... steel tube grade: T91, T23, T22, T12, T11, T5, T2, STBA 22/24/25, 10CrMo910, 13CrMo 44/12CrMo195, 3606, TUZ12C. Seamless Ferritic and ... Austenitic Alloy Steel Tube for Super heater and Heat Exchanger (1)Steel Grade: T91, T23, T22, T12, ... temperature service such as for super-heaters and reheaters. And the features are precise dimension.