Spreminjanje kemijske sestave sive litine v odvisnosti od temperature in časa zadrževanja taline v peči : diplomsko delo

Jakšič, Nejc (author), Petrič, Mitja (mentor), Balaško, Tilen (comentor)

Namen raziskave je bil ugotoviti kako temperatura litja in čas zadržanja taline v peči vplivata na kemijsko sestavo in ogljikov ekvivalent sive litine. Vhodni material sive litine z znano kemijsko sestavo smo pretalili v električni indukcijski talilni peči. Po taljenju je bila talina segreta na temperature 1300, 1350 in 1400 °C. Na vsaki temperaturi je talina bila zadržana 0, 15, 30 in 45 min. Pri teh temperaturah in časih zadržanja so bili vzeti vzorci za kemijsko analizo, kjer je bila talina ulita v bakreno kokilo. Prav tako so bili uliti vzorci za termično analizo s sistemom ATAS, pri čemur je bila talina ulita v merilno Quick cup celico. Med ohlajanjem taline se je merila temperatura. Na podlagi kemijskih sestav je bila izvedena termodinamska analiza. S programsko opremo Thermo-Calc in JMatPro smo iz kemijske sestave vhodnega materiala izračunali spremembo Gibbsovih prostih energij reakcij oksidacije pri danih temperaturah, ter ogljikov ekvivalent. Izračuni reakcij oksidacije so bili normalizirani na 1 mol kisika. Cilj je bil ugotoviti stopnjo oksidacije ogljika in ostalih legirnih elementov v sive litine, tek kako se spreminja kemijska sestava in ogljikov ekvivalent. Rezultati so pokazali, da imata temperatura litja in čas zadržanja taline v peči velik vpliv na stopnjo oksidacije in končno kemijsko sestavo. Pri višjih temperaturah litja je oksidacija ogljika in ostalih legirnih elementov bolj intenzivna kot pri nižjih temperaturah litja. Pri daljših časih zadržanja taline v peči je oksidiralo več ogljika in ostalih legirnih elementov. Opažanja so pokazala da pri nižjih temperaturah litja bolj odgorevata silicij in mangan, medtem ko pri višjih temperaturah litja bolj odgoreva ogljik. Ogljikov ekvivalent in aktivni ogljikov ekvivalent padata z višanjem temperature litja. Ugotovljeno je bilo da ima ogljik največji vpliv na ogljikov ekvivalent.

• Language: Slovenian
• Keywords: Temperatura litja, čas zadržanja, ogljikov ekvivalent, aktivni ogljikov ekvivalent, kemijska sestava.
• Work type: Bachelor thesis/paper
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Year: 2025
• PID: 20.500.12556/RUL-173953
• COBISS.SI-ID: 255965955
• Publication date in RUL: 25.09.2025

Secondary language

• Language: English
• Title: Change of chemical composition of cast iron in reliance to temperature and holding time of the melt : diploma work

Abstract

The purpose of the study was to determine how the casting temperature and the time the molten metal is kept in the furnace affect the chemical composition and carbon equivalent of gray cast iron. The input material of gray cast iron with a known chemical composition was remelted in an electric induction melting furnace. After melting, the melt was heated to temperatures of 1300, 1350, and 1400 °C. At each temperature, the melt was held for 0, 15, 30, and 45 minutes. At these temperatures and holding times, samples were taken for chemical analysis, where the melt was cast into a copper mold. Samples for thermal analysis were also cast using the ATAS system, whereby the melt was poured into a Quick cup measuring cell. The temperature was measured during the cooling of the melt. A thermodynamic analysis was performed based on the chemical compositions. Using Thermo-Calc and JMatPro software, we calculated the change in Gibbs free energy of oxidation reactions at given temperatures from the chemical composition of the input material, as well as the carbon equivalent. The oxidation reaction calculations were normalized to 1 mol of oxygen. The aim was to determine the degree of oxidation of carbon and other alloying elements in gray cast iron, how the chemical composition and carbon equivalent change. The results showed that the casting temperature and the time the melt is held in the furnace have a significant influence on the degree of oxidation and the final chemical composition. At higher casting temperatures, the oxidation of carbon and other alloying elements is more intense than at lower casting temperatures. With longer holding times of the melt in the furnace, more carbon and other alloying elements were oxidized. Observations have shown that at lower casting temperatures, silicon and manganese burn off more, while at higher casting temperatures, carbon burns off more. The carbon equivalent and active carbon equivalent decrease as the casting temperature increases. It has been found that carbon has the greatest influence on the carbon equivalent.

• Keywords: Casting temperature, holding time, carbon equivalent, active carbon equivalent, chemical composition.