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Use of laser-TIG hybrid technology for boron-doped high-strength steels
Kachlíř, Jaromír ; Šebestová, Hana (referee) ; Mrňa, Libor (advisor)
This thesis deals with the usage of arc preheating for welding high strength boron enhanced steel 22MnB5 using hybrid technology known as laserTIG and also its impact on the final weld compared to welds welded by only the laser or the arc method. During the experiment I welded five sheets of the above mentioned steel 1,3 or 1,9 milimeters wide. Except for the welds fabricated by the laser and the TIG method was the only variable the electric current of the arc (I = 20, 40, or 60 A). Welds welded this way were compared based on strength limits measured by the tensile tests. Additionally were they compared according to the metalographic survey and the progress of weld hardness, calculated using the Vickers hardness test.
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Use of laser-TIG hybrid technology for welding of different materials used in power engineering
Žák, Tomáš ; Beran, David (referee) ; Mrňa, Libor (advisor)
Thesis is focused on analyzing the influence of preheating process parameters using electric arc from TIG torch during laser welding on weld properties of stainless steel and carbon steel with higher strength. In this thesis experiment was done in which metal sheets 3 mm thick from X12Cr13 and S355 steels were welded. Welding was done first with using only laser, then laser with TIG preheating and lastly laser with preheated material by induction heater. When TIG preheating was used than set welding current was changed on the power source. The welds were subsequently evaluated based on macrostructure, microstructure and Vickers hardness test.
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Thickness of sheet and hardness of welded joins
Valášek, Daniel ; IAE, Michal Loskot, IWE, (referee) ; Molliková, Eva (advisor)
Theme of this bachelor’s thesis is to determine the effect of material thickness, laser beam power and the material itself on hardness of the weld joint created by laser welding of construction steels. In addition to description of welding technology, this thesis also includes description of the undertaken experiment and its results which include photographs of microstructure from all weld joint zones and photograph evaluation.
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Use of laser-TIG hybrid technology for welding aluminium alloys
Drápela, Petr ; Šebestová, Hana (referee) ; Mrňa, Libor (advisor)
Different problems arise from choice of setting technological parameters during welding of alluminium alloys. Choice of welding method, welding speed and material influence mechanical properties of welds. During welding of alluminium alloys come difficulties due to oxidation of thin surface layer of material. One of ways how to overcome this obtacle is to use hybrid laser-TIG welding method. In this diploma thesis is described influence of welding processes on mechanical properties of two alluminium alloys(EN AW-5754 H22, EN AW-6082 T6) and change in their microstructure during welding.
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Cobalt alloys and their weld ability
Herčík, Tomáš ; Mrňa, Libor (referee) ; Sigmund, Marian (advisor)
The bachelor thesis is focused on the evaluation of the current state of use of cobalt and cobalt alloys. Due to its shortage and the growing need for precious metal for the production of Li-on batteries, its price, which is now almost at silver prices, is also rising. Some countries even described it as critical and they have bought it in large quantities. From 2020, it is expected that all cobalt will be reserved for the automotive industry, where the use of cobalt in batteries increases their capacity. It is therefore time to look for ways in which precious metal is economised in existing applications. This also includes welding. Of the existing welding technologies, laser welding looks to be the best. In this case no additional material is needed which reduces the need for cobalt. This technology was verified in the experimental part and evaluated by destructive tests (microhardness, microstructure, macrostructure).
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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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Study of properties of laser welds of Domex 700 MC material using arc preheating
Kosinka, Jakub ; Šebestová, Hana (referee) ; Mrňa, Libor (advisor)
This thesis deals with the study of influence of preheating/reheating by TIG arc method in the laser welding process of Domex 700 MC fine-grained steel through the evaluation of laser-welds properties, respectively properties of welds made by laser-TIG hybrid technology. The main part of this thesis is experiment, in which Domex 700 MC plates 3 mm thick were welded – first using laser itself, then using laser with arc preheating and finally using laser with arc reheating. The variable parameter during the processes preheating or reheating was distance of TIG tungsten electrode and laser beam (DLA = 1 mm, 2 mm and 4 mm). The criterion for the assessment of welds properties thus produced was tensile strength verified by the tensile test. For a more detailed study of the laser-welds properties, a macrostructure / weld microstructure analysis and a Vickers hardness test were performed.
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Laser welding of plastics
Nováková, Eliška ; Mrňa, Libor (referee) ; Kubíček, Jaroslav (advisor)
The bachelor presents a brief characteristics of thermoplastics welding methods followed by a more detailed description of laser welding of thermoplastics, i.e. laser description, division and types. Then, conditions and parameters of welding are defined. The experimental part is focused namely on visual welding tests on a test sample. The sample consists of two types of material – pure polymethyl methacrylate and black polycarbonate – which are used in car headlamp production. For welding, a diode laser designed for thermoplastics welding was used. The main target of inspection were flaws that were visible on macroscopically enlarged images. The tested welds mostly showed porosity and air bubbles. Finally, an evaluation of the experiment is conducted.
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Optimization of the laser weld of overlap seam for zink layered sheet metal
Plíšek, Roman ; Kubíček, Jaroslav (referee) ; Mrňa, Libor (advisor)
This diploma thesis deals with the experiment of welding galvanized sheets using fiber laser. The experiment is based on testing of welds lap joints with different gap between the welded parts. Theoretical part of this diploma thesis describes the principles and different types of lasers, laser welding technology, welding defects, galvanizing and inspection of welded joints. In the experimental part of the thesis welding tests and analysis of the results of the experiment have been realised and evaluated.
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