Nippon Steel Corporation

Yuzuru Yoshida

Hiroshi Tamehiro

Koichiro Keira

Kazuo Funato

Rikio Chiziiwa

Yoshifumi Sakumoto

Tadashi Ishikawa

Ryuichi Honma

Akihiko Kojima

Youichi Tanaka

To form a welded joint having a sufficiently high fracture toughness value &#x3b4;c by butting welding high strength steel plates having a yield strength of the 355 MPa class or more and a plate thickness of over 50 mm by electron beam welding, the butt welded joint is made one where the hardness of the weld metal is 110% to 220% of the hardness of the base material and where the width of the weld metal is 20% A or less of the base material plate thickness.

Electron beam welded joint excellent in brittle fracture resistance

Disclosed is a process for manufacturing a building construction steel having excellent high-temperature characteristics, which can be marketed at an economically reasonable price. According to this process, a slab having a steel composition in which appropriate amounts of Mo and Nb are added to a low-C and low-Mn steel is heated at a high temperature and rolling is finished at a relatively high temperature, or a slab having a steel composition in which an appropriate amount of Mo is added to a low-C and low-Mn steel composition is heated at a high temperature, rolling is finished at a relatively high temperature, and at the subsequent air-cooling step, water cooling is started at a temperature of a ferrite fraction of 20 to 50% during the transformation from austenite to ferrite, water cooling is carried out to an arbitrary temperature lower than 550.degree. C., followed by air cooling.

Building construction steel having excellent fire resistance and low

Process for manufacturing building construction steel having excellent

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Kimitsu, Japan

Yuzuru Yoshida