Effect of hot rolling reduction on microstructure, texture and ductility of strip-cast grain-oriented silicon steel with different solidification structures

Grain-oriented silicon steel as-cast strips with the average ferrite grain sizes of 161 μm and 367 μm were produced by twin-roll strip casting. Then the as-cast strips were reheated and hot rolled with different reductions of 5-50%. The microstructure and texture evolution were investigated by optical microscopy, X-ray diffraction, and electron backscattered diffraction methods. The elongations of the hot rolled strips were examined by the tensile tests and the fracture surfaces were observed by scanning electron microscope. It was found that the microstructure of both as-cast strips consisted of ferrite and martensite. The microstructure of all the hot rolled strips was composed of ferrite and pearlite and it was gradually refined with increasing hot rolling reduction in spite of different initial solidification structures. The hot rolled fine-grained strips showed much finer microstructure at the same hot rolling reduction and thus gave rise to higher elongations. A total reduction of more than 30% was required for the fine-grained strips to achieve relatively good ductility, while that for the coarse-grained strips was as high as 50%. With increasing hot rolling reduction, α and γ fibre textures were gradually enhanced at the expense of initial {001}〈0vw〉 fibre texture in all the hot rolled strips. Relatively strong Goss texture only evolved in the 50% hot rolled strips in spite of the different initial solidification structures, though the 50% hot rolled coarse-grained strip showed much stronger Goss texture.