Performance of heavy ductile iron castings for windmills

The main objective of the present paper is to review the specific characteristics and performance obtaining conditions of heavy ductile iron (DI) castings, typically applied in windmills industry, such as hubs and rotor housings. The requirements for high impact properties in DI at low temperatures are part of the EN-GJS-400-18U-LT (SRN 1563) commonly referred to as GGG 40.3 (DIN 1693). Pearlitic influence factor (P(x)) and antinodularising action factor (K(1)) were found to have an important influence on the structure and mechanical properties, as did Mn and P content, rare earth (RE) addition and inoculation power. The presence of high purity pig iron in the charge is extremely beneficial, not only to control the complex factors P(x) and K(1), but also to improve the 'metallurgical quality' of the iron melt. A correlation of C and Si limits with section modulus is very important to limit graphite nodule flotation. Chunky and surface-degenerated graphite are the most controlled graphite morphologies in windmills castings. The paper concluded on the optimum iron chemistry and melting procedure, Mg-alloys and inoculants peculiar systems, as well as on the practical solutions to limit graphite degeneration and to ensure castings of the highest integrity, typically for this field.