Texture and Microstructure for Magnetic Properties of Two-Stage Cold-Rolled Fe-6.5 Wt Pct Si Thin Sheets
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HIGH-SILICON electrical steel containing 6.5 wt pct Si has excellent soft magnetic properties such as high permeability, low iron loss, and reduced noise.[1] Owing to the serious brittleness, it is hard to produce Fe-6.5 wt pct Si sheets through the conventional rolling procedure. Several special processing methods such as chemical vapor deposition (CVD),[2] rapid solidification,[3] and spray forming[4] have attracted more attention. However, continuous efforts have also been made on the rolling process, showing that Fe-6.5 wt pct Si thin sheets can be produced successfully by the precise control of hot band microstructure and careful selection of the rolling parameters.[5–8] Because of the high flow stress, it is basically inevitable to apply two-stage cold rolling process with intermediate annealing to fabricate Fe-6.5 wt pct Si thin sheets. Recrystallization texture is a key factor to improve the magnetic properties in spite of a lower magnetic anisotropy for Fe-6.5 wt pct Si alloy than that for the conventional silicon steel. Recrystallization g fiber (h001i//RD, rolling direction) and k fiber (h001i//ND, normal direction) are favorable to magnetic properties with h001i easy magnetization direction lying in the rolling plane, whereas c fiber (h111i//ND) is detrimental without h001i direction in the rolling plane. Limited work has been done on the texture development in Fe6.5 wt pct Si sheets. Liu et al.[7,8] obtained {001}h210i YONGCHUANG YAO, Doctoral Student, YUHUI SHA and LIANG ZUO, Professors, JINLONG LIU, Lecturer, and FANG ZHANG, Associate Professor, are with the Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110819, P.R. China. Contact e-mail: [email protected] Manuscript submitted January 31, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS A
and {210}h001i recrystallization textures in 0.5-mmthick rolled Fe-6.5 wt pct Si sheets. Fang et al.[9] reported recrystallization g and c fibers in 0.3-mm-thick rolled 6.5 wt pct Si sheets. Liu et al.[10,11] produced recrystallization k fiber in Fe-6.5 wt pct Si thin sheets by twin-roll strip casting process followed by hot rolling and warm rolling. Recrystallized g and c grains mainly nucleate at shear bands and grain boundary regions, respectively.[12–18] In two-stage cold rolling process, intermediate grain size acts as the initial grain size for second-stage rolling. The coarse initial grain size prior to final cold rolling process promotes the formation of shear bands and reduces the grain boundary regions. A number of investigations have revealed that the primary recrystallization g fiber can be enhanced by increasing the initial grain size.[19–24] Nevertheless, it is hard to ignore the fact that recrystallized g grains tend to exist in colonies during recrystallization process and are less favorable in terms of size, whereas c grains can gain number and size advantages during primary recrystallization in electrical steel and ultra-low carbon steel,[12,25–27] even in the sheets with coarse init
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