| Demo : Aluminium Sheet |
Description
Molten metal has a tendency to acquire "inclusions" of insoluble material during any operation prior to casting. These inclusions are usually solid, although liquid inclusions can form (eg Magnesium Chloride), and originate from
Why is it important ?
Removal of inclusions is essential for the manufacture of many products and is achieved by allowing particles to sink or float to the surface during fluxing in the holding furnace, and by correct degassing and filtration practices. Note that filtration cannot alone produce clean metal if the other practices are not correctly followed.
How is it measured ?
The cleanliness of molten metal may be measured by "LiMCA ("Liquid Metal Cleanliness Analyser), a technique developed by Alcan, which gives a quantitative analysis of the number and size range of inclusions. "PoDFA" ("Porous Disc Filtration Apparatus") is an older techniques which analyses a solidified piece of metal containing inclusions filtered out from a larger volume of metal. This technique has the advantage of identifying inclusion type, but has the disadvantage of being off-line and slower. More recently "Prefil" has quantified the PoDFA measurement.