Influence of Tension due to Improvement of Iron Loss in TiN-Coated Grain Oriented Silicon Steel Sheet

In order to clarify the mechanism by which the iron loss in TiN-coated grain oriented silicon steel sheet was improved dramatically, the relations between the tension and improvement of iron loss were investigated.For magnetic properties in tension from 0 to 30 MPa of the polished silicon steel sheets, the magnetic flux density B8(T) showed a moderate increase of 0.008-0.013 T and the iron loss W17⁄50(W/kg) showed a dramatical improvement of 0.15-0.20 W/kg. This improvement in iron loss was more marked in the silicon steel sheet with a higher magnetic flux density, and was remarkable with slight tensions from 2 to 5 MPa.With increasing tension after TiN coating, B8(T) also showed a slight increase of 0.006-0.011 T and W17⁄50(W/kg) showed a moderate improvement of 0.05-0.07 W/kg. Moreover, the improvement of iron loss of twice TiN coatings with a thickness of 0.5 μm was similar to one-time TiN coating with a thickness of 1 μm.From the relationship between iron loss and tension in the polished steel sheet, it was estimated that the tension of about 6.5-10 MPa was added to the TiN-coated silicon steel sheet. This value was consistent with the previous results (8 MPa) obtained from the compressive stress dependence of magnetostriction.