Abstract: A high-Ni alloy having excellent weld-hot-cracking resistance includes, in mass %, Cr: 16-30%, Ni: 18-50%, Al: 0.01-1.0%, and Ti: 0.01-1.5%. In a first aspect of the invention, a relationship between number density of TiC precipitates having 1.0 ?m or more of equivalent circle diameter and Mg content in steel satisfies formula (1) below. In a second aspect of the invention, S average concentration in oxide- and sulfide-inclusions is 0.70 mass % or more. In a third aspect of the invention, mass ratios of CaO, MgO, and Al2O3 in inclusions, where O or S is detected, satisfy formula (2), the mass ratios being respectively calculated from average concentrations of Ca, Mg and Al in the inclusions, (1) number density of TiC (number of pieces/mm2)?463?9.5×Mg concentration in steel (mass ppm) and (2) [CaO?0.6×MgO] (mass %)/[CaO+MgO+Al2O3] (mass %)?0.20.

Abstract: An austenitic stainless steel, which consists of by mass percent, C: not more than 0.02%, Si: not more than 1.5%, Mn: not more than 2%, Cr: 17 to 25%, Ni: 9 to 13%, Cu: more than 0.26% not more than 4%, N: 0.06 to 0.35%, sol. Al: 0.008 to 0.03%. One or more elements selected from Nb, Ti, V, TA, Hf, and Zr in controlled amounts can be included with the balance being Fe and impurities. P, S, Sn, As, Zn, Pb and Sb among the impurities are controlled as P: 0.006 to 0.04%, S: 0.0004 to 0.03%, Sn: 0.001 to 0.1%, As: not more than 0.01%, Zn: not more than 0.01%, Pb: not more than 0.01% and Sb: not more than 0.01%. The amounts of S, P, Sn, As, Zn, Pb and Sb and the amounts of Nb, Ta, Zr, Hf, and Ti are further controlled using formulas.

Abstract: A high-Ni alloy having excellent weld-hot-cracking resistance includes, in mass %, Cr: 16-30%, Ni: 18-50%, Al: 0.01-1.0%, and Ti: 0.01-1.5%. In a first aspect of the invention, a relationship between number density of TiC precipitates having 1.0 ?m or more of equivalent circle diameter and Mg content in steel satisfies formula (1) below. In a second aspect of the invention, S average concentration in oxide- and sulfide-inclusions is 0.70 mass % or more. In a third aspect of the invention, mass ratios of CaO, MgO, and Al2O3 in inclusions, where O or S is detected, satisfy formula (2), the mass ratios being respectively calculated from average concentrations of Ca, Mg and Al in the inclusions, (1) number density of TiC (number of pieces/mm2)?463?9.5×Mg concentration in steel (mass ppm) and (2) [CaO?0.6×MgO] (mass %)/[CaO+MgO+Al2O3] (mass %)?0.20.

Abstract: A method for producing an austenitic heat resistant steel in which a difference between a content of Nb and an amount of Nb analyzed as extraction residues satisfies [0.170?Nb?NbER?0.480], the method including: a forming step of machining and forming a steel having a predetermined chemical composition into a product shape; a solution heat treatment step of performing, after the forming step, heat treatment under conditions including a heat treatment temperature satisfying [?250Nb+1200?T??100Nb+1290] and a soaking time satisfying [405?0.3T?t?2475?1.5T]; and a cooling step of performing cooling after the solution heat treatment step.

Abstract: There is provided a duplex stainless steel tube including a chemical composition consisting of, in mass %, C: 0.008 to 0.030%, Si: 0.10 to 0.70%, Mn: 0.80 to 2.60%, P: 0.030% or less, S: 0.0001 to 0.0050%, O: 0.0004 to 0.0150%, Sn: 0.0001% or more to less than 0.0100%, Cu: 0.10 to 2.50%, Ni: more than 2.50 to 5.50% or less, Cr: 21.5 to 25.5%, Mo: 0.10 to 0.50%, N: 0.050 to 0.200%, Al: 0.200% or less, and optional elements, with the balance: Fe and impurities, wherein 4S+8O+Sn is 0.0040 to 0.0900, and 4S+Sn is 0.0180 or less.

