A study of the deformation of patented steel wire
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C o m p a r i s o n s of t r a n s m i s s i o n e l e c t r o n m i c r o g r a p h s of t r a n s v e r s e s e c t i o n s of h e a v i l y d r a w n p a t e n t e d s t e e l w i r e with e x i s t i n g m e t a l l o g r a p h i c and s t r e n g t h d a t a w e r e m a d e with the a i d of a c o m p u t e r . B o t h f r a g m e n t a t i o n of the c e m e n t i t e and the l o c a l d e f o r m a t i o n m o d e w i t h i n the w i r e , i . e . , p l a n e s t r a i n e l o n g a t i o n , an e f f e c t of the (110} w i r e t e x t u r e of the f e r r i t e , w e r e t a k e n into a c c o u n t in o r d e r to o b t a i n a m o d e l f o r l a r g e - s t r a i n d e f o r m a t i o n of p e a r l i t i c o r b a i n i t i c m i c r o s t r u c t u r e s which i s c o n s i s t e n t with the o b s e r v e d m i c r o s t r u c t u r a l c h a n g e s and s t r a i n h a r d e n i n g r a t e . The f u n c t i o n a l d e p e n d e n c e of t h i s m o d e l on t r u e s t r a i n and o r i g i n a l s u b s t r u c t u r a l s p a c i n g is s i m i l a r to the e q u a t i o n of E m b u r y and F i s h e r for the s t r a i n h a r d e n i n g of d r a w n p e a r l i t e b e c a u s e t h e i r a s s u m p t i o n s (no f r a g m e n t a t i o n of the c e m e n t i t e a n d h o m o g e n e o u s , a x i a l l y s y m m e t r i c e l o n g a t i o n ) p r o d u c e d o f f s e t t i n g e r r o r s . The p r e s e n t m o d e l a l l o w s f o r a d d i t i o n a l s e n s i t i v i t y of the s t r a i n h a r d e n i n g r a t e of d r a w n p a t e n t e d s t e e l w i r e to m e t a l l u r g i c a l and p r o c e s s i n g v a r i a b l e s o v e r and a b o v e the s i m p l e d e p e n d e n c e on o r i g i n a l s u b s t r u c t u r a l s c a l e p r e d i c t e d by the m o d e l of E m b u r y and F i s h e r .
DRAWNp a t e n t e d
carbon steel wire has a fibrous m i c r o s t r u c t u r e when v i e w e d in a l o n g i t u d i n a l c r o s s s e c t i o n with the e l e c t r o n m i c r o s c o p e 1,2 but a " w a v y " m i c r o s t r u c t u r e when v i e w e d in a t r a n s v e r s e c r o s s section.~'4 E m b u r y a n d F i s h e r 1 found, f r o m t h e i r m e a s u r e m e n t s on l o n g i t u d i n a l s e c t i o n s , a d i r e c t p r o p o r t i o n a l i t y b e t w e e n the c h a r a c t e r i s t i c t r a n s v e r s e d i m e n s i o n of t h i s s u b s t r u c t u r e and the d i a m e t e r of the a s - d r a w n w i r e . T h i s s e e m e d to i n d i c a t e that the c a r b i d e p a r t i c l e s o r lamellae completely inhibited dynamic recovery. They t h e r e f o r e p r o p o s e d an e q u a t i o n which a c c o u n t e d s i m p l y f o r the o b s e r v e d s t r e n g t h - p r i o r s t r a i n r e l a t i o n of these wires : ky (~ = ao + ~
exp(E/4)
[1]
w h e r e CSo is the " l a t t i c e f r i c t i o n " s t r e s s , do is the o r i g i n a l s u b s t r u c t u r a l s p a c i n g , ky i s the H a l l - P e t c h p r o p o r t
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