Technical Paper

Processing of niobium-containing steels by Steckel mill rolling

International Symposium Niobium 2001

The Steckel mill is a reversing rolling mill in which steel strip is coiled after each rolling pass in a heated coilbox positioned on either side of the mill. In addition to the lower capital costs associated with a single stand mill in comparison to multi-stand finishing mills, the Steckel mill offers a high degree of flexibility in the steel rolling process. IPSCO has pioneered the use of the Steckel mill for the production of flat-rolled high-strength steel for linepipe and structural applications. Much of this development has been based on an Nb-microalloying strategy. Niobium plays a key role in development of a fine-grained high strength steel in a number of ways: a) Nb(C,N) precipitation in austenite retards recrystallization effectively refining grain size; b) Solute Nb acts to enhance the hardenability of the steel, promoting formation of an acicular ferrite microstructure; and c) Nb(C,N) precipitation in ferrite subsequent to transformation provides substantial precipitation strengthening. This paper will review the use of niobium in microstructure development during Steckel mill rolling. (AU)
Technical Paper (PDF 2.36 MB)