Pipe for steam turbine, manufacturing process of same, main steam pipe and reheat pipe for steam turbine, and steam turbine power plant using those pipes

摘要

A pipe for a steam turbine is formed of a centrifugal casting material to achieve resistance against higher temperatures and improve reliability of the pipe by employing, as a pipe material, a centrifugal casting material normalized to contain uniform and finer crystal grains. The centrifugal casting material is made of steel having a columnar structure in the radial direction with the crystal grain size number of 5 or more in a plane perpendicular to the radial direction. The steel includes 0.05-0.5% by mass C, not more than 1.0% Si, 0.05-1.5% Mn, 0.01-2.5% Ni, 8.0-13.0% Cr, 0.05-2.5% Mo, not more than 3.0% W, 0.05-0.35% V, 0.01-0.5% Nb, not more than 5% Co, 0.01-0.1% N, not more than 0.03% B, and not more than 0.05% Al.