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Centrifugal pneumatic atomization for production of fine powders
Processing of soft magnetic composites P.Jansson. (Hi~ganasAB, Hi~ganas,Sweden.) It was noted that soft magnetic composites are based on insulated Fe powder particulates and that flexibility in processing and materials allowed materials with a variety of properties to be made. Processing must be closely controlled if specified magnetic and mechanical properties are to be attained. Additives, lubricants and resins, and part shape were shown to determine compaction pressures and subsequent heat treatments.
Property assurance for soft magnetic automotive PM parts J.Taylor et al. (SG Magnets Ltd, Rainham, UK.) The need for test procedures for soft magnetic components for automotive uses was emphasized. It was reported that rapid, reproducible and nondestructive tests for magnetic properties of parts had been developed. Examples of the tests were presented and compared with conventional tests on toroidal samples. The tests were used to determine effects of changes in process conditions on properties.
Application of soft magnetic powders in electric motors A.Lange. (Voith Turbo & Co KG, Heidenheim, Germany.) Development of a novel electric motor using soft magnetic powder was reported. For this a means of measuring electrical conductivity of powder materials was devised, which makes use of induction to produce the required field strength. Comparison was made between powder materials and laminated steel with regard to losses at typical working frequencies. A model was constructed to describe sizing effects and to predict efficiency and thermal conditions in the new electrical machines.
Comparison of powder soft magnetic composites with electrical sheet materials T.Janta et al. (Universityof Technology, Wroclaw, Poland.) PM magnetic composites were discussed with regard to use in cores of magnetic devices, parts shapes and properties. The basic features required were described and a proposal was made for a classification of materials. The classification comprised soft-, hard- and thermomagnetic composites. PM soft magnetic composites were compared with sheet materials such as Si-steel notably in respect of energy losses. Some examples of cores made from powder and from sheet materials were compared.
Comparison of sintered and bonded iron-base soft magnetic materials J.A.Bas et al. (AMES Barcelona, Spain.) Characteristics and production requirements of sintered soft magnetic materials,
46
MPR October 2ool
including Fe, Fe-Si, Fe-P, Fe-Ni, Fe-Co and resin bonded encapsulated Fe base materials were compared with respect to DC and A C applications. Examples from automotive and other applications were described. Rotor and stator parts for motors, made from both types of material, were considered. The new materials were shown to have advantages in lower hysteresis loss and anisotropy of magnetic properties.
Application of PM soft magnetic materials K.Asaka. (HitachiPowderedMetals Co Ltd, Chiba,Japan.) Difficulty in replacing soft magnetic sheet with powder materials due to cost and unsuitable magnetic properties was discussed. It was shown that PM could be used with advantage for thin wall components at high frequency in a range of magnetically soft materials where constant permeability between high and low flux densities is required.
Issues in measurement of properties of soft magnetic materials M.Hall et al. (National PhysicalLaboratory, Teddington, UK.) Measurement of properties of soft magnetic materials was discussed in detail. Standards and methods of measurement are well established for frequencies up to 400 Hz. Effect of specimen geometry was considered with regard to magnetic path. At high frequencies, up to 100 kHz, there are numerous effects to be considered. The instrumentation must be calibrated for the frequencies in use. There are effects due to wire insulation since this may affect capacitance and introduce errors. Core temperature and waveform shape were amongst other parameters that were discussed.
Production of automotive DC motors P.Marchal. (FAURECIA, Audincourt, France.) It was reported that a 310 W 12 V DC motor, for automotive use, had been constructed making use of PM to produce parts and to demonstrate feasibility. The design was shown to be a compromise between technological constraints linked to material forming and mechanical and magnetic performance.
Development of multi-coordinate drives using bonded soft iron magnetic parts T.Busch, G.Henneberger. (Aachen Inst. of Technology, Aachen, Germany.) It was reported that a soft magnetic composite material had been used to make a spherical rotor, in a spherical guide, for an electric motor with three degrees of freedom. Laminated steel sheet cannot be used in this application. The paper described the numerical/analytical design methods and some aspects of production.
