A cold-rolled flat steel product for packaging materials has a thickness of less than 0.6 mm, which has been cold-rolled from steel along a rolling direction (0°) and which has an excellent isotropy with respect to its mechanical properties.

The disclosed martensitic stainless steel is defined in its composition is by specified ranges of weight percentages of C; Mn; Si; ≤Mn+Si; ≤S; 10,000×Mn×S; P; Cr, with [Cr−10.3−80*(C+N).sup.2]≤(Mn+Ni); Ni; Mo; Mo+2W; Cu; Ti; V; Zr; Al; O; Ta; Nb; (Nb+Ta)/(C+N); Nb; N; Co; Cu+Co; Cu+Co+Ni; B; rare earths+Y; Ca; the remainder being iron and impurities resulting from processing. Its microstructure includes at least 75% martensite, at most 20% ferrite and at most 0.5% carbides, the size of the ferrite grains being between 4 and 80 μm, preferably between 5 and 40 μm. Also disclosed is a method of manufacturing such steel.

The present invention relates to a zinc plated steel sheet having excellent surface quality and spot weldability, and a manufacturing method therefore. A zinc plated steel sheet according to one aspect of the present invention comprises a base steel sheet and a zinc-based plating layer formed on the surface of the base steel sheet, wherein the GDOES profile of oxygen, which is measured in the depth direction from the surface of the base steel sheet, has a form in which a local minimum point and a local maximum point alternately appear in the depth direction from the surface, and the difference (a local maximum value—a local minimum value) between the oxygen concentration (a local minimum value) at the local minimum point and the oxygen concentration (a local maximum value) at the local maximum point can be 0.1 wt % or more.

There is provided a high strength high formable aluminum alloys (Al—Mg—Mn alloy). The aluminum alloy exhibits improved castability by achieving lower required torque at high temperature, while meeting or exceeding the ambient temperature strength and formability requirements for high strength applications. The aluminum alloy comprises in weight percent Mg 1.0-2.0, 0.2-0.95 Mn, 0.05-0.35 Cr with the balance being aluminum and inevitable impurities.

The present invention provides a high-strength tin blackplate and a manufacturing method therefor.

The tin blackplate according to an exemplary embodiment of the present invention includes: by wt %, 0.03 to 0.09% of carbon (C); 0.2 to 0.4% of manganese (Mn); 0.01 to 0.06% of aluminum (Al); 0.15 to 0.45% of chromium (Cr); 0.05 to 0.25% of copper (Cu); 0.03 to 0.08% of titanium (Ti); and the balance of iron (Fe) and inevitable impurities, and has a yield strength of 570 to 700 MPa.

The present embodiments relate to a cold-rolled steel sheet for a flux-cored wire and a method for manufacturing the same. According to an exemplary embodiment, a cold-rolled steel sheet for a flux-cored wire, including: by wt %, 0.0005 to 0.01% of carbon (C), 0.05 to 0.25% of manganese (Mn), 0.03% or less (except for 0%) of silicon (Si), 0.0005 to 0.01% of phosphorus (P), 0.001 to 0.008% of sulfur (S), 0.0001 to 0.010% of aluminum (Al), 0.0005 to 0.003% of nitrogen (N), 0.5 to 1.7% of nickel (Ni), 0.0005 to 0.0030% of boron (B), and the balance Fe and inevitable impurities, can be provided.

A steel sheet including a chemical composition satisfying an equivalent carbon content of 0.60% or more and less than 0.85%, and a steel microstructure with an area fraction of ferrite: less than 40%, tempered martensite and bainite: 40% or more in total, retained austenite: 3% to 15%, and ferrite, tempered martensite, bainite, and retained austenite: 93% or more in total. A 90-degree bending at a curvature radius/thickness ratio of 4.2 in a rolling (L) direction with respect to an axis extending in a width (C) direction causes a change of 0.40 or more in (a grain size in a thickness direction)/(a grain size in a direction perpendicular to the thickness) of the tempered martensite in an L cross section in a 0- to 50-μm region from a surface of the steel sheet on a compression side. The steel sheet has a tensile strength of 980 MPa or more.

An embodiment of the present invention provides a steel material, for a pressure vessel, comprising, in weight %, 0.06-0.25% of carbon (C), 0.05-0.50% of silicon (Si), 1.0-2.0% of manganese (Mn), 0.005-0.40% of aluminum (Al), 0.010% or less of phosphorus (P), 0.0010% or less of sulfur (S), 0.001-0.03% of niobium (Nb), 0.001-0.03% of vanadium (V), 0.001-0.03% of titanium (Ti), 0.01-0.20% of chromium (Cr), 0.05-0.15% of molybdenum (Mo), 0.01-0.50% of copper (Cu), 0.05-0.50% of nickel (Ni), 0.0005-0.0050% of magnesium (Mg), 0.0005-0.0050% of calcium (Ca), 0.0020% or less of oxygen (O), and the remainder being Fe and other unavoidable impurities. A microstructure comprises in terms of area fraction 30% or less of pearlite and the remainder being ferrite. A non-metallic inclusion contains Mg—Al—Ca—O composite oxide.

Provided is a stainless steel sheet having a predetermined chemical composition, in which a total volume fraction of Cr-based carbides with a grain size of 2.0 μm or more is 10% or less.

A method is for manufacturing a high-strength steel sheet having a tensile strength of more than 1100 MPa and a yield strength of more than 700 MPa, a uniform elongation UE of at least 8.0% and a total elongation of at least 10%, made of a steel containing in percent by weight: 0.1%≤C≤0.25%, 4.5%≤Mn≤10%, 1%≤Si≤3%, 0.03%≤Al≤2.5%, the remainder being Fe and impurities resulting from the smelting, the composition being such that CMnIndex=C×(1+Mn/3.5)≤0.6. The method includes annealing a rolled sheet made of said steel by soaking it at an annealing temperature TA higher than the Ac.sub.1 transformation point of the steel but less than 1000° C., cooling the annealed sheet to a quenching temperature QT between 190° C. and 80° C. at a cooling speed sufficient to obtain a structure just after cooling containing martensite and retained austenite, maintaining the steel sheet at an overaging temperature PT between 350° C. and 500° C. for an overaging time Pt of more than 5 s cooling the sheet down to the ambient temperature.