Postavitev tehnološko procesnega okna za doseganje usmerjenega strjevanja ulitka grelne plošče iz sive litine z lamelnim grafitom

• Main Author: Menegatti, Aleš
• Other Authors: Mrvar, Primož
• Format: Bachelor Thesis
• Language: Slovenian
• Published: A. Menegatti 2021
• Subjects: siva litina z lamelnim grafitom; usmerjeno strjevanje; dovodni kanal; krčilna poroznost; flake graphite cast iron; unidirectional solidification; gate; shrinkage porosity; info:eu-repo/classification/udc/669; Kanala; The Gate; sami
• Online Access: https://repozitorij.uni-lj.si/IzpisGradiva.php?id=131176; https://repozitorij.uni-lj.si/Dokument.php?id=148438&dn=; https://plus.si.cobiss.net/opac7/bib/85820163?lang=sl

Diplomsko delo je bilo izvedeno z namenom optimizacije elementov ulivno napajalnega sistema ulitkov grelnih plošč iz sive litine z lamelnim grafitom, kjer nastane krčilna poroznost. Napaka nastane zaradi neoptimalnega geometrijskega načrtovanja ulivno napajalnega sistema in še posebej dovodnega kanala, kjer se litina v ulitku nazadnje strjuje. Najprej smo izvedli merjenje temperatur pri litju v sami formi in na podlagi tega izračunali parametre prenosa toplote iz ulitka na formo in obratno. Na podlagi meritev smo izračunali koeficient prestopa toplote v formi. Pomagali smo si tudi z virtualnimi orodji in v ta namen uporabili program ProCast, ki izvede simulacije na podlagi metode končnih elementov. Za izračun simulacije smo potrebovali 3D virtualni CAD (Computer aided design) model forme, ki smo ga vnesli v program. V programu smo pripravili ustrezno geometrijo z mreženjem, koeficiente prestopa toplote med volumni in opredelili materialne lastnosti ter robne pogoje. Rezultat izračuna livarskih procesov je virtualni potek litja (strujanja) ? natančneje, strujanja tekoče litine po elementih ulivno napajalnega sistema in v livnih votlinah, strjevanja taline in nastanka mikro in makro krčilne poroznosti pri strjevanju. Da bi se izognili krčilni poroznosti, smo spremenili geometrijo samega dovodnega kanala, ki se je do sedaj strjeval pred samim ulitkom, zaradi česar so na površini ulitka nastali vidni lunkerji. Vzrok je bil premajhen geometrijski modul dovodnega kanala. Pri prvem popravku smo povečali geometrijo samega dovodnega kanala, da smo dosegli usmerjeno strjevanje. Pri drugem popravku smo zmanjšali dimenzije dovodnega kanala, ker so nastali problemi pri lomljenju ulitkov iz ulivno napajalnega sistema. The bachelor’s thesis was carried out to optimize the elements of the casting-feeding system of grey cast iron heating plate castings with lamellar graphite where shrinkage porosity occurred. The defect was caused by a sub-optimal geometric design of the casting-feeding system and in particular of the gate where the casting metal was last solidified in the casting. First, we measured the casting temperatures in the mold and calculated the heat transfer parameters within the mold. The measurements were used to calculate the heat transfer coefficient in the mold. We also used virtual tools to help us, using ProCast which performs simulations based on the finite element method. To calculate the casting, we needed a 3D virtual CAD model of the mold which we opened into the program. We prepared the appropriate geometry with meshing. We set heat transfers between volumes and defined material properties and boundary conditions. The result of the casting process calculation is a virtual casting flow. Specifically, the flow of liquid metal through the elements of the casting-feeding system and casting cavities, solidification of the metal, and the formation of micro- and macro-shrinkage porosity during solidification. To avoid shrinkage porosity, we changed the geometry of the gate, which had been hardening before the casting creating visible shrinkage cavities on the casting surface. This was due to the insufficient geometric modulus of the gate. In the first correction, the geometry of the gate was increased to achieve unidirectional solidification. In the second correction, the dimension of the channel was reduced because there were problems with breaking the castings from the casting-feeding system.