Mechanical Properties and Crystallographic Texture of Symmetrical and Asymmetrical Cold Rolled IF Steels

Nina Do Amaral Sardinha,Igor Cuzzuol Dos Santos,Ramón Alves Botelho,Bárbara Vaz Andrade,Luiz Paulo Brandao,Andersan Dos Santos Paula,Saulo Brinco Diniz,Rebeca Vieira De Oliveira

doi:10.1590/1980-5373-mr-2015-0449

Abstract

The crystallographic texture developed during cold rolling and subsequent annealing of interstitial free sheet steels aims to increase conformability. For this, it is necessary to obtain partial α-fiber and continuous and homogeneous γ-fiber texture components. In this work, the influence of symmetric (SR) and asymmetric (AR) cold rolling on crystallographic texture and mechanical properties of an interstitial free steel (IF) was investigated. Symmetric cold rolling yields α- and γ-fibers, which are enhanced as deformation increases. Moreover, α-fiber weakening occurs due to recrystallizations, improving formability. The same fibers are produced by asymmetric cold rolling, but in this case, the γ-fiber is slightly shifted in psi, which is one of Euler angles second ROE's notation1,2, and more homogeneous than in symmetric rolling. The best mechanical properties were achieved by asymmetric cold rolling/annealed with about 80% deformation.

Highlights

Interstitial free steels (IF) are widely used in the automotive industry3,4 thanks to their low tensile strength (100 to 350 MPa) and high formability
A hot-rolled IF steel with 4.9 mm thickness produced by Companhia Siderúrgica Nacional (CSN) – Brazil was used in this research
The φ2 = 45o sections of the Orientation Distribution Function (ODF) for the symmetrical cold rolled and annealed samples are shown in Figure 1. α- and γ-fibers can be observed for 70, 80 and 90 % cold rolled samples

Summary

Introduction

Interstitial free steels (IF) are widely used in the automotive industry thanks to their low tensile strength (100 to 350 MPa) and high formability. The industry tries to improve these properties even more, through appropriate thermomechanical processes such as cold rolling and annealing. Cold rolling is one of the techniques used to obtain preferred orientations in the material that will improve its mechanical properties, especially the formability. Cold rolling may be symmetrical or asymmetrical. The rolls have the same diameter, the same speed and the same friction coefficient. At least one of those conditions is different, leading to an additional shear strain, which may improve the mechanical properties and the formability

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Conclusion