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Study of properties of laser welds of Hardox 450 material using arc preheating
Debs, Martin ; Kubíček, Jaroslav (referee) ; Mrňa, Libor (advisor)
In this thesis is studied the influence of arc TIG preheating during laser welding of 2 mm Hardox 450 material sheets. This material achieves its good mechanical properties by processes of heat treatment. That causes problems during welding because of heat degradation. Experimental sheets were welded within various configurations of welding parameters and positions of TIG nozzle. Testing specimens were cut out by laser and were used for tension testing, Vickers hardness testing and metallographical testing (macro and microstructure). The results of using the second heat source are: wider heat affected zone, smoother transitions among its zones, reduction of toughness and hardness, finer grain structure and occurring ferritic microstructure. This hybrid technology, combination of laser welding and TIG preheating, is very productive creating joints with greatly good quality. The thesis also contains a comparison with common MAG welding method.
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Influence of shielding gas on weld properties of conductive laser welding of sheet from carbon steel
Kotrík, Marcel ; Sigmund, Marian (referee) ; Mrňa, Libor (advisor)
In the thesis are analysed influences of three shield gases, based on literary pursuit. Compared was influence of the gas consisting of pure Ar, mixture Ar with 3vol.% CO2 and the mixture Ar with 18vol.% CO2 on mechanical properties of conduction laser welded blunt welds made from structural steel DC01 and S235JR with thickness 3mm and 2mm. Compared were strength properties of the welds in tension, weld hardness and hardness of the heat affected area under the low stress. Further was observed and compared stream of the gases during welding process and its influences on the appearance of the trial welds. On the metallographical cuts of the welds were evaluated mistakes and dimensions of the welds.
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Measurement of cutting edge roughness in the process of laser metal cutting using the Yb-YAG laser
Maňas, Petr ; Hála, Michal (referee) ; Mrňa, Libor (advisor)
The project elaborated in frame of bachelor´s degree program B-STG (“Mechanical Engineering Technology”, 2303R002), evaluates the roughness of samples of cutting edge laser cutting. Cutting performed the fiber Yb:YAG laser. The samples consisted of structural steel J235JR and DC01, stainless steel X5CrNi18-10 and aluminium alloys AIMg3. They were evaluated according to the ČSN EN ISO 9013 standard. The classification of samples into classes according to the standards of accuracy. The theoretical part is consists of a description of the methods of cutting, a basic principle of the laser and its types. It includes cutting parameters and their influence on the quality of subsequent defects. It is described roughness measurement and standard ČSN EN ISO 9013.
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Welding of deep-drawing steels with protective layer by laser-TIG hybrid technology
Brehovský, Patrik ; Sigmund, Marian (referee) ; Mrňa, Libor (advisor)
The diploma thesis focuses on laser welding of extra deep-drawn steel sheet according to the standard WSS-M1A365-A14 with a protective zinc surface layer. A 0,9 mm thick steel sheet with a zinc layer with coating weight 50 g · m^-2 is welded by a hybrid welding method Laser-TIG. The laser, as the primary energy source, is used for welding the material. The arc, provided by a non-melting tungsten electrode, is used for preheating the material for melting and evaporation of the zinc layer. Based on the initial experiments, the magnitude of the laser power with the welding speed was chosen as a constant parameter. The magnitude of the electric current, as the variable parameter, was set up to 0, 20, 30 and 40 ampers for welding the lap and the butt welds. Only one piece of the each weld type combination was made. The welds were afterwards tested to verify their quality and material properties. The first differences between laser welding with or without TIG preheating were visible during the experiment. The positive effects of the laser welding with preheating by TIG were confirmed. The material properties of the joints achieved better values and a influence of the welding defects on the quality of the joints was reduced. The Laser-TIG is a good choice for welding galvanized steel sheets in the mass production of automotive industry and it could be improved by more researches.
