Gray iron

Grey iron is grey cast iron with slatted graphite. En-GJL-150 is the type of gray iron that has the longest slats. It's the graphite that gives it gray color.

Grey cast ironthat are easy to cast and machine. Here carbon is released as graphite flakes in different sizes depending on its shape. The shorter the lamellae, the easier it is to machine the cast iron. It has a strength equivalent to aluminium alloysbut is brittle.

The reason why the carbon in grey cast iron occurs as graphite is as follows: firstly, grey 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. Grey cast iron contains austenite at higher temperatures, which turns into perlite or ferrite. The graphite does not bond with the iron, so grey cast iron is actually steel and graphite in one structure. There is a difference in how much drag grey cast iron can withstand. It depends on how much perlite and ferrite is in the grey cast iron. The more perlite the stronger the iron, but to a certain limit. Grey cast iron contains more silicon than white cast iron, as mentioned above, and it also contains more carbon than white cast iron. Grey cast iron also contains small amounts sulphur, manganese and phosphorus.

Compared to white cast iron, grey cast iron welded, however, white cast iron may form on the welded area due to the heating of the iron. Therefore, it is necessary to cool it slowly. Grey cast iron is not nearly as hard as white cast iron. This also makes it workable. The more ferrite the iron contains, the easier it is to work. Grey cast iron is used for various purposes, but as it is sound-absorbent, it is used for machine parts and also for brake discs for cars and trucks.

For technical data on grey irons and our advice on material selection, depending on use, contact us on +45 0045 97 40 65 10.

Normal alloys within Grey Iron:
EN-GJL-150 / GG15 - typically used for stoves and grates
EN-GJL-200 / GG20 - typically used for gearboxes
EN-GJL-250 / GG25 - typically used for pump casings
EN-GJL-300 / GG30 - typically used for valves
EN-GJL-350 / GG35 - typically used for cylinders