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Properties of amine tungstates and their application to tungsten powder production
POWDER PRODUCTION IIII II
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PROPERTIES OF AMINE TUNGSTATES AND THEIR APPLICATION TO TUNGSTEN POWDER PRODUCTION Z. Zou et al, (Central South University of Technology, China), J. Central South lnst, Mining and Metall, No 6, 1990, 622-631. (In Chinese). Preparation, properties and hydrogen reduction of diamine and ethyienediamine tungstates are discussed. The effects of selfradioactivity of these tungstates on the W oxide reduction process were investigated. It is reported that by a combination of self and hydrogen reduction fine W powders can be produced. The mechanisms of the process and its applications to production of submicron W powder are discussed. EQUIPMENT AND SAFETY IN THE DESIGN ENGINEERING AND CONSTRUCTION OF SPRAY DEPOSITION PLANTS
Edmonton, Canada), Int. J. Powder Metallurgy, Vol 28, No 2, 1992, 149-160. The control of powder quality, particle size distribution and yield of powder in atomization is discussed and is said to be largely dependent on operator experience with powder assessment being carried out after processing. The need for on-line sensors to monitor powder parameters is emphasized since this would result in increased yields of quality powder. An i n s t r u m e n t for on-line sensing of Zn atomization is described and it is shown that particle sizes are reduced by increased atomization pressure. Consistent measurements were made at 0.91 m and 2.5 m from the nozzle and the results for 0.91 m gave detailed measurements of atomization characteristics. For process control it is shown that near field and d o w n s t r e a m m e a s u r e m e n t s show the applicability of on-line process monitoring for p o w d e r p r o d u c t i o n a n d s p r a y deposition respectively.
Compaction II
B. Fuchs et ai, (Mannesmann-Demag, Ohlerkirchweg, Germany), Powder Metallurgy Science and Technology, Vol 3, No 1, 1991, 23-35. Spray deposition equipment is described in detail including the spray chamber, fittings for manipulation and e x h a u s t systems. Safety features are discussed and instrumentation and control techniques are described. Secondary plant for gas cleaning and overspray recycling are also described. INTELLIGENT CONTROL OF PARTICLE SIZE DISTRIBUTION IN GAS ATOMIZATION S.D. Ridder et al, (National Inst of Standards and Technology, Gaithersburg, Maryland, USA), Int. J. Powder Metallurgy, Vol 28, No 2, 1992, 133-147. A multi-discipline research programme into intelligent control of particle size d i s t r i b u t i o n in gas a t o m i z a t i o n is described. Emphasis is placed on aspects of atomization which relate to process control including fluid dynamics, process variables, and particle size sensing. A process controller based on the findings of the research is described. It is considered that the controller can be adapted to other methods of powder production. ON-LINE MEASUREMENT OF POWDER SIZE DISTRIBUTION IN ZINC ATOMIZATION H. Henein et al, (University of Alberta,
Ill
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settling. The supernatant water is removed and the mould bottom is replaced by a porous plug and further centrifugal force applied. The water content is reduced below 2% and the green density is 60%. The merits of the technique are discussed. FREEZE COMPRESSION MOULDING OF FINE CERAMIC POWDERS USING A WATER BINDER T. Nakagawa et al, (University of Tokyo, Japan), J. Japan Soc. Powder and Powder Metallurgy, Vol 39, No 1, 1992, 44-49. (In Japanese). Experiments into the use of water instead of polymer or wax binder for the compression moulding of ceramic powders are described. Water was investigated because of the shorter debinding time. The compacts are frozen after compression and the water removed by a freeze drying technique in order to prevent cracking of the compact by shrinkage. It is shown that improved fiowability is obtained and the compacts of complex shape can be made. Examples are given.
