National Repository of Grey Literature 167 records found  previous11 - 20nextend  jump to record: Search took 0.00 seconds. 
Welding of deep-drawing steels with a protective layer by means of an oscillating laser beam
Holub, Kamil ; Sigmund, Marián (referee) ; Mrňa, Libor (advisor)
This thesis deals with the topic of procedural parameters influence on the properties of welded joint in zinc-coated deep-drawing steels in laser welding with wobbling. First part of the thesis serves as an overview of laser welding technology, welding of steel with protective zinc layer and weld quality testing. Second part is dedicated to a proposal, process flow and evaluation of an experiment. Seven trial lap welding joints of DC04+ZE steel have been welded using different welding parameters. Specimens from these trial welds were used for metallurgical testing by macro-etch examination and for tensile strength break testing to get mechanical properties of welded joints.
Welding of deep-drawing steels with protective layer by laser-TIG hybrid technology
Brehovský, Patrik ; Sigmund, Marián (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.
Renovation of casting molds by laser cladding technology
Cicha, Tereza ; Kubíček, Jaroslav (referee) ; Mrňa, Libor (advisor)
The diploma thesis deals with study of laser cladding technology and possibilities of its use in renovation of casting molds made of hot-work tool steel. The theoretical part describes methods of laser cladding, testing methods and characteristics of the base material and its heat treatment. In the experimental part the test clads, and the metallographic samples were made. The samples were evaluated in terms of macrostructure and microstructure, especially clad geometry, dilution, and defects like pores and cracks. Microhardness was also measured. In conclusion a technical and economic evaluation was performed.
Welding parameters optimalization of robotic welding for car industry
Soprunenko, Valeriia ; Mrňa, Libor (referee) ; Sigmund, Marián (advisor)
Thesis deals with individual technology of new welding processes "specifically FRONIUS TPSi". The greatest emphasis is on welding technology, especially on the differences between the individual methods. The experimental part of the thesis is focused on finding suitable parameters for welding filled welds.Everythingwith respect to required welds quality welded by robotic welding. The samples were evaluated in terms of penetration depth, amount of heat introduced and the number of defects.
Weldability of cobalt alloys by hybrid method Laser-TIG
Herčík, Tomáš ; Mrňa, Libor (referee) ; Sigmund, Marián (advisor)
The master thesis summarizes the critical situation of the lack of a cobalt used in different industry branches. Due to its increasing price, it will not be possible to use in existing applications. One of these applications is production of cobalt alloys where the replacement of this element is impossible. This type of material keeps mechanical properties at high temperature. However, a suitable choice of technology can achieve at least its savings. In the field of welding, the alloys are joined without any use of an additional material. The possible solution could be the use of hybrid technologies or electron beam. Verification of weldability of both methods was realised in experimental parts and evaluated by destructive methods. The investigation was performed on wear resistant alloy Stellite 6B.
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.
Orbital welding assembly welds in the Nuclear Power by the TIG method
Lukášek, Zdeněk ; Mrňa, Libor (referee) ; Kubíček, Jaroslav (advisor)
The Bachelor's thesis looks at the possibility of using orbital welding by the TIG method on mounting welds in JE Dukovany. In the opening section, we deal with the issue of weldability, primarily carbon steels. Furthermore, the work focuses on TIG welding technology, both in the manual and mechanised way it details, including the advantages and disadvantages of both variants. In the experimental section, five test samples of ferric-perlithic material pipes were welded. The samples were assembled to simulate possible combinations that occur during pipeline assembly. Non-destructive and destructive controls followed, verifying the quality and mechanical properties of the resulting weld joints. In conclusion, the results of the trials were assessed and evaluated.
Repair TS tubes of the steam generator by manual welding
Zeman, Tomáš ; Mrňa, Libor (referee) ; Kubíček, Jaroslav (advisor)
This bachelor thesis deals with repair of heat exchange tubes of steam generator of Dukovany Nuclear Power Plant. Defects in the material of the collector of the steam generator were to such an extent that it was necessary to proceed with manual repair by workers inside the collector. A number of inspection welds, thorough training and preparation were performed to obtain the qualification of the repair. The repair was followed by a series of tests and trials, which ended in a satisfactory result and the equipment was put into operation.
Dependence of the laser weld geometry on the bevel size
Man, Antonín ; Kubíček, Jaroslav (referee) ; Mrňa, Libor (advisor)
This work deals with laser welding technology. It explains in more detail advantages and disadvantages, applications and direction in which this relatively young technology develops. The main topic of this work is welding of martensitic stainless steel with carbon structural steel. Components of this type can be found, for example, in the power industry, specifically the stator part of a steam turbine. Part of this work is also an experiment that will explain the dependence of the geometric dimensions of the material to be welded on the quality of the weld. The welded test specimens were subsequently tested by both the non-destructive and destructive methods. It can be stated from the results, that the size of the bevel does not affect the quality of the weld, nor geometry.
Friction welding of part chains for forest machines
Houdek, Radim ; Mrňa, Libor (referee) ; Sigmund, Marián (advisor)
The bachelor's thesis is focused on the condition of the weldment of the part of the track, specifically the welding of the cube to the crossbar made of steel 50CrV4 and 27MnCrB5-2. The parts were welded by linear friction welding. The first part of the work is a literature search on the topic of linear friction welding and joined materials. The second part of the work presents the results of a closer examination of weldments. Their macrostructure, microstructure, microhardness were examined in all areas of the welded joint, the amount of residual austenite was determined by X-ray diffraction analysis, the materials were tested for chemical composition and the weldment was tested for breakage.

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