A steel sheet for the manufacture of a press hardened part is provided, having a composition of: 0.15%≤C≤0.22%, 3.5%≤Mn<4.2%, 0.001%≤Si≤1.5%, 0.020%≤Al≤0.9%, 0.001%≤Cr≤1%, 0.001%≤Mo≤0.3%, 0.001%≤Ti≤0.040%, 0.0003%≤B≤0.004%, 0.001%≤Nb≤0.060%, 0.001%≤N≤0.009%, 0.0005%≤S≤0.003%, 0.001%≤P≤0.020%. A microstructure has less than 50% ferrite, 1% to 20% retained austenite, cementite, such that the surface density of cementite particles larger than 60 nm is lower than 10{circumflex over ( )}7/mm.sup.2, and a complement of bainite and/or martensite, the retained austenite having an average Mn content of at least 1.1*Mn %. Press-hardened steel part obtained by hot forming the steel sheet, and manufacturing methods thereof.

The invention relates to a method for removing residues present on a metal strip at the outlet of a cooling stage of a continuous line, the residues being formed during a cooling of said metal strip by a non-oxidizing liquid solution for the metal strip and a stripping liquid solution for the oxides present on the surface of the strip, or by a mixture of this liquid solution and a gas. The method according to the invention is characterized in that it comprises a step of reducing the residues by hydrogen.

The present invention has as its object the provision of a coated steel member and coated steel sheet excellent in hydrogen embrittlement resistance in a corrosive environment and methods for manufacturing the same. The coated steel member of the present invention is provided on its surface with an Al—Fe-based coating containing Cu and one or more of Mo, Ni, Mn, and Cr in a total by mass % of 0.12% or more by heating, cooling, and manufacturing a coated steel sheet having a layer containing Cu on its surface under predetermined conditions.

The high strength steel sheet of the present invention has a specific chemical composition, and contains, in terms of area fraction relative to an entire steel microstructure, 30% or more and 100% or less ferrite, 0% or more and 70% or less martensite, and less than 20% in total of pearlite, bainite and retained austenite, and the ferrite contains, in terms of area fraction relative to an entire microstructure, 0% or more and 10% or less non-recrystallized ferrite, with a difference of the area fraction of the non-recrystallized ferrite in the longitudinal direction of the steel sheet of 5% or smaller.

A method for the manufacture of a TWIP steel is provided including: (A) feeding of a slab comprising by weight: 0.5<C<1.2%, 13.0≤Mn<25.0%, S≤0.030%, P≤0.080%, N≤0.1%, Si≤3.0%, 0.051%≤Al≤4.0%, 0.1≤V≤2.5%, and on a purely optional basis, one or more of Nb≤0.5%, B≤0.005%, Cr≤1.0%, Mo≤0.40%, Ni≤1.0%, Cu≤5.0%, Ti≤0.5%, 0.06≤Sn≤0.2%, the remainder of the composition being made of iron and inevitable impurities resulting from the elaboration, (B) reheating the slab and hot rolling the slab to provide a hot rolled slab, (C) coiling the hot rolled slab to provide a coiled slab, (D) first cold-rolling the coiled slab to provide a first cold rolled slab, (E) recrystallization annealing the first cold rolled slab such that an annealed steel sheet having an UTS.sub.annealed is obtained and (F) second cold-rolling the annealed steel sheet with a reduction rate CR % that satisfies the following equation A: 1216.472−0.98795*UTS.sub.annealed≤(−0.0008*UTS.sub.annealed+1.0124)*CR %.sup.2+(0.0371*UTS.sub.annealed−29.583)*CR %.

A high-strength steel sheet having a low yield ratio and a method for producing the same. The high-strength steel sheet has a specified chemical composition and a microstructure in which ferrite is present as a major phase, and martensite is present in an area fraction of 10% or greater and less than 50% relative to an entire area of the microstructure. The martensite has an average grain diameter of 3.0 μm or less, in an entirety of the martensite, a proportion of martensite having an aspect ratio of 3 or less is 60% or greater, and the martensite having an aspect ratio of 3 or less has a carbon concentration of 0.30% or greater and 0.90% or less in mass %.

The present invention provides steel sheet products having controlled compositions that are subjected to two-step annealing processes to produce sheet products having desirable microstructures and favorable mechanical properties such as high strength and ultra-high formability. Steels processed in accordance with the present invention exhibit combined ultimate tensile strength and total elongation (UTS.Math.TE) properties of greater than 25,000 MPa-%. Steels with these properties fall into the category of Generation 3 advanced high strength steels, and are highly desired by various industries including automobile manufacturers.

An apparatus for the continuous hot dip coating of a metal strip is provided. The apparatus includes a vessel intended to contain a liquid metal bath, a bottom roller and a displacement casing for the metal strip. The casing includes an upper portion and a lower portion. The lower portion includes a pouring box delimiting at least two liquid metal pouring compartments. Each pouring compartment is inwardly delimited by an inner wall including an upper rim. The casing is provided with the pouring box, is rotatable relative to the metal strip around a first rotation axis and the pouring box is rotatable relative to the upper portion of the casing around a second rotation axis. A method for coating the metal sheet is also provided.

There is provided a high-strength hot-dipped steel sheet having excellent coating adhesion and a method for manufacturing the steel sheet. The steel sheet has a chemical composition, and a coating layer is disposed on the steel sheet. The chemical composition includes, by mass %, C: 0.02% or greater and 0.30% or less, Si: 0.01% or greater and 2.0% or less, Mn: 0.2% or greater and 3.0% or less, P: 0.08% or less, S: 0.02% or less, and Al: 0.001% or greater and 0.40% or less, with the balance being Fe and incidental impurities. The coating layer has a coating weight per side of 30 to 90 g/m.sup.2 and contains exfoliated base steel in an amount of 0.3 to 1.5 g/m.sup.2.

A steel sheet, a plated steel sheet, and methods for producing a hot-rolled steel sheet, a cold-rolled full hard steel sheet, and a steel sheet. The steel sheet has a specified composition and a microstructure including 0 to 80% of polygonal ferrite and 20 to 100% of a total of martensite, bainite, and residual austenite in terms of an area ratio within 20 μm of the steel sheet surface. The content of Mn in martensite present within 20 μm of the steel sheet surface ([Mn].sub.SM) and the content of Mn in a bulk ([Mn].sub.B) satisfy [Mn].sub.SM/[Mn].sub.B≤1.5. At a location 300 μm from the steel sheet surface, an area ratio of the martensite is in a range of 20 to 50%.