Modelling approach to support design of new high nitrogen austenitic steel for wind turbines components

Abstract

The alloy design of a new high nitrogen austenitic steel for bearing used in wind turbine gearboxes has been approached. The alloy design was based on a modelling approach to the different aspects of manufacturing routes. The mechanical strength was predicted by means of empirical models. Nitrogen solubility in liquid steel was estimated on the basis of Sievert’s law and Thermo-Calc calculations. Scheil calculations and models developed by Centro Sviluppo Materiali SpA (CSM) were used for estimating nitrogen solubility. The stability of austenite has been studied by thermodynamic calculations. The results show that amounts of at least N = 0.5% are required to fall in austenite domain approaching the required mechanical strength. Vacuum induction melting + pressure electroslag remelting is required to manufacture alloys with N ⩾ 0.6%, but the addition of elements as Mn can potentially allow to increase N amounts achievable with only vacuum induction melting route processing.