Abstract: It is selfevident that the metal material is very important for thermal power plants, it influences directly the unit service life and safety and economical operation. The chemical composition and main physical property of T91/P91 steel were introduced, and the mechanical property and oxidation corrosion resistance were analyzed. The welding technology and method of T91/P91 steel were given, and some problems needing further research were pointed out.

Key words: T91/P91 steel, main steam pipe, pipes in heating surface, refractory steel, weldability