Experimental investigation of the transformation texture in hotrolled ferritic stainless steel using single orientation
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I.
INTRODUCTION
FERRITIC stainless steels containing 16 to 17 mass pct chromium and about 0.05 mass pct carbon represent an important group of high grade steels owing to their good corrosion resistance, high strength, and sufficiently good ductility. In some technical domains, e.g., in the chemical, household, and automotive industry, ferritic stainless steels increasingly gain importance, since they can to a certain extent compete even with the expensive austenitic stainless steels. The distribution of the crystallographic grain orientations of roiled and annealed ferritic stainless steels, which is hereafter referred to as texture, has been the subject of numerous studies in the past using the etch-pitting technique,E~l two-dimensional (2-D) centrosymmetric pole figures,t2J or the three-dimensional orientation distribution function (ODF).t 3~] The determination of the texture of ferritic stainless steels is of great importance for two reasons. (1) The ODF represents an important weighting function of numerous macroscopical directional properties of a polycrystalline aggregate. In this context, especially the plastic properties, e.g., the deep drawing behavior, more precisely the so-called ridging phenomenon, and the determination of the Lankfort value are of relevance. The ridging phenomenon, which is sometimes referred to as roping, is a surface defect which is developed during large strain deep drawing processes. This surface defect, which was identified by various authors to depend on the texture of the steel,B-4,7,81 oc-
curs parallel to the rolling direction and appears as narrow raised areas, similar to corrugations. (2) The development of the texture during the various production steps is often determined by the physical processes involved in a rigorous crystallographic manner. Consequently, its determination provides a useful diagnostic probe for identifying the underlying metallurgical mechanisms of the main processing steps. In this context, the most important goals are the examination of crystallographic slip by correlating rolling textures with Taylor-type simulations,t3-s,9,1~ of phase transformation by interpreting annealing and hot-rolling textures in terms of transformation rules and variant selection models, tHj and of recrystallization by correlating annealing textures with approaches based on growth selection,t12] preferred nucleation at grain boundaries,[~31 and recovery,t~~ This investigation is concerned with the influence of the hot-rolling procedure on the texture of two ferritic stainless steels with about 16.5 mass pct Cr content which reveal up to 40 vol pct phase transformation during hot rolling. For the first time, the textures of both the transformed and the nontransformed regions were individually investigated employing a selective etching technique combined with single orientation determination in the scanning electron microscope. The results were compared to textures obtained by X-ray diffraction. II.
EXPERIMENTAL PROCEDURE
A. Processing of the Specimens D. RAABE, Group Head
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