Abstract: A method produces a press-molded article having a hat shaped cross-section with flanges at both sides, a top plate, vertical walls at both sides, and having a shape curved in the vertical direction to an inverted checkmark shape along the longitudinal direction when the molded article is viewed from a side face with the top plate section on the top side. An intermediate molded body is formed by drawing a metal stock sheet into an intermediate shape, and after preparing the outside shape of the intermediate molded body by trimming, drawing is subsequently performed to form the final shape.

Abstract: The top plate section of the metal stock is pressed and clamped against a punch by a pad, a portion that will be at the outside of the L shaped curve is pressed and camped against a die by a blank holder, a bender is moved, and a vertical wall portion at the inside of the L shaped curved of the metal stock sheet and the flange portion joined to the vertical wall at the inside of the L shaped curve are molded. The metal stock sheet is moved in the direction toward the blank holder while the metal stock sheet being pressed and clamped, and a vertical wall portion at the outside of the L shaped curve of the L shaped hat shaped cross-section and the flange portion joined to the vertical wall at the outside of the L shaped curve are molded.

Abstract: A center pillar reinforcement is produced satisfactorily by using a high-tensile material having a low ductility as a blank. The center pillar reinforcement is produced by performing a first step for producing a first intermediate formed product on which a body is partially formed by press-forming the blank using a first press-forming device for drawing, and a second step for pressing the first intermediate formed product by using a second press-forming device for bend-forming.

Abstract: A curved part 10 having a hat-shaped cross section is produced by press-forming without causing cracks and wrinkles. When producing a curved part 10, which is made up of a top plate 11, vertical walls 12a and 12b extended in parallel with each other along ridgelines 14a and 14b of the top plate, and outwardly directed flanges 13a and 13b which connect to leading edges of the vertical walls, and has a generally hat-shaped cross section, by press forming, the metal material sheet 601 is interposed and constrained by the die 502 and the blank holder 505 and is press-formed while the metal material sheet 601 being interposed and constrained by the pad 503 and the punch 504.

Abstract: The present invention provides a method for manufacturing a hot stamped body, the method including: a hot-rolling step; a coiling step; a cold-rolling step; a continuous annealing step; and a hot stamping step, in which the continuous annealing step includes a heating step of heating the cold-rolled steel sheet to a temperature range of equal to or higher than Ac1° C. and lower than Ac3° C.; a cooling step of cooling the heated cold-rolled steel sheet from the highest heating temperature to 660° C. at a cooling rate of equal to or less than 10° C./s; and a holding step of holding the cooled cold-rolled steel sheet in a temperature range of 550° C. to 660° C. for one minute to 10 minutes.

Abstract: The present invention provides a steel sheet with chemical components including, by mass%, 0.18-0.35% of C, 1.0%-3.0% of Mn, 0.01%-1.0% of Si, 0.001%-0.02% of P, 0.0005%-0.01% of S, 0.001%-0.01% of N, 0.01%-1.0% of Al, 0.005%-0.2% of Ti, 0.0002%-0.005% of B, and 0.002%-2.0% of Cr, and the balance of Fe and inevitable impurities, wherein: by volume%, a fraction of the ferrite is 50% or more, and a fraction of a non-recrystallized ferrite is 30% or less; and Cr?/CrM is 2 or less, where Cr? is a concentration of Cr subjected to solid solution in iron carbide and CrM is a concentration of Cr subjected to solid solution in a base material, or Mn0/MnM is 10 or less, where Mn0 is a concentration of Mn subjected to solid solution in an iron carbide, and MnM is a concentration of Mn subjected to solid solution in a base material.

Abstract: The present invention provides a method for manufacturing a hot stamped body having a vertical wall, the method including: a hot-rolling step; a coiling step; a cold-rolling step; a continuous annealing step; and a hot stamping step, in which the continuous annealing step includes a heating step of heating the cold-rolled steel sheet to a temperature range of equal to or higher than Ac1° C. and lower than Ac3° C.; a cooling step of cooling the heated cold-rolled steel sheet from the highest heating temperature to 660° C. at a cooling rate of equal to or less than 10° C./s; and a holding step of holding the cooled cold-rolled steel sheet in a temperature range of 550° C. to 660° C. for one minute to 10 minutes.

