Abstract
The Nb-bearing grain-oriented silicon steel sheets were produced by conventional route and novel twin-roll casting route, respectively. The microstructure, texture and precipitate evolution were comparatively investigated by using electron backscattered diffraction (EBSD) and transmission electron microscope (TEM). The findings revealed that the precipitation behavior and the texture evolution were totally different between the two processing routes. In the conventional route, a great number of nanoscale niobium nitride particles (NbN), which acted as mainly grain growth inhibitors were precipitated during hot rolling, while in the twin-roll casting route, due to the rapid solidification, the precipitation of NbN were suppressed and a new type Nb-bearing precipitate enriched with sulfur element was observed in the as-cast strip. Besides, the primary recrystallized texture of conventional specimens was characterized by strong γ-fiber with a peak at {111} <110>, together with very few Goss components. While in the case of twin-roll casting specimens, the strongest primary recrystallized texture was {111} <112> texture and the area fraction of Goss component was much higher than that of conventional specimens. After final high temperature annealing, complete secondary recrystallization was obtained in twin-roll casting specimens and the magnetic induction of B8 was 0.1 T higher than that of conventional specimens.
Highlights
Grain oriented silicon steel is widely used as the core material in electrical transformers because of its high magnetic induction and low iron loss [1]
The fine and dispersed second phase particles, which called as grain growth inhibitors in grain-oriented silicon steels, play a significant role in controlling the matrix grain size and promoting the abnormal growth of Goss texture [3]
The conventional hot rolled strip had a significantly microstructure and texture gradient, which can be divided into three layers
Summary
Grain oriented silicon steel is widely used as the core material in electrical transformers because of its high magnetic induction and low iron loss [1]. The fine and dispersed second phase particles, which called as grain growth inhibitors in grain-oriented silicon steels, play a significant role in controlling the matrix grain size and promoting the abnormal growth of Goss texture [3]. In industrial, according to the inhibitor acquisition approaches, the production technology of grain-oriented silicon steel can be classified into two categories, the inherent inhibitor method and the acquired inhibitor method [4]. The inherent inhibitor method is adding inhibitors elements to melt steel directly, and the effectively inhibitors are precipitated during hot rolling or hot strip annealing. The main challenge of this method is that the slab must be reheated up to a very high temperature
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