(source: https://www.rsc.org/periodic-table/element/41/niobium)

Niobium is used in alloys including stainless steel: A method for the production of niobium containing steel (1949). It improves the strength of the alloys, particularly at low temperatures: Niobium-Containing Ferritic Stainless Steel Excellent In Low Temperature Toughness Of Hot Rolled Sheet (1998).

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All patent information has been obtained from Espacenet (European Patent Office).