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Compaction
Literature
Review~~~~~~~~~~~!!!!
gas atomization process. Investigations. on the effects of different processing parameters such as superheating, gas pressure and nozzle diameter on grain size and microstructureof the dental amalgam powders will be conducted in this work.
manufactured on production equipment and statistically evaluated for density distribution, copper distribtuion, and dimensional accuracy. The results substantiate the by far superior performance of the diffusion bonded copper additions.
COMPACTION PROPERTIES OF SEGREGATION·LESS MIXED POWDERS T Hayami, et al (Kobe Steel Ltd) This report describes the properties of segregation-less mixed powders m comparison with those ofconventionallymixed powders. These mixed powders were rust pressed by a continuous compacting press and were then sintered. Properties such as variation ofcarbon, dimensional change,hardness and radial crushing strength were measured after sintering. The behaviour of dimensional change of the compacts with the binder was investigated using a dilatometer.
VISION SYSTEM TO PROTECT PRESSES AND TOOLING D R Freese, J'Porter (Cincinnati, Inc) 'Double hit' is a majorcause of press overload and tool damage resulting from parts sticking to the upper punch and falling back into the die cavity. Even where overload protection is fitted mechanical presses may stop too slowly to prevent damage. The paper describes a vision system and software that detects, warns of a potential double strike and stops the press. A MECHANICAL · ELECTROHYDRAULIC APPROACH TO COMPACTING
PM PARTS FABRICATION EXPERIENCE WITH 'ANCORBOND' (BINDER TREATED) PREMIXES M JMcDermott (Hoeganaes Corporation) Improvements in the homogeneity and filling characteristics observed with AncorDond premixes and their effectson density control, weightcontrol, dimensional stability and fabrication rates are described. A review of production trials that resulted in up to 30% increases in pressing rate while reducing dimensional and weight variations . by as much as 50% are provided. EFFECTS OF DECREASED Ni CONTENT IN AN 'ANCORBOND' PROCESSED Ni·C STEEL POWDERMIX F J Semel (Hoeganaes Corporation)
Studies wereconducted to determine the properties of an AncorBond processed FN·0208 mix containing 1.25% nickel versus those of a similarly processed regular mix containing nominally 2.0% nickel. The process effects on powder properties and on several parts properties were determined. The powder properties included the traditional green and sintered properties and the graphite and nickel dusting resistances. The parts properties surveyed included both green and sintered properties and sintered carbonand nickel contents. Compared with the regular mix, the bonded mix exhibited marked improvements in graphite and nickel dusting resistance and in powder flow properties.
R F Unkel (Cincinnati Inc) A mechanical- electrohydraulic press is described which combines the speed and accuracy of the mechanical press with controllability of the hydraulic in the production of complex parts. PROGRAMMABLE SYSTEM FORPRESS AUfOMATION A Bhide (Data Instruments, Wintriss Controls Group) The increasing demand for just-in-time (]IT) deliveries is makingquick-die-changeover systems (QDC) and programmable automation necessary to manufacturing operations. Programmable automation means the ability to change manufacturingfrom one part to the next with speed and ease.A programmable system fora press which would provide repeatabletimingcontrolfromsetup to setup is described here. The system includes a programmablerotary limit (cam)switch, a tonnage monitor,and a die protection monitor.Eachofthese functions would contain the features necessary to allow quick die changes, provide accurate, repeatable timing signals, and protect against die smash-ups and press overloads. The system could also be connected to a computer to collect data for statistical process control. DENSIFICATION AND MICROSTRUCTURE OF COMPACTS CONSOLIDATED BYHOTTRUUITAL COMPACTION H R Piehler,D Watkins, [Carnegie-Mellon University)
DIMENSIONAL STABILITY OF Fe·Cu STEEL T Esser, et al, (Sintermetallwerk Krebsoge) In this investigation two powder mixes of identical chemical composition, raw material and blending cycle were prepared, one with elemental copper additions and one by adding a master alloy based on the same iron powder to which the copper was diffusion bonded. Ring shaped specimens were
570
Hot triaxial compaction (HTC) is a novel compaction process which .utilizes controlled levels of both shear and hydrostatic stress to consolidate compactsat elevatedtemperatures.The shear component is imposed by applying an axial compressive force via a ram and movable seal in a modified HIPunit. The current systemis capable of achievinga pressure of60,000psi, a temperature of 1200C and an axial force of 100,000 lbs. The
principal benefits of hot triaxially compaclino particulates are enhanced densification as well a~ enhanced performance in the resulting compact. Enhanced densificationresults fromthe additional shear stress imposed during HTCing. Enhanced performance can result from improved particle bonding caused by the shear-induced interparticle sliding during HTCing. Hot triaxial compaction of composites can also be used to reduce the extent of reaction zonesbycompacting atlower temperatures or for shorter times than necessary to achieve comparable densitiesby HIPing, in essence trading shear stress for temperature. The densification and microstructures of several HTCed monolithic and composite powder compacts are described and compared to similar compactsdensified by HIPing.
