Influence of boron on the decomposition of austenite in low carbon alloyed steels
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Ph. MAITREPIERRE is Research Engineer, Groupe M6tallurgie Physique, Institut de Recherches de la Sid6rurgie Franqaise (IRSID), 78104 Saint Germain en Laye, France. D. THIVELLIER is Research Engineer and R. TRICOT is Director, respectively, Centre de Recherches d'Ugine-Aciers 73400, Ugine, France. Manuscript submitted March 14, 1974 METALLURGICALTRANSACTIONS A
l o c a t i o n of b o r o n in the m i c r o s t r u c t u r e a f t e r v a r i o u s h e a t t r e a t m e n t s , which r e q u i r e d the e x t e n s i v e use of 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 , a l p h a g r a p h y and ion m i c r o s c o p y . I -- MATERIALS -- E X P E R I M E N T A L PROCEDURE 1 -- M a t e r i a l s The study was c a r r i e d out both on l a b o r a t o r y and i n d u s t r i a l h e a t s . The c o m p o s i t i o n of the l a b o r a t o r y h eat s was s e l e c t e d so that the s t e e l s (even without boron) would have f a i r l y l a r g e incubation t i m e s f or the V ~ p r o - e u t e c t o i d f e r r i t e r e a c t i o n . This led to s e l e c t Fe-Ni6-Co.l~ a l l o y s (with o r without 50 ppm B - wt pet). The c h o i c e of n i c k e l was b r o u g h t about by the f a c t that this e l e m e n t is a known V - s t a b i l i z e r with no affinity f o r c a r b o n and full s o l u b i l i t y in Fe. The c a r b o n conc e n t r a t i o n was c h o s e n in the " l o w - c a r b o n " r a n g e s i n c e it is w e l l d o c u m e n t e d that the e f f e c t of b o r o n is p a r t i c u l a r l y i n t e n s e in l o w - c a r b o n s t e e l s . The full c h e m i c a l c o m p o s i t i o n s of t h e s e l a b o r a t o r y h e a t s ( s t e e l s A and B) a r e given in T a b l e I (wt. pct). T h e s e h e a t s w e r e v a c u u m m e l t e d and c a s t into 3 kg ingots which w e r e h o m o g e n i z e d at 1200~ (4 h) and r o l l e d to 17 • 17 m m r o d s (finishing t e m p e r a t u r e 1000~ Two i n d u s t r i a l h e a t s w e r e a l s o s e l e c t e d f o r this study and t h e i r c h e m i c a l c o m p o s i t i o n s a r e given in Tab l e II ( s t e e l s I A and IB). T h e y a r e M n - C r g r a d e s with C ~ 0.18.
Table I. Composition of Laboratory Heats A and B, Wt Pct
Steel A Steel B
Ni
C
B
AI
N
O
Fe
6.30 6.25
0, [ 2 0.12
0.0 0.0050
0.006 0.005
0,003 0.003
0.003 0.002
compl compl
VOLUME 6A, FEBRUARY 1975-287
Table II. Composition of Industrial Heats IA and IB, Wt Pct
Steel IA Steel 1B
C
Si
Mn
Ni
Cr
Mo
0.185 0.174
0.235 0.237
1.24 1.25
0.296 0.294
0.942 0.929
0.027 0.028
AI
B
0.012
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