發(fā)布時間：2018-06-29 22:59

  本文選題：鋁合金 + 擠壓鑄造�。� 參考：《武漢理工大學》2015年碩士論文

【摘要】：汽車輕量化是指在保證汽車綜合性能的前提下,盡可能降低自身重量,以實現(xiàn)減重、降耗、環(huán)保、安全的目的。據統(tǒng)計,汽車重量降低10%,燃油效率可提高6%~8%,輕量化還有助于汽車操縱的穩(wěn)定性和沖撞安全性。螺簧座是汽車后橋上用于安裝彈簧的支撐件,通常采用的是Q235。為實現(xiàn)汽車的輕量化,本課題選擇高強度比的A356.2鋁合金材料代替碳鋼,采用擠壓鑄造工藝成型螺簧座,力學性能要求本體取樣滿足屈服強度220MPa、伸長率4%。在研發(fā)鋁合金螺簧座的過程中,對擠壓鑄造技術進行了全面而深入的研究。本實驗采用宇部HVSC350PL型擠鑄機成型螺簧座,主要研究鑄造壓力、充型速度以及T6熱處理對組織和性能的影響,并結合Anycasting計算機模擬技術,對充型情況和凝固情況進行分析。其中,擠壓鑄造領域受實驗設備的限制而對充型速度的研究很少。在研究過程中,量化實驗條件以保證實驗的可重復性,如跟蹤材料成分、檢測含氫量和含渣量以確定熔煉質量等。T6熱處理方案為545℃×6h+70℃水淬+180℃×4h,對固溶爐進行溫度均勻性實驗,并采用分級升溫的方法使熱處理方案能夠準確執(zhí)行。對螺簧座本體取樣進行拉伸實驗,并結合計算機模擬結果和SEM、EDS分析,尋找斷裂原因并給出進一步提高力學性能的方案。另外,本文還對試驗中遇到的問題,如Sr-B的變質效果、孔洞缺陷、熱處理氣泡、Si偏析等進行研究。研究表明,壓力增加凝固時的溫度梯度并且促進壓力過冷,提高凝固階段的形核驅動力和降低晶粒的線生長速度,在顯微組織中,a-Al相的晶粒度相比于重力鑄造明顯減小,并且隨著鑄造壓力的增加,晶粒度逐漸減小,不均勻性有所增加,形貌也有團塊狀的發(fā)展趨勢,在固溶處理后,共晶相中Si元素析出成團狀存在于鋁基體中,不同壓力下的金相組織趨于一致。隨著鑄造壓力的增加,鑄態(tài)與T6狀態(tài)螺簧座的力學性能有較小的增加趨勢,但是在一定鑄造壓力范圍內,不建議通過提升壓力來提高力學性能。隨著充型速度的增加,鑄態(tài)與T6狀態(tài)螺簧座的力學性能有明顯提高的趨勢。較高的充型速度會產生渦流,但是強烈的對流以及沖刷型腔壁也促使產生“游離晶�！�,在一定范圍內,可以考慮通過增加充型速度提高力學性能。
[Abstract]:Vehicle lightweight is the purpose of reducing weight, reducing consumption, environmental protection and safety on the premise of guaranteeing the comprehensive performance of the car to achieve weight reduction, consumption reduction, environmental protection and safety. According to statistics, the vehicle weight can be reduced by 10%, the fuel efficiency can be increased by 6%~8%, the light weight is also helpful to the stability and impact safety of the vehicle control. The screw reed seat is used for installation on the rear axle of a car. The support part of spring usually uses Q235. to realize the lightweight of the automobile. This topic chooses the A356.2 aluminum alloy material with high strength ratio instead of carbon steel. The squeeze casting process is used to form the screw reed seat. The mechanical properties require the bulk sampling to meet the yield strength 220MPa. The elongation 4%. is used for the extrusion casting technology in the development of the aluminum alloy spring reed seat. In this experiment, a complete and thorough study was carried out. In this experiment, the effect of the casting pressure, filling speed and the effect of T6 heat treatment on the structure and properties was mainly studied by the molding of the space HVSC350PL type extrusion casting machine, and the filling and solidification conditions were analyzed with the computer simulation technology of Anycasting. The field of extrusion casting was set up by experiment. In the course of the study, the experimental conditions are quantified to ensure the repeatability of the experiment, for example, the.T6 heat treatment scheme, such as the tracking material composition, the determination of the hydrogen content and the slag content to determine the melting quality, is 545 C 6h+70 C water quenched +180 C for 4h, and the temperature uniformity experiment of the solid solution furnace is carried out and the classification is adopted. The heating method can make the heat treatment scheme be carried out accurately. The experiment on the body sampling of the screw reed body is carried out, and the computer simulation results and SEM, EDS analysis are used to find the cause of the fracture and give a scheme to further improve the mechanical properties. In addition, the problems encountered in the experiment, such as the deterioration effect of Sr-B, the hole defect and the heat in the heat, are also discussed in this paper. The study shows that the pressure increases the temperature gradient in the solidification and promotes the pressure supercooling, increases the nucleation driving force in the solidification stage and reduces the line growth speed of the grain. In the microstructure, the grain size of the a-Al phase decreases obviously compared with the gravity casting, and the grain size decreases with the increase of the casting pressure. The inhomogeneity increases and the morphology also has a mass trend. After solid solution treatment, the Si element in the eutectic phase exists in the aluminum matrix, and the metallographic structure under the different pressure tends to be consistent. With the increase of the casting pressure, the mechanical properties of the cast and T6 state reed seats have a smaller increasing trend, but they are cast in certain casting. In the range of pressure, it is not recommended to improve the mechanical properties through the lifting pressure. With the increase of the filling speed, the mechanical properties of the cast and T6 state reed seats are obviously improved. The higher filling speed will produce eddy current, but the strong convection and the scouring cavity wall also cause "free grain", which can be found in a certain range. It is considered to improve the mechanical properties by increasing the filling speed.
【學位授予單位】：武漢理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TG249.2;U466

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