According to the results obtained in the characterization on Stopper rod and SEN, type A and B, heated at 1200°C during 4 hours in O_2 and N_2 atmosphere is possible to infer that: 1,-The behavior of the glaze during heating is a key factor on refractory life. For refractory A, as the glaze became vitreous and did not form pores, the protection was more effective. In samples type B the glaze developed porosity during heating. This porosity allows oxygen penetration and brings about carbon oxidation in both SENs and stopper rods. 2.- The chemistry of the glaze is important regarding the erosion behavior of SENs and stopper rods. Refractories Type A contain certain basic elements and Cr. The surface characteristic acquired by heat treatment at 1200°C in both atmospheres, according to Ellingham diagram, means a better protection than the glaze corresponding to refractory type B. This glaze does not contain Cr, and it develops pores during heating. Nevertheless, Cr protection gets lost at temperatures higher than 1200°C. 3.- The thermal shock resistance of refractory B is smaller than for refractory A, as cracks were detected in the interior and in the interface between refractory and glaze, after the thermal treatment in both atmospheres. 4.- According to the Ellingham diagram, Al_2O_3, MgO and SiO_2 are more stable than carbon at 1200°C. Therefore the oxidation of the graphite will be favored under preheating conditions when the atmosphere contains oxygen. 5. - High decarburization and an increase in porosity were observed in the refractory material type B after heating at 1200°C compared with type A. SENs and stopper rods type B are more susceptible to the attack by slag and metal penetration. The corrosion could affect the matrix of the black refractory. 6. - In SENs, decarburization of the ZrO_2 insert took place where the glaze was taken off. Reactions with Fe, Al, Si and Ca by contact with the steel and the molten slag could take place.
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