PURPOSE: To provide a continuously cast billet for seamless stainless steel pipe base stock, by which an inner surface flaw of the pipe does not develop at the time of pierce-rolling, by shifting the internal gap developed at the last solidified position of the continuously cast billet to the outer part from the center part of the cross sectional surface of the cast billet.
CONSTITUTION: In the continuous casting of the square or the round billet, cooling intensity in the peripheral direction of the cast billet is changed at a secondary cooling zone 4 having ≥3m length while the cast billet 5 becomes from just below a mold 3 to the perfect solidification, and the last solidified position of the cast billet is shifted to the outside from the cast billet center. Further, the cast billet 5 whose last solidified position is shifted from the center, is heated to rolling temp. under condition of the round shape, in the case of the round billet, as it is, and in the case of the square billet, after working to the round billet, and the seamless steel pipe is produced from the steel pipe base stock after pierce-rolling while centering the billet central part.
WATABE TADAO
NAGASE YUTAKA
AKIYAMA MASAYOSHI
| JPH02182347A | 1990-07-17 |