Grey iron gets its name from the colour of the internal metallic structure that's visible when the iron is fractured. It is also known as Flake Iron because when viewed under a microscope, the graphite is flake-like. The flakes are connected throughout the structure. These interconnections form natural lines of weakness making this form of iron relatively unyielding up to the point of failure. This aspect of the metal has to be managed especially in thin sections.
We produce our Grey iron mostly in our Cupola Blast furnaces; arguably the best method for Grey Iron production because of the natural carburization of the iron during melting (carbon pick-up from the coke), high metling rate and comparatively lower cost.
Grey iron is used for castings where tensile strength is non-critical, such as engine cylinder blocks, pump housings, valve bodies, electrical boxes, general engineering and architectural castings. Grey iron's high thermal conductivity can be enhanced to make cast iron melting pots, ingot moulds and disc brakes. It has excellent machining qualities, compression & load bearing properties making it ideal for machine bases, press tools and the bodies of our Norton Presses.
Grey Iron has been specified under many national and international standards. Commonly specified standards include
BS1452:1990 (now superceded)
BS EN 1561:2011
All grades are produced under controlled conditions and melts are grade certified by an independent UKAS laboratory when required.
BS EN 1561 Grades Offered:
Other grades of iron produced for specialised purposes include
GM241 a flame hardenable grade used in Press Tool manufacture
Hematite for heat resisting castings.
Grey Iron is occasionally specified by UK customers with reference to the old imperial grades 10,14,17,20 and 23 (tonnes/in2) for early versions of BS1452. These have metric equivalents 150, 200, 250, 300, 350 (N/mm2) found in the later versions of the same standard.