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Influence of sintering atmosphere on decarburization of steel parts
The laboratory scale production of Fe p o w d e r from Fe ore c o n c e n t r a t e s containing less than 0.14%Si and low concentrations of other impurities was described. The powder was characterized and found to be suitable for use in PM. PRODUCTION OF ELECTROLYTIC IRON POWDER FROM SPONGE IRON FINES I~R. Dash et al, (National Metallurgical Laboratory, Jamshedpur, India). The production of electrolytic Fe powder using sponge Fe fines (3 mm in size) as anode material was described. Process variables were selected to allow a single cell to yield 60 kg/day. The powder was dendritic in shape and was found to have good compaction properties and sintering characteristics. Low impurity levels were reported. The use of the powder for production of PM parts was reported to be cost-effective.
PRESSING A N D $1NTERING ADAPTIVE FILL CONTROL OF A COMPACTING PRESS KS. Brown et al, (Cincinnati Inc, Cincinnati, USA). The paper described a project which had the o b j e c t i v e of a s s e s s m e n t of t h e performance of an automatic adaptive die filling and press control system. Process variables and control logic were investigated particularly powder properties. The system is intended to automatically adjust the fill portion of each tooling level. CONTROL OF A MULTI-PLATEN COMPACTING SYSTEM ON A MECHANICAL PRESS T.G. Mulcavage, (Dorst America Inc, Bethlehem, Pennsylvania, USA). An account of the advantages of a multiplaten die set used on a 50 ton press was given. Computer control functions were reviewed and two forms of die set were described. The control functions were discussed with regard to powder fill compensation, tool movements and forces. Improvements in part quality and machine utilization were reported. ENHANCEMENT IN FAST SET-UP OF POWDER METAL COMPACTING PRESSES G. Venzin, (Cincinnati Inc, Cincinnati,
uSA). The paper described the response of press manufacturers to the change from high volume production of PM parts to medium or even short runs. Enhanced fast set-up compacting presses were discussed M
MPR July/August 1991
with respect to part change over time. The importance of numerical process control was emphasized. Future possible developments to further reduce change over time were considered. INFLUENCE OF 8INTERING ATMOSPHERE ON DECA~RURIZATION OF STEEL PARTS M. Renowden, P. Pourtalet, (Liquid Air Corp, Countryside, Illinois, USA). Atmospheres used in the sintering of steel were reviewed. Emphasis was placed on decarburization and chemical reactions which occur during sinterin~ Comparison was made between synthetic and industrial gases including mixtures containing N, H, H20, COz and CH4. EFFECT OF OXYGEN IN POWDER ON DIMENSIONAL CHANGES S. Masuhara, S. Kawal, (Kobelco Metal Powder of America Inc, Seymour, Indiana,
both increased with reduction in oxide level. The kinetics of oxide reduction were studied and related to property changes and changes in process variables. LIMITATIONS IN NET SHAPING BY LIQUID PHASE SINTERING (LPS) R~M. German, (Rensselaer Polytechnic Inst, Troy, New York, USA). Some problems arising in L/~, solid/ liquid segregation which leads to distortion, compositional and microstructural gradients and property variations, were reviewed. Experimental work on W-Ni-Fe heavy alloys was described. The solid/liquid segregation during LPS was found to lead to differential rates of grain growth and pronounced density, grain size, connectivity and contiguity gradients. The results were reported to provide a basis for improved understanding of net shaping of components with uniform properties using LPS and allows prediction of possible tooling and processing corrections.