Powders Close coupled gas atomization J,T.Strauss, J.J.Dunkley. (Atomizing Systems Ltd, Sheffield, UK.) Studies of the effects, in close coupled gas atomization, of process and material parameters on particle size were described. Melt and gas properties and operating conditions were stated. The experimental data were analysed to outline an empirical, verified correlation for powder particle sizes.
Effect of gas velocity distribution on particle size distribution in gas atomized powders T.Fukuda et al. (Sumitomo Metal Industries Ltd, Itami, Japan.) Relationships between distribution of gas velocity, near the nozzles, in gas atomizers and particle size distribution were discussed. Gas velocity distributions and particle size distributions were measured and calculated. Good agreement between these was reported. Design of atomizer, for control of particle size distribution, was discussed.
Advances in gas atomization technology W.G.Hopkins. (Phoenix Scientific Industries Ltd, UK.) It was reported that superheating of atomizer gas was effective in improving capability and efficiency of atomizers, in terms of reducing mean particle size. This and other process refinements were reviewed.
Low melting point metal powders by centrifugal atomization Y.Y.Zhao. (University of Liverpool, Liverpool, UK.) Centrifugal atomization was discussed with reference to ability to produce spherical powders with narrow particle size distributions. Spherical powders are used in production of filters. Centrifugal atomization was used to make spherical powders of low melting point metals and was discussed in terms of melt disintegration and powder characteristics.
Centrifugal pneumatic atomization for production of fine powders S.Sheikhaliev,J.Dunkley. (AtomisingSystems Ltd, UK.) It was reported that centrifugal pneumatic atomization produces fine powders, less
www.metal-powder.net
than 20 pm at low flow rates and gas pressures. The process was used to make fine Sn-Pb, Zn and A1 powders for use in solders and paints. Effects of process parameters on particle size distribution, structure and morphology were described. Production rates of 25 kg.h "1 with 90% of powder below 20 pm was reported.
Applications of ultrafine gas atomized metal powders G.Schulz. (Wideflow Metal Powder Production and EngineeringGmbH, Ohrdruf, Germany.) The need for ultrafine metal powders, produced at low cost, was noted. It was shown that a novel process, melt film atomization, can make powders, smaller than 10 pm in size, in a range of alloys. Applications were outlined.
Water atomized fine powder technology J.Hamill, C.Schade. (HoeganaesCorp, USA.) Developments in water atomization, for production of fine powders, were reported. Applications, particularly with binder systems, were reviewed.
Design of large scale powder production equipment M.Hohmann, SD.Pleier. (ALD Vacuum Technologies AG, Erlensee,FRG.) The demand for powders of high quality, with regard to purity, structure and spherical shape, was discussed with regard to bulk production methods. A n investigation of melting methods, vacuum induction melting and electroslag remelting, were used with inert gas atomization. Characteristics of the methods were described. Qualities of powder were compared.
Production of refractory metal powders by explosion of wire M.Umakoshi et al. (Kurume National College of Technology, Fukuoka,Japan,.) It was reported that wires of W, Mo, Nb and Ta had been exploded to powder in air or in Ar. The powders consisted of fine spherical particles of metal or oxide. Oxidation was suppressed in Ar. Particle sizes were 2.4 to 3.7 pm for Mo and 2.5 to 4.6 pm for W. Reduction was required to produce only metal particles.
Composite materials Microstructure and properties of alumina-titanium carbonitride composites K.Hayashi et al. (Universityof Tokyo, Tokyo,Japan.) Microstructure and properties of hot pressed A1203-TI(C,N) were investigated with regard to use as cutting tool materials and for wear
www.meta[-powder.net
resistance. The effects of N:C+N ratio and %TiC were studied. Cutting performance against steel was evaluated with regard to crater and flank wear. Comparison was made with AI203-TiC tool alloys.
be used to reinforce metal matrix composites. The most effective production method was sintering by infiltration of loose powders and hot pressing. Properties of some materials were described.