Abstract: Provided is an austenitic stainless steel weld joint that is excellent in polythionic acid SCC resistance and naphthenic acid corrosion resistance, and is also excellent in creep ductility. An austenitic stainless steel weld joint includes a base material and a weld metal. The weld metal has a chemical composition at its width-center position and at its thickness-center position consisting of, in mass %, C: 0.050% or less, Si: 0.01 to 1.00%, Mn: 0.01 to 3.00%, P: 0.030% or less, S: 0.015% or less, Cr: 15.0 to 25.0%, Ni: 20.0 to 70.0%, Mo: 1.30 to 10.00%, Nb: 0.05 to 3.00%, N: 0.150% or less, and B: 0.0050% or less, with the balance: Fe and impurities.

Abstract: There is provided an austenitic heat resistant steel including a chemical composition that consists of, in mass %, C: 0.04 to 0.12%, Si: 0.01 to 0.30%, Mn: 0.50 to 1.50%, P: 0.001 to 0.040%, S: less than 0.0050%, Cu: 2.2 to 3.8%, Ni: 8.0 to 11.0%, Cr: 17.7 to 19.3%, Mo: 0.01 to 0.55%, Nb: 0.400 to 0.650%, B: 0.0010 to 0.0060%, N: 0.050 to 0.160%, Al: 0.025% or less, and O: 0.020% or less, with the balance: Fe and impurities and that satisfies [0.170?Nb?NbER?0.480].

Abstract: Provided is an austenitic stainless steel weld joint that is excellent in polythionic acid SCC resistance and naphthenic acid corrosion resistance, and is also excellent in creep ductility. An austenitic stainless steel weld joint includes a base material and a weld metal. The weld metal has a chemical composition at its width-center position and at its thickness-center position consisting of, in mass %, C: 0.050% or less, Si: 0.01 to 1.00%, Mn: 0.01 to 3.00%, P: 0.030% or less, S: 0.015% or less, Cr: 15.0 to 25.0%, Ni: 20.0 to 70.0%, Mo: 1.30 to 10.00%, Nb: 0.05 to 3.00%, N: 0.150% or less, and B: 0.0050% or less, with the balance: Fe and impurities.

Abstract: An austenitic stainless steel material is provided that has high creep strength even when used at an average operation temperature of more than 600 to 750° C. after welding with higher heat input, and furthermore, has excellent stress relaxation cracking resistance even after use for a long time period at the average operation temperature after welding with higher heat input. The steel material has a chemical composition which consists of, in mass %, C: 0.030% or less, Si: 1.50% or less, Mn: 2.00% or less, P: 0.045% or less, S: 0.0300% or less, Cr: 15.00 to 25.00%, Ni: 8.00 to 20.00%, N: 0.050 to 0.250%, Nb: 0.10 to 1.00%, Mo: 0.05 to 5.00%, and B: 0.0005 to 0.0100%, with the balance being Fe and impurities, and a ratio of the dissolved N amount (mass %) with respect to the content of N (mass %) in the steel material is 0.40 to 0.90.

Abstract: An austenitic stainless steel material is provided that has excellent sensitization resistance properties even after use for a long time period at an average operation temperature of 400 to 700° C. after welding with higher heat input. The steel material of the present disclosure has a chemical composition which contains, in mass %, C: 0.020% or less, Si: 1.50% or less, Mn: 2.00% or less, P: 0.045% or less, S: 0.0300% or less, Cr: 15.00 to 25.00%, Ni: 9.00 to 20.00%, N: 0.05 to 0.15%, Nb: 0.1 to 0.8%, Mo: 0.10 to 4.50%, and W: 0.01 to 1.00%, and satisfies Formula (1). The content of Nb in a residue obtained by an extraction residue method is, in mass %, 0.050 to 0.267%, and the content of Cr in the residue is, in mass %, 0.125% or less. 21.9Mo+5.9W?5.

Abstract: There is provided an austenitic heat resistant alloy including a chemical composition that contains, in mass percent: C: 0.04 to 0.18%, Si: 1.5% or less; Mn: 2.0% or less, P: 0.020% or less, S: 0.030% or less, Cu: 0.10% or less, Ni: 20.0 to 30.0%, Cr: 21.0 to 24.0%, Mo: 1.0 to 2.0%, Nb: 0.10 to 0.40%, Ti: 0.20% or less, Al: 0.05% or less, N: 0.10 to 0.35%, and B: 0.0015 to 0.005%, with the balance: Fe and impurities, the austenitic heat resistant alloy satisfying [P+6B?0.040].

