Summary
During service in the casting of killed steel, zirconium containing nozzles took on a zonal structure. The least changed zone of the nozzles is scarcely distinguishable from the refractories before service. The working zones during service are saturated with oxides of iron, manganese, aluminum, silicon and titanium, and their amount is strictly related to the compositon and quantity of deoxidant.
Highly refractory nozzles of ZrO2 and made of a mixture of ZrO2 and zircon, possessing a higher apparent porosity, acquire a larger working zone than nozzles made of zircon with clay additions.
The dense working zone is more rapidly formed in nozzles made of zircon and clay. The oxides adsorbed in the pores of the refractory contribute to the tightening up of the aperture of the nozzles.
Zircon nozzles with clay additions used at the Donets Steel Mill proved to have excellent wear resistance and the lowest tendency to closing up when casting low-carbon killed steels and can be recommended for permanent use in continuous steel casting plants.
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Literature cited
V. M. Strelets and N. V. Pitak, Trans. All-Union Conference of Refractory Producers, Metallurgizdat, Moscow (1961).
N. V. Pitak and V. M. Strelets, Ogneupory, No. 1 (1962).
N. V. Pitak and V. M. Strelets, TsIIN, ChM., series 8, Information 2 (1962).
V. M. Strelets and N. V. Pitak, Ogneupory, No. 2 (1960).