Abstract: A vehicle seat including: a seat structure member including a seat back and a seat cushion; and a support member configured to support the seat structure member and fastened to a vehicle compartment structural body, wherein the support member is a flat plate member which elongates in a longitudinal direction and has a convex bead portion extending in the longitudinal direction of the support member, wherein the bead portion includes a first bead portion and a second bead portion, and a stress concentrating portion of the support member, to which stress is configured to concentrate when vehicle collision occurs, is interposed between the first bead portion and the second bead portion, and wherein the stress concentrating portion of the support member includes a weakened portion configured to promote breakage of the support member.

Abstract: A hot-dip galvanized steel sheet contains specific amounts of C, Si, Mn, P, S, Ti, Al, and N with the remainder being iron and unavoidable impurities. Bainitic ferrite, martensite, retained ?, and ferrite (?) are present each in a specific area ratio. The remainder ? has a specific C concentration. Sub-grains in the recrystallized ? and un-recrystallized ? have a specific grain diameter. The surface area ratio of ? and worked ? having a grain diameter of 5 ?m or more is 5% or less. The average particle diameter of TiC particles inside a grains is 10 nm or less.

Abstract: A spot welding method joins metal sheets by: clamping a stacked section of two or more stacked metal sheets with a pair of electrodes at a load of 100 N or more; applying pressure around the electrodes at a load, which is 5-1000% of the load due to the pair of electrodes, using a pressurizing member, which applies pressure on the stacked section in regions that are 20% or more of the total outer circumference of the electrode tips and for which the continuous regions of the entire outer circumference of the electrode tips that are not pressed are 30% or less (including 0%) of the entire outer circumference of the electrode tips; and passing welding current from the electrodes to the stacked section.

Abstract: In a steel sheet having a specific chemical composition and having a microstructure including ferrite that is a soft first phase by 20-50% in terms of the area ratio, the remainder being tempered martensite and/or tempered bainite that is a hard second phase, the microstructure of steel of a surface layer section of the steel sheet from the surface to the depth of 100 ?m and a center section of t/4-3t/4 (t is the sheet thickness) is controlled.

Abstract: In a high strength cold-rolled steel plate having a specific chemical composition, a soft first phase (ferrite) has an area ratio of 20-50%, the remainder being a hard second phase (tempered martensite and/or tempered bainite), among all the ferrite grains, ferrite grains that have an average grain diameter of 10-25 ?m account for a total area ratio of 80% or more, the number of the cementite grains that have an equivalent circle diameter of 0.3 ?m or more is more than 0.15 piece and 1.0 piece or less per 1 ?m2 of ferrite, and the tensile strength is 980 MPa or more.

Abstract: A steel sheet for hot pressing use according to the present invention has a specified chemical component composition, wherein some of Ti-containing precipitates contained in the steel sheet, each of which having an equivalent circle diameter of 30 nm or less, have an average equivalent circle diameter of 6 nm or less, the precipitated Ti amount and the total Ti amount in the steel fulfill the relationship represented by formula (1) shown below, and the sum total of the fraction of bainite and the fraction of martensite in the metal microstructure is 80 area % or more. Precipitated Ti amount (mass %)?3.4[N]?0.5×[(total Ti amount (mass %))?3.4[N]]??(1) (In the formula (1), [N] represents the content (mass %) of N in the steel.

Abstract: A steel sheet for hot pressing use according to the present invention has a specified chemical component composition, wherein some of Ti-containing precipitates contained in the steel sheet, each of which having an equivalent circle diameter of 30 nm or less, have an average equivalent circle diameter of 3 nm or more, the precipitated Ti amount and the total Ti amount in the steel fulfill the relationship represented by formula (1) shown below, and the sum total of the fraction of bainite and the fraction of martensite in the metal microstructure is 80 area % or more. Precipitated Ti amount (mass %)?3.4[N]>0.5×[total Ti amount (mass %)?3.4[N]]??(1) (In the formula (1), [N] represents the content (mass %) of N in the steel.

Abstract: In the present invention, a press-formed product is manufactured by heating a steel sheet for hot pressing use to a temperature of 900° C. or above and 1,100° C. or below, the steel sheet for hot pressing use having a predetermined chemical component composition, some of Ti-containing precipitates contained in the steel sheet, each of which having an equivalent circle diameter of 30 nm or less, having an average equivalent circle diameter of 6 nm or less, and the precipitated Ti amount and the total Ti amount in the steel fulfilling the relationship represented by formula (1) shown below, thereafter starting press-forming, and holding at the bottom dead point and cooling to a temperature lower than the martensite transformation starting temperature Ms while securing the average cooling rate of 20° C./s or more within a tool. Precipitated Ti amount(mass %)?3.4[N]<0.5×[total Ti amount (mass %)?3.4[N]]??(1) (In the formula (1), [N] represents the content (mass %) of N in the steel.