Abstract: High strength, hot rolled steel plate providing high level of bore expandability and high level of ductility. Also, method of manufacturing same. In first aspect, steel plate comprises steel having, by mass, C:0.01-0.15%; Si:0.30-2.00%; Mn:0.50-3.00%; P?0.03%; S?0.005%; Ti:0.01-0.50%; and/or Ni:0.01-0.05%, with balance Fe and unavoidable impurities. In this steel, ?80% of all grains have ratio of minor axis to major axis of ?0.1. This steel plate has steel structure comprising ?80% ferrite and balance bainite. In second aspect, steel plate has above composition, and ferrite-bainite duplex steel structure in which proportion of ferrite having grain diameter ?2 ?m is ?80%. In third aspect, steel plate has above composition. wherein contents of C, Si, Mn, Ti, and Nb satisfy requirement represented by formula: 115 ?(917?480[C %]+100[Si %]?100[Mn %])?(790×([Ti %]+[Nb %]/2)0.05)?235. This steel plate has steel structure comprising ?80% ferrite and balance bainite.

Abstract: Disclosed are a high strength hot rolled steel plate, preventing a deterioration in bore expandability and ductility involved in an increase in strength to not less than 690 N/mm2 and, despite high strength, providing a high level of bore expandability and a high level of ductility, and a producing process thereof. The steel plate according to the first aspect is a steel plate, comprising a steel comprising, by mass, C: 0.01-0.15%; Si: 0.30-2.00%; Mn: 0.50-3.00%; P ≦0.03%; S ≦0.005%; Ti: 0.01-0.50% and/or Ni: 0.01-0.05%; and the balance consisting of Fe and unavoidable impurities, not less than 80% of all grains being accounted for by grains having a ratio (ds/dl) of minor axis (ds) to major axis (dl) of not less than 0.1, the steel plate having a steel structure comprising not less than 80% of ferrite and the balance consisting of bainite, the steel plate having a strength of not less than 690 N/mm2.

Abstract: A compound structure steel sheet excellent in burring workability made of a steel containing, by mass, 0.01 to 0.3% of C, 0.01 to 2% of Si, 0.05 to 3% of Mn, 0.1% or less of P, 0.01% or less of S, and 0.005 to 1% or Al, and having the microstructure being a compound structure having ferrite as the main phase and martensite or retained austenite mainly as the second phase, the quotient of the volume percentage of the second phase divided by the average grain size of the second phase being 3 or more and 12 or less, and the quotient of the average hardness of the second phase divided by the average hardness of the ferrite being 1.5 or more and 7 or less; or a compound structure steel sheet excellent in burring workability made of a steel containing, by mass, 0.01 to 0.3% of C, 0.01 to 2% of Si, 0.05 to 3% of Mn, 0.1% or less of P, 0.01% or less of S, and 0.

Abstract: A compound structure steel sheet excellent in burring workability made of a steel containing, by mass, 0.01 to 0.3% of C, 0.01 to 2% of Si, 0.05 to 3% of Mn, 0.1% or less of P, 0.01% or less of S, and 0.005 to 1% or Al, and having the microstructure being a compound structure having ferrite as the main phase and martensite or retained austenite mainly as the second phase, the quotient of the volume percentage of the second phase divided by the average grain size of the second phase being 3 or more and 12 or less, and the quotient of the average hardness of the second phase divided by the average hardness of the ferrite being 1.5 or more and 7 or less; or a compound structure steel sheet excellent in burring workability made of a steel containing, by mass, 0.01 to 0.3% of C, 0.01 to 2% of Si, 0.05 to 3% of Mn, 0.1% or less of P, 0.01% or less of S, and 0.