Study of steel 10Kh9V2MFBR-Sh properties for steam pipes after prolonged thermal aging

Abstract

Changes in structure and properties are studied as a result of prolonged thermomechanical aging for pipe metal of a new high-chromium steel 10Kh9V2MFBR-Sh, intended for pipelines of live steam and a hot steam reheating unit based on supercritical steam parameters, with the aim of determining the level of reduction in proposed material properties during long-term aging, and also choice of a procedure and criteria for evaluating its reliability during prolonged operation.Keywords: supercritical steam parameters unit, high-chromium steels, short-term mechanical properties, stress-rupture strength, metal aging, live steam, hot industrial reheating, steam pipes, operating reliability criteria, residual life.Over the extent of the last three years (2007 -2010) JSC "VTI" together with leading power generation institutes JSC "NPO TsKTI," JSC "NPO TsNIIMASh," and power generation engineering plants JSC Émal'yans, Silovye Mashiny, has carried out a development program for building a pilot project of a power generation unit based on supercritical steam parameters (SCSP) (live steam parameters: t = = 600°C, p = 28 MPa; intermediate reheating steam: t = = 620°C, p = 4 MPa). Within the framework of this program work has been accomplished for calculating the heating scheme, different versions of boiler installation have been considered, and calculations have been performed for the strength of the main standard sizes of steam pipes for live steam and hot reheating steam.Particular attention is devoted to choice of materials for the main power generation unit elements operating at high temperature: cast casing components, turbine rotor, and steam pipes. The main requirements laid down for these materials are provision of a strength level of not less than 100 MPa at 600°C for a life of 200,000 h, high metal resistance to scaling, good technological efficiency, and workability. World experience has shown that 9 -10% chromium steels of the martensitic class correspond to these specifications to a considerable extent.Within Russia in the 1960s there was experience of creating a SCSP power generation unit, i.e., the power generation unit SKR-100 at the Kashir state power station. However, this installation was aimed at considerably more steadystate operating regimes with a rated life of 100,000 h. High-temperature elements of the power generation unit were manufactured from various austenitic steels. Use of these steels in contemporary power generation units is undesirable since their high linear expansion coefficient limits maneuverability properties of the equipment. In new projects more rigid requirements are laid down for life and maneuverability, and also for unification of domestic materials and technical specifications, and existing overseas analogs [1]. In developing domestic steels very favorable experience has been used, obtained in creating an assimilating high-chromium steels.Development of new materials is currently carried out in order to achieve the maximum unification with overseas materials. Among the latest Russian d...