【作者】 林海；

【导师】 万里；

【作者基本信息】 华中科技大学 ， 材料加工工程， 2010， 硕士

【摘要】 基于低碳经济及汽车行业的竞争日趋激烈,轿车轻量化技术是汽车工业可持续发展的必然方向。其中汽车底盘悬架关键零部件的轻量化及其成形技术是当前国内外重点开发的前沿领域之一。为配合广汽集团国产自主品牌轿车的开发,本文针对该车中的底盘后副车架零件,首次在国内研发了具有自主知识产权的轿车底盘后副车架用高强韧压铸铝合金及其高真空压铸成形技术,满足了自主品牌轿车的开发需求。本课题对于提升我国汽车零部件的制造技术水平,特别是压铸工业的技术水平,促进我国汽车行业的发展,有着非常重要的理论和实际意义。本文设计并优化了铝合金后副车架的高真空压铸工艺。采用FLOW-3D数值模拟软件分析了铝合金后副车架在不同工艺下的压铸充型过程,优化出了合理的浇注系统及排气/溢流系统。设计并制作了高真空压铸用模具密封结构,在使用自主研发的高真空压铸控制系统及真空截止阀时,模具型腔的真空度可在1s内达到91kPa以上。以Al-Mg合金为基础,研究了Mg、Si、Mg /Si比值、Ti、Cu、Be等微量元素对后副车架随铸试样力学性能的影响,获得了适用于后副车架高真空压铸技术的新型高强韧压铸铝合金,其化学成分约为Mg 5.6%,Si 1.78%,Cu 0.0142%,Ti 0.182%,Be 0.0035%。研究了高真空压射工艺参数如模具型腔真空度、抽真空时间、压射速度及高速切换点位置等对铸件内部质量及力学性能的影响。试验结果表明:该铝合金轿车底盘后副车架在最佳高真空压铸工艺参数:抽真空启动/停止位置分别为110mm和700mm;冲头慢压射速度0.19m/s,快压射速度5.8m/s;高速切换点240mm;型腔真空度91kPa以上时,铸件外观成形良好,组织致密,无缩孔气孔缺陷。铸件本体抗拉强度达240MPa以上、屈服强度达145MPa以上、延伸率达6%以上。最后针对后副车架压铸生产中常出现的典型缺陷如冷隔、裂纹、气孔、缩孔、粘模拉伤等,分析了它们的特征、形成机理、影响因素,并提出了防止措施和解决方案,取得了良好的效果。更多还原

【Abstract】 Based on low carbon economy and automotive increasingly fierce competition, Car lightweight technology is the inevitable direction of sustainable development in automotive industry. The development of lightweight and forming technique for car chassis suspension key parts is one of the foremost field at home and abroad today. To cater for the development of homebred own-brand cars for Guangzhou automobile group, innovative die casting aluminium alloy which is high strength and ductility, and high vacuum die-casting forming technology for the rear sub-frame of car chassis is researched and developed for the first time in domestic in this paper, which meet the development requirements for own-brand cars. This research will have significant iMPacts in theoretical and practical on automotive parts manufacturing technology level, especially on die-casting industrial technology level, and promote the development of automobile in China.The high vacuum die-casting technology for aluminium alloy rear sub-frame is designed and optimized in this paper. Die-casting filling process in different techniques is simulated with FLOW-3D numerical simulation software, and optimized a reasonable pouring and overflowing system. The mould sealing structure for high vacuum die-casting is desinged and manufactured, which can make the vacuum level of cavity being up to 91 kPa in a second through the use of an innovative high vacuum control system and vacuum stop valve.Based on Al-Mg alloy, the effects of composition including magnesium, silicon, the ratio of magnesium and silicon, titanium, beryllium copper on casting mechanical properties were investigated in this paper. A new die casting aluminium alloy with high strength and ductility is developed for the rear sub-frame high vacuum die casting, the composition of which is about Mg 5.6%, Si 1.78%, Cu 0.0142%, Ti 0.182%, Be 0.0035%.Effects of shot parameters including vacuum level, venting time, shot velocity and switch position of fast velocity on casting quality and mechanical properties were investigated for the high vacuum die-cast car chassis part in this paper. The results showed that the vacuumed startup and stop position are 110mm and 700mm respectively, and the vacuum level of cavity is up to 91 kPa. Meanwhile the slow and fast velocity of the injection punch are 0.19 and 5.8 m/s, and switch position of fast velocity is 240mm. The round car chassis part can be achieved under above parameters, whose tensile strength is over 240 MPa, yield strength over 145 MPa and elongation up to 6%. At the end of the paper, the characteristics, formation mechanisms and influencing factors of high vacuum die casing defects during the process of production of rear sub-frame were analyzed, which included cold lap, cracks, porosity, shrinkage, etc. and prevent measures and solutions were proposed.更多还原