Partition coefficient of molybdenum in the Fe-Mo-Si-O system
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J. M. DAHL,
AND
L. H. VAN
VLACK
An e x p e r i m e n t a l d e t e r m i n a t i o n of the p a r t i t i o n c o e f f i c i e n t of m o l y b d e n u m , defined as the wt pct Mo in the slag d iv id e d by that in the liquid m e t a l phase, in the F e - M o - S i - O s y s t e m is r e p o r t e d . The e x p e r i m e n t s w e r e p e r f o r m e d in the t e m p e r a t u r e r a n g e f r o m 1600 ~ to 1800~ and the s y s t e m was studied at m o l y b d e n u m o r s i l i c a s a t u r a t i o n by e q u i l i b r a t i n g F e - M o - S i - O c h a r g e s in m o l y b d e n u m o r s i l i c a c r u c i b l e s . D a t a a r e p r e s e n t e d f o r the F e - M o b i n a r y liquidus l i n e in the t e m p e r a t u r e r a n g e of this study and on the 1600~ i s o t h e r m a l s e c t i o n in the F e - M o - O s y s t e m , as well as the m o l y b d e n u m p a r t i t i o n c o e f f i c i e n t s . An i d e a l solution m o d e l is p r e s e n t e d that d e s c r i b e s the e q u i l i b r i u m r e l a t i o n s h i p b e t w e e n i r o n and m o l y b d e n u m in the slag and m e t a l p h a s e s in t e r m s of the r e a c t i o n : 2(FeO) + Mo ~ 2 F e + (MOO2) Two g e n e r a l c o n c l u s i o n s can be d r a w n f r o m this i n v e s t i g a t i o n : 1) the p a r t i t i o n c o e f f i c i e n t of m o l y b d e n u m b e t w e e n m o l y b d e n u m - s a t u r a t e d liquid s l a g and liquid m e t a l in the F e - M o - S i - O s y s t e m is highly dependent on the s i l i c a content of the slag p h a s e , r a n g i n g f r o m 0.34 at 0 pct s i l i c a and 1600~ to l e s s than 0.01 at s i l i c a s a t u r a t i o n ; and 2) within the t e m p e r a t u r e r a n g e studied, the m o l y b d e n u m p a r t i t i o n c o e f f i c i e n t i n c r e a s e s with i n c r e a s i n g t e m p e r a t u r e , but the r a t e of i n c r e a s e d e c r e a s e s with i n c r e a s i n g s i l i c a content in the slag. I N this study, s l a g - m e t a l e q u i l i b r i a of the F e - M o - S i - O s y s t e m w e r e e x a m i n e d with the goal of p r o v i d i n g s o m e i n s i g h t into the m e t a l l u r g i c a l p h e n o m e n a e n c o u n t e r e d in the p r o d u c t i o n of f e r r o m o l y b d e n u m by the t h e r m i t e p r o c e s s . An F e - M o alloy containing about 60 wt p ct Mo is p r o d u c e d by r e d u c i n g m o l y b d e n u m t r i o x i d e with s i l i con and a l u m i n u m p o w d e r s in the p r e s e n c e of e x c e s s i ro n . The p r o d u c t i o n of f e r r o m o l y b d e n u m by the m e t a l l o t h e r m i c r e d u c t i o n of m o l y b d i c oxide has been d e s c r i b e d by D u r r e r and V o l k e r t ~ and Elyutin e t a l . z in t h e i r books on f e r r o a l l o y m a n u f a c t u r e . T h e s e a u t h o r s have d e s c r i b e d the p r o c e s s in t e r m s of the r e a c t i o n s l i s t e d in T a b l e I. Elyutin e t a l . have r e p o r t e d , h o w e v e r , that a s m a l l amount o
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