Creep life prediction of weld-repaired chromium-molybdenum-vanadium steam turbine rotors.

摘要

The extension of useful service life of steam turbine rotors in fossil power plants is a topic of considerable research. Weld repair of service damaged rotors by replacing the hot stage by a new piece and joining them by welding is an economical alternative to complete replacement of the rotor. This work studied the reproducibility of the welding process used for repair, analyzed the reliability of the extrapolation techniques and explained the location and time to rupture of the weld repaired High Pressure/Intermediate Pressure section of retired rotors. Crossweld specimens wee submitted to stress rupture tests at near service temperatures and at the operating stress.;In this study, the Gas Tungsten Arc Welding (GTAW) process was used for making narrow groove welds with a heat input of 90 kJ/in (3.54 kJ/mm) on test coupons machined from ASTM A 470 Class 8 rotors(1.0Cr-1.0M-0.25V). Iso-stress rupture tests were conducted at 12 ksi (83 MPa) stress over the temperatures range 1125 to 1275;The welding process established with small scale test coupons was reproducible on a regular Full Scale Rotor and in either case a life of 20 years at 950