Heat Treated Cast Irons | Austempered Ductile Iron

Background to Austempered Ductile Iron

Austempered Ductile Iron is a family of heat treated cast irons available in ASTM 897M and EN1564 standard grades.

The austempering heat treatment converts ductile iron to austempered ductile iron (ADI), bringing about excellent strength, toughness, and fatigue characteristics. ADI is stronger per unit weight than aluminium, as wear resistant as steel and has the potential for up to 50% cost savings.

For the designer ADI is a most versatile material, enabling innovative solutions to new and current problems. By selecting precise heat treatment parameters a specific set of properties can be achieved. The lower hardness ductile iron castings are used in structural applications, often where weight and cost reduction are important. Wear resistance is superior to steel at any given hardness level, making the higher hardness grades ideal for mining, construction, agricultural and similar high abrasion applications.

ADI competes favourably with steel forgings, especially for heavy-duty parts where reliability is paramount. It is used to upgrade from standard ductile irons, and as a substitute for manganese steel and nickel-hard materials. When strength is required ADI is particularly cost-effective: tensile and yield values are twice those of standard ductile iron; fatigue strength is 50% higher and it can be enhanced by shot peening or fillet rolling. With its high strength-to-weight ratio ADI can even replace aluminium when reduced section sizes are acceptable.

Nearly 60 years after its discovery Austempered Ductile Iron is still widely regarded as a "new material". A major reason for this was the slow commercialisation of the Austempering process. ADI remained a laboratory curiosity until 1972 when a limited facility was set up to process a small compressor crankshaft in the USA. However the first truly viable commercial service was delayed until the introduction of new furnace developments at Applied Process Inc in Michigan during 1984. Considerable process modelling and material evaluation has followed, resulting in wider understanding and acceptance of ADI.

In 1996 ADI Treatments Ltd was formed to provide the technology in Europe. Now part of an international network of associates, we continue to work with Applied Process on the development of improved austempering systems and processes to solve tough engineering problems.

To help realise the benefits of ADI in your manufacture, we would be pleased to explore any design opportunities with you. We can advise on all aspects of engineering with ADI including: alloy selection, foundry practice, dimensional stability and machining. We can discuss potential applications and perform material and cost analyses to help you justify selection of ADI for your products.

We also invite you to visit our operations where we can demonstrate the process and our ISO9001:2000 credentials.