Nippon Kokan Kabushiki Kaisha

Kenzi Araki

Shiro Fukunaka

Takao Kurihara

Kuniki Uchida

Kazuhide Nakaoka

Haruo Kubotera

Kozi Iwase

Akihiko Nishimoto

Nobuo Tanaka

Hirosi Narita

In a continuous annealing process for a cold reduced steel strip substantially including a rapid cooling stage and a carbon precipitation treating stage into said process, the rapid cooling rate which is obtained by initial heating to above the recrystallization temperature and then slowly cooled for about 100 seconds to be above 200.degree. C./sec; and the starting temperature is controlled to be between 500.degree. C. and lower than 600.degree. C., thereby to obtain good press-formability of the continuously annealed steel strip.

Continuous annealing method for cold reduced steel strip

When an Al-killed steel consisting of, specially, 0.005% .ltoreq. [N] .ltoreq. 0.007%; 10 .times. [N] .ltoreq. Sol.Al. .ltoreq. 0.12%; and the ratio Sol.Al.%/[N]% controlled within the range of 10 to 20, is continuously cast, hot rolled, coiled at a high temperature, cold reduced and finally continuously annealed under special requirements, the steel strip is not at all inferior to the commercial base strip in mechanical properties and is made under high productivity and exhibits excellent uniformity in qualities.

Method of making cold-reduced Al-killed steel strip for press-forming by

A high tension Al-killed steel of which the yield point is more increased by the ensuing heat treatment after press-forming than that of the properties in which the tensile strength is above 40 to 80 Kg/mm.sup.2, is made by the following main steps:

Process of making high tension cold-reduced Al-killed steel excellent in

A steel consisting essentially of 0.04 to 0.10% C, 0.04 to 0.20% P, not more than 0.02% S, and [S]% .times. 10 to 0.7% Mn is conventionally hot and cold rolled. It is then subjected to the following continuous annealing:

Method of making high strength cold reduced steel by continuous

A steel being substantially made and adjusted within the range of 0.04 to 0.12% C, 0.50 to 2.00% Si, and 0.10 to 1.60% Mn, passed through ordinary hot and cold rolling processes, is subjected to a full continuous annealing process comprising the following steps:

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Kenzi Araki