Improving Hydro-formability of a Ferritic Stainless Steel Tube Through Severe Plastic Deformation

The aim of this work is to improve the hydro-formability of a 409L ferritic stainless tube through a treatment involving severe plastic deformation followed by annealing. For this purpose, the variation in hydro-formability is determined in terms of parameters like the circumferential R-value and the circumferential elongation after application of the abovementioned treatment. In addition, the deformation-induced surface roughening of the tube, called ridging, is measured through tension tests before and after the treatment. Moreover, the evolution in tube texture caused by the treatment is studied to reveal the relationship between the hydro-formability parameters and the texture. The results show that the treatment dramatically improves the hydro-formability through a marked modification in texture. For example, the emergence of the {110}〈100〉 texture component through the present treatment causes a noticeable increase in the circumferential elongation and the circumferential R-value of the tube while decreasing the degree of ridging.