Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Masaharu Oka

Nobusato Kojima

Masayuki Abe

Riki Okamoto

Nobuhiro Fujita

Manabu Takahashi

Eiji Tsuru

Takashi Morohoshi

Kenichiro Miyamoto

Masafumi Zeze

Yuji Koyama

Hiroshi Sugano

Ryusuke Miura

Shintaro Kusunoki

Yasuhiro Kinari

Akira Nakashima

Mamoru Saito

Mitsuru Yoshida

Chisato Wakabayashi

Seijun Higuchi

Tatsuya Kumagai

Akira Usami

Tetsuya Okada

Kenichiroh Matsumura

Yuta Dairokuno

Kazushi Maruyama

Haruyuki Nagayoshi

Masahito Sakaki

Kentarou Hirata

Kazumi Sagara

Ryusuke Inoue

Satoshi Akamatsu

Michihiro Nono

Toshio Akiyama

A hot-rolled steel sheet has a predetermined chemical composition in which a microstructure includes 99% or more of martensite by volume fraction and a remainder in microstructure including residual austenite and ferrite, in a cross section parallel to a rolling direction, an average aspect ratio of prior austenite grains is less than 3.0, a proportion of sulfides having an aspect ratio of more than 3.0 among sulfides having an area of 1.0 μmor more is 1.0% or, less, in a thickness middle portion, and a pole density of {211}<011> orientation is 3.0 or less, and a tensile strength TS is 980 MPa or higher.

Hot rolled steel sheet and production method thereof

A hot-rolled steel sheet which has excellent rigidity along with high strength, excellent workability, and excellent LME resistance is provided. A hot-rolled steel sheet of the present embodiment consists of, in mass %, C: 0.040 to 0.120%, Si: 0.01 to 0.60%, Mn: 0.50 to 1.50%, P: 0.025% or less, S: 0.010% or less, Al: 0.010 to 0.070%, N: 0.0070% or less, Ti: 0.055 to 0.200%, and B: 0.0010 to 0.0050%, with the balance being Fe and impurities. In the microstructure of the hot-rolled steel sheet, an area fraction of bainitic ferrite is 85% or more and the dislocation density is 8.0×10to 100.0×10/m. The average equivalent circular diameter of Ti carbides in the hot-rolled steel sheet is 10 nm or less, and the average equivalent circular diameter of grains of the bainitic ferrite is 15 μm or less.

Hot-rolled steel sheet, hot-dip coated steel sheet, and method for producing hot-rolled steel sheet

A steel sheet for a drawn can has a predetermined chemical composition and has a ferrite single-phase structure with a crystal grain size number of 11.0 or more, the sheet thickness is 0.15 to 0.50 mm, in an L direction of the steel sheet after an ageing treatment at 100&#xb0; C. for one hour, an yield strength YP is 220 to 290 MPa, a tensile strength TS is 330 to 390 MPa, a total elongation EL is 32% or more, an yield point elongation YP-EL is 0%, an average plastic strain ratio ris more than 1.35, and an in-plane anisotropy &#x394;r is &#x2212;0.30 to +0.15.

Cold rolled steel sheet for drawn can and method for manufacturing same

Provided is a galvannealed steel sheet having high strength and excellent deep drawability, and being further excellent in slab cracking resistance and secondary working embrittlement resistance. A base metal steel sheet of the galvannealed steel sheet has a chemical composition containing, in mass %: C: 0.0080% or less; Si: 0.7% or less; Mn: 1.0 to 2.5%; P: more than 0.030 to 0.048%; S: 0.025% or less; Al: 0.005 to 0.20%; N: 0.010% or less; Ti: 0.005 to 0.040%; Nb: 0.005 to 0.060%; and B: 0.0005 to 0.0030%, with the balance being Fe and impurities, satisfying Formula (1) to (4). A galvannealed layer contains 7 to 15 mass % of Fe.25&#xd7;P+4&#xd7;Si&#x2264;3.6&#x2003;&#x2003;(1)B&#x2212;X1&#x2265;0.0005&#x2003;&#x2003;(2)C&#x2212;(12/93)&#xd7;Nb&#x2212;X2&#x2265;&#x2212;0.0035&#x2003;&#x2003;(3)110&#xd7;Si+48&#xd7;Mn+550&#xd7;P&#x2265;120&#x2003;&#x2003;(4)

Galvannealed steel sheet and production method thereof

A galvanized steel sheet according to the present invention includes a steel sheet and a galvanizing layer which is formed on a surface of the steel sheet. The steel sheet includes as a chemical component, by mass %, C: more than 0.100% to 0.500%, Si: 0.0001% to less than 0.20%, Mn: more than 0.20% to 3.00%, Al: 3.0% to 10.0%, N: 0.0030% to 0.0100%, Ti: more than 0.100% to 1.000%, P: 0.00001% to 0.0200%, S: 0.00001% to 0.0100% and a remainder including Fe and impurities. The galvanizing layer includes as a chemical composition, by mass %, Fe: 0.01% to 15% and a remainder including Zn and impurities. The galvanized steel sheet has a specific gravity of 5.5 to less than 7.5.

