FORMATION OF METALLIC IRON SHELLS AND THEIR STICKING TOGETHER DURING THE REDUCTION OF IRON ORE PELLETS.

Abstract

Pellet samples taken from an industrial blast furnace during reduction were large and very hard masses with an outer metallic shell and an unreduced core. Further reduction, in the liquid state after melting of this mass, was undesirable. Chemical analysis and microscopic investigation showed that the shell consists of much metallic iron, a little wustite, and slag. Its melting point is 1560 degree C. The core consists of much wustite and small amounts of metallic iron and slag. Its melting point is 1360 degree C. When a pellet prereduced to wustite is reduced by containing 30%CO plus 70%N//2 at 1200 degree to 1250 degree C in 30 to 60 min, a dense metallic iron shell about 1. 5 mm thick is formed. Strong cohesion of the pellet particles is obtained by heating the pellets with iron shells in a nitrogen atmosphere at 1250 to 1300 C for 30 to 60 min under a load of 1. 0 kg/cm**2.