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Advanced Course in Heat and Mass Transfer in Metallurgical Systems
September, 1979 , Dubrovnik, Yugoslavia

The Influence of High Exothermic Heats of Dissolution on the Solution of Solid Alloy Additions into Molten Baths of Steel

pages 159-174
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ABSTRAKT

An essential feature of conditioning steel following its primary refining in B.O.F. steelmaking vessels and the like is to subsequently add solid alloy additions to the 'raw' steel for adjusting the melt's chemistry to a set of close metallurgical specifications.
In the present work, the mechanisms whereby solid additions having high heats of dissolution dissolve in liquid steel baths are considered, since kinetic phenomena play an important role in the efficiency and alloy recovery figures obtained by steelmakers.
Particular attention is given to ferro-silicon alloy additions for which tonnage quantities are commonly used. It is shown that the customary frozen shell of steel encases the ferro-alloy cylinder following its initial immersion. Premature internal melting of the cylinder then begins as a result of liquid eutectic of Fe2Si composition forming at the inner steel shell boundary. This phenomenon triggers an exothermic dissolution and erosion of the inner steel shell. The outer boundary of the steel shell concurrently melts back as a result of convective heat transfer from the steel bath. The net result is considerably shortened shell dissolution times in comparison with more conven¬tional ferro-alloy/steel systems.
A mathematical model of the process has been developed to describe the coupled heat and mass transfer phenomena involved, and this is shown to provide a good quantitative representation of the processes studied.

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