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On-line measurements in water atomization process
PM
T h i s will d i s s o l v e a l a r g e n u m b e r of o r g a n i c c o m p o u n d s a n d t h e m e t h o d is rapid, d e b i n d i n g a t h i c k s p e c i m e n in 1 hour. P r o p e r t i e s of CO 2 a n d t h e r m a l l y debound m a t e r i a l s were nearly identical. EVALUATION OF BINDER BURNOUT BY THERMAL ANALYSIS D.Rodrigues, A.P.Tschiptschin. (University of Sao Paulo, Brasil.) Use of differential scanning calorimetry and thermogravimetric a n a l y s i s to e v a l u a t e d e b i n d i n g of injection moulded carbonyl Fe was discussed. A polypropylene-paraffin wax-stearine b i n d e r was used in experiments. Effects of a t m o s p h e r e a n d h e a t i n g r a t e s were studied. Debinding mechanisms were reviewed. MICROWAVE-ASSISTED BINDER DECOMPOSITION
A.Trowley et al. (EA Technology Ltd, UK.) The c r u c i a l n a t u r e of d e b i n d i n g of M I M p a r t s was d i s c u s s e d in t e r m s of p r o d u c t q u a l i t y a n d process t i m e s . It was r e p o r t e d t h a t m i c r o w a v e - a s s i s t e d debinding had been investigated and t h a t this accelerated debinding without loss of p r o d u c t quality. E x a m p l e s were given. C O M P U T E R MODELLING AND OPTIMIZATION OF THERMAL DEBINDING IN POWDER INJECTION MOULDING
O . v a n d e r Biest, A . L . M a x i m e n k o . (Katholic U n i v e r s i t y Leuven, Heverlee, Belgium.) Thermal debinding was reviewed with reference to defect formation due to i n a p p r o p r i a t e h e a t i n g conditions. A model for s i m u l t a n e o u s diffusion, capill a r y flow a n d t h e r m a l d e c o m p o s i t i o n w a s p r e p a r e d . I n t e r n a l s t r e s s e s were considered. An empirical fracture criter i o n w a s s u g g e s t e d a n d safe h e a t i n g regimes were calculated.
Sintering I N F L U E N C E OF B I N D E R ON COS I N T E R I N G OF C O M P O S I T E P A R T S
F . P e t z o l d t et al. ( F r a u n h o f e r I n s t . (IFAM), Germany.) The need for p a r t s c o n t a i n i n g more t h a n one m a t e r i a l was noted. Co-sintering of such a p a r t was discussed. It was shown t h a t s i n t e r i n g of both m a t e r i a l s m u s t t a k e place s i m u l t a n e o u s l y w i t h similar s h r i n k a g e to avoid stresses a n d resultant distortion and defects. Production of a complex p a r t with a tool steel a n d a F e - N i alloy, by i n j e c t i o n moulding, was described.
LITERATURE
REVIEW
LIQUID PHASE SINTERING OF A LOW ALLOY S T E E L P O W D E R
L.Nyborg et al. (Chalmers U n i v e r s i t y of Technology, Sweden.) It was noted t h a t p a r t s s i n t e r e d from coarse powders a n d with low green densities r e q u i r e liquid p h a s e s i n t e r i n g to a t t a i n full d e n s i t y . S t u d i e s of F e - C - P a n d Fe-C-B were described. The compositions used were deduced from thermodynamics. Loose powders were s i n t e r e d in N and initial densities of 40-50% gave s i n t e r e d densities of 70-90%. There was a correlation between sintered density a n d a m o u n t of liquid. O n l y M I M gave densities of 99% for 25% liquid. Pore dist r i b u t i o n was a s s e s s e d from microstructures.
EUROPEAN CONFERENCE ON] A D V A N C E S IN S T R U C T U R A L PM COMPONENT PRODUCTION. The Abstracts that follow are of papers p r e s e n t e d at t h e C o n f e r e n c e , h e l d in M u n i c h , G e r m a n y , in O c t o b e r 1997.
