| Summary: | 碩士 === 國立高雄應用科技大學 === 模具系碩士在職專班 === 103 === Electronics industry, medical equipment and automotive parts related products constantly shorten the life cycle of the products. The situation leads to the need in the simplification of manufacturing processes which are capable to produce the metal products with complex geometries. Thus, the lead time can be shorten in order to meet rapidly change in market demands.
The study used copper powder with dendritic shape and an average size of 45 μm in micro forward and backward extrusion processes with a single stage to produce copper parts having an forward-extruded rod and a backward-extruded cup. The study investigated the effect of forming load on the porosity and hardness of the produced parts. In the processes, only pure copper powder was used, and no binder and lubricant were applied. The process neither used a preforming stage in order to reduce the processing time and costs. The forming loads, 4 kN, 5 kN, 6 kN, 10 kN and 12 kN, were considered to produce green compacts. The green compacts were then sintered at 600 ºC for 1 hour and cooled in the furnace. The dimensions, rod length, cup height and wall thickness of the sintered parts were measured. The microstructures were also examined by an optical microscope and a scanning electron microscope in order to understand the variation in material flows and porosity. Moreover, the hardness of the parts was also measured and compared with the copper wire.
The results showed that an increase in forming load caused an increase in hardness and density, and a decrease in porosity. The average relative density of the parts was in a range between 81% and 93% and the average porosity was from 11.3% to 18.23%. The regions near the rim had lower hardness with an average value of 60 Hv, and the regions in the rod however had higher hardness with an average value of 90 Hv. Moreover, the images of microstructure also showed that an increase in forming load does reduce the porosity in the parts.
Keywords: micro forward and backward extrusion, micro extrusion, copper powder
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