Characterization of Microstructure and Texture in Grain-Oriented High Silicon Steel by Strip Casting

doi:10.1007/s40195-015-0338-1

Abstract

Abstract:

Grain-oriented 4.5 wt% Si and 6.5 wt% Si steels were produced by strip casting, warm rolling, cold rolling, primary annealing, and secondary annealing. Goss grains were sufficiently developed and covered the entire surface of the secondary recrystallized sheets. The microstructure and texture was characterized by OM, EBSD, TEM, and XRD. It was observed that after rolling at 700 °C, the 6.5 wt% Si steel exhibited a considerable degree of shear bands, whereas the 4.5 wt% Si steel indicated their rare presence. After primary annealing, completely equiaxed grains showing strong γ-fiber texture were presented in both alloys. By comparison, the 6.5 wt% Si steel showed smaller grain size and few favorable Goss grains. Additionally, a higher density of fine precipitates were exhibited in the 6.5 wt% Si steel, leading to a ~30-s delay in primary recrystallization. During secondary annealing, abnormal grain growth of the 6.5 wt% Si steel occurred at higher temperature compared to the 4.5 wt% Si steel, and the final grain size of the 6.5 wt% Si steel was greater. The magnetic induction B ₈ of the 4.5 wt% Si and the 6.5 wt% Si steels was 1.75 and 1.76 T, respectively, and the high-frequency core losses were significantly improved in comparison with the non-oriented high silicon steel.

Key words: Strip casting, Grain-oriented high silicon steel, Microstructure Texture

Xiang Lu, Yun-Bo Xu, Feng Fang, Yuan-Xiang Zhang, Yang Wang, Hai-Tao Jiao, R. D. K. Misra, Guang-Ming Cao, Guo-Dong Wang. Characterization of Microstructure and Texture in Grain-Oriented High Silicon Steel by Strip Casting[J]. Acta Metallurgica Sinica (English Letters), 2015, 28(11): 1394-1402.

Figures/Tables 14

Table 1 Chemical composition of the silicon steels

Steel	Si	C	Mn	S	Al	N	Nb	Fe
4.5Si	4.48	<0.003	0.225	0.021	0.011	0.007	0.031	Bal.
6.5Si	6.45	<0.003	0.250	0.020	0.012	0.010	0.041	Bal.

Fig. 1 As-rolled microstructures of the 4.5Si steel a, c, e and the 6.5Si steel b, d, f

Fig. 2 Final cold-rolled sheets of the 4.5Si a and the 6.5Si b steels

Fig. 3 Textures of the 4.5Si a and the 6.5Si b steels after final cold rolling

Fig. 4 Microhardness evolution for the 4.5Si and the 6.5Si steels during primary annealing

Fig. 5 Microstructures of the 4.5Si a and the 6.5Si b primary annealed sheets

Fig. 6 {200} XRD peak profiles for the 4.5Si and the 6.5Si cold-rolled sheets

Fig. 7 Precipitates in primary annealed the 4.5Si steel a, the 6.5Si steel b and the particles size distribution c

Fig. 8 Texture a and γ-fiber texture averaged over surface and center layer b of the 4.5Si and the 6.5Si steels after primary annealing

Fig. 9 Goss grains in the 4.5Si a and the 6.5Si b primary annealed sheets

Fig. 10 Microstructures of samples for the 4.5Si a and the 6.5Si b steels

Fig. 11 Macrostructures of the 4.5Si a and the 6.5Si b steels after secondary recrystallization

Fig. 12 Textures of secondary annealed sheets for the 4.5Si a and the 6.5Si b steels

Table 2 Magnetic properties of the high silicon steels

Material	Thickness (mm)	B ₈ (T)	P _10/400 (W/kg)	P _10/1K (W/kg)	Ref.
Grain-oriented 4.5% Si steel (strip cast)	0.20	1.75	10.21	42.37	This work
Grain-oriented 6.5% Si steel (strip cast)	0.20	1.76	8.659	32.24	This work
Non-grain-oriented 6.5% Si steel (CVD)	0.20	1.09	14.5	51.6	JNHF-Core [36]

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