Effects of some carbide stabilizing elements on creep-rupture strength and microstructural changes of 18-10 austenitic s
- PDF / 3,550,540 Bytes
- 10 Pages / 612 x 792 pts (letter) Page_size
- 44 Downloads / 170 Views
a u t h o r s have c l a r i f i e d that f i n e l y and u n i f o r m l y d i s p e r s e d M23C6 is v e r y e f f e c t i v e to i n c r e a s e long t e r m c r e e p r u p t u r e s t r e n g t h of this type of s t e e l . R. N a k a gawa et al. 9 p r e v i o u s l y r e p o r t e d the e f f e c t s of t i t a n i u m and n i o b i u m on the high t e m p e r a t u r e p r o p e r t i e s of 1 8 C r - 1 2 N i s t e e l , but the d u r a t i o n of c r e e p r u p t u r e t e s t i n g in t h e i r w o r k s e e m s not long enough to e x a m ine the influence of the e l e m e n t s . Though v a n a d i u m is a l s o a c a r b i d e s t a b i l i z i n g e l e ment, t h e r e is l i t t l e w o r k r e p o r t e d l~ on the e f f e c t s of t h i s e l e m e n t on the high t e m p e r a t u r e s t r e n g t h and the m i c r o s t r u c t u r e s , p r e s u m a b l y b e c a u s e of its a d v e r s e effect on the o x i d a t i o n r e s i s t a n c e at e l e v a t e d t e m p e r a t u r e s . R e c e n t d e v e l o p m e n t of technique 13 to p r o t e c t s t e e l f r o m high t e m p e r a t u r e o x i d a t i o n s e e m s f a v o r a b l e f o r the the u t i l i z a t i o n of v a n a d i u m for heat r e s i s t i n g a u s t e n i t i c s t e e l s . Thus, v a n a d i u m has a l s o b e e n t a k e n a s an a l l o y i n g e l e m e n t in the p r e s e n t work. I) M A T E R I A L S AND E X P E R I M E N T A L PROCEDURES The c o m p o s i t i o n of 18 p c t C r - 1 0 p c t Ni, s i m i l a r to 321 and 347 s t e e l s , with c a r b o n content of about 0.1 pct, which is a l i t t l e h i g h e r than that f o r c o m m e r c i a l s t e e l s , has been chosen as a base alloy composition. Chemical c o m p o s i t i o n of the s t e e l s u s e d a r e l i s t e d in Table I. S t e e l s S1 and V0 having a b a s e c o m p o s i t i o n w e r e i n t e n d e d for c o m p a r i s o n s . The t i t a n i u m contents of the s t e e l s T i l to TiT, r a n g e d f r o m 0.04 p c t to 1.13 pct. The niobium and v a n a d i u m contents of the s t e e l s N b l to Nb8 and V1 to V4 r a n g e d f r o m 0.07 to 1.20 p c t and 0.4 to 1.5 pct, r e s p e c t i v e l y . All of the s t e e l s w e r e m e l t e d in a 50-kg induction f u r n a c e and c a s t to 10-kg ingots. The ingots w e r e f o r g e d and h o t - r o l l e d followed b y s o l u t i o n t r e a t m e n t at l l 0 0 ~ for 1 h. C r e e p r u p t u r e t e s t i n g w e r e c a r r i e d out a t 650 ~ and 700~ for t i t a n i u m and niobium b e a r i n g s t e e l s , and at 600 ~ 700 ~ and 800~ for v a n a d i u m c o n t a i n i n g s t e e l s . The long t e r m aging t r e a t m e n t s w e r e a l s o m a d e at 650 ~ and 700~ VOLUME 4, MAY 1973-1213
Table I. Chemical Composition and Austenite Grain Size of Steels Used, Wt Pct
N Steel
C
Si
Mn
Cr
Ni
Sol. N
Austenite Grain Size Number
Atomic Ratio
Insol. N
Total N
Ti
Nb
V
Ti/C
Nb/C
V/C
-
-
7 to 8
SI
0.08
0.54
1.54
18. 31
9.86
-
-
0.0195
tr.
0.016
Data Loading...