Tribological properties of aluminasilicon carbide nanocomposites
Synthesis of Ti matrix composites by in situ gas-solid reaction
K.Niihar et al. (Osaka University, Ibaraki,Japan.) A1203-SiC composites were hot pressed and mechanical and wear properties, in air and water, were measured to investigate the effects of SiC. Relationships between mechanical and wear properties were discussed. Worn surfaces were examined by scanning electron microscopy and found to show plastic deformation and trans- and inter-granular fractures.
H .Chunget al. (Ajou University, Kyung~, Korea.) It was reported that Ti matrix composites, reinforced with "13C, had been synthesized in situ by a gas/solid reaction process. Powders, without TiC, were cold pressed, reacted with CH 4 at elevated temperature, vacuum sintered and HIPed to full density. TIC was shown to be uniformly distributed and mechanical properties were said to be high.
Sintered AI-SiC composites for use in semiconductor devices
Fabrication of cubic zirconia composites with oxide and carbide reinforcements
S-I.Yamagata, A.Fukui. (Sumitomo Electric Industries Ltd, Japan.) The properties required for materials to be used as heat sinks in electronic devices - high thermal conductivity and low thermal expansion - were reviewed. It was reported that an A1-SiC material had been developed for this use. How this material meets the requirements was discussed with regard to control of properties by adjustments to composition.
Differential thermal analysis of AI-silicon carbide composites R.Orban et al. (Universityof Cluj-Napoca, Romania.) A1 alloy matrix-carbide composites were discussed with reference to use at elevated temperatures. Results of differential thermal analysis of PM composites were used to evaluate high temperature properties, which were found to be influenced by production conditions.
Structure-property relationships in aluminium matrix composites B.V.R.Bhat et al. (Defence Metallurgical Research Laboratory, Hyderabad, India.) A1 alloy matrix composites were reviewed with regard to effects of process conditions. A n investigation of 2124A1 alloy, reinforced with SiC particles, of different sizes, processed by vacuum hot pressing and hot extrusion, was described. Effects of material and process parameters on structure and properties were studied. Increased extrusion ratio was shown to increase mechanical properties, attributed to refinement and alignment of particles. Extruded flat samples showed anisotropy.
Ni base matrix composites reinforced with fused WC particles R.L.Orban et al. (Universityof Cluj-Napoca, Romania.) Fused tungsten carbide was shown to be a quasi-eutectoid of W C and W2C. This has higher hardness and toughness than W C alone. It was suggested that fused W C could
J.Hojo et al. (Kyushu University,Japan.) Development of cubic ZrO 2 composites reinforced with Ta203, La203, A1203 or SiC was described. Sintering was at 1600 °C in air. Second phases were formed by reaction between oxide additions and ZrO 2. Effects on mechanical properties were said to be beneficial.
Sintering Anisotropy of shrinkage in consolidation of powders E.Olevsky. (CaliforniaState University,San Diego, USA.) Anisotropy of shrinkage during deformation processing of powders was reviewed. The study considered shape change non-uniformity due to structure, morphology, gravity, the effect of container in isostatic pressing and pressure transmitting medium in quasi-isostatic pressing. Modelling based on continuum theory was used. Technological recommendations related to compact green shape and spatial density distributions were made.
Effect of milling on densification of molybdenum disilicide Y.D.Kim et al. (HanyangUniversity, Seoul, Korea.) Effects of milling on sintering of MoSi 2 powder, by spark plasma sintering, were investigated. Milling reduced powder from 10 pm to <1 pm in size. Sintering was at 1200- 1500 °C, heated at 20-200 °C.min "1 and held at temperature for 15 min. Structural evolution and densification were correlated with process conditions. Compacts sintered from milled powder had lower densities, 94-98%, than samples made from un-milled powder. This was attributed to contamination by O during milling, forming SiO 2 which dissociated, giving a gaseous phase during sintering.
