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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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Study of the influence of process parameters on welding properties of ferritic stainless steel in laser oscillation welding
Křepela, Petr ; Kubíček, Jaroslav (referee) ; Mrňa, Libor (advisor)
The aim of this work was to carry out an experiment to assess the influence of the individual welding parameters in the laser welding method with the beam wobbling on the made weld, respectively. welds. The material which was welded was ferritic stainless steel with the designation 1.4016, which, like all ferritic steels, is susceptible to coarse grains and the resulting brittleness which leads to degradation of the mechanical properties of the weld. The welds were compared to a sample welded without wobbling an between themselves. Unfortunately, however, the evaluation of the test samples did not bring significant differences from laser welding without wobbling, however some changes are evident, such as grain orientation, weld defects, or uniformity of mechanical properties over the weld length, where wobbling frequency is most important. Further research should focus on limiting the porosity at higher wobbling frequencies in the shape of a circle or ellipse.
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Study of the influence of process parameters on welding properties of ferritic stainless steel in laser oscillation welding
Křepela, Petr ; Kubíček, Jaroslav (referee) ; Mrňa, Libor (advisor)
The aim of this work was to carry out an experiment to assess the influence of the individual welding parameters in the laser welding method with the beam wobbling on the made weld, respectively. welds. The material which was welded was ferritic stainless steel with the designation 1.4016, which, like all ferritic steels, is susceptible to coarse grains and the resulting brittleness which leads to degradation of the mechanical properties of the weld. The welds were compared to a sample welded without wobbling an between themselves. Unfortunately, however, the evaluation of the test samples did not bring significant differences from laser welding without wobbling, however some changes are evident, such as grain orientation, weld defects, or uniformity of mechanical properties over the weld length, where wobbling frequency is most important. Further research should focus on limiting the porosity at higher wobbling frequencies in the shape of a circle or ellipse.
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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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Strenght, fracture and fatigue properties of base materials and weld joint of inflow piping to water turbine (PART I - Weld plate to plate)
Dlouhý, Ivo ; Kruml, Tomáš ; Čupera, Pavel ; Chlup, Zdeněk ; Šiška, Filip
Sets of strength, strain, fracture toughness and fatigue properties are summarised in the report characterising the base material, heat affected zones and weld joint material of steel used in water turbine system. Data obtained from 30 mm sheet materials and its weld joint are given. Tests have been carried out in agreement with recent standards and loading curves for finite element calculations have been also supplied. Crack resistance curves have been also generated by unloading technique at 0 and +20°C. Tests of compact tensions in transition regions enabling to determine reference temperature have been carried out. There are also data from fatigue tests, namely cyclic response and fatigue life curves, for the same materials.
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Evaluation of Strain Rate Effects on Transition Behaviour Applying the Master Curve Methodology
Dlouhý, Ivo ; Kohout, J. ; Jurášek, Ladislav ; Holzmann, Miloslav
Master curve methodology has been used for an evaluation of strain rate effects on transition behaviour of wrought CrMo and cast ferritic C Mn steel.The physical aspects of strain rate effect on reference temperature has been analysed as a base for the prediction of this dependence.Statistical aspects of the strain rate effects on the master curve have been discussed showing capability of the method for the prediction of strain rate susceptibility of steel fracture behaviour. It has been experimentally proved that the master curve shape does not depend on the loading rate.The relationship between reference temperature T0 (or the shift of T0 with respect to quasi-static loading rate)and loading rate can be described with linear dependence if logarithmic scale of temporal change of stress intensity factor is considered.For experimental establishing of the dependence of reference temperature on loading rates only two T0 values as determined at different loading rates are sufficient.However,it is useful to achieve the comparable accuracy of both T0 determinations that may demand larger number of specimens for the measurement of T0 at the higher loading rate.Standard quasistatic fracture toughness has been predicted from small pre-cracked Charpy type specimens tested dynamically applying the reference temperature shift obtained experimentally.The predicted fracture toughness temperature diagram has been proved experimentally.
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