Ultra low carbon bainitic weathering steel

摘要

An ultra-low carbon weathering steel has a carbon content of from about 0.015 wt % to about 0.035 wt %; a copper content of from about 0.20 wt % to about 0.40 wt %; a chromium content of from about 0.40 wt % to about 0.70 wt %; a nickel content of from about 0.20 wt % to about 0.50 wt %; a titanium content of from about 0.02 wt % to about 0.05 wt %; a niobium content of from about 0.03 wt % to about 0.06 wt %; a boron content of from about 0.0015 wt % to about 0.003 wt %; a manganese content of from about 2.0 wt % or less; a phosphorous content of from about 0.012 wt % or less; a sulphur content of from about 0.005 wt % or less; a silicon content of from about 0.40 wt % or less; a molybdenum content of from about 0.50 wt % or less; a vanadium content of from about 0.10 wt % or less; an aluminum content of from about 0.03 wt % or less; and a nitrogen content of from about 0.006 wt % or less. The steel is formed by austenitizing a steel slab, conditioning the austenite microstructure of the steel slab at a deforming temperature between the austenitizing temperature and the austenite recrystallization stop temperature followed by deforming the austenite microstructure at a temperature below the austenite recrystallization stop temperature and above the Ar₃ temperature of the slab, deforming the slab to a minimum reduction ratio below the austenite recrystallization stop temperature of from about 2.5:1 or more to form a steel plate and cooling the steel plate to ambient temperature.