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Nitrocarburizing of PM steels
PRINCIPLES OF STANDARDIZATION OF ARTICLES OF COMPLEX P R O D U C E D BY POWDER METALLURGY Y.G. Dorofeev et al, Poroshkovaya Metallurgiya, No 8, 1992, 97-104. (In Russian). Information concerning the S t a n d a r d for PM P a r t s is p r e s e n t e d . GOST29278-92 c o n t a i n s t h e r e q u i r e m e n t s for s t a n d a r d p a r t s m a d e by a range of PM techniques. The S t a n d a r d is u n d e r l a i n by a classification of p a r t s by form a n d size. The S t a n d a r d is considered to provide a code of practice for makers a n d users of PM parts. I
LITERATURE REVIEW: PM'93 The a b s t r a c t s which follow are of p a p e r s w h i c h were p r e s e n t e d a t t h e 1993 Powder Metallurgy World Congress which was held in Kyoto, Japan, from 12th to 15th July 1993.
Compaction modelling and simulation CONSTITUTIVE BEHAVIOUR OF POWDERS DURING C O M P A C T I O N S.B. Brown, G. Abou-Chedid (Massachusetts Inst of Technology, Cambridge, USA). It was n o t e d t h a t rate d e p e n d e n t models of p o w d e r c o m p a c t i o n r e q u i r e a yield function for t h e t r a n s i t i o n from elastic to plastic behaviour. E x p e r i m e n t a l r e s u l t s characterizing yield functions in spherical a n d irregular powders were presented. It was suggested t h a t some c u r r e n t yield functions may be incorrect a n d t h a t a m i n i m u m of two p a r a m e t e r s , density a n d i n t e r p a r t i c l e c o h e s i o n , a r e n e e d e d to characterize yield. A NEW MODEL FOR E S T I M A T I O N OF DENSITY IN PACKED B E D S OF NONSPHERICAL PARTICLES T. Itoh, Y. Wanibe (University of Nagoya, Nagoya, J a p a n ) . The p a c k i n g of p a r t i c l e s p r i o r to compaction was discussed with reference to p a r t i c l e sizes a n d s h a p e s a n d t h e difficulty of analysis in the case of nonspherical powders. A new packed bed model for non-spherical particles, which gives a q u a n t i t a t i v e e x p l a n a t i o n of the relationship between particle properties a n d packing density, was described. Use was m a d e of a wide range of powders in the e x p e r i m e n t a l stage of t h e study. SIMULATION OF COMPACTION OF HARD METAL C O M P O N E N T S USING XRAY VERIFICATION OF DENSITY H - ~ Hgtggblad, M. Oldenburg (Lule~ University of Technology, Sweden). The die compaction of h a r d m e t a l s was s i m u l a t e d by explicit i n t e g r a t i o n methods.
52 MPR April 1994
The density variations d e t e r m i n e d by finite e l e m e n t a n a l y s i s were c o m p a r e d w i t h e x p e r i m e n t a l m e a s u r e m e n t s using X-ray methods. Various m e t h o d s of evaluating t h e frictional c o m p o n e n t of various models were compared. Use was m a d e of variations in density close to t h e die wall a n d punch. A contact friction model was shown to have a significant influence on t h e results of t h e simulation. SPRING BACK IN PARTS WITH G R E E N DENSITY E X C E E D I N G 7.1 L. A c k e r m a n n (Sintertech, France). Spring back in dies due to large elastic d e f o r m a t i o n s , c a u s e d by c o m p a c t i n g powders to high density, was discussed. It was considered t h a t spring back exerts considerable pressure on c o m p o n e n t s a n d t h a t this can lead to f u r t h e r compression of p a r t s during ejection a n d less spring back t h a n t h a t calculated from the elastic model. T H R E E - D I M E N S I O N A L GRANULAR M O D E L L I N G FOR SIMULATION OF POWDER COMPACTION BEHAVIOUR S. T a m u r a et al (University of Tokyo, Tokyo, Japan). T h e u s e of g r a n u l a r m o d e l l i n g to d e s c r i b e t h e m e c h a n i c a l b e h a v i o u r of powder during compaction was discussed a n d it was n o t e d t h a t the two-dimensional analysis does not adequately describe density distribution, particle