Arcelormittal

Sebastian Cobo

Emmanuel Lucas

Martin Beauvais

Matthieu Salib

Guillaume Stechmann

Christian Allely

Anis Aouafi

Catherine Vinci

François Stouvenot

Juan David Puerta Velasquez

A steel sheet has a chemical composition including in wt % C: 0.2-0.4%, Mn: 0.8-2.0%, Si: 0.1-0.5%, Al: 0.01-0.1%, Ti: 0.01-0.1%, B: 0.0005-0.005%, P≤0.040%, Ca≤0.01%, S≤0.006%, N≤0.01%. The steel sheet includes from the bulk to the surface of the coated steel sheet a bulk and a skin layer occupying the outermost 10% of the thickness on either side of the bulk. The bulk includes an inclusion population in which the sum of clustering indexes of MnS and TiN/Ti(C,N) inclusions is less than or equal to 300 μm/mm. This allows to manufacture hot pressed parts having a tensile strength equal to or greater than 1300 MPa and a bending anisotropy equal to or lower than 7°.

Steel sheet and high strength press hardened steel part having excellent bending anisotropy and method of manufacturing the same

A steel sheet made of a steel having a composition including, C: 0.3-0.4%, Mn: 0.5-1.0%, Si: 0.4-0.8%, Cr: 0.1-1.0%, Mo: 0.1-0.5%, Nb: 0.01-0.1%, Al: 0.01-0.1%, Ti: 0.008-0.03%, B: 0.0005-0.003%, P≤0.020%, Ca≤0.001%, S≤0.004%, N≤0.005% and including optionally Ni<0.5%, having a microstructure including, in surface fraction, from 60% to 95% of ferrite, the rest being martensite-austenite islands, pearlite or bainite, and including a bulk and a skin layer occupying the outermost 10% of the thickness on either sides of the bulk, the skin layer having a skin layer inclusion population wherein the surface fraction of oxides is equal to or below 60*10.

Steel sheet and high strength press hardened steel part and method of manufacturing the same

A steel sheet has a chemical composition including in wt % C: 0.2-0.4%, Mn 0.8-2.0%, Si: 0.1-0.5%, Al: 0.01-0.1%, Ti: 0.01-0.1%, B: 0.0005-0.005%, P≤0.040%, Ca≤0.01%, S≤0.006%, N≤0.01%. The steel sheet includes from the bulk to the surface of the coated steel sheet a bulk and a skin layer occupying the outermost 10% of the thickness on either side of the bulk. The bulk includes an inclusion population in which the sum of clustering indexes of MnS and TiN/Ti(C,N) inclusions is less than or equal to 300 μm/mm. This allows to manufacture hot pressed parts having a tensile strength equal to or greater than 1300 MPa and a bending anisotropy equal to or lower than 7°.

A rolled steel sheet, for press hardening is provided, having a chemical composition where Ti/N>3.42, and the carbon, manganese, chromium and silicon contents satisfy: The sheet has a nickel content Niat any point of the steel in the vicinity of the surface over a depth Δ, such that: Ni>Ni, Nidenoting the nominal nickel content of the steel, and such that, Nidenoting the maximum nickel content within Δ: and such that: and the surface density of all of the particles D, and the surface density of the particles Dlarger than 2 micrometers satisfy, at least to a depth of 100 micrometers in the vicinity of the surface of said sheet:6.75<270Dand Dbeing expressed as number of particles per square millimeter, and said particles denoting all the oxides, sulfides, and nitrides, either pure or combined such as oxysulfides and carbonitrides, present in the steel matrix.

Method for producing high-strength steel parts with improved ductility, and parts obtained by said method

A rolled steel sheet, for press hardening is provided, having a chemical composition where Ti/N&#x3e;3.42, and the carbon, manganese, chromium and silicon contents satisfy: The sheet has a nickel content Niat any point of the steel in the vicinity of the surface over a depth &#x394;, such that: Ni&#x3e;Ni, Nidenoting the nominal nickel content of the steel, and such that, Nidenoting the maximum nickel content within &#x394;: and such that: and the surface density of all of the particles Dand the surface density of the particles Dlarger than 2 micrometers satisfy, at least to a depth of 100 micrometers in the vicinity of the surface of said sheet:+6.75 D&#x3c;270Dand Dbeing expressed as number of particles per square millimeter, and said particles denoting all the oxides, sulfides, and nitrides, either pure or combined such as oxysulfides and carbonitrides, present in the steel matrix.

The present invention provides a rolled steel sheet, for press hardening, for which the chemical composition includes, with contents expressed by weight, 0.24%&#x2266;C&#x2266;0.38%, 0.40%&#x2266;Mn&#x2266;3%, 0.10%&#x2266;Si&#x2266;0.70%, 0.015%&#x2266;Al&#x2266;0.070%, 0%&#x2266;Cr&#x2266;2%, 0.25%&#x2266;Ni&#x2266;2%, 0.015%&#x2266;Ti&#x2266;0.10%, 0%&#x2266;Nb&#x2266;0.060%, 0.0005%&#x2266;B&#x2266;0.0040%, 0.003%&#x2266;N&#x2266;0.010%, 0.0001%&#x2266;S&#x2266;0.005%, 0.0001%&#x2266;P&#x2266;0.025%, it being understood that the titanium and nitrogen content satisfy: Ti/N&#x3e;3.42, and that the carbon, manganese, chromium and silicon content satisfy: with the chemical composition optionally including one or more of the following elements: 0.05%&#x2266;Mo&#x2266;0.65%, 0.001%&#x2266;W&#x2266;0.30%, 0.0005%&#x2266;Ca&#x2266;0.005%, with the remainder made up of iron and inevitable impurities coming from preparation. The sheet includes a nickel content Niat any point of the steel near the surface of said sheet over a depth &#x394;, such that Ni&#x3e;Ni, where Nidesignates the nominal nickel content of the steel, and such that Nidesignates the maximum nickel content within &#x394;: and such that: with the depth &#x394; expressed in microns and the Niand Nicontents expressed in percentages by weight.

Growing community of inventors

Ancy-sur-Moselle, France

Sebastian Cobo