MPR October 2OOl
47
Property assurance for soft magnetic automotive PM parts J.Taylor et al. (SG Magnets Ltd, Rainham, UK.) The need for test procedures for soft magnetic components for automotive uses was emphasized. It was reported that rapid, reproducible and nondestructive tests for magnetic properties of parts had been developed. Examples of the tests were presented and compared with conventional tests on toroidal samples. The tests were used to determine effects of changes in process conditions on properties.
Application of soft magnetic powders in electric motors A.Lange. (Voith Turbo & Co KG, Heidenheim, Germany.) Development of a novel electric motor using soft magnetic powder was reported. For this a means of measuring electrical conductivity of powder materials was devised, which makes use of induction to produce the required field strength. Comparison was made between powder materials and laminated steel with regard to losses at typical working frequencies. A model was constructed to describe sizing effects and to predict efficiency and thermal conditions in the new electrical machines.
Comparison of powder soft magnetic composites with electrical sheet materials T.Janta et al. (Universityof Technology, Wroclaw, Poland.) PM magnetic composites were discussed with regard to use in cores of magnetic devices, parts shapes and properties. The basic features required were described and a proposal was made for a classification of materials. The classification comprised soft-, hard- and thermomagnetic composites. PM soft magnetic composites were compared with sheet materials such as Si-steel notably in respect of energy losses. Some examples of cores made from powder and from sheet materials were compared.
Comparison of sintered and bonded iron-base soft magnetic materials J.A.Bas et al. (AMES Barcelona, Spain.) Characteristics and production requirements of sintered soft magnetic materials,
46
MPR October 2ool
including Fe, Fe-Si, Fe-P, Fe-Ni, Fe-Co and resin bonded encapsulated Fe base materials were compared with respect to DC and A C applications. Examples from automotive and other applications were described. Rotor and stator parts for motors, made from both types of material, were considered. The new materials were shown to have advantages in lower hysteresis loss and anisotropy of magnetic properties.
Application of PM soft magnetic materials K.Asaka. (HitachiPowderedMetals Co Ltd, Chiba,Japan.) Difficulty in replacing soft magnetic sheet with powder materials due to cost and unsuitable magnetic properties was discussed. It was shown that PM could be used with advantage for thin wall components at high frequency in a range of magnetically soft materials where constant permeability between high and low flux densities is required.
Issues in measurement of properties of soft magnetic materials M.Hall et al. (National PhysicalLaboratory, Teddington, UK.) Measurement of properties of soft magnetic materials was discussed in detail. Standards and methods of measurement are well established for frequencies up to 400 Hz. Effect of specimen geometry was considered with regard to magnetic path. At high frequencies, up to 100 kHz, there are numerous effects to be considered. The instrumentation must be calibrated for the frequencies in use. There are effects due to wire insulation since this may affect capacitance and introduce errors. Core temperature and waveform shape were amongst other parameters that were discussed.
Production of automotive DC motors P.Marchal. (FAURECIA, Audincourt, France.) It was reported that a 310 W 12 V DC motor, for automotive use, had been constructed making use of PM to produce parts and to demonstrate feasibility. The design was shown to be a compromise between technological constraints linked to material forming and mechanical and magnetic performance.
Development of multi-coordinate drives using bonded soft iron magnetic parts T.Busch, G.Henneberger. (Aachen Inst. of Technology, Aachen, Germany.) It was reported that a soft magnetic composite material had been used to make a spherical rotor, in a spherical guide, for an electric motor with three degrees of freedom. Laminated steel sheet cannot be used in this application. The paper described the numerical/analytical design methods and some aspects of production.
