Direct Experimental Observations on Concurrent Microstructure and Magnetic Property Developments in Non-Grain Oriented E
- PDF / 2,044,229 Bytes
- 4 Pages / 593.972 x 792 pts Page_size
- 39 Downloads / 174 Views
Semi-processed cold-rolled non-grain oriented (CRNO) electrical steel is, arguably, the cheapest lamination material used in electrical equipment under rotating magnetic field(s).[1–3] The laminations are made after slitting and punching of the coils.[1–5] It is normally reported that deformation, in general, is detrimental to magnetic properties.[6,7] The only exception is relatively minor (elastic) tensile loading, where clear improvements in magnetic properties are reported.[8] Most of these studies are phenomenological, with ‘‘limited’’ tracking of concurrent microstructural developments. S.K. SHEKHAWAT and V. BASAVARAJ, Research Scholars, R. CHAKRABARTY, M-Tech Student, and I. SAMAJDAR, Professor, are with the Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai 400076, India. Contact e-mail: [email protected], satishshekhawat@ iitb.ac.in V.D. HIWARKAR, Manager (R&D), and J. NEMADE, Senior Manager (R&D), are with the Global R&D centre, Crompton Greaves Ltd. Mumbai 400042, India. P.J. GURUPRASAD, Professor, is with the Department of Aerospace Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India. K.G. SURESH, Professor, is with the Department of Physics, Indian Institute of Technology Bombay, Mumbai 400076, India. R.D. DOHERTY, Professor, is with the Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, and also with the Department of Materials Science and Engineering, Drexel University, Philadelphia PA 19104. Manuscript submitted December 2, 2013. Article published online July 20, 2014 METALLURGICAL AND MATERIALS TRANSACTIONS A
The present study was designed to correct this omission by the direct observation of developments in microstructure and magnetic properties in a semi-processed CRNO after interrupted small tensile strains. Semiprocessed CRNO, as used in the present study, is an example of clean steel. The content of sub-micron (maximum 300 nanometer) second phase was below 0.002 in relative area fraction. They are not expected to have significant influence on the deformed microstructure developments. Tensile samples were prepared from a semi-processed CRNO grade (chemical composition listed in Table I) according to ASTM E8. After standard interrupted tensile testing to small strains, data were extracted on dr vs e, where r the dynamic hardening[9–11] behavior: d2 and e are true stress and strain, respectively. Through these interrupted tensile tests, the same surface region was characterized for B–H (the strengths of the induced and imposed magnetic fields) measurements, electron backscattered diffraction (EBSD), and residual stress. Standard electropolishing[7] was used for the sample preparation. EBSD measurements were made in a FEIä Quanta 3d-Feg (field-emission gun) SEM (scanning electron microscope), with EDX-TSLä EBSD system. An area of 1 9 2 mm2 was measured with 1 lm step sizes, while an additional 100 9 100 lm2 were also scanned at 100 nm steps. Beam and video conditions
Data Loading...
