Creep, Stress-Relaxation, and Metallurgical Properties of Steels for Steam Power Plant Operating with Steam Temperatures above 950 Deg. F. (510 Deg. C.)

Abstract

INTRODUCTIONUNTIL A FEW YEARS AGO the most advanced steam conditions in common use in power stations in Great Britain were 900 lb. per sq. in. and 900 deg. F. (482 deg. C.), and the components operating at high temperatures were normally of either carbon steel or 3 per cent molybdenum steel (with small chromium additions in some instances). The latest stations operated by the Central Electricity Authority (C.E.A.) use steam at 1,500 lb. per sq. in. and 1,050 deg. F. (565 deg. C.), and these conditions necessitated the use of steels of higher alloy content for the components in the sections of the plant operating at the highest temperatures. These steels and the design stresses were chosen, at the design stage, in the light of the best information then available, but it was clear that more comprehensive data were necessary before full advantage could be taken of the properties of which the types of steel in question were capable. In particular, tests of longer duration were required. Furthermore, some of the data then available referred to material in bar form rather than in the form of actual turbine components.With this background in mind, Sub-Committee J/E ('Steels for High Temperatures') of the Electrical Research Association-the Committee in Great Britain primarily concerned with steels for steam power plant-decided to sponsor a series of investigations to provide long-time information on the creep and metallurgical properties of chosen steels. This work was undertaken at the N.P.L., and follows similar investigations on the high-temperature properties of pipes and tubes of carbon steels and + per cent molybdenum steels and of 3 per cent molybdenum4 per The MS. of this paper was$rst received at the Institution

Fatigue, tensile, and relaxation behavior of stainless steels

“…This relation, although extremely valuable, is only approximate and must be used with caution since many eases are known where the exponent on Nf differs from -\ and the constant is different from 6f/2. A similar equation was proposed by Manson 16 ' 18 in tin; form of Eq. 1.5, where the value of b was taken to be 0.6 to yield:…”