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ISO 9001 in ferrous powder manufacture
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Powder production M E C H A N I S M S OF F O R M A T I O N O F TUNGSTEN OXIDE POWDER DURING T H E R M A L D E C O M P O S I T I O N OF AMMONIUM PARATUNGSTATE
Y.Yamamoto et al (Tokyo T u n g s t e n C., Toyama, J a p a n ) , J. Japan Soc. Powder and Powder Metallurgy, Vol 40, No 8, 1993, 784-788. (In J a p a n e s e ) . An investigation of t h e t h e r m a l decomposition of ammonium paratungstate to t u n g s t e n o x i d e is described the objective being to d e t e r m i n e t h e factors influencing WO particle size. The p r o p o r t i o n of a m m o n i u m t u n g s t e n bronze i n t e r m e d i a t e is r e p o r t e d to influence t h e o x i d e p a r t i c l e size. T h e h i g h e r t h e t e m p e r a t u r e t h e larger is t h e particle size.
Pressing AUTOMATIC GENERATION AND ANALYSIS OF P O W D E R C O M P A C T I O N DIAGRAMS
R.E. R i m a n et al (Rutgers, The S t a t e University of New Jersey, USA), Powder Technology, Vol 79, No 2, 1994, 111-119. An investigation aimed at t h e a u t o m a t i c d e t e r m i n a t i o n of p o w d e r c o m p a c t i o n d i a g r a m s is d e s c r i b e d . The e q u i p m e n t used is described and employs a u t o m a t i c d a t a k)gging of c o m p a c t i o n p a r a m e t e r s . Elastic d e f o r m a t i o n of t h e tooling a n d springback of t h e c o m p a c t are t a k e n into a c c o u n t . The a p p r o a c h is r e p o r t e d to improve the accuracy, take less time a n d to give greater scope for analysis of t h e results t h a n previously used methods.
Sintering D E T E R M I N A T I O N OF P O R E M O B I L I T Y DURING SINTERING
Y. Liu, B.R. Patterson (University of Alabama, Birmingham, Alabama, USA), MetaU. and Mater. Trans. A, Vol 25A, No 1, 1994, 81 87. The mobility of pores, caused by grain b o u n d a r y m o t i o n , d u r i n g s i n t e r i n g is modelled in t e r m s of s h a p e i n d e p e n d e n t microstructural parameters using stereological m e t h o d s . The m o b i l i t y is correlated with grain b o u n d a r y porosity. The m o b i l i t y of p o r e surface diffusion controlled m o t i o n is shown to be inversely p r o p o r t i o n a l to m e a n pore i n t e r c e p t a n d to be i n d e p e n d e n t of pore s h a p e a n d volume
LITERATURE
REVIEW
fraction. It is reported t h a t pore mobility increases in t h e initial stage b u t d i m i n i s h e s as densiflcation proceeds in t h e final stage of sintering. The findings are discussed with respect to grain b o u n d a r y a n d pore surface a r e a c h a n g e s d u r i n g sintering. A N O M A L O U S D I F F U S I O N MASS T R A N S F E R I N I N I T I A L S T A G E OF SINTERING
A.V. Ragulya, V.V. S k o r o k h o d (Inst. for Problems of Materials Science, Kiev, Uk r a i n e ) , Poroshkovaya Metallurgiya, No 12, 1992, 16-20. (In Russian). A d e s c r i p t i o n of a n o m a l o u s surface a n d grain b o u n d a r y diffusion in t h e initial stage of s i n t e r i n g is given, t h e theory is b a s e d on t h e hypothesis t h a t grain b o u n d a r i e s a n d particle surfaces have a fractal geometry. It is s h o w n t h a t grain b o u n d a r y growth, as fractal clusters, results in p a r a m e t e r s in diffusion e q u a t i o n s being six or seven t i m e s g r e a t e r t h a n for surface a n d b o u n d a r y diffusion. S I N T E R I N G VELOCITY IN PARTS S I N T E R E D BY H I G H F R E Q U E N C Y ELECTRIC CURRENTS
V.G. Plekhanov, Poroshkovaya Metallurgiya, No 12, 1992, 96-99. (In Russian). A s t u d y of t h e e f f e c t s o f t i m e , t e m p e r a t u r e a n d frequency of i n d u c t i o n s i n t e r i n g of powders of varying granularity is described. A c o m p u t e r p r o g r a m m e was used to derive a n e q u a t i o n describing t h e velocity of sintering. ISO 9 0 0 1 IN F E R R O U S P O W D E R MANUFACTURE
Y. Trudel, A. G a l i p e a u ( Q u e b e c Metal Powders Ltd, Sorel, Quebec, C a n a d a ) , Int. J. Powder Metallurgy, Vol 30, No 2, 1994, 151-155. The evolution a n d i m p l e m e n t a t i o n of a c o m p r e h e n s i v e Quality Assurance system, w h i c h m e e t s t h e r e q u i r e m e n t s of ISO 9001, is described. ISO 9001, as applied to t h e m a n u f a c t u r e of iron a n d steel powders, is discussed.
