Prevention of Coil Breaks at the Coil Line Entry by Using an Anti-Coil Break Roll

摘要

Hot rolled steel strip that exhibits a characteristic yield point during a tensile test is sensitive to coil breaks when processed at the pickle line. Coil break lines, also known as stretcher strains, may manifest during uncoiling or strip leveling processes. These surface defects are undesirable in he finished hot rolled product. Increasingly, anti-coil break equipment is being installed at the pickle line to negate the requirement for a prior skin pass. This paper addresses how the product mix of such equipment may be modified to optimize its efficiency. Trials have been conducted that clearly demonstrate the superior effectiveness of anti-coil break roll equipment on medium to heavy gauge hot rolled strip. The treatment of light gauge hot rolled strip can prove problematic if a satisfactory standard of surface quality is to be achieved. These studies have also shown that an anti-coil break roll can remove the characteristic yield point extension alone is not sufficient evidence of coil break sensitivity. The behavior of narrow strip specimens bent over a small work roll is also discussed. It is suggested that specimen width has an effect on the propagating ability of a coil break line.