New method for producing fine spherical iron powders

Fine spherical iron powders are used for example as a component of the binder matrix in diamond tools, for magnetorheological fluids, materials absorbing microwaves but mostly for metal injection molding (MIM). Although the yearly growth rate of MIM production is considerable, the high powder costs are a limiting fact for many applications. In this paper a new cost efficient processing route is introduced, which allows to produce fine iron powder by hydrogen reduction. The process is based on a hematite powder which is a recycling product from steelmakers. After a granulation process the iron oxide is reduced at a first heat treatment step. A further increase of the temperature is necessary to reduce the high specific surface and to achieve a sintering of the primary iron particles to fully dense and non pyrophoric spherical powder particles. The experimental results have shown that iron powder < 32 µm can be produced.