| Summary: | 碩士 === 國立中山大學 === 機械與機電工程學系研究所 === 106 === This research is focused on hot extrusion of aluminum alloy 6061 circular tubes. Die geometries are discussed and some factors are used to analyze material flow, plastic deformation, and length of transverse seam during continuous aluminum hot extrusion using QForm simulation software. Die geometries are modified for enhancing welding pressure and decreasing transverse seam length. Effects of extrusion load on the die are also discussed to avoid overloading. Taguchi Quality Engineering is adopted to optimize die geometries and obtain best forming conditions.
Hot extrusion experiments are conducted with a billet of 7 inches in diameter by 2100 tons extrusion machine. The feasibility of finite element model is validated by comparing the simulation and experiments results. Factors chosen in the Taguchi method are porthole radius, bridge width, welding chamber height, and bearing length. Simulation results showed a higher welding pressure is obtained with a larger porthole radius, welding chamber height, and bearing length. However, a larger bridge width can increase the welding pressure slightly. A shorter transverse seam length can be obtained with a smaller porthole radius and welding chamber height. The effects of bridge width and bearing length are slight on the transverse seam length. Higher welding pressure and shorter transverse seam length are required for high productivity. A formula J is adopted to gain the best combination for the best design. Corrosion test and expansion test are conducted to verify strength and transverse seam of the product. It is found the fractured position did not occur at welding line, which means the bonding strength is stronger than the base metal Al6061. The bonding strength of extruded tubes can reach about 160MPa.
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