Powder production OPTIMIZATION OF P R O P E R T I E S OF
ATOMIZED HIGH ALLOY S T E E L POWDERS
M.Miskovicova et al. (Slovak A c a d e m y of Sciences, Slovak Republic.) A n investigation of effect of consolid a t i o n a n d t h e r m a l t r e a t m e n t conditions on p r o p e r t i e s of s i n t e r e d high alloy steels was described. Atomized M2 high speed steel powders, optimized for composition a n d solidified in N, were used. Hot powder forging or HIP were used for consolidation. S I N T E R I N G OF I R O N P O W D E R S WITH A D D I T I O N S OF PM S W A R F S
L . E . G . C a m b r o n e r o et al. (Polytechnic U n i v e r s i t y of Madrid, Madrid, Spain.) It w a s r e p o r t e d t h a t PM swarfs, from m a c h i n i n g of PM p a r t s , h a d been u s e d in p r o d u c t i o n of f u r t h e r p a r t s . The s w a r f was c h a r a c t e r i z e d a n d attritor m i l l e d before b l e n d i n g w i t h n e w a t o m i z e d Fe powder. C o n s o l i d a t i o n w a s by die p r e s s i n g a n d s i n t e r i n g in N-5%H at 1150°C. P r o p e r t i e s a n d structure, density and dimensions were evaluated. ON-LINE M E A S U R E M E N T S IN W A T E R ATOMIZATION P R O C E S S
J.Raimann et al. ( L e h r s t u h l ffir S t r S m u n g s m e c h a n i k , Germany.) O n - l i n e m o n i t o r i n g a n d control of w a t e r a t o m i z a t i o n was d i s c u s s e d w i t h r e g a r d to p o w d e r c h a r a c t e r i s t i c s , costs
a n d methods used. Atomizer conditions r e q u i r e u s e of n o n - i n t r u s i v e m e t h o d s . Use of p h a s e / D o p p l e r a n e m o m e t r y for on-line m e a s u r e m e n t of size a n d velocity of particles was described. The technique can d i s t i n g u i s h b e t w e e n m e t a l a n d w a t e r droplets. Problems a n d difficulties were outlined. The m e t h o d was v a l i d a t e d by comparison with sieve t e s t results.
Sintering GAS FORMATION DURING SINTERING OF PM S T E E L S CONTAINING CARBON H.Danninger et al. (Technical University, Vienna, Austria.) Degassing of a r a n g e of 0.8%C steels d u r i n g s i n t e r i n g in a v a c u u m dilatometer was investigated. Degassing occurred during heating and three p e a k s in the gas e v o l u t i o n curve were o b s e r v e d . The first a n d s m a l l e s t was a r o u n d 400°C a n d t h e l a s t close to the t r a n s i t i o n to i s o t h e r m a l s i n t e r i n g . The m o s t p r o n o u n c e d gas e v o l u t i o n p e a k , w i t h oxides of C p r o d u c e d , w a s below the c~ to • t r a n s i t i o n a n d was associated w i t h s h r i n k a g e . This p e a k o c c u r r e d at h i g h e r t e m p e r a t u r e w h e n t h e ~ to y t r a n s i t i o n was e l e v a t e d by alloying. 'ALNAT I' - AN ADVANCED ATMOSPHERE GENERATION SYSTEM FOR S I N T E R I N G
F.Heine et al. (Air Liquide SA, France.) A method for producing N 'on site' for use in h e a t - t r e a t m e n t f u r n a c e s , was described. The process is b a s e d on selective p e r m e a t i o n of a i r g a s e s t h r o u g h polymer filters. N is purified from O by c a t a l y t i c oxidation of a h y d r o c a r b o n to maximize the a m o u n t s of H a n d CO and minimize CO 2 a n d H20. The N was comp a r e d with endogas a n d N-10%H for use in s i n t e r i n g in r e s p e c t of p r o p e r t i e s of t h r e e sintered alloys. The N was reported to be c o m p a r a b l e with N-10%H a n d b e t t e r t h a n endogas. MODIFIED T15 H S S S I N T E R E D TO FULL DENSITY IN NITROGEN-RICH GAS BELOW 1150°C M.M.Oliveira et al. (INETI, Portugal.) A n i n v e s t i g a t i o n of s i n t e r i n g a n d h e a t t r e a t m e n t of T15 HSS, modified by a d d i t i o n of V a n d C, was d e s c r i b e d . W a t e r - a t o m i z e d p o w d e r was u s e d a n d s i n t e r i n g w a s in N - 9 v o l % H - I % C H 4. D e n s i t y of 99% w a s a t t a i n e d below 1150°C. S t r u c t u r e s w e r e d e s c r i b e d . C a r b o n i t r i d e s were formed in the steel. A f t e r oil q u e n c h i n g a n d t e m p e r i n g a p e a k V i c k e r ' s h a r d n e s s of 940 was reached.
