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Isostatic pressing of balls
PM
Powder production FIELD S T R E N G T H E F F E C T ON POWDER SIZE AND E M I S S M T Y IN ELECTROHYDRODYNAMIC ATOMIZATION
S.I~ Day et al (Inst of Aeronautical Materials, China) Powder Metall Int., Vol 25, No 5, 1993, 224c-226. It is reported that the relationships between field strength, powder sizes and emissivity of powders in the e l e c t r o h y d r o d y n a m i c p r o c e s s , for t h e production of rapidly solidified powders, has been modelled and studied experimentally. SIZE DISTRIBUTION ANALYSIS OF POWDERS
M.H. Poech et al (Max-Planck Inst. for Metals Research, Stuttgart, Germany) Powder Metall Int., Vol 25, No 5, 1993, 233237. A comparison is made between methods for the measurement of powder particle size and size of intersect data into true spatial sizes for s p h e r i c a l p a r t i c l e s a n d fair agreement is reported for gas atomized p o w d e r s . The d i f f e r e n t m e t h o d s are considered to yield comparable results. CAST IRON SWARF -- PROBLEMS AND PM APPLICATION
J.M. Torralba et al (Polytechnic University of Madrid, Madrid, Spain) Revista Metall, Madrid, Vol 29, No 2, 1993, 99-111, In Spanish. A review of the literature concerning the recycling of cast iron swarf in the form of Fe powder is presented. It is noted that the Spanish PM industry makes extensive use of imported powders and that the use of cast iron swarf p r e s e n t s a n u m b e r of problems. It is concluded that cast iron swarf has potential for conversion into PM raw materials. PRODUCTION OF IRON-CHROMIUM POWDERS FROM WASTE S T E E L PICKLING SOLUTIONS AND WASTE FROM CHROMIUM PLATING
S.W. Kang et al (Kong-A University, Pusan, Korea) J. Korean Inst. of Metals, Vol 31, No 4, 1993, 507-515 (In Korean) It is reported that an Fe-Cr powder had been produced from spent steel pickling s o l u t i o n s and Cr p l a t i n g sludge. The solutions were treated with NaOH solution. The hydroxide precipitates were
56 MPR May 1994
LITERATURE
REVIEW
o x i d i z e d to Fe a n d Cr o x i d e s . The oxides were mixed with starch and r e d u c e d to m e t a l , in H, at 1200°C. Metal powders, with a particle size of 23 pm w e r e o b t a i n e d by s u b s e q u e n t grinding. A NOVEL METHOD FOR THE PRODUCTION OF FINELY DIVIDED TIN METAL POWDERS
ALE. Riviello et al (University of Oklahomka, Norman, Oklahomka, USA) Powder .Technology, Vol 78, No 1, 1994, 19-24. A centrifugal technique for the production o f f i n e Sn p o w d e r s is described. A high rotor speed, 6000 to 11 500 rpm, is said to result in gas e n t r a i n m e n t in the molten metal. The m e a n p a r t i c l e size is 5 9 m a n d t h e powders are reported to be spherical. The yield of powder is shown to increase with temperature of the molten metal.
Pressing ISOSTATIC P R E S S I N G OF BALLS
Amon (Frey GmbH, Lenggries-Fleck, Germany) Powder Metall Int., Vol 25, No 5, 1993, 238-239. Use of wet and dry bag tools for isostatic pressing of grinding mill balls is described. R e q u i r e m e n t of g r i n d i n g b o d i e s a r e outlined and it is shown that these are met by isostatically pressed balls when process parameters are optimized.
D E S I G N OF AUTOMATIC DIE J I G S FOR PRODUCTS WITH MULTIPLE S T A G E S
I~ Zhoushuang, (Chuangde Textile Machinery Factory, Hunan, China.) PM Technology, Vol 11, No 1, 1993, 25-27. (In Chinese). Structure features, operating procedures, applications of an automatic die and die filling apparatus for multi-stage parts, u s e d in a 6000 kN p r e s s are described.
