Austenite-based stainless steel pipe and method of manufacturing the same

An austenite-based stainless steel pipe having a chemical composition of, in mass %:

• up to 0.030% C;
• 0.10 to 1.00% Si;
• 0.10 to 2.00% Mn;
• 15.00 to 25.00% Cr;
• 6.00 to 15.00% Ni;
• 0.020 to 0.200% N;
• up to 0.030% sol. Al;
• 0.001 to 0.045% P;
• up to 0.010% S;
• 0.20 to 1.00% Nb;
• 0 to 2.00% Mo;
• 0 to 2.50% Cu;
• 0 to 0.0050% B;
• and
• balance Fe and impurities,
• an outer diameter being not smaller than 200 mm,
• a wall thickness being not smaller than 15 mm,
• an austenite crystal grain size being 20 to 300 μm,
• a recrystallization ratio X being not lower than 0.90,
• wherein the recrystallization ratio X is measured by:
• taking a sample from a middle portion, as determined along a wall-thickness direction, of the austenite-based stainless steel pipe;
• conducting an electron backscatter diffraction measurement in a grid with a scan spacing not larger than 2.0 μm, where a region not smaller than 10.0 mm2 of a cut surface perpendicular to a pipe-axis direction is measured;
• and classifying those of crystal grains within the measured region which have a GOS value not less than 1.0° as non-recrystallized grains and those with a GOS value less than 1.0° as recrystallized grains, where the defining angle for a crystal grain boundary is 4.0° and the recrystallization ratio X is defined as the ratio of the area of the recrystallized grains SR to the area of the measured region S, SR/S.