Abstract
The crushing strength of the metallised iron pellets of original basicities ranging from 0.64 to 2.54 was tested at room temperature after hydrogen reduction at temperatures between 973 and 1273 K.
The slag phase in the lowest basicity pellet is mainly calcium silicate. As its strength decreases remarkably with an increase in temperature, the degree of swelling increases correspondingly. Consequently, the crushing strength of the pellet decreases as the reduction temperature rises.
On the contrary, the amount of calcium ferrite in the slag phase prevails as the basicity increases.
As the strength of calcium ferrite decreases very gradually with an increase in temperature, the degree of swelling varies slightly with it for the pellets of high basicities.
However, the crushing strength of the pellets is unexpectedly low despite their small degrees of swelling, because the partial disintegration of the iron particles is enhanced even at relatively low temperatures as the basicity increases.
A hypothetical correlation between the crushing strength and the isothermal reduction temperature was presented, with the influences of the degree of maximum swelling, the partial disintegration of the iron particles in the pellet and the sintering of iron particles during later periods of reduction at higher temperatures taken into consideration.
