Modelling of coagulation

processes and removal

of non-metallic inclusions

at melt's inert gas

flushing inside a ladle

The present work is devoted to optimization based upon physical and

mathematical modelling of calcium treatment processes for low-alloy steel

grades in Ladle, using Steel Refining Unit (SRU).

The widely applicable method of calcium injection into ladle on Steel

Refining Unit by means of Flux-Cored Wire (FCW) or the method of

silicocalcium blowing-in often requires significant flow rate of calcium

containing alloys to ensure the necessary concentration of calcium and

sulfur in the finished steel.

Methods of mathematical modelling are widely applied for the purpose

of improvement of calcium alloys injection modes into ladle. However,

mainly heating processes in the ladle are taken into consideration in

this connection ; meanwhile hydrodynamic processes are accounted

only partially. At the same time, interfacial reactions of the metal with

steam bubbles play a significant role in the processes of interaction

between calcium and supernatant liquid, whereby sulfur and oxygen

that are dissolved in steel take part in the reactions described above.

Nevertheless, only single quantitative estimates are known for kinetics of

mass exchanging processes in the ladle.

Finally, efficiency of calcium treatment depends on chemical composition

of steel. Probability of low-melting calcium aluminates formation,

which ensure improvement of pouring capacity, depends not only on the

frequently used proportion of [Ca] to [Al], but also on conditions of steel

oxidation and sulfur content in the steel.

Therefore, optimization of injection modes for calcium containing alloys

based on the thermodynamic and kinetic analysis of steel deoxidation

and modification conditions, as well as on the mathematical modelling of

mass exchanging processes, represents a crucial scientific and technical

challenge of nowadays.