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Structure and properties of weldment of rotor steels
Jech, David ; Jan,, Vít (referee) ; Foret, Rudolf (advisor)
The object of this thesis is to assess the structural stability of heterogeneous weld joint, which consists of two different base materials (16,537 steel and 16,236 steel) and weld metal NiCrMo2.5-IG with buttering layer P24-IG. All these materials belong to the group of low-alloyed creep-resistant steels that are to be used mainly in the power industry. The weld joint was made by application of the TIG hot wire welding method. Structural stability of this joint was evaluated by carbon redistribution and microstructural changes after annealing in temperature 300 °C and 400 °C during 500 hours. For modelling the phase composition of particular steels was used the ThermoCalc software. All gained results should be employed to appraise whether the heterogeneous weld joint of the steam turbine´s rotor is eligible for long-term operation in hard working conditions.
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Modelling of Phase Composition of Heat Resistant Steels and their Welds
Dvořáček, Ondřej ; Foret, Rudolf (referee) ; Jan, Vít (advisor)
This work deals with the effects of high temperature exposition of low alloyed creep resistant steels on their structural stability and structural stability of their weld joint. The theoretical part of this work gives an overview of creep resistant steels considering their chemical and phase composition and their connection to high temperature mechanical properties. The CALPHAD method is presented as generally accepted approach for equilibrated calculations and Thermo-Calc and DICTRA software packages are introduced as CALPHAD applications. Thermo-Calc software is used for calculation of phase composition of the examined materials and for calculation of the phase diagrams. Software DICTRA is used for simulations of diffusion controlled phase reactions in the analysed weld. Experimentally one weld joint of the steels 15 128 and 15 313 has been studied after four different annealing procedures. The experimental results include chemical profiles across the welds, microhardness profiles and metallographic analysis of significant regions of the welds. These experimental results are compared with the simulation results. The comparison shows a reasonable agreement between experimental and simulation data.
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Structural Stability of Creep-Resistant Steels and their Weldmets
Šohaj, Pavel ; Jan, Vít (referee) ; Foret, Rudolf (advisor)
The structural stability of creep-resistant steels P22, P91 and Eurofer´97 and structural stability of weld joint P22/P91 have been studied. The microstructural changes during annealing at temperatures of 500 – 900°C were examined. The state of equilibrium have been simulated using the ThermoCalc software. The computed results were compared with published data. A good agreement between the simulation and the published data was observed.
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Welding of titanium alloys using electron beam
Schiffer, Martin ; Foret, Rudolf (referee) ; Havlík, Petr (advisor)
This bachelor´s thesis is focused on issue of welding of titanium alloys using electron beam. It is dedicated to description of principle of electron beam welding technology. There is described interaction of electron beam with the welded material, electron beam characterisation and configuration of device for electron beam welding. Next part is focused on evaluation of weldability of titanium alloys. It includes general description of weldability of materials, description, distribution and weldability of titanium alloys and finally evaluation of effect of electron beam welding on the microstructure. As an example, there is described effect of EBW on mechanical properties of alloy Ti-6Al-4V. In the end this technology is compared with other methods of fusion welding as laser beam welding, arc welding methods and plasma arc welding.
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Microstructure and hardness of bainitic weld deposits on rails
Havlík, Petr ; Stránský, Karel (referee) ; Foret, Rudolf (advisor)
Surfacing worn crane railways as renovation technology can make several possible ways, so as manual welding whit coated electrode, with filled electrode or automatic submerged arc. The resulting mechanical properties will depend on the additional materials, which was used to create surfacing. This thesis deals whit evaluation of integrity and microstructure single - layer to three - layer surfacing with filled electrode on the rail with predominantly pearlitic structure. Were evaluated areas with the greatest heat dissipation during cooling, due to the possible occurrence of side structures. The study employed the interaction light microscopy, the scanning electron microscopy equipped by energy dispersive chemical microanalysis, the macro and micro hardness measurement by Vickers.
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Analysis of Circular Bars Shearing Process
Dohnalová, Eva ; Hůlka, Jiří (referee) ; Foret, Rudolf (advisor)
In these days customers require a high quality as well as precision of products together with a cost that is as low possible. The cost of products can be reduced in a way of batch production. Implementation of the batch production requires a detailed plan of a technological process to avoid making depreciated products or series of products. A software package can be used to simulate the technological process of shearing to avoid difficulties of particular technological process. This bachelor paper contains analysis of technological process of shearing of circular section rods. The results of the analysis are going to be included in FEM simulations. The effect of the technological process of shearing on material was determined by optical and scanning electron microscopy method. The microhardness measurement was used to analyse the deformation hardening of the examinated material.
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Structure of Heat Resistant Steels
Skýba, Pavel ; Foret, Rudolf (referee) ; Jan, Vít (advisor)
This work is a compilation essay about structure of heat-resistant steels, creep, strengthening and heat treatment based on available literature sources. The main chapters of the work deal with creep deformation, its mechanisms and the ways of strengthening used in heat-resistant steels. Separate chapters deal specifically with precipitation strengthening, minority phases that can be found in heat-resistant steels and their heat treatment.
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The calculations of equilibrium states in high-alloy chromium steels
Foret, R. ; Unucka, P. ; Buchal, A. ; Kroupa, Aleš
The paper presents the results of calculation of equilibrium states in high-alloy chromium steels obtained by Thermo-Calc program and the continuously extended Steel 16. database. The calculation were made for 9 to 12% chromium steels with graded contents of molybdenum and vanadium. The calculcations have been supplemented with analyses of the minority phases encountered. The analyses were performed using the method of TEM,EDS extraction replicas and X-ray phase analysis.
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