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Influence of aluminium on the formation of pinholes in cast irons

Elbel T., Hampl J., Vladik R., Koukal R.

Archives of Foundry Engineering

2008

Vol. 8, iss. 2

27-32

Purpose: This study concerns the formation of pinholes in castings by reaction between cast iron with compacted graphite and green sand mould. Methodology: Experiments were done on bar castings moulded in green bentonite mixtures without carbonaceous matters. Moulding sand moisture and aluminium content in the melt were purposely changed. Metal was melted in a 100 kg furnace by remelting the uniform charge of return material. Metal was inoculated all at once in a ladle and modified in a reaction chamber in a mould or as sandwich method in a pouring ladle. Findings: The formation of pinholes was not caused by high moisture of the mould but this defect was sensible to aluminium content in metal. In castings with high aluminium content > 0.2 % the pinholes occurred in high numbers, and namely under low and also high moistures [> 4 %]. In previous melts with aluminium contents < 0.02 % defects occurred in small range. Practical implications: Thus the conclusions known from literature about the influence of Al on pinholes occurrence in cast irons were confirmed. Oxygen activity in metal during its flowing and cooling in the mould was also measured but this quantity was not changed too in dependence on pinholes content. Morphological analyses near the defect have indicated that it is a physical type of pinholes caused by hydrogen. Originality: A number of works were aimed at explanation of causes of pinholes formation in lamellar graphite iron castings and spheroidal graphite ones. But this defect is formed in castings from compacted graphite cast iron too and the research was aimed just to this material. The contribution is in such a way an exceptional one.

Niektoré poznatky z analýzy chýb odliatkov z hliníkových zliatin

Schützová D., Bobok L'., Lukáč I.

Archiwum Odlewnictwa

2004

R. 4, nr 11/2

154--159

Chyby odliatkov súvisia s fyzikálno - metalurgickými vlastnost'ami kovov a zlilitin z ktorých sú odliatky vyrobené, s metalurgickými aspektami ich tavenia a ošetrenin, resp. s kvalitou realizácie zlievarenskej technológie. V príspevku sú uvedené niektoré poznatky z analýzy chýb konkrétnych typov odliatkov vyrobených zo zlintin na báze hliníka odlievaním do trvalých foriem.

Defects of castings relate to physical-metallurgical properties of metals and alloys of which castings are made, metallurgical aspects of their melting and treatment, and quality of foundry technology realization, as well. In the contribution some experience from analysis of defects of certain types of castings made from alloys on aluminium basis cast into permanent moulds is given.