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Surface quenching of ductile cast iron
Neduchal, Bronislav ; Roučka, Jaromír (referee) ; Záděra, Antonín (advisor)
This diploma thesis is focused on the surface hardening of cast irons with spheroidal graphite. The work describes a theoretical analysis of the structure and properties of cast irons and individual methods suitable for surface hardening. The practical part describes the production of cast iron castings with spheroidal graphite, on which the surface hardening is performed, tensile test, hardening of produced castings by induction and laser surface hardening, preparation of samples for measuring microhardness and metallographic analysis of metal structures.
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Effect of lead and antimony on the degradation of graphite shape in cast iron
Hlobil, Albert ; Kaňa, Václav (referee) ; Záděra, Antonín (advisor)
The bachelor thesis focuses on the effect of lead and antimony on the degradation of graphite in cast iron in relation to the lowered mechanical characteristics. This leads to the subsequent summary of the formation of degraded structures and unfavourable elements – the elements that are the cause of the formation. In the practical segment of the thesis, I will prove the effects of lead (or the combination of lead and antimony) on the degradation of graphite in cast iron with the focus lying at flake graphite. Furthermore, the thesis examines the mechanical characteristics and the attenuation of cast iron in relation to the formation of degraded graphite structures.
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Low Cycle and High Cycle Fatigue Properties of Austempered Ductile Iron
Zapletal, Josef ; Bokůvka, Otakar (referee) ; Kunz, Ludvík (referee) ; Věchet, Stanislav (advisor)
The thesis is focused on assessment of fatigue behaviour of austempered ductile iron with nodular graphite. Optimal period of transformation was determined based on the best combination of stress and strain characteristics established by tensile test. Cyclic response and low-cycle fatigue life were studied under both stress-control and longitudinal strain-control mode at room temperature. For both modes, shapes of cyclic hardening curves are dependent on stress amplitude. Cyclic deformation curves (CDC) were fitted by power regression function. Results were compared with CDC established by multiple step test in both modes with verification of the influence of cyclic creep (high stress levels, stress-control mode). Experimental data of S-N curves are in agreement with the Manson-Coffin and the Basquin law. Fatigue and cyclic parameters were compared. Fatigue life time in high-cycle fatigue region was determined. Experimental data were fitted by suitable regression functions. Regression parameters and fatigue limit were established by means of each regression function. Experimental data in low- and high-cycle fatigue regions were used to construct S-N curve and to determine relevant parameters. Discontinuity of experimental data was not observed. Low-cycle fatigue behaviour was predicted. Approximation of tolerance bands was realized in high-cycle and both high and low cycle fatigue regions.
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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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Production of Ductile Iron with Feritic Matrix
Blaha, Marek ; Šupálek, Milan (referee) ; Molliková, Eva (advisor)
This bachelor thesis deals with the properties and production of ductile cast iron with ferritic matrix. Theoretical part is focused on basic information about ductile iron, its chemistry, structure and mechanical properties. The production of ductile iron with ferritic matrix in JMA Hodonín Ltd is described in the next chapter of this thesis. In the experimental part the real cast is described together with its production technology and material. The practical part is concentrated on comparison of chemical composition, structure and mechanical properties of material of cast and keel blocks made of the same melt. Finally the results of experiments are summarized and the arrangements for improving conformity between material of cast and of keel block are suggested.
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Heat treatment processes optimalization of ADI with graded Ni content
Klimentová, Jiřina ; Stránský, Karel (referee) ; Pavloušková, Zina (advisor)
This work is focused on segregation processes in the matrix of spheroidal graphite cast iron with different silicon and nickel content during heat treatment. The aim of this work is to trace the redistribution of the elements of interest during homogenization annealing with different dwell time by comparison of the effective distribution coefficients. Comparison of some specific properties and description of structure development of spheroidal graphite cast iron matrix from initial state to the state after ferritization and homogenization annealing is included in this work.
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The study of increase in efficiency of manufacturing preparation of technology
Šudoma, Michal ; Lána, Ivo (referee) ; Jurová, Marie (advisor)
This paper discusses different alternatives of more efficient preparation of spheroided graphite cast iron production. Secondary metallurgy and chemical heating technology are used to recast cast iron fused in copula furnace. The work applies the known physical-chemical rules used in the production of quality spheroided graphite cast iron in regular production conditions. Based on the previous developments, the aim was to prepare implementation of verified secondary metallurgy processes in adjusted casting ladle. The casting ladle was adjusted in order to allow execution of all processes required in order for the relevant standards and material lists requirements to be met in respect to spheroided graphite cast iron quality. Comments regarding the trends in ferroalloy metallurgy and related marketing approach of the company. The work is concluded by a summary of advantages brought in by the new approaches compared to the traditional ones from the economical as well as environmental perspective.
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Optimation of inoculation process of ductile iron
Ulm, Daniel ; Pecina, Vladimír (referee) ; Roučka, Jaromír (advisor)
The master‘s thesis deals in theoretical part with the casting classification, ductile iron casting, its inoculation and modification and quality evaluation using thermal analysis, image analysis and testing of mechanical properties. The aim of the practical part was to test the effects of preconditioning on the properties of ductile iron and to find out whether it is able to replace the current method of inoculation or to increase the mechanical properties of ductile iron castings. The state of the ductile iron was under control by spectral and thermal analysis. The mechanical properties and image analysis were checked on finished casting.
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