Vacuum treatments for hydrogen removal in 140 ton ladle for big ingots casting

Abstract

Hydrogen removal can be accomplished via different steelmaking routes (VOD, ASEA, RH). Focus was given
on the first two technologies. As main differences between the systems based on a (multi)-plug equipped ladle,
in VOD the vacuum chamber is obtained by coupling a roof with a tank, in ASEA plant
–where electromagnetic melt stirring is also exploited - coupling occurs directly with the ladle, leading often
to a non perfect sealing. Moreover, VOD plant is able to perform under vacuum steel degassing treatment
at pressure values lower than usually reached in ASEA plant, and is also equipped with a oxygen lance
allowing to produce stainless steels with very low carbon and nitrogen content. The industrial need
of achieving very low hydrogen contents for big ingots casting with an acceptable costs/benefits ratio called
for a comparison between performances of different vacuum treatments strategies. A CSM numerical
degassing model was applied to 140 ton ladle conditions either after ASEA or VOD treatment.