Abstract: 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 ?m 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 ?m or more. The lowest Si concentration LSi and the lowest Mn concentration LMn in the region within 4.9 ?m from the surface of the steel sheet and a Si concentration TSi and a Mn concentration TMn at a quarter thickness position of the steel sheet satisfy the following formula (1): LSi+LMn?(TSi+TMn)/4??(1).

Abstract: A high strength galvanized steel sheet having a yield strength of not less than 1,000 MPa is disclosed. An amount of diffusible hydrogen is not more than 0.60 mass ppm. The chemical composition of the steel sheet includes, by mass %, C: 0.150 to 0.450%, Si: 0.50 to 3.00%, Mn: 1.50 to 4.00%, P: not more than 0.100%, S: not more than 0.0200%, Al: not more than 0.100%, O: not more than 0.0100%, and N: not more than 0.0100%, with a balance being Fe and inevitable impurities. In the microstructure of the steel sheet, a total area fraction of tempered martensite and bainite is 55 to 95%, an area fraction of retained austenite is 5 to 30%, and a presence ratio X/Y of a structure X having a nanohardness of 7.0 GPa or more to a structure Y having a nanohardness of 6.5 GPa or less is 0.5 to 2.5.

Abstract: A high strength steel sheet having a yield strength of not less than 800 MPa is disclosed. The amount of diffusible hydrogen in steel is not more than 0.50 mass ppm. The chemical composition includes, by mass, C: 0.150 to 0.500%, Si: 0.01 to 3.00%, Mn: 1.50 to 4.00%, P: not more than 0.100%, S: not more than 0.0200%, Al: not more than 0.100%, N: not more than 0.0100%, and O: not more than 0.0100%, with a balance being Fe and inevitable impurities. The total area fraction of tempered martensite and bainite is 55 to 95%. The presence ratio A/B of a structure A to a structure B is 0.8 to 2.5, the structure A having a nanohardness of 7 GPa or more, and the structure B having a nanohardness of 6 GPa or less. The concentration of solid solution carbon in retained austenite is 0.50 to 0.90 mass %.

Abstract: A steel sheet has a specific chemical composition and a steel microstructure including, in terms of area fraction, ferrite: 60% or more and 85% or less, bainite: 3% or more and 15% or less, retained austenite: 3% or more and 15% or less, fresh martensite: 3% or more and 15% 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 590 MPa or more and less than 780 MPa.

Abstract: 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.

Abstract: A high-strength steel sheet having a tensile strength of 1320 MPa or more is disclosed. The above-described high-strength steel sheet includes a specific component composition, wherein a diffusible hydrogen in steel is 0.50 ppm by mass or less, tempered martensite and bainite are 70.0% or more, fresh martensite is 15.0% or less, iron-based carbides existing in the tempered martensite and the bainite have an average equivalent circular radius of 0.10 ?m or less and an average aspect ratio of 4.5 or less, and a proportion p of tempered martensite and bainite including iron-based carbides, which have major axes facing the same direction within a range of 0 to 10°, at a number density of 7 to 35/?m2 among the tempered martensite and the bainite is 25 to 70%.

Abstract: A high-strength steel sheet that has a predetermined component composition, that has a steel microstructure in which, in a thickness cross-section in a rolling direction, an area percentage of ferrite ranges from 5% to 30%, a total area percentage of tempered martensite and bainite ranges from 40% to 90%, pearlite constitutes 0% to 5%, a total area percentage of fresh martensite and retained ? ranges from 5% to 30%, a ratio of a total area percentage of the fresh martensite and the retained ? to a total area percentage of the tempered martensite, bainite, and pearlite is 0.5 or less, and a ratio of the fresh martensite and the retained ? adjacent to the ferrite with respect to the fresh martensite and the retained ? is 30% or more in total area percentage, and that has a yield strength of 550 MPa or more.

