Microcracks in carburized and hardened steel
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Microcracks in Carburized and Hardened Steel L . J E N A AND P . H E I C H
MICROCRACKS( m i c r o s c o p i c
cracks) across martens i t e p l a t e s in high c a r b o n a c i c u l a r m a r t e n s i t e h a v e b e e n o b s e r v e d f o r m a n y y e a r s . T h e h i s t o r y of m i c r o c r a c k s d a t e s b a c k to 1925 w h e n R a w d o n and E p s t e i n ~ r e p o r t e d finding m i c r o c r a c k s in m a r t e n s i t i c c a r b o n s t e e l s . In 1931 L u c a s 2 r e f e r r e d to m i c r o c r a c k s in his H o w e M e m o r i a l L e c t u r e b e f o r e the A m e r i c a n I n s t i t u t e of M i n i n g and M e t a l l u r g i c a l E n g i n e e r s . D a v e n p o r t e t a t . 3 m a d e a d e t a i l e d s t u d y of m i c r o c r a c k s in h a r d e n e d s t e e l s . T h e y o b s e r v e d that the s e v e r i t y of m i c r o c r a c k ing i n c r e a s e d w i t h i n c r e a s i n g a u s t e n i t i c g r a i n s i z e . R a u c h and T h u r t l e 4 i n v e s t i g a t e d the p r e s e n c e of m i c r o c r a c k s in c a s e - h a r d e n e d s t e e l s and c o n c l u d e d t h a t the n u m b e r of m i c r o c r a c k s w a s d e p e n d e n t on the g r a i n s i z e , the c o a r s e - g r a i n e d s t r u c t u r e c o n t a i n e d m o r e m i c r o c r a c k s than the f i n e - g r a i n e d s t r u c t u r e . M a r d e r a n d B e n s c o t e r s i n v e s t i g a t e d m i c r o c r a c k i n g in q u e n c h e d , h i g h - c a r b o n F e - C a l l o y s and p r o p o s e d that m i c r o c r a c k i n g was c a u s e d by i m p i n g e m e n t of a c i c u l a r m a r tensite plates. L. JENA and P. HEICH are Principal Materials Research Metallurgist and Research Metallurgist, respectively, Materials Division, Engineering Research, International Harvester Co., Hinsdale, Ill, Manuscript submitted August 12, 1971.
588-VOLUME 3, FEBRUARY 1972
p l o t t e d a g a i n s t the c o p p e r in the m a t t e p h a s e at 1300~ T h e p r e s e n t c a l c u l a t e d r e s u l t s a r e in e x c e l lent a g r e e m e n t w i t h t h e e x p e r i m e n t a l d a t a of Y a z a w a and K a m e d a , ~ in s p i t e of the a s s u m p t i o n that m a t t e s a r e e u t e c t i f e r r o u s m i x t u r e s of Cu2S and F e S w h i l e i n d u s t r i a l m a t t e s a r e known to c o n t a i n c o n s i d e r a b l e a m o u n t s of o x y g e n . In F i g . 5 t h e c o p p e r l o s s e s in c o m m e r c i a l r e v e r b e r a t o r y f u r n a c e s l a g s r e p o r t e d by Beals 7 for various reverberatory furnace operations h a v e a l s o b e e n p l o t t e d . It
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