Disclosed is an austenitic stainless steel having an increased yield ratio. The disclosed austenitic stainless steel is characterized by comprising, in percent by weight (wt %), 0.1% or less (exclusive of 0) of C, 0.2% or less (exclusive of 0) of N, 1.5 to 2.5% of Si, 6.0 to 10.0% of Mn, 15.0 to 17.0% of Cr, 0.3% or less (exclusive of 0) of Ni, 2.0 to 3.0% of Cu, and the remainder of Fe and other inevitable impurities, and satisfying Expressions (1) and (2) below.

3.2≤5.53+1.4Ni−0.16Cr+17.1(C+N)+0.722Mn+1.4Cu−5.59Si≤7  Expression (1):

551-462(C+N)−9.2Si−8.1Mn−13.7Cr−29(Ni+Cu)≤110  Expression (2): wherein C, N, Si, Mn, Cr, Ni, and Cu indicate the content (wt %) of respective elements.

A normalizing heat-treated steel sheet having good low-temperature impact toughness and a method for manufacturing the same is provided. The normalizing heat treated steel sheet of the present invention contains, by weight %, C: 0.04 to 0.1%, Si: 0.05 to 0.5%, Mn: 1.0 to 2.0%, Sol. Al: 0.015 to 0.04%, Nb: 0.003 to 0.03%, Ti: 0.005 to 0.02%, Cu: 0.35% or less, Ni: 0.05 to 0.8%, N: 0.002 to 0.008%, P: 0.01% or less (excluding 0%), S: 0.003% or less, and a balance of Fe and unavoidable impurities and has a steel microstructure composed of 70 to 90 area % of polygonal ferrite having a grain size of 20 μm or less, and 10 to 30 area % of spheroidized pearlite.

A hot stamped body with high strength and good bendability, comprising a chemical composition consisting of: in mass %, C: 0.06% or more to less than 0.20%, Si: 0.010 to 1.00%, Mn: 1.20 to 3.00%, P: 0.100% or less, S: 0.010% or less, Al: 0.010 to 0.500%, N: 0.010% or less, Nb: 0.0010 to 0.020%, Ti: 0 to 0.10%, V: 0 to 0.10%, Cr: 0 to 0.50%, Mo: 0 to 1.00%, B: 0 to 0.0100%, Ni: 0 to 0.50%, REM: 0 to 0.0100%, Mg: 0 to 0.010%, Ca: 0 to 0.0100%, and Co: 0 to 2.0%, with the balance: Fe and impurities, wherein a microstructure includes martensite: 85% or more, a proportion of regions in the martensite where GAIQ values are 35000 or more to less than 45000 is 30 area % or more, and TS×α, is 105000 or more, and α is 75 or more.

A cold-rolled and heat-treated steel sheet having a microstructure of, in surface fraction: between 10% and 30% of retained austenite, said retained austenite being present as films having an aspect ratio of at least 3 and as Martensite Austenite islands, less than 8% of such Martensite Austenite islands having a size above 0.5 μm, at most 10% of fresh martensite and
recovered martensite containing precipitates of at least one element chosen among niobium, titanium and vanadium. A manufacturing method thereof is also provided.

A cold-rolled and heat-treated steel sheet having a microstructure consisting of, in surface fraction: between 10% and 30% of retained austenite, the retained austenite being present as films having an aspect ratio of at least 3 and as Martensite Austenite islands, less than 8% of the Martensite Austenite islands having a size above 0.5 μm, at most 1% of fresh martensite, at most 50% of tempered martensite, and recovered martensite containing precipitates of at least one element chosen among niobium, titanium and vanadium. A method for manufacturing the cold-rolled and heat-treated steel sheet is also described.

The rail having a chemical composition containing C: 0.70-0.85 mass %, Si: 0.50-1.60 mass %, Mn: 0.20-1.00 mass %, P: 0.035 mass % or less, S: 0.012 mass % or less, Cr: 0.40-1.30 mass %, the chemical composition satisfying the formula (1)
0.30≤[% Si]/10+[% Mn]/6+[% Cr]/3≤0.55  (1) where [% M] is the content in mass % of the element M,
the balance being Fe and inevitable impurities, where Vickers hardness of a region between positions where a depth from a surface of a rail head of 0.5 and 25 mm is ≥370 HV and <520 HV, a total area ratio of a pearlite microstructure and a bainite microstructure in the region is ≥98%, and an area ratio of the bainite microstructure in the region is >5% and <20%.

A high-strength galvanized steel sheet includes a steel sheet containing a predetermined component element, a mass ratio of a content amount of Si to a content amount of Mn in the steel (Si/Mn) being 0.2 or more, and a steel structure in which an average grain size of inclusions existing in an area extending from a surface to a position of ⅓ of a sheet thickness is 50 μm or less, and an average nearest distance between ones of the inclusions is 20 μm or more; and a galvanized layer provided on a surface of the steel sheet, in which an amount of diffusible hydrogen contained in the steel is less than 0.25 mass ppm, oxides containing predetermined elements in an outer layer portion of the steel sheet account for 0.010 g/m.sup.2 or more per one surface, and a tensile strength is 1100 MPa or more.

A low-carbon iron-chromium-molybdenum alloy comprises, in weight percent: carbon from about 0.1 to about 0.8 percent; manganese from about 0.1 to about 4 percent; silicon from about 0.1 to about 0.5 percent; chromium from 14 to about 16 percent; nickel up to about 8 percent; vanadium up to about 0.1 percent; molybdenum from 14 to about 16 percent; tungsten up to about 6 percent; niobium from about 0.1 to about 0.8 percent; cobalt up to about 0.2 percent; boron up to 0.1 percent; nitrogen up to about 0.1 percent; copper up to about 1.5 percent; sulfur up to about 0.05 percent; phosphorus up to about 0.05 percent; balance iron from about 50 to about 65 percent; and incidental impurities wherein the alloy contains a ratio of Cr/Mo of about 0.9 to about 1.1. The alloy can be used as a valve seat insert for combustion engines.

Provided is a high strength steel sheet that has a predetermined chemical composition and is manufactured under optimum conditions, the high strength steel sheet having a steel microstructure including, by area, ferrite: 30% or more and 80% or less, tempered martensite: 3.0% or more and 35% or less, and retained austenite: 8% or more, wherein the quotient of the area fraction of grains of the retained austenite, the grains having an aspect ratio of 2.0 or more and a minor axis length of 1 μm or less, divided by the total area fraction of the retained austenite is 0.3 or more, wherein the quotient of the average Mn content (mass %) in the retained austenite divided by the average Mn content (mass %) in the ferrite is 1.5 or more.

Provided is a high strength steel sheet that has a predetermined chemical composition and is manufactured under optimum conditions, the high strength steel sheet having a steel microstructure including, by area, ferrite: 30% or more and 80% or less, martensite: 5% or more and 35% or less, and retained austenite: 8% or more, wherein the quotient of the area fraction of grains of the retained austenite, the grains having an aspect ratio of 2.0 or more and a minor axis length of 1 μm or less, divided by the total area fraction of the retained austenite is 0.3 or more, wherein the quotient of the average Mn content (mass %) in the retained austenite divided by the average Mn content (mass %) in the ferrite is 1.5 or more.