【作者】 赵康培；

【导师】 于彦东；

【作者基本信息】 哈尔滨理工大学 ， 材料加工工程， 2004， 硕士

【摘要】 镁合金是目前最轻的工程金属材料,具有很高的比强度、比刚度、比弹性模量、导热性、优良的流动性、切削加工性、抗电磁干扰及屏蔽性能、可回收性等一系列优良性能,在航空航天工业、汽车工业、电子通讯工业正在得到日益广泛的应用,前景十分广阔。浇口及浇注系统对获得高质量的压铸件起着非常重要的作用。低劣的浇注系统会导致产生气孔、缩松、变形流线、冷隔以及粗糙的表面等缺陷,尤其是镁合金。镁合金特殊的凝固性质使得充型速度为铝合金的两倍,实际上薄壁镁合金压铸件浇注速度能达到120m/s。因此通过浇口及浇注系统的优化设计,来达到充型的优化显得非常重要。然而,由于金属模具的不透明性和熔融金属的高压使得很难对充型过程做出视觉化评估。这样,数值模拟技术便受到关注,并成为一种极富成本效益的工具。本文首先建立了镁合金材料性能库,借助于Pro/Engineer软件设计了两种不同类型的浇注系统,并进行了充型过程的数值模拟。初步设计中采用普通浇口,产生了紊流式填充,铸件中存在较多的气孔和冷隔缺陷,铸件质量较差。优化设计中采用连续的锥形双切向浇注系统和较大的浇口尺寸,使浇注面积增加,浇注速度略微降低。充型模拟结果表明:优化设计充型过程均匀,最后填充区域位于易放置溢流槽和排气槽的部位,且铸件气孔等缺陷少,铸件整体质量较高。在优化设计基础上完成了压铸模具各成型部件,包括动、定模套板,动、定模座板,支承板,垫块等及辅助机构的设计,并将模具各部分按实际生产的顺序进行装配,组合成一套完整的三维模具装配图,将所有零件的3D模型转换成2D工程图。利用选择性激光烧结技术,生产出外形良好的薄壁镁合金通讯样件,从样件的结构等诸方面看,很好的体现并验证了模具设计的思路。更多还原

【Abstract】 Magnesium alloy is so far the lightest metal, it’s series of excellent properties, such as high specific strength, heat conductivity, elastic modular, liquidity, resisting shielding property and electromagnetic interference, make it widely used in automobile, aerospace, electron and communication. What’s more, it will take on an extensive prospect.Runner and gating systems play a very important role in the die casting of high quality product. Poor gating system designs can lead to various defects such as gas porosity, shrinkage porosity, flow lines, cold shuts and poor finish. This is particularly so for magnesium alloys, as, due to their specific solidification behaviour, the die cavity is filled at very high gate speeds, which are normally double those commonly used in aluminium die casting. Indeed, the gate speed for a thin-walled magnesium part can be as high as 120 m/s. Optimization of the mold filling patterns through improvement of the runner and gating system design becomes very important. However, the opacity of the metal mould and the high metal pressure during casting make the mould filling process very hard to be directly and visually evaluated. Therefore, numerical simulation has obtained great attention and is considered as the most cost-effective way in optimization of the runner and gating design.In this paper, the property database of magnesium alloys is established firstly. At the same time, two types of gating systems are designed and analyzed by means of Pro/Engineer software. A preliminary design with a common gating system results in swirling filling and a high possibility of air entrapment in the casting. The design is improved by using a continuous double tangential tapered gating system and a bigger size runner. The gate area is increased and the gating speed is slightly reduced. Numerical simulation shows that the new design provides a homogenous mould filling pattern with the last filled areas being located in the places that overflows and vents are conveniently attached. What’s more, on the whole, the quality of casting is <WP=7>very good. Based on this optimized runner and gating system, the mould ingredients, including the moving mold cleading, fixed mold cleading, moving mold bed plate, fixed mold bed plate, bolster plate, cushion blocks and the complementary units, are designed. Subsequently, an entire three-dimensional mold assembly diagram is completed in the actual manufacturing order, and all three-dimensional models are converted into two-dimensional engineering drawings. Finally, good quality thin-walled telecommunication prototype parts with a good finish are obtained by means of selective laser sintering technology. From the aspect of structures, the design frame of mould occurs and is justified.更多还原