USA). Dimensional changes occurring during sintering, in N based gases, of Fe-l.5wt%Cu1%Graphite with 0.8% Zn stearate, as a function of sintering atmosphere, were investigated. Dilatometry was used to study the effect of 0 which was found to influence dimensional changes. Lower O contents in the powder resulted in greater carburization and compact growth during sintering. PROCESS AND APPARATUS FOR CONVERTING M ATMOSPHERE OF A GAS FLOW R.M. Rubiner, (Metallurgical Resources International Inc, USA). A description was given of a process and the e q u i p m e n t for conversion of the atmosphere of a gas flow to or from any v o l u m e for c h e m i c a l a n d p h y s i c a l interaction including the sintering of PM parts, particularly those with thermally unstable binders. The objective was the minimization of environmental pollution. THE REDUCTION OF IRON OXIDES DURING SINTERING OF IRON COMPACTS LJ. Cuddy, G.K White, (Pennsylvania State Univ, Pennsylvania, USA). The reduction of iron oxides during s i n t e r i n g of Fe c o m p a c t s in N/H a t m o s p h e r e s w a s i n v e s t i g a t e d by m o n i t o r i n g the H2O c o n t e n t of the emergent gases. The reactions described were the reduction of Fe203 to Fe304, at 600°C, and then to FeO which was complete at 1120°C. Complete reduction of oxide to metal required 30 minutes at 1120°C in pure H. The degree of oxide reduction was found to significantly influence compact shrinkage and mechanical properties which
GRAVITATIONAL EFFECT8 ON MICROSTRUCTURAL PARAMETERS DURING LIQUID PHASE 81NTERING
(LPS) S. Mani, RM. German, (Rensselaer Polytechnic Inst, Troy, New York, USA). Structures observed in LPS materials were reviewed and it was shown that in the case of W-Ni-Fe heavy alloys there is solid/ liquid segregation when the W content is less than 83wt%. Experimental work on the flow behaviour of W grains during LPS was described and provides an insight into preferential orientation occurring during sintering. Gravity effects on parameters such as grain size, connectivity a n d contiguity were measured for samples at different heights. The results were said to be of value in modelling growth behaviour and designing experiments to be carried out under microgravity conditions.
POWDER CHARACTERIZATION USE OF IMAGE ANALYSIS FOR CHARACTERIZATION OF DENSITY DEFECTS INCLUSIONS AND GRAIN SIZE IN PM PARTS E. Akpan, (Reliance Electric, Weaverville, North Carolina, USA). The relationships between density of PM parts and mechanical properties were discussed with respect to variations in density. Causes of e r r o r in d e n s i t y measurement were outlined and attention was drawn to the fact that the most i m p o r t a n t p r o p e r t y of PM materials, density, is the most difficult to measure
PRESSING A N D $1NTERING ADAPTIVE FILL CONTROL OF A COMPACTING PRESS KS. Brown et al, (Cincinnati Inc, Cincinnati, USA). The paper described a project which had the o b j e c t i v e of a s s e s s m e n t of t h e performance of an automatic adaptive die filling and press control system. Process variables and control logic were investigated particularly powder properties. The system is intended to automatically adjust the fill portion of each tooling level. CONTROL OF A MULTI-PLATEN COMPACTING SYSTEM ON A MECHANICAL PRESS T.G. Mulcavage, (Dorst America Inc, Bethlehem, Pennsylvania, USA). An account of the advantages of a multiplaten die set used on a 50 ton press was given. Computer control functions were reviewed and two forms of die set were described. The control functions were discussed with regard to powder fill compensation, tool movements and forces. Improvements in part quality and machine utilization were reported. ENHANCEMENT IN FAST SET-UP OF POWDER METAL COMPACTING PRESSES G. Venzin, (Cincinnati Inc, Cincinnati,
uSA). The paper described the response of press manufacturers to the change from high volume production of PM parts to medium or even short runs. Enhanced fast set-up compacting presses were discussed M
MPR July/August 1991
with respect to part change over time. The importance of numerical process control was emphasized. Future possible developments to further reduce change over time were considered. INFLUENCE OF 8INTERING ATMOSPHERE ON DECA~RURIZATION OF STEEL PARTS M. Renowden, P. Pourtalet, (Liquid Air Corp, Countryside, Illinois, USA). Atmospheres used in the sintering of steel were reviewed. Emphasis was placed on decarburization and chemical reactions which occur during sinterin~ Comparison was made between synthetic and industrial gases including mixtures containing N, H, H20, COz and CH4. EFFECT OF OXYGEN IN POWDER ON DIMENSIONAL CHANGES S. Masuhara, S. Kawal, (Kobelco Metal Powder of America Inc, Seymour, Indiana,
both increased with reduction in oxide level. The kinetics of oxide reduction were studied and related to property changes and changes in process variables. LIMITATIONS IN NET SHAPING BY LIQUID PHASE SINTERING (LPS) R~M. German, (Rensselaer Polytechnic Inst, Troy, New York, USA). Some problems arising in L/~, solid/ liquid segregation which leads to distortion, compositional and microstructural gradients and property variations, were reviewed. Experimental work on W-Ni-Fe heavy alloys was described. The solid/liquid segregation during LPS was found to lead to differential rates of grain growth and pronounced density, grain size, connectivity and contiguity gradients. The results were reported to provide a basis for improved understanding of net shaping of components with uniform properties using LPS and allows prediction of possible tooling and processing corrections.
