A new technique for evaluating magnesia-graphite refractories was developed during the course of this study. The exposure technique improves on currently employed simulations because it produces realistic thermal and chemical gradients in the specimens, and because several specimens of varying compositions may be exposed and evaluated simultaneously.
During the exposure, thermal gradients were measured by thermocouples implanted in the specimens at several distances from the exposed or hot face. Thermal gradients were found to be similar to those reported from previous gradient simulations and measurements of service linings. The slope of the gradient appears to operate in two distinct regions. Near the hot face (the first 7-8 cm of the specimen) the gradient is on the order of 100-200°C/cm. More than 8 cm from the hot face, the observed gradient is on the order of 25-35°C/cm.
After exposure the phase assemblages and microstructure of the specimens were investigated with powder x-ray diffraction and various microscopic techniques. The formation of secondary phases is explained by correlating thermal data to chemical and microscopic findings.
Exposed specimens were found to be very similar to those produced by previous gradient exposure methods and post-mortem specimens recovered from service vessels. Magnesia dense zone formation was observed in all exposed specimens, and appears to have formed quickly, as graphite was frequently observed immediately behind the dense zone.
Moore, Robert E., 1930-2003
Ramsay, Christopher W.
Materials Science and Engineering
M.S. in Ceramic Engineering
University of Missouri--Rolla
ix, 84 pages
© 1996 Kenneth Allen Gerber, All rights reserved.
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Gerber, Kenneth Allen, "Simulative exposure of magnesia graphite refractories by the improved gradient technique" (1996). Masters Theses. 1645.
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