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Trouble shooting guide for sintering furnace atmospheres
1
LTigra~ne Pd n~-:a-~4~,~were Droduc~2 by
POWDER PRODUCTION LN'TELLIGENT SENSORS FOR USE LN ATOMIZATION: A REVIEW G Jiang, et al, (Research Inst. Electric Light Source Materials, Nanjing, China), Int J_ PowderMetallu-ryy, Vol 26, No 3, 1990, 253268. T h e p r i n c i p l e s of a t o m i z a t i o n a r e introduced with respect to t h e p a r a m e t e r s which require m e a s u r e m e n t d u r i n g the process to ensure a d e q u a t e control. The most i m p o r t a n t variables are droplet size a n d velocity. Possible i n s t r u m e n t a t i o n for t h e s e m e a s u r e m e n t s is given a n d different types compared. The possibilities include laser diffraction particle analysis, particle counting, sizing a n d velocity m e a s u r e m e n t , p h a s e / D o p p l e r particle analysis, various imaging t e c h n i q u e s for particle sizing a n d infra-red image analysis. Particles may also be s a m p l e d directly by use of a n isokinetic p r o b e w h i c h may be inserted a t any p o i n t in t h e atomized spray. The use of i n s t r u m e n t s for intelligent processing of materials is discussed. P A R A M E T E R S OF CENTRIFUGAL ATOMIZATION ( C A ) OF METAL POWDERS K Haladi, H Suga, J.Japan Soc. Pawcler and PowderMetaUurgy, Vol 37, No 4, 1990, 492499. In Japanese. T h e p a r a m e t e r s of CA h a v e b e e n analysed theoretically. Four m e c h a n i s m s of particle formation are discussed in t h e light of particle size a n d s t o p p i n g distance. The m e c h a n i s m s are direct drop formation, l i g a m e n t formation, film f o r m a t i o n a n d column formation. Mathematical expressions are given relating particle size to disc r o t a t i o n speed a n d d i a m e t e r a n d surface tension, density a n d viscosity of t h e molten metal. P R O D U C T I O N OF ULTRAFINE TiB2 POWDERS K Nishiyama, J.Japan Soc. Powder and PowderAfetallurgy, Vol 37, No 4, 1990, 500507. In J a p a n e s e . The p r o d u c t i o n of u l t r a f i n e TiB., by m a g n e s i u m - t h e r m i c reduction of Ti02 a n d BzO3, in t h e range 500-1000~C a n d in a flow of Ar gas is described. Particles in the size range 0.35-2.5 pm with a plate-like m o r p h o l o g y w e r e p r o d u c e d . T h e TiB.~ p r o d u c e d is a p p r o x i m a t e l y e q u a l t o stoichiometric composition.
GAS EVOLUTION FROM ULTRAFINE Pd POWDERS T Uchikoshi, et al, J. Japan Soc. Pmvder and Powder Metallurgy, Vol 37, No 4, 1990, 508-512. In Japanese.
,d:~q-~a-m#tS reaction r~ehn{uu# ~q~ g~-~ c o n t e n t s of the powders produc~J a n d p,_~wders which had been exposed to -dr were
d~-~_e, - ~ ( t l n e _ ,
by
l~]i~S
~DO('+,roRCODV a n d
CO=e, CO a n d H.e w e r e d e ~ e c t e d . A m e c h a n i s m for ge~ absorption is proposed. PRODUCTION OF METAL POVVDERS BY U%TR.:LSONIC GAS ATOMIZATION W Zolkowski, e t al, ( I n s t y t u t M e t a l i Niezelaznych, Gli,~ce, Poland), Metallurgist Proszkow, No 2, 1990, 49-.54. In Polish. The ultrasonic gas atomization process a n d the H a r t m a n n high frequency shock ~ v e tube are described. CaIculations of gas pressure d i s t r i b u t i o n in the shock ~ a v e t u b e are given. Effects of a t o m i z a t i o n variables on powder sizes are diseussed. Characteristics of the powder with regard to solidification rates are given.
