Assessments of relationship between microstructures and mechanical properties for heavy section ductile cast irons

Abstract

The relationships between microstructures and mechanical properties of heavy section ductile cast irons used in large scale wind turbines have been assessed in this study. In addition, the required conditions for meeting either the tensile property requirements (+10%) or the impact toughness requirements (+10%) of specification EN-GJS-400-18U-LT for heavy section ductile cast irons have been obtained. Furthermore, the optimal conditions in terms of microstructure (nodule count and pearlite content) and tensile properties for fully complying with specification EN-GJS-400-18-U-LT have been established and are summarised as follows: 112 mm⁻²⩽NC (Nodule Count)⩽173 mm⁻², 3%⩽P (Pearlite)⩽6%, 407 MPa⩽TS (Tensile Strength)⩽438 MPa, El (Elongation)⩾16··2%. Please define ‘NC’, ‘P’, ‘TS’ and ‘El.’ at the first mention. In addition, the change in I_−20°C value as a function of casting section thickness or casting modulus Mc² had been drawn. Finally, late inoculation can be considered a crucial and necessary step in melt treatments to attain satisfactory microstructures and hence to conform to the target specification.

Keywords:

• Heavy section ductile iron
• Microstructure
• Tensile property
• Impact property

This research was supported by the National Science Council of Taiwan (grant no. NSC100-3113-E-002-002).