Abstract: A casting method of an active metal includes, in an induction melting furnace using a water-cooled crucible, tapping a molten metal into a mold from a tapping hole provided at a bottom of the water-cooled copper crucible to cast an ingot of the active metal. In conducting the casting under a casting condition in which the ingot has a diameter (D) of 10 mm or more and a ratio (H/D) of an ingot height H to the ingot diameter D of 1.5 or more and a weight of the molten metal tapped in the casting is 200 kg or less, a temperature of the molten metal in the casting is set to be higher than the melting point of the active metal and a casting velocity V (mm/sec) is controlled to satisfy V?0.1H in relation with the ingot height H by adjusting an opening diameter of the tapping hole.

Abstract: A steel sheet for hot pressing includes in a chemical composition, in percent by mass, C of 0.1% to 0.4%, Si of greater than 0% to 2.0%, Mn of 0.5% to 3.0%, P of greater than 0% to 0.015%, S of greater than 0% to 0.01%, B of 0.0003% to 0.01%, N of greater than 0% to 0.05%, Al in a content of 2×[N]% to 0.3% at a Si content of greater than 0.5% to 2.0%; or Al in a content of (0.20+2×[N]?0.40×[Si]N)% to 0.3% at a Si content of 0% to 0.5%, where [N] and [Si] are contents of N and Si, respectively, in mass percent, with the remainder being iron and inevitable impurities, where contents of Ti, Zr, Hf, and Ta, of the inevitable impurities, are each controlled to 0.005% or lower. The steel sheet includes nitride-based inclusions with an equivalent circle diameter of 1 ?m or more in a number density of 0.10 per square millimeter.

Abstract: A casting method of an active metal includes, in an induction melting furnace using a water-cooled crucible, tapping a molten metal into a mold from a tapping hole provided at a bottom of the water-cooled copper crucible to cast an ingot of the active metal. In conducting the casting under a casting condition in which the ingot has a diameter (D) of 10 mm or more and a ratio (H/D) of an ingot height H to the ingot diameter D of 1.5 or more and a weight of the molten metal tapped in the casting is 200 kg or less, a temperature of the molten metal in the casting is set to be higher than the melting point of the active metal and a casting velocity V (mm/sec) is controlled to satisfy V?0.1H in relation with the ingot height H by adjusting an opening diameter of the tapping hole.

Abstract: A steel sheet for hot-pressing includes a specific chemical component composition. In the steel sheet, an average equivalent-circle diameter of a Ti-containing precipitate having an equivalent-circle diameter of 30 nm or less among Ti-containing precipitates contained in the steel sheet is 3 nm or more. A precipitated Ti amount and a total Ti amount in the steel satisfy the relationship of: Precipitated Ti amount (mass %)?3.4[N]?0.5×[(total Ti amount (mass %))?3.4[N]], in which [N] indicates the content (mass %) of N in the steel. A ferrite fraction in the metal microstructure of the steel sheet is 30 area % or more.

Abstract: A steel sheet for hot pressing includes in a chemical composition, in percent by mass, C of 0.1% to 0.4%, Si of greater than 0% to 2.0%, Mn of 0.5% to 3.0%, P of greater than 0% to 0.015%, S of greater than 0% to 0.01%, F3 of 0.0003% to 0.01%, N of greater than 0% to 0.05%, Al in a content of 2×[N]% to 0.3% at a Si content of greater than 0.5% to 2.0%; or Al in a content of (0.20+2×[N]-0.40×[Si]N)% to 0.3% at a Si content of 0% to 0.5%, where [N] and [Si] are contents of N and Si, respectively, in mass percent, with the remainder being iron and inevitable impurities, where contents of Ti, Zr, Hf, and Ta, of the inevitable impurities, are each controlled to 0.005% or lower. The steel sheet includes nitride-based inclusions with an equivalent circle diameter of 1 ?m or more in a number density of 0.10 per square millimeter.

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: 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: 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: There is provided a hot press-formed product, including a thin steel sheet formed by a hot press-forming method, and having a metallic structure that contains bainitic ferrite at 70% to 97% by area, martensite at 27% by area or lower, and retained austenite at 3% to 20% by area, the remainder structure of which is at 5% by area or lower, whereby balance between strength and elongation can be controlled in a proper range and high ductility can be achieved.

Abstract: There is provided a hot press-formed product, including a thin steel sheet formed by a hot press-forming method, and having a metallic structure that contains retained austenite at 3% to 20% by volume, whereby balance between strength and elongation can be controlled in a proper range and high ductility can be achieved.

Abstract: Provided is a press-forming product manufacturing method of manufacturing a forming product having satisfactory formability for a drawing process by press-forming a metal sheet using a press-forming tool with high productivity, including: heating the metal sheet to a transformation temperature Ac1 or more; cooling the metal sheet to 600° C. or lower; forming the metal sheet by a forming tool; ending the forming process at a martensite transformation start temperature Ms or more; taking out the metal sheet from the forming tool; and cooling the metal sheet.