~:LNA.LYSIS AND CONTROL OF GAS ATOMIZATION ILa.TE T .amdo, et al, (Massachusetts Institute of Technology, C a m b r i d g e , M a s s a c h u s e t t s , USA), Int J.Pawder MetaUurgy, Vol 26, No 4, 1990, 311-318. Bernoulli's t h e o r e m has been used to develop a fluid d ) m a m i c s m e t h o d for d e t e r m i n a t i o n of pressure characteristics at the e ~ t of the metal delivery tube during gas atomization. Exit pressures differ from a m b i e n t pressure in confined liquid-gas atomization. A linear ultrasonic gas atomizer was used to study gas atomization with water used as a model m a t e r i a l The usefulness of the method, applied to metal powder making a n d solid preform production, is discussed.
PRESSING A N D SlNTERING . . . . . . . . . . . .
I N F L U E N C E O F SONIC WAVE C H A R A C T E R I S T I C S ON SONIC SIEVLNG EFFICIENCY W Chengyi, et al, (University of Science a n d Technology, Beijing, China), PM Technology, Vol 8, No 3, 1990, 165-169. In Chinese. The effects of sonic wave frequency, pressure, sieve capacity a n d properties of the materials sieved on the efficiency of sieving have been studied. Applications of t h e results are discussed. APPLICATION OF HIGH FREQUENCY ELECTRIC FIELDS TO THE R E D U C T I O N O F FERRIC OXIDE V L Shvartzman, Poroskovaya Metallurgia, No 3, 1990, 1-4. In Russian. It h a s been shown t h a t the application of a high frequency electric field intensifies t h e r e d u c t i o n of Fe20a to metal. It is s u g g e s t e d t h a t t h i s is d u e t o t h e additional energy i n p u t a n d the effect t h a t t h e field h a s on the microporosity of t h e particles. Frequencies of 440kHz a n d a t e m p e r a t u r e r a n g e of 500-7000°C were used. It is r e c o m m e n d e d t h a t t h e reduced product is r e h e a t e d to a higher t e m p e r a t u r e a f t e r reduction, to r e d u c e porosity in t h e m e t a l powder particles. CENTRIFUGAL-PNEUMATIC D I S P E R S I O N OF M E L T S S M S h e i k h a l i e v , e t al, Poroskovaya Metallurgia, No 3, 1990, 4-8. In Russian. A m e t h o d for c e n t r i f u g a l - p n e u m a t i c dispersion of m o l t e n metal is described. Metal a n d gas are supplied to the mixing c h a m b e r a l o n g a t a n g e n t i a l p a t h . The effects of v a r i a t i o n s in t h e e q u i p m e n t design a n d process ~-ariables were studied. It was found t h a t as the gas pressure was increased the powder particle size decreased to a m a x i m u m pressure of 1.01.22 MPa.
IIIII
INFLUENCE OF GRAIN BOUNDARIES IN THE VOLUME REDUCTION IN SINTERING OF SPHERICAL PARTICLES H Yagi, et al, J.Japan Soc. Powder and PawderMetallurgy, Vol 37, No 4, 1990, 526531. In Japanese. Mechanisms of shrinkage in sintering of two-particle spherical systems are discussed. Pairs of particles in t h e size range 45-53 ~m were sintered at 950°C for six hours. I n t e r p e n e t r a t i o n a n d shrinkage between the particles is discussed with reference to three mechanisms: variable or c o n s t a n t i n t e r p e n e t r a t i o n a n d deformation interpenetration, a n d t h e location of the g r a i n b o u n d a r i e s in t h e c o n t a c t zone between the particles.
TROUBLE SHOOTING GUIDE FOR S I N T E R I N G FURNACE A T M O S P H E R E S T Philips, (Airco Industrial Gases, Murray Hill, New Jersey, USA), Int J.Powder Metalturgy, Vol 26, No 3, 1990, 245-250. Practical e x p e r i e n c e s with s i n t e r i n g furnaces are reviewed with reference to N2-based atmospheres. Cause a n d effect relationships for some a t m o s p h e r e - r e l a t e d problems are discussed and possible solutions offered. The i n s t r u m e n t s w h i c h m ~ ~ be used to aid a t m o s p h e r e control are listed. P R O B L E M S IN D E V E L O P M E N T SINTERING FURNACES
OF
H Fenglin, (Beijing PM Co, Beijing, China), PM Technology, Vol 8, No 3, 1990, 170-178. In Chinese. The problems encountered in d e v e l o p m e n t of s i n t e r i n g f u r n a c e s are reviewed including lubricant removal, control of carbon contents in sintering of ferrous materials a n d energy efficiency.
