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Application of Castings on Wheel-End and Suspension


A study shows considerable opportunity remains for


lightweighting on already proven applications. ANDREW HALONEN, MAYFLOWER CONSULTING LLC (CALUMET, MICHIGAN)


W


ith the increasing CAFÉ 2025 fuel economy targets, automobile manu-


facturers are using many methods to improve fuel economy. Engine down- sizing, turbo systems, electrification, aerodynamics and lightweighting are among the most effective methods. In 2017, there was much discussion about electrification: will it gain market acceptance and if so, how will it affect the material selection? Logically, range- limited vehicles will benefit most from lightweight materials, yet because car manufacturers are adding expensive batteries and related operating systems, they need to carefully manage costs. On the materials front, each issue


of an automotive magazine includes color-coded images representing different materials that make up the “multi-material vehicle.” Most of the time, this is a vehicle body structure, commonly referred as the body-in- white, yet it often includes the clo- sures, the doors, hood and trunk. Te body and closures cover a significant


portion of the weight of a light-duty vehicle, on the order of 30% of the whole vehicle. What about underneath the body?


Which materials are used? Which processes are used? To find out, a study looked at 89 vehicles over 16 brands and includes five performance cars, 24 cars, 38 cross-overs/SUVs, 15 pickups, four minivans and three work vans (Table 1).


Te wheel-end and suspension


components are roughly 20% of the total vehicle weight, yet these compo- nents and systems get little attention in the automotive press and across the material consortiums promoting their respective materials and process inno- vations. Tese components include wheels, brake calipers, brake discs, steering knuckles and suspension arms and links (Fig. 1).


Wheels Most wheels on light duty vehicles


are cast aluminum. Years ago, steel dominated the wheel market. Te first cast aluminum wheels were a weight-


add, meaning they were heavier than steel. You can find steel versus aluminum weight studies dated back to 2009, yet regardless of weight, the vehicle designers desire the look of aluminum wheels. Te casting process is versatile,


providing an open palette of wheel designs. In the car study, 22 of the 24 cars had aluminum wheels. Te Chevy Spark had steel wheels and unsurpris- ingly, the other car with steel was a Toyota Camry hybrid. While it might be surprising that a hybrid had steel wheels, this OEM selects mostly fer- rous materials. In all of the vehicles across all seg-


ments, nine of 10 wheels are alumi- num. Industry insiders say the overall aluminum wheel content is around 75% because most spare tires are steel. Tat is, until OEMs replace that spare tire and the jack with a can of “fix-a- flat,” saving about 30 lbs. and reducing the vehicle cost.


Brake Discs and Drums Typically, brake discs are made


April 2018 MODERN CASTING | 37


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