Galvanized steel sheet and method for producing the same

A steel sheet including, by mass %, C: more than 0.100% and 0.500% or less, Si: 0.0001% or more and less than 0.20%, Mn: more than 0.20% and 0.50% or less, Al: 3.0% or more and 10.0% or less, N: 0.0030% or more and 0.0100% or less, Ti: more than 0.100% and 1.000% or less, P: 0.00001% or more and 0.0200% or less, S: 0.00001% or more and 0.0100% or less, and a remainder including Fe and impurities, in which a sum of a C content and a Ti content satisfies 0.200&#x3c;C+Ti&#x2264;1.500 by mass %, a product of an Al content and an Si content satisfies Al&#xd7;Si&#x2264;0.8 by mass %, and a specific gravity is 5.5 to less than 7.5.

High-strength low-specific-gravity steel sheet having superior spot weldability

The present invention provides a bake-hardenable high-strength cold-rolled steel sheet having excellent bake hardenability, cold aging resistance, and deep-drawability, and reduced planar anisotropy, containing chemical components in % by mass of: C: 0.0010% to 0.0040%, Si: 0.005% to 0.05%, Mn: 0.1% to 0.8%, P: 0.01% to 0.07%, S: 0.001% to 0.01%, Al: 0.01% to 0.08%, N: 0.0010% to 0.0050%, Nb: 0.002% to 0.020%, and Mo: 0.005% to 0.050%, a value of [Mn %]/[P %] being in the range of 1.6 to 45, where [Mn %] is an amount of Mn and [P %] is an amount of P, an amount of C in solid solution obtained from [C %]&#x2212;(12/93)&#xd7;[Nb %] being in the range of 0.0005% to 0.0025%, where [C %] is an amount of C and [Nb %] is an amount of Nb, with a balance including Fe and inevitable impurities, wherein the bake-hardenable high-strength cold-rolled steel sheet satisfies the following Equation (1), where X(222), X(110), and X(200) represent ratios of integrated intensity of X-ray diffraction of {222} plane, {110} plane, and {200} plane, respectively, being parallel to a plane located at a depth of &#xbc; plate thickness measured from the surface of the steel sheet, and the bake-hardenable high-strength cold-rolled steel sheet has tensile strength in the range of 300 MPa to 450 MPa.

Bake-hardenable high-strength cold-rolled steel sheet and method of manufacturing the same

A high-strength steel plate includes the following composition: 0.18 to 0.23 mass % of C; 0.1 to 0.5 mass % of Si; 1.0 to 2.0 mass % of Mn; 0.020 mass % or less of P; 0.010 mass % or less of S; greater than 0.5 mass % and equal to or less than 3.0 mass % of Cu, 0.25 to 2.0 mass % of Ni; 0.003 to 0.10 mass % of Nb; 0.05 to 0.15 mass % of Al; 0.0003 to 0.0030 mass % of B; 0.006 mass % or less of N; and a balance composed of Fe and inevitable impurities. A weld crack sensitivity index Pcm of the high-strength steel plate is calculated by Pcm=[C]+[Si]/30+[Mn]/20+[Cu]/20+[Ni]/60+[Cr]/20+[Mo]/15+[V]/10+5[B], and is 0.39 mass % or less. The Atransformation point is equal to or less than 850&#xb0; C., the percentage value of a martensite structure is equal to or greater than 90%, the yield strength is equal to or greater than 1300 MPa, and the tensile strength is equal to or greater than 1400 MPa and equal to or less than 1650 MPa. If the tensile strength is less than 1550 MPa, the prior austenite grain size number N&#x3b3; satisfies the formula N&#x3b3;&#x2267;([TS]&#x2212;1400)&#xd7;0.006+7.0, and if the tensile strength is equal to or greater than 1550 MPa, the prior austenite grain size number N&#x3b3; satisfies the formula&#x3b3;&#x2267;([TS]&#x2212;1550)&#xd7;0.01+7.9.

High-strength steel plate and producing method therefor

A cast steel with excellent workability, characterized in that not less than 60% of the total cross section thereof is occupied by equiaxed crystals, the diameters (mm) of which satisfy the following formula:&#x3c;1.2+0.75,wherein D designates each diameter (mm) of equiaxed crystals in terms of internal structure in which the crystal orientations are identical, and X the distance (mm) from the surface of the cast steel. The cast steel and the steel material obtained by processing the cast steel have very few surface flaws and internal defects.

Cast steel and steel material with excellent workability, method for processing molten steel therefor and method for manufacturing the cast steel and steel material

Cast steel piece and steel product excellent in forming characteristics and method for treatment of molted steel therefor and method for production thereof

Oil well pipe threaded joint

Joint for steel pipe having high galling resistance and surface

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Tokyo, Japan

Masaharu Oka