MPR January 1991 49
LTigra~ne Pd n~-:a-~4~,~were Droduc~2 by
POWDER PRODUCTION LN'TELLIGENT SENSORS FOR USE LN ATOMIZATION: A REVIEW G Jiang, et al, (Research Inst. Electric Light Source Materials, Nanjing, China), Int J_ PowderMetallu-ryy, Vol 26, No 3, 1990, 253268. T h e p r i n c i p l e s of a t o m i z a t i o n a r e introduced with respect to t h e p a r a m e t e r s which require m e a s u r e m e n t d u r i n g the process to ensure a d e q u a t e control. The most i m p o r t a n t variables are droplet size a n d velocity. Possible i n s t r u m e n t a t i o n for t h e s e m e a s u r e m e n t s is given a n d different types compared. The possibilities include laser diffraction particle analysis, particle counting, sizing a n d velocity m e a s u r e m e n t , p h a s e / D o p p l e r particle analysis, various imaging t e c h n i q u e s for particle sizing a n d infra-red image analysis. Particles may also be s a m p l e d directly by use of a n isokinetic p r o b e w h i c h may be inserted a t any p o i n t in t h e atomized spray. The use of i n s t r u m e n t s for intelligent processing of materials is discussed. P A R A M E T E R S OF CENTRIFUGAL ATOMIZATION ( C A ) OF METAL POWDERS K Haladi, H Suga, J.Japan Soc. Pawcler and PowderMetaUurgy, Vol 37, No 4, 1990, 492499. In Japanese. T h e p a r a m e t e r s of CA h a v e b e e n analysed theoretically. Four m e c h a n i s m s of particle formation are discussed in t h e light of particle size a n d s t o p p i n g distance. The m e c h a n i s m s are direct drop formation, l i g a m e n t formation, film f o r m a t i o n a n d column formation. Mathematical expressions are given relating particle size to disc r o t a t i o n speed a n d d i a m e t e r a n d surface tension, density a n d viscosity of t h e molten metal. P R O D U C T I O N OF ULTRAFINE TiB2 POWDERS K Nishiyama, J.Japan Soc. Powder and PowderAfetallurgy, Vol 37, No 4, 1990, 500507. In J a p a n e s e . The p r o d u c t i o n of u l t r a f i n e TiB., by m a g n e s i u m - t h e r m i c reduction of Ti02 a n d BzO3, in t h e range 500-1000~C a n d in a flow of Ar gas is described. Particles in the size range 0.35-2.5 pm with a plate-like m o r p h o l o g y w e r e p r o d u c e d . T h e TiB.~ p r o d u c e d is a p p r o x i m a t e l y e q u a l t o stoichiometric composition.
GAS EVOLUTION FROM ULTRAFINE Pd POWDERS T Uchikoshi, et al, J. Japan Soc. Pmvder and Powder Metallurgy, Vol 37, No 4, 1990, 508-512. In Japanese.
,d:~q-~a-m#tS reaction r~ehn{uu# ~q~ g~-~ c o n t e n t s of the powders produc~J a n d p,_~wders which had been exposed to -dr were
d~-~_e, - ~ ( t l n e _ ,
by
l~]i~S
~DO('+,roRCODV a n d
CO=e, CO a n d H.e w e r e d e ~ e c t e d . A m e c h a n i s m for ge~ absorption is proposed. PRODUCTION OF METAL POVVDERS BY U%TR.:LSONIC GAS ATOMIZATION W Zolkowski, e t al, ( I n s t y t u t M e t a l i Niezelaznych, Gli,~ce, Poland), Metallurgist Proszkow, No 2, 1990, 49-.54. In Polish. The ultrasonic gas atomization process a n d the H a r t m a n n high frequency shock ~ v e tube are described. CaIculations of gas pressure d i s t r i b u t i o n in the shock ~ a v e t u b e are given. Effects of a t o m i z a t i o n variables on powder sizes are diseussed. Characteristics of the powder with regard to solidification rates are given.
