Different forms of molten metal filtration are routinely employed in all aluminum shape casting processes by many foundries and diecasters. It is generally understood by most metalcasters that "filtration is good" and offers key benefits to the metal caster such as improved fluidity during the casting process, better casting mechanical properties, surface finish, machinability, etc. Overall scrap rates and customer rejects can also often be reduced when scrap is inclusion-related. However, getting a handle on both quantitative and qualitative assessment of filtration efficiency and effectiveness is sometimes very difficult for the foundry to evaluate. Several metal cleanliness evaluation devices, and additional methods for assessing filtering effectiveness are available to help to overcome this difficulty. This paper presents a laboratory study complemented by foundry practice approach for the foundry/diecaster to evaluate filtration benefits using these many techniques. Actual examples are presented as applicable for in-furnace (normally bonded particle) filtering systems commonly used by many foundries/diecasters.
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