Effect of pre-annealing prior to cold rolling on the precipitation, microstructure and magnetic properties of strip-cast non-oriented electrical steels. Issue 12 (December 2017)

• Record Type: Journal Article
• Authors: Xu, Yunbo; Jiao, Haitao; Zhang, Yuanxiang; Fang, Feng; Lu, Xiang; Wang, Yang; Cao, Guangming; Li, Chenggang; Misra, R.D.K.
• Is Part Of: Journal of materials science & technology. Volume 32:Issue 12(2016:Dec.)
• Page Start: 1465
• Page End: 1474
• Publication Date: 2017-12
• Subjects: Strip casting -- Non-oriented electrical steel -- As-cast strip annealing -- Precipitates -- Magnetic properties; Metals -- Periodicals; Materials science -- Periodicals; Materials science; Metals; Periodicals; 620.1105
• DOI: 10.1016/j.jmst.2017.08.002
• Languages: English
• ISSNs: 1005-0302

Abstract

Highlights: Non-oriented electrical steels was fabricated by a novel strip casting process involving pre-annealing. Precipitation characteristic and its effects on microstructure, texture and magnetic properties was investigated. Pre-annealing increased the grain size and {100} recrystallization texture in finally annealed sheets. Excellent magnetic properties with P15/50 of 3.26 W/kg and B50 of 1.735 T were obtained. Abstract: A novel processing route involving strip casting, pre-annealing treatment, cold rolling and recrystallization annealing was applied to a Fe-2.6%Si steel to improve the magnetic properties. The impact of as-cast strip pre-annealing on the microstructure, texture, precipitation and magnetic properties were investigated by electron probe micro-analysis, transmission electron microscopy, and X-ray diffraction analysis, etc. It was found that the precipitation of second-phase particles during strip casting was restrained by rapid solidification. The absence of pre-annealing led to the occurrence of a large amount of 20–50 nm MnS precipitates in the final annealed sheets, which is responsible for fine grains and high core loss (4.01 W/kg) due to grain boundary pinning effect. Although the microstructure and texture of 900–1000 °C pre-annealed samples were similar to those of as-cast strip, significant grain coarsening together with the strengthening of λ-fiber texture was observed in the 1100 °C pre-annealed strips. In comparison with the case of as-cast strip, a higher amount of large-sized precipitates consisting of manganese sulfide and/or aluminum nitride occurred in matrix after pre-annealing. Correspondingly, in the final annealed sheets, the number density of precipitates with sizes smaller than 100 nm was substantially reduced, and 100–200 nm and 200–500 nm sized particles became more dominant in samples subjected to 30-min and 120-min pre-annealing treatments respectively. In addition, the average grain size of final annealed sheets increased with the pre-annealing temperature and time because of the weakened pining effect of coarsen precipitates. Ultimately, the magnetic induction of samples subjected to pre-annealing was slightly increased and ranged from 1.73 T to 1.75 T owing to the enhancement of {100} recrystallization texture, and simultaneously the core loss significantly decreased until a minimum of 3.26 W/kg was reached. Nevertheless, large number of 200–500 nm particles presented during pre-annealing for 120 min could weaken the improvement in core loss which is likely associated with the pinning effect on magnetic domain wall.