METHOD OF MANUFACTURING BAR STEEL

摘要

PROBLEM TO BE SOLVED: To provide a method of manufacturing bar steel by which misroll and contamination of heterogeneous materials are not caused and which is excellent in productivity and material yield. SOLUTION: A billet 6 is provided with a main part 8 and a forward part 10. The forward part 10 is situated in front of the main part 8. the forward part 10 has a tapered shape. Multistage rolling including rolling with a roughing mill train is applied to this billet 6. The forward part 10 contributes to the suppression of a fish tail in this rolling with the roughing mill train. The ratio (B/C) of the tip diameter B of the forward part of the billet 6 to the finished diameter C after the rolling with the roughing mill train is≥0.7 to≤0.9. The length L of the forward part of the billet 6 is larger than the value Y obtained by a formula (1): Y=(A2/C2)×25. Wherein A shows the diameter of the main part 8 of the billet 6. COPYRIGHT: (C)2008,JPO&INPIT