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Uniaxial compression tests of metal powder compacts
statistically designed study of the effects of heat treatments on dimensional changes during carbonitriding was described. Optimum conditions for any material in any property condition were reported to have been established. A PROCESS FOR CONTINUOUS STEAM TREATMENT - ‘CONTIBLU’ F.Sarnes, R.Sarnes. (Sarnes Ingenieure, Ostfildern, Germany.) It was reported that a steam treatment furnace had been developed which did not require the use of a boiler to generate steam. Partial combustion of natural gas or C4H10 gives a gas containing CO, and H,O which provides protection to the parts being treated but allows the required level of surface oxidation. The system is said to be cost effective. Unburnt hydrocarbons are after-burnt to provide heat for the process. Exhaust gases do not require cleaning. The process is computer controlled.
Compaction EFFECTS OF LUBRICANTS ON COMPACTING PERFORMANCE H.Suzuki et al. (Kobelco Metal Powder of America, Inc, Seymour, USA.) Flow of powders was discussed with regard to use of lubricants and measurement of flowability. The importance of consistency of powder flow for die filling was emphasized. A new improved test for powder flow, which simulates die filling, was proposed. The test was said to allow comparison of the effects of different lubricants including those developed to give increased green strength and low ejection loads. ADVANCED PROCESSING OF METAL PROFILES BY EXTRUSION M.Weber, MKniiwer. (Fraunhofer Inst. (IFAM), Bremen, Germany.) It was noted that extrusion is usually limited to ductile metals and that materials with high strength for use at high temperatures require forging and machining. It was shown that high strength metal powder-binder mixtures can be extruded on conventional polymer extrusion machines to a wide range of shapes. Debinding is by methods similar to those used in metal injection moulding. Sintering can be to dense or porous conditions. Examples of materials produced were presented. COMBINED ELASTIC-PLASTICVISCOUS MODEL FOR PM DEFORMATION PROCESSES VGorokhov, E.A.Doroshkevich. (Belarussian State Research and PM Production Concern, Minsk, Belarus.)
A mathematical simulation of powder compaction was presented. Factors taken into account included addition of strain rate to the transition from the elastic to plastic states, and introduction of viscous and plastic stresses into the non-elastic deformation region. An equation for combined elastic-plastic-viscous flow of a porous compactible material was described. Comparison was made between experimental and predicted results for compaction and free upsetting in a closed die. MODELLING OF COMPACTION WITH REPRESENTATIVE CELLS H.J.Glass, G.de With. (Eindhoven University of Technology, Eindhoven, Netherlands.) It was noted that in compaction modelling it is important to consider the particle level. A model for representative cells, a cell being a group of particles round a pore, was given. The whole compact was represented by a number of such cells. The approach was reported to be of value in the initial stages of compaction process design. UNIAXIAL COMPRESSION TESTS OF METAL POWDER COMPACTS M.D.Riera, J.M.Prado. (Polytechnic University of Cataluna, Barcelona, Spain.) It was emphasized that knowledge of mechanical properties of green compacts is important for modelling and to understand behaviour during handling before sintering. Compression tests were carried out on green compacts, compacted to various densities. Axial and radial strains were measured and volumetric strain calculated. Three stages of deformation were identified for which explanations were given. These were initial consolidation under low stress, elasto-plastic deformation and thirdly a dilatancy stage leading to failure.
Warm compaction COMBINATION OF WARM COMPACTION TECHNOLOGY AND NUMERICAL CONTROL PRESS TECHNOLOGY K.Komatsu et al. (Sumitomo Electric Industries Ltd, Itami City, Japan.) Use of a numerically controlled press and warm compaction technology was evaluated in terms of density attained and uniformity of green density. A fully monitored 350 tonne press and warm compaction system and a real part were used. Comparison was made with conventional pressing.
PRODUCTION AND PROPERTIES OF HIGH STRENGTH HIGH DENSITY HELICAL GEARS A.Mahn, H.Cohrt. (Schunk Sintermetalltechnik GmbH, Oberhausen, Germany. ) Warm compaction with advanced tooling was reviewed with regard to higher density and improved density distribution attained. Density was said to be significantly increased in the teeth of gears resulting in a 30% increase in strength. The higher green density also resulted in less damage during ejection and handling. Production experiences were discussed.
