Texture and Microstructure Control in Zinc Coated Steel Sheets.Effect on Formability of the Coatings

Abstract

Many commercial galvanised steel sheets have been characterised before deformation (grain size, grain distribution in the coatings, pre-cracking, individual orientations, misorientations between neighbouring grains, local and global textures) in connection with the zinc alloy which was used and the process parameters.The samples were bent by a biaxial expansion and examined afterwards. All the coatings were pre-cracked before deformation.The extent of the pre-cracking depends on the intensity and the sharpness of the basal planes texture of the coating and also on the misorientations across the grain boundaries. In the same way, zinc primary dendrites and recrystallised grains can hinder the crack propagation, limiting their extent.We can establish a correlation between the texture, the microstructure of the coatings (using a concept that corresponds to the mean free path of the crack) and the formability. As we know the process parameters, it is now conceivable that the texture of the coatings could be controlled.

Formation of zinc interlayer texture during dissimilar ultrasonic spot welding of magnesium and high strength low alloy steel

“…parallel to the ND of Zn interlayer surface remained undeformed [26]. Eventually, the c-axis of the all the grains lie parallel to the ND of Zn interlayer surface.…”

The relationship between the fracture toughness and grain boundary characteristics in hot-dip galvanized zinc coatings

“…of the crystallographic texture [9]. There is thus certainly a relation between texture and the cracking resistance of the galvanized coating [10]. To grasp this relation, we characterized the coating on various scales.…”

Correlation between substrate steel texture and coating texture of two industrially produced galvanised and galvannealed steels

“…Surprisingly, not much attention has been paid to date into investigating in detailing the nature of the substrate and coating textures in industrially produced galvanised and galvannealed steels. Some preliminary ideas about the texture of the coated galvanised layer have been reported by Gaignard and Esling 7 and by Vincent et al 8 These papers basically dealt with the effect of skin pass reductions on the microstructural and textural modification in galvanised sheet steel. The solidification texture of the galvanised coating (of Zn) on steels has been reported by Simoroz et al 9 Similarly, rather preliminary idea about the texture of the d layer of galvannealed steel coating has been reported by Moon et al 10 The effect of substrate steel texture on the formation and growth of the d layer in industrially produced galvannealed steel sheet has recently been reported by Chakraborty and Ray.…”