Cast iron, ductile (nodular)

The material. The foundations of modern industrial society are set, so to speak, in cast iron: it is the material that made the Industrial Revolution possible. Today it holds a second honor: that of being the cheapest of all engineering metals. Cast iron contains at least 2% carbon; most have 3-4%—and from 1-3% silicon. The carbon makes the iron very fluid when molten, allowing it to be cast to intricate shapes. There are five classes of cast iron: gray, white, ductile (or nodular), malleable, and alloy. The two that are most used are gray and ductile. This record is for ductile cast iron.

Composition

Fe/3.2-4.1% C/1.8-2.8% Si/ < 0.8% Mn/ <0.1% P/ <0.03% S

General properties

Density

7050 – 7250 kg/m3

Price

*0.7 – 0.8 USD/kg

Mechanical properties

Young’s modulus

165

– 180

GPa

Yield strength (elastic limit)

250

– 680

MPa

Tensile strength

410

– 830

MPa

Elongation

3

– 18

%

Hardness—Vickers

115

– 320

HV

Fatigue strength at 107 cycles

180

– 330

MPa

Fracture toughness

22

– 54

MPa. m1/2

Thermal properties

Melting point

1130 –

1250

°C

Maximum service temperature

350 –

7450

°C

Thermal conductor or insulator?

Good conductor

Thermal conductivity

29 –

44

W/m. K

Specific heat capacity

460 –

495

J/kg. K

Thermal expansion coefficient

10 –

12.5

p, strain/°C

Electrical properties

Electrical conductor or insulator?

Good conductor

Electrical resistivity

49 –

56

pnhm. cm

Ductile or malleable cast irons are used for heavily loaded parts such as gears and automotive suspension components.

Ecoproperties: material

Annual world production

1.1 X 109

– 1.2 X 109 tonne/yr

Reserves

78 X 109

– 79 X 109

tonne

Embodied energy, primary production

16

– 18

MJ/kg

CO2 footprint, primary production

1.0

– 1.1

kg/kg

Water usage

*13

– 39

l/kg

Eco-indicator

38

– 42

millipoints/kg

Ecoproperties: processing

Casting energy

*3.2

– 3.7

MJ/kg

Casting CO2 footprint

*0.19

– 0.22

kg/kg

Deformation processing energy

*2.5

– 3.1

MJ/kg

Deformation processing CO2 footprint

*0.2

– 0.24

kg/kg

Recycling

Embodied energy, recycling

4.9

– 5.5

MJ/kg

CO2 footprint, recycling

0.29

– 0.32

kg/kg

Recycle fraction in current supply

60

– 80

%

Typical uses. Brake discs and drums; bearings; camshafts; cylinder liners; piston rings; machine tool structural parts; engine blocks, gears, crank­shafts; heavy-duty gear cases; pipe joints; pump casings; components in rock crushers.