POWDER FORGING TIlEORETICAL ANALYSIS OF POWDER FORGING R Sharan, et ai, (West Virginia University) The paper reviews work carried out on powder forging. Amathematicalsolution was developed for axisymmetric forging of iron powder preforms (solid and hollow) under the frictional conditions based on the yield criteria proposed by Tabata and Masakifor porousmaterials.The theoreticalvalues agreed with experimental values within accuracy (85-05%). INFLUENCE OFNON·METALLIC INCLUSIONS AND POROSITY ONMECHM'ICAL PROPERTIES
OF POWDER FORGED 4645 STEEL
J L Seefelt, et ai, (Michigan Technological University) The tensile ductility and low cycle fatigue behaviour of powder forged 4645 steel are examined and correlated to the type, level, and distribution of nonmetallic inclusions present in the microstructureas well as the relative density of the forged material. Tempered martensitic microstructures are examined. Oxide inclusion levels are maintained at low levels (maximum oxygen content is less than 100 ppm), while MnS levels vary by a factor of about four. Data on the effects of forging strain and peak average forging pressure on forged density and mechanical properties are also presented. Bothtensile ductility and fatigue life are improved'as a result of lower MnS levels. At forged density below 7.83 gm/cm" the tensile ductility appears to be influenced by residual porosity. Fractographic evidence is presented to support the influence of pores and MnS inclusions on the initiation of ductile fracture in these high strength microstructures.
SINTERING ATMOSPHERES EFFECT OF SINTERING ATMOSPHERE ON STRUCTURE AND PROPERTIES OF SINTERED Fe POWDER COMPACTS D Ryan, L JCuddy (Pennsylvania State University) This study seeks to establish the levels of the contaminants oxygen and water vapour that can be tolerated in hydrogen- nitrogen mixtures without MPR July/August 1990
Review~~~~~~~~~~~!!!!
gas atomization process. Investigations. on the effects of different processing parameters such as superheating, gas pressure and nozzle diameter on grain size and microstructureof the dental amalgam powders will be conducted in this work.
manufactured on production equipment and statistically evaluated for density distribution, copper distribtuion, and dimensional accuracy. The results substantiate the by far superior performance of the diffusion bonded copper additions.
COMPACTION PROPERTIES OF SEGREGATION·LESS MIXED POWDERS T Hayami, et al (Kobe Steel Ltd) This report describes the properties of segregation-less mixed powders m comparison with those ofconventionallymixed powders. These mixed powders were rust pressed by a continuous compacting press and were then sintered. Properties such as variation ofcarbon, dimensional change,hardness and radial crushing strength were measured after sintering. The behaviour of dimensional change of the compacts with the binder was investigated using a dilatometer.
VISION SYSTEM TO PROTECT PRESSES AND TOOLING D R Freese, J'Porter (Cincinnati, Inc) 'Double hit' is a majorcause of press overload and tool damage resulting from parts sticking to the upper punch and falling back into the die cavity. Even where overload protection is fitted mechanical presses may stop too slowly to prevent damage. The paper describes a vision system and software that detects, warns of a potential double strike and stops the press. A MECHANICAL · ELECTROHYDRAULIC APPROACH TO COMPACTING
PM PARTS FABRICATION EXPERIENCE WITH 'ANCORBOND' (BINDER TREATED) PREMIXES M JMcDermott (Hoeganaes Corporation) Improvements in the homogeneity and filling characteristics observed with AncorDond premixes and their effectson density control, weightcontrol, dimensional stability and fabrication rates are described. A review of production trials that resulted in up to 30% increases in pressing rate while reducing dimensional and weight variations . by as much as 50% are provided. EFFECTS OF DECREASED Ni CONTENT IN AN 'ANCORBOND' PROCESSED Ni·C STEEL POWDERMIX F J Semel (Hoeganaes Corporation)
Studies wereconducted to determine the properties of an AncorBond processed FN·0208 mix containing 1.25% nickel versus those of a similarly processed regular mix containing nominally 2.0% nickel. The process effects on powder properties and on several parts properties were determined. The powder properties included the traditional green and sintered properties and the graphite and nickel dusting resistances. The parts properties surveyed included both green and sintered properties and sintered carbonand nickel contents. Compared with the regular mix, the bonded mix exhibited marked improvements in graphite and nickel dusting resistance and in powder flow properties.