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Surface hardening of cast iron by high power diode laser
Bezděk, Pavel ; Daněk, Ladislav (referee) ; Mrňa, Libor (advisor)
The Master’s thesis deals with the technology of surface hardening by laser. High power diode laser is used for this purpose. Surface hardening is performed on cast iron BS 1452-77, at different speeds laser head and laser power. In introduction, the theoretical part deals with possible ways of hardening focusing on the benefits of laser hardening. There are mentioned basic parts of laser, type industrial lasers and their application in industry. The final part is mentions the using of material and methods used to evaluate samples. The practical part describes the using devices and carries out evaluation macrostructure and microstructure and evaluation of hardness depending on the distance from the surface.
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Simulation of geometry of key hole depending on the welding parametrs in laser deep penetration welding
Křivan, Miloš ; Šarbort, Martin (referee) ; Mrňa, Libor (advisor)
The diploma thesis is focused on simulation of keyhole creation in laser deep penetration welding and on the effect of welding parameters on the geometry of keyhole (weld). With reference to this issue theories of keyhole creation are described. 2D simulation model that is created in mathematical software Matlab is verified pursuant welding results of non-alloy constructional steel 1. 0122 and stainless steel 1.4301. Effect of welding parameters on the geometry of keyhole and on the quality of weld is investigated through the welds in non-alloy steel 1.0122.
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Welding of finegrain steel from range of DOMEX steel by YbYAG fiber laser.
Němeček, Tomáš ; Daněk, Ladislav (referee) ; Mrňa, Libor (advisor)
The project elaborated within the engineering studies of the branch Manufacturing technology presents an experiment of welding of high strength steel by fiber laser. The project includes a theoretical study, which deals with the welding material properties, principles and types of lasers and laser welding technology. The practical part contains a verification of the welding parameters according to the standard ČSN EN ISO 15614-11. The final evaluation results of the experiment at the close of the project are presented.
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Unconventional methods of welding of wrought magnesium alloys
Klimčáková, Kateřina ; Mrňa, Libor (referee) ; Doležal, Pavel (advisor)
Master's thesis deals with consideration possibility of conventional and unconvetional welding methods of wrought magnesium alloys. Methods of Friction Stir Welding, Pulsed Nd:YAG laser and Continuous Fiber laser was used to join magnesium alloy sheets AZ31, AZ61, ZE10 and ZE41. For studying influence of processing parameters on microstructure and mechanical properties were used methods of light microscopy, scanning electron microscopy, tensile tests and microhardness measurements. The results of tensile tests show that from the point of view of keeping ultimate tensile strength is the best methods for welding magnesium alloys Friction Stir Welding. Compared with Nd:YAG laser, fiber laser give better properties of welds. From comparing microstructure and mechanical properties . It wasn't found publications about Friction Stir Welding of magnesium ZE alloys or about FSW sheets with thickness only 0,8 mm and 1,6 mm.
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Utilization of laser welding methods for fixation of electrotechnical sheet bundles
Adam, Tomáš ; Kubíček, Jaroslav (referee) ; Mrňa, Libor (advisor)
Thesis deals with individual technologies of packaging stator sheets and their use in practice. The greatest emphasis is placed on welding technologies, especially on the differences between the individual methods. The experimental part of the thesis is focused on finding suitable parameters for welding the stator package using a laser with a special wobling head. The samples were evaluated in terms of penetration depth, the number of defects, especially pores and grain coarsening.
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Comparison of cladding by the electron beam and plasma process
Rudyk, Martin ; Mrňa, Libor (referee) ; Kubíček, Jaroslav (advisor)
This diploma thesis deals with plasma cladding and electron beam cladding. The theoretical part is divided into several chapters which is focused on description of these methods of cladding process. In the practical part the particular experiment of electron beam cladding (EBC) and plasma cladding (PC) is described. In the conclusion overall results were assessed, both methods were compared each other and possible exploitation in industry was described.
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