1957 Volume 43 Issue 6 Pages 619-623
In the previous paper, (Tetsn-to-Hagané vol, 39 (1953) p 297; Nippon Kinzoku Gakkaisi, 17 (1953) 122; 126 the authors described on the agglomerating mechanism of green pellets. This report deals with the sintering mechanism of pellets at elevated temperatures. At first, the authors observed a great difference in the microstructure of a sintered pellets which had contained a little carbon powder before it was roasted in comparison with pellets from the combustion-chamber-type pelletizing furnace. In the former one, there were angular hematite crystals caused by grain growth of magnetite in earlier time of roasting, but the latter was usually constructed with hematite crystals network.
According to this fact, the relation between grain growth of iron oxide crystal and the atmospher of roasting was very important. And then the authors investigated the phenomena of colour changes of roasted pellets by electron-diffraction, and decided that the colour (dark blue) was only caused by the dissociation of ferric oxide film, and it suggested that the dissociation should have promoted the bonding of each particle.
On the other hand, the separation of water and some amount of basic gangue increased the bonding in the form of a solid reaction.