Razvoj nove aktivne komore za tlačno litje s hladno komornim strojem

Mitrović, Danijel (author), Mrvar, Primož (mentor)

IZVLEČEK Izvedena je bila izdelava in karakterizacija nove komore za tlačno litje (HPDC) s hladno komornim strojem po dveh industrijskih testih, in sicer: Po 16.000 ciklih s uporabo komore večje dimenzije ter po 21.500 ciklih polnjenja Al komore manjše dimenzije v stroju za tlačno litje. Po umestitvi komor v proizvodno proces je bila izvedena podrobna analiza poškodb. Komori za tlačno litje sta bili namesto tradicionalno uporabljenega kovanega jekla za delo v vročem (HWTS), izdelani ter razviti iz SiMoCr litega železa z dodatkom silicija ter vermikualarno obliko grafita (SiMoCr CGI). Nov material kaže izboljšano toplotno prevodnost napram obstoječi tehnologiji in sprejemljive mehanske lastnosti. V delu doktorske disertacije je razkrit ter pojasnjen mehanizem ter napredovanje poškodbe na komori SiMoCr CGI po uporabi. Ugotovljen je nastanek razpok na ostrih robovih grafitnih delcev ter zmanjšanje adhezije med mejami zrn po uporabi materiala v aplikaciji komore za tlačno litje. Razpoke so dodatno lokalno napredovale in povzročile lokalno porušitev zlitine, kar je mogoče pripisati kombinaciji toplotnega utrujenja in mehanskih obremenitev kot posledici vzajemnih učinkov temperaturno pogojenim napetostim (gradienta) na površini komor ter različnimi deklaracijskimi lastnostmi med delci grafita in materialom matrice ter pojavom koncentracije napetosti na ostrih konicah grafitnih delcev. Opredeljen pristop omogoča cenovno ugodnejšo aplikacijo v primerjavi z obstoječimi materiali, ki se uporabljajo za izdelavo komor hladno komornega stroja za tlačno litje, ki so tradicionalno izdelane iz H11 oz. H13 orodnega jekla (HWTS).

• Language: Slovenian
• Keywords: Ključne besede: Hladno komorni stroj, tlačno litje, Al, komora, SiMoCr CGI, HWTS, analiza napak, propagacija razpoke, napredovanje razslojevanja.
• Work type: Doctoral dissertation
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Year: 2020
• PID: 20.500.12556/RUL-114097
• COBISS.SI-ID: 304072192
• Publication date in RUL: 14.02.2020

MITROVIĆ, Danijel, 2020, Razvoj nove aktivne komore za tlačno litje s hladno komornim strojem [online]. Doctoral dissertation. [Accessed 26 March 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=114097

Secondary language

• Language: English
• Title: Development of new active shot sleeve for a cold chamber die casting machine

Abstract

ABSTRACT Analysis of damages on cold chamber shot sleeve of Al high pressure die casting machine (HPDC) was carried out after two industrial tests, namely: after 16.000 shots with use of larger shot sleeve and after 21.000 shots with smaller size shot sleeve. The shot sleeves were characterized and were made from newly developed SiMo cast iron with vermicular graphite shape, alloyed with Cr and with increased amount od Si (SiMoCr CGI) instead of the commonly used hot forged tool steel material (HWTS). New material exhibits improved thermal conductivity and acceptable mechanical properties. The progress of the damages is further revealed and explained in this study. The formation of cracks on the sharp shaped edges on graphite particles and decrease in adhesion between grain boundaries has been identified. Cracks have progressed further locally and resulted in material spalling. This can be attributed to the fatigue nature of thermal (mechanical) loads as a consequence of the mutual effects of thermal stresses (gradient) on the surface layer and the different thermal dilatation properties between graphite particles and matrix material, and the occurrence of stress concentration on the sharp shaped spots of the graphite particles. This approach enables us to make the price of the unit more economical compared to the existing forged one, made from H11 or H13 (HWTS) grade tool steel.

• Keywords: Key words: HPDC, cold chamber, Al, shot sleeve, SiMoCr CGI, HWTS, damages analysis, crack propagation, delamination progress.