Title: Method of manufacturing high strength low alloys steel plates with superior low temperature toughness

Abstract: A steel slab or bloom containing 0.3.about.0.15% by weight of C, 0.05.about.0.60% by weight of Si, 0.60.about.2.5% by weight of Mn, 0.010.about.0.15% by weight of Nb, 0.005.about.0.10% by weight of soluble Al and the remainder of iron is heated to such a temperature region above 1050.degree. C. and below the reheating temperature where the austenitic grain size would be 150.mu.. The heated slab or bloom is then hot rolled with total rolling reduction of more than 40% with respect to a finished thickness at the non-recrystallized austenitic region and the hot rolled stocks are subjected to accelerated cooling at a rate of 5.degree..about.20.degree. C./sec. from a temperature higher than the Ar.sub.3 transformation point to a temperature within 550.degree..about.650.degree. C. Finally the stocks are air cooled.

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Other info:

Inventors: Ouchi, Chiaki (Yokohama, JP)
Okita, Tomoyoshi (Yokohama, JP)
Matsumoto, Kazuaki (Yokohama, JP)

Application Number: 923500
Filing Date: 1978-07-11
Publication_date: 1980-01-22
Assignee: Nippon Kokan Kabushiki Kaisha (Tokyo, JP)
Primary Class(es): 148/654 148/320, 148/332, 148/336, 148/624
Other Classes:
US Patent Ref:

3787250	Jan, 1974	Korchynsky et al.	148/12.
3860456	Jan, 1975	Repas	148/12.
4092179	May, 1978	Charpentier et al.	148/12.

Other Refs:
Primary Examiner: Stallard, W.
Assistant Examiner:
Attorney: Frishauf, Holtz, Goodman & Woodward