Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Nobuo Yoshikawa

Tohru Yoshida

Shigeru Yonemura

Jun Nitta

Tatsuo Yokoi

Hiroshi Yoshida

Kazuya Ootsuka

Yasuhiro Ito

Jun Maki

Yuki Suzuki

Masahiro Fuda

Soshi Fujita

Naruhiko Nomura

Satoshi Shirakami

Mitsuharu Yamagata

Hideaki Irikawa

Yasushi Tsukano

A manufacturing method includes: heating an overlapped blank; transferring the heated overlapped blank; and a step of performing presswork on the heated overlapped blank by using a die. In the heating step, when sheet-thicknesses of the first and second steel sheets are set, respectively, and an average heating rate at a sheet temperature from 20 to 800° C. of a portion with a total sheet thickness of an overlapped portion, and a non-overlapped portion are set, the total sheet thickness is 2.5 to 5.0 mm, a maximum length of the overlapped portion is 100 to 1100 mm, an area of the first steel sheet, an area of a portion, of the second steel sheet, overlapped with the first steel sheet, and the average heating rates satisfy Expressions (1) to (3), and heating is performed at a temperature and for a time within a specific range on a plane of coordinates.

Method of manufacturing overlapped hot stamp molded body, and overlapped hot stamp molded body

There is provided a method for estimating a hardness of a cold worked component including: preparing a test piece for hardness measurement having a dent portion of a shape corresponding to a shape of the contact surface of the punch by using a mounting base on which a test piece is mounted and a punch of which a contact surface to be in contact with the test piece is a curved surface, and compressing the test piece mounted on the mounting base using the punch; measuring hardnesses of the test piece for hardness measurement at a plurality of hardness measurement positions in a measurement direction while taking, as the measurement direction, a direction in the dent portion in which a sheet thickness changes; performing numerical analysis to calculate equivalent plastic strains of the test piece for hardness measurement, and acquiring a hardness-equivalent plastic strain curve on the basis of the hardnesses and the equivalent plastic strains at the hardness measurement positions; and specifying a hardness from the calculated value of equivalent plastic strain of an arbitrary part of the cold worked component on the basis of the hardness-equivalent plastic strain curve by performing numerical analysis to calculate a value of equivalent plastic strain of a cold worked component.

Method for estimating hardness of cold worked component and method for acquiring hardness-equivalent plastic strain curve of steel material

A hot rolled steel sheet having a chemical composition consisting of, in mass %, C: 0.020-0.180%, Si: 0.05-1.70%, Mn: 0.50-2.50%, Al: 0.010-1.000%, N: 0.0060%, P&#x2264;0.050%, S&#x2264;0.005%, Ti: 0-0.150%, Nb: 0-0.100%, V: 0-0.300%, Cu: 0-2.00%, Ni: 0-2.00%, Cr: 0-2.00%, Mo: 0-1.00%, B: 0-0.0100%, Mg: 0-0.0100%, Ca: 0-0.0100%, REM: 0-0.1000%, Zr: 0-1.000%, Co: 0-1.000%, Zn: 0-1.000%, W: 0-1.000%, the balance: Fe and impurities, wherein a metal microstructure includes, in area %, at a position &#xbc; W or &#xbe; W from an end face of the steel sheet and &#xbc; t or &#xbe; t from a surface, martensite: more than 2%-10%, retained austenite &#x3c;2%, bainite 40%, pearlite 2%, the balance: ferrite, an average circle-equivalent diameter of a metallic phase constituted of martensite/retained austenite is 1.0-5.0 &#x3bc;m, an average of minimum distances between adjacent metallic phases is 3 &#x3bc;m or more, and a standard deviation of nano hardness is 2.0 GPa or less.

Hot rolled steel sheet

A hot rolled steel sheet including a chemical composition consisting of, in mass %, C: 0.07-0.22%, Si: 1.00-3.20%, Mn: 0.80-2.20%, Al: 0.010-1.000%, N&#x2264;0.0060%, P&#x2264;0.050%, S&#x2264;0.005%, Ti: 0-0.150%, Nb: 0-0.100%, V: 0-0.300%, Cu: 0-2.00%, Ni: 0-2.00%, Cr: 0-2.00%, Mo: 0-1.00%, B: 0-0.0100%, Mg: 0-0.0100%, Ca: 0-0.0100%, REM: 0-0.1000%, Zr: 0-1.000%, Co: 0-1.000%, Zn: 0-1.000%, W: 0-1.000%, Sn: 0-0.050%, the balance: Fe and impurities, wherein a metal microstructure includes, in area %, at a position &#xbc; W or &#xbe; W from an end face of the steel sheet and &#xbc; t or &#xbe; t from a surface, retained austenite: more than 2%-10%, martensite &#x2264;2%, bainite: 10-70%, pearlite &#x2264;2%, the balance: ferrite, an average circle-equivalent diameter of a metallic phase constituted of retained austenite/martensite is 1.0 to 5.0 &#x3bc;m, an average of minimum distances between adjacent metallic phases is 3 &#x3bc;m or more, and a standard deviation of nano hardness is 2.5 GPa or less.

[Object] To enable flexible molding of a punch-nose in press working for obtaining a molded product including a U-shaped portion in a cross-section. [Solution] Provided is a press-working apparatus configured to provide a molded product by performing press working on a work, the molded product including, in a cross-section, a U-shaped portion including a bottom, a wall, and a punch-nose between the bottom and the wall, the press-working apparatus including: a die in which a recessed portion to receive the U-shaped portion is formed; a first punch that sandwiches a central area of the bottom with a bottom surface of the recessed portion; and a second punch that is pushed into the recessed portion later than the first punch, to restrain the wall between the second punch and a side surface of the recessed portion, and sandwich the work with the bottom surface to mold a peripheral area of the bottom and the punch-nose. A sandwiching width of the first punch that sandwiches the central area of the bottom and a setback amount of the second punch from the first punch in a push-in direction are set on the basis of a target sheet thickness of the punch-nose.

Press-working apparatus, press-working method, and press-molded product

A method for manufacturing a press-formed product includes: a first step of preparing a long material having a bending portion; and a second step of decreasing curvature of the bending portion while restricting both ends of the long material in a longitudinal direction.

Method for manufacturing press-formed product, device for manufacturing press-formed product, mandrel, and press-formed product

An evaluation method of a plastic material includes: a first shearing process of performing simple shearing deformation with respect to a first plastic sheet; a second shearing process of performing simple shearing deformation with respect to a second plastic sheet; a first partial stress-strain curve data obtaining process of obtaining first partial stress-strain curve data; a second partial stress-strain curve data obtaining process of obtaining second partial stress-strain curve data; and a synthesized stress-strain curve data obtaining process of obtaining synthesized stress-strain curve data based on the first partial stress-strain curve data and the second partial stress-strain curve data.

Evaluation method of plastic material and evaluation method of deformation processing of plastic material

[Object] To provide a press-molding apparatus capable of appropriately thickening a vertical wall portion while preventing the occurrence of buckling. [Solution] Provided is a press-molding apparatus configured to mold a press-molded product by performing press working on a work, the press-molding apparatus including: a support member that supports the work with a first thickness having a hat-shaped cross-section or a U-shaped cross-section; a punch member that moves relative to the support member to execute press working so as to reduce a height of a vertical wall portion of the work and thicken the vertical wall portion to a second thickness; and a pad member that faces the support member with the vertical wall portion to be thickened placed therebetween, the pad member being biased by a biasing member and having its distance to the support member kept equal to or smaller than the second thickness during the press working.

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Tokyo, Japan

Nobuo Yoshikawa