Re-oxidation behaviour of a porous metallised iron pellet and morphologies of oxides formed at temperatures between 973 and 1173 K were studied. The increase in oxygen concentration resulted in not only an enhanced rate of re-oxidation but also a higher temperature rise in the pellet.
The re-oxidation proceeded usually with two stages; i.e. the initial stage of a high rate and the latter stage of a low rate. The physical nature of the oxide formed during the initial stage has a decisive influence upon the subsequent oxidation behaviour.
The oxide layers were associated with various deffects such as remaining pores, cracks and blisters. Furthermore, needle-like hematite crystals grew as a general occurrence for the re-oxidation of several metallised iron pellets. The compressive stresses developed by the rapid re-oxidation was considered to be a possible reason for the growth.