Producing high quality niobium-bearing steels using the CSP process at Nucor Steel Berkeley

In the 16 years since the first hot band coil was rolled using the Compact Strip Production (CSP) at NUCOR Steel Crawfordsville, the product line produced by the sheet division of NUCOR and other minimills has grown in complexity and sophistication. Today, at Nucor Steel Berkeley (NSB), advanced high strength steels such as HSLA and Dual-Phase steels can be produced from electric furnace melts either as hot band or in cold rolled gauges produced on continuous annealing (CA) or continuous galvanizing (CG) lines. Similarly, with the addition of vacuum degassing, Interstitial-Free steels and AKDQ steels can also be produced on CA or CG lines. Niobium has already achieved its normal, prominent position in the HSLA steels and will soon appear in the DP and IF steels, as well. A recent, important development at NSB is the new intensified hot rolling sequence, where by heavy gauge skelp of niobium strengthened HSLA steel for X52-X70 API pipe can be rolled resulting in a uniform ferrite microstructure, impressive improvement in strength and toughness, and the absence of aberrant non-destructive test reflections. The ductility and formability of the CAL or CGL sheet grades is good, while the surface quality is more than adequate. It is now clear that high performance steels can be produced by the EAF plus thin slab casting route. This paper will review some recent advances in skelp production for ERW pipe and their underlying physical and mechanical metallurgy. (AU)