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Hot band Fe-3%Si steel (CRGO or cold rolled grain oriented) was cold rolled with different reductions. The main objective of this study was an overall understanding of deformation texture and microstructure development. Hot band CRGO had a strong a-fiber (RD//͗110͘) texture. Cold reduction strengthened the a and g (ND//͗111͘) fibers, but weakened q (ND//͗100͘). All Taylor type deformation texture models were reasonably successful in predicting these bulk texture developments, and the Lamel model seems to be the 'best-fit' model, both in terms of a 'deviation' parameter (indicating differences between experimental and simulated values of idealized texture components) and a 'trend' parameter (indicating the relative change(s) in texture components with strain). The striking feature of the microstructure was the 'selective' appearance of grain interior strain localization's. These appeared at approximately 37°with the rolling direction (RD). Though 37°bands appeared only in orientations with high Taylor factor (M ), the absolute value of the Taylor factor alone, was not enough for the appearance of such bands. Negative textural softening or (dM/de) values, on the other hand, were always associated with the appearance of 37°bands, justifying or explaining their formation on the basis of a macroscopic plastic instability theory.KEY WORDS: cold rolling; texture; grain oriented electrical steel; microstructure; strain localizations.* 1 However excellent review articles on CRGO are perhaps limited, 4) as compared to forming grade steels. [23][24][25][26] a previous study of the present authors, it was suggested that the relative presence of the respective strain localization's may determine the frequency and 'perfection' of the primary recrystallized Goss grains, perhaps determining the effectiveness of the subsequent secondary recrystallization process. 11) A recent study in low carbon steel 34) has indicated that at least the 37°strain localization's are first generation micro bands forming on the so-called 'high Taylor Factor' orientations. How such strain localization's may evolve in a cold-deformed CRGO and if both 37°and 20°b ands are of the same nature and origin remains to be explored. Experimental MethodsA 200 kg Fe-3%Si steel ingot was hot rolled from 50 to 2.1 mm thickness (pre-heating temperature being 1 330°C). The chemical composition of the hot rolled strip is given in Table 1. The hot rolled strip was annealed at 1 000°C for 60 s and then quenched. The annealed hot-band material was subsequently cold rolled with a laboratory mill to 5 different reductions -25 %, 40 %, 60 %, 77 % and 88 %. Samples were obtained for all these conditions for bulk texture and OIM (Orientation Imaging Microscopy) measurements, using respectively the mid-thickness sections of the rolling plane (containing rolling and transverse directions, i.e. RD and TD) and the long transverse plane (containing rolling and normal directions, i.e. RD and ND).Bulk texture measurements were analyzed by inversion of 4 incomplete pole figures a...

Despite a long history of continuously improved magnetic properties, the further development of grain-oriented electrical steel is still an exciting field for industrial and joint fundamental research. Today, the driving forces for research and development (R&D) are on one hand increasing quality demands, i.e, still lower losses for more energy-efficient transformers and less transformer noise, and on the other hand the pressure to reduce manufacturing costs in order to stay competitive on the market. Evidently in the last years, the latter aspect has become the mainspring for most of the industrial R&D activities. Now nearly all producers are aiming at more compact and less expensive production routes. From the new techniques under development, most advanced in commercial realization is the application of low slab reheating temperatures in the range 1150...1300°C instead of up to 1400°C in the classical processes. A radical new method is thin slab casting and direct hot rolling used for steels with a system of inherent plus acquired inhibitors, the latter formed by nitriding the cold rolled strip. This method is very promising and far advanced in industrial tests. Another way for process shortening is to cast directly the hot strip from the steel melt by a twin-roll method. In pilot line tests, good cold workability and good magnetic properties have been achieved by optimising chemical composition, casting conditions, and subsequent thermo-mechanical treatments and by working with inherent plus acquired inhibitors. Another theoretical potential for cost and time saving is to replace box annealing for secondary recrystallization by short-time continuous annealing. Such processes are under development, partly using special in-line procedures to realize fast inhibitor creation after primary recrystallization, but are today still far away from commercial realization.1.3%Si steel hot bands were produced by hot rolling in a Steckel mill with two entrance temperatures: 1000°C (y rolling) and 910°C (u+y rolling). Hot band samples were processed with and without hot band annealing (900°C for 30s), cold rolled to final thickness of 0.5mm and annealed in H 2-25%N2 at 900°C for 40s. The combination of high hot rolling temperature and hot band annealing resulted in lower core loss and higher permeability. Although no significant differences were observed on the hot band microstructures, after hot band annealing the y rolled sample showed a larger grain size. The final results were attributed to the effect of the initial grain size prior to cold rolling on microstructure and texture after annealing.

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