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RELATIONSHIP BETWEEN INTERNAL FRICTION
AND TEMPER BRITTLENESS OF ALLOY STEELS
Chih-Hsiou Tang, Mei Su, Ting-Chuan Lei
To cite this version:
RELATIONSHIP BETWEEN INTERNAL F R I C T I O N AND TEMPER BRITTLENESS OF ALLOY STEELS
Chih-Hsiou T a n g , Mei Su and Ting-Chuan Lei
Department o f Metals and Technology, Harbin I n s t i t u t e o f TeehnoZogy, Raybin, Republic o f China ABSTRACT I m p a c t t e s t s a n d i n t e r n a l f r i c t i o n m e a s u r e m e n t s w e r e c a r r i e d o u t f o r s t e e l s 4 0 Y n 2 , 40Mn2Mo a n d 3 O C r M n S i N i Z . E x p e r i m e n t a l r e s u l t s s h o w e d t h a t t h e p h e n o m e n o n o f t e m p e r b r i t t l e n e s s i s r e l a t e d t o t h e a g i n g e f f e c t o f d - s o l i d s o l u t i o n i n s t e e l s w i t h p r e c i p i t a t i o n o f F e 3 ( C , N ) p a r t i c l e s c a u s i n g d e a d - p i n n i n g o f d i s l o c a t i o n s . INTRODUCTION T e m p e r b r i t t l e n e s s w a s f i r s t l y r e p o r t e d i n 1 9 1 7 ' 1 1 . h a s b e e n e x - t e n s i v e l y s t u d i e d u n t i l now a n d m a n y t i m e s r e v i e ~ e d ' ~ ' ~ ' ~ ' . T h e r e c e n t l y r e c e p t e d m e c h a n i s m o f t h i s p h e n o m e n o n i s t h a t s u g g e s t e d b y McMahon e t a ~ ( ~ ' ~ ' o f s e g r e g a t i o n a t a u s t e n i t e g r a i n - b o u n d a r i e s o f i m p u r i t i e s ( s u c h a s P , A s , S n , S b e t c ) a n d a l l o y i n g e l e m e n t s ( M i , C r . M n , S i ) . H o w e v e r , t h i s m e c h a n i s m c a n n o t b e u s e d t o e x p l a i n m a n y s p e c i f i c f e a t u r e s o f t h e p h e n o m e n o n s u c h a s e m b r i t t l e m e n t a f t e r s l o w c o o l i n g f r o m t e m p e r i n g t e m p e r a t u r e s , t h e r e v e r s i b i l i t y o f t o u g h n e s s b y r e d u c t i l i z i n g t r e a t m e n t , e t c . T e m p e r b r i t t l e n e s s w a s e x a m i n e d w i t h i n t e r n a l f r i c t i o n r n o t h ~ d s b y s e v e r a l a u t h o r s f 7 , 8 J , b u t n o d e f i n i t e m e c h a n i s m o t h e r t h a n M c M a h o n f s h a s b e e n i n t r o d u c e d . T h e a i m o f t h i s p a p e r i s t o s t u d y m o r e s y s t e - m a t i c a l l y t h e r e l a t i o n s h i p o f i n t e r n a l f r i c t i o n w i t h t e m p e r b r i t t l e n e - s s o f s e v e r a l a l l o y s t e e l s i n o r d e r t o o b t a i n s o m e n e w c o n c e p t s i n t h e m e c h a n i s m o f t h i s p h e n o m e n o m . EXPERIEIENTAL T h e c h e m i c a l c o m p o s i t i o n o f s t e e l s s t u d i e d a r e g i v e n i n T a b l e 1. T a b l e 1. C h e m i c a l c o m p o s i t i o n o f s t e e l s
(X)
-
