The evolutions of microstructure and texture of ultra-thin high-grade non-oriented silicon steel for new energy vehicles were investigated in this paper, and the formation mechanism of typical recrystallized α*-fiber texture was described. The results show that: The microstructure of the hot rolled plate was inhomogeneous along the thickness direction because of the shear force and temperature gradient, resulting in the texture in each layer of the hot rolled plate appearing rotational distribution around the Goss orientation. After normalizing, the fully recrystallized microstructure was obtained, and α*-fiber texture was formed. Banded structure was obtained in the cold rolled sheet, with α-fiber texture {114}〈110〉 dominated. The typical α*-fiber texture was formed after annealing recrystallization, which mainly consist of {114}<481 > and {113}<361>. The {114}<481 > oriented grains were mainly nucleated within the deformed {114}<110 > grains and at the grain boundaries of α-fiber deformed grains, and without size, quantity and strength advantages. {111}<112 > is dominated in the early stage of recrystallization, but {114}<481 > became the main texture with size, strength and quantitative advantages in the late stage of recrystallization.

A new method to fabricate a high grade non-oriented silicon steel was provided, in which the significant feature is low Si high Mn. Metallographic microscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to investigate the microstructure, texture evolution and precipitates characteristics, respectively. It is found that hot rolled sheet had a distinct stratification appearance. Fine equiaxed grains occupy the surface while subsurface and center regions were dominated by deformed microstructure and equiaxed grains. After normalizing, the microstructure of hot rolled sheet completely recrystallized. A number of shear bands were observed attributed to cold rolling. With the increase of annealing temperature or time, the average grain size of final annealed sheet increases. Annealed at 1000 °C for 7 min, annealed sheet exhibits highest and lowest fraction of {001} cube texture and {112} copper texture, respectively. The average grain size of final sheet also reaches peak, and it is 117.65 µm. In addition, the fine precipitates mainly include spherical MnS, CuS, regular hexahedral AlN, TiN and partly approximate spherical composite precipitates. The average size and distribution density are 132.10 nm and 1.62 × 10¹² cm⁻³, respectively. Under the condition annealed at 1000 °C for 7 min, the core loss P_1.5/50 is 2.461 W · Kg⁻¹ and the magnetic induction B₅₀ is 1.699 T.

Industrialization trial production of high permeability (Hi-B) steel was carried out by “one cold rolled + decarburization and nitridation technologies”. The finished product reached the level of 23Q100 with an average grain size of 5.47 cm, magnetic flux density B₈ of 1.902T, and the iron loss P_1.7/50 of 0.975 W/Kg. The evolution law of the microstructure and texture under different processes was analyzed with the help of OM, EBSD, and XRD. The results showed that the microstructure of the hot rolled plate was equiaxed crystals in the surface layer, a mixture of recrystallization grains and banded fiber in the quarter of the thickness layer, and banded fiber in the center layer. The texture gradient of the hot rolled plate from the surface layer to the center layer was {112} + {110} → {441} → {001}~{111}. The texture of the normalized plate was in major {110} in the surface layer, diffuse α-fiber texture and {441} in the quarter of the thickness layer, and sharp α texture {001}~{111} in the center layer. The texture of the cold-rolled sheet was concentrated in {001}~{332}. The average grain size of the decarburizing and nitriding sheet was 26.4 μm, and the texture of the first recrystallization is sharp α*-fiber and weak {111}. The finished product has a sharp single Goss texture. For Hi-B steel, the Goss secondary nucleus originated from the surface layer to 1/4 layer of the hot rolled plate and reached the highest content of 11.5% in the quarter of the thickness. The content of the Goss texture decreased with the subsequent normalization and cold rolling, then the Goss grains nucleated again during the decarburization annealing and high temperature annealing processes.

The effects of cooling modes (air, furnace and water) on the variation of microstructure and mechanical properties of medium carbon steel were investigated. SEM, TEM and EBSD techniques were used to observe the microstructure. The observed results show that the effect of cooling mode on the grain size is insignificant. The average sizes of ferrite grain obtained under different cooling modes were little different. Moreover, in all the cases, most of the cementite lamellas were transformed into cementite particles, except for some of the residual cementite lamellas which were present on the original pearlite colonies. It has also been found that the ferrite substructure and precipitation of cementite particles are significantly affected by the cooling modes. Compared to other cooling modes, the furnace cooling is beneficial to the homogeneity of microstructure. The particles are distributed on the ferrite matrix more homogeneously after furnace cooling which results in a better combination of strength and ductility.

A grain-oriented silicon steel sheet was manufactured by slab reheated at “medium temperature” and two-stage cold rolling method. The function of heating rate on secondary recrystallization in grain-oriented silicon steel was investigated. The results show that: compared with 30 °C/h heating rate, the initial temperature of the secondary recrystallization can increase by 10 °C at the heating rate of 20 °C/h. Furthermore, the temperature region of secondary recrystallization also extended either with the increased heating rate. Even though the inhibitors maintain AlN, complex precipitation of AlN and sulphide in both heating rate, the average diameter and Zener factor of inhibitors are distinct. Inhibitors in the route of 20 °C/h heating rate express stronger inhibition than that of 30 °C/h, and the average diameter and Zener factor are 17.519 nm and 3.925 × 10⁻⁴ nm⁻¹, respectively. In addition, more Goss texture component and less γ-fiber texture ({111}//ND) component form at the heating rate of 30 °C/h than 20 °C/h at 1000 °C, but the final Goss texture component of 20 °C/h is greater than 30 °C/h. The average grain size of the final annealing sheets increased with the heating rate decreasing from 30 °C/h to 20 °C/h, and iron loss reduced by 0.05 W/Kg, the magnetic induction intensity increased by 0.025 T.