Rate of molybdenum solution in carbon-saturated liquid iron
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B. GUNDLACH
AND
ROBERT
D. PEHLKE
The rate of solution of molybdenum in molten iron saturated with carbon was studied by r o t a t i n g c y l i n d r i c a l m o l y b d e n u m s p e c i m e n s in a s t a t i o n a r y graphite c r u c i b l e c o n taining the i r o n - b a s e m e l t . Weight changes w e r e u s e d to d e t e r m i n e the solution r a t e in the t e m p e r a t u r e r a n g e 1315 ~ to 1425~ T h e o r e t i c a l and e x p e r i m e n t a l c o r r e l a t i o n s of the solution r a t e coefficient a r e c o m p a r e d . Molybdenum diffusion in the liquid phase is shown to be r a t e l i m i t i n g . T H E m e l t i n g p r a c t i c e s for s t e e l or c a s t i r o n often r e q u i r e that the alloying e l e m e n t s be added to the m e l t in the p o u r i n g spout or in the ladle as the f u r nace is being tapped. In m o s t o p e r a t i o n s the heat is c a s t i m m e d i a t e l y following tapping, and solution of the alloy additions m u s t be c o m p l e t e in a m a t t e r of m i n u t e s . I n c o m p l e t e s o l u t i o n can r e s u l t in u n d e r alloyed s t e e l or i r o n . Molybdenum is an i m p o r t a n t alloying e l e m e n t in many s t e e l s and e a s t i r o n s . In p l a n t p r a c t i c e , additions of m o l y b d e n u m to s t e e l a r e u s u a l l y made in the f o r m of m o l y b d e n u m oxide, w h e r e a s alloying additions to e a s t i r o n s a r e made in the f o r m of f e r r o - m o l y b d e n u m . In view of the high m e l t i n g point of m o l y b d e n u m and the l i m i t e d s o l u b i l i t y in liquid i r o n a l l o y s , addition of m e t a l l i c m o l y b d e n u m ts r a r e l y made in i n d u s t r i a l p r a c t i c e . It is u n d e r s t a n d a b l e that t h e r e is little published i n f o r m a t i o n r e g a r d i n g the k i n e t i c s of s o l u tion of m o l y b d e n u m in m o l t e n i r o n . N e v e r t h e l e s s , t h e r e is s i g n i f i c a n c e f r o m both a s c i e n t i f i c and e n g i n e e r i n g viewpoint in having a b a s i c u n d e r s t a n d i n g of the m e c h a n i s m of solution of m o l y b d e n u m in m o l t e n i r o n . With this o b j e c t i v e , the p r e s e n t study was undertaken. In this i n v e s t i g a t i o n the r a t e of solution of m o l y b d e n u m in m o l t e n i r o n s a t u r a t e d with c a r b o n was studied by r o t a t i n g c y l i n d r i c a l m o l y b d e n u m s p e c i m e n s in a s t a t i o n a r y graphite c r u c i b l e c o n t a i n i n g the m e l t . The s a m e a p p a r a t u s was u s e d to d e t e r m i n e the m o l y b d e n u m s a t u r a t i o n c o n c e n t r a t i o n in c a r b o n - s a t u r a t e d liquid i r o n over the s a m e t e m p e r a t u r e r a n g e . A s e r i e s of e x p e r i m e n t s was conducted in which m o l y b d e n u m rod s p e c i m e n s w e r e r o t a t e d at d i f f e r e n t s p e e d s in an i r o n - c a r b o n bath at t e m p e r a t u r e s of 1315
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