Study on the Corrosion Mechanism on Refractories Used in a Zebra Roof of a Basic Open-Hearth Furnace.
Takeo Ao, Takeji Oyama
Two sample bricks, a conventional silica brick and a metal-encased Chrome-magnesia unburned brick, were taken from a zebra roof of a 40-ton basic open-hearth furnace after 402 heat services. Results of study on the process of slagging reaction on the bricks, mutual reaction between two bricks and chemical changes of the steel plate are described in this paper. The microscopical observation and chemical analysis of each coloured zone are carried out and mineralogical constitution are determined by microscopy and heavy-liquid separation method.
The maximum content of iron oxide in the hottest zone of silica brick may be due to formation of magnetite by the decomposition of ferrous silicate in oxidizing atmosphere.
On the hottest area of silica brick adjoined to the chrome-magnesia brick, iron oxide and magnesia are migrated into the matrix of silica brick from the basic one.
On the chrome-magnesia brick adjoined to the silica brick, much silicious liquid was penetrated into the hotter area of chrome-magnesia brick from the silica brick. Results of microscopical observation and chemical analysis of the spinel crystals separated from the silicious glass matrix in such region might suggest that the destruction of spinel crystals in silicious liquid is caused by selected dissolution of the MgO·Al2O3 portion in the spinel crystals into the liquid.