Long-term strength and allowable stresses of grade 10Kh9MFB and X10CrMoVNb9-1 (T91/P91) chromium heat-resistant steels

Abstract

At present, Russia is building a great number of combined cycle plants (CCPs) with an operating tem perature of 565-580°C, is realizing the modernization and renovation of equipment of traditional coal fired power units with an increase in a temperature to 565°C, and is designing coal fired power units operat ing under supercritical parameters of vapor (t = 600-620°C, p = 25-30 MPa). The efficiency of these plants is 6-7% higher than for the efficiency of power units operating at a vapor temperature of 545°C [1,2]. Such results are attained because of the application of new manufacturable chromium steels having enhanced high temperature strength. These are domestic grade 10Kh9MFB steel and foreign grade X10CrMoVNb9 1, T91, and P91 steels [3][4][5][6]. Grade 10Kh9MFB steel was used for making steam pipelines of the Kharanokhorskaya district power sta tion (DPS) (t = 565°C, p = 14.5MPa) and the South Ural DPS (t = 567°C, p = 12.2 MPa), steam pipelines of hot reheat for the Cherepetskaya DPS (t = 570°C, p = 3.2 MPa), internal water pipelines of the Nizhne vartovskaya DPS (t = 561°C, p = 14 MPa), and pipe lines of in turbine drainages of the Serovskaya DPS (t = 567°C, p = 39 MPa). Grade X10CrMoVNb9 1 (T91, P91) steel was used for making heat recovery steam generators (HRSGs) and pipelines of CCPs of the Novokuybyshevskaya heat and power plant (HPP) no. 1, Adlerskaya HPP, Krasnodarskaya HPP, South Ural DPS 2, Mosenergo HPP 26, etc. Foreign chromium steels are often used because of a 20 year lag of Russia in the field of making and using chromium heat resistant steel in power machine build ing (operation life of foreign pipe systems made of grade X10CrMoVNb9 1 steel exceeds 100000 h) and because of the wide application of foreign design solutions for making the boiler and steam pipeline equipment designed for the increased parameters of vapor. In 2006-2013, the Central Research Institute of Engineering Technology (RPA CNIITMASH), Pol zunov Scientific Production Association for Research and Design of Power Equipment (NPO CKTI), and the All Russia Heat EngineeringResearch Institute (VTI) tested pipes of domestic grade 10Kh9MFB (10Kh9MFB Sh) chromium mar tensitic steel and foreign grade X10CrMoVNb9 1 (T91, P91) steel. The aim of the test was the substan tiation of the possibility for application of these steels Abstract-Currently, grade X10CrMoVNb9 1 (T91, P91) and 10Kh9MFB (10Kh9MFB Sh) chromium steels are widely applied in equipment manufacturing for thermal power plants in Russia and abroad. Com pilation and comparison of tensile, impact, and long term strength tests results accumulated for many years of investigations of foreign grade X10CrMoVNb9 1, T91, P91, and domestic grade 10Kh9MFB (10Kh9MFB Sh) steels is carried out. The property identity of metals investigated is established. High strength and plastic properties of steels, from which pipes and other products are made, for operation under creep conditions are confirmed. Design characteristics of long term strength on the basis of tests with more than one million...