Magnesia-chrome Refractories Research Articles

SEM and electron microprobe observations of some phenomena occurring in magnesia-chrome refractories

Abstract Scanning electron microscopy (SEM) and electric microproble (EMP) were used to study some phenomena occurring in the production of magnesia and magnesia-chrome clinkers, with special reference to the sintering process and to the formation of secondary spinel phases. Transformations occurring during firing of chrome-magnesite bricks, especially the development of the so-called ⪡ direct bonds ⪢ have also been reported.

Compatibility of refractories with simulated MHD environment consisting of a molten-coal-slag/alkali-seed mixture

In an investigation of the possible use of a refractory material on the water walls of a radiant boiler in a simulated coalfired opencycle MHD plant, the corrosion of a wide variety of commercial refractories was studied under reducing conditions at ∼1500 °C in a coalslag/potassiumseed mixture. Several refractories gave promising results. A comparison with earlier results obtained at ∼1500 °C with slag only showed that the presence of ∼10 wt pet K2O seed in the Montana Rosebud slag did not result in increased corrosion, and may actually have improved the corrosion resistance of many of the refractories that were tested. Of the fusedcast materials, the chromespinel refractory exhibited superior corrosion resistance. The magnesiachrome refractories showed more resistance to corrosion than the other sintered materials that were tested. A phosphatebonded chromeore ramming mix performed better than the other ramming mixes, but not as well as any of the sintered or fusedcast bricks.

SEM and electron microprobe observations of some phenomena occurring in magnesia-chrome refractories

Scanning electron microscopy (SEM) and electric microproble (EMP) were used to study some phenomena occurring in the production of magnesia and magnesia-chrome clinkers, with special reference to the sintering process and to the formation of secondary spinel phases. Transformations occurring during firing of chrome-magnesite bricks, especially the development of the so-called ⪡ direct bonds ⪢ have also been reported.

Phase changes in zirconia refractories used in carbon black manufacturing

The serviceability of zirconia blocks in carbon-black production chamber linings working with gaseous fuels is some 2 1/2–3 times better than that of magnesia-chrome refractories.

Electrical Resistivity of Refractories

Electrical resistivity was measured on commercially available materials, including high‐alumina, magnesia, magnesia‐chrome, zircon, and stabilized‐zirconia refractories, at temperatures to 2650°F. The tests were made using two‐, three‐, and four‐terminal measurements and the results are discussed. The four‐terminal measurements were made by a new method.

Grain-Boundary Reactions in Magnesia-Chrome Refractories: Application of the Electron Probe, I

The technique for the preparation of polyphase refractories for electron probe investigations is described. Chemical changes occurring during heating of an unused chemically bonded magnesia-chrome refractory were studied and the spatial distribution of Fe, Cr, Al, Mg, Ca, and Si at different temperatures was determined. The development of the reaction layer around the chromite grains, the migration of ions into the periclase grains, and the distribution of ions in silicates were followed qualitatively using Kα X-ray and electron back-scattering displays.

Studies on Wettability of Refractories by Molten Steels

Wettabilities of various refractories by two kinds of carbon steel were determined at 1550°C in N2 atmosphere by sessile drop method using a heating microscope. Samples from stabilized zirconia, zircon, magnesia, alumina, high-alumina, fireclay, silica and magnesiachrome refractories were served to the test. Stabilized zirconia was found the least wettable and aluminous refractories the most.Discussions on the correlation between wettability and chemical composition of refractories were given. The effects of surface conditions and reactions between steel and refractory on the wettability was also discussed. Several cases which are actually observed in steel plant refractories and with which the wetting properties have close relation were explained.These wetting tests may also be applied to evaluate the corrosion resistance of refractories against molten steel.