Nippon Steel Sumitomo Metal Corporation

Nippon Steel Corporation

Tdk Corporation

Mitsubishi Denki Kabushiki Kaisha

Konica Corporation

Kaoru Kawasaki

Naoki Yoshinaga

Nobuhiro Fujita

Manabu Takahashi

Toshimasa Tomokiyo

Satoshi Kato

Toshiki Nonaka

Koji Hashimoto

Hiroshi Yamamoto

Kiyokazu Ishizuka

Masashi Gotoh

Yasuhiro Shinohara

Shinya Sakamoto

Takehide Senuma

Mutsuko Nakano

Junji Haji

Kunio Hayashi

Riki Okamoto

Kohichi Sano

Natsuko Sugiura

Yasunobu Miyazaki

Genki Abukawa

Ikuo Kikuchi

Kazumi Nishimura

Hiroshi Yagi

Ryo Kobayashi

Kazuya Sato

Kazuo Hikida

Minoru Ozaki

Yasunori Chiba

Kazuo Koyama

Chisato Wakabayashi

Akihiko Seki

Takaya Ishigaki

Masatoshi Ito

Yasuaki Naito

Ryuji Hosogaya

Takashi Abe

Fumio Matsuda

Yasushi Izumibe

Yoshimi Yodokawa

Kazuyuki Shimazaki

Eizou Tsunoda

Shigehiko Shirai

Minoru Kanzaki

Takahiro Yoshinaga

Hiroshi Harada

Yoshihito Sekito

Takahiro Mori

Hiroyuki Kawata

Masafumi Azuma

Kenichi Yamamoto

Hajime Kuwajima

Wataru Ohashi

Masaaki Mizumura

Takeshi Kawachi

Toshiyuki Niwa

Hideaki Yamamura

Atsushi Seto

Takashi Matsuno

Shunji Hiwatashi

Yasuharu Sakuma

Masayoshi Suehiro

Akira Saitoh

Eizo Tsunoda

Hatsuhiko Oikawa

Kuniichi Yoda

Nobutaka Shimizu

Teruaki Yamada

Atsushi Itami

Katsuhiro Sasai

Masaharu Kameda

Seiichi Daimaru

Mutsumi Sakakibara

Hisato Kato

Matsuo Usuda

Nobuhiko Matsuzu

Taketoshi Taira

Tamaki Suzuki

Tatsuya Sakiyama

A blank material is formed from a steel sheet, a first quenching of the blank material is performed, and a second quenching of the blank material is performed after the first quenching. When the first quenching is performed, the blank material is heated to a first temperature of not lower than (Ac3 point&#x2014;50)&#xb0; C. nor higher than 1200&#xb0; C. at an average heating rate of 2&#xb0; C./sec or more, and the blank material is cooled from the first temperature to a second temperature of 250&#xb0; C. or lower. When the second quenching is performed, the blank material is heated from the second temperature to a third temperature of not lower than (Ac3 point&#x2014;50)&#xb0; C. nor higher than 1200&#xb0; C. at an average heating rate of 2&#xb0; C./sec or more, and the blank material is cooled from the third temperature to a fourth temperature of 250&#xb0; C. or lower. Forming of the blank material is performed in the first quenching or the second quenching or both of the above.

Hot stamped part and manufacturing method thereof

A hot press-formed part according to an aspect of the present invention contains a predetermined chemical composition; in which a microstructure in a thickness &#xbc; portion includes, by unit vol %, tempered martensite: 20% to 90%, bainite: 5% to 75%, and residual austenite: 5% to 25%, and ferrite is limited to 10% or less; and a pole density of an orientation {211}&#x3c;011&#x3e; in the thickness &#xbc; portion is 3.0 or higher.

Hot press-formed part

A steel sheet for hot stamping includes a steel structure represented by an area fraction of bainite, fresh martensite and tempered martensite: 80% or more in total, and a product of a number density (pieces/&#x3bc;m) of carbides and a proportion of carbides precipitated into prior austenite grains in carbides: 0.50 or more.

Steel sheet for hot stamping

A tailored blank for hot stamping includes a welded portion formed by butt-welding a first aluminum-plated steel sheet and a second aluminum-plated steel sheet, an Average Al concentration of a weld metal in the welded portion is in a range of 0.3 mass % to 1.5 mass %, an Acpoint of the weld metal is 1250&#xb0; C. or lower, and furthermore, an aluminum layer formed during the butt-welding is present on a surface of the welded portion.

