Sulfidation of binary iron alloys containing cerium or lanthanum

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Table I. Ce, La, and 0 Contents of the Iron Alloys Used for the Sulfidation Experiments

Total Wt Pct R (2 Analyses)

Alloy No.

Effective Wt Pet R Based On

Average Total Wt Pet R

Wt Pct O

RO2*

R203t

0.0200 0.0260 0.0060 0.0045 0.0078 0.0101 0.0095

0.075 0,151 0.216 0.300

0.069 0.140 0.201 0.286

0 0120 0.0050 0.0073 0.0135 0.0111 0.0210 0.1360

G. J . W. KOR A D D I T I O N S of e l e m e n t s of the r a r e - e a r t h group to s t e e l , m o s t l y in the f o r m of " m i s c h m e t a l " , a r e g e n e r a l l y made to i m p r o v e on the deoxidation and d e s u l f u r i z a t i o n . Spring 1 was the f i r s t to c a r r y out e x p e r i m e n t s with the addition of m i s c h m e t a l to c e r t a i n types of s t e e l as far back as 1918. A c o m p r e h e n s i v e r e v i e w of the effects of l a n t h a n u m and c e r i u m additions to s t e e l was given by R i c h e r d . 2 L a n g e n b e r g and C h i p m a n 3 i n v e s t i g a t e d the c e r i u m s u l f u r r e a c t i o n in liquid i r o n contained in CeS c r u c i b l e s or oxide c r u c i b l e s . F o r the e q u i l i b r i u m CeS (solid) = C__ee(in Fe) + S (in Fe) they obtained the s o l u b i l i t y p r o d u c t [pet Ce] [pet S] = (1.5 + 0.5) x 10 -3 at 1600~ In only one e x p e r i m e n t , c a r r i e d out in an oxide c r u c i b l e , a s u f f i c i e n t a m o u n t of [slag] was f o r m e d to o b s e r v e the b r a s s - c o l o r e d slag t y p i c a l of CeS. No f u r t h e r p o s i t i v e i d e n t i f i c a t i o n of the n a t u r e of the sulfide phase was r e p o r t e d . R i c h e r d 2 added about 0.5 wt pct Ce or La to liquid i r o n c o n t a i n i n g 0.1 wt pct s u l f u r . After the r a r e - e a r t h addition the m e l t was kept liquid for about 10 rain and then allowed to cool. The s o l i d i fied slag p a r t i c l e s had a b r i g h t yellow color and s u b s e q u e n t X - r a y a n a l y s i s showed that they c o n s i s t e d of the m o n o s u l f i d e s of c e r i u m and l a n t h a n u m . Singleton4 added c e r i u m to v a c u u m - r e f i n e d s t e e l c o n t a i n i n g sulfur and found that the e l e c t r o l y t i c a l l y e x t r a c t e d i n c l u s i o n s w e r e o r a n g e - and p i n k - c o l o r e d , i n d i c a t i n g the p r e s e n c e of Ce2S~. C e r i u m and l a n t h a n u m f o r m four types of s u l fides: 5 RS, R3S4, R2S3, and RS2 having m e l t i n g points 5 of about 2500 ~ 2100 ~ 2050 ~ and 1650~ respectively. The p r e s e n t work was u n d e r t a k e n to d e t e r m i n e the s t o i c h i o m e t r y of the r a r e - e a r t h sulfide f o r m e d upon sulfidation of solid i r o n c o n t a i n i n g c e r i u m or lanthanum. E x p e r i m e n t a l . The a l l o y s used in this work w e r e p r e p a r e d in a s m a l l v a c u u m - m e l t i n g f u r n a c e using v a c uum m a t e r i a l . C e r i u m and l a n t h a n u m w e r e taken f r o m h i g h - p u r i t y stock and added to the m e l t s in the f o r m of l