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High temperature sintering of stainless steels and soft magnetic materials
properties. Results of a study of t h e e f f e c t s of p r o c e s s c o n d i t i o n s o n physical a n d mechanical properties were p r e s e n t e d a n d d i s c u s s e d for s t e e l s in the h e a t t r e a t e d or sinter h a r d e n e d states. NEW MATERIALS AND OPTIMIZED P R O C E S S E S FOR POWDER FORGED COMPONENTS
E. Eilrich, H. Neubert (Kresbsoge Sinterholding GmbH, Radevormwald, Germany). Powder forging of a u t o m o t i v e p a r t s w a s d i s c u s s e d w i t h c o n s i d e r a t i o n of t h e recent application to t h e p r o d u c t i o n of c o n n e c t i n g rods. It w a s c o n s i d e r e d that powder forging has significant technical a n d economic benefits arising from close d i m e n s i o n a l tolerances, weight reduction a n d e l i m i n a t i o n of machining. It was reported t h a t f u r t h e r i m p r o v e m e n t s m a y be possible in p r o p e r t i e s by h e a t t r e a t m e n t or new alloys.
Delubrication CASE HISTORIES OF DELUBRICATION PROBLEMS IN THE POWDER METALLURGY INDUSTRY
H.S. Nayar (BDC Group, USA). A study of the delubrication of PM c o m p a c t s was d e s c r i b e d . P r o b l e m s arising in t h e case studies, d e p o s i t i o n of soot, d i m e n s i o n a l c o n t r o l , p r o p e r t y changes and environmental emissions, were considered. Characteristics and p r o c e s s c o n d i t i o n s for e a c h p a r t were given. D a t a was analyzed to d e t e r m i n e common factors and variables in delubrication. E F F E C T S OF CHEMISTRY AND COMPACT DENSITY ON DECOMPOSITION OF PM LUBRICANTS
J.N. Aubon, J.S. Choo ( S h a m r o c k Technologies Inc, USA). The decomposition of olefins, b i s t e a r a m i d e s a n d m e t a l s t e a r a t e s was investigated with the objective of establishing relationships between c o m p a c t c h a r a c t e r i s t i c s a n d effects of l u b r i c a n t decomposition. DELUBRICATION OF PM IRONCOPPER-CARBON S T E E L S AND MODELLING
A. Griffo et al (Pennyslvania State University, Pennsylvania, USA). A study of delubrication of low, m e d i u m and high density Fe-2wt%Cu-0.8%C/ Acrawax compacts was described. Heating and cooling rates, dwell time and t e m p e r a t u r e were varied a n d p a r t s were c h a r a c t e r i z e d for d i m e n s i o n s , C a n d O c o n t e n t s a n d presence of soot. The d a t a d e t e r m i n e d was reported to allow more effective a n d efficient delubrication.
40 MPR November 1994
Sintering MODELLING OF PORE SIZE DISTRIBUTION AND E F F E C T ON LIQUID PHASE SINTERING
R.M. G e r m a n et al (Pennsylvania State University, Pennsylvania, USA). Use of c o m p u t e r simulation to model pore size distribution a n d to predict density was d e s c r i b e d for varying p o w d e r size mixtures. The simulations were c o m p a r e d with e x p e r i m e n t a l data. The predicted pore size d i s t r i b u t i o n s were u s e d to m o d e l densification in liquid p h a s e sintering by identifying t h e limiting factors. O p t i m u m p a c k i n g of p a r t i c l e s is p r e d i c t e d for i n t e n d e d microstructures. The implications were discussed. COMPUTER MODELLING AND D E S I G N OF SINTERING FURNACE ATMOSPHERES
