Study Of Austempered Ductile Iron Using In The Wind Turbine Main Shaft

Main shaft is an important component in the wind power generator. With wind power generator developing to large-scale and high-power, the weight of main shaft is becoming more heavier accordingly, which increases the burden of bracing structure and makes the main shaft productive process that is using forging method more time-assuming and strenuous, the success rate declines as well. Therefore, it has a realistic significance to optimize the structure and the process of main shaft. If the method of casting could instead of forging, the cost and production cycle will be decreased. To this end, this paper carries out the relevant works.In this paper, austempered ductile iron is selected to be the material of wind turbine main shaft and be analysed the practicability that using the method of casting. Considering the hardenability of austempered ductile iron and stress distribution in the main shaft when it works, the structure of main shaft is redesigned, thickness is reduced to average of90mm and the thickest position is120mm more or less. The stress distribution of the redesigned main shaft has been simulated by finite element analysis software ANSYS, it shows that the maximum stress is590Mpa.Gating system has been designed to the redesigned main shaft, filling process and temperature changes in the solidification has also been simulated by ProCAST software. Through simulation, the method of bottom filling and putting flange to top which adds150mm as rising head shows that it has a stable filling process without spatter, the solidification process appears a "v" from bottom to top, which meets the principle of progressive solidification, there hasn’t been shrinkage porosity in the main shaft body as well.By using the method of adding alloy element(Ni,Mo,Cu) to improve the hardenability of nodular cast iron and observing the hardenability changes through adjusting the content of Cu and Mo(on the basis of1%Ni),5nodular cast iron samples of150mm diameter and200mm height have been prepared. In this paper, the samples have been processed as900℃austenitizing for3h and385℃austempering for1.5h, the results show that the hardenability of Cu is not so high as Mo, and the hardenability of casting has a significant improvement when Cu is0.75%, Mo is0.36%, Ni is1%. In this way, only5%pearlitic structure appears in the core of the casting, the yield strength also meet the allowable stress of main shaft.