Comparison of nodularization processes at production of spheroidal cast iron

Namen diplomskega dela je nodulacija taline z dvema različnima postopkoma. Talino smo nodulirali po postopku sandwich in po postopku žica. Poleg obeh postopkov smo naredili primerjavo postopka sandwich, ki smo ga izdelali v Ivančni Gorici ter v Črnomlju. Postopek nodulacije z žico smo izdelali le v Črnomlju, ker v Ivančni Gorici tega postopka ne uporabljajo. Testne ulitke smo analizirali in analize primerjali vizualno, s termično analizo, kemijsko analizo ter metalografsko analizo. Eksperimentalni del smo izvedli v livarni v podjetju Livar. Celotno gledano se postopek nodulacije na obeh lokacijah ter z obema postopkoma izdeluje zadovoljivo. To lahko potrdimo z dokazom, da kocke oz. vzorci niso bili vidno porozni. Razlike in pomanjkljivosti smo opazili v ploščicah z valjčki. Najboljši primer nodulacije smo izvedeli s postopkom žica v Črnomlju. Ugotovili smo, da je bila velikost grafita največja v primeru nodulacije s postopkom sandwich v Črnomlju, najmanjša pa v primeru nodulacije s postopkom sandwich v Ivančni Gorici, kar pomeni, da smo primer nodulacije s postopkom sandwich v Ivančni Gorici bolje izvedli, kot primer nodulacije s sandwich postopkom v Črnomlju. Ugotovili smo, da se delež perlita v vseh primerih nekoliko razlikuje, kar je posledica deleža perlitotvornih elementov. V vseh primerih smo ugotovili pomanjkljivost in sicer, da grafit ni lepo razporejen po celotni matrici. Pojavljajo se mesta kjer grafita sploh ni zaznati, kar je posledica slabega cepljenja taline. Poleg nehomogene razporeditve grafita smo ugotovili tudi, da se v mikrostrukturi pojavljajo velikostni razredi grafita 6, 7, 8. V mirkostrukturi pri primeru nodulacijes postopkom žica v Črnomlju smo zaznali degenerirani grafit.The purpose of this diploma paper is the nodule count of cast iron by means of two different methods: sandwich method and cored wire method. Besides using both methods, a comparison was made between the sandwich methods done in Ivančna Gorica and Črnomelj respectively. The cored wire method was only used in Črnomelj as it is not being used in Ivančna Gorica. Test castings were analyzed and then analyses were compared visually, with thermal analysis, chemical analysis, and metallographic analysis. The experimental part was done in the foundry of Livar company. Generally speaking, the process of nodule count done on both locations and with both methods is satisfactory, which can be confirmed by the proof that samples were not visibly porous. Differences and imperfections were detected in small panels with rollers. The best example of nodule count was made with the cored wire method in Črnomelj. The study showed that the graphite size was the largest in the case of nodule count done with the sandwich method in Črnomelj, and the smallest in the case of nodule count done with the sandwich method in Ivančna Gorica, meaning that the nodule count done with the sandwich method in Ivančna Gorica was done better than the nodule count with the sandwich method in Črnomelj. The study revealed that the percentage of perlite in all cases differs somewhat, which is the result of perlite-forming elements. All cases revealed an imperfection, namely that graphite is not evenly distributed across the entire matrix. There are places where graphite cannot be spotted at all, which is the result of poor melt grafting. Besides a non-homogenous distribution of graphite, I also found that in microstructure there appeared graphite size grades 6, 7 and 8. In the microstructure of the nodule count done with the cored wire method in Črnomelj, I detected degenerated graphite