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Compactibility of porous sintered billets during triaxial deformation
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Powder production DECARBURIZATION OF R E D U C E D IRON POWDERS
S-W. Du et al China Steel Technical Reports,
1992, 156-161. The decarburization of Fe powder, made by reduction of mill scale by heating at 690 to 850°C in H-25at%N, is described. The optimum temperature for decarburization decreases with reduction in C content. Effect of O in the powders is to increase decarburization rate in the reduced Fe powder. PREPARATION OF TITANIUM CARBIDE FROM TITANIUM OXIDE BY SELF PROPAGATING HIGH TEMPERATURE SYNTHESIS
B.S. Kang et al (National University, Daejeon, Korea), J. Korean Inst. of Metals,
Vol 31, No 5, 1993, 599-605. (In Korean). It is reported that TiC powder had been prepared from SiO 2 by self combustion in presence of Mg and C. Controlling factors are said to be concentrations of Mg and C and the time of mixing, MgO and residual Mg are removed by leaching with HC1. Particles are reported to be spherical and 0.3 to 0.4 I~m in size, with a narrow range of sizes and 99.9% purity. THERMAL DECOMPOSITION OF AMMONIUM PARATUNGSTATE
Y. Yamanoto et al (Tokyo Tungsten Co, Toyama, Japan) J. Japan Soc. Powder and
Powder Metallurgy, Vol 40, No 6, 1993, 609-613. (In Japanese). Studies of the thermal decomposition of APT are described. Thermogravimetric analysis in a N atmosphere was used and very fine grained W oxide was the product. The process is shown to take place in stages forming amorphous phases, hexagonal tungsten bronze and monoclinic WOa in ultrafine particles. PREPARATION AND SINTERING OF T U N G S T E N POWDER WITH D I S P E R S E D RARE EARTHS BY SPRAY DRYING
IC Koyama, M. Morishita, (Himeji Inst. of Technology, Himeji, Japan), J. Japan Soc.
Powder and Powder Metallurgy, Vol 40, No 7, 1993, 707-712. (In Japanese). It is reported that W powder with rare earth dispersoids can be produced by spray drying of an acetic acid solution of ammonium tungstate para pentahydrate and l a n t h a n u m oxide, pyrolysis and reduction. The La203 is shown to be
48 MPR September 1994
LITERATURE
REVIEW
dispersed in the sintered W in finer particles than is the case with blended powders. EVALUATION OF ATOMIZATION BY THE RAPIDLY S P I N N I N G CUP P R O C E S S
ICP. Cooper, J.D. Ayres, (Naval Research Laboratory, Washington DC, USA), Int. J.
Powder Metallur~, Vol 30, No 1, 1994, 7789. A study of atomization by the rapidly rotating cup technique is described. Molten metal is injected by gas pressure into oil contained in the rim of a rapidly spinning cup. Melt fragmentation is by shearing by oil on the melt stream. The objective of the study w a s to determine the effects of process conditions on powder characteristics. Reduced particle size was obtained by increased rotation and speed, reduced orifice diameter and increased temperature of the molten metal. High melt injection pressure reduced melting loss. The results are discussed in terms of the metai/oil interactions and the forces responsible for shape of the particles.
Pressing COMPACTION AND E J E C T I O N OF G R E E N POWDER COMPACTS
D.T. Gethin et al (University of Swansea, Swansea, UK), Powder Metallur~, Vol 37,
No 1, 1994, 42-52. An i n v e s t i g a t i o n of c o m p a c t i o n , relaxation and ejection of compacts of different lengths made from different materials is described. The compaction stage confirmed the effects of friction and the existence of density gradients. The force r e l a x a t i o n b e t w e e n c o m p a c t i o n and ejection is reported to be non-elastic for ceramics and approximately elastic for other powders. The ejection stage force/ distance curve depends on compact length and force diminishes at the start of ejection movement, larger forces being required for longer compacts. As the compact emerges from the die the force diminishes to zero at the completion of ejection. A N E W COMPACTION EQUATION FOR POWDER MATERIALS
S. Li et al (Foundation for Advanced Materials Science, Hengelo, The Netherlands), Int. J. Powder Metallurgy, Vol 30,
No 1, 1994, 47-57. A new compaction equation linking green density and compaction pressure is presented. The equation contains three
empirical constants for which physical explanations are given. Good agreement with experiment in the pressure range studied is reported for the five powders used. It is concluded that the equation is applicable for pure metal powders, metal/ ceramic mixtures and metallized ceramic powders. COMPACTIBILITY OF POROUS S I N T E R E D BILLETS D U R I N G TRIAXIAL DEFORMATION
S.E. Vinogradov, Stal, No 7, 1992, 79-82. (In
Russian). An equation is presented which links changes in porosity as a function of shear during compaction and sintering of steel powders. Three controlling factors are i d e n t i f i e d as p o w d e r c h a r a c t e r i s t i c s , compaction pressure and sintering temperature. Sintering t e m p e r a t u r e is reported to have the largest effect on factors in the equation.
