Influence of recrystallization behavior on the mechanical properties of XM-19 stainless steel (22Cr-13Ni-5Mn-2Mo-0.3N)
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1. I N T R O D U C T I O N THE
u s e of A S T M X M - 1 9 s t a i n l e s s s t e e l * i s a n a t -
*This alloy is known commercially as Nitronic 50 and is manufactured by Armco Steel Corp. tractive alternative t o more conventional stainless s t e e l s , p a r t i c u l a r l y in a p p l i c a t i o n s w h e r e t h e r e is need for enhanced strength and r e s i s t a n c e to corrosion. X M - 1 9 is a fully a u s t e n i t i c s t a i n l e s s s t e e l t h a t c o n t a i n s h i g h e r Cr, M o , and N i than more conventional s t a i n l e s s s t e e l s . T h e t e n s i l e y i e l d s t r e n g t h of X M - 1 9 is about t w i c e t h a t o f T y p e - 3 0 4 s t a i n l e s s s t e e l . T h i s e n h a n c e d s t r e n g t h is a t t r i b u t e d t o n i t r o g e n i n t e r s t i t i a l s o l i d s o l u t i o n s t r e n g t h e n i n g . It also c o n t a i n s 5 p c t M n to i n c r e a s e t h e n i t r o g e n solubility a n d a u s t e n i t e s t a b i l i t y . T h e n i t r o g e n c o n t e n t i s 0.20 t o 0 . 4 0 pct, c o n s i d e r a b l y i n e x c e s s of t h e 0.04 p c t t y p i c a l l y f o u n d i n T y p e - 3 0 4 s t a i n l e s s s t e e l . T h e r e a r e also m i n o r a d d i t i o n s of N b (Cb) a n d V t o p r o v i d e g r a i n r e f i n e m e n t and c a r b o n gettering. T h e nominal composition and s t r e n g t h p r o p e r t i e s a r e shown in T a b l e I a l o n g w i t h a c o m p a r i s o n to T y p e - 3 0 4 s t a i n l e s s s t e e l . O n e of t h e i n i t i a l a p p l i c a t i o n s of X M - 1 9 f o r n u c l e a r a p p l i c a t i o n was a t u b u l a r c o m p o n e n t t h a t is s u b j e c t e d to c y c l i c l o a d i n g at l o w s t r e s s a m p l i t u d e s w i t h o c casional c y c l e s at h i g h e r s t r e s s amplitudes a n d m o d e r ately high s t r a i n r a t e s . O p e r a t i o n t e m p e r a t u r e v a r i e s f r o m a m b i e n t t o 5 5 0 ° F (561 K). T h e t u b i n g w a s p r o d u c e d by t h e f o l l o w i n g m a j o r p r o c e s s s t e p s : e l e c t r i c furnace melting, a r g o n oxygen decarburization refini n g , f o r g i n g t o b i l l e t , hot e x t r u s i o n i n t o t u b i n g , c o l d drawing, a n d solution heat t r e a t m e n t . I n a r e l a t e d s t u d y ,1 i t h a s b e e n f o u n d t h a t X M - 19 m a y be s u b j e c t e d t o t h e r m a l t r e a t m e n t s s u c h a s g a s n i t r i d i n g w i t h o u t c o n c o m i t a n t e n h a n c e d s u s c e p t a b i l i t y to i n t e r g r a n u l a r s t r e s s c o r r o s i o n c r a c k i n g ( I G S C C ) that i s J. N. KASS is Manager, Experimental Mechanics, W. L. BELL and M. T. WANGare Senior Engineers, General Electric Nuclear Technology Department, San Jose, CA 95125. J. BOB1CK is Engineer, General Electric Materials and Properties Laboratory, Schenectady, NY. Manuscript submitted June 1 9 , 1978. METALLURGICAL
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f o u n d in m o r e c o n v e n t i o n a l s t a i n l e s s s t e e l s .
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