Fundamentals A C O N S I D E R A T I O N OF T H E SINTERING PROCESS
W. S c h a t t (Dresden University of Technology, Dresden, Germany), Science of Sintering, Vol 25, No 3, 1993, 99-107. A m e s o s t r u c t u r a l a c c o u n t of sintering is
given on a basis of shrinkage, shrinkage velocity and position lifetime m e a s u r e m e n t s . It is n o t e d t h a t sintering is a very c o m p l e x p r o c e s s a n d t h a t t h e m e c h a n i s m s operating are d e p e n d e n t on t h e technological conditions as well as powder characteristics. The role of crystal defects is considered. Some d a t a is given for Cu, Ni a n d WC-Co. The course of sintering is expressed as partial adhesion and diffusional flow, p a r t i c l e r e a r r a n g e m e n t a n d m a s s t r a n s f e r all of which c o n t r i b u t e to densification. YIELD F U N C T I O N S FOR M E T A L POWDER COMPACTION
S. Brown, G. Abou-Chedid ( M a s s a c h u s e t t s Inst. of Technology, Cambridge, Massachu setts, USA), Sc~ripta Metall. Mater., Vol 28, No 1, 1993, 11 16. An e x p e r i m e n t a l investigation of the c o m p a c t i o n of spherical Cu powders is described. M e a s u r e m e n t s of yield surface t h r o w d o u b t on t h e correctness of c u r r e n t y i e l d f u n c t i o n s w h i c h m a y l e a d to inaccurate p r e d i c a t i o n s of flow behaviour. The model for porous plastic materials c a n n o t be applied to powder compaction. The results are discussed in detail. M A T H E M A T I C A L M O D E L OF ELASTOPLASTIC DEFORMATION M E C H A N I S M OF P O R O U S M A T E R I A L S
A.K. Grigoriev eta al (St Petersburg State Technical University, St Petersburg, Russia), Poroshkovaya Metallurgiya, Nn 12, 1992, 1-10. (In Russian). It is reported t h a t mechanical analogues characterizing t h e deformation of porous m a t e r i a l s h a d b e e n u s e d to c o n s t r u c t general rheological models. E q u a t i o n s for sintered materials are suggested which take into account physico-mechanical properties a n d m a c r o - a n d micro-heterogeneities.
PRODUCTS: Aluminium MATERIAL MECHANICAL MODELLING OF S I N T E R E D A L U M I N I U M ALLOY
H. I s m a r et al (University of the Saar, Sarrbrucken, Germany), Z. Metallkunde, Vol 85, No 4, 1994, 249-255. (In German). It is r e p o r t e d t h a t modelling of the m e c h a n i c a l p r o p e r t i e s of s i n t e r e d A1 l l % Z n - 3 % M g 1.5%Cu 0.6%Mn h a d b e e n c a r r i e d out. D e v e l o p m e n t of t h e yield surface a n d isotropic a n d kinematic work h a r d e n i n g w e r e d e t e r m i n e d for cyclic loading a n d small plastic deformations.
