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Design of a technology and checking the production of small steel ingots
Jakubčíková, Lucie ; Čamek, Libor (referee) ; Záděra, Antonín (advisor)
The thesis deals with the design of ingots from duplex (austenitic-ferritic) stainless steels in terms of minimal occurrence of axial porosity. The optimal shape and dimension of the ingot and the casting conditions are determined based on numerical simulations. The resulting internal quality of the realized ingot is evaluated. The presence of shrinkage porosity is determined by penetrant testing. The degree of chemical heterogeneity, the extent of macrosegregation, of selected elements in given ingot locations is measured by an optical emission spectrometer. Segregation values are compared with simulation results. The micro-purity of the ingot is assessed on the basis of metallographic samples.
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Manufacturing and defects of steel castings
Smilovský, David ; Čamek, Libor (referee) ; Záděra, Antonín (advisor)
A content of this thesis is an analysis of a steel castings production mismatch in Tatra Metallurgy foundry. Most common defects found on castings are gas holes. Thesis shows a theoretical research on casting defects caused by gases in steel castings. It also describes melting and degassing problematics of molten steel and procedures to reduce gas contents. The last part of theoretical research describes oxidation of steel in contact with silica mold. Practical part of thesis analysis production of steel castings to determine the cause of origin of gas holes. Main attention is paid to mold mixture, chemical composition, casting temperatures and casting time. The last chapter metallographically analysis two defected castings to determine the origin of defects. Main attention is paid to shape and chemical composition of gas holes and to morphology of steel inclusions.
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Measurement of oxygen activity in ferro-alloys
Žák, Štěpán ; Čamek, Libor (referee) ; Záděra, Antonín (advisor)
The thesis deals with determination of the oxygen content in ferro-alloys with emphasis on direct oxygen activity measurement in the meltage. The practical part of the thesis contains statistical analysis of oxygen activity values measured in austenitic and duplex stainless steel meltages. The measurements were done in vacuum furnace before vacuuming and afterwards. Statistically significant dependency of oxygen activity on the temperature of meltage was discovered among the values measured after the vacuuming. Therefore, its value can be predicted based just on the temperature of the meltage. No statistically significant dependency was found among the values measured before vacuuming (except for the low Chromium austenitic stainless steel meltages). Hence, other factors need to be considered when predicting oxygen activity before vacuuming.
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Production of steel for castings in an electric arc furnace
Hejčl, Pavel ; Záděra, Antonín (referee) ; Čamek, Libor (advisor)
The thesis deals with electric arc furnaces, especially electric arc furnaces of the foundry-type which are used for production of steel for castings. The theoretical part first mentions variants of electric arc furnaces according to their construction and determined place. Then, it focuses only on foundry-type furnaces for which it describes construction and main production phases. The practical part deals with the evaluation of a group of melts of low-alloy chromium molybdenum steel for castings G17CrMo9-10 from the OTO 5 electric arc furnace.
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Structure and properties of martensitic stainless steels
Rimko, Marcel ; Čamek, Libor (referee) ; Záděra, Antonín (advisor)
The final thesis deals with martensitic stainless steel and their mechanical properties. The theoretical part consists of information about corrosion, chemical composition, heat treatment and mechanical properties of various types of steel. The practical part deals with the influence of the cooling rate during heat treatment and nickel content on the mechanical properties and microstructure of the GX4CrNi13-4 steel.
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Possibilities of removing lead and other harmful elements from waste from metallurgical processes
Jedličková, Veronika ; Kurka, Vladislav (referee) ; Čamek, Libor (advisor)
The work describes an overview of individual variants of processing and recycling of metallurgical waste. From the economic and especially ecological point of view, the possibility of landfilling this waste seems to be very unsatisfactory. Currently a considerable amount of material from previous production is stored in landfills. The presence of hazardous elements in this waste means a certain risk to the environment. Undesirable elements include Zn, Pb, Cd and others. In these experiments, changes in the chemical composition of blast furnace sludge were observed with a focus on changing the concentration of lead and zinc in the form of oxides. The sludge was heated in a rotary kiln to different temperatures and under different atmospheres. Lead oxide has been shown to be effectively removed in oxidizing atmosphere, while zinc oxide concentration is effectively reduced in reducing atmosphere.
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Possibilities of removing lead and other harmful elements from waste from metallurgical processes
Jedličková, Veronika ; Kurka, Vladislav (referee) ; Čamek, Libor (advisor)
The work describes an overview of individual variants of processing and recycling of metallurgical waste. From the economic and especially ecological point of view, the possibility of landfilling this waste seems to be very unsatisfactory. Currently a considerable amount of material from previous production is stored in landfills. The presence of hazardous elements in this waste means a certain risk to the environment. Undesirable elements include Zn, Pb, Cd and others. In these experiments, changes in the chemical composition of blast furnace sludge were observed with a focus on changing the concentration of lead and zinc in the form of oxides. The sludge was heated in a rotary kiln to different temperatures and under different atmospheres. Lead oxide has been shown to be effectively removed in oxidizing atmosphere, while zinc oxide concentration is effectively reduced in reducing atmosphere.
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Production of steel for castings in an electric arc furnace
Hejčl, Pavel ; Záděra, Antonín (referee) ; Čamek, Libor (advisor)
The thesis deals with electric arc furnaces, especially electric arc furnaces of the foundry-type which are used for production of steel for castings. The theoretical part first mentions variants of electric arc furnaces according to their construction and determined place. Then, it focuses only on foundry-type furnaces for which it describes construction and main production phases. The practical part deals with the evaluation of a group of melts of low-alloy chromium molybdenum steel for castings G17CrMo9-10 from the OTO 5 electric arc furnace.
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Measurement of oxygen activity in ferro-alloys
Žák, Štěpán ; Čamek, Libor (referee) ; Záděra, Antonín (advisor)
The thesis deals with determination of the oxygen content in ferro-alloys with emphasis on direct oxygen activity measurement in the meltage. The practical part of the thesis contains statistical analysis of oxygen activity values measured in austenitic and duplex stainless steel meltages. The measurements were done in vacuum furnace before vacuuming and afterwards. Statistically significant dependency of oxygen activity on the temperature of meltage was discovered among the values measured after the vacuuming. Therefore, its value can be predicted based just on the temperature of the meltage. No statistically significant dependency was found among the values measured before vacuuming (except for the low Chromium austenitic stainless steel meltages). Hence, other factors need to be considered when predicting oxygen activity before vacuuming.
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Structure and properties of martensitic stainless steels
Rimko, Marcel ; Čamek, Libor (referee) ; Záděra, Antonín (advisor)
The final thesis deals with martensitic stainless steel and their mechanical properties. The theoretical part consists of information about corrosion, chemical composition, heat treatment and mechanical properties of various types of steel. The practical part deals with the influence of the cooling rate during heat treatment and nickel content on the mechanical properties and microstructure of the GX4CrNi13-4 steel.
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