Arcelormittal

Arcelormittal Investigacion Y Desarrollo, S.l.

Frederic Kegel

Astrid Perlade

Kangying Zhu

Coralie Jung

Artem Arlazarov

Samuel Vignier

Jean-Christophe Hell

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 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 having a microstructure of, in surface fraction:

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

A cold-rolled and heat-treated steel sheet having a microstructure consisting of, in surface fraction: between 10% and 30% of retained austenite, the retained austenite being present as films having an aspect ratio of at least 3 and as Martensite Austenite islands, less than 8% of the Martensite Austenite islands having a size above 0.5 &#x3bc;m, at most 1% of fresh martensite, at most 50% of tempered martensite, and recovered martensite containing precipitates of at least one element chosen among niobium, titanium and vanadium. A method for manufacturing the cold-rolled and heat-treated steel sheet is also described.

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&#x2264;C&#x2264;0.21%, 4.0&#x2264;Mn&#x2264;7.0%, 0.5&#x2264;Al&#x2264;3.5%, Si&#x2264;2.0%, Ti&#x2264;0.2%, V&#x2264;0.2%, Nb&#x2264;0.2%, P&#x2264;0.025%, B&#x2264;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 &#x3bc;mand containing more than the steel nominal phosphorus content.

Spot welded joint using high strength and high forming steel and its production method

The present invention provides a spot welded joint of at least two steel sheets. 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&#x2264;C&#x2264;0.21%, 4.0&#x2264;Mn&#x2264;7.0%, 0.5&#x2264;Al&#x2264;3.5%, Si&#x2264;2.0%, Ti&#x2264;0.2%, V&#x2264;0.2%, Nb&#x2264;0.2%, P&#x2264;0.025%, B&#x2264;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 &#x3bc;mand containing more than the steel nominal phosphorus content.

Growing community of inventors

Maizieres-les-Mets, France

Frederic Kegel