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Copper segragation in PM parts
PM
LITERATURE
REVIEW
Diffusion bonding and particulates
r e p o r t e d to have a tensile s t r e n g t h of 270 MPa with 39% elongation . . . . . .
E F F E C T S OF CYCLIC HEATING ON DIFFUSION BONDING OF STEEL POWDERS
......... ~ .....
High temperature sintering
D.W. Walsh et al (California Polytechnic State University, California, USA). An i n v e s t i g a t i o n of t h e e f f e c t s of m e t h o d s of heating, in which t h e r m a l l y cycled s p e c i m e n s were c o m p a r e d w i t h isothermally treated samples, was described. Image analysis w a s used to study microstructures. Pore area fraction, pore size distribution, pore s h a p e factors a n d grain sizes were d e t e r m i n e d from which t h e e x t e n t of b o n d i n g w a s d e d u c e d . Diffusion b o n d i n g was r e p o r t e d to be markedly e n h a n c e d by t h e r m a l cycling a n d the effect was e x p l a i n e d on t h e basis of a u g m e n t e d diffusion c a u s e d by t h e r m a l gradients, stress gradients, interphase interface creation and phase transformations. C O P P E R S E G R E G A T I O N IN PM PARTS
"
P R O C E S S I N G T E C H N I Q U E S FOR H I G H T E M P E R A T U R E S I N T E R I N G OF P E R M A N E N T MAGNET MATERIALS R.R. Taylor, D.H. Herring (Arnold Engineering Co., Marrengo, Illinois, USA). A c o m p a r i s o n was m a d e of b a t c h a n d continuous methods for processing magnetic materials with respect to p r e d i c t i o n a n d control of v a r i a t i o n s in p r o p e r t i e s of t h e p r o d u c t s . Effects of p r o c e s s v a r i a b l e s were i n v e s t i g a t e d in o r d e r to develop t h e o p t i m u m conditions for alloys of t h e ALNICO series. E q u i p m e n t design r e q u i r e m e n t s for m a s s p r o d u c t i o n of m a g n e t i c sensors, using high t e m p e r a t u r e sintering, a n d t h e economic aspects were reviewed. E F F E C T S OF S I N T E R I N G TEMPERATURE AND ATMOSPHERE ON SOFT MAGNETIC P R O P E R T I E S OF PM MATERIALS
K.H. L i n d e r et al ( M a n n e s m a n n Demag Pulvermetall, Ohlerkirchweg, Germany). A t t e n t i o n was d r a w n to t h e fact t h a t segregation of alloy elements, Cu, Ni a n d Mo, in PM steel prior to sintering can result in reduced d i m e n s i o n a l stability a n d t h a t this can be minimized by t h e use of Fe p o w d e r w i t h d i f f u s i o n b o n d e d Cu. A c o m p a r i s o n of specimens m a d e from Cu diffusion b o n d e d Fe powders a n d e l e m e n t a l powders was reported. Ring s p e c i m e n s were fabricated and dimensions a n d Cu distribution were measured. It was r e p o r t e d t h a t t h e s t a n d a r d deviations of inner and outer ring diameters were reduced by 70% for t h e s p e c i m e n s m a d e from the diffusion bonded powder compared with the elemental powder mixtures.
C. Lall (Midwest Sintered Products Corporation, Riverdale, Illinois, USA). The properties of soft magnetic materials, m a d e by PM, were discussed as a function of i m p u r i t y levels, density a n d sintering conditions. An investigation of t h e effects of wide range of sintering practice on t h e soft m a g n e t i c p r o p e r t i e s of Fe, Fe-0.45% P, Fe-3%Si, Fe-50%Ni a n d 410L stainless steel was described. The p r o p e r t i e s were correlated with O a n d N c o n t e n t s a n d dew p o i n t s of t h e sintering a t m o s p h e r e s a n d t h e C, O, a n d N c o n t e n t s of t h e s i n t e r e d alloys a n d t h e m i c r o s t r u c t u r e s . For best soft magnetic performance it was shown t h a t density a n d sintering t e m p e r a t u r e should be m a x i m i z e d a n d c o n t a m i n a t i o n by O, N a n d C should be minimized.
