Texture evolution during annealing of high silicon steel sheet
High silicon steel containing 6.5% (mass fraction) of Si has high magnetic permeability, very low iron loss and low noise, etc. Excellent soft magnetic properties, it is an ideal core material with low energy consumption, miniaturization, high speed, and environmental friendliness. The magnetic properties of high-silicon steel are very sensitive to recrystallization texture, but due to its high hardness and brittleness, long-term research on high-silicon steel has mainly focused on how to improve the processing and forming problems. There has been little progress in the optimization and control of high-silicon steel texture.
Machado et al. studied the warm-rolled texture of Fe-6.5% (mass fraction) Si alloy containing 1.0% (mass fraction) Al. Ros-Yanze et al. characterized the texture characteristics of high silicon steel after hot rolling, cold rolling and annealing.
In their research, the hot rolled texture of high silicon steel consists of cubic texture {001}<100>), γ texture and Goss texture ({110}<001>), cold rolled Afterwards, it mainly evolved into γ texture, and after annealing, γ texture with {111}<110> as the peak was formed. As for magnetism, γ recrystallization texture is the most unfavorable texture component in silicon steel, so their research did not involve the optimization of high silicon steel recrystallization texture.
Using the traditional hot rolling, cold rolling and annealing process to manufacture high silicon steel sheet, and using X-ray diffraction technology to analyze the evolution law and control effect of its recrystallization texture.
Recrystallization texture of high silicon steel sheet at different annealing temperatures
The cold-rolled structure is mainly composed of elongated grains containing a large number of shear bands, and the surface layer and 1/ The strength and density of the shear band between the 4 layers are greater than that of the core. The cold-rolled texture of high silicon steel sheet is mainly composed of α texture (<110>∥RD) with {112}<110> as the strong point and γ texture with {111}<112> as the strong point.
High-silicon steel cold-rolled sheets are recrystallized after annealing at 700, 900, 1000, and 1100°C for 10 minutes. The average grain sizes are 18, 139, 172, and 191μm, respectively.
When annealing at 700℃, the recrystallized texture is mainly {001} texture with {001}<210> as the peak and γ texture with {111}<112> as the peak, and { The strengths of 111}<112> and {001}<210> are similar, and the orientation density is 4.3 and 4.1, respectively. When annealed at a temperature higher than 900℃, the γ-texture orientation density drops below 2.0, while the {001}<210> texture orientation density increases to above 9.7, and {001} texture is the dominant texture component. In general, with the increase of annealing temperature in the range of 700-900℃, {001}<210> quickly became the dominant texture component, and the γ texture was significantly weakened. In the range above 900℃, as the annealing temperature increases, {001}<210> continues to increase, but the increase rate decreases. In short, annealing at temperatures above 900°C is conducive to the optimization of the recrystallization texture of non-oriented high-silicon steel sheets.
Texture evolution during grain growth
The recrystallization texture of high silicon steel sheet may be affected by annealing temperature for two reasons:
(1) The temperature dependence of the nucleation rate of grains with different orientations;
(2) The temperature dependence of the growth rate of grains with different orientations.
For this reason, annealing experiments at different times at 900℃ were carried out to investigate the texture evolution during grain growth. Both annealing processes were completely recrystallized, and the average grain size was 22 and 151 μm, respectively. When annealing for 0.4min, the recrystallized texture is mainly {001} texture with {001}<210> as the peak and γ texture with {111}<112> as the peak, and the two strengths are similar; when annealing for 100min , {001} texture is the dominant texture component. Obviously, with the extension of annealing time in the range of 0.4～10min, the γ texture with {111}<112> as the peak is significantly weakened, and {001}<210> develops into the dominant texture component; in the range of 10～100min Inside, the texture type and orientation density change are relatively small.
The similarity of the texture at the stage of recrystallization at 700 and 900℃ just after the completion of the recrystallization shows that the difference in the texture of recrystallization at different temperatures is formed during the process of grain growth. As the recrystallized grains grow up, {001} grains gradually swallow other orientation grains and become the dominant texture component, while γ grains are gradually swallowed and weakened. The grain size and recrystallization texture of non-oriented silicon steel are two key structural parameters that affect the magnetic properties. The annealing process currently used is oriented to obtain the optimal grain size, and in this process the recrystallization texture usually changes in unfavorable directions as the grains grow. The recrystallized texture of high-silicon steel exhibits different evolution laws: as the grains grow, the unfavorable γ texture gradually weakens or even disappears, while the favorable {001} texture continues to increase as the main texture component.
Summary
On the use of hot rolling, cold rolling and annealing processes to prepare high silicon steel sheets, and analyze the effect of annealing temperature on the recrystallization texture. Annealing temperature has a significant effect on the recrystallization texture of cold-rolled high-silicon steel sheets. Annealed above 900℃ can obtain a strong {001} recrystallization texture with a peak value of {001}<210>. The evolution of the recrystallized texture of high-silicon steel is different from that of ordinary silicon steel: as the recrystallized grains grow, the {001} texture gradually increases and becomes the main texture component, while the γ texture gradually weakens.