Heavy wall steel material having superior weldability and method for producing the same

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(11)

EP 1 031 636 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	03.04.2002 Bulletin 2002/14

(43)	Date of publication A2:
	30.08.2000 Bulletin 2000/35

(21)	Application number: 00301481.8

(22)	Date of filing: 24.02.2000

(51)	International Patent Classification (IPC)⁷: C22C 1/10, C22C 38/04, C21D 8/00

(84)	Designated Contracting States:
	AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE
	Designated Extension States:
	AL LT LV MK RO SI

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Priority:

25.02.1999 JP 4896299

(71)	Applicants:
	Japan as represented by Director General of National Research Institute for Metals Tsukuba-shi, Ibaraki (JP) Mitsubishi Heavy Industries, Ltd. Tokyo (JP)

(72)	Inventors:
	Nakajima, Hiroshi 1-2-1 Sengen Tsukuba-shi Ibaraki (JP) Torizuka, Shiro 1-2-1 Sengen Tsukuba-shi Ibaraki (JP) Tsuzaki, Kaneaki 1-2-1 Sengen Tsukuba-shi Ibaraki (JP) Nagai, Kotobu 1-2-1 Sengen Tsukuba-shi Ibaraki (JP)

(74)	Representative: Calamita, Roberto
	Frank B. Dehn & Co., European Patent Attorneys, 179 Queen Victoria Street London EC4V 4EL London EC4V 4EL (GB)

(54)	Heavy wall steel material having superior weldability and method for producing the same

(57) A tough high strength heavy wall steel material having superior weldability is provided, said steel material has a diameter or a side 5 mm or more in length, and comprises oxides 1 µm or less in particle diameter homogeneously dispersed at a dispersion density in a range of from10,000 to 100,000 particles/mm² and uniform ferrite grains 2 µm or less in grain diameter formed over the entire plane making a right angle with respect to the rolling direction.

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