THICK STEEL PLATE HAVING YIELD STRENGTH IN 500 TO 550 MPa CLASS AND EXCELLENT CTOD PROPERTY IN HEAT AFFECTED ZONE

Japanese Patent JP3711249

B2

PROBLEM TO BE SOLVED: To provide a thick steel plate which has yield strength in a 500 to 550 MPa class and, in which CTOD(crack tip opening displacement) at -10°C in HAZ(heat affected zone) is ≥0.2 mm, and which has the maximum plate thickness of ≤76.2 mm (3 inches).
SOLUTION: The thick steel plate having yield strength in a 500 to 550 MPa class and excellent CTOD properties in the heat affected zone has chemical components containing, by mass, 0.04 to 0.14% C, ≤0.4% Si, 1.0 to 2.0% Mn, ≤0.02% P, ≤0.005% S, 0.001 to 0.01% Al, 0.005 to 0.03% Ti, 0.005 to 0.05% Nb, 0.0001 to 0.005% Mg, 0.001 to 0.005% O and 0.001 to 0.01% N, and the balance iron with inevitable impurities, and in which Ti/(Mg+Al)≥1 is satisfied. TiN of 0.01 to 0.5 μm including oxides of Mg and Al is present in ≥10,000 pieces/mm2, and also, oxides of 0.5 to 10 μm are present in ≥10 pieces/mm2.

JPS61270355	HIGH STRENGTH STEEL EXCELLING IN RESISTANCE TO DELAYED FRACTURE
JP3233827	HIGH STRENGTH PC STEEL BAR EXCELLENT IN DELAYED FRACTURE CHARACTERISTIC AND ITS PRODUCTION

Akihiko Kojima
Yoshio Terada
Akito Kiyose
Yuzuru Yoshida
Ryuji Uemori

JP2001135947A

November 02, 2005

May 07, 2001

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Nippon Steel Corporation

C22C38/00; C22C38/14; C22C38/58; (IPC1-7): C22C38/00; C22C38/14; C22C38/58

JP11293382A
JP2000096139A
JP2000109947A

WO2001086013A1

Hisataka Tanaka
Shunta Naito

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