Arashk Memarpour

Studies of effect of glass/silicon powder coatings on clogging behaviour of submerged entry nozzles when using REM alloyed stainless steels

Abstract The internal surfaces of modern submerged entry nozzles (SENs) were coated with a glass/silicon powder layer to prevent SEN graphite oxidation during preheating. The effects of the interaction between the coating layer and the SEN base refractory materials on clogging were studied. The results indicated that penetration of the formed alkaline rich glaze into the alumina/graphite base refractory occurs during preheating. More specifically, the glaze reacts with graphite to form carbon monoxide gas. Thereafter, dissociation of CO at the SEN/molten metal interface takes place. This leads to reoxidation of dissolved rare earth metals, which form ‘in situ’ rare earth metal oxides at the interface between the SEN and the molten steel. In addition, the interaction of the penetrated glaze with alumina in the SEN base refractory materials leads to the formation of a high viscous alumina rich glaze during the SEN preheating process. This, in turn, creates a very uneven surface at the SEN internal surface. The ‘in situ’ formation of the rare earth metal oxides together with the uneven internal surface of the SEN may facilitate the accumulation of the primary inclusions on the refractory walls.

Studies of new coating materials to prevent clogging of submerged entry nozzle (SEN) during continuous casting of Al killed low carbon steels

The possibility to reduce clogging in the submerged entry nozzle when casting Al killed low carbon steel has been evaluated. The coating materials have been tested in laboratory trials and pilot plant trials. Totally, two mixes of the coating material have been tested, containing 4.8 and 9.1% CaTiO3 mixed with yttria stabilised zirconia powder. The chemical composition was analysed using a field emission gun–scanning electron microscopy equipped with energy dispersive X-ray spectrometry. The major result showed that alumina reacted with CaTiO3 in the temperature interval from 1550 to 1600°C. In addition, the clogging ratio showed a decreased clogging tendency for coated nozzles compared to standard nozzles. In addition, the results showed that an approximately three times higher steel mass could be teemed through the coated nozzles before clogging occurred compared to trials with uncoated standard nozzles. Overall, it is concluded that plasma sprayed CaTiO3 coatings can reduce the clogging tendency during the continuous casting process.

Studies on the decarburization of the commercial Submerged Entry Nozzles

Decarburization behaviours of Al2O3-C, ZrO2-C and MgO-C refractory materials constituting a commercial Submerged Entry Nozzle (SEN), have been investigated in different gas atmospheres consisting o ...