Heavy austempered ductile iron components

Abstract

A component for wind turbines includes cast austempered ductile iron containing about 3.0 to about 3.8 weight percent carbon, about 1.9 to about 2.8 weight percent silicon, up to about 0.3 weight percent manganese, up to about 0.8 weight percent copper, up to about 2.0 weight percent nickel, up to about 0.3 weight percent molybdenum, about 0.03 to about 0.06 weight percent magnesium, less than about 0.05 weight percent chromium, less than about 0.02 weight percent vanadium, and less than about 0.01 weight percent sulfur. The component is preferably a drive shaft or gearbox component having a mass of more than about 3 tons. A method of manufacturing the component is also provided.

Description

BACKGROUND OF THE INVENTION[0001]The invention relates to austempered ductile iron for use in wind turbine shafts and gearbox components.[0002]Wind turbines have a main shaft that transmits power from a rotor to a generator. As wind turbines increase their outputs from 1.5 and 2.5 megawatts (MW) to 3, 4, 5, and 6 MW, the size and required properties of the wind turbine drive shaft increases. In addition, the loads gearbox components, such as planet gear carriers, handle are too high for conventional ductile iron grades (ferrtitic / pearlitic grades). Forged / hardened steel is the material of choice for gearbox components and drive shafts having sizes greater than 3 tons. This shaft is typically machined out of a steel forging. The material of the shaft is usually quenched-tempered high-strength low alloy steel with critical fatigue properties. Examples include nickel chromium steels such as 34CrNiMo6 steel.[0003]Processing of heavy forged steel wind components from large ingots is comp...

AI Technical Summary

Problems solved by technology

In addition, the loads gearbox components, such as planet gear carriers, handle are too high for conventional ductile iron grades (ferrtitic / pearlitic grades).

Processing of heavy forged steel wind components from large ingots is complex, requiring numerous hot working operations (a.k.a., forging) and heat treatment operations to sufficiently refine the structure to provide a suitable microstructure responsive to the subsequent quality heat treatment to develop desired mechanical properties.

Such exhaustive processing paths and the extensive machining attributed to the limited freedom of geometry come at a steep cost relative to the straightforward production of cast ADI counterparts.