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

Abstract

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.

Keywords:

• Clogging
• Submerged entry nozzle
• Pilot plant trials
• Al killed steel
• Calcium titanate
• Coating
• Plasma spraying

Acknowledgements

The committees TO23 and TO24 at Jernkontoret as well as VINNOVA are acknowledge for their financial support to this study. The University West in Trollhättan, Sweden, is acknowledged for their technical support to coat the nozzles. SSAB Special Steels AB in Oxelösund, Sweden, is acknowledged for their technical support and for their assistance in determining the chemical composition of the dual thickness steel samples. Finally, Erik Roos at SSAB Special Steels AB is acknowledged for his guidance regarding the analysis of the clogging data.