Nippon Kokan Kabushiki Kaisha

Toru Izawa

Makoto Yamada

Itaru Watanabe

Kazuaki Matsumoto

Masataka Suga

Seishi Tsuyama

Hisatoshi Tagawa

Nobuhiro Iwasaki

Kazuhide Takahashi

Masaharu Honda

Shigeyasu Matsumoto

Akira Tagane

Kazuyuki Matsui

A method for manufacturing a high-strength clad steel plate excellent in corrosion resistance, which comprises the steps of: placing a cladding sheet comprising stainless steel onto at least one of the surfaces of a substrate sheet comprising any one of carbon steel and low-alloy steel; welding together the peripheries of the substrate sheet and the cladding sheet to prepare a slab; heating the prepared slab to a temperature of from 1,050.degree. to 1,300.degree. C.; hot-rolling the heated slab at a finishing temperature of at least 800.degree. C. to obtain a clad steel plate comprising the substrate sheet and the cladding sheet; and cooling the obtained clad steel plate at a cooling rate of from 2.degree. to 60.degree. C. per second until the temperature of the clad steel plate is less than 450.degree. C. The above-mentioned slab may be a composite slab prepared by: placing a first cladding sheet onto a first substrate sheet, applying a peeloff material onto the upper surface of the first cladding sheet, placing a second cladding sheet onto the first cladding sheet through the peeloff material therebetween, placing a second substrate sheet onto the second cladding sheet, and welding together the peripheries of the first and second substrate sheets through spacers.

Method for manufacturing high-strength clad steel plate excellent in

The steel plate having a high tensile strength is manufactured from a steel consisting essentially of 0.04-0.16% by weight of C, 0.02-0.50% by weight of Si, 0.4-1.2% by weight of Mn, 0.2-5.0% by weight of Ni, 0.2-1.5% by weight of Cr, 0.2-1.0% by weight of Mo, 0.01-0.10% by weight of acid soluble Al, 0.03-0.15% by weight of one or more of V, Ti and Nb, 0.015% or less by weight of P, 0.006% or less by weight of S and the balance of iron and inherent impurities. The steel is heated to a temperature above a temperature at which carbo-nitrides of V and Nb and carbides of Ti become complete solid solution state, rolled with total reduction of 40% or more below 950.degree. C., quenched by simultaneous cooling immediately after completion of the rolling from a temperature above (A.sub.3 -50).degree.C. and tempered at a temperature lower than Ac.sub.1 temperature. The density of cooling water (W) for the quenching is detemined by the following equation (I) or (II) in accordance with the plate thickness (t):

Method of manufacturing high tensile strength steel plates

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Hiroshima, Japan

Toru Izawa