【摘要】：國內(nèi)汽車工業(yè)的飛速發(fā)展以及汽車輕量化的結構趨勢,使得鋁合金鑄件的應用需求大幅上升。在具有復雜內(nèi)腔或彎曲管道結構的鋁合金鑄件生產(chǎn)中,遇水即可潰散、污染小能耗低的水溶芯技術擁有廣泛的應用前景。目前水溶芯的局限主要在于其強度相對偏低、抗吸濕性能差、對設備要求高等方面。本文以水溶性砂芯為研究對象,在歸納了目前水溶性砂芯各種制芯工藝的優(yōu)缺點后,在熱壓法和壓制燒結的基礎上提出了熱壓燒結法制芯。以十水碳酸鈉為粘結劑、硅砂為基體材料,研究了熱壓工藝中的配方工藝和成型工藝、燒結工藝對型芯的強度、水溶潰散性能的影響。本文的主要內(nèi)容如下:(1)研究了熱壓燒結工藝中十水碳酸鈉加入量、膨潤土加入量、加熱溫度、加熱時間、燒結溫度、燒結時間對型芯抗拉強度的影響規(guī)律。研究結果表明,型芯的強度隨參數(shù)的變化均為先增大后減小的趨勢。當十水碳酸鈉加入量為40%wt、膨潤土加入量為7%wt、加熱溫度為150℃、加熱時間為10min時,得到的型芯熱壓初始抗拉強度最高,為1.1MPa;當燒結溫度為850℃、燒結時間為30min時,得到的型芯燒結強度最高,為6.4MPa。(2)分析了熱壓工藝的粘結機理。使用熱重分析法研究了加熱時間、加熱溫度對型芯含水量及型芯強度的影響,合理的加熱制度使無機鹽橋充分結晶析出的同時,令膨潤土保留微量的水分從而提供型芯增強效果。使用電鏡掃描分析形貌結合型芯強度,分析了十水碳酸鈉加入量、膨潤土加入量對無機鹽在砂粒表面結晶形態(tài)的影響。(3)分析了燒結工藝的強化機理。燒結反應可隨時間分為三個階段:第一階段,型芯由于脫水而低于初始強度;第二階段,型芯的粘結力由碳酸鈉在砂粒表面的附著力轉(zhuǎn)變?yōu)樘妓徕c的內(nèi)聚力,型芯此時獲得較高的燒結強度;第三階段,碳酸鈉基本全部轉(zhuǎn)換為新相,水溶性能大幅減少,此時粘結力主要由新相提供,型芯強度降低甚至彎曲變形無法使用。
[Abstract]:With the rapid development of domestic automobile industry and the structural trend of automobile lightweight, the application demand of aluminum alloy castings has increased greatly. In the production of aluminum alloy castings with complex inner cavity or curved pipe structure, water collapses can be caused by water, and the water-soluble core technology with low pollution and low energy consumption has a wide application prospect. At present, the limitation of water-soluble core is that its strength is relatively low, its moisture absorption performance is poor, and the requirement of equipment is high. In this paper, the water-soluble sand core is taken as the research object. After summarizing the advantages and disadvantages of the current water-soluble sand core making process, the hot pressing sintering method and pressing sintering method are proposed. Using sodium carbonate decahydrate as binder and silica sand as matrix material, the formula and forming process of hot pressing process and the influence of sintering process on strength and water-soluble collapsibility of mould core were studied. The main contents of this paper are as follows: (1) the effects of sodium carbonate decahydrate, bentonite addition, heating temperature, sintering time, sintering temperature and sintering time on the tensile strength of the core were studied. The results show that the strength of the core increases first and then decreases. When the amount of sodium carbonate decahydrate is 40 wt, bentonite is 7 wts, heating temperature is 150 鈩，

本文編號：2300511