National Repository of Grey Literature 84 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Precipitation of Intermetallic Phases in Austenitic-Ferritic Duplex Steels
Myška, Martin ; Foret, Rudolf (referee) ; Čech, Jan (referee) ; Záděra, Antonín (advisor)
This PhD thesis addresses the issue of precipitation of intermetallic phases in cast duplex stainless steel according to the ASTM A890 Gr4A standard. The aim of the thesis was to determine the amount of precipitated intermetallic phases depending on the temperature and holding time during isothermal annealing and under anisothermal conditions during cooling of the material in the temperature range from 1000 to 600 °C. The partial aim of the work was to determine the relationship between the amount of precipitated intermetallic phases and the mechanical properties of cast steel ASTM A890 Gr4A. As part of the work, the description and prediction of the kinetics of precipitation of intermetallic phases using the Johnson-Mehl-Avrami equation were verified. The relationship between the amount of precipitated intermetallic phases and the failure character of the material was determined by fractographic evaluation. The critical cooling rate of the casting was determined to ensure the minimum toughness of the steel that is desirable to reduce the risk of cracking during cooling of duplex stainless steel castings.
Structure and properties of high silicon ductile iron
Paták, Daniel ; Kaňa, Václav (referee) ; Záděra, Antonín (advisor)
The diploma thesis was focused on the production of solid solution strengthened ductile iron. In the first part, research dealing with nucleation embryos and nucleation mechanisms of graphite was developed. Furthermore, the mechanical properties of high silicon ductile irons, their tendency to form chunky graphite and its effect on mechanical properties were described. In the experimental part, 3 melts with 4; 4.5 and 4.1% Si content were cast. Tensile tests, metallographic samples and numerical simulations were performed to compare the mechanical properties, microstructure and chunky graphite appearance as a function of solidification time and silicon content.
Degassing of aluminum alloys in the production of castings
Višvader, David ; Myška, Martin (referee) ; Záděra, Antonín (advisor)
The bachelor's thesis contains a literature review addressing the issue of degassing of aluminum alloys and the measurement of degassing level. The practical part involved experimental verification of the degassing effect using a rotary device at various rotor rotation speeds to achieve a certain degassing level, which is evaluated according to DI.
Manufacture and Properties of Cast Ceramic Cores based on Ethyl Silicate
Bořil, Petr ; Trunec, Martin (referee) ; Vasková,, Iveta (referee) ; Záděra, Antonín (advisor)
The doctoral thesis is focused on the production and properties of cast ceramic cores based on ethyl silicate. The main motivation is to develop a new technology for cast ceramic cores that would solve the shortcomings of Shaw’s original cast ceramic technology and would be viable. Shaw’s original technology has low handling strength of the cores, which lead to the necessity to use steel reinforcements for larger cores and even then the cores were broken due to the different thermal expansion of the reinforcements and ceramics. The Experimental part of the thesis is therefore devoted to the possibility of increasing the handling strength of cast ceramic cores. The influence of granulometric composition of the refractory material, addition of fibers, addition of organic substances and penetration of phosphate on the strength of the cores is described in the individual stages. The knowledge gained in the individual stages led to the development of a new cast ceramic cores technology whose properties are described in the final chapter.
Determination of operating costs depending on production technology of casting
Černocký, Libor ; Horák, Michal (referee) ; Záděra, Antonín (advisor)
The diploma thesis compares the costs of potting instrument transformers and sensors using vacuum potting technology and potting technology of automatic pressure gelation. The principles of managerial accounting, which are theoretically summarized, were used for the solution. The analysis of the potting operation of instrument transformers and sensors was carried out in the company ABB s. r. o. The technological processes of potting of transformers and sensors were described in their production, and the reasons for the cost of potting technologies were found. The relationships between higher costs and the amount of instrument transformers and sensors produced by a given potting technology were determined. For the year 2023, the costs of potting technologies were estimated and the hourly technology rate was determined, according to which individual transformers will cover the technology costs for this year. Furthermore, the break-even point of the total technological costs of both potting technologies was calculated. It was found for the current condition that for the number of transformers up to the break-even point is more advisable to use vacuum potting technology, and when exceeding the break-even point quantity, it is more advantageous to choose the technology of automatic pressure gelation. Finally, it was created a tool to select the necessary number of casting molds of the new type of transformer and to choose the potting technology according to the predicted production volume.
