Thermal strength characteristics and mechanism of iron ore and carbon pellets in the non-isothermal reduction process

Abstract

The thermal strength characteristics and mechanism of iron ore and carbon pellets (ICP) in the non-isothermal heating process, including the effect of reducing agent, carbon content and heating rate on the thermal strength, were studied by the on-line test device of thermal strength, combined with the TG/DTG-DTA data, the samples microstructure and porosity after reduction. When ICP was damaged by external force at high temperatures, it existed in two states: crush and plastic deformation. The thermal strength of ICP slightly increased at 200°C–800°C, significantly decreased after 800°C and reached the minimum value at 1 000°C. The thermal strength of ICP was changed by the combination of combined water evaporation, the reducing agent volatilization and the reduction reaction. At 200°C–1 000°C, the thermal strength was derived from the molecular attraction between the particles and viscous force from bonding agent. But when the temperature higher than 1 000°C, the thermal strength was served by metal iron continuous crystal. To obtain high thermal strength, the iron oxides in ICP should be reduced fast by using the reducing agent with low volatility, improving the heating rate and choosing the suitable reducing agent ratio, made the iron crystal grown rapidly and dense.