What’s your car made of? There was a time that the answer to that question was pretty simple, at least for most parts of it: iron. But, today, the answer is just as likely to be something else. Here, a steelworker explains how that transition happened — and why it might swing back.

Commenter amp0730 filled us in on some of the pros and cons of steel vs. aluminum for car-manufacturers, from inside of the foundry. While iron once ruled the land, aluminum has popped up to occasionally steal the crown — although iron’s not exactly down for the count yet.

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But, just as aluminum arrived to unsettle iron, there’s yet another bright young contender on the horizon:

Even as someone who works in a cast iron (ductile) foundry, our biggest competitor for the parts we make are actually companies that make aluminum forgings. There are positives and negatives to both.

When you are talking mass production, cost is obviously as important as effectiveness. Aluminum is much lighter than steel and iron components, which is the easiest way to improve gas mileage. Problem is iron is WAY cheaper. It’s a lot easier to find recycled iron than aluminum, and mining iron is also much cheaper.

Long term strength though, iron and steel win again. So there is a lot to be considered when jumping back and forth between materials, which has happened to us quite a lot. We have 3 or 4 jobs that were aluminum and we are now making out of ductile cast iron. We also have a few jobs we might lose to aluminum forgings.

Long term, composites like carbon fiber will be thrown in that mix too, but for now that isn’t a factor. It will be interesting to see how advancements in that technology will affect manufacturing processes in the future.

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Image: Tesla Model S assembly / Steve Jurvetson