CONSIDERATIONS ON THE KAWAKITA COMPACTION EQUATION
R. Ge (Central South University of Technology, Changsha, Hunan, China) Powder Metallurgy Science and Technology, Vol 4, No 2, 1993, 15-23. An experimental analysis of the validity of t h e p o w d e r c o m p a c t i o n e q u a t i o n p r o p o s e d by Kawakita is presented. It is s h o w n t h a t t h e d e v i a t i o n of t h e
experimental result from those predicted can be m o r e e f f e c t i v e l y t e s t e d by a l i n e a r c o r r e l a t i o n c o e f f i c i e n t of t h e relationship between the reciprocals of the degree of volume reduction, C, and the compaction pressure, P, rather than t h e r e l a t i o n s h i p b e t w e e n P/C a n d P. The physical significance of the constants in the Kawakita equation are discussed a n d a n e w c o m p a c t i o n e q u a t i o n is proposed which gives improved agreement with experimental data. PACKING D E N S I F I C A T I O N A N D MICROSTRUCTURAL E F F E C T S IN HOT ISOSTATIC P R E S S I N G OF POWDER MIXTURES A N D C O M P O S I T E S
E.K.H. Li, P.D. Funkenbusch, (University of Rochester, New York, USA) Metallurgical Trans, A, Vol 24A, No 6, 1993, 1345-1354. HIP of powder, mixtures with different sized constituents is a n a l y z e d a n d d i s c u s s e d w i t h r e s p e c t to m o d e l s . Experimentally, it is shown that powders densify to greater density with a range of particle sizes t h a n w h e n monosized powders are used. This is i n t e r p r e t e d with reference to models and is partly a t t r i b u t e d to h i g h e r i n i t i a l p a c k i n g density. The models also predict greater d e f o r m a t i o n of s m a l l e r p a r t i c l e s in a m i x t u r e a n d t h i s is c o n f i r m e d by preferential recrystallization. Composites containing hard but deformable particles a r e also c o n s i d e r e d . D e n s i f i c a t i o n is reported to be inhibited by the presence of hard particles and greater deformation of the matrix is noted.
UNIAXIAL C O M P R E S S I O N OF S I N T E R E D POROUS ALLOY S T E E L PREFORMS AT AMBIENT AND ELEVATED T E M P E R A T U R E S
H.K. Cho et al (Ponhang Inst. of Science and Technology, Pohang, Korea) J. Korean Inst. of Metals, Vol 31, No 4, 1993, 516525, (In Korean). Responses to deformation and d e n s i f i c a t i o n of s i n t e r e d a l l o y s t e e l preforms were investigated with respect to initial density, temperature and strain rate. It is reported the modelling, using published yield function data, did not agree with the e x p e r i m e n t a l results. A new yield function, based on Kim's yield system, is shown to fit the experimental data for cyclindrical specimens. Comparisons are made with finite element method simulations using the proposed y i e l d f u n c t i o n a n d t h o s e of S h i m a and Oyane.
Powder production FIELD S T R E N G T H E F F E C T ON POWDER SIZE AND E M I S S M T Y IN ELECTROHYDRODYNAMIC ATOMIZATION
S.I~ Day et al (Inst of Aeronautical Materials, China) Powder Metall Int., Vol 25, No 5, 1993, 224c-226. It is reported that the relationships between field strength, powder sizes and emissivity of powders in the e l e c t r o h y d r o d y n a m i c p r o c e s s , for t h e production of rapidly solidified powders, has been modelled and studied experimentally. SIZE DISTRIBUTION ANALYSIS OF POWDERS
M.H. Poech et al (Max-Planck Inst. for Metals Research, Stuttgart, Germany) Powder Metall Int., Vol 25, No 5, 1993, 233237. A comparison is made between methods for the measurement of powder particle size and size of intersect data into true spatial sizes for s p h e r i c a l p a r t i c l e s a n d fair agreement is reported for gas atomized p o w d e r s . The d i f f e r e n t m e t h o d s are considered to yield comparable results. CAST IRON SWARF -- PROBLEMS AND PM APPLICATION
J.M. Torralba et al (Polytechnic University of Madrid, Madrid, Spain) Revista Metall, Madrid, Vol 29, No 2, 1993, 99-111, In Spanish. A review of the literature concerning the recycling of cast iron swarf in the form of Fe powder is presented. It is noted that the Spanish PM industry makes extensive use of imported powders and that the use of cast iron swarf p r e s e n t s a n u m b e r of problems. It is concluded that cast iron swarf has potential for conversion into PM raw materials. PRODUCTION OF IRON-CHROMIUM POWDERS FROM WASTE S T E E L PICKLING SOLUTIONS AND WASTE FROM CHROMIUM PLATING
S.W. Kang et al (Kong-A University, Pusan, Korea) J. Korean Inst. of Metals, Vol 31, No 4, 1993, 507-515 (In Korean) It is reported that an Fe-Cr powder had been produced from spent steel pickling s o l u t i o n s and Cr p l a t i n g sludge. The solutions were treated with NaOH solution. The hydroxide precipitates were
56 MPR May 1994
LITERATURE
REVIEW
o x i d i z e d to Fe a n d Cr o x i d e s . The oxides were mixed with starch and r e d u c e d to m e t a l , in H, at 1200°C. Metal powders, with a particle size of 23 pm w e r e o b t a i n e d by s u b s e q u e n t grinding. A NOVEL METHOD FOR THE PRODUCTION OF FINELY DIVIDED TIN METAL POWDERS
ALE. Riviello et al (University of Oklahomka, Norman, Oklahomka, USA) Powder .Technology, Vol 78, No 1, 1994, 19-24. A centrifugal technique for the production o f f i n e Sn p o w d e r s is described. A high rotor speed, 6000 to 11 500 rpm, is said to result in gas e n t r a i n m e n t in the molten metal. The m e a n p a r t i c l e size is 5 9 m a n d t h e powders are reported to be spherical. The yield of powder is shown to increase with temperature of the molten metal.