PRESS POWDER FLOW MOULDING OF PURE IRON POWDER
INTELLIGENT PROCESSING IN HOT ISOSTATIC PRESSING
S. Takahashi and T. Nakagawa~ (University of Tokyo, Japan), J. Japan Soc. Powder and Powder Metallurgy, Vol 39, No 1, 1992, 1015. (In Japanese). It is shown that PPFM can be used to produce deep cups from powder, which is difficult by conventional pressing. The powder is mixed with a FVA resin binder or Zn stearate and liquid paraffin. The latter additives were found to give little difference in the densities of cup wall and bottom. Flowability of the powder was assessed from the density distribution in the green compact. It is suggested that there is powder flow from the cup bottom into the wall because of the lubrication effect of the liquid paraffin. The method is claimed to be better than metal injection moulding as less binder is used.
RJ. Schaefer, (National Inst of Standards and Technology, Galthersburg, Maryland, USA), Int. J. Powder Metallurgy, Vol 28, No 2, 1992, 161-173. The application of intelligent process control to HIP is discussed with respect to advances in process modelling, advanced process sensors and intelligent control systems generally. The benefits are said to be refinement of process models, optimization of workplace design and process schedules and feed back control based on sample characterization. An eddy current device used to measure sample dimensions is described.
CENTRIFUGAL COMPACTION OF HIGH PURITY SUBMICRON ALUMINA POWDERS. Tashima et al, (Hiroshima University, Japan), J. Japan Soc. Powder and Powder Metallurgy, Vol 39, No 2, 1992, 39-43. (In Japanese). The application of a centrifugal force in the compaction of Al20a is described, 0.22 pm powder is dispersed in water and ball milled to form a slip which is cast into a mould. Centrifugal force is applied to aid
SINTERING IIII
SINTERING OF WIRE WOUND COMPACTS AFTER PRESSING AND DEFORMATION K. Kuroki et al, (University of Hiroshima, Japan), J. Japan Soc. Powder and Powder Metallurgy, Vol 39, No 1, 1992, 16-23. (In Japanese). Compacts were formed by winding 18/8 stainless steel wire on to a stainless steel former. The compacts were deformed to give a contact area between wires of about 1/3 of the wire diameter and were then s i n t e r e d in H. Optical and e l e c t r o n
MPR September 1992 37
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I
PROPERTIES OF AMINE TUNGSTATES AND THEIR APPLICATION TO TUNGSTEN POWDER PRODUCTION Z. Zou et al, (Central South University of Technology, China), J. Central South lnst, Mining and Metall, No 6, 1990, 622-631. (In Chinese). Preparation, properties and hydrogen reduction of diamine and ethyienediamine tungstates are discussed. The effects of selfradioactivity of these tungstates on the W oxide reduction process were investigated. It is reported that by a combination of self and hydrogen reduction fine W powders can be produced. The mechanisms of the process and its applications to production of submicron W powder are discussed. EQUIPMENT AND SAFETY IN THE DESIGN ENGINEERING AND CONSTRUCTION OF SPRAY DEPOSITION PLANTS
Edmonton, Canada), Int. J. Powder Metallurgy, Vol 28, No 2, 1992, 149-160. The control of powder quality, particle size distribution and yield of powder in atomization is discussed and is said to be largely dependent on operator experience with powder assessment being carried out after processing. The need for on-line sensors to monitor powder parameters is emphasized since this would result in increased yields of quality powder. An i n s t r u m e n t for on-line sensing of Zn atomization is described and it is shown that particle sizes are reduced by increased atomization pressure. Consistent measurements were made at 0.91 m and 2.5 m from the nozzle and the results for 0.91 m gave detailed measurements of atomization characteristics. For process control it is shown that near field and d o w n s t r e a m m e a s u r e m e n t s show the applicability of on-line process monitoring for p o w d e r p r o d u c t i o n a n d s p r a y deposition respectively.
