Conclusions
Chromite, added in amounts of 10% to dolomitic magnesite containing 8.35% CaO by bonding with it completely during firing, is an effective stabilizer.
An increase in the chromite content of the batch of more than 10% lowers the quality of the refractory.
The hydrothermal treatment of the calcined dolomitic magnesite with 10% chromite accelerates the process of hydrating the free CaO and disperses the material, which helps the refractory to sinter during firing.
The proposed technique provides for combined grinding and firing of a mixture of dolomitic magnesite with chromite, excludes aging of the body, reduces the firing temperature of the body and increases the quality of the refractory compared with the periclase-spinel technique.
The calcium oxide in dolomitic magnesite with the addition of 10% chromite is bonded mainly with theCr2O3 into calcium oxychromite 9CaO · 4CrO3 · Cr2O3 and the ferric oxide is introduced into the lattice of the periclase with the formation of a solid solution. With 30% chromite in the batch 3CaO · 2CrO3 · 2Cr2O3 is formed, and the ferric oxide enters the magnesio-ferrite.
Calcium oxychromite, existing in the refractory with 10% chromite and being a secondary phase, at its fusing temperature (>1250–1290°C) reversibly converts to calcium monochromite with a fusing temperature of 2170°C, which explains the increase in the refractoriness under load.
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Budnikov, P.P., El'-Rafii, É.A. Magnesite refractory with a high CaO content. Refractories 4, 401–409 (1963). https://doi.org/10.1007/BF01285136
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DOI: https://doi.org/10.1007/BF01285136