MPR N o v e m b e r 1994 37
Powder production M E C H A N I S M S OF F O R M A T I O N O F TUNGSTEN OXIDE POWDER DURING T H E R M A L D E C O M P O S I T I O N OF AMMONIUM PARATUNGSTATE
Y.Yamamoto et al (Tokyo T u n g s t e n C., Toyama, J a p a n ) , J. Japan Soc. Powder and Powder Metallurgy, Vol 40, No 8, 1993, 784-788. (In J a p a n e s e ) . An investigation of t h e t h e r m a l decomposition of ammonium paratungstate to t u n g s t e n o x i d e is described the objective being to d e t e r m i n e t h e factors influencing WO particle size. The p r o p o r t i o n of a m m o n i u m t u n g s t e n bronze i n t e r m e d i a t e is r e p o r t e d to influence t h e o x i d e p a r t i c l e size. T h e h i g h e r t h e t e m p e r a t u r e t h e larger is t h e particle size.
Pressing AUTOMATIC GENERATION AND ANALYSIS OF P O W D E R C O M P A C T I O N DIAGRAMS
R.E. R i m a n et al (Rutgers, The S t a t e University of New Jersey, USA), Powder Technology, Vol 79, No 2, 1994, 111-119. An investigation aimed at t h e a u t o m a t i c d e t e r m i n a t i o n of p o w d e r c o m p a c t i o n d i a g r a m s is d e s c r i b e d . The e q u i p m e n t used is described and employs a u t o m a t i c d a t a k)gging of c o m p a c t i o n p a r a m e t e r s . Elastic d e f o r m a t i o n of t h e tooling a n d springback of t h e c o m p a c t are t a k e n into a c c o u n t . The a p p r o a c h is r e p o r t e d to improve the accuracy, take less time a n d to give greater scope for analysis of t h e results t h a n previously used methods.
Sintering D E T E R M I N A T I O N OF P O R E M O B I L I T Y DURING SINTERING
Y. Liu, B.R. Patterson (University of Alabama, Birmingham, Alabama, USA), MetaU. and Mater. Trans. A, Vol 25A, No 1, 1994, 81 87. The mobility of pores, caused by grain b o u n d a r y m o t i o n , d u r i n g s i n t e r i n g is modelled in t e r m s of s h a p e i n d e p e n d e n t microstructural parameters using stereological m e t h o d s . The m o b i l i t y is correlated with grain b o u n d a r y porosity. The m o b i l i t y of p o r e surface diffusion controlled m o t i o n is shown to be inversely p r o p o r t i o n a l to m e a n pore i n t e r c e p t a n d to be i n d e p e n d e n t of pore s h a p e a n d volume
LITERATURE
REVIEW
fraction. It is reported t h a t pore mobility increases in t h e initial stage b u t d i m i n i s h e s as densiflcation proceeds in t h e final stage of sintering. The findings are discussed with respect to grain b o u n d a r y a n d pore surface a r e a c h a n g e s d u r i n g sintering. A N O M A L O U S D I F F U S I O N MASS T R A N S F E R I N I N I T I A L S T A G E OF SINTERING
A.V. Ragulya, V.V. S k o r o k h o d (Inst. for Problems of Materials Science, Kiev, Uk r a i n e ) , Poroshkovaya Metallurgiya, No 12, 1992, 16-20. (In Russian). A d e s c r i p t i o n of a n o m a l o u s surface a n d grain b o u n d a r y diffusion in t h e initial stage of s i n t e r i n g is given, t h e theory is b a s e d on t h e hypothesis t h a t grain b o u n d a r i e s a n d particle surfaces have a fractal geometry. It is s h o w n t h a t grain b o u n d a r y growth, as fractal clusters, results in p a r a m e t e r s in diffusion e q u a t i o n s being six or seven t i m e s g r e a t e r t h a n for surface a n d b o u n d a r y diffusion. S I N T E R I N G VELOCITY IN PARTS S I N T E R E D BY H I G H F R E Q U E N C Y ELECTRIC CURRENTS
V.G. Plekhanov, Poroshkovaya Metallurgiya, No 12, 1992, 96-99. (In Russian). A s t u d y of t h e e f f e c t s o f t i m e , t e m p e r a t u r e a n d frequency of i n d u c t i o n s i n t e r i n g of powders of varying granularity is described. A c o m p u t e r p r o g r a m m e was used to derive a n e q u a t i o n describing t h e velocity of sintering. ISO 9 0 0 1 IN F E R R O U S P O W D E R MANUFACTURE
Y. Trudel, A. G a l i p e a u ( Q u e b e c Metal Powders Ltd, Sorel, Quebec, C a n a d a ) , Int. J. Powder Metallurgy, Vol 30, No 2, 1994, 151-155. The evolution a n d i m p l e m e n t a t i o n of a c o m p r e h e n s i v e Quality Assurance system, w h i c h m e e t s t h e r e q u i r e m e n t s of ISO 9001, is described. ISO 9001, as applied to t h e m a n u f a c t u r e of iron a n d steel powders, is discussed.
