Investigation of the 'tiger skin' defect on indefinite chill rolls

Hot strip mills (HSMs) are used to roll steel slabs down from their initial size to plate or sheet, which are then used to manufacture a wide variety of goods for various industrial markets. The surface quality of the rolls that contact and deform the strip must be maintained during rolling, as roll imperfections can be imposed onto the strip, affecting the quality. For many years various roll producers have experienced the occurrence of a surface defect, commonly referred to as 'tiger skin' (TS), on indefinite chill (IC) work rolls, but the cause of the defect has not been thoroughly investigated. The characteristics of the TS defects on the roll surface were studied in an attempt to identify the cause and prevent its occurrence. In this paper, the characterization results of the defects are highlighted. Various techniques were utilized in the analysis: visual inspection, chemical analysis, optical microscopy, hardness testing, scanning electron microscopy and X-ray diffraction. The purpose of the testing was to identify any variations in the roll microstructure that could give rise to the surface variation. The results confirmed that the TS defects appeared as a pattern that is not related to a variation in the surface profile, surface cracking, chemical segregation, graphite characteristics, carbide characteristics, primary phase characteristics, bulk hardness, or microhardness. Further investigations are recommended.