汽车用铝合金压铸件的工艺优化与组织及缺陷控制

发布时间：2018-05-04 11:12

  本文选题：压铸铝合金 + 压铸工艺　； 参考：《东南大学》2017年硕士论文

【摘要】：随着汽车轻量化的快速发展,压铸技术及高强韧压铸铝合金在汽车关键零部件上的应用一直是压铸领域研发的热点之一。本文系统了研究压铸过程中工艺参数对试样性能的影响,以及组织变化、缺陷控制对试样性能的影响,同时探讨了压铸合金在热处理过程中组织和性能变化规律,对压铸铝合金生产,提高产品质量具有重要的理论及实际意义。结合压力铸造的特点,本论文研究了在高压铸造下工艺参数对铝合金铸件的组织特征、力学性能和缺陷控制的影响。实验采用了正交试验设计和分析方法,通过优化压铸工艺实验参数:浇注温度、高速切换点位置和压射速度,探讨了不同压铸工艺条件下ADC12合金显微组织和力学性能的关系。研究结果表明:铸件的综合力学性能受浇注温度影响最大,临界压射速度、高低速切换点位置次之。当浇注温度为680 ℃,快压射临界速度为3.0 m/s,高速切换点位置440 mm时,铸件中显微组织α-Al枝晶细小且分布均匀,微孔缺陷较少,合金密度达到最大值2.73 g/cm3,其综合力学性能最好,其最大抗拉强度达到235.5 MPa,断后延伸率2.8%,高于标准铸态ADC12铝合金的力学性能。从拉伸试样的宏观端口分析得到,试样断裂机制是脆性断裂。为进一步控制压铸件内部孔洞缺陷,来提升其力学性能,本文采用超低速慢压射工艺,考虑到压铸机、压铸模具与压铸合金的有机结合,改用AC4CH合金能较好的匹配本实验用的压铸机的技术参数与压铸模具,得到的压铸件压铸缺陷更少、性能更高,在此基础上从熔体净化处理和优化压射速度工艺参数两个方面分析AC4CH合金的显微组织、力学性能和缺陷控制的关系。结果表明,当精炼剂添加量为0.3 wt%,静置时间30 min,铝熔体获得较佳的精炼净化效果,铝熔体含氢量控制在0.30 ml/100 g以下;再通过工艺的优化,当慢压射临界速度为0.18 m/s时,压铸件中微观组织枝晶α-Al相对细小致密,孔洞缺陷明显减小,合金密度达到最高,铸态下其综合性能达到最大,即抗拉强度、断后延伸率分别达到 267.5 MPa、15.4%。对超低速慢压射的压铸铝合金AC4CH进行了固溶和时效工艺的优化,以进一步提高合金的力学性能。实验结果表明,采用低温固溶和时效工艺(510 ℃×6 h+170℃×3 h),合金的抗拉强度和延伸率可分别达到334.7MPa和9.5%,同时大幅度地减少了铸件表面"起泡"缺陷,降低了产品的废品率。
[Abstract]:With the rapid development of automobile lightweight, the application of die casting technology and high strength and toughness die casting aluminum alloy in automobile key parts has been one of the hot spots in the field of die casting. In this paper, the influence of the process parameters on the properties of the samples during die casting, the change of the microstructure and the effect of the defect control on the properties of the specimens are studied systematically. The changing rules of the microstructure and properties of the die casting alloys during the heat treatment are also discussed. It has important theoretical and practical significance for die-casting aluminum alloy production and improving product quality. Combined with the characteristics of pressure casting, the effect of process parameters on the microstructure, mechanical properties and defect control of aluminum alloy castings under high pressure casting was studied in this paper. The orthogonal experimental design and analysis method were adopted. The relationship between microstructure and mechanical properties of ADC12 alloy under different die casting conditions was discussed by optimizing the parameters of die casting process, such as pouring temperature, position of high speed switching point and injection speed. The results show that the comprehensive mechanical properties of the castings are most affected by the pouring temperature, the critical injection speed and the position of the high and low speed switching point are the second. When the casting temperature is 680 鈩，

本文编号：1842819