Abstract
The continuously developing power generation sector, including boilers with supercritical parameters, requires applications of new creep-resistant steel grades for construction of boilers steam superheater components. Therefore, this paper contains selected information, results of the research and implementation process including: - evaluation, comparison of requested properties of base material and welded joints, such as tensile strength, impact strength and technological properties, - destructive examinations with evaluation of welded joints and HAZ structure and hardness distribution, - influence of manufacturing process in large boilermaker conditions and after simulated operation. A new creep-resistant steels to be used, in order to comply with the operational requirements, as to assure the appropriate reliability and safety of the boiler equipment in operation process. This document presents a simplified analysis of martensitic steels from group 9-12% Cr (T91, T92, HCM12A, VM12) and austenitic steels Cr-Ni (TP347FG, SUPER 304H, HR3C), having the chemical composition as presented in tables 1 and 2, which are to be applied for steam superheater components.
Highlights
The boilers of supercritical working parameters and the requested low emission level of harmful substances into the atmosphere, require higher and higher outlet steam parameters
Among the critical boiler pressure parts superheater components play a vital role. They have been elaborated as the result of grade scale research works, mainly within the European programmes COST 511, 522 and COST 536, where steel making, welding materials developments and manufacturing technologies have been worked out with the objective to make boiler components of them [1,2,3]
The base material structure, depending on the examined steel grade, is mainly tempered martensite, the steel containing 9%Cr, frequently with lower bainite and few ferrite areas
Summary
The boilers of supercritical working parameters and the requested low emission level of harmful substances into the atmosphere, require higher and higher outlet steam parameters Any increase of those parameters necessitates a search for and application of new materials, having higher strength parameters and more complex technological manufacturing process for boiler pressure part components, made of such materials [1,2,3]. The creep-resisting steels, which are used for superheater components in the “typical” power units having supercritical parameters, steam temperature of approx. The thinwalled steam superheater coils, located in the flue gas environment and made of martensitic steels, having approx.
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