Nippon Steel Patente

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Provided is a method for producing a grain-oriented electrical steel sheet in which a plurality of grooves extending in a direction generally parallel to the width direction is formed in the longitudinal direction of the steel sheet, the method including: a first groove formation step for forming a first groove comprising a plurality of grooves which extends in a direction generally parallel to the width direction on a cold-rolled steel sheet; a secondary recrystallization annealing step for annealing the cold-rolled steel sheet, so as to align the easy axis of magnetization of the cold-rolled steel sheet in the longitudinal direction to form a grain-oriented electrical steel sheet; and a second groove formation step for forming a second groove comprising a plurality of grooves which extends in a direction generally parallel to the width direction on the grain-oriented electrical steel sheet using a contact-type groove formation process.

A steel product having a specific chemical composition, wherein α is from 5.0 to 16.0 and β is 0.017 or less, the steel product having a tensile strength of from 615 MPa to 930 MPa, and having a microstructure at a portion that is 1/4 of a thickness from a surface of the steel product comprising lower bainite and martensite, wherein a total area ratio of the lower bainite and the martensite is 15.0% or more, a total area ratio of upper bainite, the lower bainite, and the martensite is 90.0% or more, and an area ratio of retained austenite is less than 1.7%. α = 0.50 × √[C] × (1 + 0.64[Si]) × (1 + 4.10[Mn]) × (1 + 0.27[Cu]) × (1 + 0.52[Ni]) × (1 + 2.33[Cr]) × (1 + 3.14[Mo]), β = [Mn] × [P] - [Mo]/100

A welded joint having a specific chemical composition having Ceq represented by the following Formula (1) of from 0.350 to 0.490, the tensile strength of from 490 MPa to 720 MPa, the inclusion having a circle-equivalent diameter from 0.01 µm to 0.50 µm, and containing Ti and N, has the number density of 1.0 × 10⁵/mm² or more, at a portion that is 1/4 of a thickness and at a portion that is 1/2 of a thickness, in the thickness direction from the surface, the inclusion containing Ti and N has an average grain diameter of 150 nm or less, at the 1/4 portion and the 1/2 portion, and an effective crystal grain diameter in a region between a fusion line of the welded portion and a position 1 mm away from the fusion line in a heat-affected zone is 100.0 µm or less. A pressure vessel containing the welded joint. Ceq=C+Mn/6+Ni/15+Cu/15+Cr/5+Mo/5+V/5

A steel product having a specific chemical composition in which Ceq represented by the following Formula (1) is 0.350 or more, a tensile strength is from 490 MPa to 720 MPa, a microstructure of a portion that is 1/4 of a thickness from the surface, has low-temperature transformation structures whose total area ratio is 70.0% or more, and has an average crystal grain size of 25.0 µm or less. Ceq=C+Mn/6+Ni/15+Cu/15+Cr/5+Mo/5+V/5

A steel product and a pressure vessel that contains the steel product, having a specific chemical composition having α represented by the formula below of from 5.0 to 16.0, the tensile strength is from 615 MPa to 930 MPa, the microstructure of a portion that is 1/4 of the thickness from the surface includes lower bainite and martensite, the total area ratio of the lower bainite and the martensite is 15.0% or more, the total area ratio of upper bainite, the lower bainite, and the martensite is 90.0% or more, the area ratio of retained austenite is less than 1.7%, and the Mn concentration in a center segregation region in a portion that is 1/2 of the thickness is 2.00% or less. α = 0.50 × √[C] × (1 + 0.64[Si]) × (1 + 4.10[Mn]) × (1 + 0.27[Cu]) × (1 + 0.52[Ni]) × (1 + 2.33[Cr]) × (1 + 3.14[Mo])

Provided is a hot-stamp formed body comprising a steel base material and a plating layer arranged on a surface of the steel base material, wherein the plating layer has a predetermined chemical composition, and includes an Fe₂ Al₅ phase, a Zn content of the Fe₂ Al₅ phase is 1.5 to 15.0 mass%, at a cross-section of the plating layer, an Si content in the Fe₂ Al₅ phase is 5 to 20 mass% and projected lengths Li of Fe-Al-Si phases with a circle equivalent diameter of 2 µm or more and a length L₀ of the surface of the steel base material satisfy ΣL_i/L₀ ≤0.70, and an amount of deposition of the plating layer is 20 g/m² or more per side.

Provided is a hot-stamp formed body comprising a steel base material and a plating layer arranged on a surface of the steel base material, wherein the plating layer has a desired chemical composition, and includes an Fe₂ Al₅ phase and a surface oxide film, at a cross-section of the plating layer, an Si content in the Fe₂ Al₅ phase is 5 to 20 mass% and projected lengths Li of Fe-Al-Si phases with a circle equivalent diameter of 2 µm or more and a length L₀ of the surface of the steel base material satisfy ΣL_i/L₀ ≤0.70, an Mg content in the surface oxide film is 0.10 at% or more, and an amount of deposition of the plating layer is 20 g/m² or more per side.

Provided is a hot-stamp formed body comprising a steel base material and a plating layer arranged on a surface of the steel base material, wherein the plating layer has a predetermined chemical composition, and includes, in order from the side of the steel base material, an Fe<2> Al<5> phase and a Fe-Al phase having an Fe content of 20 to 40 mass%, a Zn content of the Fe-Al phase is 1.5 to 15.0 mass%, at a cross-section of the plating layer, an Si content in the Fe<2> Al<5> phase is 5 to 20 mass% and projected lengths L<i> of Fe-Al-Si phases with a circle equivalent diameter of 2 µm or more and a length L<0> of the surface of the steel base material satisfy ΣL<i> /L<0> ≤0.70, and an amount of deposition of the plating layer is 20 g/m<2> or more per side.

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The present application discloses a ceramic sintered body in which both toughness and wear resistance are satisfied. The ceramic sintered body of the present disclosure contains a first compound and a second compound. The first compound is silicon carbide, and the second compound is a diboride of a Group 4 element. A ratio of the second compound in the ceramic sintered body is 50% by mass or more and 70% by mass or less. When a 300 µm × 300 µm region of a polished surface of the ceramic sintered body is divided into 400 sections of 15 µm × 15 µm and an area ratio of the first compound is specified for each of the sections, a coefficient of variation CV of the area ratio of the first compound is more than 0.14 and less than 0.23.

The steel sheet has a desired chemical composition, and in a microstructure at a position at a 1/4 sheet thickness from a surface, by area%, prior austenite grains having an aspect ratio less than 2.0 account for less than 20%, prior austenite grains having an aspect ratio of 2.0 or more and less than 6.0 account for 40% or more, prior austenite grains having an aspect ratio of 6.0 or more account for less than 30%, bainite accounts for 70% to 95%, and martensite accounts for 5% to 30%.

An Fe-based amorphous alloy according to an aspect of the present disclosure contains, in atom%, B: 8.0% or more and 18.0% or less, Si: 0% or more and 2.0% or less, C: 0.10% or more and 5.00% or less, P: 0.10% or more and 3.50% or less, Mn: 0% or more and 0.60% or less, Fe: 78.00% or more and 86.00% or less, and a remainder including impurities, in which a microstructure of the Fe-based amorphous alloy is amorphous.

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