Abstract: Disclosed is a high-strength steel plate with excellent warm workability that has a component composition comprising, in mass %, 0.05 to 0.4% C, 0.5 to 3% Si+Al, 0.5 to 3% Mn, no more than 0.15% P (not including 0%), and no more than 0.02% S (including 0%), with the remainder comprising iron and impurities, and a composition that includes a total of 45 to 80% martensite and/or bainitic ferrite in terms of the area ratio relative to the entire composition, 5 to 40% polygonal ferrite in terms of the area ratio relative to the entire composition, and 5 to 20% retained austenite in terms of the area ratio relative to the entire composition, wherein the C concentration (C?R) within said residual austenite is in the range of 0.6 mass % to less than 1.0 mass %, and that furthermore may include bainite. In the high-strength steel plate, TRIP effects are achieved to the fullest extent in warm working, and increased ductility over prior steel plates is reliably achieved.

Abstract: A method of the present invention includes the steps of heating a steel sheet for hot pressing use to a temperature of Ac3 transformation point or above and 950° C. or below, the steel sheet for hot pressing use containing a predetermined chemical component composition, some of Ti-containing precipitates contained in the steel sheet, each of which having an equivalent circle diameter of 30 nm or less, having an average equivalent circle diameter of 3 nm or more, and the precipitated Ti amount and the total Ti amount in the steel fulfilling the relationship represented by formula (1) shown below, thereafter starting press forming, and being held at the bottom dead point and being cooled to a temperature lower than martensite transformation starting temperature Ms while securing the average cooling rate of 20° C./s or more within a tool. Precipitated Ti amount (mass %)?3.4[N]?0.5×[total Ti amount (mass %)?3.4[N]]??(1) (In the formula (1), [N] represents the content (mass %) of N in the steel.

Abstract: This high-strength steel sheet contains, in mass %, 0.05 to 0.3% of C, 1 to 3% of Si, 0.5 to 3% of Mn, up to 0.1% (inclusive of 0%) of P, up to 0.01% (inclusive of 0%) of S, 0.001 to 0.1% of Al and 0.002 to 0.03% of N with the balance consisting of iron and unavoidable impurities, and has a microstructure which comprises, in area fraction relative to the microstructure, 40 to 85% of bainitic ferrite, 5 to 20% of retained austenite (?R), 10 to 50% (in total) of martensite and ?R, and 5 to 40% of ferrite. The retained austenite (?R) has a C concentration of 0.5 to 1.0 mass %, while the quantity of ?R present in the ferrite grains is 1% or more (in area fraction) relative to the microstructure.

Abstract: Provided is a hot-press molded article that can achieve a high level of balance between high strength and extension by region and has a region corresponding to an energy absorption site and a shock resistant site within a single molded article without applying a welding method by means of having first region having a metal structure containing both 80-97 area % of martensite and 3-20 area % of residual austenite, the remaining structure comprising no more than 5 area %, and a second region having a metal structure comprising 30-80 area % of ferrite, less than 30 area % (exclusive of 0 area %) of bainitic ferrite, no greater than 30 area % (exclusive of 0 area %) of martensite, and 3-20 area % of residual austenite.

Abstract: A hot-press formed product can be achieved which has regions corresponding to a shock resistant portion and an energy absorption portion within a single formed product without applying a welding method and achieves the balance of high strength and elongation with a high level according to each region by means of having a first forming region exhibiting a metal structure containing martensite: 80-97 area % and retained austenite: 3-20 area % respectively, the remaining structure being 5 area % or less, and a second forming region exhibiting a metal structure containing annealed martensite or annealed bainite: 30-97 area %, martensite as quenched: 0-67 area %, and retained austenite: 3-20 area %.

Abstract: Disclosed is a high-strength cold-rolled steel sheet having improved stretch-flange formability and excellent hydrogen embrittlement resistance. In addition to Fe, C, Si, Mn, P, S, N, and Al, the steel sheet contains V or at least one element of Nb, Ti and Zr. The contents of the at least one element of Nb, Ti and Zr, if present, satisfy the expression of [% C]?[% Nb]/92.9×12?[% Ti]/47.9×12?[% Zr]/91.2×12>0.03. The steel sheet has an area ratio of tempered martensite of 50% or more with ferrite as the remainder. The number of precipitates having a circle-equivalent diameter of 1 to 10 nm is 20 particles or more per 1 ?m2 of the tempered martensite. The number of precipitates containing V or the at least one element of Nb, Ti and Zr and having a circle-equivalent diameter of 20 nm or more is 10 particles or less per 1 ?m2 of the tempered martensite.

