Formation of Smudges and Iron Oxide Film in the Course of Cold Rolling

Abstract

The effects of the cold rolling conditions on the amount of smudge has been investigated. The smudge formed on the edge of cold rolled steel sheet surface causes the dewetting of tin plate since it can not be removed by the conventional electrolytic cleaning. It is estimated that the smudge consists of iron powders and iron oxide powders, and it deteriorates palm oil. Inhomogeneous distributions of the smudge and the iron oxide film are observed in the strip width. The amount of smudge at the edge of the strip is more than twice as much as that at the center.
The results suggests that the cold rolling conditions significantly affect the amount of smudge and the iron oxide film thickness on the surface of cold rolled steel sheet.
The amount of smudge and oxide film thickness increase with the increase of rolling speed and the reduction at the final stand (stand No. 5), but are reduced by supplying the more oil at the final stand. Furthermore, the calculated temperature of the strip at the exit of roll bite suggests that the amount of smudge and oxide film thickness depends on the temperature. It is revealed that the amount of smudge and the iron oxide film thickness are reduced by adding the antioxidant additive to the rolling oil.