CHARACTERISTICS OF ROLLING IN A CONTINUOUS BILLET MILL WITH DRIVE-FREE VERTICAL ROLLS

A compact continuous billet mill with an arrangement of H-V-H stands, where the vertical stands are drive-free was developed. In this continuous billet mill, materials are pushed into the non-driven vertical stands by the upstream driven horizontal stands and are then pulled out by the downstream driven horizontal stands. In order to adopt this type of mill as a commercial mill, it is necessary to investigate phenomena such as buckling between stands, slip in the driven horizontal stands and the dimensional fluctuation in rolled material due to inter-stand tension or compression and to clarify the adequate rolling conditions. Therefore, characteristics of rolling in a continuous billet mill with drive-free vertical rolls were investigated through experiments to determine the rolling conditions. The results are promising. The reduction in thickness of rolled material at non-driven vertical stands was almost the same as that at driven horizontal stands and amounted to 23% under the most adequate rolling conditions. Then it was shown that the variation in inter-stand tension or compression is less than 23 N/mm2, and that the dimensional fluctuation in rolled material is within 6.6% of width and 1.1% of thickness. As a result, it was concluded that this type of mill could be used as continuous billet mills or as roughing train in a bar mill.