This specification covers ductile iron castings that are subsequently heat treated by an austempering process. The chemical composition requirements may be agreed upon between the manufacturer, heat treater, and the purchaser. Requirements for the microstructure constituents such as graphite, ausferrite (acicular ferrite and high carbon, stable austenite), pearlite, and martensite are prescribed. The iron shall conform to the mechanical property requirements including tensile strength, yield strength, elongation, impact energy, and Brinell hardness. Castings shall be heat treated by an austempering process detailed in this specification. The standard specimens for tension and Charpy impact tests are illustrated.

1.1 This specification covers ductile iron castings that are subsequently heat treated by an austempering process as defined in .

1.2 The application of the austempering heat treatment extends the range of properties achievable in ductile iron castings.

1.3 No precise quantitative relationship can be stated between the properties of the iron in various locations of the same casting or between the properties of castings and those of a test specimen cast from the same iron (see ). However, austempering heat treatment will tend to diminish any differences in mechanical properties.

1.4 The production of castings, machining (if required), and the austempering heat treatments may be performed by different manufacturers, as covered in Section . The purchaser should establish by contract agreement, at the time of ordering, the responsibility of the various parties for meeting the specification requirements.

1.5 The values stated in either inch-pound or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets [ ]. The values stated in each system are not exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the specification.