Identification of Fe 9 S 8 inclusions in a hot rolled Fe-0.07 Pct C alloy
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Identification of FegS8 Inclusions in a Hot Rolled Fe-O.07 Pct C Alloy IAN F. HUGHES AND E L L I O T W. PAGE
AN
e l e c t r o l y t i c i r o n of the usual p u r i t y was c h o s e n as the b a s e m a t e r i a l in a r e c e n t i n v e s t i g a t i o n I on the e f f e c t of c e m e n t i t e on the r e c r y s t a l l i z a t i o n c h a r a c t e r i s t i c s of F e - C a l l o y s . T h i s p a p e r d e s c r i b e d the u n e x p e c t e d a p p e a r a n c e of l a r g e i n c l u s i o n s of FegS8 in an alloy prepared from electrolytic iron containing a total s u l f u r l e v e l of only 0.0035 wt pct. It will be shown that t h e s e i n c l u s i o n s a r e s t a b l e a f t e r a t w o - s t a g e hot r o l l i n g t r e a t m e n t and r e q u i r e a n o r m a l i z i n g p r o c e s s for h o m o g e n e o u s sulfur d i s t r i b u t i o n . A m e c h a n i s m for the f o r m a t i o n of the FegS8 i n c l u s i o n s is p r o p o s e d . An F e 0.07 wt pct C a l l o y , p r e p a r e d f r o m e l e c t r o l y t i c i r o n , was induction m e l t e d under a r g o n and c a s t into a r e c t a n g u l a r s t e e l m o ld . The a s - c a s t ingot was s o a k e d f o r 2 hr at 2150~ in an A r - 3 pct H a t m o s p h e r e and then hot r o l l e d to J in., f i n i s h i n g at 1785~ The ~ in. plate was r e l e a t e d for 30 min at 2150~ and then hot r o l l e d to -~ in., f i n i s h i n g at 1695~ A f t e r both s t a g e s of hot r o l l i n g , the p l a t e s w e r e a l l o w e d to a i r 1 c oo l . S a m p l e s of the z in. p l a t e , which w e r e g i v en a f u r t h e r solution t r e a t m e n t at 2150~ w e r e a i r c o o l e d to l l 0 0 ~ b e f o r e w a t e r q u e n c h in g to r o o m t e m p e r a t u r e . Optical m e t a l l o g r a p h y was p e r f o r m e d on longitudinal s a m p l e s cut f r o m the c e n t e r of the hot r o l l e d plate. S a m p l e s for t r a n s m i s s i o n e l e c t r o n m i c r o s c o p y , which w e r e taken as c l o s e a s p o s s i b l e to t h o s e f o r o p t i c a l m i c r o s c o p y , were p r e p a r e d by e l e c t r o p o l i s h i n g in a s o d i u m c h r o m a t e - a c e t i c a c i d e l e c t r o l y t e using the B o l l m a n technique 2 and then e x a m i n e d in a H i t a c h i H U - 11 e l e c t r o n m i c r o s c o p e . C h e m i c a l a n a l y s i s of d r i l l i n g s taken f r o m the ~ in. IAN F. HUGHES and ELLIOT W. PAGE are Senior Research Engineer and Research Engineer, respectively, Inland Steel Research Laboratories, East Chicago, Ind. Manuscript submitted September 19, 1969. METALLURGICALTRANSACTIONS
Table I. Chemical Analysis in wt pct of the 1/2 in. Hot-Rolled Plate C
N
O
S
Mn
P
Si
Cu
Ni
As
A1
0.067 0.002 0.006 0.0035 0.002 0.005
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