The tempering of low carbon steels containing tungsten
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BOTHt u n g s t e n
and m o l y b d e n u m f o r m the c a r b i d e
M2C known to confer s e c o n d a r y h a r d e n i n g c h a r a c t e r i s t i c s to quenched and t e m p e r e d s t e e l s . Kuo, using X r a y t e c h n i q u e s , has i n v e s t i g a t e d the t e m p e r i n g b e h a v i o r of a n u m b e r of m e d i u m c a r b o n s t e e l s containing t u n g s t e n o r m o l y b d e n u m . 1 The r e s u l t s show that MzC h a s a g r e a t e r s t a b i l i t y in m o l y b d e n u m s t e e l s . T h i s fact, t o g e t h e r with the h i g h e r c o s t of tungsten ( a g g r a v a t e d by a much g r e a t e r a t o m i c weight) h a s c e n t e r e d s u b s e quent r e s e a r c h on the m o l y b d e n u m s y s t e m while t u n g s t e n s t e e l s , in p a r t i c u l a r low c a r b o n tungsten s t e e l s , have been l i t t l e d o c u m e n t e d . The p r e s e n t i n v e s t i g a t i o n using e l e c t r o n m i c r o s c o p y and t h e r m o m a g n e t i c a n a l y s i s w a s i n i t i a t e d to a s s e s s the p e c u l i a r i t i e s of a l l o y c a r b i d e p r e c i p i t a t i o n in low c a r b o n tungsten s t e e l s and to t e s t the v a l i d i t y of a n a l o g i e s p r e s u m e d to e x i s t b e tween t h e s e and m o l y b d e n u m s t e e l s . C o n c u r r e n t l y , o b s e r v a t i o n s w e r e m a d e on the effect of tungsten on the p r e c i p i t a t i o n of i r o n c a r b i d e s . 1) E X P E R I M E N T A L DETAILS 1.1) M a t e r i a l s The t h r e e s t e e l s u s e d in the i n v e s t i g a t i o n , Table I, w e r e p r e p a r e d f r o m high p u r i t y m a t e r i a l s in a 2 kg v a c u u m f u r n a c e . The ingots w e r e hot r o l l e d to 15 m m d i a m b a r , s u r f a c e c l e a n e d , a n a l y z e d to p r o v i d e a check on m a c r o s e g r e g a t i o n , and s u b s e q u e n t l y cold s w a g e d to 6 m m d i a m b a r . An h o m o g e n i z i n g t r e a t m e n t of 50 h at 1250~ in a s e a l e d a r g o n a t m o s p h e r e w a s given at t h i s s t a g e to r e d u c e any m i c r o s e g r e g a t i o n . S a m p l e s of e a c h b a r w e r e f u r t h e r cold s w a g e d to p r o v i d e 1.5 m m d i a m by 3 m m long m a g n e t i z a t i o n s p e c i m e n s . A c e n t e r t r a n s v e r s e notch about 0.75 m m deep w a s u s e d to a c c o m m o d a t e a t h e r m o c o u p l e when the s p e c i m e n w a s in p o s i t i o n in the S u c k s m i t h B a l a n c e . J. B. LUPTON, formerly Research Student, Metallurgy Department, University of Sheffield, England, is now Scientific Officer, The British Railways Research Department, The Railway Technical Centre, Derby, England. S. MURPHY, formerly Research Fellow, Metallurgy Department, University of Sheffield, is now Research Fellow, Metallurgy Department, University of Aston-in-Birmingham, England. J. H. WOODHEAD is Senior Lecturer, Metallurgy Department, University of Sheffield. Manuscript submitted March 22, 1971. METALLURGIC
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