PROCESS TECHNOLOGY FOR CONTINUOUS CASTING OF ALUMINIUM KILLED STEELS

摘要

Presence of Al_2O_3 in steel as de-oxidation product or its formation by re-oxidation of liquid steel during transfer from ladle to mould leads to clogging of submerged entry nozzles (SEN) during continuous casting process of steel and is a source of surface defects on the steel product. Present work was carried out at one of the integrated steel plant of Steel Authority of India Limited (SAIL) i.e. Durgapur Steel Plant (DSP) keeping in view the prime objective to develop steel refining process technology for production of aluminium killed steel grades through bloom caster without any clogging. Clogging in aluminium killed steel is being experienced by many experienced steelmakers but it was more difficult at DSP due to poor infra-structural facility with the bloom caster in terms of lower SEN diameter (32 mm only), thick viscous ladle top slag, absence of ladle to tundish argon-shrouding and very high casting duration. Designing of suitable flux & de-oxidation practice during tapping in converter and in Ladle Furnace (LF), selection of optimum CaSi injection window for modification of solid alumina inclusion to liquid calcium aluminates and its absorption by ladle top slag and introduction of in-house designed ladle to tundish argon sealing system eliminated incidences of SEN clogging during casting of aluminium killed grades of steel.