Abstract: A steel sheet having a tensile strength (TS) of 780 MPa or more and less than 1180 MPa, 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 ?m in a thickness direction from a surface of the steel sheet have an average grain size in the range of 3 to 10 ?m, the lowest Si concentration LSi and the lowest Mn concentration LMn in the region within 4.9 ?m in the thickness direction from the surface of the steel sheet and a Si concentration TSi and a Mn concentration TMn at a quarter thickness position of the steel sheet satisfy a specified formula.

Abstract: A high strength galvanized steel sheet is disclosed having a tensile strength of 1,320 MPa or more. A chemical composition of a steel sheet contains, by mass, C: 0.150 to 0.450%, Si: 0.80 to 3.00%, Mn: 2.00 to 4.00%, P: not more than 0.100%, S: not more than 0.0200%, Al: not more than 0.100%, O: not more than 0.0100%, and N: not more than 0.0100%, with a balance of Fe and inevitable impurities. An amount of diffusible hydrogen in steel is not more than 0.60 mass ppm. A total of tempered martensite and bainite is 60 to 95%, retained austenite is 5 to 30%, and retained austenite having an aspect ratio of 5.5 or higher with respect to an entire retained austenite is not more than 50%, and fresh martensite having a diameter of 2.0 ?m or less is not more than 20%.

Abstract: A high-strength steel sheet that has a predetermined component composition, that has a steel microstructure in which, in a thickness cross-section in a rolling direction, an area percentage of ferrite ranges from 5% to 30%, a total area percentage of tempered martensite and bainite ranges from 40% to 90%, pearlite constitutes 0% to 5%, a total area percentage of fresh martensite and retained ? ranges from 5% to 30%, a ratio of a total area percentage of the fresh martensite and the retained ? to a total area percentage of the tempered martensite, bainite, and pearlite is 0.5 or less, and a ratio of the fresh martensite and the retained ? adjacent to the ferrite with respect to the fresh martensite and the retained ? is 30% or more in total area percentage, and that has a yield strength of 550 MPa or more.

Abstract: Provided is a high strength, cold rolled steel flat product with reduced sensitivity to hydrogen embrittlement including a steel substrate which, in % by mass, consists of C: 0.20 to 0.40%, Mn: 1.50 to 3.00%, Si: 0.90 to 1.50%, Al: 0.005 to 1.00%, V: 0.01 to 0.30%, optionally Cr: 0.01 to 1.00%, optionally Mo: 0.005 to 0.20%, optionally B: 0.00001 to 0.002%, optionally Nb and Ti the total content of Nb and Ti being 0.005 to 0.2%, P: up to 0.020%, S: up to 0.005%, N: up to 0.008%, and as the remainder Fe and unavoidable impurities, the sum of the shares of the impurities being ?0.8%. A method for the manufacture of the high strength, cold steel flat product is also provided.

Abstract: A steel sheet with a tensile strength (TS) of 1180 MPa or more, a member, and a method for producing them. In a region of the steel sheet within 4.9 ?m 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 ?m or more. The lowest Si concentration LSi and the lowest Mn concentration LMn in the region within 4.9 ?m in the thickness direction from the surface of the steel sheet and a Si concentration TSi and a Mn concentration TMn at a quarter thickness position of the steel sheet satisfy the following formula (1): LSi+LMn?(TSi+TMn)/4??(1).

Abstract: A steel sheet according to the present invention has a specific chemical composition and a steel microstructure including, in terms of area fraction, ferrite: 40% or more and 70% or less, a total of bainite and tempered martensite: 5% or more and 30% or less, retained austenite: 4% or more and 18% or less, fresh martensite: 8% or more and 35% 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 780 MPa or more and less than 980 MPa.

Abstract: A high-strength steel sheet having a tensile strength of 1320 MPa or more is disclosed. The above-described high-strength steel sheet includes a specific component composition including Ti and the like, wherein a diffusible hydrogen amount in steel is 0.50 ppm by mass or less, tempered martensite and bainite are 70.0 to 95.0%, fresh martensite is 15.0% or less, retained austenite is 5.0 to 15.0%, an average grain size of a precipitate A, which is a carbide, nitride, or carbonitride containing at least one selected from the group consisting of Ti, Nb, and V is 0.001 to 0.050 ?m, a number density NS of the precipitate A having a major axis of 0.050 ?m or less is 10/?m2 or more, and a ratio of the number density NS and a number density NL of the precipitate A having a major axis of more than 0.050 ?m is 10.0 or more.

