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Influence of the electron beam trajectory on the surface properties of steel 42CrMo4
Mikuš, Tomáš ; Kouřil, Miloslav (referee) ; Foret, Rudolf (advisor)
The thesis deals with surface quenching of steel 42CrMo4 by electron beam. Influence of technologic parameters and beam deflection on properties and structure of prepared layers is studied. Electron beam surface quenching was applicated with and without melting of the surface. Structures of layers made by electron beam quenching were compared with structures made by laser and electromagnetic induction. Structures and phases were analysed by optical microscopy, SEM and roentgen diffraction. Hardness was measured on hardened layers.
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Macro and microstructure of weld joints made of titanium alloy TiAl6V4 by electron beam
Prachař, Václav ; Havlík, Petr (referee) ; Foret, Rudolf (advisor)
The aim of this bachelor thesis is to evaluate macro and microstructures of weld joints made of titanium alloy Ti6Al4V by electron beam welding with different processing parameters of electron beam and evaluate the impact of this processing parameters to the structure of resultant weld joints. The theoretical part deals with titanium and its alloys, the titanium alloy Ti6Al4V and electron beam welding technology. In the experimental part, 11 weld joints are evaluated, their macro and microstructures and hardness profiles.
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Optimization of heat treatement for steel beams
Dyčka, Martin ; Foret, Rudolf (referee) ; Jan, Vít (advisor)
This thesis deals with heat treatment of pearlitic steel beams with using of induction heating. The aim of this heat treatment is to improve mechanical properties of steel beams. In theoretical part are described pearlitic steels and theory of induction heating. In experimental part of this thesis analysis of current state of technology with its results was made. Numerical model describing current state of technology was assembled. Then this model was used to recommend adjustments in current technology of heat treatment, which leads to enlargement of heat treated depth. Experiments with adjusted parameters were executed on heat treating machine. Analysis of microstructure using LM and EM, measurement of hardness and fractographic analysis were done. The result of adjustments is enlargement of heat treated depth about half compared with current technology.
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Structure and properties of welded joint TiAl6V4 / 6061 made by electron beam technology
Král, Michael ; Jan, Vít (referee) ; Foret, Rudolf (advisor)
Titanium and aluminium alloys are among the most used construct materials due to their physical and mechanical properties except steels. The joining of these alloys can improve properties of whole construction but it is still difficult task. Especially welding of titanium and aluminium alloys is difficult cause formation of undesirable intermetalic phases in the weld. This thesis focuses on influences of electron beam welding parameters especially focusing and deflection of beam and preheating of base material to quality of heterogeneous join of titanium alloy Ti6Al4V and aluminium alloy EN AW-6061 – T651. There is described preparation of welded joins and brazed joins in the thesis, which are evaluated by light microscopy, scanning electron microscopy and EDS analysis of chemical composition. There was evaluated presence and chemical composition of formated intermetalic phases in the welded joins and quality and defects in the brazed joins.
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Influence of heat treatment on the microstructure of alloy TiAl6V4
Fišara, Šimon ; Němec, Karel (referee) ; Foret, Rudolf (advisor)
The main goal of this bachelor thesis is to summarize influence of heat treatment on microstructures and mechanical properties of titanium alloy Ti6Al4V. There are summarized basic facts about titanium and its alloys in the first section of theoretical part. The second section is focused on description of phase transformation, mechanical properties, microstructures and heat treatment of Ti6Al4V. There were made several types of heat treatment in the experimental part and after that there were made metallographic analysis and evaluation of microstructures.
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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 electron beam penetration produced in steel AMS 5659
Říčan, Daniel ; Foret, Rudolf (referee) ; Kouřil, Miloslav (advisor)
This master thesis deals with the electron beam welding of the AMS 5659 steel used in industry for special hydraulic cylinders (Fig. 1). A theoretical analysis of electron beam welding and analysis of the influence of selected welding parameters on penetration characteristics are in the first part of the thesis. The second part contains an evaluation of the implemented experimental penetrations on samples of the steel in the hardened condition H1025 and after solution heat. It was also done a properties assessment of the same samples that were been hardened again. The light microscopy (SM), the scanning electron microscopy (SEM) and the measurement method of hardness according to Vickers were used for evaluation and comparison of the steel properties in the region of penetration and the heat affected zones properties.
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Analysis of the causes of cracks on the wheeel rims
Plundrák, David ; Němec, Karel (referee) ; Foret, Rudolf (advisor)
This thesis looks for the causes of cracks in bicycle rims in the most stressed areas (in places holes for wires). For this reason, in this work is the stress and strain analysis of a simple model of the rim to the working load is given and further the complete production process of the rim is described. As an experimental material were used rims from different producers of aluminum alloy EN AW 6061 and EN AW 6082 T6 temper, in which a crack started to spread. For assessment of rims materials the methods of optical spectroscopy, optical microscopy, scanning electron microscopy, Vickers hardness test were used and for finding another crack penetration test was performed. Based on the performed experiments bad design solution of rivets was found in the rim 1. Broken rivets initiated fatigue cracks. Material of rim 1 was alright. The other two rims were deficiencies in materials. For the rim 2 was a problem with coarse-grained recrystallized structure. The insufficiently rapid cooling for the rim 3 caused exclusion hardening phase (particularly copper phase) at grain boundaries. Moreover, the rim 3 is not cured to the required parameters. Aluminium alloys are an ideal material for bicycle rims. However, they require reliable design solutions and meeting the physical metallurgy, which lies in the knowledge and use of influences of chemical composition, forming and heat treatment on mechanical, chemical, physical and technological properties.
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Structural stability heterogeneous weldment of carbon/austenitic steels
Havlík, Petr ; Stránský, Karel (referee) ; Foret, Rudolf (advisor)
Heterogeneous welded joints – type ferrite/austenite is inseparable part of structure for energy industry. Welding conditions and post weld heat treatment have a significant impact on the structural stability of welded joint. The structure determines resulting mechanical properties that determine lifetime of these joints. At the same time in microstructure changes in heat affected zone of the base material is diffusion of carbon through the weld interface. This work is focused on the analysis of structural stability of heterogeneous weld carbon/austenitic steel, which was formed carbon steel 22K (base material) and austenitic buttering layer EA 395/9 with a higher content of nickel. Evaluation of the structure was focused on the structure of weld metal (Böhler FOX SAS 2) and structure of the heat affected zone of base material. Metallographic evaluation was performed on the light microscope and scanning electron microscope equipped with the energy and wave dispersive analysis, which identified the contents of substitutional elements and carbon on the interface of carbon/austenitic steel. The results of metallographic analysis were compared with measurements of Vickers hardness and microhardness and calculations using Thermo-Calc software and software SVARY. The description and evaluation of the stability of the weld joints was determined by carbon content of the course interface using wave dispersive spectroscopy. The results of energy dispersive analysis were used to determine the type of carbides present at the interface of carbon/austenitic steel.
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