T.Philips et al (Airco Bulk Gases, Murray Hill, New Jersey, USA). It was n o t e d t h a t a sintering process may require gases of different c o m p o s i t i o n in different p a r t s of t h e furnace in order to optimize metallurgical requirements. Fluid flow dynamics were modelled numerically with effects of variables incorporated. The c o m p u t e r s i m u l a t i o n s were used to design o p t i m u m s i n t e r i n g a t m o s p h e r e systems. C o m p a r i s o n s were m a d e w i t h e x i s t i n g industrial systems. SCIENTIFIC PRINCIPLES OF HIGH TEMPERATURE SINTERING OF FERROUS MATERIALS
m a d e between low-alloy steels sintered at high a n d conventional t e m p e r a t u r e s a n d m a d e from mixed, partially alloyed a n d prea l l o y e d p o w d e r s . E f f e c t of s i n t e r i n g t e m p e r a t u r e on s t r u c t u r e a n d p r o p e r t i e s were reviewed. D E S I G N I S S U E S IN HIGH T E M P E R A T U R E S I N T E R E D PARTS
H.I. S a n d e r o w ( M a n a g e m e n t a n d Engineering Technologies Inc, Dayton, Ohio, USA). Design issues arising from t h e use of h i g h t e m p e r a t u r e s for s i n t e r i n g w e r e discussed a n d t h e need for t h e designer to u n d e r s t a n d high t e m p e r a t u r e sintering a n d it's effects was e m p h a s i z e d t o g e t h e r with t h e i m p o r t a n c e of good process a n d quality control. It was n o t e d t h a t some form of sizing o p e r a t i o n m a y be needed in p a r t s which s i n t e r to full density. Some p r o b l e m s a n d t h e need to modify process e q u i p m e n t were noted. HIGH T E M P E R A T U R E SINTERING OF STAINLESS S T E E L S AND SOFT MAGNETIC MATERIALS
C. Lall (Midwest Sintered Products Corp, Riverdale, Illinois, USA). Effects of high t e m p e r a t u r e sintering on stainless steels a n d a range of soft m a g n e t i c alloys were described. High t e m p e r a t u r e s i n t e r i n g was s h o w n to m i n i m i z e t h e a b s o r p t i o n of N a n d p r e c i p i t a t i o n of nitrides on cooling a n d to p r o m o t e t h e reduction of oxides which i n h i b i t b o n d i n g of particles. A study of sintering 316L steel and magnetic alloys was described. Properties were correlated with C, N a n d O c o n t e n t s of t h e s i n t e r e d alloys. O p t i m u m process c o n d i t i o n s were d e t e r m i n e d for maximum density and minimum contamination.
R.M. G e r m a n et al (Pennsylvania S t a t e University, Pennsylvania, USA). The scientific principles underlying t h e use of high t e m p e r a t u r e sintering for steels were reviewed. Consideration was given to changes in sintering m e c h a n i s m s arising from t h e increase in t e m p e r a t u r e . It was e m p h a s i z e d t h a t a good u n d e r s t a n d i n g of t h e process is essential to avoid sintering at too high a t e m p e r a t u r e or for too long a time, w i t h c o n s e q u e n t d e g r a d a t i o n in properties. Analysis of t h e r e s p o n s e of steel to sintering at progressively i n c r e a s i n g t e m p e r a t u r e s was p r e s e n t e d w i t h d u e r e g a r d to p r o p e r t i e s . It was shown t h a t i m p r o v e m e n t s in p r o p e r t i e s can be achieved w h e n p r o p e r a t t e n t i o n is given to selection a n d control of p o w d e r characteristics a n d process conditions.
J. Szymorski, J. P r e g o w s k i ( R o t a p r e s s I n t e r n a t i o n a l Inc, C a n a d a ) , The h a r d w a r e for process m o n i t o r i n g a n d control of a rotary cold repressing system, used for sintering preforms, was described. The system was r e p o r t e d to a l l o w c o n t r o l of a n y p a r t of t h e process a n d to enable optimization to be carried out.
