Investigation on Inclusions in Non-oriented Silicon Steels
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Inclusions in non-oriented electrical steels (NO-ES) play an important role for the reduction of the core loss.[1] AlN, MnS, and Al2O3 are common inclusions since the high content of aluminum and manganese exist in non-oriented electrical steels. Coarsening AlN precipitates favor to decrease the core loss with the increase of aluminum, and MnS should be well controlled since deterioration of the core loss caused by the retardation of the grain growth occurs at the recrystallization annealing by the fine MnS.[1–3] Two AlN varieties have been observed in different annealing temperature, which are stable hexagonal (wurtzite) and metastable cubic
YANG LIU, PEI WANG, and DIANZHONG LI are with the Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, P.R. China. Contact e-mail: [email protected] XIAO ZHANG is with the Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences and also with the School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, P.R. China. Manuscript submitted July 23, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS B
(NaCl-type) structures.[4–6] For the low core loss, the grain size should be kept at an optimum size with properly dispersed AlN and MnS precipitates.[1] The type, amount, size and distribution of inclusions significantly influence the properties of non-oriented electrical steels. Several analysis methods have been introduced in the characterization of inclusions in steels, such as EDS, EELS, TEM, EBSD, XRD, and so on.[4] For the identification of the type and the structure of inclusions in steel, micro-XRD test is a preferred method than TEM since abundant inclusions are measured simultaneously and the preparation for specimen is relatively easy. However, the XRD spectrum is normally very noisy since the density of extracted precipitates in steels is relatively low and sometimes mixed with impurities using a filtering method.[7,8] In the current study, another method of the specimen preparation for XRD is employed in order to obtain a desired XRD spectrum. Currently, inclusions in the hot-rolled plate sample of non-oriented electrical steels were extracted with a nonaqueous solution electrolytic method, and the chemical composition of steel is listed in Table I. The steel sample with the size of 80 mm 9 6 mm 9 3 mm was used as anode and a stainless steel sheet as cathode. The electrolyte consisted of 1 pct 4-methyl ammonium chloride, 5 pct tri-ethanolamine, 5 pct glycerin and 89 pct methyl alcohol (in volume fraction). During the electrolysis process, a regulated DC power supply (Model DH1720A-1) was used to keep an electric current density between 40 and 60 mA/cm2. The temperature of the electrolyte was kept in the range from 268 K to 278 K. After 6 hours of electrolysis, about 2.0 g steel has been dissolved. The detailed experimental procedure has been described in our previous paper.[9] After the extraction, the wate
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