Abstract: A high-strength cold-rolled steel sheet has a chemical composition including C of 0.05% to 0.30%, Si of greater than 0% to 3.0%, Mn of 0.1% to 5.0%, P of greater than 0% to 0.1%, S of greater than 0% to 0.02%, Al of 0.01% to 1.0%, and N of greater than 0% to 0.01%, in mass percent, with the remainder including iron and inevitable impurities. The steel sheet has a microstructure containing ferrite as a soft primary phase in an area percentage of 20% to 50% with the remainder including tempered martensite and/or tempered bainite as a hard secondary phase. The ferrite grains are adapted to contain cementite particles having an appropriate size in an appropriate number density.

Abstract: A cold-rolled steel sheet of the present invention which has a composition containing, in terms of % by mass, C: 0.05-0.30%, Si: 3.0% or less (including 0%), Mn: 0.1-5.0%, P: 0.1% or less (including 0%), S: 0.010% or less (including 0%), and Al: 0.001-0.10%, and remainder being mainly iron, and which has a structure comprising, in terms of area ratio, 10-80% ferrite, less than 5% (including 0%) of the sum of retained austenite and martensite, and a hard phase as the remainder. The steel sheet gives a KAM value frequency distribution curve in which the relationship between the proportion of frequency having a KAM value ?0.4, XKAM?0.4°, and the area ratio of ferrite, V? satisfies XKAM?0.4°/V??0.8 and the proportion of frequency having a KAM value in the range of 0.6-0.8, XKAM=0.6-0.8° is 10-20%. In the hard phase adjoining the ferrite, cementite, grains having an equivalent circle diameter of 0.1 ?m or larger exist so that three or less such cementite grains are dispersed per ?m2 of the hard phase.

Abstract: This high-strength steel plate has a component composition including, by mass %, C: 0.02-0.3%, Si: 1-3%, Mn: 1.8-3%, P: 0.1% or less, S: 0.01% or less, Al: 0.001-0.1%, N: 0.002-0.03%, the rest consisting of iron and impurities. Said steel plate has a microstructure including, in terms of area ratio relative to the entire microstructure, each of the following phases: bainitic ferrite: 50-85%; retained ?; 3% or greater; martensite+the aforementioned retained ?; 10-45%; and ferrite: 5-40%. The C concentration (C?R) in the aforementioned retained austenite is 0.3-1.2 mass %, part or all of the N in the aforementioned component composition is solid solution N, and the amount of said solid solution N is 30-100 ppm.

Abstract: This high-strength hot-rolled steel plate contains specific amounts of C, Si, Mn, Al, V and also Ti and/or Nb so as to fulfill C?12(V/51+Ti/48+Nb/93)>0.03, and the rest consists of iron and unavoidable impurities. Ferrite is the main microstructure, the remaining microstructure is one or more selected from the group consisting of bainite, martensite and retained austenite, wherein the average particle diameter of precipitated carbides (the total content of V, Ti and Nb is 0.02% or greater) in the ferrite is less than 6 nm.

Abstract: A vehicle seat including: a seat structure member including a seat back and a seat cushion; and a support member configured to support the seat structure member and fastened to a vehicle compartment structural body, wherein the support member is a flat plate member which elongates in a longitudinal direction and has a convex bead portion extending in the longitudinal direction of the support member, wherein the bead portion includes a first bead portion and a second bead portion, and a stress concentrating portion of the support member, to which stress is configured to concentrate when vehicle collision occurs, is interposed between the first bead portion and the second bead portion, and wherein the stress concentrating portion of the support member includes a weakened portion configured to promote breakage of the support member.

Abstract: The invention provides a high-strength cold-rolled steel sheet which is improved in elongation and stretch-flangeability and exhibits more excellent formability. The high-strength cold-rolled steel sheet has a composition which contains by mass C: 0.03 to 0.30%, Si: 0.1 to 3.0%, Mn: 0.1 to 5.0%, P: 0.1% or below, S: 0.005% or below, N: 0.01% or below, and Al: 0.01 to 1.00% with the balance consisting of iron and unavoidable impurities. The high-strength cold-rolled steel sheet has a structure which comprises at least 40% (up to 100% inclusive) in terms of area fraction of tempered martensite having a hardness of 300 to 380 Hv and the balance ferrite. The cementite particles in the tempered martensite take such dispersion that 10 or more cementite particles having equivalent-circle diameters of 0.02 to less than 0.1 ?m are present per one ?m2 of the tempered martensite and three or fewer cementite particles having equivalent-circle diameters of 0.