Thermodynamics of iron alumino-chromite spinel inclusions in steel
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I N a p r e v i o u s p a p e r , ~ the m a n g a n e s e / o x y g e n content of m o l t e n i r o n in e q u i l i b r i u m with i r o n - m a n g a n e s e a l u m i n a t e s was d e t e r m i n e d and the c o n d i t i o n s which g o v e r n t h e i r f o r m a t i o n , e s t a b l i s h e d . In this p a p e r the effect of up to 20 pct c h r o m i u m on the r e s i d u a l oxygen c o n c e n t r a t i o n in the s t e e l and on the c o m p o s i t i o n of v a r i o u s s p i n e l deoxidation p r o d u c t s will be d i s c u s s e d . P a r t i c u l a r a t t e n t i o n has b e e n g i v e n to the effect of s m a l l c h r o m i u m c o n c e n t r a t i o n s r a n g i n g up to about 0.5 pct. T h e r e have b e e n a n u m b e r of i n v e s t i g a t i o n s c o n c e r n ing the r e l a t i o n s h i p s b e t w e e n m o l t e n i r o n - c h r o m i u m oxygen alloys and v a r i o u s deoxidation p r o d u c t s conr a i n i n g c h r o m i u m . 2-~4 In m a n y of t h e s e s t u d i e s e q u i l i b r a t i o n e x p e r i m e n t s w e r e conducted using e i t h e r i n e r t c r u c i b l e s o r c r u c i b l e s c o n s i s t i n g of the s a m e m a t e r i a l as the oxide r e a c t i o n p r o d u c t in o r d e r to m i n i m i z e i n t e r f e r e n c e c a u s e d by c r u c i b l e e f f e c t s . R e s u l t s obt a i n e d f r o m e x p e r i m e n t s of this type w e r e p a r t i c u l a r l y i m p o r t a n t with r e s p e c t to d o c u m e n t a t i o n of t h e r m o d y n a m i c data for r e a c t i o n s involving m o l t e n i r o n a l l o y s and r e l a t i v e l y s i m p l e r e a c t i o n p r o d u c t s . D u r i n g a c t u a l s t e e l m a k i n g , s i l i c o n or a l u m i n u m i s g e n e r a l l y used as a deoxidizing e l e m e n t . If a l u m i n u m is used alone, and other alloying e l e m e n t s a r e a b s e n t , the deoxidation r e a c t i o n p r o d u c t s will be h e r c y n i t e and a l u m i n a . In the p r e s e n c e of s m a l l a m o u n t s of c h r o m i u m , c o m p l e x r e a c t i o n p r o d u c t s c o n t a i n i n g both c h r o m i u m and a l u m i n u m will be f o r m e d . The m a j o r objective of the p r e s e n t i n v e s t i g a t i o n was to d e t e r m i n e the c h r o m i u m / oxygen r e l a t i o n s h i p s for m o l t e n i r o n in e q u i l i b r i u m with i r o n a l u m i n o - c h r o m i t e s p i n e l s . F o r this p u r p o s e e x p e r i m e n t s w e r e conducted using a l u m i n a c r u c i b l e s , with and without the addition of h e r c y n i t e , and with i r o n m e l t s of e i t h e r low or high i n i t i a l oxygen c o n t e n t s for t e m p e r a t u r e s of 1550, 1600, and 1650~
C. K. KIM and A. McLEAN are Senior Research Associate and Professor of Metallurgy and Materials Science, respectively, University of Toronto, Toronto, Ontario, Canada MSS 1A4. Manuscript submitted April 30, 1979. METALLURGICALTRANSACTIONSB
EXPERIMENTAL ASPECTS The e x p e r i m e n t
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