A vacuum solid solution method for nickel-free high manganese and nitrogen is provided and relates to the technical field of metal material heat treatment. By vacuumizing, heat homogenizing, keeping the temperature in the final temperature range, deoxidation, and rapid cooling treatment, the present method forms a single austenitic structure from the raw materials, and promotes full and uniform dispersion of nitrogen carbide, providing a nickel-free high nitrogen stainless steel with more stable comprehensive performance and wider range of application.

Grain-oriented electrical steel sheet excellent in magnetic properties and adhesion of a primary coating to a base steel sheet and with few defects where the base metal is exposed in point defects and a method for manufacturing grain-oriented electrical steel sheet are provided. This is characterized by being provided with a base steel sheet and a primary coating. The primary coating satisfies (1) Number density D3 of Al concentrated regions: 0.015 to 0.150/μm.sup.2 (2) (Area S5 of regions comprised of anchoring oxide layer regions and Al concentrated regions)/(area S3 of Al concentrated regions)≥0.30, (3) Distance H5 of mean value of heights in thickness direction of regions of comprised of anchoring oxide layer regions and Al concentrated regions minus HO: 0.4 to 4.0 μm, (4) (Perimeter L5 of regions comprised of anchoring oxide layer regions and Al concentrated regions)/(observed area S0): 0.020 to 0.500 μm/μ.sup.2, and (5) (Area S1 of anchoring oxide layer regions)/(observed area S0)≥0.15.

An austenitic stainless steel having excellent processability and surface characteristics and a method of manufacturing the austenitic stainless steel are disclosed. The austenitic stainless steel includes, by weight %, 0.005% to 0.15% of carbon (C), 0.1% to 1.0% of silicon (Si), 0.1% to 2.0% of manganese (Mn), 6.0% to 10.5% of nickel (Ni), 16% to 20% of chromium (Cr), 0.005% to 0.2% of nitrogen (N), the remainder iron (Fe) and other unavoidable impurities, wherein a degree of Ni surface negative segregation defined by the following Formula (1) is in a range of 0.6 to 0.9.
(C.sub.Ni-Min)/(C.sub.Ni-Ave)  Formula (1), where C.sub.Ni-Min is a minimum concentration of Ni on the surface of the austenitic stainless steel and C.sub.Ni-Ave is an average concentration of Ni on the surface of the austenitic stainless steel.

A seamless steel pipe of the present invention is a seamless steel pipe having a composition that includes, in mass %, C: 0.02 to 0.12%, Si: 0.010 to 1.00%, Mn: 0.10 to 2.00%, P: 0.050% or less, S: 0.004% or less, Al: 0.010 to 0.100%, Cu: 0.03 to 0.80%, Ni: 0.02 to 0.50%, Cr: 0.55 to 1.00%, Sb: 0.005 to 0.20%, and the balance Fe and incidental impurities, and satisfying the following formula (1),

1.7×Cu*+11×Cr*+3.8×Sb*≥13.5   (1), where Cu*, Cr*, and Sb* represent average concentrations of Cu, Cr, and Sb, respectively, in mass %, as measured in a region 0.5 to 2.0 mm away from an outer surface of the steel pipe, the seamless steel pipe having a yield strength of 230 MPa or more, and a tensile strength of 380 MPa or more.

Provided is a steel used for chassis parts, etc. of an automobile and, more specifically, to a hot rolled steel plate for an electric resistance welded steel pipe, which shows an excellent weldability in electric resistance welding, and a manufacturing method thereof.

A stainless steel material including a base material made of ferritic stainless steel, a Cr oxide layer formed on a surface of the base material, and a spinel oxide layer formed on a surface of the Cr oxide layer, wherein a chemical composition of the base material satisfies [16.0≤Cr+3×Mo−2.5×B−17×C−3−Si≤35.0], a thickness of the Cr oxide layer (T.sub.Cr) and a thickness of the spinel oxide layer (T.sub.S) satisfy [0.55≤T.sub.Cr/T.sub.S≤6.7], the base material contains precipitate including one or more kinds selected from a M.sub.23C.sub.6, a M.sub.2B, a complex precipitate in which M.sub.2B acts as a precipitation nucleus, and M.sub.23C.sub.6 precipitates on a surface of the M.sub.2B, and a complex precipitate in which NbC acts as a precipitation nucleus, and M.sub.23C.sub.6 precipitates on a surface of the NbC, and a part of the precipitate protrude from the surface of the Cr oxide layer.

A duplex stainless steel has reduced precipitation risks of Al nitride and Cr nitride which are undesirable precipitates, and has superior low temperature toughness. The duplex stainless steel has in mass %, indicated as “%”, C: 0.001 to 0.030%, Si: 0.05 to 0.5%, S: not more than 0.002%, Ni: 6 to 7.5%, Cr: 23 to 26%, Mo: 2 to 4.0%, N: 0.20 to 0.40%, Al: 0.005 to 0.03%, Mn: 0.05 to 0.3%, B: 0.0001 to 0.0050% and Fe, and the remainder being inevitable impurities. The duplex stainless steel has an impact value of not less than 87.5 J/cm.sup.2 at −46±2° C. as defined in Japanese Industrial Standards Z2242.

An aluminum-based plated steel sheet according to an aspect of the present invention includes: a base material; an aluminum-based plating layer located above the base material; and an intermetallic compound layer that is located between the base material and the aluminum-based plating layer and contains an intermetallic compound of Al and Fe, in which the base material has a chemical component within a predetermined range, the aluminum-based plating layer contains, on average, 80 mass % or more and 97 mass % or less of Al, 3 mass % or more and 15 mass % or less of Si, 0 mass % or more and 5 mass % or less of Zn, 0 mass % or more and 5 mass % or less of Fe, 0 mass % or more and 3 mass % or less in total of one or more selected from the group consisting of Mg and Ca, and impurities so that a total amount thereof is 100 mass %, an average value of a thickness of the intermetallic compound layer is 2 μm or more and 10 μm or less, a maximum value of the thickness of the intermetallic compound layer is 10 μm or more and 25 μm or less, and a standard deviation of the thickness of the intermetallic compound layer is 2 μm or more and 10 μm or less.

The present invention relates to steel used for a sash component and the like of a vehicle and, more specifically, to a hot-rolled steel sheet having excellent durability and a method for manufacturing same, the hot-rolled steel sheet having no cracks formed on a material and a welding heat-affected zone (HAZ) even after pipemaking and molding due to a smaller decrease in the strength of the welding heat-affected zone formed during electric resistance welding in comparison with the strength of the material (base material).

A steel for forging mechanical parts including the following elements, expressed in percentage by weight 0.2%≤C≤0.5%; 0.8%≤Mn≤1.5% ; 0.4%≤Si≤1%; 0.15%≤V≤0.6%; 0.01%≤Nb≤0.15%; 0.01%≤Cr≤0.5%; 0.01%≤P≤0.05%; 0.04%≤S≤0.09%; 0.01%≤N≤0.025%; and can contain one or more of the following optional elements 0%≤Al≤0.05%; 0%≤Mo≤0.5%; 0.01%≤Ni≤0.5%; 0%≤Ti≤0.2%; 0%≤B≤0.008%; 0%≤Cu≤0.5%; the remainder composition being composed of iron and unavoidable impurities caused by processing, the microstructure of said steel comprising 50% to 90% of Pearlite, 10% to 40% of Ferrite, with an optional presence of acicular ferrite between 0% and 2%, a niobium equivalent of 80% or more.