Warp Control in Strip Processing Plant

Abstract

Strip is bent many times by turn rolls in the continuous annealing and surface treatment lines. Roll diameter of the turn rolls is usually made as small as possible due to limitation of space and cost. Therefore, plastic bending occurs and at the same time, the strip thus treated develops longitudinal and transverse warps (curvatures). It is proposed in this paper to refer to these two features as "curl" and "gutter", respectively.
Curl is restrained by line tension, but gutter (crossbow) appears down-stream of the turn roll. Gutter causes some line problem, especially in the plating line where it causes nonuniformity of coating thickness across the strip width.
This report provides theoretical analysis and basic information about gutter and how to control it in order to unify coating thickness in electrogalvanizing and hot dip galvanizing line. In the former line, gutter elimination just before the vertical plating cells, in the latter line, configuration of pot rolls are the main technical points to be discussed.