Heat treated materials are composed by different steels, most notably plain carbon (unalloyed, considered obsolete today) and high-speed steels.
Ihe mejupụtara ihe ọkụ na -arụ bụ steels dị iche iche, ọkachasị carbon dị mfe (nke anaghị arụ ọrụ, nke a na -ahụta ka ọ bụrụzi ihe mgbe ochie) na steels dị elu.