Sintering MAGNETO-PULSED T R E A T M E N T OF S I N T E R E D PSEUDO-ALLOYED MATERIALS
A_~ Kot et al F1z. Khim. Obrab. Mater.,
No 2, 1992, 132-135. (In Russian). The possibility of using non-contact pulsed magnetic induction heating to modify the structure of Fe30%Cu alloys containing macroscopic heterogeneities is considered. Constituents of the material melt during treatment and the electromagnetic pressure can bring about changes in the materials. COMPOUND S I N T E R I N G
F. Vollertsen (University of Erlangen-Nfirnberg, Germany), Unformtechnik, Vol 26,
No 2, 1992, 431-434. (In German). The principles of compound sintering are discussed with regard to the production of green p a r t s and t h e s t r e n g t h of a n i s o t r o p i c s i n t e r e d parts. S i n t e r i n g distortion is reported to be~the main problem arising in sintered parts. In layered parts distortion is more significant in radially layered parts than in axially layered ones. Ways to improve part accuracy are shown. Application to Ni-steels is discussed. COMPACTION AND S I N T E R I N G OF ULTRAFINE POWDERS
RJ~. Andievski (Russian Academy of Sciences, Moscow, Russia), Int. J. Powder Metal-
lur~, Vol 30, No 1, 1994, 59-66.
Powder production DECARBURIZATION OF R E D U C E D IRON POWDERS
S-W. Du et al China Steel Technical Reports,
1992, 156-161. The decarburization of Fe powder, made by reduction of mill scale by heating at 690 to 850°C in H-25at%N, is described. The optimum temperature for decarburization decreases with reduction in C content. Effect of O in the powders is to increase decarburization rate in the reduced Fe powder. PREPARATION OF TITANIUM CARBIDE FROM TITANIUM OXIDE BY SELF PROPAGATING HIGH TEMPERATURE SYNTHESIS
B.S. Kang et al (National University, Daejeon, Korea), J. Korean Inst. of Metals,
Vol 31, No 5, 1993, 599-605. (In Korean). It is reported that TiC powder had been prepared from SiO 2 by self combustion in presence of Mg and C. Controlling factors are said to be concentrations of Mg and C and the time of mixing, MgO and residual Mg are removed by leaching with HC1. Particles are reported to be spherical and 0.3 to 0.4 I~m in size, with a narrow range of sizes and 99.9% purity. THERMAL DECOMPOSITION OF AMMONIUM PARATUNGSTATE
Y. Yamanoto et al (Tokyo Tungsten Co, Toyama, Japan) J. Japan Soc. Powder and
Powder Metallurgy, Vol 40, No 6, 1993, 609-613. (In Japanese). Studies of the thermal decomposition of APT are described. Thermogravimetric analysis in a N atmosphere was used and very fine grained W oxide was the product. The process is shown to take place in stages forming amorphous phases, hexagonal tungsten bronze and monoclinic WOa in ultrafine particles. PREPARATION AND SINTERING OF T U N G S T E N POWDER WITH D I S P E R S E D RARE EARTHS BY SPRAY DRYING
IC Koyama, M. Morishita, (Himeji Inst. of Technology, Himeji, Japan), J. Japan Soc.
