Influence of chemistry and runout table parameters on hot coil collapse in C-Mn steels

Abstract

The key metallurgical parameters affecting the incidence of coil collapse (soft slump) of C-Mn steels has been investigated using industrial data and laboratory simulation. Runout table (ROT) cooling/coiling simulations were performed on a Gleeble 1500D to study transformation before and during coiling of thin strip. For low C (< 0.07%) grades, coiling temperatures above 650˚C coupled with high nitrogen contents decreased the transformation-end temperature, Ar1, and increased collapse. Coiling temperatures above the Ar1 for ROT cooling increased both dilation and the time to complete transformation during coiling. These effects correlated with industrial conditions where a high frequency of coil collapse was observed.