MPR April 1998 39
T h i s will d i s s o l v e a l a r g e n u m b e r of o r g a n i c c o m p o u n d s a n d t h e m e t h o d is rapid, d e b i n d i n g a t h i c k s p e c i m e n in 1 hour. P r o p e r t i e s of CO 2 a n d t h e r m a l l y debound m a t e r i a l s were nearly identical. EVALUATION OF BINDER BURNOUT BY THERMAL ANALYSIS D.Rodrigues, A.P.Tschiptschin. (University of Sao Paulo, Brasil.) Use of differential scanning calorimetry and thermogravimetric a n a l y s i s to e v a l u a t e d e b i n d i n g of injection moulded carbonyl Fe was discussed. A polypropylene-paraffin wax-stearine b i n d e r was used in experiments. Effects of a t m o s p h e r e a n d h e a t i n g r a t e s were studied. Debinding mechanisms were reviewed. MICROWAVE-ASSISTED BINDER DECOMPOSITION
A.Trowley et al. (EA Technology Ltd, UK.) The c r u c i a l n a t u r e of d e b i n d i n g of M I M p a r t s was d i s c u s s e d in t e r m s of p r o d u c t q u a l i t y a n d process t i m e s . It was r e p o r t e d t h a t m i c r o w a v e - a s s i s t e d debinding had been investigated and t h a t this accelerated debinding without loss of p r o d u c t quality. E x a m p l e s were given. C O M P U T E R MODELLING AND OPTIMIZATION OF THERMAL DEBINDING IN POWDER INJECTION MOULDING
O . v a n d e r Biest, A . L . M a x i m e n k o . (Katholic U n i v e r s i t y Leuven, Heverlee, Belgium.) Thermal debinding was reviewed with reference to defect formation due to i n a p p r o p r i a t e h e a t i n g conditions. A model for s i m u l t a n e o u s diffusion, capill a r y flow a n d t h e r m a l d e c o m p o s i t i o n w a s p r e p a r e d . I n t e r n a l s t r e s s e s were considered. An empirical fracture criter i o n w a s s u g g e s t e d a n d safe h e a t i n g regimes were calculated.
Sintering I N F L U E N C E OF B I N D E R ON COS I N T E R I N G OF C O M P O S I T E P A R T S
F . P e t z o l d t et al. ( F r a u n h o f e r I n s t . (IFAM), Germany.) The need for p a r t s c o n t a i n i n g more t h a n one m a t e r i a l was noted. Co-sintering of such a p a r t was discussed. It was shown t h a t s i n t e r i n g of both m a t e r i a l s m u s t t a k e place s i m u l t a n e o u s l y w i t h similar s h r i n k a g e to avoid stresses a n d resultant distortion and defects. Production of a complex p a r t with a tool steel a n d a F e - N i alloy, by i n j e c t i o n moulding, was described.
LITERATURE
REVIEW
LIQUID PHASE SINTERING OF A LOW ALLOY S T E E L P O W D E R
L.Nyborg et al. (Chalmers U n i v e r s i t y of Technology, Sweden.) It was noted t h a t p a r t s s i n t e r e d from coarse powders a n d with low green densities r e q u i r e liquid p h a s e s i n t e r i n g to a t t a i n full d e n s i t y . S t u d i e s of F e - C - P a n d Fe-C-B were described. The compositions used were deduced from thermodynamics. Loose powders were s i n t e r e d in N and initial densities of 40-50% gave s i n t e r e d densities of 70-90%. There was a correlation between sintered density a n d a m o u n t of liquid. O n l y M I M gave densities of 99% for 25% liquid. Pore dist r i b u t i o n was a s s e s s e d from microstructures.
EUROPEAN CONFERENCE ON] A D V A N C E S IN S T R U C T U R A L PM COMPONENT PRODUCTION. The Abstracts that follow are of papers p r e s e n t e d at t h e C o n f e r e n c e , h e l d in M u n i c h , G e r m a n y , in O c t o b e r 1997.
