Volume and structural changes occurring during the isothermal and non-isothermal reduction of high grade hematite pellets

The major cause of swelling during isothermal reduction at temperatures in the range 600-1000 degree C was disruptive stresses set up during transformation to magnetite. The severity of the disruption was temperature dependent. Under non-isothermal reduction conditions in which pellet temperatures were increased at constant heating rates over the temperature range 500-1000 degree C, minor swelling (6-8%) occurred in the initial stages of reduction followed by contractions of up to 15% in the final reduction stages.