packing or p o w d e r flow. T h e u s e o f a t h r e e d i m e n s i o n a l g r a n u l a r m o d e l l i n g system was described. The results were applied to powder density, co-ordination n u m b e r a n d o r i e n t a t i o n distribution. The effectiveness of t h e a p p r o a c h was d e m o n s t r a t e d using a range of powders. NUMERICAL SIMULATION OF POWDER BEHAVIOUR IN COMPACTION S. S h i m a ( U n i v e r s i t y of Kyoto, Kyoto, Japan). T h e i m p o r t a n c e of m o d e l l i n g a n d s i m u l a t i o n of c o m p a c t i o n a n d p r o p e r c o n t r o l a n d d e s i g n of p o w d e r s w e r e reviewed with regard to t h e e s t a b l i s h m e n t of constitutive e q u a t i o n s for compaction. Constitutive equations were described a n d application to simulation of compaction, by u s e of f i n i t e e l e m e n t m e t h o d s , w a s d i s c u s s e d . O p t i m a l d e s i g n of powder, e f f e c t s of p o w d e r c h a r a c t e r i s t i c s o n material p a r a m e t e r s were examined. The results were discussed making comparison between e x p e r i m e n t a n d prediction. Effects of friction, cohesion between particles a n d plastic deformation were considered. NUMERICAL SIMULATION OF E F F E C T S O F PARTICLE CHARACTERISTICS ON COMPACTION OF POWDERS S. S h i m a et al (University of Kyoto, Kyoto, Japan).
A two-dimensional simulation of powder compaction was discussed. Particle i n t e r p r e t a t i o n characteristics were t a k e n into a c c o u n t w i t h s t r a i n r a t e s in two dimensions, corresponding to closed die a n d isostatic compactions, being varied. It was shown t h a t t h e higher t h e friction a n d cohesion t h e h i g h e r is t h e pressure required to a t t a i n a given density. Good a g r e e m e n t with the prediction using constitutive equations was reported.
Secondary operations NITROCARBURIZING OF PM S T E E L S M. Rosso, G. Scavino (Polytechnic of Turin, Turin, Italy). The use of nitrocarburizing to form h a r d surfaces on h e a t t r e a t e d steel p a r t s was discussed. Fe alloys with Cu, S, Ni, P, Cr a n d Mo were p l a s m a or gas nitrocarburized a n d the effects of alloy composition a n d process parameters on microstructure and h a r d n e s s were determined. Results of tests d e m o n s t r a t i n g e n h a n c e m e n t of fatigue a n d wear properties were described. E F F E C T S OF N I T R O G E N A D S O R P T I O N ON PERMEABILITY OF S T E E L PARTS S I N T E R E D IN N I T R O G E N BASE A T M O S P H E R E S AND STEAM T R E A T E D J.B. Yang et al (Mitsubishi Metals Corp, Niigata, J a p a n ) . It was noted t h a t N a d s o r p t i o n can occur during t h e system t r e a t m e n t of sintered steels. N a d s o r p t i o n during sintering in N base gases a n d endogas was investigated. It was reported t h a t to improve ferrous p a r t s s i n t e r e d in N a d e - n i t r o g e n i z a t i o n t r e a t m e n t in H is beneficial. A model for N adsorption a n d de-sorption was p r o p o s e d a n d discussed. TENSILE A N D FATIGUE P R O P E R T I E S OF S I N T E R E D AND CASE H A R D E N E D CHROMIUM STEELS S. Unami, O. Furukimi (Kawasaki Steel Corp, Kawasaki, J a p a n ) . A s t u d y of t h e effects of g r a p h i t e content, h e a t t r e a t m e n t a n d carburizing on t h e m e c h a n i c a l p r o p e r t i e s of l%Cr0.7%Mn-0.3%Mo steel was described. Small additions of C, O to 0.15% h a d small effects on tensile strength. The s t r e n g t h of sintered a n d case h a r d e n e d steel with a n additional 0.15%C h a d a tensile s t r e n g t h of 1100 MPa a n d a fatigue s t r e n g t h of 2350 MPa. This was a t t r i b u t e d to less r e t a i n e d a u s t e n i t e in the structure. COMPARISON OF P R O P E R T I E S OF PLASMA VACUUM A N D G A S E O U S CARBURIZED S I N T E R E D S T E E L S M. Rosso et al (Polytechnic of Turin, Turin, Italy).