R F Unkel (Cincinnati Inc) A mechanical- electrohydraulic press is described which combines the speed and accuracy of the mechanical press with controllability of the hydraulic in the production of complex parts. PROGRAMMABLE SYSTEM FORPRESS AUfOMATION A Bhide (Data Instruments, Wintriss Controls Group) The increasing demand for just-in-time (]IT) deliveries is makingquick-die-changeover systems (QDC) and programmable automation necessary to manufacturing operations. Programmable automation means the ability to change manufacturingfrom one part to the next with speed and ease.A programmable system fora press which would provide repeatabletimingcontrolfromsetup to setup is described here. The system includes a programmablerotary limit (cam)switch, a tonnage monitor,and a die protection monitor.Eachofthese functions would contain the features necessary to allow quick die changes, provide accurate, repeatable timing signals, and protect against die smash-ups and press overloads. The system could also be connected to a computer to collect data for statistical process control. DENSIFICATION AND MICROSTRUCTURE OF COMPACTS CONSOLIDATED BYHOTTRUUITAL COMPACTION H R Piehler,D Watkins, [Carnegie-Mellon University)
DIMENSIONAL STABILITY OF Fe·Cu STEEL T Esser, et al, (Sintermetallwerk Krebsoge) In this investigation two powder mixes of identical chemical composition, raw material and blending cycle were prepared, one with elemental copper additions and one by adding a master alloy based on the same iron powder to which the copper was diffusion bonded. Ring shaped specimens were
570
Hot triaxial compaction (HTC) is a novel compaction process which .utilizes controlled levels of both shear and hydrostatic stress to consolidate compactsat elevatedtemperatures.The shear component is imposed by applying an axial compressive force via a ram and movable seal in a modified HIPunit. The current systemis capable of achievinga pressure of60,000psi, a temperature of 1200C and an axial force of 100,000 lbs. The
principal benefits of hot triaxially compaclino particulates are enhanced densification as well a~ enhanced performance in the resulting compact. Enhanced densificationresults fromthe additional shear stress imposed during HTCing. Enhanced performance can result from improved particle bonding caused by the shear-induced interparticle sliding during HTCing. Hot triaxial compaction of composites can also be used to reduce the extent of reaction zonesbycompacting atlower temperatures or for shorter times than necessary to achieve comparable densitiesby HIPing, in essence trading shear stress for temperature. The densification and microstructures of several HTCed monolithic and composite powder compacts are described and compared to similar compactsdensified by HIPing.
POWDER FORGING TIlEORETICAL ANALYSIS OF POWDER FORGING R Sharan, et ai, (West Virginia University) The paper reviews work carried out on powder forging. Amathematicalsolution was developed for axisymmetric forging of iron powder preforms (solid and hollow) under the frictional conditions based on the yield criteria proposed by Tabata and Masakifor porousmaterials.The theoreticalvalues agreed with experimental values within accuracy (85-05%). INFLUENCE OFNON·METALLIC INCLUSIONS AND POROSITY ONMECHM'ICAL PROPERTIES
OF POWDER FORGED 4645 STEEL
J L Seefelt, et ai, (Michigan Technological University) The tensile ductility and low cycle fatigue behaviour of powder forged 4645 steel are examined and correlated to the type, level, and distribution of nonmetallic inclusions present in the microstructureas well as the relative density of the forged material. Tempered martensitic microstructures are examined. Oxide inclusion levels are maintained at low levels (maximum oxygen content is less than 100 ppm), while MnS levels vary by a factor of about four. Data on the effects of forging strain and peak average forging pressure on forged density and mechanical properties are also presented. Bothtensile ductility and fatigue life are improved'as a result of lower MnS levels. At forged density below 7.83 gm/cm" the tensile ductility appears to be influenced by residual porosity. Fractographic evidence is presented to support the influence of pores and MnS inclusions on the initiation of ductile fracture in these high strength microstructures.
SINTERING ATMOSPHERES EFFECT OF SINTERING ATMOSPHERE ON STRUCTURE AND PROPERTIES OF SINTERED Fe POWDER COMPACTS D Ryan, L JCuddy (Pennsylvania State University) This study seeks to establish the levels of the contaminants oxygen and water vapour that can be tolerated in hydrogen- nitrogen mixtures without MPR July/August 1990