【摘要】：鋁型材因其質量輕、機械性能優(yōu)良、整體成型度高等特點,其應用領域已從傳統(tǒng)的建筑行業(yè)拓展到以航空航天、交通運輸為代表的工業(yè)領域中,并朝大型化、截面復雜化的方向發(fā)展。這不僅對鋁型材的性能提出了更高的要求,也使型材擠壓成形工藝面臨著更嚴峻的挑戰(zhàn)。扭擰、波浪、裂紋、表面粗糙等是鋁型材常見的缺陷,這些缺陷多與鋁錠的質量、模具的結構、工藝參數有關。本課題從鋁型材擠壓過程入手,首先探究了鋁錠均勻化處理對擠壓過程的影響,接著以一種空心異型材為例,進行了分流組合模的設計,借助于擠壓模擬軟件HyperXtrude對模具結構和擠壓工藝進行了改進和優(yōu)化。本文主要研究的內容如下:(1)對未均勻化和均勻化處理過的6063鋁合金鑄錠進行了金相組織觀察和硬度測試。結果顯示:在570℃的加熱條件下,保溫時間越長,合金成分越均勻,硬度隨保溫時間的延長逐漸降低;但當保溫時間由8h變?yōu)?2h,金相組織和硬度差別并不大。實際生產試驗情況表明,經均勻化處理過的鋁錠變形抗力較低,可以用更小的擠壓力進行擠壓生產,對未均勻化鋁錠進行擠壓前長時間加熱(480℃)也可以達到部分均勻化的效果,但其效果并不明顯。(2)針對選取的型材產品的結構,從分流孔、分流橋、焊合室、橋墩、工作帶等方面進行了擠壓模具設計。使用擠壓模擬軟件HyperXtrude進行了擠壓過程模擬分析,發(fā)現模橋與模芯結合處出現了應力集中,型材出料口流速差異較大,針對此問題對分流橋、分流孔和工作帶進行了改進,最終使最大模具應力由1183MPa降至872MPa,并將型材出料口各部位速度差降低到10mm/s內,相比改進之前有了較大的改善。(3)三溫一速是擠壓過程中最重要的工藝參數。采用正交實驗的方法研究了擠壓速度、鋁錠溫度、模具溫度、擠壓筒溫度對擠壓力和型材出料時速度均勻程度的影響。以擠壓力和速度均方差作為考察指標,對正交實驗結果進行極差分析,得到最佳工藝參數組合(擠壓速度2mm/s、模具溫度470℃、坯料溫度500℃、擠壓筒溫度460℃)。(4)實際生產試驗表明,采用改進過的分流模和擠壓工藝參數可以擠制出表面質量良好,沒有波浪、扭擰等缺陷的型材產品。本文將有限元模擬技術和數學優(yōu)化方法應用于型材擠壓過程的分析和工藝參數優(yōu)化中,能夠給模具的設計和擠壓工藝的制定提供一定的指導,這對企業(yè)提高產品質量和生產效率,增強市場競爭力有重要意義。
[Abstract]:Because of its light weight, excellent mechanical properties and high overall formability, aluminum profiles have been extended from the traditional construction industry to the aerospace, transportation and other industrial fields, and are developing towards large-scale, cross-sectional complex direction. This not only puts forward higher requirements for the performance of aluminum profiles, but also makes the profile extrusion. Forming process is facing more severe challenges. Torsion, wave, crack, surface roughness and other common defects of aluminum profiles, these defects are mostly related to the quality of aluminum ingot, die structure, process parameters. The main contents of this paper are as follows: (1) The microstructure and hardness of 6063 Aluminium alloy ingot which has not been homogenized and homogenized were observed and tested. The longer the holding time is, the more homogeneous the alloy composition is, and the hardness decreases gradually with the extension of holding time. However, when the holding time is changed from 8 h to 12 h, the difference of microstructure and hardness is not great. The actual production test shows that the deformation resistance of the homogenized aluminum ingot is lower, and it can be extruded with smaller extrusion force. The effect of partial homogenization can also be achieved by heating the non-homogenized aluminum ingot for a long time before extrusion (480 C), but the effect is not obvious. (2) According to the structure of the selected profiles, the extrusion die was designed from the diversion hole, diversion bridge, welding chamber, pier, working belt and so on. The extrusion simulation software HyperXtrude was used to carry out the extrusion die design. The simulation analysis of extrusion process shows that the stress concentration appears at the joint of die bridge and die core, and the flow velocity at the outlet of profile material varies greatly. In view of this problem, the diversion bridge, diversion hole and working belt are improved. Finally, the maximum die stress is reduced from 1183 MPa to 872 MPa, and the velocity difference at each part of the profile outlet is reduced to 10 mm/s. (3) Three temperatures and one velocity are the most important parameters in the extrusion process. The effects of extrusion speed, aluminum ingot temperature, die temperature and extrusion cylinder temperature on the extrusion force and velocity uniformity are studied by orthogonal experiment. The optimum combination of process parameters (extrusion speed 2mm/s, mold temperature 470, billet temperature 500, extrusion tube temperature 460) was obtained by range analysis. (4) The actual production test showed that the profile products with good surface quality, no wave, twist and other defects could be extruded by using the improved splitting die and extrusion process parameters. Finite element simulation technology and mathematical optimization method are applied to the analysis of profile extrusion process and the optimization of process parameters, which can provide certain guidance for the design of die and the formulation of extrusion process. It is of great significance for enterprises to improve product quality and production efficiency and enhance market competitiveness.
【學位授予單位】：江蘇大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG379

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