Eroded refractory samples removed from the lining of a blast furnace were examined petrographically by means of chemical analysis, microscopic observation, and X-ray powder photography. From the results obtained, it is concluded that the erosive actions on the refractories were to be classified as follows;
(a) Erosive action by alkali (especially by potash)
Alkali salts, sublimated from ores and fuels, reacted with the refractories used in the stack and the tuyeres level wall, resulting in the formation of alkaline minerals such as kaliophilite, leucite, (K, Na)2CO3, etc. Incongruent melting of mullite also occurred accompanied with this reaction, resulting in the formation of corundum crystals.
(b) Erosive action by slag
It is marked that the slag attack against the refractories used in the tuyeres level wall was very severe. Here, calcareous minerals such as melilite, olivine, pyroxene, plagioclase, etc, were produced. Their mineral association seems to have some regularities.
(C) Re-crystallization at high temperature
The refractories used in the hearth were completely re-crystallized, though there was no addition of foreign materials. Corundum crystals, almost absent in the original fire-clay brick, were created and developed through incongruent melting of mullite.
(D) Erosive actions by other factors
Disintegration by co is suggested by the presence of carbon in many samples. The formation of Zn compounds, metals, Spinel group minerals, etc, are also noteworthy.