Dissimilar Welded Rotors for High Tempererature Steam Turbines

摘要

The welded rotor for steam turbine has been developing in order to meet the market demand for high temperature operation, large capacity and short delivery times. The dissimilar welded rotor for high and intermediate pressure turbine was composed of modified 12% Cr steel and CrMoV steel. The narrow gap TIG welding process with hot wire was developed for the welded rotor, and the verification tests of the joint strength, thermal stability and inspection were carried out. Also, In process monitoring system was developed for quality confirmation during welding. This system has the functions of monitoring the molten pool shape, bead shape and the inner defects. The molten pool shape during welding and the bead shape after welding can be measured by using CCD camera and the special filtering technique. The inner defects can be visualized by using laser-ultrasonic testing during welding. As a result, the rotor has been applied to the high pressure turbine for Mikawa power station unit-2, where its successful performance has been confirmed under actural machine condition.