Effect of alloying elements on properties of vermicular cast iron and the economic analysis of costs

Magistrsko delo v splošnem govori o postopkih litja vermikularne litine, vplivu elementov na njene lastnosti s primerjavo vrednosti, kot jih predvideva teorija. Vsebuje še analizo nastalih stroškov pri reševanju problema v podjetju Omco Feniks Slovenija, d. o. o. V prvem poglavju je razloženo, kaj je livarstvo, opisane so železove litine, vermikularna litina in pojasnjen je vpliv zlitinskih elementov na lastnosti litine. Nato sledi predstavitev postopkov in naprav za preiskavo mikrostrukture ter nekaj podatkov o programu za statistično obdelavo podatkov. Na koncu poglavja so razloženi osnovni pojmi statistične analize in pojasnjena je teorija stroškov. V drugem delu je opisana celotna tehnologija litja vermikularne litine v podjetju Omco Feniks Slovenija, d. o. o. Postopek zajema pripravo modelov, taljenje železovih zlitin, izdelavo jeder in peščenih form ter ulivanje in čiščenje ulitkov. Vključeni so še še pomožni procesi, kot sta skladiščenje in vzdrževanje. V tem poglavju so tudi opisani različni postopki pridobivanja sive litine z vermikularnim grafitom z izhodiščno sestavo in obdelavo taline. Predstavljen je kupec oziroma njegovi odlitki za ladijske motorje, ki so iz omenjene litine, ter samo podjetje Omco Feniks Slovenija, d. o. o. V raziskovalnem delu so najprej določene mehanske, kemijske in metalografske lastnosti vzorcev EN-GJV-350. Sledi statistična obdelava rezultatov v programu R z izračunom korelacij in določanjem statistične značilnosti le-teh oziroma s primerjavo izmerjenih vrednosti in značilnosti, kot jih predvideva teorija. Pri vplivu lastnosti in elementov na raztezek so napravljeni in utemeljeni tudi še linearni modeli. Pri tem je bilo ugotovljeno, da ima ključno vlogo element magnezij, hkrati pa linearni modeli po večini niso smiselni. Vzrok je najverjetneje v pojavu multikolinearnosti in zaradi prisotnih osamelcev. Raziskovalni del vključuje še opis problema, ki ga je imelo podjetje, in analizo nastalih stroškov pri tem.Master\u27s thesis speaks about the casting process of the compacted graphite iron, the impact of the elements on its properties by comparing the values as foreseen by the theory. This work includes the analysis of the costs incurred in resolving the difficulties in the company Omco Feniks Slovenia Ltd. In the first section are explained general terms, such as foundry, cast iron, compacted graphite iron. The impact of alloying elements on the properties of cast iron is clarified. Furthermore, procedures and devices to investigate the microstructure and the program for statistical analysis are presented. At the end of the chapter are shown the basic concepts of statistical analysis and the theory of the cost is explained. The second section describes the complete vermicular cast iron casting technology in the company Omco Feniks Slovenia Ltd. The process includes the preparation of models, melting of ferro-alloys, production of cores and sand forms, and casting and cleaning castings. Included are also secondary processes, such as storage and maintenance. This chapter also describes the different methods for production of cast iron with compacted graphite with the source composition and processing of the melt. The customer or his castings for marine engines are presented and also the company Omco Feniks Slovenia Ltd itself. In the research part of this work the mechanical, chemical and metallographic properties of the samples EN-GJV-350 are determined. This is followed by the statistical treatment of the results in the R program with the calculation of correlations and determination of the statistical significance of these, and comparing the measured values and characteristics, as foreseen by the theory. Linear models are used for determining of the effect of the properties and the elements on expansion. It was found out that the key role plays magnesium, while the linear models for the most part are not meaningful. This is most likely attributed to the occurrence of multicolinearity and due to the presence of outliers. Research part includes also a description of the problem presented in the company and the analysis of the costs incurred.