Pressing ISOSTATIC P R E S S I N G OF BALLS
Amon (Frey GmbH, Lenggries-Fleck, Germany) Powder Metall Int., Vol 25, No 5, 1993, 238-239. Use of wet and dry bag tools for isostatic pressing of grinding mill balls is described. R e q u i r e m e n t of g r i n d i n g b o d i e s a r e outlined and it is shown that these are met by isostatically pressed balls when process parameters are optimized.
D E S I G N OF AUTOMATIC DIE J I G S FOR PRODUCTS WITH MULTIPLE S T A G E S
I~ Zhoushuang, (Chuangde Textile Machinery Factory, Hunan, China.) PM Technology, Vol 11, No 1, 1993, 25-27. (In Chinese). Structure features, operating procedures, applications of an automatic die and die filling apparatus for multi-stage parts, u s e d in a 6000 kN p r e s s are described.
CONSIDERATIONS ON THE KAWAKITA COMPACTION EQUATION
R. Ge (Central South University of Technology, Changsha, Hunan, China) Powder Metallurgy Science and Technology, Vol 4, No 2, 1993, 15-23. An experimental analysis of the validity of t h e p o w d e r c o m p a c t i o n e q u a t i o n p r o p o s e d by Kawakita is presented. It is s h o w n t h a t t h e d e v i a t i o n of t h e
experimental result from those predicted can be m o r e e f f e c t i v e l y t e s t e d by a l i n e a r c o r r e l a t i o n c o e f f i c i e n t of t h e relationship between the reciprocals of the degree of volume reduction, C, and the compaction pressure, P, rather than t h e r e l a t i o n s h i p b e t w e e n P/C a n d P. The physical significance of the constants in the Kawakita equation are discussed a n d a n e w c o m p a c t i o n e q u a t i o n is proposed which gives improved agreement with experimental data. PACKING D E N S I F I C A T I O N A N D MICROSTRUCTURAL E F F E C T S IN HOT ISOSTATIC P R E S S I N G OF POWDER MIXTURES A N D C O M P O S I T E S
E.K.H. Li, P.D. Funkenbusch, (University of Rochester, New York, USA) Metallurgical Trans, A, Vol 24A, No 6, 1993, 1345-1354. HIP of powder, mixtures with different sized constituents is a n a l y z e d a n d d i s c u s s e d w i t h r e s p e c t to m o d e l s . Experimentally, it is shown that powders densify to greater density with a range of particle sizes t h a n w h e n monosized powders are used. This is i n t e r p r e t e d with reference to models and is partly a t t r i b u t e d to h i g h e r i n i t i a l p a c k i n g density. The models also predict greater d e f o r m a t i o n of s m a l l e r p a r t i c l e s in a m i x t u r e a n d t h i s is c o n f i r m e d by preferential recrystallization. Composites containing hard but deformable particles a r e also c o n s i d e r e d . D e n s i f i c a t i o n is reported to be inhibited by the presence of hard particles and greater deformation of the matrix is noted.
UNIAXIAL C O M P R E S S I O N OF S I N T E R E D POROUS ALLOY S T E E L PREFORMS AT AMBIENT AND ELEVATED T E M P E R A T U R E S
H.K. Cho et al (Ponhang Inst. of Science and Technology, Pohang, Korea) J. Korean Inst. of Metals, Vol 31, No 4, 1993, 516525, (In Korean). Responses to deformation and d e n s i f i c a t i o n of s i n t e r e d a l l o y s t e e l preforms were investigated with respect to initial density, temperature and strain rate. It is reported the modelling, using published yield function data, did not agree with the e x p e r i m e n t a l results. A new yield function, based on Kim's yield system, is shown to fit the experimental data for cyclindrical specimens. Comparisons are made with finite element method simulations using the proposed y i e l d f u n c t i o n a n d t h o s e of S h i m a and Oyane.