Evolution of microstructure and texture of ultra-thin non-oriented electrical steel manufactured by CSP

Abstract

The evolution of the microstructure and texture of CSP thin-gauge non-oriented silicon steel was investigated by OM, XRD and EBSD. Results show: (1) the equiaxed surface grains with 28.13 µm average grains size accounted for 19.14% of through-thickness, while deformed band structure dominated the center layer and the other maintained at a composite structure with the first two. With the cold-rolled reduction rate enhancing to 91.15%, the stratification structure transformed into a complete fibrous structure. Annealing from 925 °C to 975 °C, the average grain size of the annealing plate similarly increased, which begins with 67.3 µm and ends at 80.58 µm. (2) The texture of the hot-rolled sheets mainly located at Cube and Goss texture, while with the cold-rolled process executing, the type and volume of texture change and finally stabilize at α fiber texture ({110}//RD) with the peak at {114}<110> at 91.15% reductions rate. The {411}<148> texture on the α* fiber line throughout maintained the strongest texture at different annealing temperatures. (3) The initial re-crystallization temperature is in the range of 600–620 °C, and the re-crystallization is roughly completed at 700 °C. Part of {411}<148> oriented grains nucleated at {411}<148> sub-grains originated from α fiber deformed structure, and the others nucleate at the grains boundaries of the deformed α fiber grains or in the inner of {111}<110> and {111}<112> grains. When the re-crystallization was accomplished at 750 °C, {411}<148> oriented grains are significantly larger than other oriented grains compared to 680 °C or the less. (4) Best magnetic properties were obtained at 975 °C with the B50 = 1.506 T and P10/400 = 16.19 W/kg.