Compaction II
B. Fuchs et ai, (Mannesmann-Demag, Ohlerkirchweg, Germany), Powder Metallurgy Science and Technology, Vol 3, No 1, 1991, 23-35. Spray deposition equipment is described in detail including the spray chamber, fittings for manipulation and e x h a u s t systems. Safety features are discussed and instrumentation and control techniques are described. Secondary plant for gas cleaning and overspray recycling are also described. INTELLIGENT CONTROL OF PARTICLE SIZE DISTRIBUTION IN GAS ATOMIZATION S.D. Ridder et al, (National Inst of Standards and Technology, Gaithersburg, Maryland, USA), Int. J. Powder Metallurgy, Vol 28, No 2, 1992, 133-147. A multi-discipline research programme into intelligent control of particle size d i s t r i b u t i o n in gas a t o m i z a t i o n is described. Emphasis is placed on aspects of atomization which relate to process control including fluid dynamics, process variables, and particle size sensing. A process controller based on the findings of the research is described. It is considered that the controller can be adapted to other methods of powder production. ON-LINE MEASUREMENT OF POWDER SIZE DISTRIBUTION IN ZINC ATOMIZATION H. Henein et al, (University of Alberta,
Ill
I I Illll
settling. The supernatant water is removed and the mould bottom is replaced by a porous plug and further centrifugal force applied. The water content is reduced below 2% and the green density is 60%. The merits of the technique are discussed. FREEZE COMPRESSION MOULDING OF FINE CERAMIC POWDERS USING A WATER BINDER T. Nakagawa et al, (University of Tokyo, Japan), J. Japan Soc. Powder and Powder Metallurgy, Vol 39, No 1, 1992, 44-49. (In Japanese). Experiments into the use of water instead of polymer or wax binder for the compression moulding of ceramic powders are described. Water was investigated because of the shorter debinding time. The compacts are frozen after compression and the water removed by a freeze drying technique in order to prevent cracking of the compact by shrinkage. It is shown that improved fiowability is obtained and the compacts of complex shape can be made. Examples are given.
PRESS POWDER FLOW MOULDING OF PURE IRON POWDER
INTELLIGENT PROCESSING IN HOT ISOSTATIC PRESSING
S. Takahashi and T. Nakagawa~ (University of Tokyo, Japan), J. Japan Soc. Powder and Powder Metallurgy, Vol 39, No 1, 1992, 1015. (In Japanese). It is shown that PPFM can be used to produce deep cups from powder, which is difficult by conventional pressing. The powder is mixed with a FVA resin binder or Zn stearate and liquid paraffin. The latter additives were found to give little difference in the densities of cup wall and bottom. Flowability of the powder was assessed from the density distribution in the green compact. It is suggested that there is powder flow from the cup bottom into the wall because of the lubrication effect of the liquid paraffin. The method is claimed to be better than metal injection moulding as less binder is used.
RJ. Schaefer, (National Inst of Standards and Technology, Galthersburg, Maryland, USA), Int. J. Powder Metallurgy, Vol 28, No 2, 1992, 161-173. The application of intelligent process control to HIP is discussed with respect to advances in process modelling, advanced process sensors and intelligent control systems generally. The benefits are said to be refinement of process models, optimization of workplace design and process schedules and feed back control based on sample characterization. An eddy current device used to measure sample dimensions is described.
CENTRIFUGAL COMPACTION OF HIGH PURITY SUBMICRON ALUMINA POWDERS. Tashima et al, (Hiroshima University, Japan), J. Japan Soc. Powder and Powder Metallurgy, Vol 39, No 2, 1992, 39-43. (In Japanese). The application of a centrifugal force in the compaction of Al20a is described, 0.22 pm powder is dispersed in water and ball milled to form a slip which is cast into a mould. Centrifugal force is applied to aid
SINTERING IIII
SINTERING OF WIRE WOUND COMPACTS AFTER PRESSING AND DEFORMATION K. Kuroki et al, (University of Hiroshima, Japan), J. Japan Soc. Powder and Powder Metallurgy, Vol 39, No 1, 1992, 16-23. (In Japanese). Compacts were formed by winding 18/8 stainless steel wire on to a stainless steel former. The compacts were deformed to give a contact area between wires of about 1/3 of the wire diameter and were then s i n t e r e d in H. Optical and e l e c t r o n
MPR September 1992 37