Magnetic properties of iron alloys

Abstract

The purpose of this work was to compare the properties of high purity atomized iron powder compacts with conventional high purity irons and to show the effects of porosity on magnetic properties. It was found that if powders were hot repressed so that no porosity was present, the magnetic properties were as good as or better than conventional high purity irons, depending on the sintering conditions employed. Intrinsic properties were similar because the amount of iron available to magnetize was equivalent. Structure-sensitive properties depended on the grain size. If the compacts were sintered above the delta transition temperature, these properties were equivalent to the purest of the conventional high purity irons. As the compacts became less dense and more porosity was present, induction and remanent magnetization decreased linearly with density; resistivity increased. In the case of structure-sensitive properties, porosity restricted grain growth. Small, closely spaced pores caused the greatest degradation of properties. Equations were derived through regression analyses and were found to explain more than 90% of the data. The intrinsic properties: induction, remanent magnetization, and resistivity were all linear functions of the density. The maximum permeability and the coercive force were power functions of the mean grain size intercept. These equations provide a basis for design of magnetic components using P/M compacts. If the properties that are desired are known, the density or the grain size required may be calculated. From this, the powder and the processing conditions required can be established to provide the desired properties.