Evolution of Non-metallic Inclusions and Precipitates in Oriented Silicon Steel
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ed silicon steel plays a significant role in the transformer manufacturing industry. Magnetic property is one of the most important properties of oriented silicon steel. Non-metallic inclusions have a great influence on magnetic properties, they can either directly hinder the motion of domain wall, or induce the small grain size by the pinning effect, which affects the motion of domain wall indirectly. Therefore, inclusions in oriented silicon steel have been reported in the published literature.[1–16] Jenkins and Lindenmo[1] reported the effect of the sulfide-based inclusions in oriented silicon steel on the properties. A similar study was also shown by Kononov and Mogutnov.[8] Nonetheless, many types of research focused on the relationship between inclusions and texture in oriented silicon steel. Liu et al.,[9] Lu et al.,[13] and Harase et al.[16] reported that inclusions in oriented silicon steel affected the texture evolution. Inclusions, including oxides, nitrides, sulfides, and their compounds, in steel are mainly generated during the processes of secondary refining, solidification, and cooling. However, there are few kinds of literature
YAN LUO, WEN YANG, QIANG REN, ZHIYUAN HU, MING LI, and LIFENG ZHANG are with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China. Contact e-mail: yangwen-fl[email protected] Manuscript submitted January 17, 2018. METALLURGICAL AND MATERIALS TRANSACTIONS B
regarding the characteristic of inclusions in oriented silicon steel due to the complex and strict production technology. Yang et al.[17] reported that (Al, Si)N particles were the main inhibitors in the final annealing process with the change of N2 fraction in the atmosphere. However, the systematic study on the evolution of inclusions in the oriented silicon steel during the manufacturing process has been rarely reported. The objective of the current work is, therefore, to provide the information. The production route of oriented silicon steel is ‘‘basic oxygen furnace (BOF) fi RH refining fi continuous casting fi rolling process.’’ Bottom blowing technology is used in BOF. The main function of RH refining is the composition adjustment by adding alloys of Al-Fe, Si-Fe, and Mn-Fe. The casting speed was 1.0 m/min, resulting in a casting period of 45-50 min. The casted slabs were subsequently reheated to 1250 C to 1350 C for 24 hours and then were rolled into the product through a complicated rolling process. Steel samples were taken at the start, adding alloying, and after the alloying during RH refining, at the end of RH refining, in the slab, and after the hot rolling. The main compositions of steels were measured using spectrum analysis, as shown in Table I. The samples were then cut, polished, and etched using partial and full non-aqueous electrolysis method[18] for the inclusion characteristic. During the electrolysis, the steel samples were etched for various times at the current density of 50 mA/mm2, rinsed with alcohol, dried, and subsequently observed using a field em
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