Engineering castings Iron, in its many forms, often alloyed with other metals and materials has been solving engineering design problems for centuries. The metal became so important that a whole period of history was named after it, The Iron Age, as the use of wrought and forged iron and steel superseded the use of bronze. All of this early use was based around two forms of iron, wrought iron and forged steel. Wrought iron is a very pure form of iron, commonly 99.9% Fe, which can be heated and forged into shape.