~:LNA.LYSIS AND CONTROL OF GAS ATOMIZATION ILa.TE T .amdo, et al, (Massachusetts Institute of Technology, C a m b r i d g e , M a s s a c h u s e t t s , USA), Int J.Pawder MetaUurgy, Vol 26, No 4, 1990, 311-318. Bernoulli's t h e o r e m has been used to develop a fluid d ) m a m i c s m e t h o d for d e t e r m i n a t i o n of pressure characteristics at the e ~ t of the metal delivery tube during gas atomization. Exit pressures differ from a m b i e n t pressure in confined liquid-gas atomization. A linear ultrasonic gas atomizer was used to study gas atomization with water used as a model m a t e r i a l The usefulness of the method, applied to metal powder making a n d solid preform production, is discussed.
PRESSING A N D SlNTERING . . . . . . . . . . . .
I N F L U E N C E O F SONIC WAVE C H A R A C T E R I S T I C S ON SONIC SIEVLNG EFFICIENCY W Chengyi, et al, (University of Science a n d Technology, Beijing, China), PM Technology, Vol 8, No 3, 1990, 165-169. In Chinese. The effects of sonic wave frequency, pressure, sieve capacity a n d properties of the materials sieved on the efficiency of sieving have been studied. Applications of t h e results are discussed. APPLICATION OF HIGH FREQUENCY ELECTRIC FIELDS TO THE R E D U C T I O N O F FERRIC OXIDE V L Shvartzman, Poroskovaya Metallurgia, No 3, 1990, 1-4. In Russian. It h a s been shown t h a t the application of a high frequency electric field intensifies t h e r e d u c t i o n of Fe20a to metal. It is s u g g e s t e d t h a t t h i s is d u e t o t h e additional energy i n p u t a n d the effect t h a t t h e field h a s on the microporosity of t h e particles. Frequencies of 440kHz a n d a t e m p e r a t u r e r a n g e of 500-7000°C were used. It is r e c o m m e n d e d t h a t t h e reduced product is r e h e a t e d to a higher t e m p e r a t u r e a f t e r reduction, to r e d u c e porosity in t h e m e t a l powder particles. CENTRIFUGAL-PNEUMATIC D I S P E R S I O N OF M E L T S S M S h e i k h a l i e v , e t al, Poroskovaya Metallurgia, No 3, 1990, 4-8. In Russian. A m e t h o d for c e n t r i f u g a l - p n e u m a t i c dispersion of m o l t e n metal is described. Metal a n d gas are supplied to the mixing c h a m b e r a l o n g a t a n g e n t i a l p a t h . The effects of v a r i a t i o n s in t h e e q u i p m e n t design a n d process ~-ariables were studied. It was found t h a t as the gas pressure was increased the powder particle size decreased to a m a x i m u m pressure of 1.01.22 MPa.
IIIII
INFLUENCE OF GRAIN BOUNDARIES IN THE VOLUME REDUCTION IN SINTERING OF SPHERICAL PARTICLES H Yagi, et al, J.Japan Soc. Powder and PawderMetallurgy, Vol 37, No 4, 1990, 526531. In Japanese. Mechanisms of shrinkage in sintering of two-particle spherical systems are discussed. Pairs of particles in t h e size range 45-53 ~m were sintered at 950°C for six hours. I n t e r p e n e t r a t i o n a n d shrinkage between the particles is discussed with reference to three mechanisms: variable or c o n s t a n t i n t e r p e n e t r a t i o n a n d deformation interpenetration, a n d t h e location of the g r a i n b o u n d a r i e s in t h e c o n t a c t zone between the particles.
TROUBLE SHOOTING GUIDE FOR S I N T E R I N G FURNACE A T M O S P H E R E S T Philips, (Airco Industrial Gases, Murray Hill, New Jersey, USA), Int J.Powder Metalturgy, Vol 26, No 3, 1990, 245-250. Practical e x p e r i e n c e s with s i n t e r i n g furnaces are reviewed with reference to N2-based atmospheres. Cause a n d effect relationships for some a t m o s p h e r e - r e l a t e d problems are discussed and possible solutions offered. The i n s t r u m e n t s w h i c h m ~ ~ be used to aid a t m o s p h e r e control are listed. P R O B L E M S IN D E V E L O P M E N T SINTERING FURNACES
OF
H Fenglin, (Beijing PM Co, Beijing, China), PM Technology, Vol 8, No 3, 1990, 170-178. In Chinese. The problems encountered in d e v e l o p m e n t of s i n t e r i n g f u r n a c e s are reviewed including lubricant removal, control of carbon contents in sintering of ferrous materials a n d energy efficiency.
MPR January 1991 49