Fundamentals A C O N S I D E R A T I O N OF T H E SINTERING PROCESS
W. S c h a t t (Dresden University of Technology, Dresden, Germany), Science of Sintering, Vol 25, No 3, 1993, 99-107. A m e s o s t r u c t u r a l a c c o u n t of sintering is
given on a basis of shrinkage, shrinkage velocity and position lifetime m e a s u r e m e n t s . It is n o t e d t h a t sintering is a very c o m p l e x p r o c e s s a n d t h a t t h e m e c h a n i s m s operating are d e p e n d e n t on t h e technological conditions as well as powder characteristics. The role of crystal defects is considered. Some d a t a is given for Cu, Ni a n d WC-Co. The course of sintering is expressed as partial adhesion and diffusional flow, p a r t i c l e r e a r r a n g e m e n t a n d m a s s t r a n s f e r all of which c o n t r i b u t e to densification. YIELD F U N C T I O N S FOR M E T A L POWDER COMPACTION
S. Brown, G. Abou-Chedid ( M a s s a c h u s e t t s Inst. of Technology, Cambridge, Massachu setts, USA), Sc~ripta Metall. Mater., Vol 28, No 1, 1993, 11 16. An e x p e r i m e n t a l investigation of the c o m p a c t i o n of spherical Cu powders is described. M e a s u r e m e n t s of yield surface t h r o w d o u b t on t h e correctness of c u r r e n t y i e l d f u n c t i o n s w h i c h m a y l e a d to inaccurate p r e d i c a t i o n s of flow behaviour. The model for porous plastic materials c a n n o t be applied to powder compaction. The results are discussed in detail. M A T H E M A T I C A L M O D E L OF ELASTOPLASTIC DEFORMATION M E C H A N I S M OF P O R O U S M A T E R I A L S
A.K. Grigoriev eta al (St Petersburg State Technical University, St Petersburg, Russia), Poroshkovaya Metallurgiya, Nn 12, 1992, 1-10. (In Russian). It is reported t h a t mechanical analogues characterizing t h e deformation of porous m a t e r i a l s h a d b e e n u s e d to c o n s t r u c t general rheological models. E q u a t i o n s for sintered materials are suggested which take into account physico-mechanical properties a n d m a c r o - a n d micro-heterogeneities.
PRODUCTS: Aluminium MATERIAL MECHANICAL MODELLING OF S I N T E R E D A L U M I N I U M ALLOY
H. I s m a r et al (University of the Saar, Sarrbrucken, Germany), Z. Metallkunde, Vol 85, No 4, 1994, 249-255. (In German). It is r e p o r t e d t h a t modelling of the m e c h a n i c a l p r o p e r t i e s of s i n t e r e d A1 l l % Z n - 3 % M g 1.5%Cu 0.6%Mn h a d b e e n c a r r i e d out. D e v e l o p m e n t of t h e yield surface a n d isotropic a n d kinematic work h a r d e n i n g w e r e d e t e r m i n e d for cyclic loading a n d small plastic deformations.
MPR N o v e m b e r 1994 37