Austempered Ductile Iron
Austempered Ductile Iron is also referred to as ADI. This material has been developed to offer enhanced strength and wear resistant properties. Impact resistance of Ductile Iron is retained. This material also offers enhanced fatigue properties.
Post casting austempering is an isothermal heat treatment applied to SG Iron materials. The chemical analysis of the SG Iron has to be controlled very carefully to ensure that the maximum mechanical properties resulting from the post casting solution treatment are achieved.
Additions of copper, nickel and molybdenum are made to improve hardenability. Austempered Ductile Iron (ADI) is being used for demanding applications and is replacing carbon steel castings and forged components due to the following benefits:
When compared to carbon steel castings and steel forgings and fabrications ADI – Austempered Ductile iron has a lower manufacturing cost.
ADI has a lower casting temperature than steel and this allows for a superior surface finish and the ability to cast complex shapes incorporating changes of section.
1600 N/mm2 can be achieved with certain grades of Austempered Ductile Iron.
ADI has a lower density than steel. Casting designs incorporate near net shape offering significant weight savings over steel castings.
Improved Noise Damping
The presence of graphite in the Austempered Ductile Iron improves noise damping.
Superior Wear and Abrasion Resistance
The wear characteristics of ADI improve in service. Hardening occurs during normal operational use. Therefore ADI is a perfect choice high abrasion application.
The ability to cast to near net shape reduces the machining costs of ADI castings when compared to steel products.
|Material designation; symbol and (number)|
|Characteristic||Unit||Minimum values for properties 1) (normative)|
|Tensile Strength Rm||N/mm2||800||1000||1200||1400|
|0.2% proof stress R po.2||N/mm2||500||700||850||110|
|Impact resistance valuesCharpy notched, at (23±5) °C||J||10||2) mean value of 3 tests|
|9||3) individual value|
Minimum values for properties 1) (informative)
|0.2% proof stress||N/mm2||620||770||1040||1220|
|0.2% proof stress||N/mm2||350||490||590||770|
|Impact resistance valuesCharpy notched, at (23±5) °C||J||100||80||60||30|
|Fracture tougness K||Mpa-m 1/2||62||58||54||50|
|Fatigue limit (Wöhler)(rotating bending) unnotched(dia. 10.6mm)||N/mm2||375||425||450||375|
|Fatigue limit (Wöhler)(rotating bending) notched 4)(dia. 10.6mm)||N/mm2||225||260||280||275|
|Brinell hardness||HN||260 to 320||300 to 360||340 to 440||380 to 480|
|Modulus of elasticity E||kN/mm2||170||168||167||165|
|Poisson’s ratio v||–||0.27||0.27||0.27||0.27|
|Linear expansioncoefficient a||mm/(m.K)||14.6||14.3||14||13.8|
Note 1: The mimimum values can be obtained on wall thickness up to 50mm. For heavier sections agreement between purchaser and manufacturer is recommended.
Note 4: Notched after heat-treatment.