S t e e l 40?4n2 40Mn2Mo 3 O C r M n S i N i 2 C 0 . 4 2 0 . 4 0 0 . 3 0 Mn 1 . 8 0 1 . 8 9 1 . 1 5P
0 . 0 1 3 0 . 0 1 5 0 . 0 1 5 Mo-
0 . 5 4 - S i 0 . 2 1 0 . 1 4 1 . 0 3 C r - - ' 1 . 0 2N
O . U l 6 0 . 0 1 9-
S 0 . 0 2 0 0 . 0 3 2 0 . 0 0 8 N i-
-
1 . 6 82
-
f u r n a c e c o o l i n g ( b r i t t l e s t a t e )C5-920 JOURNAL DE PHYSIQUE
Fig.4 Impact t o u g h n e s s ( a k ) : Fig.5 Internal friction
(Q-')
1 - 6 5 0 k Zh WC (ductile) curves: 1 , 2 same a s Fig.4
2 - a s 1 + 5 0 0 t 1 2 h (embrittled)
Fig. 6 Internal friction (Q-l) c u r v e s for quenched
30CrMnSiNi2 with various initial microstructures:
1 - 6 5 0 1 ~ 2hr water cooling (ductile)
2
-
65@C 2hr furnace cooling (brittle)3
-
a s 1 +50OUC 50hr embrittled4 - a s 1 +500?2 lOOhr embrittled
Fig. 7 Internal friction (0-l) c u r v e s
for quenched 3OCrMnSiNiZ:
JOURNAL DE PHYSIQUE
Table 3. Effect of embrittling and reductilizing t r e a t m e n t s on impact t o u g h n e s s (ak) of s t e e l 3 O C r M n S i N i 2 with different initial microstructures in embrittled and redoctilized
2 s t a t e s (Ka m/cm ) I n i t i a l microstructure 8 8 0 ~ ~ oil quench 880% heat+300? 2h austemper 8 8 0 P C n o r m a l i z e C O N C L U S I O N S 8 8 0 3 C a n n e a l
1. Temper brittleness of s t e e l 4 0 M n 2 w a s caused by a precipita-
tion process of - p h a s e of the steel. The addition of+0.5%Mo t o the
Embrittled
5.9
s t e e l (for t h e c a s e of 40Mn-2Mo) prevents t h i s precipitation process Reductilized -. - . -- . - -- 650'~ 2h VJC +506'~ 50h 5.8 7.0 5.6
and t h u s e l i m i n a t e s i t s susceptibility to temper brittleness.
65& 2h WC +500% 50h +650? 2h
WC
17.2 20.0 20.3 -- -- 6 5 d ' ~ 2h VJC + 5 0 0 " ~ lOOh 10.0 10.2 8.2 6.01
6.52. All initial microstructures with d -phase (quenched, a u s t e -
mpered, normalized and annealed) of s t e e l 3 O C r M n S i N i 2 are susceptible 65& 2h INC + 5 0 0 * ~ lOOh + 6 5 0 " ~ 2h WC 24.5 20.5 24.3 8.4
t o temper brittleness, though t h e susceptibility i s n o t the s a m e f o r e a c h case.
3. The mechanism of temper brittleness of alloy s t e e l s w a s proved
a s an aging process of -solid solution causing dead-pinning of dislo
c a t i o n s b y precipited Fe3C(N) particles. The reversibility of the
phenomenon may be considered a s a r e s u l t of re-solutioning of the aged
R E F E R E N C E S
1. Brearly H . Proc. Inst. Automobile Eng.
,
N o ll(1916-1917),3u72. Low 3.R. Fracture of Engineering Materials
,
ASN, 1 9 6 4 , p.1273. McMahon C.3. Temper Embrittlement in s t e e l , ASTM S T P 4 U 7 , 1 9 6 8 ,
p. 1 2 7
4. Olefjord I. International Metals R e v i e w s , 4(1977), 1 4 9
5. McMahon C.3., Briant C.L., Banerji K. F r a c t u r e , 1(1977), 3 6 3
6. Ucisik A.3., McMahon C.3., Feng C.3. Met. Trans. 9A(1978), 321
7. Wert 3.3., Rosenthal P.C., Trans. A S M , 55(1962), 4 3 9
