Contacting problems associated with aluminum and ferro-alloy additions in steelmaking-hydrodynamic aspects
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addition of solids to liquid s t e e l baths for a d j u s t i n g s t e e l c h e m i s t r y to r e q u i r e d s p e c i f i c a t i o n s or for cooling p u r p o s e s is c o m m o n s t e e l m a k i n g p r a c t i c e . Specific e x a m p l e s of solid additions to molten s t e e l i n c l u d e the o c c a s i o n a l u s e of s c r a p m e t a l in B . O . F . f u r n a c e s for cooling 'hot' heats, as well as the r e g u l a r u s e of ladle additions of f e r r o - a l l o y s , c a r b o n and a l u m i n u m for alloying a n d / o r deoxidation p u r p o s e s . In g e n e r a l , these alloying additions a r e made to the ladle e i t h e r before or d u r i n g f u r n a c e tapping o p e r a t i o n s . Although much i n f o r m a t i o n has b e e n gathered in the p a s t on the way in which specific d i s s o l v e d a l l o y ing e l e m e n t s i n t e r a c t with oxygen and sulfur in the s t e e l to f o r m o x i d e / s u l f i d e type i n c l u s i o n s (e.g., Ref. 1), the i n i t i a l d i s s o l u t i o n p r o c e s s e s t h e m s e l v e s have b e e n l a r g e l y n e g l e c t e d . However, in o r d e r that o p t i m u m injection methods be identified and some of the p r e s e n t e m p i r i c i s m in plant p r o c e d u r e s be r a t i o n a l i zed, it is n e c e s s a r y to u n d e r s t a n d the b a s i c p h e n o m e n a involved in these f i r s t s t e p s . So far, it has b e e n d e m o n s t r a t e d 2,s that a solid s t e e l s h e l l will i n i t i a l l y f o r m around any object that is i m m e r s e d in a bath of molten s t e e l . Also, provided the m e l t i n g ' p o i n t ' of the addition is lower than the f r e e z i n g ' p o i n t ' of the steel, the object will n o r m a l l y p r o c e e d to melt i n s i d e this shell. 4 Thus, one c o m m o n l y ends up with the s i t u a t i o n of a m o l t e n core of f e r r o a l l o y or a l u m i n u m s u r r o u n d e d by a solid j a c k e t . The j a c k e t then takes an a p p r e c i a b l e t i m e to melt back and r e l e a s e its c o n t e n t s to the bath. Much of this l a t t e r work has c o n c e n t r a t e d on t h e r m a l a s p e c t s , and has supposed that the additions r e m a i n i m m e r s e d during the c o u r s e of t h e i r m e l t i n g h i s t o r y . T h i s will not n e c e s s a r i l y be the c a s e in actual p l a n t p r a c t i c e s , s i n c e many of the additions c o m m o n l y made to t e e m i n g l a d l e s , e t c . a r e l e s s d e n s e than m o l t e n s t e e l and e x p e r i e n c e buoyancy f o r c e s . This is p a r t i c R. I. L. GUTHRIEis Associate Professor, Department of Miningand Metallurgical Engineering,McGiIlUniversity, R. CLIFT is Associate Professor, Department of Chemical Engineering,McGiflUniversity, and H. HENEIN is Research Metallurgist,Sidbec-Dosco, Contrecoeur, Quebec, and was formerly Graduate Student, Department of Mining and MetallurgicalEngineering,McGillUniversity. Manuscript submitted May 16, 1974. METALLURG
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