HIGH TEMPERATURE SINTERING OF LOW-ALLOY F E R R O U S MATERIALS
GEAR MANUFACTURE USING ROTARY REPRESSING
W.B. J a m e s (Hoeganaes Corp Inc, Riverton, New Jersey, USA). S t r u c t u r e / p r o p e r t y r e l a t i o n s h i p s in sintered steels were discussed with respect to powder properties, alloy composition a n d process conditions. A comparison was
J. Szymborski, J. Pregowski ( R o t a p r e s s I n t e r n a t i o n a l Inc, C a n a d a ) . Rotary repressing was r e p o r t e d to be a n effective m e a n s of fabricating near-nets h a p e c o m p o n e n t s w i t h h i g h densities. The use of t h e t e c h n i q u e for m a n u f a c t u r e
Post sintering operations QUALITY CONTROL THROUGH P R O C E S S MONITORING OF ROTARY FORMING P R E S S
E. Eilrich, H. Neubert (Kresbsoge Sinterholding GmbH, Radevormwald, Germany). Powder forging of a u t o m o t i v e p a r t s w a s d i s c u s s e d w i t h c o n s i d e r a t i o n of t h e recent application to t h e p r o d u c t i o n of c o n n e c t i n g rods. It w a s c o n s i d e r e d that powder forging has significant technical a n d economic benefits arising from close d i m e n s i o n a l tolerances, weight reduction a n d e l i m i n a t i o n of machining. It was reported t h a t f u r t h e r i m p r o v e m e n t s m a y be possible in p r o p e r t i e s by h e a t t r e a t m e n t or new alloys.
Delubrication CASE HISTORIES OF DELUBRICATION PROBLEMS IN THE POWDER METALLURGY INDUSTRY
H.S. Nayar (BDC Group, USA). A study of the delubrication of PM c o m p a c t s was d e s c r i b e d . P r o b l e m s arising in t h e case studies, d e p o s i t i o n of soot, d i m e n s i o n a l c o n t r o l , p r o p e r t y changes and environmental emissions, were considered. Characteristics and p r o c e s s c o n d i t i o n s for e a c h p a r t were given. D a t a was analyzed to d e t e r m i n e common factors and variables in delubrication. E F F E C T S OF CHEMISTRY AND COMPACT DENSITY ON DECOMPOSITION OF PM LUBRICANTS
J.N. Aubon, J.S. Choo ( S h a m r o c k Technologies Inc, USA). The decomposition of olefins, b i s t e a r a m i d e s a n d m e t a l s t e a r a t e s was investigated with the objective of establishing relationships between c o m p a c t c h a r a c t e r i s t i c s a n d effects of l u b r i c a n t decomposition. DELUBRICATION OF PM IRONCOPPER-CARBON S T E E L S AND MODELLING
A. Griffo et al (Pennyslvania State University, Pennsylvania, USA). A study of delubrication of low, m e d i u m and high density Fe-2wt%Cu-0.8%C/ Acrawax compacts was described. Heating and cooling rates, dwell time and t e m p e r a t u r e were varied a n d p a r t s were c h a r a c t e r i z e d for d i m e n s i o n s , C a n d O c o n t e n t s a n d presence of soot. The d a t a d e t e r m i n e d was reported to allow more effective a n d efficient delubrication.
40 MPR November 1994
Sintering MODELLING OF PORE SIZE DISTRIBUTION AND E F F E C T ON LIQUID PHASE SINTERING
R.M. G e r m a n et al (Pennsylvania State University, Pennsylvania, USA). Use of c o m p u t e r simulation to model pore size distribution a n d to predict density was d e s c r i b e d for varying p o w d e r size mixtures. The simulations were c o m p a r e d with e x p e r i m e n t a l data. The predicted pore size d i s t r i b u t i o n s were u s e d to m o d e l densification in liquid p h a s e sintering by identifying t h e limiting factors. O p t i m u m p a c k i n g of p a r t i c l e s is p r e d i c t e d for i n t e n d e d microstructures. The implications were discussed. COMPUTER MODELLING AND D E S I G N OF SINTERING FURNACE ATMOSPHERES
T.Philips et al (Airco Bulk Gases, Murray Hill, New Jersey, USA). It was n o t e d t h a t a sintering process may require gases of different c o m p o s i t i o n in different p a r t s of t h e furnace in order to optimize metallurgical requirements. Fluid flow dynamics were modelled numerically with effects of variables incorporated. The c o m p u t e r s i m u l a t i o n s were used to design o p t i m u m s i n t e r i n g a t m o s p h e r e systems. C o m p a r i s o n s were m a d e w i t h e x i s t i n g industrial systems. SCIENTIFIC PRINCIPLES OF HIGH TEMPERATURE SINTERING OF FERROUS MATERIALS
