Variation of mechanical properties in large steel forgings
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v a r i a t i o n s e n c o u n t e r e d in m e c h a n i c a l p r o p e r t i e s of l a r g e s t e e l f o r g i n g s have b e e n a p a r t i c u l a r l y troublesome problem for many years. These aberrat i o n s a r e f r e q u e n t l y r e s p o n s i b l e f o r high r e j e c t i o n r a t e s d u r i n g p r o d u c t i o n and a l s o m a y c o n t r i b u t e to the f a i l u r e of s t r u c t u r a l c o m p o n e n t s t h r o u g h o u t a b r o a d s p e c t r u m of the s t e e l m a k i n g and s t e e l f a b r i c a t ing i n d u s t r y . A s e a r l y a s 1918, G e o r g e s C h a r p y I c o n c l u d e d that the a m o u n t of d e f o r m a t i o n u n d e r g o n e at high t e m p e r a t u r e , by a b l o c k of s t e e l , a f f e c t s the p r o p e r t i e s of the m e t a l a c c o r d i n g to a c o m p l e x law which i n v o l v e s the i n i t i a l s t a g e of the ingot and a l l s u b s e q u e n t d e f o r m a t i o n s . W h e r e b y , the chief c h a r a c t e r i s t i c of t h e d e f o r m a t i o n i s to c r e a t e s t r o n g l y m a r k e d h e t e r o g e n e i t y . He w i s e l y c o n c l u d e d that g e n e r a l r u l e s w e r e i m p o s s i b l e to a p p l y to a l l f o r g i n g s . F o r c o m p o n e n t s o p e r a t i n g under applied transverse stresses, such as pressuri z e d c y l i n d e r s o r wide b e a m s , l o n g i t u d i n a l f o r g i n g can undoubtedly have an i n j u r i o u s effect upon the m e chanical properties required for satisfactory performance. P o s t W o r l d W a r II i n v e s t i g a t i o n s of the t r a n s v e r s e m e c h a n i c a l p r o p e r t i e s in h e a t t r e a t e d w r o u g h t s t e e l p r o d u c t s v e r i f i e d C h a r p y ' s c o n c l u s i o n s . W e l l s and M e h l ~ f o r e x a m p l e , d e m o n s t r a t e d that v a r i a t i o n s in p c t r e d u c t i o n of a r e a (pct RA) within s o l i d f o r g i n g s o r t u b e s f r e q u e n t l y a m o u n t to 30 p c t RA and o c c a s i o n a l l y 40 p c t RA o r h i g h e r . T h e y a l s o i m p l i e d t h a t the s o l i d i f i c a t i o n of the " p r i m a r y c a s t i n g " o r ingot can affect the f i n a l p r o p e r t i e s of the f i n i s h e d f o r g i n g , and that e l o n g a t e d n o n m e t a l l i c i n c l u s i o n s along with the h e t e r o geneous d i s t r i b u t i o n of c h e m i c a l e l e m e n t s in s o l u t i o n a r e t o g e t h e r l a r g e l y r e s p o n s i b l e f o r the t r a n s v e r s e d u c t i l i t y of f o r g i n g s b e i n g l o w e r than l o n g i t u d i n a l d u c tility. R e c e n t s t u d i e s by the a u t h o r s 3 on high s t r e n g t h , low a l l o y s t e e l c y l i n d e r s , have shown that p c t RA in f o r g ings of e q u i v a l e n t c o n f i g u r a t i o n e x h i b i t e d s i g n i f i c a n t v a r i a t i o n when the f o r g i n g s r e s u l t e d f r o m d i f f e r e n t i n PETER A. THORNTON and VITO J. COLANGELO are M
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