PREPARATION AND PROPERTIES OF IRON-NICKEL BI-METALLIC STRIP MADE BY A PM ROUTE
P R O P E R T I E S OF F E R R O U S ALLOYS S I N T E R E D USING A HIGH T E M P E R A T U R E S I N T E R I N G FURNACE WITH A CERAMIC BELT
R.K. Dube, B.N. S i n g h ( I n d i a n Inst. of Technology, Kanpur, India). The p r o d u c t i o n of a n Fe-Ni bi-metallic strip from powders was described. Free flowing slurries of Fe a n d Ni powders were prepared. The Fe slurry was d e p o s i t e d on a s u b s t r a t e a n d d r i e d a n d t h e Ni slurry applied. After drying a n d sintering, a t 1000°C, a n d hot roiling a t 1150°C a fully dense strip was produced. The effects of p r o c e s s p a r a m e t e r s on p r o p e r t i e s a n d s t r u c t u r e of t h e strip a n d a m e c h a n i s m for densification were discussed. The strip with a n Fe to Ni thickness ratio of 5 to 1 was
H.I. Sanderow, B. Cole ( M a n a g e m e n t a n d E n g i n e e r i n g Technologies, Dayton, Ohio, USA). The use of a high t e m p e r a t u r e sintering furnace with a ceramic belt was discussed with regard to ferrous materials. A test programme of sintering, at high t e m p e r a t u r e s , a range of low alloy steels, stainless steel a n d soft m a g n e t i c m a t e r i a l s was described. The properties of t h e s e were c o m p a r e d with p u b l i s h e d d a t a for similar materials. The cost effectiveness of t h e ceramic belt furnace was discussed.
58 MPR October 1992
Sintering atmospheres .
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CARBON CONTROL FOR S I N T E R I N G ATMOSPHERES M.A. Philips, M. R e n o w d e n ( L i q u i d Air Corp, Countryside, Illinois, USA). The effects of furnace a t m o s p h e r e on c a r b u r i z a t i o n or d e c a r b u r i z a t i o n d u r i n g t h e sintering of steel were discussed. In a n i n v e s t i g a t i o n t h e r m o g r a v i m e t r i c analysis (TGA) was used to quantify C t r a n s f e r between c o m p a c t s a n d furnace a t m o s p h e r e u n d e r a range of sintering conditions. It was r e p o r t e d t h a t it was now possible to control C c o n t e n t to -{-0.05% by use of synthetic gases a n d analysis of furnace a t m o s p h e r e s . COMPARATIVE S T U D I E S OF PM LUBRICANTS U N D E R D I F F E R E N T ATMOSPHERES J. Dwyer et al (Airco I n d u s t r i a l Gases, Murray Hill, New Jersey, USA). The use of t h e r m o g r a v i m e t r i c analysis (TGA) to s t u d y t h e b e h a v i o u r of PM l u b r i c a n t s d u r i n g sintering was described. V o l a t i l i z a t i o n a n d r e a c t i o n s in varying a t m o s p h e r e s w a s i n v e s t i g a t e d . It was suggested that the study provided an improved u n d e r s t a n d i n g of l u b r i c a n t s a n d t h a t t h e results could be used to design more effective a n d t h o r o u g h delubricating a t m o s p h e r e s a n d systems. N I T R O G E N PICK-UP DURING S I N T E R I N G OF S T A I N L E S S STEEL N. Frisk et al (Swedish Inst. for Metals Research, Stockholm, Sweden). The c o n t a m i n a t i o n of stainless steel by N from s i n t e r i n g a t m o s p h e r e s a n d t h e effects of N were discussed. Some effects s u c h as solid s o l u t i o n h a r d e n i n g were b e n e f i c i a l b u t o t h e r s , p r e c i p i t a t i o n of nitrides, were d e t r i m e n t a l . In the work described 316L stainless steel was sintered u n d e r a range of conditions a n d the up-take of N determined. The m e a s u r e d N c o n t e n t s were correlated with thermodynamic calculations. The results were said to be u s a b l e for t h e p r e d i c t i o n of s i n t e r i n g conditions.
Ferrous mechanical properties E F F E C T S OF ALLOYING M E T H O D S ON THE MICROSTRUCTURE AND P R O P E R T I E S OF PM S T E E L S J. Tengzelius, I~S. N a r a s i m h a m , (HSganas AB, HSganas, Sweden). Alloying methods u s e d in PM,
LITERATURE
REVIEW
Diffusion bonding and particulates
r e p o r t e d to have a tensile s t r e n g t h of 270 MPa with 39% elongation . . . . . .
