Metallurgy of Ultra-Low-C Interstitial-Free Sheet Steel for Automobile Applications

Abstract

A review is made on the metallurgy of ultra‐low‐carbon interstitial‐free sheet steel for automotive applications. Basic principles in the development of (111) texture are summarized and differences in Ti and Nb additions are discussed. Development of sheet steel with the r‐value of 2.9 is reported as an application of the present understanding of metallurgy, by employing the currently developed technique of ferrite rolling with lubricant.

Physical Metallurgy and Drawability of Extra Deep Drawing and Interstitial Free Steels

“…Oriented nucleation is the hypothesis that explains, grains with an orientation that dominates the fully recrystallized texture, nucleate more frequently than do grains of all other orientations. In other words, the oriented nucleation theory assumes orientation selection in the nucleation process based on the orientation dependence of the deformation energy stored in the grains during cold rolling (Tsunoyama, 1998). The high…”

“…The strength of {111} texture in turn is influenced by chemistry of the steel (Perera et al, 1991; Wilshynsky-Dresler et al, 1995 ) and the prior technological processing steps, such as hot rolling (Wilshynsky-Dresler et al, 1995& Perera et al, 1991, cold rolling (Perera et al, 1991) and annealing (Perera et al, 1991, Wilshynsky-Dresler et al, 1995. Many studies have been made on the effect of process conditions and the following principles are obtained for the development of (111) recrystallization texture (Tsunoyama, 1998):…”

Characterisation of the plane anisotropy and its effect on interstitial free steel thin sheet metal forming simulation

“…The excellent formability of IF steel sheets is due to their very low carbon and nitrogen contents which confer low yield strengths and high resistance to thinning. 8,[13][14][15][16] IF steels are normally produced in a plate form using the hot rolling and cold rolling processes and are used to manufacture the spare wheel well, doors inner panels and the rear floor pan of vehicles and so on. 13,17 Due to their crystallographic structure and the characteristics of the rolling process, IF steels generally exhibit a significant anisotropy of mechanical properties.…”

“…8,[13][14][15][16] IF steels are normally produced in a plate form using the hot rolling and cold rolling processes and are used to manufacture the spare wheel well, doors inner panels and the rear floor pan of vehicles and so on. 13,17 Due to their crystallographic structure and the characteristics of the rolling process, IF steels generally exhibit a significant anisotropy of mechanical properties. They have a particular texture characterised by a preferred orientation of the grains constituting the material.…”

Biaxial Stretching Behavior of a Copper-Alloyed Interstitial-Free Steel by Bulge Test

“…[1][2][3] The specialty of these steels is characterized by an extremely low level of interstitial content (typically, C and N £ 40 ppm each) achieved through the use of modern degassing techniques. These remaining interstitials are further removed from the matrix as various types of carbide, sulfide, carbosulfide, and carbonitride by addition of small amounts of stabilizing elements such as Ti and/or Nb.…”