Effects Of Silicon On Microstructure And Mechanical Properties Of Low Temperature High-toughness As-cast Ductile Iron For Wind Power Equipment

Low-temperature high-ductility ductile iron, as an excellent engineering material,was widely used to manufacture important parts of wind power equipment, such aswheel hub and taper support. Because of the harsh working conditions those partswould experience, low-temperature impact toughness was strictly required for them.In this paper, the effect of silicon on the microstructure and properties oflow-temperature high-ductility ductile iron was systematically investigated by changethe addition of silicon. Firstly the key casting steps of taper support which used forwind turbine generator was carefully analyzed according to its technical requirementand by optimization of techniques as well as other techniques taper supports withquality meeting all the technical requirements had been scally produced.The result of the research indicated:1) There were ferrite, pearlite, spheroidalgraphite and some cementite in the microstructure of low-temperature and hightoughness ductile cast iron. The grade of graphite size was between6and7, and thespheroidization rate reached1-2.2) the more the silicon content in the sample, themore the spheroidal graphites in the microstructure, and the smaller their size as wellas, the higher uniformity their distribution in the substrate.3) The amount of ferrite inan as-cast sample increased as silicon content was raised.4) There was cementite inwhile the silicon content was below1.80%, and when silicon content was1.81%~2.18%, no cementite was inspected in the sample.There was relationship between the hardness and tensile strength of as-castsamples and the amount of both pearlite and Si content. When the Si content wasbelow1.80%, there was amount of pearlite as well as a little of cementite of the alloy.In this condition, the hardness and the tensile strength reached155HBW and420MParespectively. By the way, the hardness and tensile strength would be gradually raised,when Si content increased from1.81%to2.18%.Within the scope of investigation silicon content,1.59%~2.18%, the sample with1.59%Si held the lowest impact energy at-40℃, but all the samples with siliconcontent in the above-mentioned scope had impact energy at-40℃more than15J,which meant they all obtain outstanding low-temperature impact toughness.The final conclusions from the investigation could come to that: The ductile cast ironwith the ferrite and small, fruity spheroidal graphite in its microstructure has high quality, and its tensile strength, the elongation and the impact energy reached morethan350MPa,22%and15J at-40℃. Its mechanical properties have meet theuniversal requirements for ductile iron used in wind power equipments.