Abstract
In this paper, the texture formation of Ti-added extra low carbon sheet steels hot rolled below Ar3 transformation temperature has been investigated. A remarkable feature of the texture of the sheet hot-rolled below Ar3 is an inhomogeneous formation through the thickness. In the case of Ti-added extra low carbon sheet steels, the recrystallization texture of the surface layer is characterized by a high intensity of Goss orientation while ND // {111} is the main orientation of the recrystallization texture in the midplane. A calculation deriving r-values from data of a three dimensional analysis of the texture shows that the surface layer deteriorates the deep drawability of the sheet.
With the aid of a computer program calculating the strain distribution in the roll bite and a crystal rotation model developed by DILLARMORE and KATOH, the cause of the inhomogeneous texture formation has been studied. The calculation result shows that the surface texture is strongly influenced by the friction between roll and sheet. With decreasing friction, the surface texture gradually becomes similar to that of the midplane.
In the consideration of the calculated result, hot rolling experiments were carried out at a newly developed laboratory multipass hot rolling mill equipped with a lubrication facility. Ti-added low carbon steel sheet hot-rolled below Ar3 in a lubricated condition shows a nearly homogeneous texture through the thickness with a main orientation of ND // {111} and consequently a high r-value.