Abstract: An austenitic stainless steel is provided which has a chemical composition that consists, by mass %, of: C: 0.015% or less, Si: 1.00% or less, Mn: 2.00% or less, P: 0.05% or less, S: 0.030% or less, Cr: 16.0% or more and less than 22.0%, Ni: 11.0 to 16.0%, Mo: 2.5 to 5.0%, N: 0.07% or more and less than 0.15%, Nb: 0.20 to 0.50%, Al: 0.005 to 0.040%, Sn: 0 to 0.080%, Zn: 0 to 0.0060%, Pb: 0 to 0.030%, and the balance: Fe and impurities, and that satisfies the formula [MoSS/Mo?0.98] (MoSS: Mo amount dissolved in the steel).

Abstract: Provided is an austenitic stainless steel weld joint that is excellent in polythionic acid SCC resistance and naphthenic acid corrosion resistance, and is also excellent in creep ductility. An austenitic stainless steel weld joint includes a base material and a weld metal. The weld metal has a chemical composition at its width-center position and at its thickness-center position consisting of, in mass %, C: 0.050% or less, Si: 0.01 to 1.00%, Mn: 0.01 to 3.00%, P: 0.030% or less, S: 0.015% or less, Cr 15.0 to 25.0%, Ni: 20.0 to 70.0%, Mo: 1.30 to 10.00%, Nb: 0.05 to 3.00%, N: 0.150% or less, and B: 0.0050% or less, with the balance: Fe and impurities.

Abstract: A duplex stainless steel with occurrence of pitting suppressed is provided. A duplex stainless steel according to the present disclosure has a chemical composition consisting of, in mass %, Cr: more than 27.00% to 29.00%, Mo: 2.50 to 3.50%, Ni: 5.00 to 8.00%, W: 4.00 to 6.00%, Cu: 0.01 to less than 0.10%, N: more than 0.400% to 0.600%, C: 0.030% or less, Si: 1.00% or less, Mn 1.00% or less, sol.Al: 0.040% or less, V: 0.50% or less, O: 0.010% or less, P: 0.030% or less, and S: 0.020% or less with the balance being Fe and impurities and satisfying Formula (1), a microstructure consisting of 35 to 65 volume % of ferrite phase with the balance being the austenite phase, and the area fraction of Cu precipitated in the ferrite phase is 0.5% or less. Cr+4.0×Mo+2.0×W+20×N?5×ln(Cu)?65.

Abstract: A high-strength austenitic stainless steel, which has good hydrogen embrittlement resistance and hydrogen fatigue resistance, has a chemical composition including, in mass %, C: up to 0.10%; Si: up to 1.0%; Mn: not less than 3.0% and less than 7.0 %; Cr: 15 to 30%; Ni: not less than 12.0% and less than 17.0%; Al: up to 0.10%; N: 0.10 to 0.50%; P: up to 0.050%; S: up to 0.050%; at least one of V: 0.01 to 1.0% and Nb: 0.01 to 0.50%; and other elements, the balance being Fe and impurities, wherein the ratio of the minor axis to the major axis of the austenite crystal grains is greater than 0.1, the crystal grain size number of austenite crystal grains is not lower than 8.0, and the tensile strength is not less than 1000 MPa.

Abstract: An austenitic stainless steel, which consists of by mass percent, C: not more than 0.02%, Si: not more than 1.5%, Mn: not more than 2%, Cr: 17 to 25%, Ni: 9 to 13%, Cu: more than 0.26% not more than 4%, N: 0.06 to 0.35%, sol. Al: 0.008 to 0.03%. One or more elements selected from Nb, Ti, V, TA, Hf, and Zr in controlled amounts can be included with the balance being Fe and impurities. P, S, Sn, As, Zn, Pb and Sb among the impurities are controlled as P: 0.006 to 0.04%, S: 0.0004 to 0.03%, Sn: 0.001 to 0.1%, As: not more than 0.01%, Zn: not more than 0.01%, Pb: not more than 0.01% and Sb: not more than 0.01%. The amounts of S, P, Sn, As, Zn, Pb and Sb and the amounts of Nb, Ta, Zr, Hf, and Ti are further controlled using formulas.

