Cast iron

Cast iron may contain 2-4% carbon and varying amounts of silicon, manganese, phosphorus, and sulfur to obtain a wide range of physical and mechanical properties. Alloying elements (silicon, nickel, chromium, molybdenum, copper, titanium, and so on) may be added in ampounts varying from a few tenths to 30% or more. Many of the alloyed cast irons have proprietary compositions.

(from "Iron alloys" in McGraw-Hill Encyclopedia of Science and Technology vol 9 p 448 [1997])

Pig iron contains more than 4% carbon and significant amounts of manganese, silicon, and phosphorus. Pig iron must be refined in subsequent steelmaking operations.

(from "Iron metallurgy" in McGraw-Hill Encyclopedia of Science and Technology vol 9 p 455 [1997])