PURPOSE: To reduce generation of surface flaws by performing preliminary working by drafting under a specific condition at solidification of a continuously cast billet, keeping the billet in a specific temp. range and then rolling the billet.
CONSTITUTION: Preliminary working is performed to roll a continuously cast billet at just before or after completion of solidification of the billet under a condition of a strain rate of ≤1×10-1/sec and draft of ≥2%. Then, the billet is kept at a temp. in the γ single phase region to coarsen precipitated fine MnS. After that, the billet is rolled by a hot rolling mill. High temp. ductility is recovered and cracks during rolling are reduced by coarsed MnS. The above preliminary working is preferably performed at a solid phase ratio in the billet central part is ≥0.7.
MIYAHARA SHINOBU
UCHINO KAORU
KUBOTA ATSUSHI
MASAOKA TOSHIO
YAMAZAKI YOSHIMASA
| JPS60262915A | 1985-12-26 |