Abstract: A high-strength steel sheet having a tensile strength of 1320 MPa or more is disclosed. The above-described high-strength steel sheet includes a specific component composition, wherein a diffusible hydrogen in steel is 0.50 ppm by mass or less, tempered martensite and bainite are 70.0% or more, fresh martensite is 15.0% or less, iron-based carbides existing in the tempered martensite and the bainite have an average equivalent circular radius of 0.10 ?m or less and an average aspect ratio of 4.5 or less, and a proportion p of tempered martensite and bainite including iron-based carbides, which have major axes facing the same direction within a range of 0 to 10°, at a number density of 7 to 35/?m2 among the tempered martensite and the bainite is 25 to 70%.

Abstract: Disclosed is the use of a mesencephalic astrocyte-derived neurotrophic factor (Manf) in the preparation of a drug for treating herpes simplex keratitis (HSK). Manf has an anti-herpes simplex virus type I (HSV-1) effect and can inhibit corneal vascular proliferation, corneal inflammatory response, and corneal nerve regression caused by HSV-1 infection. Manf can be used to prepare drugs for treating the HSK.

Abstract: A high-strength steel sheet that has a predetermined component composition, that has a steel microstructure in which an area percentage of ferrite ranges from 5% to 50% in a thickness cross-section in a rolling direction, a total area percentage of fresh martensite and retained ? ranges from 2% to 30%, each of the fresh martensite and the retained ? has an average grain size of 5 ?m or less, and a ratio of the fresh martensite and the retained ? adjacent only to ferrite with respect to the fresh martensite and the retained ? from a surface to 200 ?m in the thickness direction is 30% or less in total area percentage, and that has a yield strength of 550 MPa or more.

Abstract: 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 ?m in a thickness direction from a surface of the steel sheet have an average grain size in the range of 3 to 10 ?m, the lowest Si concentration LSi and the lowest Mn concentration LMn in the region within 4.9 ?m in the thickness direction from the surface of the steel sheet and a Si concentration TSi and a Mn concentration TMn at a quarter thickness position of the steel sheet satisfy a specified formula.

Abstract: A high strength galvanized steel sheet is disclosed having a tensile strength of 1,320 MPa or more. A chemical composition of a steel sheet contains, by mass, C: 0.150 to 0.450%, Si: 0.80 to 3.00%, Mn: 2.00 to 4.00%, P: not more than 0.100%, S: not more than 0.0200%, Al: not more than 0.100%, O: not more than 0.0100%, and N: not more than 0.0100%, with a balance of Fe and inevitable impurities. An amount of diffusible hydrogen in steel is not more than 0.60 mass ppm. A total of tempered martensite and bainite is 60 to 95%, retained austenite is 5 to 30%, and retained austenite having an aspect ratio of 5.5 or higher with respect to an entire retained austenite is not more than 50%, and fresh martensite having a diameter of 2.0 ?m or less is not more than 20%.

Abstract: An automotive member and a resistance spot welding method. The automotive member includes a resistance spot weld formed by resistance-spot-welding a plurality of steel sheets including at least one high strength steel sheet. The high strength steel sheet has a specific chemical composition. The microstructure in the vicinity of the edge of the nugget of the resistance spot weld is a composite microstructure containing ferrite at a volume fraction of 1 to 30%, martensite at a volume fraction of 1 to 50%, and tempered martensite at a volume fraction of 20% or more. The average number density of Nb-based precipitate grains having a grain diameter less than 0.09 ?m and Ti-based precipitate grains having a grain diameter less than 0.09 ?m is 10 or more grains per 100 ?m2 in a sheet cross section.