The invention relates a duplex ferritic austenitic stainless steel having high formability utilizing the TRIP effect and high corrosion resistance with the balanced pitting resistance equivalent. The duplex stainless steel contains less than 0.04 weight % carbon, less than 0.7 weight % silicon, less than 2.5 weight % manganese, 18.5-22.5 weight % chromium, 0.8-4.5 weight % nickel, 0.6-1.4 weight % molybdenum, less than 1 weight % copper, 0.10-0.24 weight % nitrogen, the rest being iron and inevitable impurities occurring in stainless steels.

The invention relates a duplex ferritic austenitic stainless steel having high formability utilizing the TRIP effect and high corrosion resistance with the balanced pitting resistance equivalent. The duplex stainless steel contains less than 0.04 weight % carbon, less than 0.7 weight % silicon, less than 2.5 weight % manganese, 18.5-22.5 weight % chromium, 0.8-4.5 weight % nickel, 0.6-1.4 weight % molybdenum, less than 1 weight % copper, 0.10-0.24 weight % nitrogen, the rest being iron and inevitable impurities occurring in stainless steels.

To provide an austenitic stainless steel material having a high creep strength and a high creep ductility even in a high-temperature environment at 800° C. or more. An austenitic stainless steel material according to the present disclosure has a chemical composition that includes, in mass %: C: 0.060% or less; Si: 1.0% or less; Mn: 2.00% or less; P: 0.0010 to 0.0400%; S: 0.010% or less; Cr: 10 to 25%; Ni: 25 to 45%; Nb: 0.2 to 2.0%; W: 2.5 to 6.0%; B: 0.0010 to 0.0100%: Al: 2.5 to 4.5%; and the balance being Fe and impurities, and satisfies Formulae (1) and (2), and the sum of the content of dissolved Nb and the content of dissolved W is 3.2 mass % or more.
(W/184+Nb/93)/(C/12)≥5.5  (1)
(W/184+Nb/93)/(B/11)≤450  (2) In Formulae (1) and (2), the content in mass % of the corresponding element is substituted for each symbol of element.

To provide an austenitic stainless steel material having a high creep strength and a high creep ductility even in a high-temperature environment at 800° C. or more. An austenitic stainless steel material according to the present disclosure has a chemical composition that includes, in mass %: C: 0.060% or less; Si: 1.0% or less; Mn: 2.00% or less; P: 0.0010 to 0.0400%; S: 0.010% or less; Cr: 10 to 25%; Ni: 25 to 45%; Nb: 0.2 to 2.0%; W: 2.5 to 6.0%; B: 0.0010 to 0.0100%: Al: 2.5 to 4.5%; and the balance being Fe and impurities, and satisfies Formulae (1) and (2), and the sum of the content of dissolved Nb and the content of dissolved W is 3.2 mass % or more.
(W/184+Nb/93)/(C/12)≥5.5  (1)
(W/184+Nb/93)/(B/11)≤450  (2) In Formulae (1) and (2), the content in mass % of the corresponding element is substituted for each symbol of element.

A high-strength structural steel material having excellent fatigue crack propagation inhibitory characteristics according to an aspect of the present invention contains, by weight, 0.02-0.12% of C, 1.7-2.5% of Mn, 0.01-0.8% of Si, 0.005-0.5% of Al, and the balance Fe and unavoidable impurities, wherein a microstructure of the structural steel sheet material is divided into a surface layer portion outside and a central portion inside along a thickness direction; the surface layer portion comprises tempered bainite as a matrix structure, fresh martensite as a second structure, and austenite as a residual structure; and the central portion comprises lath bainite.

