Low Si high-temperature strength steel tube with improved ductility and toughness

摘要

A low Si high-temperature strength steel tube with improved ductility and toughness which consists essentially of: not more than 0.10 wt % of carbon (C), not more than 0.15 wt % of silicon (Si), not more than 5 wt % of maganese (Mn), 20 to 30 wt % of cromium (Cr), 15 to 30 wt % of nickel (Ni), 0.15 to 0.35 wt % of nitrogen (N), 0.10 to 1.0 wt % of niobium (Nb) and not more than 0.005 wt % of oxygen (O.sub.2); and at least one of 0. 020 to 0.1 wt % of aluminum (Al) and 0.003 to 0.02 wt % of magnesium (Mg) in an amount defined by the following formula:P P0.006 (%). ltoreq.1/5Al(%)+Mg(%)0.020 %PPthe balance being Fe and inevitable impurities.