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一、概述精铸型壳的性能是影响铸件质量的主要因素之一。目前国内生产精铸叶片所用型壳一般以硅酸乙酯为粘结剂,以电熔刚玉作耐火材料制作而成。但是刚玉价格昂贵,供不应求。而且由于其中Na_2O含量较高,在1050～1100℃的高温下开始与酸性粘结剂硅酸乙酯中的SiO_2起化学作用,形成Na_2O—Al_2O3—SiO_2三元低熔点液态物质,使型壳高温强度急剧下降,以致经受不住外界压力(液态金属的动、静压力和造型砂的压力)而变形,使叶片增厚或减薄,满足不了无余量叶片铸造的要求。
First, an overview Casting shell performance is one of the main factors affecting the quality of castings. At present, the domestic production of casting blade shell generally used ethyl silicate as a binder, fused fused alumina made of refractory material. However, corundum is expensive and in short supply. In addition, due to the high content of Na 2 O, chemical interaction with SiO 2 in acidic ethyl silicate begins to occur at a high temperature of 1050-1100 ° C to form a ternary low-melting liquid of Na 2 O-Al 2 O 3 -SiO 2, The strength drops sharply so that it can not withstand the external pressure (liquid metal dynamic and static pressure and the pressure of sand) and deformation, so that the leaves thickening or thinning, can not meet the requirements of margin casting leaves.