Powder and Powder Metallurgy, Vol 40, No 7, 1993, 707-712. (In Japanese). It is reported that W powder with rare earth dispersoids can be produced by spray drying of an acetic acid solution of ammonium tungstate para pentahydrate and l a n t h a n u m oxide, pyrolysis and reduction. The La203 is shown to be
48 MPR September 1994
LITERATURE
REVIEW
dispersed in the sintered W in finer particles than is the case with blended powders. EVALUATION OF ATOMIZATION BY THE RAPIDLY S P I N N I N G CUP P R O C E S S
ICP. Cooper, J.D. Ayres, (Naval Research Laboratory, Washington DC, USA), Int. J.
Powder Metallur~, Vol 30, No 1, 1994, 7789. A study of atomization by the rapidly rotating cup technique is described. Molten metal is injected by gas pressure into oil contained in the rim of a rapidly spinning cup. Melt fragmentation is by shearing by oil on the melt stream. The objective of the study w a s to determine the effects of process conditions on powder characteristics. Reduced particle size was obtained by increased rotation and speed, reduced orifice diameter and increased temperature of the molten metal. High melt injection pressure reduced melting loss. The results are discussed in terms of the metai/oil interactions and the forces responsible for shape of the particles.
Pressing COMPACTION AND E J E C T I O N OF G R E E N POWDER COMPACTS
D.T. Gethin et al (University of Swansea, Swansea, UK), Powder Metallur~, Vol 37,
No 1, 1994, 42-52. An i n v e s t i g a t i o n of c o m p a c t i o n , relaxation and ejection of compacts of different lengths made from different materials is described. The compaction stage confirmed the effects of friction and the existence of density gradients. The force r e l a x a t i o n b e t w e e n c o m p a c t i o n and ejection is reported to be non-elastic for ceramics and approximately elastic for other powders. The ejection stage force/ distance curve depends on compact length and force diminishes at the start of ejection movement, larger forces being required for longer compacts. As the compact emerges from the die the force diminishes to zero at the completion of ejection. A N E W COMPACTION EQUATION FOR POWDER MATERIALS
S. Li et al (Foundation for Advanced Materials Science, Hengelo, The Netherlands), Int. J. Powder Metallurgy, Vol 30,
No 1, 1994, 47-57. A new compaction equation linking green density and compaction pressure is presented. The equation contains three
empirical constants for which physical explanations are given. Good agreement with experiment in the pressure range studied is reported for the five powders used. It is concluded that the equation is applicable for pure metal powders, metal/ ceramic mixtures and metallized ceramic powders. COMPACTIBILITY OF POROUS S I N T E R E D BILLETS D U R I N G TRIAXIAL DEFORMATION
S.E. Vinogradov, Stal, No 7, 1992, 79-82. (In
Russian). An equation is presented which links changes in porosity as a function of shear during compaction and sintering of steel powders. Three controlling factors are i d e n t i f i e d as p o w d e r c h a r a c t e r i s t i c s , compaction pressure and sintering temperature. Sintering t e m p e r a t u r e is reported to have the largest effect on factors in the equation.
Sintering MAGNETO-PULSED T R E A T M E N T OF S I N T E R E D PSEUDO-ALLOYED MATERIALS
A_~ Kot et al F1z. Khim. Obrab. Mater.,
No 2, 1992, 132-135. (In Russian). The possibility of using non-contact pulsed magnetic induction heating to modify the structure of Fe30%Cu alloys containing macroscopic heterogeneities is considered. Constituents of the material melt during treatment and the electromagnetic pressure can bring about changes in the materials. COMPOUND S I N T E R I N G
F. Vollertsen (University of Erlangen-Nfirnberg, Germany), Unformtechnik, Vol 26,
No 2, 1992, 431-434. (In German). The principles of compound sintering are discussed with regard to the production of green p a r t s and t h e s t r e n g t h of a n i s o t r o p i c s i n t e r e d parts. S i n t e r i n g distortion is reported to be~the main problem arising in sintered parts. In layered parts distortion is more significant in radially layered parts than in axially layered ones. Ways to improve part accuracy are shown. Application to Ni-steels is discussed. COMPACTION AND S I N T E R I N G OF ULTRAFINE POWDERS
RJ~. Andievski (Russian Academy of Sciences, Moscow, Russia), Int. J. Powder Metal-
lur~, Vol 30, No 1, 1994, 59-66.