For over three decades, open gearing for many applications has been successfully designed and
manufactured from ductile iron.
Examples spanning a full range of size and transmitted power are in service in various process industries
throughout the world, proving the soundness of this material selection in technical as well as economical
terms.
The latest metallurgical and manufacturing developments have re-established the practical limits for this
material, well beyond what was considered possible as recently as a few short years ago. A ductile iron
gear of 1 6m diameter, 340 BHN (min.) hardness, module 42, with a face width of 1 200 mm and having
AGMA Q1 0 teeth quality, capable of transmitting 2×1 0 000+ kW was previously a concept. Today, such a
gear can be manufactured.
Despite its long and successful service history, ductile iron remains a somewhat lesser known commodity
as an open gearing material.
The goal of this paper is to present the current “state-of-the-art” with respect to ductile iron as a gear
material, including its mechanical properties as applicable to gear design, structural characteristics,
typical manufacturing and inspection plans, and in-service behavior. For each of these aspects, ductile
iron will be compared to other available materials for open gearing design and manufacture, such as cast
steel, forged/fabricated steel and austempered ductile iron.