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Effect of Phosphorus on the Magnetic Properties of Non-oriented Electrical Steel

Title
Effect of Phosphorus on the Magnetic Properties of Non-oriented Electrical Steel
Authors
이세일
Date Issued
2012
Publisher
포항공과대학교
Abstract
The addition of Si to electrical steel is used to reduce the core losses, which are a consequence of induced eddy currents. As the electrical resistivity increases by the addition of Si-the induced eddy current losses are reduced. P is also very effectively increases the electrical resistivity of α-Fe. However the effect of P on the magnetic properties of electrical steels has not been studied in detail. The effect of P as a alloying addition for a development of a new type of non-oriented electrical steel was therefore investigated in the present dissertation research. P is known to segregate to grain boundaries in steel and this has been reported cause brittle fracture during deformation. In order to utilize P-added steels, an in depth analysis was needed of the deformation behavior of P-added steels in production conditions. In the present study, the hot workability of the Fe-2%Si steels with varying P contents was characterized by the high temperature compression tests. The activation energies for plastic flow at high temperature were found to increase with increasing P content. In addition dynamic recrystallization was suppressed in Fe-2% Si-0.15% P steel. The intrinsic magnetic properties of a P-added 2% Si steels were investigated. The electrical resistivity values increased sharply with increasing P content up to 0.1% in both Fe-0.05% Si and Fe-2% Si steels. The magnetic induction values decreased and the coercivity values increased with increasing P content. The effect of P on the grain boundary migration was also investigated. The activation energy for grain boundary migration increased due to 0.1% P addition in Fe-Si steels. The effect of P on an increase of the activation energy for grain boundary migration was however reduced by addition of 20 ppm B. Abnormal grain growth by the solute drag effect of P was observed in Fe-3%Si-0.1%P steel annealed at 800℃ for 150 min and at 900℃ for 10 min. The grain growth of grains having near {111}<112> orientation was suppressed whereas the grain growth of the {112}<361> oriented grains was clearly accelerated. The addition of B was found to weaken the effect of P on both of the grain growth and crystallographic texture evolution. A decrease of anomalous losses and an increase of hysteresis losses occurred in the Fe-2%Si-0.05%P steel. Both types of magnetic losses increased in the Fe-2%Si-0.10%P steel. Small secondary domains, so-called spikes, formed near at precipitates were observed in Fe-2%Si-0.10% P steel. A complex magnetic domain structure was created in Fe-2%Si-0.05%P steel due to the interaction of the domain wall with the fine P precipitates.
URI
http://postech.dcollection.net/jsp/common/DcLoOrgPer.jsp?sItemId=000001216299
http://oasis.postech.ac.kr/handle/2014.oak/1377
Article Type
Thesis
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