E F F E C T S OF CYCLIC HEATING ON DIFFUSION BONDING OF STEEL POWDERS
......... ~ .....
High temperature sintering
D.W. Walsh et al (California Polytechnic State University, California, USA). An i n v e s t i g a t i o n of t h e e f f e c t s of m e t h o d s of heating, in which t h e r m a l l y cycled s p e c i m e n s were c o m p a r e d w i t h isothermally treated samples, was described. Image analysis w a s used to study microstructures. Pore area fraction, pore size distribution, pore s h a p e factors a n d grain sizes were d e t e r m i n e d from which t h e e x t e n t of b o n d i n g w a s d e d u c e d . Diffusion b o n d i n g was r e p o r t e d to be markedly e n h a n c e d by t h e r m a l cycling a n d the effect was e x p l a i n e d on t h e basis of a u g m e n t e d diffusion c a u s e d by t h e r m a l gradients, stress gradients, interphase interface creation and phase transformations. C O P P E R S E G R E G A T I O N IN PM PARTS
"
P R O C E S S I N G T E C H N I Q U E S FOR H I G H T E M P E R A T U R E S I N T E R I N G OF P E R M A N E N T MAGNET MATERIALS R.R. Taylor, D.H. Herring (Arnold Engineering Co., Marrengo, Illinois, USA). A c o m p a r i s o n was m a d e of b a t c h a n d continuous methods for processing magnetic materials with respect to p r e d i c t i o n a n d control of v a r i a t i o n s in p r o p e r t i e s of t h e p r o d u c t s . Effects of p r o c e s s v a r i a b l e s were i n v e s t i g a t e d in o r d e r to develop t h e o p t i m u m conditions for alloys of t h e ALNICO series. E q u i p m e n t design r e q u i r e m e n t s for m a s s p r o d u c t i o n of m a g n e t i c sensors, using high t e m p e r a t u r e sintering, a n d t h e economic aspects were reviewed. E F F E C T S OF S I N T E R I N G TEMPERATURE AND ATMOSPHERE ON SOFT MAGNETIC P R O P E R T I E S OF PM MATERIALS
K.H. L i n d e r et al ( M a n n e s m a n n Demag Pulvermetall, Ohlerkirchweg, Germany). A t t e n t i o n was d r a w n to t h e fact t h a t segregation of alloy elements, Cu, Ni a n d Mo, in PM steel prior to sintering can result in reduced d i m e n s i o n a l stability a n d t h a t this can be minimized by t h e use of Fe p o w d e r w i t h d i f f u s i o n b o n d e d Cu. A c o m p a r i s o n of specimens m a d e from Cu diffusion b o n d e d Fe powders a n d e l e m e n t a l powders was reported. Ring s p e c i m e n s were fabricated and dimensions a n d Cu distribution were measured. It was r e p o r t e d t h a t t h e s t a n d a r d deviations of inner and outer ring diameters were reduced by 70% for t h e s p e c i m e n s m a d e from the diffusion bonded powder compared with the elemental powder mixtures.
C. Lall (Midwest Sintered Products Corporation, Riverdale, Illinois, USA). The properties of soft magnetic materials, m a d e by PM, were discussed as a function of i m p u r i t y levels, density a n d sintering conditions. An investigation of t h e effects of wide range of sintering practice on t h e soft m a g n e t i c p r o p e r t i e s of Fe, Fe-0.45% P, Fe-3%Si, Fe-50%Ni a n d 410L stainless steel was described. The p r o p e r t i e s were correlated with O a n d N c o n t e n t s a n d dew p o i n t s of t h e sintering a t m o s p h e r e s a n d t h e C, O, a n d N c o n t e n t s of t h e s i n t e r e d alloys a n d t h e m i c r o s t r u c t u r e s . For best soft magnetic performance it was shown t h a t density a n d sintering t e m p e r a t u r e should be m a x i m i z e d a n d c o n t a m i n a t i o n by O, N a n d C should be minimized.
