The stress intensities for slow crack growth in steels containing hydrogen
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is a w e l l - k n o w n p r o b l e m in high s t r e n g t h s t e e l s . Many s t u d i e s have shown, for e x a m p l e , that when s t e e l t e n s i l e s a m p l e s a r e p r e c h a r g e d with h y d r o g e n and d e a d w e i g h t l o a d e d slow c r a c k growth and e v e n t u a l f a i l u r e will t a k e p l a c e . A l though t h e s e s t u d i e s have shown the s e v e r i t y of the p r o b l e m , t h e r e h a s b e e n l i t t l e done thus f a r to r e l a t e the s t r e s s I n t e n s i t y for c r a c k i n g to the h y d r o g e n c o n tent. One p u r p o s e of the p r e s e n t w o r k was to d e v e l o p a t e s t p r o c e d u r e to m e a s u r e the s t r e s s i n t e n s i t y n e e d e d f o r slow c r a c k growth in h y d r o g e n - c h a r g e d s t e e l s and to m e a s u r e the s t r e s s I n t e n s i t y for c r a c k i n g a s a f u n c tion of h y d r o g e n content in t h r e e m a r a g t n g s t e e l s and a 300M s t e e l . A s e c o n d p u r p o s e of t h i s w o r k was to e x a m i n e the q u e s t i o n of h y d r o g e n e m b r t t t l e m e n t d u r i n g s t r e s s c o r r o s i o n t e s t i n g of s t e e l s . S t r e s s c o r r o s i o n c r a c k i n g of high s t r e n g t h s t e e l s In aqueous e n v i r o n m e n t s ts g e n e r a l l y c o n s i d e r e d to be due to h y d r o g e n e m b r i t t l e m e n t . ~-7 That t s , the c o r r o s i o n r e a c t i o n at the s t e e l s u r f a c e g e n e r a t e s h y d r o g e n that is a b s o r b e d b y the s t e e l , and cracking results from embrtttlement by this hydrogen. To d a t e , h o w e v e r , no e s t i m a t e s have b e e n m a d e of the q u a n t i t i e s of h y d r o g e n a b s o r b e d d u r i n g s t r e s s c o r r o s i o n and thus r e s p o n s i b l e f o r c r a c k i n g . The s t r e s s Int e n s i t y for s t r e s s c o r r o s i o n , K1scc, of e a c h of the p r e s ent s t e e l s was a l s o d e t e r m i n e d . By c o m p a r i n g t h e s e v a l u e s with the h y d r o g e n e m b r l t t l e m e n t r e s u l t s , the n o m i n a l h y d r o g e n c o n t e n t s n e e d e d to c a u s e c r a c k i n g at a s t r e s s I n t e n s i t y of Klscc could b e e s t i m a t e d . Thus, an e s t i m a t e of the h y d r o g e n pickup b y the s t e e l s d u r i n g s t r e s s c o r r o s i o n c r a c k i n g could be m a d e . E X P E R I M E N T A L PROCEDURE AND RESULTS Sample Preparation T h r e e m a r a g i n g s t e e l (19 kg (40-1/0.)) l a b o r a t o r y h e a t s w e r e p r e p a r e d b y v a c u u m induction m e l t i n g . The ingots w e r e s o a k e d and hot f o r g e d at 1260~ (2300~ and then hot r o i l e d to 1.27 c m (89-in.) p l a t e at 1040~ (1900~ The 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 T a b l e I. The t i t a n i u m contents w e r e v a r i e d b e t w e e n 0.35 and 0.65 p e t to p r o d u c e t h r e e d i f f e r e n t s t r e n g t h D. P. DAUTOV
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