Grey iron

Grey iron is grey cast iron with lamellar graphite. EN-GJL-150 is the type of grey iron that has the longest lamellae. It is the graphite that gives it the grey colour.

Grey cast iron, which is easy to cast and process. Here carbon is separated as graphite flakes in different sizes depending on the shape it has. The shorter the slats, the easier it is to work the cast iron. It has strength equivalent to aluminum alloys, but is crispy.

The reason why the carbon in gray cast iron occurs as graphite is the following: Firstly, gray cast iron has a high content of silicon, and secondly, the cooling of grey cast iron is slow compared to the cooling of white cast iron. Gray cast iron contains austenite at higher temperatures, which results in perlite or ferrite. The graphite does not connect with the iron, so gray cast iron is actually steel and graphite, which are in a structure. There is a difference in how much tension gray cast iron can withstand. It depends on how much pearlite and ferrite are in the gray cast iron. The more pearlite, the stronger the iron, but only up to a certain limit. As mentioned, gray cast iron contains more silicon than white cast iron, and it also contains more carbon than white cast iron. Gray cast iron also contains small amounts of sulphur, manganese og phosphorus.

Compared to white cast iron, grey cast iron can welded, however, white cast iron can form in the welded area due to the heating that occurs with the iron. Therefore, it is necessary to cool it slowly. Grey cast iron is not nearly as hard as white cast iron. This also means that it is machinable. The more ferrite the iron contains, the easier it is to machine. Grey cast iron is used for various purposes, but since it is soundproof, it is used, among other things, for machine parts and also for brake discs for cars and trucks.

For technical data on gray iron and our advice on material selection, depending on application, contact us by phone 0045 97 40 65 10.

Normal alloys within Grey Iron:
EN-GJL-150 / GG15 – typically used for wood-burning stoves and grates
EN-GJL-200 / GG20 – typically used for gear housings
EN-GJL-250 / GG25 – typically used for pump housings
EN-GJL-300 / GG30 – typically used for valves
EN-GJL-350 / GG35 – typically used for cylinder