Editing Cast iron (section)

===Grey cast iron===
[[File:BLW Pair of firedogs.jpg|thumb|Pair of English [[firedog]]s, 1576. These, with [[Fireplace fireback|fireback]]s, were common early uses of cast iron, as little strength in the metal was needed.]] 
{{Main|Grey iron}}

Grey cast iron is characterised by its graphitic microstructure, which causes fractures of the material to have a grey appearance. It is the most commonly used cast iron and the most widely used cast material based on weight. Most cast irons have a chemical composition of 2.5–4.0% carbon, 1–3% silicon, and the remainder iron. Grey cast iron has less [[tensile strength]] and [[shock resistance]] than steel, but its [[compressive strength]] is comparable to low- and medium-carbon steel. These mechanical properties are controlled by the size and shape of the graphite flakes present in the microstructure and can be characterised according to the guidelines given by the [[ASTM International|ASTM]].<ref>{{Cite web|title = Test Method for Evaluating the Microstructure of Graphite in Iron Castings|url = http://www.astm.org/cgi-bin/resolver.cgi?A247-10|doi = 10.1520/a0247-10|first = A04|last = Committee}}</ref>