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The Segregation in Ferrous Alloys when Casting Heavy Castings
Pernica, Vítězslav ; Čech, Jan (referee) ; Vodárek, Vlastimil (referee) ; Havlíček,, František (referee) ; Šenberger, Jaroslav (advisor)
This thesis is dedicated to the field of manufacture of heavy steel castings with resulting properties which are influenced by long solidification time. During the long solidification time a segregation process of additives in the steel occurs which results in numerous metallurgical defects. The work was intended to observe the macrosegregation effects in the wall of a heavy experimental steel casting respectively a part of a real superheavy casting intended for cement furnaces (weight 210 t). The steel casting for the research was manufactured in the joint-stock company of VHM where such heavy castings are commonly produced for the market. The supplied piece of the steel casting was cut into the smaller pieces for the better examination. The examination resulted in information about the casting macrostructure and chemical heterogeneity of chosen elements in the casting wall. The heterogeneity of the chosen elements (C, Mn, Si, Cr, S, P) is clearly shown in the worked out visual concentration maps. Based on the experimental data the measured results of segregations were confronted with the results of segregation modelling with the use of the commercial simulation software ProCAST. It resulted in the conclusion that the prediction of segregations is not in accordance with the reality. Furthermore, the results from the experimental casting are shortly compared with previously manufactured castings of the same type and the results summarizing the found range of macrosegregations of the tested sample are interpreted in the work conclusion.
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Electric induction furnaces in foundries
Bruštík, Josef ; Kaňa, Václav (referee) ; Šenberger, Jaroslav (advisor)
The main aim of this Bachelor thesis is to create a technical summary on the topic of “The electric induction furnaces in foundries” and be more closely familiar with this issue. A division of furnaces and ways of melting by particular types of furnaces are briefly described. On the basis of gained knowledge, an evaluation of economic and technical advantages of these melting devices was performed and subsequently it is recommended for further usage in the foundries.
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Research, Optimization and Starting the Production of Heavy High-Alloy Cast Irons
Kaňa, Václav ; Elbel, Tomáš (referee) ; Martínek, Ludvík (referee) ; Šenberger, Jaroslav (advisor)
The work is particularly aimed at metallurgical problems connected with manufacture of castings of weight about 1 up to 40 tons from high-alloy austenitic nickel cast irons also known under the trade name Ni-resist. The main aim is to check and complement the knowledge about manufacture of heavy castings from austenitic nickel cast irons in a field of control of tapping and casting temperature, carbon content control with regard to the prediction of eutectic composition and in a field of setting a suitable chemical composition of cast iron with regard to the formation of chunky graphite and stability of the austenitic matrix and further on also possibilities of cast iron filtration during pouring the castings. Based on done experiments the formulae were determined that enable to calculate eutectic and liquidus temperatures on the basis of chemical composition of the cast iron. The use of several formulae given in the literature for calculating the carbon equivalent of austenitic nickel cast irons was compared and evaluated. For utilization of determined results in practice a calculating programme has been compiled making possible to be used in operational practice. This programme is named Calculation of casting temperature of Ni-resist cast irons. After the entry of the melt chemical composition the programme calculates the all important parameters necessary to know and to be controlled for manufacture of high quality castings from austenitic nickel cast irons. Eutectic temperature, liquidus temperature and then based on it the tapping and casting temperatures are included among those parameters. Further on there are eutectic concentration of carbon, carbon equivalent, nickel equivalent, and a criterion evaluating a danger of chunky graphite formation.
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Reasons for pin holes formation in ductile iron castings
Opačitý, Radim ; Palán, Petr (referee) ; Šenberger, Jaroslav (advisor)
The aim of this thesis was to analyze the formation of defects in a given casting of ductile cast iron EN - GJS - 600-3 cast in sand molds bentonite, which is formed jolting with coining and then find a solution to remedy these defects. To resolve this issue, the influence of the composition of the sand mixture, the effect of metal flow in a cavity forms and the influence of deoxidation of metal in the presence of defects. Obtained results showed the importance of the influence Reoxidation metal cavity mold. Specifically, in this case succeeded in reducing the incidence of PINHOLES. Removal of PINHOLES to achieve deoxidation aluminum melt. This has reduced the production of nonconforming castings under 3% from the original 6.5%.
