PURPOSE: To manufacture efficiently the titled stainless steel pipe superior in high temp. characteristic, by heat treating and hot extruding a steel billet having a specified compsn. composed of C, Si, Mn, Cr, Ni, Nb, B, N and Fe.
CONSTITUTION: The billet of steel composed of, by weight, 0.04W0.12% C, 0.1W0.8% Si, ≤2% Mn, 15W25% Cr, 9W20% Ni, ≤1% Nb under 8W12 Nb/C wt. ratio, ≤0.005% B under B≥0.001×(Nb/C)-0.01%, 0.005W0.100% N, as impurities ≤0.02% P, ≤0.006% S under P+0.04×Si≤0.035%, if necessary, further 0.01W2.5% Mo and the balance Fe with inevitable impurities is heated to enter carbide into solid soln. and cooled at ≥0.3°C/sec average rate until 500°C. Then, the billet is hot extruded at ≥1,100°C, then cooled rapidly to prevent coarse carbide ppt., to obtain austenitic stainless steel pipe having fine grain structure, superior high temp. corrosion resistance, and creep rupture strength.
TAKAHASHI TSUNETOSHI
ONOYAMA YUKIO
OTOGURO YASUO
OMURA KEIICHI
MIMURA HIROYUKI
