基于A356.2铝合金汽车螺簧座挤压铸造技术研究

发布时间：2018-06-29 22:59

本文选题：铝合金 + 挤压铸造　；参考：《武汉理工大学》2015年硕士论文

【摘要】：汽车轻量化是指在保证汽车综合性能的前提下,尽可能降低自身重量,以实现减重、降耗、环保、安全的目的。据统计,汽车重量降低10%,燃油效率可提高6%~8%,轻量化还有助于汽车操纵的稳定性和冲撞安全性。螺簧座是汽车后桥上用于安装弹簧的支撑件,通常采用的是Q235。为实现汽车的轻量化,本课题选择高强度比的A356.2铝合金材料代替碳钢,采用挤压铸造工艺成型螺簧座,力学性能要求本体取样满足屈服强度220MPa、伸长率4%。在研发铝合金螺簧座的过程中,对挤压铸造技术进行了全面而深入的研究。本实验采用宇部HVSC350PL型挤铸机成型螺簧座,主要研究铸造压力、充型速度以及T6热处理对组织和性能的影响,并结合Anycasting计算机模拟技术,对充型情况和凝固情况进行分析。其中,挤压铸造领域受实验设备的限制而对充型速度的研究很少。在研究过程中,量化实验条件以保证实验的可重复性,如跟踪材料成分、检测含氢量和含渣量以确定熔炼质量等。T6热处理方案为545℃×6h+70℃水淬+180℃×4h,对固溶炉进行温度均匀性实验,并采用分级升温的方法使热处理方案能够准确执行。对螺簧座本体取样进行拉伸实验,并结合计算机模拟结果和SEM、EDS分析,寻找断裂原因并给出进一步提高力学性能的方案。另外,本文还对试验中遇到的问题,如Sr-B的变质效果、孔洞缺陷、热处理气泡、Si偏析等进行研究。研究表明,压力增加凝固时的温度梯度并且促进压力过冷,提高凝固阶段的形核驱动力和降低晶粒的线生长速度,在显微组织中,a-Al相的晶粒度相比于重力铸造明显减小,并且随着铸造压力的增加,晶粒度逐渐减小,不均匀性有所增加,形貌也有团块状的发展趋势,在固溶处理后,共晶相中Si元素析出成团状存在于铝基体中,不同压力下的金相组织趋于一致。随着铸造压力的增加,铸态与T6状态螺簧座的力学性能有较小的增加趋势,但是在一定铸造压力范围内,不建议通过提升压力来提高力学性能。随着充型速度的增加,铸态与T6状态螺簧座的力学性能有明显提高的趋势。较高的充型速度会产生涡流,但是强烈的对流以及冲刷型腔壁也促使产生“游离晶粒”,在一定范围内,可以考虑通过增加充型速度提高力学性能。
[Abstract]:Vehicle lightweight is the purpose of reducing weight, reducing consumption, environmental protection and safety on the premise of guaranteeing the comprehensive performance of the car to achieve weight reduction, consumption reduction, environmental protection and safety. According to statistics, the vehicle weight can be reduced by 10%, the fuel efficiency can be increased by 6%~8%, the light weight is also helpful to the stability and impact safety of the vehicle control. The screw reed seat is used for installation on the rear axle of a car. The support part of spring usually uses Q235. to realize the lightweight of the automobile. This topic chooses the A356.2 aluminum alloy material with high strength ratio instead of carbon steel. The squeeze casting process is used to form the screw reed seat. The mechanical properties require the bulk sampling to meet the yield strength 220MPa. The elongation 4%. is used for the extrusion casting technology in the development of the aluminum alloy spring reed seat. In this experiment, a complete and thorough study was carried out. In this experiment, the effect of the casting pressure, filling speed and the effect of T6 heat treatment on the structure and properties was mainly studied by the molding of the space HVSC350PL type extrusion casting machine, and the filling and solidification conditions were analyzed with the computer simulation technology of Anycasting. The field of extrusion casting was set up by experiment. In the course of the study, the experimental conditions are quantified to ensure the repeatability of the experiment, for example, the.T6 heat treatment scheme, such as the tracking material composition, the determination of the hydrogen content and the slag content to determine the melting quality, is 545 C 6h+70 C water quenched +180 C for 4h, and the temperature uniformity experiment of the solid solution furnace is carried out and the classification is adopted. The heating method can make the heat treatment scheme be carried out accurately. The experiment on the body sampling of the screw reed body is carried out, and the computer simulation results and SEM, EDS analysis are used to find the cause of the fracture and give a scheme to further improve the mechanical properties. In addition, the problems encountered in the experiment, such as the deterioration effect of Sr-B, the hole defect and the heat in the heat, are also discussed in this paper. The study shows that the pressure increases the temperature gradient in the solidification and promotes the pressure supercooling, increases the nucleation driving force in the solidification stage and reduces the line growth speed of the grain. In the microstructure, the grain size of the a-Al phase decreases obviously compared with the gravity casting, and the grain size decreases with the increase of the casting pressure. The inhomogeneity increases and the morphology also has a mass trend. After solid solution treatment, the Si element in the eutectic phase exists in the aluminum matrix, and the metallographic structure under the different pressure tends to be consistent. With the increase of the casting pressure, the mechanical properties of the cast and T6 state reed seats have a smaller increasing trend, but they are cast in certain casting. In the range of pressure, it is not recommended to improve the mechanical properties through the lifting pressure. With the increase of the filling speed, the mechanical properties of the cast and T6 state reed seats are obviously improved. The higher filling speed will produce eddy current, but the strong convection and the scouring cavity wall also cause "free grain", which can be found in a certain range. It is considered to improve the mechanical properties by increasing the filling speed.
【学位授予单位】：武汉理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG249.2;U466

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