eli5 – why is cast metal weaker than forged metal?
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Cast metal is poured into a cast in a liquid state. Mold fills up, metal cools down and becomes solid. Forged metal is essentially compressed metal. The metal is heated enough to be malleable and then struck with hammers, which compresses the metal and makes it more dense. So a piece of forged metal compared to an equally sized piece of cast metal actually has more material, more mass, and is thus heavier, it’s just been pounded down to the same size, but the density compared to volume is higher. Each metal has a natural density it settles to but forged metal is forced to become more dense. This means that aside from heavier it’s also stronger. Since pounding something into an exact shape with gigantic hydraulic hammers is not exactly easy, forged parts are usually machined out of a bigger block of forged metal. In contrast cast parts come out of the cast pretty much done, only needing minor processing to remove casting marks and imperfections, basically just surface finish.
So Forged metal is stronger but also more expensive.
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