USA). Dimensional changes occurring during sintering, in N based gases, of Fe-l.5wt%Cu1%Graphite with 0.8% Zn stearate, as a function of sintering atmosphere, were investigated. Dilatometry was used to study the effect of 0 which was found to influence dimensional changes. Lower O contents in the powder resulted in greater carburization and compact growth during sintering. PROCESS AND APPARATUS FOR CONVERTING M ATMOSPHERE OF A GAS FLOW R.M. Rubiner, (Metallurgical Resources International Inc, USA). A description was given of a process and the e q u i p m e n t for conversion of the atmosphere of a gas flow to or from any v o l u m e for c h e m i c a l a n d p h y s i c a l interaction including the sintering of PM parts, particularly those with thermally unstable binders. The objective was the minimization of environmental pollution. THE REDUCTION OF IRON OXIDES DURING SINTERING OF IRON COMPACTS LJ. Cuddy, G.K White, (Pennsylvania State Univ, Pennsylvania, USA). The reduction of iron oxides during s i n t e r i n g of Fe c o m p a c t s in N/H a t m o s p h e r e s w a s i n v e s t i g a t e d by m o n i t o r i n g the H2O c o n t e n t of the emergent gases. The reactions described were the reduction of Fe203 to Fe304, at 600°C, and then to FeO which was complete at 1120°C. Complete reduction of oxide to metal required 30 minutes at 1120°C in pure H. The degree of oxide reduction was found to significantly influence compact shrinkage and mechanical properties which
GRAVITATIONAL EFFECT8 ON MICROSTRUCTURAL PARAMETERS DURING LIQUID PHASE 81NTERING
(LPS) S. Mani, RM. German, (Rensselaer Polytechnic Inst, Troy, New York, USA). Structures observed in LPS materials were reviewed and it was shown that in the case of W-Ni-Fe heavy alloys there is solid/ liquid segregation when the W content is less than 83wt%. Experimental work on the flow behaviour of W grains during LPS was described and provides an insight into preferential orientation occurring during sintering. Gravity effects on parameters such as grain size, connectivity a n d contiguity were measured for samples at different heights. The results were said to be of value in modelling growth behaviour and designing experiments to be carried out under microgravity conditions.
POWDER CHARACTERIZATION USE OF IMAGE ANALYSIS FOR CHARACTERIZATION OF DENSITY DEFECTS INCLUSIONS AND GRAIN SIZE IN PM PARTS E. Akpan, (Reliance Electric, Weaverville, North Carolina, USA). The relationships between density of PM parts and mechanical properties were discussed with respect to variations in density. Causes of e r r o r in d e n s i t y measurement were outlined and attention was drawn to the fact that the most i m p o r t a n t p r o p e r t y of PM materials, density, is the most difficult to measure