How much niobium can I use?

Upon casting, the liquid steel solidifies as it cools. During this process of cooling, the Nb combines with available atoms of Carbon and Nitrogen present to form a precipitate (i.e. fine particle) of Niobium Carbo-Nitride, Nb(C,N). Importantly, the more Carbon and Nitrogen that is in the steel, the earlier these precipitates will form (i.e. at a higher temperature) as the cast cools. Consequently, these precipitates of Niobium with higher Carbon and Nitrogen content are more “stable” at higher temperatures. Now, for the purpose of using Nb during hot-rolling and making the steel properties we need to have it available in its atomic form, as Nb (i.e. alone, without the Carbon and Nitrogen).