Advances in insulated powder technology

Abstract
The powder metallurgy technique is a well established process for the cost effective production of near net shape products in long series. Soft magnetic materials utilise the premix and compacting techniques of powder metallurgy. High purity powder particles with high compressability are required to ensure good soft magnetic properties. Improvements in the compressability of the powder combined with advances in compacting techniques such as warm compacting result in high density components suitable for commercial production. High induction in powder based products is dependant on the density. In order to ensure low eddy current loss at medium frequency a continuous insulation layer between particles is applied. The thickness of the insulation layer should be minimised in order to maintain the compressibility of the powder and resultant induction. The insulation layer should remain intact after compacting at high pressure. Additives are a normal requirement in the mass production of powder components as lubrication for easy removal of the component from the tool is required. In the case of insulated powder particles where the thin insulation layer must be maintained, additives may also be used to increase the strength. In the case of conventional irregular particle form, the magnetic and thermal properties which can be achieved are isotropic. This permits the design of motors with three dimensional flux and limits the constraints imposed by anisotropic materials.