After melting, purifying and alloying the iron or steel, the molten metal is poured into an ingot mold where it is
allowed to solidify. Most impurities rise to the top of the ingot before the metal is completely solid. However, some of
the foreign materials can become trapped within the ingot during solidification. Because such entrapment is usually
concentrated near the top, the ingot is cropped to remove most of the impurities.
Primary and Secondary Processing.
Ingots undergo primary processing to form the metal into basic shapes according to end-product requirements.
Secondary processing is subsequently used to manufacture the final products. Figure 3-41 is a pictorial story of steel
processing which shows in sequence the principal stages or operations where defects may be created, and indicates the
defects most likely to be found in the material as it leaves each stage. This illustration should be studied in conjunction
with the text in this section.