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Use of the preheating by electric arc during laser welding of steels with higher carbon content
Mach, Martin ; Sigmund, Marian (referee) ; Mrňa, Libor (advisor)
The thesis is focused on the study of the use of electric arc preheating, in this case source WIG, during laser welding of steel with a higher carbon content, specifically for this work steel 1.1191 thickness 2 mm. Based on the calculation of the carbon equivalent, the preheating was determined to 208 °C. The welding parameters were selected on the basis of the first experiments. In the experimental section, the samples were welded with laser with preheating using a source WIG, which were then made to a tensile test, Vickers microhardness, macrostructure and microstructure. By using a second heat source, the heat-affected area of the samples was expanded. Samples that cracked in the middle of the weld during the tensile test were heat influenced by cutting samples. The remaining samples was broken in the base material, thus the weld produced was of good quality. Combination of laser welding with WIG electric arc preheating is a very productive method over conventional methods and one of the few pre-heating solutions for laser welding. These are the initial experiments for the use of the WIG arc for preheating in laser welding, to be followed by further research, mainly for the automotive industry.
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CMT advanced application in industrial practice
Šoulák, Petr ; Sigmund, Marian (referee) ; Kubíček, Jaroslav (advisor)
In presented diploma thesis is studied problematics of welding of high strength steels. This work also describes arc welding in protective atmosphere CMT Advanced. In experimental part of this work is CMT Advanced method compared with conventional arc welding in protective atmosphere in shortcut mode used for welding of Hardox 450 and Weldox 700 E. Comparing of mechanical properties of weld material are realized via transverse tensile testing and measuring of microhardness. Macrostructure and microstructure of weld was evaluated too. In the last part of this thesis is a brief economical assessment of both studied methods.
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Nickel alloy overlay welding parameters optimalization
Lauš, Lukáš ; Kubíček, Jaroslav (referee) ; Sigmund, Marian (advisor)
The aim of these master's thesis is to choose and optimize parameters of the Venturi tube throat weld cladding. The Venturi tube is made from carbon steel ASME SA-106 Grade C. The weld cladding is performed by plasma transferred arc welding. The throat is weld overlaid with nickel base powder Inconel 625. The overlays are made without oscilation. The main requirement was to find a maximum possible powder feed rate and others welding parameters to develop maximum welding speed and productivity on automat. Visual and penetrant testing on the overlays were performed. Metalographic samples were prepared. On the samples was meassured dilution, overlay thickness and width of the heat affected zone. Results are compared with parameters succesfully used in the cooperating company.
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Comparison of the welding productivity MAG and FCAW
Kutil, Petr ; Sigmund, Marian (referee) ; Kubíček, Jaroslav (advisor)
This thesis is focused on arc welding with MAG and FCAW methods. The first part contains a brief description of these technologies. Emphasis is laid on the principle of arc welding in active shielding gas and on additional materials, especially on solid and flux-cored tubular wires. The second, experimental part, centres on the comparison of MAG (135) and FCAW (136 and 138) methods in terms of the productivity, costs and, last but not least, the quality of fillet welds made in PF welding position. Based on the calculated and measured figures obtained from the experiment, the most suitable method for the given welding position was chosen.
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Modification of a laser welding system for welding materials releasing excessive amounts of fumes
Kohout, Jaroslav ; Sigmund, Marian (referee) ; Mrňa, Libor (advisor)
The thesis deals with the implementation of a suction system for laser welding. The specific product is grate used for outdoor drainage. The original GMAW production technology is to be replaced by a laser. During the welding of S235JR steel, a significant development of exhaust gases was observed, which subsequently made the actual process impossible. Practical experiments were performed and evaluated using tensile testing and metallographic cut. Based on the results, the optimal position of the suction nozzle and welding parameters were recommended. The obtained values were re-verified by experiment. Furthermore, a suitable extraction device was proposed and an economic evaluation was performed.
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Materials change of parts for harvester chain production
Houdek, Radim ; Kubíček, Jaroslav (referee) ; Sigmund, Marian (advisor)
The work is focused on the track element, namely the replacement of the crossbar material from steel 27MnCrB5-2 to steel 30MnB5 from which the other parts of the cell, the cubes, and the bar are made and welded by the GMAW method. Changing the material and omitting the preheating phase would reduce the production time of the cell by approximately half the time. The theoretical preheating temperature calculated according to the relevant standard for both steels exceeded 200 ° C. Test specimens imitating the weld between the crossbar and the cube were welded on which a qualitative evaluation was performed. These were weldments of 30MnB5 steel with preheating (sample 10), 30MnB5 steel without preheating (sample 11) and 27MnCrB5-2 steel with preheating (sample 9). In terms of macrostructure, non-penetrations were found on all samples. Martensitic structure was found in all areas by microstructural observation. When measuring the hardness according to the Vickers method, approximately the same hardness profile was obtained in all weld areas of samples 10 and 11. The highest value reached 450 HV1 and exceeds the maximum hardness recommended by the standard. Due to very similar test results for 30MnB5 steel weldments with and without preheating, it is possible not to perform preheating. However, the results may be skewed by the relatively small size of the test specimens. For a reliable evaluation and final decision, it is necessary to perform tests on a real crossbar after complete production.
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Thermal spray by electric arc
Eliáš, Vojtěch ; Sigmund, Marian (referee) ; Kubíček, Jaroslav (advisor)
This thesis deals with the issue of thermal spraying by means of an electric arc. First of all, a theoretical part is processed using a literary study dealing with corrosion and thermal spraying technology. The experimental part contains a description of the technological procedure and evaluation of four thermally sprayed samples. Zinacor 850, consisting of 85% zinc and 15% aluminum, was used as a coating. The evaluation involves measurements of thickness, adhesion and roughness as well as the macro-structural analysis of the coating. Two samples showed unusually low adhesion, and all samples also had a large fluctuation of the measured thicknesses. This was also confirmed by the macro-structural analysis, which showed that the sample with low adhesion also had high porosity. These defects may have multiple causes, but the recommendation for further practice is to reduce the spraying distance from the base material.
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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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Welding of hot-dip galvanized sheets using hybrid Laser-TIG technology
Bukvic, Tomáš ; Sigmund, Marian (referee) ; Mrňa, Libor (advisor)
Thesis is focused on verification of suitability of Laser-TIG technology for penetrating welding of galvanized sheets, made of WSS M1A 365-A14 50G steel and DC01 steel. Electric arc functions here as a preheating for evaporation of zink layer. Electric current was chosen as a variable parameter of magnitudes 0, 20, 30 and 40 A. Test welds were made, which have been subjected to a tensile test and metallographic evaluation. The positive influence for electrolytically galvanized steel WSS M1A 365-A14 50G was registered and determination of optimal welding parameters was successful. The electric arc also had a positive effect on welding of hot-dip galvanized steel DC01, but at the selected test parameters not enough to achieve a reliable connection.
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Possible design and performance mistakes of welds for resulting chemical threatment by pickling
Hendrych, Marek ; Kubíček, Jaroslav (referee) ; Sigmund, Marian (advisor)
The diploma thesis deals with the issue of surface treatment by pickling. In the research part the pickling technology is described in detail. The next chapters are focused on the TIG welding method and the weldability of austenitic stainless steels. In the experimental part an experiment is carried out focusing on the comparison of weight loss and surface quality depending on the pickling time. Part of the conclusion is the implementation of pWPS documentation for the specified component and a brief manual for customers of pickling plant.
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