Svařitelnost a vlastnosti svarových spojů 9 ÷ 12% Cr modifikovaných žárupevných ocelí

Abstract

Doctoral thesis deals with the weldability of modified materials and properties of welded joints from 9 ÷ 12% Cr of steel for high temperature service, which are focused on the welded joint from material grade P92. Steel P92 for high temperature service and other steels from this group find their use in reconstruction, alteration and construction of new energy source. The theoretical part of this doctoral thesis is aimed to describe the current state of development of modified steels for high temperature service and their properties. The work is focused on P92 steel as one of the main representatives of this group of steels. The historical development and characterization of 9 ÷ 12% Cr is described in the introduction. The next section describes the microstructure and heat treatment of steel P92. Due to the use of steel P92 in terms of long thermal exposure (creep), the behavior of steel during creep exposure is analyzed in this dissertation. The weldability of steel P92 and problems of heterogeneous welded joint of steel for high temperature service is characterized in conclusion of the theoretical parts. Based on theoretical analysis were defined objectives and proposed the solution procedure, which enables the study of properties and verification of weldability of steel P92. The practical part of the thesis is divided into two phases. The first phase is focused on execution of real welded joints with determined welding processes. The influence of welding processes and different mode of heat treatments are investigated on the properties of welded joints in this section. Second part of dissertation is aimed on the study of HAZ (Heat Affected Zone) of steel P92, where was applied simulation technique. Simulator SMITWELD was used for this part of investigation. Modeled samples from the simulation were subsequently tested in order to obtain mechanical properties and analysis of the final microstructure. Creep tests of base metal and real welded joints were simultaneously performed during realization of both phases of this practical part.