Powders Close coupled gas atomization J,T.Strauss, J.J.Dunkley. (Atomizing Systems Ltd, Sheffield, UK.) Studies of the effects, in close coupled gas atomization, of process and material parameters on particle size were described. Melt and gas properties and operating conditions were stated. The experimental data were analysed to outline an empirical, verified correlation for powder particle sizes.
Effect of gas velocity distribution on particle size distribution in gas atomized powders T.Fukuda et al. (Sumitomo Metal Industries Ltd, Itami, Japan.) Relationships between distribution of gas velocity, near the nozzles, in gas atomizers and particle size distribution were discussed. Gas velocity distributions and particle size distributions were measured and calculated. Good agreement between these was reported. Design of atomizer, for control of particle size distribution, was discussed.
Advances in gas atomization technology W.G.Hopkins. (Phoenix Scientific Industries Ltd, UK.) It was reported that superheating of atomizer gas was effective in improving capability and efficiency of atomizers, in terms of reducing mean particle size. This and other process refinements were reviewed.
Low melting point metal powders by centrifugal atomization Y.Y.Zhao. (University of Liverpool, Liverpool, UK.) Centrifugal atomization was discussed with reference to ability to produce spherical powders with narrow particle size distributions. Spherical powders are used in production of filters. Centrifugal atomization was used to make spherical powders of low melting point metals and was discussed in terms of melt disintegration and powder characteristics.
Centrifugal pneumatic atomization for production of fine powders S.Sheikhaliev,J.Dunkley. (AtomisingSystems Ltd, UK.) It was reported that centrifugal pneumatic atomization produces fine powders, less
www.metal-powder.net
than 20 pm at low flow rates and gas pressures. The process was used to make fine Sn-Pb, Zn and A1 powders for use in solders and paints. Effects of process parameters on particle size distribution, structure and morphology were described. Production rates of 25 kg.h "1 with 90% of powder below 20 pm was reported.
Applications of ultrafine gas atomized metal powders G.Schulz. (Wideflow Metal Powder Production and EngineeringGmbH, Ohrdruf, Germany.) The need for ultrafine metal powders, produced at low cost, was noted. It was shown that a novel process, melt film atomization, can make powders, smaller than 10 pm in size, in a range of alloys. Applications were outlined.
Water atomized fine powder technology J.Hamill, C.Schade. (HoeganaesCorp, USA.) Developments in water atomization, for production of fine powders, were reported. Applications, particularly with binder systems, were reviewed.
Design of large scale powder production equipment M.Hohmann, SD.Pleier. (ALD Vacuum Technologies AG, Erlensee,FRG.) The demand for powders of high quality, with regard to purity, structure and spherical shape, was discussed with regard to bulk production methods. A n investigation of melting methods, vacuum induction melting and electroslag remelting, were used with inert gas atomization. Characteristics of the methods were described. Qualities of powder were compared.
Production of refractory metal powders by explosion of wire M.Umakoshi et al. (Kurume National College of Technology, Fukuoka,Japan,.) It was reported that wires of W, Mo, Nb and Ta had been exploded to powder in air or in Ar. The powders consisted of fine spherical particles of metal or oxide. Oxidation was suppressed in Ar. Particle sizes were 2.4 to 3.7 pm for Mo and 2.5 to 4.6 pm for W. Reduction was required to produce only metal particles.
Composite materials Microstructure and properties of alumina-titanium carbonitride composites K.Hayashi et al. (Universityof Tokyo, Tokyo,Japan.) Microstructure and properties of hot pressed A1203-TI(C,N) were investigated with regard to use as cutting tool materials and for wear
www.meta[-powder.net
resistance. The effects of N:C+N ratio and %TiC were studied. Cutting performance against steel was evaluated with regard to crater and flank wear. Comparison was made with AI203-TiC tool alloys.
be used to reinforce metal matrix composites. The most effective production method was sintering by infiltration of loose powders and hot pressing. Properties of some materials were described.