Tailored blank for hot stamping, hot stamped member, and methods for manufacturing same

A hot-stamped part includes a chemical composition represented by, in mass %: C: 0.120% to 0.400%; Si: 0.005% to 2.000%; Mn or Cr, or both thereof: 1.00% to 3.00% in total; Al: 0.005% to 0.100%; B: 0.0003% to 0.0020%; P: not more than 0.030%; S: not more than 0.0100%; O: not more than 0.0070%; N: not more than 0.0070%; Ti: 0% to 0.100%; Nb: 0% to 0.100%; V: 0% to 0.100%; Ni: 0% to 2.00%; Cu: 0% to 2.00%; Mo: 0% to 0.50%; Ca or REM, or both thereof: 0% to 0.0300% in total; and the balance: Fe and impurities, and a structure represented by: an area fraction of martensite or bainite, or both thereof: not less than 95% in total; a coverage factor of prior austenite grain boundary by iron-based carbides: not more than 80%; and a number density of iron-based carbides in prior austenite grains: not less than 45/&#x3bc;m.

Hot-stamped part and method of manufacturing the same

A cold-rolled steel sheet has a predetermined chemical composition, in which a structure before and after a hot-stamping includes ferrite: 30 area % to 90 area %, martensite: 0 area % or more and less than 20 area %, pearlite: 0 area % to 10 area %, retained austenite: 5 volume % to 20 volume %, and rest structure: bainite, a hardness of the retained austenite measured with a nano indenter before and after the hot-stamping satisfies relations of H/H&#x3c;1.1 and &#x3c3;HM&#x3c;20, and a relation of TS&#xd7;El&#x2265;20000 MPa&#xb7;% is satisfied.

Cold-rolled steel sheet and method for manufacturing same, and hot-stamp formed body

A hot stamped article has a component composition containing, in terms of % by mass, 0.002% to 0.1% of C, 0.01% to 0.5% of Si, 0.5% to 2.5% of Mn+Cr, 0.1% or less of P, 0.01% or less of S, 0.05% or less of t-Al, 0.005% or less of N, and 0.0005% to 0.004% of B which is optionally contained in a case where the Mn+Cr is 1.0% or more, the remainder being Fe and unavoidable impurities. The hot stamped article has a microstructure composed of, in terms of an area ratio, 0% or more and less than 90% of martensite, 10% to 100% of bainite, and less than 0.5% of unavoidable inclusion structures, or a microstructure composed of, in terms of an area ratio, 99.5% to 100% of bainitic ferrite, and less than 0.5% of unavoidable inclusion structures.

Hot stamped article, method of producing hot stamped article, energy absorbing member, and method of producing energy absorbing member

The present invention provides a method of production of hot dip galvannealed steel sheet with excellent workability compared with the Sendzimir method or non-oxidizing furnace method and further with excellent powdering or slidability, that is, a method of production of hot dip galvannealed steel sheet with excellent workability, powdering, and slidability characterized by processing a slab containing, by mass %, C: 0.01 to 0.12%, Mn: 0.05 to 0.6%, Si: 0.002 to 0.1%, P: 0.05% or less, S: 0.03% or less, sol. Al: 0.005 to 0.1%, and N: 0.01% or less and having a balance of Fe and unavoidable impurities by hot rolling, pickling, cold rolling, then annealing at 650 to 900&#xb0; C., cooling to 250 to 450&#xb0; C., holding at said temperature range for 120 seconds or more, then cooling to room temperature, pickling, preplating Ni or Ni&#x2014;Fe without intermediate temper rolling, heating by 5&#xb0; C./sec or more down to 430 to 500&#xb0; C., galvanizing in a galvanization bath, wiping, then heating by a rate of temperature rise of 20&#xb0; C./sec or more up to 460 to 550&#xb0; C., not providing any soaking time or holding for soaking for less than 5 seconds, then cooling by 3&#xb0; C./sec or more, and final temper rolling by a 0.4 to 2% elongation rate.

Method of production of hot dip galvannealed steel sheet with excellent workability, powderability, and slidability

A cold-rolled steel sheet includes a predetermined chemical composition, and includes a structure expressed by: an area fraction of ferrite: 95% or more; an area fraction of retained austenite and an area fraction of martensite: 1% to 3% in total; a product of the area fraction of retained austenite and a carbon concentration in retained austenite: 1 or more; a value of I(111)/{I(100)+I(110)} at a region where a depth from a surface is &#xbc; of a thickness of the cold-rolled steel sheet when intensity of a (hkl) plane is expressed by I(hkl): 2 or less.

