The main revision proposed in this work item is to add one grade of austenitic ductile iron, 25% Ni, called as Ni25 for the time being. The rational was presented at the Committee meeting of May 2013 Indianapolis, IN, and is given here as well. (1) Austenitic ductile irons are widely used for high temperature environment. It was found that D-2 (20% Ni) grade shows severe oxidation at high temperature, and 25%Ni austenitic ductile shows comparable oxidation resistance as compared to D-5S (35% Ni). Obviously Ni25 advantages include lower cost than D-5S, and improved high-temperature properties over D-2. (2) In ASTM standard A439, this is a gap in nickel content between D-2 and D-3 and iron. This work item is registered to fill this gap using Ni25, i.e., 24 to 28% Ni, in addition to the optimized carbon and silicon contents developed.
Keywordsaustenitic; corrosion resistant; ductile iron; mechanical properties; nodular iron; tensile strength; yield strength; Austenitic iron castings--specifications; Ductile iron castings--specifications;
Ballot Item Approved as A439/A439M-2015 and Pending Publication