Powder production OPTIMIZATION OF P R O P E R T I E S OF
ATOMIZED HIGH ALLOY S T E E L POWDERS
M.Miskovicova et al. (Slovak A c a d e m y of Sciences, Slovak Republic.) A n investigation of effect of consolid a t i o n a n d t h e r m a l t r e a t m e n t conditions on p r o p e r t i e s of s i n t e r e d high alloy steels was described. Atomized M2 high speed steel powders, optimized for composition a n d solidified in N, were used. Hot powder forging or HIP were used for consolidation. S I N T E R I N G OF I R O N P O W D E R S WITH A D D I T I O N S OF PM S W A R F S
L . E . G . C a m b r o n e r o et al. (Polytechnic U n i v e r s i t y of Madrid, Madrid, Spain.) It w a s r e p o r t e d t h a t PM swarfs, from m a c h i n i n g of PM p a r t s , h a d been u s e d in p r o d u c t i o n of f u r t h e r p a r t s . The s w a r f was c h a r a c t e r i z e d a n d attritor m i l l e d before b l e n d i n g w i t h n e w a t o m i z e d Fe powder. C o n s o l i d a t i o n w a s by die p r e s s i n g a n d s i n t e r i n g in N-5%H at 1150°C. P r o p e r t i e s a n d structure, density and dimensions were evaluated. ON-LINE M E A S U R E M E N T S IN W A T E R ATOMIZATION P R O C E S S
J.Raimann et al. ( L e h r s t u h l ffir S t r S m u n g s m e c h a n i k , Germany.) O n - l i n e m o n i t o r i n g a n d control of w a t e r a t o m i z a t i o n was d i s c u s s e d w i t h r e g a r d to p o w d e r c h a r a c t e r i s t i c s , costs
a n d methods used. Atomizer conditions r e q u i r e u s e of n o n - i n t r u s i v e m e t h o d s . Use of p h a s e / D o p p l e r a n e m o m e t r y for on-line m e a s u r e m e n t of size a n d velocity of particles was described. The technique can d i s t i n g u i s h b e t w e e n m e t a l a n d w a t e r droplets. Problems a n d difficulties were outlined. The m e t h o d was v a l i d a t e d by comparison with sieve t e s t results.
Sintering GAS FORMATION DURING SINTERING OF PM S T E E L S CONTAINING CARBON H.Danninger et al. (Technical University, Vienna, Austria.) Degassing of a r a n g e of 0.8%C steels d u r i n g s i n t e r i n g in a v a c u u m dilatometer was investigated. Degassing occurred during heating and three p e a k s in the gas e v o l u t i o n curve were o b s e r v e d . The first a n d s m a l l e s t was a r o u n d 400°C a n d t h e l a s t close to the t r a n s i t i o n to i s o t h e r m a l s i n t e r i n g . The m o s t p r o n o u n c e d gas e v o l u t i o n p e a k , w i t h oxides of C p r o d u c e d , w a s below the c~ to • t r a n s i t i o n a n d was associated w i t h s h r i n k a g e . This p e a k o c c u r r e d at h i g h e r t e m p e r a t u r e w h e n t h e ~ to y t r a n s i t i o n was e l e v a t e d by alloying. 'ALNAT I' - AN ADVANCED ATMOSPHERE GENERATION SYSTEM FOR S I N T E R I N G
F.Heine et al. (Air Liquide SA, France.) A method for producing N 'on site' for use in h e a t - t r e a t m e n t f u r n a c e s , was described. The process is b a s e d on selective p e r m e a t i o n of a i r g a s e s t h r o u g h polymer filters. N is purified from O by c a t a l y t i c oxidation of a h y d r o c a r b o n to maximize the a m o u n t s of H a n d CO and minimize CO 2 a n d H20. The N was comp a r e d with endogas a n d N-10%H for use in s i n t e r i n g in r e s p e c t of p r o p e r t i e s of t h r e e sintered alloys. The N was reported to be c o m p a r a b l e with N-10%H a n d b e t t e r t h a n endogas. MODIFIED T15 H S S S I N T E R E D TO FULL DENSITY IN NITROGEN-RICH GAS BELOW 1150°C M.M.Oliveira et al. (INETI, Portugal.) A n i n v e s t i g a t i o n of s i n t e r i n g a n d h e a t t r e a t m e n t of T15 HSS, modified by a d d i t i o n of V a n d C, was d e s c r i b e d . W a t e r - a t o m i z e d p o w d e r was u s e d a n d s i n t e r i n g w a s in N - 9 v o l % H - I % C H 4. D e n s i t y of 99% w a s a t t a i n e d below 1150°C. S t r u c t u r e s w e r e d e s c r i b e d . C a r b o n i t r i d e s were formed in the steel. A f t e r oil q u e n c h i n g a n d t e m p e r i n g a p e a k V i c k e r ' s h a r d n e s s of 940 was reached.
MPR April 1998 39