An annealing separator composition for a grain-oriented electrical steel sheet according to an exemplary embodiment of the present invention contains a composite metal oxide containing Mg and a metal M, wherein the metal M is one or more of Be, Ca, Ba, Sr, Sn, Mn, Fe, Co, Ni, Cu, and Zn.

An austenitic stainless steel material that has a passivation film on a surface is provided. The austenitic stainless steel material has a chemical composition consisting of, in mass%, C: 0.10% or less, Si: 1.0% or less, Mn: 8.0-10.0%, P: 0.030% or less, S: 0.003% or less, Cr: 15.0-18.0%, Ni: 7.0-9.0%, N: 0.15-0.25%, Al: 0.005-0.20%, Ca: 0.0005-0.01%, Cu: less than 1.0%, Mo: less than 1.0%, B: 0-0.0050%, Nb: 0-0.50%, Ti: 0-0.50%, V: 0-0.50%, W: 0-0.50%, Zr: 0-0.50%, Co: 0-0.50%, Mg: 0-0.005%, Ga: 0-0.005%, Hf: 0-0.10%, REM: 0-0.10%, and the balance: Fe and impurities. An f value, namely, [Ni + 0.72Cr + 0.88Mo + 1.11Mn - 0.27Si + 0.53Cu + 12.93C + 7.55N], is more than 29.5 and less than 32.5.

A bolt of the present invention has a composition comprising: 0.50 mass % or greater and 0.65 mass % or less of carbon (C), 1.5 mass % or greater and 2.5 mass % or less of silicon (Si), 1.0 mass % or greater and 2.0 mass % or less of chromium (Cr), 0.2 mass % or greater and 1.0 mass % or less of manganese (Mn), 1.5 mass % or greater and 5.0 mass % or less of molybdenum (Mo), wherein a total amount of phosphorous (P) and sulfur (S) as impurities is 0.03 mass % or less, the remaining is iron (Fe), and the bolt comprises an iron based oxide film with a film thickness of 3 μm or greater and 20 μm or less on the surface thereof. The bolt has excellent delayed fracture resistance and reliably provides a fastening axial force.

A method of forming a shaped steel object is provided. The method includes cutting a blank from an alloy composition including 0.05-0.5 wt. % carbon, 4-12 wt. % manganese, 1-8 wt. % aluminum, 0-0.4 wt. % vanadium, and a remainder balance of iron. The method also includes heating the blank until the blank is austenitized to form a heated blank, transferring the heated blank to a press, forming the heating blank into a predetermined shape to form a stamped object, and decreasing the temperature of the stamped object to a temperature between a martensite start (Ms) temperature of the alloy composition and a martensite final (Mf) temperature of the alloy composition to form a shaped steel object comprising martensite and retained austenite.

A method for treating an inner wall surface of a treatment object uses a treatment object that is at least one of a container housing an ozone gas, a treatment container housing an object to be subjected to a surface treatment using an ozone gas and a pipe configured to supply an ozone gas. The method for treating an inner wall surface of a treatment object includes the steps of: determining whether an abnormal part is present in the inner wall surface of the treatment object or not; and distributing an ozone gas having a concentration of 10% by volume or more and 30% by volume or less and a temperature of 60° C. or less such that the ozone gas contacts the inner wall surface of the treatment object after the step of determining whether an abnormal part is present or not.

A method for treating an inner wall surface of a treatment object uses a treatment object that is at least one of a container housing an ozone gas, a treatment container housing an object to be subjected to a surface treatment using an ozone gas and a pipe configured to supply an ozone gas. The method for treating an inner wall surface of a treatment object includes the steps of: determining whether an abnormal part is present in the inner wall surface of the treatment object or not; and distributing an ozone gas having a concentration of 10% by volume or more and 30% by volume or less and a temperature of 60° C. or less such that the ozone gas contacts the inner wall surface of the treatment object after the step of determining whether an abnormal part is present or not.

A method of forming a shaped steel object is provided. The method includes cutting a blank from an alloy composition including 0.05-0.5 wt. % carbon, 4-12 wt. % manganese, 1-8 wt. % aluminum, 0-0.4 wt. % vanadium, and a remainder balance of iron. The method also includes heating the blank until the blank is austenitized to form a heated blank, transferring the heated blank to a press, forming the heating blank into a predetermined shape to form a stamped object, and decreasing the temperature of the stamped object to a temperature between a martensite start (Ms) temperature of the alloy composition and a martensite final (Mf) temperature of the alloy composition to form a shaped steel object comprising martensite and retained austenite.

A method for manufacturing a metal ring laminate includes: performing an aging treatment on a metal ring laminate in which a plurality of metal rings made of maraging steel are laminated; and performing a nitriding treatment on the metal ring laminate that has been nitrided. Oxidizing treatment is performed after the aging treatment but before the nitriding treatment at a temperature equal to or higher than 350° C. and lower than an aging treatment temperature.

A method for manufacturing a metal ring laminate includes: performing an aging treatment on a metal ring laminate in which a plurality of metal rings made of maraging steel are laminated; and performing a nitriding treatment on the metal ring laminate that has been nitrided. Oxidizing treatment is performed after the aging treatment but before the nitriding treatment at a temperature equal to or higher than 350° C. and lower than an aging treatment temperature.

Provided is a stainless steel substrate for a solar cell, the stainless steel substrate including, by mass %, Cr: 9% to 25%, C: 0.03% or less, Mn: 2% or less, P: 0.05% or less, S: 0.01% or less, N: 0.03% or less, Al: 0.005% to 5.0%, Si: 0.05% to 4.0%, and a remainder including Fe and unavoidable impurities, in which an oxide film containing (i) Al.sub.2O.sub.3 in an amount of 50% or more or containing (i) Al.sub.2O.sub.3 and (ii) SiO.sub.2 in a total amount of 50% or more is formed on a surface of stainless steel having a composition which contains Al: 0.5% or more and/or Si: 0.4% or more and satisfies the following expression (1).
Cr+10Si+Mn+Al>24.5  (1)