發(fā)布時(shí)間：2018-10-30 16:20

【摘要】：國(guó)內(nèi)汽車工業(yè)的飛速發(fā)展以及汽車輕量化的結(jié)構(gòu)趨勢(shì),使得鋁合金鑄件的應(yīng)用需求大幅上升。在具有復(fù)雜內(nèi)腔或彎曲管道結(jié)構(gòu)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(shù)擁有廣泛的應(yīng)用前景。目前水溶芯的局限主要在于其強(qiáng)度相對(duì)偏低、抗吸濕性能差、對(duì)設(shè)備要求高等方面。本文以水溶性砂芯為研究對(duì)象,在歸納了目前水溶性砂芯各種制芯工藝的優(yōu)缺點(diǎn)后,在熱壓法和壓制燒結(jié)的基礎(chǔ)上提出了熱壓燒結(jié)法制芯。以十水碳酸鈉為粘結(jié)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(jié)工藝對(duì)型芯的強(qiáng)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(jié)工藝中十水碳酸鈉加入量、膨潤(rùn)土加入量、加熱溫度、加熱時(shí)間、燒結(jié)溫度、燒結(jié)時(shí)間對(duì)型芯抗拉強(qiáng)度的影響規(guī)律。研究結(jié)果表明,型芯的強(qiáng)度隨參數(shù)的變化均為先增大后減小的趨勢(shì)。當(dāng)十水碳酸鈉加入量為40%wt、膨潤(rùn)土加入量為7%wt、加熱溫度為150℃、加熱時(shí)間為10min時(shí),得到的型芯熱壓初始抗拉強(qiáng)度最高,為1.1MPa;當(dāng)燒結(jié)溫度為850℃、燒結(jié)時(shí)間為30min時(shí),得到的型芯燒結(jié)強(qiáng)度最高,為6.4MPa。(2)分析了熱壓工藝的粘結(jié)機(jī)理。使用熱重分析法研究了加熱時(shí)間、加熱溫度對(duì)型芯含水量及型芯強(qiáng)度的影響,合理的加熱制度使無(wú)機(jī)鹽橋充分結(jié)晶析出的同時(shí),令膨潤(rùn)土保留微量的水分從而提供型芯增強(qiáng)效果。使用電鏡掃描分析形貌結(jié)合型芯強(qiáng)度,分析了十水碳酸鈉加入量、膨潤(rùn)土加入量對(duì)無(wú)機(jī)鹽在砂粒表面結(jié)晶形態(tài)的影響。(3)分析了燒結(jié)工藝的強(qiáng)化機(jī)理。燒結(jié)反應(yīng)可隨時(shí)間分為三個(gè)階段:第一階段,型芯由于脫水而低于初始強(qiáng)度;第二階段,型芯的粘結(jié)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(shí)獲得較高的燒結(jié)強(qiáng)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(shí)粘結(jié)力主要由新相提供,型芯強(qiáng)度降低甚至彎曲變形無(wú)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(hào)：2300511