Nkk Corporation

Other

Jfe Steel Corporation

Kenichi Mitsuzuka

Takeshi Fujita

Nobuyuki Nakamura

Yasushi Tanaka

Naoki Matsui

Hideki Matsuoka

Hideyuki Kimura

Reiko Sugihara

Tatsuhiko Hiratani

Toshiaki Urabe

Satoshi Ueoka

Hiroaki Kato

Kenji Tahara

Satoshi Kodama

Hiroshi Sawada

Toru Inazumi

Yoshimasa Funakawa

Katsutoshi Ito

Hideyuki Tsurumaru

Chohachi Sato

Naoya Aoki

Kenichiro Takayanagi

Masamichi Okada

Jun Taniai

The present invention provides an ultra soft high carbon hot-rolled steel sheet. The ultra soft high carbon hot-rolled steel sheet contains 0.2% to 0.7% of C, 0.01% to 1.0% of Si, 0.1% to 1.0% of Mn, 0.03% or less of P, 0.035% or less of S, 0.08% or less of Al, 0.01% or less of N, and the balance being Fe and incidental impurities and further contains 0.0010% to 0.0050% of B and 0.05% to 0.30% of Cr in some cases. In the texture of the steel sheet, an average ferrite grain diameter is 20 &#x3bc;m or more, a volume ratio of ferrite grains having a grain diameter of 10 &#x3bc;m or more is 80% or more, and an average carbide grain diameter is in the range of 0.10 to less than 2.0 &#x3bc;m. In addition, the steel sheet is manufactured by the steps, after rough rolling, performing finish rolling at a reduction ratio of 10% or more and at a finish temperature of (Ar&#x2212;20&#xb0; C.) or more in a final pass, then performing first cooling within 2 seconds after the finish rolling to a cooling stop temperature of 600&#xb0; C. or less at a cooling rate of more than 120&#xb0; C./sec, then performing second cooling so that the steel thus processed is held at 600&#xb0; C. or less, then performing coiling at 580&#xb0; C. or less, followed by pickling, and then performing spheroidizing annealing at a temperature in the range of 680&#xb0; C. to the Actransformation point.

Method for manufacturing an ultra soft high carbon hot-rolled steel sheet

The present invention relates to a steel sheet that consists essentially of 0.10 to 0.37% C, 1% or less Si, 2.5% or less Mn, 0.1% or less P, 0.03% or less S, 0.01 to 0.1% sol.Al, 0.0005 to 0.0050% N, 0.0003 to 0.0050% B, by mass, and balance of Fe, &lsqb;14B/(10.8N)&rsqb; being 0.5 or more, average particle size of precipitate BN being 0.1 &mgr;m or more, and grain size of prior austenite after the hardening treatment being 2 to 25 &mgr;m. The steel sheet according to the present invention allows an inexpensive hardening treatment method to be applied to improve the strength to a level required for the structural components and the functional components of automobiles, while providing excellent toughness after the hardening treatment.

Steel sheet and method for manufacturing the same

A method of making a steel sheet for a tension mask, including the steps of: hot rolling a steel consisting essentially of, by weight %, C: less than 0.1%, Si: 0.05% or less, Mn: 0.4 to 2%, P: 0.03% or less, S: 0.03% or less, sol.Al: 0.01% or less, N: 0.010% or more, and the balance of Fe; and annealing the cold rolled steel sheet, followed by a secondary cold rolling at a reduction rate of 35% or higher. The steel sheet produced by this method shows excellent creep resistance during blackening treatment and excellent magnetic shielding property with an anhysteretic permeability of 3400 or more at a DC bias magnetic field of 0.35 Oe, and therefore causes no color-deviation when applied to the tension mask.

Steel sheet for tension mask, making method thereof and tension mask

A soft cold-rolled steel sheet contains: 0.06 wt. % or less C, 0.1 wt. % or less Si, 0.5 wt. % or less Mn, 0.03 wt. % or less P, 0.03 wt. % or less S, 0.006 wt. % or less N, 0.009 wt. % or less B and the balance being Fe. The method comprises the steps of: continuously casting a steel to produce a slab; hot-rolling the slab to form a hot-rolled steel sheet; cold-rolling the hot-rolled steel sheet to produce a cold-rolled steel sheet; and continuously annealing the cold-rolled steel sheet.

Soft cold-rolled steel sheet and method for making the same

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Fukuyama, Japan

Kenichi Mitsuzuka