LITERATURE REVIEW: PM'93 The a b s t r a c t s which follow are of p a p e r s w h i c h were p r e s e n t e d a t t h e 1993 Powder Metallurgy World Congress which was held in Kyoto, Japan, from 12th to 15th July 1993.
Compaction modelling and simulation CONSTITUTIVE BEHAVIOUR OF POWDERS DURING C O M P A C T I O N S.B. Brown, G. Abou-Chedid (Massachusetts Inst of Technology, Cambridge, USA). It was n o t e d t h a t rate d e p e n d e n t models of p o w d e r c o m p a c t i o n r e q u i r e a yield function for t h e t r a n s i t i o n from elastic to plastic behaviour. E x p e r i m e n t a l r e s u l t s characterizing yield functions in spherical a n d irregular powders were presented. It was suggested t h a t some c u r r e n t yield functions may be incorrect a n d t h a t a m i n i m u m of two p a r a m e t e r s , density a n d i n t e r p a r t i c l e c o h e s i o n , a r e n e e d e d to characterize yield. A NEW MODEL FOR E S T I M A T I O N OF DENSITY IN PACKED B E D S OF NONSPHERICAL PARTICLES T. Itoh, Y. Wanibe (University of Nagoya, Nagoya, J a p a n ) . The p a c k i n g of p a r t i c l e s p r i o r to compaction was discussed with reference to p a r t i c l e sizes a n d s h a p e s a n d t h e difficulty of analysis in the case of nonspherical powders. A new packed bed model for non-spherical particles, which gives a q u a n t i t a t i v e e x p l a n a t i o n of the relationship between particle properties a n d packing density, was described. Use was m a d e of a wide range of powders in the e x p e r i m e n t a l stage of t h e study. SIMULATION OF COMPACTION OF HARD METAL C O M P O N E N T S USING XRAY VERIFICATION OF DENSITY H - ~ Hgtggblad, M. Oldenburg (Lule~ University of Technology, Sweden). The die compaction of h a r d m e t a l s was s i m u l a t e d by explicit i n t e g r a t i o n methods.
52 MPR April 1994
The density variations d e t e r m i n e d by finite e l e m e n t a n a l y s i s were c o m p a r e d w i t h e x p e r i m e n t a l m e a s u r e m e n t s using X-ray methods. Various m e t h o d s of evaluating t h e frictional c o m p o n e n t of various models were compared. Use was m a d e of variations in density close to t h e die wall a n d punch. A contact friction model was shown to have a significant influence on t h e results of t h e simulation. SPRING BACK IN PARTS WITH G R E E N DENSITY E X C E E D I N G 7.1 L. A c k e r m a n n (Sintertech, France). Spring back in dies due to large elastic d e f o r m a t i o n s , c a u s e d by c o m p a c t i n g powders to high density, was discussed. It was considered t h a t spring back exerts considerable pressure on c o m p o n e n t s a n d t h a t this can lead to f u r t h e r compression of p a r t s during ejection a n d less spring back t h a n t h a t calculated from the elastic model. T H R E E - D I M E N S I O N A L GRANULAR M O D E L L I N G FOR SIMULATION OF POWDER COMPACTION BEHAVIOUR S. T a m u r a et al (University of Tokyo, Tokyo, Japan). T h e u s e of g r a n u l a r m o d e l l i n g to d e s c r i b e t h e m e c h a n i c a l b e h a v i o u r of powder during compaction was discussed a n d it was n o t e d t h a t the two-dimensional analysis does not adequately describe density distribution, particle packing or p o w d e r flow. T h e u s e o f a t h r e e d i m e n s i o n a l g r a n u l a r m o d e l l i n g system was described. The results were applied to powder density, co-ordination n u m b e r a n d o r i e n t a t i o n distribution. The effectiveness of t h e a p p r o a c h was d e m o n s t r a t e d using a