Kabushiki Kaisha Kobe Seiko Sho

Zenichi Shibata

Shunichi Hashimoto

Masatoshi Sudo

Ichiro Kokubo

Ichiro Tsukatani

Hiromi Hori

Kazuhiko Kourida

Kazuhiro Mimura

A high strength hot rolled steel sheet for wheel rims contains, by weight, from 0.05 to 0.15% of C, from 0.05 to 0.5% of Si, from 1.0 to 1.6% of Mn, from 0.01 to 0.05% of Al, from 0.005 to 0.025% of Ti and from 15 to 60 ppm of N, with the content of P limited to 0.030% or below and the content of S limited to 0.010% or below, the balance being iron and unavoidable impurities. The steel sheet optionally contains, by weight, from 0.01 to 0.06% of Nb or at least one selected from the group consisting of from 0.0005 to 0.01% of Ca and from 0.005 to 0.1% of rare earth metals.

High strength hot rolled steel sheet for wheel rims

A cold-rolled high strength steel plate with excellent formability and baking hardenability, has the composition (% by weight) 0.2-0.15% of C, 0.02-0.7% of Mn, 0.01-0.1% of Al and 0.002-0.01% of N, optionally at least one element selected from the group consisting of 0.01-0.8% of Si, 0.01-0.1% of P, 0.0002-0.005% of B and 0.01-0.5% of V, and a microstructure comprising ferrite containing 2-30% of bainite and less than 8% of martensite. The steel plate is produced by hot and cold rolling steel of the defined composition followed by rapidly heating to a temperature between the Ac.sub.1 and Ac.sub.3 transformation points, holding at this temperature for less than 5 minutes, and quenching to a temperature below 500.degree. C. at a cooling rate between 50.degree. and 500.degree. C./sec.

Cold-rolled high strength steel plate with composite steel structure of

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Kobe, Japan

Zenichi Shibata