Cracking and Microstructure Transition of Iron Ore Containing Goethite in Fe-C Melt Based on the HIsmelt Process

The phenomenon of cracking and deterioration of iron ore particles is a widespread scientific problem in the field of mineral processing and metallurgy. In this paper, the thermal decomposition properties of iron ore were investigated by a non-isothermal method using thermogravimetric equipment, and the crack evolution behavior of iron ore within Fe-C melt was investigated experimentally, by scanning electron microscopy and Micro-CT. The results show that the start decomposition temperature of #2 iron ore is 292.7 degrees C, which is 37.3 degrees C higher compared to that of #1 iron ore, because of its smaller pores and the difficulty of water vapor diffusion. The initial decomposition of iron ore is the decomposition goethite to form water vapor, and as heat transfer continues, hematite particles break into smaller particles and decompose to form Fe3O4. During the smelting reduction process, the Crack index (CI) of #1 iron ore was 5.50% at 4 s, and the CI index increased to 23.54% when time was extended to 16 s, and the internal evolved from locally interconnected holes to cracked structure. The iron ore maintains a relatively intact form during reduction within the Fe-C melt, and interfacial reduction reaction is dominant in the later stage.