Study on the Production of Heavy Section Ductile Irons with Specified Low Temperature Impact Property
Date Issued
2011
Date
2011
Author(s)
Su, Tzu-Ming
Abstract
The global installed wind turbines capacity has increased from 17,400MW in 2000 to 194,390 MW in 2010, and these wind turbines require several heavy-section DI castings, i.e. hub, rotor shaft, main frame, etc.. Due to the increased melted mass and the extended solidification time encountered in heavy-section ductile irons, the stringent metallurgical and process control is a must and requires special attention. In addition, because the wind mills are often installed in a cold environment, the ductile iron castings normally requires excellent low temperature impact properties, in addition to meet the tensile/yield strength and elongation requirements.
The primary purpose of this research is to investigate the effects of chemical compositions and selected processing parameters, including nodularization treatment, post inoculation, pouring time and pouring temperature, on microstructures (nodularity, nodule count and pearlite percentage) and mechanical properties (tensile strength, yield strength, elongation and low temperature impact value) of key cast components used in large-scale windmills. This study has established the optimal alloy design and process conditions for different targeted castings. In addition, regression analysis had been performed to correlate the mechanical properties with chemical compositions and microstructures. The attained regression equations can be used to obtain the appropriate alloy design for castings with specified specification. Furthermore, by employing these regression equations, we can predict the mechanical properties of alloys based upon the chemical composition and microstructure.
Subjects
Large-scale windmill
ductile cast iron
alloy design
tensile property
impact property
Type
thesis
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