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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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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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Microstructural Stability of Weld Joints of Austenitic and Ferritic Steels
Šohaj, Pavel ; Stránský, Karel (referee) ; Sopoušek, Jiří (referee) ; Foret, Rudolf (advisor)
This doctoral thesis summarizes the theoretical and experimental knowledge in the field of dissimilar weld joint of progressive austenitic and ferritic creep-resistant steels. The following materials were selected for the presented study: 316Ti stabilized austenitic stainless steel, martensitic 9-12 %Cr steel P92 and ferritic ODS steel MA 956. The main attention was focused on the long-term microstructural stability during high temperature exposure of heterogeneous joints of the austenite / ferrite type. The literature analysis critically evaluates the current state of knowledge in the field of microstructural stability of advanced creep-resistant steels weld joints. The practical experimental part was carried out in two directions. On the basis of the chemical composition phase equilibrium calculations were performed for each steel using the ThermoCalc software, giving the basic concepts about the dependence of the phase composition and the chemical composition of phases on temperature. In parallel with these calculations the laboratory joints 316Ti/P92 made by resistance welding and the MA 956/316Ti electron beam weld joints were prepared, analyzed in as-weld state and further annealed at different temperature conditions. Exposed joints were subjected to microstructure and phase analysis. The stability of the weld interface was mainly observed. Attention was also focused on the agreement between the calculation and experimental data in comparison with data published in the literature. Based on the calculations, experimental results and published data the suitability of the combination of materials is discussed in the thesis and reasoning about the behavior of studied weld joints during long-term high temperature exposure was formulated. Based on the results the expected degree of microstructural stability of 316Ti/P92 joint was confirmed, while the joints MA 956/316Ti were found to be unstable.
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Microstructure stability of tungsten -ODS hetergeneous welds
Adam, Ondřej ; Sonnek, Pavel (referee) ; Jan, Vít (advisor)
The thesis is focused on microstructural stability of heterogeneous weld joint of ODS steel and tungsten. The theoretical part summarizes the basic information about the structure and properties of ODS steels and describes the methods of joining these steels with tungsten. In the experimental part, materials MA956 and WL10 were welded by using electron beam. The individual samples differ by preheating temperature or use filler material. After annealing at 800 °C/1h and 1000 °C/5h, a change of the weld metal microstructure was evaluated by using scanning electron microscope. The chemical composition was measured by energy dispersive spectroscopy. It has been found that during annealing, massive precipitation of particles occures in the whole volume of the weld metal. These particles were identified as Laves phase.
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Microstructure stability of tungsten -ODS hetergeneous welds
Adam, Ondřej ; Sonnek, Pavel (referee) ; Jan, Vít (advisor)
The thesis is focused on microstructural stability of heterogeneous weld joint of ODS steel and tungsten. The theoretical part summarizes the basic information about the structure and properties of ODS steels and describes the methods of joining these steels with tungsten. In the experimental part, materials MA956 and WL10 were welded by using electron beam. The individual samples differ by preheating temperature or use filler material. After annealing at 800 °C/1h and 1000 °C/5h, a change of the weld metal microstructure was evaluated by using scanning electron microscope. The chemical composition was measured by energy dispersive spectroscopy. It has been found that during annealing, massive precipitation of particles occures in the whole volume of the weld metal. These particles were identified as Laves phase.
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Microstructural Stability of Weld Joints of Austenitic and Ferritic Steels
Šohaj, Pavel ; Stránský, Karel (referee) ; Sopoušek, Jiří (referee) ; Foret, Rudolf (advisor)
This doctoral thesis summarizes the theoretical and experimental knowledge in the field of dissimilar weld joint of progressive austenitic and ferritic creep-resistant steels. The following materials were selected for the presented study: 316Ti stabilized austenitic stainless steel, martensitic 9-12 %Cr steel P92 and ferritic ODS steel MA 956. The main attention was focused on the long-term microstructural stability during high temperature exposure of heterogeneous joints of the austenite / ferrite type. The literature analysis critically evaluates the current state of knowledge in the field of microstructural stability of advanced creep-resistant steels weld joints. The practical experimental part was carried out in two directions. On the basis of the chemical composition phase equilibrium calculations were performed for each steel using the ThermoCalc software, giving the basic concepts about the dependence of the phase composition and the chemical composition of phases on temperature. In parallel with these calculations the laboratory joints 316Ti/P92 made by resistance welding and the MA 956/316Ti electron beam weld joints were prepared, analyzed in as-weld state and further annealed at different temperature conditions. Exposed joints were subjected to microstructure and phase analysis. The stability of the weld interface was mainly observed. Attention was also focused on the agreement between the calculation and experimental data in comparison with data published in the literature. Based on the calculations, experimental results and published data the suitability of the combination of materials is discussed in the thesis and reasoning about the behavior of studied weld joints during long-term high temperature exposure was formulated. Based on the results the expected degree of microstructural stability of 316Ti/P92 joint was confirmed, while the joints MA 956/316Ti were found to be unstable.
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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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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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