What is Grey Iron?

Grey Iron is the oldest and most common type of iron in existence. It is probably what most people think about when they think about cast iron. It is used in general engineering applications where high strength or ductility is not required. It is however used in applications, which involve sliding surfaces due to its unique bearing properties.

 

The microstructure of Grey Iron

 

Properties:

Cost
It is the cheapest of all the cast iron family to produce

Easy to Cast
Has the lowest melting temperature of all the ferrous metals and is highly fluid in its molten state

Excellent Bearing Properties
The free graphite within the structure acts as lubrication. This has led to it being used on machine tool beds, hydraulic pistons etc.

Excellent Machinability
The free graphite break up the continuity of the structure resulting in the formation of small chips during machining.

Excellent Damping properties

Excellent Wear Characteristics

Metallurgy
Grey or Cast iron has graphite in the form of flakes, which cause discontinuities through the matrix structure, resulting in relatively low strength and very little, if any, ductility.

 

Grade Tensile Strength in separately cast sample
  Rm N/mm² min
EN-GJL-150 150
EN-GJL-200 200
EN-GJL-250 250