Provided is a high-strength steel sheet having high impact resistance. The steel sheet includes: by weight %, carbon (C): 0.05% to 0.14%, silicon (Si): 0.01% to 1.0%, manganese (Mn): 1.5% to 2.5%, aluminum (Al): 0.01% to 0.1%, chromium (Cr): 0.005% to 1.0%, phosphorus (P): 0.001% to 0.05%, sulfur (S): 0.001% to 0.01%, nitrogen (N): 0.001% to 0.01%, niobium (Nb): 0.005% to 0.06%, titanium (Ti): 0.005% to 0.11%, and the balance of iron (Fe) and inevitable impurities. The steel sheet has a microstructure comprising ferrite and bainite in a total area fraction of 90% or more. The steel sheet has a value of 0.05 to 1.0 as a shear texture ({110}<112>, {112}<111>) area ratio of a center region (ranging deeper than 1/10t to ½t in a thickness direction, t refers to thickness (mm)) and a surface region (ranging from a surface to 1/10t in the thickness direction).

Provided is a high-strength steel sheet having high impact resistance. The steel sheet includes: by weight %, carbon (C): 0.05% to 0.14%, silicon (Si): 0.01% to 1.0%, manganese (Mn): 1.5% to 2.5%, aluminum (Al): 0.01% to 0.1%, chromium (Cr): 0.005% to 1.0%, phosphorus (P): 0.001% to 0.05%, sulfur (S): 0.001% to 0.01%, nitrogen (N): 0.001% to 0.01%, niobium (Nb): 0.005% to 0.06%, titanium (Ti): 0.005% to 0.11%, and the balance of iron (Fe) and inevitable impurities. The steel sheet has a microstructure comprising ferrite and bainite in a total area fraction of 90% or more. The steel sheet has a value of 0.05 to 1.0 as a shear texture ({110}<112>, {112}<111>) area ratio of a center region (ranging deeper than 1/10t to ½t in a thickness direction, t refers to thickness (mm)) and a surface region (ranging from a surface to 1/10t in the thickness direction).

A method of producing a high performance stainless steel exhibiting corrosion resistance even under a very severe corrosion environment at temperatures of equal to or higher than 180° C., for example, 220° C., while maintaining strength and toughness by improving the corrosion resistance of a conventional martensitic stainless steel with high strength. The martensitic stainless steel includes, in mass %, C: 0.005% to 0.05%, Si: equal to or less than 1.0%, Mn: equal to or less than 2.0%, Cr: 16 to 18%, Ni: 2.5 to 6.5%, Mo: 1.5 to 3.5%, W: equal to or less than 3.5%, Cu: equal to or less than 3.5%, V: 0.01 to 0.08%, Sol.Al: 0.005 to 0.10%, N: equal to or less than 0.05%, and Ta: 0.01 to 0.06%, and the balance Fe with inevitable impurities.

A method of producing a high performance stainless steel exhibiting corrosion resistance even under a very severe corrosion environment at temperatures of equal to or higher than 180° C., for example, 220° C., while maintaining strength and toughness by improving the corrosion resistance of a conventional martensitic stainless steel with high strength. The martensitic stainless steel includes, in mass %, C: 0.005% to 0.05%, Si: equal to or less than 1.0%, Mn: equal to or less than 2.0%, Cr: 16 to 18%, Ni: 2.5 to 6.5%, Mo: 1.5 to 3.5%, W: equal to or less than 3.5%, Cu: equal to or less than 3.5%, V: 0.01 to 0.08%, Sol.Al: 0.005 to 0.10%, N: equal to or less than 0.05%, and Ta: 0.01 to 0.06%, and the balance Fe with inevitable impurities.

A high strength galvanized steel sheet having excellent surface qualities, plating adhesion, and formability is provided, wherein a galvanized layer is formed on a cold-rolled steel sheet comprising 0.1-0.3 wt % of C, 1-2.5 wt % of Si, 2.5-8 wt % of Mn, 0.001-0.5 wt % of sol. Al, at most 0.04 wt % of P, at most 0.015 wt % of S, at most 0.02 wt % of N (excluding 0 wt %), 0.1-0.7 wt % of Cr, at most 0.1 wt % of Mo, (48/14)*[N] to 0.1 wt % of Ti, 0.005-0.5 wt % of Ni, 0.01-0.07 wt % of Sb, at most 0.1 wt % of Nb, and at most 0.005 wt % of B, with the remainder being Fe and other inevitable impurities.