Whisker Growth During the Reduction of lron Ores

During several experimental programs conducted at the Institute of Ferrous Metallurgy, Technical University, Aachen, whisker formation was observed when iron ores were reduced at low as well as at high temperatures. Thus, in an attempt to find the reason for the volume change taking place during reduction, iron whisker growth was observed. Whisker growth appears to be one of the important reasons for the swelling of pellets. One set of experimental observations determined that when iron forms as needles rather than as a crust on the surface of oxide, the pellets became very porous. In related experiments, the beneficiation of finely disseminated iron ores, in which the metallic iron is separated from the gangue in granular or nodular form, was achieved by a reduction-concentration method. In this process, which is conducted at sufficiently high temperatures, oxide whisker growth, resulting from the formation of volatile suboxides and a gas transport mechanism, plays a vital role in the joint deposition of SiO, and iron from the vapor stage.