镁合金航空铸件用复杂砂芯成型性及溃散性调控机制

The new generation aviation castings use a lot of high strength and low density magnesium or aluminum or titanium alloy as materials, and the structures of casting part are developed toward to integration, hollow thin-walled and complication, so that it makes the casting　parts and the foundry sand cores to be very complex, and the intracavity pores of casting parts are also difficult to be clean, and the performance of the foundry sand cores becomes very harsh. Which requires the sand core possessing good formability, sufficient normal temperature strength, little gas evolution and outstanding casting collapsibility. The production of easy collapsibility complex sand cores has been considering the bottleneck technique of magnesium alloy aviation castings production. This project will study controlling mechanism of complicated sand cores formability and collapsibility for magnesium alloy aviation castings, and reseach foundry sand core new materials which possess good formability, sufficient normal temperature strength, little gas evolution and their structure evolvement in the casting process, and investigate the collapsibility mechanism of complex sand cores and the efficient cleaning method of complex magnesium alloy castings under the outer force and temperature fields. It will lay a theoretical and technical foundation to solve the difficult problems for the production of complex magnesium alloy aviation castings. The typical aviation complex casting will be used to study the formability, collapsibility and their token methods of the complicated sand cores. The high strength water-soluble sand cores hardened by microwave heating will be used to investigate the new materials structure evolvement in the casting process. The vibration and jet flow will be helped to sand cores collapsing, and it will be studied aslo that the sand cores collapsing mechanism and the casting efficient cleaning method under outer force field action.

新一代航空铸件大量采用高强度、低密度的镁铝钛合金材料，铸件结构向整体化、空心薄壁化、复杂化方向发展，铸造砂芯变得十分复杂、铸件内腔很难清理。对砂芯的性能要求也十分苛刻，要兼有优良的成型性、足够强度、低发气量和杰出的铸后溃散性。复杂砂芯的成型及其铸件清理一直是镁合金航空铸件生产的瓶颈。本课题将研究镁合金航空铸件用复杂砂芯的成型性、溃散性及其调控机制，研究优良成型性、足够强度、低发气量的新型砂芯材料及其在铸造过程中的结构演化规律，研究外温度场和力场作用下复杂砂芯的溃散机理及其铸件高效清理新方法，为突破复杂镁合金航空铸件的制造难题奠定理论基础。拟以典型航空复杂镁合金铸件为对象，研究复杂砂芯的成型性、溃散性及其表征方法；采用微波加热获得高强度水溶性陶瓷砂芯，研究新型砂芯材料组成及其在铸造过程中的结构演化；辅助振动、射流等方法实施砂芯溃散，研究外力场作用下复杂砂芯的溃散机理及其铸件的高效清理方法。

为了解决复杂镁合金铸件成形及其高效清理难题，开展了复杂细长砂芯的成形性、溃散性及其表征方法研究；研究了微波加热硬化水溶性硫酸镁砂芯的性能特征及其抗湿强化机理；研究了可溶性氧化铝基型芯的性能特征及其高效脱芯方法；提出了一种综合化学溶解、振动破碎和超声空化的型芯复合清理新技术，采用发明的清理新装置研究了不同工艺参数对型芯清理效率的影响；模拟分析了镁合金浇注时型芯的受热温度变化；研究了不同型芯材料铸造成形复杂内腔镁合金零件的实际效果。研究结果表明：影响砂芯成形性的因素有砂芯的形状、原砂种类和射芯压力等，影响砂芯溃散性的因素有受热温度和原砂种类等；微波加热硬化水溶性硫酸镁砂芯具有良好的常温强度、表面安定性、高温溃散性及水溶清理性，发气性小，但抗吸湿性较差；采用硫酸铝、高岭土或硫酸钠改性硫酸镁水溶液，均能较大提高砂芯的抗吸湿性；采用硫酸镁砂芯表面涂刷凡士林或石蜡的方法，可大幅提高砂芯的抗吸湿性；可溶性氧化铝基型芯较佳配方为浆料粉液比2.4~2.6g/ml、固化剂加入量1~2wt.%、粗粉加入量0~20wt.%，较佳的烧结工艺为烧结温度800~900℃、保温时间2~3小时；烧结温度的升高可增加莫来石相的含量，氧化钛的加入可提高型芯的强度、降低型芯的溶失率和显气孔率，硼砂的加入可大幅提高型芯的强度、降低型芯的显气孔率和溶失率，石英粉的加入可提高型芯的溶失率和显气孔率、降低型芯的强度，氢氧化钠碱液可较快溶失脱除氧化铝基型芯；发明的型芯清理新方法及装置可较快地清理内腔中的残留型芯，较优的清理工艺参数为清理液NaOH浓度5wt.%、振动电机偏心块夹角2/18π、超声波功率1200W。镁合金浇注时热容量低，型芯的受热温度低，温度超过300℃的时间较短；采用本研究发明的型芯新材料及其清理新方法可完成复杂内腔结构镁合金铸件的高效清理，验证了本研究成果在复杂内腔镁合金零件实际铸造中的应用。本项目研究成果对提高我国航空航天镁铝合金复杂铸件及其它复杂铸件的制造水平，都具有重要的理论与实际意义。