range of powders. NUMERICAL SIMULATION OF POWDER BEHAVIOUR IN COMPACTION S. S h i m a ( U n i v e r s i t y of Kyoto, Kyoto, Japan). T h e i m p o r t a n c e of m o d e l l i n g a n d s i m u l a t i o n of c o m p a c t i o n a n d p r o p e r c o n t r o l a n d d e s i g n of p o w d e r s w e r e reviewed with regard to t h e e s t a b l i s h m e n t of constitutive e q u a t i o n s for compaction. Constitutive equations were described a n d application to simulation of compaction, by u s e of f i n i t e e l e m e n t m e t h o d s , w a s d i s c u s s e d . O p t i m a l d e s i g n of powder, e f f e c t s of p o w d e r c h a r a c t e r i s t i c s o n material p a r a m e t e r s were examined. The results were discussed making comparison between e x p e r i m e n t a n d prediction. Effects of friction, cohesion between particles a n d plastic deformation were considered. NUMERICAL SIMULATION OF E F F E C T S O F PARTICLE CHARACTERISTICS ON COMPACTION OF POWDERS S. S h i m a et al (University of Kyoto, Kyoto, Japan).
A two-dimensional simulation of powder compaction was discussed. Particle i n t e r p r e t a t i o n characteristics were t a k e n into a c c o u n t w i t h s t r a i n r a t e s in two dimensions, corresponding to closed die a n d isostatic compactions, being varied. It was shown t h a t t h e higher t h e friction a n d cohesion t h e h i g h e r is t h e pressure required to a t t a i n a given density. Good a g r e e m e n t with the prediction using constitutive equations was reported.
Secondary operations NITROCARBURIZING OF PM S T E E L S M. Rosso, G. Scavino (Polytechnic of Turin, Turin, Italy). The use of nitrocarburizing to form h a r d surfaces on h e a t t r e a t e d steel p a r t s was discussed. Fe alloys with Cu, S, Ni, P, Cr a n d Mo were p l a s m a or gas nitrocarburized a n d the effects of alloy composition a n d process parameters on microstructure and h a r d n e s s were determined. Results of tests d e m o n s t r a t i n g e n h a n c e m e n t of fatigue a n d wear properties were described. E F F E C T S OF N I T R O G E N A D S O R P T I O N ON PERMEABILITY OF S T E E L PARTS S I N T E R E D IN N I T R O G E N BASE A T M O S P H E R E S AND STEAM T R E A T E D J.B. Yang et al (Mitsubishi Metals Corp, Niigata, J a p a n ) . It was noted t h a t N a d s o r p t i o n can occur during t h e system t r e a t m e n t of sintered steels. N a d s o r p t i o n during sintering in N base gases a n d endogas was investigated. It was reported t h a t to improve ferrous p a r t s s i n t e r e d in N a d e - n i t r o g e n i z a t i o n t r e a t m e n t in H is beneficial. A model for N adsorption a n d de-sorption was p r o p o s e d a n d discussed. TENSILE A N D FATIGUE P R O P E R T I E S OF S I N T E R E D AND CASE H A R D E N E D CHROMIUM STEELS S. Unami, O. Furukimi (Kawasaki Steel Corp, Kawasaki, J a p a n ) . A s t u d y of t h e effects of g r a p h i t e content, h e a t t r e a t m e n t a n d carburizing on t h e m e c h a n i c a l p r o p e r t i e s of l%Cr0.7%Mn-0.3%Mo steel was described. Small additions of C, O to 0.15% h a d small effects on tensile strength. The s t r e n g t h of sintered a n d case h a r d e n e d steel with a n additional 0.15%C h a d a tensile s t r e n g t h of 1100 MPa a n d a fatigue s t r e n g t h of 2350 MPa. This was a t t r i b u t e d to less r e t a i n e d a u s t e n i t e in the structure. COMPARISON OF P R O P E R T I E S OF PLASMA VACUUM A N D G A S E O U S CARBURIZED S I N T E R E D S T E E L S M. Rosso et al (Polytechnic of Turin, Turin, Italy).