Cold-rolled steel sheet, galvanized cold-rolled steel sheet and method of manufacturing the same

A hot stamped steel according to the present invention satisfies an expression of (5&#xd7;[Si]+[Mn])/[C]&#x3e;11 when [C] represents an amount of C by mass %, [Si] represents an amount of Si by mass %, and [Mn] represents an amount of Mn by mass %, a metallographic structure after hot stamping includes 40% to 90% of a ferrite and 10% to 60% of a martensite in an area fraction, a total of an area fraction of the ferrite and an area fraction of the martensite is 60% or more, a hardness of the martensite measured with a nanoindenter satisfies an H2/H1&#x3c;1.10 and &#x3c3;HM&#x3c;20, and TS&#xd7;&#x3bb;, which is a product of a tensile strength TS and a hole expansion ratio &#x3bb; is 50000 MPa&#xb7;% or more.

Hot stamped steel and method for producing hot stamped steel

A cold rolled steel sheet according to the present invention satisfies an expression of (5&#xd7;[Si]+[Mn])/[C]&#x3e;11 when [C] represents an amount of C by mass %, [Si] represents an amount of Si by mass %, and [Mn] represents an amount of Mn by mass %, a metallographic structure before hot stamping includes 40% to 90% of a ferrite and 10% to 60% of a martensite in an area fraction, a total of an area fraction of the ferrite and an area fraction of the martensite is 60% or more, a hardness of the martensite measured with a nanoindenter satisfies an H2/H1&#x3c;1.10 and &#x3c3;HM&#x3c;20 before the hot stamping, and TS&#xd7;&#x3bb; which is a product of a tensile strength TS and a hole expansion ratio &#x3bb; is 50000 MPa&#xb7;% or more.

Cold rolled steel sheet and method for producing cold rolled steel sheet

In a hot stamped steel, when [C] represents an amount of C (mass %), [Si] represents an amount of Si (mass %), and [Mn] represents an amount of Mn (mass %), an expression of 5&#xd7;[Si]+[Mn])/[C]&#x3e;10 is satisfied, a metallographic structure includes 80% or more of a martensite in an area fraction, and optionally, further includes one or more of 10% or less of a pearlite in an area fraction, 5% or less of a retained austenite in a volume ratio, 20% or less of a ferrite in an area fraction, and less than 20% of a bainite in an area fraction, TS&#xd7;&#x3bb;, which is a product of TS that is a tensile strength and &#x3bb; that is a hole expansion ratio is 50000 MPa&#xb7;% or more, and a hardness of the martensite measured with a nanoindenter satisfies H2/H1&#x3c;1.10 and &#x3c3;HM&#x3c;20.

Hot stamped steel and method for producing the same

A high-strength steel sheet includes: 0.03 to 0.20% of C, 0.08 to 1.5% of Si, 0.5 to 3.0% of Mn, 0.05% or less of P, 0.0005% or more of S, 0.008 to 0.20% of acid-soluble Ti, 0.0005 to 0.01% of N, more than 0.01% of acid-soluble Al, and 0.001 to 0.04% of one or both of Ce and La in terms of mass %; and the balance including Fe and inevitable impurities. The ratio of (Ce+La)/acid-soluble Al is equal to or more than 0.1 and the ratio of (Ce+La)/S is in the range of 0.4 to 50 in a mass base, and the density of the number of inclusions, having a circle equivalent diameter of 2 &#x3bc;m or less, which are present in the steel sheet is equal to or more than 15/mm.

High-strength steel sheet and method of producing molten steel for high-strength steel sheet

When the amount of C, the amount of Si and the amount of Mn are respectively represented by [C], [Si] and [Mn] in unit mass %, the cold rolled steel sheet satisfies a relationship of (5&#xd7;[Si]+[Mn])/[C]&#x3e;10, the metallographic structure contains, by area ratio, 40% to 90% of a ferrite and 10% to 60% of a martensite, further contains one or more of 10% or less of a pearlite by area ratio, 5% or less of a retained austenite by volume ratio and 20% or less of a bainite by area ratio, the hardness of the martensite measured using a nanoindenter satisfies H20/H10&#x3c;1.10 and &#x3c3;HM0&#x3c;20, and TS&#xd7;&#x3bb; representing the product of TS that is a tensile strength and &#x3bb; that is a hole expansion ratio is 50000 MPa&#xb7;% or more.

Cold rolled steel sheet and manufacturing method thereof

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Tokyo, Japan

Kaoru Kawasaki