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RESEARCH OF HEAVY CASTING METALLURGICAL DEFECTS
Čech, Jan ; Elbel, Tomáš (referee) ; Jelínek, Petr (referee) ; Šenberger, Jaroslav (advisor)
A massive castings defects are examined in this doctoral thesis, specialise in steels passing through peritectic transformation. There are typical types of defects at massive steel castings, as contrasted to „ordinary“ internal and surface ones. For massive steel castings are typical defects under feeders like conchoidal fractures, segregations, microporesities, reoxidation products. Combination of Al and Zr is an ordinary final deoxidation of EOP and LF steel for castings in ŽĎAS a.s. foundry. The aim of Al + Zr combination was to both deep deoxidation by Al (decrease of bubbles risk) and denitrification by Zr (decrease of conchoidal fractures). This theses refute premission mentioned above and verified persisting risk of defects under massive feeders, even though Al + Zr deoxidation is used. A final deoxidation by increased amount of Al was examinated, in combination with other deoxidation agents. Castings had 11 [cm] maximal modulus, and occurence of conchoidal fracture, reoxidation products and primary austenite grain size was evaluated. A selected optimal final deoxidations (Al, Al+Ti, Al+Zr) as a result from experiment described above, were evaluated on castings with 15 [cm] maximal modulus. The result of experiment is, that is not possible to repeatedly produce massive steel casting using EOP metallurgical equipment without defects under feeders, despite of deoxidation and pouring temperature optimalization. The defect indications look like conchoidal fracture, but there are microporesity and impurities instead. Finally, castings with maximal modulus 15 [cm] were produced using so called secondary metallurgy (LF, VD). Secondary metallurgy allowed to both significant decrease of sulfur and degassing of melted metal. Only this metallurgical procedure guarantees production of heavy steel castings without typical defects under massive feeders
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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.
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Casting of manganese steels and their use
Dufka, Martin ; Šenberger, Jaroslav (referee) ; Pernica, Vítězslav (advisor)
Austenitic manganese steel, often referred as Hadfield´s steel after its discoverer, has an irreplaceable place in foundry due to its specific properties. Due to local pressures and shocks, surface of castings is hardened, but the cast core retains its toughness. Thus, manganese steel is used for castings of highly stressed machine parts that are subject to abrasive wear. This bachelor thesis is concerned about methods of production, chemical composition, influence of some alloying elements on properties and structure of steel, heat treatment, material properties, reinforcement mechanisms and types of individual deformation reinforcements. Further attention is paid to the most frequent use of manganese castings in practice.
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History of ferrous alloy manufacture at Czech-Moravian Highlands
Kolníková, Eliška ; Kaňa, Václav (referee) ; Šenberger, Jaroslav (advisor)
This thesis deals with the history of steel production focused on the Czech-Moravian Highlands in the 14th – 19th century. The introduction provides a survey of chemical and physical reactions taking place in the steel production. The next chapter focuses on technology of production of raw iron and steel, there are also mentioned raw materials and equipment for their production. The last part deals with the various localities in the Czech-Moravian Highlands in the 14th - 19 century.
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Optimation of heavy steel castings
Pernica, Vítězslav ; Veselý, Pavel (referee) ; Šenberger, Jaroslav (advisor)
Diploma thesis deal with definnig the casuses of stell castings defects in the DSB EURO s.r.o Foundry. The main target is to optimise technological parameters for avoiding the surface casting defects. The first stage is the identification of the defects, describing of the main reasons and mechanic. Defect quantification is make from measuring of area and volume of the mended defects. In association with surface defects, the number of the crackings was observed. Finally there are suggested correction actions based on the previous investigation.
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