DRUŠTVO LIVARJEV SLOVENIJESLOVENIAN FOUNDRYMEN SOCIETY
Član The World Foundry OrganizationMember of World Foundry Organization

  NEW TECHNOLOGICAL SOLUTIONS – ANSWER OF PRESSURE-DIE CASTER TO CHALLENGES OF AUTOMOTIVE INDUSTRY TO INCREASED INTEGRATION OF COMPONENTS AND INCREASED QUALITY DEMANDS

Pressure die casting process is known to automotive industry for long time. Aluminium and magnesium parts, made in this way, are widely used because of their favourable properties. In recent time development is increasingly directed towards integrated structures. Structural elements are thus more complex and more complicated that higher effectiveness is achieved. Therefore greater technological problems appear and they must be solved by further development of pressure die casting process with application of new technological solutions. This way of manufacturing structural parts can be justifiably called high-tech die casting.

Precise diagnosis of casting defects and implementation of remedies are necessary for reduction of rejections and production costs in foundries. Diagnosis and analysis of casting defects are complex problems. Recognition of a defect is a key to its elimination. This paper aimed at providing a systematic approach for defect identification, determination of causes and recommendations for remedies. The systematic approach to defects diagnosis and prevention was based on following steps:

1. Anamnesis (occurrence survey, history)
2. Identification (external marks or visual observation)
3. Differential diagnostics
4. Special material analyses (chemical, structural and microscopic examination)
5. Final diagnosis
6. Determination of defect formation cause, measures for remedies to the defect elimination
7. Prevention of defect formation and its realization
8. Evaluation

Key words: Defect identification, prevention, cause determination

STUDY OF THE INFLUENCE OF REPEATED CASTING ON THE BIOCOMPATIBILITY OF A DENTAL GOLD ALLOY

The aim of this work was to study the effect of repeated casting procedures on the microstructure and biocompatibilty of a high noble Au dental alloy. The prepared samples of one- four- and eight times melted/cast Dentor S were used to study primary cutaneous irritation and sensibilization on experimental animals. The extract of the alloy prepared by conditioning the Dentor S samples in a cell culture medium was used to study the cytotoxicity on L929 cells. The elemental composition and surface changes of the alloy were examined by Energy Dispersive X-ray (EDX) analysis and optical microscopy, respectively. Our results showed that repeated casting decreased the biocompatibility of Dentor S, manifested as decreased metabolic and proliferative activities of L929 cells and that the effect correlated with the number of melting/casting procedures. However, neither sample of Dentor S caused irritation and sensibilization on experimental animals. EDX showed that recasting slightly incresed the content of Au and Cu and slightly decreased the content of Pt, Pd and Zn. These changes correlated with the observations by optical microscopy. In conclusion, our results show that repeated casting of high noble Au alloy changes its microstructure and decreases the biocompatibilty, suggesting that this procedure should be avoided in dental practice.

Key words: high noble dental alloy, biocompatibility, microstructure