Methods of forming and austempering a ductile iron article and article made thereby

摘要

A method of making a ductile iron article is disclosed. The method includes providing a ductile iron article preform. The method also includes deforming the ductile iron article preform by hot-working to provide a hot-worked portion of the article. The method further includes cooling the article to an austempering temperature. Still further, the method includes austempering the ductile iron article preform for a predetermined time sufficient to provide an austempered article preform comprising an austempered microstructure, wherein the austempered microstructure of the hot-worked portion is different than in other portions of the article. A ductile iron wind turbine shaft is also disclosed. The ductile iron wind turbine shaft has an austempered microstructure comprising an ausferrite matrix and a plurality of graphite nodules. The austempered microstructure has a deformed portion, the deformed portion has a microstructure that is different than the microstructure of the other portion of the shaft.

主权项

1. A method of making a ductile iron article, comprising:
providing a ductile iron article preform; deforming the ductile iron article preform by hot-working to provide a hot-worked portion of the ductile iron article preform, the hot-working performed at a temperature above a eutectoid temperature of the ductile iron to provide a microstructure of stable austenite; cooling the ductile iron article preform to an austempering temperature; austempering the ductile iron article preform for a predetermined time sufficient to provide an austempered ductile iron article preform comprising an austempered microstructure; and ausforming the ductile iron article preform after cooling and prior to the predetermined time to provide an ausformed portion of the ductile iron article preform, wherein the austempered microstructure of the hot-worked portion and the ausformed portion are different than in other portions of the austempered ductile iron article preform, and wherein the different austempered microstructure of the hot-worked portion and the ausformed portion comprises at least one of a refined acicular ferrite phase having a reduced platelet width, a shape of deformed graphite nodules, or a reduced porosity, as compared to the other portions of the austempered ductile iron article preform.