PREPARATION AND PROPERTIES OF IRON-NICKEL BI-METALLIC STRIP MADE BY A PM ROUTE
P R O P E R T I E S OF F E R R O U S ALLOYS S I N T E R E D USING A HIGH T E M P E R A T U R E S I N T E R I N G FURNACE WITH A CERAMIC BELT
R.K. Dube, B.N. S i n g h ( I n d i a n Inst. of Technology, Kanpur, India). The p r o d u c t i o n of a n Fe-Ni bi-metallic strip from powders was described. Free flowing slurries of Fe a n d Ni powders were prepared. The Fe slurry was d e p o s i t e d on a s u b s t r a t e a n d d r i e d a n d t h e Ni slurry applied. After drying a n d sintering, a t 1000°C, a n d hot roiling a t 1150°C a fully dense strip was produced. The effects of p r o c e s s p a r a m e t e r s on p r o p e r t i e s a n d s t r u c t u r e of t h e strip a n d a m e c h a n i s m for densification were discussed. The strip with a n Fe to Ni thickness ratio of 5 to 1 was
H.I. Sanderow, B. Cole ( M a n a g e m e n t a n d E n g i n e e r i n g Technologies, Dayton, Ohio, USA). The use of a high t e m p e r a t u r e sintering furnace with a ceramic belt was discussed with regard to ferrous materials. A test programme of sintering, at high t e m p e r a t u r e s , a range of low alloy steels, stainless steel a n d soft m a g n e t i c m a t e r i a l s was described. The properties of t h e s e were c o m p a r e d with p u b l i s h e d d a t a for similar materials. The cost effectiveness of t h e ceramic belt furnace was discussed.
58 MPR October 1992
Sintering atmospheres .
.
.
.
.
.
.
.
.
CARBON CONTROL FOR S I N T E R I N G ATMOSPHERES M.A. Philips, M. R e n o w d e n ( L i q u i d Air Corp, Countryside, Illinois, USA). The effects of furnace a t m o s p h e r e on c a r b u r i z a t i o n or d e c a r b u r i z a t i o n d u r i n g t h e sintering of steel were discussed. In a n i n v e s t i g a t i o n t h e r m o g r a v i m e t r i c analysis (TGA) was used to quantify C t r a n s f e r between c o m p a c t s a n d furnace a t m o s p h e r e u n d e r a range of sintering conditions. It was r e p o r t e d t h a t it was now possible to control C c o n t e n t to -{-0.05% by use of synthetic gases a n d analysis of furnace a t m o s p h e r e s . COMPARATIVE S T U D I E S OF PM LUBRICANTS U N D E R D I F F E R E N T ATMOSPHERES J. Dwyer et al (Airco I n d u s t r i a l Gases, Murray Hill, New Jersey, USA). The use of t h e r m o g r a v i m e t r i c analysis (TGA) to s t u d y t h e b e h a v i o u r of PM l u b r i c a n t s d u r i n g sintering was described. V o l a t i l i z a t i o n a n d r e a c t i o n s in varying a t m o s p h e r e s w a s i n v e s t i g a t e d . It was suggested that the study provided an improved u n d e r s t a n d i n g of l u b r i c a n t s a n d t h a t t h e results could be used to design more effective a n d t h o r o u g h delubricating a t m o s p h e r e s a n d systems. N I T R O G E N PICK-UP DURING S I N T E R I N G OF S T A I N L E S S STEEL N. Frisk et al (Swedish Inst. for Metals Research, Stockholm, Sweden). The c o n t a m i n a t i o n of stainless steel by N from s i n t e r i n g a t m o s p h e r e s a n d t h e effects of N were discussed. Some effects s u c h as solid s o l u t i o n h a r d e n i n g were b e n e f i c i a l b u t o t h e r s , p r e c i p i t a t i o n of nitrides, were d e t r i m e n t a l . In the work described 316L stainless steel was sintered u n d e r a range of conditions a n d the up-take of N determined. The m e a s u r e d N c o n t e n t s were correlated with thermodynamic calculations. The results were said to be u s a b l e for t h e p r e d i c t i o n of s i n t e r i n g conditions.
Ferrous mechanical properties E F F E C T S OF ALLOYING M E T H O D S ON THE MICROSTRUCTURE AND P R O P E R T I E S OF PM S T E E L S J. Tengzelius, I~S. N a r a s i m h a m , (HSganas AB, HSganas, Sweden). Alloying methods u s e d in PM,