2004 Volume 45 Issue 6 Pages 1891-1894
Powder magnetic cores are candidates for a new type of motor core. However, both their magnetic flux and their strength are less than those of laminated steel. The lesser properties are caused by a small green density. In order to increase the green density, the cores need to reduce the admixed lubricant and use high-pressure compaction. We developed a new warm compaction using die wall lubrication with lithium stearate. By using this method, a very high-density compact could be fabricated without scoring. In this instance a starting powder was Somaloy500 without resin, the powder magnetic core compacted at 1176 MPa with heat treatment at 673 K had properties as follows: d = 7.77 Mg/m3, μm = 1000, B2k = 1.41 T, B5k = 1.61 T, B10k = 1.80 T, bHc = 300 A/m, ρ = 4 μΩm, TRS = 210 MPa, σmax = 150 MPa, and in case of Bmax = 1.0 T and f = 400 Hz, Pc = 900 kW/m3, Ph = 350 kW/m3, Pe = 550 kW/m3.