Nippon Steel Corporation

Sony Corporation

Kazuo Koyama

Atsushi Itami

Hiroshi Katoh

Nobuhiko Matsuzu

Hiroshi Takechi

Takashi Furukawa

Kaoru Kawasaki

Yasuharu Sakuma

Masayoshi Suehiro

Kunihiko Komiya

Hiromi Toyota

Takeshi Kubota

Manabu Takahashi

Naoki Yoshinaga

Shigeru Ogawa

Toshiaki Mizoguchi

Eiichi Takeuchi

Hiroaki Kato

Munetsugu Matsuo

Satoru Tanaka

Shunji Hiwatashi

Hiroaki Masui

Yoshiyuki Ueshima

Tsuyoshi Kawano

Teruo Takeuchi

Yoshikazu Matsumura

Satoshi Akamatsu

Yujiro Miyauchi

Matsuo Usuda

Kiyomi Shio

Chohachi Sato

Taketoshi Taira

Yoshio Morimoto

Natsuko Hashimoto

Chikara Fujii

Kazuhide Usami

Takahito Watanabe

Hirohide Asano

Takaji Takahashi

Provided are a high strength cold rolled steel sheet and a high strength plated steel sheet possessing improved geomagnetic shielding properties, that is, having a high relative permeability in a d.c. magnetic field around 0.3 Oe, a process for producing the same, and an explosion-proof band or an outer magnetic shielding material, for television cathode-ray tubes, using the steel sheet. An ultra low carbon steel, which has a carbon content of not more than 0.0060% and has been subjected to solid solution strengthening utilizing silicon and magnesium without relying upon precipitation strengthening, is deoxidized with silicon so that aluminum is substantially absent in the steel. Alternatively, when the ultra low carbon steel is deoxidized with aluminum, boron is added to inhibit the precipitation of AlN. Next, the deoxidized steel is finish rolled at 750 to 980.degree. C., cold rolled with a reduction ratio of 60 to 90%, and then annealed in the temperature range of 750.degree. C. to the Ac.sub.3 point in a continuous annealing equipment or an in-line annealing type continuous galvanizing equipment to bring the ferrite grain diameter in the metallographic structure to 10 to 200 .mu.m.

High-strength cold rolled steel sheet and high-strength plated steel

Cold rolled steel sheet and galvanized steel sheet having improved

Twin-roll continuous casting method

High-strength steel sheet suitable for deep drawing and process for

Continuously cast slab of extremely low carbon steel with less surface

A building low yield ratio hot-dip galvanized cold rolled steel sheet having an improved refractory property, consists essentially of, by weight, 0.1% or less of C, 0.1 to 1.5% of Mn, 0.1% of less of P, 0.06% or less of Al, 0.6 to 2.0% of Cu, and a remainder of Fe and unavoidable impurities and having a 0.6 times or more yield point strength at 600.degree. C. compared to that at normal temperatures. The method of forming the steel sheet comprises the steps of: forming a slab from a steel consisting essentially of, by weight, 0.1% or less of C, 0.1 to 1.5% of Mn, 0.1% or less of P, 0.06% or less of Al, 0.6 to 2.0% of Cu, and a remainder of Fe and unavoidable impurities, immediately or after heating the slab at a temperature of 1200.degree. C. or less, hot rolling the slab at a temperature of 750.degree. C. or more and cold rolling, effecting a continuous hot-dip galvanizing process, heating the rolled slab at a temperature of 700.degree. to 900.degree. C. in a reducing atmosphere, cooling the rolled slab at an average cooling rate of 3.degree. C./sec or more and dipping the rolled slab in a hot-dip galvanizing bath.

Building low yield ratio hot-dip galvanized cold rolled steel sheet

Disclosed are processes for producing cold rolled steel sheets and strips having excellent press formability and ageing property by a continuous annealing method, in which specific heating cycles are adopted in combination with steel compositions with lowered phosphorus contents.

Process for producing cold rolled steel sheets having excellent press

A process for producing a cold-rolled high strength steel sheet having an excellent formability and conversion-treatability, comprising the steps of: heating to a temperature of 1150.degree. C. or lower, a steel slab comprising; 0.005 wt % or less of C, 0.5-1.5 wt % of Si, 0.1-0.5 wt % of Mn, 0.003-0.05 wt % and at least 3.4.times.N wt % of Ti, 0.003-0.05 wt % and at least 7.8.times.C wt % of Nb, 0.01-0.1 wt % of Al, 0.05-0.15 wt % of P, 0.010 wt % or less of S, 0.005 wt % or less of N, 0.0001-0.0050 wt % of B, the balance consisting of Fe and unavoidable impurities; hot-rolling the steel slab with a finishing rolling temperature of the A.sub.r3 point of the steel or higher to obtain a hot-rolled steel sheet; cooling the hot-rolled steel sheet at a cooling rate of 10.degree. C./sec or more in the stage between said finishing rolling and the following coiling step, with the provision that said cooling is started not later than 2 sec after the hot-rolling is finished and is continued for a duration of at least 3 sec; coiling the steel sheet at a temperature of 650.degree. C. or higher; cold-rolling the steel sheet at a usual rolling draft; and continuous-annealing the cold-rolled steel sheet at a heat-cycle of holding for 1 sec or longer at a temperature of 930.degree. C. or lower to complete the recrystallization of the cold-rolled steel sheet.

