Not all metals are amenable to the mechanical deformation which occurs with mechanical forming processes discussed in the previous sections. Those metals that can undergo mechanical forming are referred to as wrought metals. For those metals that are not amenable to mechanical deformation, they are typically cast.
Casting is the process in which molten metal is poured (or cast) into molds. In the reading, you were introduced to five different casting techniques: sand, die, investment, lost foam, and continuous. Typically, it is more economical to use mechanical forming processes, since it requires more energy to heat metals until molten in the casting process. However, there are times when casting makes more sense, in addition to the obvious case of a metal not being amenable to mechanical deformation. Some of those cases include when making complicated shapes or when prototyping a part. When prototyping, the cost of making a forging die might be much more expensive than the cost of molds.
Now, please go to the second reading (2 of 3) of this lesson and read about how ceramics are fabricated.