Interaction of melted nickel alloys with materials of ceramic cores
Feller, Šimon ; Pernica, Vítězslav (referee) ; Záděra, Antonín (advisor)
This study focuses on the interactions between the IN713LC alloy and various oxide ceramics and oxide coatings commonly used for casting applications in the aerospace or medical industries. The investigated ceramics are based on SiO2, ZrO2, ZrSiO4, Al2O3 and Y2O3. An experimental design proposed for the purpose of this study produced samples used to examine the chemical composition of the metal-oxide ceramic interface. This study compares the findings from the samples with assumptions derived from thermodynamic calculations or thermodynamic conclusions stated in scientific articles with similar themes.
Manufacturing, structure and properties of cast iron with globular graphite produced on electric furnaces
Tvrdoň, Tomáš ; Pernica, Vítězslav (referee) ; Záděra, Antonín (advisor)
The diploma thesis deals with the technology of production of ductile iron with lower production costs. The thesis takes into account quality in terms of internal structure and mechanical properties. The thesis consists of two parts. The first part is about theoretical analysis of the topic of graphite cast irons with a more detailed discussion of the chemical composition, structure and properties of ductile iron. The experimental part deals with the production of ductile iron on electric arc and induction furnaces with different metall charging. Subsequently, the structures and mechanical properties of the ductile iron produced on these two melting aggregates are compared. An important part of this work is also an economic evaluation, where the proposed variants are compared in terms of metall charging and used melting aggregates.
Production of LKG castings and cost comparison depending on the melting furnace
Exner, Zbyněk ; Šenberger, Jaroslav (referee) ; Záděra, Antonín (advisor)
This thesis is focused on technology of manufacturing ductile cast iron by using metal melted in cold blast cupola. The temperatue of cast iron melted in cupola furnace is often insufficient for subsequent metalurgicall processing of the cast iron, i.e. modification. Chemical heating could be used as an alternative for the needed increasement in temperatue of the melted metal before a modification. For the purposes of the experiment, a ladle for chemical heating was designed and manufactured within the diploma thesis. Furthermore, the work presents the results of two test melts, in which cast iron corresponding to EN-GJS-500-7 was produced after heat treatment. The thesis includes images of the structure of cast samples and samples even after heat treatment. Furthermore, the work presents an optimization solution for the charge comosition to the cupola furnace in order to reduce the phosphorus content. For the overall economic evaluation, the composition the charge comosition for the production of sferoidical graphite (SG) iron on the electric induction furnace was proposed and its costs were compared with the possibilities of SG iron production at the cupola furnace. Based on the determined costs of individual variants, the return on the transition from a cupola furnace to an electric induction furnace was calculated.
Influence of sand size of core mixtures on surface quality of cast iron castings
Brůža, František ; Krutiš, Vladimír (referee) ; Záděra, Antonín (advisor)
The diploma project deals with the mechanisms of burn-on casting defects on castings made of spheroidal graphite cast iron. It discusses the elimination of their occurrence in the conditions of the German foundry MAT Ueckermünde by changing the granulometry of the core sand. Subsequently, the thesis deals with the influence of this change on the greensand. Furthermore, the thesis compares three refractory coatings supplied by the foundry. The coatings are compared both by laboratory measurements and by experimental tests during casting in conditions simulating the operation of this foundry. Finally, the individual tests are evaluated, including the effect of the individual measures in the case of their use in MAT Ueckermünde.
Influence of concentration of selected pearlitic elements on structure and properties of spheroidal graphite cast iron
Kazdera, Vojtěch ; Kaňa, Václav (referee) ; Záděra, Antonín (advisor)
This masters thesis deals with the influence of selected pearlitic elements on the mechanical properties and structure of spheroidal graphite cast iron. The theoretical part analyses the parameters that have a major impact on the mechanical properties and structure of cast irons. In the practical part, the influence of Cu, Mn and thickness on the mechanical properties and structure of spheroidal graphite cast iron is determined by means of a planned experiment. The measured values were then statistically processed and the result is equations for the theoretical calculation of mechanical properties.

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