Abstract: An austenitic alloy material is provided that includes a base metal having a surface, and a film containing chromium oxide having a thickness of 0.1 to 50 ?m on at least one portion of the surface. A chemical composition at a depth position in the film at which the Cr concentration is highest contains, by atom %, 50% or more of Cr as a proportion occupied among components excluding O, C and N. The chemical composition of the base metal consists of, by mass %, C: 0.001 to 0.6%, Si: 0.01 to 5.0%, Mn: 0.1 to 10.0%, P: 0.08% or less, S: 0.05% or less, Cr: 15.0 to 55.0%, Ni: 30.0 to 80.0%, N: 0.001 to 0.25%, O: 0.02% or less, Mo: 0 to 20.0%, Cu: 0 to 5.0%, Co: 0 to 5.0%, W: 0 to 10.0%, Ta: 0 to 6.0%, Nb: 0 to 5.0%, Ti: 0 to 1.0%, B: 0 to 0.1%, Zr: 0 to 0.1%, Hf: 0 to 0.1%, Al: 0 to 1.0%, Mg: 0 to 0.1%, and Ca: 0 to 0.1%, the balance being Fe and impurities.

Abstract: A welded joint having high strength and good hydrogen embrittlement resistance is provided. A welded joint is a welded joint obtained by welding a base material using a welding material. The base material has a chemical composition of, in mass %: C: 0.005 to 0.1%; Si: up to 1.2%; Mn: 2.5 to 6.5%; Ni: 8 to 15%; Cr: 19 to 25%; Mo: 0.01 to 4.5%; V: 0.01 to 0.5%; Nb: 0.01 to 0.5% Al: less than 0.05%; N: 0.15 to 0.45%; O: up to 0.02%; P: up to 0.05%; and S: up to 0.04%, and a balance being iron and impurities, and which satisfies Equation (1). The welding material has a chemical composition which satisfies Equations (1) and (2). Ni+0.65Cr+0.98Mo+1.05Mn+0.35Si+12.6C?29??(1) 0.31C+0.048Si?0.02Mn?0.056Cr+0.007Ni?0.013Mo??1.

Abstract: An objective of the present invention is to provide an austenitic stainless steel that is excellent in polythionic acid SCC resistance and also excellent in creep ductility. An austenitic stainless steel according to the present invention includes a chemical composition consisting of, in mass %, C: 0.030% or less, Si: 0.10 to 1.00%, Mn: 0.20 to 2.00%, P: 0.040% or less, S: 0.010% or less, Cr: 16.0 to 25.0%, Ni: 10.0 to 30.0%, Mo: 0.1 to 5.0%, Nb: 0.20 to 1.00%, N: 0.050 to 0.300%, sol.Al: 0.0005 to 0.100%, and B: 0.0010 to 0.0080%, with the balance being Fe and impurities, and satisfying Formula (1): B+0.004?0.9C+0.017Mo2?0??(1) where symbols of elements in Formula (1) are to be substituted by contents of corresponding elements (mass %).

Abstract: An austenitic stainless steel includes base metal and a coating film formed on at least part of a surface of the base metal, a chemical composition of the base metal containing, in mass percent: C: 0.05% or less; Si: 1.0% or less; Mn: 2.0% or less; P: 0.040% or less; S: 0.010% or less; O: 0.020% or less; N: less than 0.050%; Ni: 12.0 to 27.0%; Cr: 15.0% or more to less than 20.0%; Cu: more than 3.5% to 8.0% or less; Mo: more than 2.0% to 5.0% or less; Co: 0.05% or less; Sn: 0.05% or less, V: 0 to 0.5%, Nb: 0 to 1.0%, Ti: 0 to 0.5%, W: 0 to 5.0%, Zr: 0 to 1.0%, Al: 0 to 0.5%, Ca: 0 to 0.01%, B: 0 to 0.01%, REM: 0 to 0.01%, and the balance: Fe and impurities, wherein a chemical composition at a maximum-Cr depth where a concentration of Cr in the coating film reaches a maximum satisfies, in at %, [(Cr+Ni+Cu+Mo)/Fe?1.0].