SG Ductile Iron
Ductile iron, also known as nodular cast iron, spheroidal graphite iron and SG iron, is a type of cast iron invented in 1943 by Keith Millis. In contrast to grey iron which is brittle, SG iron has much more impact and fatigue resistance, hence its common name ductile iron. In the production process, the graphite is formed into individual spheroids, isolating it in microscopic pools within the metal matrix. The strength of this iron predominantly comes from the matrix of ferrite/pearlite. Alloys can be used to alter the ratio between ferrite/pearlite to produce varying properties.
SG is typicallly used in high load bearing castings where longitudinal and dynamic forces are involved. Suspension arms, brake calipers, high pressure pump bodies are the types of castings made in SG iron, even architectural castings are increasingly being requested in this grade to mitigate against future repairs required where grey iron fracturing has occurred.
SG Ductile iron is alloyed to produce variations in the properties the resulting castings show, allowing an enhanced set of applications.
SG Iron has been specified under national and international standards. Commonly specified standards include
BS2789:1985 (now superceded)
BS EN 1563:2011
SG iron grades offered are produced in a tighlty controlled process and can be certified by an independent UKAS laboratory when required.