The present disclosure relates to an austenitic stainless alloy comprising in weight % (wt %): C less than 0.03; Si less than 1.0; Mn less than or equal to 1.2; Cr 26.0 to 30.0; Ni 29.0 to 37.0; Mo 6.1 to 7.1 or (Mo+W/2) 6.1 to 7.1; N 0.25 to 0.36; P less than or equal to 0.04; S less than or equal to 0.03; Cu less than or equal to 0.4; balance Fe and unavoidable impurities and to the use thereof and to products made thereof. Thus, the austenitic stainless alloy comprises a low content of manganese in combination with a high content of nitrogen. The present disclosure also relates to the use of said austenitic stainless alloy, especially in highly corrosive environments and to products made of thereof.

A high-ductility, high-strength steel sheet having excellent close-contact bendability and a method for producing the same. The steel sheet has a specified chemical composition and a microstructure comprising, by area percentage, 50% or more of a ferrite phase, 5% to 30% of a pearlite phase, and 15% or less in total of bainite, martensite, and retained austenite, in which the area percentage of ferrite grains each containing three or more cementite grains having an aspect ratio of 1.5 or less is 30% or less, and the number of inclusions having a particle size of 10 μm or more present in a portion extending from a surface to a ¼ thickness position is 2.0 particles/mm.sup.2 or less.

A high-strength steel sheet with a tensile strength of 1,180 MPa or more has a predetermined chemical composition and a steel microstructure in which the area fraction of ferrite is 5% or less, the area fraction of martensite is 2% to 10%, the area fraction of bainite is 5% to 37%, the area fraction of tempered martensite is 42% to 65%, the volume fraction of retained austenite is 3% to 15%, the average grain size of ferrite and bainite is 3 μm or less, in a region extending 50 μm from a surface of the steel sheet in a through-thickness direction, and the average grain size of prior austenite grains is 10 μm or less, the average grain size of the prior austenite grains in the through-thickness direction is 0.9 or less of the average grain size thereof in a rolling direction.

A steel sheet according to the present invention has a specific chemical composition and a steel microstructure including, in terms of area fraction, ferrite: 20% or more and 60% or less, a total of bainite and tempered martensite: 25% or more and 60% or less, retained austenite: 7% or more and 20% or less, fresh martensite: 8% or more and 40% or less, and the remainder: 5% or less. Cementite particles are present in the retained austenite, a ratio of an area fraction of the cementite particles in the retained austenite to an area fraction of the retained austenite is 5% or more and 25% or less, and the steel sheet has a tensile strength of 980 MPa or more.

This austenitic stainless steel contains, in terms of % by mass: C: 0.100% or less, Si: 3.00% or less, Mn: 0.01% or more and 5.00% or less, P: 0.100% or less, S: 0.0050% or less, Ni: 7.00% or more and 38.00% or less, Cr: 17.00% or more and 28.00% or less, Mo: 10.00% or less, and N: more than 0.100% and 0.400% or less, with a remainder being Fe and impurities, and a brightness difference ΔL of a surface of a stainless steel is 5 or less.

A high-strength stainless steel seamless pipe for oil country tubular goods has a composition that comprises, in mass%, C : 0.002 to 0.05%, Si: 0.05 to 0.50%, Mn: 0.04 to 1.80%, P: 0.030% or less, S: 0.002% or less, Cr: more than 14.0% and 17.0% or less, Ni: 4.0 to 8.0%, Mo: 1.5 to 3.0%, Al: 0.005 to 0.10%, V : 0.005 to 0.20%, Co: 0.01 to 1.0%, N : 0.002 to 0.15%, and O: 0.006% or less, and that satisfies the predetermined formulae, and in which the balance is Fe and incidental impurities, the high-strength stainless steel seamless pipe having a microstructure containing prior austenite having an average grain size of 40 .Math.m or less, the high-strength stainless steel seamless pipe having a yield strength of 758 MPa or more.

A steel sheet having a tensile strength (TS) of 1180 MPa or more, high LME resistance, and good weld fatigue properties. The steel sheet has a specific chemical composition and a specific steel microstructure. Crystal grains containing an oxide of Si and/or Mn in a region within 4.9 μm in a thickness direction from a surface of the steel sheet have an average grain size in the range of 3 to 10 μm, the lowest Si concentration L.sub.Si and the lowest Mn concentration L.sub.Mn in the region within 4.9 μm in the thickness direction from the surface of the steel sheet and a Si concentration T.sub.Si and a Mn concentration T.sub.Mn at a quarter thickness position of the steel sheet satisfy a specified formula.

A steel sheet with a tensile strength (TS) of 780 MPa or more and less than 1180 MPa, a member, and a method for producing them. In a region of the steel sheet within 4.9 μm in the thickness direction, a region with a Si concentration not more than one-third of the Si concentration in the chemical composition of the steel sheet and with a Mn concentration not more than one-third of the Mn concentration in the chemical composition of the steel sheet has a thickness of 1.0 μm or more. The lowest Si concentration L.sub.Si and the lowest Mn concentration L.sub.Mn in the region within 4.9 μm from the surface of the steel sheet and a Si concentration T.sub.Si and a Mn concentration T.sub.Mn at a quarter thickness position of the steel sheet satisfy the following formula (1):

L.sub.Si+L.sub.Mn≤(T.sub.Si+T.sub.Mn)/4  (1).

Provided is a metal gasket including, expressed in mass %, C: 0.10% or less, Si: 1.0% or less, Mn: 2.0% or less, P: 0.04% or less (including 0%), S: 0.01% or less (including 0%), Ni: 25.0-60.0%, Cr: 10.0-20.0%, either Mo or W alone, or both Mo+W/2:0.05-5.0%, Al: more than 0.8% to 3.0% or less, Ti: 1.5-4.0%, Nb: 0.05-2.5%, V: 1.0% or less (including 0%), B: 0.001-0.015%, Mg: 0.0005-0.01%, S/Mg: 1.0 or less, N: 0.01% or less (including 0%), and O: 0.005%) or less (including 0%), with the remainder being Fe and unavoidable impurities. The metal gasket has a metal structure in which a precipitate γ′ phase having an average equivalent circle diameter of 25 nm or larger is not present within the austenite base.

The present invention provides a hot stamping component having a tensile strength of 1350 Mpa or greater, including a microstructure including prior austenite grains (PAG), wherein an average particle diameter of the PAGs is 35 μm or less.