A roll-bonded clad metal sheet and a method for producing a roll-bonded clad metal sheet is provided. The roll-bonded clad sheet includes a metallic base material layer and a metallic cladding material layer which are joined to one another by a metallurgical bond. The metallic cladding material layer includes a nickel-based material whose chemical composition includes, in % by mass, a proportion of more than 50% of Ni and a proportion of 3.1% of Nb. The metallurgical bond is obtained by a thermomechanical rolling process including a first rolling phase for prerolling, a second rolling phase for final forming and a cooling time between the first rolling phase and the second rolling phase, wherein a final rolling temperature of the second rolling phase is set to a value equal to or less than 880° C.

The present invention provides an ultra high strength cold rolled steel sheet having excellent spot weldability and formability. The ultra high strength cold rolled steel sheet, according to one embodiment of the present invention, comprises, in weight percent,: 0.05% to 0.09% of carbon (C); 0.5% to 1.0% of silicon (Si); 2.0% to 2.8% of manganese (Mn); 0.2% to 0.5% of aluminum (Al); 0.8% to 1.2% of chromium (Cr); 0.05% to 0.10% of molybdenum (Mo); 0.03% to 0.06% of titanium (Ti); 0.001% to 0.003% of boron (B); 0.02% to 0.05% of antimony (Sb); 0.001% to 0.015% of phosphorus (P); more than 0% to 0.003% of sulfur (5); 0.004% to 0.006% of nitrogen (N); and a balance of iron (Fe) and other inevitable impurities, and the ultra high strength cold rolled steel sheet comprises a microstructure comprising ferrite and low hardness martensite.

A high strength steel strip having medium amounts of C, Mn, Si, Cr and Al, wherein the steel strip has a microstructure consisting of, in vol. %: ferrite and bainite together 50-90%, martensite<15%, retained austenite 5-15%, the remainder being pearlite, cementite, precipitates and inclusions together up to 5%.

Provided is a black stainless steel sheet that has excellent weldability, that can ensure good toughness and corrosion resistance, and that can maintain the blackness of the surface thereof, even after being welded. This black ferrite-based stainless steel sheet having excellent weldability includes, as a base, a stainless steel containing, in mass %, 0.020% or less of C, 1.0% or less of Si, 0.35% or less of Mn, 0.04% or less of P, 0.005% or less of S, 11-25% of Cr, 1.0% or less of Mo, 0.020% or less of N, 0.4% or less of Al, 10(C+N) to 0.3% of Ti, 0.05% or less of Nb, and 0.01% or less of O, and has a surface in which an oxide coating is formed on the base, wherein the surface has a lightness index (L*) satisfying L*≤45, chromaticity indices (a*, b*) satisfying −5≤a*≤5 and −5≤b*≤5, and a blackness (E) satisfying E=(L*2+a*2+b*2)1/2≤45.

This steel sheet has a predetermined chemical composition, the metallurgical structure at a thickness ¼ portion is, by area ratio, martensite: 40% to 97%, ferrite+bainite: 50% or less, residual austenite: 3% to 20% and a remainder in microstructure: 5% or less, the aspect ratio of residual austenite having an aspect ratio of 3 or more is 80% or more with respect to the total area of residual austenite, and the number of carbides having a grain diameter of 8 to 40 nm per square micrometer is five or more in the residual austenite.

Hot rolling stock (1) made of metal which is rolled in at least one roll stand (2) and then cooled in a cooling section (5) arranged downstream of the at least one roll stand (2). Sound generated by means of a sound generator arrangement (8) is coupled into the rolling stock (1) by a coupling device (1) so that a standing sound wave is formed at least in the region of the rolling stock (1) which is located in the vicinity of the coupling device (10).

A high-strength steel sheet includes a chemical composition including: by mass %, C: 0.080 to 0.500%, Si: 2.50% or less, Mn: 0.50 to 5.00%, P: 0.100% or less, S: 0.0100% or less, Al: 0.001 to 2.500%, N: 0.0150% or less, O: 0.0050% or less, and the balance: Fe and inevitable impurities. The high-strength steel sheet satisfying a predetermined formula has a microstructure in a region from ⅛t to ⅜t from a steel sheet surface. The microstructure includes: by volume %, 20% or more of acicular ferrite, 20% or more of an island-shaped hard structure including residual austenite, 2% to 25% of residual austenite, and 20% or less of aggregated ferrite.

A hot-pressed member has a predetermined chemical composition. In the hot-pressed member, a steel sheet has a microstructure in which a prior austenite average grain diameter is 8 μm or less, and martensite is present in a volume fraction of 95% or greater in a region within 30 μm of a surface; a Ni diffusion region having a thickness of 0.5 μm or greater exists in a surface layer; a standard deviation of Vickers hardness values is 35 or less; Mndif (mass %) in a sheet thickness direction ≤0.20, where Mndif (mass %) is a degree of Mn segregation; and a tensile strength is 1780 MPa or greater.

A steel sheet for cans has a chemical composition containing, in mass percent, C: 0.085% to 0.130%, Si: 0.04% or less, Mn: 0.10% to 0.60%, P: 0.02% or less, S: more than 0.010% to 0.020%, Al: 0.02% to 0.10%, N: 0.0005% to 0.0040%, Nb: 0.007% to 0.030%, and B: 0.0010% to 0.0050%, B/N that is the ratio of the content (mass percent) of B to the content (mass percent) of N being 0.80 or more, the remainder being Fe and inevitable impurities, and a ferrite microstructure containing 1.0% or more pearlite in terms of area fraction. The steel sheet for cans has a yield stress of 500 MPa or more, a tensile strength of 550 MPa or more, a uniform elongation of 10% or more, and a yield elongation of 5.0% or less.

A hot stamped article excellent in strength having a predetermined composition, having an average crystal grain size of prior austenite of 3 μm or less, containing at least one of lower bainite, martensite, and tempered martensite in an area rate of 90% or more, and having a grain boundary solid solution ratio Z, defined by Z=(mass % of one or both of Nb and Mo at the grain boundaries)/(mass % of one or more of Nb and Mo at time of dissolution) of 0.3 or more.