIQUE (FR)

PCT/IB2016/000780

October 19, 2017

June 09, 2016

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ARCELORMITTAL (LU)

C23C2/02; C21D8/02; C21D8/04; C21D9/46; C21D9/48; C22C38/00; C22C38/02; C22C38/04; C22C38/06; C22C38/12; C22C38/14; C22C38/18; C22C38/26; C22C38/28; C22C38/32; C22C38/38; C23C2/06; C23C2/28; C23C2/40; C23C14/02; C23C14/06

EP2426230A1	2012-03-07
EP2578718A1	2013-04-10
EP2123786A1	2009-11-25

PLAISANT, Sophie (FR)

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