Yoshikuni Kadoya

Development of Welded Rotors for High-Temperature Steam Turbines

Steam turbine plants face strict market demand for high-temperature operation, streamlining, and shortened delivery times. The welded rotor enables streamlining through the use of material most appropriate for high to low-temperature parts. The use of materials will also enable a shift to larger capacity and shorter delivery times. The hetero-material welded rotor consisting of 2.25CrMoV, 9%Cr, and 3.5NiCrMoV steel was developed to meet these demands and verified at Takasago combined cycle plant. The plant has been conducting commercial and proving operations on the rotors. In this paper the authors introduce verification of work execution, strength, thermal stability, inspection for the welded rotor, and actual machine commercial operation.© 2005 ASME

Nondestructive Evaluation of Temper Embrittlement in Turbine Casing Steels.

In order to develop a nondestructive method of evaluating embrittlement for turbine casing steels, a study was conducted using lab-charged P-doped steels. P-doped steels showed evident embrittlement due to segregation of P at grain boundaries. The chemical etching test used was found to be a very good measure of embrittlement for casing steels. There was a good correlation between the width W of the etched grain boundary measured by the penetration of replicas and FATT. The correlation between W and FATT was also recognized for the samples taken from long-term-serviced casings. Multiple regression analysis was conducted in order to express FATT using W and other variables which are known or nondestructively measurable. The regression equation obtained gave an estimate of the actual FATT with the scatter of ±20°C. On the basis of this result a nondestructive evaluation method of temper embrittlement for turbine casing is proposed.