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ADI and Its Advantages
What is Austempered Ductile Iron (ADI)?
Austempered ductile iron (ADI) is ductile cast iron, heat-treated using a tightly controlled process that produces a unique microstructure. ADI is available in six ASTM standard grades, covering a wide range of strength and hardness characteristics.
Advantages of Austempered Ductile Iron:
ADI provides high strength, good fatigue properties, superior wear qualities, excellent toughness, and cost-effectiveness.
Tensile and Yield Strength:
ADI's tensile and yield strengths are at least twice those of standard ductile irons.
Fatigue Strength:
ADI's fatigue strength is typically 50% higher than that of standard ductile irons. It can be further increased by shot peening or fillet rolling. The lower hardness grades of ADI work well in structural applications.
Toughness:
ADI's excellent impact and fracture-toughness properties make it ideal for applications such as ground-engaging tools.
Wear Characteristics:
The higher hardness grades of ADI are excellent for wear applications. Unlike case-hardened materials, typically the ADI is uniformly hardened throughout the part. Also, ADI work-hardens when stressed. This produces a thin surface of very hard martensite where wear resistance is most needed.
Cost-effectiveness:
ADI is usually 15% to 20% less costly than steel forgings or castings. It is the most economical way of obtaining tensile, yield, or fatigue strength. ADI often competes favorably with heat-treated and alloy steels for heavy-duty applications where reliabilty is crucial. It is a useful upgrade from standard grades of ductile iron. In some cases it replaces manganese steel and nickel-chrome iron. Because of ADI's high strength-to-weight ratio, it has even replaced aluminum where the design allows reduced section sizes.
Properties of ADI Compared to Steel:
- ADI is much easier to cast than steel
- ADI is approximately 9% lighter than steel
- ADI has minimal draft requirements compared with steel forgings
- ADI loses less of its toughness than steel at sub-zero temperatures
- ADI work hardens when stressed
- ADI has more damping capacity than steel
