"Nozzle clogging during the casting of aluminum-killed steels reduces both the productivity by s lowing the casting process and the quality of the steel when a lumina accretions break away from the clog and become entrapped in the cast strand. The objective of this research was to utilize thermal spray technology to modify casting nozzles and reduce or eliminate nozzle clogging. Experiments were conducted using a casting simulator, with bottom-tapping capability, to closely reproduce industrial methodology.
Experiments were performed to determine the effect of air aspiration, through the refractory, on nozzle clogging during casting. Simulation nozzles were produced from industrial magnesia and alumina-graphite refractory nozzles and from magnesia and alumina-graphite refractory produced at UMR. Simulation nozzles from each material were coated with zirconia by air plasma spray to reduce permeability, which resulted in a group of low permeability nozzles that could be compared to uncoated nozzles with higher permeability. Laboratory produced alumina-graphite nozzles could not be coated by the plasma spray process as the residual stresses in the coating exceed the strength of the refractory and caused the coating to spall. No significant difference in the clogging rate was observed between the high and low permeability nozzle groups. It was concluded that air aspiration does not play a significant role in nozzle clogging at the levels of permeability studied here.
Experiments were performed to determine the effect of a coating of calcium-titanate to the nozzle bore on alumina clogging during continuous casting of aluminum- killed steel. Simulation nozzles were produced in two sections. The nozzle bore was plasma-spray coated with calcium-titanate and the nozzle was assembled into one piece. Analysis of the simulation nozzles revealed that the alumina clog was forming in the uncoated taper section of the nozzle. An additional nozzle was produced that was coated in the taper section as well as the bore. This nozzle did not show signs of alumina clogging and cast 14.66 kg of steel before the nozzle froze closed. It was concluded that a coating of calcium-titanate was sufficient to reduce or eliminate alumina clogging"--Abstract, page iv.
Van Aken, David C.
Smith, Jeffrey D.
Peaslee, Kent D., 1956-2013
Materials Science and Engineering
M.S. in Metallurgical Engineering
University of Missouri--Rolla
xii, 61 pages
© 2004 Otto James Rajtora III, All rights reserved.
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Rajtora, Otto James III, "The use of air plasma spray coatings in the reduction of alumina clogging in the continuous casting of steel" (2004). Masters Theses. 3610.
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