Nkk Corporation

Jfe Steel Corporation

Katsutoshi Ito

Takeshi Fujita

Nobuyuki Nakamura

Yasuyuki Takada

Toshiaki Urabe

Kenichi Mitsuzuka

Hideyuki Tsurumaru

To provide a high carbon steel sheet having excellent hardenability and toughness, and low planar anisotropy of tensile properties affecting workability, and a method of producing the same. A high car steel sheet having chemical composition specified by JIS G 4051 (Carbon steels for machine structural use), JIS G 4401 (Carbon tool steels) or JIS G 4802 (Cold-rolled steel strips for springs), wherein more than 50 carbides having a diameter of 1.5 &#x3bc;m or larger exist in 2500 &#x3bc;m, the ratio of number of carbides having a diameter of 0.6 &#x3bc;m or less with respect to all the carbides is 80% or more, and the &#x394;r is more than &#x2212;0.15 to less than 0.15, herein &#x394;r=(r0+r90&#x2212;2&#xd7;r45)/4, and r0, r45, and r90 shows a r-value of the directions of 0&#xb0; (L), 45&#xb0; (S) and 90&#xb0; (C) with respect to the rolling direction respectively.

High carbon steel and production method thereof

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

The present invention relates to a high carbon steel sheet having chemical composition specified by JIS G 4051 (Carbon steels for machine structural use), JIS G 4401 (Carbon tool steels) or JIS G 4802 (Cold-rolled steel strips for springs), wherein the ratio of number of carbides having a diameter of 0.6 &mgr;m or less with respect to all the carbides is 80% or more, more than 50 carbides having a diameter of 1.5 &mgr;m or larger exist in 2500 &mgr;m of observation field area of electron microscope, and the &Dgr;r is more than &minus;0.15 to less than 0.15. The high carbon steel sheet of the invention is excellent in hardenability and toughness, and formable with a high dimensional precision.

High carbon steel sheet

Growing community of inventors

Fukuyama, Japan

Katsutoshi Ito