Structure of cast iron
The two most important types of cast iron are grey cast iron and spheroidal
graphite cast iron:
Grey cast iron
Structure: Graphite flakes in a iron matrix
Compressive stress: Excellent compressive strength and low elastic modulus
Wear behaviour: The friction coefficient is low (graphite lubrication)
Brittleness: Percentage elongation after fracture is very low, extremely notch
sensitive
Strength: Tensile strength is relatively low ( in function of grade), no yield
point - no overload capacity
Machining / Cutting: Very good machinability for drilling and machining, cannot
be sheared
Oxyacetylene cutting is difficult.
![Grey cast iron structure](img/castiron/greycastiron1.jpg)
Grey cast iron structure
![Typical stress elongation curve for grey cast iron](img/castiron/spannungsdehnunge.png)
Typical stress elongation curve for grey cast iron
Spheroidal graphite cast iron
Structure: Spheroidal graphite in a iron matrix
Compressive stress: Excellent compressive strength, slightly more elastic than
steel
Wear behaviour: Similar to cast steel
Brittleness: Plastic deformation (percentage elongation) after fracture is much
higher than for grey cast iron
Strength: Tensile strength up to 800 MPa, elastic limit is at least half the
tensile strength
Machining / Cutting: Very good machinability for drilling and machining, cannot
be sheared
Oxyacetylene cutting is difficult.
![Spheroidal graphite cast iron structure](img/castiron/sphero.jpg)
Spheroidal graphite cast iron structure
![Typical stress elongation curve for spheroidal graphite cast iron](img/castiron/spheroidalspde.png)
Typical stress elongation curve for spheroidal graphite cast iron
Typical components
Grey cast iron
- Heavy parts in general
- Machine bases
- Gears, heavy gear boxes
- Pulleys, transmission cases
- Housings, casings
- Machine guards
- Engine cylinder blocks and heads
- Furnace parts, moulds, glass moulds
- Cold cropping tools
- Valves, gates, pump bodies
Spheroidal graphite cast iron
- Heavy parts in general
- Machine bases
- Gears, crankshafts
- Pulleys
- Housings, casings
- Machine guards
- Heavy tubes, pipelines, fittings
- Cold cropping tools
- Stamping tools and dies
- Valve and pump bodies (steam, etc.)
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contact us.
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