m a d e between low-alloy steels sintered at high a n d conventional t e m p e r a t u r e s a n d m a d e from mixed, partially alloyed a n d prea l l o y e d p o w d e r s . E f f e c t of s i n t e r i n g t e m p e r a t u r e on s t r u c t u r e a n d p r o p e r t i e s were reviewed. D E S I G N I S S U E S IN HIGH T E M P E R A T U R E S I N T E R E D PARTS
H.I. S a n d e r o w ( M a n a g e m e n t a n d Engineering Technologies Inc, Dayton, Ohio, USA). Design issues arising from t h e use of h i g h t e m p e r a t u r e s for s i n t e r i n g w e r e discussed a n d t h e need for t h e designer to u n d e r s t a n d high t e m p e r a t u r e sintering a n d it's effects was e m p h a s i z e d t o g e t h e r with t h e i m p o r t a n c e of good process a n d quality control. It was n o t e d t h a t some form of sizing o p e r a t i o n m a y be needed in p a r t s which s i n t e r to full density. Some p r o b l e m s a n d t h e need to modify process e q u i p m e n t were noted. HIGH T E M P E R A T U R E SINTERING OF STAINLESS S T E E L S AND SOFT MAGNETIC MATERIALS
C. Lall (Midwest Sintered Products Corp, Riverdale, Illinois, USA). Effects of high t e m p e r a t u r e sintering on stainless steels a n d a range of soft m a g n e t i c alloys were described. High t e m p e r a t u r e s i n t e r i n g was s h o w n to m i n i m i z e t h e a b s o r p t i o n of N a n d p r e c i p i t a t i o n of nitrides on cooling a n d to p r o m o t e t h e reduction of oxides which i n h i b i t b o n d i n g of particles. A study of sintering 316L steel and magnetic alloys was described. Properties were correlated with C, N a n d O c o n t e n t s of t h e s i n t e r e d alloys. O p t i m u m process c o n d i t i o n s were d e t e r m i n e d for maximum density and minimum contamination.
R.M. G e r m a n et al (Pennsylvania S t a t e University, Pennsylvania, USA). The scientific principles underlying t h e use of high t e m p e r a t u r e sintering for steels were reviewed. Consideration was given to changes in sintering m e c h a n i s m s arising from t h e increase in t e m p e r a t u r e . It was e m p h a s i z e d t h a t a good u n d e r s t a n d i n g of t h e process is essential to avoid sintering at too high a t e m p e r a t u r e or for too long a time, w i t h c o n s e q u e n t d e g r a d a t i o n in properties. Analysis of t h e r e s p o n s e of steel to sintering at progressively i n c r e a s i n g t e m p e r a t u r e s was p r e s e n t e d w i t h d u e r e g a r d to p r o p e r t i e s . It was shown t h a t i m p r o v e m e n t s in p r o p e r t i e s can be achieved w h e n p r o p e r a t t e n t i o n is given to selection a n d control of p o w d e r characteristics a n d process conditions.
J. Szymorski, J. P r e g o w s k i ( R o t a p r e s s I n t e r n a t i o n a l Inc, C a n a d a ) , The h a r d w a r e for process m o n i t o r i n g a n d control of a rotary cold repressing system, used for sintering preforms, was described. The system was r e p o r t e d to a l l o w c o n t r o l of a n y p a r t of t h e process a n d to enable optimization to be carried out.
HIGH TEMPERATURE SINTERING OF LOW-ALLOY F E R R O U S MATERIALS
GEAR MANUFACTURE USING ROTARY REPRESSING
W.B. J a m e s (Hoeganaes Corp Inc, Riverton, New Jersey, USA). S t r u c t u r e / p r o p e r t y r e l a t i o n s h i p s in sintered steels were discussed with respect to powder properties, alloy composition a n d process conditions. A comparison was
J. Szymborski, J. Pregowski ( R o t a p r e s s I n t e r n a t i o n a l Inc, C a n a d a ) . Rotary repressing was r e p o r t e d to be a n effective m e a n s of fabricating near-nets h a p e c o m p o n e n t s w i t h h i g h densities. The use of t h e t e c h n i q u e for m a n u f a c t u r e
Post sintering operations QUALITY CONTROL THROUGH P R O C E S S MONITORING OF ROTARY FORMING P R E S S