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Contact between bare aluminum and steel can lead to gal- vanic corrosion, so mitigation strategies needed to be devised. Two aluminum-steel joining methods were used in the con- struction of the MMLV. In the traditional method used, an adhesive/sealant electrically isolates the materials (typically galvanized steel panels and hard-coat anodized aluminum casting surfaces) prior to being joined using self-piercing riv- ets. Te protruding end of the rivet also is sealed. Afterward, the assembly is submerged in a phosphate bath and e-coated. In the alternative method, the steel components are e-coated and the aluminum castings are hard coat anodized before the adhesive is applied and the parts are connected with self- piercing rivets. In this case, a phosphate and e-coat treatment is not required after assembly. “Going to an all-aluminum vehicle structure is expensive,”


Conklin said. “But with a bimetallic structure, every joint needs an adhesive barrier, and every joint has self-pierced rivets because you can’t spot weld steel to aluminum.” Te joints are more complicated, but incorporating alumi-


num extrusions and castings with some thoughtfully located steel frames leads to a reduction of parts. “Fewer parts to design means fewer tools to manu-


facture and less labor to join the parts,” Skszek said. “The number of parts has a cumulative effect. Less parts, means less bodies to make the parts and less assembly costs. It’s a gain in efficiency.” Te MMLV body-in-white design consists of 32 fewer components (12% reduction) than the baseline vehicle.


Next Steps Te MMLV is a concept car. It won’t go into volume pro-


duction, and Ford has not adopted the design for future Ford Fusion models. But the program has successfully served as a showcase of the weight reducing possibilities achievable with existing materials and processes. “All of the aluminum diecast applications demonstrated with the MMLV are being implemented with other custom- ers,” said Randy Beals, global engineering specialist-casting, Cosma International. The opportunity to design a car from the ground up


for a customer will probably not present itself to sup- pliers like Magna, but the increase in application of an aluminum casting in a structurally significant area of the vehicle is promising. “OEMs designing a new vehicle still set their weight tar-


gets,” Conklin said. “Based on their targets and requirements, we try to figure out the best location and application of castings where we feel we can get the best bang for our buck.” After the successful creation and testing of the first


MMLV concept car, Magna and Ford continued the pro- gram with a second version, this time with future concept materials and processes, such as magnesium castings and carbon-fiber parts. Tis version is only a “paper study” and was intended to identify the gaps that have to be addressed to enable use of the new materials as mainstream technol- ogy. It also poses another scenario for future research and development: “What if even lighter materials were used to make a vehicle body-in-white?” 


不同材质的连接方式


在设计由不同材质组成的结构中,选择不同材质 零部件的连接方式是最大的挑战。直接将铝合金和 合金钢连接将引起电化学腐蚀,因此,应设计缓解 措施。MMLV项目中使用了两种铝-合金钢的连接方 法。传统方法是,在用自穿透铆钉连接之前(一般是 镀锌钢板和阳极氧化处理的铝合金铸件)用粘结剂/密 封剂将材料进行电隔离。铆钉的突出部分也被密封。 之后,将连接体浸入磷酸盐池,并进行电镀。另一种 方法是,在使用粘结剂之前以及两个部分通过自穿透 铆钉连接之前,将合金钢零部件进行电镀、将铝合金 铸件进行阳极硬化处理。在此情况下,部件连接后不 需进行磷酸盐和电镀处理。


“汽车使用全铝合金结构是昂贵的,”Conklin 说:“但是,双金属结构中,每个连接处都需要粘结 剂保护,而且由于不能将合金钢和铝合金焊接在一 起,每个连接处都有自穿透铆钉。”


焊接点更加复杂,但是,将铝合金挤压件和小心放 置的合金钢框架铸件进行焊接能够减少部件的数量。 “需要设计的部件数量减少意味着生产较少的模 具、使用较少的工人来焊接部件,”Skszek说:“部 件数量具有累积效应。较少的部件意味着需要较少的 工人来生产部件,以及组装成本较低。因此,效益提 高。”


下一步计划


MMLV是一款概念车,将不会批量生产,而且福特 汽车公司没有采用未来福特福星汽车的设计。但是, 该项目已成为一个采用现有材料和工艺减轻汽车重量 的成功案例。


Cosma 国际公司的全球工程压铸专家Randy


Beals 表示:“MMLV展示的所有铝合金压铸件正在 被其他客户应用。”


“OEM供应商设计一款新车仍然需要设置重量目 标,”Conklin认为:“按照他们的目标和要求,我 们需尽量设计出最好的铸件位置和应用,从而使我们 能够获得最好的回报。” 经过首款MMLV概念车的成功生产和测试 后,Magna公司和福特汽车公司继续开展了第二版汽 车的合作项目,并采用了未来的概念材料和工艺,例 如镁合金铸件和碳纤维铸件。新版车目前尚处于讨论 阶段,还需弥补存在的差距,使新材料的使用成为主 流技术。它还为今后的科研提出了新的挑战:“是否 可以使用更轻的材料制造一款白车身汽车呢?” 


December 2015 FOUNDRY-PLANET.COM | MODERN CASTING | CHINA FOUNDRY ASSOCIATION | 53


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