Process for producing cold-rolled high strength steel sheet having

A hot-rolled steel sheet suitable for enamelling on one side is disclosed. The steel consists essentially of 0.0050-0.07 wt % C, 0.05-1.5 wt % Mn, 0.03 0.15 wt % P, 0.03-0.1 wt % Al, 0.003-0.010 wt % N, provided that the N content is the sum of at least 0.002 wt % of free nitrogen not bound to Al and the content of nitrogen in other states, the nitrogen content as defined above satisfying the condition of Al/N.gtoreq.10 on the basis of weight percents and the balance being Fe and incidental impurities.

One-sided enamelable hot-rolled steel sheet and process for producing

An r value of a hot-rolled steel sheet is enhanced by: a specific composition consisting of not more than 0.015 wt % of C, from 1.0 to 2.5 wt % of Mn, from 0.005 to 0.10 wt % of Al, from 0.01 to 0.06 wt % of Nb, from 0.01 to 0.1 wt % of Ti; and, controlled rolling, characterized by in the rough rolling, imparting, in a temperature range of from 980.degree. to 1100.degree. C., a heavy reduction of not less than 20% per pass to the steel sheet; completing a finishing rolling at from Ar.sub.3 to 930.degree. C. and maintaining a total reduction at a temperature of not more than Ar.sub.3 +150.degree. C. to not less than 90%; and, coiling at a temperature of from 600.degree. to 800.degree. C.

Process for producing hot-rolled steel sheet having high r value

A high-strength cold-rolled steel sheet with dual-phase structure, recently developed by the Japanese steel producers have a low yield ratio of approximately 0.6 or lower, is free of the yield-point elongation and is of excellent press-formability. One of the production methods of this steel is a continuous annealing at a temperature range of two-phase structure of ferrite (.alpha.)+austenite (.gamma.). In order to improve the formability, the artificial-aging hardenability after forming, yield ratio and ductility over those of the known dual-phase steel, the present invention provides a method for producing a dual-phase steel, which comprise a step of cooling from the annealing temperature to a temperature not higher than 200.degree. C. at an average cooling rate (R.sub.1) in the range of 1.degree. C./second.gtoreq.R.sub.1 .ltoreq.30.degree. C./second over the primary cooling stage from the annealing temperature down to an intermediate temperature (T) in the range of 420.degree. C..ltoreq.T.ltoreq.700.degree. C., and at an average cooling rate (R.sub.2) in the range of 100.degree. C./second.ltoreq.R.sub.2 .ltoreq.300.degree. C./second over the secondary cooling stage from the intermediate temperature (T) down to the temperature not higher than 200.degree. C.

Method for producing a dual-phase steel sheet having excellent

A high strength cold rolled strip having excellent deep drawability and resistance to deterioration by natural aging and to planar cracking and useful for motor vehicles, is produced by hot rolling a steel slab comprising

Process for producing cold rolled steel strip having excellent

A method of producing a dual phase structure cold rolled steel sheet having tensile strength 35 to 50 kg/mm.sup.2, yield ratio less than 60% and high elongation which comprises hot rolling and cold rolling by conventional process a steel containing 0.01 to 0.05% C, less than 0.2% Si, 1.7 to 2.5% Mn, 0.01 to 0.10 Al with the balance being Fe and unavoidable impurities, holding the produced steel sheet for 20 seconds to 20 minutes at a temperature 720.degree. to 850.degree. C., and cooling the steel sheet at a cooling speed between 3.degree. and 50.degree. C. per second and also above a value (.degree.C. per second) shown by following formulae:

Method of producing dual phase structure cold rolled steel sheet

Process for producing a high strength, low yield ratio and high ductility dual-phase structure steel sheet having a structure composed mainly of a ferrite phase and a rapidly cooled transformation phase and having excellent formability with a tensile strength of 40 kg/mm.sup.2 or higher. The process comprises cooling the continuously annealed steel sheet under the following conditions:

Process for producing high-strength, low yield ratio and high ductility

Growing community of inventors

Futtsu, Japan

Kazuo Koyama