Control of texture and formability in ferritic stainless steels.

The effects of processing variables on the microstructures, textures and press-formability of commercial 17 Cr, 0.05C (430) steel and low-interstitial Ti-stabilised 12 Cr (409) and 17 Cr (430 Ti) steels have been studied. The annealing textures have beencorrelated with tensile strain ratio measurements and from this correlation it has been possible to select combinations of cold rolling reduction and annealing treatments for texture control to improve deep drawability. Electron microscope examination has been used to identify possible nucleation mechanisms for the observed recrystallisation textures. Cold rolling texture development and tensile strain ratios have been discussed from theoretical considerations of slip in bcc metals.Pronounced differences in microstructural features between high interstitial 4-30 and low-interstitial Ti-stabilised steels are reflected in differences in texture development at all stages. Hot band condition is an important variable, affecting texture development during subsequent cold rolling and annealing. All three steels develop similar cold rolling textures, consisting mainly of ~{100} , ~{111} and ~{112} components. The ~{112} orientation is more prominent in 430 Ti steel than in 430 steel, and it is suggested that this difference may be due to irregular flow in high interstitial 430 steel. Other differences in cold rolling textures are attributed to texture inheritance from the hot band. Recrystallisation textures in 430 steel are mainly ~{114} , with ~{223} present after high reductions, and r-values are generally low. Recrystallisation textures in 409 and 430 Ti steels are mainly ~{110} after low cold rolling reductions, ~{554} after moderate or high reductions and -{223} after very high reductions. In most cases, ~{100} is only a minor component. Batch annealing of the hot rolled strip followed by cold rolling to 90% RA and rapid final annealing promotes maximum ~{554} intensity with low ~{100} intensity, and a correspondingly high r-value. The ~{223} and ~{114} orientations, attributed to grain boundary nucleation, have not been reported previously in 17 Cr ferritic stainless steels, although they have been reported occasionally in other low-carbon ferritic steels.