Niobium in modern steels

It is well known that niobium is added to a wide range of steels for improving processing, microstructure, properties and performance. Over the past 20 years, the use of niobium has also permitted new steels with attractive properties to be developed. Furthermore, the addition of niobium to existing steels such as ferritic stainless steels has also led to improvement. The goal of this paper is to review the basic behaviour of niobium in a wide range of steels, including not only the traditional steels but also some of the newer versions. Particular emphasis has been placed on the basic metallurgical principles that apply to these steels, for it is the application of these principles that allows the composition- processing-microstructure-mechanical property relationships to be rationalised and exploited. The application of basic metallurgical principles has resulted in a predictive capability that has led to alterations in composition and processing for the purpose of producing steels with superior mechanical properties and improved overall performance.