The rapid heat treatment of steel
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heat treatment of s t e e l most often involves conp o s s i b i l i t y of s h o r t e n i n g t h e a u s t e n i t i z i n g c y c l e p r e s e n t s t r o l l i n g , by a s u i t a b l e t e m p e r a t u r e - t i m e c y c l e , s o l i d i t s e l f . T h e q u e s t i o n t h e n a r i s e s as to w h e t h e r a n y a d v a n state p h a s e changes or precipitation and coalescence of t a g e s m a y be d e r i v e d f r o m a v e r y s h o r t , o r r a p i d , ausc a r b i d e p a r t i c l e s with t h e aim o f developing a m i c r o tenitizing treatment. Aside from the s a v i n g of time s t r u c t u r e h a v i n g the c o m b i n a t i o n o f m e c h a n i c a l p r o p w h i c h , o n a n e c o n o m i c b a s i s , m a y be m o r e t h a n o f f s e t e r t i e s b e s t s u i t e d f o r t h e i n t e n d e d u s e o f the p r o d u c t . by t h e m o r e s o p h i s t i c a t e d h e a t - t r e a t i n g e q u i p m e n t r e In d e s i g n i n g a s p e c i f i c h e a t - t r e a t m e n t c y c l e , t e m p e r a q u i r e d , a n o b v i o u s a d v a n t a g e o f a r a p i d c y c l e i s that ture and t i m e are interdependent variables. Solid-state oxidation and decarburization of the s t e e l are m i n i m a l r e a c t i o n s i n v o l v e d in a u s t e n i t i z i n g o c c u r f a s t e r as t h e a n d c o n t r o l l e d a t m o s p h e r e s w i l l o f t e n be u n n e c e s s a r y . t e m p e r a t u r e is h i g h e r . A m o d e s t i n c r e a s e in t e m p e r a A n a d d i t i o n a l a d v a n t a g e w o u l d seem to lie in t h e p r o b a t u r e m a y be e q u i v a l e n t t o a n o r d e r of m a g n i t u d e b i l i t y that r a p i d a u s t e n i t i z i n g w i l l m i n i m i z e g r o w t h o f i n c r e a s e in t i m e in a n i s o t h e r m a l t r e a t m e n t . T h i s s i t a u s t e n i t e g r a i n s a n d h e n c e l e a d to a f i n e r - g r a i n e d h e a t u a t i o n m a k e s i t p o s s i b l e t o s p e e d up a v a r i e t y o f h e a t t r e a t e d p r o d u c t . T h e aim o f t h i s p a p e r is to d e m o n s t r a t e t r e a t i n g p r o c e s s e s , but t h e o n e t o be d i s c u s s e d i s t h e h o w v e r y s m a l l g r a i n s c a n o f t e n be d e v e l o p e d i n a wide a u s t e n i t i z a t i o n t r e a t m e n t p r e p a r a t o r y to c o o l i n g in a v a r i e t y o f s t e e l s by r a p i d a u s t e n i t i z i n g . m a n n e r w h i c h c a u s e s a u s t e n i t e to t r a n s f o r m to t h e m i c r o s t r u c t u r e d e s i r e d . M o s t f r e q u e n t l y t h i s w i l l be m a r MINIMIZING A U S T E N I T E GRAIN G R O W T H tensite. BY RAPID HEATING T h e p o s s i b i l i t y of a r a p i d c y c l e t o a u s t e n i t i z e s t e e l T h e p o s s i b i l i t y o f r e f i n i n g a u s t e n i t e g r a i n s by a r a p i d h a s long b e e n r e c o g n i z e d a n d i n d e e d i s u s e d i n p r a c t i c e a s , f o r e x a m p l e , i n h a r d e n i n g by
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