Abstract: A method for manufacturing a press-formed article includes: heating a specific steel sheet for hot-pressing at 900° C. or more and 1,100° C. or less; starting press forming of the steel sheet which has been heated; and then, cooling the steel sheet to a temperature equal to or less than a temperature 100° C. below a bainite transformation starting temperature Bs and equal to or more than a martensite transformation starting temperature Ms, while ensuring an average cooling rate of 20° C./sec or more in a mold during forming and after the completion of forming; and further cooling the steel sheet, which has been cooled, to 200° C. or less at an average cooling rate of less than 20° C./sec.

Abstract: A steel sheet for hot-pressing includes a specific chemical component composition. In the steel sheet, an average equivalent-circle diameter of a Ti-containing precipitate having an equivalent-circle diameter of 30 nm or less among Ti-containing precipitates contained in the steel sheet is 3 nm or more. In the steel, a precipitated Ti amount and a total Ti amount in a steel satisfy the relationship of: Precipitated Ti amount (mass %)?3.4[N]?0.5×[(total Ti amount (mass %))?3.4[N]] in which [N] indicates the content (mass %) of N in the steel. In the steel sheet, a ferrite fraction in a metal microstructure is 30 area % or more.

Abstract: Provided is a hot-pressing steel plate useful for obtaining a press-molded article having excellent anti-softening characteristics in heat-affected zones (HAZ) while attaining a press-molded article that can achieve a high level of balance between high strength and stretchability if uniform characteristics within the molded article are required, and a high level of balance between high strength and stretchability in respective regions if regions corresponding to shock-resistant portions and energy-absorbing portions are required within one molded article; molding and processing prior to hot-pressing being facilitated by the hot-pressing steel plate having a prescribed chemical composition, having the equivalent circular diameter of Ti-containing deposits included in the steel plate be 30 nm or less with the average equivalent circular diameter of the Ti-containing deposits being 6 nm or less, having the deposited Ti amount and the total Ti amount within the steel satisfy a prescribed relation, and having a me

Abstract: There is provided a useful method for producing a press-formed product without making the structure of a press tool complicated, which product has favorable formability in a level so as to be able to be produced by deep drawing, and which product is produced by press-forming a thin steel sheet with a punch and a die, in which the thin steel sheet is heated to a temperature not lower than an Ac3 transformation point thereof, and the press-forming is then started, wherein the forming is carried out so that a temperature difference in the thin steel sheet is adjusted to be not higher than 200° C. at a stage when the thin steel sheet has reached one third of a forming height.

Abstract: There is provided a useful method for producing a press-formed product without causing disadvantages such as hardness variation, which product has favorable formability in a level so as to be able to be produced by deep drawing, and which method is carried out by heating a thin steel sheet to a temperature not lower than an Ac3 transformation point thereof; and then cooling the thin steel sheet at a rate not lower than a critical cooling rate, during which the thin steel sheet is formed into the press-formed product, wherein the forming is started from a temperature higher than a martensitic transformation start temperature Ms thereof, the cooling rate is kept to be 10° C./sec. or higher during the forming, and the forming is finished in a temperature range not higher than the martensitic transformation start temperature Ms.

Abstract: A hot press molding including: a first forming region exhibiting a metal structure, which contains 80-97 area % of martensite and 3-20 area % of retained austenite, respectively, and in which the residual structure is 5 area % or less; and a second forming region exhibiting a metal structure, which contains 70-97 area % of bainitic ferrite, 27 area % or less of martensite, and 3-20 area % of retained austenite, respectively, and in which the residual structure is 5 area % or less. As a result, hot press moldings, which have at least a region corresponding to a shock-resistant area and a region corresponding to an energy-absorbing area in a single molding and in which a high level of balancing of high strength with elongation according to the respective region can be achieved, are provided without using a welding method.

Abstract: A dual phase steel sheet with good bake-hardening properties is provided. The steel sheet is characterized in containing (in terms of percent by mass) C: no less than 0.06% and less than 0.25%; Si+Al: 0.5 to 3%; Mn: 0.5 to 3%; P: no more than 0.15%; and S: no more than 0.02%; and also meeting the following condition (in terms of space factor) that retained austenite is at least 3%, bainite is at least 30%, and ferrite is no more than 50%, and further characterized in differing in stress larger than 50 MPa before and after application of 2% pre-strain and ensuing heat treatment for paint baking at 170° C. for 20 minutes. The steel sheet has well-balanced strength and workability, exhibits good bake-hardening properties at the time of paint baking, and offers good resistance to natural aging.

Abstract: A high-strength cold-rolled steel sheet excellent in uniform elongation, including in percent by mass: 0.10-0.28% of C; 1.0-2.0% of Si; and 1.0-3.0% of Mn, and the structures of the same having the space factors below to the entire structure: 30-65% of bainitic ferrite; 30-50% of polygonal ferrite; and 5-20% of residual austenite.