Improvement of Long Time Creep Rupture Properties of High WCoB containing 12Cr Rotor Steels for use at 650°C in USC Power Plants

摘要

A new 12%Cr rotor material has been studied for application in future high-efficiency ultra supercritical pressure steam (USC) power plants designed to operate at 650°C steam temperature while protecting the natural environment and fossil fuel reserves. At steam temperatures exceeding 600°C, conventional 12%Cr steels are not expected to be used as rotor material due to their low creep rupture strength and deterioration of their long-time creep rupture properties. A new WCoB12%Cr steel based on our past research has been developed recently. Both 20 and 80-ton trial rotor shafts were forged and tested especially for their long-time creep rupture properties. Addition of W, Co and B to the steel improved its creep rupture strength at elevated temperatures, while reduction of Ni and Al impurities suppressed deterioration of long time creep rupture properties at about 650°C. These results showed that the new steel has satisfactory properties to be a candidate material for turbine rotor shafts of 650°C-steam generating USC power plants.