Preferred Orientation in 18/10, 18/12 and 18/14 Chromium/Nickel Steels and its Relation to Tensile and Press Forming Properties

Abstract

The cold rolling and primary recrystallization textures of 18% chromium steels containing 10%, 12%, and 14% nickel have been determined, and their tensile and press forming properties have been compared in sheet processed to obtain: (a) a randomly oriented grain structure, and (b) a strong primary recrystallization texture. During cold rolling to 93% reduction, all the steels partly transform to α1 martensite, the extent of transformation increasing with decreasing nickel content. The 18/10 steel exhibits a texture mainly consisting of {111}<112>α1, {112}<110>α1, and {001}<110> α1 orientations, with a small amount of untransformed austenite having the orientation {110}<112>. In the cold rolling texture of the 18/12 and 18/14 steels, the {110}<112>γ orientation is predominant. The primary recrystallization texture of the 18/10 steel consists of two orientations: ~{230}<321> and ~{230}<32,13>. Whereas, the recrystallization texture of the 18/12 and 18/14 steels can be described as ~{113}<211>. The effect of the martensite transformation on the cold rolling and annealing textures is discussed. The recrystallization textures are associated with marked planar variations in the strain ratio, R, and a mean strain ratio, R, only slightly greater than that in randomly oriented material. Deep drawability is not significantly affected by the presence of the textures. The amount of earing associated with the texture in the 18/10 steel is the same as that in randomly oriented material (~3%). Whereas, the texture in the 18/12 and 18/14 steels gives rise to a larger amount of earing (6-8%). In a fully annealed condition, the rate of work hardening, the extent of uniform elongation, and the stretch formability increase with decreasing nickel content. Stretch formability is not significantly affected by the presence of strong preferred orientation. Neither temper annealing for 1/2h at 800°C (instead of full annealing) nor cold reductions of up to 12.5% have any marked effect on deep drawability, but both treatments lower the stretch formability.