Sintering SINTERING OF FERROUS MATERIALS AT MODERATE TEMPERATURES H.Danninger et al. (Technical University of Vienna, Vienna, Austria.) Various ferrous materials were sintered at 750 to 900°C to determine the levels of mechanical properties attained. It was shown that to obtain high values of strength highly irregular shaped particles are essential. There is poor interface bonding between particles with smooth surfaces. Added graphite should be dissolved since residual graphite interferes with formation of sintering necks. Low temperatures and short sintering times should be avoided for materials containing graphite. SIMULTANEOUS SINTERING AND QUENCHING OF NITRIDED HIGH SPEEDSTEEL S.Talacchia et al. (CEIT, San Sebastian, Spain.) Samples of T42 high speed steel, with 0.4% added graphite, were nitrided at different pressures and sintered in N at 121O”C, quenched from the sintering temperature and tempered under various conditions. Responses to this treatment were analysed. After quenching there was a high proportion of retained austenite, most of which decomposed during tempering. The structures contained M,C carbides and carbo-nitrides. Mechanical properties were similar to those of directly sintered high speed steels. SUPERFICIAL DENSIFICATION OF PLASMA SINTERED IRON J.C.K.Neves et al. (LABMAT, Florianopolis, Brazil.) Samples of unalloyed Fe were compacted at 600 MPa and sintered in an abnormal glow discharge at pressures of 600 to 2000 Pa, in Ar-H. Temperatures were 900 to 1100°C and
MPR June 1999 47
Compaction EFFECTS OF LUBRICANTS ON COMPACTING PERFORMANCE H.Suzuki et al. (Kobelco Metal Powder of America, Inc, Seymour, USA.) Flow of powders was discussed with regard to use of lubricants and measurement of flowability. The importance of consistency of powder flow for die filling was emphasized. A new improved test for powder flow, which simulates die filling, was proposed. The test was said to allow comparison of the effects of different lubricants including those developed to give increased green strength and low ejection loads. ADVANCED PROCESSING OF METAL PROFILES BY EXTRUSION M.Weber, MKniiwer. (Fraunhofer Inst. (IFAM), Bremen, Germany.) It was noted that extrusion is usually limited to ductile metals and that materials with high strength for use at high temperatures require forging and machining. It was shown that high strength metal powder-binder mixtures can be extruded on conventional polymer extrusion machines to a wide range of shapes. Debinding is by methods similar to those used in metal injection moulding. Sintering can be to dense or porous conditions. Examples of materials produced were presented. COMBINED ELASTIC-PLASTICVISCOUS MODEL FOR PM DEFORMATION PROCESSES VGorokhov, E.A.Doroshkevich. (Belarussian State Research and PM Production Concern, Minsk, Belarus.)
A mathematical simulation of powder compaction was presented. Factors taken into account included addition of strain rate to the transition from the elastic to plastic states, and introduction of viscous and plastic stresses into the non-elastic deformation region. An equation for combined elastic-plastic-viscous flow of a porous compactible material was described. Comparison was made between experimental and predicted results for compaction and free upsetting in a closed die. MODELLING OF COMPACTION WITH REPRESENTATIVE CELLS H.J.Glass, G.de With. (Eindhoven University of Technology, Eindhoven, Netherlands.) It was noted that in compaction modelling it is important to consider the particle level. A model for representative cells, a cell being a group of particles round a pore, was given. The whole compact was represented by a number of such cells. The approach was reported to be of value in the initial stages of compaction process design. UNIAXIAL COMPRESSION TESTS OF METAL POWDER COMPACTS M.D.Riera, J.M.Prado. (Polytechnic University of Cataluna, Barcelona, Spain.) It was emphasized that knowledge of mechanical properties of green compacts is important for modelling and to understand behaviour during handling before sintering. Compression tests were carried out on green compacts, compacted to various densities. Axial and radial strains were measured and volumetric strain calculated. Three stages of deformation were identified for which explanations were given. These were initial consolidation under low stress, elasto-plastic deformation and thirdly a dilatancy stage leading to failure.
Warm compaction COMBINATION OF WARM COMPACTION TECHNOLOGY AND NUMERICAL CONTROL PRESS TECHNOLOGY K.Komatsu et al. (Sumitomo Electric Industries Ltd, Itami City, Japan.) Use of a numerically controlled press and warm compaction technology was evaluated in terms of density attained and uniformity of green density. A fully monitored 350 tonne press and warm compaction system and a real part were used. Comparison was made with conventional pressing.
PRODUCTION AND PROPERTIES OF HIGH STRENGTH HIGH DENSITY HELICAL GEARS A.Mahn, H.Cohrt. (Schunk Sintermetalltechnik GmbH, Oberhausen, Germany. ) Warm compaction with advanced tooling was reviewed with regard to higher density and improved density distribution attained. Density was said to be significantly increased in the teeth of gears resulting in a 30% increase in strength. The higher green density also resulted in less damage during ejection and handling. Production experiences were discussed.
Sintering SINTERING OF FERROUS MATERIALS AT MODERATE TEMPERATURES H.Danninger et al. (Technical University of Vienna, Vienna, Austria.) Various ferrous materials were sintered at 750 to 900°C to determine the levels of mechanical properties attained. It was shown that to obtain high values of strength highly irregular shaped particles are essential. There is poor interface bonding between particles with smooth surfaces. Added graphite should be dissolved since residual graphite interferes with formation of sintering necks. Low temperatures and short sintering times should be avoided for materials containing graphite. SIMULTANEOUS SINTERING AND QUENCHING OF NITRIDED HIGH SPEEDSTEEL S.Talacchia et al. (CEIT, San Sebastian, Spain.) Samples of T42 high speed steel, with 0.4% added graphite, were nitrided at different pressures and sintered in N at 121O”C, quenched from the sintering temperature and tempered under various conditions. Responses to this treatment were analysed. After quenching there was a high proportion of retained austenite, most of which decomposed during tempering. The structures contained M,C carbides and carbo-nitrides. Mechanical properties were similar to those of directly sintered high speed steels. SUPERFICIAL DENSIFICATION OF PLASMA SINTERED IRON J.C.K.Neves et al. (LABMAT, Florianopolis, Brazil.) Samples of unalloyed Fe were compacted at 600 MPa and sintered in an abnormal glow discharge at pressures of 600 to 2000 Pa, in Ar-H. Temperatures were 900 to 1100°C and
MPR June 1999 47