Tribological properties of aluminasilicon carbide nanocomposites
Synthesis of Ti matrix composites by in situ gas-solid reaction
K.Niihar et al. (Osaka University, Ibaraki,Japan.) A1203-SiC composites were hot pressed and mechanical and wear properties, in air and water, were measured to investigate the effects of SiC. Relationships between mechanical and wear properties were discussed. Worn surfaces were examined by scanning electron microscopy and found to show plastic deformation and trans- and inter-granular fractures.
H .Chunget al. (Ajou University, Kyung~, Korea.) It was reported that Ti matrix composites, reinforced with "13C, had been synthesized in situ by a gas/solid reaction process. Powders, without TiC, were cold pressed, reacted with CH 4 at elevated temperature, vacuum sintered and HIPed to full density. TIC was shown to be uniformly distributed and mechanical properties were said to be high.
Sintered AI-SiC composites for use in semiconductor devices
Fabrication of cubic zirconia composites with oxide and carbide reinforcements
S-I.Yamagata, A.Fukui. (Sumitomo Electric Industries Ltd, Japan.) The properties required for materials to be used as heat sinks in electronic devices - high thermal conductivity and low thermal expansion - were reviewed. It was reported that an A1-SiC material had been developed for this use. How this material meets the requirements was discussed with regard to control of properties by adjustments to composition.
Differential thermal analysis of AI-silicon carbide composites R.Orban et al. (Universityof Cluj-Napoca, Romania.) A1 alloy matrix-carbide composites were discussed with reference to use at elevated temperatures. Results of differential thermal analysis of PM composites were used to evaluate high temperature properties, which were found to be influenced by production conditions.
Structure-property relationships in aluminium matrix composites B.V.R.Bhat et al. (Defence Metallurgical Research Laboratory, Hyderabad, India.) A1 alloy matrix composites were reviewed with regard to effects of process conditions. A n investigation of 2124A1 alloy, reinforced with SiC particles, of different sizes, processed by vacuum hot pressing and hot extrusion, was described. Effects of material and process parameters on structure and properties were studied. Increased extrusion ratio was shown to increase mechanical properties, attributed to refinement and alignment of particles. Extruded flat samples showed anisotropy.
Ni base matrix composites reinforced with fused WC particles R.L.Orban et al. (Universityof Cluj-Napoca, Romania.) Fused tungsten carbide was shown to be a quasi-eutectoid of W C and W2C. This has higher hardness and toughness than W C alone. It was suggested that fused W C could
J.Hojo et al. (Kyushu University,Japan.) Development of cubic ZrO 2 composites reinforced with Ta203, La203, A1203 or SiC was described. Sintering was at 1600 °C in air. Second phases were formed by reaction between oxide additions and ZrO 2. Effects on mechanical properties were said to be beneficial.
Sintering Anisotropy of shrinkage in consolidation of powders E.Olevsky. (CaliforniaState University,San Diego, USA.) Anisotropy of shrinkage during deformation processing of powders was reviewed. The study considered shape change non-uniformity due to structure, morphology, gravity, the effect of container in isostatic pressing and pressure transmitting medium in quasi-isostatic pressing. Modelling based on continuum theory was used. Technological recommendations related to compact green shape and spatial density distributions were made.
Effect of milling on densification of molybdenum disilicide Y.D.Kim et al. (HanyangUniversity, Seoul, Korea.) Effects of milling on sintering of MoSi 2 powder, by spark plasma sintering, were investigated. Milling reduced powder from 10 pm to <1 pm in size. Sintering was at 1200- 1500 °C, heated at 20-200 °C.min "1 and held at temperature for 15 min. Structural evolution and densification were correlated with process conditions. Compacts sintered from milled powder had lower densities, 94-98%, than samples made from un-milled powder. This was attributed to contamination by O during milling, forming SiO 2 which dissociated, giving a gaseous phase during sintering.
MPR October 2OOl
47