Evaluation of Annealing Texture in IF and EDD Steel Sheets

Abstract

The textural and microstructural studies of cold-rolled-batch annealed (CRBA) interstitial free-Ti (IF-Ti) stabilized steel and extra deep drawing steel (EDD) produced at Tata Steel have been investigated. In the IF steels, -fiber has been found to be strong even after batch annealing, which is not desirable for deep drawing applications. The presence of a stronger recrystallization texture in the surface region rather than in the central region accounts for the deformation and orientation path history of cold-rolling texture components and the texture inherited from hot band. The hot band of IF steel has been observed to have mixture of grain structure along with inhomogeneous texture throughout the thickness. While the inhomogeneity in EDD steel, pancake grain structure in the through-thickness direction, milder pancake grains in the transverse section, and polygonal grain structure in the longitudinal section have led to the inference that the undesirable -fiber is present. This observation has been explained by the early precipitation of AlN during coiling. The results of all the steels have been explained with the help of the orientation distribution functions, volume fraction of alpha and gamma fiber along with their components, volume fraction ratio ( / , and the microstructure. The analysis of the present data suggests that the deep drawability of both steels can be improved by modifying the hot-rolling and annealing parameters. IntroductionThe deep drawing steels interstitial free (IF) and extra deep drawing (EDD) are widely used structural materials. To improve the drawability of the deep drawing sheet and at the same time to make the edge on the top of a drawn cup smooth without the phenomenon of earing, the steel needs to possess a high normal anisotropy (Lankford parameter), r m , and low planar anisotropy, r. The r-value is defined as the ratio of the true strains in the width and thickness directions. Conventionally, this is obtained from measurements of width and length strains because of the large uncertainties of thickness strains. While, the variation of r with angle around the sheet gives further information about the extent of planar anisotropy, r. An average rvalue r m and r are defined as follows:

Site-specific quasi in situ investigation of primary static recrystallization in a low carbon steel

“…by Hölscher et al [13], Raabe and Lücke [32,33], Inagaki [20], Hutchinson [19], Samajdar et al [36,37], Barnett [3], and Barnett Kestens [5]. From these previous studies 2 it is known that a comprehensive understanding of recrystallization requires to consider the full thermo-chemo-mechanical history of the material, starting at least with its state after hot rolling. Some features already present in the hot rolled state remain mostly unchanged during cold rolling and can, therefore, influence the recrystallization behavior.…”

“…These features include chemical inhomogeneity and-with the exception of changes due to internal fracture-precipi tate size and distribution. Moreover, despite the severe texture formation during cold rolling, even certain recovery texture components from the hot rolling texture can be passed down to the deformation texture [32,31,2].…”

“…r and Δr denote the Lankford coefficient and the planar anisotropy, respectively[6] 2. see also the older overview articles by Hutchinson[18] and Ray et al[34] and the concise, recent one by Kestens Pirgazi[22] 3.…”