Testiranje premazov, ki se uporabljajo za litje v peščene forme in so narejeni po postopku sol-gel : diplomsko delo

Gudžulić, Tara (author), Medved, Jože (mentor), Čevka, Janko (comentor)

Premazi so v livarski industriji znani kot pomožni materiali pri ulivanju taline v peščeno formo. Za doseganje želenih lastnosti morajo biti sestavljeni iz ognjevzdržnega polnila, tekočega nosilca, suspenzijskega sredstva, veziva in v našem primeru tudi sol-gel komponente. Namen uporabe premazov je: ustrezna površin ulitka, prekrivanja neravnih poroznih površin ter preprečevanje penetracije taline in reakcije s peščeno mešanico. Sol-gel postopek je metoda kemijske sinteze, ki se običajno uporablja pri zaščiti anorganskih materialov, kot so kovine, steklo in keramika, lahko pa se uporabljajo tudi v metalurški industriji, kjer so različni materiali v stiku s staljeno kovino. V diplomski nalogi smo preiskovali sol-gel premaz kot zaščito peščene forme pri litju jeklene litine. Uporabili smo premaz s cirkonijevim polnilom – Aquadur ZP (Exoterm-it), s sestavo: 83 mas.% ognjevzdržno polnilo (ZrO2), 2 mas.% organsko vezivo in 15 mas.% voda. Osnovnemu premazu smo dodali sol-gel komponento. Pri eksperimentalnem delu smo opravili preizkuse litja jeklene litine ujete v merilne celice izdelane po postopku Croning. Analizirali smo potek strjevanja, površino jeklenega ulitka in morebitno reakcijo peščene mešanice in jeklene litine. Izvedli smo vizualno analizo površine ulitkov ter ugotavljali, kolikšna količina peska se je "pripekla" na površino ulitkov. Ulivanje je potekalo v dveh serijah. V prvi seriji smo "pripečeni" pesek opazili na površini vzorcev U2 in U3, ta se je nahajal le v majhnih količinah. Notranjost croning merilne celice je bila v primeru U2 premazana s SP v primeru U3 pa z NP. Pri drugi seriji ulivanja je "pripečeni" pesek ostal na površini vzorcev U6 in U7. Notranjost croning merilne celice je bila pri U6 premazana z NP, pri vzorcu U7 pa notranjosti celice nismo premazali. Meritve so pokazale, da se je premaz dobro obnesel med ulivanjem, da ni kemično reagiral s talino in merilnimi celicami izdelanimi po postopku Croning, ter da je pripomogel k zmanjšanju "pripečenega" peska na vzorce ulitkov.

• Language: Slovenian
• Keywords: sol-gel premazi, jeklena litina, enostavna termična analiza, reakcija med formo in talino
• Work type: High school thesis
• Typology: 2.11 - Undergraduate Thesis
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Place of publishing: Ljubljana
• Publisher: [T. Gudžulić]
• Year: 2021
• Number of pages: XII, 33 f.
• PID: 20.500.12556/RUL-131168
• UDC: 669
• COBISS.SI-ID: 85676035
• Publication date in RUL: 23.09.2021

Secondary language

• Language: English
• Title: Testing of coatings used for casting in sand forms and made by the sol-gel procedure : diploma work

Abstract

Coatings are known in the foundry industry as auxiliary materials for casting melt into a sand mold. To achieve the desired properties, they must consist of a refractory filler, a liquid carrier, a suspending agent, a binder and, in our case, a sol-gel component. The purpose of the application of coatings is: suitable surfaces of the casting, covering uneven porous surfaces and preventing the penetration of the melt and the reaction with the sand mixture. The sol-gel process is a method of chemical synthesis commonly used to protect inorganic materials such as metals, glass and ceramics, but can also be used in the metallurgical industry where various materials are in contact with molten metal. In the diploma thesis we investigated the sol-gel coating as protection of the sand form in the casting of steel cast iron. We used a coating with zirconium filler - Aquadur ZP (Exoterm-it), with the composition: 83 wt.% Refractory filler (ZrO2), 2 wt.% Organic binder and 15 wt.% Water. A sol-gel component was added to the base coat. In the experimental work, we performed tests of casting steel cast iron trapped in measuring cells made by the Croning procedure. We analyzed the solidification process, the surface of the steel casting and the possible reaction of the sand mixture and cast iron. We performed a visual analysis of the surface of the castings and determined how much sand had "burned" on the surface of the castings. The casting took place in two series. In the first series, calcined sand was observed on the surface of samples U2 and U3, which was found only in small quantities. The inside of the croning measuring cell was coated with SP in case of U2 and with NP in case of U3. In the second batch series, the sintered sand remained on the surface of samples U6 and U7. The inside of the croning measuring cell was coated with NP in U6, and the inside of the cell was not coated in sample U7. Measurements showed that the coating performed well during casting, did not react chemically with the melt and measuring cells made by the Croning process, and that it helped to reduce the baked sand to the casting samples.

• Keywords: sol-gel coatings, cast steel, simple thermal analysis, reaction between mold and melt