Microstructure, Texture and Microhardness Evolution during Annealing Heat Treatment and Mechanical Behavior of the Niobium-Stabilized Ferritic Stainless Steel ASTM 430 and Niobium-Titanium-Stabilized Ferritic Stainless Steel ASTM 439: a Comparative Study

Abstract

A comparison of the influence of microstructure and texture on mechanical behavior between the niobium-stabilized ferritic stainless steel type ASTM 430, 430Nb, and the niobium-titanium-stabilized ferritic stainless steel type ASTM 439 was performed. The two steels were supplied as cold rolled thin sheets and the annealing was interrupted in different temperatures aiming the characterization of the microstructure and texture in different stages of recrystallization using optical microscopy, Vickers microhardness and Electron Backscatter Diffraction. The annealed samples were tensile tested to determine the mechanical properties and undergone to Swift test to evaluate the drawability. The steel 430Nb showed smaller grain size and greater yield stress. The steel ASTM 439 presented higher normal anisotropy coefficient, R, and higher Limit Drawing Ratio due to greater proportion of γ fiber. These results are presented and discussed in terms of precipitates and crystallographic texture developed in the recrystallization of both steels.

Effect of grain size on the drawability of the niobium-stabilized ferritic stainless steel ASTM 430

“…The increase in the r, i.e, the ability to withstand thinning, is strongly related to the increase in the Gamma fiber components intensity and the reduction of Theta fiber components intensity [4,8,10,11]. The increase in the Theta fiber's length reduces the material formability due to the low r of the crystallographic orientations present in this fiber, especially in r 45 [5].…”

Design of a Tribo-Simulator for Investigation of the Tribological Behavior of Stainless-Steel Sheets Under Different Contact Conditions

“…In general, FSS sheets have a higher limiting drawing ratio (LDR) (ratio of the blank diameter/punch diameter) and mean normal anisotropy coefficient ( R ) compared to ASS sheets, which indicates greater resistance to deformation in the thickness direction, thus allowing for deeper drawing. However, ASS sheets have a higher limiting dome height (LDH) and lower planar anisotropy coefficient ( R ∆ ) compared to FSS sheets, which indicates better performance in pure forming by stretching and lower levels of earing, thus producing less waste in the production line [10][11][12] . However, there has not been a comparative study of the tribological *e-mail: valmir@cefetmg.br Materials Research behavior of these steels under the different contact conditions present in SMF processes.…”